A total of 217 kidney tumors induced in rats with basic lead acetate, N-nitrosodimethylamine, N-butyl-N-(4-hydroxybutyl) nitrosoamine, 3-methylcholanthrene, and 4-nitroquinoline 1-oxide were classified histologically. Thirty-four (15.7%) were renal cell tumors, 140 (64.5%) embryonal cell tumors, 39 (18.0%) transitional cell tumors, and 4 (1.8%) hemangioendotheliomas. Renal cell tumors were induced by basic lead acetate and N-nitrosodimethylamine, embryonal cell tumors by N-nitrosodimethylamine and N-butyl-N-(4-hydroxybutyl) nitrosoamine, transitional cell tumors by N-butyl-N-(4-hydroxybutyl) nitrosoamine, 3-methylcholanthrene, and 4-nitroquinoline 1-oxide, and hemangioendotheliomas only by N-nitrosodimethylamine. These results showed a close relation between the kind of chemical carcinogen used and histological classification of kidney tumors in rats. The histogenesis of kidney tumors induced by these chemical carcinogens in rats was also discussed.

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The histogenesis of esophageal tumors in male Wistar strain rats on oral administration of 0.03% N-nitrosopiperidine was studied by light and electron microscopy. Hyperplasia of the esophageal epithelium was seen within 4 weeks and papilloma within 8 weeks. Cancer developed after 12 weeks administration of N-nitrosopiperidine. After administration of N-nitrosopiperidine for 20 weeks, 9 of 11 rats (81.8%) had developed esophageal cancer. Histologically, the esophageal cancer in rats induced by N-nitrosopiperidine was a squamous cell carcinoma, which was rich in cornification and closely resembled those produced in the esophagus on administration of other chemical carcinogens. No adenocarcinoma or benign neoplasia of the esophagus was observed. Histological changes in the esophageal epithelium increase in frequency and extent with the period of administration of N-nitrosopiperidine. The present investigation suggests that hyperplasia is a precursor of esophageal carcinoma in rats administered with N-nitrosopiperidine but that cornification and hyperkeratosis of the esophageal epithelium were not significant preneoplastic changes.

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Immune response against sheep red blood cells was compared between normal mice and mice bearing Ehrlich ascites tumor by counting the number of hemolytic plaque formers in the spleen. Although the number of hemolytic plaque-forming cells consistently decreased in ascites tumor-bearing mice, the weight of spleen decreased in parallel. In solid tumor-bearing mice, the number of hemolytic plaqueforming cells decreased as above, but the weight of spleen increased. The peak response which is found on the 4th day after immunization in normal mice was not discernible in tumor-bearing mice.

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Effect of phosphomucolipid derived from lipopolysaccharide of E. coli on reticuloendothelial system was examined in mice bearing Ehrlich ascites tumor. Results of repeated intraperitoneal injection of phosphomucolipid, which was effective against the tumor, were as follows: (i) Stimulation of phagocytic activity was indicated by carbon clearance test, (ii) splenomegaly occurred due to cell proliferation, (iii) the number of peritoneal exudate cells increased while the number of tumor cells decreased, (iv) increase in peritoneal exudate cells was explicable by the decrease in nucleated cells in thymus, spleen, and mesenteric lymph nodes, and (v) when transplanted, the cells from the spleen of mice, in which the growth of Ehrlich ascites cells was inhibited by phosphomucolipid, were effective against the tumor cells of host mice irradiated with X-rays. The peritoneal exudate cells can be considered as migrants from the above three lymphatic organs.

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Intestinal tumors were induced in 96 (51%) out of 188 Buffalo rats which were fed basal commercial diet containing 0.025% N, N'-2, 7-fluorenylenebisacetamide. About 50% of the tumors was found in the distal part of the ileum and the proximal part of the colon. Average number of tumors per rat was 3.8 in both sexes and most of the tumors was less than 1cm in diameter. A gross and histological classification of the induced tumors is proposed. Histological atypism was most prominent in umbilicated type and metastasis to regional lymph nodes was found in 3 cases (12.5%) of this type.
At one hour after intraperitoneal injections of tritiated thymidine, distribution pattern of labeled cells in the intestinal mucosa was entirely different between nonneoplastic and neoplastic tissues. In the latter, the labeled cells were distributed diffusely in the whole neoplastic glands, while in the former they were found exclusively in the proliferative zone of glandular epithelia in the mucosa. Population density of the labeled cells in the proliferative zone exceeded that of neoplastic tissues.

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Four nitrofurans were compared for their effect on carcinogenesis induced by 4-(dimethylamino)azobenzene (DAB). The nitrofurans tested were 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (N1), 2-amino-5-[2-(5-nitro-2-furyl)-1-(2-furyl)-vinyl-1-]-1, 3, 4-oxadiazole (N2), 5-nitro-2-furaldehyde semicarbazone (N3), and 5-morpholinomethyl-3-(5-nitrofurfurylideneamino)-2-oxazolidone (N4). Male Donryu rats were maintained on a diet containing 0.06% DAB and 0.2% of a nitrofuran until they consumed 1g of DAB (about 3.5 months), and succeedingly on a basal diet for 1 month. The liver of these animals was compared histopathologically with those of the animals fed a diet containing DAB alone. The induction of histopathological changes in the liver due to the administration of DAB was almost completely inhibited by the concurrent administration of N1 or N2. A similar activity was noted in N3, but the activity was moderate, and hyperplasia of small bile ducts and regenerative cell nodules were seen in the liver of the animals fed DAB and N3. No such inhibitory activity was found in N4, and typical trabecular hepatoma, cholangiofibrosis and atypical cell growths were seen in the animals fed DAB and N4.
The liver enzyme activity of metabolizing azo dye was not significantly changed by 3.5-months' administration of any of the nitrofurans. The effect of nitrofurans on the levels of free and protein-bound dyes in the liver was more important for the mode of their action in hihibiting DAB carcinogenesis. However, it was noted that N2 and N3, both of which inhibited DAB carcinogenesis, showed no significant activity to reduce the protein-bound dye level.

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Mammary tumors, mostly adenocarcinoma, were successfully induced in young female rats of Wistar/Furth (W/Fu) strain by a continuous oral administration of N-nitrosobutylurea (NBU) in a daily dose of 2.5 or 5mg per rat, with a relatively short latent period ranging from 6 to 8 months. A larger dose of NBU (10mg per day) caused marked suppression in body growth, estrous cycle, and the induction rate of mammary tumors. Ovariectomy prior to NBU treatment also abolished the mammary tumorigenic effect of NBU, while orchidectomy was apparently not effective in eliciting mammary tumor in male rats.
Restoration of mammary tumor development was attained in castrated rats of both sexes either by supplemental treatment of biweekly injections of 0.4mg of progesterone and 0.01mg of estradiol benzoate combined, or by ovarian isograft implanted under the kidney capsule. There was a slowdown in the restoration of mammary tumor development in the ovariectomized and hormone-treated rats as compared to the male counterparts. Nevertheless, shortly after the cessation of hormone treatment in 7th month after the beginning of NBU treatment, there occurred a rapid increase in induction rate of mammary tumors in the ovariectomized and hormone-treated rats.
The castrated male rats were found to be a useful tool for testing the mammary tumorigenicity of unknown agents, if conditioned adequately with ovarian hormones, by their excellent productivity of mammary tumors in terms of incidence, multiplicity, and growth rate of the tumor.

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A continuous oral administration of N-nitrosobutylurea (NBU) for 6 months induced a variety of tumors besides mammary tumors in variously conditioned Wistar/Furth (W/Fu) rats of both sexes. The animals were castrated before the NBU treatment or castrated and supplemented with biweekly injections of 0.4mg of progesterone and 0.01mg of estradiol benzoate or with an ovarian graft under the kidney capsule.
Leukemias of myeloid and undifferentiated-cell types developed in 7 rats with a mean latent period of 237±37 days, kidney tumors mostly of the so-called nephroblastoma and clear-cell carcinoma in 8 rats with a latent period of 289±34 days, and brain tumors in 14 rats, mostly oligodendrogliomas except one case of ependymoma, with a latent period of 320±21 days, out of 64 rats. In a single or a few rats, tumors of the thyroid, liver, ear duct, duodenum, and peripheral nerve were found.
This study clearly demonstrated the multicarcinogenicity of NBU and strain specificity of the experimental animals in regard to the spectrum of the target organs by NBU; low incidence of leukemias and gastrointestinal tumors compared to the prevalence of those neoplasms in other strains of rats, and subsequent occurrence of tumors in the kidney and brain at a relatively high rate among the long survivors of W/Fu rats.
There have been no evidences indicating the hormonal implications in the genesis and progression of the afore-mentioned tumors other than mammary tumors.

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A human cell line was newly established from a lymph node with metastasis from oat cell carcinoma of the lung. The cultured cells grew floating free in the culture fluid and have been serially subcultured for 80 generations to date. Multilobulated nuclei and well-developed Golgi apparatus were prominent and secretory granules were occasionally observed. No virus particles were found. Repeated examination by immunofluorescence revealed no evidence of immunoglobulin synthesis and EB virus production. Chromosomal analysis of cultured cells in the 8th generation revealed the modal chromosome number of 47 and the karyotypic anomaly of B5q+, t(Alq+; Cq-) in all of the mitotic cells. These characteristics of this cell line obviously differ from those of the lymphoblastoid cell lines derived from the human lymphoid tissues, strongly supporting the possibility of cancer cell origin. This cell line was therefore designated as OAT line after oat cell carcinoma.

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Search for possible tumor-specific reaction in human lung cancer was attempted by an indirect membrane immunofluorescence technique. Living cells of the established cell line, OAT, derived from human lung cancer of oat cell type, were used as the target cells and both fluorescein isothiocyanate-conjugated anti-human IgG and IgM goat sera were used as the second reagent. Five out of 8 sera from the patients with primary lung cancer of oat cell type gave positive membrane immunofluorescence reaction with anti-IgM reagent but not with anti-IgG. However, 27 sera from the patients with other types of carcinoma, including 9 cases of primary adenocarcinoma of the lung, and 8 sera from healthy individuals gave no positive reaction. No membrane immunofluorescence reaction was given by the selected positive sera, when it was tested against the cell line of Burkitt lymphoma origin, P3HR-1. These results strongly suggest that the antibody against the cell surface of OAT cells resides in IgM fraction of sera from the patients with oat cell carcinoma and, in other words, that the antigen is specific for and common to oat cell carcinomas of the lung.

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The differential flow dichroism (expressed as Δ∈/M) and the reduced dichroism (Δ∈/∈) of DNA isolated from the livers of intact rats as welt as of rats injected intraperitoneally with dimethylnitrosamine (DMN) and diethylnitrosamine (DEN) were studied in 0.001, 0.01, and 0.1M NaCl (pH 7). The Δ∈/M spectra of normal liver DNA approximate its typical absorption spectrum and the increase of ionic strength has a strong hypochromic effect. Increase of ionic strength has, however, considerably less hypochromic effect on the Δ∈/M of DMN-alkylated DNA and no effect on DEN-alkylated DNA. The Δ∈/∈ of normal rat liver DNA increases about five-fold between 220 and 290nm. The upward trend of the Δ∈/∈ spectrum is interrupted by a peak at 250nm (approximating the deoxyguanilic acid max. at pH 7) and a shoulder at 270-280nm (approximating the highest absorption range of deoxycytidylic acid at pH 7). Increase of ionic strength brings about progressive lowering of the whole Δ∈/∈ spectrum of normal DNA, but has little or no effect on the 250-nm peak and 270-280nm shoulder. The Δ∈/∈ spectra of the alkylated DNA's is appreciably lower in 0.001M NaCl than the Δ∈/∈ of normal DNA, but then change little with increase of the ionic strength. In contrast, unlike in normal DNA, the 250-nm peak of the alkylated DNA's progressively flattens by decreasing the ionic strength. The data suggest that at the alkylated G+G-rich segments the helix opens and "puffs" appear because of loss of hydrogen bonding. The "puffs", large at low ionic strength, are minimized by hydrophobic compression at high ionic strength.

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Electron microscopic observations revealed that a long-term cultured clonal cell line from an ascites sarcoma of C3H/He mouse induced by chicken Rous sarcoma cells spontaneously produced type C virus. This virus had morphological characteristics to be classified in murine type C virus. The cells did not contain demonstrable Rous sarcoma virus (RSV) but did contain RSV genome in a form transmissible to chicken cells. The evidence presented here suggests that the virogene of the murine type C virus is originally present in the mouse ascites sarcoma cells and that the oncogene of the cultured cells is not associated with the virogene of the murine type C virus but with the RSV genome.

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Further studies were made on the particular mouse sarcoma cell line, SR-C3H-2127, which was at first induced in a C3H/He mouse by Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV) and now producing a kind of murine leukemia virus. The SR-RSV could be rescued from this cell line by the aid of a cell fusion with chicken cells. The virus produced by this SR-C3H-2127 (2127 virus) could infect only mouse cells and not chicken cells. Possibility of phenotypic mixing between SR-RSV genome and murine C-type virus was traced using cell fusion, but failed to be detected. The active transport of tritiated 2-deoxy-D-glucose was accelerated in the SRC3H-2127, but not in C3H2K, an XC-test-negative mouse cell line, infected with the 2127 virus. Thus the expression of SR-RSV sarcoma genome in the SR-C3H-2127 cells was confirmed.

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Ehrlich carcinoma LP-12 was inoculated intravenously into mice, giving metastatic tumor foci in the brain. This cell suspension was cycle-passaged peritoneal to brain three times to establish a new line which is of different cell diameter, chromosome number, and chemical properties from the original and the LP-12 line.

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A new cell line was obtained from non-malignant human endometrium in monolayer culture and it demonstrated the ability to form aggregates in rotation culture and tumors in hamster cheek pouch. The histopathology of these aggregates and tumors has some resemblance to the original endometrial glands.

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A remarkable acceleration of carbon clearance activity was observed in mice which received inoculation with tumor cells and intraperitoneal injection of yeast glucan or mannan in a dose of 150mg/kg/day, 10 times, but the mice that received polysaccharide administration only had less of this activity.

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Leukemia and mammary tumor occurred in Wistar-King Aptekman/Mk rats administered N-nitrosobutylurea. Sex and age dependency was observed in determining the target organ of N-nitrosobutylurea to produce leukemia and/or mammary tumor.

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