Mitotic Spindle Assembly Inhibition Through Aurora A (MLN8237) Plus Vincristine Is Synthetic Lethal and Synergizes with Rituximab As a Curative Therapy in Aggressive B-Cell Non-Hodgkin Lymphoma

Abstract 2721

Most aggressive B-cell non-Hodgkin lymphomas (B-NHL) are not curable with current chemo-immunotherapy combinations. Synthetic lethal interactions with novel agents may yield effective combination therapies with minimal toxicity for aggressive B-NHL. Auroras (A and B) are a family of mitotic oncogenic serine/threonine kinases intimately involved in high fidelity regulation of cell division. Aberrant over-expression of Auroras leads to genetic instability, polyploidy, tumor initiation and progression. Over-expression of Auroras in aggressive B-NHL promotes resistance to microtubule targeted agents (MTA, taxanes and vinca alkaloids). Si-RNA knockdown or pharmacologic inhibition of Aurora with MLN8237 [M], an ATP-site small molecule inhibitor, leads to enhanced sensitivity of B-NHL cells to MTAs. We hypothesized that promotion of microtubule de-polymerization with vincristine [V] would be more effective in synergizing with M than a microtubule polymerizing agent docetaxel [D]. We demonstrated that M plus V is synergistic while M plus D is additive in B-NHL cell culture models. Further, the addition of rituximab [R] enhanced apoptosis of B-NHL cells treated with MV or MD therapy. Mouse xenograft models of mantle cell lymphoma show modest single agent activity for M, R, D and V with tumor growth inhibition (TGI) of ∼10–15% (p=0.01). Of the doublets, MV caused tumor regression while MD and MR caused TGI (∼55–60%) and (∼20–25% (p=0.001) respectively. Although MV caused tumor regression, mice relapsed after 2 weeks of stopping therapy. In contrast, MVR had no relapses 120 days after stopping therapy, while MDR led to TGI of ∼85% (p=0.001). Kaplan-Meier analysis of overall survival showed that the mice treated with MV and MVR had a statistically significant improvement in overall survival when compared with the control (p<0.0001) or MR (p=0.0043). Gene expression profiling (human HG-U133A) and confirmatory Western blotting of harvested tumors at the end of treatment (3 weeks) confirmed reactivation of cell cycle regulatory genes including PCNA, Aurora B, cyclin B1 and cyclin D1, in MV versus MVR. Moreover, MVR therapy continues to inhibit Aurora B by repressing genes regulating mitotic sister chromatid segregation by repressed gene expression analyzed by Gene Ontology. Thus, addition of R to MV represents a novel therapeutic strategy that warrants clinical trial evaluation in aggressive B-NHL [Funded by the Lymphoma SPORE 1 P50 CA 130805 01A1].