ERK1/2-Dependent Inhibition of Glycolysis in Curcumin-Induced Cytotoxicity of Prostate Carcinoma Cells

Object. Extracellular acidosis of the tumor microenvironment plays an important role in cancer progression. In the 2D monolayer and 3D spheroid cultures of prostate cancer cells, we investigated the efficacy of curcumin in targeting glycolysis and the role of ERK1/2 as an upstream signaling molecule in this process. Methods. Cell viability, glycolytic activity, Annexin V-PE binding activity, reactive oxygen species levels, mitochondrial membrane potential, ATP content, Western blot analysis, and spheroid viability were measured for this study. Results. Acidic pH-tolerant prostate cancer cells, PC-3AcT and DU145AcT, increased cytotoxicity with ERK1/2 inhibition in a curcumin concentration-dependent manner at concentrations that resulted in >90% cell viability in normal prostate epithelial HPrEC cells. ERK1/2 inhibition by curcumin and/or PD98059 suppressed cell growth, reduced glucose consumption, and downregulated the expression of key regulatory enzymes in glucose metabolism including hexokinases, phosphofructokinase, and pyruvate dehydrogenase. In addition, these compounds caused loss of mitochondrial membrane potential with increased intracellular ROS levels, decreased levels of complexes I, III, and IV in the mitochondrial electron transport chain, and cellular ATP depletion, leading to upregulation of marker proteins in apoptosis (cleaved caspase-3 and cleaved PARP) and necroptosis (p-MLKL and p-RIP3). The results of curcumin and/or PD98059 treatment in 3D cultures showed similar trends to those in 2D cultures. Conclusion. Taken together, the results provide mechanistic evidence for the antiglycolytic and cytotoxic roles of curcumin through inhibition of the MEK/ERK signaling pathway in prostate carcinoma cells preadapted to acidic conditions.