Hypoxia enhances tumor-stroma crosstalk that drives progression in hepatocellular carcinoma

Abstract

Introduction: The crosstalk between tumor cells and their microenvironment plays a crucial role in the development, progression and metastasis of HCC. Hypoxia, a common feature of advanced hepatocellular carcinoma (HCC), has been known to modulate the development and evolution of the tumor microenvironment. However, the mechanism and functional impact of the tumor-stroma co-evolution in hypoxic HCC remains poorly understood. In this study, we investigated the effects of hypoxia on the tumor-stroma crosstalk in HCC. Methods: Human HCC cells (Huh-BAT and HepG2) were co-cultured with activated human hepatic stellate cells (HSCs

LX-2) either in a normoxic or hypoxic condition. Cell growth, migration capacity and apoptosis were assessed using the MTS assay, wound healing assay and DAPI staining. Global gene expression profiling under chronic hypoxia was determined by microarray analysis. Results: Co-culturing HCC cells with HSCs in hypoxia significantly enhanced proliferation and migration of both cells as compared to normoxic condition by upregulation of PDGF-BB. Co-culturing also decreased bile acid- or TRAIL-induced HCC cell apoptosis. The effects of hypoxic tumor-stroma crosstalk on proliferation and migration were meaningfully inhibited by the PI3K inhibitor compared to cells in a normoxic condition. Unsupervised genome-wide expression profiling showed that 1887 genes were differentially expressed in co-cultured HCC cells with HSCs and 503 genes in HSCs with HCC cells under hypoxia, including genes that encode cell cycle, signaling transduction, cell surface receptors and redox reaction. Hepatocyte–HSC cross-talk was bidirectional and resulted in the deregulation of functionally relevant gene profiles. Conclusions: These results indicate that the enhanced bidirectional cross-talk between HCC cells and activated HSCs is an important feature of HCC progression under hypoxia.