CLDN8 promotes colorectal cancer cell proliferation, migration, and invasion by activating MAPK/ERK signaling

Cancer Management and Research Dovepress open access to scientific and medical research O r i g i n a l R e s e a rc h Cancer Management and Research downloaded from https://www.dovepress.com/ by 115.94.98.51 on 24-Apr-2020 For personal use only. Open Access Full Text Article CLDN8 promotes colorectal cancer cell proliferation, migration, and invasion by activating MAPK/ERK signaling This article was published in the following Dove Medical Press journal: Cancer Management and Research Bo Cheng 1 Aimei Rong 2 Quanbo Zhou 3 Wenlu Li 4 1 Department of Emergency Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, China; 2Department of Gastroenterology, Zhengzhou Central Hospital Affiliated to Zhengzhou University, Zhengzhou, Henan 450000, China; 3Department of Anus and Intestine Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, China; 4 Department of Stomatology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, China Introduction Correspondence: Wenlu Li Department of Stomatology, The First Affiliated Hospital of Zhengzhou University, 1 East Jianshe Road, Zhengzhou, Henan 450000, China Tel: +86 0371 6796 2251 Email Colorectal cancer (CRC) is one of the most common carcinomas worldwide and causes significant mortality.1–3 There are >1.2 million newly diagnosed cases of CRC and >600,000 deaths from this disease every year.4–6 Although recent advances in surgical resection techniques have increased the survival rate for patients with early-stage CRC, the long-term prognosis for most CRC patients remains poor, mainly due to recurrence and metastases.5,7,8 The molecular profiling (including DNA and proteins) of CRC has had increasing importance for the identification of prognostic biomarkers and the development of novel therapeutic strategies.3,4,6,8–12 However, the exact mechanisms underlying CRC development remain unknown. Therefore, identifying the key molecules involved in CRC progression may help provide novel therapeutic targets and improve the prognosis of CRC. Claudin 8 (CLDN8), which is located in the cell membrane, is a member of the CLDN superfamily that constitutes tight junctions.13,14 CLDN8 is overexpressed in several human cancer cell lines and plays a vital role in the progression of several human 3741 submit your manuscript | www.dovepress.com Cancer Management and Research 2019:11 3741–3751 Dovepress © 2019 Cheng et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). http://dx.doi.org/10.2147/CMAR.S189558 Powered by TCPDF (www.tcpdf.org) Background: Claudin 8 (CLDN8), an integral membrane protein that constitutes tight junctions in cell membranes, was recently implicated in tumor progression. However, its roles in colorectal cancer (CRC) progression and metastasis remain unknown. Methods: In this study, we examined the effect of CLDN8 on the progression of CRC, including cell proliferation, migration, and invasion, and determines its underlying molecular mechanism using in vitro CRC cell lines and in vivo mouse xenograft models. Results: We found that CLDN8 expression in human CRC tissues was significantly higher than that in adjacent normal tissues. The knockdown of CLDN8 markedly suppressed the proliferation, migration, and invasion of SW480 and HT-29 CRC cells, whereas the overexpression of CLDN8 notably promoted tumor progression in SW480 and HT-29 CRC cells. Mechanistic studies revealed that CLDN8 upregulated p-ERK (p-PKB/AKT) and MMP9 in CRC cells. Notably, the MAPK/ERK inhibitor PD98095 dramatically attenuated the effects of CLDN8 on p-ERK and MMP9. Moreover, PD98095 remarkably blocked the tumor-promoting activity of CLDN8. The knockdown of CLDN8 also inhibited the in vivo tumor growth in a nude mouse xenograft model. Collectively, CLDN8 promoted CRC cell proliferation, migration, and invasion, at least in part, by activating the MAPK/ERK signaling pathway. Conclusion: These findings suggest that CLDN8 exhibits an oncogenic effect in human CRC progression. Keywords: CLDN8, colorectal cancer, MAPK/ERK signaling Dovepress Cancer Management and Research downloaded from https://www.dovepress.com/ by 115.94.98.51 on 24-Apr-2020 For personal use only. Cheng et al cancers, including prostate cancer, renal cell carcinoma, and osteosarcoma.13–23 In prostate cancer, functional analyses of CLDN8 by overexpression and knockdown have indicated that CLDN8 promotes the migration, invasion, and metastasis of prostate cancer cells via intracellular signal transduction.13 These data indicate that CLDN8-mediated signaling pathways are involved in human tumor metastasis. However, the roles of CLDN8 in CRC cells have not been elucidated. This study examines the effect of CLDN8 on the progression of CRC, including cell proliferation, migration, and invasion, and determines its underlying molecular mechanism using in vitro CRC cell lines and in vivo mouse xenograft models. Here, we demonstrate that CLDN8 promotes CRC cell proliferation, migration, and invasion via the MAPK/ ERK signaling pathway. These findings suggest that CLDN8 plays an important role in regulating CRC progression and may serve as a prognostic biomarker for CRC. Materials and methods Tissue samples Fresh CRC tumor tissue samples and corresponding adjacent normal tissues were obtained from 20 patients diagnosed with CRC following surgical resection through laparotomy. The demographic data are shown in Table 1. No distant metastasis was observed among these patients. All the patients did not receive neoadjuvant therapy, radiotherapy, or chemotherapy prior to surgery. Tissue samples were immediately frozen in liquid nitrogen for further analysis. The study protocol was approved by the Medical Ethics Committee of the First Affiliated Hospital of Zhengzhou University with written informed consent obtained from Table 1 Demographic data of the patients Clinical variables Gender Female Male Age Median Range Tumor location Rectum Ascending Cecum Descending Transverse Sigmoid Distant metastasis Yes No 3742 Powered by TCPDF (www.tcpdf.org) No. of patients (N=20) 12 8 55.2 41–73 4 3 5 5 1 2 0 20 submit your manuscript | www.dovepress.com Dovepress each patient. This study was conducted in accordance with the Declaration of Helsinki. Cell lines and cell culture The human CRC cell lines SW480, HT-29, Caco-2, DLD1, (...truncated)