Abstract
e14105 Background: Aurora Kinase A (AURKA) is overexpressed in HNSCC, and correlates with poor prognosis. It has been identified as a potential therapeutic target, yet the response rate for the AURKA inhibitor MLN8237 is only 9% in treatment refractory HNSCC. We hypothesized that although AURKA inhibitors lead to defective spindle assembly, they may also reduce mitotic entry, undermining cytotoxic effect. We predicted that adding a WEE1 inhibitor to an AURKA inhibitor would mitigate this effect and enhance cell death Methods: Cell viability assays were performed on FaDu ( p53 mut.), Detroit562 ( p53 mut.), and UNC7 ( p53 WT) HPV negative HNSCC cell lines treated with AZD1775 (AZD), MLN8237 (MLN), and combination of AZD+MLN. Oncosphere formation assays were used to confirm findings of cell death, and western blot analysis and confocal microscopy were used to investigate mechanism of synergy. The above drugs were also given at varying doses via oral gavage to FaDu xenografted nude mice. Results: There was clear synergy of AZD and MLN in-vitro. Combination Indices were determined by the Chou-Talalay method: FaDu 0.4, Detroit562 0.5, and UNC7 0.6 (synergy = < 0.8). Oncopshere assays showed inability of AZD+MLN treated cells to re-differentiate. FaDu cells treated with MLN had increased p-CDK1 and reduced phospho-histone H3 (pHH3), suggesting reduced mitotic entry. AZD+MLN treated cells had reduced p-CDK1 and increased pHH3, similar to AZD treated cells; they also had spindle disarray with poor chromatin organization on confocal microscopy indicating mitotic catastrophe. In mice, the combination of AZD+MLN inhibited tumor growth, with no apparent toxicity. Mice treated with either drug alone had tumor volumes over 1000mm3 and were sacrificed at day 21; those treated with AZD 90mg/kg and MLN 30mg/kg had tumors volumes around 300mm3 on day 28. Conclusions: AZD and MLN synergistically enhance cell death in HNSCC cell lines and significantly inhibit tumor growth in mouse xenograft models. The ability of AZD to overcome intrinsic resistance to MLN may underlie mechanism of synergy. We recommend further investigation of AURKA and WEE1 inhibition in other cancers with high AURKA expression, and in patients with HNSCC.
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