Effect of cigarette tar upon tissue culture cells. Neoplastic transformation of hamster lung cells by tobacco tar in tissue culture.

Hamster lung fibroblastic cells were transformed into malignant cells in vitro by exposure to crude cigarette tar for 3 hours. Primary injuries of cells were observed between 2 and 48 hours after the treatment. Tar-treated cells showed nuclear pyknosis, cell necrosis, and enlarged, vacuolated cytoplasm. In one case giant cells were found at about 48 hours after treatment. Transformation occurred over 100 days after the treatment. The characteristics of transformed cells were random orientation of cells, with piling-up and criss-crossing, and continuous growth in vitro for over 300 days. Plating efficiency with treated cells was different from untreated cells. The transformed cells, cultured for 100 to 160 days, produced tumours when transplanted in cheek pouch of hamsters. The five of nine animals inoculated with 100 μg./ml. of tar treated cells (HT-100 strains) over 160 days in vitro died from tumours and others were killed for histological examinations and one of five animals transplanted with the cells of HT-10 strains within 121 days after the tar treatment. Histologically, the tumours were pleomorphic fibrosarcomas. Low doses (1 × 10(5) or less) of control cells failed to produce tumours after 270 days in culture. Contrarily, higher doses of 10(7) of control cells produced tumours when injected into the animals after 270 days in culture.