Delivery, structure, and function of bacterial genotoxins.

Bacterial genotoxins are peptide or protein virulence factors produced by several pathogens, which make single-strand breaks (SSBs) and/or double-strand DNA breaks (DSBs) in the target host cells. If host DNA inflictions are not resolved on time, host cell apoptosis, cell senescence, and/or even bacterial pathogen-related cancer may occur. Two multi-protein AB toxins, cytolethal distending toxin (CDT) produced by over 30 bacterial pathogens and typhoid toxin from Salmonella Typhi, as well as small polyketide-peptides named colibactin that causes the DNA interstrand cross-linking and subsequent DSBs is the most well-characterized bacterial genotoxins. Using these three examples, this review discusses the mechanisms by which these toxins deliver themselves into the nucleus of the target host cells and exert their genotoxic functions at the structural and functional levels.

An Asia-specific variant of human IgG1 represses colorectal tumorigenesis by shaping the tumor microenvironment.

Emerging studies have focused on ways to treat cancers by modulating T cell activation. However, whether B cell receptor signaling in the tumor microenvironment (TME) can be harnessed for immunotherapy is unclear. Here, we report that an Asia-specific variant of human IgG1 containing a Gly396 to Arg396 substitution (hIgG1-G396R) conferred improved survival of patients with colorectal cancer (CRC). Mice with knockin of the murine functional homolog mIgG2c-G400R recapitulated the alleviated tumorigenesis and progression in murine colon carcinoma models. Immune profiling of the TME revealed broad mobilizations of IgG1+ plasma cells, CD8+ T cells, CD103+ DCs, and active tertiary lymphoid structure formation, suggesting an effective antitumor microenvironment in hIgG1-G396R CRC patients. Mechanistically, this variant potentiated tumor-associated antigen-specific (TAA-specific) plasma cell differentiation and thus antibody production. These elevated TAA-specific IgG2c antibodies in turn efficiently boosted the antibody-dependent tumor cell phagocytosis and TAA presentation to effector CD8+ T cells. Notably, adoptive transfer of TAA-specific class-switched memory B cells harboring this variant exhibited therapeutic efficacy in murine tumor models, indicating their clinical potential. All these results prompted a prospective investigation of hIgG1-G396R in patients with CRC as a biomarker for clinical prognosis and demonstrated that manipulating the functionality of IgG1+ memory B cells in tumors could improve immunotherapy outcomes.