Inhibition of cancer cell epithelial mesenchymal transition by normal fibroblasts via production of 5-methoxytryptophan

// Huei-Hsuan Cheng 1, 2, * , Ling-Yun Chu 1, * , Li-Yi Chiang 1 , Hua-Ling Chen 3 , Cheng-Chin Kuo 2, 3 , Kenneth K. Wu 1, 2, 3, 4 1 Metabolomic Medicine Research Center, China Medical University Hospital, Taichung, Taiwan 2 Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan 3 Institute of Cellular and System Medicine, National Health Research Institutes, Zhunan, Taiwan 4 Institute of Biotechnology, National Tsing-Hua University, Hsinchu, Taiwan * These authors contributed equally to this work Correspondence to: Kenneth K. Wu, email: kkgo@nhri.org.tw Huei-Hsuan Cheng, email: t24023@mail.cmuh.org.tw Keywords: epithelial mesenchymal transition, fibroblasts, lung cancer, 5-methoxytryptophan, tryptophan hydroxylase-1 Received: January 29, 2016      Accepted: April 11, 2016      Published: April 29, 2016 ABSTRACT We reported previously that human fibroblasts release 5-methoxytryptophan (5-MTP) which inhibits cancer cell COX-2 overexpression and suppresses cancer cell migration and metastasis. To determine whether fibroblasts block cancer cell epithelial mesenchymal transition (EMT) via 5-MTP, we evaluated the effect of Hs68 fibroblasts (HsFb) on A549 cancer cell EMT in a two-chamber system. Co-incubation of A549 with HsFb prevented TGF-β1-induced reduction of E-cadherin and increase in Snail and N-cadherin. Transfection of HsFb with tryptophan hydroxylase-1 siRNA, which inhibited tryptophan hydroxylase-1 protein expression and 5-MTP release in HsFb abrogated the effect of HsFb on A549 EMT. Direct addition of pure 5-MTP to cultured A549 cells followed by TGF-β1 prevented TGF-β1-induced reduction of E-cadherin, and elevation of Snail, vimentin and matrix metalloproteinase 9. Administration of 5-MTP to a murine xenograft tumor model reduced vimentin protein expression in the tumor tissues compared to vehicle control which was correlated with reduction of metastasis in the 5-MTP treated mice. Our experimental data suggest that 5-MTP exerted its anti-EMT actions through inhibition of p38 MAPK activation, p65/p50 NF-κB nuclear translocation and transactivation without the involvement of COX-2 or p300 histone acetyltransferase. Our findings indicate that fibroblasts release a tryptophan metabolite, 5-MTP, to reduce cancer cell EMT, migration, invasion and metastasis.