Evaluation of Malignancy in Tumors Produced in X-radiated and Cortisone-treated Rats Injected with Human Cells in Continuous Culture^*

The histological and cytological characteristics of tumors produced in x-radiated and cortisonetreated rats by inoculation of cells of the FL, Chang conjunctiva, HeLa, Detroit-6, AH, 14–87, and MF strains have been presented. The FL, AH, 14–87, and MF strains now differ from their tissue of origin (human amniotic epithelium) to approximately the same degree that the HeLa strain differs from normal cervical stratified squamous epithelium with respect to the acquisition of abilities for local invasion, anaplasia, pleomorphism, necrosis, coarse-appearing and densely staining nuclear chromatin, increase of nucleolar/nuclear ratios, striking increase of nuclear/cytoplasmic ratios, increased mitotic activity, and the presence of multipolar mitotic spindles (except for strain 14–87). Tumors produced by the Chang and Detroit-6 strains exhibited these same characteristics, and in similar degree.

No metastases were found. The tumors produced by the HeLa, FL, and Detroit-6 strains appear to fulfill Toolan's suggested criteria for malignancy in the conditioned heterologous host. The other strains fulfill three of these four criteria; there is insufficient statistical evidence on which to judge the fourth criterion. The FL strain appears to satisfy the criteria of Warren for malignancy in the untreated host. Tumors produced in rats by all strains except 14–87 exhibited multipolar mitotic spindles.