Nestin-positive progenitor cells derived from adult human pancreatic islets of Langerhans contain side population (SP) cells defined by expression of the ABCG2 (BCRP1) ATP-binding cassette transporter

ABC transporters, neural stem cells and neurogenesis – a different perspective

“…In particular, ABCB1 is expressed in human CD34+ stem cells, which can be identified by their ability to transport fluorescent dyes like Rh123 and Hoechst-33342 [128,129,[137][138][139][140][141][142][143]. Interestingly, the SP phenotype in rodent and human tissues often appears to be specifically determined by the expression of an ABC transporter: for example, both ABCB1 and ABCG2 transporters are highly expressed in the SP of stem cells from different tissues such as brain, bone marrow, pancreas, liver and others, all of which can be isolated based on the cells' ability to promote the efflux of the Hoechst-33342 fluorescent dye [9,[129][130][131][132][133][134][135][136][142][143][144][145][146][147][148][149][150]. Moreover, different research teams have demonstrated that ABCA3 and ABCG2 were expressed at higher levels in SP cells than in non-SP cells in human, rhesus monkey and mouse hematopoietic tissues; and microarray analysis indicated that several genes related to stem cells were substantially upregulated in the SP cells in comparison to non-SP cells [130,151,152].…”

“…This SP phenotype is present in several kinds of stem cells from different tissues, including the hematopoietic, meschenchymal, heart, liver, and pancreatic stem cells; it disappears with verapamil treatment thus indicating that the SP phenotype might result from the expression of ABC transporters in a primitive subset of stem cells in mammals [140,142,131,145,146,148,153,154]. Since SP stem cells show high repopulating activity and ABCA3, ABCB1 and ABCG2 expression, it has been hypothesized that the special phenotype of SP cells might be controlled or regulated by the expression of ABC transporters [142,144,145,149,155,156].…”

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].…”

Human limbal epithelium contains side population cells expressing the ATP-binding cassette transporter ABCG2

“…SP cells have also been identified in hematopoietic compartments in a number of animals [7][8][9][10]. In addition, SP cells have been isolated from various types of adult tissue where they demonstrate stem cell activity [6,[10][11][12][13][14][15][16]. These findings suggest that the SP phenotype represents a common feature of stem cells.…”