Research Article Gene Expression Profile Analysis of T1 and T2 Breast Cancer Reveals Different Activation Pathways

License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Breast cancers today are of predominantly T1 (0.1 ≥ 2.0 cm) or T2 (> 2 ≤ 5 cm) categories due to early diagnosis. Molecular profiling using microarrays has led to the notion of breast cancer as a heterogeneous disease both clinically and molecularly. Given the prognostic power and clinical use of tumor size, the purpose of this study was to search for molecular signatures characterizing clinical T1 and T2. In total 46 samples were included in the discovery dataset. After adjusting for hormone receptor status, lymph node status, grade, and tumor subclass 441 genes were differently expressed between T1 and T2 tumors. Focal adhesion and extracellular matrix receptor interaction were upregulated in the smaller tumors while p38MAPK signaling and immune-related pathways were more dominant in the larger tumors. The T-size signature was then tested on a validation set of 947 breast tumo