Differential Expression Of CSAG1 Gene In Breast Cancer With Different Molecular Types And Its Clinical Significance

Breast cancer from breast epithelial tissue,is a common malignant tumor in women.Breast cancer has become a major public health problem in current society.The incidence of breast cancer increased in recent years.With the development of medicine,although early diagnosis and treatment can reduce the mortality of patients with breast cancer,but for now,breast cancer is still a high mortality rate of malignant tumors.Breast cancer is a highly heterogeneous disease.With the same pathological type,histological grade,clinical stage and treatment,the survival and prognosis of breast cancer still has great difference.According to the molecular classification of breast cancer,Perou and Sorlie et al,divided breast cancer into five subtypes including Basal-like,Luminal A,Luminal B,HER2 over expression and Normal several types.Different types of breast cancer patients need different treatment and has difference prognosis.Therefore,the detailed molecular typing can effectively reflect the biological characteristics of breast cancer,and guide clinical treatment options.Chondrosarcoma related gene 1(CSAG1)located in Xq28,and is expressed in normal testicular tissues.CSAG1 has been reported to be highly expressed in melanoma cell line,K562 cell leukemia and malignant schwannoma tissue,which is associated with tumor occurrence and development.However,no relative study has been done to elucidate the expression of CSAG1 in different molecular subtypes breast cancer.OBJECTIVE: To explore the expression and function of CSAG1 in different breast cancer molecular subtypes,and provide the theoretical basis for clinical treatment and prognosis of breast cancer.METHODS:1.Immunohistochemistry was used to analyze the expression of ER,PR,HER2 and Ki-67 in 100 cases of breast cancer FFPE tissue samples.2.The CSAG1 gene expression levels of different types of breast cancer FFPE tissue samples and breast cancer cell lines were detected with RT-PCR.3.The protein expression level of CSAG1 in different molecular type's breast cancerFFPE tissue samples was detected by immunohistochemistry.4.Statistical analysis of the relative expression and the correlations between CSAG1 with clinicopathological parameters in breast cancer was done by Chi square test and Spearman rank correlation.5.Survival analysis was done with GraphPad Prism 5 and cBioPortal.RESULTS:1.According to the 2011 St.Gallen consensus and the postoperative pathological and immunohistochemical staining results of ER,PR,HER2,Ki-67,100 cases of breast cancer were subtyped into 18 cases Luminal A subtype,29 cases Luminal B subtype,4 cases HER-2over expression subtype,35 cases Basal-like subtype and 14 cases Normal subtype.2.The relationship analysis results between the molecular subtypes of breast cancer and clinical pathological characters showed the proportion of histological grade I-II was higher in Luminal A subtype compared with the other groups(P < 0.0001).3.The RT-PCR results of breast cancer FFPE tissue samples showed CSAG1 gene expression was higher in Luminal A molecular subtype than that of other molecular subtypes,with a statistically significant difference between the groups(P<0.05).4.RT-PCR results with breast cancer cell lines showed that CSAG1 gene expression level is significantly higher in T47 D cell line(Luminal A,ER and/or PR+,HER2-,Ki-67<14%)than that of other cell lines'(breast cancer ZR75.1,HDQ-P1,CAL-120,CAL-51,MDA-MB-436,MDA-MB-231 and normal mammary epithelial cell line HBL-100)(P<0.0001).5.According to immunohistochemical results of clinical breast cancer FFPE tissue samples,the positive rate of CSAG1 expression was statistically significant higher in Luminal A molecular subtype breast cancer than that of other molecular subtypes,with a difference between the groups(P<0.05).6.The relationship between CSAG1 protein expression and clinicopathological parameters was analyzed.The results showed that the expression level of CSAG1 protein was higher in grade I-II than that of grade III,and the difference was statistically significant(P<0.05).But there was no significant difference in the analysis according to pathological type,TNM staging,age,tumor diameter and lymph node metastasis.7.Correlation with clinicopathological parameters analysis showed the expression of CSAG1 protein was negatively associated with histopathological grading,the difference was statistically significant(P<0.05);but there was no correlation with age,tumor size,lymph node metastasis,clinical staging and pathological types of TNM.8.The relationship analysis results between the expression of CSAG1 protein and the classical markers of breast cancer showed that the expression of CSAG1 protein in ER+/Ki-67+ group was higher than that in ER-/Ki-67-group and HER2-group.The relative expression level in the HER2-group was higher than that in the HER2+ group,but there was no significant difference in the expression levels between PR+ and PR-groups.9.Correlation analysis with breast cancer classical markers showed the expression of CSAG1 was positively correlated with ER and PR(r=0.237?0.173).CSAG1 was negatively correlated with Ki-67 proliferation index(r=-0.251),the differences were statistically significant(P<0.05);but it was not correlated with HER2 expression.10.Kaplan-Meier survival analysis results showed there was no statistically significant difference between breast cancer patients with CSAG1 protein positive and negative expression which might be the follow of present study phase is too short.CONCLUSION:1.CSAG1 was highly expressed in Luminal A subtype breast cancer,which suggest the expression of CSAG1 might play a role in Luminal A subtyping of breast cancer.2.The breast cancer patients with CSAG1 gene expression have a low clinical pathological grade,a better survival and a relatively better prognosis.3.The expression of CSAG1 was positively correlated with the expression of ER and PR,which could be used to guide the clinical treatment and prognosis.4.The expression of CSAG1 was negatively associated with Ki-67,which might adjuvant Ki-67 for molecular classification of breast cancer and guides the clinical prognosis.