Long Non-Coding RNA AFAP1-AS1 Promotes Non-Small Cell Lung Cancer Cell Proliferation and Migration via Binding with LSD1 and Repressing HBP1 Expression

Background: Emerging research indicates that long non-coding RNAs are involved in physiological and pathological processes, especially cancer. AFAP1-AS1 is a 6810-nt lncRNA located on chromosome 4p16.1 that was first reported to be up-regulated in esophageal adenocarcinoma tissues. However, its biological activities and underlying mechanisms in non-small cell lung cancer (NSCLC) remain to be fully elucidated.   Methods: qRT-PCR was performed to determine AFAP1-AS1 expression in 96 paired NSCLC tissues and cell lines. The effect of AFAP1-AS1 on cell phenotype was assessed by CCK-8, colony formation, flow cytometry and EdU experiments, and a xenograft mouse model was used for in vivo studies. Transwell assays were arranged to detect cell migration. RNA transcriptome sequencing, RIP, ChIP and rescue assays were used to highlights the potential molecular mechanism. Findings: AFAP1-AS1 was generally up-regulated in NSCLC, and higher AFAP1-AS1 expression was significantly correlated with larger tumor size (p=0.008), lymph node metastasis (p=0.025), higher TNM stage (p=0.024), and worse overall survival in NSCLC patients. In vitro experiments revealed that AFAP1-AS1 down-regulation inhibited cell proliferation, migration and induced cell apoptosis; AFAP1-AS1 knockdown also hindered tumorigenesis in vivo. Moreover, mechanistic investigations revealed that AFAP1-AS1 repressed HBP1 (HMG box-containing protein 1) expression via recruiting demethylase LSD1 to the HBP1 promoter regions. Furthermore, rescue assays showed that the oncogenic function of AFAP1-AS1 is partially dependent on the epigenetic silencing of the tumor suppressor HBP1.   Interpretation: Our results indicate that AFAP1-AS1 is carcinogenic and that the AFAP1-AS1 / LSD1 / HBP1 axis may constitute a potential factor or a new therapeutic direction for NSCLC.   Funding: This work was supported by grants from the National Natural Science Foundation of China (No. 81672307, 81871871), the Medical Innovation Team Foundation of the Jiangsu Provincial Enhancement Health Project (No. CXTDA2017021), the “333 high class Talented Man Project” (No. BRA2016509), the Nanjing Science and Technology Development Project (No. 2017sc512046), and the Jiangsu Graduate Scientific Research Innovation Program (No. KYCX18_1494). Declaration of Interest: The authors have no conflicts of interest to declare. Ethical Approval: We obtained written informed consent from all patients before surgery and the study was approved by the Research Ethics Committee of The Second Affiliated Hospital of Nanjing Medical University.