PCSK9 and gastric cancer: To conclude, we validated in our study that PCSK9 could function as a deleterious biomarker in GC; that high PCSK9 expression levels in GC tissue could be correlated with GC progression and prognosis; and that PCSK9 could promote GC metastasis and suppress apoptosis via facilitating MAPK signaling pathway through HSP70 up-regulation.