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The transformation of nonhuman primate marmoset cells by Rous sarcoma virus of Schmidt-Ruppin strain (RSV-SR) generates transformants which lack tumorigenicity in allo- and xenogeneic hosts. Marmoset cells acquire this property when they are transformed by RSV rescued from non-tumorigenic allogeneic cells. One of the rescued RSV, when used to infect marmoset kidney cells in vitro, yielded transformants which became tumorigenic in adult allogeneic hosts. Cytogenetic and molecular analyses of transformants revealed progressive genetic changes from cell diploidy to aneuploidy and from the presence to the loss of v- src during propagation in vitro. The loss of v- src in transformed cells coincided with the evolution of aneuploid cell clone with specific marker chromosome (M1). Although both early passage diploid and late passage aneuploid transformants were tumorigenic, the induced tumors originated from different type of cells. Tumors induced by diploid- and v- src —positive transformants were derived predominantly from the host cells, while tumors induced by late-passage transformants and with deleted v- src originated from an aneuploid cell clone that contained a rearranged M1 marker chromosome. These results suggest that besides the v- src oncogene, proviral integration can facilitate chromosomal rearrangements that contribute to tumorigenic transformation of nonhuman primate cells in vitro.

Type C virus produced by dog thymus cells (A7573) that were infected with virus (HL-23V), isolated from cultured leukocytes of an acute myelogenous leukemia patient, transformed marmoset and horse cells in vitro and induced virus-producing fibromas in marmosets. The tumors and transformed foci were indistinguishable morphologically from those induced by simian sarcoma virus, type 1 (SSV-1/SSAV-1). HL-23V was indistinguishable from SSV-1/SSAV-1 by immunofluorescence and neutralization tests, and the nontransforming virus associated with HL-23V completely inhibited SSV-1 focus induction in interference tests. Cell cultures established from a marmoset fibroma produced transforming and nontransforming virus biologically and antigenically indistinguishable from HL-23V and SSV-1/SSAV-1.

Skin fibroblasts derived from three patients with familial polyposis coli (FPC) were treated in vitro with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) alone or in combination with the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). None of the cultures treated four times with MNNG alone (1 microgram/ml) or in combination with TPA (eight applications, 0.1 microgram/ml each) showed either morphological transformation or anchorage-independent growth for 18 months after treatments. FPC cells treated with MNNG alone showed cell growth inhibition, breakage and loss of chromosomes, as well as the deletion of 5.7 kilobase (kb) EcoRI fragment in the c-K-ras locus as detected by Southern blot analysis with v-K-ras specific probe (clone KBE-2). The control cells contained two EcoRI fragments of 5.7 and 4.2 kb. On the other hand, cells treated with MNNG first and then followed by treatment with TPA not only showed an increase in the rate of cell growth but also exhibited two novel EcoRI fragments of 9.4 and 12 kb. Treatment with TPA alone appeared to stimulate cell division long after application and to induce chromosomal aberrations but had no effect on c-K-ras sequences. The most likely explanation for the appearance of chromosome pulverization and hyperploidy in FPC cells treated with TPA is the induction of premature chromosome condensation of the S phase cells due to fusion with the mitotic chromosomes.

The tumors induced in white-lipped marmosets (Saguinus fuscicollis, S. nigricollis) by Rous sarcoma virus (RSV) of chicken origin (RSV-SR) were not transplantable to allogeneic hosts. In contrast, RSV rescued from these tumors (RSV-M) induced sarcomas that were transplantable to young but not to adult marmosets. The tumors induced by RSV-M and the transplants rapidly enlarged, metastasized to various organs, and killed the recipients 29-59 days post inoculation. Cell lines were readily established from all transplantable sarcomas. No virus expression was detected in transplantable tumor cell lines by electron microscopy or by biochemical and biological assays. However, RSV of the same subgroup as RSV-SR was rescued from both short-term and long-term tumor cell cultures by cocultivation with chicken embryo fibroblasts (CEF). The rescued viruses transformed marmoset cells 100-fold more efficiently than CEF cells, although CEF cells remained permissive for virus replication. Cytogenetic studies revealed extensive chromosome abnormalities in tumor transplants but not in RSV-M-induced sarcomas. All cell lines were hyperploid and contained structurally abnormal, large metacentric and telocentric chromosomes. Immunologic studies failed to detect group-specific (gs) antigen of the avian sarcoma-leukemia complex in either RSV-M-induced, transformed cells or tumor transplants. By complement-dependent cytotoxicity assays, with the use of marmoset anti-gs serum, RSV-associated antigen could be detected on the surfaces of tumor cells. No differences in the expression of this antigen existed between transplantable and nontransplantable marmoset sarcomas. All transplantable cell lines contained abnormal amounts of lipids and glycogen in comparison to RSV-SR-induced tumors and normal marmoset cell lines. The glycogen was associated with unique cytoplasmic membrane complexes and was surrounded by either single- or double-membraned vesicles.

Rat embryo cells subjected in vitro to transient incubation at an elevated temperature (39 degrees C) became transformed and induced fibrosarcomas in both homologous and heterologous hosts. Malignant transformation correlated with the occurrence of karyotypic changes which appeared long after incubation at 39 degrees C and subsequent return to 37 degrees C. Control cultures incubated at only 37 degrees C did not show similar chromosomal changes or induce tumors and remained predominantly diploid during the same observation period. In contrast to rat embryo cells, marmoset monkey cell cultures incubated at 39 degrees C did not develop characteristics of transformed cells.