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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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Transition zones between undifferentiated and differentiated hESCs simultaneously express full-length MUC1 and OCT4.hESCs grown without bFGF for 14 days appeared to be MUC1-FL positive and OCT4/MUC1* negative. However, rare transition regions were found that expressed all three proteins. A–C. The leading edge of an undifferentiated stem cell colony that has begun to differentiate stains positive for: A. MUC1-FL. B. OCT4. C. The merged image shows that MUC1-FL and OCT4 are expressed by the same cells. The border between undifferentiated and differentiated portions of the colony is marked by the dotted line. D–F. Another transition region simultaneously expressed: D. MUC1-FL. E. MUC1*. F. OCT4. However, tracking of individual cells indicates that MUC1* appears to faithfully co-localized with OCT4. Scale bars = 100 µm.
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pone-0003312-g004: Transition zones between undifferentiated and differentiated hESCs simultaneously express full-length MUC1 and OCT4.hESCs grown without bFGF for 14 days appeared to be MUC1-FL positive and OCT4/MUC1* negative. However, rare transition regions were found that expressed all three proteins. A–C. The leading edge of an undifferentiated stem cell colony that has begun to differentiate stains positive for: A. MUC1-FL. B. OCT4. C. The merged image shows that MUC1-FL and OCT4 are expressed by the same cells. The border between undifferentiated and differentiated portions of the colony is marked by the dotted line. D–F. Another transition region simultaneously expressed: D. MUC1-FL. E. MUC1*. F. OCT4. However, tracking of individual cells indicates that MUC1* appears to faithfully co-localized with OCT4. Scale bars = 100 µm.

Mentions: We further investigated the observed switch from MUC1* to MUC1-FL as stem cells enter the differentiation process. Closer inspection of many antibody-stained colonies revealed that there were rare transition regions that simultaneously expressed OCT4, the gold-standard marker for pluripotency, and full-length MUC1, which appears to be a marker for differentiation. Figure 4A–C shows that the edge of a colony that has begun to differentiate simultaneously expressed OCT4 and MUC1-FL. Other transition zones expressed MUC1-FL, MUC1* and OCT4 (Fig. 4D–I). It is notable that within these mixed populations, MUC1* appeared to faithfully co-localize with OCT4, while OCT4 sometimes co-localized with MUC1-FL.


MUC1* mediates the growth of human pluripotent stem cells.

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

Transition zones between undifferentiated and differentiated hESCs simultaneously express full-length MUC1 and OCT4.hESCs grown without bFGF for 14 days appeared to be MUC1-FL positive and OCT4/MUC1* negative. However, rare transition regions were found that expressed all three proteins. A–C. The leading edge of an undifferentiated stem cell colony that has begun to differentiate stains positive for: A. MUC1-FL. B. OCT4. C. The merged image shows that MUC1-FL and OCT4 are expressed by the same cells. The border between undifferentiated and differentiated portions of the colony is marked by the dotted line. D–F. Another transition region simultaneously expressed: D. MUC1-FL. E. MUC1*. F. OCT4. However, tracking of individual cells indicates that MUC1* appears to faithfully co-localized with OCT4. Scale bars = 100 µm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2553196&req=5

pone-0003312-g004: Transition zones between undifferentiated and differentiated hESCs simultaneously express full-length MUC1 and OCT4.hESCs grown without bFGF for 14 days appeared to be MUC1-FL positive and OCT4/MUC1* negative. However, rare transition regions were found that expressed all three proteins. A–C. The leading edge of an undifferentiated stem cell colony that has begun to differentiate stains positive for: A. MUC1-FL. B. OCT4. C. The merged image shows that MUC1-FL and OCT4 are expressed by the same cells. The border between undifferentiated and differentiated portions of the colony is marked by the dotted line. D–F. Another transition region simultaneously expressed: D. MUC1-FL. E. MUC1*. F. OCT4. However, tracking of individual cells indicates that MUC1* appears to faithfully co-localized with OCT4. Scale bars = 100 µm.
Mentions: We further investigated the observed switch from MUC1* to MUC1-FL as stem cells enter the differentiation process. Closer inspection of many antibody-stained colonies revealed that there were rare transition regions that simultaneously expressed OCT4, the gold-standard marker for pluripotency, and full-length MUC1, which appears to be a marker for differentiation. Figure 4A–C shows that the edge of a colony that has begun to differentiate simultaneously expressed OCT4 and MUC1-FL. Other transition zones expressed MUC1-FL, MUC1* and OCT4 (Fig. 4D–I). It is notable that within these mixed populations, MUC1* appeared to faithfully co-localize with OCT4, while OCT4 sometimes co-localized with MUC1-FL.

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