Tateshi Kataoka

In vivo tumor growth enhancement by granulocyte colony-stimulating factor.

The intraperitoneal administration of human recombinant granulocyte colony‐stimulating factor (G‐CSF) enhanced the growth of intradermally inoculated tumor in mice; in a Meth A fibrosarcoma model, G‐CSF administration significantly shortened the latency before tumor appearance, accelerated the increase of tumor size, shortened the survival time of tumor‐bearing mice and increased the incidence of lethal tumor growth. A similar growth‐enhancing effect of G‐CSF was observed in models employing Meth 1 fibrosarcoma, colon carcinoma 26, and L1210 leukemia, although not all the effects were statistically significant. In vitro study showed that G‐CSF did not enhance Meth A growth in suspension culture or in soft agar. These data suggest that G‐CSF enhances the Meth A growth not directly but through the mediation of host factors. The accumulation of neutrophils was histologically observed in the tumor nodule, the blood, and the spleen in mice given G‐CSF repeatedly. The spleen cells and the peripheral blood leukocytes of G‐CSF‐injected mice enhanced Meth A growth in vitro as compared with those of mice injected with physiological saline. These results suggest the possibility that the in vivo growth of tumor cells was enhanced by G‐CSF‐induced overproduction of cells including neutrophils.

Enhancement of chemotherapeutic effect by entrapping 1-beta-d- -arabinofuranosylcytosine in lipid vesicles and its mode of action.

a-beta-D-arabinofuranosylcytosine (ara-C) trapped in multilamellar liposomes exerted enhanced chemotherapeutic effect against L1210 murine leukemia. Among four types of liposomes, the one composed of sphingomyelin, stearylamine and cholesterol was most potent in enhancing chemotherapeutic effect of ara-C. And the findings that ara-C was released gradually from liposome in vitro and that ara-C in liposome was chemotherapeutically effective against subsequently inoculated L1210 cells suggested that slow but long-lasting release of ara-C from liposome was partially responsible for enhanced chemotherapeutic effect.

Characteristics of in vitro antiproliferation activity of human interferon-β

SummaryWe compared the in vitro antiproliferative activity of highly purified interferon (IFN)-β (>107 U protein/mg in antiviral activity) with that of IFNs-α and lymphoblastoid, using human cells of malignant and non-malignant origin. IFN-β was the least active of three IFNs in suppressing Daudi cell proliferation. Three hematological cells other than Daudi cells cultivated in suspension were insensitive to each of three IFNs. IFN-β was more active than IFNs-α and lymphoblastoid in suppressing all eight epithelioid cells tested and, particularly with respect to five epithelioid cells sensitive to IFN, IFN-β was seven to 49 times as active as IFN-α. These results indicate that suppression of cell proliferation by IFN depends not only on the target cell species but also on the IFN species, and emphasize the need for careful selection of the most appropriate IFN species in therapy.We found that the antiproliferative characteristics of the present IFN-β preparation were consistent with those reported previously, supporting the idea that IFN-β molecules in the present preparation were responsible for suppressing cell proliferation. The antiproliferation activity of our preparation was species-specific but not selective for cells of malignant origin; it was absorbable by IFN-sensitive but not by IFN-insensitive cells; and it was achieved by a cytostatic effect.

Effect and Mode of Action of N4-Behenoyl-β-D-Arabinofuranosylcytosine

N 4-Behenoyl-β-D-arabinofuranosylcytosine (behenoyl ara-C, NSC 239336) enhanced che-motherapeutic activity against L1210 murine leukemia as compared with 1-β-D-arabino-furanosylcytosine (ara-C). Behenoyl ara-C was resistant to deamination by cytidine deaminase, which was supposed to be liable for inactivating ara-C in vivo. Behenoyl ara-C exerted chemotherapeutic activity when administered before implantation of leukemic cells, suggesting prolonged circulation in the body fluid. These two findings indicate that the resistance to the enzymatic deamination and hydrophobicity endowed by behenic residue were responsible for the enhanced chemotherapeutic activity of behenoyl ara-C. This idea was supported by the finding that ara-C encapsulated in liposome enhanced chemotherapeutic activity.

In vitro and in vivo antitumor activity of the interferon inducer bropirimine

In vivo and in vitro antitumor effects of an interferon (IFN)-alpha inducer, bropirimine (2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone), were examined in the murine tumor system. The antitumor effects were studied in Meth A cells, which were the most sensitive to bropirimine in the murine cell lines tested. The direct inhibitory activity of the drug was not reduced when Meth A cells were incubated with bropirimine and anti-IFNs, indicating that the inhibition is not due to autocrine IFN induction from tumor cells. The drug partially inhibited the uptake of [3H]thymidine, [3H]uridine and [3H]leucine. Cell cycle analysis with flow cytometry showed that the drug decreased G0/G1 phase and increased G2/M phase Meth A cells. The drug administered i.p. exhibited a remarkable antitumor effect against Meth A cells which were implanted i.p. These results suggested that the drug induced the in vivo antitumor effect by its direct antitumor activity.

The Lyt phenotype of the T cells responsible for in vivo tumor rejection in syngeneic mice

SummarySpleen cells of BALB/c mice hyperimmunized with a transplantable methylcholanthrene-induced sarcoma Meth A (Meth A-Im-SPL) inhibited the growth of Meth A tumor in vivo in a tumor neutralizing test. Meth A-Im-SPL did not neutralize another antienically distinct sarcoma, Meth 1, indicating that the antitumor activity is tumor specific. Lyt-1+2− cells of Meth A-Im-SPL (Im-Lyt-1+2−) were the effectors since in vitro treatment of Meth A-Im-SPL with anti-Thy 1.2 or anti-Lyt 1.2 antibody plus complement completely abrogated their neutralizing activity, whereas treatment with anti-Lyt 2.2 plus complement did not. To further confirm the effector activity of Im-Lyt-1+2− cells, T cell subpopulations were separated from Meth A-Im-SPL by the panning method. The purified Im-Lyt-1+2−, but not Im-Lyt-1+2+ cells neutralized the tumor in athymic nu/nu mice as efficiently as in +/+ mice, suggesting that the donor Im-Lyt-1+2− cells but not recipient T cells were primarily responsible for neutralizing the tumor. The present study, however, did not exclude the possible contribution of recipient T cells to the tumor neutralization and this is open to further investigation.

The antitumor effects of human lymphoblastoid interferon on human renal cell carcinoma in athymic nude mice

SummaryThe antitumor effects of human lymphoblastoid interferon (HLBI) on human renal cell carcinomas transplanted in nude mice, i.e., KU-2 and RCC-1, were investigated and compared with those on other human tumors, viz. HeLa (cervical carcinoma), KB (nasopharyngeal carcinoma), H.Ep#2 (laryngeal carcinoma), and MX-1 (breast cancer). A pharmacokinetic study on HLBI was also carried out in non-tumor-bearing nude mice.HLBI therapy was performed with a dose of 105 IU/mouse by daily SC or IT (intratumoral) injection for 2–4 weeks. Two renal cell carcinomas, KU-2 and RCC-1, proved to be highly sensitive to HLBI. The growth of these tumors was inhibited not only by IT but also by SC injection of HLBI. In contrast, HLBI exerted only a slight effect or none at all on the other human tumors, namely, MX-1, KB, H.Ep#2, and HeLa, even when given by IT injection. The data show that the antitumor effects of HLBI depend on the types of human tumors and may be relevant to the clinical observation that renal tumors are sensitive to HLBI.The serum HLBI reached a peak level of 4,390 U/ml 1 h after a single SC injection at a dose of 105 IU/mouse and declined with a half-life of 4h to 128 U/ml 24 h later. This time-course was not affected by 10 consecutive daily injections of HLBI. In nude mice, the consecutive administration of HLBI at this dose level appears to result in neither accumulation nor rapid clearance due to antibody formation. From this range of serum HLBI levels and its in vitro anticellular activity, the in vivo antitumor effects of HLBI in nude mice seemed to depend on its direct anticellular action.

Mechanism of the antitumor activity of 5,5'-bis(2'-tetrahydropyranyl) secalonic acid D against Meth-A.

SummaryThe mechanism of the antitumor activity of 5,5′-bis (2′-tetrahydropyranyl) secalonic acid D (PSA) was examined in Balb/c mice bearing Meth-A fibrosarcoma. IP-injected PSA showed remarkable antitumor activity against IP-implanted Meth-A tumor. Antitumor activity of PSA was not abolished by treatment with silica as an antimacrophage agent or anti-asialo GM1 antiserum that selectively eliminates natural killer cells. Although it was significantly supprssed by treatment with antithymocyte globulin in Balb/c mice, PSA was effective against Meth-A tumors implanted in athymic Balb/c mice. PSA inhibited in vitro Meth-A proliferation as effectively as mitomycin C and was not effective against Meth-A tumor implanted SC at a site where direct contact of PSA and Meth-A cells was unlikely. These results suggest that the antitumor activity of PSA was mainly achieved by inhibiting Meth-A cell proliferation, although the host T cell-mediated immunity was partly involved in the eventual therapeutic efficacy of PSA.

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.

Identification of effector T cells responsible for enhanced antitumor immunity induced by tumor vaccine and pyran copolymer

SummaryThe combination of concanavalin A-bound, but not concanavalin A-free, L1210 murine leukemia vaccine and pyran copolymer produced an enhanced therapeutic response in L1210-bearing mice. Immunoprophylactic experiments showed that the effective combination produced enhanced antitumor immunity as determined by refractoriness to the inoculation of live L1210 cells. In vitro antiproliferation and intraperitoneal adoptive transfer tests showed that antitumor effector cells were detected in the spleen and peritoneal cavity of primed mice after, but not before, live L1210 cell inoculation. These effector cells were identified as T cells on the basis of their non-adherence to plastic flasks and sensitivity to treatment with anti-mouse brain-associated T cell antigen antisera and complement. Although non-T cell populations, including macrophages of mice primed with L1210 vaccine and pyran copolymer, inhibited the in vitro proliferation of L1210 cells, we obtained evidence suggesting that they were not the primary antitumor effector cell populations responsible for the in vivo elimination of the inoculated L1210 cells.