ABSTRACT
In recent decades, considerable evidence has emerged indicating the involvement of tRNA-derived fragments (tRFs) in cancer progression through various mechanisms. However, the biological effects and mechanisms of tRFs in lung adenocarcinoma (LUAD) remain unclear. In this study, we screen out tRF-29-79, a 5'-tRF derived from tRNAGlyGCC, through profiling the tRF expressions in three pairs of LUAD tissues. We show that tRF-29-79 is downregulated in LUAD and downregulation of tRF-29-79 is associated with poorer prognosis. In vivo and in vitro assay reveal that tRF-29-79 inhibits proliferation, migration and invasion of LUAD cells. Mechanistically, we discovered that tRF-29-79 interacts with the RNA-binding protein PTBP1 and facilitates the transportation of PTBP1 from nucleus to cytoplasm, which regulates alternative splicing in the 3' untranslated region (UTR) of SLC1A5 pre-mRNA. Given that SLC1A5 is a core transporter of glutamine, we proved that tRF-29-79 mediate glutamine metabolism of LUAD through affecting the stability of SLC1A5 mRNA, thus exerts its anticancer function. In summary, our findings uncover the novel mechanism that tRF-29-79 participates in glutamine metabolism through interacting with PTBP1 and regulating alternative splicing in the 3' UTR of SLC1A5 pre-mRNA.
Subject(s)
Adenocarcinoma of Lung , Amino Acid Transport System ASC , Cell Proliferation , Disease Progression , Gene Expression Regulation, Neoplastic , Heterogeneous-Nuclear Ribonucleoproteins , Lung Neoplasms , Polypyrimidine Tract-Binding Protein , Humans , Adenocarcinoma of Lung/pathology , Adenocarcinoma of Lung/genetics , Adenocarcinoma of Lung/metabolism , Polypyrimidine Tract-Binding Protein/metabolism , Polypyrimidine Tract-Binding Protein/genetics , Amino Acid Transport System ASC/metabolism , Amino Acid Transport System ASC/genetics , Lung Neoplasms/pathology , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Mice , Heterogeneous-Nuclear Ribonucleoproteins/metabolism , Heterogeneous-Nuclear Ribonucleoproteins/genetics , Animals , Minor Histocompatibility Antigens/genetics , Minor Histocompatibility Antigens/metabolism , Cell Movement , Prognosis , Cell Line, Tumor , Alternative Splicing , Female , Glutamine/metabolism , MaleABSTRACT
BACKGROUND AND PURPOSE: Heparanase is the only confirmed endoglycosidase that cleaves heparan sulfate (HS), a ubiquitous glycosaminoglycan with various essential roles in multiple pathological processes. Thus, the development of heparanase inhibitors has become an attractive strategy for drug discovery, especially in tumour therapy, in which HS mimetics are the most promising compounds. The various biological effects of heparanase also suggest a role for HS mimetics in many non-cancer indications, such as type 1 diabetes. However, the potential benefits of HS mimetics in obesity-related type 2 diabetes have not been elucidated. EXPERIMENTAL APPROACH: In this study, we investigated muparfostat (PI-88), a developed HS mimetic currently enrolled in Phase III clinical trials, in obese mouse models and in vitro cultured murine hepatocytes. KEY RESULTS: Daily administration of muparfostat for 4 weeks caused hyperlipidaemia and aggravated hepatic steatosis in obese mice models, but not in lean animals. In cultured hepatocytes, muparfostat did not alter lipid accumulation. Acute tests suggested that muparfostat binds to lipoprotein lipase in competition with HS on vascular endothelial cell surfaces, thereby reducing the degradation of circulating triglycerides by lipoprotein lipase and subsequent uptake of fatty acids into vascular endothelial cells and causing hyperlipidaemia. This hyperlipidaemia aggravates hepatic steatosis and causes liver injury in muparfostat-treated obese mice. CONCLUSIONS AND IMPLICATIONS: The binding activity of HS mimetics to lipoprotein lipase should be investigated as an additional pharmacological effect during heparanase inhibitor drug discovery. This study also provides novel evidence for an increased risk of drug-induced liver injury in obese individuals.
