Evaluation of Curcumin as a Supplement to Improve Mitotane Effects on Adrenocortical Carcinoma

For many types of cancer, pre-clinical studies have shown that dietary interventions and supplements can be effective in reducing the toxicity and increasing the efficacy of chemotherapeutics. In this context, the polyphenol curcumin is an attractive molecule. We have previously demonstrated that curcumin inhibits adrenocortical carcinoma (ACC) cell growth, has an impact on ACC cell metabolism, decreasing cholesterol availability and promoting glucose and glutamine metabolism. In this study, we evidenced that curcumin downregulates the transcription factors SF-1 and SREBPs and their targets, while inducing a ROS-dependent, HIF1 alpha- and NRF2-mediated metabolic rewiring. NRF2 sustained an adaptive antioxidant mechanism dependent on glutamine, cysteine, and glycine uptake to support glutathione synthesis and avoid lipid peroxidation. Furthermore, the combination of curcumin with mitotane demonstrated synergistic effects in inhibiting ACC cell viability and reducing steroidogenic gene expression. These synergistic effects were observed with sub-therapeutic doses of mitotane, which are reached by patients who fail to attain the therapeutic plasma concentrations of the drug. Crucially, in vivo, curcumin administration to tumor-free mice significantly upregulated NRF2 expression and preserved liver tissue integrity. These results warrant further preclinical evaluation of the proposed combination therapy, particularly for those patients who fail to achieve or maintain mitotane plasma concentrations in the therapeutic range.