BackgroundGastric cancer (GC) is a malignancy with the worst prognosis that seriously threatens human health, especially in East Asia. Apolipoprotein C1 (apoc1) belongs to the apolipoprotein family. In addition,apoc1has been associated with various tumors. However, its role in GC remains unclear.MethodsFirstly, we quantified its expression in GC and adjacent tumor tissues, using The Cancer Genome Atlas (TCGA). Next, we assessed cell invasion and migration abilities. Finally, we revealed the role ofapoc1in the tumor microenvironment (TME), immune cell infiltration and drug sensitivity.ResultsFirstly, in TCGA database, it has been shown that elevated expression ofapoc1was identified in various cancers, including GC, then we found that high expression ofapoc1was significantly correlated with poor prognosis in GC. Histologically,apoc1expression is proportional to grade, cancer stage, and T stage. The experimental results showed thatapoc1promoted cell invasion and migration. Then GO, KEGG, and GSEA pathway analyses indicated thatapoc1may be involved in the WNT pathway and immune regulation. Furthermore, we found out the tumor-infiltrating immune cells related toapoc1in the tumor microenvironment (TME) using TIMER. Finally, we investigated the correlation betweenapoc1expression and drug sensitivity, PD-1 and CTLA-4 therapy.ConclusionsThese results suggest thatapoc1participates in the evolution of GC, and may represent a potential target for detection and immunotherapy in GC.