Analysis Of Expression Mechanism And Anticancer Function Of CREB In Prostate Cancer Cell DU145

Cell signaling plays an important role in cell proliferation, differentiation, apoptosis, and cellular interaction. It is regulated by various factors. CREB, a second messenger cAMP response element binding protein is a nuclear transcription factor. It contains341amino acids and belongs to leucine zipper (bZIP) protein family. Its secondary structure contains two functional regions. The C-terminal region is rich in basic amino acids, forming a leucine zipper domain (Leucine zipper region) of approximately50amino acids where the leucine residue appear periodically. The helical crimp conformation of the C-terminal displays strong affinity to DNA, is thus called DNA binding domain. The N-terminal is a transcriptional regulatory domain, which is rich in acidic amino acids. This domain is further subdivided into the following subdomains:KID area (multiple kinases-induced subdomain), X zone (the zone mediating antagonistic function against KID), A zone (enhancing CREB transcription function), Q3district (stimulation of key parts of the transcriptional activity), Q2region (secondary transcription) and PRO Zone (help to play a role in transcription). These domains work together to regulate transcription of its target genes.As a nuclear transcription factor, CREB is involved in various cellular activities. Depending on the phosphorylation status, CREB responds to various signaling pathways and regulate different target gene promoters. Ultimately, it affects transcription of various cell cycle-related proteins such as CDKs, Cyclins, CKIs to mediate cell cycle regulation. CREB also relates cell apoptosis. Studies have shown that in human cardiac cells, peroxisome can stimulate expression of receptor a (PPARa) and thus inhibit Bcl-2to induce apoptosis. While an increase in CREB expression can alleviate such inhibition. Furthermore, CREB is also closely related to apoptosis of tumor cells. Study of non-small cell lung cancer cell lines (NSCLC) reveals that downregulation of CREB with RNAi can inhibit apoptosis in NSCLC. Since CREB is implicated in regulation of cell cycle and apoptosis, and it is also involved in apoptosis of lung cancer cells, it is likely to play important roles in carcinogenesis. Therefore, we have conducted experimental analysis on CREB regulation of prostate cancer development using DU145cells as a testing system.Through the establishment of the CREB (the PP2A positive regulatory factor) over-expression cell line, DU145-CREB and the vector-transfected cell line DU145-Neo, we have conducted a series of experiments including cell growth analysis, cell migration assay, nude mice xenograft experiments and Western blot analysis to explore the CREB regulation mechanisms in prostate cancer DU145. Our results have shown following results. First, the growth rate of DU145-CREB is slower than that of DU145-Neo. Second, DU145-CREB cells migrate much slower than DU145-Neo cells in wounding assay. Third, tumors derived from DU145-CREB cells in nude mice is significantly smaller than those injected with DU145-Neo cells. Moreover, the tumors from DU145-CREB cells is less vascularized and display lower proliferative rate than the tumors derived from DU145-Neo cells. These results suggest that CREB may have inhibitory function on prostate cancer development.