Effect of vitamin K, KO, and warfarin on FIXgla-PC carboxylation and secretion. Carboxylated (■) and total () FIXgla-PC secreted from HEK293 cells under different culture conditions was measured by ELISA as described in “FIXgla-PC measurement in cell-culture medium using ELISA.” Control, complete medium (no added vitamin K); K, complete medium with 11μM vitamin K; KO, complete medium with 5μM KO; KO + W, complete medium with 5μM KO + 2μM warfarin