The effects of tamoxifen (TAM), its 3-hydroxy congener droloxifene (DROL) and 17 beta-estradiol were investigated on leukemogenesis induced in BALB/c mice by Rauscher murine leukemia virus (RLV). Multiple applications of each compound, in a dose-dependent manner, resulted in reduced virus titer in the serum, delayed onset of splenomegaly and significant prolongation of survival. Although 17 beta-estradiol proved most effective, prevention of disease was not achieved either by short- or long-term treatment with any of the drugs tested.

Among human sarcomas, osteosarcomas usually display high intrinsic mdr1 expression while malignant fibrous histiocytomas (MFH) do not. A comparative polymerase chain reaction (PCR)-based sequence analysis of the mdr1 promoter revealed point mutations in seven out of nine osteosarcomas at nucleotides +103 (2 cases T-->C) and +137 (5 cases G-->T). No changes were seen in eight MFHs. When COS cells transfected with CAT constructs containing the T-->C chloramphenicol acetyltransferase mutant mdr1 promoters were treated with vincristine or doxorubicin, expression of the CAT gene was enhanced to a higher extent than with constructs containing wild-type or G-->T-mutant mdr1 promoters. We suggest that there is a correlation between the type of mdr1 promoter mutation and responsiveness to MDR relevant drugs.

The expression of the mdr1 gene was evaluated at the RNA level by northern and slot blot analysis, and at the protein level by immunohistochemistry, in a total of 29 bone and 32 soft tissue sarcomas. All patients, mainly adults, had not received previous chemotherapy. Of the tumours investigated, 69% were mdr1-positive. An intermediate mdr1 expression was observed most frequently, with the exception of osteosarcomas (high) and malignant fibrous histiocytomas (low). Detection of P-glycoprotein in selected tumours revealed consistent results. However, no conclusion can be drawn as yet regarding correlation of mdr1 expression and drug resistance in patients.

The main goal of this meeting was to provide the scientists and clinicians active in this field with a comprehensive overview of the progress that has been made. The meeting was a forum in which new advances in membrane transport were discussed in depth and which gave new impulses for clinical applied research. Again, the importance of intensive cooperation between basic research and clinical use became evident during this symposium.

The main goal of this meeting was to provide the scientists and clinicians active in this field with a comprehensive overview of the progress that has been made. The meeting was a forum in which new advances in membrane transport were discussed in depth and which gave new impulses for clinical applied research. Again, the importance of intensive cooperation between basic research and clinical use became evident during this symposium.

Type D retroviruses constitute a group of RNA tumor viruses so far isolated exclusively from primates. 4 groups of isolates are known to date (Mason-Pfizer virus, agents of simian acquired immunodeficiency syndrome--SAIDS, endogenous viruses of Old World and New World monkeys, and some isolates from cell lines--PMF virus). The members of the latter group are well characterized at protein-chemical and immunological levels. Briefly described in this paper are the results of our studies into the molecular structure of the viral genome of PMFV in relation to other members of the group (SAIDS-retrovirus/NE, MPMV, and SRV-1).

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on cultivated human cells infected with a human cell line derived retrovirus were examined by using scanning electron microscopy. The most prominent immediate morphological changes were the rounding up of cell surfaces, an enhanced formation of blebs and an increasing tendency to cell detachment. The production of virus particles under TPA treatment was markedly augmented, reaching 300 to 500 particles in individual cells. The production of particles appeared nearly random over the cell surface.

Unintegrated circular proviral DNA of a type D retrovirus (PMFV) isolated from a permanent human cell line was molecularly cloned in the bacteriophage vector L47.1 and subcloned in the plasmid vector pGEM-2. A restriction endo-nuclease map of PMFV DNA was established using 10 different enzymes for single and multiple digestions of closed circular and cloned DNA molecules. By restriction endonuclease analysis cloned PMFV DNA represented full-length viral DNA with one long terminal repeat (LTR). The comparison of the physical map of cloned PMFV to those of other cloned type D retroviruses revealed closest homology to the map of retrovirus D/New England (pD398) and SAIDS retrovirus type 1 (SRV-1). The relatedness of PMFV to further type D retroviruses (Mason-Pfizer monkey virus, MPMV; SAIDS retrovirus type 2, SRV-2) was also demonstrated by cross-hybridization of cloned DNAs under different stringencies (i) using full-length genomic probes of PMFV, MPMV, and SRV-2 and (ii) by DNA sequence analysis of regions of the group specific antigen (gag) protease (prt), polymerase (pol), and envelope (env) genes.

Haloperidol, a butyrophenon, is widely used for the treatment of psychotic disorders in man. Recently we reported that this drug causes, with high incidence, the development of monocytic-myeloid leukemias in male NMRI mice upon 5 X 5 mg/kg i.p. administration. Here we present evidence for the leukemogenic effect of haloperidol in two other strains of mice (XVII AKF1 hybrids, and the low leukemic BALB/c/BOM). The strain-dependent incidence of leukemias ranged both in males and females between 34% (AKR) and 69% (XVII AKF1) with average latencies between approximately 200 (AKR) and 600 (BALB/c) days. On the basis of cytological and cytochemical criteria the predominating type of leukemias was classified as monocytic-myeloid. These leukemic were serially transplantable. Cell-free extracts of leukemic tissues did not induce the disease indicating that no virus was activated by haloperidol. However, when the drug was administered to AKR mice after a suboptimal dose of nitrosomethylurea (NMU), a higher incidence of mixed-type leukemias was observed as with haloperidol alone. NMU alone induced lymphatic leukemias with proven viral involvement. The tumor promoter 12-0-tetradecanoylphorbol-13-acetate did not influence haloperidol-induced leukemogenesis.

Biochemical and immunological properties of retrovirus-D/New England (here referred as R-D/NE) recently isolated at the New England Regional Primate Research Center, Southborough, Ma, from a rhesus monkey with acquired immune deficiency syndrome were investigated and compared to the prototype type D retroviruses Mason-Pfizer monkey virus (MPMV) and permanent human fibroblast virus (PMFV) isolated from a breast carcinoma of a rhesus monkey and a continuous human cell line, respectively. The polypeptide composition of R-D/NE propagated in a human lymphoid B cell line (Raji cells) has been investigated using SDS-polyacrylamide gel electrophoresis. Staining with Coomassie blue and labelling with14C amino acids revealed seven viral polypeptides with molecular weights of 4,000, 10,000, 12,000, 15,000, 18,000, 27,000, and 80,000 Da which were also shared by MPMV and PMFV. The 80,000 Da protein was shown to be a glycoprotein by incorporation of3H glucosamine. The 18,000 Da protein was identified as a phosphoprotein of R-D/NE. p 18 structural proteins of MPMV and PMFV represent phosphoproteins of their respective viruses as well. All three phosphorylated proteins contain O-phosphoserine as major phosphoamino acid. The comparison of tryptic peptide maps of the major internal structural proteins of R-D/NE, MPMV, and PMFV revealed a striking similarity among p 10/p 12 and p 15. proteins. A minor difference was detected among the tryptic peptide digests of p 4 and p 27 proteins. Antiserum against p 15 of MPMV showed a significantly weaker binding to R-D/NE than to MPMV and PMFV at high dilutions. compared to our earlier findings of a gp 70 might be due to the different host cell lines used for virus propagation.

An animal system is described that allows the analysis of the interaction of persisting hamster papovavirus (HaPV) genomes with the tumor-promoting phorbol ester TPA. In a colony of HaPV-bearing Syrian golden hamsters, extrachromosomal HaPV genomes were detected by Southern blot hybridization in DNA isolated from skin biopsies. Chronic topical treatment of hamsters with TPA resulted in a dramatic increase of viral DNA in skin cells at the site of TPA application. After finishing the TPA treatment, the amount of extrachromosomal viral DNA declined but was still enhanced more than three months thereafter. This model offers the possibility of investigating, at the molecular level, the initiating role of virus in tumorigenesis.

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.

Phenolic polymers synthesized by enzymatic oxidation of coffeic acid, chlorogenic acid, and gentisinic acid were found to strongly inhibit RNA-dependent DNA polymerase (revertase) of retroviruses. Except of two type C retroviruses inhibition became reversible by the addition of bovine serum albumin to the exogenous revertase test. The phenolic polymers tested did not influence the propagation of retroviruses in the cell culture. The replication of Rauscher leukemia virus in mice was diminished by a short-time preincubation of virus suspension with coffeic acid polymer (KOP). In contrast, the preincubation of a virus-containing serum with KOP increased the leukemogenic effect of the virus. KOP given to mice at a high dose subsequently to virus inoculation resulted in high revertase activities and in an elevation of spleen weights too.

The effect on retroviruses of two transition metal complexes of known antiviral activity, 4-methyl-2-amino-pyridine-palladium-chloride (MAP) and cis-dichloro-diammine-platinum(II) (cis-DDP) has been investigated. The experiments included the evaluation of the action of compounds on virus particle-associated reverse transcriptase in exogenous assays, on virus propagation in persistently infected cell cultures and on virus infectivity in mice. In disrupted viruses and in the absence of excess protein, the reverse transcriptase was inhibited by MAP but not by cis-DDP. The same results were obtained when examining the activity of the virus-associated RNA polymerase of influenza virus A/WSN. Both compounds did not inhibit the replication of retroviruses in cell cultures, except at high dose levels which exerted toxic action on both cells and virus formation. The leukemogenicity of Rauscher murine leukemia virus was strongly inhibited when the virus had been incubated with MAP before inoculation. A similar treatment with cis-DDP did not influence viral leukemogenicity. Despite somewhat different results with both compounds tested, we conclude from the present results that the above mentioned compounds cannot be considered as antiretroviral drugs.