Capn4 overexpression underlies tumor invasion and metastasis after liver transplantation for hepatocellular carcinoma

Abstract

Liver transplantation (LT) is one of the best therapeutic options for nonresectable hepatocellular carcinoma (HCC). Unfortunately, some HCC patients succumb to the disease after LT, which reduces long- and medium-term survival. To identify the proteins associated with HCC invasion and metastasis, HCC patients undergoing LT with complete follow-up data were included in this study and were categorized into recurrence and nonrecurrence groups. We extracted the total protein from the acquired homogeneous tumor cells and applied a cleavable isotope-coded affinity tag technology to quantitate relative changes in protein levels between the two groups. We identified a total of 149 proteins with two-dimensional liquid chromatography coupled with tandem mass spectrometry, including 52 differentially expressed proteins by at least two-fold. Among them, calpain small subunit 1 (Capn4), a protein with relevant interactions with many migration-invasion-related proteins, has attracted more attention. First, Capn4 overexpression in the recurrence group was confirmed via real-time polymerase chain reaction and western blotting in another cohort of 40 HCC patients undergoing LT. Second, Capn4 was associated with enhanced invasiveness in vitro. The small interfering RNA-mediated knockdown expression of Capn4 in HCC cell lines significantly inhibited its mobile and invasive ability. Tissue microarray in a further 192 cases revealed that Capn4 significantly correlated with invasive phenotype of HCC, and univariate and multivariate analyses indicated that Capn4 is an independent prognostic factor for recurrence and survival of HCC patients. Our study revealed that Capn4 overexpression underlies invasion and metastasis after LT for HCC and might be a candidate biomarker for future diagnosis and a target for therapy.