cel-mir-237 and its homologue, hsa-miR-125b, modulate the cellular response to ionizing radiation

Abstract

Elucidating the mechanisms involved in sensitizing radioresistant tumors to ionizing radiation (IR) treatments while minimizing injury to surrounding normal tissue is an important clinical goal. Due to their sequence-derived specificity and properties as gene regulators in IR-affected pathways, microRNAs (miRNAs) could serve as adjuvant therapeutic agents that alter cellular sensitivity to radiation treatment. To identify radiosensitizing miRNAs, we initially utilized the C. elegans vulval cell model, an in vivo system developed to study IR-dependent radiosensitivity as a measure of clonogenic cell death. We tested several candidate miRNA deletion mutants post γ-irradiation and identified cel-mir-237 as a miRNA which when deleted caused animals to be more resistant to IR, while cel-mir-237 overexpressing strains were IR-sensitive. Additionally, wild-type animals downregulated cel-mir-237 levels post IR in a time-dependent manner. We identified jun-1 (JUN transcription factor homolog) as a novel target of cel-mir-237. Specifically, jun-1 transcript levels increased in wild-type animals post-γ-irradiation, and loss of cel-mir-237 also resulted in higher jun-1 expression. As expected, loss of jun-1 resulted in IR sensitivity, similar to the phenotype of cel-mir-237 overexpressors. Since miR-237 is the homologue of human miR-125, we validated our findings in MCF-7 and MDA-MB-231 breast cancer cell lines, which harbor lower hsa-miR-125b levels than normal HMECs. Forced expression of hsa-miR-125b in these cells resulted in radiosensitivity, as seen by reduced clonogenic survival, enhanced apoptotic activity, and enhanced senescence post IR. Finally, re-expression of c-JUN in MDA-MB-231 cells promoted radio-resistance and abrogated miR-125-mediated radio-sensitization. Our findings suggest that overexpression of cel-mir-237 and its homologue, hsa-miR-125b, functions as sensitizers to γ-irradiation in both a nematode in vivo model and breast cancer cells, and could potentially be utilized as an adjuvant therapeutic to enhance radiation sensitivity.

miRNAs as radio‐response biomarkers for breast cancer stem cells

“…Besides, miR-142, which downregulates BCSC phenotype and decreases radioresistance in vitro (Troschel et al, 2018), and miR-15b that belongs to the miR-15 family related to BC cell radiosensitivity by influencing G 2/M checkpoint proteins (Mei et al, 2015) increased at 6 Gy in MCF-7-BCSCs. In agreement with these results, several miRNAs such as miR-139, miR-125b, and mir-223 considered as tumor suppressors and that increase after IR are related to radiosensitivity and as markers of response to RT (Fabris et al, 2016;Metheetrairut et al, 2017;Pajic et al, 2018).…”

Exercise and weight loss interventions and miRNA expression in women with breast cancer

“…The criterion for candidate miRNA inclusion was as follows, 1) to be associative with known breast tumorigenic processes 25, 48–50 ; and/or 2) known to regulate pathways associated with metabolism 51–53 , adipogenesis, and/or obesity 54–56 ; and/or 3) previously identified to be detectable in circulating biofluids such as plasma or serum 57–59 . We identified 68 miRNAs eligible for analysis; these miRNA were assessed in crude serum isolates from the HOPE trial utilizing the probe-hybridization multiplex profiling assay mentioned above 44 .…”

Animal Models to Study MicroRNA Function

“…In multiple human cancers, the two miR-125 family members, miR-125a/b are severely under-expressed, specifically in leukemia 144 and melanoma 145 , and ovarian 146 , breast 147 , oral 148 and thyroid 149 carcinomas. In concert, ectopic miR-125 prevents cellular proliferation and migration in bladder cancer 150 , inhibits epithelial–mesenchymal transition (EMT) of triple-negative breast cancer cells 151 , and induces radiosensitivity and chemosensitivity in breast cancer and osteosarcoma, respectively 152,153 .…”