Combined TRIP13 and Aurora Kinase Inhibition Induces Apoptosis in Human Papillomavirus-Driven Cancers

Purpose: Human papillomavirus (HPV) causes >5% of cancers, but no therapies uniquely target HPV-driven cancers. Experimental Design:Wetested the cytotoxic effect of 864 drugs in 16 HPV-positive and 17 HPV-negative human squamous cancer cell lines. We confirmed apoptosis in vitro and in vivo using patientderived xenografts. Mitotic pathway components were manipulated with drugs, knockdown, and overexpression. Results: Aurora kinase inhibitors were more effective in vitro and in vivo in HPV-positive than in HPV-negative models. We hypothesized that themechanismof sensitivity involves retinoblastoma (Rb) expression because the viral oncoprotein E7 leads to Rb protein degradation, and basal Rb protein expression correlates with Aurora inhibition-induced apoptosis. Manipulating Rb directly, or by inducing E7 expression, altered cells' sensitivity to Aurora kinase inhibitors. Rb affects expression of the mitotic checkpoint genes MAD2L1 and BUB1B, which we found to be highly expressed in HPV-positive patient tumors. Knockdown of MAD2L1 or BUB1B reducedAurora kinase inhibition-induced apoptosis,whereas depletion of the MAD2L1 regulator TRIP13 enhanced it. TRIP13 is a potentially druggable AAA-ATPase. Combining Aurora kinase inhibition with TRIP13 depletion led to extensive apoptosis in HPV-positive cancer cells but not in HPV-negative cancer cells. Conclusions: Our data support a model in which HPV-positive cancer cells maintain a balance of MAD2L1 and TRIP13 to allow mitotic exit and survival in the absence of Rb. Because it does not affect cells with intact Rb function, this novel combination may have a wide therapeutic window, enabling the effective treatment of Rb-deficient cancers.