Establishment and immunohistochemical characterization of an experimentally induced transplantable malignant schwannoma in the rat and two derived cell lines.

Oral administration of N-methyl-N'-nitro-N-nitrosoguanidine induced gastrointestinal tumors in 15 out of 19 rats: six adenomas, seven adenocarcinomas, one fibrosarcoma and one malignant schwannoma that was homotransplantable. Both the original and transplantable tumor exhibited characteristic morphological features and immunoreactivity identical to that of a human malignant schwannoma: positive reaction for S-100 protein, neuron specific enolase, glial fibrillary acidic protein, myelin basic protein and vimentin. In addition, alpha-smooth muscle actin was expressed in both tumors. Cultured tumor cells derived from the transplantable tumor at passage 3 produced 18 clones which showed anchorage independent growth in soft agar. From these clones, two cell lines showing characteristic immunoreactivity, designated as RMS-1 and 2, were established. In general, the immunoreactivities of the two cell lines were similar to those of the original tumor; however, the RMS-1 cell line demonstrated positive immunoreaction for neurofilaments and RMS-2 was negative for alpha-smooth muscle actin. Subcutaneous, injection of cultured cells from both cell lines into athymic BALB/c nude mice induced tumors identical to the original tumor. In the present study, transplantable malignant schwannoma was established in the rat and two phenotypes were isolated and established as cell lines.