title: Ganetespib synergizes with cyclophosphamide to improve survival of mice with autochthonous tumors in a mutant p53-dependent manner.
abstract: The DNA-alkylating cytotoxic agent cyclophosphamide (CTX) is commonly used in the clinic to treat hematological malignancies like lymphomas and leukemias as well as solid tumors, but shows dose-dependent potentially life-threatening toxicities and can induce secondary malignancies. Thus, the clinical utility of CTX would be improved if a companion drug could be identified that allows lowering the CTX dose, while maintaining or even increasing its antineoplastic therapeutic efficacy. In mouse models, high-dose CTX (300 mg/kg) is effective in treating T-lymphomas, while low dose (defined here as 100 mg/kg) is ineffective. We previously showed that the HSP90 inhibitor ganetespib potently suppresses T-lymphoma initiation and progression and extends overall survival (OS) in hotspot knockin mice expressing the p53 gain-of-function mutants R175H and R248Q (mutp53) by 30-59%. Here we asked whether ganetespib could potentiate the effect of low-dose CTX (100 mg/kg) in the autochthonous T-lymphoma-bearing mutp53 R248Q mouse model. Indeed, combinatorial CTX/ganetespib synergistically suppresses growth of autochthonous T-lymphomas in R248Q (p53Q/-) but not p53-/- control mice by reducing mutp53 levels and triggering apoptosis. Combinatorial treatment extends progression-free (PFS) and OS in p53Q/- mice significantly longer than in p53-/- mice. Specifically, PFS of p53Q/- mice improves 8.9-fold over CTX alone versus 3.6-fold in p53-/- mice. Likewise, OS of R248Q/- mice improves 3.6-fold, but worsens in p53-/- mice (0.85-fold) over CTX alone. Moreover, half of the p53Q/- mice on combinatorial treatment lived over 60 days, and one animal reached 121 days. In contrast, p53Q/- mice on single-drug treatment and p53-/- mice on any treatment lived less than 24 days. In sum, ganetespib synergizes with a sub-effective dose of CTX in mutp53 T-lymphomas by suppressing tumor growth and extending survival. Our results provide a potential strategy to reduce the effective clinical dose of CTX in mutant p53-bearing malignancies and attenuate CTX toxicity.
authors.affiliation: Department of Pathology, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Evguenia M
authors.initials: EM
authors.lastname: Alexandrova
authors.affiliation: Department of Pathology, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Sulan
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Pathology, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Ute M
authors.initials: UM
authors.lastname: Moll
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003520:Cyclophosphamide / Q000494:pharmacology*; D004195:Disease Models, Animal; D004357:Drug Synergism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D008223:Lymphoma / Q000188:drug therapy* / Q000235:genetics; D051379:Mice; D014230:Triazoles / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D018841:HSP90 Heat-Shock Proteins; C533237:STA 9090; D014230:Triazoles; D016159:Tumor Suppressor Protein p53; D003520:Cyclophosphamide