In addition, circPDE8A secreted by tumor cells can be released into the blood circulation through exosomes to regulate MACC1 as a miRNA-338 sponge and promote invasive metastasis through MET/mitogen-activated protein kinase 1 (mitogen activated protein kinase-1-MAPK1) or the protein kinase B pathway. Here, MAP4K1 is linked to neoplasm.