In vitro transformation of cells from human neoplasms.

The possible involvement of RNA tumor virus genomes in human cell transformation was investigated. Forty-nine cell cultures from neoplastic, normal, or embryo tissues were examined for transformation, following inoculation of murine leukemia virus (MuLV), feline leukemia virus (FeLV) grown in human cells, or bone marrow aspirates from leukemia patients. Five cultures exhibited transformation (1 after inoculation of MuLV grown in human cells; 4 after inoculation of human leukemic bone marrow), and 4 were established as cell lines. They were derived from giant cell tumor and fibrosarcomas. The established transformed cells formed colonies in soft agar, grew progressively in immunosuppressed mice, and carried antigens common to FeLV and MuLV. Although virus particles were not seen in these cultures, 68S RNA was detected in their media. Medium from nontransformed parent cultures also contained 68S RNA but in amounts about 15 times less than in transformed cultures. Transformed human cells passaged in mice produced both type C virus particles and 68S RNA. Antigens common to MuLV and FeLV were found in these particles. However, the results of biological and serological studies indicate their difference from conventional MuLV and FeLV. The relationship of this virus and 68S RNA found in transformed cultures remains to be determined.