Co-Existence Of Epithelioid And Fibroblastoid Subsets In A Sarcomatoid Renal Cell Carcinoma: Comparative Studies Between Clonal Sublines And Cytofluorometrically Sorted Cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Currently, understanding of the pathobiology of sarcomatoid renal cell carcinoma (sRCC) is incomplete. We previously reported the co-existence of epithelioid and fibroblastoid subsets in the sRCC cell line known as RCC52 with total loss of HLA class I expression through genetic and clonal cell studies (Cancer Immunol Immunother, 2009;58:395-408; Anticancer Res, 2013;35:4875-90). We argued that the conclusions drawn from data generated by clonal studies might have not been objective, since only a limited number of sublines from each morphologically distinct cell type were investigated. In this study, using anti-CD44 and anti-CD24 mAbs, we have been able to sort out the two subsets revealing that the CD44+/CD24- phenotype is for the epithelioid subset and the CD44+/CD24+ phenotype is for the fibroblastoid subset. The differential expression of two markers could also be used to identify the two morphologically distinct clonal sublines and the phenotypic results turned out to be consistent with those of sorted cell subsets, for examples: (i) in both differently prepared subsets, the respective phenotypic features in terms of the differential expression of CD44 and CD24 remained persistently stable after 12 in vitro passages; (ii) only epithelioid but not fibroblastoid cells expressed surface E-Cadherin; (iii) expression of surface CD105 was found much more abundant in epithelioid cells as compared with fibroblastoid ones; (iv) epithelioid cells exhibited stronger clonogenicity in semisolid agar as compared with fibroblastoid ones; and (v) fibroblastoid cells displayed greater migratory/invasive ability than epithelioid ones in in vitro assays. However, one inconsistent result between clonal and sorted cells was found that in xenotransplantation experiments with NOD/SCID immunodeficient mice, only epithelioid, but not fibroblastoid clonal sublines, developed tumors at the injection site, in contrast to sorted fibroblastoid cells which gave rise to larger tumor masses and faster growth rates than sorted epithelioid cells. The results obtained with sorted cells were more reflective of the whole tumor population and in vivo situations. Our findings highlight the difference in the functional properties of the two distinct subsets in this sRCC cell line. Further investigations with additional sRCC cell lines/tumors are needed to determine if the co-existence of epithelioid and fibroblastoid subsets, the total loss of HLA class I and other noted characteristics are indeed the common features of all sRCCs. Improved understanding of tumor heterogeneity, metastatic niche and stromal progression may have a profound consequence on disease progression and metastasis, and promises to open up new strategies for therapy of this type of malignancy. Citation Format: Chin-Hsuan Hsieh, Ming-Ling Kuo, Cheng-Keng Chuang, Shuen-Kuei Liao. Co-existence of epithelioid and fibroblastoid subsets in a sarcomatoid renal cell carcinoma: Comparative studies between clonal sublines and cytofluorometrically sorted cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1198. doi:10.1158/1538-7445.AM2014-1198