Cytolethal Distending Toxin Promotes Replicative Stress Leading to Genetic Instability Transmitted to Daughter Cells

Area of Science:

• Microbiology
• Genetics
• Cancer Biology

Background:

• Cytolethal distending toxin (CDT) is a virulence factor from Gram-negative bacteria implicated in inflammation and potentially cancer.
• CDT's protumoral role is suggested by its ability to cause cell transformation and carcinogenesis in experimental models.
• The genotoxic CdtB subunit is believed to mediate CDT's effects on DNA.

Purpose of the Study:

• To elucidate the mechanism by which CDT induces genetic instability in human cell lines and colorectal organoids.
• To investigate the impact of CDT on DNA replication, chromosomal integrity, and cell proliferation.
• To determine if CDT preferentially affects cycling versus quiescent cells.

Main Methods:

• Treatment of human cell lines and colorectal organoids with CDT holotoxin.
• Analysis of DNA replication dynamics, chromosomal aberrations, and mitotic events.
• Assessment of nuclear morphology and cell growth in response to CDT exposure.

Main Results:

• CDT holotoxin induces CdtB-dependent replicative stress, primarily in late S phase.
• CDT treatment leads to fragile sites, chromosomal aberrations, and DNA bridges during mitosis and G1 phase.
• Proliferating cells, including those in colorectal organoids, are preferentially affected, showing nuclear distension and reduced growth.

Conclusions:

• CDT acts as a bacterial virulence factor that targets proliferating cells, inducing replicative stress and genetic instability.
• These CDT-induced DNA abnormalities, transmitted to daughter cells, may contribute to colorectal carcinogenesis.
• Targeting CDT-producing bacteria presents a potential therapeutic strategy for colorectal cancer.