herbimycin and Neoplasms

The currently used Hsp90 inhibitors, geldanamycin, herbimycin A and radicicol, were isolated many years ago from Streptomyces and fungi originally for their antiprotozoal activity, herbicidal activity and antifungal activity, respectively. In the mid 1980s, it was found that the benzoquinone ansamycin antibiotics (herbimycin A, geldanamycin, and macbecin) reversed v-Src transformed cells to normal phenotypes, and Bcr-abl was subsequently suggested to be the molecular target for the treatment of chronic myelogenous leukemia through a study using herbimycin A for its selective antioncogenic activity. In 1994, these ansamycins were found to bind to Hsp90 and to cause the degradation of client proteins including Src kinases; further efforts to develop anticancer drugs were made using geldanamycin analogs, and 17AAG was chosen as the best candidate for clinical trials. The number of novel natural products isolated from microbial origins is continuing to increase and is doubling every 10 years. Thus, screening of bioactive substances from natural origins, using assays including defined targets, and developing leads toward drugs via optimized derivatization is a conventional but still promising strategy for drug discovery and development.

Topics: Animals; Anti-Bacterial Agents; Benzoquinones; Biological Factors; Drug Delivery Systems; Fusion Proteins, bcr-abl; HSP90 Heat-Shock Proteins; Humans; Lactams, Macrocyclic; Neoplasms; Plants, Medicinal; Quinones; Rifabutin

Topics: Adjuvants, Immunologic; Animals; Antibiotics, Antineoplastic; Benzoquinones; Bleomycin; Drug Evaluation; Humans; Lactams, Macrocyclic; Mice; Mitomycins; Neoplasms; Neoplasms, Experimental; Oncogenes; Quinones; Rifabutin

Organ-specific sites of metastastic lesions are determined in part by integrin-mediated adhesion to extracellular matrix (ECM) components. Using poorly (HT-29P) and highly liver-metastatic (HT-29LMM) colon carcinoma cells we previously found different integrin-mediated adhesion to various ECM components, but similar integrin expression of both cell lines. These HT-29 cell lines were used to study adhesion to collagen I (C I) and possible intracellular signaling mechanisms that could explain different adhesive properties. HT-29LMM cells had significantly poorer rates of adhesion to C I (P < 0.05) than HT-29P cells. For examination of the integrin subunits involved in adhesion to C I, cells were treated with various anti-integrin antibodies. These results demonstrated that adhesion of HT-29 cells to C I is mediated in part by the alpha 2 beta 1 integrin. Using immunoprecipitation and Western blotting, both cell lines expressed similar patterns of integrins (alpha 2, alpha 3, alpha 6, and beta 1). Weaker signals were found for the expression of alpha v and beta 5 integrins. Although poorly and highly metastatic cells possessed different patterns of adhesion to C I, these differences were not caused by different expression of integrin subunits. For investigation of the involvement of phosphotyrosine kinases in adhesion, cells were pretreated with the Erbstatin analog, Genistein, or Herbimycin A. Genistein transiently stimulated the adhesive properties of both cell lines. In contrast, Herbimycin A had biphasic effects. At lower concentrations of Herbimycin A stimulation of adhesion was found after 30 and 90 min. However, higher concentrations inhibited adhesive properties. The stimulatory effect was more pronounced in poorly metastatic HT-29P cells. The Erbstatin analog had no effect, probably because of the lack of epidermal growth factor receptor expression in both cell lines. The results suggest that adhesion of tumor cells to ECM components may be dependent on signal transduction into the cell, and tyrosine phosphorylation appears to be involved.

Topics: Benzoquinones; Cell Adhesion; Collagen; Genistein; HT29 Cells; Humans; Integrins; Lactams, Macrocyclic; Neoplasms; Phosphorylation; Protein-Tyrosine Kinases; Quinones; Receptors, Vitronectin; Rifabutin; Tyrosine

The signal transduction events which govern major histocompatibility complex-unrestricted tumour cell destruction by nonspecific killer T lymphocytes induced with anti-CD3 antibody have not yet been determined. In this study we used pharmacologic inhibitors to investigate the role of protein tyrosine kinases (PTK) and protein kinase C (PKC) in this process. The PTK-inhibitors herbimycin A, genistein, and methyl 2,5-dihydroxycinnamate blocked anti-CD3-activated killer T (AK-T) lymphocyte-mediated killing of tumour target cells. The PKC-inhibitors staurosporine, calphostin C, and myristoylated PKC pseudosubstrate peptide, as well as PKC desensitization by phorbol 12-myristate 13-acetate pretreatment, also suppressed the cytolytic effector function of AK-T lymphocytes. Lack of tumoricidal activity was not due to reduced AK-T lymphocyte binding to tumour target cells but was associated with the abrogation of granule exocytosis, indicating that PTK and PKC are involved in the postbinding process which results in delivery of the 'lethal hit' by AK-T lymphocytes.

Topics: Animals; Antibody-Dependent Cell Cytotoxicity; Benzoquinones; Cinnamates; Female; Genistein; Granzymes; Immunosuppressive Agents; Isoflavones; Killer Cells, Natural; Lactams, Macrocyclic; Mice; Mice, Inbred C57BL; Muromonab-CD3; Neoplasms; Protein Kinase C; Protein-Tyrosine Kinases; Quinones; Rifabutin; Serine Endopeptidases; Signal Transduction

We have described a microplate colorimetric assay to quantitate anchorage-independent cell growth, using plates coated with an anti-adhesive polymer poly (2-hydroxyethyl methacrylate) (polyHEMA).We investigated whether this method could be applied to human cancer cells of epithelial origin. HAG-1, a non-tumorigenic human gall-bladder carcinoma cell line, and its pSVneo and c-H-ras transfectants, which are also non-tumorigenic, did not grow on a polyHEMA-surface. In contrast, the v-src transformant which produced tumors in nude mice and formed colonies in soft agar, was able to proliferate on the coated surface, suggesting that tumorigenicity of human cancer cells correlates with the ability to grow on a polyHEMA-coated surface. We report on the feasibility of this method as a screening system for inhibitors of oncogenic transformation. Herbimycin A and radicicol, which have been reported to block Src function, suppressed the growth of v-src-transformed NRK and HAG-1 cells on the non-adhesive polyHEMA-surface at concentrations significantly lower than on plastic. Differences in the inhibitory concentrations were not observed with KB cells, and cytotoxic agents such as adriamycin did not show any selectivity between the 2 surfaces. Growth of ras-transformed cells on the coated surface was selectively blocked by L-739,749, a farnesyltransferase inhibitor. The results demonstrate that compounds causing reversion of transformed cells to normal, hence, selectively inhibiting cell growth in anchorage-independent conditions, can be screened using this microtiter plate assay.

Topics: Adenocarcinoma; Animals; Benzoquinones; Cell Adhesion; Cell Division; Cell Line, Transformed; Drug Screening Assays, Antitumor; Humans; Lactams, Macrocyclic; Lactones; Macrolides; Methacrylates; Mice; Neoplasms; Oligopeptides; Protein-Tyrosine Kinases; Quinones; Rifabutin; Tumor Cells, Cultured; Urinary Bladder Neoplasms

Accumulating evidence indicates that the activation of cellular oncogenes is a cause of some human cancers. ErbB-1, erbB-2 and abl oncogenes encoding tyrosine kinases, ras oncogenes encoding GTP binding proteins and myc oncogenes whose functions are not well understood are some examples. Therefore, agents which inhibit the activity of these oncogene products may provide new means to overcome certain human tumors. Herbimycin A and tyrphostins have been found and developed as inhibitors of tyrosine kinases and the effectiveness of these agents against tumors of Ph1-positive leukemia (CML, ALL) or squamous cell carcinomas has been reported. Although specific inhibitors of ras or myc oncogene products have not yet been described, recent studies on the processing of Ras proteins toward the cell membrane provide a strategy to search for inhibitors of ras functions.

Topics: Antibiotics, Antineoplastic; Benzoquinones; Carcinoma, Squamous Cell; Catechols; Cyclin D1; Female; Genes, ras; Humans; Lactams, Macrocyclic; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Male; Neoplasms; Nitriles; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Quinones; Rifabutin; Tyrphostins