Depletion of MRPL35 inhibits gastric carcinoma cell proliferation by regulating downstream signaling proteins

Mitochondrial ribosomal proteins: potential targets for cancer prognosis and therapy

Mitochondrial ribosomal proteins (MRPs) are essential components of mitochondrial ribosomes, responsible for translating proteins encoded by mitochondrial DNA and maintaining mitochondrial energy metabolism and function. Emerging evidence suggests that MRPs exhibit significant expression changes in multiple cancer types, profoundly affecting tumor biology through modulating oxidative stress levels, inducing metabolic reprogramming, disrupting cell cycle regulation, inhibiting apoptosis, promoting mitophagy, and remodeling the tumor microenvironment. Specifically, MRPs have been implicated in tumor cell proliferation, migration, invasion, and apoptosis, highlighting their potential as therapeutic targets. This review summarizes the multifaceted roles of MRPs in cancer, focusing on their impact on the tumor microenvironment and their potential as prognostic biomarkers and therapeutic targets. We also explore the implications of MRPs in precision oncology, particularly in patient stratification and the design of metabolic targeted therapies, offering new insights and research directions for the precise prevention and treatment of cancer.

Mitochondrial Ribosomal Proteins and Cancer

Mitochondria play key roles in maintaining cell life and cell function, and their dysfunction can lead to cell damage. Mitochondrial ribosomal proteins (MRPs) are encoded by nuclear genes and are assembled within the mitochondria. MRPs are pivotal components of the mitochondrial ribosomes, which are responsible for translating 13 mitochondrial DNA-encoded proteins essential for the mitochondrial respiratory chain. Recent studies have underscored the importance of MRPs in cancer biology, revealing their altered expression patterns in various types of cancer and their potential as both prognostic biomarkers and therapeutic targets. Herein, we review the current knowledge regarding the multiple functions of MRPs in maintaining the structure of the mitochondrial ribosome and apoptosis, their implications for cancer susceptibility and progression, and the innovative strategies being developed to target MRPs and mitoribosome biogenesis in cancer therapy. This comprehensive overview aims to provide insights into the role of MRPs in cancer biology and highlight promising strategies for future precision oncology.

Mitochondrial ribosomal proteins in metastasis and their potential use as prognostic and therapeutic targets

The mitochondrion is an essential cell organelle known as the powerhouse of the cell. Mitochondrial ribosomal proteins (MRPs) are nuclear encoded, synthesised in the cytoplasm but perform their main functions in the mitochondria, which includes translation, transcription, cell death and maintenance. However, MRPs have also been implicated in cancer, particularly advanced disease and metastasis across a broad range of cancer types, where they play a central role in cell survival and progression. For some, their altered expression has been investigated as potential prognostic markers, and/or therapeutic targets, which is the focus of this review. Several therapies targeting MRPs are currently approved by the Food and Drug Administration and the European Medicines Agency for use in other diseases, revealing the opportunity for repurposing their use in advanced and metastatic cancer. Herein, we review the evidence supporting key MRPs as molecular drivers of advanced disease in multiple cancer types. We also highlight promising avenues for future use of MRPs as precision targets in the treatment of late-stage cancers for which there are currently very limited effective treatment options.

MRPL35 Induces Proliferation, Invasion, and Glutamine Metabolism in NSCLC Cells by Upregulating SLC7A5 Expression

BACKGROUND

Mitochondrial ribosomal protein L35 (MRPL35) has been reported to contribute to the growth of non-small cell lung cancer (NSCLC) cells. However, the functions and mechanisms of MRPL35 on glutamine metabolism in NSCLC remain unclear.

METHODS

The detection of mRNA and protein of MRPL35, ubiquitin-specific protease 39 (USP39), and solute carrier family 7 member 5 (SLC7A5) was conducted using qRT-PCR and western blotting. Cell proliferation, apoptosis, and invasion were evaluated using the MTT assay, EdU assay, flow cytometry, and transwell assay, respectively. Glutamine metabolism was analyzed by detecting glutamine consumption, α-ketoglutarate level, and glutamate production. Cellular ubiquitination analyzed the deubiquitination effect of USP39 on MRPL35. An animal experiment was conducted for in vivo analysis.

RESULTS

MRPL35 was highly expressed in NSCLC tissues and cell lines, and high MRPL35 expression predicted poor outcome in NSCLC patients. In vitro analyses suggested that MRPL35 knockdown suppressed NSCLC cell proliferation, invasion, and glutamine metabolism. Moreover, MRPL35 silencing hindered tumor growth in vivo. Mechanistically, USP39 stabilized MRPL35 expression by deubiquitination and then promoted NSCLC cell proliferation, invasion, and glutamine metabolism. In addition, MRPL35 positively affected SLC7A5 expression in NSCLC cells in vitro and in vivo. Moreover, the anticancer effects of MRPL35 silencing could be rescued by SLC7A5 overexpression in NSCLC cells.

CONCLUSION

MRPL35 expression was stabilized by USP39-induced deubiquitination in NSCLC cells, and knockdown of MRPL35 suppressed NSCLC cell proliferation, invasion, and glutamine metabolism in vitro and impeded tumor growth in vivo by upregulating SLC7A5, providing a promising therapeutic target for NSCLC.

Knockdown of MRPL35 promotes cell apoptosis and inhibits cell proliferation in non-small-cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) is a major pathological type of lung cancer. However, its pathogenesis remains largely unclear. MRPL35 is a regulatory subunit of the mitoribosome, which can regulate the assembly of cytochrome c oxidases and plays an important role in the occurrence of NSCLC.

METHODS

The expression of MRPL35 in NSCLC was detected by tissue microarray and immunohistochemistry. H1299 cells were infected with lentivirus to knockdown MRPL35, and the cells were subjected to crystal violet staining to assess the results of colony formation assays. A549 cells were infected by lentiviral particles-expressing shMRPL35 or shControl, and then subcutaneously injected into nude mice. Tumorigenesis in mice was detected by in vivo imaging. The potential pathway of MRPL35 in NSCLC was assessed by Western blotting.

RESULTS

MRPL35 was over-expressed in NSCLC tissue compared to para-cancerous and normal tissues. Knockdown of MRPL35 suppressed cell proliferation and decreased NSCLC progression both in vitro and in vivo. The possible molecular mechanisms were also clarified, which indicated that MRPL35 could be involved in cell apoptosis and proliferation by modulating the expression levels of CDK1, BIRC5, CHEK1, STMN1 and MCM2. Knockdown of MRPL35 activated p53 signaling pathway and inhibited cell cycle regulation.

CONCLUSIONS

The oncogenic role of MRPL35 in NSCLC was potentially mediated through the cell cycle regulatory genes such as BIRC5, STMN1, CDK1, CHEK1 and MCM2, as well as activation of P53 signaling pathway.

Identification and validation of a fatty acid metabolism gene signature for the promotion of metastasis in liver cancer

Metastasis is a fatal status for liver cancer, and the identification of an effective prediction model and promising therapeutic target is essential. Given the known relationship between fatty acid (FA) metabolism and the liver, the present study aimed to investigate dysregulation of genes associated with FA metabolism in liver cancer. Bioinformatics analyses were performed on data from patients with hepatocellular carcinoma (HCC) obtained from The Cancer Genome Atlas database using R software packages. Online public tools such as the Human Protein Atlas, Tumor Immune Single-Cell Hub and the University of Alabama at Birmingham Cancer Data Analysis portal were also utilized. Some essential results were further verified using in vitro experiments using HepG2 liver cancer cells. A signature consisting of three genes associated with the progression and prognosis of HCC and FA metabolism was identified. When samples were scored based on the expression of these genes and divided according to the median value, the higher score group showed a worse outcome and repressive immune microenvironment than the lower score group. Downstream pathways such as hypoxia, IL6/JAK/STAT3 and epithelial-mesenchymal transition were found to be significantly activated in the higher score group. As the core factor in the signature, mitochondrial ribosomal protein L35 (MRPL35) was found to be upregulated in HCC and to have certain impacts on the dysregulation of effective immunity. Further investigations and in vitro experiments indicated that MRPL35 facilitates the migration and invasion abilities of liver cancer, and the resistance of HCC to treatment. These findings have important implications regarding the characteristics and mechanisms of metastasis in liver cancer, and provide a promising signature based on FA metabolism-related genes that may be used to predict outcomes and explored as a novel therapeutic target in liver cancer.

Potential of Mitochondrial Ribosomal Genes as Cancer Biomarkers Demonstrated by Bioinformatics Results

Next-generation sequencing and bioinformatics analyses have clearly revealed the roles of mitochondrial ribosomal genes in cancer development. Mitochondrial ribosomes are composed of three RNA components encoded by mitochondrial DNA and 82 specific protein components encoded by nuclear DNA. They synthesize mitochondrial inner membrane oxidative phosphorylation (OXPHOS)-related proteins and participate in various biological activities via the regulation of energy metabolism and apoptosis. Mitochondrial ribosomal genes are strongly associated with clinical features such as prognosis and foci metastasis in patients with cancer. Accordingly, mitochondrial ribosomes have become an important focus of cancer research. We review recent advances in bioinformatics research that have explored the link between mitochondrial ribosomes and cancer, with a focus on the potential of mitochondrial ribosomal genes as biomarkers in cancer.

18β-glycyrrhetinic acid regulates mitochondrial ribosomal protein L35-associated apoptosis signaling pathways to inhibit proliferation of gastric carcinoma cells

BACKGROUND

Gastric carcinoma (GC) is a common gastrointestinal malignancy worldwide. Based on the cancer-related mortality, the current prevention and treatment strategies for GC still show poor clinical results. Therefore, it is important to find effective drug treatment targets.

AIM

To explore the mechanism by which 18β-glycyrrhetinic acid (18β-GRA) regulates mitochondrial ribosomal protein L35 (MRPL35) related signal proteins to inhibit the proliferation of GC cells.

METHODS

Cell counting kit-8 assay was used to detect the effects of 18β-GRA on the survival rate of human normal gastric mucosal cell line GES-1 and the proliferation of GC cell lines MGC80-3 and BGC-823. The apoptosis and cell cycle were assessed by flow cytometry. Cell invasion and migration were evaluated by Transwell assay, and cell scratch test was used to detect cell migration. Furthermore, a tumor model was established by hypodermic injection of 2.5 × 10⁶ BGC-823 cells at the selected positions of BALB/c nude mice to determine the effect of 18β-GRA on GC cell proliferation, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect MRPL35 expression in the engrafted tumors in mice. We used the term tandem mass tag (TMT) labeling combined with liquid chromatography–tandem mass spectrometry to screen for differentially expressed proteins (DEPs) extracted from GC cells and control cells after 18β-GRA intervention. A detailed bioinformatics analysis of these DEPs was performed, including Gene Ontology annotation and enrichment analysis, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, and so on. Moreover, STRING database (https://string-db.org/) was used to predict protein-protein interaction (PPI) relationships and Western blot was used to detect the expression of proteins of interest in GC cells.

RESULTS

The results indicated that 18β-GRA could inhibit the proliferation of GC cells in a dose- and time-dependent manner. It could induce GC cell apoptosis and arrest the cell cycle at G0/G1 phase. The proportion of cells arrested at S phase decreased with the increase of 18-GRA dose, and the migration and invasiveness of GC cells were inhibited. The results of animal experiments showed that 18β-GRA could inhibit tumor formation in BALB/c nude mice, and qRT-PCR results showed that MRPL35 expression level was significantly reduced in the engrafted tumors in mice. Using TMT technology, 609 DEPs, among which 335 were up-regulated and 274 were down-regulated, were identified in 18β-GRA intervention compared with control. We found that the intervention of 18β-GRA in GC cells involved many important biological processes and signaling pathways, such as cellular processes, biological regulation, and TP53 signaling pathway. Notably, after the drug intervention, MRPL35 expression was significantly down-regulated (P = 0.000247), TP53 expression was up-regulated (P = 0.02676), and BCL2L1 was down-regulated (P = 0.01699). Combined with the Retrieval of Interacting Genes/Proteins database, we analyzed the relationship between MRPL35, TP53, and BCL2L1 signaling proteins, and we found that COPS5, BAX, and BAD proteins can form a PPI network with MRPL35, TP53, and BCL2L1. Western blot analysis confirmed the intervention effect of 18β-GRA on GC cells, MRPL35, TP53, and BCL2L1 showed dose-dependent up/down-regulation, and the expression of COPS5, BAX, and BAD also increased/decreased with the change of 18β-GRA concentration.

CONCLUSION

18β-GRA can inhibit the proliferation of GC cells by regulating MRPL35, COPS5, TP53, BCL2L1, BAX, and BAD.

Identifying novel therapeutic targets in gastric cancer using genome-wide CRISPR-Cas9 screening

Genome-scale CRISPR-Cas9 screening technology is a powerful tool to systematically identify genes essential for cancer cell survival. Herein, TKOv3, a genome-scale CRISPR-Cas9 knock-out library, was screened in the gastric cancer (GC) cells, and relevant validation experiments were performed. We obtained 854 essential genes for the AGS cell line, and 184 were novel essential genes. After knocking down essential genes: SPC25, DHX37, ABCE1, SNRPB, TOP3A, RUVBL1, CIT, TACC3 and MTBP, cell viability and proliferation were significantly decreased. Then, we analysed the detected essential genes at different time points and proved more characteristic genes might appear with the extension of selection. After progressive selection using a series of open datasets, 41 essential genes were identified as potential drug targets. Among them, methyltransferase 1 (METTL1) was over expressed in GC tissues. High METTL1 expression was associated with poor prognosis among 3 of 6 GC cohorts. Furthermore, GC cells growth was significantly inhibited after the down-regulation of METTL1 in vitro and in vivo. Function analysis revealed that METTL1 might play a role in the cell cycle through AKT/STAT3 pathways. In conclusion, compared with existing genome-scale screenings, we obtained 184 novel essential genes. Among them, METTL1 was validated as a potential therapeutic target of GC.