Citations

Abstract Introduction: Peripheral blood leukocyte (PBL) telomere length is associated with colon cancer (CC) risk, but the relationship of PBL telomere length to survival in CC patients receiving chemotherapy is unknown. Methods: We measured relative telomere length (RTL) by qPCR of PBL DNA from 2,748 cases (53% male, 85% white, median age 58 yrs) in the North American Phase III Intergroup Trial N0147 that compared disease-free survival (DFS) among completely resected Stage III CC treated with mFOLFOX6 +/- cetuximab. Tumor markers were assessed, and 12% were BRAF mutant; 35% Kras mutant, and 12% deficient mismatch repair (dMMR). Linear and non-linear prognostic associations of PBL RTL to the primary endpoint of DFS were assessed by Cox models. Optimal categories of RTL were developed using cumulative martingale residual plots, designated from shortest to longest RTL (Table 1). Results: Never smokers had longer PBL RTL (p = 0.0006) than past or current smokers. Those with diabetes mellitus (DM) had longer PBL RTL than those without DM (p = 0.0165). PBL RTL was not associated with any tumor markers (MMR status; p = 0.7174; BRAF mutant vs wild-type (wt); p =0.4039; Kras mutant vs wt; p= 0.1149). PBL RTL was significantly associated with DFS in a non-linear form (p = 0.0389). Cases in the longer RTL category had more favorable DFS than those with shorter or longest RTL, (Table), which remained after adjusting for age, sex , T/N stage, grade, tumor markers, and treatment (p = 0.0230). We observed no significant interaction (p = 0.1490) between RTL categories and treatment. Conclusion: We observed a non-linear association between RTL and DFS in stage III CC, suggesting that an optimal range telomere length can influence tumor behavior in CC patients. Future studies of telomere maintenance mechanisms may help to explain the association of RTL with improved DFS. RTL is associated with smoking and DM in CC cases but further studies are needed to determine if either tobacco use or DM affect survival from CC by modulating PBL telomere length. Citation Format: Nivedita Basu, Ruth A. Johnson, Qian Shi, Garth D. Nelson, Julie M. Cunningham, Richard M. Goldberg, Frank A. Sinicrope, Daniel J. Sargent, Steven R. Alberts, Gloria M. Petersen, Stephen N. Thibodeau, Halcyon G. Skinner, Kristin Litzelman, Songwon Seo, Russell J. Vanderboom, Ronald E. Gangnon, Corinne D. Engelman, David N. Rider, Lisa A. Boardman. Telomeres and survival in stage III colon cancers: Findings from NCCTG N0147 (Alliance) study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5102. doi:10.1158/1538-7445.AM2014-5102

Abstract Background: Both shorter and longer telomeres in peripheral blood leukocyte (PBL) DNA have been associated with cancer risk. However, associations remain inconsistent across studies of the same cancer type. This study compares DNA preparation methods to determine telomere length from patients with colorectal cancer. Methods: We examined PBL relative telomere length (RTL) measured by quantitative PCR (qPCR) in 1,033 patients with colorectal cancer and 2,952 healthy controls. DNA was extracted with phenol/chloroform, PureGene, or QIAamp. Results: We observed differences in RTL depending on DNA extraction method (P < 0.001). Phenol/chloroform-extracted DNA had a mean RTL (T/S ratio) of 0.78 (range 0.01–6.54) compared with PureGene-extracted DNA (mean RTL of 0.75; range 0.00–12.33). DNA extracted by QIAamp yielded a mean RTL of 0.38 (range 0.02–3.69). We subsequently compared RTL measured by qPCR from an independent set of 20 colorectal cancer cases and 24 normal controls in PBL DNA extracted by each of the three extraction methods. The range of RTL measured by qPCR from QIAamp-extracted DNA (0.17–0.58) was less than from either PureGene or phenol/chloroform (ranges, 0.04–2.67 and 0.32–2.81, respectively). Conclusions: RTL measured by qPCR from QIAamp-extracted DNA was less than from either PureGene or phenol/chloroform (P < 0.001). Impact: Differences in DNA extraction method may contribute to the discrepancies between studies seeking to find an association between the risk of cancer or other diseases and RTL. Cancer Epidemiol Biomarkers Prev; 22(11); 2047–54. ©2013 AACR.

Abstract Background: Telomeres, the ends of chromosomes, are critical for maintaining genomic stability and grow shorter with age. Shortened telomeres in pancreatic tissue play a key role in the pathogenesis of pancreatic cancer, and shorter telomeres in peripheral blood leukocytes (PBL) have been associated with increased risk for several cancer types. We hypothesized that shorter blood telomeres are associated with higher risk for pancreatic cancer. Methods: Telomere length was measured in PBLs using quantitative real-time PCR in 499 cases with pancreatic cancer and 963 cancer-free controls from the Mayo Clinic. ORs and confidence intervals (CI) were computed using logistic generalized additive models (GAM) adjusting for multiple variables. Results: In multivariable adjusted models, we observed a significant nonlinear association between telomere length in peripheral blood samples and the risk for pancreatic cancer. Risk was lower among those with longer telomeres compared with shorter telomeres across a range from the 1st percentile to 90th percentile of telomere length. There was also some evidence for higher risk among those with telomeres in the longest extreme. Conclusions: Short telomeres in peripheral blood are associated with an increased risk for pancreatic cancer across most of the distribution of length, but extremely long telomeres may also be associated with higher risk. Impact: Although the temporality of this relationship is unknown, telomere length may be useful as either a marker of pancreatic cancer risk or of the presence of undetected pancreatic cancer. If telomere shortening precedes cancer incidence, interventions to preserve telomere length may be an effective strategy to prevent pancreatic cancer. Cancer Epidemiol Biomarkers Prev; 21(11); 2095–100. ©2012 AACR.

Abstract Aberrantly methylated genes represent attractive and broadly informative markers for colorectal cancer (CRC). As demographics, numerous ingestants, environmental exposures, and obesity variably influence both gene methylation rates and CRC incidence, it is important to understand the effects of such covariates on the clinical performance of CRC screening tests that incorporate assay of methylated gene markers. Based on a recent multicenter study (Ahlquist et al. Gastroenterology 2012 (in press)), stool assay of carefully selected methylated gene marker candidates (NDRG4, BMP3, vimentin, TFPI2), alone or in combination, yield high detection rates of both CRC and large adenomas. Aim: To assess the impact of demographic, exposure, body mass, and other patient variables on stool levels of the above 4 methylated gene markers. Methods: We studied buffered stools collected within 3 years of a normal colonoscopy from 500 patients undergoing average-risk screening or polyp surveillance (median age 64 (range 44-85); 53% women). Upon receipt, stools were promptly homogenized, aliquoted, and frozen at –80°C. On supernatants from thawed/spun aliquots, target genes were purified by hybrid capture, bisulfite treated, and assayed using the analytically-sensitive QuARTS method (quantitative allele-specific real-time target and signal amplification), as described (above citation). The reference gene β-actin was assayed along with methylation of NDRG4, BMP3, vimentin, TFPI2. Log-converted data were normalized to allow comparison of effects between markers, and effect size was expressed as % change relative to standard deviation for each marker (standardized relative change (SRβ)). Results: The only patient characteristic that significantly influenced all methylated marker levels in stool was age (p<0.0001 for each marker); SRΔ was greatest with TFPI2 at +91.3 (p<0.001 vs other markers), least with BMP3 at +29.7 (p<0.001 vs others), and intermediate with vimentin at +46.0 and NDRG4 at +45.1. In contrast to methylation markers, levels of β-actin did not change across age. The other demographic variables of sex, race, and geographic residence had no effect on methylation markers. Marker levels were also not affected by exposure variables (smoking, alcohol consumption, or analgesic use), by family history of CRC or polyps, or by personal history of polyps. Finally, neither overweight status (n=176) nor obesity (n=148) had an effect on marker levels. Conclusions: Age significantly affects stool levels of tumor-associated methylated gene markers in colonoscopy-normal patients, and the degree of this age effect differs across markers. In contrast, other key patient variables had no effect on stool marker levels. Comment: Optimal use of these methylation markers for stool screening of CRC may require age-adjustment of normal cutoff levels to maximize test specificity. 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 3572. doi:1538-7445.AM2012-3572

Background Colorectal cancer (CRC) can be prevented by the early detection and removal of advanced adenomas (AAs) by colonoscopy. Our aim was to evaluate peripheral blood leukocyte (PBL) telomere length as a potential biomarker for the presence of AAs. Methods PBL telomere length was measured in patients with AAs (n=35), in a control group of similarly aged patients who had a normal colonoscopy (n=145) and in a separate population group with no history of cancer, again similarly aged (n=495). Telomere measurements were performed using a quantitative PCR assay and reported as ratios of telomere and single copy gene measurements. Results Telomere lengths tended to be lower in patients with AAs than in patients in the normal colonoscopy group (p<0.001) as well as those in the population group (p=0.011). A telomere/single copy gene ratio of 0.5 was found to have an estimated 94% sensitivity and a 56% specificity for AAs; a combination of sensitivity and specificity for which a value of >0.5 would reduce the odds of a patient having AAs by a factor of 0.11 (the negative likelihood ratio). Thirty three percent of individuals in the population group tested above this cutoff and could be considered at low risk for AAs. Conclusions PBL telomeres are shortened in patients with colorectal neoplasia, suggesting that PBL telomere length could be a promising non-invasive blood biomarker to pre-screen for risk of AAs prior to colonoscopy.

Abstract Introduction: Short constitutional telomere length is associated with aging and cancer, but the correlation of telomere length and age at diagnosis of CRC has not been evaluated. Methods: We measured telomere length using quantitative PCR of peripheral blood leukocyte DNA in 1026 individuals diagnosed with MSS CRC who were ≤60 years of age and were chemo-radiotherapy naïve at the time of blood draw. We compared telomere length with 1972 unrelated healthy controls who were frequency matched for gender and age at time of blood collection. We used constructed percentiles of telomere length using the data from the controls. Results: Overall, regardless of cancer status, there was a weak negative correlation of telomere length with age such that as age increased telomere length decreased (Pearson correlation coefficient =−0.1, p&lt; 0.0001); and men had shorter telomeres than women (p=0.0002). The odds ratio (OR) for MSS CRC increased with longer telomere length (OR 1.62 [CI: 1.31-1.99] for those with telomere lengths in the 90th percentile compared to those with telomere lengths in the 50th percentile. In multivariate analysis with adjustment for gender, BMI, smoking, alcohol, and diabetes, telomere length remained an independent risk factor for CRC (p&lt; 0.001), with interaction between telomere length and age (≤50, longer telomeres increased CRC risk; &gt; 50 years old, increasing telomere length associated with decreased CRC risk). Risk was higher for MSS CRC ≤50 years for patients with telomere lengths in the 90th percentile compared to those in the 50th percentile (OR 2.31; CI:1.65-3.23). For subjects diagnosed 50-60 yrs, longer telomere length was associated with lower risk of CRC, and shorter telomere length was associated with the development of CRC (OR 1.22 for telomere lengths in the 10th percentile compared to those in the 50th percentile (OR 1.22:CI; 1.05-1.43). Conclusion: Telomere dynamics appear to influence MSS CRC risk and may differ on the basis of age of cancer diagnosis. 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 2994. doi:10.1158/1538-7445.AM2011-2994

Abstract Short constitutional telomere length has been associated with aging and cancer, but how telomere length is affected by other epidemiologic or environmental variables in health has not been thoroughly studied. Understanding these associations with telomere length in health is important for studies to evaluate the relationship of telomere length and diseases such as cancer. We measured peripheral blood leukocyte DNA telomere length with quantitative PCR in 1977 non-related healthy controls collected through the Colon Cancer Family Registry (an NCI cooperative group) and through the Mayo Biobank and Biobank for Gastrointestinal Health Research, two IRB approved prospective biospecimen collections based at Mayo Clinic, Rochester, MN. The controls were a median age of 50.6 years old, and 49.6% of the controls were male. Ninety-six percent of the controls were white; 1.8% were Asian, and &lt;1% were either black, Pacific Islander, or Native American. Less than 1% of controls were Hispanic. On univariate analysis, as age increased, telomere length decreased (Pearson correlation coefficient = −0.07, 95% CI: −0.11, −0.03). Telomeres were longer in people who consumed more fruits (p&lt;0.01) and vegetables (p&lt;0.01); took aspirin on a regular basis (p&lt;0.01); or had a family history of cancers of any type (p=0.05). Women had longer telomeres than men (p=0.03). Telomeres were shorter in people who consumed alcohol (p&lt;0.01), took folate on a regular basis (p=0.01), or who consumed red meat (p&lt;0.01). Statistical significance was not found in the following variables: tobacco use, diagnosis of diabetes, intake of calcium, use of hormone replacement therapy in women, or body mass index. On multivariate analysis, age, vegetable consumption, family history of colorectal cancer or any type of cancer, and folate intake were identified as being significantly associated with telomere length. Telomere length may be associated with multiple environmental and demographic variables in healthy individuals, and adjusting for these may be important for studies that test for an association between telomere length and diseases such as cancer. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A82.