Vitamin C counteracts miR‐302/367‐induced reprogramming of human breast cancer cells and restores their invasive and proliferative capacity

Abstract

Epigenetic reprogramming by embryonic stem cell-specific miR-302/367 cluster has shown some tumor suppressive effects in cancer cells of different tissues such as skin, colon, and cervix. Vitamin C has been known as a reprogramming enhancer of human and mouse somatic cells. In this study, first we aimed to investigate whether exogenous induction of miR-302/367 in breast cancer cells shows the same tumor suppressive effects previously observed in other cancer cells lines, and whether vitamin C can enhance reprogramming of breast cancer cells and also improve the tumor suppressive function of miR-302/367 cluster. Overexpression of miR-302/367 cluster in MDA-MB-231 and SK-BR-3 breast cancer cells upregulated expression of miR-302/367 members and also some core pluripotency factors including OCT4A, SOX2 and NANOG, induced mesenchymal to epithelial transition, suppressed invasion, proliferation, and induced apoptosis in the both cell lines. However, treatment of the miR-302/367 transfected cells with vitamin C suppressed the expression of pluripotency factors and augmented the tumorigenicity of the breast cancer cells by restoring their proliferative and invasive capacity and compromising the apoptotic effect of miR-302/367. Supplementing the culture medium with vitamin C downregulated expression of TET1 gene which seems to be the reason behind the negative impact of vitamin C on the reprogramming efficiency of miR-302/367 cluster and its anti-tumor effects. Therefore application of vitamin C may not always serve as a reprogramming enhancer depending on its switching function on TET1. This phenomenon should be carefully considered when considering a reprogramming strategy for tumor suppression.

miR‐16 enhances miR‐302/367‐induced reprogramming and tumor suppression in breast cancer cells

“…Therefore, suppression of BMI‐1 by miR‐16 may provide a good reason for repression of EMT in the breast cancer cells we studied. Furthermore, BMI‐1 is also repressed by miR‐302 cluster, and therefore miR‐16 may augment the suppressive impact of miR‐302 on both invasiveness and proliferative capacity of different cancer cells as we reported previously …”

“…Previously, we demonstrated some antitumor effects of miR‐302abcd and miR‐302/367 clusters in melanoma, colon, and breast cancer cells . We showed that overexpression of miR‐302/367 cluster upregulated OCT4A , SOX2 , NANOG , LIN28A , and KLF4 expression in MDA‐MB‐231 and SK‐BR‐3 cells while MYC was downregulated . Although the transcription factors in this study did not show exactly the same expression pattern following the miR‐16 transfection, exogenous miR‐16 augmented, miR‐302/367‐induced reprogramming by upregulating OCT4A , SOX2 , NANOG , and LIN28A expression in MDA‐MB‐231 and OCT4A , NANOG , LIN28A , and KLF4 expression in SK‐BR‐3 cells.…”

“…As previously reported miR‐302 or miR‐302/367 clusters target some of the cell cycle regulators and induces cell cycle arrest at in G1/G2 phases . Also, miR‐302 promotes somatic cell reprogramming, directly targets CDK2 , CCND1 / CCND2 , and BMI1 , and accumulates the cells in G1/S checkpoint .…”

“…Upregulation of β‐catenin protein in the breast cancer cells by miR‐16 inhibitor indicates a significant role for miR‐16 in regulation of β‐catenin expression and Wnt/β‐catenin signaling pathway. We previously reported downregulation of vimentin and β‐catenin in BC cells after transfection with miR‐302/367 vector . Here, we detected that these proteins are suppressed even more by miR‐16 after miR‐302/367 overexpression in the BC cells.…”

“…Accumulating evidence is indicating miR‐302 cluster as a miRNA family with tumor suppressive characteristics, which can alleviate tumorigenicity of cancer cells by reversal of EMT, induction of apoptosis, and its antiproliferative effect . Previously, we demonstrated some antitumor effects of miR‐302abcd and miR‐302/367 clusters in melanoma, colon, and breast cancer cells . We showed that overexpression of miR‐302/367 cluster upregulated OCT4A , SOX2 , NANOG , LIN28A , and KLF4 expression in MDA‐MB‐231 and SK‐BR‐3 cells while MYC was downregulated .…”