title: Screening for phenotype selective activity in multidrug resistant cells identifies a novel tubulin active agent insensitive to common forms of cancer drug resistance.
abstract: BACKGROUND
  Drug resistance is a common cause of treatment failure in cancer patients and encompasses a multitude of different mechanisms. The aim of the present study was to identify drugs effective on multidrug resistant cells.
  
  
  METHODS
  The RPMI 8226 myeloma cell line and its multidrug resistant subline 8226/Dox40 was screened for cytotoxicity in response to 3,000 chemically diverse compounds using a fluorometric cytotoxicity assay (FMCA). Follow-up profiling was subsequently performed using various cellular and biochemical assays.
  
  
  RESULTS
  One compound, designated VLX40, demonstrated a higher activity against 8226/Dox40 cells compared to its parental counterpart. VLX40 induced delayed cell death with apoptotic features. Mechanistic exploration was performed using gene expression analysis of drug exposed tumor cells to generate a drug-specific signature. Strong connections to tubulin inhibitors and microtubule cytoskeleton were retrieved. The mechanistic hypothesis of VLX40 acting as a tubulin inhibitor was confirmed by direct measurements of interaction with tubulin polymerization using a biochemical assay and supported by demonstration of G2/M cell cycle arrest. When tested against a broad panel of primary cultures of patient tumor cells (PCPTC) representing different forms of leukemia and solid tumors, VLX40 displayed high activity against both myeloid and lymphoid leukemias in contrast to the reference compound vincristine to which myeloid blast cells are often insensitive. Significant in vivo activity was confirmed in myeloid U-937 cells implanted subcutaneously in mice using the hollow fiber model.
  
  
  CONCLUSIONS
  The results indicate that VLX40 may be a useful prototype for development of novel tubulin active agents that are insensitive to common mechanisms of cancer drug resistance.
authors.affiliation: Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University, Uppsala, Sweden.
authors.forename: Mårten
authors.initials: M
authors.lastname: Fryknäs
authors.forename: Joachim
authors.initials: J
authors.lastname: Gullbo
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Linda
authors.initials: L
authors.lastname: Rickardson
authors.forename: Malin
authors.initials: M
authors.lastname: Jarvius
authors.forename: Malin
authors.initials: M
authors.lastname: Wickström
authors.forename: Saadia
authors.initials: S
authors.lastname: Hassan
authors.forename: Claes
authors.initials: C
authors.lastname: Andersson
authors.forename: Mats
authors.initials: M
authors.lastname: Gustafsson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Westman
authors.forename: Peter
authors.initials: P
authors.lastname: Nygren
authors.forename: Stig
authors.initials: S
authors.lastname: Linder
authors.forename: Rolf
authors.initials: R
authors.lastname: Larsson
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D005434:Flow Cytometry; D006912:Hydroxyquinolines / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D051379:Mice; D009369:Neoplasms; D020411:Oligonucleotide Array Sequence Analysis; D014404:Tubulin / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; D006912:Hydroxyquinolines; D014404:Tubulin; C584431:VLX40
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