The lncRNA LAMP5-AS1 drives leukemia cell stemness by directly modulating DOT1L methyltransferase activity in MLL leukemia

Abstract

Background: Mixed-lineage leukemia (MLL) gene rearrangements trigger aberrant epigenetic modification and gene expression in hematopoietic stem and progenitor cells, which generates one of the most aggressive subtypes of leukemia with an apex self-renewal. It remains a challenge to directly inhibit rearranged MLL itself because of its multiple fusion partners and the poorly annotated downstream genes of MLL fusion proteins; therefore, novel therapeutic targets are urgently needed. Methods: qRT-PCR, receiver operating characteristic (ROC), and leukemia-free survival analysis were used to validate LAMP5-AS1 (LAMP5 antisense 1) expression and evaluate its clinical value. We performed in vitro and in vivo experiments to investigate the functional relevance of LAMP5-AS1 in MLL leukemia progression and leukemia cell stemness. RNA electrophoretic mobility shift assays (EMSA), histone methyltransferase assay, RNA pull-down assay, and RNA fluorescence in situ hybridization (FISH) were used to validate the relationship between LAMP5-AS1 and the methyltransferase activity of DOT1L. The downstream ectopic target genes of LAMP5-AS1/DOT1L were validated by the chromatin immunoprecipitation (ChIP) and western blot. Results: We discovered that a long noncoding RNA (lncRNA) LAMP5-AS1 can promote higher degrees of H3K79 methylation, followed by upregulated expression of the self-renewal genes in the HOXA cluster, which are responsible for leukemia stemness in context of MLL rearrangements. We found that LAMP5-AS1 is specifically overexpressed in MLL leukemia patients (n = 58) than that in the MLL-wt leukemia (n = 163) (p < 0.001), and the patients with a higher expression level of LAMP5-AS1 exhibited a reduced 5-year leukemia-free survival (p < 0.01). LAMP5-AS1 suppression significantly reduced colony formation and increased differentiation of primary MLL leukemia CD34+ cells. Mechanistically, LAMP5-AS1 facilitated the methyltransferase activity of DOT1L by directly binding its Lys-rich region of catalytic domain, thus promoting the global patterns of H3K79 dimethylation and trimethylation in cells. These observations supported that LAMP5-AS1 upregulated H3K79me2/me3 and the

Principles and innovative technologies for decrypting noncoding RNAs: from discovery and functional prediction to clinical application

“…Growing studies have uncovered the characteristics of these ncRNAs, including their origins, mechanisms of generation, structures, and potential functions [6,8,12], which can be summarized into a principle for the identification of known species of ncRNAs or even novel ncRNA discovery. As many ncRNAs exhibit highly tissue-specific expression patterns and important roles in biological processes related to cancer [13][14][15][16][17][18][19], ncRNAs have been considered as ideal therapeutic targets for cancer diagnosis and treatment [20][21][22]. Due to the enormous transcription potential of mammalian genomes and multiple mechanisms of ncRNA generation [8,9,23,24], the ncRNA world is still full of infinite mysteries, in which unknown species of RNAs could play important roles.…”

Cis-acting lnc-eRNA SEELA directly binds histone H4 to promote histone recognition and leukemia progression

“…We reported that lnc-eRNAs, such as SEELA, are tethered by histone H4 and act as the “assistants” to bind BRD4, facilitating the activation of SERINC2 by the MLL-BRD4 complex. Our results suggested that lnc-eRNAs are the pivotal mediators of MLL-BRD4-driven oncogene activation, highlighting the potential roles of dysregulated lncRNAs in MLL leukemia progression [ 28 , 60 ]. Furthermore, targeting metabolism is becoming an important strategy for treating diverse cancers [ 61 ], and several lncRNAs have been reported to be associated with metabolic pathways [ 62 , 63 ].…”

Long noncodingRNA MCF2L‐AS1promotes the cancer stem cell‐like traits in non‐small cell lung cancer cells through regulatingmiR‐873‐5p level

“…LncRNA can exert its functions through various ways, such as transcriptional or post‐transcription modification and epigenetic change 4,5 . Notably, there are so many studies showing that lncRNA can function through acting as an miRNA regulator, 13,14 this promotes us to explore whether MCF2L‐AS1 can promote the CSC‐like traits through regulating miRNA activity. We then performed bioinformatic analysis and found that there are several miRNAs with potential binding sites on MCF2L‐AS1, among which miR‐873‐5p attracted our attention as miR‐873‐5p showed a relative higher score and has been shown to suppress the stemness of breast cancer cells 11 .…”