Arezoo Rasti - Oncopathology Research Centre, Iran University of medical Sciences (IUMS),Tehran, Iran
Mitra Mehrazma - Hasheminejad Kidney Center, Iran University of Medical Sciences, (IUMS),Tehran, Iran
Zahra Madjd - Department of Molecular Medicine, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran, Iran
Maryam Abolhasani - Hasheminejad Kidney Center, Iran University of Medical Sciences, (IUMS),Tehran, Iran

Objective: Cancer stem cells (CSCs) are characterized by self-renewal, resistance to apoptosis, and conventional therapies. The aim of this study was to evaluate OCT4 expression as a stemness marker in Renal Cell Carcinoma (RCC). Methods: The nuclear and cytoplasmic expression of OCT4 in specimens from RCC patients was evaluated by immunohistochemistry on a tissue microarray (TMA). Two hundred and thirty-seven consecutive patients treated surgically for renal cell carcinoma (RCC) between 2010 and 2015 including 162 (68.4%) Clear Cell Renal Cell Carcinoma (ccRCC), 41(17.3%) Papillary and 34 (14.3%) Chromophobe were selected. The association between OCT4 and tumor characteristics was then analyzed. Results: OCT4 was observed as cytoplasmic or nuclear expression but it was mainly localized to the cytoplasm of tumour cells. The mean cytoplasmic expression of OCT4 is significantly different in RCC subtypes (P< 0.001).There was a signiï پcant difference in the cytoplasmic expression of OCT4 in the ccRCC samples compared to the ChRCC and pRCC samples (P <0.001). A signiï پcant difference in the cytoplasmic expression levels of OCT4 in different tumor grades was observed (P =0.01). Nuclear expression of OCT4 was significantly correlated with tumor stage (P =0.04). A significant association was found between cytoplasmic expression of OCT4and tumor size. No significant association was found between nuclear and cytoplasmic expression of OCT4 and clinicopathologic parameters including regional lymph node & renal vein involvements, microvasulcar invasion (MVI) and metastasis to the Gerota’s fascia, adrenal gland, peripheral fat, and renal pelvis.Conclusion: These findings suggest that both cytoplasmic and nuclear expression of OCT can be considered as a valuable tool for the study of renal CSCs.

OCT4, Cancer stem cells (CSCs), Renal cell carcinoma (RCC), Tissue microarray (TMA)