Transformed human pluripotent stem cells and associated methods

Abstract

The present disclosure provides transformed human pluripotent stem cell (t-hPSC). t-hPSCs are not dependent on Oct4 for renewal and survival, however exhibit a sensitivity to reduced levels of the transcription factor Nanog. Also provided are methods of culturing cells for use in a cell-based screening assay comprising placing one or more transformed human pluripotent stem cells into a receptacle and culturing said stem cells in the receptacle to form a monolayer of stem cells without cell overlap. Methods of screening compounds using t-hPSCs are also described.

1 . A transformed human pluripotent stem cell (t-hPSC) wherein the cell does not require bFGF for maintenance of an undifferentiated state. 
     
     
         2 . The transformed human pluripotent stem cell of  claim 1 , wherein:
 a) the cell co-expresses FGFR1 and IGFR1,   b) the cell maintains expression of SSEA3 in the absence of bFGF, or   c) the cell requires Nanog for self-renewal and cell survival.   
     
     
         3 . The transformed human pluripotent stem cell of  claim 1 , wherein the cell exhibits reduced neuronal differentiation or reduced hematopoietic potential in vitro compared to a normal human pluripotent stem cell. 
     
     
         4 . The transformed human pluripotent stem cell of  claim 1 , wherein t-hPSC-derived neural precursors do not form metastasis in vivo. 
     
     
         5 . The transformed human pluripotent stem cell of  claim 1 , wherein the cell can be passaged as a single cell. 
     
     
         6 . A method of screening a compound for a biological activity comprising:
 a) contacting one or more transformed human pluripotent stem cells (t-hPSCs) of  claim 1  with the compound;   b) detecting an effect of the compound on the one or more t-hPSCs, wherein the effect is indicative of the biological activity of the compound.   
     
     
         7 . The method of  claim 6 , wherein the biological activity is cell differentiation activity or loss of pluripotency. 
     
     
         8 . The method of  claim 7 , wherein step b) comprises detecting the emergence of progenitor or precursor cells from the one or more t-hPSCs that are otherwise refractory to differentiation. 
     
     
         9 . The method of  claim 7 , wherein step b) comprises detecting the expression of one of more biomarkers selected from the group consisting of Oct4, Sox2, Nanog, SSEA3, SSEA4, TRA-1-60, TRA-1-81, IGF1 receptor, connexin 43, E-cadherin, Alkaline phosphatase, REX1, CRIPTO, CD24, CD90, CD29, CD9 and CD49f. 
     
     
         10 . The method of  claim 6 , wherein the biological activity is anticancer activity and step b) comprises detecting a reduction in colony initiating cells. 
     
     
         11 . The method of  claim 6 , wherein the biological activity is anticancer activity and step b) comprises detecting an increase in cell differentiation, an increase in loss of pluripotency, a decrease in cell proliferation, a decrease in cell number, a decrease in DNA content, a decrease in cell growth, an increase in cytotoxicity, or an increase in apoptosis. 
     
     
         12 . The method of  claim 6 , further comprising comparing the effect of the compound on the one or more t-hPSCs determined in step b) to an effect of the compound on one or more normal stem cells (SCs). 
     
     
         13 . The method of  claim 12 , wherein the effect of the compound on one or more normal stem cells (SCs) is determined by
 c) contacting one or more stem cells (SCs) with the compound;   d) detecting an effect of the compound on the one or more SCs, wherein the effect is indicative of the biological activity of the compound.   
     
     
         14 . The method of  claim 13 , further comprising identifying compounds that exhibit a different level of biological activity on the one or more t-hPSCs compared to the one or more SCs. 
     
     
         15 . The method of  claim 6 , further comprising placing one or more t-hPSCs into a receptacle and culturing the cells in the receptacle to form a monolayer prior to contacting the cells with the compound. 
     
     
         16 . The method of  claim 15 , wherein a single t-hPSC is placed into the receptacle and the monolayer of t-hPSCs is a homogeneous clonal colony of the single t-hPSC. 
     
     
         17 . A cell culture comprising a plurality of transformed human pluripotent stem cells (t-hPSCs) of  claim 1 . 
     
     
         18 . A method of identifying transformed pluripotent stem cells or transformed induced pluripotent stem cells comprising identifying stem cells that maintain expression of SSEA-3 when deprived of bFGF. 
     
     
         19 . The method of  claim 18  comprising:
 a) culturing pluripotent stem cells with bFGF; 
 b) analyzing the cells for SSEA-3 to provide a first level of SSEA-3 expression; 
 c) depleting the cell culture of bFGF; 
 d) analyzing the cells for SSEA-3 to provide at least a second level of SSEA-3 expression; 
 e) identifying those cells that maintain expression of SSEA-3 upon depletion of bFGF by comparing the first and second levels of SSEA-3 expression. 
 
     
     
         20 . A method of identifying transformed pluripotent stem cells comprising
 a) inhibiting Oct4 expression in a population of pluripotent stem cells; and   b) identifying undifferentiated cells that maintain expression of SSEA3.