XL-888

Combination therapy has been frequently preferred in treating various types of cancer in recent years. Targeted cancer therapy has also become one of the remarkable treatment modalities. Therefore, the aim of the study to investigate its cytotoxic and apoptotic effects on liver cancer cell lines by combining the classical chemotherapeutic drug doxorubicin (DOX) and a targeted agent, the new generation HSP90 inhibitor XL-888. The molecular docking method was used to predict the binding conformation of XL-888 on the human Hsp90. The single and combined cytotoxic effects of DOX and XL-888 on liver cancer cell lines HepG2 and HUH-7 were determined by MTT assay. The effect of the combined use of two drugs was evaluated using Chou and Talalay method. The levels of apoptotic genes and heat shock proteins gene and protein expression levels were investigated by quantitative real-time polymerase chain reaction and western blotting, respectively. Molecular docking results showed that XL-888 selectively binds to the ATP binding pocket of HSP90 with an estimated free binding energy of - 7.8 kcal/mol. DOX and XL-888 and their combination showed dose-dependent cytotoxic effect. The combination of drugs showed a synergistic effect on both cell lines. The results revealed that the combination of DOX and XL-888 potently induced apoptosis in liver cancer cell lines rather than using drugs alone. The combined treatment of DOX and XL-888 demonstrated synergistic cytotoxic and apoptotic effects on liver cancer cell lines, presenting a promising approach for combination therapy in liver cancer.

Radiofrequency ablation (RFA) is the first-line option for early-stage hepatocellular carcinoma (HCC). However, the residual tumor attributed to insufficient RFA (iRFA) led to tumor recurrence and metastasis. Novel combination strategies are urgently needed to enhance efficiency of RFA.

For in vitro iRFA models, HCC cells were placed in a water bath at 46 °C for 10 min and then returned to the original incubator. For in vivo models, HCC cells were implanted subcutaneously into nude mice. The nude mice were then randomly assigned into 4 groups: control group, XL888 group, iRFA group, combination of XL888 and iRFA group. CCK8 was performed to detect cell viability; Hoechst 33258 was used to explore nuclear morphology; The expression levels of proteins were demonstrated by western blotting; Co-localization of HSP90 and STAT3 was elucidated by immunofluorescence confocal microscopy; Immunohistochemistry was used to explore expression levels of proteins at tissue level.

XL888 promoted apoptosis of HCC cells induced by heat via inhibiting expression levels of Mcl-1 and cleaved-caspase 3 in vivo and in vitro. XL888 attenuated the complex formation of HSP90 and STAT3, leading to decreased expression levels of STAT3 and p-STAT3. In human HCC tissues, IHC scores of HSP90 were positively correlated with those of STAT3. Overexpression of STAT3 rescued cell apoptosis induced by co-treatment of XL888 and heat.

We implied that XL888 promoted apoptosis of HCC cells induced by heat via disrupting the binding of HSP90 and STAT3, providing theoretical basis for a novel combination strategy for HCC.