Low-Dose Celastrol Modulates IL-6 Secretion to Overcome Resistance to Sorafenib in Hepatocellular Carcinoma Cells.

Background: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality, with sorafenib being a key treatment option. However, resistance to sorafenib often develops, limiting its effectiveness. Celastrol, a phytochemical derived from Objectives: This study investigated whether celastrol at plasma-achievable concentrations could modulate sorafenib resistance in HCC cells in-vitro. Methods: Cytotoxicity experiments were conducted using MTT assays to assess the effects of celastrol and sorafenib on HCC cells and normal hepatocytes. Immunofluorescence (IF) and ELISA assays were employed to measure IL-6 expression and secretion in HCC cells. Bioinformatics analyses were performed on publicly available gene expression data to identify pathways associated with sorafenib resistance. Conditioned media (CM) from treated cells were used to evaluate the impact of celastrol on sorafenib sensitivity in untreated HCC cells. Results: High concentrations of celastrol enhanced sorafenib's inhibitory effects on HCC cells but also increased cytotoxicity in normal hepatocytes. Low concentrations of celastrol mitigated sorafenib-induced tumor cell inhibition but reversed acquired sorafenib resistance without increasing cytotoxicity in normal hepatocytes. The reversal of resistance by low-dose celastrol was associated with the inhibition of sorafenib-induced IL-6 secretion. The CM from tumor cells treated with low-dose celastrol plus sorafenib increased the sensitivity of untreated tumor cells to sorafenib, an effect reversed by the addition of exogenous IL-6 or by using IL-6-neutralizing antibodies. Conclusions: Low-dose celastrol can reverse sorafenib resistance in HCC cells by inhibiting sorafenib-induced IL-6 secretion, without increasing hepatotoxicity.