Targeting HSP60 by subcutaneous injections of jetPEI/HSP60-shRNA destabilizes cytoplasmic survivin and inhibits hepatocellular carcinoma growth

Heat shock protein 60 (HSP60) overexpresses in various types of cancer, but its expression levels and functions in hepatocellular carcinoma (HCC) are still in dispute. We aim to clarify this issue and examine whether HSP60 could be a therapeutic target for HCC. We found drastically enhanced cell apoptosis and suppressed cell proliferation in two HCC cell lines with HSP60-silencing, and also indicated survivin was involved in this regulatory process in vitro and in vivo. However, HSP60-silencing in normal human hepatocytes only resulted in a minimal reduction of cell proliferation but without effects on cell apoptosis. We also showed HSP60 interacted with cytosolic but not mitochondrial survivin by immunoprecipitation assay. A rigorous method was used to standardize quantification from immunoblot assay to obtain more precise expression levels of HSP60 and survivin. The expression of HSP60 and survivin positively correlated in both cancerous and non-cancerous liver tissues (P<0.001) after analyzing 145 surgically removed HCC tissues. A total of 56.6% of HCC patients overexpressed HSP60 in cancerous tissues, and 40.0% under-expressed HSP60. Higher expression of HSP60 and survivin in non-cancerous tissues both correlated with shorter overall survival (P=0.029 and P<0.001, respectively). Finally, we evaluated the therapeutic potential of HSP60 using extraneous delivery of jetPEI/shHSP60 complexes. The treatment results showed significant reduction of tumor weight by 44.3% (P<0.05), accompanied by under-expression of survivin. These studies suggested that HSP60 not only served as a prognostic marker but also served as a novel therapeutic target for HCC.