Expression And Clinical Significance Of HIF-2α In Breast Carcinoma And Its Relationship With Epithelial Mesenchymal Transition

Research background:Breast cancer is one of the world’s malignant tumors of women,its infiltration and metastasis makes breast cancer patients with poor prognosis.Non-specific type of invasive carcinoma is the most common histological type of invasive breast cancer,accounting for about 40-70%.It has been found that hypoxia microenvironment is a typical feature of solid tumors,and it’s considered to be a leading factor in the malignant progression and poor prognosis of tumors.The tumor undergoes a series of biological changes to adapt to hypoxia microenvironment,mainly regulated by HIFs(hypoxia induced factors).HIFs have been found to have three subtypes so far: HIF-1α,HIF-2α and HIF-3α.There are more reports about HIF-1α,mainly in HIF-1α and angiogenesis factor,tumor proliferation and metastasis,drug-related proteins and other studies,and for HIF-2α relatively little mention.Epithelial mesenchymal transition(EMT)refers to the transition from non-moving,polar epithelial cells to moving,nonpolar interstitial cells,and the potential to migrate,grow,and grow to distant organs.In malignant tumors,EMT can lead to enhanced tumor cell migration and invasive ability,increased tumor invasion.HIF-2α is a transcription factor produced by hypoxia stress.Its expression can effectively regulate the activity of target genes to break the imbalance of intracellular oxygen,such as neovascularization gene(CEGF,PIGF),proliferation and metastasis gene MMP,SDF1,CXCR4,LOX),epithelial stromal transformation(SNAIL,TWIST,SIP),etc.,playing an important role in maintaining neovascularization and promoting tumor invasion and metastasis.The study found that high expression of HIF-2α is associated with tumor chemoradiotherapy resistance,suggesting that HIF-2α may be involved in the poor prognosis of the tumor and expected to be the target of treatment in the future.Twist family is one of the specific target genes for HIF-2α,and Twist2 is also known as Dermo1,which is the main transcription factor involved in the regulation of epithelial mesenchymal transition,which can induce the process of tumor cell EMT and its migration,invasion and metastasis.The epithelial mesenchymal transition of breast invasive carcinoma to a certain extent determines the tumor metastasis,improve the mortality rate shortened the survival period,seriously affecting the prognosis of patients.At present,the relationship between HIF-2α and epithelial mesenchymal transition in breast cancer is less reported.In this study,non-specific type of invasive breast carcinoma was treated as research object,the immunohistochemical SP method and the ISH technique were used to detect the expression of HIF-2α protein and mRNA in invasive primary breast carcinoma,fibroadenoma,and adjacent normal tissue,and then detect the expression of Twist2,E-cadherin and vimentin.In this way,we can investigate the relationship between HIF-2α and epithelial-mesenchymal transition,and analyze the influencing factors of HIF-2α on the prognosis of breast cancer,and to provide more experimental evidence for HIF-2α as a target for clinical treatment of breast cancer.Method:1.Collected paraffin specimens from August 2011 to January 2012 into three groups: breast non-special type of invasive cancer in 92 cases,the corresponding adjacent tissue in 30 cases,21 cases of fibroadenoma.Immunohistochemical SP method was used to detect the expression of HIF-2α,Twist2,E-cadherin and vimentin,and then analyzed the correlation between their expression and clinicopathological parameters.2.Collected paraffin specimens from 2015 to 2016 into three groups: breast non-special type of invasive cancer in 20 cases,the corresponding adjacent tissue in 20 cases,20 cases of fibroadenoma.ISH method was used to detect the expression of HIF-2αmRNA,and then detected the differences expression of HIF-2αmRNA in the gene level.3.The follow-up was performed on 92 cases of breast cancer.Survival analysis was performed by Kapln-Meier method and Log rank test.Multivariate Cox proportional regression model was used to analyze the prognostic factors of breast cancer.Result:1.The positive rates of HIF-2α protein in 92 cases of breast cancer,21 cases of fibroadenoma and 30 cases of adjacent tissues were 71.73%(66/92),42.85%(9/21)and 36.66%(11/30).The positive rates of HIF-2α mRNA in 77 cases of breast cancer,20 cases of fibroadenoma and 20 cases of adjacent tissues were 77.27%(17/22),25.00%(5/20)and 15.00%(3/20).HIF-2α protein and mRNA in the breast tissue were consistent,the positive rate of breast cancer and adenoma group were higher than the adjacent group(P<0.05).The positive expression of HIF-2α protein was correlated with tumor size,lymph node metastasis and molecular typing(P<0.05),but not correlated with age(P=0.921),histological grade(P=0.566),TNM staging(P=0.209).2.The positive rates of Twist2 protein in 97 cases of breast cancer,21 cases of fibroadenoma and 30 cases of adjacent tissues were 57.60%(53/92),19.04%(4/21)and 16.66%(5/30)(P<0.05).The expression of Twist2 protein was correlated with histological grade,lymph node metastasis and molecular typing(P<0.05),but not correlated with age(P=0.915),Tumor size(P=0.736),TNM staging(P=0.757).3.The positive rate of E-cadherin in breast cancer group was 58.69%(54/92),lower than that in adenoma group(85.71%(18/21)and 93.33%(28/30)in adjacent tumor group,and its expression was correlated with tumor size,histological grade,lymph node metastasis and molecular typing(P<0.05),but not correlated with age(P=0.615)and TNM staging(P=1.000).The positive rate of vimentin in breast cancer group was 46.73%(43/92),higher than that in adenoma group(23.83%,5/21)and 13.33%(4/30)in the adjacent group,and its expression was correlated with lymph node metastasis,TNM staging and molecular typing(P<0.05),but not correlated with age(P=0.724),tumor size(P=0.970),histological grade(P=0.129).4.There was a significant negative correlation between the expression of HIF-2α and Twist2 in breast cancer(r=0.452,P=0.000),and there was a significant negative correlation between the expression of E-cadherin and vimentin(r=-0.570,P=0.000).The expression of HIF-2α and Twist2 protein was negatively correlated with E-cadherin and positively correlated with vimentin(P<0.05).5.HIF-2αnegative group,Twist2 negative group,E-cadherin positive group and vimentin negative group had higher overall survival rate and longer survival time than the other one,but only HIF-2αand E-cadherin group has significant difference(P<0.05),Twist2 and vimentin group has no significant difference(P>0.05).6.Multivariate survival analysis showed that only lymph node metastasis(RR=6.022,95% CI 2.852 ~ 12.717,P=0.000),tumor size(RR=2.621,95% CI 1.123 ~ 6.117,P=0.026)and positive HIF-2α(RR=3.821,95%CI 1.092~13.372,P=0.036)could be used as an independent prognostic factor for breast cancer patients(P<0.05),and other prognostic factors,such as age,histological grade,TNM stage,molecular classification,etc.,could not be used as an independent prognostic factor(P>0.05).Conclusion:HIF-2α is abnormally expressed in breast cancer,and may be involved in breast cancer EMT process according to Twist2,causing tumor invasion and metastasis and affecting the survival prognosis.