Activated fos oncogene in rat embryo fibroblasts transformed by ras and myc oncogenes.

Rat embryo fibroblasts (REF) were transformed by simultaneous gene transfer of the complementary oncogenes ras and myc using the calcium phosphate coprecipitation method. Cell lines derived from transformation foci expressed in addition to ras and myc cellular oncogene fos while normal REF did not express ras, myc and fos according to the hybridization methods used. The transformed cell lines produced colonies in soft agar and tumors in newborn syngeneic rats.

In vitro transformation of rat cells by 3-methylcholanthrene: activation of the ras oncogene.

Rat cells of the established, immortalized line rat-2 were treated with the polycyclic aromatic hydrocarbon 3-methylcholanthrene. No characteristic morphological transformation occurred during three weeks after treatment. However, the carcinogen-treated cells formed colonies in soft agar.

Transformation of rodent immortalized and embryo cells by oncogenes. II. Rat embryo fibroblasts (REF).

Rat embryo fibroblasts were transformed by co-transfer of two plasmids carrying the oncogenes ras and myc, respectively. In contrast to immortalized cells gene transfer of ras alone was not sufficient for transformation of rat embryo cells. Embryo cells transformed by both oncogenes showed an altered morphology and produced colonies in soft agar.

Transformation of rodent immortalized and embryo cells by oncogenes. I. Mouse (NIH 3T3) and rat (FR 3T3) immortalized fibroblasts.

Immortalized mouse NIH 3T3 cells were transformed by gene transfer of DNA isolated from a human bladder tumor cell line and plasmids containing an activated human Ha-ras oncogene insert. For gene transfer the calcium-phosphate co-precipitation method was used. Transformation was evaluated by morphological focus formation, growth in soft agar and tumor development in nude mice.

Suppression of human lymphocyte mitogen response by proteins of the type-D retrovirus PMFV.

A type-D retrovirus, derived from a human cell line and designated PMFV, which is related to, but distinct from the Mason-Pfizer monkey virus (MPMV) suppressed the in vitro mitogen response of human lymphocytes. PMFV was suppressive either as intact virus or after disruption by ether or detergents. In kinetic studies, the time course of the interaction between suppressive virus components and lymphocytes was characterized.

[Immunosuppression by retroviruses in tumors and immune deficiency diseases].

Most retroviruses are immunosuppressive in vitro and in vivo. They are able to enhance virus-induced tumor development and/or to induce acquired immune deficiency syndromes (AIDS) which are characterized by malignant tumors and opportunistic infections. Experimental evidence for the immunosuppressive properties of several type D viruses derived from human cell lines and other retroviruses is presented.

Suppression of human lymphocyte mitogen response by retroviruses of type D. II. Non-activity of Mason-Pfizer monkey virus versus activity of human cell line derived virus PMFV.

In contrast to the human cell line derived type D retrovirus PMFV, the Mason-Pfizer monkey virus (MPMV) does not suppress the mitogen response of normal human lymphocytes. Both viruses have been propagated on the same cell lines and purified by the same methods. MPMV did not contain a factor able to abolish PMFV-induced suppression of the mitogen response.

Suppression of human lymphocyte mitogen response by retroviruses of type D. I. Action of highly purified intact and disrupted virus.

The type D retrovirus PMFV, derived from a human cell line, suppresses the in vitro response of human lymphocytes to different T-cell mitogens as well as the mixed lymphocyte reaction. The suppressive effect is virus-specific and the active fraction copurifies with the virus particles. The suppression is produced by both crude and highly purified intact and disrupted virus preparations.

[Etiology of colon cancer--current aspects].

Multiple factors such as tumour initiating, tumour promoting, tumour inhibiting are known to be involved in the aetiological process of most colon tumours. Dominant factors are associated with life style habits. Yet in spite of many experimental and epidemiological data it has not been possible, hitherto to give convincing recommendations for the primary prevention of this type of tumours.

Further evidence from tryptic peptide analysis for heterogeneity among type D retroviruses.

Tryptic peptide analyses were performed on the major internal structural proteins of type D retroviruses isolated originally from subhuman primate species (MPMV, SMRV, LV) and from permanent human cell lines (HeLaV, HEp-2V, PMFV). The p25 peptide maps of MPMV, LV, PMFV and HEp-2V were very similar but showed a striking dissimilarity to the p25 map of HeLaV and the p35 map of SMRV. All type D viruses included in this study could be distinguished by peptide maps of at least two of their three low-molecular-weight proteins p10, p12 and p15.

The detection of distinct epitopes of human alpha-fetoprotein (AFP) by solid phase radioimmunoassay using hybridoma culture fluid.

A solid phase radioimmunoassay was developed for the epitope analysis of human alpha-fetoprotein (AFP) using hybridoma culture fluids. The following incubation sequence was performed: anti-mouse Ig, hybridoma culture fluid, normal mouse serum, and a mixture of 125I-labeled AFP and hybridoma culture fluid. Seven epitopes were detected by monoclonal antibodies produced by 15 presumably independent hybridoma clones.

Determination of immunoglobulin class and subclass of monoclonal antibodies to human alpha-fetoprotein by solid phase radioimmunoassay.

A solid phase radioimmunoassay using the incubation sequence: mouse immunoglobulin (Ig) rabbit anti-mouse Ig, monoclonal antibody and 125I-labeled antigen was performed to determine the class and subclass of seven murine monoclonal antibodies against human alpha-fetoprotein. All antibodies belonged to the IgG class. The subclass type was IgG 2a for four antibodies, IgG 1 for two antibodies and IgG 2b for one antibody.

Use of Sepharose bead immunofluorescence assay for comparison of the type D retroviruses MPMV and PMFV.

Mason-Pfizer monkey virus (MPMV) and PMFV, an isolate from a human continuous cell line, were compared by Sepharose bead immunofluorescence assay. According to the results with p27-specific assays the main structural protein of both viruses seems to be identical in the prominent antigenic determinants. Differences were found when comparing the p15s indicating that this viral protein contains type-specific antigenic determinants.

Suppression of human lymphocyte mitogen response by disrupted primate retroviruses of type C (baboon endogenous virus) and type D (PMFV).

Disrupted primate retroviruses of type C (baboon endogenous virus, BaEV) and type D (human cell line-derived isolate PMFV) considerably suppressed Concanavalin A - induced blastogenic response of human lymphocytes. Rauscher mouse leukemia virus (RLV) displayed a suppressive activity on murine splenic lymphocytes when tested under analogous conditions. The immunosuppressive activities were shown not to result from cytotoxicity or from virus-mitogen binding.

Common antigenic determinants on structural proteins p10--12 of PMFV and MPMV type D retroviruses.

PMFV, a type D retrovirus isolated from a malignant human embryo cell line, was compared with Mason-Pfizer monkey virus (MPMV) in a sensitive tannic acid enhanced indirect immunodiffusion test. In addition to the previously shown common antigens, both viruses contain identical group-specific antigenic determinants on their p 10--12 as demonstrated with a specific p 10--12 MPMV test system. Interspecies mammalian type C virus antigens were not detected in highly concentrated PMFV preparations.

Small virus-like particles in leukosis-like syndrome induced by certain antigens and immunostimulators.

A transmissible syndrome which is characterized by splenomegaly and myeloid metaplasia was induced in BALB/c mice by injections of certain homologous and heterologous antigens and complete Freund's adjuvant or dextransulfate. From the plasma of these animals small viruslike particles (30--50 nm) were isolated.

[Oncogenic virus induction by halogenated pyrimidines (author's transl)].

Oncongenic DNA and RNA Viruses are integrated into the cell genome of vertebrates. Physical, chemical and biological agents, among them the halogenated pyrimidines ododeoxyuridine (IdU) and bromodeoxyuridine (BdU) cause the induction of these viruses in cells of many species. In this review the action of IdU and BdU in certain cell differentiation systems chondrogenesis, myogenesis and others) and on activation of oncogenic viruses, first of all of type C-RNA viruses, is described and some possible mechanisms of induction are discussed.

[About the heterogeneity of the murine oncornavirus group-specific antigen gs-1 (author's transl)].

In isoelectric focusing of twofold gradienpturified and Tween 80-ether disrupted RLV the groupspecific antigen (gs-1) was found in 3 pH-zones (4,45-5,5; 5,65-6,0; 6,45-6,6). For the gs-1 from plasma und spleen cells of leukemic mice was shown heterogeneity by several methods: 1. Gs-1 from plasma showed in isoelectric focusing a scattering along the whole elution profile.