METTL5 promotes gastric cancer progression via sphingomyelin metabolism

BACKGROUND The treatment of gastric cancer(GC)has caused an enormous social burden worldwide.Accumulating studies have reported that N6-methyladenosine(m6A)is closely related to tumor progression.METTL5 is a m6A methyltransferase that plays a pivotal role in maintaining the metabolic stability of cells.However,its aberrant regulation in GC has not been fully elucidated.AIM To excavate the role of METTL5 in the development of GC.METHODS METTL5 expression and clinicopathological characteristics were analyzed via The Cancer Genome Atlas dataset and further verified via immunohistochemistry,western blotting and real-time quantitative polymerase chain reaction in tissue microarrays and clinical samples.The tumor-promoting effect of METTL5 on HGC-27 and AGS cells was explored in vitro by Cell Counting Kit-8 assays,colony formation assays,scratch healing assays,transwell assays and flow cytometry.The tumor-promoting role of METTL5 in vivo was evaluated in a xenograft tumor model.The EpiQuik m6A RNA Methylation Quantification Kit was used for m6A quantification.Next,liquid chromatography-mass spectrometry was used to evaluate the association between METTL5 and sphingomyelin metabolism,which was confirmed by Enzyme-linked immunosorbent assay and rescue tests.In addition,we investigated whether METTL5 affects the sensitivity of GC cells to cisplatin via colony formation and transwell experiments.RESULTS Our research revealed substantial upregulation of METTL5,which suggested a poor prognosis of GC patients.Increased METTL5 expression indicated distant lymph node metastasis,advanced cancer stage and pathological grade.An increased level of METTL5 correlated with a high degree of m6A methylation.METTL5 markedly promotes the proliferation,migration,and invasion of GC cells in vitro.METTL5 also promotes the growth of GC in animal models.METTL5 knockdown resulted in significant changes in sphingomyelin metabolism,which implies that METTL5 may impact the development of GC via sphingomyelin metabolism.In addition,high METTL5 expression led to cisplatin resistance.CONCLUSION METTL5 was found to be an oncogenic driver of GC and may be a new target for therapy since it facilitates GC carcinogenesis through sphingomyelin metabolism and cisplatin resistance.

PD-1/PD-L1 antagonists in gastric cancer:Current studies and perspectives

Immune checkpoints release suppressive signals for T cells,which enable the tumors to escape from immune destruction and provide a new concept that uses the capabilities of the immune system as a therapeutic target for tumors.At present,programmed death receptor 1(PD-1)/programmed death ligand-1(PDL1) has become the most promising therapeutic target.PD-1/PD-L1 blockades exhibit long-lasting antitumor efficacy and safety in patients with various cancers,such as melanoma and non-small-cell lung cancer.Moreover,PD-L1 is highly expressed in the peripheral blood and tumor specimens of patients with cancer,and the expression of PD-L1 is positively correlated with various pathological features and may serve as a predictor of poor prognosis or a diagnostic tool.Clinical trials have verified that PD-1/PD-L1 blockade therapy benefits patients with advanced gastric cancer or gastroesophageal junction cancer.Furthermore,there are many molecules involved in the regulation of PD-1/PD-L1 expression,and the modification of these molecules via drugs and combinations with PD-1/PD-L1 inhibitors may further improve the efficacy of immunotherapy for gastric cancer.In this review,the efficacy,safety,and possible combination treatment options of PD-1/PD-L1 in gastric cancer are reviewed in experimental and clinical settings.