AIM: To investigate whether Recql5, a DNA helicase that plays an important role in the maintenance of genome integrity, is a tumor suppressor in the gastrointestinal tract in mice. METHODS: We generated cohorts of both Recql5-pro- ficient and Recql5-deficient Apc~(min)/+ mice and compared the tumor susceptibility in their gastrointestinal tracts. RESULTS: Recql5 deficiency in Apc~(min/+) mice resulted in a significant increase in the tumor incidence in both the colon (P=0.0162) and the small intestine (P