The Study Of Neoadjuvant Chemotherapy Responsiveness And Endocrine Resistance In Breast Cancer

ObjectiveBreast cancer neoadjuvant or pre-operative chemotherapy is treatment given before primary therapy,treatingdistant micro-metastases,downstaging tumors,sometimes allowing breastconserving surgery to take place.Pathologic complete response(pCR),in which no invasive and no in siteresiduals present in breast and nodes after treatment,is a criteria used to discriminate between patientswith favorable and unfavorable outcomes of neoadjuvant chemotherapy.However,a proportion of patients may not achieve pCR after neoadjuvant chemotherapy and there is an unmet clinical need to identify biomarkers for prediction of pCR to treatment.MicroRNAs are a class of small non-coding RNA which can regulate gene expression by posttranscriptional mechanism involved in diverse cellular physiological and pathological processes.The aim of this study was to evaluate whether microRNA gene expressionprofiles in breast cancer,at the time of diagnosis,could predictpCR to taxane-anthracycline basedneoadjuvant chemotherapy.Our hypothesis is that a baseline,pretreatment microRNA expression pattern of breast cancer holds information aboutresponse to chemotherapy,and that this information can be be utilized as aclinical outcome predictor.Endocrine therapy is impotant therapy for hormonal receptor(HR+)breast cancer,its useless is limited by resistance,which can result in disease progression and patient’s death ultimately.Though molecular basis for resistance have been proposed by many investigators over the past decade,underlying mechanisms remain largely unknown.Increased expression of human epidermal growth factor receptor 2 and loss of ER expression are two key factors in endocrine resistance.The aim of the study is to analyse the expression of hematopoietic PBX-interaction protein(HPIP)in breast tissue by immunohi stochemi stry,and association with clinicopathological parameters,prognostic significance and endocrine resistance.MethodsPatients with at least four cycle of systemic neoadjuvant chemotherapy treatment:pCR(pathologic complete response)and non-pCR(non pathologic complete response)cohorts were included and archival needle aspiration tumor samples were obtained.No patient included inthis study received radiotherapy,chemotherapy orendocrine therapy before needle aspiration.MicroRNA expression profile was evaluated in the cohorts using the miRNA TaqMan Low-Density Arrays(TLDA).Through enforced or blocked expression of miR-125b and miR-141 in MCF7 and BT549 cells,we evaluated cell viability after administration of taxane and anthracycline using CCK8.Then,target gene analysis was done for predicting target genes of candidate miRNAs and those genes were further analyzed for different signaling pathways by MAS 3.0.306 primary invasive breast cancer cases dignosed between 2003 to 2007 were detected by immunohistochemistry for the expression of HPIP.We observed the correlation between expression of HPIP and prognosis(OS and DFS)and clinicopathological parameters.Besides,we determined HPIP protein expression in 208 pairs of breast tumors and matched nontumor breast tissues by immunohi stochemi stry.Results1.In an unsupervised hierarchical cluster analysis,the total miRNA expression profile could not generate a tree with clear distinction between pathologic complete response(pCR)and non-pCR classes,but we found that elevated expression of miR-125b and miR-141 are associated with non-pCR(miR-125,P=0.010;miR-141,P=0.016).2.In vitro experiments:co-transfection with miR-125b and miR-141 mimics increased the resistance of MCF7 and BT549 cells to taxane-anthracycline induced cytotoxicity.3.Furthermore,the inhibition of miR-125b and miR-141 expression reduced cellular survival in response to taxane-anthracycline treatment.4.KEGG pathway anaylysis and TargetScan was uesed to predict the upstream regulator and down stream targets,respectly.ATM was a potential upstream regulator of miRNA-125b biogenesis and most of the downstream targets of miR-125b are involved in apoptotic pathways and cell cycle control.The upregulation of miR-141is most likely due to stress induced senescence,which resulting from the activation of the DNA damage repair pathway.But the targets of miR-141 are directly linked to cell proliferation and apoptosis pathways,but not directly linked to DNA damage response pathways.5.We determined HPIP protein expression in 208 pairs of breast tumors and matched nontumor breast tissues by immunohistochemistry.Compared with their corresponding nontumorous counterparts,HPIP expression was upregulated in breast cancer tissues(P=4.66×10-28).6.Expression of HPIP correlated negatively with ERα expression and positively with HER-2 expression in 306 breast cancer tissues(P=0.008 and P=0.002,respectively)7.Using a total of 306 breast cancer patients,we observed a strong correlation between higher HPIP expression and shorter disease-free(P=0.012)and overall survival(P=0.002)8.After univariate analysis by Cox proportional hazards model,HPIP status was demonstrated as significant prognostic parameters for disease-free survival(DFS)and overall survival(OS).A multivariate analysis revealed that HPIP status was independent prognostic factors of DFS and OS.9.Among 306 breast cancer patients,199 of them received tamoxifen treatment.For the patients who received tamoxifen,those with tumors that highly expressed HPIP revealed significantly poorer DFS and OS than those with tumors with low HPIP expression(DFS:P=0.006;overall survival:P=0.002).In contrast,the remaining 107 patients,who were not treated with tamoxifen,had no significant differences in their DFS and OS regardless of the HPIP amounts in the tumors(DFS:P=0.593;OS:P=0.224).ConclusionsThe level of miR-125b and miR-141 was elevated in non-pCR cohort compared with pCR cohort.We speculate that the increased level was asscioated with chemotherapeutic resistance.A series of in vitro experiments(such as CCK-8)was empolyed to validate the hypothesis.KEGG pathway analysis indicated that activation of the DNA damage repair pathway can induce the biogenesis of miR-125b and miR-141.The targets of miR-125b involved in apoptotic pathways and cell cycle control.Together,we provide evidence that elevated miR-125b and 141 expression predicts a poor clinical responsiveness of taxane-anthracycline based neoadjuvant chemotherapy.The expression of HPIP is an independent prognostic predictor of breast cancer patients,therefore it may have the potential to serve as a novel target for breast cancer therapy.Besides,it can promotes tamoxifen resistance in breast cancer through regulating ERα expression negatively and HER-2 expression positively,so they may provide new theoretical basis for endocrine resistance.