Absence of OCT4 Expression in Somatic Tumor Cell Lines

Abstract

The POU-domain transcription factor OCT4 is associated with the pluripotent state of cells comprising the inner cell mass of pre-implantation embryos and has been known to play a critical role in the maintenance of pluripotency of embryonic stem cells. Reactivation of OCT4 expression is postulated to occur in differentiated cells that have undergone carcinogenesis, or tumor formation. In contrast to earlier studies, recent reports describe OCT4 expression in several human tumor cell lines. To resolve the apparent discrepancy in OCT4 expression between earlier and recent studies, we determined OCT4 expression in the cervical carcinoma cell line HeLa and the breast cancer cell line MCF7 in comparison with the human teratoma cell line nTera by immunofluorescence, Western blot, and RT-PCR analyses. We were unable to detect staining of the OCT4 transcription factor in the nucleus of HeLa and MCF7 cells by immunofluorescence using two different monoclonal antibodies. Faint cytoplasmic staining in HeLa and MCF7 cells was observed; however, no OCT4 signal could be detected by Western blot analysis. In addition, we were unable to detect significant levels of OCT4 mRNA in HeLa and in MCF7 cells by RT-PCR. Furthermore, the OCT4 promoter region is highly methylated in HeLa and MCF7 cells. We argue that recent reports of OCT4 expression in these and other cancer cell lines could actually be attributed to OCT4 pseudogene expression or misinterpretation of background signals in immunofluorescence experiments. In conclusion, we emphasize the need for adequate controls in investigations of OCT4 expression in somatic cell lines by immunofluorescence and RT-PCR. STEM CELLS 2008;26:692-697 Disclosure of potential conflicts of interest is found at the end of this article.

In Vivo Osteoprogenitor Potency of Human Stromal Cells from Different Tissues Does Not Correlate with Expression of POU5F1 or Its Pseudogenes

“…Primer pairs designed to amplify only true POU5F1A and not its pseudogenes confirmed the expression of POU5F1A in embryonic carcinoma cells but failed to amplify PCR products from peripheral blood mononuclear cells (PBMNC), suggesting POU5F1A is not transcribed in these cells [20]. Indeed, we demonstrated that, like human PBMNC [21], human tumor cell lines [22], and murine mesenchymal stromal cells [23], neither the multipotent BM-MSC nor the non-UVSC in fact expressed detectable levels of POU5F1A protein.…”

Progenitor stem cell marker expression by pulmonary carcinomas

“…The absence of staining in pulmonary carcinomas for OCT-4, an embryonic stem cell marker, is confirmatory. 35,36 The OCT-4 staining is positive in germ-cell tumors, such as seminomas and embryonal carcinomas, but not in somatic tumors.…”

Sox2 expression in breast tumours and activation in breast cancer stem cells

“…Moreover, we did not observe expression of any of the other pluripotencyassociated genes in MCF7-derived spheres, consistently with the results obtained in human tumours. Despite some reports claiming expression of Oct4 and Nanog in breast carcinoma cell lines, expression of several pseudogenes have been reported for both Oct4 and Nanog (Suo et al, 2005;Zhang et al, 2006;Cantz et al, 2007;Ambady et al, 2010), therefore, particular care must be taken to avoid PCR amplification of those pseudogenes. We base our conclusions in antibodybased assays, thus, looking specifically at the protein level to avoid pseudogene detection.…”