| Objective: The morbidity and mortality of lung cancer remain high all over the world.Lung adenocarcinoma is the most common pathological type of lung cancer.In addition to traditional surgery and chemoradiotherapy,targeted therapy and immunotherapy provide new options for lung cancer patients,but there are still a large number of patients who cannot benefit from the existing treatment programs due to a variety of reasons such as lack of specific gene mutations,drug resistance after treatment and immune escape.In recent years,blocking malignant phenotypes of tumor cells by inhibiting energy metabolism has become an emerging anticancer strategy.Rab22 a is a small GTP-binding protein that belongs to the Ras superfamily and is a key regulator of intracellular vesicular transport.It plays a very wide range of biological functions inside the cell.Current studies have found that its expression is up-regulated in a variety of tumors and can participate in the malignant progression of tumors.The formation,transport,fusion and decomposition of lipids are closely related to vesicle transport,which is regulated by a variety of Rab proteins.The mechanism of abnormal lipid metabolism and promotion of malignant phenotype of tumor cells has not been reported.This study aims to explore the regulatory effect of Rab22 a on lipid metabolism and its molecular mechanism in lung adenocarcinoma.Methods: GEPIA and UALCAN databases were used to analyze the expression of Rab22 a in lung adenocarcinoma,and then analyze the relationship between Rab22 a and prognosis of lung adenocarcinoma patients.The expression of Rab22 a and ADRP was detected by immunohistochemistry in 90 lung adenocarcinoma tissues,and the expression and correlation were analyzed.Rab22 a protein was bidirectional regulated in H1299 and A549 cells.The effect of Rab22 a on lipid accumulation in cells was detected by oil red O and Nile red tests after Rab22 a protein was up-regulated and down-regulated.The lipid accumulation was further observed by electron microscopy.Lipidomics analysis was performed for Rab22 a transfection and interference groups.The expression of adipose de novo synthetase FASN in lung adenocarcinoma was detected by immunohistochemistry,and the expression and correlation were analyzed,and the expressions of lipid metabolism related indexes FASN,ACC1 and ACLY were detected by western blot to analyze the changes of adipose acid de novo synthesis in lung adenocarcinoma.In order to further explore the molecular mechanism,PI3 K inhibitor LY294002 was added after transfection of Rab22 a,and DMSO,oil red O and Nile red were added in the control group to test the effect of inhibition of PI3K/AKT/mTOR pathway on lipid accumulation.The influence of Rab22 a on the expression of FASN,ACC1 and ACLY was detected by western blot.Lipase inhibitor C75 was added into the cells transfected with Rab22 a protein.The effects of adipose de novo synthesis inhibition on the proliferation of lung adenocarcinoma cells were observed by clonal formation and CCK8 tests.The effects of inhibiting postmetabolic invasion and migration were analyzed by scratch test and Transwell test.Results: 1.Database analysis and IHC results show that Rab22 a is highly expressed in lung adenocarcinoma and is associated with poor prognosis.2.Immunohistochemistry showed that ADRP expression was up-regulated in lung adenocarcarcinoma tissues,and was correlated with Rab22 a.The results of oil red O staining,Nile red assay and electron microscopy showed that Rab22 a promoted lipid droplet accumulation.3.The results of lipidomics analysis showed that compared with the sample group that interfered with endogenous Rab22 a,transfected Rab22 a mainly increased the contents of intracellular triglycerides,phosphatidyl ethanolamine and ceramide.Immunohistochemistry showed that the expression of FASN was up-regulated in lung adenocarcinoma tissues,and was correlated with Rab22 a.western blot experiment showed that the expressions of FASN,ACC1 and ACLY related indexes of lipid metabolism were increased after Rab22 a protein was overexpressed in cells,and the opposite trend was observed after Rab22 a was down-expressed.4.After treatment with PI3 K inhibitor LY294002 inhibition of PI3K/AKT/mTOR pathway,oil red O staining and Nile red experiments showed that lipid accumulation was inhibited,and western blot showed that the expressions of FASN,ACC1 and ACLY were inhibited.5.After treament with C75 inhibition of fat synthesis,the results of clonogenesis and CCK8 assays showed that cell proliferation was inhibited,and scratch and Transwell tests indicated that invasion and migration was inhibited.Conclusion:1.Rab22 a is highly expressed in lung adenocarcinoma and positively correlated with the expression of adipose differentiation-related protein and Fatty Acid Synthase.2.Rab22 a activates PI3K/AKT/mTOR pathway to promote lipid accumulation and de novo lipid synthesis in lung adenocarcinoma cells.3.After inhibiting lipid de novo synthesis,proliferation,invasion and migration of lung adenocarcinoma cells was inhibited. |
PDF Full Text Request