Biological studies are reported on spontaneous hepatoma occurring in C3HO and ddO mice. Incidence of such hepatomas in male mice was higher than that in female mice, and castrated male mice had median rate between them. The size of hepatoma cells varied between that of normal liver cells and one-half the normal size.
This tumor was histologically benign but there was at least one case of pulmonary metastasis. To know their biological character the growth rate of hepatomas was studied in several ways; actual measurement of the diameter of individual hepatoma in two different age groups (4 to 16 weeks), ratio of the hepatoma cells to endothelial cells, use of the mitotic index in histological sections, and use of the labeling index in autoradiography.
From the data obtained in autoradiography, the expected life cycle of hepatoma cells was calculated and compared with that of other tissue cells. It was concluded that spontaneous hepatoma in mice has one of characters of malignancy, a capacity to grow with a slow rate.

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Transplantation immunity against methylcholanthrene-induceds arcomas in the rat can be produced in the primary autochthonous host at a high rate and a high grade by the ligation and release method.
According to the variety of antigenic properties of tumor cells with which high, moderate, and low immune states were demonstrated in the tumor autoimmunity, a classification of the tumors into a high-antigenic tumor (HAT), moderate-antigenic tumor (MAT), and low-antigenic tumor (LAT) was proposed (HML-classification-Takeda). This was convinced by investigation on induced transplantation immunity in the isogenic host-tumor system. Since recurrences of the tumors occurred frequently in animals in which a low-antigenic tumor developed and in none of animals in which a high-antigenic tumor developed, it may be stated that the HML-classification of the tumors was directly related to the recurrence and infiltration of the tumors.
Induced antitransplantability against methylcholanthrene-induced sarcomas in the autoimmunity was individually specific with some exception. Transplantation immunity against the sarcomas of recent origin induced in the isogenic hosts was similarly individually specific in many strains. There was, however, a tendency that transplantation immunities induced in the isogenic hosts against methylcholanthrene-induced sarcomas and spontaneous subcutaneous sarcomas which had been transferred for many generations were common between these tumors.

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Rous sarcoma virus (RSV) was mostly included in the "pH 5 enzyme" fraction from Rous sarcoma homogenates. The enzyme fraction was analysed by means of column at linear gradient concentration of sodium chloride. As controls, normal liver and muscle from 10-day-old chicken were employed. A sarcoma-specific RNA was eluted by 0.55M sodium chloride from alkali eluates of the sarcoma RNAs by DEAE-cellulose column chromatography. The DNA fractions from the sarcoma and control samples were also analysed by column chromatography through DEAE-cellulose, epichlorohydrin-triethanolamine cellulose, and methylated albumin. However, no visible difference occurred between the sarcoma and controls. On the other hand, incorporation of radioactive inorganic phosphorus (³²P) into nucleic acids in the nuclei of cultured sarcoma cells was examined with methylated albumin column chromatography. Three labeling peaks were obtained in 0.5, 0.55, and 0.7M sodium chloride eluates. Importance of the 0.55M sodium chloride eluate was discussed in relation to the induction of the sarcoma.

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Histological and histochemical observations were made during an experimental carcinogenesis in the salivary glands of mice.
Pellets containing 5mg of 9, 10-dimethyl-1, 2-benzanthracene were introduced into the submaxillary and/or sublingual glands of ddO mice. Epidermoid carcinoma was frequently induced in conjunction with degeneration of the gland parenchyma, and regeneration, dilatation, cyst formation, and squamous metaplasia in the duct system. Characteristic enzyme patterns during one carcinogenic process were followed with some respiratory, glycolytic, and non-specific enzymes, i.e., succinate dehydrogenase, lactate dehydrogenase, glucose 6-phosphate dehydrogenase, alkaline phosphatase, etc. Histochemical pattern of epidermoid carcinoma induced in the salivary gland was very similar to that of other epidermoid carcinoma induced from the squamous epithelia or occurring spontaneously. Acinar cells and myoepithelial cells did not appear to participate directly in the proliferation or in malignant transformation, either morphologically or histochemically.

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Sialic acids were extracted and purified from cell surface membrane and whole cells of various ascites hepatoma as well as of normal rat liver cells. Thin-layer or paper chromatography revealed some difference to exist in compositional proportion of sialic acid derivatives between hepatoma and normal liver. It was suggested that the chemical structure of tumor cell surface membrane may be different from that of normal cells. As far as one type of cell is concerned, the composition pattern of sialic acids was found to be entirely identical between surface and intracellular membranes.

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4-Nitroquinoline 1-oxide, when added in an appropriate concentration to the synchronous culture of Tetrahymena, at the division stage, produces distorted karyokinesis, involving uneven distribution of DNA and irregularity in cell sizes. On following the fate of these abnormal cells it was found that they can be established as clones with the same curious characteristics. Thus it was demonstrated that new clones of Tetrahymena with cell pleomorphism as a phenotype can be produced experimentally.

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Increased activity of lysosomal enzymes, β-glucuronidase, deoxyribonuclease, and acid phosphatase in parallel with the occurrence of cytomorphological effect on the cells in vivo, was determined with Yoshida sarcoma treated with several antitumor agents. Increasing rate of β-glucuronidase activity by the agents was more marked than those found with the other two enzymes. Elevation of β-glucuronidase activity was also observed in the in vitro experiments.

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A substance prepared from a saline extract of human leiomysarcoma showed a growth-inhibiting activity against a subcutaneously transplanted Ehrlich ascites tumors in mice. This was soluble in 70% ethanol non-dialysable against water, non-adsorbable on charcoal, and insoluble in chloroform-methanol.

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The activity of acid phosphatase, one of the most typical lysoeomal enzymes, was studied at the very early stages of regenerating liver of rats. There was no marked change in the activity in either the cell sap fraction or in the whole homogenate.

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Four skin tumors were found in the mice treated percutaneously with acetone solution of thio-TEPA (0.2%) or nitrogen mustard N-oxide (1%) 6 times a week for 17×20 weeks. Strain differences in the depigmentation property of thio-TEPA, nitrogen mustard N-oxide, cyclophosphamide, or Carainophilin were observed among the C3H/He, Al, and (dd/N×C57L)F₂ mice.

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Effect of adrenalectomy and gonadectomy on the induction of lung cancer and leukemia by the injection of 4-nitroquinoline 1-oxide was observed in rats. Adrenalectomy and ovariectomy seemed to repress the induction of lung cancer. Of the 32 effective gonadectomized animals, 5 developed leukemia.

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A brief incubation of Ehrlich ascites tumor cells with glucose in physiological NaCl solution renders them incapable of producing tumors when implanted subcutaneously in susceptible mice. That these glucose-treated cells are viable was shown by their active proliferation when injected intraperitoneally, and their failure to grow in subcutaneous site was accounted for by their inability to provoke supporting local tissue reaction in the host. Induction of such a peculiar physiological state in the cell by a simple experimental means was emphasized.

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