TPH1 and cancer: This conclusion is based on the observations that; 1) TNBCs (MDA-MB-231, HCC-1395, and Hs578T) expressed higher levels of TPH1 and 5-HT7 receptor, and secreted more 5-HT than hormone-positive cells (MCF-7 and T47D), 2) silencing of TPH1 or 5-HT7 receptor blocked cancer invasion and proliferation.