Multi-step process of human breast carcinogenesis: a role for BRCA1, BECN1, CCND1, PTEN and UVRAG

In the female population in Asia, systematic investigation concerning alterations in cancer-related genes in breast carcinoma is rare, and the correlation among oncogene or suppressor gene expression with tumor cell apoptosis, cell cycle regulation and tumor cell autophagy remains to be clarified. In this study, a tissue microarray consisting of 360 individual samples from three different breast tissues was generated. By comparing the expression of the tumor-suppressor genes (BRCA1, BECN1, CCND1, PTEN and UVRAG) in ductal breast cancer and normal breast tissues, respectively, we were able to assign changes in the expression of these mRNAs to specific stages and allocate them to define the roles in the multi‑step process of breast carcinogenesis. Tumor-suppressor genes, such as BRCA1 and BECN1, usually had lower signals in the carcinomatous tissues (10.2 and 6.6%) compared to the normal tissues (31 and 32.6%), while stronger positive dots (positive cells >30%) usually existed in the normal tissues. The patients in the oldest age group had the lowest expression rate. Only BECN1 and CCND1 expression showed a significant association with patient age (p=0.030 and p=0.003). A significant association was observed between BRCA1 and BECN1 expression and tumor size (p=0.028 and p=0.021). BECN1 gene expression was positively correlated with UVRAG and PTEN expression (p=0.006 and p=0.000). CCND1 was negatively correlated with PTEN, BECN1 and BRCA1 expression (p=0.011, p=0.000 and p=0.000). Abnormal expression of BRCA1, BECN1, CCND1, PTEN and UVRAG may play a role in human breast carcinogenesis through dysregulated mRNA expression. Overexpressed CCND1 may shorten the G1 phase of the cell cycle, suppress cell apoptosis and contribute to the formation of invasive ductal carcinoma (IDC).