Interaction of glutathione S-transferase M1 and T1 genotypes and malignant melanoma

The mu and theta classes of glutathione S-transferases (GST) may affect the development of cutaneous malignant melanoma (CMM) by decreasing cellular oxidative stress in skin. These isozymes are absent in a large proportion of the population because of germ-line homozygous deletions in the genes encoding GSTM1 and GSTT1. To determine the association between GSTM1 and GSTT1 homozygous deletions (GSTM1 null and GSTT1 null, respectively) and CMM, we studied 212 patients with CMM, 150 patients with CMM and dysplastic nevi (DN), 147 patients with DN alone, and 124 healthy persons without CMM or DN. Comparing CMM cases (n = 362) to participants without CMM (n = 271), we found no association with GSTM1 null [odds ratio (OR), 1.2; 95% confidence interval (CI), 0.86-1.6] or GSTT1 null (OR, 0.82; 95% CI, 0.56-1.2), either independently or in combination (OR, 1.4; 95% CI, 0.81-2.2), after adjusting for age. However, among the subset of participants with red or blond hair, those with CMM were twice as likely to carry GSTM1 null (OR, 2.2; 95% CI, 1.2-4.2) and nearly 10-fold more likely to carry both GSTM1 null and GSTT1 null (OR, 9.5; 95% CI, 1.2-73) compared with those without CMM. These data suggest that among persons with hair colors traditionally associated with increased risk for melanoma, absence of both GSTM1 and GSTT1 may act to further elevate CMM risk.

BAG-1: a novel biomarker predicting long-term survival in early-stage breast cancer

PURPOSE

Among women with early-stage breast cancer treated with lumpectomy and radiation therapy, 30% to 40% will develop metastatic disease, which is often fatal. A need exists therefore for biomarkers that distinguish patients at high risk of relapse. We performed a retrospective correlative analysis of BAG-1 protein expression in breast tumors derived from a cohort of early-stage breast cancer patients.

PATIENTS AND METHODS

Archival paraffin blocks from 122 women with stages I to II breast cancer treated with lumpectomy and radiation therapy (median follow-up, 12.1 years) were analyzed by immunohistochemical methods using monoclonal antibodies recognizing BAG-1 and other biomarkers, including Bcl-2, estrogen receptor, progesterone receptor, p53, and HER2/Neu. Immunostaining data were correlated with distant metastasis-free survival (DMFS) and overall survival (OS).

RESULTS

Cytosolic immunostaining for BAG-1 was upregulated in 79 (65%) of 122 invasive breast cancers (P <.001) compared with normal breast. Elevated BAG-1 was significantly associated with longer DMFS and OS, overall (stages 1 and II) and in node-negative (stage I only) patients, on the basis of univariate and multivariate analyses (DMFS, P =.005; OS, P =.01, in multivariate analysis of all patients; DMFS, P =.005; OS, P =.001, in multivariate analysis of node-negative patients). All other biomarkers failed to reach statistical significance in multivariate analysis. Clinical stage was an independent predictor of OS (P =.04) and DMFS (P =.02).

CONCLUSION

These findings provide preliminary evidence that BAG-1 represents a potential marker of improved survival in early-stage breast cancer patients, independent of the status of axillary lymph nodes.

Etoposide metabolites enhance DNA topoisomerase II cleavage near leukemia-associated MLL translocation breakpoints

Chromosomal breakage resulting from stabilization of DNA topoisomerase II covalent complexes by epipodophyllotoxins may play a role in the genesis of leukemia-associated MLL gene translocations. We investigated whether etoposide catechol and quinone metabolites can damage the MLL breakpoint cluster region in a DNA topoisomerase II-dependent manner like the parent drug and the nature of the damage. Cleavage of two DNA substrates containing the normal homologues of five MLL intron 6 translocation breakpoints was examined in vitro upon incubation with human DNA topoisomerase IIalpha, ATP, and either etoposide, etoposide catechol, or etoposide quinone. Many of the same cleavage sites were induced by etoposide and by its metabolites, but several unique sites were induced by the metabolites. There was a preference for G(-1) among the unique sites, which differs from the parent drug. Cleavage at most sites was greater and more heat-stable in the presence of the metabolites compared to etoposide. The MLL translocation breakpoints contained within the substrates were near strong and/or stable cleavage sites. The metabolites induced more cleavage than etoposide at the same sites within a 40 bp double-stranded oligonucleotide containing two of the translocation breakpoints, confirming the results at a subset of the sites. Cleavage assays using the same oligonucleotide substrate in which guanines at several positions were replaced with N7-deaza guanines indicated that the N7 position of guanine is important in metabolite-induced cleavage, possibly suggesting N7-guanine alkylation by etoposide quinone. Not only etoposide, but also its metabolites, enhance DNA topoisomerase II cleavage near MLL translocation breakpoints in in vitro assays. It is possible that etoposide metabolites may be relevant to translocations.

Sulfation pharmacogenetics: SULT1A1 and SULT1A2 allele frequencies in Caucasian, Chinese and African-American subjects

Sulfotransferase (SULT) enzymes catalyze the sulfate conjugation of drugs, other xenobiotics, neurotransmitters and hormones. The genes for SULT1A1 and SULT1A2 contain common genetic polymorphisms that are associated with individual variations in levels of enzyme activity as well as variations in biochemical and physical properties. We set out to compare the frequencies of common SULT1A1 and SULT1A2 alleles in Caucasian, Chinese and African-American subjects. Allele frequencies for SULT1A1*1, *2 and *3 in 242 Caucasian subjects were 0.656, 0.332 and 0.012, respectively. Frequencies of those same alleles were significantly different in 290 Chinese subjects: 0.914, 0.080 and 0.006, respectively, as were frequencies in 70 African-American subjects: 0.477, 0.294 and 0.229, respectively. Ethnic variation in allele frequencies was also observed for SULT1A2, with frequencies in Caucasian subjects for SULT1A2*1, *2 and *3 of 0.507, 0.389 and 0.104; frequencies in Chinese of 0.924 and 0.076 with no *3 alleles observed; and, finally, in African-Americans frequencies of 0.637, 0.249 and 0.114, respectively. We also found that SULT1A1*2 and SULT1A2*2, the most common variant alleles for these two genes, were in positive linkage disequilibrium in all three populations studied, with D' values of 0.776 in Caucasian (P < 0.001), 0.915 in Chinese (P < 0.001) and 0.864 in African-American subjects (P < 0.001). These observations represent a step towards determining the possible functional implications for individual variations in sulfate conjugation of common genetic polymorphisms for SULT1A1 and SULT1A2.

Differential expression of E-cadherin in lobular and ductal neoplasms of the breast and its biologic and diagnostic implications

We studied the pattern of E-cadherin expression in 183 invasive carcinomas (100 ductal, 42 lobular, 41 with mixed ductal and lobular features) and 198 in situ carcinomas (131 ductal, 53 lobular, 14 in situ with ductal and lobular features) by immunohistochemistry. We found a highly significant correlation of E-cadherin membrane expression with the histologic phenotype of the tumors. While moderate to strong membrane expression of E-cadherin was seen in all invasive and in situ ductal carcinomas, 41 of 42 invasive and 50 of 53 in situ lobular carcinomas showed complete loss of expression. All in situ carcinomas diagnosed histologically as showing mixed ductal and lobular features demonstrated complete loss of staining. Invasive carcinomas with ductal and lobular features showed 3 staining patterns: (1) complete or almost complete lack of membrane staining similar to that seen in lobular carcinomas, (2) uniform membrane expression throughout the tumor similar to ductal carcinomas, and (3) focal loss of E-cadherin staining, which correlated well with the histologic impression of focal lobular features. In tumors with histologically equivocal features, immunohistochemical detection of E-cadherin expression can be a useful diagnostic tool for the differentiation of ductal and lobular carcinomas of the breast.

The glutathione S-transferase-mu and -theta genotypes in the etiology of prostate cancer: genotype-environment interactions with smoking

It has been reported that individuals who express GSTT1, the gene coding for the theta class of the glutathione S-transferases (GSTs), have an elevated risk of prostate cancer (CaP). This result is supported by studies that show glutathione conjugation of some xenobiotics by the GSTs can produce mutagenic intermediates. However, the potential role of environmental factors in modifying the risk of CaP conferred by GSTT1 is not known. We investigated whether there was an interaction between smoking and the non-deleted genotypes of the mu (GSTM1) and theta (GSTT1) GST genes using a clinic-based study of 276 CaP cases and 499 controls. We observed no main effect of smoking (odds ratio, 0.95; confidence interval, 0.69-1.29) or GSTM1 (odds ratio, 1.00; confidence interval, 0.73-1.36) with CaP, but did observe a statistically significant main effect of GSTT1 with CaP (odds ratio, 1.61; confidence interval, 1.14-2.28) as reported previously. No interaction between smoking and GSTM1 was observed. A significant increase in the probability of having CaP was observed in men who were both smokers and carried a non-deleted GSTT1 genotype compared with men who had neither or only one of these risk factors (P = 0.049). Approximately 30.9% of CaP cases in this study could be attributed to the smoking x GSTT1 interaction. Whereas the mechanism of this interaction is not known, it is plausible that the metabolism of carcinogenic intermediates or the response to chronic inflammation associated with smoking may be modulated by the GSTT1 genotype and may modify CaP risk.

Localization of a hereditary neuroblastoma predisposition gene to 16p12-p13

BACKGROUND

Hereditary predisposition to develop neuroblastoma segregates as an autosomal dominant Mendelian trait.

PROCEDURE

We have performed linkage analysis on 10 families with neuroblastoma to localize a hereditary neuroblastoma predisposition gene (HNB1).

RESULTS

A single genomic interval at chromosome bands 16p12-p13 was consistent with linkage (lod = 3.46), and identification of informative recombinants defined a 25.9-cM critical region between D16S748 and D16S3068. Loss of heterozygosity was identified in 5/12 familial (42%) and 55/259 nonfamilial (21%) neuroblastomas at multiple 16p polymorphic loci. A 12.8-cM smallest region of overlap of deletions was identified within the interval defined by linkage analysis (tel-D16S764-D16S412-cen).

CONCLUSIONS

Taken together, these data suggest that HNB1 is located at 16p12-p13 and that inactivation of this gene may contribute to the pathogenesis of nonfamilial neuroblastomas.

BRCA1 and BRCA2 mutations in breast cancer families with multiple primary cancers

Ninety-eight women ascertained from high-risk breast/ovarian cancer clinics with breast cancer reporting at least one other primary cancer in themselves or in a relative with breast cancer were compared with 99 women with breast cancer who reported a family history of breast cancer only. All DNA was screened for coding region mutations in BRCA1 and BRCA2 using heteroduplex analysis, followed by direct sequencing. Our data indicate that 42.9% of families reporting breast and any second nonbreast type of primary cancer in the same individual had a BRCA1 or BRCA2 mutation, as compared with the 12.1% of families reporting breast cancer only (P < 0.001). Among the 66 women reporting breast cancer and a nonovarian second primary cancer, 15 (22.7%) had mutations in BRCA1 or BRCA2 (P = 0.04). Among the 32 families where ovarian cancer was the second primary cancer, 27 (84.4%) had a mutation in BRCA1 or BRCA2 (P < 0.001). BRCA1 and BRCA2 mutations were twice as common in the presence of a reported second nonovarian cancer. These data suggest that the presence of multiple primary cancer of any kind may predict for an increased likelihood of finding a BRCA1 or BRCA2 mutation and supports previous studies suggesting that BRCA1 and BRCA2 mutations may be associated with an increased susceptibility to cancers other than breast and ovarian cancer.

Prophylactic oophorectomy in BRCA1 and BRCA2 mutation carriers

The availability of genetic testing for inherited mutations in the BRCA1 and BRCA2 genes provides potentially valuable information to women at elevated risk of breast or ovarian cancer. Unfortunately, women who have inherited a mutation in BRCA1 or BRCA2 have relatively few clinical management options available to reduce their risk of developing breast or ovarian cancer. Because most options for ovarian cancer prevention are not highly efficacious, many high-risk women consider the option of bilateral prophylactic oophorectomy (BPO), in the hope that removal of healthy ovarian tissue will reduce their risk of developing invasive malignancy. It is clear that BPO cannot completely prevent the subsequent development of ovarian cancers because reports have been made of patients who have developed cancers of epithelial ovarian origin subsequent to surgery. However, a number of studies have suggested that BPO may reduce the risk of subsequent breast or ovarian cancers in women. In general, these studies have been conducted in women who represent a heterogeneous group with respect to breast/ovarian cancer risk. Only one study of BPO has been undertaken in women whose elevated cancer risk has been based on knowledge of inherited mutations. This study indicated that a 50% to 70% breast cancer risk reduction could be achieved in women with BRCA1 mutations who underwent BPO. However, substantial additional information is required to provide clinically useful information about cancer prevention to women who carry mutations in BRCA1 or BRCA2.

Association of HPC2/ELAC2 genotypes and prostate cancer

HPC2/ELAC2 has been identified as a prostate cancer (CaP) susceptibility gene. Two common missense variants in HPC2/ELAC2 have been identified: a Ser-->Leu change at amino acid 217, and an Ala-->Thr change at amino acid 541. Tavtigian et al. reported that these variants were associated with CaP in a sample of men drawn from families with hereditary CaP. To confirm this report in a sample unselected for family history, we studied 359 incident CaP case subjects and 266 male control subjects that were frequency matched for age and race and were identified from a large health-system population. Among control subjects, the Thr541 frequency was 2.9%, and the Leu217 frequency was 31.6%, with no significant differences in frequency across racial groups. Thr541 was only observed in men who also carried Leu217. The probability of having CaP was increased in men who carried the Leu217/Thr541 variants (odds ratio = 2.37; 95% CI 1.06-5.29). This risk did not differ significantly by family history or race. Genotypes at HPC2/ELAC2 were estimated to cause 5% of CaP in the general population of inference. These results suggest that common variants at HPC2/ELAC2 are associated with CaP risk in a sample unselected for family history or other factors associated with CaP risk.

Prophylactic surgery in women with a hereditary predisposition to breast and ovarian cancer

PURPOSE

To review the published literature on the efficacy and adverse effects of prophylactic mastectomy (PM) and prophylactic oophorectomy (PO) in women with a hereditary predisposition to breast and ovarian cancer and to provide management recommendations for these women.

METHODS

Using the terms "prophylactic," "preventive," "bilateral," "mastectomy," "oophorectomy," and "ovariectomy," a MEDLINE search of the English-language literature for articles related to PM and PO was performed. The bibliographies of these articles were reviewed to identify additional relevant references.

RESULTS

There have been no prospective trials of PM or PO for the reduction of breast cancer or ovarian cancer incidence or mortality. Most of the available retrospective studies are composed of women who had surgery for a variety of indications and in whom genetic risk was not well characterized. However, some reports in women at increased risk of breast or ovarian cancer have shown that PM and PO can reduce cancer incidence.

CONCLUSION

Interest in and use of PM and PO are high among physicians and high-risk women. PM and PO seem to be associated with considerable reduction in the risk of breast and ovarian cancer, albeit incomplete. The surgical morbidity of PM and PO is low, but the complications of premature menopause may be significant, and few studies address quality-of-life issues in women who have opted for PM and PO. Management recommendations for high-risk individuals are presented on the basis of the available evidence.

Association of SRD5A2 genotype and pathological characteristics of prostate tumors

The enzyme product of SRD5A2, 5alpha-reductase type II, is responsible for converting testosterone to the more metabolically active dihydrotestosterone. Therefore, SRDSA2 may be involved in the development or growth of prostate tumors. To examine the effects of allelic variants in the gene SRDSA2 on the presentation of prostate tumors, we studied a sample, primarily Caucasian, of 265 men with incident prostate cancer who were treated by radical prostatectomy. We assessed the relationship of the A49T and V89L polymorphisms at SRD5A2 with clinical and pathological tumor characteristics of these patients. We found no association of V89L genotypes with any of the characteristics studied. The presence of the A49T variant was associated with a greater frequency of extracapsular disease [odds ratio (OR), 3.16; 95% confidence interval (CI), 1.03-9.68] and a higher pathological tumor-lymph node-metastasis (pTNM) stage (OR, 3.11; 95% CI, 1.01-9.65). In addition, the A49T variant was overrepresented in two poor prognostic groups, which have been correlated with reduced rates of biochemical disease-free survival. One group included men with at least two of the following poor prognostic variables: (a) stage T3 tumor; (b) PSA level >10; and/or (c) Gleason score, 7-10 (OR, 3.46; 95% CI, 1.04-11.49). The second group included men with positive margins and high Gleason score (OR, 6.28; 95% CI, 1.05-37.73). Our results suggest that the A49T mutation may influence the pathological characteristics of prostate cancers and, thus, may affect the prognosis of these patients.

Characterization of an allelic variant in the nifedipine-specific element of CYP3A4: ethnic distribution and implications for prostate cancer risk. Mutations in brief no. 191. Online

CYP3A4 is involved in the metabolism of numerous biologically active compounds, including testosterone. A genetic variant located in the P450NF (nifedipine) specific element (NFSE) has been identified that disrupts a transciptional regulatory element located in the 5' regulatory region of CYP3A4. The CYP3A4 variant (CYP3A4-V) is associated with the clinical presentation of prostate cancer. There are significant differences in CYP3A4 metabolism and rates of prostate cancer across ethnic groups that may be associated with CYP3A4 genotypes. Therefore, we estimated the frequency of the CYP3A4 variant in three ethnic groups with different prostate cancer incidence rates. The frequency (q) of CYP3A4-V was significantly different (p<0.0001) in African Americans (q=0.53), U.S. Caucasians (q=0.09), and Taiwanese (q=0.0). CYP3A4-V segregated in a Mendelian manner in one large African American family, and 7 of 16 (44%) biologically unrelated "marry-ins" carried a CYP3A4 variant allele. Reflecting population-specific prostate cancer incidence rates, our results suggest a high frequency of this variant in African Americans compared with U.S. Caucasians and Taiwanese.

Inherited genetic predisposition in breast cancer. A population-based perspective

Two classes of inherited susceptibility genes may be considered in the etiology of breast and other common cancers. First, genes have been identified that confer a high degree of breast cancer (BC) risk, usually associated with hereditary syndromes, but disease-associated germline variants in these genes are relatively rare in the general population. These include BRCA1, BRCA2, and TP53. The proportion of BC in the general population that can be explained by these genes is relatively small. Second, variant genotypes at other loci may confer a relatively smaller degree of cancer risk, but they are carried by a larger proportion of the general population. As a result, the proportion of BC that could be explained by these genes may be relatively large. To understand the genetic basis for BCs in the general population, both of these classes of genes may need to be considered. This paper presents an overview of genes thought to be involved in BC susceptibility. Genes that confer a high degree of risk are more likely to result in hereditary patterns of cancer that are amenable to identification by genetic epidemiologic methods using pedigree data. More common (e.g., nonhereditary) forms of BC may be optimally analyzed by molecular epidemiologic studies using case-case, case-control, or cohort designs. The use of an appropriate study design is crucial to the identification of genes with relatively small effects on BC risk. To understand the inherited factors that explain BC in the general population, consideration should be given to genes with different allele frequencies and magnitudes of effect, using appropriate analytical approaches. By understanding the complex interactions of these genes with one another and with exposures, improved risk assessment and potential for targeted cancer prevention strategies may be possible.

Breast cancer risk after bilateral prophylactic oophorectomy in BRCA1 mutation carriers

BACKGROUND

The availability of genetic testing for inherited mutations in the BRCA1 gene provides potentially valuable information to women at high risk of breast or ovarian cancer; however, carriers of BRCA1 mutations have few clinical management options to reduce their cancer risk. Decreases in ovarian hormone exposure following bilateral prophylactic oophorectomy (i.e., surgical removal of the ovaries) may alter cancer risk in BRCA1 mutation carriers. This study was undertaken to evaluate whether bilateral prophylactic oophorectomy is associated with a reduction in breast cancer risk in BRCA1 mutation carriers.

METHODS

We studied a cohort of women with disease-associated germline BRCA1 mutations who were assembled from five North American centers. Surgery subjects (n = 43) included women with BRCA1 mutations who underwent bilateral prophylactic oophorectomy but had no history of breast or ovarian cancer and had not had a prophylactic mastectomy. Control subjects included women with BRCA1 mutations who had no history of oophorectomy and no history of breast or ovarian cancer (n = 79). Control subjects were matched to the surgery subjects according to center and year of birth.

RESULTS

We found a statistically significant reduction in breast cancer risk after bilateral prophylactic oophorectomy, with an adjusted hazard ratio (HR) of 0.53 (95% confidence interval [CI] = 0.33-0.84). This risk reduction was even greater in women who were followed 5-10 (HR = 0. 28; 95% CI = 0.08-0.94) or at least 10 (HR = 0.33; 95% CI = 0.12-0.91) years after surgery. Use of hormone replacement therapy did not negate the reduction in breast cancer risk after surgery.

CONCLUSIONS

Bilateral prophylactic oophorectomy is associated with a reduced breast cancer risk in women who carry a BRCA1 mutation. The likely mechanism is reduction of ovarian hormone exposure. These findings have implications for the management of breast cancer risk in women who carry BRCA1 mutations.

Evaluation of genotype data in clinical risk assessment: methods and application to BRCA1, BRCA2, and N-acetyl transferase-2 genotypes in breast cancer

Associations of numerous susceptibility genes with disease risk have been reported. However, objective methods have not been developed to evaluate the conditions under which translation of knowledge about susceptibility genotypes may be clinically informative. We describe and apply a statistical approach to evaluate when genotype information may be clinically informative in disease risk assessment. We estimate an interval of cumulative cancer incidences where it may be appropriate to use these genes in disease risk assessment. We also estimate the magnitude of a log odds ratio (H) that measures genotype-disease association. We illustrate this method with three breast cancer susceptibility genotypes: population screening data evaluating the 185delAG mutation at BRCA1 and the 6174delT mutation at BRCA2 in a Ashkenazi Jewish population, and case control data for the slow acetylation genotype at the N-acetyl transferase 2 (NAT2) gene in combination with smoking. Knowledge of the 185delAG mutation in BRCA1 (HdelAG = 3.42; 95% CI: 3.04, 3.79) or the 6174delT mutation in BRCA2 (HdelT = 1.98; 95% CI: 1.16, 2.30) can be clinically informative in distinguishing individuals who are and are not at breast cancer risk in populations with cumulative breast cancer incidences of > or = 4% and > or = 13%, respectively. NAT2 genotypes alone are much less clinically informative in predicting breast cancer risk (HNAT2 = 0.10). However, knowledge of both heavy smoking 20 years ago and NAT2 genotype is a more clinically informative predictor of postmenopausal breast cancer risk with HNAT2 = 2.19, when the cumulative breast cancer incidence in the target population is at least 31%. These results indicate that knowledge of the 185delG mutation-status may be clinically informative even in populations with low cumulative breast cancer incidences, whereas the 6174delT mutation and NAT2 genotypes may only be clinically informative in a population with higher cumulative breast cancer incidence. The proposed approach can be used to objectively evaluate the conditions under which susceptibility genotypes may be applied for risk assessment or genetic screening.

Collection of genomic DNA by buccal swabs for polymerase chain reaction-based biomarker assays

Studies in molecular and genetic epidemiology require a high-throughput, low cost, and reliable means of genomic DNA collection. Buccal (cheek) swabs have been proposed as a means of achieving these goals, but there is little information about the practical application of this approach. From January 1995 to December 1997, we processed 995 buccal swabs for use in polymerase chain reaction (PCR)-based genotype assays in the context of ongoing molecular epidemiologic studies. Six hundred forty-seven of these swabs were processed immediately after collection and 348 were received by mail. We were able to obtain at least one genotype from 99.7% (645 of 647) of fresh-processed and 97.4% (330 of 339) of mailed biosamples. A PCR success rate of 90.3% (2,546 genotypes from 2,819 assays) was achieved. Genotypes were obtained from 96.1% (1, 865 genotypes from 1,941 assays) of fresh-processed biosamples and 77.6% (681 genotypes from 878 assays) of mailed biosamples. PCR success rates at any single locus ranged from 92.6 to 98.8% (fresh-processed) and 75.5 to 79.6% (mailed). The PCR success rate among fresh-processed biosamples was significantly higher than among mailed biosamples (Fisher's exact test p < 0.0001), and more attempts were required to obtain a successful PCR result for mailed biosamples as compared to fresh-processed biosamples. For one locus (CYP3A4), a subset of mailed biosamples was purified if two or more PCR failures occurred. Additional genotypes were obtained in 58.3% of these previously failed biosamples. Time from biosample receipt to DNA extraction had no effect on PCR success. After storage of processed biosamples for as long as 3 years, there was no appreciable decrease in the rate of PCR success. These results suggest that adequate DNA for PCR-based applications can be obtained from buccal swabs, but sampling or processing considerations may be important in obtaining optimal results.

Modification of BRCA1-associated breast cancer risk by the polymorphic androgen-receptor CAG repeat

Compared with the general population, women who have inherited a germline mutation in the BRCA1 gene have a greatly increased risk of developing breast cancer. However, there is also substantial interindividual variability in the occurrence of breast cancer among BRCA1 mutation carriers. We hypothesize that other genes, particularly those involved in endocrine signaling, may modify the BRCA1-associated age-specific breast cancer risk. We studied the effect of the CAG repeat-length polymorphism found in exon 1 of the androgen-receptor (AR) gene (AR-CAG). AR alleles containing longer CAG repeat lengths are associated with a decreased ability to activate androgen-responsive genes. Using a sample of women who inherited germline BRCA1 mutations, we compared AR-CAG repeat length in 165 women with and 139 women without breast cancer. We found that women were at significantly increased risk of breast cancer if they carried at least one AR allele with >/=28 CAG repeats. Women who carried an AR-CAG allele of >/=28, >/=29, or >/=30 repeats were given a diagnosis 0.8, 1.8, or 6.3 years earlier than women who did not carry at least one such allele. All 11 women in our sample who carried at least one AR-CAG allele with >/=29 repeats had breast cancer. Our results support the hypothesis that age at breast cancer diagnosis is earlier among BRCA1 mutation carriers who carry very long AR-CAG repeats. These results suggest that pathways involving androgen signaling may affect the risk of BRCA1-associated breast cancer.

Glutathione S-transferase-mu (GSTM1) and -theta (GSTT1) genotypes in the etiology of prostate cancer

The glutathione S-transferases (GSTs) are involved in the metabolism of numerous potential prostate carcinogens. Common homozygous germ-line deletions exist in the genes that encode GST-mu (GSTM1) and GST-theta (GSTT1) and preclude enzyme expression. To evaluate whether GSTM1 and/or GSTT1 contribute to prostate cancer (CaP) etiology, we studied 237 incident CaP cases and 239 age- and race-matched controls. The probability of having CaP was increased in men who had nondeleted (functional) genotypes at GSTT1 (odds ratio, 1.83; 95% confidence interval, 1.19-2.80) but not GSTM1 (odds ratio, 1.07; 95% confidence interval, 0.74-1.55). No interaction of these genes in CaP etiology was observed. GST-theta is highly expressed in the prostate and can produce genotoxic effects upon exposure to specific carcinogens. These results suggest that GSTT1 is associated with CaP risk.

Common variant in AMPD1 gene predicts improved clinical outcome in patients with heart failure

BACKGROUND

This study was undertaken to identify gene(s) that may be associated with improved clinical outcome in patients with congestive heart failure (CHF). The adenosine monophosphate deaminase locus (AMPD1) was selected for study. We hypothesized that inheritance of the mutant AMPD1 allele is associated with increased probability of survival without cardiac transplantation in patients with CHF.

METHODS AND RESULTS

AMPD1 genotype was determined in 132 patients with advanced CHF and 91 control reference subjects by use of a polymerase chain reaction-based, allele-specific oligonucleotide detection assay. In patients with CHF, those heterozygous (n=20) or homozygous (n=1) for the mutant AMPD1 allele (AMPD1 +/- or -/-, respectively) experienced a significantly longer duration of heart failure symptoms before referral for transplantation evaluation than CHF patients homozygous for the wild-type allele (AMPD1 +/+; n=111; 7.6+/-6.5 versus 3.2+/-3.6 years; P<0.001). The OR of surviving without cardiac transplantation >/=5 years after initial hospitalization for CHF symptoms was 8.6 times greater (95% CI: 3.05, 23.87) in those patients carrying >/=1 mutant AMPD1 allele than in those carrying 2 wild-type AMPD1 +/+ alleles.

CONCLUSIONS

After the onset of CHF symptoms, the mutant AMPD1 allele is associated with prolonged probability of survival without cardiac transplantation. The mechanism by which the presence of the mutant AMPD1 allele may modify the clinical phenotype of heart failure remains to be determined.

Polymorphisms in PTEN in breast cancer families

Germline mutations in PTEN are the underlying genetic defect in Cowden disease, which is associated with a lifetime risk of 25-50% of developing breast cancer. To investigate the role of PTEN in inherited breast cancer in the absence of manifestations of Cowden disease, we screened 177 unrelated subjects with breast cancer who also had a family history of breast cancer in at least one relative. We found no disease associated PTEN mutations in this cohort, supporting previous studies suggesting that PTEN mutations do not contribute to inherited susceptibility to breast cancer without associated manifestations of Cowden disease. We did identify an association between a common polymorphism in intron 4 and lower mean age of diagnosis of breast cancer. While preliminary, these findings suggest that further study is warranted to determine whether this allelic variant of PTEN could function as a low penetrance breast cancer susceptibility allele.

Association of CYP3A4 genotype with treatment-related leukemia

Epipodophyllotoxins are associated with leukemias characterized by translocations of the MLL gene at chromosome band 11q23 and other translocations. Cytochrome P450 (CYP) 3A metabolizes epipodophyllotoxins and other chemotherapeutic agents. CYP3A metabolism generates epipodophyllotoxin catechol and quinone metabolites, which could damage DNA. There is a polymorphism in the 5' promoter region of the CYP3A4 gene (CYP3A4-V) that might alter the metabolism of anticancer drugs. We examined 99 de novo and 30 treatment-related leukemias with a conformation-sensitive gel electrophoresis assay for the presence of the CYP3A4-V. In all treatment-related cases, there was prior exposure to one or more anticancer drugs metabolized by CYP3A. Nineteen of 99 de novo (19%) and 1 of 30 treatment-related (3%) leukemias carried the CYP3A4-V (P = 0.026; Fisher's Exact Test, FET). Nine of 42 de novo leukemias with MLL gene translocations (21%), and 0 of 22 treatment-related leukemias with MLL gene translocations carried the CYP3A4-V (P = 0. 016, FET). This relationship remained significant when 19 treatment-related leukemias with MLL gene translocations that followed epipodophyllotoxin exposure were compared with the same 42 de novo cases (P = 0.026, FET). These data suggest that individuals with CYP3A4-W genotype may be at increased risk for treatment-related leukemia and that epipodophyllotoxin metabolism by CYP3A4 may contribute to the secondary cancer risk. The CYP3A4-W genotype may increase production of potentially DNA-damaging reactive intermediates. The variant may decrease production of the epipodophyllotoxin catechol metabolite, which is the precursor of the potentially DNA-damaging quinone.