Identifying molecular mediators of the relationship between body mass index and endometrial cancer risk: a Mendelian randomization analysis

Background: Endometrial cancer is the most common gynaecological cancer in high-income countries. Elevated body mass index (BMI) is an established modifiable risk factor for this condition and is estimated to confer a larger effect on endometrial cancer risk than any other cancer site. However, the molecular mechanisms underpinning this association remain unclear. We used Mendelian randomization (MR) to evaluate the causal role of 14 molecular risk factors (hormonal, metabolic, and inflammatory markers) in endometrial cancer risk. We then evaluated and quantified the potential mediating role of these molecular traits in the relationship between BMI and endometrial cancer. Methods and Findings: Genetic instruments to proxy 14 molecular risk factors and BMI were constructed by identifying single-nucleotide polymorphisms (SNPs) reliably associated (P < 5.0 x 10-8) with each respective risk factor in previous genome-wide association studies (GWAS). Summary statistics for the association of these SNPs with overall and subtype-specific endometrial cancer risk (12,906 cases and 108,979 controls) were obtained from a GWAS meta-analysis of the Endometrial Cancer Association Consortium (ECAC), Epidemiology of Endometrial Cancer Consortium (E2C2), and UK Biobank. SNPs were combined into multi-allelic models and odds ratios (ORs) and 95% confidence intervals (95% CIs) were generated using inverse-variance weighted random-effects models. The mediating roles of the molecular risk factors in the relationship between BMI and endometrial cancer were then estimated using multivariable MR. In MR analyses, there was strong evidence that BMI (OR per SD increase: 1.88, 95% CI: 1.69 to 2.09, P = 3.87 x 10-31), total testosterone (OR per inverse normal transformed nmol/L increase: 1.64, 95% CI: 1.43 to 1.88, P = 1.71 x 10-12), bioavailable testosterone (OR per inverse normal transformed nmol/L increase: 1.46, 95% CI: 1.29 to 1.65, P = 3.48 x 10-9), fasting insulin (OR per natural log transformed pmol/L increase: 3.93, 95% CI: 2.29 to 6.74, P = 7.18 x 10-7) and sex hormone-binding globulin (SHBG, OR per inverse normal transformed nmol/L increase: 0.71, 95% CI: 0.59 to 0.85, P = 2.07 x 10-4) had a causal effect on endometrial cancer risk. Additionally, there was suggestive evidence that total serum cholesterol (OR per mg/dL increase: 0.90, 95% CI: 0.81 to 1.00, P = 4.01 x 10-2) had an effect on endometrial cancer risk. In mediation analysis using multivariable MR, we found evidence for a mediating role of fasting insulin (19% total effect mediated, 95% CI: 5 to 34%, P = 9.17 x 10-3), bioavailable testosterone (15% mediated, 95% CI: 10 to 20%, P = 1.43 x 10-8), and SHBG (7% mediated, 95% CI: 1 to 12%, P = 1.81 x 10-2) in the relationship between BMI and endometrial cancer risk. The primary limitations of this analysis include the assumption of linear relationships across univariable and multivariable analyses and the restriction of analyses to individuals of European ancestry. Conclusions: Our comprehensive Mendelian randomization analysis provides insight into potential causal mechanisms linking BMI with endometrial cancer risk and suggests pharmacological targeting of insulinemic and hormonal traits as a potential strategy for the prevention of endometrial cancer.

Multi-tissue transcriptome-wide association study identifies eight candidate genes and tissue-specific gene expression underlying endometrial cancer susceptibility

Genome-wide association studies (GWAS) have revealed sixteen risk loci for endoemtrial cancer but the identification of candidate susceptibility genes remains challenging. Here, we perform transcriptome-wide association study (TWAS) analyses using the largest endometrial cancer GWAS and gene expression from six relevant tissues, prioritizing eight candidate endometrial cancer susceptibility genes, one of which (EEFSEC) is located at a potentially novel endometrial cancer risk locus. We also show evidence of biologically relevant tissue-specific expression associations for CYP19A1 (adipose), HEY2 (ovary) and SKAP1 (whole blood). A phenome-wide association study demonstrates associations of candidate susceptibility genes with anthropometric, cardiovascular, diabetes, bone health and sex hormone traits that are related to endometrial cancer risk factors. Lastly, analysis of TWAS data highlights candidate compounds for endometrial cancer repurposing. In summary, this study reveals endometrial cancer susceptibility genes, including those with evidence of tissue specificity, providing insights into endometrial cancer aetiology and avenues for therapeutic development.

Use of antidepressants and endometrial-cancer risk: a nationwide nested case–control study

Background Preclinical studies have suggested that antidepressant drugs may possess antineoplastic properties. In a nationwide case–control study, we examined the association between use of antidepressants and endometrial-cancer risk with a particular focus on selective serotonin reuptake inhibitors (SSRIs). Methods From the Danish Cancer Registry, we identified all women with a histologically verified diagnosis of endometrial cancer between 2000 and 2016, and, for each woman, 15 age-matched controls. We obtained information on use of SSRIs, tricyclic antidepressants (TCAs) and other antidepressants based on records of filled prescriptions from the National Prescription Register. Using conditional logistic regression, we calculated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for associations between use of antidepressants and endometrial-cancer risk compared with non-use. In active comparator analyses, SSRI use was compared with TCA use. Results The study population comprised 8164 cases and 122 432 controls. Compared with non-use, SSRI use was associated with an OR of 0.88 (95% CI 0.82–0.96) for endometrial cancer, whereas the association with TCA use was close to unity (OR 1.05, 95% CI 0.90–1.22). Use of other antidepressants yielded an OR of 0.86 (95% CI 0.71–1.03). We observed no apparent trends in associations according to cumulative amount. The inverse association with SSRI use persisted when compared with TCA use (OR 0.81, 95% CI 0.66–0.99). Conclusions Use of SSRIs was associated with a decreased risk of endometrial cancer, whereas no inverse association appeared with use of TCAs. The antineoplastic potential of SSRIs should be investigated in future studies.

Endometrial Cancer Incidence in Endometriosis and Adenomyosis

Women with histologically proven endometriosis/adenomyosis have an increased risk of ovarian cancer. Small studies show conflicting results on the endometrial cancer risk in women with endometriosis/adenomyosis. Therefore, we assessed the incidence of endometrial cancer in women with histologically proven endometriosis or adenomyosis. We performed a population-based retrospective cohort study of 129,862 women with histologically proven endometriosis/adenomyosis, matched with 132,700 women with a nevus selected from the Dutch pathology registry between 1990 and 2015. Histology results for endometrial cancer were retrieved. Crude and age-adjusted odds ratios for endometrial cancer were estimated. In the endometriosis/adenomyosis group, 1827 (1.4%) women had a histological report on endometrial cancer, and in the nevus group, 771 (0.6%) women. The age-adjusted OR for endometrial cancer was 2.58 (95%CI 2.37–2.81). After excluding the first year of follow-up, the age-adjusted OR was 0.76 (95%CI 0.63–0.92), indicating that endometrial cancer is most often found at time of histological diagnosis of endometriosis/adenomyosis. In around 20% of the endometrial cancer cases, the endometrial cancer was not recognized until after hysterectomy. Of these women, 35% had no prior (micro)curettage or biopsy. This study shows an increased incidence of endometrial cancer in women with histologically proven endometriosis and adenomyosis.

Multi-trait genome-wide association study identifies novel endometrial cancer risk loci that are associated with obesity or female testosterone levels

We have performed genetic correlation and Mendelian randomization analyses using publicly available genome-wide association study (GWAS) data to identify endometrial cancer risk factors. These and previously established risk factors of endometrial cancer were then included in a multi-trait Bayesian GWAS analysis to detect endometrial cancer susceptibility variants, identifying three novel loci (7q22.1, 8q24.3 and 16q12.2); two of which were replicated in an independent endometrial cancer GWAS dataset. These loci are hypothesized to affect endometrial cancer risk through altered sex-hormone levels or through effects on obesity. Consistent with this hypothesis, several genes with established roles in these pathways (CYP11B1, CYP3A7, IRX3 and IRX5) were prioritized as candidate endometrial cancer risk genes by interrogation of quantitative trait loci data and chromatin capture assays in endometrial cell lines. The findings of this study identify additional opportunities for hormone treatment and further support weight loss to reduce the risk of developing endometrial cancer.