Study On ER-α36and EGFR Mediated Signaling Pathway In Gastric Cancer

Gastric cancer represents the fourth most common cancer and the second leading cause of cancer death worldwide. It remains difficult to cure and has a poor overall prognosis. Surgical resection with total or subtotal gastrectomy is a major treatment. The molecular and cellular events during development of gastric cancer remain unclear. Findings of recent studies have shown that there is a possible correlation of estrogen with the biological activity of gastric cancer cells. The incidence of gastric cancer is higher in men than in women before menopause. The incidence of gastric cancer in women after menopause reaches a level similar to men.Recently, estrogen receptor-a36(ER-a36), a novel variant of the full-length66kDa ER-a66, was identified and cloned. This variant differs from ER-a66by lacking the transcriptional activation function domains (AF-1and AF-2), but retains the partial dimerization and ligand-binding domains and DNA-binding domain. ER-a36possesses unique27-aa domain to replace the last138-aa encoded by extrons7and8of ER-a66gene. Current research found that ER-a36is mainly localized on the membrane and modulates nongenomic signaling pathways, such as MAPK/ERK, PI3K/Akt, and PKC pathway, which participate in the development and progression of many types of cancers. Breast cancer cell line MCF-7that constitutively express high levels of recombinant ER-a36exhibited insensitivity to tamoxifen treatment. Although ER-α36has been extensively studied in other types of cancer, no investigation has been conducted in gastric cancer.Epidermal growth factor receptor (EGFR), is a cellular transmembrane glycoprotein receptor for the members of EGF family of extracellular protein ligands. It constitutes one of four members of erbB family of tyrosine kinase receptors:HER1, HER2(c-erbB-2), HER3(c-erbB-3) and HER4(c-erbB-4). EGFR is overexpressed in a majority of solid tumors and has been associated with poor prognosis and decreased survival. Over expression of EGFR plays an important role in activating the growth factor signaling. Researches found that EGFR is involved in the development of gastric cancer. Studies have shown that EGF could stimulate the mitogen-activated protein kinase (MAPK) pathway, causing an increase in the level of phosphorylation of AF-1domain of ER-a66, which results in the expression of estrogen-response genes. Taken together, estrogen receptor and EGFR may act coordinately in the development of gastric cancer.In the present study, we aimed to establish the evidence that ER-a36plays a role in the EGFR-related gastric cancer and explore its potential mechanism, hoping to provide a new insight to the complicated genesis and treatment of gastric cancer.Objective To study of correlation with expression of ER-a36and clinicopathological parameters in gastric cancer tissue. Methods To develop tissue microarray of gastric cancer. The expression of ER-a36was determined on the section of tissue microarray by immunohistochemistry using anti-ER-a36antibody. To analyze correlation expression of ER-a36with clinicopathological parameters in gastric cancer.Results ER-a36mainly localizes in the cytoplasm and plasma membrane in gastric cancer tissue.33cases of67gastric cancer caseswere ER-a36positive (62.3%). There is a correlation between expression of ER-a36with histological differentiation. ER-a36expression was not associated with gender, age, tumor size, tumor stage and lymph node metastasis. Conclusion The ER-a36positive rate was62.3%in gastric cancertissue.The ER-α36positive rate was higher in high differentiation group than that of low differentiation group. Objective To study of correlation between expression of ER-a36、EGFR and phospho-ERK in human gastric cancer tissue. Methods24human gastric cancer frozen tissue were collected. Expression of protein ER-a36、EGFR and phospho-ERK in human gastric cancer tissue was determined using Western blot. Results The ER-a36positive rate was75%(18/24). The EGFR positive rate was70.8%(17/24). The pERK positive rate was58.3%(14/24). The EGFR positive rate in the ER-a36positive group (88.9%,16/18) was higher than that of ER-a36negative group (16.7%,1/6)(P<0.01). The ER-a36positive rate in the EGFR positive group (94.1%,16/17) was higher than that of (94.1%,16/17) negative group (28.6%,2/7)(P<0.01). The phospho-ERK positive rate in the ER-a36positive group (72.2%,13/18) was higher than that of negative group (16.7%,1/6))(P<0.01). The phospho-ERK positive rate in the EGFR positive group (76.5%,13/17) was higher than that of negative group (14.3%,1/7)(P<0.01). In addition, the ER-a36positive rate in the13EGFR-positive and phospho-ERK-positive samples was92.3%(12/13). The EGFR positive rate in the13ER-a36-positive and phospho-ERK-positive samples was also92.3%(12/13). Conclusion There is a correlation between expression of ER-α36、EGFR and phospho-ERK in human gastric cancer tissue. Dbjective To study of ER-a36and EGFR-ERK signaling pathway in gastric cancer cell line SGC7901. Methods We established stable SGC7901cell lines transfected with knocked-down levels of ER-a36expression using the small hairpin RNA (shRNA) method (SGC7901-Low36cells). Similarly, SGC7901cell lines with overexpressed levels of ER-a36was also established using the shRNA method (SGC7901-High36cells).Results EGF induced dose-dependent and time-dependent increase in ERK1/2phosphorylation. The level of ERKl/2phosphorylation of SGC7901-High36cell was higher than that of SGC7901-Low36cells by EGF stimulated. Conclusion ER-a36mediates EGF-stimulated ERK activation in gastric cancer cell.