Adjuvant chemotherapy enhances long-term survival of patients with advanced gastric cancer following curative resection

We examined the effectiveness of postoperative adjuvant chemotherapy with mitomycin C (MMC), 1-(2-tetrahydrofuryl)-5-fluorouracil (tegafur), plus PSK, an immunomodulator, for patients with advanced gastric cancer who underwent histological curative resection. The effect of chemotherapy on prognostic serosal (ps) invasion [ps(-) or ps(+)] and lymph node metastasis [n(-) or N(+)] was examined. One hundred eighteen patients were in the no-chemotherapy group and 137 were on the drugs. The median follow-up time for the 86 survivors at the time of analysis was 13.8 years. With regard to prognostic factors, there were no differences between the two groups. Generalized Wilcoxon test of the two survival patterns revealed a P value of .0351, and the survival rate for 15 years was 45.7% for patients in the no-chemotherapy group and 56.9% for those of the chemotherapy group. In particular, adjuvant chemotherapy was effective for patients with ps(-)n(+) (P less than .05) and ps(+)n(-) (P less than .05), but not for those with ps(-)n(-) and ps(+)n(+). Our findings show that the concomitant prescription of MMC, tegafur, and PSK improves the 15-year survival rate for patients with advanced gastric cancer, following curative resection. As the survival rate is low for the patients with ps(+)n(+), an even more aggressive postoperative chemotherapy is recommended.

5-Fluorouracil is converted to F-nucleotides more extensively and is more cytotoxic in poorly differentiated than in well differentiated human gastric carcinoma

The sensitivity to 5-fluorouracil (5-FU) was examined in 40 well differentiated and 50 poorly differentiated gastric cancer tissues and 15 normal tissues, using the in vitro succinate dehydrogenase inhibition (SDI) test. The tissue phosphorylating and degrading activities of 5-FU were compared in each type of tumor and in the normal tissues. Decreases in succinate dehydrogenase (SD) activity were more apparent in the poorly differentiated cancer tissues than in the well differentiated cancer tissues (p less than 0.005), and than in the normal tissues (p less than 0.001), exposed to 5-FU. The rate of sensitivity to 5-FU was higher in the poorly differentiated than in the well differentiated tissues and than in the normal tissues. The phosphorylating activities of 5-FU, in pathways involving uridine (Urd) phosphorylase and Urd Kinase, and thymidine (dThd) phosphorylase and dThd Kinase, were 1.7 fold higher in the poorly differentiated than in the well differentiated tissues and several fold higher than in the normal tissues (p less than 0.05-p less than 0.001). The degrading activity of 5-FU was similar in both types of tumor and in the normal tissues. Our findings show that 5-FU is actively metabolized to 5-FU-nucleotides in poorly differentiated tissues after incorporation into the tumor cells. 5-FU seems to have an increased susceptibility in cases of poorly differentiated gastric carcinoma.

Comparison of pyrimidine nucleotide synthetic enzymes involved in 5-fluorouracil metabolism between human adenocarcinomas and squamous cell carcinomas

The activities of orotate phosphoribosyltransferase (OPRT), cytidine triphosphate (CTP) synthetase, deoxycytidine monophosphate (dCMP) deaminase, thymidine monophosphate (dTMP) kinase, uridine (Urd) kinase, thymidine (dThd) kinase, Urd and dThd phosphorylases, and DNA polymerase were examined in the eight human lung squamous cell carcinomas and five lung adenocarcinomas, and five tumor-adjacent normal lung tissues. All of these enzymes are involved in pyrimidine nucleotide synthesis. The metabolism of 5-fluorouracil (5-FU) was determined. The levels of these enzymes, except for OPRT, were high in tumor tissues and almost the same between lung squamous cell carcinomas and adenocarcinomas, with no statistical difference. The activities for phosphorylation and degradation of 5-FU were similar in each tissue type of tumor. As 5-FU is incorporated into tumor cells and is metabolized actively to 5-FU nucleotides in squamous cell carcinoma tissues, at almost the same level seen in adenocarcinoma tissues, this drug should have a wide clinical application.

Presence of sex difference of cytochrome P-450 in the rat preoptic area and hypothalamus with reference to coexistence with oxytocin

Localization of female type cytochrome P-450 (F1) in the preoptic area and hypothalamus of the rat was examined immunocytochemically using antiserum against purified hepatic P-450 (F1). This antiserum recognizes both P-450 (F1) and P-450 (M3). Western immunoblotting using the antiserum demonstrated that female rat brain contains P-450 (F1) but not P-450 (M3), since microsomes from the brain and liver displayed only one immunoreactive band at 50 kD, coinciding with that of P-450 (F1) purified from female rat liver. On the other hand, the male brain has P-450 (M3) but not P-450 (F1), as liver- and brain-derived microsomes produced single band at 49 kD, which represents a mol. wt. identical to that of P-450 (M3) extracted from male rat liver. These results indicate that P-450 (F1)-like immunoreactivity (LI) occurs in the female rat brain, while P-450 (M3)-LI takes place in the male rat brain. Immunocytochemical analysis further demonstrated the detailed cellular localization of these two P-450-LIs in the preoptic area and hypothalamus of female and male rats. Localization of P-450 (F1)-LI in the female rat hypothalamus resembled that of P-450 (M3)-LI in the male rat hypothalamus. Magnocellular neurosecretory neurons in the paraventricular nucleus and supraoptic nucleus were labeled and were found to contain oxytocin but lack vasopressin when serial sections of these areas were analyzed. In addition, groups of immunoreactive cells were seen in the median preoptic nucleus, medial and lateral preoptic area, caudal portion of the bed nucleus of the stria terminalis, lateral hypothalamus at the level of the paraventricular nucleus, periventricular zone from the preoptic area to the paraventricular nucleus, and parvocellular portion of the paraventricular nucleus.

Primary and metastatic liver lesions of clinical colorectal cancer differ in chemosensitivity

The succinate dehydrogenase inhibition (SDI) test was used to examine eight pairs of samples obtained simultaneously from primary colorectal cancers and metastatic liver lesions. The chemosensitivity of the metastatic lesions to six antitumour drugs, carboquone (CQ), adriamycin (ADM), mitomycin C (MMC), aclacinomycin A (ACR), cisplatin (DDP), and 5-fluorouracil (5-FU), differed from that of the primary lesions - the metastatic lesions were less sensitive to all these drugs. There were no correlations of chemosensitivities between the primary and the metastatic lesions (r = -0.4331-0.4857). Thus, in patients with liver metastasis from a primary colorectal cancer, treatment with these drugs may not be so effective. When selecting antitumour drugs for metastatic liver lesions of colorectal cancer, the chemosensitivity of the primary tumour should first be assessed.

[In vitro chemosensitivity test: succinate dehydrogenase inhibition (SDI) test]

The succinate dehydrogenase inhibition (SDI) test was used for determining chemosensitivity of various human tumors. This test was based on the correlation between the cellular succinate dehydrogenase activity as determined by 3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT), and cell viability. The chemosensitivity varied in the tissue. Some factors are involved in the chemosensitivity, that is origin of a tumor, tissue differentiation and tissue DNA synthetic activity. This test is a convenient method for clinical use and provides important information about chemosensitivity.

Estrogen-receptor-negative breast cancer tissue is chemosensitive in vitro compared with estrogen-receptor-positive tissue

The chemosensitivities of 18 estrogen-receptor-positive (ER+) tissues were compared with that of 38 estrogen-receptor-negative (ER-) tissues, using the in vitro succinate dehydrogenase inhibition test. These human breast tissue were exposed to six antitumor drugs: carboquone, adriamycin, mitomycin C, aclacinomycin A, cisplatin and 5-fluorouracil. Decrease in succinate dehydrogenase activity was noted in ER- compared to ER+ tissues, exposed to six antitumor drugs, in particular to adriamycin (p less than 0.001) and aclacinomycin A (p less than 0.05). The sensitive rates were higher in ER- than in ER+ tissues, against all six antitumor drugs. The resistance rates to all drugs tested were 25% in ER- and 45% in ER+ tissues. A higher chemosensitivity is associated with the absence of ER. It appeared that the ER status in case of breast cancer is an important predictor of the response to chemotherapy.

Detection of DNA strand breaks in HeLa cells in vitro and in mouse sarcoma 180 cells in vivo induced by an alkylating agent, carboquone, using in situ nick translation

We determined the correlation between DNA strand breaks and the toxicity of carboquone (CQ) in HeLa cells in vitro and in mouse sarcoma 180 (S-180) cells in vivo, using in situ nick translation. The break sites in the DNA were translated artificially in the presence of Escherichia coli DNA polymerase I and [3-H]-labelled dTTP, and sites in the DNA were visualized by autoradiographic observation of grains in the nuclei. These breaks appeared as early as 5 min in the CQ-treated HeLa cells and increased in a dose- and time-dependent manner compared to findings in the control cells, i.e., 10.2-fold at 3 x 10(-6) M in 60 min. Strand breaks in the S-180 cells appeared in a dose- and time-dependent manner, i.e., 6.1-fold after the mice had been exposed to CQ (3.6 mg/kg) for 2 h. This level correlated with the increase in host life span. Our findings show that the survival response of cells decreases, while the level of DNA strand breaks increases following exposure to CQ. The nick translation method is a rapid in situ assay for determining drug-induced DNA damage of tumor cells, under in vitro and in vivo conditions and in a semiquantitative manner.

Combined treatment of adriamycin and dipyridamole inhibits lung metastasis of B16 melanoma cells in mice

The combined effects of adriamycin (ADM) and dipyridamole (DP) on lung metastasis of B16 melanoma cells in mice were investigated. First, the antitumor effects of ADM and DP were examined both in vitro and in vivo. The clonogenicity of B16 melanoma cells was suppressed by the combination of ADM and the nontoxic dose of DP in vitro, and growth of the B16 melanoma solid tumor implanted subcutaneously in mice was inhibited with this drug combination, compared to findings with ADM alone in vivo. To examine events related to experimental lung metastasis, 2 X 10(5) B16 melanoma cells were given intravenously into the tail vein of mice and the efficacy was determined by counting the number of metastatic tumor nodules. DP in doses of 25-100 mg/kg given alone reduced the number of metastasis to about 85% that in the control group. ADM in doses of 1-4 mg/kg for 3 days inhibited the metastasis, in a dose-dependent manner. When combined with DP, the antimetastatic effect of ADM was enhanced and the number of metastasis prominently decreased, compared to single application of the drug (p less than 0.05). We speculate that ADM given concomitantly with DP may have the potential to inhibit metastatic growth of a tumor.

Adriamycin-induced DNA strand breaks in HeLa and in P388 leukaemia cells detected using in situ nick translation

DNA strand breaks produced by adriamycin (ADR) were measured in HeLa cells and ADR-sensitive and -resistant P388 leukaemia cells, using the in situ nick translation method. The break sites in the DNA were translated artificially in the presence of Escherichia coli DNA polymerase I and 3H-labelled dTTP, and were visualized by autoradiographic observation of the grains. The DNA strand breaks in the HeLa cells increased in a dose-dependent manner, compared with findings in the untreated control cells, i.e., 15.2 fold at 20 micrograms/ml of ADR for 1 h. This level correlated with DNA single-strand breaks detected by the alkaline elution method. DNA breaks were also noted in the ADR-sensitive P388 cells, but in the ADR-resistant cells the level of DNA strand breaks was low. The enhanced cytotoxicity is apparently the consequence of the enhanced potential of ADR to cause breaks in the DNA strands. Our findings show that the survival response of the cells decreases and the level of DNA strand breaks increases following exposure to ADR. ADR resistance may be mediated by a reduction in the level of DNA strand breaks.

[Detection of cellular DNA strand breaks induced by antitumor drug and heat using in situ nick translation]

Cellular DNA strand break induced by an alkylating agent: Carboquone (CQ), and heat (43 degrees C) was detected in HeLa cells in vitro and mouse sarcoma-180 cells in vivo. The break sites in the DNA were translated artificially in the presence of Escherichia coli DNA polymerase I and [3H]-labeled dTTP and sites in the DNA were visualized by autoradiographic observation of grains in the nuclei. These breaks increased in a dose and time dependent manner, compared to findings in the control cells. Our findings show that the surviving response of cells decreases while the level of DNA strand breaks increases following exposure to CQ or heat. The nick translation method is a rapid in situ assay for determining drug and heat induced DNA damage of tumor cells, under in vitro and in vivo conditions and in a semi-quantitative manner.

Preventive effect of 3-aminobenzamide on the reduction of NAD levels in rat liver following administration of diethylnitrosamine

Nicotinamide adenine dinucleotide is utilized as the substrate of a chromatin-bound enzyme, poly(ADP-ribose) polymerase. The effects of diethylnitrosamine and/or 3-aminobenzamide, a potent inhibitor of poly(ADP-ribose) polymerase, on the cellular NAD levels in rat liver were investigated. 3-Aminobenzamide (600 mg/kg) administered intraperitoneally was not detectable in the liver within 12 hr after administration; the inhibitor had a calculated half life of 90 min. Diethylnitrosamine reduced the NAD levels in rat liver in a dose-dependent way. The NAD content reached a minimum level at 8 hr, returning to 78% of the control value after 48 hr. The reduction of the NAD levels caused by diethylnitrosamine was completely prevented when 3-aminobenzamide was administered either simultaneously with diethylnitrosamine or 4 hr after diethylnitrosamine treatment. Furthermore, an immunohistochemical study showed that nuclear poly(ADP-ribose) decreased 1 hr after the administration of 3-aminobenzamide. These results suggest that inhibition of poly(ADP-ribosyl)ation is involved in the initiation of liver carcinogenesis by diethylnitrosamine and 3-aminobenzamide.

Synthesis of sex-specific forms of cytochrome P-450 in rat liver is transiently suppressed by hepatic monooxygenase inducers

The effects of phenobarbital (PB), 3-methylcholanthrene (MC), and alpha-naphthoflavone (alpha-NF) on the synthesis of drug-inducible forms of cytochrome P-450, P-450(PB-1), and P-450(MC-1), and sex-specific forms of cytochrome P-450, P-450(M-1), and P-450(F-1), in male and female rats were studied. Whereas P-450(PB-1) and P-450(MC-1) in liver microsomes were markedly induced in both sexes by treatment with PB and MC, respectively, the contents of P-450(M-1) and P-450(F-1) were significantly decreased by the treatments. alpha-NF, which is not a P-450 inducer, did not change the contents of sex-specific forms of cytochrome P-450. The translatable mRNAs of the P-450s were also determined by using an in vitro translation system. The mRNAs coding for P-450(PB-1) and P-450(MC-1) were increased by drug administrations. On the other hand, the mRNAs coding for P-450(M-1) and P-450(F-1) were transiently decreased by the drugs, and then returned to the normal levels. The time courses of the induction of the drug-inducible P-450s and the repression of the sex-specific P-450s showed no close correlation. alpha-NF had no effect on the synthesis of P-450(M-1) and P-450(F-1). We also found that the synthesis of P-450(M-1) in the livers of untreated rats showed no diurnal variations.

Purification and characterization of three male-specific and one female-specific forms of cytochrome P-450 from rat liver microsomes

Three forms of cytochrome P-450, tentatively designated P-450(M-1), P-450(M-2), and P-450(M-3), and one form of cytochrome P-450, P-450(F-1), were purified from the liver microsomes of untreated male and female rats, respectively. Each purified form of the cytochrome showed a single protein band on SDS-polyacrylamide gel electrophoresis, and gave a minimum molecular weight of 51,000 for P-450(M-1), 48,000 for P-450(M-2), 49,000 for P-450(M-3), and 50,000 for P-450(F-1). The carbon monoxide-difference spectra of reduced P-450(M-1), P-450(M-2), P-450(M-3), and P-450(F-1) showed an absorption maximum at 451, 451, 448, and 449 nm, respectively. Judging from the absolute absorption spectra, the four forms of cytochrome P-450 were of low-spin type in the oxidized forms. The antibodies against P-450(M-2) did not crossreact with the other forms in the Ouchterlony double diffusion test, whereas the immunodiffusion test showed immunocrossreactivity between P-450(M-1) and P-450(F-1), P-450(M-1) and P-450(M-3), and P-450(M-3) and P-450(F-1). The NH2-terminal amino acid sequences of the four forms confirmed that they were different molecular species, although significant homology was noticed among P-450(M-1), P-450(M-3), and P-450(F-1). The quantitation of P-450(M-1) and P-450(F-1) in liver microsomes by quantitative immunoprecipitation confirmed that these two forms of cytochrome P-450 were developmentally induced in male and female rats, respectively. P-450(M-2) was also developmentally induced in male rats. In a reconstituted system containing NADPH and NADPH-cytochrome P-450 reductase, P-450(M-1) oxidized benzphetamine at a high rate, whereas the other forms had low activity toward benzphetamine. None of the four forms showed high activity toward benzo(a)pyrene. P-450(M-1) catalyzed the hydroxylation testosterone at the 16 alpha and 2 alpha positions, whereas P-450(M-2) catalyzed the 15 alpha hydroxylation of the same substrate.

Accumulation of surfactant phospholipids in lipid pneumonia induced with methylnaphthalene

Lipid analyses were carried out on the lungs of female B6C3F1 mice treated with methylnaphthalene. Cholesteryl ester, which could not be detected in lungs of control animals, was present in lungs of treated animals. Cholesterol and dipalmitoylglycerophosphocholine (DPPC) content was increased about five times in lungs of treated mice compared with control mice, and the content of a minor phospholipid was increased six times. The latter phospholipid was purified by high performance liquid chromatography and identified as phosphatidylglycerol by thin layer chromatography and by fast atom bombardment-mass spectrometry. Both DPPC and phosphatidylglycerol are known to be pneumonal surfactants produced from type II pneumocytes. Therefore, the accumulation of these lipids in lung tissue was assumed to be caused by the proliferation of type II cells induced by the administration of methylnaphthalene. The results provide important information concerning the underlying mechanism of endogenous lipid pneumonia in mice.

Inhibitory effect of organic solvents on the mutagenicity of N-nitrosodialkylamines in Salmonella

The influence of organic solvents on the mutagenicity of 11 N-nitrosamines was examined in Salmonella typhimurium TA100 using the Ames's liquid incubation assay in the presence of rat-liver S9. The mutagenic activities of N-nitrosodimethylamine, N-nitrosodiethylamine, 6 oxidative derivatives of N-nitrosopropylamine and N-nitroso-2,6-dimethylmorpholine were considerably decreased by addition of dimethyl sulfoxide, dimethyl formamide, acetone, 95% ethanol or acetonitrile, which are recommended for use as solvents in the assay by Ames's group, to the incubation mixture. The mutagenic activities of N-nitrosodipropylamine and N-nitrosodibutylamine, which are barely soluble in water, were also suppressed by increasing concentrations of dimethyl sulfoxide. These organic solvents did not appear to exert their influence by desmutagenic and antimutagenic actions. In contrast, the recoveries of unmetabolized carcinogens from preincubation mixtures and from agar plates were significantly higher in the presence of organic solvents than in their absence. The results indicate that the inhibitory effect is a result of interference with the process of metabolic activation by liver S9.

Enhancement of DEN initiation of liver carcinogenesis by inhibitors of NAD+ ADP ribosyl transferase in rats

The effect of inhibitors of NAD+ ADP ribosyl transferase (ADPRT) on the early stage of liver carcinogenesis of diethylnitrosamine (DEN) was studied by estimating the number and size of gamma-glutamyltranspeptidase (gamma-GTP) positive foci assayed as markers of cell populations initiated by DEN in the rat liver. ADPRT inhibitors investigated were 3-aminobenzamide (ABA), 5-methylnicotinamide (MNAM), and thymidine. A single i.p. injection of ABA at greater than 150 mg/kg body weight (B.W.) enhanced dose-dependently the induction of gamma-GTP positive foci in rat liver initiated by 20 mg/kg B.W. of DEN. The magnitude of the effect was similar to that observed when partial hepatectomy (PH) was performed instead of ABA administration. Single i.p. injections of MNAM or thymidine at a dose of 600 mg/kg B.W. also enhanced the induction of foci in rat liver initiated by the 20 mg/kg dose of DEN. Based on the above results, ABA was used as a representative ADPRT inhibitor for clarifying the mechanisms underlying the effects. Administration of ABA at a dose of 600 mg/kg B.W. was effective in enhancing the induction of foci if given 1 day before DEN, simultaneously to DEN, and 1 day after DEN initiation but it was ineffective if it was given 3 days after DEN or thereafter. Liver cell necrosis was not detectable either by analysis of serum enzymes or histologically 1, 3, 5, 7 and 14 days after 20 mg/kg B.W. of DEN with or without administration of 600 mg/kg B.W. of ABA. No initiating activity was observed for ABA administered at doses of 600 and 1200 mg/kg B.W. as assayed by development of gamma-GTP positive foci. Long term ABA administration in the diet at concentrations of 0.05, 0.1 and 0.2% did not show any promoting activity for liver carcinogenesis initiated by DEN. Furthermore, chronic administration of 0.2% ABA in the diet did not result in detectable toxicity and/or carcinogenic effects. These results suggest that ADPRT and associated DNA repair plays an important role in the early initiating stage of liver carcinogenesis and provide the basis for a new experimental approach to the analysis of the mechanisms of chemical carcinogenesis and in establishing a more sensitive assay system for liver carcinogenesis in rats.

Carcinogenic effects of 3-di(hydroxymethyl)-amino-6-(5-nitro-2-furylethenyl)-1,2,4-triazine in the small intestine of Ishibashi and Wistar rats

The carcinogenic effect of an oral administration of 3-di(hydroxymethyl)-amino-6-(5-nitro-2-furylethenyl)-1,2,4-triazin e (DHNT) was studied in two strains of rats. Ishibashi (IS) rats have a perpetual absorption disturbance while Wistar Imamichi (WI) rats have no such disturbance. Small intestinal carcinomas developed in 10 out of 15 (66.7%) IS rats and in all 8 (100%) Wistar rats given 3,500 ppm DHNT for 43 weeks. The total number of lesions in the small intestine was 24 in IS rats and 21 in WI rats. Histologically, the lesions consisted of 7 mucosal dysplasias, 4 adenomas and 12 tubular and 1 papillary adenocarcinoma in IS rats, and 3 mucosal dysplasias, 1 adenomas, and 15 tubular and 2 papillary adenocarcinomas in WI rats. The levels of plasma leucine aminopeptidase, copper and total protein were lower, while blood urea nitrogen was higher in both strains of rats given DHNT than in control rats.

Establishment of an alpha-fetoprotein-producing human gastric carcinoma in nude mice

An alpha-fetoprotein (AFP)-producing human gastric carcinoma was transplanted into BALB/c-nu/nu nude mice. The original tumor tissue had been obtained by gastrectomy from a 72-year-old patient with gastric carcinoma. The tumor had been transplanted serially (20 passages) in nude mice. The transplantability was 100%. The doubling time of the tumor ranged from 5.6 days to 11.2 days. AFP appeared in the serum of nude mice 3 to 4 weeks after subcutaneous (sc) transplantation and 6 weeks after intraperitoneal (ip) transplantation of the tumor cell suspension prepared from sc transplanted tumors. A positive correlation was observed between serum AFP level and tumor size. Serum AFP level of mice given ip transplantation increased as a function of time after transplantation. AFP was stained positively by an immunochemical technique in the original and transplanted tumors and was located in the cytoplasms of the tumor cells. The histology of the original tumor was retained. The malignant potential of these transplanted tumor cells was expressed as carcinomatous peritonitis and liver and/or lung metastases.

Experimental studies on malignant fibrous histiocytomas. II. Ultrastructure of malignant fibrous histiocytomas induced by 4-(hydroxyamino)-quinoline 1-oxide in rats

The ultrastructures of six subcutaneous and six bone malignant fibrous histiocytomas (MFH) induced in rats by local application of the carcinogen, 4-(hydroxyamino)-quinoline 1-oxide (4-HAQO) were studied. The MFHs could be classified histologically into three subtypes: of the six subcutaneous MFHs, four were fibrous, one was giant cell, and one was myxoid; of the osseous MFHs, three were fibrous, one was giant cell, and two were myxoid. Five different types of cells were found in the MFHs: fibroblast-like cells, histiocyte-like cells, undifferentiated cells, xanthomatous cells, and multinucleated giant cells; the xanthomatous cells and multinucleated giant cells, however, were probably derived from histiocyte-like cells. Fibroblast-like cells predominated in storiform areas of the fibrous subtype; histiocyte-like cells and undifferentiated cells predominated in the giant cell subtype; intermediate cells predominated in the myxoid subtype. Acid phosphatase activity was found in lysosomes and myelin figures of the histiocyte-like cells in fibrous type MFH. The giant cell subtype of bone MFH has been transplanted serially into syngeneic rats and is now at the 17th generation. Transplantability exceeded 80%; doubling time was 3.8 to 6.1 days. Until the 3rd generation, the histology of the original tumor was retained; from the 4th generation, however, giant cells and xanthoma cells were no longer observed, and the tumor was composed mainly of undifferentiated cells. These results indicate that (a) MFH induced in the rat by 4-HAQO have an ultrastructure similar to human MFH and (b) the giant cell subtype transplanted serially is gradually transformed with a probable selection of stem cells and undifferentiated cells.

Effects of caffeine on pancreatic tumorigenesis by 4-hydroxyaminoquinoline 1-oxide in partially pancreatectomized rats

The effects of caffeine on pancreatic tumorigenesis by 4-hydroxyaminoquinoline 1-oxide (4-HAQO) and on pancreatic DNA synthesis were studied in partially pancreatectomized male Wistar rats. 4-HAQO was injected i.v. as a single dose of 7 mg/kg body weight 3 days after partial pancreatectomy. Caffeine was injected s.c. every 12 h at the maximum tolerated dose (m.t.d.) of 120 mg/kg body weight, half the m.t.d., and one quarter the m.t.d. from 12 to 72 h before and 0 to 72, 72 to 132, and 0 to 132 h after 4-HAQO treatment. Post-treatment with caffeine from 0 to 132 h had a dose-dependent biphasic effect on pancreatic tumorigenesis: post-treatment with the m.t.d. of caffeine decreased the total number of nodules, whereas treatment with one quarter the m.t.d. of caffeine increased their number. Decrease in the number of nodules was also observed on post-treatment with the m.t.d. of caffeine from 0 to 72 or from 72 to 132 h. Pretreatment with the m.t.d. of caffeine had no significant effect on the number of nodules. Recovery of pancreatic DNA synthesis was slower after simultaneous treatment with the m.t.d. of caffeine and 4-HAQO than after treatment with 4-HAQO alone. The possible mechanism of the effect of caffeine on pancreatic tumorigenesis induced by 4-HAQO in rats is discussed.

Effects of chrysotile asbestos on lung and pleural carcinogenesis of N-bis(2-hydroxypropyl)nitrosamine in rats

The effects of chrysotile asbestos on lung and pleural carcinogenesis by N-bis(2-hydroxypropyl)nitrosamine (DHPN) in male Wistar rats were studied. Chrysotile, 30 mg per rat, was injected into the left pleural cavity and 3 g/kg body wt. DHPN was injected once into the abdominal cavity. Lung tumors (adenoma, adenocarcinoma, squamous cell carcinoma, and combined carcinoma) occurred at the highest incidence (100%). Adenocarcinoma was seen in 4 of 11 (36%) rats killed at 35 weeks and in 6 of 12 (50%) rats killed at 52 weeks, squamous cell carcinoma occurred in 1 of 11 (9%) rats killed at 35 weeks and 3 of 12 (25%) rats killed at 52 weeks, and mixed carcinoma was seen in 1 of 12 (8%) rats killed at 52 weeks, which received chrysotile and DHPN. Adenocarcinoma was seen in 9 of 11 (82%) rats which received DHPN only and killed at 52 weeks. Mesotheliomas were seen in 2 of 11 (18%) rats, killed at 35 weeks, and 3 of 12 (25%) rats, killed at 52 weeks, which received chrysotile and DHPN. Hyaline thickening of the pleura was seen in 100% of rats receiving chrysotile. Mesothelial cell hyperplasia and adenomatous and/or fibromatous growth of the mesothelium were seen in the pleura on both sides, ranging from 36% to 50% and 31% to 64% in rats receiving chrysotile and DHPN, respectively. Asbestos bodies were seen in the pleura on both sides and in the lung.