%0 Journal Article %T Keystone symposium: The role of microenvironment in tumor induction and progression, Banff, Canada, 5¨C10 February 2005 %A Jamie L Bascom %A Paraic A Kenny %J Breast Cancer Research %D 2005 %I BioMed Central %R 10.1186/bcr1030 %X It is now apparent that reciprocal interactions between tumor cells and their microenvironment ¨C extracellular matrix (ECM), growth factors, fibroblasts, immune and endothelial cells ¨C play an essential role in the earliest stages of transformation to malignant progression and metastasis. By better understanding the complex interactions between all of these factors, it is hoped that therapies might be effectively targeted against both epithelial and stromal determinants of tumor progression. In this regard, there were several encouraging presentations on novel clinical approaches that target these processes.Skiers and snowboarders among the delegates were blessed with 67 cm of fresh snow just prior to arrival, resulting in a stampede for the ski buses each day at 11 am. The quality of the meeting was perhaps best reflected by an equally urgent stampede back to the conference center in time for the evening sessions and posters.Zena Werb (University of California, San Francisco) set the scene for the meeting with a wide ranging plenary lecture detailing crucial interactions between epithelial and stromal cells during both normal mammary development and tumorigenesis. She described a series of wild-type/knockout tissue recombination experiments used to dissect the requirements for epithelially and stromally expressed growth factors and receptors in mammary gland development. In a lecture that was both visually and intellectually stimulating, she showed that intravital imaging technology is a valuable tool with which to interrogate the interactions between stromal and epithelial cells in tumorigenesis. Time-lapse fluorescent videos using mouse mammary tumor virus-polyoma middle T antigen (MMTV-PyMT) transgenic mice bearing various fluorescent markers demonstrated the dynamic interactions between the tumor and host cellular components.In the second keynote address, Joan Massagu¨¦ (Memorial Sloan Kettering Cancer Center, New York), described a series of experiments that pr %U http://breast-cancer-research.com/content/7/3/113