Stem Cells and Cancer

Stem cells are undifferentiated cells that can differentiate into specialized cell and can divide to produce more stem cells. The concept of cancer stem cells has been discussed in the scientific literature since the 19th century. Circumstantial evidence suggests that most tumors are heterogeneous and contain a small population of cancer stem cells that exhibit distinctive self-renewal, proliferation and differentiation capabilities, which are believed to play a crucial role in tumor progression, drug resistance, recurrence and metastasis in multiple malignancies. Unlike normal adult stem cells that remain constant in number, cancer stem cells can increase in number as tumors grow, and give rise to progeny that can be both locally invasive and colonize distant sites-the two hallmarks of malignancy. Rapid advances in the cancer stem cell feld have provided cause for optimism for the development of more reliable cancer therapies in the future. Strategies aimed at effcient targeting of cancer stem cells are becoming important for monitoring the progress of cancer therapy and for evaluating new therapeutic approaches.