IGF-1R inhibition induces schedule-dependent sensitization of human melanoma to temozolomide.
Prior studies implicate type 1 IGF receptor (IGF-1R) in mediating chemo-resistance. Here, we investigated whether IGF-1R influences response to temozolomide (TMZ), which generates DNA adducts that are removed by O6-methylguanine-DNA methyltransferase (MGMT), or persist causing replication-associated double-strand breaks (DSBs). Initial assessment in 10 melanoma cell lines revealed that TMZ resistance correlated with MGMT expression (r = 0.79, p = 0.009), and in MGMT-proficient cell lines, with phospho-IGF-1R (r = 0.81, p = 0.038), suggesting that TMZ resistance associates with IGF-1R activation. Next, effects of IGF-1R inhibitors (IGF-1Ri) AZ3801 and linsitinib (OSI-906) were tested on TMZ-sensitivity, cell cycle progression and DSB induction. IGF-1Ri sensitized BRAF wild-type and mutant melanoma cells to TMZ in vitro, an effect that was independent of MGMT. Cells harboring wild-type p53 were more sensitive to IGF-1Ri, and showed schedule-dependent chemo-sensitization that was most effective when IGF-1Ri followed TMZ. This sequence sensitized to clinically-achievable TMZ concentrations and enhanced TMZ-induced apoptosis. Simultaneous or prior IGF-1Ri caused less effective chemo-sensitization, associated with increased G1 population and reduced accumulation of TMZ-induced DSBs. Clinically relevant sequential (TMZ → IGF-1Ri) treatment was tested in mice bearing A375M (V600E BRAF, wild-type p53) melanoma xenografts, achieving peak plasma/tumor IGF-1Ri levels comparable to clinical Cmax, and inducing extensive intratumoral apoptosis. TMZ or IGF-1Ri caused minor inhibition of tumor growth (gradient reduction 13%, 25% respectively), while combination treatment caused supra-additive growth delay (72%) that was significantly different from control (p < 0.01), TMZ (p < 0.01) and IGF-1Ri (p < 0.05) groups. These data highlight the importance of scheduling when combining IGF-1Ri and other targeted agents with drugs that induce replication-associated DNA damage.
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Roger
R
Ramcharan
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Tamara
T
Aleksic
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Wilfride Petnga
WP
Kamdoum
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Shan
S
Gao
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Sophia X
SX
Pfister
Biomedical Services, John Radcliffe Hospital, Oxford, UK.
Jordan
J
Tanner
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Esther
E
Bridges
Department of Pathology, John Radcliffe Hospital, Oxford, UK.
Ruth
R
Asher
Cancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, Manchester, UK.
Amanda J
AJ
Watson
Cancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, Manchester, UK.
Geoffrey P
GP
Margison
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Mick
M
Woodcock
Computational Biology Research Group, Weatherall Institute of Molecular Medicine, Oxford, UK.
Emmanouela
E
Repapi
Department of Oncology, Old Road Campus Research Building, Oxford, UK.
Ji-Liang
JL
Li
Oxford Cancer Centre, Churchill Hospital, Oxford, UK.
Mark R
MR
Middleton
Department of Oncology, Old Road Campus Research Building, Oxford, UK.|Oxford Cancer Centre, Churchill Hospital, Oxford, UK.
Valentine M
VM
Macaulay
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D003606:Dacarbazine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D004334:Drug Administration Schedule; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology; D008545:Melanoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016019:Survival Analysis; D000077204:Temozolomide; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
C551528:3-(8-amino-1-(2-phenylquinolin-7-yl)imidazo(1,5-a)pyrazin-3-yl)-1-methylcyclobutanol; D007093:Imidazoles; D011719:Pyrazines; D016159:Tumor Suppressor Protein p53; D003606:Dacarbazine; D017526:Receptor, IGF Type 1; D048493:Proto-Oncogene Proteins B-raf; D000077204:Temozolomide
IGF-1R; apoptosis; chemo-sensitization; double strand break; temozolomide