PCTK1 Regulates Polyamine Metabolism To Promote Development Of Pancreatic Ductal Adenocarcinoma By Positively Regulating Wnt/β-Catenin Signaling Pathway

Background:Pancreatic ductal adenocarcinoma(PDAC)is one of the most common gastrointestinal malignancies.PDAC is usually diagonized at late stage and prone to blood or lymph node metastasis,which leads to less than 5% of the 5-year survival rate.Thus,it is urgent to elucidate its pathogenesis,identify new therapeutic targets and develop effective small-molecule inhibitors for PDAC.Wnt/β-catenin signaling pathway plays an important role in the early initiation and progression of PDAC.Identification of important intervention targets in the Wnt/β-catenin signaling pathway may provide a new approach to the treatment of PDAC.Object:PCTK1 was screened as one of the novel Wnt/β-catenin signaling candidate kinases from our previous studies.In this study,we aim to identify and validate PCTK1 as an important kinase involved in the regulation of Wnt/β-catenin signaling,to explore the mechanism by which PCTK1 regulates Wnt/β-catenin signaling pathway and polyamine metabolism,therefore to provide potential targets for treatment of PDAC.Method: The bioinformatics method was used to mine the database and analyze the expression of PCTK1 in PDAC.The expression of PCTK1 in pancreatic cancer cells was analyzed by western blots.The effect of PCTK1 expression level on the growth,proliferation and invasion of pancreatic cancer cells was examined by colony forming,CCK8 assay,EdU assay,soft agar and Transwell assay.The effect of PCTK1 on the tumorigenicity of pancreatic cancer cells was tested in nude mice.The role of PCTK1 in pancreatic carcinogenesis and progression was studied by xegograft tumor model in nude mice,PDAC GEMMs and in simulating pathophysiological conditions related to pancreatic carcinogenesis.The interaction between PCTK1 and LRP6 was studied by immunoprecipitation and in vitro kinase activity assay to reveal the mechanism of PCTK1 regulating Wnt/β-catenin signaling pathway.The downstream genes of PCTK1 were screened by RNA-Seq,and the relationship between PCTK1,Wnt/β-catenin signaling pathway and downstream genes was analyzed by immunoprecipitation and ubiquitination assay.Result: In this study,PCTK1 was found to be up-regulated in pancreatic cancer,and its expression level was negatively correlated with prognosis.In vitro,overexpression of PCTK1 promotes proliferation,invasion and unanchored growth of pancreatic cancer cells.The xegograft tumor model in nude mice and PDAC GEMMs showed that PCTK1 promoted development of PDAC.Mechanistically,PCTK1 activated the Wnt/β-catenin signaling pathway through phosphorylating LRP6 at the serine 1490.Polyamine metabolism rate-limiting enzyme ODC1 is a downstream target gene of beta-catenin.The biological function of PCTK1 was shown to be highly dependent on polyamine metabolism.ODC1 inhibitors significantly inhibited unanchored growth of pancreatic cancer cells.Conclusion: This study suggests a novel role of PCTK1 in tumorigenesis of PDAC through regulating the Wnt/β-catenin signaling pathway.PCTK1 activates the Wnt/β-catenin signaling pathway through phosphorylation of LRP6.PCTK1-mediated Wnt signalling regulates polyamine anabolism,thus promoting pancreatic cancer cell growth,proliferation and invasion.Therefore,PCTK1 and ODC1 inhibitors may have potential therapeutic effects on pancreatic cancer.