Yasuji Suhara

NEW α-AMYLASE INHIBITOR, TRESTATINS

Trestatin complex which exhibited a potent inhibitory activity on various alpha-amylases has been isolated from the culture filtrate of Streptomyces dimorphogenes nov. sp. NR-320-OM7HB. Three major components, trestatins A, B and C, have been purified by adsorption and ion-exchange chromatography. Their spectral and chemical properties suggested that trestatins were novel basic oligosaccharide homologues each characterized by the possession of a trehalose moiety at the non-reducing end of the molecule.

Antitumor and antimetastatic activities of human recombinant interferon alpha A/D

Human recombinant interferon alpha A/D (αA/D) was examined for its antitumor activity in several mouse tumor models using metastatic tumors, such as B16 melanoma F1, BL6 and F10, UV2237m fibrosarcoma, and K1735m melanoma. Therapeutic treatment with αA/D reduced the incidence of pulmonary metastasis and inhibited the tumor growth resulting in an increase of the mean survival time. Since αA/D also showed a prophylactic activity against the metastasis, its antitumor activity was suggested to be due to augmentation of the host defense systems. This was confirmed by the fact that αA/D inhibited thein vivo growth and incidence of pulmonary metastasis of B16 F1 sublines regardless of their sensitivity to the direct antiproliferative activity of the IFNin vitro.

Antitumor Activity of Host T and Non-T Cells Recovered from Tumor Nodules after Interferon Therapy

We examined the modification of host T cells of tumor nodules by interferon (IFN) therapy in mouse models. The host cells were recovered from regressing tumor nodules of mice at Day 13 after intradermal tumor inoculation at Day 0 and administration of 5 × 105 U/mouse/day IFN at Day 6 to Day 10. These host cells neutralized in vivo Meth A growth in a dose‐dependent fashion. In vitro treatment of these cells with anti‐Thy 1.2 monoclonal antibody and rabbit sera as a source of complement abrogated their tumor‐neutralizing activity, but only partially, indicating that both T cells and non‐T cells were involved in tumor neutralization. The finding that host cells from regressing tumor nodules of either Meth A or Meth 1, an antigenically distinct fibrosarcoma, neutralized both Meth A and Meth 1 tumors without much selectivity was consistent with possible non‐T cell involvement. Most of these characteristics of host cells of regressing nodules of IFN‐administered mice were also noted with host cells of progressing nodules of placebo‐administered mice and there was no significant difference in neutralizing activity qualitatively or quantitatively between the two sources of host cells. There was no significant difference in host T and B cell numbers and compositions of regressing and progressing nodules either. These essentially negative findings raise the possibility, among others, that the primary target host cells to be modified by IFN were not T cells, although the therapeutic effect of IFN was dependent on the host T cells.

Restoration by recombinant interferon alpha A/D of host defense systems against tumor in immunosuppressed mice

Recombinant human interferon alpha A/D (αA/D) restored or augmented host defense systems against tumors in immunosuppressed mice. In normal C57BL/6 mice, inoculation of B16 melanoma F1 cells caused few pulmonary metastasis, whereas in mice pretreated with cyclophosphamide (CY) it caused a high incidence of pulmonary metastasis, leading to earlier death than in the normal mice inoculated with the same dose of the tumor. αA/D given after the CY treatment counteracted the deleterious effects of the CY treatment. Since such restorative activity was seen even against the subline of B16 F1 which had been made resistant to its direct antiproliferative effect, αA/D seems to exert its effect indirectly through host defense systems. However, this activity of αA/D in the mice pretreated with CY was abrogated by inoculation of anti-asialo GM1 serum but not by i-carrageenan. The CY treatment reduced NK activity, while α A/D given after the CY treatment restored or augmented the NK cell activity in lung cells and peripheral blood mononuclear cells, but not in spleen cells. These findings suggest that the restoration or augmentation of NK activity in the lung and/or peripheral blood might be the major factor leading to the antimetastatic activity of αA/D in the mice treated with CY.

Effect of Co‐administration of Granulocyte Colony‐stimulating Factor on Interferon Therapy

The effect of co‐administration of granulocyte colony‐stimulating factor (G‐CSF), as an anti‐neutropenia agent, on interferon therapy was examined in a mouse model, in anticipation of an enhancement of interferon efficacy, because neutrophils induced by G‐CSF are thought to act as antitumor effectors. G‐CSF was intraperitoneally co‐administered with human interferon α A/D (IFN) on Day 6 to Day 10 after intradermal inoculation of Meth A fibrosarcoma. Although the co‐administration of G‐CSF could protect against neutropenia and leukopenia induced by IFN, it did not enhance the regression of tumor, and rather reduced the prolongation of survival time and the long‐term survival incidence of IFN therapy. The subsequent in vitro study showed that the antiproliferative activity of peripheral blood leukocytes from Meth A‐bearing mice given both IFN and G‐CSF was much weaker than that of mice given IFN alone. Whether the observed nullifying effect of G‐CSF on IFN therapy is also the case with tumors other than Meth A is open to further study.

Desferrioxamine B, an Inhibitor of Escherichia coli Motility, Reversing the Stimulating Effect of Cyclic Adenosine 3′,5′-Monophosphate

A substance inhibiting Escherichia coli motility was isolated by “motilometry” assay from the culture broth of Streptomyces sp. strain NR9GG8 and was found to be identical with desferrioxamine B. Its inhibitory effect was reversed by cyclic adenosine 3′,5′-monophosphate (cAMP), while the motility stimulation by cAMP was diminished by this inhibitor. Its effects on various enzymes involved in cAMP metabolism of function of cAMP were examined.