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J M Rice

Publications and source records attributed to J M Rice.

At least 73 records · Page 4Linked to original sources
PubMed1994

Iron accelerates while magnesium inhibits nickel-induced carcinogenesis in the rat kidney.

Effects of magnesium basic carbonate (MgCarb) and metallic iron powder (Fe0) on nickel subsulfide (Ni3S2)-induced carcinogenesis were studied in kidneys of male F344/NCr rats. The rats, 20-40/group, received injections of Ni3S2 alone (62 mumol Ni) or with equimolar doses of MgCarb or Fe0 into the renal cortex of each pole of the right kidney. Control rats were given MgCarb, Fe0, or 0.1 ml of 50% aqueous glycerol, the injection vehicle. Final incidence of renal tumors 2 years after the injection of Ni3S2 alone or mixed with Fe0 was 60%. However, rats given Ni3S2 + Fe0 developed renal tumors much more rapidly. In contrast, the incidence of renal tumors in rats given Ni3S2 + MgCarb was only 20% (P < 0.01 vs. Ni3S2 alone). No kidney tumors were observed in the control rats. Between weeks 4 and 32 post injection, Ni3S2 alone caused erythrocytosis. This effect was attenuated by Fe0, but not by MgCarb. Hence, there is no firm correlation between carcinogenic activity of nickel and its ability to induce erythropoiesis. All kidney tumors were of mesenchymal cell origin and resembled the sarcomatous variant of the classic rat renal mesenchymal tumor. Some of them metastasized to the lungs and other organs. In 3-35 days post-injection, kidneys of rats treated with Ni3S2 alone showed moderate to extensive necrosis, inflammation, fibrosis, and degenerative and regenerative proliferative changes in the proximal tubular epithelium at the injection site. Similar, but more severe and multifocal changes were observed in the kidneys of Ni3S2 + Fe0-treated rats. The necrosis was less severe in kidneys injected with Ni3S2 + MgCarb, but fibrosis and degenerative and regenerative changes in proximal tubular epithelium were similar to those observed in other treatment groups. Ni3S2 deposits were seen inside macrophages and proximal tubular epithelial cells of Ni3S2 and Ni3S2+ Fe0-treated kidneys more frequently than in Ni3S2 + MgCarb-treated kidneys. Thus, magnesium antagonizes nickel carcinogenesis in the rat kidney while iron tends to enhance it. This result may be related to respectively attenuating or enhancing effects of magnesium and iron on the inflammatory response to Ni3S2.

Animals↗
PubMed1994

Low incidence of point mutations detected in the p53 tumor suppressor gene from chemically induced rat renal mesenchymal tumors.

Previous studies have shown renal mesenchymal tumors (RMTs) induced in rats by a single intrarenal injection of nickel subsulfide and iron are more pleomorphic and metastatically aggressive than RMTs induced by a single ip injection of methyl(methoxymethyl)nitrosamine (DMN-OMe). While both RMT types contain high levels of K-ras activation, the specific mutational spectra within codon 12 of K-ras are quite different. Nickel subsulfide and iron-induced tumors exhibited codon 12 GGT-->GTT transversions exclusively, while DMN-OMe RMTs showed a wide array of codon 12 mutations, as well as mutations within codons 61 and 63 [K. G. Higinbotham, J. M. Rice, B. A. Diwan, K. S. Kasprzak, C. D. Reed, and A. O. Perantoni, Cancer Res., 52: 4747-4751, 1992; K. G. Higinbotham, J. M. Rice, and A. O. Perantoni, Mol. Carcinog., 5: 136-139, 1992]. In an effort to further correlate carcinogen-specific molecular events in renal tumors, we investigated the p53 tumor suppressor gene in RMTs induced by these two carcinogens for the presence of point mutations. The evolutionarily conserved portion of the coding region of the gene, including part of exon 4 through exon 10, was surveyed for point mutations utilizing single-strand conformation polymorphism and chemical cleavage of mismatches analyses. None (0 of 10) of the nickel subsulfide and iron-induced RMTs and only 1 of 10 DMN-OMe-induced tumors that were evaluated contained point mutations within this portion of the p53 gene. Direct sequencing of the one single-strand conformation polymorphism and chemical cleavage of mismatches-"positive" DMN-OMe-induced RMT revealed a GCC-->GTC (Ala-->Val) transition in codon 345 within exon 10. These results suggest that the different tumorigenic phenotypes exhibited by these two RMTs are not the result of specific mutations or patterns of mutations within the portion of the p53 gene examined and that the mutated p53 tumorigenic pathway, whereby p53 plays a major role in many human neoplasms, does not function in RMTs induced by either agent.

Animals↗
PubMed1994

Infrequent transforming mutations in the transmembrane domain of the neu oncogene in spontaneous rat schwannomas.

Ethylnitrosourea (ENU) given transplacentally to rats induces schwannomas of the cranial, spinal, and peripheral nerves, with a high frequency of mutations in the neu proto-oncogene. To establish the requirement for such mutations in tumorigenesis of the Schwann cell, spontaneous schwannomas from BD-VI rats were evaluated for transforming mutations in the transmembrane domain of the protein encoded by the neu proto-oncogene. While all five schwannomas induced transplacentally with ENU were shown to contain T-->A transversions in base 2012 of neu by selective oligonucleotide hybridization and dideoxy sequencing of polymerase chain reaction-amplified products from paraffin sections, only one of nine spontaneous schwannomas from untreated rats had the same mutation. Examination of tumors for mutations in codon 12 of Ki-ras revealed normal alleles. Therefore, the high frequency of mutations in neu in ENU-induced tumors may be directly attributable to the carcinogen or to the period of development at which exposure occurred, and transforming mutations of the transmembrane domain of neu are not required for tumorigenesis of the Schwann cell.

Animals↗
PubMed1994

Comparative hyaline droplet nephropathy in male F344/NCr rats induced by sodium barbital and diethylacetylurea, a breakdown product of sodium barbital.

Hyaline droplet nephropathy in male rats due to alpha 2u-globulin accumulation in proximal tubules is caused by chemicals from several chemical classes. We have previously shown that the well-known sedative/hypnotic barbiturate, sodium barbital, and its breakdown product, diethylacetylurea, are renal toxins and renal tumor promoters. To determine comparative induction of hyaline droplets in renal tubules by sodium barbital and diethylacetylurea, male F344/NCr rats, 6 weeks of age, were given diets containing 0, 170, 341, 500, or 1000 ppm of diethylacetylurea or containing 500, 1000, or 4000 ppm of sodium barbital for periods of 2 or 10 weeks. Rats were terminated at 2 or 10 weeks and the histology of the kidney was evaluated using light microscopy with hematoxylin and eosin staining and staining by the Heidenhain method. Quantitative analysis showed dose responses for the degree of droplet accumulation in the P2 and P3 segments of the proximal tubules. Diethylacetylurea was more potent. Immunohistochemistry and ultrastructural evaluation revealed the nature of the droplets. Western blotting confirmed the presence of alpha 2u-globulin. Renal tubular necrosis, regeneration, and increased levels of cell proliferation using proliferating cell nuclear antigen immunohistochemistry were also found. Female rats similarly exposed to each chemical did not show tubule droplet accumulations nor renal lesions. We confirm for the first time that these two chemicals can be added to the enlarging list of nephrotoxic chemicals inducing alpha 2u-globulin nephropathy and possessing tumor promoting and renal carcinogenic properties.

Animals↗
PubMed1994

Enhancement of hepatocarcinogenesis and induction of specific cytochrome P450-dependent monooxygenase activities by the barbiturates allobarbital, aprobarbital, pentobarbital, secobarbital and 5-phenyl- and 5-ethylbarbituric acids.

To test predictions that barbiturates which are long-acting sedatives and/or strong inducers of CYP2B-mediated monooxygenase activities would be effective promoters of hepatocarcinogenesis, a series of clinically-useful barbiturates and structural analogs were tested for ability to promote hepatocellular carcinogenesis in male F344/NCr rats initiated with N-nitrosodiethylamine and for efficacy as inducers of CYP2B activity in non-initiated rats of the same sex and strain. The barbiturates were administered in the diet at concentrations equimolar to 500 p.p.m. of the known liver tumor promoter phenobarbital, which served as the positive control for this study. Phenobarbital, which has the longest duration of sedative action of this series of compounds, caused the greatest induction of CYP2B activity, and displayed strong liver tumor promoting effects. Allobarbital and aprobarbital, two intermediate-duration sedatives, were found to promote hepatocarcinogenesis, with allobarbital proving to be as effective as phenobarbital in this respect and aprobarbital being somewhat weaker as a promoter. These intermediate-duration sedatives were each relatively weak CYP2B-type inducers, causing approximately 25% of the induction displayed by phenobarbital. The nonsedatives, 5-phenyl- and 5-ethyl-barbituric acids, were essentially inactive as CYP2B-type inducers and were also found to be relatively inactive as promoters of hepatocarcinogenesis. Of the shorter-duration sedatives, pentobarbital was found to promote, and was relatively effective as a CYP2B-type inducer, while secobarbital showed little or no promoting activity and was less effective as an inducer of CYP2B activities. Pentobarbital thus proved an important exception to our hypothesis that only long-acting sedative barbiturates would promote hepatocarcinogenesis. Although both the durations of sedative action and the degrees of CYP2B-type induction exhibited by these compounds correlate with a quantitative parameter for liver tumor-promoting activity (relative promotion index), neither parameter appears to be sufficient, by itself, as a predictor of promoting activity for rat liver.

Animals↗
PubMed1994

Alteration of the p53 tumor suppressor gene occurs independently of K-ras activation and more frequently in serous adenocarcinomas than in other common epithelial tumors of the human ovary.

To clarify the role of the p53 tumor suppressor gene in the development of human ovarian epithelial tumors and to study the association of p53 alterations with K-ras activation, a series of 70 common epithelial ovarian tumors from Japanese patients was studied. These included 31 serous adenocarcinomas, 12 mucinous adenocarcinomas, 5 mucinous tumors of borderline malignancy, 13 endometrioid adenocarcinomas, and 9 clear cell carcinomas. Allelic loss, recognized at the polymorphic site in codon 72 of the p53 gene, was detected in 14 of 36 (39%) informative cases by restriction fragment length polymorphism analysis and by single-strand conformation polymorphism (SSCP) analysis of polymerase chain reaction (PCR)-amplified DNA fragments. Mutations in the highly conserved regions of the p53 gene were detected by SSCP analysis of PCR-amplified fragments. Mutations were found in 22 of 70 (31%) ovarian tumors, including 1 of 5 mucinous tumors of borderline malignancy. Mutations were subsequently characterized by direct sequencing. Single missense base substitutions were detected in 13 ovarian carcinomas and in one case of mucinous tumor of borderline malignancy. Short (1-8 bp) deletions and insertions were found in 8 cases. Mutations in the p53 gene occurred more frequently in serous adenocarcinomas (14/31, 45%) than in all nonserous types of malignant epithelial tumors combined (7/34, 21%; P = 0.032). Point mutations in K-ras were identified by dot blot hybridization analysis of PCR-amplified fragments with mutation-specific oligonucleotides and by direct sequencing. The overall frequency of K-ras mutations was 19/70 (27%). K-ras mutations were found in 12 of 17 (71%) mucinous tumors (8/12 mucinous carcinomas [67%] and 4/5 mucinous tumors of borderline malignancy [80%]), and occurred more frequently than in serous carcinomas (4/31, 13%; P = 0.00009) or in all nonmucinous types of ovarian epithelial tumors combined (7/53, 13%; P = 0.00002). These data suggest that different combinations of oncogenes and/or tumor suppressor genes may be involved in the genesis and development of histologically distinct categories of common epithelial tumors of the human ovary.

Adenocarcinoma, Clear Cell↗
PubMed1994

Activation of the K-ras gene by insertion mutations in chemically induced rat renal mesenchymal tumors.

Previously we reported the detection of transforming K-ras sequences in methyl(methoxymethyl)nitrosamine (DMN-OMe)-induced rat renal mesenchymal tumors by NIH3T3 transfection assays. Subsequent analysis by selective oligonucleotide hybridization revealed a variety of activating point mutations in codon 12 of K-ras in most of these tumors and in their NIH3T3 transformants, but in some, point mutations could not be detected by this technique. In the current study, insertion mutations were detected in two DMN-OMe-induced tumors from this group with previously undefined transforming K-ras alterations. These primary tumors and their NIH3T3 transformants contained K-ras sequences with either a 9 bp or a 12 bp repeat in exon one, both of which included codon 12. No other mutations in the entire coding region of the K-ras gene were observed. Site-directed mutagenesis studies by others have determined that deletions and insertions near codon 12 can activate the ras gene, but this is the first demonstration of insertional activation of K-ras in a chemically induced rat tumor.

3T3 Cells↗
PubMed1993

Transplacental carcinogenicity of cisplatin: initiation of skin tumors and induction of other preneoplastic and neoplastic lesions in SENCAR mice.

cis-Dichlorodiammineplatinum (cis-DDP), an anticancer agent sometimes used in pregnant women for the treatment of malignant ovarian and uterine tumors, was tested for transplacental carcinogenic and/or tumor-initiating effects in SENCAR mice. Pregnant mice were given a single i.p. injection of either cis-DDP (7.5 mg/kg body weight) in 2.5% NaCl or the same weight-adjusted volume of NaCl (5 ml/kg body weight) on day 17 of gestation. Offspring were delivered and raised by their natural mothers until weaning at 3 weeks of age. Starting at week 4, offspring in experimental groups received topical applications of 2 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA) in acetone twice a week for 20 weeks while those in control groups received only acetone (0.2 ml/application) for the same duration. The experiment was terminated at 25 weeks of age. A high incidence (18 of 37; 48.7%) of papillomas was observed in offspring exposed transplacentally to cis-DDP and postnatally to TPA, while only 10% (4 of 40) of offspring exposed to TPA alone developed such tumors (P < 0.0002). Although no skin tumors were observed without TPA promotion, transplacental administration of cis-DDP resulted in development of thymic lymphomas, lung tumors, and proliferative kidney lesions in offspring. These results provide the first evidence that cis-DDP can initiate and/or induce preneoplastic and neoplastic lesions in multiple tissues transplacentally.

Animals↗
PubMed1993

Alterations of the p53 tumor suppressor gene and its association with activation of the c-K-ras-2 protooncogene in premalignant and malignant lesions of the human uterine endometrium.

We previously reported (T. Enomoto et al., Cancer Res., 50: 6139-6145, 1990; T. Enomoto et al., Cancer Res., 51: 5308-5314, 1991) a significant frequency of activating point mutations in codon 12 of the c-K-ras-2 protooncogene in endometrial adenocarcinoma and its premalignant precursor lesions (series 1 and 2). To reveal the role of the p53 tumor suppressor gene in the development of endometrial adenocarcinoma and to study the association of p53 alterations with K-ras activation, an additional 28 endometrial adenocarcinomas and an additional 11 premalignant atypical uterine hyperplasias (series 3), as well as 12 cases of endometrial adenocarcinoma (10 having K- or N-ras activation) and 2 cases of atypical hyperplasia from series 1 and 2, were screened for the presence of p53 alterations. Allelic loss, recognized at the polymorphic site in codon 72 of the p53 gene, was detected in 6 of 19 (32%) informative cases of endometrial adenocarcinoma and 1 of 4 (25%) informative cases of endometrial atypical hyperplasia by restriction fragment length polymorphism analysis and by single-strand conformation polymorphism analysis of polymerase chain reaction (PCR)-amplified DNA fragments. Mutations in the highly conserved regions of the p53 gene were detected by single-strand conformation polymorphism analysis of PCR-amplified DNA fragments. Mutations were found in 9 of 40 (23%) endometrial adenocarcinomas and 1 of 13 (8%) atypical hyperplasias that were studied. Mutations in p53 were significantly more frequently found in clinical grade 3 (G3) cancers (6 of 14, 43%) than in G1-G2 cancers (3 of 26, 12%) (P = 0.033). Mutations were subsequently confirmed by direct sequencing. Single missense base substitutions were detected in 6 cases of endometrial carcinoma and in one case of atypical hyperplasia. Deletions of a single base and of 2 bases were each detected in single cases of endometrial carcinoma, and a single base insertion was found in a third case. Point mutations in K-ras were also identified in tumors of series 3 by direct sequencing of PCR-amplified DNA fragments of exons 1 and 2. Point mutations in codons 12 and 13 in K-ras were detected by direct sequencing of PCR-amplified DNA in 7 of 28 adenocarcinomas in series 3, but none were found in exon 2 (codons 59.63. The spectrum of point mutations in p53 in endometrial adenocarcinomas was almost identical to what we found in K-ras in series 1 and 2 and in series 3, suggesting the possible role of a mutagen that might be responsible for mutations in both K-ras and p53.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1993

Specific induction of hepatic cytochrome P4501a-2 in C57BL/6 and DBA/2 mice treated with 2-amino-3-methylimidazo[4,5-f]quinoline (IQ).

The food mutagen/carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is activated by cytochrome p4501a-2 via N-hydroxylation; various P450s may contribute to detoxification via ring hydroxylation. Alterations in P450 levels by IQ treatment might therefore influence its toxicity. To examine the role of Ah locus genotype on the biochemical effects of IQ, C57BL/6 (AhbAhb; p450Ia-1/2 inducible) and DBA/2 (AhdAhd, noninducible) mice of both sexes were given IQ at varying doses, with different vehicles and routes of administration. Livers taken after 24 hours were assessed for total cytochrome p450 and activities of ethoxyresorufin-O-deethylase (EROD, a p4501a-1 activity, inducible in Ahb mice), methoxyresorufin-O-demethylase (MROD, a p4501a-2 activity), and benzyloxyresorufin-O-dealkylase (BzROD, an activity of p4502b). There was little effect on total cytochrome p450, but all three enzyme activities were often induced, a maximum of 2.5-fold, in both sexes and in DBA/2 as well as C57BL/6 mice. However, Western immunoblot analysis with monoclonal antibodies demonstrated an increase only in p4501a-2 protein. p4501a-1 remained undetectable. A monoclonal antibody to p4502-b recognized one protein band in liver microsomes from males and two bands in female mice of both strains. Amounts of these proteins were not altered by IQ treatment. Thus, IQ specifically, if moderately, induces its activating enzyme, p4501a-2, in a process that was not clearly related to Ah responsiveness.

Animals↗
PubMed1993

Tumor promotion by an anticonvulsant agent, phenytoin, in mouse liver: correlation with CYP2B induction.

To investigate the liver tumor promoting effects of phenytoin (5,5-diphenylhydantoin; DPH), 5 week old male D2B6F1 mice were given a single i.p. dose of 90 mg N-nitrosodiethylamine (NDEA)/kg body wt in tricaprylin. Control groups received tricaprylin alone. After 2 weeks, the mice were given a diet containing 500, 250 or 125 p.p.m. DPH. Ten mice from each treatment group were killed at 30 weeks of age, at which time 10/10 mice given 500 p.p.m. DPH after NDEA initiation had developed multiple hepatocellular foci and adenomas. Such lesions were found only in 2/10 mice given NDEA alone. By 60 weeks, when the experiment was concluded, the incidences (and multiplicities, in units of tumors per tumor-bearing mouse) of hepatocellular adenomas were 60% (1.8 +/- 0.8), 100% (11.6 +/- 5.5), 77% (4.4 +/- 3.3) or 71% (2.6 +/- 1.3) in mice exposed to NDEA alone, or NDEA followed by 500, 250 or 125 p.p.m. DPH respectively. Hepatocellular carcinomas (87% incidence) and hepatoblastomas (33% incidence) were found only in mice given 500 p.p.m. DPH following NDEA initiation. Dose-dependent and profound increases in hepatic CYP2B-mediated benzyloxyresorufin O-dealkylase activity were detected in livers of B6C3F1 mice exposed for 14 days to dietary DPH (125, 250, 500 or 1000 p.p.m.). Similar increases in this activity were observed in D2B6F1 mice exposed to 500 and 250 p.p.m. for 30 or 60 weeks. Thus, increased hepatic CYP2B activity in mice exposed to DPH correlates with the tumor promoting effect of this compound.

Adenoma↗
PubMed1993

Metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in the patas monkey: pharmacokinetics and characterization of glucuronide metabolites.

The metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was examined in the patas monkey, in order to provide further information about NNK metabolic pathways in primates. Female patas monkeys were given i.v. injections of [5-3H]NNK, and metabolites in serum and urine were analyzed by HPLC. Metabolism by alpha-hydroxylation of NNK was rapid and extensive, and the products of this pathway, 4-hydroxy-4-(3-pyridyl)butyric acid and 4-oxo-4-(3-pyridyl) butyric acid, accounted for a relatively large proportion of serum and urinary metabolites at all time points. This is significant because the formation of these products is associated with modification of DNA by NNK. The other major metabolic pathway was carbonyl reduction to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which detected both unconjugated and diastereomeric O-glucuronides. One of these glucuronides had been previously identified in rat urine, but the other diastereomer, which was the more prevalent of the two in serum and urine, had not been observed in studies of NNK metabolism in rodents. It was characterized by its spectral properties, by enzymatic hydrolysis to NNAL, and by derivatization of the released NNAL enantiomer with (R)-(+)-alpha-methylbenzylisocyanate. The two NNAL glucuronides accounted for 15-20% of the urinary metabolites in monkeys given 0.1 micrograms/kg NNK, which is similar to a smoker's dose, suggesting their use as dosimeters of NNK exposure in humans. Pharmacokinetic parameters were consistent with those observed in previous studies of nitrosamines, and varied predictably with body weight of five species. The results of this study have provided new insights relevant to assessing human metabolism of NNK.

Animals↗
PubMed1993

Persistence, gestation stage-dependent formation and interrelationship of benzo[a]pyrene-induced DNA adducts in mothers, placentae and fetuses of Erythrocebus patas monkeys.

Since DNA adducts have been detected in the placentae of pregnant women who smoke cigarettes, the importance of these adducts as biomarkers of fetal exposure and risk has been evaluated using a non-human primate as a model. Pregnant Erythrocebus patas monkeys on days 50, 100 or 150 of gestation (term = 160 +/- 5 days) were treated once with 5-50 mg/kg benzo[a]pyrene (B[a]P), p.o. Fetuses were removed by Cesarean section 1-50 days after treatment and analyzed for DNA adducts by the nuclease P1 version of the 32P-postlabeling method. B[a]P induced high levels of DNA adducts in all fetal organs, placentae and maternal livers in all three trimesters of gestation. DNA adduct levels were higher in mid-gestation compared to early and late gestation. The major adduct detected was 10 beta-(deoxyguanosin)-N2-yl-7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10- tetrahydro-B[a]P. The adduct levels in fetal tissues increased with B[a]P dose, but at a much lower rate than in placentae or maternal livers. Preference in binding to DNA of various fetal organs was more apparent in early gestation compared to late gestation and at lower doses compared to higher doses. During early gestation and at low doses, B[a]P produced a similar level of DNA adducts in fetal lung, fetal liver, maternal liver and placenta. Individual fetal organ adduct levels correlated significantly with placental adduct levels, indicating placental and/or maternal contribution to genotoxic injuries in fetuses. However, the slopes of linear regression lines of correlation analyses varied among organs and among gestation stages at treatment, indicating fetal contribution to its own genotoxic injuries. DNA adduct levels in fetal skin were the lowest of all fetal organs tested and less affected by gestational stages at time of treatment. In contrast, DNA adduct levels in fetal liver exhibited distinct gestation stage specificity with higher adduct levels attained during mid-gestation compared to other stages of gestation. Adduct levels decreased at a much faster rate during the first 10-15 days compared to 15-50 days after B[a]P treatment. However, 10% of DNA adducts persisted 50 days after treatment in all organs studied. Together, the results suggest that placental adduction accurately indicates fetal exposure. Toxicokinetics of B[a]P and its metabolites as well as maternal, placental and fetal competence in activation and deactivation of B[a]P may be critical determinants in overall fetal risk to genetic damage. Importantly, maximal sensitivity to transplacental DNA damage may be during mid-gestation.

Animals↗
PubMed1993

Low frequency of H-ras activation in naturally occurring hepatocellular tumors of C3H/HeNCr mice.

Previous reports from several laboratories have consistently shown that approximately 30% of spontaneous hepatocellular adenomas and 70-80% of spontaneous hepatocellular carcinomas found in aged B6C3F1 [C57BL/6 (liver tumor resistant) x C3H (liver tumor susceptible)] male mice contain one of three missense point mutations in codon 61 of the H-ras oncogene, CAA-->AAA, CGA or CTA. Irrespective of subline, the C3H mouse, the paternal parent strain of the B6C3F1 hybrid, is more susceptible to spontaneous liver tumorigenesis than the B6C3F1 mouse. However, the role of H-ras in the pathogenesis of hepatocellular tumors in C3H mice is less clear, as widely different frequencies of activation of this gene, but by the same point mutations in codon 61, have been reported by various laboratories. The present study was undertaken to characterize H-ras involvement in hepatocellular tumors of aged C3H/He mice from the NCI-Frederick Cancer Research and Development Center Colony (C3H/HeNCr). Oncogene activation was evaluated in 45 C3H/HeNCr hepatocellular tumors by the NIH 3T3 transfection assays, and point mutations in the H-ras oncogene were detected and characterized in DNA fragments amplified by PCR, using dot blot hybridization analysis with mutation-specific oligonucleotide probes and direct dideoxy sequencing of PCR products. The only transforming gene detected in these tumors by NIH 3T3 transfection was H-ras. Only 17% (1/6) of spontaneous carcinomas and 8% (3/39) of spontaneous adenomas contained transforming H-ras sequences, each with a point mutation in codon 61. In all four cases with H-ras mutations, mutated sequences comprised a minor fraction of total H-ras gene copies in DNA extracted from primary tumors. H-ras mutations thus appear to have arisen relatively late in the pathogenesis of the neoplasms. For comparison, sections of formalin-fixed, paraffin-embedded hepatocellular tumors that occurred in untreated B6C3F1 hybrid mice sired by C3H/HeNCr males were assayed for the same H-ras mutations by PCR and dot blot hybridization. Nine of 13 such tumors (4/6 carcinomas, 5/7 adenomas) were positive. The overall difference in frequency of H-ras codon 61 mutations in hepatocellular tumors in C3H/HeNCr (4/45) versus B6C3F1 (9/13) was highly significant (P = 0.000035, Fisher's exact test). These data indicate that point mutations in H-ras do not generally play a major or an initiating role in spontaneous hepatocarcinogenesis of inbred C3H/HeNCr mice and contrast with the high rate of ras mutations in liver tumors of the B6C3F1 hybrid.

3T3 Cells↗
PubMed1993

Pathology of preneoplastic and neoplastic renal tubular lesions induced in F-344 rats by sodium barbital, a nongenotoxic renal carcinogen and nephrotoxin.

Sodium barbital (NaBB), a long-duration sedative/hypnotic barbiturate, is a nongenotoxic nephrotoxin and induces chronic persistent increases in rates of cell proliferation in renal cortical tubules of male F-344/NCr rats. In 5 of our 2-stage carcinogenesis experiments with NaBB at doses of 500, 1,000, or 4,000 ppm for periods of up to 106 wk of age, renal tubular cell tumors were found in incidences of up to 25% in rats receiving only NaBB while fewer than 1% of controls had renal epithelial tumors. We reviewed renal tubular proliferative lesions found in these studies and classified the lesions based on morphology, histogenesis, and immunohistochemical findings. Renal dysplastic tubules (DTs; atypical hyperplasia), putative preneoplastic lesions rarely seen in controls, were found in the renal cortex of more than 50% of the NaBB-exposed rats. DTs were classified into grades 1-3, based on lesion size and growth patterns. All renal adenomas were usually of the basophilic phenotype, and 70% of basophilic adenomas displayed solid patterns, while tumors with papillary, cystic, or tubular patterns were seen less commonly. By serial or step sectioning of the DTs and tumors, evidence was found indicating that the high grades (grade 2 or 3) of DTs, some of which arose in the P1 or P2 segment of the proximal tubules, were sometimes connected to the adenomas. Vimentin expression was demonstrated immunohistochemically in NaBB-induced renal tubular adenomas but not in normal tubules. Tumors were usually not immunoreactive for glutathione S-transferase, placental form, but heterogeneous immunoreactivity was also seen in some tumors. Lysozyme was absent in preneoplastic and neoplastic lesions induced by NaBB, while some intact normal proximal convoluted tubules were immunoreactive. The common tumor phenotype induced by NaBB, the basophilic solid adenoma, was similar to the most common type of spontaneous renal tumor found in untreated aging F-344 rats. NaBB may promote naturally occurring renal preneoplastic or neoplastic tubular lesions of this unique phenotype, but it is also possible that it may induce these lesions de novo.

Adenoma↗
PubMed1993

Infiltrating angiolipoma of skeletal muscle. Transplacental induction in nonhuman primates by N-nitrosoethylurea.

BACKGROUND: In humans, relatively little is known on the association of prenatal exposure to cancer-causing agents and the development of specific tumors later in life as a consequence. Therefore, the effects on the offspring of carcinogen exposure during gestation and the development of tumors later in life were studied in nonhuman primates. EXPERIMENTAL DESIGN: Pregnancy was confirmed in Erythrocebus patas (patas) and Macaca mulatta (rhesus) by palpation at 27 to 40 days of gestation. Pregnant animals were treated once weekly intravenously from that time with N-nitrosoethylurea according to different dosing regimens for 6 to 19 weeks with 0.05 to 0.2 mmol/kg/injection. RESULTS: A common lesion developing in only the offspring of mothers treated early in pregnancy was identical with the human condition referred to as intramuscular angioma, hemangioma, or infiltrating angiolipoma of skeletal muscle. In the rhesus, one of 7 animals, and in the patas, 18 of 78 monkeys developed these processes (10 to 40% per group). The lesions typically arose within, infiltrated and displaced skeletal muscle. They occurred most commonly in the lower extremities, followed by the upper extremities and the head; they recurred in three cases of incomplete resection but did not metastasize. The tumors were seen mainly in young adults of both sexes (latency range: 4 to 76 months) and consisted of vessels of variable caliber, and to varying degrees, mature adipose and connective tissue, undifferentiated mesenchymal cells, and lymphoid cell aggregates. Ultrastructurally, the endothelium possessed numerous Weibel-Palade bodies and showed strong immunoreactivity for von Willebrand factor by immunohistochemistry and immunoelectron microscopy. CONCLUSIONS: The present investigation suggests a classification of these lesions as infiltrating angiolipoma of skeletal muscle originating from a pluripotent mesenchymal stem cell, caused by exposure to carcinogens during early pregnancy. The great clinical and morphologic similarity of this condition with that observed in humans suggests that it may likewise be caused by exposure to an agent during pregnancy.

Animals↗