Gunter, Marc J.

Background: Considering the pathophysiological importance of the intestine-passing microbiota, we hypothesized that the mutational and microbial profiles of colorectal cancer might gradually change along detailed anatomical locations and that these trends might differ by the age of diagnosis and the microsatellite instability (MSI) status. Methods: We assessed somatic mutations and selected bacterial species in colorectal carcinomas along the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum, utilizing targeted sequencing data ( N = 5685) from the Genetics and Epidemiology of Colorectal Cancer Consortium and tissue microbial data ( N = 1389) from the Health Professionals Follow-up Study and Nurses’ Health Study. Results: There were decreasing trends from the cecum to rectum in the prevalence of gene mutations in the IGF/PI3K, receptor tyrosine kinase (RTK)/RAS, TGFB, and WNT signaling pathways (all P trend < 0.0001), as well as high levels of Bacteroides fragilis ( P trend < 0.0001) and high levels of Fusobacterium nucleatum ( P trend = 0.0029) (but not enterotoxigenic Bacteroides fragilis or pks+ Escherichia coli ). Conversely, TP53 pathway mutations showed an increasing cecum-to-rectum trend ( P trend < 0.0001). Similar to later-onset cases diagnosed at ages 50 years and older, in early-onset cases diagnosed under the age of 50 years, we found generally decreasing cecum-to-rectum trends of IGF/PI3K, RTK/RAS, TGFB, and WNT pathway mutations and an increasing cecum-to-rectum trend in TP53 pathway mutations. By contrast, the cecum-to-rectum prevalence-changing trends in IGF/PI3K, RTK/RAS, TGFB, and TP53 pathway mutations were present in non–MSI-high tumors but not in MSI-high tumors (all P interaction < 0.0052). Conclusion: Non–MSI-high colorectal cancers exhibited decreasing cecum-to-rectum trends of IGF/PI3K, RTK/RAS, and TGFB pathway mutations (and an increasing trend of TP53 pathway mutations), in contrast to MSI-high tumors that demonstrated no such trends. Our study highlights the importance of detailed colorectal subsite information combined with tumor molecular and microbial characteristics in colorectal cancer research.

Abstract Background Physical activity is associated with lower colorectal cancer (CRC) risk, but its association with molecular subtypes defined by genetic and epigenetic alterations of the disease is unclear. Such information may enhance the understanding of the mechanisms related to the benefits of physical activity. Methods Pooled observational (cases: n = 5386; controls: n = 6798; studies n = 5) and genome-wide association data (cases: n = 8178; controls: n = 10 472; studies n = 5) were used. We used multivariable logistic regression models and Mendelian randomization to assess the association between physical activity and the risk of CRC subtypes defined by individual tumor markers (and marker combinations), namely microsatellite instability status, CpG island methylator phenotype status, and BRAF and KRAS mutations. We used case-only analysis to test for differences between molecular subtypes. We applied Bonferroni correction to account for multiple tests. Results In the pooled observational analysis, higher levels of physical activity were associated with lower CRC risk (Obs-per 1SD, odds ratio [OR] = 0.94, 95% confidence interval [CI] = 0.90 to 0.97), with an association that was stronger in males (Obs-per 1SD, OR = 0.91, 95% CI = 0.87 to 0.96) than in females (Obs-per 1SD, OR = 0.97, 95% CI = 0.91 to 1.03; Pinteraction = .04). Higher physical activity was associated with a lower risk of CRC across all molecular subtypes, especially in males. There was no difference in the associations by subtypes by pooled observational or Mendelian randomization analyses. The findings did not differ by study design, anatomical site, and early or late age onset of CRC. Conclusions Our findings suggest that physical activity is not differentially associated with the 4 major molecular subtypes involved in colorectal carcinogenesis, indicating that its benefits extend broadly across colorectal cancer pathogenesis.

Abstract Recent research suggests higher circulating lymphocyte counts may protect against colorectal cancer (CRC). However, the role of specific lymphocyte subtypes and activation states remain unclear. CD4+ T cells—a highly dynamic lymphocyte subtype—undergo gene expression changes upon activation that are critical to their effector function. Previous studies using bulk tissue have limited our understanding of their role in CRC risk to static associations. We applied Mendelian randomization (MR) and genetic colocalisation to evaluate causal relationships of gene expression on CRC risk across multiple CD4+ T cell subtypes and activation states. Genetic proxies were obtained from single-cell transcriptomic data, allowing us to investigate the causal effect of expression of 1,805 genes across CD4+ T cell activation states on CRC risk (78,473 cases; 107,143 controls). Analyses were stratified by CRC anatomical subsites and sex, with sensitivity analyses assessing whether the observed effect estimates were likely to be CD4+ T cell-specific. We identified 6 genes—FADS2, FHL3, HLA-DRB1, HLA-DRB5, RPL28, and TMEM258—with strong evidence for a causal role in CRC development (FDR-P &lt; 0.05; colocalisation H4 &gt; 0.8). Causal estimates varied by CD4+ T cell subtype, activation state, CRC subsite and sex. However, many of genetic proxies used to instrument gene expression in CD4+ T cells also act as eQTLs in other tissues, highlighting the challenges of using genetic proxies to instrument tissue-specific expression changes. We demonstrate the importance of capturing the dynamic nature of CD4+ T cells in understanding CRC risk, and prioritize genes for further investigation in cancer prevention.

Abstract Introduction There is convincing evidence that overall adiposity increases the risks of several cancers. Whether the distribution of adiposity plays a similar role is unclear. Methods We used 2-sample Mendelian randomization (MR) to examine causal relationships of 5 adiposity distribution traits (abdominal subcutaneous adipose tissue (ASAT); visceral adipose tissue (VAT); gluteofemoral adipose tissue (GFAT); liver fat; and pancreas fat) with the risks of 12 obesity-related cancers (endometrial, ovarian, breast, colorectal, pancreas, multiple myeloma, liver, kidney (renal cell), thyroid, gallbladder, esophageal adenocarcinoma, and meningioma). Results Sample size across all genome-wide association studies (GWAS) ranged from 8407 to 728 896 (median: 57 249). We found evidence that higher genetically predicted ASAT increased the risks of endometrial cancer, liver cancer, and esophageal adenocarcinoma (odds ratios (OR) and 95% confidence intervals (CI) per standard deviation (SD) higher ASAT = 1.79 (1.18 to 2.71), 3.83 (1.39 to 10.53), and 2.34 (1.15 to 4.78), respectively). Conversely, we found evidence that higher genetically predicted GFAT decreased the risks of breast cancer and meningioma (ORs and 95% CIs per SD higher genetically predicted GFAT = 0.77 (0.62 to 0.97) and 0.53 (0.32 to 0.90), respectively). We also found evidence for an effect of higher genetically predicted VAT and liver fat on increased liver cancer risk (ORs and 95% CIs per SD higher genetically predicted adiposity trait = 4.29 (1.41 to 13.07) and 4.09 (2.29 to 7.28), respectively). Discussion Our analyses provide novel insights into the relationship between adiposity distribution and cancer risk. These insights highlight the potential importance of adipose tissue distribution alongside maintaining a healthy weight for cancer prevention.

Abstract Background Physical activity (PA) is an established protective factor for colorectal cancer (CRC), but it is unclear if genetic variants modify this effect. To investigate this possibility, we conducted a genome-wide gene–PA interaction analysis. Methods Using logistic regression and two-step and joint tests, we analyzed interactions between common genetic variants across the genome and PA in relation to CRC risk. Self-reported PA levels were categorized as active (≥ 8.75 MET-h/wk) vs. inactive (< 8.75 MET-h/wk) and as study- and sex-specific quartiles of activity. Results PA had an overall protective effect on CRC (OR [active vs. inactive] = 0.85; 95%CI = 0.81–0.90). The two-step GxE method identified an interaction between rs4779584, an intergenic variant near the GREM1 and SCG5 genes, and PA for CRC risk (p-interaction = 2.6×10 − 8 ). Stratification by genotype at this locus showed a significant reduction in CRC risk by 20% in active vs. inactive participants with the CC genotype (OR = 0.80; 95%CI = 0.75–0.85), but no significant PA–CRC association among CT or TT carriers. When PA was modeled as quartiles, the 1-d.f. GxE test identified that rs56906466, an intergenic variant near the KCNG1 gene, modified the association between PA and CRC (p-interaction = 3.5×10 − 8 ). Stratification at this locus showed that increase in PA (highest vs. lowest quartile) was associated with a lower CRC risk solely among TT carriers (OR = 0.77; 95%CI = 0.72–0.82). Conclusions In summary, we identified two genetic variants that modified the association between PA and CRC risk. One of them, related to GREM1 and SCG5 , suggests that the bone morphogenetic protein (BMP)-related, inflammatory, and/or insulin signaling pathways may be associated with the protective influence of PA on colorectal carcinogenesis.

Abstract Background: Waist circumference (WC) and its allometric counterpart, “a body shape index” (ABSI), are risk factors for colorectal cancer; however, it is uncertain whether associations with these body measurements are limited to specific molecular subtypes of the disease. Methods: Data from 2,772 colorectal cancer cases and 3,521 controls were pooled from four cohort studies within the Genetics and Epidemiology of Colorectal Cancer Consortium. Four molecular markers (BRAF mutation, KRAS mutation, CpG island methylator phenotype, and microsatellite instability) were analyzed individually and in combination (Jass types). Multivariable logistic and multinomial logistic models were used to assess the associations of WC and ABSI with overall colorectal cancer risk and, in case-only analyses, to evaluate heterogeneity by molecular subtype, respectively. Results: Higher WC (ORper 5 cm = 1.06, 95% confidence interval, 1.04–1.09) and ABSI (ORper 1-SD = 1.07, 95% confidence interval, 1.00–1.14) were associated with elevated colorectal cancer risk. There was no evidence of heterogeneity between the molecular subtypes. No difference was observed regarding the influence of WC and ABSI on the four major molecular markers in proximal colon, distal colon, and rectal cancers, as well as in early- and late-onset colorectal cancers. Associations did not differ in the Jass-type analysis. Conclusions: Higher WC and ABSI were associated with elevated colorectal cancer risk; however, they do not differentially influence all four major molecular mutations involved in colorectal carcinogenesis but underscore the importance of maintaining a healthy body weight in colorectal cancer prevention. Impact: The proposed results have potential utility in colorectal cancer prevention.

Abstract Background: Epidemiological and laboratory-based studies have provided conflicting evidence for a role of ghrelin in colorectal cancer development. We conducted two-sample Mendelian randomization (MR) analyses to evaluate evidence for an association of circulating ghrelin and colorectal cancer risk overall and by sex, cancer subsite, and age at diagnosis. Methods: Genetic instruments proxying plasma total ghrelin levels were obtained from a recent genome-wide association study of 54,219 participants. Summary data for colorectal cancer risk were obtained from a recent meta-analysis of several genetic consortia (up to 73,673 cases and 86,854 controls). A two-sample MR approach and several sensitivity analyses were applied. Results: We found no evidence for an association of genetically predicted plasma total ghrelin levels and colorectal cancer risk (0.95, 95% confidence interval, 0.81–1.12; R2 of ghrelin genetic instruments: 4.6%), with similarly null results observed when stratified by sex, anatomical subsite, and for early-onset colorectal cancer. Conclusions: Our study suggests that plasma ghrelin levels are unlikely to have a causal relationship with overall, early-onset, and sex- and cancer subsite–stratified colorectal cancer risk. Impact: This large-scale analysis adds to the growing body of evidence that plasma total ghrelin levels are not associated with colorectal cancer risk.

Regular, long-term aspirin use may act synergistically with genetic variants, particularly those in mechanistically relevant pathways, to confer a protective effect on colorectal cancer (CRC) risk. We leveraged pooled data from 52 clinical trial, cohort, and case-control studies that included 30,806 CRC cases and 41,861 controls of European ancestry to conduct a genome-wide interaction scan between regular aspirin/nonsteroidal anti-inflammatory drug (NSAID) use and imputed genetic variants. After adjusting for multiple comparisons, we identified statistically significant interactions between regular aspirin/NSAID use and variants in 6q24.1 (top hit rs72833769 ), which has evidence of influencing expression of TBC1D7 (a subunit of the TSC1-TSC2 complex, a key regulator of MTOR activity), and variants in 5p13.1 (top hit rs350047 ), which is associated with expression of PTGER4 (codes a cell surface receptor directly involved in the mode of action of aspirin). Genetic variants with functional impact may modulate the chemopreventive effect of regular aspirin use, and our study identifies putative previously unidentified targets for additional mechanistic interrogation.

AbstractLow physical activity and high sedentary behaviour have been clearly linked with colorectal cancer development, yet data on their potential role in colorectal cancer survival is limited. Better characterisation of these relationships is needed for the development of post‐diagnosis physical activity and sedentary behaviour guidance for colorectal cancer survivors. We searched PubMed and Embase through 28 February 2022 for studies assessing post‐diagnosis physical activity, and/or sedentary behaviour in relation to all‐cause and cause‐specific mortality and recurrence after colorectal cancer diagnosis. Total and recreational physical activity were assessed overall and by frequency, duration, intensity, and volume using categorical, linear, and non‐linear dose–response random‐effects meta‐analyses. The Global Cancer Update Programme (CUP Global) independent Expert Committee on Cancer Survivorship and Expert Panel interpreted and graded the likelihood of causality. We identified 16 observational studies on 82,220 non‐overlapping patients from six countries. Physical activity was consistently inversely associated with colorectal cancer morbidity and mortality outcomes, with 13%–60% estimated reductions in risk. Sedentary behaviour was positively associated with all‐cause mortality. The evidence had methodological limitations including potential confounding, selection bias and reverse causation, coupled with a limited number of studies for most associations. The CUP Global Expert panel concluded limited‐suggestive evidence for recreational physical activity with all‐cause mortality and cancer recurrence. Total physical activity and its specific domains and dimensions, and sedentary behaviour were all graded as limited‐no conclusion for all outcomes. Future research should focus on randomised trials, while observational studies should obtain objective and repeated physical activity measures and better adjustment for confounders.

AbstractBased on the World Cancer Research Fund Global Cancer Update Programme, we performed systematic reviews and meta‐analyses to investigate the association of post‐diagnosis adiposity, physical activity, sedentary behaviour, and dietary factors with colorectal cancer prognosis. We searched PubMed and Embase until 28th February, 2022. An independent expert committee and expert panel graded the quality of evidence. A total of 167 unique publications were reviewed, and all but five were observational studies. The quality of the evidence was graded conservatively due to the high risk of several biases. There was evidence of non‐linearity in the associations between body mass index and colorectal cancer prognosis. The associations appeared reverse J‐shaped, and the quality of this evidence was graded as limited (likelihood of causality: limited‐no conclusion). The evidence on recreational physical activity and lower risk of all‐cause mortality (relative risk [RR] highest vs. lowest: 0.69, 95% confidence interval [CI]: 0.62–0.77) and recurrence/disease‐free survival (RR: 0.80, 95% CI: 0.70–0.92) was graded as limited‐suggestive. There was limited‐suggestive evidence for the associations between healthy dietary and/or lifestyle patterns (including diets that comprised plant‐based foods), intake of whole grains and coffee with lower risk of all‐cause mortality, and between unhealthy dietary patterns and intake of sugary drinks with higher risk of all‐cause mortality. The evidence for other exposures on colorectal cancer outcomes was sparse and graded as limited‐no conclusion. Analyses were conducted excluding cancer patients with metastases without substantial changes in the findings. Well‐designed intervention and cohort studies are needed to support the development of lifestyle recommendations for colorectal cancer patients.