Proinflammatory Cytokines Increase Hepatocellular Carcinoma Cells Thermotolerance: Evidence of How Local Inflammation May Negatively Impact Radiofrequency Ablation Local Control Rates

Background: Hepatocellular carcinomas (HCC) associated with inflammation that undergo radiofrequency ablation (RFA) appear to have poorer local control rates. Little is known of how mediators of inflammation influence HCC cellular thermotolerance, which in part is mediated by heat shock protein 70 (HSP70). This study determines how inflammatory mediators affect cellular thermotolerance and provides insight into how associated inflammation may impact HCC RFA local control rates. Methods: HepG2 cell lines were cultured in control medium (CM) or CM containing conditioned medium of endotoxin-activated macrophage (CMM). Serial dilutions of CMM established microenvironments approximating low, medium, and high CMM. All groups underwent a heat shock challenge (HSC) at 45°C for 10 min. Western blot, Northern blot, densitometric analysis, along with thymidine and clonogenic assays determined how inflammation influenced multiple biological endpoints. Results: Cells cultured in low CMM expressed significantly more HSP70 RNA and protein compared with control cells after HSC. The cells also had a higher proliferative and survival rate after HSC compared with control cells. Medium CMM cultured cells had no significant difference in HSP70 RNA and protein production or proliferation and survival rates after HSC, compared with CM cultured cells. AT high CMM, the inhibitory effects of inflammatory mediators prevailed and all of the measured endpoints were significantly less compared with CM cultured cells. Conclusions: This study demonstrates that inflammation can alter the responsiveness of HCC cells to a HSC in a dose-dependent manner. This study supports the clinical observation that HCC associated with chronic inflammation have worse RFA local control rates.