The association between leukocyte telomere length and cigarette smoking, dietary and physical variables, and risk of prostate cancer

Abstract

Telomeres consist of nucleotide repeats and a protein complex at chromosome ends that are essential to maintaining chromosomal integrity. Several studies have suggested that subjects with shorter telomeres are at increased risk of bladder and lung cancer. In comparison to normal tissues, telomeres are shorter in high-grade intraepithelial neoplasia and prostate cancer. We examined prostate cancer risk associated with relative telomere length as determined by quantitative PCR on prediagnostic buffy coat DNA isolated from 612 advanced prostate cancer cases and 1049 age-matched, cancer-free controls from the PLCO Cancer Screening Trial. Telomere length was analyzed as both a continuous and a categorical variable with adjustment for potential confounders. Statistically significant inverse correlations between telomere length, age and smoking status were observed in cases and controls. Telomere length was not associated with prostate cancer risk (at the median, OR = 0.85, 95% CI: 0.67, 1.08); associations were similar when telomere length was evaluated as a continuous variable or by quartiles. The relationships between telomere length and inflammation-related factors, diet, exercise, body mass index, and other lifestyle variables were explored since many of these have previously been associated with shorter telomeres. Healthy lifestyle factors (i.e., lower BMI, more exercise, tobacco abstinence, diets high in fruit and vegetables) tended to be associated with greater telomere length. This study found no statistically significant association between leukocyte telomere length and advanced prostate cancer risk. However, correlations of telomere length with healthy lifestyles were noted, suggesting the role of these factors in telomere biology maintenance and potentially impacting overall health status.

Figure 1

Mean relative telomere length for lifestyle scores in tertiles for all subjects combined (n = 1661). Total sample sizes vary for each lifestyle due to missing information for one or more of the selected variables (only persons with information for all of the combined variables were included in the analysis). T1 = tertile 1; T2 = tertile 2; T3 = tertile 3. Lifestyle 1 includes the following variables: pack-years smoked, fruit and vegetable intake, BMI, and physical activity; lifestyle 2: fruit, vegetable, and fat intake; and, lifestyle 3: β-carotene, vitamin E, lycopene, and selenium intake. See the Methods section for an explanation of the lifestyle score determination. Error bars show the standard error of each mean estimate. A regression line, slope, sample size (n), and Spearman rank correlation coefficients (r) are shown for each lifestyle after adjustment for age and/or pack-years smoked (lifestyle 1 was only adjusted for age).