Abstract | PURPOSE:
Papillary thyroid carcinomas are associated with nonoverlapping activating mutations of RET, NTRK, RAS and BRAF, which altogether are present in approximately 70% of cases. We postulated that compounds that inhibit a distal effector in the mitogen-activated protein kinase (MAPK) pathway would inhibit growth and tumorigenicity of human thyroid cancer cell lines with mutations of RET or BRAF. EXPERIMENTAL DESIGN AND RESULTS: We first examined the effects of AAL-881 and LBT-613, two inhibitors of RAF kinase activity, on RAF-MAPK/ extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK activation in thyroid PCCL3 cells after conditional induction of expression of H-RAS(G12V) or BRAF(V600E). Both compounds blocked RAS and RAF-dependent MEK and ERK phosphorylation. They also potently blocked MEK phosphorylation in human thyroid cancer cell lines with either RET/PTC1 (TPC1) or BRAF(V600E) (NPA, ARO, and FRO) mutations. Inhibition of ERK phosphorylation was transient in TPC1 and ARO cells, with recovery of ERK phosphorylation associated with concomitant down-regulation of the MAPK phosphatases MKP-3 and DUSP5. Both compounds inhibited growth of all cell lines, with LBT-613 being approximately 10-fold more potent than AAL-881. TPC1 cells were more sensitive to growth inhibition (IC50 0.1-0.25 and approximately 0.05 micromol/L for AAL-881 and LBT-613, respectively) than BRAF + lines (IC50 2.5-5 and 0.1-0.5 micromol/L, respectively). Growth inhibition was associated with G1 arrest, and induction of cell death. Growth of ARO and NPA tumor xenografts was inhibited by LBT-613 or AAL-881. MEK and ERK phosphorylation was inhibited by both compounds in ARO but not in NPA cell xenografts. CONCLUSIONS:
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Authors | Bin Ouyang, Jeffrey A Knauf, Eric P Smith, Lei Zhang, Tim Ramsey, Naeem Yusuff, David Batt, James A Fagin |
Journal | Clinical cancer research : an official journal of the American Association for Cancer Research
(Clin Cancer Res)
Vol. 12
Issue 6
Pg. 1785-93
(Mar 15 2006)
ISSN: 1078-0432 [Print] United States |
PMID | 16551863
(Publication Type: Journal Article, Research Support, N.I.H., Extramural)
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Chemical References |
- AAL 881
- Isoquinolines
- LBT 613
- Protein Kinase Inhibitors
- RNA, Messenger
- Proto-Oncogene Proteins c-ret
- RET protein, human
- BRAF protein, human
- Proto-Oncogene Proteins B-raf
- raf Kinases
- DUSP5 protein, human
- DUSP6 protein, human
- Dual Specificity Phosphatase 6
- Dual-Specificity Phosphatases
- Dusp6 protein, mouse
- Protein Tyrosine Phosphatases
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Topics |
- Animals
- Blotting, Western
- Cell Cycle
(drug effects)
- Cell Line, Tumor
- Cell Proliferation
(drug effects)
- Dual Specificity Phosphatase 6
- Dual-Specificity Phosphatases
- Enzyme Activation
(drug effects)
- Female
- Humans
- Isoquinolines
(pharmacology)
- Mice
- Mice, Nude
- Mutation
(genetics)
- Phosphorylation
(drug effects)
- Protein Kinase Inhibitors
(pharmacology)
- Protein Tyrosine Phosphatases
(genetics, metabolism)
- Proto-Oncogene Proteins B-raf
(genetics, metabolism)
- Proto-Oncogene Proteins c-ret
(genetics, metabolism)
- RNA, Messenger
(genetics, metabolism)
- Reverse Transcriptase Polymerase Chain Reaction
- Thyroid Neoplasms
(genetics, pathology, prevention & control)
- Xenograft Model Antitumor Assays
- raf Kinases
(antagonists & inhibitors, metabolism)
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