A side population (SP) in flow cytometry is a sub-population of cells that is distinct from the main population on the basis of the markers employed.
For example, a CD44Drug treatment has also been shown to enrich for populations of SCC CSCs. These cells maintain a high efflux capability for antimitotic drugs. These SP cells were found to be enriched in stem cell activity, multipotent, capable of self-renewal, and expressing many known stem cell markers.
The first demonstration of a nonhematopoietic SP population was reported in the muscle.This list of tissues in which the SP is demonstrated and related to the primitive stem/progenitor cell populations is far from complete.
Common inhibitors used to confirm the SP phenotype include Fumitremorgin C, cyclosporine A, verapamil, or reserpine. We show that mouse testicular cells also display a \`Side Population' that express Bcrp1 mRNA, the ABC transporter responsible for Hoechst efflux in hematopoietic cells. (ABC transporters are transmembrane proteins that use energy derived from the hydrolysis of adenosine triphosphate to enable transmembrane movement, usually in a unidirectional manner, to move a variety of structurally unrelated compounds from the cytoplasm to the outside of the cell. BibTeX These are a subpopulation of cells within a tumor that are functionally distinct from the bulk tumor cells, being capable of extensive self-renewal, while the bulk tumor cells are generally differentiated and have a limited replicative ability.
Cell Stem Cell 8(2):136–147Goodell MA, Brose K, Paradis G, Conner AS, Mulligan RC (1996) Isolation and functional properties of murine hematopoietic stem cells that are replicating in vivo. The isolation of SP cells from total tumor cells has been used as a tool for cancer stem cell research. By definition, cells in a side population have distinguishing biological characteristics (for example, they may exhibit stem cell-like characteristics), but the exact nature of this distinction depends on the markers used in identifying the side population. Upon Hoechst 33342 exposure, SP cells efficiently clear the fluorescent dye thereby becoming a “Hoechst-low” population In 2002, SP cells were first isolated from the heart: myocardial tissue was enzymatically digested and the presence of a side population comprising 1% of total myocardial cells was demonstrated Regarding the expression of c-kit, both groups claim that no c-kitIn another work by Pfister and coworkers, the identity of the ATP-binding cassette transporter in cardiac SP cells was analyzed Engraftment and differentiation of Sca-1+/CD31- cardiac SP cells were studied in a myocardial infarction mouse model Finally, until very recently, the existence of cardiac SP cells in human hearts had never been demonstrated. They enrich for progenitor cells from a variety of tissue types ( 17– 20); furthermore, data have proved that some cancer cell lines and primary tumors contain SP cells. Side population (SP) cells display these characteristics and are defined as adult stem cells. CSCs are low-abundance cells with the ability to proliferate and form tumors, and thought to be responsible for tumor recurrence and metastasis . ABC transporters that are known to confer on cells the ability to efflux out chemotherapeutic drugs include ABCA2, ABCB1, ABCC1, ABCC2, ABCC3, ABCC4, ABCC5, ABCC6, ABCC11, and ABCG2.It has been hypothesized that recurrent metastatic drug-resistant cancer could result in part due to the presence of cancer stem cells.