Protein tyrosine phosphatase nonreceptor type 2 (PTPN2) recently emerged as a promising cancer immunotherapy target. We set out to investigate the functional role of PTPN2 in the pathogenesis of human colorectal carcinoma (CRC), as its role in immune-silent solid tumors is poorly understood. We demonstrate that in human CRC, increased PTPN2 expression and activity correlated with disease progression and decreased immune responses in tumor tissues. In particular, stage II and III tumors displayed enhanced PTPN2 protein expression in tumor-infiltrating T cells, and increased PTPN2 levels negatively correlated with expression of PD-1, CTLA4, STAT1, and granzyme A. In vivo, T cell– and DC-specific PTPN2 deletion reduced tumor burden in several CRC models by promoting CD44⁺ effector/memory T cells, as well as CD8⁺ T cell infiltration and cytotoxicity in the tumor. In direct relevance to CRC treatment, T cell–specific PTPN2 deletion potentiated anti–PD-1 efficacy and induced antitumor memory formation upon tumor rechallenge in vivo. Our data suggest a role for PTPN2 in suppressing antitumor immunity and promoting tumor development in patients with CRC. Our in vivo results identify PTPN2 as a key player in controlling the immunogenicity of CRC, with the strong potential to be exploited for cancer immunotherapy.

In recent years, the gut microbiome has been recognized as one influential factor in cancer development. Particularly in colorectal cancer (CRC), several studies observed a major imbalance of the intestinal microbiota, marked by a reduction in beneficial bacterial species, such as Roseburia intestinalis, and an increase in opportunistic pathobionts, like Peptostreptococcus stomatis. We previously observed that specific Eubacteriales, including R. intestinalis, were significantly reduced in CRC patients and have a potent anti-tumor immune effect when applied as oral monotherapy in mice. Here, we investigate the molecular mechanism of R. intestinalis on various cell types in vitro, highlighting its potential therapeutic value in CRC. Co-culture experiments with macrophages demonstrated that R. intestinalis exposure induced an increase in the M1 phenotype and decreased the M2 phenotype, suggesting macrophage-polarizing properties of these bacteria. R. intestinalis also triggered a gene expression profile resembling M1 macrophages and led to distinct chemokine and cytokine secretion in cancer cells, suggesting an immune-activating environment. However, we did not observe direct cytotoxic effects in cancer cells. Our research provides insights into the potential of R. intestinalis to activate immune responses, supporting further investigation into its therapeutic role in CRC. These findings underscore the need for deeper studies on the bacterium’s impact on CRC pathogenesis and treatment.

Environmental and genetic factors have been demonstrated to contribute to the development of inflammatory bowel disease (IBD). Recent studies suggested that the food additive; titanium dioxide (TiO₂) might play a causative role in the disease. Therefore, in the present study we aimed to explore the interaction between the food additive TiO₂ and the well-characterized IBD risk gene protein tyrosine phosphatase non-receptor type 2 (Ptpn2) and their role in the development of intestinal inflammation. Dextran sodium sulphate (DSS)-induced acute colitis was performed in mice lacking the expression of Ptpn2 in myeloid cells (Ptpn2^LysMCre) or their wild type littermates (Ptpn2^fl/fl) and exposed to the microparticle TiO₂. The impact of Ptpn2 on TiO₂ signalling pathways and TiO₂-induced IL-1β and IL-10 levels were studied using bone marrow-derived macrophages (BMDMs). Ptpn2^LysMCre exposed to TiO₂ exhibited more severe intestinal inflammation than their wild type counterparts. This effect was likely due to the impact of TiO₂ on the differentiation of intestinal macrophages, suppressing the number of anti-inflammatory macrophages in Ptpn2 deficient mice. Moreover, we also found that TiO₂ was able to induce the secretion of IL-1β via mitogen-activated proteins kinases (MAPKs) and to repress the expression of IL-10 in bone marrow-derived macrophages via MAPK-independent pathways. This is the first evidence of the cooperation between the genetic risk factor Ptpn2 and the environmental factor TiO₂ in the regulation of intestinal inflammation. The results presented here suggest that the ingestion of certain industrial compounds should be taken into account, especially in individuals with increased genetic risk

Protein tyrosine phosphatase nonreceptor type 2 (PTPN2) plays a critical role in the pathogenesis of inflammatory bowel diseases (IBD). Mice lacking PTPN2 in dendritic cells (DCs) develop skin and liver inflammation by the age of 22 weeks due to a generalized loss of tolerance leading to uncontrolled immune responses. The effect of DC-specific PTPN2 loss on intestinal health, however, is unknown. The aim of this study was to investigate the DC-specific role of PTPN2 in the intestine during colitis development. PTPN2^fl/flxCD11c^Cre mice were subjected to acute and chronic DSS colitis as well as T cell transfer colitis. Lamina propria immune cell populations were analyzed using flow cytometry. DC-specific PTPN2 deletion promoted infiltration of B and T lymphocytes, macrophages, and DCs into the lamina propria of unchallenged mice and elevated Th1 abundance during acute DSS colitis, suggesting an important role for PTPN2 in DCs in maintaining intestinal immune cell homeostasis. Surprisingly, those immune cell alterations did not translate into increased colitis susceptibility in acute and chronic DSS-induced colitis or T cell transfer colitis models. However, macrophage depletion by clodronate caused enhanced colitis severity in mice with a DC-specific loss of PTPN2. Loss of PTPN2 in DCs affects the composition of lamina propria lymphocytes, resulting in increased infiltration of innate and adaptive immune cells. However, this did not result in an elevated colitis phenotype, likely because increased infiltration of macrophages in the intestine upon loss of PTPN2 loss in DCs can compensate for the inflammatory effect of PTPN2-deficient DCs.