Jonathan N. Hofmann

Long-term Variation in Serum 25-Hydroxyvitamin D Concentration among Participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

Molecular epidemiologic studies of vitamin D and risk of cancer and other health outcomes usually involve a single measurement of the biomarker 25-hydroxyvitamin D [25(OH)D] in serum or plasma. However, the extent to which 25(OH)D concentration at a single time point is representative of an individuals long-term vitamin D status is unclear. To address this question, we evaluated within-person variability in 25(OH)D concentrations across serum samples collected at three time points over a 5-year period among 29 participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Blood collection took place year-round, although samples for a given participant were collected in the same month each year. The within-person coefficient of variation and intraclass correlation coefficient were calculated using variance components estimated from random effects models. Spearman rank correlation coefficients were calculated to evaluate agreement between measurements at different collection times (baseline, +1 year, +5 years). The within-subject coefficient of variation was 14.9% [95% confidence interval (CI), 12.4-18.1%] and the intraclass correlation coefficient was 0.71 (95% CI, 0.63-0.88). Spearman rank correlation coefficients comparing baseline to +1 year, +1 year to +5 years, and baseline to +5 years were 0.65 (95% CI, 0.37-0.82), 0.61 (0.29-0.81), and 0.53 (0.17-0.77), respectively. Slightly stronger correlations were observed after restricting to non-Hispanic Caucasian subjects. These findings suggest that serum 25(OH)D concentration at a single time point may be a useful biomarker of long-term vitamin D status in population-based studies of various diseases. Cancer Epidemiol Biomarkers Prev; 19(4); 927–31. ©2010 AACR.

An investigation of risk factors for renal cell carcinoma by histologic subtype in two case-control studies

To investigate whether renal cell carcinoma (RCC) histologic subtypes possess different etiologies, we conducted analyses of established RCC risk factors by subtype (clear cell, papillary and chromophobe) in two case‐control studies conducted in the United States (1,217 cases, 1,235 controls) and Europe (1,097 cases, 1,476 controls). Histology was ascertained for 706 U.S. cases (58% of total) and 917 European cases (84%) through a central slide review conducted by a single pathologist. For the remaining cases, histology was abstracted from the original diagnostic pathology report. Case‐only analyses were performed to compute odds ratios (ORs) and 95% confidence intervals (CI) summarizing subtype differences by age, sex and race. Case‐control analyses were performed to compute subtype‐specific ORs for other risk factors using polytomous regression. In case‐only analyses, papillary cases (N = 237) were older (OR = 1.2, 95% CI = 1.1–1.4 per 10‐year increase), less likely to be female (OR = 0.5, 95% CI = 0.4–0.8) and more likely to be black (OR = 2.6, 95% CI = 1.8–3.9) as compared to clear cell cases (N = 1,524). In case‐control analyses, BMI was associated with clear cell (OR = 1.2, 95% CI = 1.1–1.3 per 5 kg/m2 increase) and chromophobe RCC (N = 80; OR = 1.2, 95% CI = 1.1–1.4), but not papillary RCC (OR = 1.1, 95% CI = 1.0–1.2; test versus clear cell, p = 0.006). No subtype differences were observed for associations with smoking, hypertension or family history of kidney cancer. Our findings support the existence of distinct age, sex and racial distributions for RCC subtypes, and suggest that the obesity‐RCC association differs by histology.

A prospective study of circulating adipokine levels and risk of multiple myeloma

It has been hypothesized that the observed excess risk of multiple myeloma (MM) among obese persons could be the result of altered circulating levels of adipokines, polypeptide hormones with pro- and anti-inflammatory properties secreted by adipose tissue. We investigated whether circulating levels of leptin, total adiponectin, and high molecular weight adiponectin are associated with subsequent MM risk among 174 MM patients and 348 controls within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Inverse associations with MM were observed for total adiponectin (highest quartile vs lowest: odds ratio = 0.49; 95% CI = 0.26-0.93, P(trend) = .03) and high molecular weight adiponectin (0.44; 0.23-0.85, P(trend) = .01). These associations remained after restricting to MM patients diagnosed ∼ 8 years or more after blood collection. Leptin levels were not associated with MM risk. The results of this study, to our knowledge the first prospective investigation of circulating adipokines and MM, suggest that adiponectin may play an important role in obesity-related myelomagenesis.

A case-control study of peripheral blood mitochondrial DNA copy number and risk of renal cell carcinoma.

Background Low mitochondrial DNA (mtDNA) copy number is a common feature of renal cell carcinoma (RCC), and may influence tumor development. Results from a recent case-control study suggest that low mtDNA copy number in peripheral blood may be a marker for increased RCC risk. In an attempt to replicate that finding, we measured mtDNA copy number in peripheral blood DNA from a U.S. population-based case-control study of RCC. Methodology/Principal Findings Relative mtDNA copy number was measured in triplicate by a quantitative real-time PCR assay using DNA extracted from peripheral whole blood. Cases (n = 603) had significantly lower mtDNA copy number than controls (n = 603; medians 0.85, 0.91 respectively; P = 0.0001). In multiple logistic regression analyses, the lowest quartile of mtDNA copy number was associated with a 60% increase in RCC risk relative to the highest quartile (OR = 1.6, 95% CI = 1.1–2.2; P trend = 0.009). This association remained in analyses restricted to cases treated by surgery alone (OR Q1 = 1.4, 95% CI = 1.0–2.1) and to localized tumors (2.0, 1.3–2.8). Conclusions/Significance Our findings from this investigation, to our knowledge the largest of its kind, offer important confirmatory evidence that low mtDNA copy number is associated with increased RCC risk. Additional research is needed to assess whether the association is replicable in prospective studies.

Non-hodgkin lymphoma risk and insecticide, fungicide and fumigant use in the agricultural health study.

Farming and pesticide use have previously been linked to non-Hodgkin lymphoma (NHL), chronic lymphocytic leukemia (CLL) and multiple myeloma (MM). We evaluated agricultural use of specific insecticides, fungicides, and fumigants and risk of NHL and NHL-subtypes (including CLL and MM) in a U.S.-based prospective cohort of farmers and commercial pesticide applicators. A total of 523 cases occurred among 54,306 pesticide applicators from enrollment (1993–97) through December 31, 2011 in Iowa, and December 31, 2010 in North Carolina. Information on pesticide use, other agricultural exposures and other factors was obtained from questionnaires at enrollment and at follow-up approximately five years later (1999–2005). Information from questionnaires, monitoring, and the literature were used to create lifetime-days and intensity-weighted lifetime days of pesticide use, taking into account exposure-modifying factors. Poisson and polytomous models were used to calculate relative risks (RR) and 95% confidence intervals (CI) to evaluate associations between 26 pesticides and NHL and five NHL-subtypes, while adjusting for potential confounding factors. For total NHL, statistically significant positive exposure-response trends were seen with lindane and DDT. Terbufos was associated with total NHL in ever/never comparisons only. In subtype analyses, terbufos and DDT were associated with small cell lymphoma/chronic lymphocytic leukemia/marginal cell lymphoma, lindane and diazinon with follicular lymphoma, and permethrin with MM. However, tests of homogeneity did not show significant differences in exposure-response among NHL-subtypes for any pesticide. Because 26 pesticides were evaluated for their association with NHL and its subtypes, some chance finding could have occurred. Our results showed pesticides from different chemical and functional classes were associated with an excess risk of NHL and NHL subtypes, but not all members of any single class of pesticides were associated with an elevated risk of NHL or NHL subtypes. These findings are among the first to suggest links between DDT, lindane, permethrin, diazinon and terbufos with NHL subtypes.

A prospective study of 67 serum immune and inflammation markers and risk of non-Hodgkin lymphoma.

Although severe immune dysregulation is an established risk factor for non-Hodgkin lymphoma (NHL), the importance of subclinical immunologic effects is unclear. We compared baseline serum levels of 67 immune and inflammation markers between 301 patients with NHL diagnosed 5+ years after blood collection and 301 control patients within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. We observed associations with NHL for elevated B-cell-attracting chemokine 1 (BCA-1; fourth quartile vs first: odds ratio [OR], 2.7; 95% confidence interval [CI], 1.7-4.2; Ptrend = 1.0 × 10(-6)), soluble tumor necrosis factor receptor 2 (sTNFR2; OR, 3.4; 95% CI, 2.0-5.8; Ptrend = 1.1 × 10(-6)), and soluble vascular endothelial growth factor receptor 2 (sVEGFR2; OR, 2.3; 95% CI, 1.4-3.9; Ptrend = .0005) that remained significant after Bonferroni correction, simultaneous model adjustment, and restriction to cases diagnosed 8 to 13 years after blood collection. Associations with other markers were observed, although none remained associated with NHL after adjustment for BCA-1, sTNFR2, and sVEGFR2. Our findings suggest that circulating BCA-1, sTNFR2, and sVEGFR2 are associated with NHL risk well in advance of diagnosis. Additional research is needed to replicate these findings and elucidate the underlying biologic mechanisms.

Serum Cholinesterase Inhibition in Relation to Paraoxonase-1 (PON1) Status among Organophosphate-Exposed Agricultural Pesticide Handlers

Background Animal studies have demonstrated that low paraoxonase-1 (PON1) status (i.e., low catalytic efficiency and/or low plasma PON1 activity) is associated with neurotoxic effects after exposure to several organophosphate (OP) insecticides. However, few human studies have investigated associations between PON1 status and intermediate end points, such as serum cholinesterase [butyrylcholinesterase (BuChE)] inhibition, among OP-exposed individuals. Objectives We evaluated the relation between plasma PON1 status and BuChE inhibition among OP-exposed agricultural pesticide handlers. Methods Agricultural pesticide handlers in Washington State were recruited during the 2006 and 2007 spray seasons when they were seen for follow-up ChE testing by collaborating medical providers as part of a statewide monitoring program. Blood samples were collected from 163 participants and tested for PON1 status based on plasma PON1 activity [arylesterase (AREase)] and PON1 Q192R genotype. We evaluated percent change in BuChE activity from baseline level in relation to PON1 status. Results We observed significantly greater BuChE inhibition among QQ homozygotes relative to RR homozygotes (p = 0.036). Lower levels of plasma PON1 activity were significantly associated with greater BuChE inhibition (p = 0.004). These associations remained after adjustment for year, days since baseline test, age, and OP exposure in the last 30 days. Conclusions We found that both low PON1 catalytic efficiency (i.e., the Q192 alloform) and low plasma PON1 activity were associated with BuChE inhibition among OP-exposed agricultural pesticide handlers. Corroborative findings from future studies with prospective collection of blood samples for PON1 testing, more sensitive markers of OP-related effects, and larger sample sizes are needed.

Body size and multiple myeloma mortality: a pooled analysis of 20 prospective studies

Multiple myeloma (MM) is a rare but highly fatal malignancy. High body weight is associated with this cancer, but several questions remain regarding the aetiological relevance of timing and location of body weight. To address these questions, we conducted a pooled analysis of MM mortality using 1·5 million participants (including 1388 MM deaths) from 20 prospective cohorts in the National Cancer Institute Cohort Consortium. Proportional hazards regression was used to calculate pooled multivariate hazard ratios (HRs) and 95% confidence intervals (CIs). Associations with elevated MM mortality were observed for higher early‐adult body mass index (BMI; HR = 1·22, 95% CI: 1·09–1·35 per 5 kg/m2) and for higher cohort‐entry BMI (HR 1·09, 95% CI: 1·03–1·16 per 5 kg/m2) and waist circumference (HR = 1·06, 95% CI: 1·02–1·10 per 5 cm). Women who were the heaviest, both in early adulthood (BMI 25+) and at cohort entry (BMI 30+) were at greater risk compared to those with BMI 18·5 ≤ 25 at both time points (HR = 1·95, 95% CI: 1·33–2·86). Waist‐to‐hip ratio and height were not associated with MM mortality. These observations suggest that overall, and possibly also central, obesity influence myeloma mortality, and women have the highest risk of death from this cancer if they remain heavy throughout adulthood.

Intra-individual variability over time in serum cytokine levels among participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

BACKGROUND Serum measurements of cytokines, mediators of various B and T cell activities, are important markers of inflammation and immune dysregulation. We assessed the reproducibility of serum cytokine measurements over a five-year period among participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). METHODS Levels of 13 cytokines [interleukin (IL) 1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, interferon-gamma (IFNγ), granulocyte macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-α (TNFα)] in stored sera from three collections (study baseline,+1 year, and+5 years) among 28 randomly selected PLCO participants were measured using a high-sensitivity Luminex xMap-based multiplex panel. Within- and between-subject components of variance were estimated from random effects models and were used to calculate the coefficient of variation (CV) and intraclass correlation coefficient (ICC) for analytes with <30% of samples below the limit of detection (LOD). Spearman correlation coefficients between measurements of the same analyte over time and between analytes were also calculated. RESULTS Among the six cytokines with <30% of samples below the LOD, we observed excellent reproducibility for IL-6, IL-7, IL-13, and TNFα (ICC≥0.73), and fair to good reproducibility for IL-8 (ICC=0.55) and IL-10 (ICC=0.60). Spearman correlation coefficients comparing paired measurements of each cytokine at baseline and at +5 years were high (ρ≥0.74) with the exception of IL-10 (ρ=0.44). CONCLUSIONS These results suggest that measurements of most of the cytokines evaluated in this study were highly reproducible over five-year periods.

A nested case-control study of leukocyte mitochondrial DNA copy number and renal cell carcinoma in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial.

Mitochondrial DNA (mtDNA) is vulnerable to mutations, and the number of copies of mtDNA per cell may increase to compensate for DNA damage. Case-control studies have reported associations between altered mtDNA copy number and risk of renal cell carcinoma (RCC); however, this association has not been investigated prospectively. We conducted a nested case-control study (252 cases and 504 controls) of RCC risk in relation to pre-diagnostic leukocyte mtDNA copy number in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. mtDNA copy number was measured in triplicate using a fluorescence-based quantitative PCR assay; samples from 22 cases and 36 controls could not be assayed, leaving 230 cases and 468 controls for analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. High mtDNA copy number was associated with an increased risk of RCC, both overall (highest quartile versus lowest: OR = 2.0, 95% CI = 1.2-3.2; P trend = 0.002) and among cases diagnosed ≥6 years after blood collection (OR = 2.6, 95% CI = 1.4-5.0; P trend = 0.003). These findings did not differ significantly by sex, body mass index, history of hypertension or smoking status (P interaction ≥ 0.3). Results of this study suggest that high pre-diagnostic leukocyte mtDNA copy number, a suspected marker of oxidative DNA damage and mitochondrial dysfunction, is associated with increased future RCC risk.