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.

T-cells are major therapeutic targets in cancer and immune-mediated diseases. Their development and differentiation require highly dynamic receptor turnover. Protein tyrosine phosphatase non-receptor type 23 (PTPN23) encodes a ubiquitously expressed pseudophosphatase involved in trafficking and internalization of specific cell receptors. Although PTPN23 has essential functions in several cell types, its role in T-cells remains unknown. We therefore investigated the role of PTPN23 in T-cells. We generated transgenic mice lacking PTPN23 specifically in T-cells (PTPN23-CD4-Cre). Flow cytometry, single-cell RNA sequencing (scRNA-seq), and proteomic analysis were performed in lymphoid and mucosal organs. PTPN23-CD4-Cre mice exhibited a significant reduction in total T-cell numbers in lymphoid organs, accompanied by increased proportions and numbers of γδ T-cells and markedly reduced naïve T-cells. Similar findings were made in mucosal organs, with γδ T-cell levels rising as age increased. In vitro functional assays revealed that residual PTPN23-CD4-Cre T-cells display an altered cytokine profile enriched for inflammatory mediators, a finding that was accompanied by proteomic and phosphoproteomic alterations consistent with changes in T-cell differentiation and inflammatory programs. scRNA-seq analysis showed altered representation of thymocytes along a shared developmental trajectory, with enrichment of PTPN23-deficient T-cells at earlier developmental states. Our study identifies PTPN23 as a previously unrecognized player of T-cell development, differentiation, and immune homeostasis.

Protein tyrosine phosphatases (PTPs) are key regulators of intracellular signaling cascades involved in cell growth, proliferation, differentiation, inflammation, and cancer. PTPN23, a non-receptor PTP, is involved in endosomal sorting and thereby regulates the internalization of growth factor receptors, such as the epidermal growth factor receptor (EGFR). PTPN23 has been proposed to exert tumor-suppressive effects in several epithelial cancers, including breast and lung cancer. PTPN23 is ubiquitously expressed in the body; however, it is particularly highly expressed in the intestine, where it plays an essential role in maintaining intestinal homeostasis. Despite these observations, its involvement in colorectal carcinoma (CRC) remains largely unexplored. To investigate the function of PTPN23 in CRC, we generated PTPN23-overexpressing CRC cell lines and evaluated their effects in vitro and in subcutaneous tumor models. Our in-vitro findings demonstrate that PTPN23 overexpression resulted in reduced proliferation levels and follow-up experiments showed suppression of colorectal cancer growth and proliferation in experimental CRC models. These effects were accompanied by changes in EGFR-associated signaling; however, the underlying mechanism, including a potential role of EGFR trafficking, remains to be established through direct experimental validation. Together, these findings expand current knowledge of PTPN23 in colorectal cancer and provide a basis for future studies addressing its biological function and therapeutic relevance.