Immunohistochemical staining using antirat glutathione S-transferase placental form (GST-P) rabbit antibody demonstrated marked binding to cells of putative preneoplastic lesions induced in both the liver and pancreas of Syrian hamsters by dihydroxy-di-n-propylnitrosamine treatment, whereas background normal-appearing tissue was negative. Thus, a protein showing immunological cross-reaction with rat GST-P is also elevated during pancreatic carcinogenesis and hepatocarcinogenesis in the hamster, suggesting its usefulness as a marker with potential relevance to the mechanisms underlying the neoplastic process.

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All the known genes of the bovine leukemia proviral genome were found to be heavily methylated in both fresh and short-term-cultured leukemic cells, the latter of which expressed viral antigens. However, the pX_BL region appeared to be mostly demethylated or at least hypomethylated in both cells, indicating that there is a non-uniform methylation pattern of the proviral genome.

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A survey of carriers of adult T-cell leukemia virus (ATLV) detected as anti-ATLV associated antigens was made in Taiwan. Among 2545 adults aged 30 years or more examined, seropositive donors amounted to 0.9% in the Han Chinese but none in the aborigines.

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A new cell line, designated RC-K8, was established from the peritoneal effusion of a patient with histiocytic lymphoma. The RC-K8 had human male karyotype with 14q+ and was found to have B-cell (B1) and monocyte/macrophage (intracytoplasmic α subunit of S-100 protein) markers. A fibrin plate method demonstrated that RC-K8 cells release plasminogen activator in culture.

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The promoting activities of phenobarbital (PB) on the development of γ-glutamyltranspeptidase-positive (γ-GT⁺) foci in rat liver with three different initiating agents were compared in a short-term system (8 weeks). Male F344 rats were initiated by a single application of 200mg/kg of diethylnitrosamine (DEN), 30mg/kg of N-hydroxy-2-acetylaminofluorene (N-OH-AAF), 1.0 or 0.5mg/kg of aflatoxin B₁ (AFB₁) or the vehicles alone. Two weeks after the initiation, animals were placed on a 0.05% PB diet for 6 weeks. Partial hepatectomy was performed at the end of the third week of the experiment. As a positive control, some animals were fed diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) after the initiation. The number and area of γ-GT⁺ foci in the liver were quantified. All three initiators showed a summation effect with 3'-Me-DAB on the appearance of γ-GT⁺ foci. Promotion by PB, however, was observed only in DEN-initiated rats and not in N-OH-AAF- or AFB₁-initiated rats. It is apparent from the present experimental data that the promoting potential of PB on liver carcinogenesis depends on the initiating agent.

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The effect of a combined treatment with radiation and N-nitrosoethylurea (NEU), or a split administration of NEU in inducing lymphoma was studied in female C57BL/6N mice. A single intragastric administration of 5mg of NEU was only slightly lymphomagenic, inducing thymic lymphomas in 20% of mice, while the incidence was elevated to 92% if the NEU treatment was preceded (by 5 days) by 400rad of total-body X-irradiation, which alone is seldom lymphomagenic. A high yield of lymphoma (84-93%) was also obtained if 5mg of NEU was delivered in two split doses of 4mg and 1mg with a 4 day interval. Drastic injury to both the thymus and bone marrow caused by either 400rad total-body X-irradiation or the first dose of NEU (4mg) was followed by a vigorous regeneration within a few days. The maximum induction rate of lymphoma was obtained when the subsequent dose of NEU (1mg) was given át the peak of DNA synthesis in the bone marrow and thymus following the first treatment. The data indicate that the principal effect of the irradiation or the first dose of NEU was to provide a susceptible cell population, and that a high yield of lymphoma was brought about through the action of the subsequent dose of NEU on a sufficient number of target cells engaged in heightened DNA synthesis.

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The in vitro metabolism of N-nitramines was investigated in order to compare it with that of N-nitrosamines and to elucidate the mode of mutagenic action. N-Nitrodibutylamine (NO₂DBA) and N-nitrodiethylamine (NO₂DEA) were incubated with liver microsomes and hepatocytes prepared from rats treated with phenobarbital, and the products were analyzed by high-performance liquid chromatography and gas-liquid chromatography. The in vitro metabolic pattern of these nitramines was similar to that of the corresponding nitrosamines, except that N-nitro-N-alkylamines (produced via α-hydroxylation) were identified after incubation of the nitrodialkylamines. In the case of NO₂DBA, besides N-nitro-N-butylamine, several nitramines produced by ω, ω-1, and ω-2 oxidations were identified as metabolites. NO₂DBA and NO₂DEA were mutagenic to Escherichia coli WP2 hcr^- but not to Salmonella typhimurium TA1535. They were mutagenic only in the presence of hepatic microsomes, whereas their metabolites, N-nitro-N-butylamine and N-nitro-N-ethylamine, were direct mutagens. Thus, N-nitrodialkylamines are also metabolically activated to mutagens through α-hydroxylation.

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The β (1→3) glucan lentinan was tested for its capacity to increase the cytotoxic effect of murine peritoneal macrophages for human tumor cells in the presence of monoclonal antibodies (MAbs). Activity was maximum in macrophages obtained on day 5 following intraperitoneal injection of CBA mice with 2.5mg of lentinan per kg body weight. Macrophages stimulated by lentinan were cytotoxic in conjunction with IgG1, IgG2a and IgG3 MAbs, but not with IgG2b, IgM, or IgA MAbs. The demonstration of a similar enhancing effect by lentinan on human macrophages might have implications for potentiating the tumoricidal effect of these macrophages in the presence of tumor antigen-specific MAbs.

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A monoclonal antibody, ST-4-39, was obtained by using a human gastric cancer xenograft, St-4, as an immunogen. Immunization was achieved by transferring immunocompetent mouse spleen cells into a nude mouse bearing St-4. Hybridomas were produced with the spleen cells of the mouse after rejection of the tumor and screened for immunohistochemical reactivity with cancers and normal tissues on formalin-fixed paraffin sections. ST-4-39 immunohistochemically reacted with various cancers including gastric, colorectal and pancreatic cancers as well as some normal tissues. ST-4-39 and NS 19-9 differed in immunohistochemical reactivity, although they reacted with some cancers and a few normal tissues in common. PBS extracts of normal and cancer tissues were examined for antigen reactive with ST-4-39 by sandwich enzyme immunoassay. Extractable antigen was detected in adenocarcinomas of colon, stomach and lung, while it was detected only in salivary gland and trachea among normal tissues examined. Gel filtration analysis of the antigen indicated a molecular weight of_??_1×10⁶, and the antigenic determinant was suggested to be a carbohydrate chain with terminal sialic acid by studies using periodic acid, neuraminidase and pronase treatments. Furthermore, the ST-4-39 antigen affinity-purified from two gastric cancer strains was shown to contain multiple carbohydrate determinants including sialyl-Lewis^a and sialyl-Lewis^x, suggesting the antigen to be a mucin.

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In vitro cytotoxicity against tumor cells of lymphocytes in sc implanted BC47 bladder tumor of ACI/N rats with or without Propionibacterium avidum (P. avidum) treatment was studied. Tumor-associated lymphoid cells (TAL) were obtained from tumor tissues by mechanical treatment (NDi fraction) and by enzymatic treatment with Dispase I, a proteolytic enzyme (Di fraction), followed by passage through glass wool columns to deplete tumor cells. NDi fraction of TAL from P. avidumtreated animals showed a significant cytolytic activity against BC47 cells, but not against other ACI/N bladder tumor cell lines, BC12 and BC50. These TAL lost the cytolytic activity on treatment with anti-rat thymocyte serum or anti-rat T cell monoclonal antibodies, R1-3B3 and R1-10B5, and complement. Natural killer activity determined with YAC-1 cells was low in the cells of NDi fraction and scarcely detectable in the cells of Di fraction from both P. avidum-treated and untreated rats. These results indicate that the antigen-specific cytotoxic T cells in the tumor in situ are induced by in vivo P. avidum treatment. On the other hand, P. avidum treatment augmented nonspecific cytolytic activity of peripheral lymphoid cells such as plastic-nonadherent peritoneal cells, spleen cells and blood lymphocytes in normal and BC47-bearing rats. However, the antigen-specific cytolytic T cells were predominantly induced and recovered in the plastic nonadherent peritoneal cells of BC47-bearing rats by the treatment with P. avidum.

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The effectiveness of a protein-bound polysaccharide, PS-K, and an immunoaugmenting antileukemia agent, busulfan (BU), was investigated for the treatment of autochthonous tumors induced by 3-methylcholanthrene in C57BL/6 mice. PS-K and BU were found to be effective in dealing with recurrence and pulmonary metastasis when applied in conjunction with the surgical removal of the primary tumor. The survival time of mice to which PS-K (300mg/kg/day×5 or ×2/week for 7 weeks, ip) or BU (50mg/kg×3, po) was administered was significantly prolonged when compared with that of mice treated by surgery alone. Moreover, the incidence of the local recurrence of tumors was significantly lower in mice treated with PS-K or BU after the surgical removal of the primary tumor. The effectiveness of the treatment on metastasis was also shown by the prolongation of mean survival time in groups of mice which showed no local recurrence of tumors. The timing-dependency of the treatment with PS-K did not seem to be an important factor and no additive therapeutic effects of PS-K and BU were observed in the present study.

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When cisplatin was incubated with mouse serum, its cytotoxicity towards P388 leukemia cells decreased with the formation of non-ultrafiltrable or protein-bound platinum. The cytotoxicity of prepared mouse serum protein-bound platinum at 100μg/ml (as the cisplatin-equivalent concentration) was less than that of cisplatin at 0.125μg/ml. The prepared protein-bound platinum exhibited antitumor activity against colon adenocarcinoma 26 in mice, when administered iv daily for 9 consecutive days at 32 and 64mg/kg (as the cisplatin-equivalent dose). Cisplatin similarly administered exhibited antitumor activity at daily doses of only 1 and 2mg/kg. Administration of the protein-bound platinum at such high doses as 32 and 64mg/kg (as the cisplatin-equivalent dose) caused elevation of serum BUN and reduction of bone marrow cells in mice. After iv administration of cisplatin to mice at 6mg/kg, ultrafiltrable platinum was detected in the plasma for the first 30min. Thereafter platinum was found only in protein-bound form. When mice were iv inoculated with colon adenocarcinoma 26 more than 30min after cisplatin administration, no prolongation of the life span was observed. From these results, it is concluded that mouse serum protein-bound platinum does not contribute significantly to cisplatin antitumor activity and toxicity in mice.

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