(A) Amounts of brequinar, UMP, UDP, UTP and uridine in the LN229 xenografts measured by LC-MS/MS. (B) qPCR of 47S pre-rRNA and 28S and 18S rRNAs in the LN229 xenografts. 47S pre-rRNA, 28S and 18S levels were normalized by ACTIN mRNA levels. (C) Amounts of brequinar, UMP, UDP, UTP and uridine measured by LC-MS/MS in the brain tissues of mice used for xenografts. (D) qPCR of 47S pre-rRNA and 28S and 18S rRNAs in the brain tissues of the mice used for LN229 xenografts. 47S pre-rRNA, 28S and 18S levels were normalized by ACTIN mRNA levels. (E) Amounts of brequinar, UMP, UDP, UTP and uridine measured by LC-MS/MS in the liver tissues of mice used for xenografts. (F) Amounts of brequinar, UMP, and uridine measured by LC-MS/MS in the serum of mice used for xenografts. Last brequinar injection was 3 h before harvesting the tissues. Numerical values for each of the experiments represented are available in S4 Data.