Background: Aurora A (AURKA) is a mitotic kinase responsible for centrosome segregation and mitotic spindle formation. In normal cells, expression of AURKA is highly regulated and is predominantly restricted to G2/M phases of the cell cycle. Unlike healthy cells, cancer cells overexpress AURKA through all phases of the cell cycle resulting in the acquisition of alternate non-mitotic functions. Little is known about cellular functions regulated by AURKA and its interaction with other signaling molecules. Here, we report a novel interaction between AURKA and the mitogen-activated protein kinase (MAPK) pathway at the level of MEK1 in breast cancer cells. This interaction may serve as a novel target as well as demonstrate by an additive cytotoxic effect of AURKA- and MEK1/2-specific inhibitors against estrogen positive (ER+) and triple negative breast cancer (TNBC) cells.

Results: We show that treatment of ER+HER2- MCF-7, ER- HER2+ SKBR3 and ER- HER2- BT549 cells with AURKA specific inhibitors alisertib, MK8745 and Aurora A Inhibitor I resulted in over 2-fold increase in relative levels of poMEK1/2 and poERK1/2 compared to untreated controls. The activation of the MAPK pathway was rapid with changes seen within 5 min after treatment with AURKA inhibitors and was sustained for at least 48 hours. Treatment with the pan RAF inhibitor TAK-632 did not diminish alisertib-induced poERK and poMEK1/2. Alternatively, treatment with the MEK1/2 specific inhibitor PD0325901 completely abrogated alisertib-induced phosphorylation of MEK1/2 and ERK1/2. In situ proximity ligation and pull down assays demonstrated AURKA and MEK1/2 direct interaction. In vitro kinase assay showed direct phosphorylation of MEK1 by AURKA. Combined treatment of alisertib and PD0325901 in vitro revealed significant additive cytotoxic effect in MCF-7 and BT549 cells when compared to either agent used alone (p< 0.008 and p<0.011; p <0.04 and p<0.028) with early trend toward significance in survival in a BT549 xenograft breast cancer in vivo model.

Conclusions: Our data shows a novel AURKA-MEK1 interaction in breast cancer cells. In depth in vivo analysis is ongoing. The results reveal a promising new strategy for the treatment TNBC patients using a combination of AURKA and MEK1/2 inhibitors.

Citation Format: Gandhi S, Gil M, Khoury T, Takabe K, Puzanov I, Gelman I, D'Assoro A, Opyrchal M. A novel interaction of AURKA with MAPK pathway in breast cancer cells as a potential therapeutic target [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-17.