MALIGNANT RHABDOID TUMOR - A STUDY WITH 2 ESTABLISHED CELL-LINES

Background. Malignant rhabdoid tumor (MRT), originally described as a rare renal sarcoma in childhood, has been known to express phenotypic diversity. In this study, unique characteristics of the MRT cells were investigated by using established cell lines. Methods. Immunocytochem ical, ultrastructural, cytogenetic, and molecular (by polymerase chain reaction, PCR) analyses were done for two MRT cell lines, one of rena l and one of extrarenal origin, before and after differentiation-induc tion with either 12-O-tetradecanoyl phorbol-13-acetate (TPA) or transr etinoic acid (RA). Results. The proliferating cells in the original tu mor tissues as well as in the established cell lines demonstrated neur al, epithelial, and mesenchymal markers morphologically. Both cell lin es had karyotypic abnormalities including chromosome 22q11.2. The cell line from the extrarenal MRT, Tm87-16, demonstrated distinct morpholo gic changes with neuroblastic differentiation and produced numerous ne uritic processes after treatment with either TPA or RA. The cell line from the renal MRT, STM91-01, suggested schwannian differentiation but did not change morphologically after chemical induction. Both cell li nes expressed c-myc, but did not express N-myc, MyoD1, tyrosine hydrox ylase, or neural cell adhesion molecule (N-CAM). With PCR and immunocy tochemical study, a high level of chromogranin expression was detected by the cells of Tm87-16 only after TPA induced differentiation. Concl usions. MRT cells demonstrated diverse phenotype of neuro-ecto-mesench ymal differentiation. The results of this study suggest that MRT may b e derived from a primitive pluripotential cell, such as neural crest o r equivalent. MRT, therefore, might be categorized as one of the subse ts of primitive neuroectodermal tumor.