Newly identified c-KIT receptor tyrosine kinase ITD in childhood AML induces ligand-independent growth and is responsive to a synergistic effect of imatinib and rapamycin.
Activating mutations of c-KIT lead to ligand-independent growth. Internal tandem duplications (ITDs) of exon 11, which encodes the juxtamembrane domain (JMD), are constitutively activating mutations found in 7% of gastrointestinal stromal tumors (GISTs) but have not been described in childhood acute myeloid leukemia (AML). DNA and cDNA from 60 children with AML were screened by polymerase chain reaction (PCR) for mutations of the JMD. A complex ITD (kit cITD) involving exon 11 and exon 12 was identified with a relative frequency of 7% (4/60). The human kit cITDs were inserted into the murine c-Kit backbone and expressed in Ba/F3 cells. KIT cITD induced factorindependent growth and apoptosis resistance, and exhibited constitutive autophosphorylation. KIT cITD constitutively activated the PI3K/AKT pathway and phosphorylated STAT1, STAT3, STAT5, and SHP-2. Imatinib (IM) or rapamycin (Rap) led to complete inhibition of growth, with IC50 values at nanomolar levels. IM and Rap synergistically inhibited growth and surmounted KIT cITD-induced apoptosis resistance. IM but not LY294002 inhibited phosphorylation of STAT3 and STAT5, suggesting aberrant cross talk between PI3K- and STAT-activating pathways. The findings presented may have immediate therapeutic impact for a subgroup of childhood AML-expressing c-KIT mutations.
Corbacioglu
Selim
S
Department of Pediatrics, University of Ulm, Eythstr 24, D-89075 Ulm, Germany. selim.corbacioglu@uniklinik-ulm.de
Kilic
Mehtap
M
Westhoff
Mike-Andrew
MA
Reinhardt
Dirk
D
Fulda
Simone
S
Debatin
Klaus-Michael
KM
D000208:Acute Disease; D000293:Adolescent; D000818:Animals; D001549:Benzamides; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D002648:Child; D002675:Child, Preschool; D004273:DNA, Neoplasm / Q000235:genetics* / Q000502:physiology; D004357:Drug Synergism; D005260:Female; D006801:Humans; D000068877:Imatinib Mesylate; D007223:Infant; D007951:Leukemia, Myeloid / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D008297:Male; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology*; D020239:Receptor Cross-Talk; D050791:STAT Transcription Factors / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology*; D020080:Tandem Repeat Sequences; D014162:Transfection
D001549:Benzamides; D004273:DNA, Neoplasm; D010879:Piperazines; D011743:Pyrimidines; D050791:STAT Transcription Factors; D000068877:Imatinib Mesylate; D019869:Phosphatidylinositol 3-Kinases; D019009:Proto-Oncogene Proteins c-kit; D020123:Sirolimus