significant impact of let-7d microrna on breast cancer cell lines post-radiation treatment

Introduction: radiotherapy is a common treatment for breast cancer treatment, that induces dna damage. these dna damages are addressed through various repair pathways, which regulate the dna repair systems and confer radio-resistance. non-coding rnas are a big proportion of genome transcripts without the potential to encode proteins. related studies demonstrated that radiation affects the expression of non-coding rnas. let-7d, a tumor suppressor in numerous cancers, has some target genes that play a role in the dna repair system.materials and methods: human breast cancer cell lines mda-mb-231 and mcf-7 were cultured in a dulbecco’s modified eagle medium. the exponentially growing cells were treated with some doses of x-rays. after radiation treatment and cell harvesting, rna was extracted, and cdna synthesis was done. the let-7d mirna expression changes were calculated with real-time quantitative reverse transcription polymerase chain reaction. results: the results implied that radiation caused increased let-7d expression in breast cancer cell lines after radiation treatment. in addition, the results showed that 24 h after radiation, the expression of let-7d in the radioresistant cell line was higher than the radiosensitive one; 48 h after radiation, the expression of let-7d in the radiosensitive cell line was higher than the other one. conclusions: the results demonstrated that radiation treatment increased let-7d mirna expression in both radiosensitive and radio-resistant breast cancer cell lines. therefore, let-7d might be involved in the radiosensitivity of breast cancer.