A hyposensitive anticancer drug induces higher surface expression and release of heat shock proteins in a human hepatocellular carcinoma cell line

Heat shock proteins (HSPs) respond to multiple stresses and have been implicated as essential immune chaperones that regulate innate and adaptive immunity. The exposure of HSPs containing tumour peptide complex to immune surveillance elements may elicit a specific anti-tumour response. The present study examined the potential of anticancer drugs to induce apoptosis of HepG2 cells and elicit the expression of HSP proteins, including HSP70 and gp96, on the membrane or their release to the extracellular environment, leading to HSP exposure. In the present study, etoposide and carboplatin were classified by an adenosine triphosphate assay as representatives of hypersensitive and hyposensitive anticancer drugs, respectively. Flow cytometry, immunofluorescence, ELIZA and reverse transcription quantitative polymerase chain reaction were all used to detect changes in the HSPs. The results demonstrated that etoposide and carboplatin induced apoptosis of HepG2 cells. In addition, following treatment with etoposide or carboplatin, HSP70/gp96 expression increased, demonstrating a 'transfer expression' pattern: The cytosol expression decreased while the surface expression increased. These alterations progressed steadily with notable alterations following treatment with etoposide for 24 h or carboplatin for 72 h. Additionally, at the end of treatment, release of HSP70/gp96 to the extracellular environment increased. Notably, following treatment with the hyposensitive anticancer drug carboplatin for 72 h, the surface expression of gp96 in HepG2 cells was significantly increased. These results suggest that when combined with cancer cell apoptosis, anticancer drugs induce the membrane expression and release of HSP70/gp96 in hepatocellular carcinoma (HCC) cells, which may represent a crucial event in the immune anti-tumour response. Notably, treatment with the hyposensitive anticancer drug for a longer time period resulted in greater surface expression and release of gp96, which suggests a potential use for hyposensitive anticancer drugs in HSP-based dendritic cell vaccine preparation and chemoimmunotherapy for HCC patients.