As inhibition of 5-HT signaling was shown to hinder the growth of a CRC cell line in a xenograft tumor model 25, we sought to examine the impact of inhibition of 5-HT signaling via Htr2b knockout on the tumorigenesis of CAC and determine whether 5-HT acts as a tumor promoter in this disease. Here, HTR2B is linked to colorectal carcinoma.