Pluripotent human embryonic stem cells (ESCs) can be differentiated in vitro into a variety of cells which hold promise for
transplantation therapy. Human embryonal carcinoma cells (ECCs), stem cells of human
teratocarcinomas, are considered a close but malignant counterpart to human ESCs. In this study, a comprehensive quantitative proteomic analysis of ESCs and ECCs was carried out using the iTRAQ method. Using two-dimensional LC and MS/MS analyses, we identified and quantitated approximately 1800
proteins. Among these are
proteins associated with pluripotency and development as well as tight junction signaling and
TGFbeta receptor pathway. Nearly approximately 200
proteins exhibit more than twofold difference in abundance between ESCs and ECCs. Examples of early developmental markers high in ESCs include
beta-galactoside-binding lectin, undifferentiated embryonic cell transcription factor-1,
DNA cytosine methyltransferase 3beta
isoform-B,
melanoma antigen family-A4, and
interferon-induced transmembrane protein-1. In contrast, CD99-antigen (CD99), growth differentiation factor-3, cellular
retinoic acid binding protein-2, and developmental pluripotency associated-4 were among the highly expressed
proteins in ECCs. Several
proteins that were highly expressed in ECCs such as heat shock 27 kDa protein-1,
mitogen-activated protein kinase kinase-1, nuclear factor of kappa light
polypeptide gene enhancer in B-cells inhibitor like-2, and S100
calcium-binding protein-A4 have also been attributed to
malignancy in other systems. Importantly, immunocytochemistry was used to validate the proteomic analyses for a subset of the
proteins. In summary, this is the first large-scale quantitative proteomic study of human ESCs and ECCs, which provides critical information about the regulators of these two closely related, but developmentally distinct, stem cells.