Expression and genetic/epigenetic alterations of dnaja1 and dnaja2 genes in breast cancer

It is particularly important to determine the biomarkers and anti-cancer drug targeting breast cancer, which is the most common cancer type in women. In this study, the expression levels and genetic / epigenetic alterations of DNAJA1 and DNAJA2 genes from the Heat Shock Proteins (HSP) family were investigated. DNAJA1 and DNAJA2 are the genes which have been associated with cancer but have not been studied in breast cancers. In this study, DNAJA1 and DNAJA2 expression in breast cell lines and breast cancer clinical samples were investigated by Q-RT-PCR, semi-quantitative RT-PCR, UALCAN web tool and immunohistochemistry methods. Genetic alterations of these genes in breast cancer patients were then examined in the Sanger-COSMIC database. Whether the genes examined were regulated by epigenetic factors such as promoter methylation, was investigated by combined bisulfite restriction analysis (COBRA) method and in-silico tools (UALCAN, Morpheus). At the end of the study, the mRNA expression of the DNAJA1 gene is found to be regulated in the breast cell lines. DNAJA1 mRNA expression was significantly higher in tumor samples (n=1097) than in normal samples (n=114) (P<1e-12). DNAJA1 protein expression is significantly more common in invasive ductal carcinoma specimens (n=115) than normal breast specimens (n=26) (P <0.0001). DNAJA1 mRNA expression is associated with poor overall survival (n=1402), relapse-free survival (n=3955) and distant metastasis-free survival (n=1747) in breast cancer patients, (P=0,00027, P=2e-14, P=9,2e-05). Genetic alterations of the DNAJA1 gene are infrequent in clinical breast cancer samples. Promoter region of the DNAJA1 gene is hypomethylated in breast cell lines and clinical breast cancer samples. There is no notable difference observed in DNAJA2 mRNA expression among the breast cell lines. DNAJA2 mRNA expression was significantly lower in tumor samples (n=1097) compared to normal samples (n=114) (P=4.36e-05). DNAJA2 protein expression was frequently observed in both invasive ductal carcinoma samples (n=115) and normal breast samples (n=21) (90.48%, 88.7%, respectively). DNAJA2 mRNA expression is unfavorable for overall-survival (n=626) and relapse-free survival (n=1764) in breast cancer patients (P=0.047, P=0.00033; respectively). Genetic alterations of the DNAJA2 gene is uncommon in breast cancer clinical samples. Promoter region of the DNAJA2 gene is hypomethylated in breast cell lines and clinical breast cancer samples. As a result, the DNAJA1 gene is overexpressed in breast cancer and unfavorable for survival. In this regard, DNAJA1 expression can be used as a prognostic biomarker. The DNAJA1 gene could be regulated by an epigenetic mechanism other than promoter methylation. DNAJA2 mRNA expression has prognostic significance in breast cancer. Genetic alterations of DNAJA2 is rare in breast cancer and it could be regulated by promoter hypomethylation. Clinical and functional studies with a larger cohort is needed to better understand the role of DNAJA1 and DNAJA2 genes in breast carcinogenesis.