The differential action of neonatal thymectomy in mice infected with Murine Sarcoma Virus-Harvey (MSV-H)

Intact C3H/Bi and BALB/c mice infected with Murine Sarcoma Virus-Harvey (MSV-H) at 3–16 days developed either ?early”? erythroblastic splenomegaly with concomitant severe anaemia and sarcomas at sites related to the route of inoculation or, after a perceptible delay, ?late”? lymphocytic leukaemia. These effects were dependent on the dilution of the virus and the age of the recipients. Neonatal thymectomy both accelerated the erythroblastosis and increased the tumour incidence in older 14–16 day recipients but prevented (or indefinitely postponed) the lymphocytic leukaemia. This differential action of neonatal thymectomy is discussed in the light of current immunological theory. A virus causing only lymphocytic leukaemia was separated by passage from the plasma of leukaemic intact or non-leukaemic thymectomized mice. Thus, in these experiments, MSV-H behaved as a complex of two viruses, one causing the early changes and a second, always present in higher concentration but slower acting, responsible for the late changes.     

Tumor induction in Praomys (Mastomys) natalensis by N,N'-2,7-fluorenylenebisacetamide

Feeding N,N'-2,7-fluorenylenebisacetamide (CAS:304-28-9) at 0.025% to 15 male and 15 female mastomys considerably shortened their life-span. At death every treated mastomys had several primary tumors; untreated animals at comparable ages had none. Several mastomys with hepatoblastomas and 1 with giant cell hepatitis and a metastasizing pancreatic carcinoma are first reported here. The tumor load per animal averaged 4.0 for treated females, 2.6 for treated males, 1.5 for untreated females, and 0.6 for untreated males. Of 24 hepatic tumors in treated mastomys, 11 metastasized, compared to none of the incipient tumors in 8 of 26 untreated animals. Pancreatic adenomas developed in 27 treated and 1 untreated mastomys, and a metastasizing adenocarcinoma developed in 1 treated animal. All treated females, 3 treated males, and 1 untreated female developed multiple villous adenomas in the small intestine. One untreated female and 8 treated females developed mammary cancers, 4 of which metastasized. Primary tumors of other sites occurred infrequently.     

A spleen weight assay for Murine Sarcoma Virus Harvey (MSV-H)

A spleen weight assay has been developed for titrating murine sarcoma virus-Harvey (MSV-H) 3 weeks after intraperitoneal infection of newborn BALB/c and random-bred albino mice. Induction of splenomegaly corresponded in time with development of sarcomas and anaemia. The assay was also used to evaluate sera for neutralizing antibodies to MSV-H. Weanling mice were much less susceptible to erythroblastic splenomegaly and tumour induction than newborns. Random-bred mice were found more satisfactory for the assays than BALB/c mice. Newborn Sprague-Dawley rats also responded to MSV-H inoculation with a dose-dependent erythroblastic splenomegaly.     

Response of two rodents, Mastomys natalensis and Mystromys albicaudatus, to the pancreatic carcinogen azaserine.

The response of two rodents to azaserine carcinogenicity for the pancreas was evaluated. Mystromys albicaudatus was not responsive; however, Mastomys natalensis developed large numbers of atypical acinar cell nodules and several adenomas in a 6-month study. Mastomys is the most responsive of several animals in which azaserine has been studied as a pancreatic carcinogen.     

Studies on Murine Sarcoma Virus: antigenic characterization of Murine Sarcoma Virus induced tumor cells

The antigenicity of Murine Sarcoma Virus (MSV) transformed mouse, rat and hamster cells has been studied by several techniques designed to detect surface antigens. Antigens were readily demonstrated on neoplastic mouse and rat cells. There was complete cross-reactivity between cells induced by the Harvey (MSV-H) or Moloney (MSV-M) strains of MSV and by Moloney Leukemia Virus (MLV). No evidence of a distinct or separate ?MSV-non-MLV”? antigen could be obtained by cross absorptions of MSV/MLV antisera and cells, or by tests designed to break MLV tolerance. Such results favor the view that MSV and MLV are closely related entities. With the 8303 line of MSV-M transformed hamster cells serological tests revealed little if any reactivity with strongly positive mouse anti-MSV/MLV antisera. In one test, however, immunization of mice with these cells gave some degree of protection against syngeneic MSV sarcoma.     

Transplantable argyrophilic gastric carcinoid of Mastomys natalensis secreting both histamine and serotonin.

A transplantable strain of gastric carcinoids of Mastomys (Praomys) natalensis secreted not only histamine but also serotonin [5-hydroxytryptamine (5-HT)]. Mastomys bearing growing transplants excreted 11.3 times more histamine and 4.4 times more 5-hydroxyindole-3-acetic acid (5-HIAA) in the urine than did Mastomys in which transplanted tumors did not grow. Mastomys that developed primary gastric carcinoids also excreted 3.9 times more histamine than did those free from primary tumors, but the difference in urinary excretion of 5-HIAA was not significant in both groups. All transplantable carcinoids contained definite amounts of both histamine and serotonin, whereas the primary gastric carcinoids contained only histamine. We also confirmed that the histamine and 5-HIAA excreted in urine increased as the size of transplanted tumors enlarged. 5-HT was histochemically demonstrated in a small number of carcinoid cells of the transplanted tumors but not in primary carcinoids.     

Production of serotonin by a transplantable strain of histamine-producing primary gastric carcinoid of Mastomys natalensis

Two biochemically distinguishable transplantable tumor strains (A and B) were established from a primary gastric carcinoid of Mastomys secreting histamine alone. Strain A in the third generation acquired a new ability to produce serotonin [5-hydroxytryptamine (5-HT)] and retained endocrine activities to produce both histamine and 5-HT through the following subpassages, whereas strain B (like the primary tumor) continued to produce histamine alone. The findings were further supported by the immunohistochemical demonstration of 5-HT-containing tumor cells in strain A after generation 3 and the absence of such cells in strain B and also by the ultrastructural demonstration of tumor cells containing pleomorphic secretory granules in strain A after the third generation but not in strain B. Sixteen samples of Formalin-fixed, paraffin-embedded primary gastric carcinoids of Mastomys were stained by the same immunohistochemical method for 5-HT detection. The positively stained tumor cells were demonstrated in 4 tumor samples, though they were scantily distributed in tumor parenchyma except for 1 metastasizing tumor. 5-HT-producing tumor cells appeared through many proliferative cycles of the deranged histamine-producing cells. The endocrinologic similarity was noted between this transplantable tumor strain and a specific type of gastric carcinoid in humans, and the possible histogenesis of the latter tumor was discussed on the basis of data obtained from the present transplantation experiments.     

Tumour-Associated Transplantation Antigens of Neoplasms Induced by a Naturally Occurring Murine Sarcoma Virus (FBJ-MSV)

FBJ osteosarcoma virus (FBJ-MSV) isolated originally from a spontaneously arising osteosarcoma in a CF1 mouse is the only known naturally occurring murine sarcoma virus (MSV). It is unique among strains of MSV in producing primarily sarcomata in mice. The capacity of tumour cells transformed in vivo by this agent to elicit specific transplantation immunity in syngeneic hosts was investigated. A low level of resistance (10⁴-10⁵ cells) was consistently induced by implantation of x-irradiated (15,000 rad) tumours or surgical excision of developing subcutaneous grafts. By contrast intraperitoneal inoculation of virus containing cellfree extracts of FBJ-MSV sarcomata was a far less effective immunization procedure. Confirmatory evidence for the antigenicity of these neoplasms was obtained in tests in which preincubation of tumour cells with lymphoid cells from specifically immune donors inhibited in vivo outgrowth of the FBJ-MSV cells in untreated syngeneic recipients. The induction of host resistance to FBJ-MSV cells by immunization with identical and independently-induced FBJ-MSV tumours established that FBJ-MSV cells possess common cell surface antigenic specificities in a manner analogous to those of experimental neoplasms induced by other oncogenic DNA and RNA viruses. Since FBJ-MSV cells release infectious virus it was not possible in this system to establish whether the tumour-rejection antigen was cellular or virion in nature. The antigenic weakness of FBJ-MSV cells in syngeneic hosts is comparable with that of virus-induced murine leukaemias of the Gross (G) or “wild” type subgroup to which category FBJ-MSV also belongs. These features suggest that FBJ-MSV exemplifies naturally occurring sarcomagenic viruses more closely than those of the Friend-Moloney-Rauscher-Graffi (FMRGr) subgroup which in general induce highly antigenic neoplasms.     

Further Characterization of a Transplantable Murine Osteogenic Sarcoma

A transplantable murine osteogenic sarcoma was characterized to determine its suitability as a model for human cancer and to evaluate specific end points to study therapeutic intervention. Palpable tumors developed at implantation sites following latent periods of 8 to 21 days and grew to 3 g masses within 60 days. The tumor model was predictable in its manner of tumor growth, tumor production of alkaline phosphatase, formation of pulmonary metastases, and the survival of the host. It was found to be sensitive to treatment with cyclophosphamide and vincristine and to a lesser extent to adriamycin and 4¹-epi-adriamycin. It did not show a response to treatment with cis-platinum, actinomycin D, or m-AMSA. Survival of the host is limited by the progression of metastatic disease and local control does not appreciably extend the median survival time. Thus, population survival should be used as a measure of the effectiveness of treatment of pulmonary metastases. Circulating alkaline phosphatase levels may best be used in assessing the response to treatment of the primary osteogenic sarcoma.     

Separation of the Tumor Rejection Antigen of Rous Sarcoma Virus-induced Murine Fibrosarcoma

The tumor antigen capable of inducing tumor resistance (tumor rejection antigen; TRA) was separated and some of its physicochemical properties were characterized. Cytosol and plasma membrane fractions were separated from Rous sarcoma virus (RSV)-induced CSA1M tumor cells. Immunization with membrane but not cytosol fraction of these tumor cells together with complete Freund's adjuvant resulted in complete protection against subsequent challenge with viable CSA1M cells. The TRA activity contained in the membrane fraction was recovered in the sodium dodecyl sulfate (SDS)-solubilized fraction after the SDS-extraction of CSA1M membranes. This CSA1M SDS-solubilized preparation gave protection against syngeneic RSV-induced CSA9F tumor cells as well as the homologous tumor cell type, but failed to induce resistance to RSV-unrelated tumor cells. The membrane or SDS-solubilized fraction from RSV-unrelated tumor cells was unable to generate anti-CSA1M protective immunity. Physicochemical analyses have demonstrated that TRA activity in the SDS-solubilized fraction was completely abolished by treatment with proteinase K but was only marginally affected after treatment with glycosidase mixture. When the SDS-solubilized preparation was applied to a Sephacryl S-300 superfine column, TRA activity was recovered in the range of molecular weight of 50-90 kD. Further fractionation of this TRA-positive fraction by SDS-polyacrylamide gel electrophoresis revealed that the molecular size of TRA is 56–68 kD. These results indicate that membrane proteins which were isolated from CSA1M tumor cells and have a molecular size of about 60 kD are capable of inducing RSV-induced tumor-specific in vivo protective immunity.