Emilia Albesiano

BACKGROUND: Enterotoxigenic Bacteroides fragilis (ETBF) produces the Bacteroides fragilis toxin, which has been associated with acute diarrheal disease, inflammatory bowel disease, and colorectal cancer (CRC). ETBF induces colon carcinogenesis in experimental models. Previous human studies have demonstrated frequent asymptomatic fecal colonization with ETBF, but no study has investigated mucosal colonization that is expected to impact colon carcinogenesis. METHODS: We compared the presence of the bft gene in mucosal samples from colorectal neoplasia patients (cases, n = 49) to a control group undergoing outpatient colonoscopy for CRC screening or diagnostic workup (controls, n = 49). Single bacterial colonies isolated anaerobically from mucosal colon tissue were tested for the bft gene with touch-down polymerase chain reaction. RESULTS: The mucosa of cases was significantly more often bft-positive on left (85.7%) and right (91.7%) tumor and/or paired normal tissues compared with left and right control biopsies (53.1%; P = .033 and 55.5%; P = .04, respectively). Detection of bft was concordant in most paired mucosal samples from individual cases or controls (75% cases; 67% controls). There was a trend toward increased bft positivity in mucosa from late- vs early-stage CRC patients (100% vs 72.7%, respectively; P = .093). In contrast to ETBF diarrheal disease where bft-1 detection dominates, bft-2 was the most frequent toxin isotype identified in both cases and controls, whereas multiple bft isotypes were detected more frequently in cases (P ≤ .02). CONCLUSIONS: The bft gene is associated with colorectal neoplasia, especially in late-stage CRC. Our results suggest that mucosal bft exposure is common and may be a risk factor for developing CRC.

STAT3 activation has been observed in several autoimmune diseases, suggesting that STAT3-mediated pathways promote pathologic immune responses. We provide in vivo evidence that the fundamental role of STAT3 signaling in autoimmunity relates to its absolute requirement for generating T(H)17 T cell responses. We show that STAT3 is a master regulator of this pathogenic T cell subtype, acting at multiple levels in vivo, including T(H)17 T cell differentiation and cytokine production, as well as induction of RORgamma t and the IL-23R. Neither naturally occurring T(H)17 cells nor T(H)17-dependent autoimmunity occurs when STAT3 is ablated in CD4 cells. Furthermore, ablation of STAT3 signaling in CD4 cells results in increased T(H)1 responses, indicating that STAT3 signaling skews T(H) responses away from the T(H)1 pathway and toward the T(H)17 pathway. Thus, STAT3 is a candidate target for T(H)17-dependent autoimmune disease immunotherapy that could selectively inhibit pathogenic immune pathways.

Myeloid-derived suppressor cells (MDSC) play a key immunosuppressive role in various types of cancer, including head and neck squamous cell carcinoma (HNSCC). In this study, we characterized CD14+HLA-DR(-/lo) cells sorted from the tumors, draining lymph nodes, and peripheral blood of HNSCC patients. CD14+HLA-DR(-/lo) cells were phenotyped as CD11b+, CD33+, CD34+, arginase-I+, and ROS+. In all 3 compartments, they suppressed autologous, antigen-independent T cell proliferation in a differential manner. The abundance of MDSC correlated with stage, but did not correlate with previous treatment with radiation or subsites of HNSCC. Interestingly, MDSC from all 3 compartments showed high phosphorylated STAT3 levels that correlated with arginase-I expression levels and activity. Stattic, a STAT3-specific inhibitor, and STAT3-targeted siRNA abrogated MDSC’s suppressive function. Inhibition of STAT3 signaling also resulted in decreased arginase-I activity. Analysis of the human arginase-I promoter region showed multiple STAT3-binding elements, and ChIP demonstrated that phosphorylated STAT3 binds to multiple sites in the arginase-I promoter. Finally, rescue of arginase-I activity after STAT3 blockade restored MDSC’s suppressive function. Taken together, these results demonstrate that the suppressive function of arginase-I in both infiltrating and circulating MDSC is a downstream target of activated STAT3.