Human melanoma cells expressing V600E B-RAF are susceptible to IGF1R targeting by small interfering RNAs.
The type 1 insulin-like growth factor receptor (IGF1R) is overexpressed by malignant melanomas compared with benign naevi, and mediates proliferation, motility and protection from apoptosis. However, the utility of IGF1R targeting as anti-cancer therapy may be limited by activating mutations in downstream signaling intermediates. We previously showed that IGF1R knockdown blocked survival of prostate cancer cells in which Akt activation was deregulated by PTEN loss. The current study investigated effects of IGF1R targeting in cells harboring activating RAS-RAF mutations, found in 70-80% of human melanomas. We assembled a panel of eight human melanoma cell lines: two expressing wild-type (WT) B-RAF and N-RAS, two with activating N-RAS mutations and four harboring V600E B-RAF. We also generated isogenic cell populations overexpressing WT or V600E B-RAF. Cells expressing V600E B-RAF were relatively resistant to apoptosis. However, IGF1R gene silencing was capable of inducing significant inhibition of survival, enhancement of apoptosis, and approximately two-fold sensitization to cisplatin and temozolomide. These effects were independent of mutation status and were associated with reduced activation of Akt and also, unexpectedly, of ERKs. These results support development of IGF1R targeting as therapy for melanoma, regardless of the presence of activating mutations in the RAS-RAF pathway.
Yeh
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AH
IGF Group, Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
Bohula
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EA
Macaulay
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VM
D000970:Antineoplastic Agents / Q000627:therapeutic use; D002470:Cell Survival; D019008:Drug Resistance, Neoplasm; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D008544:Melanocytes / Q000378:metabolism; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D017526:Receptor, IGF Type 1; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D016283:Proto-Oncogene Proteins p21(ras)