Inhibition of the phosphatidylinositol 3-kinase/AKT pathway using small molecule inhibitor (QLT0267) against ILK can be used to sensitize breast tumour cells to treatment with Docetaxel Free

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There is substantial evidence indicating that ILK inhibition is associated with cytotoxic and cytostatic effects in tumour cells, tumour growth delay and inhibition of angiogenesis. Although ILK is promising as an effective therapeutic target, it is anticipated that optimal benefits of any ILK targeting strategy will be achieved in a combination setting. In an effort to identify therapeutically active drug combinations for further development in the clinic, the activity of a novel small molecule inhibitor targeting ILK (QLT0267 (267)) in combination with cytotoxic drugs (e.g. docetaxel (Dt), doxorubicin and cisplatin) and targeted agents (trastuzumab and Imatinib Mesylate) was assessed in Her2/neu negative (MDA MB435/LCC6 (LCC6), MCF-7, MDA MB468), and Her2/neu positive (LCC6-Her2/neu, SKBR-3, KPL-4) human breast cancer cell lines. Cytotoxic and/or cytostatic activity of drug combinations was tested with the alamarBlue® assay, using a fixed molar ratio experiment design after a 72 hour exposure to drugs. Data was analyzed using the median effect methodology developed by Chou and Talalay. This analysis proved that the combination of 267 and Dt resulted in synergy (Combination Index (CI) <0.9) over a broad range of effective doses in all cell lines tested except KPL-4. The 267/Dt combination in KPL-4 cells calculated CI values close to one, indicating the interaction of these two drugs is additive in this cell line. In an effort to explore the mechanism of synergy, cell-based assays using LCC6 and LCC6-Her2/neu were used to determine AKT phosphorylation status (as a measure of ILK inhibition), changes in cell cycle progression and apoptosis after an 8 or 24 hour exposure to 267 (48.67µM) and Dt (1nM). The results show that treatment with a combination of 267/Dt resulted in very different outcomes depending on the presence of Her2/neu. LCC6 cells exhibited a synergistic (CI values < 0.9) decrease in levels of P-AKT, and an enhanced G2/M block. However, in LCC6-Her2/neu cells, Dt antagonized the effect of 267 on P-AKT, and the combination of 267/Dt resulted in an S phase block in the cell cycle. Further analysis of LCC6 cells using 267/Dt resulted in a higher percentage of Annexin-V positive cell fraction, and an increased frequency of nuclear apoptotic bodies and cells with condensed chromatin indicating that 267 can synergize with Dt to increase the incidence of apoptosis. These data strongly suggest that 267 should be used in combination with Dt for treatment of breast cancers, and that the mechanism of interaction between 267 and Dt may vary in Her2/neu positive and negative breast cancer cell lines.