PEAK1 Tumor Suppressor In Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumor(GIST)is the most common malignant tumor of gastrointestinal mesenchymal tissue.Mutations in the tyrosine kinase receptor platelet-derived growth factor receptor alpha(PDGFRA)gene and the KIT gene can trigger GIST.Approximately 85%of GIST is associated with abnormal KIT mutations and their constitutive activation,while 5-10%of GIST is associated with PDGFRA mutations and their constitutive activation.Imatinib targets KIT and PDGFRA and is currently the standard clinically specific drug for the treatment of GIST,but long-term use of imatinib may cause resistance in GIST patients.When the clinical use of imatinib fails,sunitinib and regorafenib are effective second-and third-line drugs for GIST treatment.PEAK1(pseudopodium-enriched atypical kinase 1)is an atypical tyrosine kinase associated with the actin cytoskeleton.At this stage,PEAK1 transmits a signal from the membrane receptor tyrosine kinase by interacting with SRC,SHC1,CRK,GRB2 or YAP1/TAZ to mediate the migration and proliferation of cancer cells.We analyzed 34 cases of clinical patient GIST tissue samples by 250K single nucleotide polymorphism,and found that the deletion of PEAK 1 in the 15q position of the low-risk,moderate-risk,high-risk and metastatic-lesion GIST increased significantly with the increase of risk,predicting that PEAK1 inactivation may play an important role in the occurrence of high-risk and metastatic GIST.Therefore,we hypothesized that PEAK1 functions as a tumor suppressor in the occurrence,development,and metastasis of GIST.This topic firstly detected the expression of PEAK1 in muLtiple GIST cells by western.PEAK1 expression was found to be absent in GIST882 and KIT-negative GIST882B,while other GIST cell lines including GIST430 normally expressed PEAK1.Then western detection of PEAK I expression in 16 GIST tumor samples revealed that PEAK1 was expressed normally in low-risk GIST,but expression was absent in GIST tumor samples with metastasis.We specuLated that the probability of PEAK1 expression loss increased with the increased malignancy of GIST.The western resuLts are consistent with our previous 250K SNP analysis of GIST patients.To further validate the tumor suppressor function of PEAK 1 in GIST cells,we overexpressed PEAK I in GIST882 by lentivirus-mediated knockdown of PEAK1 in GIST430.It was found that overexpression of PEAK1 inhibited the KIT/PI3K/AKT signaling pathway in GIST882 cells.Further MTT evaluation,cell clone formation and cell cycle analysis revealed that overexpression of PEAK1 significantly inhibited GIST882 growth,clone formation,and arrested GIST882 cell cycle in G1 phase;cell scratch and Matrigel invasion assay showed that overexpression of PEAK 1 inhibited GIST882 cells Migration and invasion.Contrary to the phenotype caused by GIST882 overexpressing PEAK1,MTT evaluation,cell clone formation and cycle analysis revealed that Lenti-shRNA knockdown of PEAK1 promoted proliferation and clonal formation of GIST430 cells,increased S phase in the cell cycle;cell scratches and invasion Experiments have shown that knocking down PEAK1 accelerates the migration and invasion of GIST430 cells.In summary,PEAK1 plays a role as a tumor suppressor in the development and malignant transformation of GIST.