Yoshio Kozai

Ansamitocin, a group of novel maytansinoid antibiotics with antitumour properties from Nocardia

WE have isolated a new group of ansamycin antibiotics with potent antitumour activity, from a fermentation broth of Nocardia sp. No. C-15003 (N-l) and have named it ansamitocin. Structures of ansamitocin were found to be similar to maytansine and related maytansinoids obtained from plant sources by Kupchan et al.1–4 and Wani et al.5. These comounds have strong antitumour activities, but development of production would be difficult, because plants containing maytansinoids are only harvested in tropical areas and their content in the plants is extremely low. Some attempts have been made to find a maytansinoid-producing microorganism6, but no success has been reported. We report here the microbial production, isolation and structural elucidation of these antibiotics and their antitumour activities against several experimental tumours in mice.

Inhibition of cell growth and tumorigenesis of human glioblastoma cells by a neutralizing antibody against human basic fibroblast growth factor

We report here that a neutralizing mouse monoclonal antibody against basic FGF inhibited both anchorage‐dependent and anchorage‐independent growth of U‐87MG and T98G human glioblastoma cells and HeLa cells, all of which express both the basic FGF and the FGF remptor genes. In addition, the subcutaneous administration of this antibody significantly suppressed the tumor development or these tumor cells in nude mice. Therefore, basic FGF plays an important role in neoplastic growth of these cells. The neutralization or basic FGF will be effective in controlling the growth of tumors, such as glioblastoma and other cancer cells which bear basic FGF and FGF receptors.

Ultraviolet inactivation of avian sarcoma viruses: biological and biochemical analysis.

Abstract The rate of inactivation by ultraviolet light of the focus-forming capacity of avian sarcoma virus was almost the same as that of the virus-producing capacity, measured as plaque formation. In addition, no significant difference was observed in inactivation of the transforming capacity assayed on C/BE chick embryo fibroblasts (CEF), which carry endogenous avian tumor virus DNA, and on duck embryo fibroblasts (DEF), which are known to be devoid of this DNA. All foci induced by nonirradiated virus produced infectious sarcoma virus, but some of the foci induced by uv-irradiated virus did not produce infectious virus of either transforming or transformation-defective type. The proportion of nonproducer foci was 3.4 times more in DEF than in gs− chf− CEF. RNAs extracted from uv-irradiated virions by sodium dodecyl sulfate (SDS) treatment were found to be composed of 60–70 S and 4 S RNAs by analysis in a sucrose gradient containing 0.5% SDS. The large RNA, however, became hydrophobic after irradiation and was sedimented with SDS by addition of one drop of saturated potassium chloride solution. This RNA was not dissociated into 30–40 S components by heating at 100° for 45 sec, unlike 60–70 S RNA from unirradiated virions. After SDS-Pronase treatment, the 60–70 S RNA from uv-irradiated virions no longer had these altered characteristics. Reverse transcriptase activity with the endogenous template decreased in parallel with increase in the uv dose. The reduction rate was similar to that assayed with exogenous template or in the presence of actinomycin D. These data strongly suggest that RNA damage is not the only cause of virus inactivation by uv light.

Scintigraphic detection of xenografted tumors producing human basic fibroblast growth factor

A murine monoclonal antibody 3H3 recognizes the basic fibroblast growth factor (FGF) and inhibits the growth of human glioblastoma cells both in vitro and in vivo. We studied the potential of a scintigraphic technique using the 3H3 antibody to detect tumors that produce basic FGF.125I- and111In-labeled 3H3 bound to U87MG human glioblastoma cells in vitro. U87MG cells were inoculated subcutaneously into nude mice. After development of the tumor, radiolabeled 3H3 was injected into the subcutaneous space surrounding the tumor. A high level of radioactivity from 3H3 was retained at the tumor, whereas an irrelevant antibody cleared rapidly from the injected site. Radiolabeled 3H3 was not retained in tumors that did not produce basic FGF. Scintigraphic detection of tumors expressing basic FGF would be valuable for the therapeutic application of the antibody.

Spontaneous Production of a C-Type RNA Virus in a Cell Line Derived from Rat Glioma

The spontaneous production of a rat C‐type RNA virus (ACV) in a cultured cell line (AC cells) established from a chemically induced rat glioma was studied. The characteristics of ACV were: morphology typical of C‐type RNA virus; buoyant density of 1.15 g/ml in a sucrose density gradient; RNA directed DNA polymerase activity; viral core with a density of 1.28 to 1.30 g/ml; 70S RNA with dimer structure; and structural protein composed of mainly four polypeptides. Kinetical analysis of DNA‐DNA hybridization revealed that DNA sequences homologous to DNA transcripts of RNA of ACV were present in rat cells. RNA directed DNA polymerase of ACV partially cross‐reacted with antiserum to the polymerase of Rauscher murine leukemia virus. These data suggest that ACV is an endogenous C‐type RNA virus of rat origin.