oa The Embryonic Stem (ES)-specific microRNA, miR-302, is highly expressed in a rare subpopulation of glioma cell lines

MiR-302s is a cluster of polycistronic microRNAs that are exclusively expressed in embryonic stem (ES) cells. MiR-302s' promoter is functional during embryonic development, but it is turned off in later stages. Based on cancer stem cell hypothesis, some pluripotency-associated genes are re-expressed in some tumor tissues and cell lines. In the present study, we have tried to expand our knowledge about the expression pattern and functionality of miR302s by quantifying its expression in a series of glioma (A-172, 1321N1, U87MG) and medulloblastoma (DAOY) cell lines. Furthermore, to assess the functionality of miR-302 in these cell lines, we cloned its promoter core region upstream of the EGFP or luciferase encoding genes. Our data revealed a very low expression of miR-302s in glioma cell lines, compared to that of embryonal carcinoma cell line NT2 being used as a positive control. The expression of miR-302 promoter-EGFP construct in the aforementioned cell lines demonstrated GFP expression in a rare subpopulation of the cells. Serum deprivation led to the generation of tumorospheres, enrichment of miR-302 positive cells, and upregulation of a number of pluripotency genes. To find out whether miR-302 has a causative role in these events, we transfected the 1321N1 cell line with an expression vector containing the sequences of all miR-302 members. MiR-302s expression caused tumorospheres formation as well as a significant upregulation of pluripotency genes. Taken together, our data introduces a novel putative cancer stem cell marker that could potentially be used to identify and target cancer stem cells within tumor tissues.

Afsaneh Malekzadeh Shafaroudi1, Mahmoud-Reza Rafiee2, Sara Rohban3, Hamid Reza Kalhor4, Seyed Javad Mowla1,3*

1 Parsgenome Company, Tehran, Iran 2 Nanomedicine and Tissue Engineering Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran 4 Omics Research Center, Golestan University of Medical Sciences, Gorgan, Iran