Induction of sarcomas in nude mice by implantation of Syrian hamster fetal cells exposed in vitro to nickel subsulfide.

In vitro exposure of Syrian hamster fetal cells to nickel subsulfide (alpha Ni3S2) yielded positive colony assays for morphological transformation. A dose-response relationship was found between the concentration of alpha Ni3S2 and the incidence of morphological transformation. Exposures of alpha Ni3S2 induced morphological transformation at concentrations (0.1 or 1.0 microgram/ml of culture medium) which did not impair cell plating efficiency. Nickel monosulfide (NiS) did not induce morphological transformation of Syrian hamster fetal cells under the same conditions. Clones of alpha Ni3S2-transformed cells were able to grow in soft agar medium and demonstrated increased basal and induced activities of ornithine decarboxylase. Undifferentiated sarcomas developed in 26 of 27 nude mice at the site of s.c. injection of clones of alpha Ni3S2-transformed cells. No tumors developed in 19 control nude mice which were given s.c. injections of nontransformed Syrian hamster fetal cells which had not been exposed to alpha Ni3S2. This study demonstrates that fetal cells which undergo transformation following exposure to alpha Ni3S2 are capable of producing malignant tumors in nude mice.