Up-regulation Of Muc4by β2-AR Activation Induces The Resistance To Herceptin Of Grastric Cancer Cells

Background: Many investigators have reported that grastric cancer has been a major threat topeople’s health in global especially in China. An epidemiological investigation of grastric cancer showedthat mental stress is the primary one among lots of risk factors. A plenty of experimental results haveproved an intimate relationship between chronic stress and cancer progression and poor prognosis.Epinephrine is one of stress related hormone. Sustained increased levels of epinephrine are found in cancerpatients who often experience chronic stress. In our laboratory ‘s previous study, we found that β2-AR,oneof the major receptor of epinephrine,is over epressed in many epithelial carcinomas including grastriccancer.The activation of β2-AR can regulate many signal transduction pathways of responded with theevolution of tumors advancement. However, the underlying mechanism remains largely unknown.Since Her2have been proved to have an over-expression in several kinds of gastric cancer, with apositive expression in20%to30%in advanced gastric cancer patients. In February2010, Herceptin–ahumanized monoclonal antibody directed against the HER2receptor–was approved by FDA to be used asthe first targeted therapy in advanced gastric cancer. The European Commission approved Herceptin incombination with chemotherapy for use in patients with metastatic gastric cancer exhibiting high levels ofHER2, in January2010. The data of the clinal trial showed that patients with HER2protein over-expressionbenefit from this type of anti-HER2therapy.However, resistance to Herceptin in breast cancer is common,and its cause is as yet unclear. It is an important task to understand the mechanism of Herceptin resistancein breast and other cancers,including of gastric cancer.Methods:(1)Immunohistochemical methords were employed to detect the expression models ofβ2-AR in gastric cancer tissues.(2)Dual-Luciferase reporter gene system to detecting the activity of MUC4primer.(3)RT-PCR, real time PCR, western blot and confocal immunofluorescence microscopy are usedin detecting the expression ways of MUC4in gene level and protein level.(4)We then examined the role ofStat3and Erk pathway in signal transductision by Western Blot.(5)RNA interfere technique were used to knock down the MUC4expression in gastric cancer cell line N87. Roles of MUC4in regulating theantigen binding activity of Herceptin were investigated by Flow Cytometry.(6)Established the N87Xenograft in nude mice model and investigated the role of MUC4up-regulation by activation of β2-AR..(7)Detecting the expression models of β2-AR and MUC4in human gastric cancer tissues byimmunohistochemistry.Result:(1)The pattern of β2-AR expression in gastric cancer tissue shows β2-AR may be involvedinvasion, proliferation, inflammation, and malignancy. β2-AR may be a useful malignant marker for gastriccancer.(2)Catecholamine up-regulated MUC4in Her2overexpressing gastric cancer cells, via β2-ARmediated signaling pathway.(3)Catecholamine up-regulated MUC4in gastric cancer cells at protein level.(4)Epi up-regulated MUC4in gastric cancer cells at transcription level.(5)Activation of STAT3and ERKplay key roles in up-regulation of MUC4triggered by ISO.(6)ISO induced off-target of Herceptin byupregulation of MUC4in Her2overexpressing gastric cancer cells.(7)ISO induces up-regulation of MUC4and Herceptin resistance in N87in vivo. Continuous stimulation of ISO induced liver metastasis of N87xenograft in nude mice.(8)MUC4and β2-AR co-expression in human gastric cancer tissue.Conclusion: In this study we firstly proved that β2-AR is over-expressing in advanced gastriccancer and detected the expression models of β2-AR in gastric cancer tissues. We firstly reported theup-regulation of MUC4by β2-AR activation induces the resistance to Herceptin of gastric cancer cells andthe chronic activation of β2-AR induces Herceptin fail to inhibit the growth of tumor xenograft in nudemice. Furthermore, we firstly reveal a totally novel mechanism of Herceptin resistance in gastriccancer model.demonstrate that MUC4may serve as a potential target for the therapy of gastric cancer. Thefurther development of our study may prove some scientifc theory basises for improving the clinical effectsof Herceptin and anti-resistance of Herceptin.