826

CAPNS1

calpain, small subunit 1;CAPNS1;calpain, small subunit 1

CANP small subunit|calcium-activated neutral proteinase small subunit|calcium-dependent protease small subunit 1|calcium-dependent protease, small subunit|calpain 4, small subunit (30K)|calpain regulatory subunit|calpain small subunit 1|calpain, small pol

19q13.12

protein-coding

BACKGROUND: Calpain small subunit 1 (Capn4) has been shown to correlate with the metastasis/invasion of hepatocellular carcinoma. This study aimed to investigate the role of Capn4 in intrahepatic cholangiocarcinoma (ICC). METHODS: Capn4 expression was measured in 33 ICC tissues by quantitative real-time polymerase chain reaction and western blot. The role of Capn4 in the migration, invasion and proliferation of ICC cells and matrix metalloproteinase 2 (MMP2) expression were assessed after Capn4 depletion by specific small interfering RNA. Capn4 expression was further examined by immunohistochemistry in a tissue microarray consisting of 140 ICC patients and 13 normal liver tissues, and the prognostic role of Capn4 in ICC was evaluated by Kaplan-Meier and Cox regression analyses. RESULTS: Capn4 expression was significantly higher in the ICC tissues compared to the peritumor tissues. Capn4 down-regulation impaired the migration/invasion ability of HCCC-9810 and QBC939 cells in vitro and decreased MMP2 expression. Capn4 overexpression significantly correlated with the presence of lymphatic metastasis of ICC (p = 0.026) and the tumor-node-metastasis (TNM) stage (p = 0.009). The postoperative 2- and 5-year overall survivals in patients with Capn4(low) were higher than those in the Capn4(high) group. The cumulative recurrence rate in patients with Capn4(low) was much lower than in the Capn4(high) group. Multivariate analysis showed that Capn4 overexpression was an independent prognostic marker in ICC. CONCLUSIONS: Capn4 overexpression was implicated in ICC metastasis/invasion, and Capn4 overexpression may be used as a molecular therapeutic target for ICC.

Calpain small subunit 1 (Capn4) has been identified as a major gene that promotes metastasis of hepatocellular carcinoma (HCC). However, the mechanism by which Capn4 promotes progression of HCC is not understood. In this study, we found that Capn4 expression was increased in highly metastatic HCC cell lines and in tumour tissue from HCC patients compared to healthy patient tissue. Over-expression of Capn4 in HCC cells enhanced tumour cell growth in vitro and increased invasiveness, tumourigenicity and lung metastasis in vivo. Protein microarray analyses showed that expression of multiple proteins was regulated by Capn4. Interestingly, Capn4 was found to physically associate with FAK and promoted hyperactivity of the FAK-Src signalling pathway via increased phosphorylation of specific tyrosine residues of FAK, Src and p130Cas. Knock-down of Capn4 expression suppressed the malignant behaviour of HCC cells and inhibited the FAK-Src signalling pathway. Furthermore, Capn4-mediated invasion and metastasis of HCC cells required up-regulation of matrix metalloproteinase-2 (MMP2) through activation of this signalling pathway. Our clinical data revealed that Capn4 expression correlated well with the levels of phospho-FAK, and over-expression of both Capn4 and phospho-FAK correlates with the poorest survival outcomes in HCC. In conclusion, our data showed that Capn4 can contribute to HCC growth and metastasis via activation of the FAK-Src signalling pathway and MMP2.