Oct4 transcriptionally regulates the expression of long non-coding RNAs NEAT1 and MALAT1 to promote lung cancer progression

Ying-Hung Lu,Jayu Jen,Yen-An Tang,Wu-Wei Lai,Yi-Ching Wang,Che-Chung Lin

doi:10.1186/s12943-017-0674-z

Abstract

BackgroundOct4, a key stemness transcription factor, is overexpressed in lung cancer. Here, we reveal a novel transcription regulation of long non-coding RNAs (lncRNAs) by Oct4. LncRNAs have emerged as important players in cancer progression.MethodsOct4 chromatin-immunoprecipitation (ChIP)-sequencing and several lncRNA databases with literature annotation were integrated to identify Oct4-regulated lncRNAs. Luciferase activity, qRT-PCR and ChIP-PCR assays were conducted to examine transcription regulation of lncRNAs by Oct4. Reconstitution experiments of Oct4 and downstream lncRNAs in cell proliferation, migration and invasion assays were performed to confirm the Oct4-lncRNAs signaling axes in promoting lung cancer cell growth and motility. The expression correlations between Oct4 and lncRNAs were investigated in 124 lung cancer patients using qRT-PCR analysis. The clinical significance of Oct4/lncRNAs signaling axes were further evaluated using multivariate Cox regression and Kaplan-Meier analyses.ResultsWe confirmed that seven lncRNAs were upregulated by direct binding of Oct4. Among them, nuclear paraspeckle assembly transcript 1 (NEAT1), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and urothelial carcinoma-associated 1 (UCA1) were validated as Oct4 transcriptional targets through promoter or enhancer activation. We showed that lung cancer cells overexpressing NEAT1 or MALAT1 and the Oct4-silenced cells reconstituted with NEAT1 or MALAT1 promoted cell proliferation, migration and invasion. In addition, knockdown of NEAT1 or MALAT1 abolished Oct4-mediated lung cancer cell growth and motility. These cell-based results suggested that Oct4/NEAT1 or Oct4/MALAT1 axis promoted oncogenesis. Clinically, Oct4/NEAT1/MALAT1 co-overexpression was an independent factor for prediction of poor outcome in 124 lung cancer patients.ConclusionsOur study reveals a novel mechanism by which Oct4 transcriptionally activates NEAT1 via promoter and MALAT1 via enhancer binding to promote cell proliferation and motility, and led to lung tumorigenesis and poor prognosis.

Highlights

Oct4, a key stemness transcription factor, is overexpressed in lung cancer
Unbiased ChIP-seq and ChIP-PCR/quantitative reverse transcriptasepolymerase chain reaction (qRT-PCR) analyses reveal novel Long non-coding RNA (lncRNA) controlled by Oct4 transcriptional regulation in lung cancer We previously performed ChIP-seq in A549 lung cancer cell line stably-overexpressing Oct4 to identify the Oct4 genome-wide DNA binding regions [8]
Visualization of Oct4 ChIP-seq targeting revealed significant enrichments of Oct4 binding on three lncRNAs, including the promoter region of nuclear paraspeckle assembly transcript 1 (NEAT1) and enhancer regions of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and urothelial carcinoma-associated 1 (UCA1) (Fig. 1b)

Summary

Introduction

A key stemness transcription factor, is overexpressed in lung cancer. We reveal a novel transcription regulation of long non-coding RNAs (lncRNAs) by Oct. Sox and Nanog are well-known pluripotency-associated transcription factors which maintain embryonic stem cells state [1]. Studies have shown that Oct is overexpressed in human cancers such as bladder [2], breast [3], cervical cancer [4], oral squamous cell carcinoma [5], hepatocellular carcinoma [6] and lung cancer [7, 8]. Oct has been identified to regulate transcriptions of other transcription factors, chromatin modifiers, long non-coding RNAs (lncRNAs) and microRNAs [9, 10]. Oct regulates lncRNAs expression, such as linc-RoR, which is a key reprogramming factor associated with pluripotency [11]. Transcription regulation of lncRNAs by Oct in tumorigenesis remains elusive

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