Modification of the association between recreational physical activity and survival after breast cancer by promoter methylation in breast cancer-related genes
BREAST CANCER RESEARCH
Authors: McCullough, Lauren E.; Chen, Jia; Cho, Yoon Hee; Khankari, Nikhil K.; Bradshaw, Patrick T.; White, Alexandra J.; Teitelbaum, Susan L.; Terry, Mary Beth; Neugut, Alfred I.; Hibshoosh, Hanina; Santella, Regina M.; Gammon, Marilie D.
Abstract
Background: Mechanisms underlying the inverse association between physical activity and survival after breast cancer are unresolved, but DNA methylation may play a role. We hypothesized that promoter methylation of breast cancer-related genes, as well as global methylation, may modify the association between prediagnostic recreational physical activity (RPA) and breast cancer mortality. Methods: Using a population-based sample of 1254 women diagnosed with first primary breast cancer, we examined modification of the RPA-mortality association by gene-specific promoter methylation and global methylation. Average lifetime RPA was assessed from menarche to diagnosis through structured in-home interviews. Promoter methylation of 13 breast cancer-related genes was evaluated in archived tumor by methylation-specific polymerase chain reaction and MethyLight assay. Global methylation in white blood cell DNA was determined at long interspersed nucleotide element 1 and by the luminometric methylation assay. After approximately 15 years of follow-up, 486 patients had died, and 186 of the deaths were breast cancer-related. We used Cox proportional hazards regression to estimate HRs and 95% CIs as well as likelihood ratio tests to assess multiplicative interactions. Results: All-cause mortality was lower only among physically active women with methylated promoter of APC (HR 0.60, 95% CI 0.40-0.80), CCND2 (HR 0.56, 95% CI 0.32-0.99), HIN (HR 0.55, 95% CI 0.38-0.80), and TWIST1 (HR 0.28, 95% CI 0.14-0.56) in tumors, but not among those with unmethylated tumors (significant interaction p < 0.05). We found no interaction between RPA and global methylation. Conclusions: The improved survival after breast cancer that is associated with RPA may be more pronounced in women with promoter tumor methylation in biologically plausible genes.
Sustained expression of the transcription factor GLIS3 is required for normal beta cell function in adults
EMBO MOLECULAR MEDICINE
Authors: Yang, Yisheng; Chang, Benny Hung-Junn; Chan, Lawrence
Abstract
Genome-wide association studies identified GLIS3 as a susceptibility locus for type 1 and type 2 diabetes. Global Glis3 deficiency in mice leads to congenital diabetes and neonatal lethality. In this study, we explore the role of Glis3 in adulthood using Glis3+/- and conditional knockout animals. We challenged Glis3+/- mice with high fat diet for 20 weeks and found that they developed diabetes because of impaired beta cell mass expansion. GLIS3 controls beta cell proliferation in response to high-fat feeding at least partly by regulating Ccnd2 transcription. To determine if sustained Glis3 expression is essential to normal beta cell function, we generated Glis3fl/fl/Pdx1CreERT+ animal by intercrossing Glis3fl/fl mice with Pdx1CreERT+ mice and used tamoxifen (TAM) to induce Glis3 deletion in adults. Adult Glis3fl/fl/Pdx1CreERT+ mice are euglycaemic. TAM-mediated beta cell-specific inactivation of Glis3 in adult mice downregulates insulin expression, leading to hyperglycaemia and subsequently enhanced beta cell apoptosis. We conclude that normal Glis3 expression is required for pancreatic beta cell function and mass maintenance during adulthood, which impairment leads to diabetes in adults.