[Anton Sticker (1861-1944) and the Sticker's sarcoma of dogs. A current model for infectious cancer cells]. / Anton Sticker (1861-1944) und das Sticker-Sarkom des Hundes. Ein aktuelles Modell für infektiöse Krebszellen.

Sticker's sarcoma (now known as CTVT for canine transmissible venereal tumour) is a histiocytic venereal tumour transmitted among dogs through direct contact. Recently, it has become evident that all tumours of this type existing worldwide originate from the tumour of one animal. The infectious agent that is transmitted through contact is the cancer cell itself. Sticker's sarcoma is the oldest recognised cancer line and is currently also the best model for infectious cancer cells. The sarcoma is named after the German veterinarian and physician Anton Sticker (1861-1944), who between 1902 and 1905 carried out extensive studies on the nature of this tumour at the institute headed by Paul Ehrlich in Frankfurt am Main. Sticker's hitherto relatively unknown, multifaceted career is briefly presented here.

Reverse transformation of human mammary carcinoma cells.

Exposure of cells derived from human mammary carcinoma cell line, MaTu, to daunorubicin started a selection process which reproducibly gave rise to sublines with different phenotypes. One subline exhibited a fibroblast-like morphology (MaTu/c7), while others retained the epitheloid phenotype of the parental cells (MaTu/p). Among the latter was clone 8 (MaTu/c8) which displayed piling-up structures not seen in MaTu/p cells. Striking differences were detected on immunocytochemistry using the anti-cytokeratin 19 antibody A53-B/A2 which positively reacted with cells from MaTu/c7, but not with those of MaTu/c8 and MaTu/p. In contrast, the anti-blood group H 2 antibody A46-B/B10 positively stained cells from MaTu/c8 and MaTu/p, but not those of MaTu/c7. Assays for tumorigenicity in nude mice demonstrated that MaTu/c7 is far less tumorigenic than MaTu/p, while MaTu/c8 showed a pattern distinguishing it from MaTu/p cells. Cross-resistance assays showed decreasing drug resistance in the order MaTu/c8 > MaTu/c7 > MaTu/p. These data suggest drug-induced differentiation with reversion of the neoplastic phenotype in MaTu/c7 and some form of malignant progression in MaTu/c8. This model system may be helpful for understanding cancer development, especially its relation to differentiation.

High-mobility-group proteins and cancer--an emerging link.

In the last few years, considerable interest has been generated in the role of high-mobility-group (HMG) proteins, and HMG box proteins generally, in cancer development and therapy. These proteins were discovered in the early 1970s (Goodwin et al. 1973) as a group of nonhistone proteins. Some members of the HMG protein family (i) constitute a class of important architectural proteins involved in transcriptional regulation of genes, (ii) are frequently expressed in transformed cells at levels that correlate with the degree of neoplastic cell transformation, (iii) participate in gene rearrangements, which are linked to the emergence of benign solid tumors, (iv) confer the ability to recognize DNA-cisplatin adducts selectively, and (v) provide a new delivery system for efficient gene transfer. It should be considered that some HMG proteins, acting as architectural proteins that bring many of the transcription factors into precise three-dimensional shapes, may have a similar critical role in neoplastic transformation to that of some transcription factors themselves.

Effects of tamoxifen, droloxifene and 17 beta-estradiol on Rauscher mouse leukemogenesis.

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.

Point mutations in the mdr1 promoter of human osteosarcomas are associated with in vitro responsiveness to multidrug resistance relevant drugs.

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.

Expression of the mdr1 gene in bone and soft tissue sarcomas of adult patients.

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.

Membrane transport in multidrug resistance, development, and disease. AACR special conference in cancer research.

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.

Use of molecular cloned viral genomes for studies into interrelationship between type D retroviruses from monkey and human cells.

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).

[Mutations of mitochondrial DNA and their relation to neuromuscular diseases]. / Mutationen der mitochondrialen DNA und ihre Beziehung zu neuromuskulären Erkrankungen.

According to present knowledge, mutations of mitochondrial DNA (mtDNA), implicated in the mitochondrial theory of carcinogenesis that had been inaugurated 50 years ago by Graffi, appear to be involved in malignant transformation of cells, although no definite evidence has been provided, as yet. However, as very recently elucidated, a clear-cut association exists between different classes of mutations of mtDNA (among them point mutations, deletions and duplications) and some human mitochondriopathies, particularly neuromuscular diseases. These include Leber's hereditary optic neuropathy, the Kearns-Sayre syndrome and two encephalomyopathies known by the acronyms MERRF and MELAS syndrome. The different alterations of mtDNA, though variable, can be assigned to defined positions on the genetic map of mtDNA. Point mutations of mtDNA seem to occur preferentially in conjunction with maternally inherited disorders. Although the results obtained so far are of interest mainly in terms of cognitive theory they provide new stimuli for the development of molecular diagnosis, genetic counselling and possibly for more effective treatment of the above diseases.

Molecular cloning of a type D retrovirus from human cells (PMFV) and its homology to simian acquired immunodeficiency type D retroviruses.

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 endonuclease 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.

[Effect of tumor-promoting phorbol esters on retrovirus-infected human cells: scanning electron microscopy studies]. / Wirkung eines tumorpromovierenden Phorbolesters auf Retrovirus-infizierte menschliche Zellen: Rasterelektronenmikroskopische Untersuchungen.

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.

Biochemical and immunological characterization of structural proteins from retrovirus-D/New England and comparison to Mason-Pfizer monkey virus and permanent human fibroblast virus.

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 with 14C 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 of 3H glucosamine. The 18,000 Da protein was identified as a phosphoprotein of R-D/NE. p18 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.

Further characterization of the leukemogenic activity of haloperidol in mice.

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.

A novel system for studying in vivo effects of tumor promoters on DNA tumor viruses.

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.

[The effect of phenolic polymers on retroviruses]. / Zur Wirkung von Phenolkörperpolymerisaten auf Retroviren.

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.