Al carcinoma enriched withF. nucleatummight gradually increase along the bowel subsites from rectum to cecum. METHODS: A retrospective, cross-sectional analysis was conducted on 1,102 colon and rectal carcinomas in molecular pathological epidemiology databases of the Nurses' Health Study and the Health Professionals Follow-up Study. We measured the amount ofF. nucleatumDNA in colorectal tumor tissue using a quantitative PCR assay and equally dichotomizedF. nucleatum-positive cases (high vs. low). We used multivariable logistic regression analysis to examine the relationship of a bowel subsite variable (rectum, rectosigmoid junction, sigmoid colon, descending colon, splenic flexure, transverse colon, hepatic flexure, ascending colon, and cecum) with the amount ofF. nucleatum. RESULTS: The proportion ofF. nucleatum-high colorectal cancers gradually increased from rectal cancers (2.5%; 4/157) to cecal cancers (11%; 19/178), with a statistically significant linear trend along all subsites (P<0.0001) and little evidence of non-linearity. The proportion ofF. nucleatum-low cancers was higher in rectal, ascending colon, and cecal cancers than in cancers of middle segments. CONCLUSIONS: The proportion ofF. nucleatum-high colorectal cancers gradually increases from rectum to cecum. Our data support the colorectal continuum model that reflects pathogenic influences of the gut microbiota on neoplastic and immune cells and challenges the prevailing two-colon (proximal vs. distal) dichotomy paradigm....

Objective: Evidence suggests that CD274 (programmed death-ligand 1, B7-H1) immune checkpoint ligand repress antitumour immunity through its interaction with the PDCD1 (programmed cell death 1, PD-1) receptor of T lymphocytes in various tumours. We hypothesised that tumour CD274 expression levels might be inversely associated with T-cell densities in colorectal carcinoma tissue. Design: We evaluated tumour CD274 expression by immunohistochemistry in 823 rectal and colon cancer cases within the Nurses' Health Study and Health Professionals Follow-up Study. We conducted multivariable ordinal logistic regression analyses to examine the association of tumour CD274 expression with CD3⁺, CD8⁺, CD45RO (PTPRC)⁺ or FOXP3⁺ cell density in tumour tissue, controlling for potential confounders including tumour status of microsatellite instability (MSI), CpG island methylator phenotype, long interspersed nucleotide element-1 methylation level and KRAS, BRAF and PIK3CA mutations. Results: CD274 expression in tumour cells or stromal cells (including immune cells) was detected in 731 (89%) or 44 (5%) cases, respectively. Tumour CD274 expression level correlated inversely with FOXP3⁺ cell density in colorectal cancer tissue (outcome) (p_trend=0.0002). For a unit increase in outcome quartile categories, multivariable OR in the highest (vs lowest) CD274 expression score was 0.22 (95% CI 0.10 to 0.47). Tumour CD274 expression was inversely associated with MSI-high status (p=0.001). CD274 expression was not significantly associated with CD3⁺, CD8⁺ or CD45RO⁺ cell density, pathological lymphocytic reactions or patient survival prognosis. Conclusions: Tumour CD274 expression is inversely associated with FOXP3⁺ cell density in colorectal cancer tissue, suggesting a possible influence of CD274-expressing carcinoma cells on regulatory T cells in the tumour microenvironment.

The presence of Fusobacterium nucleatum (F. nucleatum) in colorectal carcinoma tissue has been associated with microsatellite instability (MSI), lower-level T-cell infiltrates, and poor clinical outcomes. Considering differences in the tumor–immune microenvironment between MSI-high and non–MSI-high carcinomas, we hypothesized that the association of F. nucleatum with immune response might differ by tumor MSI status. Using samples from 1,041 rectal and colon cancer patients within the Nurses’ Health Study and Health Professionals Follow-up Study, we measured F. nucleatum DNA in tumor tissue by a quantitative polymerase chain reaction assay. Multivariable logistic regression models were used to examine the association between F. nucleatum status and histopathologic lymphocytic reactions or density of CD3+ cells, CD8+ cells, CD45RO (PTPRC)+ cells, or FOXP3+ cells in strata of tumor MSI status. We adjusted for potential confounders, including CpG island methylator phenotype; LINE-1 methylation; and KRAS, BRAF, and PIK3CA mutations. The association of F. nucleatum with tumor-infiltrating lymphocytes (TIL) and intratumoral periglandular reaction differed by tumor MSI status (Pinteraction = 0.002). The presence of F. nucleatum was negatively associated with TIL in MSI-high tumors [multivariable odds ratio (OR), 0.45; 95% confidence interval (CI), 0.22–0.92], but positively associated with TIL in non–MSI-high tumors (multivariable OR 1.91; 95% CI, 1.12–3.25). No significant differential association was observed for peritumoral lymphocytic reaction, Crohn-like lymphoid reaction, or T-cell densities. In conclusion, the association of F. nucleatum with immune response to colorectal carcinoma differs by tumor MSI status, suggesting that F. nucleatum and MSI status interact to affect antitumor immune reactions. Cancer Immunol Res; 6(11); 1327–36. ©2018 AACR. See related Spotlight on p. 1290.

Cancer‐associated fibroblasts contribute to cancer progression that is caused by epithelial–mesenchymal transition (EMT). Recently, mesenchymal stem cells (MSCs) were found to be the major candidate involved in the development of tumor‐promoting cancer stroma. Here we report that α‐smooth muscle actin‐positive myofibroblast‐like cells originating from MSCs contribute to inducing EMT in side population cells of pancreatic cancer. More importantly, MSC‐derived myofibroblasts function to maintain tumor‐initiating stem cell‐like characteristics, including augmenting expression levels of various stemness‐associated genes, enhancing sphere‐ forming activity, promoting tumor formation in a mouse xenograft model, and showing resistance to anticancer drugs. Furthermore, both γ‐secretase inhibitor and siRNA directed against Jagged‐1 attenuated MSC‐associated E‐cadherin suppression and sphere formation in pancreatic cancer side population cells. Thus, our results suggest that MSC‐derived myofibroblasts play important roles in regulating EMT and tumor‐initiating stem cell‐like properties of pancreatic cancer cells through an intermediating Notch signal.

Purpose: Blockade of the programmed cell death 1 (PDCD1, PD-1) immune checkpoint pathway can improve clinical outcomes in various malignancies. Evidence suggests that aspirin (a widely used nonsteroidal anti-inflammatory drug) not only prolongs colorectal cancer survival, but can also activate T cell–mediated antitumor immunity and synergize with immunotherapy through inhibition of prostaglandin E2 production. We hypothesized that the survival benefit associated with aspirin might be stronger in colorectal carcinoma with a lower CD274 (PDCD1 ligand 1, PD-L1) expression level that resulted in lower signaling of the immune checkpoint pathway. Patients and Methods: Using data from 617 patients with rectal and colon cancer in the Nurses’ Health Study and the Health Professionals Follow-Up Study, we examined the association of postdiagnosis aspirin use with patient survival in strata of tumor CD274 expression status measured by immunohistochemistry. We used multivariable Cox proportional hazards regression models to control for potential confounders, including disease stage, microsatellite instability status, CpG island methylator phenotype, long interspersed nucleotide element-1 methylation, cyclooxygenase-2 (PTGS2), and CDX2 expression, and KRAS, BRAF, and PIK3CA mutations. Results: The association of postdiagnosis aspirin use with colorectal cancer–specific survival differed by CD274 expression status ( P_interaction < .001); compared with aspirin nonusers; multivariable-adjusted hazard ratios for regular aspirin users were 0.16 (95% CI, 0.06 to 0.41) in patients with low CD274 and 1.01 (95% CI, 0.61 to 1.67) in patients with high CD274. This differential association seemed consistent in patients with microsatellite-stable or PIK3CA wild-type disease and in strata of PTGS2 expression, CDX2 expression, tumor-infiltrating lymphocytes, or prediagnosis aspirin use status. Conclusion: The association of aspirin use with colorectal cancer survival is stronger in patients with CD274-low tumors than CD274-high tumors. Our findings suggest a differential antitumor effect of aspirin according to immune checkpoint status.