N-acetylbenzidine and N,N'-diacetylbenzidine formation by rat and human liver slices exposed to benzidine

The extent to which N-acetylbenzidine and N,N'-diacetylbenzidine are formed may influence benzidine-induced carcinogenesis. This study compared the formation of these metabolites by rat and human liver slices. The relationship between the NAT2 genotype and the formation of these acetylated products was also evaluated in humans. In rat liver slices incubated with 0.05 mM [3H]benzidine for 1 h (n = 3), N-acetylbenzidine and N,N'-diacetylbenzidine represented 8.8 +/- 3.6 and 73 +/- 2.5% respectively of the total radioactivity recovered by HPLC. No unmetabolized benzidine was observed. This suggests that an equilibrium exists between benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine in rat liver slice incubations which favors N,N'-diacetylbenzidine formation. In the presence of 0.1 mM paraoxon, a deacetylase inhibitor, N-acetylbenzidine and N,N'-diacetylbenzidine increased to 13 +/- 0.6 and 79 +/- 0.3% respectively. Within 2 h after incubating human liver slices with 0.014 mM [3H]benzidine (n = 8), benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine represented 19 +/- 5, 34 +/- 4 and 1.6 +/- 0.5%, respectively, of the total radioactivity recovered by HPLC. Thus in the human, conditions in liver slices favor N-acetylbenzidine rather than N,N'-diacetylbenzidine formation. With paraoxon, benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine represented 2 +/- 0.4, 24 +/- 4 and 51 +/- 3%, respectively. This resulted in a 32-fold increase in N,N'-diacetylbenzidine formation. Individuals with rapid NAT2 genotypes formed 1.4-fold more N-acetylbenzidine than slow acetylators. However, this increase was not significant. There was no apparent correlation of N,N'-diacetylbenzidine formation with NAT2 genotype. Similar results were observed when human slices were incubated with 0.09 mM [3H]benzidine. Deacetylase, perhaps more than N-acetyltransferase, influences hepatic metabolism and subsequent carcinogenesis of benzidine in man. These results help explain the species and organ specificity of benzidine carcinogenesis.

Detailed deletion mapping of chromosome 6q in borderline epithelial ovarian tumors

We have used PCR amplification of tandem repeats and Southern blot analysis to study the pattern of allelic loss at chromosome 6q in borderline ovarian tumors and compared that with invasive ovarian carcinomas. DNA from 46 borderline ovarian tissues, 20 invasive ovarian tumor tissues, together with corresponding uninvolved (control) tissues was used. The invasive tumors demonstrated the highest percentage of loss of heterozygosity (13 of 45 informative cases, 29%) at the 6q25-27 locus site. In contrast, the borderline ovarian tumors showed only an 11% frequency of loss of heterozygosity (3 of 26). Our results display a sharp contrast in the pattern of loss of heterozygosity between invasive and borderline ovarian tumors and suggest that allelic loss at chromosome 6q may not be involved in the development of borderline ovarian tumors.

Extended-term cultures of human T-lymphocytes: a practical alternative to primary human lymphocytes for use in genotoxicity testing

A simplified method, using recombinant interleukin-2, foetal bovine serum and freeze-killed feeder cells, has been developed for the mass culture of T-lymphocytes derived from human peripheral blood. In this protocol, bulk cultures can be cryopreserved approximately 8 days after initiation, and subsequent mass cultures generated a further week after recovery. At the end of this period, the lymphocytes have maintained a normal karyotype and cultures from different donors are very similar in terms of rate of cell division and expression of key antigenic markers. Background micronucleus frequencies and dose-responses for micronucleus induction by a reference clastogen, hycanthone, were also very similar in all the cultures examined. Such extended-term T-lymphocyte cultures are potentially valuable in genotoxicity testing, providing cells with the normal human karyotype which can be characterised and handled with the practical convenience of established rodent cell lines.

p53 gene analysis of ovarian borderline tumors and stage I carcinomas

Mutations of the p53 gene are common in human ovarian carcinomas; however, their role in the early development of ovarian cancer is unclear. Twelve ovarian borderline tumors (BTs; eight of them p53 immunopositive) and 10 stage I carcinomas (four of them p53 immunopositive) were studied for genetic alterations in the p53 gene. The study was based on single-strand conformation polymorphism (SSCP) analysis and DNA sequencing of exons 2 through 11 of the p53 gene using DNA preparations from microdissected tumors. Mutations were found in 40% of the carcinomas (including a borderline component adjacent to carcinoma in one lesion) but in none of the pure BTs. These findings suggest that p53 mutations may not be commonly associated with the borderline phenotype of ovarian epithelial tumors but may occur during malignant transformation.

The role of the immunoglobulin heavy chain in human anti-DNA antibody binding specificity

OBJECTIVE

To investigate the structural basis for DNA binding of the natural human IgM lambda monoclonal antibody KIM4.6.

METHODS

An IgM lambda, non-DNA-reactive variant hybridoma was derived during in vitro subcloning of the anti-DNA antibody KIM4.6. The variable (V)-region heavy (H) and light (L) chain genes expressed by the variant hybridoma were amplified by polymerase chain reaction, cloned, sequenced, and compared with those of the KIM4.6 parent and other DNA-binding and non-DNA-binding antibodies.

RESULTS

The VL chain of the variant was identical to that of KIM4.6. In contrast, the VH chain was completely different from the VH chain of the parent but was similar or identical, except in the diversity (D) and joining regions, to the VH chain of the systemic lupus erythematosus (SLE) IgG anti-DNA antibody T14 and SLE IgM nephritogenic anti-DNA antibodies NE-1 and NE-13.

CONCLUSION

The expression of the KIM4.6 VL chain is not sufficient for DNA specificity. The VH chain and its D region play a key role in conferring DNA binding of the KIM4.6 anti-DNA antibody.

CYP1A1 messenger RNA levels in placental tissue as a biomarker of environmental exposure

The human CYP1A1 gene codes for an inducible enzyme system involved in biotransformation of certain xenobiotics, including polycyclic aromatic hydrocarbons; some of the metabolites are carcinogenic and mutagenic. Effects of environmental exposures (smoking, air pollution, and diet) on CYP1A1 gene induction in placental tissue and the modulation of induction by the CYP1A1 MspI RFLP were evaluated in two groups from Poland: 70 mother-child pairs from Krakow, a city with elevated air pollution; and 90 pairs from Limanowa, a less polluted area. Compared to placentas from nonsmoking women, CYP1A1 mRNA levels were significantly increased in placentas from current smokers (P < 0.001). Ex-smokers also had significantly higher placental mRNA levels, including women who quit smoking prior to pregnancy (P < 0.01). A marginal increase in CYP1A1 mRNA with environmental tobacco smoke exposure was evident. Within Krakow, there was an increase in CYP1A1 mRNA with ambient pollution at the place of residence for each woman, which was significant among women who were not employed away from the home (P < 0.05 controlling for smoking status, diet, and use of coal for heating). Significant increases in mRNA were associated with dietary consumption of smoked meat, cheese, and fish (P < 0.01). The CYP1A1 MspI RFLP was not a significant determinant of CYP1A1 mRNA levels after controlling for smoking and other variables. Human placenta provides a readily available and responsive system that can serve as a model for evaluating environmental and genetic determinants of CYP1A1 induction.

Nomenclature for N-acetyltransferases

A consolidated classification system is described for prokaryotic and eukaryotic N-acetyltransferases in accordance with the international rules for gene nomenclature. The root symbol (NAT) specifically identifies the genes that code for the N-acetyltransferases, and NAT* loci encoding proteins with similar function are distinguished by Arabic numerals. Allele characters, denoted by Arabic numbers or by a combination of Arabic numbers and uppercase Latin letters, are separated from gene loci by an asterisk, and the entire gene-allele symbols are italicized. Alleles at the different NAT* loci have been numbered chronologically irrespective of the species of origin. For designation of genotypes at a single NAT* locus, a slash serves to separate the alleles; in phenotype designations, which are not italicized, alleles are separated by a comma.

Immunoglobulin gene sequence analysis of anti-cardiolipin and anti-cardiolipin idiotype (H3) human monoclonal antibodies

Heavy and light chain variable region nucleotide sequences were derived from 6 human hybridoma antibodies which bear characteristics of antibodies associated with the phospholipid antibody syndrome. All antibodies originated from non-autoimmune individuals and were polyspecific. Four of these reacted with cardiolipin (and other antigens) and three carried the H3 idiotype which is expressed on a high percentage of disease-associated anti-cardiolipin antibodies. This idiotype was localized to the lambda light chain of the H3 monoclonal antibody and found on two other antibodies which like H3 expressed V lambda 4 or the related V lambda 3 subgroup light chains. The H3 idiotype however did not define these subgroups nor was it required or sufficient for anti-cardiolipin activity. Anti-cardiolipin binding was found in VH1, VH3 and VH4 heavy chain families and in a V kappa 1 light chain. The D region was diverse in both length and gene usage. Although all cardiolipin binding antibodies showed little deviation from germline variable (V) gene sequences, where mutations occurred they tended to be replacement mutations and clustered in complementarity determining regions (CDR) suggesting these B cells were derived from antigen-driven responses. These results from our panel of hybridomas and their comparison to other human antibodies provide extensive information on the diversity of genetic elements which can be used by cardiolipin-binding antibodies. We also show gene sequences which encode the disease-associated H3 idiotype and its location on lambda light chains, which imply that some labda light chains may be preferentially utilized in auto-reactive hybridomas.

Polycyclic aromatic hydrocarbon-DNA adducts in smokers and their relationship to micronutrient levels and the glutathione-S-transferase M1 genotype

Sixty-three male cigarette smokers were entered into a cross-sectional study to determine whether inverse associations existed between polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels and intake/serum levels of vitamin A, vitamin C and vitamin E. Associations between PAH-DNA adducts and intakes of carotene, as well as serum levels of beta-carotene, were also determined. Fasting blood samples were collected for assays of PAH-DNA adducts in circulating mononuclear cells, plasma cotinine and serum levels of vitamin A, beta-carotene, vitamin C and vitamin E. Since genetic deficiency in the detoxifying enzyme glutathione S-transferase M1 (GSTM1) has been associated with increased risk of lung cancer, GSTM1 genotype was also determined. Analysis of PAH-DNA adducts by competitive enzyme-linked immunosorbent assay (ELISA) indicated that 70% of the subjects had detectable adducts, with a mean of 4.38 adducts/10(8) nucleotides (range 1.00-24.1/10(8)). Pearson's method was utilized to determine whether any associations existed between the various host variables and PAH-DNA adducts. Previously, no significant associations were found between PAH-DNA adducts and cigarettes smoked/day, pack-years, daily/life-time tar exposures or plasma cotinine levels (Santella et al., Carcinogenesis, 13, 2041-2045, 1992). PAH-DNA adducts were inversely associated with serum cholesterol-adjusted vitamin E levels (r = -0.25, P < or = 0.05) and with smoking-adjusted vitamin C serum levels (r = -0.22, P < or = 0.09). Stratification by GSTM1 genotype indicated that these associations were limited to subjects with the null genotype. The relationship between adducts and serum cholesterol-adjusted vitamin E was significant in those of the null genotype (r = -0.38, P < or = 0.04), but not in those with the gene present (r = -0.12, P = 0.5). Similarly, for smoking-adjusted vitamin C, the relationship with adducts was stronger in subjects with the null genotype (r = -0.35, P < or = 0.06) than in those with GSTM1 present (r = -0.05, P = 0.77). These results are consistent with findings of prior epidemiological studies identifying significant inverse associations between anti-oxidant micronutrient status or GSTM1 genotype and the incidence of lung cancer. Additional studies should be conducted to confirm a possible role for vitamin E in PAH-DNA adduct formation and to explore further the possible roles of vitamin A, beta-carotene and vitamin C in modulating adduct formation and lung cancer risk.

p53 expression in ovarian borderline tumors and stage I carcinomas

Seventy-nine ovarian serous and mucinous borderline tumors, 36 stage I carcinomas and 39 stage II-IV carcinomas were studied for p53 protein accumulation with monoclonal antibody PAb1801.p53 protein was expressed in 14% of borderline tumors, 36% of stage I carcinomas, and 64% of higher stage carcinomas. All immunopositive carcinomas accumulated p53 protein in the primary tumor, and 95% of them showed concordance in staining among different tissue blocks. A difference in frequency of p53 protein accumulation between stage I and higher stage serous carcinomas was not statistically significant. p53 positivity was associated with microinvasion, microcarcinoma and coexistent carcinoma in mucinous borderline tumors (P = .025). An association between p53 protein expression and poor tumor differentiation in Stage I carcinomas as statistically significant (P = .03). p53 positivity was observed in a poorly differentiated endometrioid carcinoma as well as in adjacent benign endometriotic tissue. These results suggest that p53 abnormalities may be early events in ovarian cancer, possibly contributing to malignant transformation of some borderline tumors, endometriosis and other carcinoma precursors.

The emerging role of magnetic resonance imaging in rheumatology

The role of magnetic resonance imaging (MRI) in imaging the central nervous system and in orthopedic radiology is now well accepted. Numerous applications of this technique also exist in the field of rheumatology, and it is anticipated that MRI will play an important part in the evaluation of treatments for the arthritides. In addition, MRI allows noninvasive investigation of other rheumatologic problems, such as avascular necrosis, tendon disorders and myopathy. This review outlines the current applications of MRI in rheumatologic practice.

Immunoglobulin V region sequences of two human antiplatelet monoclonal autoantibodies derived from B cells of normal origin

Autoimmune thrombocytopenia has been attributed to the presence of antiplatelet autoantibodies which mediate platelet destruction. The derivation of these autoantibodies is presently unknown. While normal B cells do not produce these autoantibodies in vivo, it has been demonstrated in vitro by somatic cell hybridization that the B lymphocytes of nonthrombocytopenic individuals have the potential to produce antiplatelet autoantibodies. Antigen specificities of these antibodies are similar to those seen in autoimmune thrombocytopenic purpura and the lupus anticoagulant syndrome. The immunoglobulin V region genes encoding two such human monoclonal antiplatelet antibodies, an anti-GP IIb (STO 171) and an anti-phospholipid antibody (STO 103) derived from tonsillar lymphocytes of a non-thrombocytopenic male, have now been sequenced. These antiplatelet antibodies were found to be encoded by unmutated germline VH and VK genes. The third complementarity determining region (CDR3) of the genes encoding both of these antibodies have unique D regions with evidence of N-nucleotide additions, and the light chain genes show VK-JK junctional diversity. STO 103 is encoded by the VH4 V71-2 germline gene and a truncated JH4 gene. The light chain gene showed closest homology with the VK4 Humk18 gene and JK2 gene. STO 171 showed closest homology with the VH4.18 germline gene and had a complete germline JH6 gene. The light chain of STO 171 is encoded by the VK3 Humkv325 germline gene, which is also used by some rheumatoid factors and cold agglutinins, and a JK4 gene. Although these antibodies were not derived from circulating B cells or found to be actively producing antibody at the time they were harvested, it is possible that naturally occurring antibody producing B cells, similar to those represented here, are recruited for the development of pathogenic autoantibodies in immune thrombocytopenia.

Ethnic variation in the CYP2E1 gene: polymorphism analysis of 695 African-Americans, European-Americans and Taiwanese

Human cytochrome P4502E1 (CYP2E1) is inducible by ethanol and is involved in metabolism of many known carcinogens including N-nitrosodimethylamine, butadiene, benzene, and carbon tetrachloride. A 50-fold variability in CYP2E1 enzyme activity in humans has been observed but it is unknown whether the basis for this variation is genetic or environmental. Recently, two restriction fragment length polymorphisms (RFLPs) within the CYP2E1 gene have been suggested as genetic markers of risk for cancer. The first was a Rsa I polymorphism in the 5' regulatory region that appeared to alter transcriptional activation of the gene and the second was a Dra I polymorphism located approximately 7000 bp downstream in an intron. Rare alleles at each of these loci have been associated with a reduced risk for lung cancer in Japanese and Swedish populations. We have used a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to determine the genotype frequency for each of these CYP2E1 RFLPs in 695 individuals of Taiwanese, African-American or European-American background. Genotype and allele frequencies for Taiwanese were significantly different from those of African-Americans and European-Americans at either Rsa I or Dra I sites (p < 0.0001). Allele frequencies for African-Americans and European-Americans were significantly different at the Rsa I site (p = 0.03). The rare alleles (c2 and C) occurred at frequencies of 0.28 and 0.24 in Taiwanese, 0.01 and 0.08 in African-Americans, and 0.04 and 0.11 in European-Americans. In addition, we describe three haplotypes common to all three population samples and a fourth haplotype that was only detected in the Taiwanese population sample. This fourth haplotype may have been caused by a recombination event between these markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography

PURPOSE

To determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis.

METHODS

A retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast.

RESULTS

Three cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous).

CONCLUSION

MR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.

Early de novo ovarian carcinoma. A study of fourteen cases

BACKGROUND

The search for methods of early detection of ovarian carcinoma in recent years has emphasized the lack of information regarding the histologic features of early carcinoma or its precursor lesions; few examples of early de novo ovarian carcinoma have been reported.

METHODS

The clinicopathologic features of 14 cases of early ovarian carcinoma detected as microscopic findings in grossly normal ovaries retrieved from a consultation practice and the files of the Massachusetts General Hospital were reviewed.

RESULTS

The patients ranged in age from 27-65 years (mean, 50 years). Three women had a family history of ovarian carcinoma and six did not. The tumors ranged from microscopic to 7 mm in greatest dimension; all were unilateral and four were multifocal. One tumor involved the surface and its crypts; four, the surface and superficial cortex; eight, the superficial cortex only; and in one, surface involvement was not ascertainable. Ten carcinomas were serous; one, endometrioid; one, clear cell; and two, poorly differentiated, of undetermined cell type. Severe atypia of the noncarcinomatous surface epithelium or its inclusion cysts was additionally present in three cases. Among the seven patients whose diagnoses were made at the time of oophorectomy who had follow-up data of at least 2 years or until recurrence or death, five were alive without recurrences, one was alive with recurrence, and one died of tumor. Two of the three women died whose ovarian tumors were diagnosed retrospectively on discovery of subsequent peritoneal carcinomatosis, and the third was alive with recurrent tumor. No relation between any clinical or pathologic feature and survival was apparent in this small series except for a suggestion that well differentiated tumors had a good prognosis.

CONCLUSIONS

These findings document that at least a subset of ovarian epithelial cancers develops de novo. The guarded prognosis associated with these tumors despite their minute dimensions raises questions about the value of current screening techniques for early detection of ovarian cancer.

Prognostic significance of DNA content in epithelial ovarian cancer

The prognostic significance of cellular DNA content of epithelial ovarian cancer as determined by flow-cytometric analysis of paraffin-embedded tumor blocks was investigated in 87 patients. Seventy-five percent of tumors were DNA aneuploid and 25% were DNA diploid. The survival at median follow-up for patients with DNA diploid tumors (68%) was significantly longer than for DNA aneuploid tumors (49%; P = 0.003). The other prognostic factors which significantly affected survival were stage (P < 0.0001), tumor grade (P < 0.006), and residual disease at completion of initial surgery (P = 0.0005). When patients were separated into low-stage and advanced-stage disease, DNA content was a significant prognostic variable for survival in Stage I and II patients (P = 0.05). In Stage III and IV patients, DNA content had no independent prognostic significance. There were 33 patients who underwent second-look surgery. Seven of 15 patients (47%) with negative second-look surgery were DNA aneuploid, whereas 17 of 18 patients (94%) with positive second-look surgery were DNA aneuploid. Therefore, there was a much higher likelihood of positive second-look in the DNA aneuploid group (17/24) compared to the DNA diploid group (1/9) (P = 0.003). In addition for those patients with negative second-look surgery, none (0/8) of the DNA diploid tumors recurred; however, 3 of 7 (43%) of the DNA aneuploid tumors recurred and died. Cox proportional/hazards analysis showed that DNA content is an independent prognostic factor for survival in epithelial ovarian cancer. Aneuploid DNA content in ovarian tumors is also correlated with more aggressive biologic behavior, and therefore, a worse clinical course.

Mutation spectra in Salmonella of complex mixtures: comparison of urban air to benzo[a]pyrene

We used an ion-exchange procedure coupled to the Salmonella assay to fractionate the dichloromethane-extractable particulate organics from an urban air sample collected in Boise, Idaho. A resulting base/neutral fraction contained 81% of the mutagenic activity but only 36% of the mass of the unfractionated sample. Chemical analysis showed that polycyclic aromatic hydrocarbons (PAHs) accounted for much of the mutagenic activity of the air sample. Colony probe hybridization, PCR, and DNA sequence analysis were then used to determine the mutations induced by the complex mixtures and a model PAH, benzo[a]pyrene (BAP) in approximately 900 revertants of the frameshift hisD3052 allele and approximately 400 revertants of the base-substitution hisG46 allele. The majority (93-94%) of the mutations induced at the frameshift allele in strain TA98 by the whole or base/neutral fraction of the urban air sample was a hotspot 2-base deletion of a CG or GC within the sequence CGCGCGCG. The remaining mutations were complex frameshifts that consisted of -2 or +1 frameshifts associated with a flanking base substitution. BAP induced a somewhat similar pattern of mutations, with 70% being the hotspot mutation, 23% being complex frameshifts, and the remaining being deletions. The inferred base-substitution specificity associated with the complex frameshifts at the hisD3052 allele (primarily G.C-->T.A transversions) was consistent with the observation that this same transversion was the primary mutation induced by the whole urban air sample and BAP at the base-substitution allele in strain TA100. At the frameshift allele, adducts that promote correct incorporation/slippage could account for hotspot mutations, whereas those that promote misincorporation/slippage could account for complex frameshifts. At the base-substitution allele, a mixture of adducts or of adducts with multiple conformations could account for the observed proportion of transitions and transversions. Combined with the bioassay-directed chemical analysis, these results from the first mutation spectra of a complex mixture suggest that such spectra reflect the dominance of particular classes of chemical mutagens within the mixture.

Dioxin-responsive genes: examination of dose-response relationships using quantitative reverse transcriptase-polymerase chain reaction

The purpose of the present experiments was to examine dose-response relationships for induction of hepatic mRNA following a single administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to rats. The induction of cytochrome P450-1A1 (CYP1A1) mRNA is compared to other "dioxin-responsive" genes including UDP-glucuronosyltransferase I, plasminogen activator inhibitor 2, and transforming growth factor alpha using a sensitive reverse transcriptase-polymerase chain reaction-based method. Sample-to-sample variability in amplification is a concern in using polymerase chain reaction to quantitate biological responses. However, in the present study recombinant RNA templates were synthesized to use as internal standards in both the reverse transcription and the polymerase chain reaction steps. The induction of CYP1A1 mRNA was extremely sensitive to TCDD treatment with increases observed at doses as low as 1 ng/kg body weight. The induction of CYP1A1 mRNA correlated highly (R2 > 0.90) with an increase in ethoxyresorufin-o-deethylase activity, a CYP1A1-associated enzyme activity. However, induction of CYP1A1 mRNA levels was detected at lower TCDD doses than was ethoxyresorufin-o-deethylase activity, reflecting the greater sensitivity of the reverse transcription-polymerase chain reaction approach to detect transcriptional activation of the CYP1A1 gene. UDP-glucuronosyltransferase I mRNA was increased over control (5-fold) but required 1000-times higher TCDD doses (1 microgram/kg) to result in a significant increase than did CYP1A1. Plasminogen activator inhibitor 2 and transforming growth factor alpha mRNA, both previously shown to be induced by TCDD in human keratinocytes, were not increased in rat liver. Hence, these studies reaffirm that TCDD acts through classical receptor mechanisms with gene-to-gene differences in responsiveness. The reverse transcription-polymerase chain reaction method developed to measure mRNA for dioxin-responsive genes in rat liver will allow for measuring multigene and tissue responses to TCDD and other xenobiotics with high sensitivity, reproducibility, and adaptability and should increase our understanding of various dose-response relationships.

DNA ploidy status: its impact on early-stage endometrial adenocarcinoma

DNA ploidy status, as determined by flow cytometry, has been useful in predicting survival in certain malignancies. Between January 1975 and January 1985, 85 cases that met the inclusion criteria-pathologic stage I endometrial adenocarcinomas, primary surgical therapy, endometrioid cell type, and adequate paraffin-block samples-were analyzed by DNA flow cytometry. Depth of myometrial invasion, tumor grade, and presence of lymphatic vascular space invasion were established in all cases. Ten of the 85 tumors (12%) were aneuploid. The median follow-up was 9 years with a range of 2 to 16 years. There were 9 recurrences with 5 deaths from cancer, and 8 patients died of intercurrent disease. The relative hazards for recurrence associated with aneuploidy, S-phase fraction, grade 3 histology, and any myometrial invasion were 3.1, 3.18, 3.2, and 4.9, respectively, but did not reach statistical significance. Because of the low recurrence and mortality rate in this homogeneous group, a larger sample will be necessary to fully establish a role for DNA ploidy status in identifying a poor prognostic subset.

CYP1A1 mRNA levels as a human exposure biomarker: use of quantitative polymerase chain reaction to measure CYP1A1 expression in human peripheral blood lymphocytes

Accurate human risk assessment requires sensitive methods to evaluate dose-response relationships, especially following low level exposures. We have developed a reverse transcriptase polymerase chain reaction (RT-PCR) method to quantitative cytochrome P450-1A1 (CYP1A1) mRNA levels in human blood lymphocytes. Many polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene, and chlorinated PAH such as polychlorinated dibenzodioxins, dibenzofurans and biphenyls induce CYP1A1 expression through activation of an endogenous protein, the Ah receptor. Using a quantitative competitive RT-PCR method that included a synthetic internal standard we determined copy numbers of CYP1A1 mRNA in resting as well as mitogen-stimulated human blood lymphocytes. In mitogen-stimulated human blood lymphocytes assay variation was approximately 10% for measurement of this low expression gene and mRNA levels correlated well with ethoxyresorufin-O-deethylase (EROD) activity. The expression of mRNA was induced 20-fold upon culturing human lymphocytes with 10 nM TCDD. In nonstimulated, uninduced lymphocytes CYP1A1 levels are extremely low (1000 copies mRNA/10(4) cells) and cannot be measured by EROD activity. Studies of CYP1A1 mRNA expression in chemically-exposed populations are in progress.

Molecular analysis of mutations induced at the hisD3052 allele of Salmonella by single chemicals and complex mixtures

More single chemicals and complex environmental mixtures have been evaluated for mutagenicity at the hisD3052 allele of Salmonella, primarily in strain TA98, than in any other mutation assay. The development of colony probe hybridization procedures and the application of the polymerase chain reaction and direct DNA sequencing has permitted rapid molecular access to this allele. We discuss these techniques and the resulting mutation spectra that have been induced by a variety of environmental mutagens and complex mixtures. A common GC or CG deletion within a hot-spot region of the sequence dominates most of the spectra. In addition to this two-base deletion, we have recovered about 200 other types of mutations within the 72-base target for reversion of the hisD3052 allele. These include a variety of deletions (as large as 35 bases), duplications (as large as 46 bases), and complex mutations involving base substitutions. The quasipalindromic nature of the target sequence and its potential to form DNA secondary structures and slippage mismatches appear to be an important basis for the mutability of this allele.

Epithelial ovarian tumors of borderline malignancy: long-term follow-up

Thirty-nine patients underwent primary surgery for epithelial ovarian tumors of low malignant potential at the Massachusetts General Hospital between 1970 and 1980. Eighty-five percent of patients were found to have Stage I disease and 15% were found to have Stage III disease. Fifty-four percent of patients had a tumor with serous histology, 39% had a tumor with mucinous histology, and the remainder of patients had tumors with an endometrioid or mixed-cell type. Second malignancies and benign ovarian tumors were frequently found concomitantly with the borderline tumors or in follow-up. Gastrointestinal and endometrial adenocarcinomas were the most common second malignancies and were frequently found associated with a borderline tumor of serous histology. Follow-up was available in all 39 patients (100%). Mean time of follow-up was 11.8 years. Sixty-nine percent of patients are clinically without evidence of disease with a mean follow-up of 14.7 years, 23% died of other causes, 5% died of disease, and 3% died with disease and sepsis. All patients dying with disease did so within 7.3 years of their primary surgery. Seven patients underwent conservative surgery, defined as preservation of some ovarian tissue. Six of 7 patients are clinically free of disease with a mean follow-up of 14.6 years; 1 patient died of other causes. No patients treated conservatively had a recurrence of their disease.

Genotype/phenotype discordance for human arylamine N-acetyltransferase (NAT2) reveals a new slow-acetylator allele common in African-Americans

Carcinogenic arylamines are acetylated by the hepatic N-acetyltransferase. This enzyme is polymorphic in humans and in some epidemiological studies, the slow-acetylator phenotype has been associated with higher risk of bladder cancer and lower risk of colorectal cancer. The presence of two germline copies of any of several mutant alleles of the NAT2 gene produces a slow-acetylation phenotype. We used a PCR-RFLP technique to identify three known slow-acetylator alleles (M1, M2 and M3). Comparison of results from PCR-RFLP genotyping with caffeine metabolism phenotyping in 42 individuals suggested that an additional slow-acetylator allele was present in our sampled population. We sequenced the NAT2 gene for several discordant slow-acetylator individuals and found a G > A base-change in codon 64 that caused a Arg > Glu amino acid substitution. This sequence change, termed the 'M4' allele, was found in all of the discordant individuals in our population and apparently causes a slow-acetylation phenotype. In addition, we have determined that NAT2 allele frequencies in 372 Caucasian-Americans (WT = 0.25, M1 = 0.45, M2 = 0.28, M3 = 0.02, and M4 = 0.00) and in 128 African-Americans (WT = 0.36, M1 = 0.30, M2 = 0.22, M3 = 0.02 and M4 = 0.09) are significantly different (P < 0.0001). The M4 allele was not found in 372 unrelated Caucasians and appears to be of African origin.