Role Of Estrogen Receptors And Prothymosin Alpha In Human Gastric Adenocarcinoma

The hormone estrogen has been implicated in the development of gastric cancer, however, its role in the gastric cancer is presently unclear. Ever since the estrogen receptor (ER) beta was discovered in 1996, its value as a prognostic or predictive factor in cancer and its potential as a novel target for pharmacological intervention are still being investigated. To date, only limited data regarding the detection of ERβin gastric tumors and cell lines are available. The significance of ERs' expression and hormone manipulation in gastric cancer is not established.Prothymosin alpha (ProTα) is an abundant small unusually mammalian acidic, natively unstructured protein nuclear protein with widespread tissue distribution. While the exact mechanism of action of ProTαremains elusive, the one constant has been its relationship with the proliferating state of the cell. Recent work indicates that ProTαis involved in apoptosis. Because the overexpression of ProTαnot only maintain cells in highly proliferating status, but also increase resistance of cancer cells during apoptosis, new potential research focuses concerning its prognostic significance.The aim of this work was to investigate the presence of estrogen receptors (ERs)(ERαand ERβ) and ProTαin human gastric cancer tissue and cells and the extent of this expression and estimate the value of both ER subtypes in gastric adenocarcinoma and analyze the possible relationship of ProTαto ERs. Gastric adenocarcinoma cell lines and clinical tumor sample were analyzed for genetic and expression alteration. Constitutive ERs mRNA levels in clinical samples and cell lines (BGC-823 and SGC-7901) by reverse transcription-PCR (RT-PCR), and ERs in protein levels were further studied in 2 cells by immunocytochemistry (ICC).Partâ… andâ…¡Clinical significance of expression of estrogen receptors and ProTαin gastric adenocarcinomaImmunohistochemistry (IHC) was performed to detect ERs and ProTαprotein expression in formalin-fixed paraffin-embedded clinical paired samples of cancerous and non-cancerous tissues from patients with gastric adenocarcinoma. For ERs and ProTα, positivity was defined as nuclear staining in >10% of the cancer cells. And the protein expression was measured by a quantitative method using computer-aided Image Pro-plus 4.5 software. Another 20 normal gastric mucosa biopsy was used as control. Using reverse transcription polymerase chain reaction (RT-PCR), the expression levels of ERαand ERβmRNAs were measured. The relative expression level of ERs were compared between normal and cancer tissues, and also compared according to various clinicopathological parameters.In this study, we quantitatively examined ERαand ERβat the transcript and protein levels by RT-PCR and IHC in clinical gastric adenocarcinoma tissues to compare with that of the corresponding non-cancerous tissues. Both ERαand ERβmRNAs were detected in gastric cancer and normal matched tissues. However, at the protein level, the percentage of ERαand ERβpositive cases changed. No normal gastric tissue stained positive for ERα. ERαimmunoreactivity was only detected in poorly differential adenocarcinoma tissues and ERαpositive expression correlated with depth of invasion of the tumors. Compared with non-cancerous tissues, gastric tumors showed decreased ERβexpression and lost ERβ. ERβpositive expression in gastric adenocarcinoma correlated with decreased differentiation (P=0.041). In tumor tissue, part of tumors lost ERβcompared with corresponding non-cancer tissue and the mean ERβexpression of the other tumor was about 1/3 of that in matched non-cancer tissues(P=0.04). And the tumors involved lymph nodes metastasis showed significantly lower expression level of ERβ(P=0.036). Tumors showed, on average, 9-fold higher expression of ProTαthan that in corresponding non-cancer tissue and normal mucosa (P=0.000), and 1.4-fold higher expression of ProTαin ERβ-positive tumors than that in ERβ-negative tumor, however, the difference was not statistically significant.However, RT-PCR analyses revealed that ERαand ERβmRNAs levels were no significantly altered in gastric tumors compared with normal mucosa in patients. This information of changed ERαand ERβpositive cases at the mRNA and protein levels, suggests that the lack of ERs protein expression is not due to the lack of ERs gene expression or methylation of ERs promoter, but due to post-transcriptional or posttranslational mechanisms.Partâ…¢Effects of Estradiol and Tamoxifen on human gastric cancer cells and ProTαmRNARecently, ProTαhas also shown are one of estradiol-response genes in some cells. Whether there is a possible relationship of ProTαto ERs in gastric carcinogenesis is not known. We have analyzed whether transcripts of ERαand ERβwere expressed in two gastric cancer cell lines established from Chinese with gastric adenocarcinoma (SGC-7901 and BGC-823) by RT-PCR and ICC. In the two gastric cancer cell lines, SGC-7901 expressed ERαalong and BGC-823 cells exhibited ERαand ERβ. The ERβexpression was at a lower level than ERαin BGC-823 cell line and the level of ERs expression was lower than that observed in breast carcinoma cell line MCF-7.The aim of the current study is to demonstrate gastric cancer cells as targets for receptor-mediated estrogenic and antiestrogenic action. To evaluate the potential of using antiestrogens as gastric cancer therapies, we have assessed the growth-inhibitory action of estrogen (estradiol, E₂) and antiestrogen (tamoxifen, TAM) on these cultures. MTT assay and Hoechst 33258 staining were used to detect cytotoxicity and apoptosis. To investigate the possible mechanism of E₂ and TAM in human gastric cancer, the effects of E₂ and TAM on ProTαmRNA regulation in BGC-823 cell were estimated by RT-PCR.E₂ induced proliferation in both cell lines (P<0.05). Unlike the MCF-7 cells, which responded to the low concentration (1nM), the treated SGC7901 and BGC-823 cells have mainly been affected at a higher dose (10nM) at which a significant increase was also obtained on the ProTαmRNA level in BGC-823 (P<0.05).TAM had growth-inhibitory effects and induced apoptosis in both cell lines (P<0.05). Interestingly, BGC-823 displayed an increased apoptosis at a lower dose (1μM) of TAM than SGC7901 (10μM).Our results suggest that estrogen signaling plays a biological role in the stomach epithelium and estrogens could potentially promote ER positive gastric cancer. The E2-depending proliferation of 2 cell lines by ERαmainly. TAM has an effect of growth inhibitory and induced apoptosis on gastric cancer cells in vitro. This anti-proliferative effect of TAM in these 2 gastric cells may occur not only by blocking ERαbut also by activating ERβ. It is possible that antiestrogens may have therapeutic value to treat certain gastric adenocarcinomas. On the other hand, 1μM TAM had growth-inhibitory effects and induced apoptosis with effectively decreased the expression of ProTαmRNA (P<0.05). Our results suggest that estrogen signaling pIays a biological role in the stomach epithelium and estrogens could potentially promote ER positive gastric cancer through direct and indirect actions on ProTα.Partâ…£Effect of ProTαantisense oligodeoxynucletides on BGC-823 growthGastric cancer is the malignant tumor of harming human health. Gene therapy may become the therapy methods to those patients who losing operation time. Therefore, search of new target genes suitable for gastric cancer is needed. Inhabiting proliferation of tumor cells and inducing their apoptosis via gene transfer is one of the strategies for cancer gene therapy, and blocking proliferation of tumor maybe one of the important ways that inhibit tumor cells.In our previous study, significant increases in the expression of ProTαhave been found in gastric adenocarcinoma specimens. To deploy a possible therapeutic approach of ProTα-targeted in human gastric adenocarcinomas, ProTα-AS-ODNs were transient transfected into BGC-823 cells to down-express ProTα, MTT assay and Hoechst 33258 staining were used to detect cytotoxicity and apoptosis. RT-PCR was used to evaluate mRNA levels. The results showed that down-expressed ProTαmay induce a complete inhibition of cell proliferation to apoptosis in a dose-dependent manner. The efforts aiming at cutting down ProTαexpression may prove to be an attractive alternative therapy against gastric cancer. Our findings emphasize the role of ERs and ProTαduring gastric adenocarcinoma transformation and progression. Altered expression of ERαand ERβin tumors compared with corresponding normal gastric tissues related to lower differentiation of histologic type and malignant properties such as lymph node metastasis, which suggeste ERαand ERβexpression status could perhaps be a potential biomarker in gastric tumorigenesis/progression and clinical prognosis in certain advanced gastric adenocarcinomas. ProTαis commonly overexpressed in advantaged gastric adenocarcinoma, which indicated that ProTαmay represent an useful biomarker to assist in the diagnosis of gastric cancer. Our in vivo and in vitro observations have important clinical implications in which ERs and ProTαin tumor can be used as an important therapeutic target.