The phosphatidylethanolamine biosynthesis pathway provides a new target for cancer chemotherapy

•The phosphoethanolamine biosynthesis pathway was shown to be essential for early liver development. •Meclizine, an over the counter medication inhibits the rate limiting enzyme in the phosphoethanolamine biosynthesis pathway. •A glycolysis inhibitor reprograms cancer cell metabolism to render it susceptible to the cytotoxic effect of meclizine. •A combination of these drugs inhibited the growth of a human liver cancer cell line in vitro and in a xenograft model. •This drug combination was also highly active against acute myeloid leukemia cells. Background & Aims Since human induced pluripotent stem cells (iPSCs) develop into hepatic organoids through stages that resemble human embryonic liver development, they can be used to study developmental processes and disease pathology. Therefore, we examined the early stages of hepatic organoid formation to identify key pathways affecting early liver development. Methods Single-cell RNA-sequencing and metabolomic analysis was performed on developing organoid cultures at the iPSC, hepatoblast (day 9) and mature organoid stage. The importance of the phosphatidylethanolamine biosynthesis pathway to early liver development was examined in developing organoid cultures using iPSC with a CRISPR-mediated gene knockout and an over the counter medication (meclizine) that inhibits the rate-limiting enzyme in this pathway. Meclizine’s effect on the growth of a human hepatocarcinoma cell line in a xenotransplantation model and on the growth of acute myeloid leukemia cells in vitro was also examined. Results Transcriptomic and metabolomic analysis of organoid development indicated that the phosphatidylethanolamine biosynthesis pathway is essential for early liver development. Unexpectedly, early hepatoblasts were selectively sensitive to the cytotoxic effect of meclizine. We demonstrate that meclizine could be repurposed for use in a new synergistic combination therapy for primary liver cancer: a glycolysis inhibitor reprograms cancer cell metabolism to make it susceptible to the cytotoxic effect of meclizine. This combination inhibited the growth of a human liver carcinoma cell line in vitro and in a xenotransplantation model, without causing significant side effects. This drug combination was also highly active against acute myeloid leukemia cells. Conclusion Our data indicate that phosphatidylethanolamine biosynthesis is a targetable pathway for cancer; meclizine may have clinical efficacy as a repurposed anti-cancer drug when used as part of a new combination therapy. Lay summary The early stages of human liver development were modeled using human hepatic organoids. We identified a pathway that was essential for early liver development. Based upon this finding, a novel combination drug therapy was identified that could be used to treat primary liver cancer and possibly other types of cancer. Since human induced pluripotent stem cells (iPSCs) develop into hepatic organoids through stages that resemble human embryonic liver development, they can be used to study developmental processes and disease pathology. Therefore, we examined the early stages of hepatic organoid formation to identify key pathways affecting early liver development. Single-cell RNA-sequencing and metabolomic analysis was performed on developing organoid cultures at the iPSC, hepatoblast (day 9) and mature organoid stage. The importance of the phosphatidylethanolamine biosynthesis pathway to early liver development was examined in developing organoid cultures using iPSC with a CRISPR-mediated gene knockout and an over the counter medication (meclizine) that inhibits the rate-limiting enzyme in this pathway. Meclizine’s effect on the growth of a human hepatocarcinoma cell line in a xenotransplantation model and on the growth of acute myeloid leukemia cells in vitro was also examined. Transcriptomic and metabolomic analysis of organoid development indicated that the phosphatidylethanolamine biosynthesis pathway is essential for early liver development. Unexpectedly, early hepatoblasts were selectively sensitive to the cytotoxic effect of meclizine. We demonstrate that meclizine could be repurposed for use in a new synergistic combination therapy for primary liver cancer: a glycolysis inhibitor reprograms cancer cell metabolism to make it susceptible to the cytotoxic effect of meclizine. This combination inhibited the growth of a human liver carcinoma cell line in vitro and in a xenotransplantation model, without causing significant side effects. This drug combination was also highly active against acute myeloid leukemia cells. Our data indicate that phosphatidylethanolamine biosynthesis is a targetable pathway for cancer; meclizine may have clinical efficacy as a repurposed anti-cancer drug when used as part of a new combination therapy.