Activated Human Hepatic Stellate Cells Promote Growth of Human Hepatocellular Carcinoma in a Subcutaneous Xenograft Nude Mouse Model

Abstract

Tumor cell microenvironment defines cancer development, also in hepatocellular carcinoma (HCC). Hepatic stellate cells (HSCs) are believed to be the key contributors to tumor microenvironment in HCC, yet their precise role in cancer progression is still unclear. The aim of this study was to determine the effect of human HSCs on progression of HCC using a subcutaneous xenograft nude mouse model. Nude mice were stratified to receive subcutaneous injections of human HCC cell line HepG2 and human HSC line LX-2 (HepG2 + LX-2), HepG2 alone, LX-2 alone, or phosphate-buffered saline. Tumor growth was assessed by measuring tumor size. After 30 days, final tumor size, weight, and histology were assessed. Compared with mice that were only injected HepG2 cells, mice injected with HepG2 + LX-2 exhibited more rapid tumor growth, increased tumor size and weight, higher tumor cell numbers due to increased proliferation and reduced apoptosis, increased fibrotic bands containing LX-2 cells, and increased tumor angiogenesis. In conclusion, HSCs play a significant role in promotion of HCC growth.

The Role of Cancer-Associated Fibroblasts and Fibrosis in Liver Cancer

“…Activated HSCs produce numerous angiogenic factors such as VEGF (90, 145) and angiopoietin 1 (Angpt1) 1 or Angpt2 (91, 146, 147), which activate their respective receptors on endothelial cells to enhance their functions (143) and promote tumor vascularization and growth. This has been shown in numerous in vitro and in vivo studies using HSC/endothelial cell coculture systems and in tumor cell/HSC coimplantation models (90, 148–150). VEGF is a potent survival factor for endothelial cells that promotes their proliferation and vascular permeability thus supporting the formation of new vasculature.…”

Transformation of primary human hepatocytes in hepatocellular carcinoma

“…Activated HSCs in cellular cultures. It has been shown that HSC activation plays a crucial role in supporting inflam- mation and growth of early tumor cells in HCC (26)(27)(28)(29). Morphological evaluation of cultured cells supported the presence of HSCs.…”

Hepatic Stellate Cells and Liver Cancer

“…Angiogenesis is a hypoxia-stimulated and growth-factor mediated process in which new vessels are formed from the existing vasculature [62]. This has been shown in numerous in vitro and in vivo studies using HSC/endothelial cell co-culture systems and in tumor cell/HSC co-implantation models [39,40,66,67]. This has been shown in numerous in vitro and in vivo studies using HSC/endothelial cell co-culture systems and in tumor cell/HSC co-implantation models [39,40,66,67].…”

“…In a subcutaneous co-transplantation model, the presence of an HSC cell line increased tumor formation by neoplastic MIMR hepatocytes two-to threefold [38]. Subcutaneous implantation of HepG2 cells and the HSC cell line LX2 in nude mice resulted in more rapid tumor growth and increased tumor size and weight relative to control animals who received HepG2 alone [39]. Subcutaneous implantation of HepG2 cells and the HSC cell line LX2 in nude mice resulted in more rapid tumor growth and increased tumor size and weight relative to control animals who received HepG2 alone [39].…”

“…Enhanced proliferation of the implanted tumor cells resulted from HSC-induced autocrine TGF-β signaling and hyperactivation of nuclear Wnt/β-catenin in the neoplastic hepatocytes [38]. The tumors of co-transplanted mice exhibited increased fibrotic bands containing the LX2 cells that promoted increased angiogenesis and proliferation and reduced apoptosis of HepG2 cells [39]. The tumors of co-transplanted mice exhibited increased fibrotic bands containing the LX2 cells that promoted increased angiogenesis and proliferation and reduced apoptosis of HepG2 cells [39].…”