FOXM1 and FOXQ1 Are Promising Prognostic Biomarkers and Novel Targets of Tumor-Suppressive miR-342 in Human Colorectal Cancer

Colorectal cancer is one of leading causes of cancer-related morbidity and mortality worldwide (1). It is now well-established that multiple genetic and epigenetic alterations lead to the result in development of colorectal cancer. The classic Vogelgram described the multistep model for colorectal cancer pathogenesis outlining few critical events, in which the APC gene mutations permitted adenoma formation, activating mutations in the KRAS oncogene and genomic losses at chromosome 18 loci facilitated adenomatous growth, and inactivation of p53 triggered the final transition of adenoma to carcinoma (2). Mutations in the APC gene occur in about 80% to 90% of sporadic colorectal cancers, and alterations in the Wnt signaling pathway serve as major molecular drivers of cancer pathogenesis in the colon (3). However, data gathered in recent years have underscored the need for further refinement of these mechanisms because only 5% of adenomatous polyps progress to cancer development, which suggests that additional molecular events must occur for colorectal carcinogenesis to ensue (4, 5). Therefore, identification of previously unrecognized genomic events that propel cancer development would not just be of biologic relevance, but may as well be of clinical significance as these will allow development of novel biomarkers and/or drug targets for the management of colorectal cancer patients.

Forkhead box (FOX) proteins constitute a superfamily of evolutionarily conserved transcriptional factors, which play an important role in a wide variety of cellular processes. Accumulating evidence indicates that FOX proteins serve as the terminal effectors of multiple signal transduction pathways, such as TGFβ cascade, Wnt pathway, Sonic-Hedgehog pathway, and MAPK pathway (6). Furthermore, these FOX proteins may function as critical “nodes” in cellular networks, allowing cross-talk between parallel pathways and thus facilitate responses to environmental fluctuations. Considering their key function, it is not surprising that mutations or deregulation of FOX genes has now been associated with various developmental genetic disorders, as well as few human malignancies (7). Till date, mutations in 11 FOX genes have been linked to human hereditary diseases (8). In cancer, several FOX family members have been suggested to act as oncogenes or tumor suppressors, as these proteins have the ability to regulate cell differentiation, proliferation, and apoptosis (7). Recently, a few studies have alluded that the expression of Forkhead family members can be regulated by post-translational modifications, such as phosphorylation of serine, threonine, or tyrosine residues (9–11). However, the specific mechanism(s) of deregulation of FOX family members seem to be context-dependent in cancer progression, and no previous studies have systematically and comprehensively interrogated the functional and clinical relevance of FOX proteins in cancer, particularly colorectal cancer.

During the past decade, miRNAs have emerged as frontiers in gene regulation due to their role in regulation of a broad range of biological processes in various human diseases, particularly cancer (12). Previously published studies from our group and others have highlighted that specific miRNAs contribute to colorectal cancer pathogenesis, and several of these can be used as biomarkers for diagnosis, prognosis, and metastasis prediction in colorectal cancer patients (12–17). In fact, a few studies have shown that miRNAs may be able to regulate specific FOX genes in different cancers, including esophageal cancer (18), bladder cancer (19), and hepatocellular carcinoma (20); however, such an interaction between miRNAs and FOX proteins remains largely unclear and not interrogated in colorectal cancer.

Based upon this important gap in knowledge in the literature, we envisaged this study to systematically and comprehensively interrogate the molecular contributions of FOX family members in colorectal cancer, identify specific miRNAs that modulate their expression, and decipher whether these genes may have translational relevance as clinically-relevant disease biomarkers. Accordingly, we performed a discovery step by querying publicly available databases to identify candidate, colorectal cancer–specific FOX genes, followed by their validation in multiple cohorts of colorectal cancer patients. In addition, we performed functional assays, both in-vitro and animal models, to validate the contribution of specific FOX genes in colorectal cancer, and identified a key miRNA that regulated FOX protein expression in this malignancy.

To identify colorectal cancer–specific, differentially expressed FOX genes, we initially queried Oncomine database comprising of 24 independent studies (21). To assess the prognostic impact of FOXM1 and FOXQ1 in colorectal cancer, we analyzed two publicly available datasets as the testing cohorts, which included a total of 550 colorectal cancer patients, of which 229 patients were from the GSE 17538 dataset (22) and 321 patients from The Cancer Genome Atlas (TCGA) dataset (23, 24). In the clinical validation cohort, we analyzed 178 frozen tissues, including 134 primary colorectal cancer and 44 matched normal mucosa (NM) tissues, which were collected at the Mie University, Japan. A written informed consent was obtained from all patients, and the study was approved by the Institutional Review Boards of all participating institutions. Patients with radiotherapy or chemotherapy treatment before surgery were excluded. Survival time was calculated from the date of surgery to the date of death or last follow-up. Clinical information was collected from the medical records of each patient and shown in Supplementary Table S1. The tumor–node–metastasis (TNM) staging was performed according to American Joint Committee on Cancer standards.

All human colorectal cancer cell lines RKO, CaCO-2, HCT-116, HT-29, LoVo, SW480, and SW620 were obtained from the American Type Culture Collection and cultured in Iscove's modified Dulbecco's medium (IMDM; Invitrogen) supplemented with 10% FBS and antibiotics (100 μ/mL penicillin and 100 μg/mL streptomycin) at 37°C in 5% humidified CO₂ atmosphere. These cell lines were periodically authenticated using a panel of genetic and epigenetic biomarkers.

Validated siRNAs for FOXQ1 and FOXM1, miR-342 mimic and its inhibitor, negative control for siRNA, mimic and inhibitor were purchased from Ambion. Colorectal cancer cells were transfected with siRNA, mimic, or inhibitor at a final concentration of 50 nmol/L using Lipofectamine RNAi MAX (Invitrogen) and Opti-MEM (Gibco) according to the manufacturer's instructions. The transfection efficiency was determined at 48 and 72-hour time points for evaluating corresponding changes in the mRNA and protein expression, respectively.

The qRT-PCR assays were performed using QuantStudio 6 Flex Real-Time PCR System (Applied Biosystems). For gene-expression analysis, 2 μg of total RNA was synthesized to cDNA by using GoScript Reverse Transcription System (Promega) and the Fast SYBR Green Master Mix (Applied Biosystems). The relative expression of target genes was normalized against β-actin using the 2^−Δct method as described previously (16, 25, 26). The sequences of all primers used in this study are shown in Supplementary Table S2. For miRNA analysis, qRT-PCR was conducted using the TaqMan MicroRNA Reverse Transcription Kit and TaqMan Universal PCR Master Mix Kit (Applied Biosystems) according to the manufacturer's instructions. Relative expression of miR-342 was determined by the 2^−Δct method using miR-16 as normalizer. Taqman primers for miR-342 and miR-16 were purchased from Ambion.

The total protein extracts from cell lines were collected using RIPA lysis buffer, and 30 μg protein was loaded per sample on 10% polyacrylamide-SDS gels, which were subsequently transferred onto nitrocellulose membranes. The membranes were then blocked in 5% fat-free milk and incubated with the following primary antibodies overnight at 4°C: rabbit anti-FOXQ1 (1:1,000 dilution; Abcam), rabbit-anti-FOXM1 (1:1,000 dilution; Abcam), and monoclonal mouse anti–β-actin (1:5,000 dilution; Sigma-Aldrich). Membranes were thereafter incubated with secondary horseradish peroxidase–conjugated goat anti-rabbit antibody (1:3,000 dilution; Santa Cruz) or goat anti-mouse antibody (1:3,000 dilution; Santa Cruz) at room temperature for 1 hour. The proteins were detected using enhanced chemiluminescence system according to the manufacturer's instructions.

The SW480 and HT-29 colorectal cancer cell lines transfected with siRNA, miRNA mimics, miRNA inhibitors, or negative controls were seeded at 1,500 cells per well in 96-well plates following which MTT reagent was added at 0, 24, 48, and 72-hour time points. Optical densities were determined using the Infinite 200 Pro multi-readers and i-control 1.10 software (Tecan).

Cell migration and invasion assays were performed using Boyden chambers (Corning) with 8-μm-size pore membrane coated with Matrigel (for invasion assays) or without Matrigel (for migration assays). The transfected cells were seeded onto inserts at 2 × 10⁵ cells in serum-free medium and transferred to wells with culture medium containing 10% FBS. After 24-hour incubation, noninvading cells were removed by scraping the top surface of the membrane. Invaded cells on the bottom of the membrane were thereafter fixed and stained by using diff-quick staining kit (Thermo Scientific) according to the manufacturer's instructions. The stained cells were counted using a light microscope.

Oligonucleotide pairs containing miR-342–targeted regions within the 3′-untranslated regions (UTR) of the FOXM1 and FOXQ1 genes were annealed and ligated into the pmirGLO Vector (Promega) according to the manufacturer's instructions. The firefly luciferase activity was detected using the dual luciferase assay system (Promega) according to the manufacturer's instructions. The relative luciferase activity was quantified using a microplate luminometer (Turner Biosystems), and the transfection efficiency was normalized to Renilla's activity.

Male athymic nude mice were obtained from the Harlan Laboratories at 5 weeks of age and kept under controlled conditions (12-hour light and dark cycles). The animal protocol was approved by the Institutional Animal Care and Use Committee of the Baylor Research Institute. We generated xenograft tumors using SW480 cell line stably overexpressing miR-342, or its corresponding controls. The stable miR-342–overexpressing SW480 cells were established by lentiviral vector infection according to the manufacturer's instructions (miR-342: pLV-[hsa-mir-342] plasmid; Negative control plasmid: pLV-[mir-control], Biosettia). These cancer cells were suspended in PBS and Matrigel at 1:1 ratios (Corning), and 1 × 10⁶ cells were subcutaneously injected into the abdominal flanks of each mice. Nine mice were included in each group. The mice were monitored for 20 days following injection, and subcutaneous tumors were measured every 2 days. Tumor size was measured using calipers, and the volume was calculated using the following formula: 1/2LW², where L represents the length and W represents the width. At 20 days after injection, all animals were sacrificed. Tumor samples were dissected and stored in RNAlater (Sigma-Aldrich) for subsequent analyses.

All statistical analyses were performed using the GraphPad Prism Ver. 6.0 or Medcalc version 12.3 programs. All data were expressed as mean ± SD. Statistical differences between groups were determined by the Wilcoxon signed rank test, the χ² test, or Mann–Whitney U test. The Kaplan–Meier analysis and log-rank test were used to estimate and compare survival rates of colorectal cancer patients with high and low FOXM1 or FOXQ1 expression. ROC curves were established to determine the cutoff values to discriminate patients with or without death. The Cox's proportional hazards model was used to estimate HRs for death. All P values were two-sided, and those less than 0.05 were considered statistically significant.

To identify colorectal cancer–specific differentially expressed FOX family of genes, we performed a discovery step by comparing the expression levels of various genes in cancer versus matched normal tissues using the publicly available Oncomine microarray database (21). By systematically analyzing the expression profiles of all available FOX genes across 24 studies, we noted that 8 FOX family members (FOXQ1, FOXM1, FOXA2, FOXK1, FOXK2, FOXC1, FOXD1, and FOXG1) were significantly upregulated (≥2 fold change, and an FDR of <1 × 10⁻⁴), 13 were downregulated, and the remaining were not significantly altered in colorectal cancer (Fig. 1A; Supplementary Table S3). Since upregulated genes are more practical from a diagnostic or therapeutic view point, we thereafter focused our attention on the upregulated FOX genes. Interestingly, we found three FOX family members (FOXQ1, FOXM1, and FOXA2) were frequently overexpressed in most in silico studies, suggesting that these may play an important role in colorectal carcinogenesis, and also may serve as potential disease biomarkers (Fig. 1A and Supplementary Table S3). We next examined the expression levels of these three genes in a subset of 44 colorectal cancer and paired NM specimens by qRT-PCR. Our results revealed that, while we failed to observe any significant differences in the expression of FOXA2, the expression levels of FOXM1 and FOXQ1 were statistically higher in cancer versus normal tissues, with a 41.04-fold increase (P < 0.0001) and 9.07 fold change (P < 0.0001) in each gene, respectively (Fig. 1B), suggesting these genes to be potential oncogenes in colorectal cancer.

Next, we examined the expression patterns of FOXM1 and FOXQ1 with regard to their prognostic value in the two testing cohorts of a combined total of 550 colorectal cancer patients from the GSE (22) and TCGA datasets (23, 24). Interestingly, in the GSE dataset, FOXQ1-high expression group demonstrated a marked correlation with poor overall survival (OS; P = 0.1368; HR = 1.5167), whereas FOXM1-high expression showed weaker tendency to be associated with poor OS (P = 0.3969; HR = 1.2382; Fig. 2A). In contrast, in the TCGA dataset, FOXM1-high expression group significantly correlated with poor OS (P = 0.0170; HR = 1.88), whereas FOXQ1-high expression group demonstrated a strong tendency to correlate with poor prognosis (P = 0.06263; HR = 1.15; Fig. 2B).

To further validate the prognostic impact of FOXM1 and FOXQ1 in colorectal cancer patient survival, we interrogated these associations in an additional cohort of high-quality, fresh-frozen tissues from 134 colorectal cancer patients. The detailed correlations between FOXM1 and FOXQ1 expression and various clinicopathological variables are shown in Supplementary Table S1, and we were able to successfully validate that both FOXM1 and FOXQ1-high expression groups demonstrated shorter OS (Fig. 2C), highlighting their clinical relevance as independent prognostic biomarkers in colorectal cancer patients. Furthermore, Cox's univariate and multivariate analysis also revealed that FOXM1 and FOXQ1 were independent predictors of colorectal cancer patient survival (Table 1). Collectively, these findings elucidate that overexpression of FOXM1 and FOXQ1 has clinical significance in terms of serving as potential prognostic biomarkers in colorectal cancer patients.

To investigate whether FOXM1 and FOXQ1 expression affects biologic characteristics, we performed several functional assays to determine phenotypic alterations following siRNA knockdown of FOXM1 and FOXQ1 in colon cancer cells. In order to select most optimal cell lines for knockdown experiments, we evaluated the expression levels of FOXM1 and FOXQ1 in a panel of colorectal cancer cell lines (Supplementary Fig. S1A). RKO and HCT-116 displayed low expression, whereas SW480, SW620, and HT-29 cell lines revealed high expression of FOXQ1. In contrast, the expression levels of FOXM1 were similar across all colorectal cancer cell lines. Based upon these findings, we selected SW480 and HT-29 cell lines for siRNA knockdown of both FOXM1 and FOXQ1. We validated this siRNA knockdown efficiency for FOXM1 and FOXQ1 at both transcription and protein levels (Supplementary Fig. S1B).

Next, we determined whether inhibition of FOXM1 and FOXQ1 results in functional alterations in colorectal cancer. The MTT cell proliferation assays revealed that while FOXQ1 inhibition did not have any growth inhibitory effects in either cell line, FOXM1 knockdown significantly suppressed cell growth in both SW480 and HT-29 cell lines (Fig. 3A). To determine whether alterations in the expression of FOXM1 and FOXQ1 have any impact on the motility and invasive potential of colorectal cancer cells, we performed migration and invasion assays. As shown in Fig. 3B and Supplementary Figs. S2 and S3, FOXM1 and FOXQ1 knockdown leads to significantly reduced migration and invasion ability in both cancer cells lines compared with mock-transfected control cells.

Considering their important oncogenic role, we were interested in understanding the potential mechanisms for the dysregulated expression of FOXM1 and FOXQ1 in colorectal cancer. In addition, because of the central role miRNAs play in carcinogenesis, we hypothesized that overexpression of FOXM1 and FOXQ1 might be caused by aberrant expression of specific miRNAs in colorectal cancer. Furthermore, we aimed to identify whether there is a specific miRNA that is capable of regulating both FOX family members in colorectal cancer.

Despite complexities underlying miRNA–mRNA interactions, several algorithms are available for predicting genes targeted by specific miRNAs. To identify miRNAs that target both FOXM1 and FOXQ1, we utilized microRNA.org algorithm (www.microRNA.org) and identified 5 miRNAs (miR-342-5p, miR-320a, miR-320b, miR-320c, and miR-320d) that can bind to the 3′-UTR of both genes. However, among these 5 miRNAs, miR-342-3p had the highest mirSVR score for both FOX genes; hence, we selected this miRNA as a potential candidate for subsequent interrogation.

Because FOXM1 and FOXQ1 showed oncogenic role in colorectal cancer, we first evaluated the expression of miR-342 expression in a subset 44 colorectal cancer and matched normal tissues to determine whether miR-342 functions as tumor suppressor in this disease. Consistent with our hypothesis, miR-342 was found to be significantly downregulated in cancer tissues vis-à-vis adjacent normal tissues (P < 0.0001; Fig. 3C). Furthermore, we observed a significant inverse correlation between miR-342 expression and both FOXM1 (P < 0.0001) and FOXQ1 (P = 0.0002) in the primary colorectal cancer and normal tissues, suggesting that miR-342 regulates the expression of these genes in colorectal cancer (Fig. 3D).

The mature miR-342-3p was generated from 99-nucleotide-long pre-miRNAs (structure shown in Fig. 3E) and was identified to potentially bind to the 3′-UTR of FOXM1 and FOXQ1 genes. To determine whether miR-342 actually regulates FOXM1 and FOXQ1 expression, we overexpressed or inhibited miR-342 in colorectal cancer cells. To select appropriate cell lines for overexpression or inhibition of miR-342, we examined the expression levels of miR-342 in a panel of colorectal cancer cell lines. As shown in Supplementary Fig. S1A, miR-342 expression was markedly lower in RKO, SW620, DLD-1, and HT-29 cells, but higher in HCT-116, SW480, and CaCO-2. Based upon these results, we selected SW480 for both overexpression and inhibition of miR-342, as well as HT-29 cells for the overexpression of miR-342.

Overexpression of miR-342 by using miRNA mimics in SW480 and HT-29 cells resulted in significant downregulation of FOXM1 and FOXQ1 at both transcriptional and protein levels (Fig. 4A and B), indicating that miR-342 may regulate both FOXM1 and FOXQ1 expression. Likewise, blocking of the endogenous miR-342 expression through miR-342 inhibitor in SW480 cells resulted in upregulation of FOXM1 and FOXQ1 (Fig. 4A).

To further determine whether miR-342 regulates FOXM1 and FOXQ1 expression directly or indirectly, we conducted luciferase reporter assays. As shown in Fig. 4C, we cloned miR-342 binding region of FOXM1 and FOXQ1 into luciferase report plasmid to establish wild-type 3′-UTR report plasmids. In addition, we also mutated miR-342 binding sites and established mutant 3′-UTRs of FOXM1 and FOXQ1. HEK-293T, SW480, and HT-29 were transiently transfected with these constructs along with miR-342 mimics or negative controls (NC). In line with our previous results, miR-342 overexpression significantly suppressed luciferase activity of the reporter genes containing wild-type 3′-UTRs of FOXM1 and FOXQ1, but no inhibitory effects were observed in mutated cell lines (Fig. 4D; Supplementary Fig. S4). Collectively, these results indicate that miR-342 suppressed expression of FOXM1 and FOXQ1 through direct binding within the putative 3′-UTR binding sites of these genes.

Subsequent to our observation that miR-342 is a direct regulator of FOXM1 and FOXQ1 expression, we next examined whether modulation of miR-342 expression contributes to phenotypic alterations in colorectal cancer cells. To test this hypothesis, we first overexpressed miR-342 in SW480 and HT-29 cells using miRNA mimics and conducted MTT assays. As expected, miR-342 overexpression inhibited cellular proliferation in both colorectal cancer cell lines. Likewise, inhibition of miR-342 expression in SW480 by using inhibitors resulted in increased cellular proliferation (Fig. 5A). To determine whether miR-342 also functions as a metastasis suppressor, we overexpressed miR-342 in SW480 and HT-29 cells and observed dramatic suppression of cell motility and invasiveness in both cell lines. In support of these findings, inhibition of miR-342 in SW480 cells resulted in enhanced migration and invasion capacity (Fig. 5B and Supplementary Figs. S5–S7).

Finally, to determine whether ectopic expression of miR-342 inhibits tumorigenicity in an animal model, we established SW480 cells with stable overexpression of miR-342, and subcutaneously injected test and control cells into nude mice. As shown in Fig. 5C, during the initial 10 days after injection, there were no significant differences in tumor size. However, 12 days after injection, controls cells reported an accelerated tumor growth while miR-342–overexpressing cells grew much slowly, highlighting the tumor-suppressive role of miR-342 in colorectal cancer. Furthermore, the decreased level of FOXM1 and FOXQ1 in miR-342–overexpressing xenograft tissues supported the hypothesis that miR-342 exerts functions in colorectal cancer, at least in part through inhibition of FOXM1 and FOXQ1 expression (Supplementary Fig. S8).

Colorectal cancer is one of the most common cancers worldwide. Although patients with early stage colorectal cancer have relatively better prognosis, most patients at initial presentation of disease are diagnosed late, and the outcome of such patients is usually poor (1). Therefore, elucidating the molecular mechanisms underlying colorectal cancer progression is critical for the development of new therapeutic strategies for improving the prognosis of patients with advanced colorectal cancer. Herein, in this study, we for the first time demonstrate that FOXM1 and FOXQ1 are involved in colorectal carcinogenesis, their expression is regulated by a miR-342 tumor-suppressive miRNA, and the high expression of these genes serves as an important prognostic biomarker in colorectal cancer.

In view of recent limited evidence that FOX transcription factors play an important role in gene regulation and carcinogenesis, in the current study, we first identified key differentially expressed FOX genes in colorectal cancer. Following a systematic analysis of colorectal cancer microarray data, we identified FOXM1 and FOXQ1 as the most upregulated genes in colorectal cancer tissues. Furthermore, by measuring the expression levels of these genes in two different testing cohorts, and an independent validation cohort, we demonstrated that high expression of FOXM1 and FOXQ1 correlated with poor survival in colorectal cancer patients. Our data, which are first of its kind in colorectal cancer, are consistent with some of the other reports which showed that FOXM1 is overexpressed and associates with worse prognosis in other human cancers (27–31).

Similarly, FOXQ1 has also been reported to be upregulated in several cancer types (32–35). However, none of the previous studies have systematically explored the prognostic significance of these genes in colorectal cancer. We addressed this important gap in knowledge by evaluating the expression of these genes in two large testing cohorts (n = 553) and another independent clinical validation cohort (n = 134) to firstly identify the prognostic value of FOXM1 and FOXQ1 in colorectal cancer. However, in order to fully validate the prognostic potential of FOXM1 and FOXQ1 in colorectal cancer, additional prospective studies are required.

Recently, a few studies have suggested that FOXM1 and FOXQ1 play a key role in regulation of epithelial-to-mesenchymal transition in various types of cancers (34, 36–39). In this regard, our data are consistent with this hypothesis, because we observed that inhibition of FOXM1 and FOXQ1 caused reduced mobility and invasive capability in colorectal cancer cells. It is well-established that invasion-metastasis cascade drives colorectal cancer progression, which eventually leads to significantly worse patient survival. Several studies have shown that liver metastasis is a manifestation in nearly 20% patients with stage II colorectal cancer, and this rate increases to 50% in patients with stage III disease (40). Moreover, metastasis is responsible for more than 90% of colorectal cancer–associated deaths (41). Based upon our findings that these two FOX family members are often overexpressed in colorectal cancer and associated with poor patient survival, therapeutic targeting of FOXM1 and FOXQ1 may be a potential strategy in attenuating metastasis and improving survival of colorectal cancer patients in future.

MiRNAs have emerged as major players in the complex network of gene regulation, and dysregulation of miRNA expression has been implicated in carcinogenesis. In this study, not only we have uncovered the oncogenic role of FOXM1 and FOXQ1, we have also firstly identified that miR-342 tumor suppressor directly targets the 3′-UTR of both genes and regulates their expression in colorectal cancer. MiR-342 is encoded within an intron of the EVL gene and is frequently silenced due to aberrant hypermethylation in colorectal cancer (42). Consistent with this finding, our study revealed that miR-342 is downregulated in colorectal cancer tissues relative to adjacent normal mucosa, indicating that DNA hypermethylation may be the potential mechanism for its downregulation in colorectal cancer. In the current study, we also noted that the expression levels of miR-342 negatively correlated with those of FOXM1 and FOXQ1 in colorectal cancer tissues, and overexpression or inhibition of miR-342 modulated the expression of both FOX genes in colorectal cancer cells. In further support of these findings, our luciferase reporter assays confirmed that miR-342 overexpression led to inhibition of FOXM1 and FOXQ1 through direct binding of the 3′-UTR of these genes. Ours is the first study to demonstrate the underlying mechanisms by which miR-342 regulates the oncogenic function of both FOXM1 and FOXQ1 in colorectal cancer.

Taken together, ours is the first study that has systematically and comprehensively dissected the role of FOX family of transcription factors in colorectal cancer, both from a functional and clinical standpoint. Herein, we provide novel evidence that FOXM1 and FOXQ1 are frequently overexpressed in colorectal cancers, and contribute to cancer pathogenesis. Furthermore, high expression of these genes significantly correlated with tumor growth, metastasis, and poor prognosis in colorectal cancer. From a functional perspective, we identified that miR-342, a tumor-suppressive miRNA, directly binds and regulates the expression of both FOXM1 and FOXQ1 expression in colorectal cancer cells. Downregulation of miR-342 resulted in upregulation of both genes, and these findings were subsequently validated in a xenograft animal model. We conclude that FOXM1 and FOXQ1 are promising prognostic biomarkers for colorectal cancer patients, and modulation of miR-342 expression or therapeutic targeting of FOXM1 and FOXQ1 may be a potential treatment option for patients with colorectal cancer.

No potential conflicts of interest were disclosed.

Conception and design: W. Weng, A. Goel

Development of methodology: W. Weng, A. Goel

Acquisition of data (provided animals, acquired and managed patients, provided facilities, etc.): W. Weng, S. Toden, Y. Toiyama

Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis): W. Weng, A. Goel

Writing, review, and/or revision of the manuscript: W. Weng, A. Goel

Administrative, technical, or material support (i.e., reporting or organizing data, constructing databases): Y. Okugawa, Y. Toiyama, M. Kusunoki

Study supervision: Y. Okugawa, A. Goel

This work was supported by the grants R01 CA72851, CA181572, CA184792, and U01 CA187956 from the NCI, NIH, pilot grants from the Baylor Sammons Cancer Center and Foundation, as well as funds from the Baylor Research Institute.

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.