Role Of MiR-221 In Regulatingnormal Mammary Epithelial Hierarchy And Breast Cancer Stem-like Cells

Increasing evidence suggests that lineage specific subpopulations and stem-likecells exist in normal and malignant breast tissues. Epigenetic mechanisms maintainingthis hierarchical homeostasis remain to be investigated. In this study, we found thelevel of microRNA221 (miR-221) was higher in stem-like and myoepithelial cells thanin luminal cells isolated from normal and malignant breast tissue. In normal breastcells, over-expression of miR-221 generated more myoepithelial cells whereas knockdown of miR-221 increased luminal cells. Over-expression of miR-221 stimulatedstem-like cells in luminal type of cancer and the miR-221 level was correlated withclinical outcome in breast cancer patients. Epithelial-mesenchymal transition (EMT)was induced byoverexpression of miR-221 in normal and breast cancer cells. TheEMT related gene ATXN1 was found to be a miR-221 target gene regulating breast cellhierarchy. In conclusion, we propose that miR-221 contributes to lineage homeostasisof normal and malignant breast epithelium.Human embryonic stem cell (ES) can self-renewal and differentiation into all kinds of types of cell. Studying the mechanisms of hES regulation plays an key role in regenerative medicine and developmental biology. We used the results of gene expression profile of ES and a whole genome RNA interference screen used H1 cell line with GFP reporter gene driven by OCT4 promoter to choose 129 genes for next research, such as TAF6, PRMT5 and PHC1. We used shRNA or esiRNA to downregulate the expression of chosen genes, and determined the expression of genes which are the markers for hES. We found knockdown of some genes could cause hES differentiate, knockdown of some genes could influence the pluripotency. We chose PIM2 for further research. When PIM2was downregulated, we found the key sternness genes didn’t changed, such as OCT4, SOX2 and Nanog. We next determined the expression of marker genes of endoderm, mesoderm and ectoderm used embryoid body, we found the genes for mesoderm were upregulated, the genes for endoderm and ectoderm were downregulated, when PIM2 was downregulated. This suggested PIM2 promoted hES differentiate into mesodermal tissues. We further demonstrated the primary tissues are mesodermal tissues in teratomas, once PIM2 knockdown. These suggested PIM2 is a regulator of pluripotency.