A Study On The Prognosis Of Gastric Cancer At Different Sites And Altitudes And On The Role Of EPAS-1 In The Regulation Of Drug Resistance In Gastric Cancer

Background and aim:Cardia cancer arises from esophagogastric junction.Although the incidence of non-cardia gastric cancer(GC)is gradually decreasing worldwide,the incidence of cardia GC has been increasing in some regions including China,especially in Western countries.Cardia cancer is speculated to have different causes and clinicopathologic features than non-cardia GC.Few studies investigate the prognostic factors of patients with cardia cancer undergoing RO resection and the different prognosis between cardia GC and non-cardia GC after RO operation and their conclusions are mixed.Therefore,the clinicopathologic features and prognosis of cardia GC after RO resection remain unclear,especially to the distinct prognosis between stage-for-stage prognoses of cardia GC and non-cardia GC.The aim of this study was to evaluate clinicopathological characteristics and prognosis between cardia and non-cardia GC.Methods:From December 2009 to December 2011,consecutive patients with a histologically confirmed diagnosis of primary GC treated with RO resection(i.e.,microscopically negative)at four hospital in China were enrolled.Clinicopathological features,including age,sex,ethnicity,date of surgery,anatomic subsite,histological type,pTNM stage,type of gastrectomy,lymphovascular and perineural invasions,(neo)adjuvant chemotherapy,(neo)adjuvant radiotherapy,date of relapse,and follow-up,were analyzed.Data about disease-free survival(DFS)and overall survival(OS)were collected and analyzed.Patients were divided into the cardia GC group and the non-cardia GC group.The different clinicopathological features and survival outcomes between two groups were compared.Results:1633 patients were finally enrolled and divided into two groups:cardia GC group,n = 581 patients and non-cardia GC group,n = 1052 patients.The clinicopathological variables of the patients with cardia GC and those with non-cardia GC are compared.Ethnicity and neural invasion were similarly distributed in the two groups.However,older age at diagnosis(P<0.001),higher percentage of men(P<0.001),higher proportions of pT3 and pT4 cases(P<0.001),positive lymph node involvement(P = 0.003),pathological stage ?-?(P<0.001),moderate histological differentiation(P<0.001),and lymphatic and venous invasions(P = 0.035)were observed in the cardia GC group.For treatment variables,the prevalence of treatment with lymphadenectomy(P = 0.088),neoadjuvant chemotherapy alone(P?0.489),neoadjuvant chemoradiotherapy(P=1.000),or adjuvant chemotherapy alone(P = 0.068)did not significantly differ between the groups.However,more cardia GC than non-cardia GC were treated with adjuvant chemoradiotherapy(P =0.006).For survival analysis,compared with non-cardia GC,cardia GC had a shorter 5-year DFS(50.84%vs.59.22%,P<0.001).It is interesting that when DFS was analyzed according to each pathological stage,the patients with early-stage cardia GC had a shorter 5-year DFS(stage I:77.88%vs.86.92%,P = 0.038).However,no differences in outcome were noted for stage ?-?.For overall pTNM stage,the 5-year OS rate of the cardia GC group(55.57%)was lower than that of the non-cardia GC group(62.38%;P = 0.005).However,when OS was analyzed according to pTNM stage,no significant differences were found between the two groups.Similarly,such outcomes were also found based on the analysis according to pT or pN stage(P all>0.05).The univariate analysis of cardia GC survival revealed that OS was associated with age,pathological stage,tumor grade,lymphatic and venous invasions,and neural invasion.Specifically,Cox analysis revealed pathological stage III remained an independent prognostic factor of shorter OS(P<0.001),while stage II approached the threshold of statistical significance(P = 0.054).Conclusions:Cardia GC had older age at diagnosis,higher percentage of men,more-significant distinct clinicopathological features and more-advanced pathological stage at diagnosis than non-cardia GC.For overall pTNM stage,the 5-year DFS rate of the cardia GC was lower than that of the non-cardia GC.Most notably,cardia GC had similar prognosis as non-cardia GC,at least for stage II and III disease.Moreover,pathological stage was confirmed as an independent prognostic factor of cardia GC.More-advanced disease represents most of the cases in this Chinese population.Therefore,the outcomes in patients with cardia GC could be similar with those in patients with non-cardia GC as long as the former patients undergo early clinical examinations for early diagnosis and receive appropriate treatment.Background and aim:Among the environmental factors,Helicobacter pylori is generally accepted as the major cause for GC.Moreover,geographic factors also play an important role in GC carcinogenesis.GLOBOCAN 2012 data revealed that the highest incidence rates of GC are in Eastern Asia.High altitude is a special environment and hypoxia is one of the most prominent features in this area.Some studies report that high altitude is also related to a higher GC incidence and mortality of patients.However,no systematic study is available to date that focused on the different traits and prognosis of GC at high altitude and in the plains.This multicenter study compared different clinicopathological characteristics and prognosis of patients with resected GC coming from high altitude and plains in China.Methods:From December 2009 to December 2011,patients with resected GC were retrospectively recruited at four Chinese centers located at high altitude and in the plains.In this retrospective study,all of the patients were diagnosed with histologically proven primary GCs and received R0 resections(i.e.,microscopically negative)at Affiliated Hospital of Qinghai University,People's Hospital of Qinghai province,and Qinghai Red Cross Hospital or National Cancer Center/Cancer Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College,China.All patients were divided into two groups based on the place of birth and the place of residence:patients residing in places at a height more than 2200 m belonged to the high-altitude group while patients residing in places at a height less than 1000 m belonged to the plain group.The data included gender,age,ethnicity,surgical treatment,tumor location,pathological type,pTNM stage,neoadjuvant chemotherapy,neoadjuvant radiotherapy,adjuvant chemotherapy,adjuvant radiotherapy,and follow-up.Clinicopathological data were analyzed to explore the differences between the two groups.The Cox proportional-hazards model was used to investigate the prognostic factors for GC and estimate the independent impact of altitude on long-term survival after adjusting for covariates.Results:Patients in four Chinese centers were recruited,who underwent curative intent gastric resection for gastric adenocarcinoma.Of all the patients,251 were treated in hospitals at high altitude and 1382 in a hospital in the plains.Comparison between clinicopathological and treatment-related variables in the two groups of patients from different altitudes was made.In comparing patients with operable GC at high altitude with patients in the plains,patients at high altitude were significantly younger than patients in the plains.Surprisingly,subset analysis found that this discrimination only existed in patients with noncardia GC but not with cardia GC.Moreover,the proportion of other ethnicities at high altitude was higher than the proportion in the plains.The ratio of noncardia GC at high altitude was also higher than the ratio in the plains.And various tumor grades were also observed in the two groups.Moderate to well was more common in patients at high altitude than in patients in the plains,while poor to moderate was less common in patients at high altitude than in patients in the plains.In addition,more patients with GC in the plains accepted neoadjuvant chemotherapy alone and adjuvant chemo-radiotherapy compared with patients at high altitude.Statistically significant difference was found in GC-related overall 3-year survival of patients at high altitude and in the plains(70.35%and 72.22%,respectively,P = 0.172).When subgroup analysis was performed by tumor location including cardia GC and noncardia GC,data showed that GC-related 3-year survival of cardia GC was also not significantly different between patients at high altitude(72.09%)and patients in the plains(67.38%)(P = 0.987).However,a statistically significant difference was found in GC-related 3-year survival of noncardia GC between the two groups from different altitudes:69.94%at high altitude versus 75.23%in the plains(log-rank test:P = 0.033).High altitude was confirmed as a significant prognostic factor for noncardia GC(hazard ratio for high altitude vs.plain:1.50,95%confidence interval:1.14-1.97,P = 0.004)through Cox analysis.This prognostic value was independent from all other factors.Conclusions:Patients with resected GC from high altitude were of a younger age and showed a lower proportion of cardia GC but no gender and pathological stage difference compared with patients from the plains.Moreover,patients with noncardia GC coming from high altitude had a younger age of onset and a worse survival compared with the patients from the plains.In addition,high altitude was an independent poor prognostic factor for patients undergoing resection for noncardia GC.High altitude may play an important role in the onset and development of noncardia GC.Therefore,improvements in GC diagnosis and management at high altitude are urgently needed.Background and aim:Many solid tumors contain regions of hypoxia because of rapid cell proliferation,abnormal intratumoral blood vessels,and anemia.It is now extensively accepted that the unique micro-environmental conditions of solid tumors are mainly responsible for chemo/radioresistance.Besides being associated with various indicators of tumor metabolism,angiogenesis,and metastasis,hypoxia can also negatively impact the efficacy of radio-and chemotherapy.Endothelial PAS domain-containing protein 1(EPAS-1;Hypoxia-inducible factor-2a,HIF-2a)predominantly regulate the adaptation to hypoxia at the cellular or organismal level.An increasing number of recent studies have emerged reporting that EPAS-1 plays important roles in drug resistance in solid tumors.Many mechanisms participate in the roles of EPAS-1 in promoting drug resistance.Moreover,several mechanisms may prompt the drug resistance of EPAS-1 at the same time for an individual case.The drug resistance network is complex and varied in different patients with different cancers.Furthermore,drug resistance mechanisms may change in different stages in cancer development.So far,EPAS-1-mediated alterations in cell proliferation,increased ability to repair DNA,enhanced drug efflux,metabolic reprogramming,cancer stem cells(CSCs),and the signal transduction pathway were found to contribute to the mechanisms of EPAS-1-mediated drug resistance.Gastric cance(GC)is one of the foremost threatens to human health nowadays.The chemotherapy is an important option for GC patients.Although chemotherapeutic drugs were employed,the prognosis of GC patients was still low in past decades.Chemoresistance is the most common reason for the failure of therapy.Thus,it is urgent to discover new elements involved in anti-chemotherapy activity of GC.Besides,EPAS-1 proteins are expressed in various solid tumors.We anticipated that EPAS-1 also participated in drug resistance to.However,its precise mechanism remain unclear.Although the roles of proliferation,migration and invasion of EPAS-1 have been studied for years,its function in oncogenic transformation processes needs to be further investigated.This study evaluated the significance of EPAS-1 expression in relationship to GC and the mechanism of EPAS-1 involved in drug resistance of GC.This study evaluated the significance of EPAS-1 expression in relationship to GC and the mechanism of EPAS-1 involved in drug resistance of GC.Methods:The expression of EPAS-1 in paired GC tissue was detected by immunohistochemistry and the significance of EPAS-1 expression in relationship to clinicopathological factors and prognosis was evaluated.Serum concentrations of EPAS-1 in GC and volunteers were determined using validated enzyme-linked immunosorbent assay(ELISA)and the discrimination between two groups was analyzed.Protein-protein interaction between EPAS-1 and Pregnane X Receptor(PXR)was identified by co-immunoprecipitation and GST pull down assays.The association of EPAS-1,PXR and its target gene CYP3 A4 were detected by ChIP assays.The sub-cellular localization of PXR and EPAS-1 was determined by the subcellular fractionation assays.The invasion analysis of BGC-823 cells was performed by Trans-well assay.Anchorage-independent growth(soft agar)assays was used to observe the cell growth.Cell cycle and apoptosis analysis was determined by flow cytometry assays.The nude mice were used to examine the promotion of BGC-823 cells xenograft tumor in vivo.The influence of EPAS-1 on the resistance to Mitomycin C(MMC)and Paclitaxel(PTX)was invested by over-expression or reduction of EPAS-1.Results:The tumor tissue expression of EPAS-1 was associated with poor prognosis in patients with GC.Moreover,The serum EPAS-1 level in GC patients was higher than in healthy volunteers.Our results revealed that EPAS-1 interacts with PXR,a nuclear receptor that regulates multiple genes' transcription involved in multi-drugs resistance(MDR)process.Protein-protein interaction between EPAS-1 and PXR was identified by co-immunoprecipitation and GST pull down assays.By this interaction,EPAS-1 recruited PXR to its response elements in promoter/enhancer regions of CYP 3A4,a PXR target gene.Over-expression of EPAS-1 increased the expression of PXR responsive genes,enhanced the proliferation of BGC-823 cells and boosted the resistance of BGC-823 cells against the cytotoxicity of chemotherapeutic drugs,e.g.MMC and PTX.Reduction of EPAS-1 level via its siRNA disrupted the proliferation,and enhanced the susceptibility of BGC-823 cells to those chemotherapeutic drugs.In addition,EPAS-1 promoted tumor growth in vivo.Conclusions:Our findings suggested that EPAS-1 played a critical role in GC cell proliferation,survival or MDR process.EPAS-1 and PXR may cooperatively participate in development and especially MDR process of GC.These findings may contribute to more effective targeted drugs discovery for the GC therapy.