It stimulates cell proliferation and prevents cell apoptosis.28 However, APOC1 protein was found to be downregulated in breast cancer patients.29APOC1P1 is the pseudogene of APOC1. Generally, the antisense transcripts produced from pseudogenes can hybridize to corresponding mRNAs, forming dsRNAs cleaved by Dicer to endogenous siRNAs.30 Our findings provide an explanation for low expression levels of APOC1 in breast cancer patients. This evidence concerns the gene APOC1 and breast cancer.