Regulation Of Malignant Phenotype And Gene Expression Following Hybridization Between Rat Nucleated Erythroblastsand And Mouse Plasmocytoma (SP2/0) Cell Line

On the basis of observation on the denucleation process of mammalian erythroid cells in vito and in vitro, the present study was designed to investigate the regulatory effect and its mechanism of mammalian erythroblast cytoplasnic factor(s) on malignant phenotype and gene expression of hybrid cells formed by cellular engineering technique of cell hybridization between the mouse plasmocytomas SP(2/θ) cell line and rat erythroblasts.1. Morphological observations of the whole process of erythroid terminal differentiation in vivo from the samples of adult Vistar rat bone marrow and 15-day embryonic liver under light and electronic mcroscopy corforned that the process of denucleation could be readily seen normally during the late stage of development.2. Under in vitro conditions, cultivation of erythroid progenitor cells isolated from BALB/c or Wistar rat bone marrow were performed by using modified iscove's methylcellulose method, processes of erythroid cell differentiation and colony forming activity were observed morphologically. Experimental results indicated that (1) under condition when low concentration of erythropoitin (EPO) was added to the cultural media, "CFU-E" colonies of different size, being composed of tens of cells with various synchronization were formed froa the late erythroid progenitor cells; while in cultural media with high concentration of erythropoietin, burst forming unit-erythroid (BFU-E), the early erythroid progenitor cells were stimulated to form larger colonies consisted of several thousands to ten thousand of cells with higher level of synchronization in developing stages. (3) The consecutive processes of nuclear pycnosis and nuclei extrusion in late erythroblasts were readily observed both in CFU-E and BFU-E colonies. Fact that the denucleation process could be follow-up in vitro strongly supported the hypothesis that nuclei extrusion of late erythroblasts was exactly a self-control naturally occurring process as well as the idea that "cytoplasmic factor(s)" existing in the terminal erythroid cells have the ability to control and restrict the nuclei's activity.3. A method described by Harrison has been adopted and modified by us for the separation of intermediate and late erythroblast cells from 15-day embryonic liver of pregnant Wistar rat. The method...