Gene methylation biomarkers in sputum as a classifier for lung cancer risk

CT screening for lung cancer reduces mortality, but will cost Medicare ∼2 billion dollars due in part to high false positive rates. Molecular biomarkers could augment current risk stratification used to select smokers for screening. Gene methylation in sputum reflects lung field cancerization that remains in lung cancer patients post-resection. This population was used in conjunction with cancer-free smokers to evaluate classification accuracy of a validated eight-gene methylation panel in sputum for cancer risk. Sputum from resected lung cancer patients (n=487) and smokers from Lovelace (n=1380) and PLuSS (n=718) cohorts was studied for methylation of an 8-gene panel. Area under a receiver operating characteristic curve was calculated to assess the prediction performance in logistic regressions with different sets of variables. The prevalence for methylation of all genes was significantly increased in the ECOG-ACRIN patients compared to cancer-free smokers as evident by elevated odds ratios that ranged from 1.6 to 8.9. The gene methylation panel showed lung cancer prediction accuracy of 82–86% and with addition of clinical variables improved to 87–90%. With sensitivity at 95%, specificity increased from 25% to 54% comparing clinical variables alone to their inclusion with methylation. The addition of methylation biomarkers to clinical variables would reduce false positive screens by ruling out one-third of smokers eligible for CT screening and could increase cancer detection rates through expanding risk assessment criteria.

Abstract 3261: Gene methylation biomarkers in sputum as a classifier for lung cancer risk

Lung cancer is the leading cause of cancer death primarily because it is often diagnosed at an advanced stage. Results from the National Lung Screening Trial (NLST) showed that CT screening can reduce lung cancer mortality by 20%, but the high number of false positives and need for additional testing suggest that better risk classification of smokers prior to screening could save more lives with less cost and improved efficiency. Furthermore, eligibility criteria for NLST were restricted to smokers ages of 55-74 with >30 pack-years of smoking and < 15y since smoking cessation, which captures only ~40% of incident lung cancer cases. Molecular biomarkers could augment current risk stratification used to select smokers for screening. We have shown that gene specific promoter hypermethylation detected in sputum provides an assessment of field cancerization within the lungs of smokers that in turn predicts lung cancer. The current study addressed whether our validated 8-gene methylation panel could be extended to improve the existing risk prediction model used to recommend people for a CT screen by evaluating methylation in 487 resected Stage I lung cancer patients from the ECOG-ACRIN5597 trial (field of injury remains), 1378 current and former smokers from the Lovelace Smokers cohort (LSC) and 718 current and former smokers from the PLuSS cohort. Our initial analysis was restricted to individuals from each cohort who met NLST criteria for CT screening (n=371 ECOG-ACRIN, n=466 LSC and n=597 PLuSS). The methylation prevalence of all 8 genes was significantly increased in resected lung cancer patients compared to cancer-free smokers (odds ratios 1.6 to 8.9). The area under the receiver operator characteristic curve (AUC) was used to evaluate classification accuracy of different logistic regression models. Classification accuracy for clinical risk factors alone was 74-76%, methylation alone, 82-86%; and clinical risk factors plus methylation, 87-90% (p<10-9 - 10-16). Setting the sensitivity at 95% improved specificity from 25% to 54% with both methylation and clinical factors in the model. Assessment of the performance of the gene methylation panel in all of the cancer patients and smokers did not reduce classification accuracy or increase specificity. Implementation of gene methylation biomarkers for screening could be a paradigm shift for lung cancer management by providing a much improved risk assessment model that will allow for expanding the number of smokers considered for screening, decreasing by one-third the actual number referred, and reducing mortality through increasing the CT positive predictive value. (Supported largely by R01 CA095568 and in part P30 CA118100)

Citation Format: Maria A. Picchi, Shuguang Leng, Guodong Wu, Donna M. Klinge, Cynthia L. Thomas, Elia Casas, Christine A. Stidley, Sandra J. Lee, Seena Aisner, Jill M. Siegfried, Suresh Ramalingam, Fadlo R. Khuri, Daniel D. Karp, Steven A. Belinsky. Gene methylation biomarkers in sputum as a classifier for lung cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3261. doi:10.1158/1538-7445.AM2017-3261

Implication of a Chromosome 15q15.2 Locus in Regulating UBR1 and Predisposing Smokers to MGMT Methylation in Lung

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that protects cells from carcinogenic effects of alkylating agents; however, MGMT is silenced by promoter hypermethylation during carcinogenesis. A single-nucleotide polymorphism (SNP) in an enhancer in the MGMT promoter was previously identified to be highly significantly associated with risk for MGMT methylation in lung cancer and sputum from smokers. To further genetic investigations, a genome-wide association and replication study was conducted in two smoker cohorts to identify novel loci for MGMT methylation in sputum that were independent of the MGMT enhancer polymorphism. Two novel trans-acting loci (15q15.2 and 17q24.3) that were identified acted together with the enhancer SNP to empower risk prediction for MGMT methylation. We found that the predisposition to MGMT methylation arising from the 15q15.2 locus involved regulation of the ubiquitin protein ligase E3 component UBR1. UBR1 attenuation reduced turnover of MGMT protein and increased repair of O6-methylguanine in nitrosomethylurea-treated human bronchial epithelial cells, while also reducing MGMT promoter activity and abolishing MGMT induction. Overall, our results substantiate reduced gene transcription as a major mechanism for predisposition to MGMT methylation in the lungs of smokers, and support the importance of UBR1 in regulating MGMT homeostasis and DNA repair of alkylated DNA adducts in cells.

Satisfaction with Care of Patients on Hemodialysis

BACKGROUND AND OBJECTIVES

Little is known about patients receiving dialysis who respond to satisfaction and experience of care surveys and those who do not respond, nor is much known about the corollaries of satisfaction. This study examined factors predicting response to Dialysis Clinic, Inc. (DCI)'s patient satisfaction survey and factors associated with higher satisfaction among responders.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENT

A total of 10,628 patients receiving in-center hemodialysis care at 201 DCI facilities between January 1, 2011, and December 31, 2011, aged ≥18 years, treated during the survey administration window, and at the facility for ≥3 months before survey administration. Primary outcome was response to at least one of the nine survey questions; secondary outcome was overall satisfaction with care.

RESULTS

Response rate was 77.3%. In adjusted logistic regression (odds ratios with 95% confidence intervals), race other than black (white race, 1.23 [1.10 to 1.37]), missed treatments (1.16 [1.02 to 1.32]) or shortened treatments (≥5 treatments, 1.40 [1.22 to 1.60]), more hospital days (>3 days in the last 3 months, 1.89 [1.66 to 2.15]), and lower serum albumin (albumin level <3.5 g/dl, 1.4 [1.28 to 1.73]) all independently predicted nonresponse. In adjusted linear regression, the following were more satisfied with care: older patients (age ≥63 years, 1.84 [1.78 to 1.90]; age <63 years, 1.91 [1.86 to 1.97]; P<0.001), white patients (1.76 [1.71 to 1.81]) versus black patients (1.93 [1.88 to 1.99]) or those of other race (1.93 [1.83 to 2.03]) (P<0.001), patients with shorter duration of dialysis (≤2.5 years, 1.79 [1.73 to 1.84]; >2.5 years, 1.96 [1.91 to 2.02]; P<0.001), patients who had missed one or fewer treatments (1.83 [1.78 to 1.88]) versus those who had missed more than one treatment (1.92 [1.85 to 1.98]; P=0.002) and those who had shortened treatment (for one treatment or less, 1.84 [1.77 to 1.90]; for two to four treatments, 1.87 [1.81 to 1.93]; for five or more treatments, 1.92 [1.87 to 1.98]; P=0.004).

CONCLUSIONS

Survey results represent healthier and more adherent patients on hemodialysis. Shorter survey administration windows were associated with higher response rates. Older, white patients with shorter dialysis vintage were more satisfied.

15q12 variants, sputum gene promoter hypermethylation, and lung cancer risk: a GWAS in smokers

BACKGROUND

Lung cancer is the leading cause of cancer-related mortality worldwide. Detection of promoter hypermethylation of tumor suppressor genes in exfoliated cells from the lung provides an assessment of field cancerization that in turn predicts lung cancer. The identification of genetic determinants for this validated cancer biomarker should provide novel insights into mechanisms underlying epigenetic reprogramming during lung carcinogenesis.

METHODS

A genome-wide association study using generalized estimating equations and logistic regression models was conducted in two geographically independent smoker cohorts to identify loci affecting the propensity for cancer-related gene methylation that was assessed by a 12-gene panel interrogated in sputum. All statistical tests were two-sided.

RESULTS

Two single nucleotide polymorphisms (SNPs) at 15q12 (rs73371737 and rs7179575) that drove gene methylation were discovered and replicated with rs73371737 reaching genome-wide significance (P = 3.3×10(-8)). A haplotype carrying risk alleles from the two 15q12 SNPs conferred 57% increased risk for gene methylation (P = 2.5×10(-9)). Rs73371737 reduced GABRB3 expression in lung cells and increased risk for smoking-induced chronic mucous hypersecretion. Furthermore, subjects with variant homozygote of rs73371737 had a two-fold increase in risk for lung cancer (P = .0043). Pathway analysis identified DNA double-strand break repair by homologous recombination (DSBR-HR) as a major pathway affecting susceptibility for gene methylation that was validated by measuring chromatid breaks in lymphocytes challenged by bleomycin.

CONCLUSIONS

A functional 15q12 variant was identified as a risk factor for gene methylation and lung cancer. The associations could be mediated by GABAergic signaling that drives the smoking-induced mucous cell metaplasia. Our findings also substantiate DSBR-HR as a critical pathway driving epigenetic gene silencing.

Integrated statistical and pathway approach to next-generation sequencing analysis: a family-based study of hypertension

Genome wide association studies (GWAS) have been used to search for associations between genetic variants and a phenotypic trait of interest. New technologies, such as next-generation sequencing, hold the potential to revolutionize GWAS. However, millions of polymorphisms are identified with next-generation sequencing technology. Consequently, researchers must be careful when performing such a large number of statistical tests, and corrections are typically made to account for multiple testing. Additionally, for typical GWAS, the p value cutoff is set quite low (approximately <10⁻⁸). As a result of this p value stringency, it is likely that there are many true associations that do not meet this threshold. To account for this we have incorporated a priori biological knowledge to help identify true associations that may not have reached statistical significance. We propose the application of a pipelined series of statistical and bioinformatic methods, to enable the assessment of the association of genetic polymorphisms with a disease phenotype--here, hypertension--as well as the identification of statistically significant pathways of genes that may play a role in the disease process.

Native American ancestry affects the risk for gene methylation in the lungs of Hispanic smokers from New Mexico

RATIONALE

Gene promoter methylation detected in sputum predicts lung cancer risk in smokers. Compared with non-Hispanic whites (NHW), Hispanics have a lower age-standardized incidence for lung cancer.

OBJECTIVES

This study compared the methylation prevalence in sputum of NHWs with Hispanics using the Lovelace Smokers cohort (n = 1998) and evaluated the effect of Native American ancestry (NAA) and diet on biomarkers for lung cancer risk.

METHODS

Genetic ancestry was estimated using 48 ancestry markers. Diet was assessed by the Harvard University Dietary Assessment questionnaire. Methylation of 12 genes was measured in sputum using methylation-specific polymerase chain reaction. The association between NAA and risk for methylation was assessed using generalized estimating equations. The ethnic difference in the association between pack-years and risk for lung cancer was assessed in the New Mexico lung cancer study.

MEASUREMENTS AND MAIN RESULTS

Overall Hispanics had a significantly increased risk for methylation across the 12 genes analyzed (odds ratio, 1.18; P = 0.007). However, the risk was reduced by 32% (P = 0.032) in Hispanics with high versus low NAA. In the New Mexico lung cancer study, Hispanic non-small cell lung cancer cases have significantly lower pack-years than NHW counterparts (P = 0.007). Furthermore, compared with NHW smokers, Hispanic smokers had a more rapidly increasing risk for lung cancer as a function of pack-years (P = 0.058).

CONCLUSIONS

NAA may be an important risk modifier for methylation in Hispanic smokers. Smoking intensity may have a greater impact on risk for lung cancer in Hispanics compared with NHWs.

DNA repair variants, indoor tanning, and risk of melanoma

Although ultraviolet radiation (UV) exposure from indoor tanning has been linked to an increased risk of melanoma, the role of DNA repair genes in this process is unknown. We evaluated the association of 92 single nucleotide polymorphisms (SNPs) in 20 DNA repair genes with the risk of melanoma and indoor tanning among 929 patients with melanoma and 817 controls from the Minnesota Skin Health Study. Significant associations with melanoma risk were identified for SNPs in ERCC4, ERCC6, RFC1, XPC, MGMT, and FBRSL1 genes; with a cutoff of P < 0.05. ERCC6 and FBRSL1 gene variants and haplotypes interacted with indoor tanning. However, none of the 92 SNPs tested met the correction criteria for multiple comparisons. This study, based on an a priori interest in investigating the role of DNA repair capacity using variants in base excision and nucleotide excision repair, identified several genes that may play a role in resolving UV-induced DNA damage.

Endometrial cancer and a family history of cancer

OBJECTIVE

Lynch Syndrome (LS), an inherited genetic syndrome, predisposes to cancers such as colorectal and endometrial. However, the risk for endometrial cancer (EC) in women not affected by LS, but with a family history of cancer, is currently unknown. We examined the association between a family history of cancer and the risk for EC in non-LS patients.

METHODS

This population-based case-control study included 519 EC cases and 1015 age-matched controls and took place in Alberta, Canada between 2002 and 2006. Information about risk factors, including family history of cancer in first and second degree relatives, was ascertained via in-person interviews. Microsatellite instability (MSI) status of tumor tissue was assessed to determine involvement of DNA mismatch repair (MMR) genes.

RESULTS

A first or second degree family history of uterine cancer was modestly associated with the risk for overall EC [odds ratio (OR), 1.3; 95% confidence interval (CI), 0.9, 1.9], and the risks were similar for MSI+cancer (OR=1.5, 95%CI=0.7, 3.3) and MSI- cancer (OR=1.3, 95%CI=0.8, 2.4). Although consistent, these associations were modest and not significant. In contrast, the risk for MSI+cancer was elevated with a reported family history of colorectal cancer (OR=1.4, 95%CI=1.0, 2.2), but not for MSI- cancer.

CONCLUSIONS

A family history of uterine cancer may be modestly associated with EC risk in non-LS patients regardless of MSI status, suggesting that risk was not related to inherited defects in the MMR gene pathway. These results provide preliminary support for an EC-specific genetic syndrome.

Abstract 3624: Genetic variation in SIRT1 affects susceptibility of lung squamous cell carcinomas in former uranium miners from the Colorado plateau

Epidemiological studies of underground miners suggest that occupational exposure to radon causes lung cancer with squamous cell carcinoma (SCC) as the predominant histological type. However, the genetic determinants for susceptibility of radon-induced SCC in miners are unclear. Double-strand breaks (DSBs) induced by radioactive radon daughters are repaired primarily by non-homologous end joining (NHEJ) that is accompanied by the dynamic changes in surrounding chromatin, including nucleosome repositioning and histone modifications. Thus, a molecular epidemiological study was conducted to assess whether genetic variation in 16 genes involved in NHEJ and related histone modification affected susceptibility for SCC in radon-exposed former miners (267 SCC cases and 383 controls) from the Colorado plateau. A global association between genetic variation in the haplotype block where SIRT1 resides and the risk for SCC in miners (P=0.003) was identified. Haplotype alleles tagged by the A allele of SIRT1 rs7097008 were associated with increased risk for SCC (Odds Ratio = 1.69, P = 8.2×10−5) and greater survival in SCC cases (Hazard Ratio = 0.79, P = 0.03) in miners. Functional validation of rs7097008 demonstrated that the A allele was associated with reduced gene expression in bronchial epithelial cells and compromised DNA repair capacity in peripheral lymphocytes. Together, these findings substantiate genetic variation in SIRT1 as a risk modifier for developing SCC in miners and suggested that SIRT1 may also play a tumor suppressor role in radon-induced cancer in miners.

Citation Format: Shuguang Leng, Maria A. Picchi, Yushi Liu, Yong Lin, Christine A. Stidley, Frank D. Gilliland, Marty R. Jacobson, Steven A. Belinsky. Genetic variation in SIRT1 affects susceptibility of lung squamous cell carcinomas in former uranium miners from the Colorado plateau. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3624. doi:10.1158/1538-7445.AM2013-3624

Genetic variation in SIRT1 affects susceptibility of lung squamous cell carcinomas in former uranium miners from the Colorado plateau

Epidemiological studies of underground miners suggested that occupational exposure to radon causes lung cancer with squamous cell carcinoma (SCC) as the predominant histological type. However, the genetic determinants for susceptibility of radon-induced SCC in miners are unclear. Double-strand breaks induced by radioactive radon daughters are repaired primarily by non-homologous end joining (NHEJ) that is accompanied by the dynamic changes in surrounding chromatin, including nucleosome repositioning and histone modifications. Thus, a molecular epidemiological study was conducted to assess whether genetic variation in 16 genes involved in NHEJ and related histone modification affected susceptibility for SCC in radon-exposed former miners (267 SCC cases and 383 controls) from the Colorado plateau. A global association between genetic variation in the haplotype block where SIRT1 resides and the risk for SCC in miners (P = 0.003) was identified. Haplotype alleles tagged by the A allele of SIRT1 rs7097008 were associated with increased risk for SCC (odds ratio = 1.69, P = 8.2 × 10(-5)) and greater survival in SCC cases (hazard ratio = 0.79, P = 0.03) in miners. Functional validation of rs7097008 demonstrated that the A allele was associated with reduced gene expression in bronchial epithelial cells and compromised DNA repair capacity in peripheral lymphocytes. Together, these findings substantiate genetic variation in SIRT1 as a risk modifier for developing SCC in miners and suggest that SIRT1 may also play a tumor suppressor role in radon-induced cancer in miners.

Defining a gene promoter methylation signature in sputum for lung cancer risk assessment

PURPOSE

To evaluate the methylation state of 31 genes in sputum as biomarkers in an expanded nested, case-control study from the Colorado cohort, and to assess the replication of results from the most promising genes in an independent case-control study of asymptomatic patients with stage I lung cancer from New Mexico.

EXPERIMENTAL DESIGN

Cases and controls from Colorado and New Mexico were interrogated for methylation of up to 31 genes using nested, methylation-specific PCR. Individual genes and methylation indices were used to assess the association between methylation and lung cancer with logistic regression modeling.

RESULTS

Seventeen genes with ORs of 1.4 to 3.6 were identified and selected for replication in the New Mexico study. Overall, the direction of effects seen in New Mexico was similar to Colorado with the largest increase in case discrimination (ORs, 3.2-4.2) seen for the PAX5α, GATA5, and SULF2 genes. Receiver operating characteristic (ROC) curves generated from seven-gene panels from Colorado and New Mexico studies showed prediction accuracy of 71% and 77%, respectively. A 22-fold increase in lung cancer risk was seen for a subset of New Mexico cases with five or more genes methylated. Sequence variants associated with lung cancer did not improve the accuracy of this gene methylation panel.

CONCLUSIONS

These studies have identified and replicated a panel of methylated genes whose integration with other promising biomarkers could initially identify the highest risk smokers for computed tomographic screening for early detection of lung cancer.

Sex-specific association of sequence variants in CBS and MTRR with risk for promoter hypermethylation in the lung epithelium of smokers

Gene promoter hypermethylation is now regarded as a promising biomarker for the risk and progression of lung cancer. The one-carbon metabolism pathway is postulated to affect deoxyribonucleic acid (DNA) methylation because it is responsible for the generation of S-adenosylmethionine (SAM), the methyl donor for cellular methylation reactions. This study investigated the association of single nucleotide polymorphisms (SNPs) in six one-carbon metabolism-related genes with promoter hypermethylation in sputum DNA from non-Hispanic white smokers in the Lovelace Smokers Cohort (LSC) (n = 907). Logistic regression was used to assess the association of SNPs with hypermethylation using a high/low methylation cutoff. SNPs in the cystathionine beta synthase (CBS) and 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) genes were significantly associated with high methylation in males [CBS rs2850146 (-8283G > C), OR = 4.9; 95% CI: 1.98, 12.2, P = 0.0006] and low methylation in females [MTRR rs3776467 (7068A > G), OR = 0.57, 95% CI: 0.42, 0.77, P = 0.0003]. The variant allele of rs2850146 was associated with reduced gene expression and increased plasma homocysteine (Hcy) concentrations. Three plasma metabolites, Hcy, methionine and dimethylglycine, were associated with increased risk for gene methylation. These studies suggest that SNPs in CBS and MTRR have sex-specific associations with aberrant methylation in the lung epithelium of smokers that could be mediated by the affected one-carbon metabolism and transsulfuration in the cells.

Abstract 2633: Single nucleotide polymorphisms in one carbon metabolism genes are associated with methylation patterns and plasma metabolites in high risk smokers based on gender

Lung cancer is the leading cause of cancer related deaths and most lung cancers are detected at a late stage. Gene promoter hypermethylation is now regarded as a promising biomarker to identify early risk and progression of lung cancer. The one carbon metabolism pathway is postulated to affect DNA methylation because it is necessary for the generation of S-adenosyl methionine or (SAM), the methyl donor for cellular DNA methylation reactions, through complex interactions with metabolites including folate, homocysteine, and methionine. This study investigated the association of single nucleotide polymorphisms (SNPs) in one carbon metabolism related genes with DNA promoter hypermethylation in sputum cell DNA from current and former smokers in the Lovelace Smokers Cohort (n=907). The association of SNPs with methylation was analyzed by logistic regression using gender specific high and low methylation cutoffs from a 12 gene methylation panel as the outcome. SNPs in the cystathionine beta-synthase (CBS) and 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) genes were found to be statistically associated with methylation in a gender specific fashion (CBS SNP, OR=4.9; CI: 1.98, 12.2, p=.0006 in males) and (MTRR SNP, OR= 0.57, CI: 0.42, 0.77, p=0.0003 in females). Plasma homocysteine levels and the ratio of homocysteine to cystathionine increased in male samples with heterozygous or homozygous minor alleles of the CBS SNP compared to male samples with homozygous common alleles (n=86). This study suggests that SNPs in the CBS and MTRR genes are associated with methylation patterns in smokers by gender. The CBS SNP may be important in regulating plasma homocysteine and cystathionine levels that could theoretically mediate the aberrant DNA methylation in smokers at high risk to develop lung cancer. Grant Support: This work is supported by K01CA128823 NCI (Flores) and R01CA097356 NCI (Belinsky).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2633. doi:1538-7445.AM2012-2633

Genetic determinants for promoter hypermethylation in the lungs of smokers: a candidate gene-based study

The detection of tumor suppressor gene promoter methylation in sputum-derived exfoliated cells predicts early lung cancer. Here, we identified genetic determinants for this epigenetic process and examined their biologic effects on gene regulation. A two-stage approach involving discovery and replication was used to assess the association between promoter hypermethylation of a 12-gene panel and common variation in 40 genes involved in carcinogen metabolism, regulation of methylation, and DNA damage response in members of the Lovelace Smokers Cohort (N = 1,434). Molecular validation of three identified variants was conducted using primary bronchial epithelial cells. Association of study-wide significance (P < 8.2 × 10(-5)) was identified for rs1641511, rs3730859, and rs1883264 in TP53, LIG1, and BIK, respectively. These single-nucleotide polymorphisms (SNP) were significantly associated with altered expression of the corresponding genes in primary bronchial epithelial cells. In addition, rs3730859 in LIG1 was also moderately associated with increased risk for lung cancer among Caucasian smokers. Together, our findings suggest that genetic variation in DNA replication and apoptosis pathways impacts the propensity for gene promoter hypermethylation in the aerodigestive tract of smokers. The incorporation of genetic biomarkers for gene promoter hypermethylation with clinical and somatic markers may improve risk assessment models for lung cancer.

Abstract 2759: Association between genetic variations in DNA damage response pathways and risk for gene methylation in sputum from smokers

The detection of gene promoter hypermethylation in sputum containing exfoliated epithelial cells is a promising biomarker for detecting early incident lung cancer. Therefore, identifying factors that influence the propensity for this epigenetic process throughout the respiratory epithelium is a high priority. The genes and the pathways they modulate underlying the inter-individual susceptibility to DNA methylation remain largely elusive. Accumulating evidence from our group and others implicate DNA damage as an important step in the acquisition of de novo methylation. We hypothesized that genetic variations in genes (n=66) involved in carcinogen metabolism and DNA damage response, including DNA damage repair, cell cycle control, apoptosis, and methylation related pathways will be associated with gene methylation in sputum from lung-cancer free smokers. Three databases including HapMap Stage I database, University of Southern California DNA repair and Children Pulmonary Function Development Oligo Pool Assay (OPA) database, and NIBC dbSNPs database were used to select a comprehensive set of SNPs (OPA1, n=1536) to capture the major genetic variations in these genes. A pilot study for testing the association between these SNPs and risk for methylation was conducted in a subset of people (n=261) selected from Lovelace Smokers Cohort (LSR) based on their methylation index (8-gene panel). Two gene-based analyses were conducted to rank the genes and 683 tagging SNPs from the top 42 genes were selected based on the OPA1 and the HapMap Stage II databases and genotyped in all people (n=1177) with methylation data (12-gene panel) in baseline sputum samples in LSR. The effect of SNPs was tested under an additive inheritance model. A reproducible association was identified in SNPs from the TP53, GSTP1, LIG1, CASP8, BOK, and PMAIP1 genes between the pilot study and the entire study. Ongoing functional studies reveled an association between genotype and expression of LIG1 in bronchial epithelial cells from smokers. This study identified six genes involved in carcinogen detoxification and DNA damage response that were associated with risk for gene methylation in sputum from smokers. (Supported from National Cancer Institute R01 CA097356 and the State of New Mexico as a direct appropriation from the Tobacco Settlement Fund)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2759. doi:10.1158/1538-7445.AM2011-2759

Abstract 2018: Combination therapy with vidaza and entinostat suppresses tumor growth and reprograms the epigenome in an orthotopic lung cancer model

Epigenetic therapy for solid tumors could benefit from an in vivo model that defines tumor characteristics of responsiveness and resistance to facilitate patient selection. Here we report that combining the histone deacetylase inhibitor entinostat with the demethylating agent vidaza profoundly affected growth of K-ras/p53 mutant lung adenocarcinomas engrafted orthotopically in immunocompromised nude rats by targeting and ablating pleomorphic cells that occupied up to 75% of the tumor masses. A similar reduction in tumor burden was seen with epigenetic therapy in K-ras or EGFR mutant tumors growing orthotopically. Increased expression of pro-apoptotic genes and the cyclin dependent kinase inhibitor p21 was seen. Hundreds of genes were demethylated highlighted by the re-expression of polycomb-regulated genes coding for transcription factor binding proteins and the p16 gene, a key regulator of the cell cycle. Highly significant gene expression changes were seen in key regulatory pathways involved in cell cycle, DNA damage, apoptosis, and tissue remodeling. These findings demonstrate the promise for epigenetic therapy in cancer management and provide an orthotopic lung cancer model that can assess therapeutic efficacy and reprogramming of the epigenome in tumors harboring different genetic and epigenetic profiles to guide use of these drugs. This study was supported by the Waxman Foundation and by a research grant from NIH (R01 CA095568).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2018. doi:10.1158/1538-7445.AM2011-2018

Abstract 891: The association of single nucleotide polymorphisms in folate metabolism genes with hypermethylation patterns in smokers at high risk for lung cancer

Hypermethylation of promoter regions serve as potential biomarkers for the early detection of lung cancer. Because folate metabolism is necessary for nucleotide synthesis and DNA methylation reactions, that when perturbed, may both contribute to the development of cancer, hypermethylation of promoter regions in folate metabolism genes may be particularly important to explore. Dietary folate was recently found to protect against gene promoter hypermethylation patterns. This study investigated the association of functional and haplotype tagging single nucleotide polymorphisms (SNPs) in folate metabolism genes with promoter hypermethylation in sputum cell DNA from a cohort of current and former smokers (n=937). This cohort was a subset of the Lovelace Smokers’ Cohort of approximately 2000 high risk current and former smokers who were non-Hispanic white and for whom a complete methylation panel was obtained. Methylation panel status from a 12 gene panel was dichotomized into high and low methylation based on a cutoff of the number of genes methylated (&gt; = 3 genes for women and &gt; = 4 genes for men were categorized as high). Lymphocyte DNA was interrogated on a 96 SNP Illumina Goldengate platform. A SNP in the cystathionine-beta synthase gene (CBS), that converts homocysteine to cystathionine, was found to be significantly associated with gene promoter hypermethylation. Analyses used logistic regression and adjusted for multiple comparisons. There was an interaction between gender and CBS (p&lt;0.0001), so we conducted a stratified analysis by gender. Males with the variant allele had an increased risk of methylation (OR = 3.61; 95% CI: 1.71, 7.64); p&lt;0.001) and females with the variant allele had a decreased risk for methylation (OR = 0.64; 95% CI: 0.40, 1.00; p=0.05). A 20% reduction in CBS gene transcription was seen in bronchial epithelial cells heterozygous for the CBS variant allele compared to cells without the variant allele but was not statistically significant. Epidemiological studies have shown that men have higher levels of homocysteine compared to women but the mechanisms regulating this difference are not known. This study shows that a SNP in the CBS gene is associated with methylation patterns in smokers at high risk to develop lung cancer and differs by gender. This work may further help to elucidate the differences in lung cancer risk by gender.

Grant Support: This work is supported by K01CA128823 NCI and R01CA097356 NCI

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 891. doi:10.1158/1538-7445.AM2011-891

Discovery of common SNPs in the miR-205/200 family-regulated epithelial to mesenchymal transition pathway and their association with risk for non-small cell lung cancer

The activation of the epithelial-to-mesenchymal transition (EMT) program is an important step for tumor initiation, invasion, and metastasis in solid tumors, including lung cancer. The purpose of this study was to identify the sequence variants in the miR-205/200 family-regulated EMT pathway and test their association with risk for lung cancer. Fifty samples were resequenced to identify sequence variants in the miR-205/200 family-regulated EMT pathway. The association between tagSNPs and risk for non-small cell lung cancer was discovered and validated in New Mexico (386 cases and 514 controls) and Massachusetts (2453 cases and 1555 controls) case-control studies, respectively. The function of SNPs on miR-200b-a-429 promoter activity was tested using luciferase reporter and expression assays. Forty-one sequence variants with minor allele frequency ≥ 0.03 were identified, and 16 variants were selected as tagSNPs. Genetic association analysis identified that the G allele of rs61768479 was associated with a 50% reduced risk for lung cancer (OR=0.50, 95%CI=0.30-0.85, uncorr-P=0.01); however, this association was not validated (OR=0.90, 95%CI=0.72-1.13, uncorr-P=0.35). The G allele of rs61768479 was associated with lower promoter activity and miR expression by disrupting the binding of NKX2.5. In summary, no association was identified between sequence variants in the miR-205/200 family-regulated EMT pathway and risk for lung cancer. However, this study identified a comprehensive panel of tagSNPs (n=16) in the miR-205/200 family-regulated EMT pathway that can be applied to other EMT-related phenotypes such as cancer chemoresistence and prognosis.

The A/G allele of rs16906252 predicts for MGMT methylation and is selectively silenced in premalignant lesions from smokers and in lung adenocarcinomas

PURPOSE

To address the association between sequence variants within the MGMT (O(6)-methylguanine-DNA methyltransferase) promoter-enhancer region and methylation of MGMT in premalignant lesions from smokers and lung adenocarcinomas, their biological effects on gene regulation, and targeting MGMT for therapy.

EXPERIMENTAL DESIGN

Single nucleotide polymorphisms (SNP) identified through sequencing a 1.9 kb fragment 5' of MGMT were examined in relation to MGMT methylation in 169 lung adenocarcinomas and 1,731 sputum samples from smokers. The effect of promoter haplotypes on MGMT expression was tested using a luciferase reporter assay and cDNA expression analysis along with allele-specific sequencing for methylation. The response of MGMT methylated lung cancer cell lines to the alkylating agent temozolomide (TMZ) was assessed.

RESULTS

The A allele of rs16906252 and the haplotype containing this SNP were strongly associated with increased risk for MGMT methylation in adenocarcinomas (ORs ≥ 94). This association was observed to a lesser extent in sputum samples in both smoker cohorts. The A allele was selectively methylated in primary lung tumors and cell lines heterozygous for rs16906252. With the most common haplotype as the reference, a 20 to 41% reduction in promoter activity was seen for the haplotype carrying the A allele that correlated with lower MGMT expression. The sensitivity of lung cancer cell lines to TMZ was strongly correlated with levels of MGMT methylation and expression.

CONCLUSIONS

These studies provide strong evidence that the A allele of a MGMT promoter-enhancer SNP is a key determinant for MGMT methylation in lung carcinogenesis. Moreover, TMZ treatment may benefit a subset of lung cancer patients methylated for MGMT.

Multivitamins, folate, and green vegetables protect against gene promoter methylation in the aerodigestive tract of smokers

One promising approach for early detection of lung cancer is by monitoring gene promoter hypermethylation events in sputum. Epidemiologic studies suggest that dietary fruits and vegetables and the micronutrients they contain may reduce risk of lung cancer. In this study, we evaluated whether diet and multivitamin use influenced the prevalence of gene promoter methylation in cells exfoliated from the aerodigestive tract of current and former smokers. Members (N = 1,101) of the Lovelace Smokers Cohort completed the Harvard Food Frequency Questionnaire and provided a sputum sample that was assessed for promoter methylation of eight genes commonly silenced in lung cancer and associated with risk for this disease. Methylation status was categorized as low (fewer than two genes methylated) or high (two or more genes methylated). Logistic regression models were used to identify associations between methylation status and 21 dietary variables hypothesized to affect the acquisition of gene methylation. Significant protection against methylation was observed for leafy green vegetables [odds ratio (OR) = 0.83 per 12 monthly servings; 95% confidence interval (95% CI), 0.74-0.93] and folate (OR, 0.84 per 750 microg/d; 95% CI, 0.72-0.99). Protection against gene methylation was also seen with current use of multivitamins (OR, 0.57; 95% CI, 0.40-0.83). This is the first cohort-based study to identify dietary factors associated with reduced promoter methylation in cells exfoliated from the airway epithelium of smokers. Novel interventions to prevent lung cancer should be developed based on the ability of diet and dietary supplements to affect reprogramming of the epigenome.

Rosiglitazone prevents the progression of preinvasive lung cancer in a murine model

There is a critical need to identify efficacious chemopreventive agents for lung cancer that can be taken chronically with no side effects and whose mechanisms of action do not involve genotoxicity that could drive, rather than impede, cancer progression. We evaluated the ability of a chemopreventive cocktail that included selenium (antioxidant), rosiglitazone (peroxisome proliferator-activated receptor gamma agonist), sodium phenylbutyrate or valproic acid (histone deacetylase inhibitors) and hydralazine (cytosine-demethylating agent) to prevent the progression of lung cancer in A/J mice treated with NNK. Agents were administered alone or in various combinations. Effects of the chemopreventive agents were quantified based on the proportion of hyperplasias and adenomas within the mouse lung. Significant effects on tumor progression were seen in all treatment groups that included rosiglitazone as reflected by a 47-57% increase in number of hyperplasias and a 10-30% decrease in adenomas. Cell proliferation was also reduced in these treatment groups by approximately 40%. Interestingly, while treatment with rosiglitazone alone did not significantly affect lesion size, striking effects were seen in the combination therapy group that included sodium phenylbutyrate, with the volume of hyperplasias and adenomas decreasing by 40 and 77%, respectively. These studies demonstrate for the first time that chronic in vivo administration of rosiglitazone, used in the management of diabetes mellitus, can significantly block the progression of premalignant lung cancer in the A/J mouse model.

Concomitant promoter methylation of multiple genes in lung adenocarcinomas from current, former and never smokers

Aberrant promoter hypermethylation is one of the major mechanisms in carcinogenesis and some critical growth regulatory genes have shown commonality in methylation across solid tumors. Twenty-six genes, 14 identified through methylation in colon and breast cancers, were evaluated using primary lung adenocarcinomas (n = 175) from current, former and never smokers. Tumor specificity of methylation was validated through comparison of 14 lung cancer cell lines to normal human bronchial epithelial cells derived from bronchoscopy of 20 cancer-free smokers. Twenty-five genes were methylated in 11-81% of primary tumors. Prevalence for methylation of TNFRSF10C, BHLHB5 and BOLL was significantly higher in adenocarcinomas from never smokers than smokers. The relation between methylation of individual genes was examined using pairwise comparisons. A significant association was seen between 138 (42%) of the possible 325 pairwise comparisons. Most notably, methylation of MMP2, BHLHB4 or p16 was significantly associated with methylation of 16-19 other genes, thus predicting for a widespread methylation phenotype. Kaplan-Meier log-rank test and proportional hazard models identified a significant association between methylation of SULF2 (a pro-growth, -angiogenesis and -migration gene) and better patient survival (hazard ratio = 0.23). These results demonstrate a high degree of commonality for targeted silencing of genes between lung and other solid tumors and suggest that promoter hypermethylation in cancer is a highly co-ordinated event.

Difference in airflow obstruction between Hispanic and non-Hispanic White female smokers

Smoking-related respiratory diseases are a major cause of morbidity and mortality. However, the relationship between smoking and respiratory disease has not been well-studied among ethnic minorities in general and among women in particular. The objective of this cross-sectional study was to evaluate the risk of airflow obstruction and to assess lung function among Hispanic and non-Hispanic White (NHW) female smokers in a New Mexico cohort. Participants completed a questionnaire detailing smoking history and underwent spirometry testing. Outcomes studied included airflow obstruction, selected lung function parameters, and chronic mucus hyper-secretion. Chi square, logistic, and linear regression techniques were utilized. Of the 1,433 eligible women participants, 248 (17.3%) were Hispanic; and 319 had airflow obstruction (22.3%). Hispanic smokers were more likely to be current smokers, and report lower pack-years of smoking, compared to NHW smokers (p < 0.05 for all analyses). Further, Hispanic smokers were at a reduced risk of airflow obstruction compared to NHW smokers, with an O.R. of 0.51, 95% C.I. 0.34, 0.78 (p = 0.002) after adjustment for age, BMI, pack-years and duration of smoking, and current smoking status. Following adjustment for covariates, Hispanic smokers also had a higher mean absolute and percent predicted post-bronchodilator FEV(1)/FVC ratio, as well as higher mean percent predicted FEV(1) (p < 0.05 for all analyses). Hispanic female smokers in this New Mexico-based cohort had lower risk of airflow obstruction and better lung function than NHW female smokers. Further, smoking history did not completely explain these associations.

Association between common genetic variation in Cockayne syndrome A and B genes and nucleotide excision repair capacity among smokers

Mutagen sensitivity in in vitro cultured lymphocytes challenged by benzo[a]pyrene diolepoxide (BPDE) has been validated as an intrinsic susceptibility factor for several cancers. Bulky BPDE-DNA adducts are repaired via either transcription-coupled repair or global genome nucleotide excision repair depending on the location of lesions. Cockayne syndrome A (CSA) and B (CSB) play essential roles in integrating the recognition of damage, chromatin remodeling, and the core nucleotide excision repair proteins. This study evaluated the hypothesis that common genetic variation in CSA and CSB is associated with mutagen sensitivity induced by BPDE in 276 cancer-free smokers. Tag single nucleotide polymorphisms (SNP; n = 37) selected across the entire coding and putative regulatory regions of CSA and CSB based on a high-density SNP database were genotyped by the Illumina Golden Gate assay. Major principal components of CSA and CSB that captured the linkage disequilibrium from multiple SNPs were globally associated with the number of breaks per cell at the threshold of 80% (P < or = 0.02 for both genes). Haplotype H125 in CSA and H97 in CSB as well as SNPs in high linkage disequilibrium with these two haplotypes were significantly associated with a 13% to 15% reduction in the mean number of chromatid breaks per cell (P < 0.05). A resampling-based omnibus test supported the significant association between SNPs and haplotypes in CSA and mutagen sensitivity induced by BPDE (P = 0.035). This study implicates transcription-coupled repair in protecting the cell from BPDE-induced DNA damage.

Long-term effects of growth hormone replacement therapy on thyroid function in adults with growth hormone deficiency

BACKGROUND

Clinical studies on the effect of growth hormone (GH) on thyroid function in patients with GH deficiency are contradictory. Further, the majority of published observations are limited to the first 6-12 months of GH replacement therapy. The aim of our study was to estimate the incidence of clinically relevant hypothyroidism in a cohort of patients with adult GH deficiency (AGHD) during long-term therapy with recombinant human GH (rhGH).

METHODS

The study was designed as a retrospective collection of data on thyroid function in 49 AGHD patients of whom 44 (90%) had multiple hormone deficiency. Thirty-seven patients (76%) were on stable levothyroxine (LT4) replacement therapy (HYPO), and 12 (24%) were euthyroid (EUT). Therapy with rhGH was started at a dose of 3.5 microg/kg body weight and adjusted according to insulin-like growth factor-I (IGF-I) levels. At baseline, 6 months, 12 months, and yearly thereafter we measured free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone, and IGF-I. Study outcome was fT4 level below the normal range (9 pmol/L), irrespectively of fT3 or thyroid-stimulating hormone levels.

RESULTS

During a follow-up of 115 patient-years, mean fT4 level decreased significantly, although remaining within the normal range (p = 0.0242; month 48 vs. baseline). The largest decrease was between baseline and month 6, when fT4 decreased of 1.43 pmol/L (95% confidence interval, 0.33-2.53) per 1 unit (microg/kg body weight) increase in rhGH dose. The incidence of hypothyroidism was 1.2 (HYPO group) and 6.7 (EUT group) events per 100 patient-years.

CONCLUSION

We confirm that in patients with AGHD, rhGH therapy is associated with a small, although significant, decrement of fT4 in the first 6 months of replacement therapy. However, the incidence of hypothyroidism is low. Monitoring of thyroid function during rhGH therapy is advisable, particularly in the first year of therapy when the largest decrease in fT4 occurs.

Haplotypes of DNMT1 and DNMT3B are associated with mutagen sensitivity induced by benzo[a]pyrene diol epoxide among smokers

The mutagen sensitivity assay is an in vitro measure of DNA repair capacity used to evaluate intrinsic susceptibility for cancer. The high heritability of mutagen sensitivity to different mutagens validates the use of this phenotype to predict cancer susceptibility. However, genetic determinants of mutagen sensitivity have not been fully characterized. Recently, several studies found that three major cytosine DNA methyltransferases (DNMTs), especially DNMT1, have a direct role in the DNA damage response, independent of their methyltransferase activity. This study evaluated the hypothesis that sequence variants in DNMT1, DNMT3A and DNMT3B are associated with mutagen sensitivity induced by the tobacco carcinogen benzo[a]pyrene diol epoxide (BPDE) in 278 cancer-free smokers. Single-nucleotide polymorphisms (n = 134) dispersed over the entire gene and regulatory regions of these DNMTs were genotyped by the Illumina Golden Gate Assay. DNA sequence variation in the DNMT1 and DNMT3B loci was globally associated with breaks per cell (P < 0.04 for both). No global association between DNMT3A and breaks per cell was seen (P = 0.09). Two haplotypes in block1 of DNMT1 (H284) and 3B (H70) were associated with 16 and 24% increase in breaks per cell, respectively. Subjects with three or four adverse haplotypes of both DNMT1 and 3B had a 50% elevation in mean level of breaks per cell compared with persons without adverse alleles (P = 0.004). The association between sequence variants of DNMT1 and 3B and mutagen sensitivity induced by BPDE supports the involvement of these DNMTs in protecting the cell from DNA damage.

Double-strand break damage and associated DNA repair genes predispose smokers to gene methylation

Gene promoter hypermethylation in sputum is a promising biomarker for predicting lung cancer. Identifying factors that predispose smokers to methylation of multiple gene promoters in the lung could affect strategies for early detection and chemoprevention. This study evaluated the hypothesis that double-strand break (DSB) repair capacity and sequence variation in genes in this pathway are associated with a high methylation index in a cohort of current and former cancer-free smokers. A 50% reduction in the mean level of DSB repair capacity was seen in lymphocytes from smokers with a high methylation index, defined as three or more of eight genes methylated in sputum, compared with smokers with no genes methylated. The classification accuracy for predicting risk for methylation was 88%. Single nucleotide polymorphisms within the MRE11A, CHEK2, XRCC3, DNA-PKc, and NBN DNA repair genes were highly associated with the methylation index. A 14.5-fold increased odds for high methylation was seen for persons with seven or more risk alleles of these genes. Promoter activity of the MRE11A gene that plays a critical role in recognition of DNA damage and activation of ataxia-telangiectasia mutated was reduced in persons with the risk allele. Collectively, ours is the first population-based study to identify DSB DNA repair capacity and specific genes within this pathway as critical determinants for gene methylation in sputum, which is, in turn, associated with elevated risk for lung cancer.

Genotypes in matrix metalloproteinase 9 are a risk factor for COPD

A growing body of evidence indicates that matrix metalloproteinases (MMPs) play a role in the pathogenesis of COPD. Therefore, we conducted a candidate gene association study of 4 promoter polymorphisms that are known to modify expression levels of the MMP-1, MMP-2, and MMP-9 genes and a Gln279Arg polymorphism in exon 6 of MMP-9 that modifies the substrate-binding region. We examined the association of each variant and haplotypes in 385 male veterans with greater than 20 pack-years of cigarette smoking whose COPD status was characterized using spirometry. The association of these polymorphisms was also examined with decline of pulmonary function in a subset of participants. Only the 279Arg variant was more common in participants with COPD and the homozygous variant was associated with a 3-fold increased risk for COPD. In the haplotype analysis, the haplotype comprising the 249Arg and the CA promoter polymorphism within the MMP-9 gene was associated with risk, suggesting that either 279Arg or a linked variant on this haplotype underlies the association. No association of this polymorphism was found with decline in pulmonary function. These studies show that variants of the MMP-9 gene are associated with COPD in this cohort of veterans.

Which targets in clinical practice guidelines are associated with improved survival in a large dialysis organization?

Professional organizations have developed practice guidelines in the hope of improving clinical outcomes. The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has set targets for dialysis dosage (single-pool Kt/V), hematocrit, serum albumin, calcium, phosphorus, parathyroid hormone, and BP for hemodialysis (HD) patients. Several guidelines are largely based on results from observational studies. In contrast to other parameters, BP values within the KDOQI guidelines have been associated with increased mortality. Therefore, it was postulated that having multiple parameters that satisfy the current guidelines, except those for BP, is associated with improved survival among HD patients. A retrospective analysis was conducted of incident HD patients who were treated at facilities operated by Dialysis Clinic Inc., a not-for-profit dialysis provider, between January 1, 1998, and December 31, 2004 (n = 13,792). Cox proportional hazards models were used to assess the association between satisfying guidelines and mortality. Values within guidelines for single-pool Kt/V, hematocrit, serum albumin, calcium, phosphorus, and parathyroid hormone were associated with decreased mortality (P < or = 0.0001). The largest survival benefit was found for serum albumin (hazard ratio [HR] 0.27; 95% confidence interval [CI] 0.24 to 0.31). Satisfying these six guidelines simultaneously was associated with an 89% reduction in mortality (HR 0.11; 95% CI 0.06 to 0.19]). Conversely, BP values satisfying the guideline were associated with increased mortality (HR 1.90; 95% CI 1.73 to 2.10). Because this target was largely extrapolated from the general population, a randomized, controlled trial is needed to identify the optimal BP for HD patients.

The burden of chronic kidney disease among the Zuni Indians: the Zuni Kidney Project

The Zuni Indians of New Mexico are experiencing an epidemic of chronic kidney disease (CKD). The Zuni Pueblo created the Zuni Kidney Project (ZKP) to decrease the burden of CKD in the community. The aim of this study was to estimate the prevalence of CKD among Zuni Indians using National Kidney Foundation Kidney Disease Outcomes Quality Initiative criteria. The ZKP conducted a population-based, cross-sectional survey to estimate the prevalence of CKD and related risk factors among Zuni Indians aged > or =20 yr (n = 1113). GFR was estimated using equations based on serum creatinine, and urine albumin:creatinine ratio was calculated in a single spot urine sample. ESRD counts were obtained from health care providers. The age- and sex-adjusted prevalence of CKD among the Zuni Indians was >2.5-fold higher than that among the US composite population. The estimated prevalence of CKD stages 1 and 2 combined was three- to four-fold higher than that of CKD stages 3 and 4 combined. This ratio was significantly higher than that in the US composite population (1.4-fold). The prevalence of CKD stage 5 was eight-fold higher among the Zuni Indians than among the composite US population. The Zuni Indians have an expanded pool of CKD that contributes to the high burden of ESRD. The high prevalence of CKD stages 1 and 2 provides a unique opportunity to develop innovative treatment programs to reduce the burden of CKD in Zuni Pueblo.

Predicting gene promoter methylation in non-small-cell lung cancer by evaluating sputum and serum

The use of 5-methylcytosine demethylating agents in conjunction with inhibitors of histone deacetylation may offer a new therapeutic strategy for lung cancer. Monitoring the efficacy of gene demethylating treatment directly within the tumour may be difficult due to tumour location. This study determined the positive and negative predictive values of sputum and serum for detecting gene methylation in primary lung cancer. A panel of eight genes was evaluated by comparing methylation detected in the primary tumour biopsy to serum and sputum obtained from 72 patients with Stage III lung cancer. The prevalence for methylation of the eight genes in sputum (21–43%) approximated to that seen in tumours, but was 0.7–4.3-fold greater than detected in serum. Sputum was superior to serum in classifying the methylation status of genes in the tumour biopsy. The positive predictive value of the top four genes (p16, DAPK, PAX5 β, and GATA5) was 44–72% with a negative predictive value for these genes ⩾70%. The highest specificity was seen for the p16 gene, and this was associated with a odds ratio of six for methylation in the tumour when this gene was methylated in sputum. In contrast, for serum, the individual sensitivity for all genes was 6–27%. Evaluating the combined effect of methylation of at least one of the four most significant genes in sputum increased the positive predictive value to 86%. These studies demonstrate that sputum can be used effectively as a surrogate for tumour tissue to predict the methylation status of advanced lung cancer where biopsy is not feasible.

Mortality risk among hemodialysis patients receiving different vitamin D analogs

Intravenous vitamin D is standard therapy for secondary hyperparathyroidism in hemodialysis (HD) patients. In for-profit dialysis clinics, mortality was higher for patients on calcitriol compared to paricalcitol. Doxercalciferol, a second vitamin D2 analog, is currently available. We assessed mortality associated with each vitamin D analog and with lack of vitamin D therapy in patients who began HD at Dialysis Clinic Inc. (DCI), a not-for-profit dialysis provider. During the 1999-2004 study period we studied 7731 patients (calcitriol: n=3212; paricalcitol: n=2087; doxercalciferol: n=2432). Median follow-up was 37 weeks. Mortality rates (deaths/100 patient-years) were identical in patients on doxercalciferol (15.4, 95% confidence interval (13.6-17.1)) and paricalcitol (15.3 (13.6-16.9)) and higher in patients on calcitriol (19.6 (18.2-21.1)) (P<0.0001). In all models mortality was similar for paricalcitol versus doxercalciferol (hazard ratios=1.0). In unadjusted models, mortality was lower in patients on doxercalciferol (0.80 (0.66, 0.96)) and paricalcitol (0.79 (0.68, 0.92)) versus calcitriol (P<0.05). In adjusted models, this difference was not statistically significant. In all models mortality was higher for patients who did not receive vitamin D versus those who did (1.2 (1.1-1.3)). Mortality in doxercalciferol- and paricalcitol-treated patients was virtually identical. Differences in survival between vitamin D2 and D3 may be smaller than previously reported.

Changing relationship of blood pressure with mortality over time among hemodialysis patients

High BP is a major risk factor for atherosclerotic cardiovascular disease mortality in the general population. Surprising, studies that have been conducted among hemodialysis (HD) patients have yielded conflicting data on the relationship between BP and mortality. This study explores two hypotheses among HD patients: (1) The relationship between BP and mortality changes over time, and (2) mild to moderate hypertension is well tolerated. Incident HD patients who were treated at Dialysis Clinic Inc. facilities between 1993 and 2003 were studied. Primary end points were atherosclerotic cardiovascular disease and all-cause mortality. The relationship between BP and mortality was analyzed in two sets of Cox proportional hazards models. Model-B explored the relationship between baseline BP and mortality in sequential time periods. Model-TV assessed the relationship between BP, treated as time-varying, and mortality. The study sample (n = 16,959) was similar in characteristics to the United States Renal Data Systems population, although black patients were slightly overrepresented. Model-B demonstrated that the relationship between baseline BP and mortality changes over time. Low systolic BP (<120 mmHg) was associated with increased mortality in years 1 and 2. High systolic BP (> or =150 mmHg) was associated with increased mortality among patients who survived > or =3 yr. Low pulse pressure was associated with increased mortality. Model-TV demonstrated that mild to moderate systolic hypertension may be relatively well tolerated. In conclusion, the relationship between baseline BP and mortality changes over time. Mild to moderate systolic hypertension was associated with only modest increases in mortality.

Gene promoter methylation in plasma and sputum increases with lung cancer risk

PURPOSE

Lung cancer is the leading cause of cancer mortality in the United States, due in part to the lack of a validated and effective screening approach for early detection. The prevalence for methylation of seven and three genes was examined in DNA from sputum and plasma, respectively, from women at different risk for lung cancer.

EXPERIMENTAL DESIGN

Lung cancer survivors (n = 56), clinically cancer-free smokers (n = 121), and never smokers (n = 74) comprised the study population. Plasma was collected from all three groups, whereas sputum was collected from lung cancer survivors and smokers.

RESULTS

Methylation was detected in plasma DNA from 10 of 74 women who never smoked. Prevalence for methylation of the p16 gene in plasma was highest in lung cancer survivors. Lung cancer survivors showed a significant increase in the odds of having at least one or more genes methylated in plasma (odds ratio, 3.6; 95% confidence interval, 1.9-9.1) than never smokers. The prevalence for methylation of the O(6)-methylguanine-DNA methyltransferase, ras effector homologue 1, death associated protein kinase, and PAX5alpha genes in sputum was significantly higher in lung cancer survivors compared with smokers. Lung cancer survivors had 6.2-fold greater odds (95% confidence interval, 2.1-18.5) for methylation of three or more genes in sputum compared with smokers. Methylation was more commonly detected in sputum than plasma for O(6)-methylguanine-DNA methyltransferase and ras effector homologue 1, but not p16, in lung cancer survivors.

CONCLUSION

Concomitant methylation of multiple gene promoters in sputum is strongly associated with lung cancer risk.

Kidney disease among the Zuni Indians: The Zuni Kidney Project

BACKGROUND

There is an epidemic of kidney disease among the Zuni Indians. In collaboration with health care providers and research institutions, the Zuni Pueblo established the Zuni Kidney Project to reduce the burden of kidney disease.

METHODS

The Zuni Kidney Project conducted a population-based, cross-sectional survey to estimate the prevalence of albuminuria, hematuria, and related risk factors. Neighborhood household clusters served as the sampling frame. Participants completed a questionnaire, donated blood and urine samples, and had blood pressure, height, and weight measured. This survey provided the foundation for ongoing studies to identify genetic and environmental risk factors for disease susceptibility and progression.

RESULTS

Age and gender distributions among survey participants were similar to those in the eligible Zuni population. Prevalence of incipient albuminuria (IA) (0.03< or = urine albumin:creatinine ratio, UACR <0.3) and overt albuminuria (OA) (UACR < 0.3) were higher among diabetics [IA 34.3% (28.3, 40.4%); OA 18.6% (13.7, 23.6%)] than nondiabetics [IA 11.1% (9.3, 12.8%); OA 1.7% (1.0, 2.5%)]. Nondiabetics comprised 58.6% (52.2, 65.0%) and 30.9% (19.9, 41.9%) of participants with IA and OA, respectively. The prevalence of hematuria was higher among diabetics [> or = trace 47.0% (40.7, 53.4); > or =50 red blood cell/microL 25.8% (20.3, 31.4%)] than nondiabetics [> or = trace 31.1% (28.5, 33.7%); > or =50 red blood cell/microL 16.6% (14.5, 18.7%)]. Hypertension was associated with albuminuria among diabetic and nondiabetic participants. Hypercholesterolemia was associated with albuminuria among nondiabetic participants. Diabetes and alcohol use were associated with hematuria.

CONCLUSION

The high prevalences of albuminuria among nondiabetics and of hematuria among diabetics and nondiabetics are consistent with high rates of nondiabetic kidney disease among Zuni Indians with and without diabetes.

Inhibition of DNA methylation and histone deacetylation prevents murine lung cancer

Disruption of one allele for the cytosine-DNA methyltransferase 1 (DNMT1) gene in mice with a germ-line mutation in a tumor suppressor gene was shown previously to reduce tumor formation in juvenile animals. This effect is now reproduced in our studies of mature mice where this genetic DNMT1 reduction leads to a 50% decrease in tobacco carcinogen-induced lung cancer and a similar reduction in DNMT activity in type II pneumocytes that give rise to the tumors. Short-term treatment of DNMT wild-type female mice with low doses of the demethylating agent 5-aza-2'-deoxycytidine decreased the incidence of neoplasms by 30%. Importantly, when 5-aza-2'-deoxycytidine was combined with the histone deacetylase inhibitor sodium phenylbutyrate, lung tumor development was significantly reduced by >50%; no effect was seen with phenylbutyrate alone. This identical combination of inhibitors also acts synergistically to cause re-expression of densely hypermethylated and transcriptionally silenced tumor suppressor genes in human cancer cells. Thus, reduction in DNMT and histone deacetylase activities that likely block epigenetically mediated gene silencing might provide a novel clinical strategy to help prevent the leading cause of cancer death in the United States.

Family history, Hispanic ethnicity, and prostate cancer risk

Family history is known to be a prostate cancer (CaP) risk factor for non-Hispanic Whites (NHWs) and African Americans, but little data are available on the risk for Hispanics (Hs). This population-based case-control study used mailed surveys to assess the effects of ethnicity and family history of CaP on CaP risk in Hs and NHWs. Cases (N = 351) were those identified by the New Mexico Tumor Registry as having been newly diagnosed with CaP from October 1, 1994 to October 31, 1995. Controls (N = 618) were randomly selected and frequency-matched to cases by ethnicity and 5-year age groups. Multivariate analyses were conducted using conditional logistic regression. After controlling for age, education, and income in the models, positive family history increased risk for both Hispanics (H) (OR 2.7, 95% CI 1.5-4.7) and non-Hispanic Whites (NHW) (OR 2.0, 95% CI 1.3-3.1), suggesting that having a family history of CaP is a risk factor for both ethnic groups.

The Zuni kidney project: a collaborative approach to an epidemic of kidney disease

There is an epidemic of renal disease among the Zuni Indians. In contrast to most other American-Indian communities, the epidemic of renal disease among the Zuni Indians reflects high rates of diabetic and nondiabetic renal disease. Almost every Zuni Indian has a relative with end-stage renal disease. This epidemic offers a unique opportunity to advance our understanding of the risk factors for the susceptibility and/or progression of renal disease. Thus, Zuni Tribal leaders formed a research partnership with the University of New Mexico Health Sciences Center, Indian Health Service, Southwest Foundation for Biomedical Research and Dialysis Clinic Inc., to establish the Zuni Kidney Project (ZKP). The ZKP conducted a population-based, cross-sectional survey of the Zuni Pueblo. Age and gender distributions among survey participants were similar to those of the eligible Zuni population. Among diabetics the prevalence (95% confidence interval) of incipient albuminuria (IA) was 32.3% (25.1, 39.5) in women and 36.1% (24.7, 47.5) in men. The prevalence of IA among nondiabetics was 9.3% (6.9, 11.7) in women and 12.2% (9.7, 14.7) in men. Among diabetics, the prevalence of overt albuminuria (OA) was 17.7% (11.9, 23.5) in women and 20.8% (11.4, 30.2) in men. Among nondiabetics, OA was present in 1.2% (0.3, 2.1) of women and 2.3% (1.1, 3.5) of men. Although IA and OA were each more common among diabetics, the majority of participants with albuminuria were nondiabetics. Hematuria was common among both diabetics and nondiabetics. Among diabetics, the crude prevalence of hematuria was similar among men and women. Among nondiabetics, however, hematuria was more common among women. Diabetes and obesity were more common among women than men. In contrast, hypertension and hypercholesterolemia were more common among men than women. The ZKP is incorporating these preliminary data into planning for the development and implementation of primary and secondary prevention programs.

Prevalence of hematuria among Zuni Indians with and without diabetes: The Zuni kidney Project

BACKGROUND

There is an epidemic of kidney disease among the Zuni Indians. In contrast to other American Indian tribes, the epidemic among the Zuni Indians is attributable to diabetic and nondiabetic renal disease.

METHODS

The Zuni Kidney Project, established to reduce the burden of renal disease, conducted a population-based cross-sectional survey of Zuni Indians aged 5 years or older to precisely estimate the prevalence of hematuria. The survey used neighborhood household clusters as the sampling frame to maximize ascertainment and minimize bias. During the survey, we administered a questionnaire; collected blood and urine samples; and measured blood pressure, height, and weight.

RESULTS

Age and sex distributions in our sample (n = 1,469) were similar to those of the eligible Zuni population (n = 9,228). Prevalences of hematuria, defined as dipstick of trace or greater and 50 red blood cells/microL or greater, age- and sex-adjusted to the Zuni population aged 5 years or older, were 33.2% (95% confidence interval [CI], 30.7 to 35.6) and 17.8% (95% CI, 15.8 to 19.8), respectively. Hematuria of trace or greater was more common among females (40.6%; 95% CI, 37.0 to 44.1) than males (25.1%; 95% CI, 21.8 to 28.4). Hematuria of trace or greater was common among Zuni Indians without diabetes (females, 39.7%; 95% CI, 35.7 to 43.8; males, 22.7%; 95% CI, 19.4 to 26.1) and with diabetes (females, 47.5%; 95% CI, 39.8 to 55.2; males, 45.8%; 95% CI, 34.3 to 57.3). Diabetes and alcohol use for greater than 10 years were associated with hematuria among males, but not females.

CONCLUSION

The prevalence of hematuria is high among Zuni Indians with and without diabetes. These findings are consistent with the hypothesis that nondiabetic kidney disease is common among Zuni Indians with and without diabetes.

Epidemic of diabetic and nondiabetic renal disease among the Zuni Indians: the Zuni Kidney Project

There is an epidemic of renal disease among the Zuni Indians. The prevalence of end-stage renal disease among the Zuni Indians is 18.4-fold and 7.4-fold higher than among European Americans and American Indians/Alaskan Natives, respectively. In contrast to other American Indian tribes, nondiabetic renal disease accounts for a significant percent of the renal disease burden among the Zuni Indians. To explore this hypothesis, a community epidemiologic study of the Zuni Pueblo was conducted. A questionnaire was administered, blood and urine samples were collected, and BP, height, and weight were measured. Neighborhood household clusters were used as the sampling frame to maximize ascertainment and minimize bias. Age and gender distributions in the sample (n = 1483) were similar to those of the eligible Zuni population (n = 9228). The prevalence, age-adjusted and gender-adjusted to the Zuni population, of incipient (0.03 < or = UACR < 0.3) albuminuria (IA) (15.0% [95% confidence interval, 13.1 to 16.9%]), and overt (UACR > or = 0.3) albuminuria (OA) (4.7% [3.6 to 5.8%]) was high. The prevalence estimates for IA and OA were higher among diabetic participants (IA: 33.6% [27.6 to 39.7%]; OA: 18.7% [13.7 to 23.7%]) than nondiabetic participants (IA: 10.8% [9.0 to 12.6%]; OA: 1.8% [1.0 to 2.5%]). However, there were more nondiabetic participants; therefore, they comprised 58.0% [51.4 to 64.6%] and 30.9% [20.0 to 41.7%] of participants with IA and OA, respectively. In contrast to most other American Indian tribes, nondiabetic renal disease contributes significantly to the overall burden of renal disease among the Zuni Indians.

Prevalence of diabetes is higher among female than male Zuni indians

OBJECTIVE

Test the hypothesis that diabetes and related risk factors are more common among female than male Zuni Indians.

RESEARCH DESIGN AND METHODS

We conducted a population-based, cross-sectional survey of the Zuni Indians aged > or =5 years. We used households within neighborhood clusters as the sampling frame. We administered a questionnaire, collected blood and urine, and measured height and weight. Self-reported diabetes was used to assess previously diagnosed diabetes. Participants without a prior history of diabetes were classified as having newly diagnosed diabetes if they had HbA(1c) >7.0% or random glucose > or =11.1 mmol/l during the survey.

RESULTS

The prevalence of previously diagnosed diabetes among Zuni Indians aged > or =5 years (n = 1,503) was higher among female Zuni Indians (16.7% [95% CI 14.1-19.3]) than male Zuni Indians (9.7% [7.4-12.1]) (P < 0.001). The prevalence of newly diagnosed diabetes was similar among female Zuni Indians (2.4% [1.4-3.4]) and male Zuni Indians (2.4% [1.2-3.6]). The prevalence of previously and newly diagnosed diabetes was higher among female Zuni Indians (19.1% [16.4-21.9]) than male Zuni Indians (12.2% [9.5-14.8]) (P < 0.001). The prevalence of obesity was higher among female Zuni Indians (34.3% [30.9-37.7]) than male Zuni Indians (21.5% [18.4-24.7]) (P < 0.001). Obesity was associated with diabetes among female and male Zuni Indians. Physical inactivity was more common among female Zuni Indians (44.2% [40.7-47.8]) than male Zuni Indians (35.1% [31.5-38.7]) (P < 0.001). However, physical inactivity was not associated with diabetes among either female or male Zuni Indians. Gestational diabetes was a risk factor among female Zuni Indians.

CONCLUSIONS

Among the Zuni Indians, the prevalence of diabetes was 57% higher among female than male members of the population. Culture, tradition, and lifestyle differences may contribute to the higher prevalence of diabetes and obesity among female Zuni Indians.

Aberrant promoter methylation in bronchial epithelium and sputum from current and former smokers

Recent studies from our laboratory suggest that gene-specific methylation changes in sputum could be good intermediate markers for the early detection of lung cancer and defining the efficacy of chemopreventive interventions. The purpose of our study was to determine the prevalence for aberrant promoter methylation of the p16, O(6)-methylguanine-DNA methyltransferase (MGMT), death-associated protein (DAP) kinase, and Ras effector homologue (RASSFIA) genes in nonmalignant bronchial epithelial cells from current and former smokers in a hospital-based, case control study of lung cancer. The relationship between loss of heterozygosity, at 9p and p16 methylation in bronchial epithelium and the prevalence for methylation of these four genes in sputum from cancer-free, current and former smokers were also determined. Aberrant promoter methylation of p16 was seen in at least one bronchial epithelial site from 44% of cases and controls. Methylation of the DAP kinase gene was seen in only 1 site from 5 cases and 4 controls, whereas methylation of the RASSFIA was not detected in the bronchial epithelium. Promoter methylation for p16 and DAP kinase was seen as frequently in bronchial epithelium from current smokers as from former smokers. No promoter methylation of these genes was detected in bronchial epithelium from never-smokers. Methylation of the p16 gene was detected in sputum from 23 of 66 controls. DAP kinase gene promoter methylation was also seen in sputum from 16 controls, and 8 of these subjects were positive for p16 methylation. Methylation of the MGMT gene was seen in sputum from 9 controls, whereas RASSFIA promoter methylation was only seen in 2 controls. The correlation between p16 status in the bronchial epithelium obtained from lung lobes that did not contain the primary tumor and the tumor itself was examined. Seventeen of 18 tumors (94%) showed an absolute concordance, being either methylated in the tumor and at least 1 bronchial epithelial site, or unmethylated in both tumor and bronchial epithelium. These results indicate that aberrant promoter hypermethylation of the p16 gene, and to a lesser extent, DAP kinase, occurs frequently in the bronchial epithelium of lung cancer cases and cancer-free controls and persists after smoking cessation. The strong association seen between p16 methylation in the bronchial epithelium and corresponding primary tumor substantiates that inactivation of this gene, although not transforming by itself, is likely permissive for the acquisition of additional genetic and epigenetic changes leading to lung cancer.

A population-based, cross-sectional survey of the Zuni Pueblo: a collaborative approach to an epidemic of kidney disease

Approximately 80% of the Zuni Indians live in Zuni Pueblo in rural New Mexico. The Zuni are relatively endogamous and differ culturally and ethnically from neighboring tribes. The Zuni Pueblo is experiencing an epidemic of renal disease. The prevalence of end-stage renal disease (ESRD) among the Zuni Indians, adjusted for age and gender, is 6-fold and 21-fold higher than the prevalence rates for Native Americans and European Americans. Almost all Zuni tribal members have a relative with ESRD. This has led to strong public support for renal research. In response, the Zuni community has partnered with the Indian Health Service (IHS), University of New Mexico Health Sciences Center (UNMHSC), Southwest Foundation for Biomedical Research (SFBR), Dialysis Clinic Inc (DCI), and the National Institutes of Health (NIH) to establish a research consortium, the Zuni Kidney Project (ZKP). The goal of the ZKP is to reduce the burden of renal disease in the Zuni community. The ZKP combines traditional, population-based, epidemiologic methods with modern techniques of population genetics. The foundation of the ZKP is a population-based, cross-sectional survey (PBCSS). The PBCSS has 3 specific aims: (1) estimate the prevalence of renal disease in Zuni; (2) assess risk factors for renal disease susceptibility; and (3) identify participants for planned case-control, longitudinal cohort, and family studies designed to identify environmental, familial, and genetic risk factors for the susceptibility and/or progression of renal disease. Preliminary results of the PBCSS confirm that the epidemic of renal disease in Zuni Indians is due to high rates of both diabetic and nondiabetic renal disease.

The excess costs of breast cancer health care in Hispanic and non-Hispanic female members of a managed care organization

The differences in costs for health care services between women with breast cancer and those without were estimated for Hispanic and non-Hispanic members of a managed care organization. A total of 317 cases of breast cancer and 949 controls were selected using a comprehensive patient database. All health care costs for the 4-12 months prior to the case's diagnosis and for the 12 months following the case's diagnosis were obtained. Costs were defined as charges to the health plan. Mean differences in total health care costs between cases and controls were predicted using Tobit models for 4-12 months prior to diagnosis and the year after diagnosis by age group. Compared to controls, women diagnosed with in situ breast cancers in all age groups had significantly higher health care costs 4-12 months prior to diagnosis. For women under 50 years of age, the difference in costs for cases compared to controls 12 months after diagnosis was almost three times greater for women with regional/distant disease ($17,093 +/- $1,559) compared to in situ disease ($5,089 +/- $1,050). For women in the two other age groups (50-70 years and over 70 years), the difference was over twice as great for those with regional/distant disease compared to those with in situ disease. Mean differences between cases and controls in health care costs 12 months after diagnosis were similar for Hispanic and non-Hispanic women for all stages of disease.

Mammography utilization after a benign breast biopsy among Hispanic and non-Hispanic women

BACKGROUND

In spite of the effectiveness of mammography screening for early detection of breast carcinoma, the use of screening mammography varies widely across racial and ethnic groups. Recently, concerns have been raised about the potential adverse effect a benign breast biopsy may have on subsequent mammography utilization, including subsequent use among minority women.

METHODS

Computerized health care claims data for 1991 through 1997 from a managed care organization were used to compare mammography use among Hispanic and non-Hispanic women who had had a mammogram followed by an incisional or excisional benign breast biopsy to women who had had a mammogram and no biopsy. Through survival analysis methods, the time-to-next mammogram was compared among these three groups.

RESULTS

The sample included 693 (3.2%) and 289 (1.3%) women who had had a mammogram followed by an incisional biopsy or an excisional biopsy, respectively, and 20,540 (95.4%) women who had had a mammogram and no biopsy. Both Hispanic and non-Hispanic women with a biopsy returned sooner for subsequent mammograms than women without a biopsy (P < 0.0001). Hispanic women without a biopsy returned later than non-Hispanic women without a biopsy (P < 0.0001). However, Hispanic women with an excisional biopsy returned sooner than non-Hispanic women (P < 0.05).

CONCLUSIONS

Within a managed care organization, both Hispanic and non-Hispanic women who had had a mammogram followed by a benign breast biopsy returned sooner for a subsequent mammogram than women who had had a mammogram and no biopsy. However, ethnic differences in time-to-next mammogram were observed for women without a biopsy and those with an excisional biopsy. Hispanic women without a biopsy returned later for a subsequent mammogram than non-Hispanic women in similar groups, but those with an excisional biopsy returned sooner.

Reduced DNA-dependent protein kinase activity is associated with lung cancer

Reduced DNA repair capacity of carcinogen-induced DNA damage is now thought to significantly influence inherent susceptibility to lung cancer. DNA-dependent protein kinase (DNA-PK) is a serine-threonine kinase activated by the presence of double-strand breaks in DNA that appears to play a major role in non-homologous recombination and transcriptional control. The purpose of this study was to determine whether DNA-PK activity varies among individuals and how this affects lung cancer risk. DNA-PK activity in peripheral mononuclear cells from individuals with lung cancer (n = 41) was compared with lung cancer-free controls (n = 41). Interindividual variability was seen within each group, however, significant differences (P = 0.03) in DNA-PK activity between cases and controls were seen when comparing the distribution of enzyme activity among these two groups. The percentages of cases and controls with DNA-PK activity in the ranges 2.5-5.0 and 7.6-10.0 units were 39 versus 20% and 7 versus 29%, respectively. The enzyme activity in peripheral mononuclear cells reflected that seen in bronchial epithelial cells, one progenitor cell for lung cancer, supporting the use of peripheral mononuclear cells for larger population-based studies of DNA-PK activity. Its role as a potential modifier for lung cancer risk was supported by the fact that cell growth in bronchial epithelial cells exposed to bleomycin was directly associated with enzyme activity. The results of this study demonstrate that reduced DNA-PK repair activity is associated with risk for lung cancer.