Tumor initiating cells.

Cancer Stem cells (CSC) are defined as a population of cells found within a tumor that have characteristics similar to normal stem cells. Like normal stem cells they have the potential to self renew and differentiate. The cellular origin of these cancer stem cells--whether they originate from stem cells that have lost the ability to regulate proliferation, or they arise from more differentiated population of progenitor cells that have acquired abilities to self-renew is still unclear. Investigators have reported isolation of cancer stem cells or tumor initiating cells using techniques developed for isolating hematopoietic stem cells and assays that identify a small subset of tumor initiating cells. The TICs are thought to play an important role in tumor development, progression as well response to therapy and relapse. Strategies that combine conventional therapies with newer approaches that target the TICs may be more effective in tumor cell kill are discussed.