MiR-7-5p Is Involved in Ferroptosis Signaling and Radioresistance Thru the Generation of ROS in Radioresistant HeLa and SAS Cell Lines

Abstract

In cancer therapy, radioresistance or chemoresistance cells are major problems. We established clinically relevant radioresistant (CRR) cells that can survive over 30 days after 2 Gy/day X-ray exposures. These cells also show resistance to anticancer agents and hydrogen peroxide (H2O2). We have previously demonstrated that all the CRR cells examined had up-regulated miR-7-5p and after miR-7-5p knockdown, they lost radioresistance. However, the mechanism of losing radioresistance remains to be elucidated. Therefore, we investigated the role of miR-7-5p in radioresistance by knockdown of miR-7-5p using CRR cells. As a result, knockdown of miR-7-5p increased reactive oxygen species (ROS), mitochondrial membrane potential, and intracellular Fe2+ amount. Furthermore, miR-7-5p knockdown results in the down-regulation of the iron storage gene expression such as ferritin, up-regulation of the ferroptosis marker ALOX12 gene expression, and increases of Liperfluo amount. H2O2 treatment after ALOX12 overexpression led to the enhancement of intracellular H2O2 amount and lipid peroxidation. By contrast, miR-7-5p knockdown seemed not to be involved in COX-2 and glycolysis signaling but affected the morphology of CRR cells. These results indicate that miR-7-5p control radioresistance via ROS generation that leads to ferroptosis.

Mitochondrial Dysfunction in Diseases, Longevity, and Treatment Resistance: Tuning Mitochondria Function as a Therapeutic Strategy

“…These results show that plasma membrane status and lipid peroxidation enzyme activity are very important in oxidative stress resistance. overexpression of ALOX12 enhances ROS generation and amount of HNE, which is one of the lipid peroxidation by-products [116]. These results indicate that the CRR cells inhibit ferroptosis and show resistance from oxidative stress via decreasing mitochondrial function.…”

“…For example, when ALOX was administrated into isolated mitochondria, cytochrome c release and ROS generation were observed [ 115 ]. Furthermore, it has been reported that ALOX expression was enhanced in CRR cells, and overexpression of ALOX12 enhances ROS generation and amount of HNE, which is one of the lipid peroxidation by-products [ 116 ]. These results indicate that the CRR cells inhibit ferroptosis and show resistance from oxidative stress via decreasing mitochondrial function.…”

“…These results suggest that mitoferrin have an important role in CRR cell characteristics. Recently, inhibition of mir-7-5p decreased intracellular and mitochondrial ROS, enhanced JC-1 signal, which is an indicator of ΔΨm, downregulated the ferritin gene expression, and enhanced the ALOX12 gene expression [ 116 ]. In contrast, ρ 0 cells show high Fe 2+ amount, high lipid peroxidation, and low ALOX expression.…”

Contribution of Lipid Oxidation and Ferroptosis to Radiotherapy Efficacy

“…Additionally, lipid metabolism regulates lipid membrane composition. Repeated radiotherapy exposure to fractionated radiotherapy can generate cancer cell lines resistant to radiation [45]. Work has shown that in cervical cancer cells, upregulation of MiR-7-5p promotes radiotherapy resistance by silencing arachidonate 12-lipoxygenase (ALOX12) and other components of ferroptosis signaling, thus limiting radiotherapy efficacy [45].…”

“…Repeated radiotherapy exposure to fractionated radiotherapy can generate cancer cell lines resistant to radiation [45]. Work has shown that in cervical cancer cells, upregulation of MiR-7-5p promotes radiotherapy resistance by silencing arachidonate 12-lipoxygenase (ALOX12) and other components of ferroptosis signaling, thus limiting radiotherapy efficacy [45]. Together, these data suggest that lipid metabolism can be therapeutically targeted to improve radiotherapy efficacy.…”