Abstract C172: Concomitant disruption of WEE1 and AurKA synergistically enhances anti-cancer effects in p53 mutated head and neck squamous cell carcinoma

Head and neck cancer is a devastating disease which annually affects over half a million patients worldwide. Squamous cell carcinoma of the head and neck (SCCHN), which accounts for approximately 90% of all head and neck cancers, often harbors a disruptive mutation of the TP53 gene. Cells harboring TP53 mutations evade cisplatin-induced cellular senescence with cell cycle arrest in the G2 phase, allowing for DNA repair. Wee1 and Aurora Kinase A (AurKA) are crucial regulators of the mitotic cell cycle including G2/M phases and are significantly activated in SCCHN harboring TP53 mutations. Therefore, we hypothesized that a combination therapy aimed at these synthetic lethal targets, Wee1 and AurKA, would enhance anti-cancer effects and cisplatin sensitivity due to abrogation of G2 arrest concomitant with defects in tumor cell mitotic machinery, which is indeed caused by cisplatin. We tested this hypothesis using assays of cell viability, colony formation, anchorage independent cell growth, and finally a three-dimensional oncosphere formation assay in vitro. The combination index (CI) was calculated according to the Chou-Talalay method (CI 1.2, antagonistic). The cell viability assay indicated that the combination of the Wee1 inhibitor MK-1775 with the AurKA inhibitor MLN8237 exhibited striking synergistic inhibitory effects on the cell growth of SCCHN cell lines including FaDu (TP53 mutation, CI = 0.397004), Detroit562 (TP53 mutation, CI = 0.202677) and UNC-7 (TP53 WT, CI = 0.587106). Consistent with the cell viability data we obtained, we also confirmed this synergistic effect under anchorage dependent and independent cell growth conditions in FaDu and UNC-7 cell lines. Interestingly, this combination dramatically reduced the numbers of a stem cell-like oncosphere formation, showing a more effective combination in comparison to MK-1775 with cisplatin (inhibitory effect (% Vehicle): MK-1775+MLN8238 vs MK-1775+Cisplatin; FaDu = 74% vs 69%; UNC-7 = 43% vs 36%). Moreover, all spheroids exposed to the combination of MK-1775 with MLN8237 did not survive following further incubation under normal cell culture conditions. Induction of apoptosis, as shown gradually increased PARP cleavage at Asp214-Gly215 in FaDu and UNC-7 cells, was demonstrated. Furthermore, this synergistic synthetic lethal effect was not seen in normal human tracheobronchial epithelial (NHTBE) cells in a three-dimensional organotypic (air-liquid interface culture condition) culture system, predicting low toxicity. These results suggest that SCCHN cells, including high-risk TP53 mutations, are sensitive to the combination of MK-1775 and MLN8237 in vitro, thereby supporting the preclinical and further clinical evaluation of MK-1775 in combination with MLN8237 for the treatment of patients with TP53 inactivated HNSCC. Citation Format: Jong Woo Lee, Janaki Parameswaran, Ja Seok Koo, Barbara Burtness. Concomitant disruption of WEE1 and AurKA synergistically enhances anti-cancer effects in p53 mutated head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C172.