CD133 expression is not selective for tumor-initiating or radioresistant cell populations in the CRC cell lines HCT-116
Received 28 April 2009; received in revised form 17 June 2009; accepted 24 June 2009. published online 25 August 2009.
Abstract
Background and purpose
CD133 is controversially discussed as putative (surrogate) marker for cancer stem/tumor-initiating cell populations (CSC/TIC) in epithelial tumors including colorectal carcinomas (CRCs). We studied CD133 expression in established CRC cell lines and examined in vitro behavior, radioresponse and in vivo tumor formation of CD133+/− subpopulations of one cell line of interest.
Materials and methods
Ten CRC cell lines were analyzed for CD133 expression using flow cytometry and Western blotting. CD133+ and CD133− HCT-116 subpopulations were separated by FACS and studied in 2-D and 3-D culture and colony formation assays after irradiation. Subcutaneous xenograft formation was monitored in NMRI (nu/nu) mice.
Results and conclusions
CRC cell lines could be classified into three groups: (i) CD133−, (ii) CD133+ and (iii) those with two distinct CD133+ and CD133− subpopulations. Isolated CD133+/− HCT-116 subpopulations were studied relative to the original fraction. No difference was found in 2-D growth, spheroid formation or radioresponse in vitro. Also, tumor formation and growth rate did not differ for the sorted subpopulations. However, a subset of xenografts originated from CD133− HCT-116 showed a striking enrichment in the CD133+ fraction. Our data show that CD133 expression is not selective for sphere forming, tumor-initiating or radioresistant subpopulations in the HCT-116 CRC cell lines. This implies that CD133 cannot be regarded as a CSC/TIC marker in all CRC cell lines and that functional measurements of tumor formation have to generally accompany CSC/TIC-directed mechanistic or therapeutic studies.
aTumor Pathophysiology, OncoRay – Center for Radiation Research in Oncology, Dresden University of Technology, Germany
bInstitute of Legal Medicine, Dresden University of Technology, Germany
cOncoRay – Center for Radiation Research in Oncology, Dresden University of Technology, Germany
dDepartment of Radiation Oncology, University Hospital Dresden, Germany
eDepartment of General and Visceral Surgery, University Medicine Goettingen, Germany
fNational Cancer Institute, National Institutes of Health, Bethesda, MD, USA
Corresponding author. Address: OncoRay – Center for Radiation Research in Oncology, Faculty of Medicine Carl Gustav Carus, Dresden University of Technology, Fetscherstraße 74, PF 86, 01307 Dresden, Germany.
ABSTRACT