In Vivo Study On ERβ Inducing The Apoptosis In Hormones Independent Prostate Cancer Cell

There are two kinds of ER, estrogen receptor alpha (ERα) and estrogen receptorbeta (ERβ). Both of these two receptors are expressed in human prostate. ERβ showshigh expressed level in normal prostate, and mostly localized to the basal epithelialcompartment of the normal prostate.But there are growing evidences show that a progression loss of ERβ exprssion inprostate cancer compared with normal prostate, and is associated with normal prostateepithelium developed into prostate cancer. These studies about loss the expression ofERβ during carcinogenesis add to an accumulating body of evidences supporting apotential protective role of ERβ. Findings in ERβ knockout mice indicated that theseanimals develop prostatic hyperplasia in old age, a phenomenon that does not occur inERα knockout mice, this evidence suggestes that ERβ potential protective role inprostate epithelial cells. Furthermore, other studies have shown that ERβ may exert aprotective effect against aberrant cell proliferation and/or carcinogenesis, ERβ isanti-proliferation and proapoptotic in the prostate and also have shown that in coloncancer, breast cancer, ovarian cancer. So, ERβ have an important research value inprostate tumorigenesis and development.We have constructed the recombination plasmid pcDNA3.1-ERβ which with thehuman estrogen receptor2(ERβ) full length cDNA, and transfected it into humanandrogen-independent prostate cancer cells PC-3M and PC-3. It’s shown that ERβ caninhibit the cells’ proliferation and invasion, induce cells’ apoptosis, and we also foundthat ERβ can inhibit the expression of Akt (protein kinase B) in the pro-survivalpathway.In current research shows that Akt existed as activated phosphorylation state inprostate cancer, ovarian cancer, breast cancer, colon carcinoma etc., and closely correlated with tumorous genesis and development. Akt existed in cells as adephosphorylation state, and transported to cytoplasm or cell nucleus after activated.It was activated as a phosphorylation state by binding with substrate protein andactivated Akt (p-Akt) can regulate the downstream target gene, promote the growth ofcancer cells, angiogenesis, invasion and metastasis and inhibit the apoptosis.In this study, by construct the nude mice prostate orthotopin transplantation cancermodel, the attenuated Salmonella carrying pcDNA3.1-ERβ plasmid was given to themice prostate tumor tissue, in vivo experimental observation the effect of ERβinducing prostate orthotopin transplantation cancer apoptosis.Purpose:Construct the prostatic orthotopic transplantation cancer models of nude mice,attenuated salmonella carrying pcDNA3.1-ERβ plasmid to observe the effect of ERβon the apoptosis of orthotopic transplantation prostatic cancer in nude mice.Methods:The prostatic orthotopic transplantation cancer models of mice were built, themice were randomly divided into MOCK group treated with PBS, PQ group treatedwith attenuated salmonella alone, pcDNA3.1group treated with attenuated salmonellacarrying pcDNA3.1plasmid, pcDNA3.1-ERβ group treated with attenuatedsalmonella carrying pcDNA3.1-ERβ plasmid, three days after operation,10μl PBSand10μl1×107bacteria intranasal drug delivery to give each group respectively, onthe tenth day, the second treatment was given in the first manner. The general states ofmice and the tumors growth were observed. All animals were sacrificed when thetumor in the control group grows to a certain size. Amounts of apoptosis in tumorcells were analyzed with AnnexinⅤ and TUNEL assay. The protein expression levelsof PCNA were analyzed with immunohistochemistry. The protein expression levels ofERβ and p-Akt, Bad/Bcl-xl, cleaved caspase9, cleaved caspase3, cleaved PARP wereanalyzed with western blot. The mRNA expression levels of Akt, Bcl-xl and caspase3were analyzed by PCR. Results:Compared with Mock group, PQ group, pcDNA3.1group, the degrees of micecachexia in pcDNA3.1-ERβ group were significantly reduced, the tumor weight weredecreased and the tumor growth were inhibited. The result of AnnexinⅤ and TUNELrevealed that there are apoptosis cells in pcDNA3.1-ERβ group. The result ofimmunohistochemistry revealed that PCNA expression levels in pcDNA3.1-ERβgroup were decreased. Compared with Mock group, PQ group, pcDNA3.1group, theprotein expression levels of ERβ, Bad/Bcl-xl, cleaved caspase9, cleaved caspase3andcleaved PARP in pcDNA3.1-ERβ group were significantly increased (P<0.05), theprotein expression level of p-Akt were decreased (P<0.05). Compared with Mockgroup, PQ group, pcDNA3.1group, the Akt, Bcl-xl and caspase3mRNA expressionlevels were reduced in pcDNA3.1-ERβ group (P<0.05).Conclusion:ERβ was able to induce apoptosis of orthotopic implantation prostatic cancercells in mice, indicate that ERβ is closely related to prostate tumorigenesis. Themechanism of induce apoptosis is ERβ inhibits Akt activity, which lead relieves theAkt inhibition its downstream target genes Bad, the increased activity of pro-apoptoticprotein Bad and/or anti-apoptotic protein Bcl-xl reduced, then activation of caspase9and caspase3cascade, inducd the apoptosis of tumor cells.