[Studies on the cell models of differentiation reversal phenotypes of human rhabdomyosarcoma]

We have observed the features of malignant phenotypes in human rhabdomyosarcoma RD cells. These cells exhibited high growth rate, aberrant relation between cell proliferation and myogenic terminal differentiation, blockage of myofibrillogenesis, inhibition of gap junctional intercellular communication (GJIC) and inhibition of transcriptional expression of gap junction gene, connexin 43 (Cx43). By utilization of single cell subclone separation and cDNA cell transfection techniques, we obtained several RD subclones, among them 3 were representative of differences in phenotypes and were selected for further study. They were single-cell subclone RDL6, RDL3, and a Cx43 transfectant clone of RDL6, the RDL6/C-4. Through determination of cell growth doubling time, co-stain of 3H-TdR autoradiography with myosin heavy chain (MHC) immunofluorescence, immunofluorescent cytochemical examination and slot-blot analysis, it was demonstrated that significant differences existed between each of the 3 subclones. They were differnet in cell growth rate, cell proliferation and terminal differentiation coupling relation, progress of myogenesis, functional expression of Cx43 gene, and expression of proto-oncogenes, c-myc, Ha-ras and c-met products, therefore they could be used as cell models in the study of reverse transformation of rhabdomyosarcomas. The reversal differentiation markers, their examination approaches and practical value were discussed.