cology division at UNC’s School of Medicine, modern technologies such as microarray analysis can reveal the molecular characteristics of cancers and have shown that breast cancer is not one disease. 'It is a family of diseases that are biologically different from each other, some more aggressive than others,' Carey said. 'In this study, using the Carolina Breast Cancer Study, we were looking at how frequently these different subtypes occur in a given population.'
DNA microarray analysis allows scientists to determine the expression levels of thousands of genes simultaneously. This can reveal gene expression patterns, which, in turn, enable genomic profiling of tumor cells.
UNC School of Medicine study co-author Dr. Charles M. Perou, assistant professor of genetics, pathology & laboratory medicine, and a Lineberger member, is a pioneer in microarray technology. 'Gene expression analysis using DNA microarrays has identified several breast cancer subtypes, including luminal A, luminal B, basal-like and HER2-plus/estrogen receptor-negative,' said Perou. 'These studies were based on limited sample sets. We wanted to see if we could identify the presence of these subtypes through a population-based study and to find out if they correlate with factors such as age, menopausal status and race.'
But microarray analysis requires freshly frozen tumor tissue specimens, and the tissue available from the CBCS was collected between 1993 and 2001. Fortunately, the CBCS had many tumor tissue samples in blocks of paraffin.
The test involves immunohistochemistry (IHC) profiling, which is the testing of sections of tissue for specific proteins by attaching them to specific antibodies, and then looking for the antibodies through the enzymes to which they were connected. This IHC test was refined for the JAMA study, which was the first time the IHC method was used to examine breast cancer subtypes in a population-based study.
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