Molecular aspects involved in the development and progression of breast ductal carcinoma: investigation of carcinoma in situ progression and the role of BRCA1 mutation in the triple negative tumor

Abstract

This proposal encompasses the molecular aspects involved in risk, development and progression of breast cancer using next generation sequencing as the main approach. Mutation in the susceptibility genes, BRCA1/BRCA2, is one of the most important risk factors of developing breast cancer. The identification of the genetic cause that leads to higher risk of developing breast cancer is crucial for properly assisting women and inserting them into screening programs and also for adopting proper preventive measures. Our group has been working hereditary breast cancer syndrome and previous results based on more than 200 patients showed that 20% of patients had pathogenic mutations, and 80% did not harbored any known pathogenic alterations in these genes. By careful analysis of the pedigrees of these patients, it is clear that there is a major genetic factor that leads to increased risk, and that needs to be identified, being this one of the goals of this proposal. Other important aspect of breast cancer is the characterization of the molecular changes that occur during the progression of breast cancer, an issue that the group has been contributing. The search for more accurate and detailed information about the molecular alterations involved in the progression of ductal carcinoma in situ (DCIS) of the breast using more sensitive approaches for analysis of pre-invasive stages of BC are promising for the identification of genetic and molecular events involved in the earliest steps of the invasion process of epithelial tumor cells into the surrounding tissue. It is well known the participation of the tumor and microenviromental cells in the invasion to adjacent tissue. Thus, one of the objectives of this proposal is to investigate the changes in the gene expression profile of epithelial tumor cells and in the microenvironment, the myoepithelial cells and fibroblasts, of the two types of pre-invasive lesions with different malignant potential: pure DCIS and in situ DCIS component coexisting with invasive carcinoma (DCIS - IDC). Furthermore, we propose the identification of the somatic mutational pattern of the epithelial cells of these two pre-invasive lesions. The idea is to find biomarkers associated with a risk of progression of DCIS to invasive disease. Another study considered in this proposal, which integrates data from germline mutation and their respective tumor, is the molecular alterations in TN tumor mediated by BRCA1-germline mutation. It is well known that women with BRCA2-germline mutations preferentially develop tumors that are hormone receptor positive (ER and / or PR), and women with BRCA1-germline mutations develop hormone receptor-negative tumors, especially those TN, characterized by the lack of expression of hormone receptors, ER and PR, and no amplification and/or overexpression of HER2. TN tumors are more aggressive and have a poorer prognosis, and for which there is no targeted therapy available for the patient's treatment. In this context, we aim in this project to characterize the prevalence of BRCA1 mutations in TN tumors, and also to classify them as somatic or germline mutation. We also plan to investigate the role of the germline mutation in the development of TN tumors by the investigation of the global transcriptional and mutational profile of TN-associated or -negative to BRCA1 germline mutation. All data obtained will be correlated with clinical and pathologic features of patients being the idea to properly and detailed classify the heterogeneous group of TN. Additionally, in an exploratory way, we intend to be able to detect tumor DNA in plasma of patients with breast cancer, using tools of high sensitivity in combination with information generated by massively parallel sequencing. Our interest in this regard is to establish a sensitive and accurate method for monitoring disease progression to be inserted in clinical practice, particularly for tumor types involved in this proposal. (AU)