Metastatic clones selected from an RSV-induced mouse sarcoma share a common marker chromosome

Previous work has shown that the metastatic potential of RSV-transformed fibroblasts is correlated with the ability to form colonies in 0.6% ("hard") agar. Metastatic subclones were selected by this property from the non-metastasizing fibrosarcoma B77-313 line. A marker chromosome was found at high frequency (90% of cells) in all the subclones studied. This marker was detectable in only 0.5% of the parental B77-3T3 cells, demonstrating that metastatic clone precursors pre-existed, as a small minority, in the parental line. The genotypic marker appeared to be steadily associated with the metastatic phenotype since, after prolonged in vitro propagation, the subclones retained both the marker chromosome and the high metastatic potential. Although the marker chromosome was constantly present, chromosomal numerical and structural aberrations were also found in 20% of the long-term-propagated subclone cells, supporting the suggestion that metastatic properties are associated with cytogenetic instability.

Chromosomal aberrations in foreign body tumorigenesis of mice

Sarcomas were induced in 107 male and female isogeneic CBA/H or CBA/H-T6 mice by subcutaneous implantation of double films of unplasticized vinylchloride-acetate copolymer, 15 x 22 x 0.2 mm in size. Tumors were grouped by chromosome number. G-banding was performed on chromosomes of (a) 12 sarcomas, (b) 6 specimens of preneoplastic cells derived from foreign body (FB)-reactive tissues at 4, 6, 9, and 16 months postimplantation, and (c) 11 sarcomas which developed from clonal lines of the preneoplastic cells studied. Karyological analyses lead to the following results and conclusions: (1) Various derangements in chromosome number occurred in preneoplastic cells during early FB reaction at the time of, and possibly in causal relation to carcinogenic initiation. (2) Structural abnormalities of specific chromosomes (insertions, translocations, transpositions, etc.) were found as stable cell markers only during late preneoplasia. They may thus contribute to advanced tumor progression. (3) Ploidy deviations of specific chromosomes (secondary to the early derangements in chromosome number) were most frequently seen in chromosomes 1, 6, 7, 13, 15, 18, and 19; however, these latter aberrations were unstable and inconsistent both in vivo and in vitro.

Role of accessory cells in the induction of a secondary cytotoxic response to Moloney murine sarcoma virus-induced tumors

The role of Ia-positive accessory cells in the generation of a secondary cytotoxic response to tumor-associated antigens induced by Moloney murine sarcoma virus (M-MSV) was evaluated. Spleen cells from M-MSV-immune A.TL mice, depleted of accessory cells by anti-Iak serum plus C treatment and stimulated in secondary mixed leukocyte tumor cell culture (MLTC) with syngeneic Ia-negative A6ATL Moloney leukemic cells, failed to generate virus-specific cytotoxic T lymphocytes (CTL). CTL generation in Ia-depleted MLTC may be reconstituted by the addition of nonimmune Ia-positive spleen or peritoneal cells obtained not only from syngeneic A.TL but also from I-incompatible A.TH mice. This lack of restriction observed in accessory cell function is explained in terms of a nonspecific mechanism of CTL triggering mediated by soluble factors. In fact, IL 2 as well as supernatants obtained from I region-incompatible cultures consisting of M-MSV-immune, Ia-depleted A.TL spleen cells and A.TH Ia-positive cells, reconstituted secondary virus-specific CTL generation.

Transplacental carcinogenesis with radioactive phosphorus

1 An attempt was made to produce a model of osteogenic sarcoma using 32P transplacentally. 2 Fetal tissues appeared to be resistant to irradiation as no tumour was induced at an increased frequency in treated animals. 3 Tumours that normally occur in our strain (Sprague-Dawley rats) showed a clear tendancy to occur earlier in post-natal life in treated animals compared with controls.

Host endocrine status mediates oncogenesis: leukemia virus-induced carcinomas and reticulum cell sarcomas in acyclic or normal mice

A highly selective leukemogenic virus obtained from thymic lymphosarcomas (LS) of C57BL/6 mice was inoculated intraperitoneally into normal or gonadectomized C57BL/6 male mice and into normal or masculinized, acyclic, Charles River (CR) outbred female mice. This virus induced early onset of LS in both normal and gonadectomized C57BL/6 mice. The same virus induced a relatively late onset of many mammary adenocarcinomas in the normal CR mice and ovary adenocarcinomas and systemic neoplasms (LS and reticulum cell neoplasms) in the acyclic females. Topography, histopathology and the average latent period of the tumors were completely different between the normal and the acyclic females. This is consistent with the idea that a leukemia virus can induce tumors other than leukemia and that permanent alterations of the physiological hormonal cyclicity plays a major role in determining whether or on which target cells the ubiquitous virus will exert its carcinogenic action.

Ploidy distribution of tumour cells derived from induced and spontaneously arising metastases of a murine radiation-induced sarcoma, RIF-1

Flow cytometric analysis of the X-radiation-induced sarcoma RIF-1 has shown that the parent tumour is composed of diploid and tetraploid subpopulations of cells, each capable of independent proliferation. We have now examined artificially induced and spontaneously arising metastases of the RIF-1 tumour and have found in both cases that, unlike the parent tumour from which they are derived, they exhibit a single level of ploidy which is stable throughout successive in vivo and in vitro passaging. This finding suggests that at least in this tumour system metastasis is a clonal event.

Induction of sarcomas in athymic mice

During the course of serial passage of 50 human xenografts in the athymic mouse over a period of 5 years we have observed two cases of induction of sarcomas in the murine stromal tissue associated with the human xenografts. Both times the growth of the murine sarcomas overtook that of the human xenograft. This change was monitored by analysis of the lactate dehydrogenase isozyme profile and histology of each passage of the human xenografts in the athymic mice. The two murine sarcomas were subsequently established in tissue culture. The sarcoma cell lines were found to be malignant by morphological and growth characteristics and were tumorigenic. They contained large amounts of murine leukemia virus when assayed for reverse transcriptase activity by infection of mouse SC-1 cells and BALB/c and NIH Swiss fibroblasts with filtered supernates, and some type C virus particles were observed by electron microscopy in tumor tissues. However, we were unable to demonstrate the presence of murine sarcoma virus by in vitro transformation of fibroblasts or sarcoma formation in vivo will cell free filtrates. Preliminary biochemical data indicate that the sarcomas are extremely high in plasma membrane ATP phosphohydrolase.

Adenovirus-cell interactions early after infection: in vitro characteristics and tumourigenicity of adenovirus type 2-transformed rat liver epithelial cells

Cloned rat liver epithelial cells (clone C3) were semi-permissive for adenovirus type 2 (Ad-2) and non-permissive for adenovirus type 12 (Ad-12). Ad-2-infected C3 cells were shown to produce hexon and fibre protein, but at an m.o.i. of 20 a maximum virus yield of only 2.4 p.f.u. per cell was obtained. Forty-eight h after infection with Ad-12 'early' virus proteins (major species 8K and 60K), but no 'late' proteins (virus structural proteins) could be identified. Of six Ad-2-transformed epithelial lines isolated from clone C3 only one was tumourigenic in syngeneic rats, whereas all six transformants produced tumours in athymic nude mice. There was a remarkable variation in the morphology of the Ad-2-transformed liver cells, ranging from an epithelial morphology similar to C3 cells to cells with a distinct lymphoid morphology. The in vitro and in vivo behaviour of the Ad-2-transformed clone C3 cells reported in this communication, taken together with our previous report on the characteristics of Ad-12-transformed C3 cells, clearly show that the differences observed between Ad-2- and Ad-12-transformed rat embryo cells were also observed in our studies using cloned rat liver epithelial cultures. Our findings clearly rule out the hypothesis that the heterogeneity of Ad-2-transformation events is the result of the transformation in vitro of different types of target cell.

Relation of particle dimension to carcinogenicity in amphibole asbestoses and other fibrous minerals

In 72 experiments, durable minerals in the form of particles on respirable size and of wide chemical and structural varieties, were implanted in the pleurae of outbred female Osborne- Mendel rats for periods of more than 1 year. The incidence of induced malignant mesenchymal neoplasms correlated well with the dimensional distribution of the particles. The probability of pleural sarcoma correlated best with a number of fibers that measured 0.25 micro or less in diameter and more than 8 micrometer in length, but relatively high correlations were also noted with fibers in other size categories having diameters up to 1.5 micrometer and lengths greater than 4 micrometer. Morphologic observations indicated that short fibers and large-diameter fibers were inactivated by phagocytosis and that negligible phagocytosis of long, thin fibers occurred. The wide variety of compounds used in these experiments suggested that the carcinogenicity of fibers depended on dimension and durability rather than on physicochemical properties.

Characterization of clones of tumorigenic feline cells transformed by a chemical carcinogen

Tumorigenic clonal lines derived from soft agar colonies induced by DMBA-transformed feline embryo cells were isolated and characterized. The morphologically altered clonal cells formed large aggregates, growing in this aggregate form when suspended in liquid growth medium above an agar base and forming colonies in soft agar with high efficiency. When inoculated into athymic nude mice, chemically altered clonal cells produced progressively growing sarcomas. Cells established from the tumors morphologically resembled the DMBA-transformed feline embryo cells and were characterized as cat cells by karyological analysis. The tumorigenic lines were negative for feline oncornavirus-associated cell membrane antigen (FOCMA), and for "gag-X" the transformation-related polyprotein which is encoded by the replication defective feline sarcoma virus.

Transformation of cultured rat ovarian surface epithelial cells by Kirsten murine sarcoma virus

A method is described for the culture of rat ovarian surface epithelial cells, i.e., the cellular component thought to be the source of most ovarian cancers. These cells in culture have a characteristic epithelial morphology which distinguishes them from other ovarian cell types. Cultured surface epithelial cells are histochemically positive for 17 beta-hydroxysteroid dehydrogenase and negative for delta 5-3 beta-hydroxysteroid dehydrogenase, the same as in cryostat sections of whole rat ovary. Ultrastructurally, cultured surface epithelial cells have basement membranes, microvilli, and apical intercellular junctions. Kirsten murine sarcoma virus was used to produce three transformed cell lines from pure first-passage cultures of these cells. These three lines retained 17 beta-hydroxysteroid dehydrogenase activity and showed slight delta-3 beta-hydroxysteroid dehydrogenase activity. Tumors resulting when these cells were injected s.c. or i.p. into immunosuppressed female rats were highly malignant, resembling histologically human ovarian endometrioid stromal sarcoma. This is the first demonstration of the susceptibility of ovarian surface epithelium to an oncogenic virus.

Neoplastic transformation of mouse fibroblasts by murine sarcoma virus: a multi-step process

Infection of cultures of three different normal rodent cell lines with murine sarcoma virus (MSV) resulted in very rapid loss of contact inhibition of growth and morphological transformation. In the case of two of these lines, anchorage dependence of growth was also rapidly lost but with the 3rd, C3H10T1/2 C1.8, an established line of mouse embryo fibroblasts, there was a delay of many cell generations before the cells became anchorage independent. This was despite 100% successful infection, as assessed by focus assays of the infected cells. The acquisition of anchorage independence was correlated with a substantial increase in tumorigenicity. A number of MSV-infected clones, isolated at random from C3H10T1/2 C1.8 cultures immediately after infection with MSV, also showed a progressive increase in anchorage independence and tumorigenicity, indicating that the progressive transformation of the uncloned cells could not be entirely due to selection of rare anchorage-independent, tumorigenic clones. It was concluded that neoplastic transformation of C3H10T1/2 C1.8 cells by MSV is a multi-step process.

Cellular proliferation in the spleen of DBA/2 mice infected with a myeloproliferative sarcoma virus(MPSV)

Cellular proliferation kinetics were investigated in the spleens of DBA/2 mice infected with a myeloproliferative sarcoma virus (MPSV) at three distinct phases of spleen growth: the rapid-growth phase, the slow-growth phase and the regression phase. Using injection of tritiated thymidine in vivo and autoradiographic techniques, we showed that most blast cells proliferate rapidly (cell cycle is equal to 10 h) even during the slow-growth phase. Very massive and rapid cell loss was found during the rapid-growth phase (cell loss factor phi = 80%). By comparing the decrease in specific splenic activity after in vivo injection of 125IUdR and 3HTdR, we were able to show a large reutilization of tritiated thymidine (R = 57%), visible less than 7 h after injection of isotopic DNA precursors. Thus, MPSV-infected spleen cells were shown, for the most part, to be short-lived cells: almost one-half mature into erythrocytes and the others rapidly die in situ.

PRCII, a representative of a new class of avian sarcoma viruses

The Poultry Research Center Virus II (PRC II) is a replication-defective avian sarcoma virus with envelope determinants of the A and B subgroups. In nonproducing cells transformed by PRCII the products of the replicative genes gag, pol, and env are not demonstrable, but a single polyprotein of Mr 105,000 (p105) can be detected. P105 contains peptides of the gag proteins p19 and p27 plus transformation-specific sequences. It does not contain peptides of gPr95env of Pr180gag-pol (with the possible exception of one pol peptide). The transformation-specific sequences of p105 are distinct form those of p100 of avian carcinoma virus MH2, of p110 coded for by avian myelocytoma virus MC29, and of p75 or p40 of avian erythroblastosis virus AEV. They also show no resemblance to p60src of Rous sarcoma virus. P105 is phosphorylated on a tyrosine residue and has an associated phosphokinase activity. P105 appears to be capable of autophosphorylation and of phosphorylating homologous immunoglobulin.

Neoplastic transformation of chimpanzee cells induced by adenovirus type 12--simian virus 40 hybrid virus

The adenovirus 12--simian virus 40 hybrid virus produced neoplastic transformation of chimpanzee skin fibroblasts in vitro. The transformed fibroblasts showed morphological alteration and became permanent lines. The transformed cells contained both adenovirus 12 and simian virus 40 large tumor antigens and were virus producers. However at passage 9, one line (WES) was found to be a nonproducer, producing neither infectious virus nor virus-specific antigen detectable by the complement fixation test. Virus particles were not detected nor could infectious hybrid virus be rescued from this line by cocultivation with Vero cells. The transformed cells formed large cell aggregates and grew in liquid growth medium above an agar base, formed colonies in soft agar, and grew to high saturation densities; the normal chimpanzee skin fibroblasts did not. One transformed WES line produced tumors when transplanted subcutaneously into newborn nude mice, thus providing an important tool for studying tumor immunity in the chimpanzee.

Malignant bone tumours induced by a local injection of colloidal radioactive 144Cerium in rats as a model for human osteosarcomas

Lung metastases were observed in 80% to 85% of rats bearing advanced malignant bone tumours (osteogenic osteosarcomas and angiosarcomas). These tumours were induced in 2-month-old Sprague-Dawley rats by inoculation of a colloidal suspension of radioactive cerium (144Ce) into the hind leg, in close contact to the bones of the knee joint. Twenty-eight rats were killed or died spontaneously shortly after detection of palpable tumours at the site of injection: the incidence of lung metastases was 73.3% and 53.8%, respectively, for osteogenic sarcomas and angiosarcomas, showing that most lung metastases are present at the time of diagnosis of the primary tumour. Tumour-cell kinetic parameters were studied in 49 rats bearing tumours following intraperitoneal injection of [3H]thymidine. The labelling index (LI) of the primary tumours was significantly lower in advanced tumours (7.2% for osteosarcomas and 10.1% for angiosarcomas) than than in tumors examined at the time of detection (12.2% and 13.5%, respectively). Mitotic indices (MI) of all tumours were less than 1%. From the curve of the percentage of labelled mitoses (PLM) at different times after [3H]thymidine injection, Ts (6.5 h) and TG2 (1.75 h) were determined. TC and TG1 were also evaluated (18 h and 9.25 h, respectively). These results show that malignant bone tumours induced in rats with 144Ce may be a good model for human osteosarcomas and may be useful in studying the numerous problems in the therapy of malignant bone tumours in man.

Defective cytotoxic T-cell generation in Moloney murine sarcoma virus-infected A/Sn mice

Cytotoxic T-cells (CTL) could not be detected in spleen cell suspensions from Moloney murine sarcoma virus (M-MuSV)-induced tumor-bearing A/Sn and (A/Sn X C57BL/6) F1 mice, with the A/Sn-derived natural killer (NK)-sensitive YAC-1 lymphoma cells used as targets. However, spleen T-cells from tumor-bearing (A/Sn X C57Bl/6)F1 mice were efficient killers against C57BL/6-derived RBL-5 cells. When tested for viral antigens by sera from mice with regressing atumors, YAC-1 and RBL-5 cells cross-reacted. The anti-RBL-5 effect of spleen cells from A/Sn X C57BL/6)F1 tumor bearers was blocked in cold target competition experiments by YAC-1 cells, which suggested the expression of a CTL target structure on YAC-1 cells. The activity against YAC-1 cells in spleen suspensions of both tumor-bearing and control (A/Sn X C57BL/6)F1 mice seemed to be an NK phenomenon entirely, because blocking occurred neither with RBL-5 cells nor with freshly prepared YAC lymphoma cells, both of which have low sensitivity to NK effects. Spleen cells from (A/Sn X C57BL/6)F1 regressors were stimulated to a secondary CTL response in vitro by YAC-1 and RBL-5 cells, which further indicated that YAC-1 cells express the M-MuSV-specific CTL target structure. These experiments also showed that YAC-1 cells could be lysed by CTL. YAC-1 cells did not induce a secondary response in A/Sn regressors, which indicated a lack of M-MuSV-induced CTL memory cells in this strain. The result was not due to a general unreactivity of A/Sn mice against YAC-1 cells, because spleen cells from YAC-1-immunized mice exhibited strong T-cell-mediated anti-YAC-1 activity after in vitro cultivation. Thus tumor regression seems to occur without the production of CTL in A/Sn mice.