Frequent Alterations of MCPH1 and ATM are Associated with Primary Breast Carcinoma: Clinical and Prognostic Implications

Background. MCPH1 is a proximal regulator of DNA damage response pathway that is involved in recruitment of phosphorylated ATM to double-stranded DNA breaks. Methods. To understand the importance of MCPH1 and ATM in deregulation of DNA damage response pathway in breast carcinoma, we studied m-RNA expression and genetic/epigenetic alterations of these genes in primary breast carcinoma samples. Results. Our study revealed reduced expression (mRNA/protein) and high alterations (deletion/methylation) (96 %, 121 of 126) of MCPH1 and ATM. Mutation was, however, rare in inactivation of MCPH1. In immunohistochemical analysis, reduced protein expression of MCPH1, ATM and p-ATM were concordant with their molecular alterations (P = 0.03-0.01). Alterations of MCPH1 and deletion of ATM were significantly high in estrogen/progesterone receptor-negative than estrogen/progesterone receptor-positive breast carcinoma samples compared to early or late age of onset tumors, indicating differences in pathogenesis of the molecular subtypes (P = 0.004-0.01). These genes also showed differential association with tumor stage, grade and lymph node status in different subtypes of breast carcinoma (P = 0.00001-0.01). Their coalterations showed significant association with tumor progression and prognosis (P = 0.003-0.05). Interestingly, patients with alterations of these genes or MCPH1 alone had poor outcome after treatment with DNA-interacting drugs and/or radiation (P = 0.01-0.05). Conclusions. Inactivation of MCPH1-ATM-associated DNA damage response pathway might have an important role in the development of breast carcinoma with diagnostic, prognostic and therapeutic implications.