ABSTRACT
N6-methyladenosine (m6A) is one of the most prevalent and conserved RNA modifications. It controls several biological processes, including the biogenesis and function of circular RNAs (circRNAs), which are a class of covalently closed-single stranded RNAs. Several studies have revealed that proteotoxic stress response induction could be a relevant anticancer therapy in Acute Myeloid Leukemia (AML). Furthermore, a strong molecular interaction between the m6A mRNA modification factors and the suppression of the proteotoxic stress response has emerged. Since the proteasome inhibition leading to the imbalance in protein homeostasis is strictly linked to the stress response induction, we investigated the role of Bortezomib (Btz) on m6A regulation and in particular its impact on the modulation of m6A-modified circRNAs expression. Here, we show that treating AML cells with Btz downregulated the expression of the m6A regulator WTAP at translational level, mainly because of increased oxidative stress. Indeed, Btz treatment promoted oxidative stress, with ROS generation and HMOX-1 activation and administration of the reducing agent N-acetylcysteine restored WTAP expression. Additionally, we identified m6A-modified circRNAs modulated by Btz treatment, including circHIPK3, which is implicated in protein folding and oxidative stress regulation. These results highlight the intricate molecular networks involved in oxidative and ER stress induction in AML cells following proteotoxic stress response, laying the groundwork for future therapeutic strategies targeting these pathways.
Subject(s)
Adenosine , Leukemia, Myeloid, Acute , Oxidative Stress , RNA, Circular , Humans , RNA, Circular/genetics , RNA, Circular/metabolism , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/pathology , Leukemia, Myeloid, Acute/metabolism , Leukemia, Myeloid, Acute/drug therapy , Adenosine/analogs & derivatives , Adenosine/metabolism , Adenosine/pharmacology , Oxidative Stress/drug effects , Bortezomib/pharmacology , Cell Line, Tumor , Reactive Oxygen Species/metabolism , RNA Splicing Factors/metabolism , RNA Splicing Factors/genetics , Cell Cycle Proteins/metabolism , Cell Cycle Proteins/genetics , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/drug effects , Neoplastic Stem Cells/pathology , Heme Oxygenase-1/metabolism , Heme Oxygenase-1/genetics , Protein Serine-Threonine Kinases , Intracellular Signaling Peptides and ProteinsABSTRACT
A key mechanism driving colorectal cancer (CRC) development is the upregulation of MYC and its targets, including ornithine decarboxylase (ODC), a master regulator of polyamine metabolism. Elevated polyamines promote tumorigenesis in part by activating DHPS-mediated hypusination of the translation factor eIF5A, thereby inducing MYC biosynthesis. Thus, MYC, ODC and eIF5A orchestrate a positive feedback loop that represents an attractive therapeutic target for CRC therapy. Here we show that combined inhibition of ODC and eIF5A induces a synergistic antitumor response in CRC cells, leading to MYC suppression. We found that genes of the polyamine biosynthesis and hypusination pathways are significantly upregulated in colorectal cancer patients and that inhibition of ODC or DHPS alone limits CRC cell proliferation through a cytostatic mechanism, while combined ODC and DHPS/eIF5A blockade induces a synergistic inhibition, accompanied to apoptotic cell death in vitro and in mouse models of CRC and FAP. Mechanistically, we found that this dual treatment causes complete inhibition of MYC biosynthesis in a bimodal fashion, by preventing translational elongation and initiation. Together, these data illustrate a novel strategy for CRC treatment, based on the combined suppression of ODC and eIF5A, which holds promise for the treatment of CRC.
Subject(s)
Colorectal Neoplasms , Peptide Initiation Factors , Polyamines , Proto-Oncogene Proteins c-myc , Animals , Mice , Apoptosis , Cell Proliferation , Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/genetics , Ornithine Decarboxylase/genetics , Ornithine Decarboxylase/metabolism , Ornithine Decarboxylase/pharmacology , Polyamines/metabolism , Humans , Peptide Initiation Factors/genetics , Peptide Initiation Factors/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Eukaryotic Translation Initiation Factor 5AABSTRACT
The field of RNA modification, also referred to as "epitranscriptomics," is gaining more and more interest from the scientific community. More than 160 chemical modifications have been identified in RNA molecules, but the functional significance of most of them still needs to be clarified. In this review, we discuss the role of N6,2'-O-dimethyladenosine (m6Am) in gene expression regulation. m6Am is present in the first transcribed nucleotide close to the cap in many mRNAs and snRNAs in mammals and as internal modification in the snRNA U2. The writer and eraser proteins for these modifications have been recently identified and their deletions have been utilized to understand their contributions in gene expression regulation. While the role of U2 snRNA-m6Am in splicing regulation has been reported by different independent studies, conflicting data were found for the role of cap-associated m6Am in mRNA stability and translation. However, despite the open debate on the role of m6Am in mRNA expression, the modulation of regulators produced promising results in cancer cells. We believe that the investigation on m6Am will continue to yield relevant results in the future.
Subject(s)
Adenosine , Gene Expression Regulation , Animals , Methylation , Adenosine/genetics , Adenosine/metabolism , RNA, Messenger/metabolism , RNA Splicing , RNA, Small Nuclear/metabolism , RNA/metabolism , Mammals/metabolismABSTRACT
Despite its discovery in the early 1970s, m6A modification within mRNA molecules has only powerfully entered the oncology field in recent years. This chemical modification can control all aspects of the maturation of mRNAs, both in the nucleus and in the cytoplasm. Thus, the alteration in expression levels of writers, erasers, and readers may significantly contribute to the alteration of gene expression observed in cancer. In particular, the activation of oncogenic pathways can lead to an alteration of the global rate of mRNA translation or the selective translation of specific mRNAs. In both cases, m6A can play an important role. In this review, we highlight the role of m6A in the regulation of translation by focusing on regulatory mechanisms and cancer-related functions of this novel but still controversial field.
