Standard of care for triple-negative breast cancer (TNBC) involves the use of microtubule poisons such as paclitaxel, which are proposed to work by inducing lethal levels of aneuploidy in tumor cells. While these drugs are initially effective in treating cancer, dose-limiting peripheral neuropathies are common. Unfortunately, patients often relapse with drug-resistant tumors. Identifying agents against targets that limit aneuploidy may be a valuable approach for therapeutic development. One potential target is the microtubule depolymerizing kinesin, MCAK, which limits aneuploidy by regulating microtubule dynamics during mitosis. Using publicly available datasets, we found that MCAK is upregulated in triple-negative breast cancer and is associated with poorer prognoses. Knockdown of MCAK in tumor-derived cell lines caused a two- to five-fold reduction in the IC50 for paclitaxel, without affecting normal cells. Using FRET and image-based assays, we screened compounds from the ChemBridge 50 k library and discovered three putative MCAK inhibitors. These compounds reproduced the aneuploidy-inducing phenotype of MCAK loss, reduced clonogenic survival of TNBC cells regardless of taxane-resistance, and the most potent of the three, C4, sensitized TNBC cells to paclitaxel. Collectively, our work shows promise that MCAK may serve as both a biomarker of prognosis and as a therapeutic target.

OBJECTIVES/GOALS: Microtubule poisons, like Taxol, are used to treat triple negative breast cancer (TNBC) and may induce lethal aneuploidy in cancer cells. Patients initially respond, but often develop drug resistance. New targeted drugs that cause aneuploidy may be a valuable approach to therapy. One potential target is the Kinesin 13 MCAK, which limits aneuploidy. METHODS/STUDY POPULATION: TCGA and GSE47561 databases were probed for MCAK expression, and data was stratified by subtype and survival statistics. Knockdown studies were performed to test whether MCAK knockdown sensitizes cells to taxanes for cell proliferation and for induction of aneuploidy. FRET and image-based screens were used to identify MCAK inhibitors from small molecule inhibitor libraries. Inhibitors were then tested for functional effects in multiple cell-based assays and for clonal growth in colony formation assays. RESULTS/ANTICIPATED RESULTS: MCAK expression is upregulated in TNBC and associated with reduced overall survival. Knockdown of MCAK caused a two-to-five-fold reduction of the IC50 for Taxol in cancer cell lines, with no change in normal cell lines. Taxol treatment or MCAK knockdown increased aneuploidy induction, with no additive effect between the two. Our small molecule screen identified three putative MCAK inhibitors, which induced aneuploidy in both taxane-sensitive and taxane-resistant cells. These inhibitors also reduced clonogenic growth, and the most potent inhibitor, C4, caused an approximate five-fold reduction in the IC50 for Taxol in cell proliferation assays. DISCUSSION/SIGNIFICANCE: MCAK can serve as a biomarker of breast cancer prognosis. MCAK knockdown or inhibition sensitizes cancer cells to Taxol without affecting normal cells, making it a potential target in combination therapy. MCAK inhibitors also reduce growth as single agents in taxane resistant lines, giving them potential use as therapies in resistant disease.

Standard of care for triple negative breast cancer (TNBC) involves the use of microtubule poisons like paclitaxel, which are proposed to work by inducing lethal levels of aneuploidy in tumor cells. While these drugs are initially effective in treating cancer, dose-limiting peripheral neuropathies are common. Unfortunately, patients often relapse with drug resistant tumors. Identifying agents against targets that limit aneuploidy may be a valuable approach for therapeutic development. One potential target is the microtubule depolymerizing kinesin, MCAK, which limits aneuploidy by regulating microtubule dynamics during mitosis. Using publicly available datasets, we found that MCAK is upregulated in triple negative breast cancer and is associated with poorer prognoses. Knockdown of MCAK in tumor-derived cell lines caused a two- to five-fold reduction in the IC50 for paclitaxel, without affecting normal cells. Using FRET and image-based assays, we screened compounds from the ChemBridge 50k library and discovered three putative MCAK inhibitors. These compounds reproduced the aneuploidy-inducing phenotype of MCAK loss, reduced clonogenic survival of TNBC cells regardless of taxane-resistance, and the most potent of the three, C4, sensitized TNBC cells to paclitaxel. Collectively, our work shows promise that MCAK may serve as both a biomarker of prognosis and as a therapeutic target.

Standard of care for triple negative breast cancer (TNBC) involves the use of microtubule poisons like paclitaxel, which are proposed to work by inducing lethal levels of aneuploidy in tumor cells. While these drugs are initially effective in treating cancer, dose-limiting peripheral neuropathies are common. Unfortunately, patients often relapse with drug resistant tumors. Identifying agents against targets that limit aneuploidy may be a valuable approach for therapeutic development. One potential target is the microtubule depolymerizing kinesin, MCAK, which limits aneuploidy by regulating microtubule dynamics during mitosis. Using publicly available datasets, we found that MCAK is upregulated in triple negative breast cancer and is associated with poorer prognoses. Knockdown of MCAK in tumor-derived cell lines caused a two- to five-fold reduction in the IC50 for paclitaxel, without affecting normal cells. Using FRET and image-based assays, we screened compounds from the ChemBridge 50k library and discovered three putative MCAK inhibitors. These compounds reproduced the aneuploidy-inducing phenotype of MCAK loss, reduced clonogenic survival of TNBC cells regardless of taxane-resistance, and the most potent of the three, C4, sensitized TNBC cells to paclitaxel. Collectively, our work shows promise that MCAK may serve as both a biomarker of prognosis and as a therapeutic target.