Exposure of HeLa cells to a suspension of 3-methylcholanthrene followed by illumination with otherwise nontoxic, visible light results in death, at times related to a carcinogen concentration, to the length of time of incubation with methylcholanthrene, and to the length of illumination time. 3-Methylcholanthrene is taken up into lysosomes of HeLa cells quite rapidly, at least within 30 seconds. The photodynamic damage to HeLa cells appears to result from the cellular autolysis by hydrolytic enzymes released from the lysosomes which have been rapidly disrupted by the photosensitizing effect of methylcholanthrene.

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An in vitro system for the quantitative study of cell-mediated immune reaction was established. Lymphocytic cells were fractionated from peritoneal exudate cells of Donryu rats, which had been immunized against Yoshida sarcoma, and the cytocidal effect of the peritoneal lymphocytic cells on the target Yoshida sarcoma cells was studied quantitatively in vitro, usually with 10⁷ lymphocytic cells and 3-4×105 tumor cell sincubated in 1ml Eagle's medium containig heat-inactivated normal rat serum.
1) The cytocidal activity of lymphocytic cells was directly related to the extent of immunization of the donor animals. Lymphocytic cells obtained from the donor animals which had been immunized with as much as 10⁸ tumor cells destroyed more than 90% of tumor cells within 7 hours of culture, suggesting this cytocidal reaction proceeds very rapidly. The cytocidal effect of sensitized peritoneal lymphocytic cells on the target tumor cells was also expressed as a function of dosage of lymphocytic cells used in the culture.
2) After one hour of culture a significant number of lymphocytic cells in a sensitized peritoneal lymphocytic cell population adhered to the tumor cells, and the percentage of tumor cells with adhering lymphocytic cells was related to the cytocidal activity of the sensitized lymphocytic cell population. The percentage of lymphocytic cells capable of adhering to tumor cells was found to be less than 10% of the total number of the sensitized peritoneal lymphocytic cells even if the sensitized lymphocytic cells were obtained from the highly immunized donor animals.
3) Continuous observation of the destruction of a tumor cell by the attacking lymphocytic cells showed that usually a tumor cell with 2 to 3 sensitized lymphocytic cells adhering to it was destroyed within a few hours of culture with a morphological change of the tumor cell membrane, karyorrehexis, pyknosis, and fragmentation of the cell.

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The deoxyribonuclease (DNase) activity in normal rat liver and 4-(dimethylaminoazo) benzene-induced hepatomas was studied histochemically by means of Gomori's acid phosphatase method. DNase activity was detected mainly in nuclei and was apparently associated with the nuclear membrane. The cytoplasm showed relatively weak activity.
Intense reactions were observed in normal liver, nodular hyperplastic and cholangiofibrotic lesion. The neoplastic cells were negative but degenerating cells in tumors exhibited moderate DNase activity.

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Effect of oxygen at high pressure (OHP) and methyl-bis(2-chloroethyl)amine N-oxide hydrochloride (HN₂-O) on the growth of hypotetraploid Ehrlich ascites tumor was investigated using 2-4 atm. abs. oxygen and 2mg/kg of HN₂-O. The parameters for response were chiefly total tumor cell number in the abdominal cavity of mice, tumor weight inoculated into the back of mice, and survival time.
Four atm. abs. of oxygen alone decreased the total number of tumor cells and tumor weight, and prolonged survival time. A combination of OHP (3 and 4 atm. abs.) and HN₂-O decreased the total number of tumor cells and tumor weight. Antitumor effect was not observed in all groups treated with 2 atm. abs. oxygen. The mice treated with 3 and 4 atm. abs. oxygen exhibited a decrease in body weight. In histological observation, histological change in lung and heart was not noted in the mice treated with OHP.
The present experiments show that 4 atm. abs. OHP alone has antitumor effect and also that inhibitory effect of combination of HN₂-O and OHP (3 and 4 atm. abs.) on the tumor growth is more marked than that of treatment with HN₂-O alone.

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The crude powder of bagasse polysaccharide was fractionated into three subfractions by means of Cetavlon. Of these, the second precipitate obtained by adding borate buffer (pH 10.0) showed the most remarkable inhibitory effect on the growth of subcutaneously implanted sarcoma-180 in mice by the repeated intraperitoneal injections (10 or 100mg/kg/day×10) started 24 hours after the tumor implantation. This fraction was confirmed to be composed mainly of galactose, arabinose, xylose, and mannose along with a smaller amount of glucose, and also to be free from either nitrogen or ultraviolet-absorbing material. In the case of ascites form, however, neither any inhibitory effect nor any direct cytological effect was observed.
The most effective fraction was further fractionated into four subfractions by means of DEAE-cellulose column chromatography and one more subfraction was obtained by a partial degradation, and the antitumor activity of each fraction was compared.

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Application of two carcinogens, 4-nitroquinoline 1-oxide and β-rays, one before or after the other, both in submanifestational dose, showed the summation effect in the skin tumor formation in mice. The effect appeared different by changing the order of application.
These findings suggest that the effects produced by 4-nitroquinoline 1-oxide and β-rays are qualitatively equivalent in tumor formation.

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A quantitative assay has been established for a factor in the cell sap fraction from rat livers which specifically inhibits the DNA synthesis in some ascites hepatoma cells in vitro. In the present paper, activities of various normal tissues, malignant hepatomas, and minimal deviation hepatomas, as well as precancerous rat livers, have been investigated.
Among various tissues, the liver contains the activity at the highest level with both rats and rabbits. Livers from fetal, newborn, young, and adult rats, as well as regenerating rat livers showed similar activities. Malignant hepatomas such as 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) induced primary hepatomas and several ascites hepatomas showed an almost complete loss of the activity. However, several sublines of the Morris minimal deviation hepatomas showed variable activities scattered between the two extremes, the normal and the malignant. The activity of precancerous rat livers decreased considerably 2-4 weeks after 3'-Me-DAB feeding, where the maximal dye-protein binding was seen to rise. The activity. however, tended to recover gradually and later reached a higher level than the normal one. Such deviations in the activity disappeared within a few weeks after administration of the carcinogen was stopped, returning to the normal level. These results observed for the activity of rat liver cell-sap factor are discussed, especially with respect to the homeostatic mechanism of growth regulation and the alteration in the tumor.

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The incorporation of labeled uridine into Yoshida ascites hepatoma as well as into 3'-Me-DAB induced primary hepatoma of the rat was found to be extremely higher than that of labeled orotic acid. In normal rat liver and regenerating rat liver, orotic acid was actively utilized for RNA synthesis in contrast to uridine which was poorly utilized in these tissues for RNA synthesis.
The increased incorporation of labeled uridine into RNA of the ascites hepatoma cells was found to be not due to increased RNA polymerase activity but due to changes in the mechanisms of precursor uptake, especially to a high uridine kinase activity of the cells.

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Effect of drying on Ehrlich ascites tumor cells was investigated.
1) Some cells survived the process of freeze-drying for about 5 hours (the sample seemed dry and white powdery, its moisture content being 4.8-9.9%) when adequate media (for example, sodium glutamate) for suspension were employed. However, preservation of living cells in the freeze-dried material was unsuccessful up to the present.
2) Optimal concentration of sodium glutamate for lyophilization is considered to be 5 to 10% when the ascites is diluted two-fold with sodium glutamate solution.
3) Since the effect of vacuum itself on survival is also conceivable, drying with a current of nitrogen gas from a bomb and a hot air current from a hair drier was also tried with fairly satisfactory results.

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A complement-fixing antibody against a tumor antigen, prepared from tumors ofhamsters induced by human adenovirus type 12, was searched in patients with cancer. No positive reaction of the CF test was observed in 175 of 176 cancer patients, as well as in 50 healthy subjects. In one patient with acute myelogenous leukemia the CF antibody was detected merely in undiluted serum. The neutralization test against the virus was positive in 18% of 143 cancer patients at titers of 1:4 or over. Thus, none of the patients with positive neutralizing antibody had the CF antibody against the tumor antigen at the same time, except in one patient.

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The activities of NADPH oxidase, NADPH-cytochrome c reductase, and NADPH-neotetrozolium reductase of liver microsomes were markedly decreased in Walker-256 carcinosarcoma bearing rats. The amounts of microsomal P-450 and cyt b₅ were also decreased. These alterations were similar to those in protein-deficient rats.

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