Genetic determinants of morphological differentiation in a lymphoma-sarcoma hybrid

Hybrid cells, YACIR/MSWBS were produced by fusion of the cells of a methylcholanthrene induced murine sarcoma MSWBS and a virus induced murine lymphoma YACIR. The hybrid cells were maintained in vitro and syngenic mice challenged at various periods after fusion. Karyological analysis has been performed on the cell line, and on the tumours which arose in vivo. The tumours were also examined histologically. Over the 2 yr following fusion there was a progressive loss of chromosomes but biarmed MSWBS derived chromosomes were selectively retained. Tumours could be divided into those whith a chromosome complement similar to that of the early line in vitro, those in which chromosome loss had occurred and those in which karyology showed a mixture of the two foregoing types. Histology showed a minority of sarcoma-like tumours reminiscent of MSWBS and the majority of these showed little chromsome loss. Most tumours showed an intermediate morphology and the great majority of these had lost moderate numbers of chromosomes. There was a very small number of lymphomatoid tumours in which chromosome loss was marked.