Stem cells within established cancer cell lines: an impact on in vitro experiments

Cancer stem cells (CSCs) are described as cells within a tumor that are able to indefinite self-renewal, form tumors when transplanted in vivo, differentiate into multiple lineages, and express genes such as OCT3/4, SOX2, KLF4, NANOG. Although these traits of CSCs are commonly accepted, there is still a lot of controversy regarding these cells. There are very few methods which allow to obtain these cells, like separation based on surface markers, presence of side population, sphere forming assays, and aldefluor assays. This paper seeks the confirmation of CSCs presence in cancer cell lines such as: breast, prostate, pancreatic, liver, brain, and cervical. Nowadays, researchers use two models of cell culture: established cancer cell lines (ECCLs) and primary cell culture. A major problem with these models is that tumors in organism evolve and cell cultures represent only small fragment of tumor development. Since CSCs were found, there exist high hopes of revealing new therapies targeting CSCs. However, the appearance of new populations with the ability to induce tumors should pour a bucket of water to create a cure for cancer.