Screening for long noncoding RNAs associated with oral squamous cell carcinoma reveals the potentially oncogenic actions of DLEU1

Koyo Nishiyama,Mutsumi Toyota,Takayoshi Igarashi ,Eiko Yamamoto ,Jun’ichi Kobayashi ,Akira Miyazaki ,Akira Yorozu,Hiroyoshi Hiratsuka,Takeshi Niinuma,Yui Hatanaka,Takashi Tokino,Reo Maruyama,Masashi Idogawa,Kazuhiro Ogi,Yasushi Sasaki,Hiroshi Kitajima,Tamotsu Sugai,Masahiro Kai,Hironari Dehari,Hiromu Suzuki

doi:10.1038/s41419-018-0893-2

Abstract

Recent studies have shown that long noncoding RNAs (lncRNAs) have pivotal roles in human malignancies, although their significance in oral squamous cell carcinoma (OSCC) is not fully understood. In the present study, we identified lncRNAs functionally associated with OSCC. By analyzing RNA-seq datasets obtained from primary head and neck squamous cell carcinoma (HNSCC), we identified 15 lncRNAs aberrantly expressed in cancer tissues. We then validated their expression in 18 OSCC cell lines using qRT-PCR and identified 6 lncRNAs frequently overexpressed in OSCC. Among those, we found that knocking down DLEU1 (deleted in lymphocytic leukemia 1) strongly suppressed OSCC cell proliferation. DLEU1 knockdown also suppressed migration, invasion, and xenograft formation by OSCC cells, which is suggestive of its oncogenic functionality. Microarray analysis revealed that DLEU1 knockdown significantly affects expression of a number of cancer-related genes in OSCC cells, including HAS3, CD44, and TP63, suggesting that DLEU1 regulates HA-CD44 signaling. Expression of DLEU1 was elevated in 71% of primary OSCC tissues, and high DLEU1 expression was associated with shorter overall survival of HNSCC patients. These data suggest that elevated DLEU1 expression contributes to OSCC development, and that DLEU1 may be a useful therapeutic target in OSCC.

Highlights

In recent years, there have been 300,000 new cases of oral cancer (2.1% of all cancers) and 145,000 deaths from the disease (2.1% of all cancers), worldwide[1]
To identify long noncoding RNAs (lncRNAs) associated with the development or progression of oral squamous cell carcinoma (OSCC), we first used RNA sequencing (RNA-seq) data obtained from primary head and neck squamous cell carcinoma (HNSCC) tissues in the The Cancer Genome Atlas (TCGA) network study (Fig. 1a)
We selected 36 exons, corresponding to 15 lncRNA genes that were significantly upregulated in cancer (P < 1 × 10−35) and assessed their expression levels in a series of 18 OSCC cell lines and normal tongue tissues. Quantitative reverse-transcription PCR (qRT-PCR) analysis revealed that 14 of the 15 lncRNAs were upregulated in multiple OSCC cell lines as compared to normal tissue (Supplementary Fig. 1)

Summary

Introduction

There have been 300,000 new cases of oral cancer (2.1% of all cancers) and 145,000 deaths from the disease (2.1% of all cancers), worldwide[1]. For treatment of oral cancer, a multidisciplinary approach combining surgery, chemotherapy and radiation therapy is recommended[3]. These treatments are effective against early cancers, but are often unsatisfactory with advanced or recurrent cancers. In cases of inoperable or chemotherapy-resistant oral cancer, the efficacy of molecular targeted drugs, including cetuximab, a monoclonal antibody against EGFR, has been reported[5,6]. It is well documented that cetuximab is less effective in cancers with KRAS mutations, and discovery of new therapeutic targets in oral cancer is needed[7]

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Conclusion