Interaction between smoking, GSTM1 deletion and colorectal cancer: results from the GSEC study.

Cigarette smoking has inconsistently been associated with an increased risk of colorectal cancer. One of the enzymes responsible for the detoxification of the carcinogenic compounds present in tobacco smoke is glutathione S-transferase-mu (GST-mu). The gene that codes for this enzyme is GSTM1. In this study, we evaluated the associations and interaction between GSTM1 deletion, smoking behaviour and the development of colorectal cancer. We performed a pooled analysis within the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens (GSEC). We selected six studies on colorectal cancer, including 1130 cases and 2519 controls, and restricted our analyses to Caucasians because the number of patients from other races was too limited. In addition we performed a meta-analysis including the studies from the GSEC database and other studies identified on MEDLINE on the same subject. The prevalence of the GSTM1 null genotype was within the range reported in other studies: 51.8% of the cases had the GSTM1 null genotype versus 56.6% of the controls. No significant association between the GSTM1 null genotype and colorectal cancer was found (odds ratio 0.92, 95% confidence interval 0.73-1.14). Our results suggest a possible positive association between lack of the GST-mu enzyme and colorectal cancer for non-smoking women (odds ratio 1.47, 95% confidence interval 0.80-2.70). There was no interaction between the effects of smoking and GSTM1 genotype on colorectal cancer risk in men and women (chi2=0.007, p=0.97). Our findings do not support an association between the GSTM1 null genotype and colorectal cancer. In addition, we did not find any modification of the smoking-induced colorectal cancer risk by GSTM1 genotype

Metabolic gene polymorphism frequencies in control populations.

Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

Stereotactic breast biopsy of nonpalpable lesions: determinants of ductal carcinoma in situ underestimation rates.

PURPOSE: To measure the effect of biopsy device, probe size, mammographic lesion type, lesion size, and number of samples obtained per lesion on the ductal carcinoma in situ (DCIS) underestimation rate. MATERIALS AND METHODS: Nonpalpable breast lesions at 16 institutions received a histologic diagnosis of DCIS after 14-gauge automated large-core biopsy in 373 lesions and after 14- or 11-gauge directional vacuum-assisted biopsy in 953 lesions. The presence of histopathologic invasive carcinoma was noted at subsequent surgical biopsy. RESULTS: By performing the chi(2) test, independent significant DCIS underestimation rates by biopsy device were 20.4% (76 of 373) of lesions diagnosed at large-core biopsy and 11.2% (107 of 953) of lesions diagnosed at vacuum-assisted biopsy (P <.001); by lesion type, 24.3% (35 of 144) of masses and 12.5% (148 of 1,182) of microcalcifications (P <.001); and by number of specimens per lesion, 17.5% (88 of 502) with 10 or fewer specimens and 11.5% (92 of 799) with greater than 10 (P <.02). DCIS underestimations increased with lesion size. CONCLUSION: DCIS underestimations were 1.9 times more frequent with masses than with calcifications, 1.8 times more frequent with large-core biopsy than with vacuum-assisted biopsy, and 1.5 times more frequent with 10 or fewer specimens per lesion than with more than 10 specimens per lesion.

Absence of stimulation of poly(ADP-ribose) polymerase activity in patients predisposed to colon cancer.

Poly(ADP-ribose)polymerase (PARP) has been implicated in DNA repair mechanisms and the associated activity shown to markedly increase after DNA damage in carcinogen-treated cells. A defective DNA repair has been associated to the aetiology of human cancers. In order to assess the potential role of this enzyme in cellular response to DNA damage by gamma-radiation, we studied the activity of PARP in patients with familial adenomatous polyposis (FAP). We compared poly(ADP-ribose)polymerase activity by the rate of incorporation of radioactivity from [3H]adenine-NAD+ into acid-insoluble material in permeabilized leucocytes from FAP patients and healthy volunteers. Concomitantly, the intracellular levels of NAD+--the substrate for the PARP--and the reduced counterpart NADH were determined using an enzymatic cycling assay 30 min after [60Co] gamma-ray cells irradiation. Our results demonstrate that a marked stimulation of PARP activity is produced upon radiation of the cells from healthy subjects but not in the FAP leucocytes, which concomitantly show a marked decrease in total NAD-/NADH content. Our observations point to a role of PARP in the repair of the gamma-radiation-induced DNA lesions through a mechanism that is impaired in the cells from FAP patients genetically predisposed to colon cancer. The differences observed in PARP activation by gamma-radiation in patients and healthy individuals could reflect the importance of PARP activity dependent on treatment with gamma-rays. The absence of this response in FAP patients would seem to suggest a possible defect in the role of PARP in radiation-induced DNA repair in this cancer-prone disease.

Increased frequency of wild-type arylamine-N-acetyltransferase allele NAT2*4 homozygotes in Portuguese patients with colorectal cancer.

Here we report that colorectal cancer patients show a markedly higher frequency (3-fold) of wild-type NAT2*4 allele homozygotes than the control population. However, a marked difference in NAT2*4/NAT2*4 genotype frequency associated with the patients gender was observed pointing to a male-specific effect of this genotype as a risk factor in colon cancer. The arylamine-N-acetyltransferase (E.C. 2.3.1.5.) NAT2, a phase II detoxification enzyme, has been implicated in procarcinogen activation, namely from food contained arylamines, cigarette smoking, as well as environmental amines of various types. NAT2 is encoded by a polymorphic gene presenting several allelic variants encoding partially inactive enzymes expressed in human liver and colon. Epidemiological studies based on phenotype determination have long indicated the importance of the NAT2 active phenotype as a susceptibility factor in colorectal cancer. In the present study we investigated the NAT2 allelic frequencies and genotype distribution in a group of 114 unrelated colorectal cancer patients, in parallel with 201 healthy Portuguese subjects. We first demonstrate that the frequency of the wild-type NAT2*4 allele in the Portuguese sample population (23.4%) does not significantly differ from the values described for other Europeans. Besides the 3-fold higher frequency of NAT2*4 homozygotes found in colorectal cancer subjects, the NAT2*4/NAT2*5A compound genotype, known to determine a faster acetylator phenotype than other heterozygotic combinations, also increased by the same order of magnitude. These two genotypes represent 32% of the patients population versus 11% of the healthy controls. Taken together, our results strongly indicate that NAT2 genotype, particularly NAT2*4 allele zygosity, constitutes an individual susceptibility trait associated with sporadic colorectal cancer development, probably due to the local dietary habits in Portugal.

Identification of a functional glucocorticoid response element in the CYP3A1/IGC2 gene.

The rat CYP3A subfamily of cytochrome P450 consists of steroid- and drug-metabolizing enzymes inducible by pregnenolone 16alpha-carbonitrile and by supra-physiological doses of dexamethasone. The induction of CYP3A by dexamethasone has been proposed to be mediated by a mechanism distinct from the glucocorticoid receptor mediated response. However, a synergistic induction of CYP3A has been observed with physiological doses of glucocorticoids and other CYP3A inducers. We have identified the presence of a glucocorticoid-responsive element in the CYP3A1/IGC2 gene that mediates the induction with physiological doses of glucocorticoids. A 219-bp dexamethasone responsive fragment of the CYP3A1/IGC2 gene localized at -2100/-1882 bp upstream of the transcription initiation site was identified in transfection experiments with HepG2 cells. Maximum induction was achieved with 50-100 nM dexamethasone. DNase I footprinting analysis revealed two glucocorticoid receptor-protected sequences in the 5' flank of the CYP3A1/IGC2 gene. Point mutations in footprint I (-1982/-1960-bp) completely abolished binding and transcription activation whereas a mutation in footprint II (-2001/-1986-bp) only decreased the binding and had no effect on transcription activation. These results led to the conclusion that the glucocorticoid response element present in footprint I mediated the dexamethasone response in transfection experiments with HepG2 cells. Pregnenolone 16alpha-carbonitrile failed to induce any transcriptional effect mediated by this response element in the HepG2 cells.

Atypical ductal hyperplasia diagnosed at stereotactic breast biopsy: improved reliability with 14-gauge, directional, vacuum-assisted biopsy.

PURPOSE: To compare histologic findings of atypical ductal hyperplasia (ADH) at 14-gauge, directional, vacuum-assisted breast biopsy (hereafter, vacuum-assisted biopsy) and at 14-gauge, automated, large-core breast biopsy (hereafter, large-core biopsy) with findings at histologic examination after surgical biopsy. MATERIALS AND METHODS: Nonpalpable breast lesions were diagnosed as ADH at histologic examination after vacuum-assisted biopsy in 88 lesions in seven institutions and after large-core biopsy in 55 previously reported lesions. Histologic findings at subsequent surgical biopsy were compared for the presence of carcinoma. RESULTS: On the basis of histologic findings of carcinoma at surgical biopsy, the diagnosis of ADH was not correct in 26 (48%) of 54 lesions sampled at large-core biopsy and in 13 (18%) of 74 lesions sampled at vacuum-assisted biopsy (Fisher exact test, P < .0004). More tissue specimens were obtained at vacuum-assisted biopsy (mean, 15.8 specimens) than at large-core biopsy (mean, 9.7 specimens). Individual specimens were twice as large at vacuum-assisted biopsy (mean, 34 mg) as at large-core biopsy (mean, 17 mg) (previously reported). CONCLUSION: ADH was diagnosed 2.7 times more reliably at vacuum-assisted biopsy than at large-core biopsy (with no increase in complications) with most of the improvement as a result of acquisition of more than 10 specimens per lesion, but carcinoma was sufficiently underestimated with both methods to necessitate surgical biopsy.

Nonpalpable breast lesions: correlation of stereotaxic large-core needle biopsy and surgical biopsy results.

One hundred women, each with a single nonpalpable breast lesion evident at mammography, underwent computer-guided sterotaxic 14-gauge needle biopsy followed by hook-wire localization and open surgical biopsy. Lesions were not less than 5 mm in diameter. Core biopsy yielded essentially correct findings in 96 cases and in 35 of 36 cancers. Open surgery yielded the correct findings in 97 cases and also in 35 of 36 cancers. Two fibroadenomas were missed at core biopsy and one was missed at surgical biopsy. There was complete or partial histologic agreement in 94 cases. This is further evidence that in selected cases, stereotaxic core biopsy can be as accurate as open surgical biopsy.

Modulation of P-450 IIC7 and IIIA1,2 mRNA in pre-neoplastic liver. Effect of promotion by phenobarbital.

P-450 IIC7 and IIIA2 mRNAs are constitutively expressed in the hepatic tissue under developmental control. Both forms--as well as IIIA1, 90% homologous to IIIA2 mRNA--display positive modulation by phenobarbital a prototype inducer of the liver monooxygenases and a strong promoter of experimental chemical hepatocarcinogenesis. In the present work the variations in the concentration of these P-450 mRNA were studied in rats submitted to the hepatocarcinogenic protocol of Solt and Farber. We demonstrate that a decrease in the relative concentrations of P-450 IIC7 and IIIA1, 2 mRNA is set up along the tumor promotion stage. Animals--starting the experimental carcinogenic protocol at pubertal age--show a partial inhibition of the physiological expression of P-450 IIIA1,2 mRNA associated to male sex maturation. Administration of phenobarbital results in an acceleration of the pre-neoplastic process which is concomitant with an induction of P-450 IIC7 as well as IIIA1,2 at the earlier promotion stages. P-450 mRNA concentration markedly decreases as the preneoplastic process develops. While an impaired P-450 IIIA1,2 mRNA relative abundance is observed, an inversion of the modulation of P-450 IIC7 as well as of the male phenotype marker alpha-2u-globulin mRNA arises as the tumor promotion stage progresses, both mRNA becoming repressed in response to phenobarbital.

[Modulation of mRNAs P450 and hepatocarcinogenesis promotion]. / Modulation des mRNAs P450 et promotion de l'hépatocancérogenèse.

The adaptive response of the liver to phenobarbital is characterized by a strong cell hypertrophy and coordinate induction of specific P450 forms (IIB1, 2; IIC7, IIIA1). The pattern of active mRNA is significantly changed, demonstrating the establishment of PB phenotype. Employed as a promoting agent in experimental hepatocarcinogenesis, PB triggers a significantly different, uncoordinated response. Only P450 IIB1 is positively modulated while P450 IIC7 mRNA becomes repressed. Mechanisms underlying the differential P450 adaptative response to PB in the initiated versus non-initiated liver are discussed in the light of both the importance of epigenetic events and the possible role of P450 mono-oxygenases in hepatocarcinogenic promotion by PB.

Effect of rat developmental stage at initiation on the expression of biochemical markers during liver tumor promotion.

The phenotypic response of rat liver to a carcinogenic protocol involving initiation/selection and promotion with and without phenobarbital (PB) feeding was studied in pubertal and adult male rats. Considering the early presence of preneoplastic nodular areas, it appeared that pubertal rats, initiated at 6-7 weeks, presented a higher susceptibility to the protocol than adult rats initiated at 9-10 weeks. Altered liver phenotype was characterized by: (1) gamma-glutamyl-transpeptidase (GGT) and glutathione S-transferase (GST) activities; (2) the expression of two forms of cytochrome P-450; de novo PB-inducible P-450 II B 1,2 and P-450 II C 7 normally expressed in 45-day-old rats and PB-inducible, and (3) the expression of albumin and alpha-fetoprotein cDNAs. In the absence of PB, the susceptibility of pubertal rat liver to hepatocarcinogenesis was related to a special metabolic phenotype enriched in GGT and GST activities by comparison with the quasi-normal expression of both P-450s. Adult rat liver presented a less altered pattern closer to that of noninitiated rat liver. During PB promotion, the loss of PB inducibility of P-450 II C 7 in pubertal rat liver suggested that the hormonal status of the animals could interact with initiation to modulate specific gene expression. The late phase of PB promotion revealed the loss of highly differentiated functions (P-450s, albumin), whereas enzymatic markers associated with preneoplastic foci showed a persistent high expression.

ADP-ribosylation of nuclear proteins is increased by phenobarbital. Identification of the ADP-ribosylated histone fractions in rat liver nuclei.

Changes in the ADP-ribosylation of total proteins and purified histones of rat liver nuclei after phenobarbital treatment (80 mg/kg, 24 h) have been studied. The [32P]NAD incorporation into total trichloroacetic acid precipitated proteins, in histone Hl and in core histones was evaluated, the specific radioactivities increasing 150, 40 and 8%, respectively. Histones Hl and H2B were the best ADP-ribose acceptors. Histone H4 did not show any 32P incorporation, as revealed by autoradiography after SDS-PAGE of the purified histones, in either the control or phenobarbital treated rats. Possible involvement of ADP-ribosylation of nuclear proteins in the adaptative response of liver to phenobarbital is discussed.

Two IgM paraproteins differing in carbohydrate content in a patient with Waldenström's macroglobulinemia.

Two IgM paraproteins of different electrophoretic mobility were detected in the serum of a patient with Waldenstrom's disease. Both were type kappa, existed as high molecular weight polymers, and contained J-chain. The faster-moving protein contained a greater amount of carbohydrate, in both H and L chains.