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FOXM1-mediated regulation of reactive oxygen species and radioresistance in oral squamous cell carcinoma cells

ABSTRACT: Radioresistance is a major obstacle to the successful treatment of oral squamous cell carcinoma (OSCC). To help overcome this issue, we have developed clinically relevant radioresistant (CRR) cell lines, generated by irradiating parental cells over time, which are useful for OSCC research. In the present study, we conducted gene expression analysis using CRR cells and their parental lines to investigate the regulation of radioresistance in OSCC cells. Based on gene expression changes over time in CRR cells and parental lines subjected to irradiation, forkhead box M1 (FOXM1) was selected for further analysis in terms of its expression OSCC cell lines, including CRR cell lines, and clinical specimens. We suppressed or upregulated the expression of FOXM1 in OSCC cell lines, including CRR cell lines, and examined radiosensitivity, DNA damage, and cell viability under various conditions. The molecular network regulating radiotolerance was also investigated, especially the redox pathway, and the radiosensitizing effect of FOXM1 inhibitors was examined as a potential therapeutic application. We found that FOXM1 was not expressed in normal human keratinocytes but was expressed in several OSCC cell types. The expression of FOXM1 was upregulated in CRR cells compared with that detected in the parental cell lines. In clinical specimens, FOXM1 expression was upregulated in cells that survived irradiation. FOXM1-specific siRNA treatment increased radiosensitivity, whereas FOXM1 overexpression decreased radiosensitivity, and DNA damage was altered significantly under both conditions as well as the levels of redox-related molecules and reactive oxygen species production. Treatment with the FOXM1 inhibitor thiostrepton had a radiosensitizing effect and overcame radiotolerance in CRR cells. According to these results, the FOXM1-mediated regulation of reactive oxygen species could be a novel therapeutic target for the treatment of radioresistant OSCC; thus, treatment strategies targeting this axis might overcome radioresistance in this disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE210922 | GEO | 2022/10/01

REPOSITORIES: GEO

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Project description:Pancreatic ductal adenocarcinoma is one of the most aggressive cancer types and is well-known for its general low intrinsic radiosensitivity. In order to resolve mechanisms of how PDAC cells carry out radioresistance, a combination of proteomics and phosphoproteomics of two radiosensitive as well as radioresistant murine PDAC cell lines upon exposition to radiation was performed. A high depth of (phospho)proteomic identifications with > 13000 confidently identified phosphorylation sites and > 7800 proteins was achieved. Measuring the response of the phosphoproteome upon radiation revealed >700 phosphorylation sites on >400 proteins which were regulated in all four cell lines independently of the sensitivity status. This analysis validated already known radiomarkers but also uncovered novel members of the radiation-dependent signaling network in PDAC cells that were shown to be exclusively based on protein phosphorylation but not protein expression. Among those radioresponsive phosphoproteins were ten novel ATM substrates, which were validated by in vitro kinase assays. Comparison of radiosensitive and -resistant cells revealed a complex regulation of apoptotic processes, while changes in expression of DNA repair proteins seemed to not play a pivotal role. Especially increased expression of NQO1 was found to be a potential mechanism enabling resistance by clearing harmful reactive oxygen species from the PDAC cells. Further analysis of the radioresistance-associated-phosphoproteome, which was especially enriched in phosphoproteins with cytoskeleton organizational function, uncovered increased Actin dynamics and FAK activity in radioresistant cells. Both likely lead to increased survival, migrational capacity and perturbations in chromatin condensation which could oppose radiation. Based on the displayed adaptions in cellular protein expression and signaling in resistant PDAC cells, pharmacological inhibition of NQO1 and FAK could be suggested to sensitize towards radiation.

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FOXM1-mediated regulation of reactive oxygen species and radioresistance in oral squamous cell carcinoma cells

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