Establishment and characterisation of a human clear cell sarcoma model in nude mice

We have established a new experimental model of human clear cell sarcoma, UM-CCS1, using serial subcutaneous transplantation of intact tumour tissue in nude mice. The heterotransplanted nude mouse tumours retained characteristic morphological features of the primary clear cell sarcoma. Immunohistochemical analysis showed the retained expression patterns of S-100 protein, melanoma-associated antigen HMB-45 and vimentin in the xenografts as compared to the primary tumour. DNA index showed low variations both between the xenografts in the same passage and between the serial passages. Cytogenetic analysis of the primary tumour and the xenografts showed the unbalanced translocation der(6)t(6;12)(p23;q13). Based on the combined genetic data a reasonable interpretation of our findings is that there was a complex chromosomal rearrangement resulting in a cytogenetically cryptic EWS-ATF1 fusion gene. Analysis of cell kinetics using in vivo incorporation of iododeoxyuridine and flow cytometry showed generally short potential doubling time (T(pot)) of the xenografts. Volume doubling time showed low variations without correlation with T(pot). The retained phenotypic and genotypic characteristics of the primary tumour and the morphological and structural stability over time makes the model suitable for studies on the tumour biology and treatment of clear cell sarcoma.