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STEM CELL GENETICS AND GENOMICS

Oct-4 Expression in Adult Human Differentiated Cells Challenges Its Role as a Pure Stem Cell Marker

^aCell Factory, Center for Transfusion Medicine, Cellular Therapy and Cryobiology, Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milan, Italy;
^bLaboratory of Molecular Pharmacology, Istituto di Ricerche Farmacologiche "Mario Negri," Milan, Italy;
^cLaboratory of Molecular Genetics and Gene Expression, Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milan, Italy;
^dLaboratory of Vascular Biology and Gene Therapy, Centro Cardiologico Monzino, Istituto di Ricovero e Cura a Carattere Scientifico, Milan, Italy

Key Words. Oct-4 • Human peripheral cells • Stem cell marker

Correspondence: Lorenza Lazzari, D.Sc., Cell Factory, Center for Transfusion Medicine, Cellular Therapy and Cryobiology, Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via F. Sforza 35, 20122 Milano, Italy. Telephone: +39 02 5503 4053; Fax: +39 02 5503 2796; e-mail: cbbank{at}policlinico.mi.it

Received September 28, 2006; accepted for publication March 14, 2007.
First published online in STEM CELLS EXPRESS   March 22, 2007.



The Oct-4 transcription factor, a member of the POU family that is also known as Oct-3 and Oct3/4, is expressed in totipotent embryonic stem cells (ES) and germ cells, and it has a unique role in development and in the determination of pluripotency. ES may have their postnatal counterpart in the adult stem cells, recently described in various mammalian tissues, and Oct-4 expression in putative stem cells purified from adult tissues has been considered a real marker of stemness. In this context, normal mature adult cells would not be expected to show Oct-4 expression. On the contrary, we demonstrated, using reverse transcription-polymerase chain reaction (PCR) (total RNA, Poly A+), real-time PCR, immunoprecipitation, Western blotting, band shift, and immunofluorescence, that human peripheral blood mononuclear cells, genetically stable and mainly terminally differentiated cells with well defined functions and a limited lifespan, express Oct-4. These observations raise the question as to whether the role of Oct-4 as a marker of pluripotency should be challenged. Our findings suggest that the presence of Oct-4 is not sufficient to define a cell as pluripotent, and that additional measures should be used to avoid misleading results in the case of an embryonic-specific gene with a large number of pseudogenes that may contribute to false identification of Oct-4 in adult stem cells. These unexpected findings may provide new insights into the role of Oct-4 in fully differentiated cells.

Disclosure of potential conflicts of interest is found at the end of this article.

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