Ecto-5′-nucleotidase (CD73) is a biomarker for clear cell renal carcinoma stem-like cells

Abstract

// Lei Song 1, 5, * , Wenling Ye 2, 5, * , Yong Cui 3, 5, * , Jianzhong Lu 4, * , Yanan Zhang 5 , Nan Ding 5 , Wentao Hu 6 , Hailong Pei 6 , Zhongjin Yue 4 , Guangming Zhou 6 1 Medical College, Northwest Minzu University, Lanzhou 730030, China 2 Medical College, Henan University, Kaifeng 475001, China 3 Department of Urology Surgery, Shuyang Hospital of Traditional Chinese Medicine, Suqian 223600, China 4 Institute of Urology, Department of Urology, Gansu Nephro-Urological Clinical Center, Key Laboratory of Urological Diseases in Gansu Province, Lanzhou University Second Hospital, Lanzhou 730030, China 5 Department of Space Radiobiology, Key Laboratory of Heavy Ion Radiation Biology and Medicine, Institute of Modem Physics, Chinese Academy of Sciences, Lanzhou 730000, China 6 School of Radiation Medicine and Protection, Medical College of Soochow University, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Suzhou 215123, China * These authors contributed equally to this work Correspondence to: Guangming Zhou, email: gmzhou@suda.edu.cn Zhongjin Yue, email: yuezhongjin@sina.com Keywords: renal cell carcinoma, cancer stem cell, SILAC, cell surface biomarker, CD73 Received: August 29, 2016      Accepted: March 17, 2017      Published: March 29, 2017 ABSTRACT Identification of a specific biomarker for cancer stem cells (CSCs) is of potential applications in the development of effective therapeutic strategies for renal cell carcinoma (RCC). In this study, both the RCC cell line 786-O and surgically removed clear cell RCC (ccRCC) tissues were implemented to grew as spheroids in serum-free medium supplemented with mitogens. This subpopulation possessed key characteristics defining CSCs. We also identified that surgically removed ccRCC tissues were heterogenic and there was a subpopulation of cells that was highly stained with rhodamine-123. Based on membrane-proteomic analyses, CD73 was identified as a candidate biomarker. We further found that CD73 high cells were highly tumorigenic. As few as 100 CD73 high cells were capable of forming xenograft tumors in non obese diabetic/severe combined immunodeficiency disease mice, whereas 1 × 10 5 CD73 low cells did not initiate tumor formation. During successive culture, the CD73 high population regenerated both CD73 high and CD73 low cells, whereas the CD73 low population remained low expression level of CD73. Furthermore, the CD73 high cells were more resistant to radiation and DNA-damaging agents than the CD73 low cells, and expressed a panel of ‘stemness’ genes at a higher level than the CD73 low cells. These findings suggest that a high level of CD73 expression is a bona fide biomarker of ccRCC stem-like cells. Future research will aim at the elucidation of the underlying mechanisms of CD73 in RCC development and the distinct aspects of ccRCC stem-like cells from other tumor types.