The Relationship Between The Expression Of BRCA1 And Progesterone Receptor Isotypes A And B In Sporadic Breast Cancer

BackgroundBreast cancer is the most common cancer in women.It mostly happened in the western developed countries,whereas,the incidence in china grows rapidly in recent years.Furthermore,the patients become younger and younger.The incidence in city is higher than that in rural district.The breast tumorigenesis is involved with many factors,the study of wich provides theory basis for breast cancer prevention and therapy.BRCA1 is a tumor suppressor gene.Its mutation closely relates to hereditary breast cancer.In hereditary breast cancer,the BRCA1 mutation rate is 45%,but in hereditary breast cancer and ovarian cancer,the BRCA1 mutation is up to 80%.In sporadic breast cancer,the expression of BRCA1 is lower.BRCA1 can regulate the breast cell proliferation and differentiation.BRCA1 play roles in many biological processes directly or indirectly.BRCA1 can modulate centrosome duplication. BRCA1 knockdown induces the abnormal cell division.BRCA1 affects the DNA damage repair through homologous recombination and end-joining pathways. BRCA1 also regulates the protein expression associated with DNA damage repair. The accuracy and high efficiency of DNA repair is important for maintaining the genome stability.If the damage can't be repaired promptly,malignant transformation may happen to a cell during the continuous division and differentiation.BRCA1 plays important roles in transcriptional regulation.BRCA1 mutation weakens these functions,thereby increasing the incidence of breast cancer.Wild-type BRCA1 can induce programmed cell death and inhibit the transcription of estrogen-dependent pathway,which is associated with mammary epithelial cell proliferation,and gene mutations in this gene results in lose of the inhibitory function and thus carcinogenesis.In recent years,with in-depth study of breast cancer,it has been discovered that the role of progesterone and its receptor can not be ignored.Clinical investigations revealed that hormone replacement therapy increased the incidence of female breast cancer;moreover,the combined application of progesterone and estradiol in women caused higher the incidence of breast cancer,larger tumor size and higher degree of malignancy than the use of estrogen alone.In the breast tissue of ovariectomized mouse model,the mouse received both estradiol and progesterone has more branches and acini than that received estradiol alone.Progesterone receptor(PR) is nuclear receptor.PR has two subtypes:progesterone receptor A(PRA) and progesterone receptor B(PRB).They are controlled by different promoters,and their expression and regulation are also different.In normal breast tissue,PRA and PRB are balanced expressed in breast cancer,PRA expression is dominant compared to PRB.So, progesterone and its receptors are closely related to breast cancer.The imbalance between the expression of PRA and PRB is related to carcinigenesis.Although there are reports that BRCA1 can regulate PR functions,but the report on the relationship between the expression of BRCA1 or PRA,PRB,and on if BRCA1 can regulates PR expression,are limited.Thus,it will be significant for understanding breast cancer initiation and development in depth and prevention to study the relationship between BRCA1 and PR.In this study,the expression of BRCA1,PRA and PRB in breast tissue of adenosis and sporadic invasive ductal breast cancer are detected compared,and the relationship between the expression of BRCA1 and PRA,PRB or the ratio of PRA/PRB are analysised;further more,BRCA1 and PRs expresson relationship is also studied in MCF-7 cell with BRCA1 knockdown.Methods1.Clinicopathological characteristics analysis of of breast cancer cases259 cases of breast cancer patients and 218 cases of breast adenosis cases(as control) are analysised,in terms of the age of onset,incidence part,histology type, lymph node metastasis and estrogen receptor expression,to study the breast cancer clinical and pathological features.2.The expression of BRCA1,PRA and PRB and their relationship in breast cancer tissuesDetection(by immunohistochemistry) and comparision of the expression of BRCA1,PRA and PRB in the breast tissues of 68 cases of invasive ductal breast cancer and 68 cases of adenosis;relationship analysis between BRCA1 and PRA, PRB or the ratio of PRA/PRB in tissues of 68 cases of invasive ductal breast cancer; detection(by in situ hybridization) and comparision of the expression of BRCA1,PRB and PR mRNA in tissues of 68 cases of invasive ductal breast cancer and 68 cases of adenosis;relationship analysis between mRNA expression of BRCA1 and PR in tissues of 68 cases of invasive ductal breast cancer.3.The effects of BRCA1 knockdown on PR expression in MCF-7 cellsThe effects of BRCA1 knockdown on MCF-7 cells are observed in terms of expression of PRA and PRB both at mRNA and protein level. Results1.Clinicopathological characteristics of breast cancer cases analyzed(1).The age distribution of breast cancer cases analysed,259 in total,is of 24-86 years old,with median age at 48 years old;incidence peak at ages 41-50 years old, accounting for 39.38%of all cases;incidence part:147 cases of left side and 112 cases of right side;histological type:230 cases of invasive ductal carcinoma, accounting for(88.80%),29 cases of non-invasive ductal carcinoma,accounting for only 11.20%;lymph node metastasis:of 219 cases whom were checked to have lymph node tissues,low-risk cases without matastasis accountes for 51.14%; high-risk cases with the number of lymph node metastasis≥4 accountes for 29.68%; the expression of estrogen receptor:ER-positive rate,32.82%;PR positive rate, 36.29%;Her-2 positive rate,47.88%.(2) Age grouping:young group(≤35 years),middle-aged group(36-60 years old) and elderly group(＞60 years old);the rate of lymph node metastasis in youth group (61.90%) is higher than that in middle-aged group(49.41%) and elderly group (42.86%),but no significant difference(P＞0.05) exists between different age groups.In youth group ER,PR expression was low(18.52%and 29.63% respectively);but Her-2 was highly expressed(66.67%);the positive expression rate of ER in the young group and old group is statistically significant.2.BRCA1 expression in breast cancer tissue and its relationship with progesterone receptor isotypes expression(1).Immunohistochemistrya.BRCA1 protein expression in breast adenosis is higher than that in invasive ductal carcinoma and is statistically significant between the two groups(P＜0.01);b.PRA,PRB protein expression in breast adenosis were higher than those in invasive ductal carcinoma(P＜0.05 for both PRA and PRB).66.18%(45/68) of breast adenosis patients expressses the equal same level of PRA,PRB protein,but only 20.58%(14/68) for patients with invasive ductal carcinoma,in which 54.41%(37/68) of cases are dominant PRA protein expression.(2).In situ hybridization:BRCA1,PR mRNA expression level in breast adenosis is higher than those in invasive ductal carcinoma(P＜0.01)(3).Correlation analysis:immunohistochemistry results showes that the expression of BRCA1 and PRA,PRB are associated(P＜0.05),with contingency coefficient C as 0.274 and 0.228,respectively;In situ hybridization results showes no correlation between the expression of BRCA1 and PR(P＞0.05).3.The effects of BRCA1 knockdown on PRA and PRB expression in MCF-7 cellsThe expressions of PRA and PRB at mRNA level were not changed in MCF-7 with BRCA1 knockdown,but those at protein level were increased.Conclusions1.BRCA1 expression in sporadic breast cancer is lower than that in breast adenosis;2.In the tissues of aporadic invasive ductal breast cancer,the expression of BRCA1 is correlated with that of PRA and PRB and the rate of PRA dominant expression relative to PRB is increased;3.In MCF-7 breast cancer cells,BRCA1 knockdown up-regulates the expression of PRA,PRB at the protein level only,suggesting BRCA 1 specifcally reulate PRA and PRB expression at protein level.InnovationThis is the first report of the correlation between the expression BRCA1 and PRA or/and PRB in sporadic breast cancer tissues.