Expression data from side population cells of the human OSCC cell line SCC172

A cancer stem cell cannot be identified solely based on surface markers as none of the markers used to isolate stem cells in various normal and cancerous tissues is expressed exclusively by stem cells. Our experimental results have also identified additional fractions representing true stem-like cells in oral squamous cell carcinoma (OSCC), refuting the concept that cancer stem cells (CSCs) are a rare population, and we have also developed an in vitro model to explore the stem cell concept in oral epithelial tumorigenesis. This model expounds four distinct fractions within a homogenous cell line SCC172 that is morphologically similar (85% cells expressing CSC markers), yet varying in all functional aspects of cell cycle, dye retention, chemoresistance, tumor-forming potential, self renewal, apoptosis resistance and regulation at molecular levels. Relating to our CSC shift model, we analysed the concept of biological heterogeneity in terms of four fractions SP1, SP2, MP1 and MP2 and associated it with variations among patients in a clinical scenario. We used microarray expression profiling to determine the transcriptional profiles of representative tumorigenic SP1 and non-tumorigenic non-SP/MP1 fractions. Three batches of approximately 6x10^5 of SP1 and non-SP (MP1) cells were sorted by flow cytometry on different days as biological replicates after ensuring maximum resort purity. Only two SP1 replicates are included in this submission.