RESUMO
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. 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. 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. 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