Irene Raitman

M.Sc Candidate, Department of Molecular & Medical Genetics

Characterizing Basal vs. Luminal Discriminating Genes in Breast Cancer

Recent comprehensive molecular phenotyping of human breast cancers and using gene-expression microarray analysis has identified genetically distinct subtypes that the breast tumors can be grouped into. For my current project the luminal/ER+ and basal subtypes are of particular interest. The ER+ subtype is characterized by estrogen receptor (ER) expression, co-expression of the epithelial/luminal cytokeratins (CK) 8/18, being well differentiated, and of low grade. While the basal subtype is estrogen receptor negative, lacks HER2 overexpression, has expression of myoepithelial/basal CK 5/6 and/or 14 and 17, is poorly differentiated, often has p53 mutations, is high grade, has a high level of lymphocytic infiltrate, and has been associated with poor prognosis. A gene expression microarray study previously performed by our lab has identified genes that discriminate between these two subtypes of breast cancer. Our study has identified some of the same luminal and basal genes that previous studies have seen as being specific to their respective subtypes. However, there were also some novel genes that we identified, including those involved in the immune system. The current objective is to characterize the role of some of these genes in cancer progression, and the connection between the high lymphocytic infiltrate and worse prognosis that the basal group has.