Side population cells in human and mouse epidermis lack stem cell characteristics

Rat limbal epithelial side population cells exhibit a distinct expression of stem cell markers that are lacking in side population cells from the central cornea

“…Since adult stem cells are considered to be slow-cycling or arrested in the G0/G1 phases of the cell cycle [2,39,40], constitutive expression of TERT is unlikely to be observed in quiescent stem cells. Recent reports have shown that skin epidermal SP cells expressing ABCG2 and putative skin epidermal stem cells exhibiting slow cell cycling are two distinct cell populations [41] and we have also shown that limbal epithelial SP cells with significantly higher expression of ABCG2 represented a quiescent population with stem cell-like properties, without TERT activity [24].…”

Contribution of the ABC Transporters Bcrp1 and Mdr1a/1b to the Side Population Phenotype in Mammary Gland and Bone Marrow of Mice

“…Recently, however, it has become clear that another ABC transporter, Breast Cancer Resistance Protein (BCRP/ABCG2), is mainly responsible for the SP phenotype, at least in bone marrow [2][3][4][5][6]. Based on the initial findings in the hematopoietic compartment, SP cells have now been identified in many other tissues including the mammary gland [7][8][9], skeletal muscle, pancreas, lung, retina, liver, testis, heart, and epidermis [10][11][12][13][14][15][16][17]. In addition to normal tissues, it has further been demonstrated that cancer cell lines and primary tumor cells contain an SP [18][19][20].…”

Multidrug Resistance Transporters – Roles in maintaining Cancer Stem-Like Cells

“…It is believed that the SP fraction obtained is not a pure stem-cell population, which is greatly affected by the isolation method (Montanaro et al, 2004). There were also report demonstrating that SP cells do not identify stem cell (Triel et al, 2004). Moreover, ABCG2, the molecular determinant for Hoechst exclusion, is not an absolute requirement for stem cells.…”

“…Nevertheless, since CSCs lack distinct molecular markers, Hoechst 33342-dependent cell sorting remains the most widely employed technique for the identification and purification of putative CSCs. It is also noteworthy that expression of drug transporters (especially MDR1/Pgp) can be part of the differentiated phenotype of cells in normal tissue (Triel et al, 2004). Histopathological and molecular biological studies have reported increased expression of ABCB1 in more differentiated tumors (Mizoguchi et al, 1990;Nishiyama et al, 1993;Bates et www.intechopen.com al., 1989;Mickley et al, 1989).…”