O papel de CXCR2 em células panquimiorresistentes de câncer de ovário seroso de alto grau

Abstract

Ovarian cancer (CAOV) represents the eighth most common cancer among women, being the fifth leading cause of cancer death in the female universe. Despite the initial satisfactory response to platinum/taxane based therapy, chemoresistance still represents one of the major limitations in cancer treatment. Thus, several studies have turned their attention to better understanding the mechanisms that lead to drug resistance, in order to improve therapeutic strategies and improve patients' quality of life as well as survival rate. Data conducted by our group showed that overexpressed chemokines secreted in the conditioned medium, such as CXCL2, IL-6 and IL-8, probably play a crucial role in the chemoresistance of epithelial ovarian cancer (COE) cells. This project has focused on the role of CXCR2 and its CXCL2 and CXCL8 ligands. In this context, we point to the importance of modulating CXCR2 expression in the acquisition of chemoresistant phenotypes in CAOV. Our study model was based on two high grade CAOV cells lines, called chemosensitive A2780, and its pan-resistant derivative, ACRP, with IC50 for Cisplatin of 7.3µM for A2780 and 26.56µM for ACRP (p <0.001). Initially, we performed the expression of CXCR2 by immunofluorescence and discovered an anomalous nuclear expression of CXCR2. CXCR2 silencing was performed by interference RNA and validated by the Real Time PCR technique and its expression decreased by 2.5 fold to ACRP and 1.8 fold to A2780. The effects of CXCR2 knockdown by siRNA and a CXCR2 inhibitor, SB225002, were investigated, showing a decrease in proliferation of 3.5 fold to ACRP and 2.0 fold to A2780. In the cell viability there was less viability in the silenced ACRP cells (80%) compared to A2780 (50%), yet, this experiment showed that silencing CXCR2 increased the effectiveness of cisplatin, most evident in ACRP. The chicken embryo chorioallantoic membrane (CAM) model was used to evaluate the angiogenic and tumorigenic profile. There was a decrease in tumor growth in ACRP cells by 4 fold, when silenced. CXCR2 silencing suggested reducing the signaling pathways involved in cancer progression, such as PI3K/AKT (0.5 fold, p = 0.09) and MAPK/ERK (0.3 fold, p = 0.7), as well as how to decrease TEM-associated proteins, such as SLUG by 0.9 fold (p = 0.022) and SNAIL by 1.1 fold (p = 0.005). The Kaplan-Meier method also demonstrated that CXCR2 overexpression is associated with worse prognosis and survival in later stages of the disease (p = 0.035). Taken together, our findings present an innovative strategy for combating pan-chemoresistant high-grade serous CAOV by silencing abnormally expressed CXCR2