Helminth-based Therapy of Colitis – Influence on Tumor Growth and Progression in Colitis-associated Colon Cancer

Ulcerative colitis (UC) is a chronic inflammatory disorder of the gastrointestinal tract, associated with an increased risk of colorectal cancer development. Since the etiology of UC is still unknown, current therapies are able to alleviate the acute inflammation but fail to cure the patients. The IBD patients’ exposure to helminths appears to be a novel promising approach as helminths provoke an immunosuppressive state in the host by releasing immunomodulatory molecules and inducing regulatory T cells (Tregs). However, whether this increase in regulatory T cell numbers 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 Heligmosomoides (H.) 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 seems to strengthen the inflammatory response and to boost tumor development accompanied by a reduced frequency of colonic CD8⁺ effector T cells. Together, our results demonstrate that the therapeutic application of helminths during CAC might have tumor-promoting effects. Therefore the specific time point of helminth infection may dictate the therapeutic outcome.