The Function And Mechanism Of ULK1 In Colon Cancer

Colon cancer is the third most common disease in the world and has the fourth highest mortality rate.Colon cancer is the first solid tumor to be diagnosed by molecular typing.Many genes and pathways are involved in the development of colon cancer.Although the mechanism of colon cancer research and individualized treatment progress rapidly,its 5-year survival rate is still lower than 15%,and the mortality rate is as high as 10%.The clinical prognosis of patients with colon cancer is mainly based on the stage system of TNM(tumor-node-metastasis)of AJCC(American Joint Committee on Cancer),which is limited to the depth of tumor invasion,lymph node and hematogenous metastasis.To date,only a few molecular markers have been included in clinical diagnosis and treatment decision-making options for colon cancer(eg,RAS,Braf,MMR,etc.).Our understanding of the potential molecular biology mechanisms for the development of colon cancer remains limited.Exploration and discovery of new molecules involved in the pathogenesis of colon cancer can more accurately diagnose and improve the efficacy of comprehensive colon cancer therapy.ULK1(Unc-51-like kinase 1)is a key factor in the autophagy complex and plays an important role in the physiological processes of cell autophagy,metabolism,and cell death.Autophagy,also known as cellular digestion,is a highly conserved cellular catabolic pathway involved in the degradation and recycling of excess or damaged proteins and organelles through double-membrane vesicles called autophagosomes.This process allows cells,organs,and entire organisms to endure various stress conditions,including limited nutrients,energy supplies or hypoxia.ULK1 is a homolog of mammalian yeast ATG(autophagy-associated genes),and ULK1 forms a stable complex to sense autophagy-activated nutrient signals that initiate autophagy.The role of autophagy in tumors is complex and varies,depending on the type of tumor.Highly expressed ULK1 levels have been shown to be a biomarker of poor prognosis in esophageal squamous cell carcinoma;whereas in operable breast cancer,low expression of ULK1 is associated with tumor progression and poor prognosis.To date,the role and pathogenesis of ULK1 in colon cancer remains unclear.This study explored the role and mechanism of ULK1 in the development of colon cancer.First of all,we analyzed the expression of ULK1 in colon cancer patients and normal colon tissue through the Oncomine database.We found that ULK1 mRNA expression was significantly higher in colon cancer than in normal colon tissue.We extracted the protein and mRNA from 18 cases of colon cancer patients and applied western blot and real-time PCR to verify that the expression of ULK1 in colon cancer and adjacent normal tissues.The expression level of ULK1 was significantly higher than that in adjacent tissues.The tissue microarray of a random sample of 85 colon cancer was further constructed for immunohistochemical detection.It was found that the highly expressed ULK1 was positively correlated with the size of the tumor and negatively correlated with the prognosis of the patients.Secondly,based on the tissue and microarray results,we verified the above results in colon cancer cells RKO.SRB experiments and colony formation experiments found that interference with ULK1 can reduce the proliferation of RKO cells in vitro.Subcutaneous tumorigenesis in nude mice also confirmed that knockdown of ULK1 significantly inhibited the growth of subcutaneous xenografts.Finally,we further explored the mechanism by which ULK1 inhibits the proliferation of colon cancer.Through 2-NBDG glucose uptake assay and PI cell cycle assay,we found that ULK1 does not affect the carbohydrate uptake of colon cancer cells but plays a role in regulating the cell cycle.Our results suggest that ULKl plays an important role in the development of colon cancer.In terms of diagnosis,it can serve as a clinical prognostic biomarker for colon cancer.In terms of treatment,this study provides a theoretical basis and clue for ULK1 to become a new target for colon cancer treatment and clinical exploration combined with targeted therapy.Further in-depth mechanism research of ULK1 may hopefully become a new drug action pathway for the treatment of colon cancer.