Dual checkpoint T(h1)eamwork makes the anti-cancer dream work.

Combined anti-PD-L1+anti-CTLA-4 therapy has shown benefits over anti-PD-L1 monotherapy as a neoadjuvant treatment in head and neck cancer. In this issue of Immunity, Franken et al. report that CD4+ T cell trafficking from lymph nodes to tumors and expansion toward T helper 1 cells are features specific to combination therapy.

Helicobacter pylori promotes colorectal carcinogenesis by deregulating intestinal immunity and inducing a mucus-degrading microbiota signature.

OBJECTIVE: Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between H. pylori infection and colon cancer is lacking. DESIGN: We infected two Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive analysis of H. pylori-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments. RESULTS: H. pylori infection accelerated tumour development in Apc-mutant mice. We identified a unique H. pylori-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium, H. pylori induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from H. pylori-infected patients. Housing of Apc-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of H. pylori infection normalised the tumour incidence to the level of uninfected controls. CONCLUSIONS: Our studies provide evidence that H. pylori infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of H. pylori status into preventive measures of CRC should be considered.

Loss of endogenous RNF43 function enhances proliferation and tumour growth of intestinal and gastric cells.

Ring finger protein 43 (RNF43) is an E3 ubiquitin ligase that has been described to be frequently mutated in gastrointestinal cancers. RNF43 downregulation was associated with distant metastasis, TNM stage and poorer survival in patients with gastric and colorectal cancers. Functional analysis has shown that overexpressed RNF43 negatively regulates Wnt signalling by ubiquitinating Frizzled receptors and targeting them for degradation and by sequestering T-cell factor 4 (TCF4) to the nuclear membrane, thereby inhibiting Wnt-mediated transcription. In the stomach, RNF43 overexpression was shown to impair stem-like properties and to be negatively correlated with expression of Wnt-target genes. In this study, we show that RNF43 knockdown enhances the tumourigenic potential of gastric and colorectal cancer cell lines in vitro and in vivo. Thus, loss of RNF43 leads to increased proliferation and anchorage-independent growth as well as increased invasive capacity. In a xenograft model, RNF43 depletion enhanced tumour growth. Furthermore, we established two mouse models in which mutations in the RING domain of RNF43 were introduced. In the intestine and colon, loss of Rnf43 did not induce changes in epithelial architecture or proliferation. In contrast, in the stomach, thickening of the mucosa, hyperplasia and cellular atypia were observed in these mice. Notably, this was independent of elevated Wnt signalling. Together, our results show that RNF43 plays a tumour suppressive role in gastric and colorectal cancer cells and that the loss of its function alters gastric tissue homeostasis in vivo.

Engagement of CEACAM1 by Helicobacterpylori HopQ Is Important for the Activation of Non-Canonical NF-κB in Gastric Epithelial Cells.

The gastric pathogen Helicobacter pylori infects half of the world's population and is a major risk factor for gastric cancer development. In order to attach to human gastric epithelial cells and inject the oncoprotein CagA into host cells, H. pylori utilizes the outer membrane protein HopQ that binds to the cell surface protein CEACAM, which can be expressed on the gastric mucosa. Once bound, H. pylori activates a number of signaling pathways, including canonical and non-canonical NF-κB. We investigated whether HopQ-CEACAM interaction is involved in activating the non-canonical NF-κB signaling pathway. Different gastric cancer cells were infected with the H. pylori wild type, or HopQ mutant strains, and the activation of non-canonical NF-κB was related to CEACAM expression levels. The correlation between CEACAM levels and the activation of non-canonical NF-κB was confirmed in human gastric tissue samples. Taken together, our findings show that the HopQ-CEACAM interaction is important for activation of the non-canonical NF-κB pathway in gastric epithelial cells.