Citations

Abstract 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 in wild type BRAF breast cancer cells as well as demonstrate an additive cytotoxic effect of AURKA- and MEK1/2-specific inhibitors against estrogen positive (ER+) and triple negative (ER-, PR-, HER2-) breast cancer 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 the levels of both pMEK1/2 and pERK1/2 compared to the 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. No differences in phosphorylation of MEK1/2 or ERK1/2 were observed in BRAFG464V triple negative MDA-MB-231 cells. Treatment with AURKA inhibitors resulted in downregulation of pAURKA and a significant increase in levels of total AURKA protein. The pull-down assay with Ras-binding domain coated agarose beads followed by western blot analysis with anti-pan-RAS Ab revealed no changes in active GTP-bound RAS in alisertib-treated MCF-7 cells compared to the untreated control. Consistently, no significant changes were observed in RAS-inducible phosphorylation of RAF1 activation site at Ser338 as demonstrated by western blot. Treatment with the pan RAF inhibitor TAK-632 did not diminish alisertib-induced pERK and pMEK1/2. Alternatively, treatment with the MEK1/2 specific inhibitor PD0325901 completely abrogated alisertib-induced phosphorylation of MEK1/2 and ERK1/2. Furthermore, 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). Conclusions: Our data suggests that AURKA is a RAF1-independent negative regulator of MAPK activity in breast cancer cells. The in-depth analysis of the AURKA-MEK1/2 interaction is currently under investigation. The results reveal a promising new strategy for the treatment of wild type BRAF, TNBC patients using a combination of AURKA and MEK1/2 inhibitors. Citation Format: Malgorzata Gil, Archana Chidambaram, Thaer Khoury, Kazuaki Takabe, Igor Puzanov, Irwin Gelman, Antonio D’Assoro, Mateusz Opyrchal. Inhibition of AURKA induces Raf1-independent activation of MAPK pathway in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2123. doi:10.1158/1538-7445.AM2017-2123

Abstract Patients with metastatic melanoma whose disease progresses on ipilimumab can clearly derive benefit from subsequent anti–programmed death-1 (PD-1). However, patients experience heterogeneous outcomes with ipilimumab, including rapid or delayed progression, and it is unclear whether patterns of ipilimumab progression influence subsequent clinical responses to anti–PD-1. We retrospectively reviewed data from 116 patients with metastatic melanoma who progressed on ipilimumab and were subsequently treated with pembrolizumab. The study objectives were to determine whether progression-free survival (PFS) with ipilimumab was associated with PFS, objective response rate (ORR), and clinical benefit rate (CBR; ORR + stable disease) with pembrolizumab. Patients with PFS ≥90 days after treatment with ipilimumab generally had superior outcomes with subsequent pembrolizumab treatment compared with patients with PFS <90 days (ORR, 49% vs. 35%, P = 0.12; CBR, 66% vs. 46%, P = 0.03). Patients with prolonged ipilimumab benefit (PFS ≥ 180 days) had excellent outcomes with pembrolizumab compared with rapid progressors (PFS < 45 days; ORR, 55% vs. 25%; CBR, 80% vs. 25%; median PFS, 249 vs. 50 days). Using logistic regression models, PFS with ipilimumab was independently correlated with response to pembrolizumab (odds ratio, 1.22; 95% CI, 1.02–1.51). This study shows that prolonged PFS with ipilimumab predicts excellent outcomes with subsequent pembrolizumab treatment, offering valuable prognostic information for clinicians. Cancer Immunol Res; 4(7); 569–73. ©2016 AACR.