iN-myc/iDownstream Regulated Gene 1 Increases Differentiation Factors Level in Human Prostate Cancer Cells without Affecting Cell Proliferation and Cell Cycle Profiles

摘要

N-myc downstream regulated gene 1 (NDRG1), also known as differentiation related gene 1, was previously identified as an up-regulated gene upon cellular differentiation. Even though its sequence along with its expressional pattern in cancer cell lines are evident, the functional aspects concerning cell proliferation, viability, differentiation and cell cycle regulation of NDRG1 remains vague. The aim of the present study was to elucidate the functional role of NDRG1 in human prostate cancer. Our results showed basal levels of NDRG1 expression in PC-3 (poorly differentiated, null p53), DU-145 (moderately differentiated, mutant p53) and LNCaP (well-differentiated, wiled type p53). Nevertheless, NDRG1 sequencing assay disclosed no mutations in the gene. Furthermore, human cDNA of NDRG1 from normal placenta was cloned into a eukaryotic expression vector and transfected into the three cancer cell lines. This resulted in over-expression of NDRG1, which in turn markedly up regulated two differentiation markers of the prostate tissue, p21 and cytokeratin 8/18. Unpredictably, cell cycle progression, cell proliferation and DNA synthesis were unaffected following NDRG1 expression. These results revealed that NDRG1 is functional in prostate cancer cells and able to induce expression of differentiation factors through p53 independent pathway. However, the pathway downstream NDRG1, involving p21 and c8/18, regulating cell cycle progression and DNA synthesis is unfunctional. Loss of sensitivity to p21 cell cycle control may be associated with prostatic cancer behavior. Further studies are required to clarify the intra cellular molecular pathways affecting NDRG1 function in human prostate cancer.