LAUSR

Interfering with microtubule dynamics is a validated approach for anticancer treatment and by selectively targeting the colchicine binding site on tubulin, microtubule destabilizing agents can evade mechanisms of drug resistance that commonly develop with other antimitotic agents such as taxanes and vinca alkaloids. We have recently reported the discovery of a potent and metabolically stable tubulin inhibitor (DJ101) that specifically targets the colchicine binding site on the beta tubulin subunit, disrupts tubulin polymerization and effectively circumvents drug efflux pumps that decrease the efficacy of existing tubulin inhibitors. To further pre-clinically evaluate DJ101 as a novel tubulin inhibitor and confirm its mechanism of action, we first visually demonstrated the ability of DJ101 to disrupt microtubule dynamics and elucidated the changes in microtubule structure and cell morphology through immunofluorescence techniques. Furthermore, we solved the crystal structure of DJ101 in complex with tubulin to determine its molecular interactions with the protein. We then demonstrated the significant in vitro potency of DJ101 against a panel of metastatic melanoma cell lines harboring major clinically relevant mutations observed in tumors and also validated its cytotoxicity against a broader array of NCI-60 cell lines. Further analysis revealed that DJ101 effectively thwarted anchorage-dependent melanoma colony formation and drastically hindered cell mobility and motility of those cancer cells. We further ascertained that DJ101 shows negligible off-target effects for major physiologically important receptors and ion channels, suggesting a good safety profile. Encouraged by the preliminary results from our in vitro assessment, we evaluated the in vivo activity of DJ101 in two different mouse models. At a dose of 30 mg/kg via i.p. injections, DJ101 nearly completely suppressed tumor growth in a human A375 melanoma xenograft model. It also appreciably inhibited metastasis potential in a murine B16F10 lung metastasis model at the same dose. In conclusion, we have described a microtubule destabilizing agent that targets the colchicine binding site on tubulin, confirmed its mechanism action, determined its potency in a vast array of cancer cell lines, particularly metastatic melanoma, demonstrated its inhibitory effect on cellular proliferation, motility and migration, and evaluated its anticancer potential in terms of tumor growth inhibition and metastasis in two in vivo models. Our findings offer a compelling rationale to further develop and advance DJ101 as a tubulin inhibitor for cancer therapy. Citation Format: Kinsie Arnst, Dong-Jin Hwang, Duane D. Miller, Wei Li. Novel tubulin inhibitor DJ101 targets the colchicine binding site and suppresses melanoma growth and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3223. doi:10.1158/1538-7445.AM2017-3223