OCT-4, an Embryonic Stem Cell Marker Expressed in Breast, Brain and Thyroid Carcinomas Compared to Testicular Carcinoma

Introduction: Cancer stem cells are a small subpopulation of cells within a tumor which are responsible for maintaining the tumor mass. A number of factors such as OCT-4 that govern the fate of adult stem cells also play a role in malignant cell transformation. OCT-4 is a key regulator of self-renewal in embryonic stem cells; its expression is potentially correlated with tumorigenesis and can affect some aspects of tumor behavior such as tumor recurrence or resistance to therapies.

Methods: We have investigated the potential expression of OCT-4 on a panel of tumors including breast, brain, thyroid and testicular carcinomas, using immunohistochemistry. The level of expression of OCT-4 was then compared to different tumor types and degree of differentiation.

Results: OCT-4 was expressed at the highest levels on nuclear site of seminoma compared with other tumors. The expression of OCT-4 was detectable in both nucleus and the cytoplasm of almost all breast tumors, but it was detectable at much lower level in normal breast tissues. OCT-4 expression was noted on poorly differentiated papillary carcinoma of thyroid compared to normal follicles of thyroid gland adjacent to the tumor.

Conclusion: Breast carcinomas and papillary carcinomas of thyroid express elevated levels of embryonic stem cell gene OCT-4, suggesting that these tumors may contain cells indicative of embryonic-like stem cells. Identification of cancer stem cells in different malignant tumors may be useful for prognostic evaluation and administration of a new treatment which target this sub-population of tumor cells.