Background/Object: BORIS/CTCFL is an 11 zinc finger (ZF) protein, which is the paralog of CTCF, a ubiquitously expressed protein with diverse roles in gene expression and chromatin organization. Several studies have shown that expression of BORIS is restricted to normal adult testis, pluripotent and diverse cancer cells. Thus, it is known as a cancer-testis (CT) gene that has been hypothesized to exhibit oncogenic properties and probably involve in cancer cell proliferation. On the contrary, others reports have shown that its expression is more widespread and can be detected in differentiated and normal somatic cells; hence, it might have roles in general cellular functions. In the present study, in order to examine these contradictory ideas. Methods: The expression profile of BORIS and some pluripotent markers including; OCT4, NANOG, SSEA1 and alkaline phosphatase (AP) were evaluated during retinoic acid (RA)-induced differentiation of P19 cells as mouse embryonal carcinoma (EC) pluripotent cells at mRNA and protein levels. Moreover, transcript level of Boris was compared in some mouse non cancer (STO and 3T3) and cancer (CT26 and N2A) cell lines by real time PCR. Results: Our results indicate that down regulation of pluripotent markers and up regulation of differentiation markers during differentiation of mouse EC P19 Cells are not accompanied with significant variations of BORIS expression. Furthermore, transcription of Boris was detected at approximately the same level in cancer and non-cancer cell lines. Conclusion: These findings suggest that in contrast to some previous reports, expression of mouse BORIS is not limited to only cancerous cells and pluripotency cell states.

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