Human sarcomas in culture. Foci of altered cells and a common antigen; induction of foci and antigen in human fibroblast cultures by filtrates.

In a study of human sarcomas maintained in culture for periods up to two years, the following observations were made. The most prominent cell type in serially cultured osteosarcomas was fibroblastic in appearance. After 16-20 wk in culture some lines spontaneously developed foci of altered cells resembling the foci produced in monolayer cultures by oncogenic viruses. The presence of these foci in the sarcoma cultures was transient, and usually they did not reappear; but in one instance they recurred with a characteristic periodicity of several weeks. From one of the sarcoma lines, in which foci appeared after 5 months in culture, two subcultures were established from stored frozen cells and these both exhibited foci after approximately the same lapse of time. The same phenomenon has been seen with another line, suggesting that the time of appearance of foci is characteristic for particular sarcomas. Foci of similar type could sometimes be induced in monolayer cultures of human fibroblasts by filtered medium from cultured sarcomas; this bore no relation to the presence or absence of foci in the sarcoma cultures at the time the filtrate was prepared. Electron microscopy of the spontaneous and induced foci, and of the sarcoma cultures, revealed no demonstrable virus. 12 out of 15 sarcoma cultures contained an antigen (S) demonstrable by indirect immunofluorescence with human sera. It was not present in any of the original sarcoma specimens, nor in any culture lines other than sarcomas. At least 3-4 wk in culture appear to be required for its demonstration. The antigen was cytoplasmic, occurred in only a small proportion of the cells, and was unpredictably variable in its expression, even in the same culture line. It could be induced in monolayer cultures of human fibroblasts by filtrates of medium from sarcoma cultures. As with the foci, the induction of S antigen in indicator cultures was not dependent upon the expression of antigen in the sarcoma line from which the filtrates were obtained. There was no association between the presence of foci and of antigen, nor was there any apparent relation between the ability of filtrates to induce foci and their ability to induce antigen. 80% or more of the general population have S antibody, and the titer of antibody in patients with sarcoma is no higher than in normal subjects. Thus, as in the case of Burkitt's lymphoma antigen, it appears that most individuals have been exposed to S antigen. But unlike Burkitt's lymphoma, no relation has so far been established between any particular disease and a corresponding high titer or frequency of occurrence of S antibody. The occurrence of foci of altered cells and of a common antigen, and the transmission of these two characters to indicator cells by filtrates, are all suggestive of a virus specifically associated with human sarcomas, one to which the general population is widely exposed, as indicated by the prevalence of antibody.

DNA polymerase activities of human milk.

DNA polymerases have been partially purified from human milk. A DNA polymerase detected by phosphocellulose chromatography is similar to the enzymes of RNA tumor viruses in that a hybrid of polyriboadenylate and oligodeoxythymidylate is a better template than is DNA. However, this polymerase differed from that of the RNA tumor viruses in its chromatographic behavior. Three different methods of detecting "reverse transcriptase" activity failed to correlate with the donor's family history of cancer.

Infection of an established mouse cell line with cell-free Rauscher leukemia virus. I. Cytological study with the electron microscope.

Infecting mouse bone marrow cells (JLS-V9) with cell-free Rauscher leukemia virus demonstrated that monolayers of JLS-V9 cells were susceptible to infection with both cell-free plasma and tissue-culture-propagated Rauscher virus. The infected cultures maintained the continuous release of the virus. Cells and concentrated supernatant fluids from infected cells were periodically examined under the electron microscope by thin sectioning and negative staining techniques after inoculation with either mouse plasma or tissue-culture-propagated virus. After adsorption the virus underwent a prolonged eclipse or latent period. Virus budding was initially detected about 10 days after primary infection. These observations were further confirmed by the simultaneous appearance of extracellular virus. The budding process was followed by accelerated virus multiplication which reached maximum production 2-3 weeks later. Before the onset of budding no significant morphologic changes were seen in the infected cells.

Formation of solid human mammary carcinoma in vitro.

An established line of human breast carcinoma, MCF-7, when cultured within the artificial capillary system, formed solid masses of tissue. Acinar and ductular patterns developed, having the ultrastructural appearance of breast tissue that responds to exogenous hormones.

Transmission of mammary tumor virus in mouse strain DD: further support for the uniqueness of strain GR.

Outcrosses between high tumor mouse strain DD and low-incidence strains BALB/c and C57BL to produce reciprocal F1 susceptible offspring of both types resulted in high incidences of mammary tumors in (DD female X BALB/c male)F1 and (DD female X C57BL male)F1 females but not in the reciprocal hybrids with DD as the male parent. The finding that transmission of murine mammary tumor virus (MuMTV) in DD was through the milk, as most often observed in mouse strains, further supported the uniqueness of strain GR in which MuMTV is transmitted by either parent.

Responses of infant rhesus monkeys to inoculation with Mason-Pfizer monkey virus materials.

Rhesus monkeys neonatally inoculated with Mason-Pfizer monkey virus (M-PMV) and virus-infected cells frequently developed viral and/or bacterial pneumonia and enteritis. Three characteristic hematologic patterns occurred among the inoculated animals and correlated well with the probability of survival. Postmortem examination of the animals revealed lymphadenopathy and thymic atrophy. M-PMV was present in lymph nodes, blood, brain, spleen, thymus, kidneys, and bone marrow. The disease induced in some animals had characteristics suggestive of a slow-virus-induced autoimmune response.

A new virus in a spontaneous mammary tumor of a rhesus monkey.

PIP: This study investigated the ultrastructure and development of virus particles detected in a spontaneous mammary tumor of an 8 year old rhesus monkey. During a 3-month period of tumor growth, several biopsies were performed. Thin section electron microscopy of the tumor tissue revealed 2 types of particles: 1) an intracytoplasmic, electron-dense, ring-shaped particle, and 2) an extracellular particle with an outer unit membrane and a central dense nucleoid. The intracytoplasmic development and virus maturation by a process of budding at the level of the cell membrane was reconstructed.^ieng