Twenty-nine kinds of Mitomycin derivatives were subjected to the screening test against Hirosaki ascites sarcoma. Eleven of them were more effective than Mitomycin-C, seven derivatives showed a comparable effect, and the others were less effective.

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Out of 32 kinds of Mitomycin derivatives tested, 11 of them showed the same or better effect compared to Mitomycin-C against solid tumor of Sarcoma-180. Especially, 1a-chloroacetyl-7-amino-9a-methoxymitosane (T-12), 1a-dichloroacetyl-7-amino-9a-methoxymitosane (T-36), and 7a-isopropyl-amino-9a-methoxymitosane (T-39) were more effective than Mitomycin-C.

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A single intraperitoneal injection of 20mg of the so-called o-aminoazotoluene (4-amino-2', 3-dimethylazobenzene) (o-AT) in olive oil was administered to adult C3H/HeOs male mice (as a high hepatoma strain) and C57BL male and female mice (as a low hepatoma strain). In these animals, hepatomas developed in a high incidence at 51 to 92 weeks of age; 28 out of 56 C3H males, 8 out of 30 C57BL females, and 6 out of 24 C57BL males.
The o-AT-induced hepatomas are hepatocellular in origin and histologically similar to each other. The sizes of the tumor cells are smaller than those of spontaneous hepatomas. The growth rate of o-AT-induced hepatomas is slower and more uniformt han that of spontaneoush epatomas. These were studied by autoradiography with ³H-thymidine and by actual measurement of the size of transplants. The growth characteristics and histological appearances of these hepatomas were discussed in reference to the "minimum deviation hepatoma" of Morris and Reuber.

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The differences in the lactation performance of C3H/He and C57BL/6 strains were studied by investigating the young weight and growth rate on the 12th day, the milk yields on the 10th and 14th days, and the nucleic acid content in the mammary gland on the 14th day after birth.
In almost all the items, C3H/He was higher than C57BL/6 in the first and the second lactations, indicating that the lactation performance of C3H/He was better than that of C57BL/6.
These results indicated the presence of the strain differences in the mammary gland states during lactation, which would be related to the future tumor incidence.

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The effect of pituitary isografts on the already established spontaneous mammary tumor was studied using C3H/He strain of mice. The animals were paired according to body weight, site, size, and growth of the tumor. In each pair, one animal (experimental) received three male anterior pituitaries beneath the right kidney capsule, and the other remained untreated as control. The comparison was made within a pair as well as between the experimental and control groups. Vaginal smears were obtained from each animal once daily throughout the experiment.
No differences were observed between the experimental and control animals in the tumor size, the mean tumor growth rate per week, and the total tumor growth rate. It was argued that the established spontaneous mammary tumor was not responsive to the special hormonal stimulations, and therefore was autonomous.

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A comparative study on the cellular specific gravity of the regenerating rat liver, India ink-injected mouse liver, mouse liver tumor, liver of a mouse fed 2, 7-(diacetylamino)fluorene (2, 7-FAA), and transplantable rat liver cell carcinoma was performed by the method of multistrata-centrifuge.
The specific gravity of normal rat liver cell showed a range between 1085 and 1090, and that of mouse liver cell was between 1090 and 1095. The specific gravlty decreased in the regenerating rat liver cell, but became similar to that of the normal liver cell on the 7th day.
Third day after injection of India ink into mouse peritoneal cavity, liver cell was divided into three fractions by the specific gravity.
In the case of mouse liver tumor cell induced by 2, 7-FAA, the specific gravity showed lower value than that of the normal cell. Cells derived from non-tumorous part of tumor-bearing liver also had lower specific gravity.
Mouse liver during three stages of feeding 2, 7-FAA showed various values in each stage.
There were different populations in each generation of transplantable rat liver cell carcinomas, DEN-10893 (893) and DEN-10844 (844), 4) but all of them showed decreased value of the specific gravity compared with that of originating organ cell.
The meanings of the specific gravity of the cell were discussed from these results.

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A simple sensitivity test is introduced to predict the clinical side effect of carcinostatic agents. The method is the same as our tumor sensitivity test, except for the use of liver tissue.
Fairly good agreement of the results is observed between the inhibition index of this test in vitro and clinical side effects of the indicated drugs, and the cases with side effects show an inhibition index of over 50. This index is well paralleled with the effect of drugs on the reticuloendothelial system.

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Electron microscopic, histochemical, and autoradiographic studies were made on the significance of the so-called oval cell proliferation, especially on the origin and fate of the oval cells, during azo-dye hepatocarcinogenesis. Electron-microscopically, the cells having the intermediate characteristics between the oval cell and hepatocyte were frequently observed. This intermediate pattern was also indicated from the findings of the histochemical examination on glucose-6-phosphatase.
Furthermore, the transition from the oval cell to the hepatocyte was strongly suggested by the autoradiographic study, i.e., the labeled oval cells decreased in number, while the labeled hapatocytes increased, in the course of time after single injection of tritiated thymidine.
Therefore, it is concluded that the oval cells are able to transform into the hapetocytes during severe and prolonged injuries of hepatocytes and the oval cells play a leading rôle in the course of azo-dye hepatocarcinogenesis.

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An analysis of cellular antigens in ascites tumor cells of Friend disease origin was carried out by the transplantation method. At least two kinds of antigens may be involved in the development of transplantation resistance to tumor cells. The one is of viral nature, being demonstrated by development of resistance to tumor transplantation following immunization with inactivated virus. The other is a cellular antigen, which is independent of viral synthesis, and which may probably exist in tumor cells. Possible existence of such an antigen was reasoned by development of resistance to virus infection following immunization with tumor cells containing neither demonstrable virus nor viral antigen.

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One hundred and forty-four foci of superficial spreading carcinomas were obtained from 1, 038 cases of resected stomach and histologically examined. These superficial carcinomas were divided into 5 groups according to their largest diameter; less than 10mm, 11-20mm, 21-30mm, 31-40mm, and more than 41mm, and compared as to gross-appearance, ulcerative change in the cancerous area, and histological type.
The general conclusion drawn from these data is that the superficial carcinomas are characterized by the tendency to undergo erosion or ulceration with the progress of their extent. Consequently, the histological evidence of an ulcer-cancer, which completely excludes the possibility of the secondarily ulcerated cercinoma, is a minute cancer limited to the regenerating epithelium of the healed ulcer. It was considered that the incidence of ulcer-cancer to overall carcinomas of the stomach is strictly about 1% and its maximum may be 15% at the most.

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4-Nitroquinoline 1-oxide in diluted ethanol was administered to mice by the intragastric instillation. By this means, in addition to many papillomas and squamous cell carcinomas in the forestomach, adenocarcinomas of the glandular stomach were induced along with precancerous lesions in the form of irregular plaques, umblicated lesions, or hyperplastic foci.

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An electron microscopic study was made on NVP-type Friend tumor cells artificially exposed to Friend virus coming from Friend diseased spleen. This was referred to as NVP+V cells. A characteristic finding in this NVP+V cells was the single cluster of numerous A-type virus particles in the cytoplasmic matrix of the Golgi area.

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4-Nitroquinoline-6-carboxylic acid 1-oxide was suspended in olive oil in a concentration of 10mg/ml, and 0.1ml of this suspension was subcutaneously injected into the right buttock of the rats, once a week for 20 weeks. Fibrosarcomas developed in 8 of 21 rats.

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Chromomycin succinate specifically inhibited the synthesis of early replicating DNA unit when it was given in G₁ or early S period, the inhibition being recovered promptly and completely after the removal of Chromomycin succinate, with slight prolongation of S period. When given after the middle of DNA synthesis, no inhibitory effect was discernible.

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