Abstract
BackgroundLong noncoding RNAs (lncRNAs) constitute a major, but poorly characterized part of human transcriptome. Recent evidence indicates that many lncRNAs are involved in cancer and can be used as predictive and prognostic biomarkers. Significant fraction of lncRNAs is represented on widely used microarray platforms, however they have usually been ignored in cancer studies.ResultsWe developed a computational pipeline to annotate lncRNAs on popular Affymetrix U133 microarrays, creating a resource allowing measurement of expression of 1581 lncRNAs. This resource can be utilized to interrogate existing microarray datasets for various lncRNA studies. We found that these lncRNAs fall into three distinct classes according to their statistical distribution by length. Remarkably, these three classes of lncRNAs were co-localized with protein coding genes exhibiting distinct gene ontology groups. This annotation was applied to microarray analysis which identified a 159 lncRNA signature that discriminates between localized and metastatic stages of neuroblastoma. Analysis of an independent patient cohort revealed that this signature differentiates also relapsing from non-relapsing primary tumors. This is the first example of the signature developed via the analysis of expression of lncRNAs solely. One of these lncRNAs, termed HOXD-AS1, is encoded in HOXD cluster. HOXD-AS1 is evolutionary conserved among hominids and has all bona fide features of a gene. Studying retinoid acid (RA) response of SH-SY5Y cell line, a model of human metastatic neuroblastoma, we found that HOXD-AS1 is a subject to morphogenic regulation, is activated by PI3K/Akt pathway and itself is involved in control of RA-induced cell differentiation. Knock-down experiments revealed that HOXD-AS1 controls expression levels of clinically significant protein-coding genes involved in angiogenesis and inflammation, the hallmarks of metastatic cancer.ConclusionsOur findings greatly extend the number of noncoding RNAs functionally implicated in tumor development and patient treatment and highlight their role as potential prognostic biomarkers of neuroblastomas.
Highlights
IntroductionLong noncoding RNAs (lncRNAs) constitute a major, but poorly characterized part of human transcriptome
Long noncoding RNAs constitute a major, but poorly characterized part of human transcriptome
We found that one of the identified in this study Long noncoding RNAs (lncRNAs) transcript, termed HOXD-AS1, is induced by retinoid acid (RA), regulated by PI3K/Akt pathway and controls genes implicated in RAmediated cell differentiation and angiogenesis and inflammation, the hallmarks of metastasized cancer [29]
Summary
Long noncoding RNAs (lncRNAs) constitute a major, but poorly characterized part of human transcriptome. Significant fraction of lncRNAs is represented on widely used microarray platforms, they have usually been ignored in cancer studies. Whereas the coding sequences constitute only 1.5% of human genome, the noncoding constituent of the genome has recently come into light as functionally important. The most well studied part of noncoding transcriptome is represented by microRNAs (miRNAs), which affect expression of protein coding genes by modulating mRNA stability and translation. Long noncoding RNAs (lncRNAs) represent the largest fraction of transcriptional output in the mammalian genome. Unlike extensively studied protein coding transcripts or miRNAs, the majority of lncRNAs still remain “the dark matter of the genome” with their functionality being debatable. MALAT-1 has originally been shown to be associated with metastasis in lung carcinomas [4] and regulate invasive potential of tumor cells [5]
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