Manifestation of malignancy in somatic hybrids obtained by the cell fusion of 2 tumor lines

: Malignancy of 6 independent hybrid clones derived from fusion of two tumor cell lines of Djungarian hamster, which had been transformed with SV40 virus, was studied. In most of the hybrid clones, suppression of the ability to grow progressively in vivo and the increase in the latent period of tumor occurrence were observed. These data bear witness to suggestion about the existence of different genetic alterations in these tumor cells. Suppression of malignancy does not depend on the genome mutations leading to cell polyploidization, since no decrease in tumorigenicity was found in polyploid cell clones of the high tumor cell line. These polyploid cells can actively form colonies in the soft agar medium.