“Metabolic Reprogramming” in Ovarian Cancer Cells Resistant to Cisplatin

Abstract

The way cancer cells escape cisplatin-induced apoptosis has not been completely elucidated yet. We questioned the relevance of "metabolic reprogramming" in cisplatin-resistance by studying mitochondrial function and metabolism in human ovarian carcinoma cell lines, both cisplatin-sensitive (2008) and resistant (C13). C13 cells, in comparison to 2008 cells, showed lower apoptotic response to cisplatin exposure, lower basal oxygen consumption (4.2±0.2 vs 6.5±0.7 fmol/cell/min, p<0.005) and a lower basal transmembrane mitochondrial potential (Δψm) (18.7±1.5 vs 32.2±1 MFI p<0.001). Moreover, C13 cells showed a lower sensitivity to rotenone and oligomycin, two mitochondrial respiratory chain inhibitors. To further investigate the impact of mitochondria on cisplatin-resistance, 2008 and C13 cells were depleted of their mitochondrial DNA (rho(0)-clones). The cytotoxicity of cisplatin was lower in 2008-rho(0)clones than in 2008 cells (IC(50) of 3.56 µM and 0.72 µM, respectively) but similar between C13-rho(0) and C13 cells (IC(50) of 5.49 µM and 6.49 µM, respectively). The time-course of cell viability in glucose-free galactose medium indicated that C13 cells are more strictly dependent on glucose than 2008 cells. (1)H-NMR spectroscopy showed a higher basal content of intracellular glutathione (GSH) and mobile lipids (MLs) in C13 cells as compared to 2008 cells, with higher lipid accumulation mainly within cytoplasmic droplets of the C13 cells. These findings allow us to propose a "metabolic remodelling" of ovarian carcinoma cells to a lipogenic phenotype, which includes alteration of mitochondrial function, as an advantageous mechanism to escape cisplatin-induced apoptosis. This hypothesis is of interest to exploit new pharmacological targets to improve the clinical impact of platinum drugs.