Abstract 1547: Circulating tumor cells from a syngeneic mouse model of hepatocellular carcinoma demonstrate epithelial-mesenchymal transition, decreased MHC I expression, and increased CCR7 expression

Abstract

Abstract Metastasis is the leading cause of death in cancer patients, worldwide. A better understanding of how cancer cells detach from the primary tumor, escape from immunosurveillance while in circulation, and successfully colonize distant parts of the body, is needed. Circulating tumor cells (CTCs) are excellent tools to study this process. Using a syngeneic hepatocellular carcinoma mouse model, we were able to isolate cancer cells from the primary tumor and CTCs from the blood and establish novel primary tumor-derived cell lines and novel CTC lines. Wound healing assays revealed that CTCs have greater migratory capacity than the cancer cells from the primary tumors. However, MTT assays revealed that CTCs had less proliferative capacity than the cancer cells from the primary tumors. Furthermore, molecular characterization of the cancer cells from primary tumors and CTCs using Western blotting showed a decreased expression of E-cadherin and an increased expression of fibronectin by CTCs, suggesting that epithelial-to-mesenchymal transition (EMT) takes place in CTCs in comparison to cancer cells from primary tumors. To address the question of how CTCs may evade immunosurveillance, we investigated the profile of expression of two cell surface proteins involved in immune system function: the major histocompatibility complex class I (MHCI)- required for cytotoxic T cell activation and subsequent cancer cell killing, and chemokine receptor 7 (CCR7)- exploited by cancer cells for immune evasion. Our analysis revealed that there is decreased cell surface expression of MHCI and increased expression of CCR7 in the CTCs in comparison to the cancer cells from primary tumors. These findings indicate that although CTCs are not more proliferative, they have acquired significantly increased migratory capacity than cancer cells in primary tumors. This may be explained by their demonstration of EMT. Furthermore, their loss of MHC I expression and their gain of CCR7 expression may help with evasion of killing by cytotoxic T cells and result in enhanced metastasis. Citation Format: Jeannette A. Huaman, Ubayed Muhith, Dibash K. Das, Michelle Naidoo, Olorunseun O. Ogunwobi. Circulating tumor cells from a syngeneic mouse model of hepatocellular carcinoma demonstrate epithelial-mesenchymal transition, decreased MHC I expression, and increased CCR7 expression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1547.