Downregulation of AAA-domain-containing protein 2 restrains cancer stem cell properties in esophageal squamous cell carcinoma via blockade of the Hedgehog signaling pathway.

Yang Yu,Nuo Li,Baoming Wang

doi:10.1152/ajpcell.00133.2019

Abstract

Esophageal squamous cell carcinoma (ESCC) ranks among the five most common cancers in China and has a five-year survival rate of less than 15%. The transcription factor ATPase-family AAA-domain-containing protein 2 (ATAD2) has potential as a therapeutic target in various tumors, and microarray-based gene expression profiling reveals dysregulation of ATAD2 specifically in ESCC. Here we investigated whether ATAD2 could mediate a regulation of cancer stem cell (CSC) biological functions in ESCC. Immunohistochemical staining, reverse transcription quantitative polymerase chain reaction, and Western blot assays all revealed upregulation of ATAD2 in ESCC tissues and cell lines, which furthermore correlated with progression of ESCC. In loss-of-function experiments, silencing of ATAD2 inhibited activation of the Hedgehog signaling pathway, as indicated by reduced expression of glioma-associated oncogene family zinc finger 1 (Gli1), smoothened frizzled class receptor (SMO), and patched 1 (PTCH1). Investigations with 5-ethynyl-2'-deoxyuridine (EdU), Transwell assay, scratch test, flow cytometry, and colony formation assay showed that silencing of ATAD2 or inhibiting the Hedgehog signaling decreased the proliferation, invasion, and migration abilities along with colony formation, but elevated the apoptosis rate of CSCs. Furthermore, in vivo experiments validated the suppressive effect of siRNA-mediated ATAD2 silencing on tumor growth in nude mice. Thus, downregulation of ATAD2 can seemingly restrain the malignant phenotypes of ESCC cells through inhibition of the Hedgehog signaling pathway.

Highlights

Esophageal squamous cell carcinoma (ESCC) originates from cells on the surface of the middle and upper third of the esophagus [9]
The top 100 differentially expressed genes (DEGs) with larger fold expression change were selected to perform intersection analysis (Fig. 1A) and five DEGs (KIF4A, ATAD2, TRIP13, UBE2C, and HJURP) were identified. Among those DEGs, ATAD2 is recognized as an oncogene that closely associates with various human cancers such as ovarian carcinomas, hepatocellular carcinoma, cervical cancer, and gastric cancer [15, 26, 36, 37]
Since the role of ATAD2 in ESCC remains unclear, the study focused on the effects of ATAD2 on the progression of ESCC

Summary

Introduction

Esophageal squamous cell carcinoma (ESCC) originates from cells on the surface of the middle and upper third of the esophagus [9]. It is a highly prevalent and lethal cancer with poor prognosis, having a five-year survival rate of less than 15% [32]. Neoadjuvant therapy has emerged as an effective treatment method for operable ESCC [2], despite provoking severe adverse reactions in ~60 –70% of patients [25]. Compelling new preclinical studies have demonstrated the potential effectiveness of gene therapy in tumorigenesis and progression of ESCC [20, 25]

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Conclusion