Abstract A33: The regulation of extracellular acidosis and cell survival by the TIMP-1/CD63 axis in breast carcinoma

Abstract

Abstract Breast Cancer (BrCa) resistance to conventional therapies often leads to more aggressive and metastatic disease highlighting the importance of understanding the resistance pathway. The Tissue Inhibitor of Metalloproteinase-1 (TIMP-1) is among the most reliable prognostic markers for therapy resistance as well as metastasis of breast cancer via promotion of breast cancer cell survival through its unique interaction with the tetraspanin CD63. Recent work has shown that levels of TIMP-1 and the carbonic anhydrase family member CAIX in circulating tumor cells (CTCs) predict BrCa progression-free and overall survival. Since CAIX is known to play a critical role in the regulation of extracellular acidosis that contributes to therapy resistance, we investigated whether TIMP-1/CD63 signaling regulates extracellular acidosis involving CAIX. We utilized the murine 4T1 and human MCF10A progression models of breast cancer and demonstrated increased CAIX and TIMP-1 expression in the more aggressive 4T1 and MCF10CA1h cells. When we monitored pH change using a digital pH reader and the pH sensitive DF fluorescein dye, the more aggressive human MCF10Ca1h cells exhibited marked extracellular acidosis compared to the minimally malignant MCF10A and MCF10AneoT cells. Importantly, downregulation of TIMP-1 or CD63 in MCF10CA1h cells specifically reduced CAIX expression and its associated extracellular acidosis. To determine the functional significance of CAIX in TIMP-1/CD63-mediated extracellular acidosis, we attenuated CAIX expression and demonstrated a significant reduction of the acidosis phenotype observed in MCF10CA1h cells. Importantly, CAIX knockdown drastically reduced BrCa cell survival in a clonogenic cell survival assay. Taken together, we have identified a unique TIMP-1/CD63-mediated signaling pathway, resulting in extracellular acidosis and cell survival of BrCa cells involving CAIX. This study further provides salient information as to TIMP-1-specific function in breast cancer. Citation Format: Abdo J. Najy, Young Suk Jung, Hyeong-Reh Choi Kim. The regulation of extracellular acidosis and cell survival by the TIMP-1/CD63 axis in breast carcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A33.