Search

Tissues from 98 human hepatocellular carcinomas (HCCs) obtained from hepatic resections were subjected to somatic copy number variation (CNV) analysis. Most of these HCCs were discovered in livers resected for orthotopic transplantation, although in a few cases, the tumors themselves were the reason for the hepatectomies. Genomic analysis revealed deletions and amplifications in several genes, and clustering analysis based on CNV revealed five clusters. The LSP1gene had the most cases with CNV (46 deletions and 5 amplifications). High frequencies of CNV were also seen in PTPRD(21/98), GNB1L(18/98), KIAA1217(18/98), RP1-1777G6.2(17/98), ETS1(11/98), RSU1(10/98), TBC1D22A(10/98), BAHCC1(9/98), MAML2(9/98), RAB1B(9/98), and YIF1A(9/98). The existing literature regarding hepatocytes or other cell types has connected many of these genes to regulation of cytoskeletal architecture, signaling cascades related to growth regulation, and transcription factors directly interacting with nuclear signaling complexes. Correlations with existing literature indicate that genomic lesions associated with HCC at the level of resolution of CNV occur on many genes associated directly or indirectly with signaling pathways operating in liver regeneration and hepatocyte growth regulation.

Integrins are a family of receptors for extracellular matrix proteins that have critical roles in human tissue development. Previous studies identified down-regulation and/or mutations of integrin α7 (ITGA7) in prostate cancer, liver cancer, soft tissue leiomyosarcoma, and glioblastoma multiforme. Here we report that expression of ITGA7 induced apoptosis in the human prostate cancer cell lines PC3 and DU145. Yeast two-hybrid analysis revealed that the C-terminus of ITGA7 interacts with high temperature requirement A2 (HtrA2), a serine protease with a critical role in apoptosis. Expression of ITGA7 increases the protease activity of HtrA2 both in vitroand in vivo. Deletion of the HtrA2 interaction domain abrogates the cell death activity of ITGA7, whereas down-regulation of HtrA2 dramatically reduced cell death mediated by ITGA7. In addition, site-directed protease-null mutant HtrA2S306A expression blocked apoptosis induced by ITGA7. Interestingly, interaction between ITGA7 and its ligand laminin 2 appears to protect against cell death, since depleting laminin β2 with a small-interfering RNA significantly exacerbated apoptosis induced by ITGA7 expression. This report provides a novel insight into the mechanism by which ITGA7 acts as a tumor suppressor.