Variation in Genes Related to Obesity, Weight, and Weight Change and Risk of Contralateral Breast Cancer in the WECARE Study Population
BACKGROUND: Body mass index (BMI), a known breast cancer risk factor, could influence breast risk through mechanistic pathways related to sex hormones, insulin resistance, chronic inflammation and altered levels of adipose derived hormones. Results from studies of the relationship between BMI and second primary breast cancer have been mixed. To explore the relationship between BMI and asynchronous contralateral breast cancer (CBC), we examined whether variants in genes related to obesity, weight and weight change are associated with CBC risk. METHODS: Variants in twenty genes (182 single nucleotide polymorphisms) involved in adipose tissue metabolism, energy balance, insulin resistance and inflammation, as well as those identified through genome-wide association studies of BMI and type II diabetes were evaluated. We examined the association between variants in these genes and the risk of CBC among Caucasian participants (643 cases with CBC and 1,271 controls with unilateral breast cancer) in the population-based Women's Environmental Cancer and Radiation Epidemiology (WECARE) Study using conditional logistic regression. RESULTS: After adjustment for multiple comparisons, no statistically significant associations between any variant and CBC risk were seen. Stratification by menopausal or estrogen receptor status did not alter these findings. CONCLUSIONS: Among women with early onset disease who survive a first breast cancer diagnosis there was no association between variation in obesity-related genes and risk of CBC. Impact:Genetic variants in genes related to obesity are not likely to strongly influence subsequent risk of developing a second primary breast cancer.
Available from: Gregory S. Calip
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ABSTRACT: The prevalence of risk factors contributing to metabolic syndrome (MetS) is increasing, and numerous components of MetS are associated with increased primary breast cancer (BC) risk. However, less is known about the relationship of MetS to BC outcomes. The aim of this study was to evaluate whether MetS, characterized by increased weight, hypertension, low HDL-cholesterol, high triglycerides, and diabetes or impaired glucose tolerance, is associated with risk of second breast cancer events (SBCE) and BC-specific mortality. Retrospective cohort study of women diagnosed with incident early-stage (I-II) BC between 1990 and 2008, enrolled in an integrated health plan. Outcomes of interest were SBCE, defined as recurrence or second primary BC, and BC-specific mortality. We used multivariable Cox proportional hazards models to estimate adjusted hazard ratios (HR) and 95 % confidence intervals (CI) for time-varying exposure to MetS components while accounting for potential confounders and competing risks. Among 4,216 women in the cohort, 26 % had >/=3 MetS components and 13 % developed SBCE during median follow-up of 6.3 years. Compared to women with no MetS components, presence of MetS (>/=3 components) was associated with increased risk of SBCE (HR = 1.50, 95 % CI 1.08-2.07) and BC-specific mortality (HR = 1.65, 95 % CI 1.02-2.69). Of the individual components, only increased weight was associated with increased risk of SBCE (HR = 1.26, 95 % CI 1.06-1.49). MetS is associated with modestly increased risk of SBCE and BC-specific mortality. Given the growing population of BC survivors, further research in larger and more diverse populations is warranted.
Available from: Elena Hernández-Caballero
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ABSTRACT: The FTO (fat mass and obesity-associated) gene has a strong linkage disequilibrium block, within which SNPs have been identified that are involved in the development of obesity. Recently some of these variants have also been associated with cancer. However, identification of the possible mechanisms that could explain these associations has proven to be elusive. It has been found that FTO polymorphisms can regulate the expression of genes at large kilobases of distance as well as the expression of the FTO gene itself, and regions for transcription factor binding. To date it has been observed that variants rs9939609, rs17817449, rs8050136, rs1477196, rs6499640, rs16953002, rs11075995 and rs1121980 are associated with the risk of developing cancer. Some studies have produced negative results when comparing the same polymorphisms, but make a simple association between polymorphic variants and cancer, have proved difficult because this relation is by nature multifactorial. A certain degree of variation resulting from the improper design of studies or processing of data can lead to erroneous conclusions. However, it is now unquestionable that certain FTO polymorphisms regulate genetic expression related to cancer susceptibility, although this field is just beginning to be understood.
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Obesity and breast cancer risk is multifaceted and genes associated with energy homeostasis may modify this relationship.
We evaluated 10 genes that have been associated with obesity and energy homeostasis to determine their association with breast cancer risk in Hispanic/Native American (2111 cases, 2597 controls) and non-Hispanic white (1481 cases, 1585 controls) women.
Cholecystokinin (CCK) rs747455 and proopiomelanocortin (POMC) rs6713532 and rs7565877 (for low Indigenous American (IA) ancestry); CCK rs8192472 and neuropeptide Y (NYP) rs16141 and rs14129 (intermediate IA ancestry); and leptin receptor (LEPR) rs11585329 (high IA ancestry) were strongly associated with multiple indicators of body size. There were no significant associations with breast cancer risk between genes and SNPs overall. However, LEPR was significantly associated with breast cancer risk among women with low IA ancestry (PARTP=0.024); POMC was significantly associated with breast cancer risk among women with intermediate (PARTP=0.015) and high (PARTP=0.012) IA ancestry. The overall pathway was statistically significant for pre-menopausal women with low IA ancestry (PARTP=0.05), as was cocaine and amphetamine regulated transcript protein (CARTPT) (PARTP=0.014) and ghrelin (GHRL) (PARTP=0.007). POMC was significantly associated with breast cancer risk among post-menopausal women with higher IA ancestry (PARTP=0.005). Three SNPs in LEPR (rs6704167, rs17412175, and rs7626141), and adiponectin (ADIPOQ); rs822391) showed significant 4-way interactions (GxExMenopausexAncestry) for multiple indicators of body size among pre-menopausal women.
Energy homeostasis genes were associated with breast cancer risk; menopausal status, body size, and genetic ancestry influenced this relationship.
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