title: Prospective identification of resistance mechanisms to HSP90 inhibition in KRAS mutant cancer cells.
abstract: Inhibition of the HSP90 chaperone results in depletion of many signaling proteins that drive tumorigenesis, such as downstream effectors of KRAS, the most commonly mutated human oncogene. As a consequence, several small-molecule HSP90 inhibitors are being evaluated in clinical trials as anticancer agents. To prospectively identify mechanisms through which HSP90-dependent cancer cells evade pharmacologic HSP90 blockade, we generated multiple mutant KRAS-driven cancer cell lines with acquired resistance to the purine-scaffold HSP90 inhibitor PU-H71. All cell lines retained dependence on HSP90 function, as evidenced by sensitivity to short hairpin RNA-mediated suppression of HSP90AA1 or HSP90AB1 (also called HSP90α and HSP90β, respectively), and exhibited two types of genomic alterations that interfere with the effects of PU-H71 on cell viability and proliferation: (i) a Y142N missense mutation in the ATP-binding domain of HSP90α that co-occurred with amplification of the HSP90AA1 locus, (ii) genomic amplification and overexpression of the ABCB1 gene encoding the MDR1 drug efflux pump. In support of a functional role for these alterations, exogenous expression of HSP90α Y142N conferred PU-H71 resistance to HSP90-dependent cells, and pharmacologic MDR1 inhibition with tariquidar or lowering ABCB1 expression restored sensitivity to PU-H71 in ABCB1-amplified cells. Finally, comparison with structurally distinct HSP90 inhibitors currently in clinical development revealed that PU-H71 resistance could be overcome, in part, by ganetespib (also known as STA9090) but not tanespimycin (also known as 17-AAG). Together, these data identify potential mechanisms of acquired resistance to small molecules targeting HSP90 that may warrant proactive screening for additional HSP90 inhibitors or rational combination therapies.
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Arefeh
authors.initials: A
authors.lastname: Rouhi
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Miller
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Grasedieck
authors.affiliation: Department of Translational Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Reinhart
authors.affiliation: Department of Translational Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Stolze
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Döhner
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Kuchenbauer
authors.affiliation: Department of Internal Medicine III, Ulm University, Ulm, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Bullinger
authors.affiliation: Department of Translational Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.|Section for Personalized Oncology, Heidelberg University Hospital, Heidelberg, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Fröhling
authors.affiliation: Department of Translational Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Scholl
mesh_terms: D000072283:A549 Cells; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D052117:Benzodioxoles / Q000494:pharmacology*; D016227:Benzoquinones / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005784:Gene Amplification; D020022:Genetic Predisposition to Disease; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D009154:Mutation; D020125:Mutation, Missense; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010641:Phenotype; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D011687:Purines / Q000494:pharmacology*; D034622:RNA Interference; D014162:Transfection; D014230:Triazoles / Q000494:pharmacology
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D000970:Antineoplastic Agents; D052117:Benzodioxoles; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; C112969:HSP90AA1 protein, human; C493165:HSP90AB1 protein, human; C117307:KRAS protein, human; D047029:Lactams, Macrocyclic; D011687:Purines; C533237:STA 9090; D014230:Triazoles; C526550:9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-; C112765:tanespimycin; D016283:Proto-Oncogene Proteins p21(ras)
keywords: HSP90 inhibition; MDR1; PU-H71; drug resistance; mutant KRAS