Urinary bladder cancer (BC) inflicts a significant impairment of life quality and poses a high mortality risk. Schistosoma haematobium infection can cause BC, and the urinary microbiota of BC patients differs from healthy controls. Importantly, intravesical instillation of the bacterium Bacillus Calmette-Guerin stands as the foremost therapy for non-muscle invasive BC. Hence, studying the receptors and signaling molecules orchestrating bacterial recognition and the cellular response in the context of BC is of paramount importance. Thus, we challenged Toll-like receptor 4 (Tlr4) and myeloid differentiation factor 88 (Myd88) knock-out (KO) mice with N-butyl-N-(4-hydroxylbutyl)-nitrosamine (BBN), a well-known urinary bladder carcinogen. Gut microbiota, gene expression, and urinary bladder pathology were followed. Acute exposure to BBN did not reveal a difference in bladder pathology despite differences in the animal’s ability to recognize and react to bacteria. However, chronic treatment resulted in reduced cancer invasiveness among Myd88^KO mice while the absence of functional Tlr4 did not influence BC development or progression. These differences correlate with a heightened abundance of the Faecalibaculum genus and the lowest microbial diversity observed among Myd88^KO mice. The presented data underscore the important role of microbiota composition and MyD88-mediated signaling during bladder carcinogenesis.

Background and Objectives: This study explores the immunological landscapes of non-melanoma skin neoplasms (NMSNs), specifically keratoacanthoma (KA), squamous cell carcinoma (SCC), and common warts (VV). Although benign, KA shares histological similarities with low-grade SCC. The tumor microenvironment (TME) plays a key role in tumor progression, affecting angiogenesis, inflammation, and immune evasion. Viral infections, particularly human papillomavirus (HPV), are linked to NMSN development, with various HPV types identified in KA. VV, caused by HPV, serves as a comparative model due to its similar etiopathogenesis. Materials and Methods: This research examines the expression of CTLA4, a critical regulator of T-cell homeostasis, and IFN-γ, a cytokine with immunomodulatory and antiviral effects, in the TME of 41 KA, 37 SCC, and 55 VV samples using multichannel immunofluorescence. Results: The analysis revealed distinct patterns of CTLA4 and IFN-γ expression. SCC exhibited a higher prevalence of CTLA4+IFN-γ+ double-positive lymphocytes, suggesting a more immunosuppressive TME. In contrast, VV showed the highest expression of CTLA4+ cells, while both KA and VV had lower expressions of IFN-γ+ lymphocytes compared to SCC. The increased presence of CTLA4+IFN-γ+ double-positive lymphocytes in SCC suggests that the co-expression of these markers may exert a stronger effect on TME modulation than CTLA4 alone. Conclusions: These findings underscore the potential of immune profiling as a diagnostic tool to differentiate between benign and malignant lesions, such as KA and SCC. Furthermore, the presence of CTLA4+IFN-γ+ lymphocytes, particularly in SCC, may serve as a biomarker for tumor progression and a potential target for future immunotherapy strategies aimed at modulating the immune response in NMSN.