In fibroblastic cultures of hamster embryonic kidney cells exposed to human adenovirus type 12, early changes included cell granularity and partial lysis. Transformation was observed after five weeks. The rate of cell division increased, and cell morphology and growth pattern changed distinctly. Infectious virus could not be demonstrated in the transformed cells in the seventh passage after virus exposure. The transformed cells were heteroploid and the majority had 50 chromosomes. Undifferentiated malignant neoplasms were produced after subcutaneous inoculation of transformed cells of the 27th passage into newborn and weanling hamsters. The tumors grew by local infiltration and killed the animals. Tumor cells reestablished in culture appeared morphologically identical to the in vitro transformed cells. No virus-specific tumor antigens were detected in the transformed cells or in animal tumors, nor did hamsters bearing tumors develop antibodies to the adenovirus 12 complement-fixing tumor antigen.


This investigation was supported in part by USPHS Research Grants CA-05883 and CA-08748; by a grant from the Icelandic Science Foundation to G. Pétursson; by investigatorship grant from the Health Research Council to the City of New York, Contract No. 1–325, to E. de Harven; and by Research Career Award K6-CA-21607 to J. Fogh.

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