Fujiko Oh-hashi

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.

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.

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.

I-Ad antigen expression of pyran copolymer-induced peritoneal cells in tumor vaccine-primed mice and its association with the host antitumor response.

SummaryMice inoculated IP with L1210 murine leukemia vaccine and subsequently with pyran copolymer-induced macrophages (pyran-MΦ) lived for a prolonged time after live L1210 inoculation IP. Pyran-MΦ as tentatively identified by anti-AcM.1 monoclonal antibody expressed I-Ad antigen in tumor vaccine-primed recipient mice and contributed to maintaining I-Ad antigen positive (I-Ad+) macrophages at high cell density in the peritoneal cavity of recipient mice. The relevance of these I-Ad+ cells to the host antitumor response was examined by experiments in which I-Ad+ cell density in the peritoneal cavity and host antitumor response behaved in a parallel fashion. Human interferon-αA/D, an agent selectively inhibiting Ia antigen expression, and silica, a general antimacrophage agent, strongly suppressed I-Ad antigen expression of peritoneal mcrophages of tumor vaccine-primed and pyran-MΦ-inoculated mice and, consistently with this, the antitumor response was nullified in these mice. Tumor vaccine-primed mice inoculated with sodium caseinate or thioglycollate-induced peritoneal cells did not survive L1210 inoculation and, in these mice, I-Ad+ peritoneal macrophages were suppressed in number as compared with those of tumor vaccine-primed and pyran-MΦ-inoculated mice. These results warrant further study on the contribution of I-Ad+ macrophages to pyran copolymer-induced augmentation of the antitumor response in tumor vaccine-primed mice.

Non-cytotoxic activity of pyran copolymer-induced macrophages associated with potentiation of tumour vaccine in recipient mice

SummaryMice inoculated with both L1210 murine tumour vaccine and pyran copolymer were more resistant to L1210 than those inoculated with either of these agents alone. Rabbit anti-mouse thymocyte globulin and silica reduced the augmented resistance of these mice, suggesting the involvement of activated anti-tumour T cells and macrophages in the augmented resistance. We studied the activation of these two cells separately and examined the possible contribution of pyran copolymer-induced peritoneal cells to the augmented resistance to an inoculation of live tumour. Pyran copolymer-induced peritoneal cells endowed the tumour vaccine-primed mice, but not unprimed mice, with resistance to implanted L1210 and, among those peritoneal cell populations, macrophages but not T cells were responsible for this effect since the activity was associated with a cell population which was (1) adherent to nylon wool columns, (2) sensitive to silica and (3) insensitive to anti-Thy 1.2 antibody plus complement. The pyran copolymer-induced peritoneal cells had very little antiproliferative activity when tested against L1210 in vitro and mice inoculated with these peritoneal cells did not survive a challenge of live L1210 cells much longer (<1 day) than L1210 inoculated control mice. Furthermore, the survival of L1210 vaccine-primed mice inoculated with one-tenth the amount of live L1210 (102) was still much shorter than that of mice primed with L1210 vaccine plus pyran copolymer and challenged with ten times as many (103) live L1210 cells. Therefore, direct tumouricidal activity was probably not a major factor in the in vivo immunological augmenting activity of the pyran copolymer-induced macrophages.