Background Osteosarcoma is an aggressive and painful bone neoplasm in dogs. Previous studies have reported epidemiological associations suggesting that large body mass, long bone length and the genetics of certain breeds including the Rottweiler are associated with elevated osteosarcoma risk. However, these studies were often limited by selection bias and confounding factors, and have rarely offered insights into breed-associated protection for osteosarcoma. The current study includes 1756 appendicular and axial osteosarcoma cases presenting to VPG Histology (Bristol, UK) compared against a control population of 905,211 dogs without osteosarcoma from primary care electronic patient records in the VetCompass™ dataset. Methods and study design Retrospective, case-control study. Multivariable logistic regression analysis explored associations between demographic risk factors (including breed, chondrodystrophy, age, sex/neuter status, skull-shape, and body mass) and osteosarcoma of all anatomical sites. Results We identified several breeds with increased and reduced odds of osteosarcoma. At highest risk were the Rottweiler and Great Dane, with > 10 times the odds of osteosarcoma compared with crossbreds, and the Rhodesian Ridgeback, which has not featured in previous lists of at-risk breeds for osteosarcoma, and had an odds ratio of 11.31 (95% confidence interval 7.37–17.35). Breeds at lowest risk of osteosarcoma (protected breeds) included the Bichon Frise, the French Bulldog and the Cavalier King Charles Spaniel, all with odd ratios of less than 0.30 compared with crossbreds. Body mass was strongly associated with osteosarcoma risk; dogs over 40 kg exhibited osteosarcoma odds of 45.44 (95% confidence interval 33.74–61.20) compared with dogs less than 10 kg. Chondrodystrophic breeds had an osteosarcoma odds ratio of 0.13 (95% confidence interval 0.11–0.16) compared with non-chondrodystrophic breeds. Conclusions This study provides evidence of strong breed-associated osteosarcoma risk and protection, suggesting a genetic basis for osteosarcoma pathogenesis. It highlights that breeds selected for long legs/large body mass are generally overrepresented amongst at-risk breeds, whilst those selected for short leg length/small body mass are generally protected. These findings could inform genetic studies to identify osteosarcoma risk alleles in canines and humans; as well as increasing awareness amongst veterinarians and owners, resulting in improved breeding practices and clinical management of osteosarcoma in dogs.

The killing of tumor cells by CD8+ T cells is suppressed by the tumor microenvironment, and increased expression of inhibitory receptors, including programmed cell death protein-1 (PD-1), is associated with tumor-mediated suppression of T cells. To find cellular defects triggered by tumor exposure and associated PD-1 signaling, we established an ex vivo imaging approach to investigate the response of antigen-specific, activated effector CD8+ tumor-infiltrating lymphocytes (TILs) after interaction with target tumor cells. Although TIL–tumor cell couples readily formed, couple stability deteriorated within minutes. This was associated with impaired F-actin clearing from the center of the cellular interface, reduced Ca2+ signaling, increased TIL locomotion, and impaired tumor cell killing. The interaction of CD8+ T lymphocytes with tumor cell spheroids in vitro induced a similar phenotype, supporting a critical role of direct T cell–tumor cell contact. Diminished engagement of PD-1 within the tumor, but not acute ex vivo blockade, partially restored cell couple maintenance and killing. PD-1 thus contributes to the suppression of TIL function by inducing a state of impaired subcellular organization.

Mammary cancer is one of the most common neoplasms of dogs, primarily bitches. While studies have been carried out identifying differing risk of mammary neoplasia in different dog breeds, few studies have reported associations between dog breeds and clinical features such as number of neoplastic lesions found in an individual case or the likelihood of lesions being benign or malignant. Such epidemiological studies are essential as a foundation for exploring potential genetic drivers of mammary tumour behaviour. Here, we have examined associations between breed, age and neuter status and the odds of a diagnosis of a mammary epithelial-origin neoplastic lesion (as opposed to any other histopathological diagnosis from a biopsied lesion) as well as the odds of a bitch presenting with either a single mammary lesion or multiple lesions, and the odds that those lesions are benign or malignant. The study population consisted of 129,258 samples from bitches, including 13,401 mammary epithelial neoplasms, submitted for histological assessment to a single histopathology laboratory between 2008 and 2021.In multivariable analysis, breed, age and neuter status were all significantly associated with the odds of a diagnosis of a mammary epithelial-origin neoplastic lesion. Smaller breeds were more likely to receive such a diagnosis. In cases diagnosed with a mammary epithelial neoplasm, these three factors were also significantly associated with the odds of diagnosis with a malignant lesion and of diagnosis with multiple lesions. Notably, while neutered animals were less likely to have a mammary epithelial neoplasm diagnosed, and were less likely to have multiple neoplasms, they were more likely to have malignant disease. Exploration of the patterns of risk of developing malignant disease, or multiple lesions, across individual breeds showed no breed with increased odds of both outcomes. Breeds with altered odds compared to the Crossbreed baseline were either at increased risk of malignant disease and decreased risk of multiple lesions, or vice versa, or they were at significantly altered odds of one outcome with no change in the other outcome. Our analysis supports the hypothesis that age, neuter status and intrinsic biological and genetic factors all combine to influence the biological heterogeneity of canine mammary neoplasia.

Background: Variation in the human gut microbiome may influence cancer progression and therapy response through various mechanisms including modulation of both immune and cell signalling pathways. Whilst observational epidemiological studies have provided evidence that the gut microbiome may play a role in cancer risk, such studies are prone to residual confounding, reverse causation, and other forms of bias. Therefore, the nature of these associations still remains unclear. Mendelian randomization (MR) is a causal methodology that uses genetic variants as instruments (“proxies”) for risk factors to eliminate such biases when questioning causality in observational epidemiological associations. The statistical power and precision of MR analyses can be increased by employing a “two-sample MR” (2SMR) framework in which summary data – usually from large, independent, genome-wide association studies (GWASs) reporting associations of genetic variants with exposures (here, the gut microbiome) and outcomes (here, cancer) – are synthesised to estimate causal effects of each exposure on each outcome of interest. In this study, we utilised 2SMR to interrogate causal relationships between the gut microbiome and breast cancer (BC) risk using the largest published GWASs of the gut microbiome and of clinically utilised subtypes of BC. Methods: We performed 2SMR using summary-level data from the GWAS of the host genetic contribution to gut microbiome variation amongst European individuals (the Flemish Gut Flora Project and two German cohorts (n=3890)) combined with summary-level data from the GWAS of BC risk (Breast Cancer Association Consortium (133,384 cases stratified by Luminal A, Luminal B, Human Epidermal Growth Factor 2 (Her2) positive, Her2 negative and triple negative status and 113,789 controls, plus 18,908 BRCA1 mutation carriers (9,414 with BC)). Sensitivity analyses were also conducted to assess pleiotropy of genetic variants on BC risk, independent of gut microbiota. Analyses were conducted in R Studio using the TwoSampleMR and the MR-TRYX packages. Results: Of the 14 microbial traits (MTs) with evidence for a host genetic contribution in the GWAS of the gut microbiome, we found evidence that abundance of a genus within a certain bacterial order decreased the risk of triple negative BC (odds ratio per standard deviation increase: 0.84; 95% CI: 0.71, 0.9; p=0.03). In addition, we demonstrated that the risk of all molecular subtypes of BC may be altered by variation in these MTs, and that these relationships differed according to subtype. Sensitivity analyses demonstrated that pleiotropy was unlikely to explain these relationships Conclusions: In our study, we utilised two recent and novel GWASs in an MR context to appraise causality in relationships between the gut microbiome and BC risk and found evidence that certain bacteria may alter BC risk, effects of which vary according to molecular subtype. These important results generate hypotheses about mechanisms underlying the causal biology of BC subtypes and potentially facilitate the design of BC risk-reducing interventions and prevention strategies. Citation Format: Tim Robinson, Grace Edmunds, Bryony Hayes, Kaitlin Wade. Exploring the causal role of the human gut microbiome in breast cancer risk using mendelian randomization [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS2-06.

BackgroundOsteosarcoma is an aggressive and painful bone neoplasm in dogs. Previous studies have reported epidemiological associations suggesting that large body mass, long bone length and the genetics of certain breeds including the Rottweiler are associated with elevated osteosarcoma risk. However, these studies were often limited by selection bias and confounding, and have rarely offered insights into breed-associated protection as well as breed-associated predisposition for osteosarcoma. The current study includes 1756 osteosarcoma cases presenting to VPG Histology (Bristol, UK) that are compared against a control population of 905,211 dogs without osteosarcoma taken from primary care electronic patient records in the VetCompass™ dataset. Methods and Study DesignRetrospective, case-control study. Multivariable logistic regression analysis explored associations between demographic risk factors (including breed, chondrodystrophy, age, sex/neuter status, skull-shape, and body mass) and osteosarcoma. ResultsWe identified several breeds with increased and reduced odds of osteosarcoma. At highest risk were the Rottweiler and Great Dane, with >10 times the odds of osteosarcoma compared with crossbreeds, and the Rhodesian Ridgeback; which has not featured in previous lists of at-risk breeds for osteosarcoma, and had an odds ratio of 11.31 (95% confidence interval 7.37 - 17.35). Breeds at lowest risk of osteosarcoma (protected breeds) included the Bichon Frise, the French Bulldog and the Cavalier King Charles Spaniel, all with odd ratios of less than 0.30 compared with crossbreeds. Body mass was strongly associated with osteosarcoma risk; dogs over 40kg exhibited osteosarcoma odds of 45.44 (95% confidence interval 33.74 - 61.20) compared with dogs less than 10kg. Chondrodystrophic breeds had an osteosarcoma odds ratio of 0.13 (95% confidence interval 0.11 - 0.16) compared with non-chondrodystrophic breeds. ConclusionsOverall, this study provides evidence of strong breed-associated osteosarcoma risk and protection, suggesting a genetic basis for osteosarcoma pathogenesis. The study findings highlight that breeds bred for long legs or large body mass are generally overrepresented amongst at-risk breeds, whilst those bred for short leg length or small body mass are generally protected. These findings could inform genetic studies to identify osteosarcoma risk alleles in canines and humans; as well as increasing awareness amongst vets and owners, resulting in improved breeding practices and clinical management of osteosarcoma in dogs.