Confocal Raman imaging reveals the impact of retinoids on human breast cancer via monitoring the redox status of cytochrome c

This paper expands the current state of knowledge on impact of retinoids on redox status of cytochrome c in cancers. Little is known how the expression of cytochromes may influence the development of cancers. We studied the effect of the redox status of the central iron ion in heme of cytochrome c. We determined the redox status of the iron ion in cytochrome c in mitochondria, cytoplasm, lipid droplets, and endoplasmic reticulum of the human breast cancer cells by Raman imaging. We incubated human breast adenocarcinoma cells (SK-BR-3) with retinoic acid, retinol and retinyl ester (palmitate) at concentration of 50 μM for 24 h. We recorded the Raman spectra and images of human breast cancer in vitro SK-BR-3 cells receiving redox stimuli by retinoic acid, retinol and retinyl ester (palmitate). The paper provides evidence that retinoic acid and retinol are pivotally important for mitochondrial energy homeostasis by controlling the redox status of cytochrome c in the electron transport chain controlling oxidative phosphorylation and apoptosis. We discussed the role of retinoids in metabolism and signaling of cancer cells. The paper provides experimental support for theoretical hypothesis how retinoic acid/retinol catalyse resonance energy transfer reactions and controls the activation/inactivation cycle of protein kinase PKCδ.