Combined Biology and Bioinformatics Approaches to Breast Cancer

摘要

LMO4 is highly expressed in breast epithelial cells and is related to cell proliferation and/or invasion in vivo. Because these cellular features are associated with breast carcinogenesis and because LMO4 is overexpressed in more than 50% of breast cancer cases, we hypothesize that LMO4 may play roles in oncogenesis of breast epithelial cells by regulating proliferation, invasion and/or other cellular features. Last year (first year), I demonstrated that LMO4 can modulate the proliferative response of epithelial cells to TGF signaling and linked LMO4 to a conserved signaling pathway that plays important roles in epithelial homeostasis. This year, I continued to be trained in bioinformatics; I took classes in statistical methods, and received practical training in evaluating large microarray datasets. In addition, I evaluate the regulation by LMO4 of cellular feature of normal breast epithelial cells and cancer cell lines. Both overexpression and knockdown of the LMO4 protein did not have major effects on cell proliferation, migration, invasion and colony formation of primary mammary gland epithelial cell and cancer cell lines (MCF-7, MDA-MB-231 or T47D). However, changes in LMO4 protein level markedly increased apoptosis of mammary normal or cancer cells. Using cDNA microarrays, we screened several LMO4-responsive genes. BMP7 was identified as a key down- stream gene by ChIP assays and promoter reporter assays. Both increase and decrease in LMO4 level can increase BMP7 transcription. BMP7 signaling inhibitor blocked the LMO4 induced apoptosis of MCF-7 cells, indicating that BMP7 mediates LMO4 effects on apoptosis in MCF-7 breast cancer cells. In addition, we found a significant correlation between LMO4 and BMP7 transcript levels in a large dataset of human breast cancers, providing additional support that BMP7 is a bona fide target gene of LMO4. We further demonstrated that LMO4 binds to HDAC2 and that they are recruited together to the BMP7 promoter.