Identification of Genes Associated with Liver Metastasis in Pancreatic Cancer Reveals PCSK6 as a Crucial Mediator

SIMPLE SUMMARY: Liver metastasis is the most frequent event of tumor progression in pancreatic cancer, and available therapeutics have achieved unsatisfactory outcomes. The underlying molecular mechanisms of liver metastasis in pancreatic cancer remain unclear and critical genes participating in this process will provide new therapeutic targets. We identified the liver-metastasis-related genes via bioinformatics analysis of the molecular profiling of liver metastatic lesions in pancreatic cancer. Using CRISPR/Cas9 technology, we investigated the biological functions and molecular mechanism of PCSK6 involved in pancreatic cancer. Our findings revealed that PCSK6 inactivation could suppress liver metastasis efficiently, and PCSK6 might serve as a novel molecular target for improving the therapeutic efficacy of liver metastasis in pancreatic cancer. ABSTRACT: Liver metastasis occurs frequently in patients with pancreatic cancer. We analyzed the molecular profiling in liver metastatic lesions aiming to uncover novel genes responsible for tumor progression. Bioinformatics analysis was applied to identify genes directing liver metastasis. CRISPR/Cas9 technology was used to knock out the candidate gene. Proliferation assays, colony formation assays, cell cycle analysis, migration assays, wound healing assays, Immunofluorescence analysis, and the tumor xenograft model of intrasplenic injection were adopted to evaluate the effects of PCSK6 inactivation on cell growth, migration and liver metastasis. GSEA and Western blot were used to investigate the corresponding signaling pathway. PCSK6 was one of the obtained liver-metastasis-related genes in pancreatic cancer. PCSK6 inactivation inhibited cell growth and cell migration, due to G0/G1 cell cycle arrest and the remodeling of cell–cell junctions or the cell skeleton, respectively. PCSK6 inactivation led to fewer counts and lower outgrowth rates of liver metastatic niches in vivo. The Raf-MEK1/2-ERK1/2 axis was repressed by PCSK6 inactivation. Accordingly, we found PCSK6 inactivation could inhibit cell growth, cell migration, and liver metastasis, and explored the role of the Raf-MEK1/2-ERK1/2 axis in PCSK6 inactivation. PCSK6-targeted therapy might represent a novel approach for combatting liver metastasis in pancreatic cancer.