Onco-fetal reprogramming of endothelial cells drives immunosuppressive macrophages in Hepatocellular Carcinoma (Sharma et al)

Liver dysfunction is associated with diseases ranging from metabolic disorders to hepatocellular carcinomas (HCC). Here we employed single-cell RNA-sequencing to extensively characterise the cellular landscape of human liver, from development to disease. We analysed ~212,000 cells representing human fetal liver, HCC and mouse liver. Our analysis revealed a remarkable fetal-like reprogramming of the tumor microenvironment (TME). Specifically, the HCC ecosystem displayed features reminiscent of fetal development, including the re-emergence of fetal-associated endothelial cells (PLVAP+/VEGFR2+), and fetal-like (FOLR2+) tumor-associated macrophages (TAMs). In a cross-species comparative analysis, we discovered remarkable similarity of gene expression and regulatory networks between mouse embryonically-seeded, fetal-liver and FOLR2+ tumor macrophages. Spatial transcriptomics further corroborated a shared onco-fetal ecosystem between fetal-liver and HCC. Furthermore, gene regulatory analysis, spatial transcriptomics, and in vitro functional assays implicated VEGF and NOTCH signaling in maintaining onco-fetal ecosystem. Taken together, we report a shared immunosuppressive onco-fetal ecosystem between the human fetal-liver and HCC. Our results unravel a previously unexplored onco-fetal reprogramming of tumor ecosystem, provides a novel target for therapeutic interventions in HCC and also opens up avenues for identifying similar paradigms in other cancers and disease states.