Project name: Homo sapiens

Description: Breast cancers can be classified using whole genome expression into distinct subtypes that show differences in patient prognosis. One of these groups, the basal-like carcinomas, are poorly differentiated, highly metastatic, and genomically unstable. These tumors also contain specific genetic alterations with one example being frequent p53 mutations. The loss of the tumor suppressor gene encoded by the retinoblastoma (RB1) locus is a well-characterized occurrence in many tumor types, however, its role in breast cancer is less clear with many reports demonstrating a Loss of Heterozygosity (LOH) that does not correlate with loss of RB1 protein expression. Here we report that LOH of the RB1 locus was observed at a high frequency in basal-like and luminal B tumors. These tumors also concurrently have low expression of RB1 mRNA as assessed by DNA microarray. As in previous reports, we also did not see a significant correlation between RB1 LOH and protein expression as measured by immunohistochemistry (IHC). p16INK4a, however, was highly expressed both by microarray and IHC, in basal-like tumors only presumably due to a previously reported feedback loop caused by RB1 loss. These results suggest that the functional loss of RB1 is a common event in the progression of basal-like and luminal B breast tumors, which may play a key role in dictating therapeutic responsesKeywords: reference x sampleOverall design: Comparison of reference samples against treatment

Data type: Transcriptome or Gene expression

Sample scope: Multiisolate

Relevance: Medical

Release date: 2008-09-18

Last updated: 2008-03-18