Co-existence of epithelioid and fibroblastoid subsets in a sarcomatoid renal carcinoma cell line revealed by clonal studies.
BACKGROUND
The biology of sarcomatoid renal cell carcinoma (RCC) and its conversion from and to the clear cell RCC are not fully-understood. We aimed to analyze the sarcomatoid RCC cell line, RCC52, derived from a lymph node metastatic lesion consisting mostly of sarcomatoid RCC cells with occasional clear cell areas.


METHODS
Representative clonal epithelioid and fibroblastoid sublines isolated from the RCC52 cell line were analyzed alongside the parental line. Cytofluorometric and western blot analyses were used for phenotypic study. Xenotransplantation and in vitro invasive assays were used to determine tumorigenicity and invasiveness. Immunohistology in conjunction with antibodies to paired box gene-2 (PAX2) were used to determine if xenografts or tumor biopsies had the clear cell component.


RESULTS
RCC52 cells grown as monolayers in vitro were all PAX2-negative, and consisted mostly of epithelioid cells and partly of fibroblastoid cells as noted in a previous study, confirming the co-existence of these two cell types in the in vitro growth of exclusive sarcomatoid RCC cells. Immunohistology revealed that the parental line and all epithelioid sublines tested were able to develop into solid tumors consisting mostly of sarcomatoid cells with PAX2-positive clear cells in some areas. The RCC stem cell marker CD105 was selectively expressed by a small proportion of the epithelioid, but not fibroblastoid, sublines, which was in line with the tumorigenic property of the epithelioid sublines containing cancer stem cells (CSCs). In contrast, only fibroblastoid sublines exhibited migratory/invasive properties, as determined by in vitro assays.


CONCLUSIONS
Our findings confirm the presence of two distinct subsets in the RCC52 line, and suggest the epithelioid subset being able to de-differentiate to clear cells, albeit partially, and harboring CSCs as an emerging therapeutic target in order to achieve effective treatment of this malignancy.
Taipei Medical University, Taipei, Taiwan, R.O.C. E-mail: liaosk@h.tmu.edu.tw and Dr. Ming-Ling Kuo, Chang Gung University, Taoyuan, Taiwan, R.O.C. mingling@mail.cgu.edu.tw.
Chin-Hsuan
CH
Hsieh
Hung-Chang
HC
Chen
Ying-Hsu
YH
Chang
See-Tong
ST
Pang
Ming-Ling
ML
Kuo
Cheng-Keng
CK
Chuang
Shuen-Kuei
SK
Liao
D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000556:secondary*; D002448:Cell Adhesion; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D016130:Immunophenotyping; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016688:Mice, Inbred NOD; D008819:Mice, Nude; D016513:Mice, SCID; D008875:Middle Aged; D051762:PAX2 Transcription Factor / Q000378:metabolism*; D012509:Sarcoma / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor; D051762:PAX2 Transcription Factor
Clear cell renal carcinoma; cell line and clonal sublines; de-differentiation; epithelioid; fibroblastoid; sarcomatoid differentiation; xenotransplantation