Influence of ionizing radiation in miRNAS levels of breast cancer stem cells

Abstract

Objective: To study the difference in expression of specific microRNAs involved in hypoxia and DNA damage response in irradiated breast cancer stem cells (BCSCs) versus non-irradiated BCSCs. Methods: Breast adenocarcinoma cell line MDA-MB-231 was selected for the study. MDA-MB-231 BCSCs were isolated by using flow cytometry to detect ALDH activity, obtaining positive (sorter+) and negative (sorter-) populations. These populations were cultured in sphere culture medium including general population (non-sorted). After 72 h, cells were irradiated with different doses and incubated during 24 h for RNA isolation. RT-qPCR was used to study the expression of two selected miRNAs. Results: miRNAs examined were as follows: Hsa-mir 210, Hsa-mir 24, and standardized control GADPH. When non-sorted cells were irradiated with 2 Gy, the expression of mir 210 was 0.41 versus control; when these cells were irradiated with 6 Gy, the expression was 3.23. The expression of mir 210 in sorter+ cells was 91.40 in non-irradiated cells, 26,42 in cells irradiated with 2 Gy and 10,88 in those irradiated with 6 Gy. The expression of mir 24 in non-sorted cells was 1.49 in those irradiated with 2 Gy and 0.31 in those irradiated with 6 Gy. The expression of mir 24 expression in sorter+ cells was 3,08 in non-irradiated cells, 1-11 in in those irradiated with 2Gy and 0.87 in those irradiated with 6 Gy. Conclusions: Ionizing radiation affects the expression levels of miR 210 and miR 24 in non-sorted and ALDH+ BCSCs. Ionizing radiation decreases miR 210 and miR 24 expressions in a dose-dependent manner in ALDH+ BCSCs.