Downregulation of METTL7B Inhibits Proliferation of Human Clear Cell Renal Cancer Cells In Vivo and In Vitro

The role of RNA-modifying proteins in renal cell carcinoma

Gene expression is one of the most critical cellular processes. It is controlled by complex mechanisms at the genomic, epigenomic, transcriptomic, and proteomic levels. Any aberration in these mechanisms can lead to dysregulated gene expression. One recently discovered process that controls gene expression includes chemical modifications of RNA molecules by RNA-modifying proteins, a field known as epitranscriptomics. Epitranscriptomics can regulate mRNA splicing, nuclear export, stabilization, translation, or induce degradation of target RNA molecules. Dysregulation in RNA-modifying proteins has been found to contribute to many pathological conditions, such as cancer, diabetes, obesity, cardiovascular diseases, and neurological diseases, among others. This article reviews the role of epitranscriptomics in the pathogenesis and progression of renal cell carcinoma. It summarizes the molecular function of RNA-modifying proteins in the pathogenesis of renal cell carcinoma.

Glycolysis Modulation by METTL7B Shapes Acute Lymphoblastic Leukemia Cell Proliferation and Chemotherapy Response

Acute lymphoblastic leukemia (ALL) is a devastating hematological malignancy characterized by uncontrolled proliferation of immature lymphoid cells. While advances in treatment have improved patient outcomes, challenges remain in enhancing therapeutic efficacy and understanding underlying molecular mechanisms. Methyltransferase-like 7B (METTL7B), known for its methyltransferase activity, has been implicated in various solid tumors, yet its role in ALL remains unexplored. Here, we reveal that high METTL7B expression is correlated with poorer prognosis in ALL patients. Employing genetic manipulation strategies, we demonstrate that METTL7B depletion reduces ALL cell proliferation and enhances chemosensitivity. Mechanistically, we uncover METTL7B's involvement in modulating glycolysis, a crucial metabolic pathway supporting ALL cell growth. Furthermore, METTL7B's methyltransferase activity is identified as a determinant of its impact on glycolysis and proliferation. This study sheds light on METTL7B's multifaceted role in ALL, highlighting its potential as a therapeutic target and offering insights into the metabolic rewiring crucial for ALL progression.

METTL7A (TMT1A) and METTL7B (TMT1B) Are Responsible for Alkyl S-Thiol Methyl Transferase Activity in Liver

S-methylation of drugs containing thiol-moieties often alters their activity and results in detoxification. Historically, scientists attributed methylation of exogenous aliphatic and phenolic thiols to a putative S-adenosyl-L-methionine (SAM)-dependent membrane-associated enzyme referred to as thiol methyltransferase (TMT). This putative TMT appeared to have a broad substrate specificity and methylated the thiol metabolite of spironolactone, mertansine, ziprasidone, captopril, and the active metabolites of the thienopyridine prodrugs, clopidogrel, and prasugrel. Despite TMT's role in the S-methylation of clinically relevant drugs, the enzyme(s) responsible for this activity remained unknown. We recently identified methyltransferase-like protein 7B (METTL7B) as an alkyl thiol methyltransferase. METTL7B is an endoplasmic reticulum-associated protein with similar biochemical properties and substrate specificity to the putative TMT. Yet, the historic TMT inhibitor 2,3-dichloro-α-methylbenzylamine (DCMB) did not inhibit METTL7B, indicating that multiple enzymes contribute to TMT activity. Here we report that methyltransferase-like protein 7A (METTL7A), an uncharacterized member of the METTL7 family, is also a SAM-dependent thiol methyltransferase. METTL7A exhibits similar biochemical properties to METTL7B and putative TMT, including inhibition by DCMB (IC50 = 1.17 μM). Applying quantitative proteomics to human liver microsomes and gene modulation experiments in HepG2 and HeLa cells, we determined that TMT activity correlates closely with METTL7A and METTL7B protein levels. Furthermore, purification of a novel His-GST-tagged recombinant protein and subsequent activity experiments prove that METTL7A can selectively methylate exogenous thiol-containing substrates, including 7α-thiospironolactone, dithiothreitol, 4-chlorothiophenol, and mertansine. We conclude that the METTL7 family encodes for two enzymes, METTL7A and METTL7B, which are now renamed thiol methyltransferase 1A (TMT1A) and thiol methyltransferase 1B (TMT1B), respectively, that are responsible for thiol methylation activity in human liver microsomes. SIGNIFICANCE STATEMENT: We identified methyltransferase-like protein 7A (thiol methyltransferase 1A) and methyltransferase-like protein 7B (thiol methyltransferase 1B) as the enzymes responsible for the microsomal alkyl thiol methyltransferase (TMT) activity. These are the first two enzymes directly associated with microsomal TMT activity. S-methylation of commonly prescribed thiol-containing drugs alters their pharmacological activity and/or toxicity, and identifying the enzymes responsible for this activity will improve our understanding of the drug metabolism and pharmacokinetic (DMPK) properties of alkyl- or phenolic thiol-containing therapeutics.

Defining the elusive oncogenic role of the methyltransferase TMT1B

Methyltransferases are enzymes fundamental to a wide range of normal biological activities that can become dysregulated during oncogenesis. For instance, the recent description of the methyltransferase-like (METTL) family of enzymes, has demonstrated the importance of the N⁶-adenosine-methyltransferase (m⁶A) modification in transcripts in the context of malignant transformation. Because of their importance, numerous METTL family members have been biochemically characterized to identify their cellular substrates, however some members such as METTL7B, recently renamed TMT1B and which is the subject of this review, remain enigmatic. First identified in the stacked Golgi, TMT1B is also localized to the endoplasmic reticulum as well as lipid droplets and has been reported as being upregulated in a wide range of cancer types including lung cancer, gliomas, and leukemia. Interestingly, despite evidence that TMT1B might act on protein substrates, it has also been shown to act on small molecule alkyl thiol substrates such as hydrogen sulfide, and its loss has been found to affect cellular proliferation and migration. Here we review the current evidence for TMT1B's activity, localization, and potential biological role in the context of both normal and cancerous cell types.

METTLing in Stem Cell and Cancer Biology

The methyltransferase-like (METTL) family is a diverse group of methyltransferases that can methylate nucleotides, proteins, and small molecules. Despite this diverse array of substrates, they all share a characteristic seven-beta-strand catalytic domain, and recent evidence suggests many also share an important role in stem cell biology. The most well characterized family members METTL3 and METTL14 dimerize to form an N6-methyladenosine (m6A) RNA methyltransferase with established roles in cancer progression. However, new mouse models indicate that METTL3/METTL14 are also important for embryonic stem cell (ESC) development and postnatal hematopoietic and neural stem cell self-renewal and differentiation. METTL1, METTL5, METTL6, METTL8, and METTL17 also have recently identified roles in ESC pluripotency and differentiation, while METTL11A/11B, METTL4, METTL7A, and METTL22 have been shown to play roles in neural, mesenchymal, bone, and hematopoietic stem cell development, respectively. Additionally, a variety of other METTL family members are translational regulators, a role that could place them as important players in the transition from stem cell quiescence to differentiation. Here we will summarize what is known about the role of METTL proteins in stem cell differentiation and highlight the connection between their growing importance in development and their established roles in oncogenesis.

LncRNA ZNF674-AS1 Hinders Proliferation and Invasion of Hepatic Carcinoma Cells through the Glycolysis Pathway

Purpose. Long noncoding RNAs (lncRNAs) play important roles in regulating various functions of cells at the levels of transcription and posttranscription. Extensive investigations have illustrated that lncRNAs are critical in the glucose metabolism of tumor cells, but their mechanisms of action need to be further explored. This study evaluates the role of lncRNA ZNF674-AS1 on the apoptosis and proliferation of human hepatic carcinoma cells in vitro through the glucose metabolism and its related mechanisms. Methods. Real-time quantitative PCR was employed for detecting the level of expressions for lncRNA ZNF674-AS1 in liver cancer tissues (25 cases), paracancerous tissues, and liver cancer cell lines. The lncRNA ZNF674-AS1 high expression cell strain was constructed by the lentiviral overexpression vector. CCK-8, plate colony formation, transwell assay, lactate production, glucose consumption, and ATP levels were used to detect the change of cell proliferation, colony formation, migration, and invasion, as well as glycolytic capability. Western blot was carried out to detect the expression of HK2, PFKL, PKM2, GLUT1, and PKM1, which are the key proteins of glycolysis in cells. Result. The lncRNA ZNF674-AS1 was undesirably expressed in liver cancer cell lines and tissues. Cell function assessments showed that compared with the blank control group (vector), overexpression of lncRNA ZNF674-AS1 could substantially hinder the proliferation, colony formation, migration, and invasion capability of liver cancer cells. Furthermore, overexpression of lncRNA ZNF674-AS1 could inhibit cell glycolysis (inhibit glucose consumption and reduce intracellular lactate and ATP levels) by inhibiting the expression of key proteins (such as PFKL, HK2, PKM2, and GLUT1) in the process of glycolysis. Conclusion. As a tumor repressor gene, lncRNA ZNF674-AS1 inhibits the expression of key proteins in glycolysis to inhibit glycolysis level, thereby inhibiting cell migration and proliferation. Therefore, lncRNA ZNF674-AS1 could be a potent therapeutic target or a novel diagnostic molecule for patients suffering from liver cancer.

The lncRNA ZNF667-AS1 Inhibits Propagation, Invasion, and Angiogenesis of Gastric Cancer by Silencing the Expression of N-Cadherin and VEGFA

Purpose. Gastric cancer is one of the most common malignancies with high mortality worldwide. It is known that long noncoding RNAs (lncRNAs) play important roles in the pathogenesis of gastric cancer. This study investigates the role of lncRNA ZNF667-AS1 in gastric cancer cells. Methods. We have applied real-time quantitative PCR (qPCR) to study the levels of ZNF667-AS1 in gastric cancer biopsies and cell lines. The effects of ZNF667-AS1 on the propagation, clonogenicity, metastasis, and angiogenesis of gastric cancer cells were evaluated by calorimetry, colony formation, cell migration, and angiogenesis assays. Western blotting was used to identify the levels of proteins involved in cancer invasion and angiogenesis signaling pathways. Result. It was found that lncRNA ZNF667-AS1 was downregulated in gastric cancer biopsies. Overexpression of ZNF667-AS1 reduced the propagation, migration, and angiogenesis of gastric cancer cells. Molecular mechanism studies displayed that the high level of lncRNA ZNF667-AS1 promoted the expression of E-cadherin and inhibited the expression of N-cadherin and VEGFA, leading to the inhibition of the proliferation, migration, and angiogenesis of gastric cancer cells. Conclusion. As a tumor suppressor gene, lncRNA ZNF667-AS1 significantly hinders the propagation, metastasis, and angiogenesis of gastric cancer cells by promoting the expression of E-cadherin and inhibiting the expression of N-cadherin and VEGFA. Therefore, lncRNA ZNF667-AS1 could play a synergistic therapeutic role by targeting tumor cells and vascular endothelial cells, which represents a new therapeutic scheme for novel therapeutics of gastric cancer.

Overexpression of LINC00936 Inhibits the Proliferation and Invasion of Endometrial Carcinoma Cells

Objective. Endometrial carcinoma (EC) is one of the most common malignancies leading to death in women and poses a serious threat to women’s health. Therefore, exploring the molecular mechanisms affecting EC progression and metastasis is a clinical research hotspot. It has been shown that lncRNAs play an important role in the pathogenesis of EC. It is important to investigate the role of lncRNAs in the growth of EC to improve diagnosis and find new therapeutic targets of EC. Methods. The expression of LINC00936 in 36 EC tissues, paracancerous tissues, and cell lines was measured by fluorescence quantitative PCR. The relationship between LINC00936 expression and clinicopathological characteristics of patients was analyzed. The effects of overexpression of LINC00936 on proliferation, invasion, and migration of EC cells were examined by CCK-8 and transwell assays. Colony formation assay was also performed to evaluate the colony forming ability of EC cells. The effect of overexpression of LINC00936 on the expression of EMT-related proteins in EC cells was examined by western blot. In addition, the effect of LINC00936 overexpression on the growth of EC in vivo was examined by using tumorigenicity assay in the nude mouse. Results. LINC00936 was expressed at a low level in EC tissues and cell lines and significantly correlated with tumor size and lymphatic metastasis of patients. Overexpression of LINC00936 significantly inhibited the proliferation, invasion, and migration, as well as colony formation ability of EC cells. Western blot analysis showed that overexpression of LINC00936 significantly promoted the expression of E-cadherin and inhibited the expression of N-cadherin and vimentin in EC cells. Tumorigenic assays in the nude mouse demonstrated that overexpression of LINC00936 inhibited the growth of EC in vivo by suppressing Ki-67 and promoting E-cadherin expression. Conclusion. LINC00936 was expressed at a low level in EC tissues and significantly correlated with tumor size and lymphatic metastasis of patients. Overexpression of LINC00936 significantly inhibited the proliferation, invasion, and migration, as well as colony formation ability of EC cells. Therefore, LINC00936 could be a new target for the early diagnosis and treatment of EC patients.

Characterization of METTL7B to Evaluate TME and Predict Prognosis by Integrative Analysis of Multi-Omics Data in Glioma

Glioma is the most common and aggressive type of primary brain malignant tumor with limited treatment approaches. Methyltransferase-like 7B (METTL7B) is associated with the pathogenesis of several diseases but is rarely studied in glioma. In this study, 1,493 glioma samples (data from our cohort, TCGA, and CGGA) expressing METTL7B were used to explore its prognostic value and mechanism in the immune microenvironment. Results showed that high expression of METTL7B is associated with poor prognosis and abundant immunosuppressive cells. Further, functional enrichment showed that METTL7B is involved in the negative regulation of immunity and carcinogenic signaling pathways. Moreover, a METTL7B-related prognostic signature constructed based on multi-omics showed a good prediction of the overall survival (OS) time of glioma patients. In conclusion, METTL7B is a potential prognostic biomarker. In addition, the prognostic prediction model constructed in this study can be used in clinical setups for the development of novel effective therapeutic strategies for glioma patients and improving overall survival.

METTL7B is a novel prognostic biomarker of lower-grade glioma based on pan-cancer analysis

Methyltransferase-like 7B (METTL7B) is a member of the methyltransferase-like protein family that plays an important role in the development and progression of tumors. However, its prognostic value and the correlation of METTL7B expression and tumor immunity in some cancers remain unclear. By analyzing online data, we found that METTL7B is abnormally overexpressed in multiple human tumors and plays an important role in the overall survival (OS) of patients with 8 cancer types and disease-free survival (DFS) of patients with 5 cancer types. Remarkably, METTL7B expression was positively correlated with the OS and DFS of patients with lower-grade glioma (LGG). In addition, a positive correlation between METTL7B expression and immune cell infiltration in LGG was observed. Moreover, we identified a strong correlation between METTL7B expression and immune checkpoint gene expression in kidney chromophobe (KICH), LGG and pheochromocytoma and paraganglioma (PCPG). Furthermore, METTL7B was involved in the extracellular matrix (ECM) and immune-related pathways in LGGs. Finally, in vitro experiments showed that knockdown of METTL7B inhibited the growth, migration, invasion and the epithelial–mesenchymal transition (EMT) of LGG cells. METTL7B expression potentially represents a novel prognostic biomarker due to its significant association with immune cell infiltration in LGG.