Spheres derived from the human SN12C renal cell carcinoma cell line are enriched in tumor initiating cells.

Yanhui Zhang,Zhiyong Liu,Xiulan Zhao,Huizhi Sun,Xin Yao,Baocun Sun,Xueyi Dong,Wei Cui

doi:10.1186/s13046-016-0442-8

Abstract

BackgroundRecently, tumor initiating cells (TICs), which possess self-renewal and other stem cell properties, are regarded as the cause of tumor initiation, recurrence and metastasis. The isolation and identification of TICs could help to develop novel therapeutic strategies.MethodsIn this study, we isolated spheroid cells from human renal cell carcinoma (RCC) cell line SN12C in stem cell-conditioned medium. The stemness characteristics of spheroid cells, including tumorigenicity, self-renewal, proliferation and aldehyde dehydrogenase (ALDH) activity were evaluated; the expression levels of stemness genes and related proteins were assessed. Furthermore, study examined the differentiation of TICs into endothelial cells and the relationship between TICs and EMT.ResultsOur data demonstrated that spheroid cells cultured in defined serum-free medium possessed TIC properties, such as high tumorigenic capacity, upregulation of TIC-related genes and proteins, persistent self-renewal and extensive proliferation. Furthermore, spheroid cells were more aggressive in growth, invasion, scratch recovery, clonogenic survival and high aldehyde dehydrogenase (ALDH) activity. Interestingly, a marked increase in tumor vascularity compared to adherent tumors in vivo, and spheroid cells can differentiate into functional endothelial-like cells in vitro suggesting a role of tumor initiating cells in tumor angiogenesis. The spheroid cells also demonstrated down-regulated E-cadherin and up-regulated Vimentin expression, which is the typical phenotype of EMT.ConclusionsThese results suggest that spheroid cells with tumor initiating cells-like characteristics contributed to tumor generation, progression, high tumorigenicity, pro-angiogenic capability and relationship with EMT. Further experiments using more refined selection criteria such as a combination of two or multiple markers would be useful to specifically identify and purify TICs.

Highlights

Tumor initiating cells (TICs), which possess self-renewal and other stem cell properties, are regarded as the cause of tumor initiation, recurrence and metastasis
Detection of spheroid cells of SN12C Previous studies demonstrated that stem cells were able to form spheres in the serum-free culture
The selfrenewing capacity of these spheroid body-forming cells was assessed by dissociating them into single cell and growing in serum-free medium described in the methods section

Summary

Introduction

Tumor initiating cells (TICs), which possess self-renewal and other stem cell properties, are regarded as the cause of tumor initiation, recurrence and metastasis. It has been assumed that tumor initiating cells (TICs) constitute a reservoir of self-sustaining cells with ability to self-renew and maintain the tumor [3,4,5]. Evidence is accumulating that TICs have been isolated from several types of human tumors, such as breast cancer and brain tumors [6, 12]. The literature of investigating stem cells of kidney cancers is limited and lack of TIC-specific cell surface antigen markers. In the present study, we isolated spheroid cells from RCC cell line (SN12C) and determined whether these cells acquired TICs characteristics, including self-renewing capacity and tumorigenic capacity

Methods

Results

Conclusion