title: Asparaginyl endopeptidase improves the resistance of microtubule-targeting drugs in gastric cancer through IQGAP1 modulating the EGFR/JNK/ERK signaling pathway.
abstract: OBJECTIVE
  In recent years, understanding of the role of asparaginyl endopeptidase (AEP) in tumorigenesis has steadily increased. In this study, we investigated whether AEP expression correlates with sensitivity to chemotherapeutic drugs in gastric cancer and explored the mechanism.
  
  
  METHODS
  AEP expression in the serum of patients' peripheral blood was measured by enzyme-linked immunosorbent assay. Patient survival time was evaluated using univariate and multivariate analyses. Mass spectrometry and co-immunoprecipitation assays were utilized to discover proteins that interact with AEP. Gastric cancer cell lines were established, in which AEP was overexpressed or knocked out using lentiviral CRISPR. The proliferative abilities of these cell lines in response to chemotherapy agents were evaluated using the Cell Counting Kit-8 method. Gene expression changes in these lines were assessed by real-time polymerase chain reaction and Western blot.
  
  
  RESULTS
  Patients with low expression of AEP were significantly more likely to have a good prognosis and experience complete response or partial response after treatment with docetaxel/S-1 regimen. Mass spectrum analysis showed that several proteins in the focal adhesion and mitogen-activated protein kinase signaling pathways interacted with AEP. IQGAP1 was confirmed to be one of the proteins interacting with AEP, and its protein level increased when AEP was knocked out. AEP knockout decreased resistance to microtubule inhibitors, including paclitaxel, docetaxel, and T-DM1. The expression levels of MDR1, p-EGFR, p-JNK, p-ERK, and p-Rac1/cdc42 were decreased in AEP knockout gastric cancer cell lines, and inhibitors of both JNK and ERK could block AEP-induced expression of MDR1.
  
  
  CONCLUSIONS
  AEP was not only a prognostic factor but also a predictive marker. AEP knockout could inhibit the activity of the EGFR/JNK/ERK signaling pathway and improve sensitivity to microtubule inhibitors through interacting with IQGAP1.
authors.affiliation: Medical Oncology Department.
authors.forename: Yuehong
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Medical Oncology Department.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Medical Oncology Department.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.affiliation: Medical Oncology Department.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: General Surgery Department, Zhongshan Hospital, Fudan University, Shanghai, People's Republic of China.
authors.forename: Hongshan
authors.initials: H
authors.lastname: Wang
authors.affiliation: General Surgery Department, Zhongshan Hospital, Fudan University, Shanghai, People's Republic of China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Chen
authors.affiliation: Pathology Department, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Shangmin
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Pathology Department, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Cao
authors.affiliation: Medical Oncology Department.
authors.forename: Tianshu
authors.initials: T
authors.lastname: Liu
keywords: Asparaginyl endopeptidase; MAP kinase signaling pathway; drug resistance; stomach cancer