Abstract 1201: Hypoxia promotes not CXCR7 but CXCR4 expression and its biological activity in gastric cancer cell through activation of hypoxia-inducible factor-1β

Abstract

Abstract Background: The chemokine receptor, CXCR4 and CXCR7, which bind with high affinity same chemokine CXCL12/SDF-1, are associated with the biological behavior in several kinds of cancer, but few studies have addressed the expression and regulation of CXCR4 and CXCR7 in gastric cancer. Methods: Gastric cancer cell line KATO III was subjected to hypoxia or normoxia. The expression of CXCR4 and CXCR7 were investigated using RT-PCR, Westerning blotting, and flow cytometry before and after hypoxic conditioning. The regulation of CXCR4 and CXCR7, and their biological effects by hypoxia were evaluated using gastric cancer cells transfected with hypoxia-inducible factor (HIF)-1α shRNA. Result: mRNA and proteins of both CXCR4 and CXCR7 were detectable by RT-PCR and Western blot analysis, respectively, in KATO III cells. A small population of KATO III cells expressed membrane CXCR4 and CXCR7 as determined by flow cytometry. Hypoxia up-regulated CXCR4 proteins and enhanced membrane expression of CXCR4 in human gastric cancer KATO III cells, which constitutively expressed membrane CXCR7 and CXCR4 in a steady state, as revealed by Western blotting and flow cytometry, respectively. In contrast, CXCR7 proteins remained unchanged under hypoxia, and promotion of CXCR7 surface expression on KATO III cells could not be demonstrated by flow cytometry. Hypoxia-induced expression of CXCR4 was mediated through activation of HIF-1α with phosphorylation of AKT and ERK, as revealed by HIF-1α knockdown using shRNA. The chemical inducer of HIF-1α, cobalt chloride, induced upregulation of CXCR4 in KATO III cells under normoxic conditions. In addition, KATO III cells exposed to hypoxic condition showed enhanced wound healing, transwell migration, and invasion in response to stromal cell-derived factor (SDF)-1α, a specific ligand for CXCR4. Conclusions: These findings provide evidences for differential regulation and different role of chemokine receptor, CXCR7 and CXCR4, in gastric cancer cell in vitro. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1201. doi:1538-7445.AM2012-1201