MiR-34a is up-regulated in response to low dose, low energy X-ray induced DNA damage in breast cells

Abstract

BackgroundMicroRNAs are non-coding RNAs involved in the regulation of gene expression including DNA damage responses. Low doses of low energy X-ray radiation, similar to those used in mammographic exams, has been described to be genotoxic. In the present work we investigated the expression of miR-34a; a well described p53-regulated miRNA implicated in cell responses to X-ray irradiation at low doses.MethodsNon-cancerous breast cell line MCF-10A and cancerous T-47D and MCF-7 cell lines were submitted to a low-energy X-ray irradiation (ranging from 28–30 Kv) using a dose of 5 Gy. The expression level of miR-34a, let-7a and miR-21 was assessed by qRT-PCR at 4 and 24 hours post-irradiation. DNA damage was then measured by comet assay and micronuclei estimation in MCF-10A and MCF-7 cell lines, where an increase of miR-34a levels could be observed after irradiation. The rate of apoptotic cells was estimated by nuclear staining and fluorescence microscopy. These experiments were also performed at low doses (3; 12 and 48 mGy) in MCF-10A and MCF-7 cell lines.ResultsWe have observed an increase in miR-34a expression 4 hours post-irradiation at 5 Gy in MCF-10A and MCF-7 cell lines while its level did not change in T-47D, a breast cancer cell line bearing non-functional p53. At low doses, miR-34a was up-regulated in non-tumoral MCF-10A to a higher extent as compared to MCF-7. MiR-34a levels decreased 24 hours post-irradiation. We have also observed DNA damage and apoptosis at low-energy X-ray irradiation at low doses and the high dose in MCF-10A and MCF-7 4 and 24 hours post-irradiation relative to the mock control.ConclusionLow energy X-ray is able to promote DNA strand breaks and miR-34a might be involved in cell responses to low energy X-ray DNA damage. MiR-34a expression correlates with X-ray dose, time after irradiation and cell type. The present study reinforces the need of investigating consequences of low dose X-ray irradiation of breast cells.

MiRNA expression profile of ionizing radiation‐induced liver injury in mouse using deep sequencing

“…IR treatment on mouse could upregulate the family of miR‐34, including miR‐34a‐3p, miR‐34a‐5p, miR‐34b‐3p, and miR‐34c‐3p. The results validated by the qRT‐PCR were in consistent with former studies (Stankevicins et al, ). In fact, accumulating evidence informed that miR‐34a could be induced by IR in vitro and in vivo (He et al, ; Cong et al, ).…”

Neoadjuvant Chemotherapy in Breast Cancer Patients Induces miR‐34a and miR‐122 Expression

“…The tumor itself is a known source of circulating miRNAs. In vitro experiments have notably demonstrated that several tumor cell lines exposed to cytotoxic agents or ionizing radiation re‐expressed miR‐34a (Tazawa et al, ; Ghawanmeh et al, ; Chiyomaru et al, ; John‐Aryankalayil et al, ; Stankevicins et al, ; Wang et al, ). Our team also observed miR‐34a overexpression in breast tumor tissues after the NAC.…”

Low-Dose Gamma Irradiation Enhances Superoxide Anion Production by Nonirradiated Cells Through TGF-β1-Dependent Bystander Signaling

“…Numerous studies have demonstrated that LDIR exposure alters miRNA levels, which ultimately leads to modified protein expression profiles. miRNAs such as miR-21, miR-34a, miR-29c, miR-16, miR-202, miR-303 and miR-572 are all LDIRresponsive miRNAs implicated in radiation-induced altered gene regulation (92)(93)(94)(95). Interestingly, LDIR-mediated miRNA alterations demonstrate temporal regulation.…”