RNA methyltransferase NSUN2 promotes growth of hepatocellular carcinoma cells by regulating fizzy-related-1 in vitro and in vivo

RNA m5C methylation: a potential modulator of innate immune pathways in hepatocellular carcinoma

RNA 5-methylcytosine (m5C) methylation plays a crucial role in hepatocellular carcinoma (HCC). As reported, aberrant m5C methylation is closely associated with the progression, therapeutic efficacy, and prognosis of HCC. The innate immune system functions as the primary defense mechanism in the body against pathogenic infections and tumors since it can activate innate immune pathways through pattern recognition receptors to exert anti-infection and anti-tumor effects. Recently, m5C methylation has been demonstrated to affect the activation of innate immune pathways including TLR, cGAS-STING, and RIG-I pathways by modulating RNA function, unveiling new mechanisms underlying the regulation of innate immune responses by tumor cells. However, research on m5C methylation and its interplay with innate immune pathways is still in its infancy. Therefore, this review details the biological significance of RNA m5C methylation in HCC and discusses its potential regulatory relationship with TLR, cGAS-STING, and RIG-I pathways, thereby providing fresh insights into the role of RNA methylation in the innate immune mechanisms and treatment of HCC.

The impact of epitranscriptomic modifications on liver disease

RNA modifications have emerged as important mechanisms of gene regulation. Developmental, metabolic, and cell cycle regulatory processes are all affected by epitranscriptomic modifications, which control gene expression in a dynamic manner. The hepatic tissue is highly metabolically active and has an impressive ability to regenerate after injury. Cell proliferation, differentiation, and metabolism, which are all essential to the liver response to injury and regeneration, are regulated via RNA modification. Two such modifications, N6-methyladenosine (m6A)and 5-methylcytosine (m5C), have been identified as prognostic disease markers and potential therapeutic targets for liver diseases. Here, we describe progress in understanding the role of RNA modifications in liver biology and disease and discuss specific areas where unexpected results could lead to improved future understanding.

Suppression of NSUN2 enhances the sensitivity to chemosensitivity and inhibits proliferation by mediating cell apoptosis in gastric cancer

NSUN2 is a critical methyltransferase for adding m5C to RNA. Its upregulation promotes the growth and metastasis of several tumors including gastric cancer (GC). However, it is unclear if NSUN2 can improve the chemosensitivity of GC to treatment with therapeutic agents such as cisplatin (CDDP) and 5-fluorouracil (5-FU). Flow cytometry was used to measure the effects of knocked-down NSUN2 expression on GC cell apoptosis and cell cycle progression. Western blot analysis examined specific signaling pathways through which NSUN2 mediates control of responses underlying the GC tumorous phenotype. NSUN2 expression was upregulated in GC tissues and its levels of rises were related to the extent of lymph node metastasis and increases in Ki67 proliferative marker expression. NSUN2 shRNA transfection suppressed rises in ERK1/2 phosphorylation status and downregulated anti-apoptosis protein Bcl-2 and upregulated pro-apoptosis protein Bax. Overall, the results reveal that NSUN2 downregulation promotes the GC chemosensitivity to inverse modulation by chemotherapeutic agents of Bcl-2 and Bax expression levels and declines in ERK1/2-induced proliferation. Our results indicate that inhibition of NSUN2 activation may be an effective procedure to enhance the efficacy of chemotherapeutic agents used to clinically treat GC.

The role of RNA modification in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly mortal type of primary liver cancer. Abnormal epigenetic modifications are present in HCC, and RNA modification is dynamic and reversible and is a key post-transcriptional regulator. With the in-depth study of post-transcriptional modifications, RNA modifications are aberrantly expressed in human cancers. Moreover, the regulators of RNA modifications can be used as potential targets for cancer therapy. In RNA modifications, N6-methyladenosine (m6A), N7-methylguanosine (m7G), and 5-methylcytosine (m5C) and their regulators have important regulatory roles in HCC progression and represent potential novel biomarkers for the confirmation of diagnosis and treatment of HCC. This review focuses on RNA modifications in HCC and the roles and mechanisms of m6A, m7G, m5C, N1-methyladenosine (m1A), N3-methylcytosine (m3C), and pseudouridine (ψ) on its development and maintenance. The potential therapeutic strategies of RNA modifications are elaborated for HCC.

5-methylcytosine RNA methyltransferases and their potential roles in cancer

In recent years, 5-methylcytosine (m⁵C) RNA modification has emerged as a key player in regulating RNA metabolism and function through coding as well as non-coding RNAs. Accumulating evidence has shown that m⁵C modulates the stability, translation, transcription, nuclear export, and cleavage of RNAs to mediate cell proliferation, differentiation, apoptosis, stress responses, and other biological functions. In humans, m⁵C RNA modification is catalyzed by the NOL1/NOP2/sun (NSUN) family and DNA methyltransferase 2 (DNMT2). These RNA modifiers regulate the expression of multiple oncogenes such as fizzy-related-1, forkhead box protein C2, Grb associated-binding protein 2, and TEA domain transcription factor 1, facilitating the pathogenesis and progression of cancers. Furthermore, the aberrant expression of methyltransferases have been identified in various cancers and used to predict the prognosis of patients. In this review, we present a comprehensive overview of m⁵C RNA methyltransferases. We specifically highlight the potential mechanism of action of m⁵C in cancer. Finally, we discuss the prospect of m⁵C-relative studies.