R1507, an anti-insulin-like growth factor-1 receptor (IGF-1R) antibody, and EWS/FLI-1 siRNA in Ewing's sarcoma: convergence at the IGF/IGFR/Akt axis.
A subset of patients with Ewing's sarcoma responds to anti-insulin-like growth factor-1 receptor (IGF-1R) antibodies. Mechanisms of sensitivity and resistance are unknown. We investigated whether an anti-IGF-1R antibody acts via a pathway that could also be suppressed by small interfering (si) RNA against the EWS/FLI-1 fusion protein, the hallmark of Ewing's sarcoma. The growth of two Ewing's sarcoma cell lines (TC-32 and TC-71) was inhibited by the fully human anti-IGF-1R antibody, R1507 (clonogenic and MTT assays). TC-32 and TC-71 cells express high levels of IGF-2, while RD-ES and A4573 Ewing's cell lines, which were less responsive to R1507 in our assays, express low or undetectable IGF-2, respectively. TC-71 cells also expressed high levels of IGF-1R, and R1507 decreased steady-state levels of this receptor by internalization/degradation, an effect which was associated with a decrease in p-IGF-1R, p-IRS-1, and p-Akt. EWS/FLI-1 siRNA also decreased p-Akt, due to its ability to increase IGF-BP3 levels and subsequently decrease IGF-1 and IGF-2 levels, thus inhibiting signaling through p-IGF-1R. This inhibition correlated with growth suppression and apoptosis. The attenuation of Akt activation was confirmed in TC-71 and HEK-293 (human embryonic kidney) cells by transfecting them with IGF-1R siRNA. We conclude that antibodies and siRNA to IGF-1R, as well as siRNA to EWS/FLI-1, act via intersecting IGF/IGF-1R signals that suppress a common point in this pathway, namely the phosphorylation of Akt.
Phase I Program, Department of Investigational Cancer Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America.
Helen J
HJ
Huang
Laura S
LS
Angelo
Jordi
J
Rodon
Michael
M
Sun
Klaus-Peter
KP
Kuenkele
Henrique A
HA
Parsons
Jonathan C
JC
Trent
Razelle
R
Kurzrock
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003114:Colony-Forming Units Assay; D015536:Down-Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011110:Polymorphism, Genetic; D017434:Protein Structure, Tertiary; D051789:Proto-Oncogene Protein c-fli-1 / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D034802:RNA-Binding Protein EWS / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000737:chemistry / Q000235:genetics; D015203:Reproducibility of Results; D012512:Sarcoma, Ewing / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013002:Somatomedins / Q000378:metabolism*; D014162:Transfection
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; C106031:EWS-FLI fusion protein; C515497:IGFBP3 protein, human; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034741:RNA, Small Interfering; D034802:RNA-Binding Protein EWS; D017527:Receptor, IGF Type 2; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt; C551399:teprotumumab