title: In search of a key.
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002478:Cells, Cultured; D006224:Cricetinae; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004338:Drug Combinations; D006801:Humans; D066298:In Vitro Techniques; D007938:Leukemia / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D007942:Leukemia, Experimental / Q000201:enzymology / Q000378:metabolism; D007962:Leukocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008727:Methotrexate / Q000627:therapeutic use*; D051379:Mice; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D013942:Thymine Nucleotides / Q000096:biosynthesis
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D004338:Drug Combinations; D013942:Thymine Nucleotides; D013762:Tetrahydrofolate Dehydrogenase; D013937:Thymidine Kinase; D013936:Thymidine; D008727:Methotrexate