Senescence is a defining feature of premalignant tumors, andsenescent cells do not exist in malignant tumors. cell proliferation. Our data suggest that miR-127 may function as a tumor suppressor that modulates the oncogene BCL6. Introduction Cellular senescence was originally described by Hayflick five decades agoas an irreversible proliferation arrest of normal somatic cells . Cellular senescence occurs in culture and in vivo as a response to extracellular and intracellular stresses, including telomere dysfunction, DNA damage caused by radiation or chemicals, and oncogenic or mitogenic stimuli , . Cellular senescence causes SR3335 permanent cell cycle arrest and, thereby, acts as a potent tumor suppression mechanism that prevents the oncogenic transformation of primary human cells , . Senescence is usually a defining feature of premalignant tumors, andsenescent cells do not exist in malignant tumors. The induction and maintenance of cellular senescence is largely dependent on either or both of the p53/p21 and p16INK4a/pRB tumor suppressor pathways . Recent studies haveindicated that microRNAs regulate cellular senescence by targeting the key regulators of cellular senescence pathways . MicroRNAs (miRNAs) are small noncoding RNAs that play an important role in a variety of SR3335 biological processes by negatively regulating expression of specific target genes at the post-transcriptional level. miRNAs regulate a variety of target genes involved in multiple pathways and processes, such as development, apoptosis, proliferation, differentiation, transformation, and cellular senescence , . Using microarray, we previously identified a set of miRNAs differentially expressed in proliferating versus senescent human fibroblasts. miR-127-3p is one of the miRNAs that was up-regulated in senescent WI-38 and IMR-90 cells . miR-127-3p and miR-127-5p are two mature miRNAs that are processed from the same precursor miRNA; hereafter, miR-127-3p will be referred to as miR-127. miR-127 is located in chromosome region 14q32.2 and belongs to a cluster that includes miR-431, miR-433, miR-127, miR-432, and miR-136 . miR-127 and miR-433 are transcribed from impartial promoters in overlapping genomic regions,and expression of these two miRNAs is usually induced by estrogen related receptor gamma (ERR) and inhibited by small heterodimer partner (SHP), a unique orphan nuclear receptor and transcriptional repressor C. It was reported that miR-127targets proto-oncogene BCL6 . miR-127 is usually expressed at its highest level during the late stage of fetal lung development and may thus play an important role in this process . In addition, miR-127 has been shown to regulate BCL6-mediated expression of CDKN1A (p21). In rat liver cells, down-regulation of miR-127 promotes cell proliferation, while up-regulation of miR-127 inhibits proliferation . These observations suggest important functions for miR-127 in cell proliferation, differentiation, SR3335 and development. Here, we show that miR-127 induces senescence in human fibroblasts and inhibits the proliferation of breast malignancy cells by targeting the oncogene BCL6. Additionally, we found an inverse correlation of expression between BCL6 and miR-127 in primary breast tumors versus adjacent normal tissues. Our data suggest that miR-127 is usually a novel senescence-associated (SA)-miRNA that regulates cellular senescence. Results miR-127 Overexpression Induces Cellular Senescence in Human Fibroblasts Using microarray, we previously reported that miR-127 is usually differentially expressed in young replicating versus senescent WI-38 cells . To further confirm the microarray data, we performed real-time RT-PCR analysis on miR-127 in young proliferating and senescent WI-38 cells and IMR-90 cells. The results showed that miR-127 expression was up-regulated in senescent WI-38 cells and IMR-90 cells (Physique 1A). These findings suggest that miR-127 is usually a novel SA-miRNA. To SR3335 investigate the involvement of miR-127 in cellular senescence in human fibroblasts, we induced miR-127 expression by transfecting a miR-127 duplex mimic into the young proliferating human fibroblast cell lines WI-38 and IMR-90. We observed that induced miR-127 expression caused a remarkable inhibition of cell proliferation (Physique 1B) and increased senescence-like phenotypes with positive staining of senescence-associated–galactosidase (SA–gal) (Physique 1C) in both WI-38 and IMR-90 cells. In addition, the senescence-like phenotype was associated withup-regulation of p53 and p21 and down-regulation of cyclin D1 (a pattern associated with senescence) in both WI-38 and IMR-90 cells (Physique 1D). As expected, miR-127 overexpression induced cell cycle arrest at G0/G1 phase (Physique 1E). This indicates that over-expression of miR-127 induces Rabbit Polyclonal to STK33 cellular senescence. To ensure that the observed effects of the miR-127 duplex mimic were not associated with supraphysiologic.
Senescence is a defining feature of premalignant tumors, andsenescent cells do not exist in malignant tumors