Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the
gastrointestinal tract, strongly associated with an increased risk of
colorectal cancer development. Parasitic infections caused by helminths have
been shown to modulate the host’s immune response by releasing
immunomodulatory molecules and inducing regulatory T cells (Tregs). This
immunosuppressive state provoked in the host has been considered as a novel
and promising approach to treat IBD patients and alleviate acute intestinal
inflammation. On the contrary, specific parasite infections are well known to
be directly linked to carcinogenesis. Whether a helminth infection interferes
with the development of colitis-associated colon cancer (CAC) is not yet
known. In the present study, we demonstrate that the treatment of mice with
the intestinal helminth Heligmosomoides polygyrus at the onset of tumor
progression in a mouse model of CAC does not alter tumor growth and
distribution. In contrast, H. polygyrus infection in the early inflammatory
phase of CAC strengthens the inflammatory response and significantly boosts
tumor development. Here, H. polygyrus infection was accompanied by long-
lasting alterations in the colonic immune cell compartment, with reduced
frequencies of colonic CD8+ effector T cells. Moreover, H. polygyrus infection
in the course of dextran sulfate sodium (DSS) mediated colitis significantly
exacerbates intestinal inflammation by amplifying the release of colonic IL-6
and CXCL1. Thus, our findings indicate that the therapeutic application of
helminths during CAC might have tumor-promoting effects and therefore should
be well-considered