Purpose: Given that histone deacetylase (HDAC) inhibitors are known to induce multiple epigenetic modifications affecting signaling networks and act synergistically with phosphatidylinositol 3-kinase (PI3K) inhibitors, we developed a strategy to simultaneously inhibit HDACs and PI3K in cancer cells.

Experimental Design: We constructed dual-acting inhibitors by incorporating HDAC inhibitory functionality into a PI3K inhibitor pharmacophore. CUDC-907, a development candidate selected from these dual inhibitors, was evaluated in vitro and in vivo to determine its pharmacologic properties, anticancer activity, and mechanism of action.

Results: CUDC-907 potently inhibits class I PI3Ks as well as classes I and II HDAC enzymes. Through its integrated HDAC inhibitory activity, CUDC-907 durably inhibits the PI3K-AKT-mTOR pathway and compensatory signaling molecules such as RAF, MEK, MAPK, and STAT-3, as well as upstream receptor tyrosine kinases. CUDC-907 shows greater growth inhibition and proapoptotic activity than single-target PI3K or HDAC inhibitors in both cultured and implanted cancer cells.

Conclusions: CUDC-907 may offer improved therapeutic benefits through simultaneous, sustained disruption of multiple oncogenic signaling networks. Clin Cancer Res; 18(15); 4104–13. ©2012 AACR.

Translational Relevance

Several phosphatidylinositol 3-kinase (PI3K) inhibitors are being evaluated in clinical trials for the treatment of various cancers, but single target agents often display limited clinical activity because of the genetic, epigenetic, and phenotypic heterogeneity and adaptive nature of cancer cells. Simultaneous blockade of multiple signaling nodes to thwart adaptive and evolutionary mechanisms of cancer cells offers the potential to overcome the limited activity and acquired resistance to PI3K inhibitor monotherapy. Accordingly, we designed and synthesized a novel molecule, CUDC-907, that inhibits not only PI3K directly but also other oncogenic signaling pathways indirectly through histone deacetylase (HDAC) inhibition. We report here that CUDC-907 displays potent anticancer activity in both cultured cancer cells and xenograft models and may offer therapeutic benefits in multiple cancers through broad signaling network disruption. Importantly, our work provides a framework to generate a multitarget inhibitor that can potentially overcome the dynamic and adaptive natures of tumor cells.

The phosphatidylinositol 3-kinase (PI3K) pathway plays an important role in cancer cell initiation, growth, proliferation, and survival. The PI3 kinases are frequently activated through mutation or receptor tyrosine kinases in many cancers (1, 2). More than 20 agents targeting the PI3K/AKT pathway are currently being evaluated in clinical trials and several of these agents have shown single-agent activity in cancers with phosphatidyl inositol 3-kinase catalytic subunit (PIK3CA) mutations or PTEN deletion/mutations (3–6). However, the efficacy of PI3K inhibitors is limited by concurrent activation of other survival- and growth-related pathways (5, 7–9).

A potential strategy to overcome these limitations is to combine PI3K and MEK inhibitors to achieve synergistic antitumor activity. Preclinical studies have showed that this combination significantly improves efficacy in xenograft tumor models that carry various genetic alterations, such as KRAS mutations, HER2 amplification, or PTEN deletion/mutations (9–12). Of note, several phase I clinical trials testing combinations of PI3K and MEK pathway inhibitors are in progress (13).

Another promising strategy to overcome potential limitations of targeting the PI3K pathway is to disrupt multiple pathways through histone deacetylase (HDAC) inhibition (14, 15). By regulating both histone and nonhistone substrates, HDAC inhibitors can affect a variety of cell functions and synergize with PI3K inhibitors (16, 17).

In this report, we synthesized a novel series of dual-acting PI3K and HDAC inhibitors by incorporating HDAC inhibitory functionality into a PI3K inhibitor pharmacophore. We show the unique pharmacologic properties of one of the best of the series, CUDC-907, and its potent anticancer activity through oncogenic signaling network disruption.

Reagents

CUDC-907, vorinostat [suberoylanilide hydroxamic acid (SAHA)], panobinostat (LBH-589), GDC-0941, and BEZ-235 were synthesized in-house. CAL-101 was purchased from Active Biochem (Maplewood, NJ). For in vitro assays, compounds were dissolved in dimethyl sulfoxide (DMSO) as stock and stored at −80°C. For in vivo studies, CUDC-907 was formulated in 30% Captisol (Cydex Pharmaceuticals, Inc.).

HDAC activity and PI3K kinase assays

The activities of classes I and II HDACs were measured using the Color-de-Lys assay system (Biomol International). The activity of PI3K was measured using the ADP-Glo luminescent kinase assay (Promega). Recombinant PI3K protein, a complex of N-terminal GST-tagged recombinant full-length human p110 and untagged recombinant full-length human p85, was coexpressed in a baculovirus-infected Sf9 cell expression system.

Cancer cell growth inhibition assay

Human cancer cell lines were purchased from American Type Culture Collection (Manassas, VA) and plated at densities of 5,000 to 10,000 per well in 96-well flat-bottomed plates with the recommended culture medium. The cells were then incubated with compounds at various concentrations for 72 hours in culture medium supplemented with 0.5% (v/v) FBS. Growth inhibition was assessed by assay of cellular ATP content using the Perkin-Elmer ATPlite kit.

Western blot analysis and immunocytochemistry

Cells grown in monolayer culture were treated as indicated. Cell lysates were resolved on polyacrylamide gels and transferred to nitrocellulose filter (Invitrogen). Immunoblotting was done using standard procedures with blocking solution (Li-Cor Bioscience) containing primary and IRDye 680- or 800CW-conjugated secondary antibodies. Immunocytochemistry was conducted on cells grown in monolayer culture that were treated as indicated in figure legends and then fixed in 4% (w/v) paraformaldehyde.

Assessment of apoptosis

Apoptosis was assessed by measuring the activities of caspase-3 and -7 using the Apo-ONE Homogeneous Assay Kit (Promega).

Cell-cycle analysis

Cell-cycle arrest was measured by Accuri C6 Flow Cytometry using a Cell Cycle Phase Determination kit (Cayman Chemical Co.).

Efficacy study in a human cancer xenograft model

Six- to 8-week-old female athymic (nude nu/nu CD-1) or severe combined immunodeficient (SCID) mice obtained from Charles River Laboratories were injected subcutaneously with 3 to 20 × 106 cells in a medium suspension of 100 to 200 μL into the right hind flank region. Varying doses of CUDC-907, standard anticancer agents, or vehicle were administered orally or via tail vein injection as indicated.

HDAC and PI3K inhibitors are synergistic

To confirm the potential synergistic effect of PI3K and HDAC inhibition, we assessed the growth inhibition effect of 2 reference compounds, the HDAC inhibitor vorinostat and the PI3K inhibitor GDC-0941, on the human PC-3 prostate cancer cell line. The combined effect of these 2 compounds was then compared with the effect observed after treatment with each single compound and then analyzed using the median effect analysis (18). The combination index was significantly less than 1, which indicates that the 2 inhibitors given together act synergistically to suppress cancer cell growth (Supplementary Fig. S1) thus providing the rationale for the development of a dual PI3K and HDAC inhibitor.

CUDC-907 is a potent inhibitor of both HDAC and PI3K

We thus designed and synthesized a multitarget inhibitor, CUDC-907, which integrates HDAC inhibitory functionality (hydroxamic acid) into a core structure scaffold (morpholinopyrimidine) shared by several PI3K inhibitors (Fig. 1A). We first tested whether CUDC-907 is a potent pan-inhibitor of HDAC classes I and II enzymes and observed that its potency against class I HDACs was similar to that of panobinostat and greater than that of vorinostat (Table 1). We next tested the effect of CUDC-907 on PI3K activity and found that CUDC-907 is also a potent inhibitor of class I PI3K kinases with an IC50 of 19, 54, and 39 nmol/L for PI3Kα, PI3Kβ, and PI3Kδ, respectively. This activity is similar to that of a known PI3K inhibitor, GDC-0941 (Table 1).

Figure 1.

CUDC-907 design and its potency against PI3K and HDAC. A, schematic representation of the design for dual HDAC and PI3K inhibitors and the core chemical structure of CUDC-907. The compound was designed as a single molecule simultaneously targeting HDAC and PI3K kinase by integration of HDAC inhibitory functionality (hydroxamate moiety) into a PI3K inhibitor skeleton. B, H460 NSCLC cells were treated with DMSO, 1 μmol/L of CUDC-907, 1 μmol/L of panobinostat, or 5 μmol/L of vorinostat for 1 hour. Western blot analysis indicates that CUDC-907 increases the levels of acetylated histone H3 (Ac-H3), tubulin (Ac-Tub), p53 (Ac-p53), total p53, and p21. C, H460 NSCLC cells were treated with DMSO, 1 μmol/L of CUDC-907, 1 μmol/L of GDC-0941, or 5 μmol/L of vorinostat for 1 hour. Western blot analysis reveals that CUDC-907 inhibits AKT phosphorylation on both the T308 and S473 sites. Decreased phosphorylation of downstream 4EBP-1 and p70S6 was also detected.

Figure 1.

CUDC-907 design and its potency against PI3K and HDAC. A, schematic representation of the design for dual HDAC and PI3K inhibitors and the core chemical structure of CUDC-907. The compound was designed as a single molecule simultaneously targeting HDAC and PI3K kinase by integration of HDAC inhibitory functionality (hydroxamate moiety) into a PI3K inhibitor skeleton. B, H460 NSCLC cells were treated with DMSO, 1 μmol/L of CUDC-907, 1 μmol/L of panobinostat, or 5 μmol/L of vorinostat for 1 hour. Western blot analysis indicates that CUDC-907 increases the levels of acetylated histone H3 (Ac-H3), tubulin (Ac-Tub), p53 (Ac-p53), total p53, and p21. C, H460 NSCLC cells were treated with DMSO, 1 μmol/L of CUDC-907, 1 μmol/L of GDC-0941, or 5 μmol/L of vorinostat for 1 hour. Western blot analysis reveals that CUDC-907 inhibits AKT phosphorylation on both the T308 and S473 sites. Decreased phosphorylation of downstream 4EBP-1 and p70S6 was also detected.

Close modal
Table 1.

Inhibition of the enzymatic activities of HDACs and PI3Ks by CUDC-101 and reference compounds

IC50 (nmol/L) in enzyme assays
CompoundHDAC1HDAC2HDAC3HDAC8HDAC4HDAC5HDAC6HDAC7HDAC9HDAC10HDAC11PI3KαPI3KβPI3KδPI3Kγ
Vorinostat 42.5 156 33.1 113 NA NA 21.6 NA NA 68.4 51.3 NA NA NA NA 
Panobinostat 1.4 6.8 1.5 26.7 195.6 123.8 8.2 1864 922.2 2.1 1.6 NA NA NA NA 
GDC-0941 NA NA NA NA NA NA NA NA NA NA NA 31 55 
Cal-101 NA NA NA NA NA NA NA NA NA NA NA 354 108 18 31 
CUDC-907 1.7 5.0 1.8 191 409 674 27 426 554 2.8 5.4 19 54 39 311 
IC50 (nmol/L) in enzyme assays
CompoundHDAC1HDAC2HDAC3HDAC8HDAC4HDAC5HDAC6HDAC7HDAC9HDAC10HDAC11PI3KαPI3KβPI3KδPI3Kγ
Vorinostat 42.5 156 33.1 113 NA NA 21.6 NA NA 68.4 51.3 NA NA NA NA 
Panobinostat 1.4 6.8 1.5 26.7 195.6 123.8 8.2 1864 922.2 2.1 1.6 NA NA NA NA 
GDC-0941 NA NA NA NA NA NA NA NA NA NA NA 31 55 
Cal-101 NA NA NA NA NA NA NA NA NA NA NA 354 108 18 31 
CUDC-907 1.7 5.0 1.8 191 409 674 27 426 554 2.8 5.4 19 54 39 311 

Abbreviation: NA, not active.

The potent HDAC and PI3K inhibitory activities of CUDC-907 were further evaluated in cancer cells. CUDC-907 treatment resulted in an increase of acetylated histones as well as non-histone proteins such as tubulin and p53 (Fig. 1B). Similar to other HDAC inhibitors, CUDC-907 markedly induced p21 protein in H460, a non–small cell lung cancer (NSCLC) cell line (Fig. 1B). To confirm the specificity of the HDAC inhibition, we further showed that CUDC-907 induced the accumulation of acetylated histone H3, tubulin, and p53, as well as p21 expression in a dose-dependent manner (Supplementary Figs. S2–S5). Similarly, we observed that CUDC-907 inhibited the PI3K pathway, as indicated by the dose-dependent decreases in phosphorylation of AKT and its downstream targets, 4EBP-1 and p70S6, in H460 cells (Fig. 1C).

CUDC-907 durably inhibits AKT activation

One potential mechanism to explain how tumor cells evade single-target kinase inhibitors is the reactivation of downstream signaling through multiple compensatory mechanisms. Consistently, we observed that although GDC-0941 more potently inhibited AKT than CUDC-907 at early time points (at 1 hour after treatment), CUDC-907 led to sustained AKT inhibition and suppressed AKT more potently than GDC-0941 at 16 hours after treatment (Fig. 2A). The greater PI3K-inhibiting activity observed at later time points likely resulted from the prevention of compensatory reactivation of AKT through CUDC-907 induced HDAC inhibition, as we observed similar, although less potent effects with the other HDAC inhibitors vorinostat and panobinostat (Fig. 2A).

Figure 2.

CUDC-907 durably suppresses activation of AKT and modulates receptor tyrosine kinase, RAF-MEK-MAPK and SRC/STAT signaling. A, as indicated, H460 NSCLC cells were cultured in the presence of 10 μg/mL of insulin and treated with DMSO, CUDC-907, GDC-0941, panobinostat, or vorinostat with various concentrations as indicated for 1 or 16 hours (left). Immunocytochemical analyses indicate that GDC-0941 potently inhibits AKT phosphorylation at 1 hour; however, AKT was reactivated in cells treated with the compound at lower concentrations at 16 hours. In contrast, CUDC-907 inhibited AKT phosphorylation even at 16 hours after treatment and was more potent than GDC-0941 in reducing AKT phosphorylation at this time point. Western blot analysis (right) further confirmed the immunocytochemical results shown in the left. B, BT-474 breast, H460 NSCLC, H1975 NSCLC, and A375 melanoma cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of PLX-4720, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours as indicated. Western blot analyses indicate that CUDC-907 inhibits the phosphorylation of CRAF, MEK, and MAPK. C, as indicated, RPMI-8226 multiple myeloma cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours. Western blot analyses indicate that CUDC-907 suppresses SRC and STAT3 phosphorylation. D, H1975 NSCLC and BT-474 breast cancer cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours. Western blot analyses indicate that CUDC-907 reduces both phosphorylated and total protein levels of the tyrosine receptor kinases MET, EGFR, HER2, and HER3 in H1975 and BT-474 tumor cells. Similar reductions in levels of these receptor kinases were also observed after panobinostat treatment.

Figure 2.

CUDC-907 durably suppresses activation of AKT and modulates receptor tyrosine kinase, RAF-MEK-MAPK and SRC/STAT signaling. A, as indicated, H460 NSCLC cells were cultured in the presence of 10 μg/mL of insulin and treated with DMSO, CUDC-907, GDC-0941, panobinostat, or vorinostat with various concentrations as indicated for 1 or 16 hours (left). Immunocytochemical analyses indicate that GDC-0941 potently inhibits AKT phosphorylation at 1 hour; however, AKT was reactivated in cells treated with the compound at lower concentrations at 16 hours. In contrast, CUDC-907 inhibited AKT phosphorylation even at 16 hours after treatment and was more potent than GDC-0941 in reducing AKT phosphorylation at this time point. Western blot analysis (right) further confirmed the immunocytochemical results shown in the left. B, BT-474 breast, H460 NSCLC, H1975 NSCLC, and A375 melanoma cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of PLX-4720, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours as indicated. Western blot analyses indicate that CUDC-907 inhibits the phosphorylation of CRAF, MEK, and MAPK. C, as indicated, RPMI-8226 multiple myeloma cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours. Western blot analyses indicate that CUDC-907 suppresses SRC and STAT3 phosphorylation. D, H1975 NSCLC and BT-474 breast cancer cells were treated with DMSO, 0.1 μmol/L of CUDC-907, 0.1 μmol/L of GDC-0941, 0.1 μmol/L of panobinostat, or 0.5 μmol/L of vorinostat for 16 hours. Western blot analyses indicate that CUDC-907 reduces both phosphorylated and total protein levels of the tyrosine receptor kinases MET, EGFR, HER2, and HER3 in H1975 and BT-474 tumor cells. Similar reductions in levels of these receptor kinases were also observed after panobinostat treatment.

Close modal

CUDC-907 suppresses other signaling pathways via HDAC inhibition

We sought to evaluate whether CUDC-907 prevents cancer cells from using other growth and survival pathways via feedback mechanisms. In BRAF-mutant tumor cells (e.g., A375 melanoma cells), activation of downstream MEK sensitizes cells to treatment with the BRAF inhibitor PLX-04720, but not the single-target PI3K inhibitor GDC-0941. CUDC-907 and panobinostat were both able to inhibit the activation of MEK (Fig. 2B). In cancer cell lines with mutations other than those resulting in constitutive activation of PI3K, such as NSCLC H460 cells with KRAS mutation, breast cancer BT-474 cells with HER2 amplification, and NSCLC H1975 cells with EGFR mutations conferring drug resistance, the RAF-MEK-MAPK signaling pathway was active and insensitive to treatment with GDC-0941. In contrast, CUDC-907 and panobinostat suppressed phosphorylation of CRAF, MEK, and MAPK in these cancer cells harboring different mutations (Fig. 2B). Together, these results suggest that HDAC inhibition by CUDC-907 effectively suppresses the RAF-MEK-MAPK signaling pathway.

Furthermore, we were able to show that CUDC-907 caused the reduction of both p-STAT3 (Y-705) and p-SRC in RPMI-8226 multiple myeloma cells (Fig. 2C) and reduced both phosphorylated and total protein levels of MET and EGFR as well as HER2 and HER3 in H1975 NSCLC cells and BT-474 breast cancer cells, respectively (Fig. 2D). These results indicate that CUDC-907 can downregulate and suppress the activation of the SRC/STAT signaling pathway and multiple receptor tyrosine kinases, again presumably because of its HDAC inhibitory activity as we observed that panobinostat also induced a similar effect (Fig. 2C and D).

CUDC-907 may potentially evade drug resistance

To further explore the potential of CUDC-907 to thwart compensatory mechanisms, we generated clones stably expressing activated AKT-1 in Sk-Mel-28 melanoma cancer cells. Compared with parental cells, clones with constitutively active AKT became insensitive to the treatment of GDC-0941. However, those drug-resistant clones were still mainly sensitive to CUDC-907 and panobinostat (Fig. 3A). These results suggest that the incorporation of HDAC inhibitory activity within CUDC-907 prevents the development of drug resistance.

Figure 3.

CUDC-907 evades drug resistance and induces apoptosis and G2–M phase cell-cycle arrest. A, Sk-Mel-28 melanoma cells were transfected with myc-tagged constitutively active (myristoylated) AKT-1, and stable clones were selected and expanded. Western blot analysis indicates that stable clones expressed high levels of myc-tagged constitutively active AKT (AKT-myc) when compared with parental cells. Growth assays reveal that clones expressing AKT-myc tolerate treatment with a single-target PI3K inhibitor but remain sensitive to treatment with CUDC-907. B, RPMI-8226 multiple myeloma cells were incubated with various concentrations (as indicated) of CUDC-907, vorinostat, GDC-0941, or panobinostat for 24 hours. Cytometric analysis was used to characterize live, midapoptotic, late apoptotic, and necrotic or dead cells, characterized by double-negative, Z-DEVD, double-positive, or 7-aminoactinomycin D (7-AAD) staining, respectively. Both CUDC-907 and panobinostat induce the accumulation of apoptotic cells. Ctrl, control. C, H460 cells were treated with GDC-0941, panobinostat, vorinostat, or CUDC-907 at 1 μmol/L for 16 hours before Western blot analysis was conducted. CUDC-907 increases the levels of activated caspase-7, p21, and cleaved PARP (c-PARP), accompanied by a reduction in levels of BCL-2, BCL-xL, and survivin. D, H460 cells were treated for 24 hours with 1 μmol/L of CUDC-907 and reference compounds before propidium iodine staining. Flow cytometric analyses show that CUDC-907 and panobinostat both induce the accumulation of cells at G2–M.

Figure 3.

CUDC-907 evades drug resistance and induces apoptosis and G2–M phase cell-cycle arrest. A, Sk-Mel-28 melanoma cells were transfected with myc-tagged constitutively active (myristoylated) AKT-1, and stable clones were selected and expanded. Western blot analysis indicates that stable clones expressed high levels of myc-tagged constitutively active AKT (AKT-myc) when compared with parental cells. Growth assays reveal that clones expressing AKT-myc tolerate treatment with a single-target PI3K inhibitor but remain sensitive to treatment with CUDC-907. B, RPMI-8226 multiple myeloma cells were incubated with various concentrations (as indicated) of CUDC-907, vorinostat, GDC-0941, or panobinostat for 24 hours. Cytometric analysis was used to characterize live, midapoptotic, late apoptotic, and necrotic or dead cells, characterized by double-negative, Z-DEVD, double-positive, or 7-aminoactinomycin D (7-AAD) staining, respectively. Both CUDC-907 and panobinostat induce the accumulation of apoptotic cells. Ctrl, control. C, H460 cells were treated with GDC-0941, panobinostat, vorinostat, or CUDC-907 at 1 μmol/L for 16 hours before Western blot analysis was conducted. CUDC-907 increases the levels of activated caspase-7, p21, and cleaved PARP (c-PARP), accompanied by a reduction in levels of BCL-2, BCL-xL, and survivin. D, H460 cells were treated for 24 hours with 1 μmol/L of CUDC-907 and reference compounds before propidium iodine staining. Flow cytometric analyses show that CUDC-907 and panobinostat both induce the accumulation of cells at G2–M.

Close modal

CUDC-907 induces apoptosis and G2–M cell-cycle arrest in cancer cells

Next, we evaluated the ability of CUDC-907 to induce apoptosis and cell-cycle arrest in cancer cells. CUDC-907 induced caspase-3 and -7 activation in HCT-116 colon cancer cells in a dose-dependent manner (Supplementary Fig. S6). We next confirmed that CUDC-907 treatment resulted in the accumulation of activated caspase-3 in RPMI-8226 myeloma and annexin V binding sites in MDA-MB-468 breast cancer cells (Fig. 3B and Supplementary Fig. S7). Furthermore, we observed the accumulation of cleaved PARP, activated caspase-7, and p21, as well as the reduction of antiapoptotic proteins including BCL-2, BCL-xL, and survivin in H460 NSCLC cells (Fig. 3C). Consistent with earlier reports of other HDAC inhibitors (15, 19–21), we observed that CUDC-907 and panobinostat induced cell-cycle arrest at G2–M phase. In contrast, the PI3K inhibitors GDC-0941 and BEZ-235 predominantly induced G0/G1 cell-cycle arrest (Fig. 3D and Supplementary Fig. S8).

CUDC-907 effectively inhibits cancer cell growth

Our mechanistic studies suggest that CUDC-907 disrupts multiple oncogenic signaling pathways and induces apoptosis and cell-cycle arrest. Consistent with this observation, we found that CUDC-907 potently inhibits the growth of cancer cells derived from both hematologic and solid tumors (Table 2). Of note, in a survey of a panel of breast cancer cell lines, GDC-0941 is only effective in suppressing cells harboring a PI3K p110α mutation, conversely, CUDC-907 potently inhibits the proliferation of cells expressing either mutant or wild-type PI3K. Similarly, cancer cells with activating KRAS mutations are sensitive to CUDC-907 but not to a single-target PI3K inhibitor (Table 2).

Table 2.

Growth inhibition of human cancer cell lines by CUDC-907 and reference compounds

IC50 (μmol/L) in growth inhibition assay
Cancer typesCell linesVorinostatGDC-0941Vorinostat + GDC-0941CUDC-907
Hematologic 
 B-cell lymphoma RL 0.94 1.34 0.15 0.0020 
 DOHH2 0.57 0.03 0.01 0.0010 
 Granta 519 3.02 >20 0.59 0.0070 
 SU-DHL4 1.15 0.45 0.25 0.0030 
 Daudi 1.23 >20 0.89 0.0150 
 Raji 3.56 >20 3.90 0.0090 
 Pfeiffer 2.73 0.55 0.37 0.0040 
 T-cell lymphoma HH 0.18 0.18 0.13 0.0010 
 MJ 0.87 >20 0.98 0.0050 
 HuT78 0.09 0.15 0.05 0.0010 
 ALL MOLT4 0.31 0.29 0.13 0.0010 
 SUP-B15 0.44 7.61 0.28 0.0007 
 AML HL60 0.42 1.39 0.19 0.0020 
 U937 0.81 0.97 0.29 0.0020 
 THP-1 1.12 3.39 0.38 0.0160 
 MV-4-11 0.23 1.39 0.18 0.0004 
 CML K562 1.48 7.85 0.89 0.0310 
 MEG-01 2.79 >20 2.50 0.0060 
 Multiple myeloma RPMI-8226 1.01 >20 0.69 0.0020 
 OPM-2c 0.43 0.05 0.11 0.0010 
 ARH77 1.42 14.79 0.83 0.0050 
Solid 
 Colon WiDra 1.29 >20 0.75 0.0400 
 HCT-116a,b 1.45 7.53 0.45 0.0070 
 SW403a 2.97 >20 1.11 0.0070 
 SW620a 1.17 >20 0.53 0.0050 
 SW116a 1.72 >20 1.55 0.0060 
 T-84a 3.83 2.97 0.84 0.0300 
 NSCLC H358a 2.00 2.85 1.08 0.0090 
 H292a 2.79 1.68 0.77 0.0080 
 H2122a 1.76 1.48 0.65 0.0080 
 H460a 10.72 >20 2.46 0.0500 
 A549a 2.79 4.35 1.04 0.0100 
 Calu6a 3.10 >20 1.54 0.0200 
 Pancreas MiaPaca2a 2.39 >20 1.79 0.0200 
 CaPan2a 3.75 >20 0.93 0.0200 
 CFPAC-1a 6.22 >20 1.91 0.0500 
 PANC-1a 7.21 1.25 1.39 0.0500 
 SW1990a 2.30 >20 1.64 0.0080 
 Breast HCC1500 3.21 >20 2.00 0.0060 
 HCC1806 4.50 >20 1.22 0.0700 
 MDA-MB-231a 7.29 >20 2.67 0.1200 
 SKBr3 9.84 >20 3.69 0.0500 
 BT474b 1.26 0.49 0.26 0.0060 
 MDA-MB-361b 0.68 0.14 0.06 0.0010 
 UACC-893b 1.96 1.15 0.53 0.0100 
 MDA-MB-453b 0.53 0.64 0.31 0.0070 
 MCF-7b 1.67 0.41 0.39 0.0080 
 T47Db 2.88 >20 0.49 0.0200 
 ZR-75-1c 4.43 0.90 1.28 0.0800 
 MDA-MB-468c 6.81 0.98 1.07 0.0900 
IC50 (μmol/L) in growth inhibition assay
Cancer typesCell linesVorinostatGDC-0941Vorinostat + GDC-0941CUDC-907
Hematologic 
 B-cell lymphoma RL 0.94 1.34 0.15 0.0020 
 DOHH2 0.57 0.03 0.01 0.0010 
 Granta 519 3.02 >20 0.59 0.0070 
 SU-DHL4 1.15 0.45 0.25 0.0030 
 Daudi 1.23 >20 0.89 0.0150 
 Raji 3.56 >20 3.90 0.0090 
 Pfeiffer 2.73 0.55 0.37 0.0040 
 T-cell lymphoma HH 0.18 0.18 0.13 0.0010 
 MJ 0.87 >20 0.98 0.0050 
 HuT78 0.09 0.15 0.05 0.0010 
 ALL MOLT4 0.31 0.29 0.13 0.0010 
 SUP-B15 0.44 7.61 0.28 0.0007 
 AML HL60 0.42 1.39 0.19 0.0020 
 U937 0.81 0.97 0.29 0.0020 
 THP-1 1.12 3.39 0.38 0.0160 
 MV-4-11 0.23 1.39 0.18 0.0004 
 CML K562 1.48 7.85 0.89 0.0310 
 MEG-01 2.79 >20 2.50 0.0060 
 Multiple myeloma RPMI-8226 1.01 >20 0.69 0.0020 
 OPM-2c 0.43 0.05 0.11 0.0010 
 ARH77 1.42 14.79 0.83 0.0050 
Solid 
 Colon WiDra 1.29 >20 0.75 0.0400 
 HCT-116a,b 1.45 7.53 0.45 0.0070 
 SW403a 2.97 >20 1.11 0.0070 
 SW620a 1.17 >20 0.53 0.0050 
 SW116a 1.72 >20 1.55 0.0060 
 T-84a 3.83 2.97 0.84 0.0300 
 NSCLC H358a 2.00 2.85 1.08 0.0090 
 H292a 2.79 1.68 0.77 0.0080 
 H2122a 1.76 1.48 0.65 0.0080 
 H460a 10.72 >20 2.46 0.0500 
 A549a 2.79 4.35 1.04 0.0100 
 Calu6a 3.10 >20 1.54 0.0200 
 Pancreas MiaPaca2a 2.39 >20 1.79 0.0200 
 CaPan2a 3.75 >20 0.93 0.0200 
 CFPAC-1a 6.22 >20 1.91 0.0500 
 PANC-1a 7.21 1.25 1.39 0.0500 
 SW1990a 2.30 >20 1.64 0.0080 
 Breast HCC1500 3.21 >20 2.00 0.0060 
 HCC1806 4.50 >20 1.22 0.0700 
 MDA-MB-231a 7.29 >20 2.67 0.1200 
 SKBr3 9.84 >20 3.69 0.0500 
 BT474b 1.26 0.49 0.26 0.0060 
 MDA-MB-361b 0.68 0.14 0.06 0.0010 
 UACC-893b 1.96 1.15 0.53 0.0100 
 MDA-MB-453b 0.53 0.64 0.31 0.0070 
 MCF-7b 1.67 0.41 0.39 0.0080 
 T47Db 2.88 >20 0.49 0.0200 
 ZR-75-1c 4.43 0.90 1.28 0.0800 
 MDA-MB-468c 6.81 0.98 1.07 0.0900 

NOTE: For combination treatments, reference compounds vorinostat and GDC-0941 were added to the cells at a 1:1 molar ratio with the IC50 values were calculated as the concentrations of single agents. All results shown in this table are representative of 2 to 3 experiments.

Abbreviations: ALL, acute lymphoblastic leukemia; AML, acute myelogenous leukemia; CML, chronic myelogenous leukemia.

aCell lines with KRAS mutations.

bCell lines with PIK3CA mutations.

cCell lines with PTEN deletions/mutations.

CUDC-907 inhibits targets and tumor growth in xenograft tumor models

As HDAC inhibitors have been shown to be promising therapeutic agents in hematologic cancers, we evaluated CUDC-907 in implanted Daudi non-Hodgkin lymphoma (NHL) cancer cells. CUDC-907 is bioavailable in animal models (Supplementary Fig. S9); we also showed that oral administration of CUDC-907 inhibited growth of the Daudi cancer cell xenografts in a dose-dependent manner. Tumor stasis was observed at 100 mg/kg in this model without obvious toxicity (Fig. 4A). Importantly, in the same model, CUDC-907 achieved better efficacy than GDC-0941, vorinostat, or a combination of these 2 compounds given at their maximal tolerated doses (MTD; Fig. 4A). Furthermore, CUDC-907 caused tumor regression or stasis after intravenous (50 mg/kg) or oral administration (100 mg/kg) in a xenograft tumor model of SU-DHL4 diffuse large B-cell lymphoma (DLBCL) and caused tumor stasis in KRAS-mutant A549 NSCLC cell xenografts (Fig. 4A). CUDC-907 was also well tolerated in treated animals, suggesting a favorable safety profile in its future development as a potential clinical drug candidate.

Figure 4.

CUDC-907 suppresses tumor growth, inhibits HDAC activity, and blocks signaling of PI3K and MAPK pathways in xenograft models. A, top left, CUDC-907 was administered orally at 25, 50, and 100 mg/kg in the Daudi NHL xenograft mouse model. Pretreatment tumor size was 125 ± 80 mm3 (mean ± SE). CUDC-907 inhibits tumor growth in a dose-dependent manner. *, P < 0.05; **, P < 0.01 (ANOVA) when compared with the vehicle control group; top right, the antitumor activity of CUDC-907 was compared with either GDC-0941 or vorinostat alone or a combination of GDC-0941 and vorinostat. All compounds and vehicle controls were dosed orally, 5 times weekly. The indicated doses are the maximum tolerated dose (MTD) of each treatment, and the pretreatment tumor size was 157 ± 65 mm3 (mean ± SE). Data show that CUDC-907 is more efficacious than vorinostat, GDC-0941, or a combination of both; bottom left, CUDC-907 causes tumor stasis in the KRAS-mutant and EGFR inhibitor–resistant A549 NSCLC xenograft model after intravenous or oral administration. The pretreatment tumor size was 99.5 ± 23.4 mm3; bottom right, CUDC-907 strongly inhibits tumor growth in the SU-DHL4 diffuse large B-cell lymphoma xenograft model after intravenous (50 mg/kg) or oral administration (100 mg/kg). The pretreatment tumor size was 147 ± 21 mm3. B, pharmacodynamic studies of CUDC-907 after 100 mg/kg oral administration (p.o.; top) or 50 mg/kg intravenous administration (bottom) in the Daudi xenograft tumor model. CUDC-907 increases the levels of acetylated histone H3 (Ac-H3) and cleaved PARP and reduces the levels of p-AKT, p-MAPK, and cyclin D1. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Figure 4.

CUDC-907 suppresses tumor growth, inhibits HDAC activity, and blocks signaling of PI3K and MAPK pathways in xenograft models. A, top left, CUDC-907 was administered orally at 25, 50, and 100 mg/kg in the Daudi NHL xenograft mouse model. Pretreatment tumor size was 125 ± 80 mm3 (mean ± SE). CUDC-907 inhibits tumor growth in a dose-dependent manner. *, P < 0.05; **, P < 0.01 (ANOVA) when compared with the vehicle control group; top right, the antitumor activity of CUDC-907 was compared with either GDC-0941 or vorinostat alone or a combination of GDC-0941 and vorinostat. All compounds and vehicle controls were dosed orally, 5 times weekly. The indicated doses are the maximum tolerated dose (MTD) of each treatment, and the pretreatment tumor size was 157 ± 65 mm3 (mean ± SE). Data show that CUDC-907 is more efficacious than vorinostat, GDC-0941, or a combination of both; bottom left, CUDC-907 causes tumor stasis in the KRAS-mutant and EGFR inhibitor–resistant A549 NSCLC xenograft model after intravenous or oral administration. The pretreatment tumor size was 99.5 ± 23.4 mm3; bottom right, CUDC-907 strongly inhibits tumor growth in the SU-DHL4 diffuse large B-cell lymphoma xenograft model after intravenous (50 mg/kg) or oral administration (100 mg/kg). The pretreatment tumor size was 147 ± 21 mm3. B, pharmacodynamic studies of CUDC-907 after 100 mg/kg oral administration (p.o.; top) or 50 mg/kg intravenous administration (bottom) in the Daudi xenograft tumor model. CUDC-907 increases the levels of acetylated histone H3 (Ac-H3) and cleaved PARP and reduces the levels of p-AKT, p-MAPK, and cyclin D1. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Close modal

To determine if the observed anticancer activity of CUDC-907 is target-specific, we conducted pharmacodynamic studies in the Daudi xenograft tumor models after oral or intravenous administration of CUDC-907 (Fig. 4B). We observed that CUDC-907 inhibited HDACs as indicated by the accumulation of acetylated histone H3 (AcH3) as well as PI3K as indicated by the decrease of p-AKT. The induction of acetylated histone H3 lasted for 24 hours after oral administration as compared with 6 hours after intravenous administration. Importantly, we also observed potent inhibition of the RAF-MEK-MAPK signaling pathway as indicated by the reduction of p-MAPK after oral or intravenous administration of CUDC-907. Inhibition of multiple pathways was accompanied by the induction of apoptosis as indicated by increased PARP cleavage (Fig. 4B).

Because imatinib was approved in 2001 as the first tyrosine kinase inhibitor indicated for the treatment of CML, more than 20 agents that target key signaling kinases have been developed for the treatment of various cancers. Generally, these drugs improve patient outcomes and are less toxic than commonly used chemotherapeutics. However, limited activity, as well as intrinsic and acquired resistance are major obstacles and represent major challenges to the use of targeted drugs in the treatment of patients with cancer. Currently, there remains a need for novel drugs with improved efficacy and reduced drug resistance.

Given the experimental evidence supporting a synergistic effect of PI3K and HDAC inhibitors on cancer cell growth, we created CUDC-907, a novel compound that combines PI3K and HDAC inhibitor functionality in a single scaffold, to improve upon single-target PI3K inhibitors. Inhibition of HDACs can lead to the acetylation of histone and nonhistone proteins. This modulation subsequently regulate the expression or activity of many cellular proteins, including p53, E2F, c-Myc, NFκB, HIF-1α, STAT3, androgen receptor, α-tubulin, and heat shock protein 90 (HSP90; refs. 14, 15, 19–25). Consistently, we observed that CUDC-907 treatment triggers HDAC inhibition thus disrupting multiple signaling pathway nodes.

After the approval of 2 HDAC inhibitors, vorinostat and romidepsin, for the treatment of cutaneous T-cell lymphoma, multiple preclinical studies of HDAC inhibitors alone or in combination with other anticancer drugs have shown promising results for the treatment of hematologic malignancies (15). The PI3K pathway plays a primary role in B-cell signaling and survival. The PI3Kδ inhibitor CAL-101 has shown efficacy in the treatment of patients with indolent NHL and mantle cell lymphoma, subtypes of NHL (26). In addition, simultaneous inhibition of HDAC and PI3K/mTOR signaling with panobinostat and rapamycin has been shown to synergistically inhibit tumor cell growth and induce apoptosis in diffuse large B-cell lymphoma (27) as well as in solid tumor cells (28). Because of its integrated HDAC and PI3K inhibitory activities, CUDC-907 may therefore be well suited for future clinical development for various hematologic tumors as well as for other human cancers exhibiting both aberrant PI3K signaling and deregulated HDAC activity.

Intrinsic and acquired drug resistance to single-target PI3K inhibitors occurs through reactivation of alternative or downstream signaling pathways. Drug-resistant mutations in the oncogenic isoform of PI3K p110α have been predicted using yeast genetic screening (29), although point mutations in p110 conferring drug resistance have yet to be found in clinical samples. CUDC-907 could potentially overcome drug resistance mechanisms through its ability to simultaneously inhibit PI3K activity and broadly regulate other signaling proteins through HDAC inhibition. We found that CUDC-907 effectively inhibits the growth of cancer cells transfected with constitutively active AKT. These results suggest that the incorporation of HDAC inhibitory activity within CUDC-907 may prevent the development of drug resistance because of downstream activation of PI3K. Future studies will test whether PI3K inhibitor-resistant clones generated from cancer cell lines remain sensitive to CUDC-907.

Although animal studies have showed that hydroxamate HDAC inhibitors such as vorinostat and panobinostat have low oral bioavailability and short half-life in plasma (30–33), mouse pharmacokinetic studies show that CUDC-907 has an oral bioavailability approximately 2-fold higher than vorinostat and other HDAC inhibitors (Supplementary Fig. S8). Notably, we also observed that CUDC-907 tends to accumulate in tumor tissue with an AUC (area under the plasma concentration time curve) approximately 2-fold greater than in plasma (Supplementary Fig. S8). These results suggest that the higher intratumoral accumulation and antitumor activity of CUDC-907 compared with other HDAC inhibitors may potentially result in improved clinical activity.

Inhibition of multiple targets can be achieved by combining several drugs that each suppresses a specific target. However, a single dual-targeted inhibitor may have several advantages such as pharmacokinetic characteristics, reduced toxicity, patient compliance and ultimately, a more efficient clinical development over combination therapy. On the basis of this concept, we previously created CUDC-101, which integrates HDAC inhibitory functionality into a pharmacophore of the receptor tyrosine kinases EGFR and HER2 (34, 35). The first-in-human phase I study of CUDC-101 has provided the first evidence of the tolerability of a single multitarget inhibitor (36). These results further support the feasibility of multitarget inhibitors as anticancer therapeutics.

In summary, CUDC-907, a novel compound that combines PI3K and HDAC inhibition functionality into a single scaffold, disrupts cancer networks via potent inhibition of the PI3K pathway and epigenetic effects of HDACs. It may offer greater therapeutic benefit than other anticancer drugs currently used in the clinic.

C. Qian is a consultant/advisory board member for Curis, Inc. M. Voi has stock options in Curis, Inc. No potential conflicts of interest were disclosed by the other authors.

Conception and design: C. Qian, C.-J. Lai, R. Bao, D.-G. Wang, J. Wang, H.-X. Zhai, X. Cai

Development of methodology: C.-J. Lai, D.-G. Wang, J. Wang, G.-X. Xu, H.-X. Zhai

Acquisition of data (provided animals, acquired and managed patients, provided facilities, etc.): D.-G. Wang, J. Wang, G.-X. Xu, R. Atoyan, H. Qu, L. Yin, M. Samson, B. Zifcak, A.W.S. Ma, S. DellaRocca, M. Borek, H.-X. Zhai

Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis): C. Qian, R. Bao, D.-G. Wang, J. Wang, G.-X. Xu, X. Cai

Writing, review, and/or revision of the manuscript: C. Qian, R. Bao, X. Cai, M. Voi

Administrative, technical, or material support (i.e., reporting or organizing data, constructing databases): J. Wang

Study supervision: C. Qian, R. Bao, J. Wang

The authors thank Drs. Kenneth Pienta, Carmen Pepicelli, and Mark Noel for helpful discussion and review of the manuscript.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1.
Liu
P
,
Cheng
H
,
Roberts
TM
,
Zhao
JJ
. 
Targeting the phosphoinositide 3-kinase pathway in cancer
.
Nat Rev Drug Discov
2009
;
8
:
627
44
.
2.
Engelman
JA
. 
Targeting PI3K signaling in cancer: opportunities, challenges and limitations
.
Nat Rev Cancer
2009
;
9
:
550
62
.
3.
Serra
V
,
Markman
B
,
Scaltriti
M
,
Eichhorn
PJ
,
Valero
V
,
Guzman
M
, et al
NVP-BEZ235, a dual PI3K/mTOR inhibitor, prevents PI3K signaling and inhibits the growth of cancer cells with activating PI3K mutations
.
Cancer Res
2008
;
68
:
8022
30
.
4.
Raynaud
FI
,
Eccles
SA
,
Patel
S
,
Alix
S
,
Box
G
,
Chuckowree
I
, et al
Biological properties of potent inhibitors of class I phosphatidylinositide 3-kinases: from PI-103 through PI-540, PI-620 to the oral agent GDC-0941
.
Mol Cancer Ther
2009
;
8
:
1725
38
.
5.
Fan
QW
,
Cheng
CK
,
Nicolaides
TP
,
Hackett
CS
,
Knight
ZA
,
Shokat
KM
, et al
A dual phosphoinositide-3-kinase alpha/mTOR inhibitor cooperates with blockade of epidermal growth factor receptor in PTEN-mutant glioma
.
Cancer Res
2007
;
67
:
7960
65
.
6.
Garcia-Echeverria
C
,
Sellers
WR
. 
Drug discovery approaches targeting the PI3K/Akt pathway in cancer
.
Oncogene
2008
;
27
:
5511
26
.
7.
Raynaud
FI
,
Eccles
S
,
Clarke
PA
,
Hayes
A
,
Nutley
B
,
Alix
S
, et al
Pharmacologic characterization of a potent inhibitor of class I phosphatidylinositide 3-kinases
.
Cancer Res
2007
;
67
:
5840
50
.
8.
Sos
ML
,
Fischer
S
,
Ullrich
R
,
Peifer
M
,
Heuckmann
JM
,
Koker
M
, et al
Identifying genotype-dependent efficacy of single and combined PI3K- and MAPK-pathway inhibition in cancer
.
Proc Natl Acad Sci U S A
2009
;
106
:
18351
56
.
9.
Wee
S
,
Jagani
Z
,
Xiang
KX
,
Loo
A
,
Dorsch
M
,
Yao
YM
, et al
PI3K pathway activation mediates resistance to MEK inhibitors in KRAS mutant cancers
.
Cancer Res
2009
;
69
:
4286
93
.
10.
Hoeflich
KP
,
O'Brien
C
,
Boyd
Z
,
Cavet
G
,
Guerrero
S
,
Jung
K
, et al
In vivo antitumor activity of MEK and phosphatidylinositol 3-kinase inhibitors in basal-like breast cancer models
.
Clin Cancer Res
2009
;
15
:
4649
64
.
11.
Chappell
WH
,
Steelman
LS
,
Long
JM
,
Kempf
RC
,
Abrams
SL
,
Franklin
RA
, et al
Ras/RAF/MEK/MAPK and PI3K/PTEN/Akt/mTOR inhibitors: rationale and importance to inhibiting these pathways in human health
.
Oncotarget
2011
;
2
:
135
64
.
12.
Engelman
JA
,
Chen
L
,
Tan
X
,
Crosby
K
,
Guimaraes
AR
,
Upadhyay
R
, et al
Effective use of PI3K and MEK inhibitors to treat mutant Kras G12D and PIK3CA H1047R murine lung cancers
.
Nat Med
2008
;
14
:
1351
6
.
13.
Bendell
J
,
LoRusso
P
,
Kwak
E
,
Pandya
S
,
Musib
L
,
Jones
C
, et al
Clinical combination of the MEK inhibitor GDC-0973 and the PI3K inhibitor GDC-0941: a first-in-human phase Ib study in patients with advanced solid tumors [abstract]
. In:
Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research
;
2011 Apr 2–6; Orlando, FL. Philadelphia (PA): AACR
; 
2011
.
Abstract nr LB-89
.
14.
Kim
H-J
,
Bae
S-C
. 
Histone deacetylase inhibitors: molecular mechanisms of action and clinical trials as anti-cancer drugs
.
Am J Transl Res
2011
;
3
:
166
79
.
15.
Lemoine
M
,
Younes
A
. 
Histone deacetylase inhibitors in the treatment of lymphoma
.
Discov Med
2010
;
10
:
462
70
.
16.
Wozniak
MB
,
Villuendas
R
,
Bischoff
JR
,
Aparicio
CB
,
Martínez Leal
JF
,
de La Cueva
P
, et al
Vorinostat interferes with the signaling transduction pathway of T-cell receptor and synergizes with phosphoinositide-3 kinase inhibitors in cutaneous T-cell lymphoma
.
Haematologica
2010
;
95
:
613
21
.
17.
Ozaki
K
,
Kosugi
M
,
Baba
N
,
Fujio
K
,
Sakamoto
T
,
Kimura
S
, et al
Blockade of the MAPK or PI3K-Akt signaling pathway enhances the cytotoxicity of histone deacetylase inhibitors in tumor cells resistant to gefitinib or imatinib
.
Biochem Biophys Res Commun
2009
;
391
:
1610
5
.
18.
Chou
TC
,
Talalay
P
. 
Quantitative analysis of dose-effect relationships: the combined effects of multiple drugs or enzyme inhibitors
.
Adv Enzyme Regul
1984
;
22
:
27
55
.
19.
Cotto
M
,
Cabanillas
F
,
Tirado
M
,
García
MV
,
Pacheco
E
. 
Epigenetic therapy of lymphoma using histone deacetylase inhibitors
.
Clin Transl Oncol
2011
;
12
:
401
9
.
20.
Condorelli
F
,
Gnemmi
I
,
Vallario
A
,
Genazzani
AA
,
Canonico
PL
. 
Inhibitors of histone deacetylase (HDAC) restore the p53 pathway in neuroblastoma cells
.
Br J Pharmacol
2008
;
153
:
657
68
.
21.
Ellis
L
,
Hammers
H
,
Pili
R
. 
Targeting tumor angiogenesis with histone deacetylase inhibitors
.
Cancer Lett
2009
;
280
:
145
53
.
22.
Trepel
J
,
Mollapour
M
,
Giaccone
G
,
Neckers
L
. 
Targeting the dynamic HSP90 complex in cancer
.
Nat Rev Cancer
2010
;
10
:
537
49
.
23.
Yu
X
,
Guo
ZS
,
Marcu
MG
,
Neckers
L
,
Nguyen
DM
,
Chen
GA
, et al
Modulation of p53, ErbB1, ErbB2, and RAF-1 expression in lung cancer cells by depsipeptide FR901228
.
J Natl Cancer Inst
2002
;
94
:
504
13
.
24.
Yang
Y
,
Rao
R
,
Shen
J
,
Tang
Y
,
Fiskus
W
,
Nechtman
J
, et al
Role of acetylation and extracellular location of heat shock protein 90alpha in tumor cell invasion
.
Cancer Res
2008
;
68
:
4833
42
.
25.
Scroggins
BT
,
Robzyk
K
,
Wang
D
,
Marcu
MG
,
Tsutsumi
S
,
Beebe
K
, et al
An acetylation site in the middle domain of Hsp90 regulates chaperone function
.
Mol Cell
2007
;
25
:
151
9
.
26.
Flinn
IW
,
Schreeder
MT
,
Wagner-Johnston
N
,
Boccia
RV
,
Leonard
JP
,
Coutre
SE
, et al
A phase 1 study of CAL-101, an isoform-selective inhibitor of phosphatidylinositol 3-kinase P110δ, in combination with rituximab and/or bendamustine in patients with relapsed or refractory B-cell malignancies [abstract]
. In:
Proceedings of the 52nd Annual Meeting and Exposition of American Society of Hematology
;
2010 Dec 4–7; Orlando, FL. Washington (DC): ASH
; 
2010
.
Abstract nr 2832.
27.
Gupta
M
,
Ansell
SM
,
Novak
AJ
,
Kumar
S
,
Kaufmann
SH
,
Witzig
TE
. 
Inhibition of histone deacetylase overcomes rapamycin-mediated resistance in diffuse large B-cell lymphoma by inhibiting Akt signaling through mTORC2
.
Blood
2009
;
114
:
2926
35
.
28.
Verheul
HM
,
Salumbides
B
,
Van Erp
K
,
Hammers
H
,
Qian
DZ
,
Sanni
T
, et al
Combination strategy targeting the hypoxia inducible factor-1 alpha with mammalian target of rapamycin and histone deacetylase inhibitors
.
Clin Cancer Res
2008
;
14
:
3589
97
.
29.
Zuner
ER
,
Knight
ZA
,
Houseman
BT
,
Apsel
B
,
Shokat
KM
. 
Discovery of drug-resistant and drug-sensitizing mutations in the oncogenic PI3K isoform p110 alpha
.
Cancer Cell
2008
;
14
:
180
92
.
30.
Yeo
P
,
Xin
L
,
Goh
E
,
New
LS
,
Zeng
P
,
Wu
X
, et al
Development and validation of high-performance liquid chromatography-tandem mass spectrometry assay for 6-(3-benzoyl-ureido)-hexanoic acid hydroxyamide, a novel HDAC inhibitor, in mouse plasma for pharmacokinetic studies
.
Biomed Chromatogr
2007
;
21
:
184
9
.
31.
Venkatesh
PR
,
Goh
E
,
Zeng
P
,
New
LS
,
Xin
L
,
Pasha
MK
, et al
In vitro phase I cytochrome P450 metabolism, permeability and pharmacokinetics of SB639, a novel histone deacetylase inhibitor in preclinical species
.
Biol Pharm Bull
2007
;
30
:
1021
4
.
32.
Liu
L
,
Ju
HL
,
Zhang
J
,
Liang
Y
,
Liu
X-D
,
Xie
L
, et al
Development and validation of an LC-MS/MS method for determination of vorinostat in beagle dog plasma and its application to a pharmacokinetic study
.
Asian J Pharmacodyn Pharmacokinet
2010
;
10
:
209
19
.
33.
Kelly
WK
,
O'Connor
OA
,
Krug
LM
,
Chiao
JH
,
Heaney
M
,
Curley
T
, et al
Phase I study of an oral histone deacetylase inhibitor, suberoylanilide hydroxamic acid, in patients with advanced cancer
.
J Clin Oncol
2005
;
23
:
3923
31
.
34.
Cai
X
,
Zhai
HX
,
Wang
J
,
Forrester
J
,
Qu
H
,
Yin
L
, et al
Discovery of 7-(4-(3-ethynylphenylamino)-7-methoxyquinazolin-6-yloxy)-N-hydroxyheptanamide (CUDc-101) as a potent multi-acting HDAC, EGFR, and HER2 inhibitor for the treatment of cancer
.
J Med Chem
2010
;
53
:
2000
9
.
35.
Lai
CJ
,
Bao
R
,
Tao
X
,
Wang
J
,
Atoyan
R
,
Qu
H
, et al
CUDC-101, a multitargeted inhibitor of histone deacetylase, epidermal growth factor receptor, and human epidermal growth factor receptor 2, exerts potent anticancer activity
.
Cancer Res
2010
;
70
:
3647
56
.
36.
Shimizu
T
,
Tolcher
AW
,
Papadopoulos
K
,
Patnaik
A
,
LoRusso
P
,
Smith
LS
, et al
The first-in-human, first-in-class study of CUDC-101, a multi-targeted inhibitor of HDAC, EGFR and HER2: a phase I study in patients with advanced cancer [abstract]
. In:
Proceedings of the 22nd EORTC-NCI-AACR
;
2010; Berlin, Germany. Philadelphia (PA): AACR
; 
2010
.
Abstract nr 364
.