Background: Autophagy plays a crucial role in sustaining the homeostasis in various malignant diseases. It has also been reported to promote tumor development in multiple cancers. Glutaminolysis instead of Warburg Effect produce adequate ATP and provide nitrogen and carbon to replenish the TCA cycle which has been discovered to be a new energy source for tumor cells recently. By means of degrading intracellular particles including amino acids, nucleotides, fatty acids, sugars and aged organisms, autophagy can recycle the aforementioned particles into bioenergetics and biosynthesis pathways, finally favoring tumor cells. MicroRNA is a kind of noncoding RNA that regulates the targeting gene expression mostly at post-transcription level. Among these miRNAs, microRNA-133a-3p is reported to be a tumor suppressor in numerous cancers.
Methods: We characterized the down-regulated expression level of microRNA-133a-3p in gastric cancer via TCGA database. Subsequently, we verified the tumor suppressor role of microRNA-133a-3p in gastric cancer cells through a series biological function assay. We used immunofluorescence and transmission electron microscope to observe the negative effect of microRNA-133a-3p on autophagy and used dual-luciferase report assay to identify the candidate gene GABARAPL1 of microRNA-133A-3p.Then we used high performance liquid phase mass spectrometry and seahorse analysis to detect whether miR-133a-3p could block the glutaminolysis metabolism through autophagy. At last, we confirmed the tumor suppressor role of microRNA-133a-3p in vivo on PDX mice model.
Results: We demonstrated that microRNA-133a-3p overexpression could block the activation of autophagy to ruin the abnormal glutaminolysis and further inhibit the growth and metastasis of gastric cancer cells. We successfully proved gastric cancer cells can replenish glutaminolysis via autophagy and microRNA-133a-3p could block aforementioned pathway by targeting core autophagy participants GABARAPL1 and ATG13.We then verified the negative function of microRNA-133a-3p on autophagy-mediated glutaminolysis both in PDX model and human gastric cancer organoid model.
Conclusions: MicroRNA-133a-3p targets GABARAPL1 to block autophagy-mediated glutaminolysis, further repressing gastric cancer growth and metastasis.
Keywords: Autophagy; GABARAPLI; Gastric cancer; Glutaminolysis; Organoid; PDX model; miRNA.