| 1.Background and significance:Prostate cancer(PCa)is the most common cancer and the major cause of cancerrelated death among men in 46 countries around the world.Based on the latest cancer statistics,there will be 191,930 new PCa patients and 33,330 PCa associated deaths in the United States in 2020,ranking first in male cancer incidence and second in male cancer mortality.Therefore,we are facing the serious challenge of detecting high-risk,fatal prostate cancer at an early stage and preventing over-diagnosis and over-treatment.Cancer metabolism has now become a hot topic of research that can improve our understanding of the mechanisms of tumorigenesis.Prostate cancer is a very meaningful disease model from a metabolic point of view.Normal prostate cells accumulate zinc,inhibiting the oxidation of citric acid and the metabolism of the tricarboxylic acid(TCA)cycle.Instead,cancer cells actively oxidize citric acid and restore the classic TCA cycle function.Understanding the differences in metabolic characteristics between benign prostate and prostate cancer can also help us to understand the development of cancer and develop new diagnostic and therapeutic approaches.Citrate synthase(CS)is one of the rate-limiting enzymes in the Krebs cycle and is capable of catalyzing oxaloacetate and acetyl-CoA to citrate.CS has been found to be upregulated in a variety of cancers,and its expression and clinical significance in prostate cancer have not been known.Therefore,this study used tissue microarray and public databases to determine the relationship between CS expression and the progression and prognosis of prostate cancer.At the same time,the effects of CS knockout on cell biological behavior were observed through cell function experiments and xenograft tumor experiments,and the mechanism of CS regulation was explored to provide new ideas for the diagnosis and treatment of prostate cancer.2.Methods:In this study,the expression of CS in prostate cancer was detected by immunohistochemistry in a prostate tissue microarray,and the correlation between CS and clinicopathological features was analyzed and verified in a public database.Then,the CS knockdown cell lines PC3 and DU 145 were constructed to study the effects of CS knockdown on proliferation,colony formation,migration,invasion,cell cycle and apoptosis of prostate cancer cells in vitro by CCK-8,colony formation,scratch,Transwell,cell cycle,and apoptosis experiments.The effect of CS knockdown on the growth of transplanted tumors was studied by xenograft tumor experiment in nude mice,and the effects of CS knockdown on the metabolomics and mitochondrial function of prostate cancer cells were detected by metabolomics experiment and mitochondrial MitoTracker experiment.3.Results:The results showed that CS expression level was higher in cancer tissues than in normal tissues(P=0.029),and the high expression of CS was significantly associated with high Gleason score(PTMA=0.005;PTCGA=0.020),advanced pathological stage(P<0.001),and biochemical recurrence(P<0.001).Cell function experiments showed that CS knockdown could inhibit cell proliferation(P<0.001),colony formation(P<0.001),migration(P<0.05),invasion(P<0.01),and cell cycle progression(P<0.001)and induce cell apoptosis(P<0.001).Xenograft experiments indicated that CS knockdown inhibited tumor growth in nude mice(P<0.001).Metabolomics experiments indicated that CS knockdown might inhibit lipid metabolism in cells(P<0.05).The MitoTracker experiment showed that CS knockdown might inhibit mitochondrial function in cells(P<0.001).4.Conclusions:Prostate cancer cells might increase the production of citric acid by upregulating CS,which acts as a precursor to fatty acid/lipid synthesis in cancer cells,enhancing the potential for cell proliferation and metastasis.Therefore,our study suggested that CS upregulation might be a potential diagnostic indicator and therapeutic target for prostate cancer. |
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