Apolipoprotein C1 functions as a target of thyroid carcinoma and synergistic effects with promising candidate-cyclopamine.

There is an urgent need to identify novel therapeutic targets for papillary thyroid carcinoma (PTC). APOC1 (Apolipoprotein C1) has emerged as a candidate: it is overexpressed in several cancers and its high expression often associates with worse clinical outcomes. Using bioinformatic analysis of TCGA-THCA RNA-seq data, we found that APOC1 is highly expressed in PTC and that elevated APOC1 correlates with poorer patient prognosis and with signatures of immune-evasion. We validated these observations in PTC cell lines. Immunofluorescence, colony-formation assays, CCK-8 proliferation measurements, and flow-cytometry apoptosis analysis all indicate that APOC1 promotes proliferation, enhances colony survival, and confers resistance to apoptosis. To identify candidate therapeutics that target APOC1-related pathways, we queried the Connectivity Map using shared differentially expressed genes (DEGs) and nominated cyclopamine as the top small-molecule hit. Cyclopamine reduces PTC cell proliferation and induces apoptosis in vitro; APOC1 depletion further sensitizes cells to cyclopamine, producing greater inhibition of proliferation and increased cell death. Finally, cyclopamine suppresses tumor growth in a PTC mouse model. Together, these results implicate APOC1 as a driver of PTC progression and immune evasion and identify cyclopamine as a promising therapeutic that acts, at least in part, through APOC1-related signaling. Our study thus provides a rationale for targeting APOC1 as a novel treatment strategy for papillary thyroid carcinoma.