Abstract B271: In vitro profiling of traditional tubulin targeting and new antimitotic compounds by using a 40 cancer cell line panel in combination with Compare Analysis

Abstract Established anti-mitotic drugs interfere with the mitotic spindle by direct binding to ß-tubulin, an essential component of the mitotic spindle apparatus. These agents, by affecting the dynamic instability of microtubles, induce a transient arrest in mitosis followed by apoptosis. As a consequence of interference with neuronal tubulin, these agents also cause neuropathy in patients, which is not seen following treatment with new compounds targeting mitosis proteins distinct to tubulin. These drugs currently in clinical development inhibit proteins like motor protein kinesin-5 (Eg5), mitotic kinases Aurora-A/B (ARK) and polo-like kinases (PLKs), activating the spindle assembly checkpoint or inducing a premature release from mitosis without cytokinesis, resulting in polyploidy. Oncotest utilizes distinct panels of human tumor cell lines for cellular cytotoxicity screens, among them the 40 cell line panel comprising 24 cell lines established from patient explants passaged in nude mice and 16 commercially available cell lines, all derived from solid tumors. The cell lines were extensively characterized including chemosensitivity information currently available for 94 standard-of-care (SOC) drugs and experimental agents like inhibitors of protein kinases (e.g. EGFR, HER2, AKT, PLK1, ARK A/B), motor protein (Eg5) and traditional targets / pathways like tubulin, DNA replication / transcription, and metabolism. Using a cellular cytotoxicity /proliferation assay, activity profiles for selected anti-mitotic agents namely VX-680 (Aurora A/B), BI2536 and GSK461364A (Plk1), Ispinesib and Monastrolin (Eg5), Paclitaxel, Docetaxel and Vinca alkaloids (β-tubulin) will be presented. A spectrum of anti-tumor potency and selectivity was evident with mean IC50 values in the low or sub-nanomolar range for tubulin binders and Ispinesib. Cell cycle analysis was done for selected cell lines to identify a functional or defect G1, G2 or M checkpoint. Finally, a statistical “Compare Analysis” based on the Oncotest chemosensitivity database revealed similarities between sensitivity profiles of the Eg5 inhibitors Ispinesib and Monastrolin (rho=0.78) and between profiles of the Plk1 inhibitors BI2536 and GSK461364A (rho=0.89). Interestingly, weak similarities (rho<0.5) were identified between non-tubulin binding and traditional tubulin binding anti-mitotic drugs. Significant similarity (rho>0.6) for VX-680 to any of the SOC drugs was not evident with Monastrolin top ranked (rho=0.53). It is concluded that the Oncotest 40 solid tumor cell line panel is of high value for profiling new targeted cancer drugs like non-tubulin binding anti-mitotic agents. By Compare Analysis a postulated MoA can be studied in detail, also in order to distinguish a new mitosis targeted agent from the classical tubulin binding mechanism. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B271.