Supplementary Figure S3 : Effect of smoking on the levels of mtDNA in peripheral leukocytes and serological IL-8 levels in NAG and GC patients, compared to healthy blood donors in cohort 1. A) Quantification of MtDNA levels by quantitative PCR as described in material and methods and B) Measure of IL-8 levels by ELISA. Cohort 1 included 47%, 48% and 56% of smokers in controls, NAG and GC groups respectively. Smokers are in black symbols and non-smokers in white symbols, circled symbols among GC cases in B) correspond to samples related to mtDNA inteval II. Each symbol represents a single patient, bars correspond to mean{plus minus}SEM. Each sample was tested in triplicate in three independent experiments. *p-value>0.05 ; **p-value<0.01.
ARTICLE ABSTRACT
Background: Gastric cancer represents a major health burden worldwide and is often diagnosed at an advanced stage. Biomarkers for screening and prevention of gastric cancer are missing. Changes in peripheral blood mitochondrial DNA (mtDNA) have emerged as a potential preventive/diagnosis biomarker for cancer risk. We aimed to determine whether peripheral leukocytes mtDNA levels are associated with stages of the gastric carcinogenesis cascade.Methods: We measured mtDNA by quantitative real-time PCR assay in peripheral leukocytes of 28 patients with non-atrophic gastritis (NAG), 74 patients with gastric cancer, and 48 matched asymptomatic controls. In parallel, the serologic level of IL8 was determined.Results: Mean mtDNA level was higher in patients with gastric cancer (P = 0.0095) than in controls, with values >8.46 significantly associated with gastric cancer (OR, 3.93). Three ranges of mtDNA values were identified: interval I, <2.0; interval II, 2.0–20; and interval III, >20. Interval I included mainly NAG cases, and few gastric cancer samples and interval III corresponded almost exclusively to patients with gastric cancer. All controls fell in interval II, together with some NAG and gastric cancer cases. IL8 levels were significantly higher in patients with gastric cancer (P < 0.05), with levels >50 pg/mL observed exclusively in patients with gastric cancer, allowing to distinguish them within interval II. We validated mtDNA results in a second cohort of patients, confirming that mtDNA was significantly higher in gastric cancer than in patients with preneoplasia.Conclusions: Circulating levels of mtDNA and IL8 constitute a potential biomarker for the early detection of gastric cancer.Impact: Our findings lead us to propose a new noninvasive method to detect patients with gastric cancer risk. Cancer Epidemiol Biomarkers Prev; 23(11); 2430–8. ©2014 AACR.
