Oncogenicity in marmosets of HL-23V, a type C oncornavirus isolated from human leukemic cells, and comparison with simian sarcoma virus type 1 (SSV-1/SSAV-1)

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.

Stimulation of mouse migration inhibitory factor (MIF) production form MSV-immune lymphocytes by soluble tumor-associated antigen: requirement for histocompatible macrophages

Spleen cells from C57BL/6 mice immunized with murine sarcoma virus (MSV) are capable of producing migration inhibition factor (MIF) in response to stimulation with a specific tumor-associated antigen prepared by solubilization with 3 M KCL. We have previously demonstrated that this response is T cell-dependent. Further investigations into the effector cells involved in the production of MIF have revealed that spleen cells from mice immunized with MSV cannot produce MIF when stimulated with tumor extract if the population has been previously depleted of macrophages. However, the response can be restored by adding nonimmune syngeneic macrophages but not by allogeneic macrophages. The inability of allogeneic macrophages to provide this function was not due to their increased suppressor activity since in mixing experiments they did not interfere with the ability of immune spleen cells to produce MIF. Furthermore, they were not defective since they could supply this "cooperative function" to appropriate F1 mice. The results indicate that macrophages are required for stimulation of MIF by soluble tumor antigens and that for efficient interaction the macrophages and lymphocytes must share some genetic similarities.

Carcinogenicity of fibrous glass: pleural response in the rat in relation to fiber dimension

Seventeen fibrous glasses of diverse type or dimensional distribution induced different incidences of malignant mesenchymal neoplasms when implanted in the pleurae of female Osborne-Mendel rats for periods of more than 1 year. Neoplastic response correlated well with the dimensional distribution of fibers. Fibers less than or equal to 1.5 mu in diameter and greater than 8 mu in length yielded the highest probability of pleural sarcomas, and probability trends suggested that pleural sarcoma incidence increased with increasing lengths of fibers with diameters of less than 1.5 mu, Morphologic observations indicated that fibers less than or equal to 8 mu in length were inactivated by phagocytosis. In fibers greater than 8 mu in length, the correlation of carcinogenicity witth increasing length was difficult to explain. Since neoplastic response to a variety of types of durable fibers, particularly asbestos fibers, was similar, our experiments reinforce the idea that the carcinogenicity of fibers depends on dimension and durability rather than physicochemical properties and emphasize that all respirable fibers be viewed with caution.

Immunosuppression studies in foreign body tumorigenesis: no evidence for tumor-specific antigenicity

Sarcomas were induced in CBA/H mice by sc implantation of 15 X 22 X 0.2-mm polyvinyl chloride vinyl acetate copolymer films. The animals were immunosuppressed with azathoprine, antilymphocyte globulin, or thymectomy. Sarcoma development was not accelerated in comparison to nonimmunosuppressed demonstrated in sarcomas of immunosuppressed mice. It was concluded that foreign body tumorigenesis in mice in neither associated with nor dependent on the emergence of tumor-specific transplantation antigens.

Intratibial Moloney sarcoma virus-induced osteosarcoma in the rat: tumor incidence and pathologic evaluation

Osteosarcomas were induced in approximately 80% of young New Zealand Black rats by the intratibial inoculation of Moloney murine sarcoma virus from day 1 to day 5 after birth. The neoplasms were composed of a spectrum of well-differentiated to poorly differentiated osteoblasts, osteocytes, and osteoclasts. Budding of C-type viral particles was associated with tumor induction. Compared to rats inoculated on day 1 after birth, rats inoculated at 4 days of age developed consistently more osteoproliferative bone tumors that often were associated with hypercalcemia, increased serum alkaline phosphatase, and elevated urinary hydroxyproline.

Inhibitory effects of xenogeneic antiserum on the growth of Moloney virus-induced sarcomas

An antiserum was developed in rabbits by injections of a virus concentrate from Moloney murine sarcomas. Passive transfer of this antiserum attenuated the growth of both primary and transplanted Moloney murine sarcomas. It also facilitated tumor regression and increased survival times of young mice with primary Moloney sarcomas.

Transformation of cultured rat adrenocortical cells by Kirsten murine sarcoma virus (Ki-MSV)

Two-week-old primary cultures of normal adult rat adrenal cortex were exposed to Kirsten murine sarcoma virus (KiMSV). Within a week, the adrenal cells, which are normally fusiform and aligned in parallel, became pleomorphic and piled up extensively. Saturation density increased from 5-10 x 10(4) to 5-10 x 10(5) cells/cm2, population doubling time during exponential growth decreased from 36-40 to 16h, acid production increased and the growth rate became independent of a reduction in serum concentration from 10% to 1%. Inoculation of 2 x 10(6) of these transformed cells into immuno-depressed rats produced rapidly growing tumors within 1 week. Histologically, the tumors were pleomorphic carcinomas with areas ranging from anaplasia to near-normal, highly differentiated adrenocortical tissue. In addition to histologic evidence of differentiation, metabolic studies using 14C-prognenolone showed that the transformed cells were capable of 20alpha reduction and delta5,3beta dehydrogenation, both characteristic of normal steroid-secreting tissues. The transformed adrenocortical cells produced infectious C-type virus as indicated by electron microscopy, 3H-uridine incorporation, and focus formation in NRK (normal rat kidney) cultures. The neutralization pattern of this virus resembled that of authentic Ki-MSV. The transformation of adrenocortical cells by K-MSV demonstrates the capacity of this agent to induce carcinomas in differentiated cells after short-term culture, and widens the range of tissues known to be susceptible to K-MSV to include a secretory epithelium of mesodermal origin.

Enhancement of tumor induction in rats with Moloney murine sarcoma virus by a "new" method based on direct injection into fetuses

Undiluted, fivefold-diluted, and 25-fold-diluted doses of a stock of Moloney murine sarcoma virus were injected directly, in a volume of 0.025 ml, into the backs of fetal Sprague-Dawley rats by laparotomy through the uterine wall at 18 days of gestation. During the first 8 weeks after birth the young responded to the virus with remarkably high but dose-dependent incidences of neoplasms. When a one-fifth dilution of the virus preparation was inoculated at fetal ages 16, 18, and 20 days, the incidences of lesions decreased with advancing fetal age. The tumors developed preferentially at the virus inoculation site and/or in the proximal parts of the extremeties; all were considered to be of mesenchymal derivation, i.e., malignant mesenchymoma, rhabdomyosarcoma, osteosarcoma, fibrosarcoma or fibromyxosarcoma, hemangiosarcoma, plasmacytoma, and a giant cell tumor. This injection procedure provided us with a valuable experimental tool for the rapid screening or testing of potential chemical carcinogens and other biologic studies.

Oncornavirus-induced sarcoma formation obscured by rapid development of lethal leukemia

Injection i.v. of avian erythroblastosis virus (AEV) strain ES4 causes a high incidence of leukemia and the death of most of the inoculated chicks within 2 weeks. As found earlier, the virus is defective for replication and transforms bone marrow cultures in vitro, and surprisingly, also chick embryo fibroblasts. Inoculation of transformed AEV cells negative for virus production into newborn chicks induced the formation of sarcomas only, whereas cells superinfected with helper virus induced the formation of erythroblastosis in addition to sarcomas. The helper virus alone caused neither sarcomas nor erythroblastosis during the experimental period. These findings were explained by the hypothesis that AEV-induced erythroblastosis develops more rapidly than do AEV-induced sarcomas and that animals receiving i.v. injections die of the leukemia before sarcomas become detectable. The observation that animals receiving i.m. injections of AEV developed sarcomas at the site of injection strongly supports this concept. Most of the animals that received i.m. injections also developed an erythroblastosis that was delayed, however, in comparison to the animals receiving i.v. injections. Our data also suggest that the erythroblastosis induced by AEV does not suppress the formation of sarcomas in the same animal.

Suppression of Moloney sarcoma virus immunity following sensitization with attenuated virus

Murine sarcoma virus (Moloney strain) (MSV-M)-induced tumors are unusual in that they regularly appear less than 2 weeks after virus inoculation, progress for 1 to 2 weeks, and are rejected by normal adult BALB/c mice. Rejectio leaves the animals immune to tumor induction. In the present study, presensitization of normal adult BALB/c mice with attenuated MSV-M resulted in an altered pattern of tumor immunity. Injection of active MSV-M into the presensitized animals resulted in tumor induction and rejection similar to that observed in normal animals, but rejection failed to produce protection against the secondary inoculation with MSV-M. After the second inoculation with active MSV-M, tumors appeared and progressed but ultimately were rejected. Over 80% of the mice died, 25% after the primary challenge and the remainder after the secondary challenge. At death, all mice had histological evidence of leukemia which was the probable cause of death. The animals that died following the secondary challenge also had evidence of disseminated MSV-M. Solid tumor nodules were found in skeletal muscle distant from the original site of inoculation, and active MSV-M was isolated from spleen and lungs. The possibility that the results were produced by specific suppression of MSV-Moloney leukemia virus immunity is discussed.

A study of the development of fracture callus in the presence of an experimentally induced osteosarcoma

The results of two experiments are reported in which the formation of an osteosarcoma was induced in mice by the intraosseous injection of Moloney's virus. In the first group of fifty mice, a complete diaphyseal fracture was carried out nine days later at the site of the tumour. In the second group of 200 mice, a partial fracture was produced at the time of injection so that immobilisation was assured. The effects of cyclophosphamide and calcitonin administration were also studied in this group. The course of the repair processes of the bone was studied in both groups, and showed that, even in the presence of an osteosarcoma, these begin and can reach completion, though obstructed and delayed by the tumour.

Spontaneous tumor regression: possible relationship to in vitro parameters of tumor immunity

Evidence is discussed from three animal systems (Shope papillomas in rabbits, Moloney sarcomas in mice, Schmidt-Ruppin-Rous sarcomas in Japanese quail) that immune reactions can be important in spontaneous tumor regression. In vitro studies performed in these systems indicate that blocking serum factors can thwart cell-mediated immune responses and that "unblocking" antibodies are often found in animals whose tumors have regressed. To what extent spontaneous regressions of human neoplasms are due to immunologic mechanisms is unknown; in 2 patients who had undergone spontaneous tumor regression, tumor cell cytotoxic lymphocytes and unblocking serum factors were detected. Better animal models and better knowledge about the mechanisms of tumor immune reactions are needed before tumor regression can be more successfully induced by immunologic manipulation (to what extent that will even be feasible in man is unknown).

Evaluation of Moloney murine sarcoma and leukemia virus complex as a model for airborne oncogenic virus biohazards: survival of airborne virus and exposure of mice

Aerosols of the Moloney murine sarcoma virus (MuSV-M) and leukemia virus (MuLV-M) complex (MuSV-M/MuLV-M) were generated from refluxing atomizers and then aged in rotating drums at 21 degrees C holding temperature with relative humidities ranging from 25 to 76%. The MuSV-M and MuLV-M aerosolized from the same tumor extract preparation survived almost equally at the four humidity levels. Both viruses remained viable in the airborne state for at least 2 hours after aerosolization. When mice were exposed to airborne MuSV-M/MuLV-M, no macroscopic lesions were observed in lungs or other tissues examined during the 2-month postexposure period. On the basis of this study, MuSV-M was determined unsuitable as a "model system" in which a simple aerosol dose response could be used for biohazard evaluation of oncogenic virus aerosols.

Biological and biochemical properties of soluble tumor-specific transplantation antigen of a simian virus 40-induced neoplasm

We have solubilized by limited papain digestion and partially purified the tumor rejection antigen, tumor-specific transplantation antigens (TSTA), from membranes of a simian virus 40-induced sarcoma. Uniform-sized materials with a molecular weight range of 50,000 have retained their tumor rejection activities through the purification procedures. The simian virus 40 TSTA have been separated from H-2 activity by affinity chromatography on concanavalin A columns and no evidence was found for H-2 antigens in the unbound fraction (I) of concanavalin A containing TSTA activity. A reduced yield from the crude soluble fraction was observed with Fraction I of concanavalin A material and this may indeed represent fragmentation of antigen during papain digestion. These results stand in contrast to purification of histocompatibility antigens (H-2alpha) using the same methods and techniques. Low concentrations of simian virus 40 TSTA crude soluble materials were nervertheless biologically active. A concentration as low as 4 mug protein provided 50% tumor rejection and 0.1 mug protein provided lymphocyte stimulation. Both assays reflected specificity of response.

Induction of tumors in Syrian hamsters by a human renal papovavirus, RF strain

Injection of RF virus (RFV), a papovavirus isolated from human urine, into newborn Syrian hamsters induced subcutaneous sarcomas in 50% of the recipients with 18- to 48-week latent periods. Transplantation of 2 X 10(6) primary RFV-induced tumor cells into weaning hamsters caused tumors in 100% of the recipients within 1-2 weeks. Continuous tissue culture cell lines were established from two primary tumors; one of these was transplantable. An in vitro-transformed continuous cell line (RF-194) obtained by infection of primary hamster embryo fibroblasts with RFV was transplantable in weaning hamsters. Neither infectious RFV nor virion antigens were detected in transformed cells. No RFV was recovered when transformed cells were fused with permissive, human embryo kidney cells by means of inactivated Sendai virus. Immunoperoxidase staining was used to show that all three RFV-transformed cell lines contained an intranuclear T-antigen closely similar to that of simian virus 40(SV40)-infected cells. Most hamsters (84%) with primary or transplanted RFV tumors responded with antibodies that reacted with RFV T-antigen and the T-antigen of SV40-infected cells. Likewise, hamster antisera against SV40 T-antigen cross-reacted with RFV T-antigen. Adsorption of RFV T-antisera with an excess of lyophilized SV40-transformed cells removed all detectable activity against SV40 T-antigen but left significant activity against RFV T-antigen. The reciprocal adsorption produced an antiserum spedicic for SV40 T-antigen. Thus human and simian papovavirus T-antigens were related but immunologically separable.

Characterization of effector lymphocytes associated with immunity to murine sarcoma virus (MSV) induced tumors. I. Physical properties of cytolytic T lymphocytes generated in vitro and of their immediate progenitors

Cytolytic T lymphocytes (CTL) were generated in secondary mixed leukocyte-tumor cell cultures (MLTC) with syngeneic RB1-5 tumor cells as stimulating cells and with responding spleen cells from regressor mice that had rejected a murine sarcoma virus (MSV)-induced tumor. CTL precursor cells were found to be exclusively of thymic origin and non-T cells were apparently not required for CTL generation. When the size variations of CTL from syngeneic MLTC were analyzed by velocity sedimentation it appeared that a transition from small precursor cells to larger effector cells occurred during the first 5 days in culture; this change in cell size was then followed by a shift toward small-sized cells. Furthermore, the CTL generated in syngeneic MLTC in the MSV tumor immune system were compared with those CTL obtained in allogeneic mixed leukocyte cultures (MLC) and were shown to exhibit fundamental similarities.

Influence of regenerative capacity and innervation on oncogenesis in the adult frog (Rana pipiens)

Twenty-two sarcomas were induced in 19 adult frogs (Rana pipiens) treated with 3-methylcholanthrene pellets. Thirteen of these tumors arose first in a denervated forelimb, and only 2 arose first in normal or nerve-supplemented control forelimbs (P = 0.004). The remaining tumors developed either as a second tumor in a tumor-bearing frog or in hindlimbs. The critical role of innervation in regenerative capacity suggests that the predilection to tumor formation in the denervated limbs may have resulted from their lessened regenerative capacity.

Induction of tumors by a guinea pig herpesvirus-transformed hamster cell line

Syrian hamster embryo cells that had been transformed in vitro by guinea pig herpes-like virus (GPHLV) were found to be oncogenic when inoculated into hamster sc or ip. Of 71 animals inoculated, 30 showed tumors at the site of inoculation. Tumors appeared 4-23 weeks after inoculation of the transformed cells at passage 37 or higher. Inbred and randombred hamsters of all ages were susceptible. Upon microscopic examination the tumors were characterized as fibrosarcomas. The cultured hamster tumor cells were easily transplanted into hamsters, but produced no evidence of tumors when inoculated into guinea pigs. Infectious GPHLV was not isolated from the tumor cells, but GPHLV-specific surface antigens were detected in tumor cells by immunofluorescence of GPHLV antiserum produced in rabbits. Sera from tumor-bearing hamsters did not contain GPHLV-neutralizing antibodies, but sera from 4 of 23 hamsters bearing primary tumors and 12 of 41 bearing transplanted tumors produced nuclear fluorescence in cells infected with GPHLV, thus establishing the relationship between the guinea pig herpesvirus and the hamster tumors.

Cellular immunity in rats with primary brain tumors: inhibition of macrophage migration by soluble extracts of avian sarcoma virus-induced tumors

Rats bearing primary tumors of the brain induced by avian sarcoma virus (ASV) were studied with the migration-inhibition factor (MIF) assay for the presence of cell-mediated immunity to tumor-associated antigens. Astrocytomas and sarcomas of the brain were induced in 34 neonatal F344 rats by the intracerebral inoculation of Bratislava-77 ASV. At weekly intervals from 4 to 9 weeks after the inoculation with virus, peritoneal exudate cells (PEC) from rats bearing brain tumors were tested an an MIF assay against soluble and KCl-treated extracts of a syngeneic, ASV-induced sarcoma. Incubation of the PEC with a soluble extract of syngeneic liver or with a KCl extract of a syngeneic, chemically induced tumor served as controls. Of 14 rats tested against the soluble tumor extract, 6 (43%) had statistically significant inhibition of migration (P less than or equal to 0.05). Of 23 animals tested against the KCl extract, 16 (70%) had significant inhibition. Immunity to the KCl extract was significant in most rats at each period. Ten rats were tested against a KCl extract of a hamster ASV-induced tumor; 7 gad significant inhibition of migration. None of 3 tested against a soluble extract of a syngeneic, chemically induced tumor had significant inhibition. Rats bearing ASV-induced brain tumors displayed cell-mediated immunity to tumor-associated antigen or antigens of ASV-induced tumors, which could be solubilized.

Characterization of virus-free guinea pig tumors induced by Kirsten sarcoma virus

Tumors were induced by Kirsten sarcoma virus (KiSV) in an inbred guinea pig, strain 13. The tumor cells were established in culture and characterized. The KiSV-induced sarcoma cells were virus-free and nonproducing; however, they contained resuable sarcoma genome. A type B guinea pig retravirus was readily activated from the tumor cells after induction with 5-bromodeoxyuridine (BUDR). BUDR induction of guinea pig retravirus was further enhanced by treatment with dexamethasone, a synthetic glucocorticoid hormone.