Tumour formation by single fibroblast growth factor receptor 3-positive rhabdomyosarcoma-initiating cells.
BACKGROUND
The hypothesis that malignant tumours are generated by rare populations of cancer stem cells that are more tumourigenic than other cancer cells has gained increasing credence. The objective of this study was to identify and characterise a subpopulation of human sarcoma-initiating cells.


METHODS
We examined established rhabdomyosarcoma cell lines by flow cytometry. Tumourigenesis was examined by xenograft models. Real-time PCR and immunohistochemistry were performed to examine the gene expression using cell lines and biopsy specimens.


RESULTS
Rhabdomyosarcoma cell lines included small populations of fibroblast growth factor receptor 3 (FGFR3)-positive cells. FGFR3-positive KYM-1 and RD cells were more strongly tumourigenic than FGFR3-negative cells. In addition, xenoengraftment of 33% of single FGFR3-positive KYM-1 cells yielded tumour formation. Stem cell properties of FGFR3-positive cells were further established by real-time PCR, which demonstrated upregulation of undifferentiated cell markers and downregulation of differentiation markers. We showed that in the absence of serum, addition of basic fibroblast growth factor maintained and enriched FGFR3-positive cells. On the other hand, ciliary neurotrophic factor reduced the proportion of FGFR3-positive cells. Real-time PCR and immunohistochemical examination revealed that embryonal rhabdomyosarcoma patient biopsy specimens were found to over-express FGFR3.


CONCLUSIONS
Our findings suggest that rhabdomyosarcoma cell lines include a minor subpopulation of FGFR3-positive sarcoma-initiating cells, which can be maintained indefinitely in culture and which is crucial for their malignancy.
Hirotsu
M
M
Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
Setoguchi
T
T
Matsunoshita
Y
Y
Sasaki
H
H
Nagao
H
H
Gao
H
H
Sugimura
K
K
Komiya
S
S
D000818:Animals; D001706:Biopsy; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D014411:Neoplastic Stem Cells / Q000473:pathology*; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000032:analysis / Q000502:physiology*; D012208:Rhabdomyosarcoma / Q000473:pathology*
D051498:Receptor, Fibroblast Growth Factor, Type 3