Viability of HepG2 and MCF-7 cells is not correlated with mitochondrial bioenergetics

Abstract

Alterations in metabolism are a hallmark of cancer. It is unclear if oxidative phosphorylation (OXPHOS) is necessary for tumour cell survival. In this study, we investigated the effects of severe hypoxia, site-specific inhibition of respiratory chain (RC) components, and uncouplers on necrotic and apoptotic markers in 2D-cultured HepG2 and MCF-7 tumour cells. Comparable respiratory complex activities were observed in both cell lines. However, HepG2 cells exhibited significantly higher oxygen consumption rates (OCR) and respiratory capacity than MCF-7 cells. Significant non-mitochondrial OCR was observed in MCF-7 cells, which was insensitive to acute combined inhibition of complexes I and III. Pre-treatment of either cell line with RC inhibitors for 24–72 h resulted in the complete abolition of respective complex activities and OCRs. This was accompanied by a time-dependent decrease in citrate synthase activity, suggesting mitophagy. High-content automated microscopy recordings revealed that the viability of HepG2 cells was mostly unaffected by any pharmacological treatment or severe hypoxia. In contrast, the viability of MCF-7 cells was strongly affected by inhibition of complex IV (CIV) or complex V (CV), severe hypoxia, and uncoupling. However, it was only moderately affected by inhibition of complexes I, II, and III. Cell death in MCF-7 cells induced by inhibition of complexes II, III, and IV was partially abrogated by aspartate. These findings indicate that OXPHOS activity and viability are not correlated in these cell lines, suggesting that the connection between OXPHOS and cancer cell survival is dependent on the specific cell type and conditions.

Synthesis of Triphenylphosphonium-Linked Derivative of 3,5-Ditert-butyl-4-hydroxybenzylidene-malononitrile (SF6847) via Knoevenagel Reaction Yields an Effective Mitochondria-Targeted Protonophoric Uncoupler

“…Resazurin-based measurements of cell survival in the presence of SF-C n -TPP (Figure ) showed rather low toxicity of these compounds toward MRC5-SV40 cells at submicromolar concentrations that caused a marked decrease in mitochondrial membrane potential (Figure a). This result is consistent with recent findings indicating that cell viability could not be correlated with mitochondrial bioenergetics …”

“…This result is consistent with recent findings indicating that cell viability could not be correlated with mitochondrial bioenergetics. 46 …”

Comparison of HepaRG and HepG2 cell lines to model mitochondrial respiratory adaptations in non‑alcoholic fatty liver disease

“…It is possible that the methods used to evaluate cell death in the present study may not have been as sensitive as those used in previous studies ( 45 , 48 ). Of note, the study by Doczi et al ( 63 ) demonstrated that the viability of HepG2 cells was not decreased by the complete inhibition of mitochondrial respiration. Nonetheless, in agreement with the study by Amorim et al ( 15 ), the FFA-treated HepG2 cells exhibited compensatory mitochondrial proliferation marked by the increased expression of the PPARGC1A gene and citrate synthase activity, secondary to excessive mitochondrial damage.…”

Complex I activity in hypoxia: implications for oncometabolism

“…However, the deeper dispute is whether cancer cell survival actually depends on OXPHOS. Our recent contribution to this was to show that depending on the cancer cell culture type and targeted inhibition of respiratory components, OXPHOS can be demonstrated but could be dispensable for cell survival [ 12 ]. Therefore, we proposed that the association between OXPHOS and tumor viability likely relies on the particular cell type and the precise means of respiratory inhibition.…”