Hierarchical clustering of primary estrogen receptor-positive breast cancers based on genome-wide microarray profiling. Unsupervised hierarchical clustering of 101 primary estrogen receptor (ER)-positive breast cancers, diagnosed in younger women (age ≤ 45 years) or older women (age ≥ 70 years), based on genome-wide microarray profiling of 6,632 variably expressed probes (~5.1 K unique genes). The cluster dendrogram defines six different transcriptome subtypes of ER-positive breast cancers (Group 1A, 1B, 2A, 2B, 3A, 3B), with significant age biases (P < 0.05) but not biased by progesterone receptor (PR) status or ERBB2 status; horizontal colored bars identify the age cohort, PR status and ERBB2 status of the ER-positive samples in each column. The vertical red–green color scale shows log2 ratios from mean centered gene expression levels. Magnified views show ESR1-containing (ER-associated) probe sets within the entire cluster diagram.
Yau et al. Breast Cancer Research 2007 9:R59 doi:10.1186/bcr1765