Abstract 3548: Role of synuclein-gamma (SNCG) in paclitaxel resistance and mitogen activated protein kinase activation in uterine papillary serous carcinoma(UPSC)

Abstract

Abstract Objectives: SNCG is a novel prognostic biomarker in UPSC. We have shown that its overexpression correlates with aggressive cellular properties and resistance to paclitaxel in a UPSC cell line (SPEC2) as well as poor prognosis in a pilot set of UPSC patients. The goal of this study was to determine the mechanism of SNCG-associated taxane resistance by evaluating the effect of SNCG on the mitotic checkpoint and its propensity to modulate extracellular signal-regulated protein kinase 1/2 (ERK 1/2) signaling pathways. Methods: A stably transfected SPEC2 cell line was created using shSNCG versus shControl oligonucleotides. Similarly, Ishikawa cells were transiently transfected with an SNCG expression vector versus empty vector. Differences in cell proliferation were measured using a cell viability assay and BrdU incorporation assay after treatment with paclitaxel. Cell cycle analysis was used to study the effect of SNCG on the mitotic checkpoint. Differences in expression of the checkpoint kinase BubR1 due to SNCG were studied using real time PCR, Western blot, 26S ubiquitin-proteasome inhibition, and siRNA to BubR1. ERK and phospho-ERK levels were measured in SPEC2 cells with and without SNCG expression by Western blot. SPEC2 cells were treated with paclitaxel with and without the MEK inhibitor UO126 and apoptosis was measured using cleaved PARP analysis. Results: SNCG overexpression lead to acquired, reversible paclitaxel resistance in endometrial cancer cell lines. SNCG was noted to interfere with mitotic checkpoint function by causing degradation of the critical checkpoint protein BubR1 thereby allowing cells to escape paclitaxel-induced mitotic arrest. SPEC2 cells exhibited sustained activation of ERK which was attenuated by silencing SNCG. When SPEC2 cells were exposed to paclitaxel combined with the MEK inhibitor UO126, decreased cell viability and increased apoptosis was noted compared to either agent alone. SNCG knockdown further enhanced paclitaxel and UO126 sensitivity. Cell cycle analysis revealed that silencing SNCG in SPEC2 cells and adding UO126 acted synergistically in overcoming paclitaxel resistance. Conclusions: SNCG overexpression in UPSC leads to taxane resistance by interacting with the mitotic checkpoint kinase BubR1 causing its degradation. SNCG is also associated with sustained ERK activation. Targeting SNCG in conjunction with MEK inhibition may represent a novel therapeutic strategy to overcome taxane resistance in these cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3548.