Leukemia L1210Leukemia P388Leukemia Virus, MurineLeukemia, ExperimentalMoloney murine leukemia virusLeukemia L5178LeukemiaCell LineTrimetrexateTumor Cells, CulturedPteroylpolyglutamic AcidsHeLa CellsLeukemia, Myeloid, AcuteFolic Acid AntagonistsAKR murine leukemia virusCell Line, TumorFriend murine leukemia virusHL-60 CellsDrug ResistanceAbelson murine leukemia virusMethotrexateAntineoplastic AgentsCell DivisionCell SurvivalLeukemia, LymphoidLeukemia, MyeloidLeukemia, Lymphocytic, Chronic, B-CellBase SequenceMolecular Sequence DataRetroviridae InfectionsLeukemia, Myelogenous, Chronic, BCR-ABL PositiveDoxorubicinLeukemia, Monocytic, AcuteCell Line, TransformedK562 CellsRauscher VirusApoptosisGene Expression Regulation, LeukemicStructure-Activity RelationshipLeukemia, T-CellCell DifferentiationRNA, MessengerMice, Inbred AKRPrecursor Cell Lymphoblastic Leukemia-LymphomaLeukemia, Promyelocytic, AcuteRetroviridaeTransfectionLeukemia, Megakaryoblastic, AcuteLeukemia, B-CellXenotropic murine leukemia virus-related virusAmino Acid SequenceDrug Screening Assays, AntitumorMink Cell Focus-Inducing VirusesDNA, ViralNeoplasm Proteins