OCT-4 Challenged

Milan, Italy -

The ability of molecular and cellular biologists to distinguish cells of various potency in terms of "stemness" is greatly assisted by specific cellular markers. For example, hematopoietic stem cells are known to contain the marker CD34, which acts as an adhesion molecule, but also is somewhat specific to cells capable of producing other blood cells. CD34 for purification of the stem cell compartment out of human bone marrow samples has been extensively used for autologous transplantation in cancer, as well as concentration of stem cells for use in myocardial infarction.

Embryonic stem cells are generally believed to express several markers that are associated with pluripotency. For example, Oct-4 is a POU transcription factor that upregulations expression of genes such as Sox-2, Nanog, undifferentiated transcription factor 1 (Utf1), and Rex-1. Indeed it has been published that transfection of "Oct-4 may endow a "dedifferentiation" like effect into mature cells":https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16932739&itool=pubmed_AbstractPlus. Additionally, repression of Oct-4 induces accelerated differentiation of various stem cell types.

These above data seem to support that Oct-4 would be a prime candidate for a marker of early stem cells. However, a recent paper (Zangrossi et al. Oct-4 expression in adult human differentiated cells challenges its role as a pure stem cell marker Stem Cells. 2007 Mar 22) appears to provide evidence that Oct-4 is expressed on a variety of differentiated cells, including peripheral blood mononuclear cells.

This paper appears to demonstrate pretty extensively, using RT-PCR (total RNA - Poly A+), Real Time-PCR, immunoprecipation and Western blotting, Band Shift and immunofluorescence that Oct-4 is present in peripheral blood mononuclear cells. If these data are reproducible, it may be that certain limitations of Oct-4 as a true marker of "stemness" may have to be taken into consideration.