Invasive Fusobacterium nucleatum activates beta-catenin signaling in colorectal cancer via a TLR4/P-PAK1 cascade
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Yongyu Chen1,*, Yan Peng1,*, Jiahui Yu1, Ting Chen1, Yaxin Wu1, Lei Shi1, Qing Li1, Jiao Wu1 and Xiangsheng Fu1
1Department of Gastroenterology, The Affiliated Hospital of Southwest Medical University, Sichuan, 646000, China
*These authors have contributed equally to this work
Xiangsheng Fu, email: firstname.lastname@example.org
Keywords: Fusobacterium nucleatum, colorectal cancer, β-catenin signaling, toll-like receptor 4, p21-activated kinase 1
Received: October 20, 2016 Accepted: February 20, 2017 Published: March 07, 2017
The underlying mechanism of Fusobacterium nucleatum (Fn) in the carcinogenesis of colorectal cancer (CRC) is poorly understood. Here, we examined Fn abundance in CRC tissues, as well as β-catenin, TLR4 and PAK1 protein abundance in Fn positive and Fn negative CRCs. Furthermore, we isolated a strain of Fn (F01) from a CRC tissue and examined whether Fn (F01) infection of colon cancer cells activated β-catenin signaling via the TLR4/P-PAK1/P-β-catenin S675 cascade. Invasive Fn was abundant in 62.2% of CRC tissues. TLR4, PAK1 and nuclear β-catenin proteins were more abundant within Fn-positive over Fn-negative CRCs (P < 0.05). Fn and its lipopolysaccharide induced a significant increase in TLR4/P-PAK1/P-β-catenin S675/C-myc/CyclinD1 protein abundance, as well as in the nuclear translocation of β-catenin. Furthermore, inhibition of TLR4 or PAK1 prior to challenge with Fn significantly decreased protein abundance of P-β-catenin S675, C-myc and Cyclin D1, as well as nuclear β-catenin accumulation. Inhibition of TLR4 significantly decreased P-PAK1 protein abundance, and for the first time, we observed an interaction between TLR4 and P-PAK1 using immunoprecipitation. Our data suggest that invasive Fn activates β-catenin signaling via a TLR4/P-PAK1/P-β-catenin S675 cascade in CRC. Furthermore, TLR4 and PAK1 could be potential pharmaceutical targets for the treatment of Fn-related CRCs.
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