A novel tyrosine kinase switch is a mechanism of imatinib resistance in gastrointestinal stromal tumors.
KIT or alpha-platelet-derived growth factor receptor (alpha-PDGFR) activating mutations are the pathogenic mechanisms that characterize gastrointestinal stromal tumors (GIST). Despite excellent responses to imatinib mesylate (IM), patients are relapsing. We developed an IM-resistant GIST cell line (GIST-R) from the IM-sensitive GIST882 cell line (GIST-S) by growing these cells in IM. Gene expression profiling (GEP) of GIST-S, GIST-R cells and two IM resistant GIST patients demonstrated that KIT is downregulated implying a major role in IM resistance. Instead, GIST-R cells have acquired IM resistance by overexpressing the oncogenic receptor tyrosine kinase - AXL - in a 'kinase switch'. Further, the two IM resistant GIST patients express AXL and not c-Kit, seen by immunohistochemistry (IHC). Real time reverse transcriptase-polymerase chain reaction and Western blotting of the GIST-S and GIST-R cells confirmed the switch from Kit to AXL. In GIST-R, AXL is tyrosine phosphorylated and its ligand growth-arrest-specific gene 6 is overexpressed implying autocrine activation. The kinase switch is associated with a morphological change from spindle to epithelioid. Molecular modeling of the kinase domain of mutant c-Kit (V654A) and AXL showed no binding to IM but efficient binding to MP470, a novel c-Kit/AXL kinase inhibitor. MP470 synergizes with docetaxel (taxotere) and is cytotoxic to GIST cells.
Mahadevan
D
D
Arizona Cancer Center, Tucson, AZ 85724, USA. dmahadevan@azcc.arizona.edu
Cooke
L
L
Riley
C
C
Swart
R
R
Simons
B
B
Della Croce
K
K
Wisner
L
L
Iorio
M
M
Shakalya
K
K
Garewal
H
H
Nagle
R
R
Bearss
D
D
D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001549:Benzamides; D015153:Blotting, Western; D045744:Cell Line, Tumor; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004357:Drug Synergism; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000068877:Imatinib Mesylate; D008958:Models, Molecular; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D015513:Oncogene Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology* / Q000627:therapeutic use; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043823:Taxoids / Q000494:pharmacology; D013890:Thiourea; D000094963:Axl Receptor Tyrosine Kinase
D000970:Antineoplastic Agents; D001549:Benzamides; D015513:Oncogene Proteins; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D011993:Recombinant Fusion Proteins; D043823:Taxoids; D049452:Green Fluorescent Proteins; D000077143:Docetaxel; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases; D013890:Thiourea; C521047:amuvatinib; D000094963:Axl Receptor Tyrosine Kinase; C000722289:AXL protein, human