Angiogenesis and vasculogenic mimicry are inhibited by 8-Br-cAMP through activation of the cAMP/PKA pathway in colorectal cancer
Received 8 February 2018
Accepted for publication 25 April 2018
Published 2 July 2018 Volume 2018:11 Pages 3765—3774
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Dr Carlos E Vigil
Sen Wang,* Zhiyuan Zhang,* Wenwei Qian, Dongjian Ji, Qingyuan Wang, Bing Ji, Yue Zhang, Chuan Zhang, Ye Sun, Chunyan Zhu, Yueming Sun
Department of Colorectal Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China
*These authors contributed equally to this work
Introduction: Vasculogenic mimicry (VM) describes the formation of an epithelial-independent tumor microcirculation system that differs from traditional angiogenesis. Angiogenesis and the formation of VM are closely related through the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway and the epithelial–mesenchymal transition (EMT) process.
Materials and methods: In this study, 8-Br-cAMP, a cAMP analog and PKA activator, was used to activate the cAMP/PKA pathway to evaluate the effects of cAMP/PKA on angiogenesis and VM in colorectal cancer (CRC) cells. We used a syngeneic model of CRC in BALB/c mice.
Results: We discovered that treatment with 8-Br-cAMP significantly reduced tumor number compared to control mice after the 7th, 14th, and 28th days of treatment. VM was evaluated by periodic acid–schiff (PAS)–CD31 staining, and we found that VM was inhibited by 8-Br-cAMP treatment in vivo. Immunohistochemistry confirmed the inhibition of vascular endothelial growth factor (VEGF) and cAMP and the activation of PKA by 8-Br-cAMP; quantitative real-time-PCR (qRT-PCR) demonstrated that 8-Br-cAMP regulated the expression of vascular endothelial (VE)-cadherin, matrix metalloproteinase 2 (MMP2), ephrin type-A receptor 2 (EphA2), and VEGF in vivo. Experiments in vitro revealed that treatment with 8-Br-cAMP and U0126 decreased VEGF expression through PKA–ERK in CT26 cells by qRT-PCR. We further confirmed that tube formation of human umbilical vein endothelial cells was inhibited by 8-Br-cAMP in vitro.
Discussion: This study demonstrates that angiogenesis and VM are inhibited by 8-Br-cAMP treatment. Our data indicate that 8-Br-cAMP acts through the cAMP/PKA–ERK pathway and through EMT processes in CRC. These findings provide an insight into mechanisms of CRC and suggest that the cAMP/PKA–ERK pathway is a novel potential therapeutic target for the treatment of CRC.
Keywords: vasculogenic mimicry, angiogenesis, VEGF, 8-Br-cAMP, cAMP
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