N6-methyladenosine (m6A) modification is the most prevalent modification in eukaryotic RNAs while accumulating studies suggest that m6A aberrant expression plays an important role in cancer. HNRNPA2B1 is a m6A reader which binds to nascent RNA and thus affects a perplexing array of RNA metabolism exquisitely. Despite unveiled facets that HNRNPA2B1 is deregulated in several tumors and facilitates tumor growth, a clear role of HNRNPA2B1 in multiple myeloma (MM) remains elusive. Herein, we analyzed the function and the regulatory mechanism of HNRNPA2B1 in MM. We found that HNRNPA2B1 was elevated in MM patients and negatively correlated with favorable prognosis. The depletion of HNRNPA2B1 in MM cells inhibited cell proliferation and induced apoptosis. On the contrary, the overexpression of HNRNPA2B1 promoted cell proliferation in vitro and in vivo. Mechanistic studies revealed that HNRNPA2B1 recognized the m6A sites of ILF3 and enhanced the stability of ILF3 mRNA transcripts, while AKT3 downregulation by siRNA abrogated the cellular proliferation induced by HNRNPA2B1 overexpression. Additionally, the expression of HNRNPA2B1, ILF3 and AKT3 was positively associated with each other in MM tissues tested by immunohistochemistry. In summary, our study highlights that HNRNPA2B1 potentially acts as a therapeutic target of MM through regulating AKT3 expression mediated by ILF3-dependent pattern.
Fengjie Jiang, Xiaozhu Tang, and Chao Tang have contributed equally to this work.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Abkürzungen
m6A
N6-methyladenosine
HNRNPA2B1
Heterogeneous nuclear ribonucleoprotein A2B1
MM
Multiple myeloma
MeRIP-Seq
M6A IP seqing
ILF3
Interleukin enhancer-binding factor 3
RIP
RNA immunoprecipitation
AKT3
AKT serine/threonine kinase 3
ActD
Actinomycin D
To the Editor
N6-methyladenosine (m6A) modification is the most frequent RNA modifications in eukaryotic RNAs affecting gene expression, which is seldom investigated in MM [1‐3]. Therefore, we checked the m6A genes in MM compared to normal plasma cells and the correlation of these genes with patient outcome including HNRNPA2B1, Mettl3, Mettl14, Wtap, etc., in MM patient cohorts. Interestingly, HNRNPA2B1 was the exclusive gene, which was not only increased in MM samples but also associated with poor outcome in APEX, TT2 and HOVON65 patient cohorts (Fig. 1a, b, Additional file 1: Fig. S1a–h). HNRNPA2B1, RNA binding protein heterogeneous nuclear ribonucleoprotein A2B1, is a nuclear reader of m6A [4] and highly expressed in several cancers regulating the progression of cancer [5, 6] through multiple processes of mRNAs metabolism [7] including alternative splicing [8], cytoplasmic RNA trafficking [9], transcription and translation [10]. Here, we aimed to explore the potential functions and regulatory mechanism of HNRNPA2B1 in MM.
×
Anzeige
Initially, we performed MTT assay that demonstrated the cellular proliferation was significantly increased in HNRNPA2B1 overexpression (HNRNPA2B1OE) cells and decreased in HNRNPA2B1 knockdown (HNRNPA2B1KD) cells (Fig. 1c, d, Additional file 1: Fig. S1i). Flow cytometry and WB analyses illustrated that knockdown of HNRNPA2B1 promoted cellular apoptosis (Fig. 1e, f). The nude mouse xenograft model by subcutaneous injection of HNRNPA2B1OE cells showed overexpression of HNRNPA2B1 accelerating tumor growth in vivo (Fig. 1g and Additional file 1: Fig. S1j, k, l). These data indicated that HNRNPA2B1 promoted MM cellular growth in vitro and in vivo.
Next, m6A IP and RNA-seq analyses (MeRIP-Seq) found that ILF3 was downregulated (P < 0.05) of both m6A and transcription in HNRNPA2B1KD cells compared with controls (Fig. 1h & Additional file 1: Fig. S2). The m6A consensus sequence (RRACH) motif [11] is shown in Fig. 1i, in which the m6A modification of ILF3 was enriched in 3′-noncoding regions (Fig. 1j). Consistently, ILF3 expression was reduced in HNRNPA2B1KD cells (Fig. 1k, Additional file 1: Fig. S3a) while increased in HNRNPA2B1OE cells (Additional file 1: Fig. S3b, c). RNA immunoprecipitation (RIP)-qPCR assay revealed that ILF3 mRNA was enriched in the precipitates of HNRNPA2B1 antibody and silencing of HNRNPA2B1 decreased the abundance of the ILF3 transcript binding to HNRNPA2B1 (Fig. 1l). To further verify the role of m6A in regulation of ILF3 expression, methylation inhibitor cyclolencine was used that induced remarkable reduction of ILF3 in MM cells (Fig. 1m, Fig. S3d, e). Therefore, we can conclude that HNRNPA2B1 may stabilize ILF3 mRNA to play an important role. As expected, the stability of ILF3 was decreased in HNRNPA2B1KD cells (Fig. 1n, Additional file 1: Fig. S3f). The biological effects of HNRNPA2B1 might be related to its nucleocytoplasmic localization, as HNRNPA2B1 was distributed in both nuclear and cytoplasmic along with increased cytoplasmic localization of ILF3 (Fig. 1o, Additional file 1: Fig. S3g). The above results illustrated that HNRNPA2B1-induced expression of ILF3 was due to the enhanced stability of ILF3 mRNA transcripts upon recognition and bound of the m6A sites to HNRNPA2B1.
Notably, ILF3 expression was significantly elevated in plasma cells from MM patients (Fig. 2a) and associated with poor survival (Fig. 2b, Additional file 1: Fig. S4a, b). We established the ILF3 knockdown (ILF3KD) cells (Fig. 2c), which displayed decreased cell growth rate after induction compared to the non-induced cells (Fig. 2d). Apoptosis assay showed that ILF3 inhibited MM cellular apoptosis (Additional file 1: Fig. S4c, d, e). In addition, MTT result demonstrated that ILF3 knockdown by siRNA could reverse the cellular proliferation induced by increased HNRNPA2B1 suggesting that ILF3 is one of the most important m6A/HNRNPA2B1 targets in MM (Additional file 1: Fig. S4f, g).
×
Further RNA immunoprecipitation-sequencing (RIP-seq) analysis indicated that MAPK pathway was enriched (Fig. 2e) and AKT3 mRNA was significantly enriched by anti-ILF3 antibody in ARP1 cells. The ILF3 binding sites represented by peaks were enriched in AKT3 mRNA transcripts (Fig. 2f). In agreement with above results, decreased AKT3 was observed in ILF3KD cells (Fig. 2g, h) and RIP-qPCR using anti-ILF3 antibody confirmed a significantly reduced affinity of ILF3 to AKT3 mRNA in ARP1 ILF3KD cells compared to control (Fig. 2i). RNA decay assay showed a relatively lower stability of AKT3 transcripts in ILF3KD cells (Fig. 2j, Additional file 1: Fig S5a) correspondingly. These data suggested that ILF3 promoted MM progression through stabilization of AKT3 transcripts.
Anzeige
Finally, we verified the effect of HNRNPA2B1 on AKT3. The expression of AKT3 was decreased in HNRNPA2B1KD cells (Fig. 2k, l), whereas the elevated expression of AKT3 was observed in HNRNPA2B1OE cells (Additional file 1: Fig. S5b, c). While AKT3 was interfered with siRNA (Fig. 2m), the cellular proliferation induced by HNRNPA2B1 was attenuated (Fig. 2n). Intriguingly, immunohistochemistry correlation analysis showed that HNRNPA2B1, ILF3 and AKT3 were highly increased in MM patients with statistical-correlated expression trend significantly compared to normal controls (Fig. 2o).
In summary, we demonstrate the m6A-dependent effect of HNRNPA2B1 on regulating AKT signaling pathway and the correlation between HNRNPA2B1 and MM cell growth. It is disclosed that the HNRNPA2B1/m6A/ILF3/AKT3 axis plays a key role in MM progression.
Acknowledgements
We thank Dr. Jinjun Qian for providing technical support.
Declarations
Ethics approval and consent to participate
This study was approved by the Animal Ethics Committee of Nanjing University of Chinese Medicine (Ethics Registration No. 201905A003) in China.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Mit e.Med Innere Medizin erhalten Sie Zugang zu CME-Fortbildungen des Fachgebietes Innere Medizin, den Premium-Inhalten der internistischen Fachzeitschriften, inklusive einer gedruckten internistischen Zeitschrift Ihrer Wahl.
Unter Frauen, die ein Levonorgestrel-freisetzendes intrauterines System (IUS) verwenden, ist die Brustkrebsrate um 13% erhöht. Dafür kommt es deutlich seltener zu Endometrium-, Zervix- und Ovarialkarzinomen.
Wie stark Menschen mit fortgeschrittenem NSCLC von einer Therapie mit Immun-Checkpoint-Hemmern profitieren, hängt offenbar auch davon ab, wie sehr die Diagnose ihre psychische Verfassung erschüttert
Ein bispezifischer Antikörper formiert gezielt eine Armee neutrophiler Granulozyten gegen Krebszellen. An den Antikörper gekoppeltes TNF-alpha soll die Zellen zudem tief in solide Tumoren hineinführen.
Fast ein Viertel der Personen mit mäßig dysplastischen Stimmlippenläsionen entwickelt einen Kehlkopftumor. Solche Personen benötigen daher eine besonders enge ärztliche Überwachung.
Update Onkologie
Bestellen Sie unseren Fach-Newsletterund bleiben Sie gut informiert.