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MUC1* mediates the growth of human pluripotent stem cells.

Hikita ST, Kosik KS, Clegg DO, Bamdad C - PLoS ONE (2008)

Bottom Line: Unexpectedly, we found that newly differentiated cells no longer express the cleaved form, MUC1*, or its ligand, NM23.Antibody-induced dimerization of the MUC1* receptor on hESCs stimulated cell growth to a far greater degree than currently used methods that require the addition of exogenous basic fibroblast growth factor (bFGF) as well as factors secreted by fibroblast "feeder cells".These findings suggest that this primal growth mechanism could be utilized to propagate large numbers of pluripotent stem cells for therapeutic interventions.

View Article: PubMed Central - PubMed

Affiliation: Center for Stem Cell Biology and Engineering, University of California Santa Barbara, Santa Barbara, California, USA.

ABSTRACT
The MUC1 protein is aberrantly expressed on an estimated 75% of all human solid tumor cancers. We recently reported that a transmembrane cleavage product, MUC1*, is the predominant form of the protein on cancer cells [1]. Further, our evidence indicated that MUC1* functions as a growth factor receptor on tumor cells, while the full-length protein appeared to have no growth promoting activity. Here, we report that MUC1* acts as a growth factor receptor on undifferentiated human embryonic stem cells (hESCs). Cleavage of the full-length ectodomain to form MUC1*, a membrane receptor, appears to make binding to its ligand, NM23, possible. Unexpectedly, we found that newly differentiated cells no longer express the cleaved form, MUC1*, or its ligand, NM23. Newly differentiated stem cells exclusively present full-length MUC1. Antibody-induced dimerization of the MUC1* receptor on hESCs stimulated cell growth to a far greater degree than currently used methods that require the addition of exogenous basic fibroblast growth factor (bFGF) as well as factors secreted by fibroblast "feeder cells". Further, MUC1* mediated growth was shown to be independent of growth stimulated by bFGF or the milieu of factors secreted by feeder cells. Stimulating the MUC1* receptor with either the cognate antibody or its ligand NM23 enabled hESC growth in a feeder cell-free system and produced pluripotent colonies that resisted spontaneous differentiation. These findings suggest that this primal growth mechanism could be utilized to propagate large numbers of pluripotent stem cells for therapeutic interventions.

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The MUC1* ligand, NM23, co-localizes with MUC1* and OCT4 on undifferentiated hESCs but immuno-reactivity of all three proteins is lost in the portion of the colony that has begun to differentiate.Undifferentiated H9 hESC colonies stained positive for NM23, MUC1* and OCT4. Newly differentiating colonies did not react with antibodies against any of the three proteins. Co-expression of NM23 with OCT4 and MUC1* is best seen in colonies that have begun to differentiate. The dotted line marks the border between undifferentiated and differentiated portions of the colonies. Triple staining experiments were performed using: A. anti-NM23 (green). B. Anti-MUC1* (red). C. anti-NM23 (green), anti-MUC1* (red) and DAPI (blue). A similar colony was stained with: D. anti-NM23 (green). E. anti-OCT4 (red). F. anti-NM23 (green), anti-OCT4 (red) and DAPI (blue). Scale bar = 100 µm.
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pone-0003312-g006: The MUC1* ligand, NM23, co-localizes with MUC1* and OCT4 on undifferentiated hESCs but immuno-reactivity of all three proteins is lost in the portion of the colony that has begun to differentiate.Undifferentiated H9 hESC colonies stained positive for NM23, MUC1* and OCT4. Newly differentiating colonies did not react with antibodies against any of the three proteins. Co-expression of NM23 with OCT4 and MUC1* is best seen in colonies that have begun to differentiate. The dotted line marks the border between undifferentiated and differentiated portions of the colonies. Triple staining experiments were performed using: A. anti-NM23 (green). B. Anti-MUC1* (red). C. anti-NM23 (green), anti-MUC1* (red) and DAPI (blue). A similar colony was stained with: D. anti-NM23 (green). E. anti-OCT4 (red). F. anti-NM23 (green), anti-OCT4 (red) and DAPI (blue). Scale bar = 100 µm.

Mentions: NM23 is normally a cytoplasmic protein but is often secreted by tumor cells [33]. It can exist as a monomer, dimer, tetramer or hexamer, depending upon concentration [34]. NM23 has recently been identified as a ligand for MUC1* that stimulates the growth of tumor cells by dimerizing two MUC1* receptors [1]. We, therefore, looked for NM23 expression by hESCs. Figure 6 A–C depicts a triple staining experiment in which a hESC colony was stained with DAPI and antibodies against NM23 and MUC1*. The merged image (Fig. 6C) shows that expression of MUC1* and NM23 precisely co-localize, but are not expressed on newly differentiating cells at the edge of the colony. Another colony that had been stained with DAPI and antibodies against NM23 and OCT4 confirms that NM23-positive cells were in fact undifferentiated. Differentiated hESCs did not stain positive for the presence of NM23 (Fig. 6 D–F). These results are consistent with the idea that NM23 could also be a ligand of MUC1* on hESCs.


MUC1* mediates the growth of human pluripotent stem cells.

Hikita ST, Kosik KS, Clegg DO, Bamdad C - PLoS ONE (2008)

The MUC1* ligand, NM23, co-localizes with MUC1* and OCT4 on undifferentiated hESCs but immuno-reactivity of all three proteins is lost in the portion of the colony that has begun to differentiate.Undifferentiated H9 hESC colonies stained positive for NM23, MUC1* and OCT4. Newly differentiating colonies did not react with antibodies against any of the three proteins. Co-expression of NM23 with OCT4 and MUC1* is best seen in colonies that have begun to differentiate. The dotted line marks the border between undifferentiated and differentiated portions of the colonies. Triple staining experiments were performed using: A. anti-NM23 (green). B. Anti-MUC1* (red). C. anti-NM23 (green), anti-MUC1* (red) and DAPI (blue). A similar colony was stained with: D. anti-NM23 (green). E. anti-OCT4 (red). F. anti-NM23 (green), anti-OCT4 (red) and DAPI (blue). Scale bar = 100 µm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2553196&req=5

pone-0003312-g006: The MUC1* ligand, NM23, co-localizes with MUC1* and OCT4 on undifferentiated hESCs but immuno-reactivity of all three proteins is lost in the portion of the colony that has begun to differentiate.Undifferentiated H9 hESC colonies stained positive for NM23, MUC1* and OCT4. Newly differentiating colonies did not react with antibodies against any of the three proteins. Co-expression of NM23 with OCT4 and MUC1* is best seen in colonies that have begun to differentiate. The dotted line marks the border between undifferentiated and differentiated portions of the colonies. Triple staining experiments were performed using: A. anti-NM23 (green). B. Anti-MUC1* (red). C. anti-NM23 (green), anti-MUC1* (red) and DAPI (blue). A similar colony was stained with: D. anti-NM23 (green). E. anti-OCT4 (red). F. anti-NM23 (green), anti-OCT4 (red) and DAPI (blue). Scale bar = 100 µm.
Mentions: NM23 is normally a cytoplasmic protein but is often secreted by tumor cells [33]. It can exist as a monomer, dimer, tetramer or hexamer, depending upon concentration [34]. NM23 has recently been identified as a ligand for MUC1* that stimulates the growth of tumor cells by dimerizing two MUC1* receptors [1]. We, therefore, looked for NM23 expression by hESCs. Figure 6 A–C depicts a triple staining experiment in which a hESC colony was stained with DAPI and antibodies against NM23 and MUC1*. The merged image (Fig. 6C) shows that expression of MUC1* and NM23 precisely co-localize, but are not expressed on newly differentiating cells at the edge of the colony. Another colony that had been stained with DAPI and antibodies against NM23 and OCT4 confirms that NM23-positive cells were in fact undifferentiated. Differentiated hESCs did not stain positive for the presence of NM23 (Fig. 6 D–F). These results are consistent with the idea that NM23 could also be a ligand of MUC1* on hESCs.

Bottom Line: Unexpectedly, we found that newly differentiated cells no longer express the cleaved form, MUC1*, or its ligand, NM23.Antibody-induced dimerization of the MUC1* receptor on hESCs stimulated cell growth to a far greater degree than currently used methods that require the addition of exogenous basic fibroblast growth factor (bFGF) as well as factors secreted by fibroblast "feeder cells".These findings suggest that this primal growth mechanism could be utilized to propagate large numbers of pluripotent stem cells for therapeutic interventions.

View Article: PubMed Central - PubMed

Affiliation: Center for Stem Cell Biology and Engineering, University of California Santa Barbara, Santa Barbara, California, USA.

ABSTRACT
The MUC1 protein is aberrantly expressed on an estimated 75% of all human solid tumor cancers. We recently reported that a transmembrane cleavage product, MUC1*, is the predominant form of the protein on cancer cells [1]. Further, our evidence indicated that MUC1* functions as a growth factor receptor on tumor cells, while the full-length protein appeared to have no growth promoting activity. Here, we report that MUC1* acts as a growth factor receptor on undifferentiated human embryonic stem cells (hESCs). Cleavage of the full-length ectodomain to form MUC1*, a membrane receptor, appears to make binding to its ligand, NM23, possible. Unexpectedly, we found that newly differentiated cells no longer express the cleaved form, MUC1*, or its ligand, NM23. Newly differentiated stem cells exclusively present full-length MUC1. Antibody-induced dimerization of the MUC1* receptor on hESCs stimulated cell growth to a far greater degree than currently used methods that require the addition of exogenous basic fibroblast growth factor (bFGF) as well as factors secreted by fibroblast "feeder cells". Further, MUC1* mediated growth was shown to be independent of growth stimulated by bFGF or the milieu of factors secreted by feeder cells. Stimulating the MUC1* receptor with either the cognate antibody or its ligand NM23 enabled hESC growth in a feeder cell-free system and produced pluripotent colonies that resisted spontaneous differentiation. These findings suggest that this primal growth mechanism could be utilized to propagate large numbers of pluripotent stem cells for therapeutic interventions.

Show MeSH
Related in: MedlinePlus