BACKGROUND Aberrant Hedgehog (HH) signaling activation is important in cancer growth and mediates the interaction between cancer cells and the surrounding stromal cells. This study investigated the role of HH signaling on the growth of cholangiocarcinoma (CC), focusing on the interaction of CC cells with stromal cells.

METHODS To evaluate the interaction between human CC cells (SNU-1196, SNU-246, SNU-308, SNU-1079, and HuCCT-1) and stromal cells (hepatic stellate cell line, Lx-2), co-culture proliferation, migration, and invasion assays were performed. In vivo nude mice experiments were conducted using two groups-HuCCT-1 single implant xenograft (SX) and co-implant xenograft (CX) with HuCCT-1 and Lx-2.

RESULTS When HuCCT-1 cells were co-cultured with Lx-2 cells, the expression of HH signaling-related proteins increased in both HuCCT-1 and Lx-2 cells. Co-culture with Lx-2 cells stimulated the proliferation, migration, and invasion of CC cells, and these effects were mediated by HH signaling. Co-culture of HuCCT-1 and Lx-2 cells increased the secretion of several cytokines. In an ectopic xenograft model, Lx-2 co-implantation increased CC tumor growth and stimulated angiogenesis. Cyclopamine attenuated tumor growth in the CX group, but not in the HuCCT-1 mono-implant (SX) group. Cyclopamine treatment decreased CC cell proliferation, suppressed microvessel density, and increased tumor necrosis in the CX group, but not in the SX group.

CONCLUSION Hepatic stellate cells stimulate the proliferation, migration, and invasion of CC cells, promote angiogenesis through HH signaling activation, and render CC more susceptible to necrosis by HH inhibitor.