The Mechanism Of DDIT4 Promoting Pancreatic Cancer Invasion And Metastasis Through PPAR-γ Mediated Fatty Acid Intake

Objective:Pancreatic cancer is one of the most malignant tumors in China,which is a major highly lethal cancer jeopardizing the health of Chinese residents.The pancreatic cancer cells are characterized by obvious metabolic reprogramming,but there is still a lack of effective treatment.DNA damage-inducible transcript 4(DDIT4)is a tumor metabolism-related protein,which is involved in the proliferation and apoptosis of a variety of tumors.The purpose of our study is to clarify the role of DDIT4 in pancreatic cancer,and to clarify the mechanism of regulation of the pancreatic cancer through the intervention of DDIT4.Methods:We collected and analyzed lipid-related clinical data of pancreatic cancer patients who admitted to our hospital for surgical treatment from 2017 to 2020.To further clarify whether DDIT4 is involved in lipid metabolism in pancreatic cancer tissues,we collected tumor tissues and para-tumor tissues from the patients with pancreatic cancer meeting the inclusion criteria and constructed the wild-type animal models of pancreatic cancer and DDIT4-HET animal models of pancreatic cancer.Immunohistochemistry and Western blot were performed to detect the expression of DDIT4 in pancreatic cancer patients and animal models.And HE staining and oil red O staining was performed to compare the degree of fat infiltration in pancreatic cancer tissues and para-tumor tissues,as well as in the wild-type animal models of pancreatic cancer and DDIT4-HET animal model of pancreatic cancer.What’s more,Western blot and immunohistochemical technique were performed to verify the protein expressions of DDIT4/PPAR-γ and its downstream protein CD36 and ATGL.Finally,in order to further clarify the effect of the abnormal lipid metabolism meditated by DDIT4 in pancreatic cancer tissues,we detected the levels of apoptosis and proliferation in wild-type pancreatic cancer animal models and DDIT4-HET pancreatic cancer animal models,respectively.Results:Analysis of clinical data showed that pancreatic cancer patients with abnormal serum total cholesterol accounted for 15/76(19.7%),abnormal triglycerides accounted for26/76(34.2%),abnormal high density lipoprotein cholesterol accounted for 48/76(63.2%),abnormal low density lipoprotein cholesterol accounted for 16/76(21.1%),abnormal low density lipoprotein cholesterol accounted for 24/76(31.6%),abnormal apolipoprotein A1 accounted for 58/76(76.2%),and abnormal apolipoprotein B accounted for 27/76(35.5%).The results of immunohistochemistry and Western blot confirmed that the expression of DDIT4 in pancreatic cancer was lower than that in para-tumor tissues.Oil red O staining of clinical samples and animal models showed that the degree of fat infiltration in pancreatic cancer tissues was higher than that in control group and the degree of fat infiltration in DDIT4-HET animal models of pancreatic cancer was higher than that in wild-type pancreatic cancer group.Interestingly,the results of Western blot,immunofluorescence and immunohistochemistry showed that the expression of PPAR-γ and its downstream proteins CD36 and ATGL were significantly increased in DDIT4-HET animal models of pancreatic cancer.Finally,the results of immunohistochemistry and immunofluorescence demonstrated that the expression level of ki-67 was considerable increased and the expression level of caspase-3 was decreased in the DDIT4-HET animal models of pancreatic cancer.Conclusions:1.There was a relatively high proportion of abnormalities in the expression of lipid-related proteins in the serum of patients with pancreatic cancer.2.DDIT4 was less expressed in pancreatic cancer tissues and it was involved in lipid metabolism in pancreatic cancer tissues.3.DDIT4 regulates the lipid metabolism and invasion and metastasis of pancreatic cancer cells through PPAR-γ and its downstream proteins CD36 and ATGL.