Abstract
(V600E)B-RAF mutation is found in 50% to 60% of melanomas, and the novel agents PLX4032/vemurafenib and GSK2118436 that inhibit the (V600E)B-RAF kinase achieve a remarkable clinical response rate. However, as might be expected, acquired clinical resistance to these agents arises in most melanoma patients. PLX4032/vemurafenib resistance that arises in vivo in tumor matched short-term cultures or in vitro in melanoma cell lines is not caused by acquisition of secondary mutations in (V600E)B-RAF but rather is caused by upregulating platelet-derived growth factor receptor β (PDGFRβ) or N-RAS which results in resistance or sensitivity to mitogen-activated protein (MAP)/extracellular signal-regulated (ERK; MEK) kinase inhibitors, respectively. In this study, we define a targeted combinatorial strategy to overcome PLX4032/vemurafenib resistance in melanoma cell lines or short-term culture where the resistance is driven by PDGFRβ upregulation, achieving synergistic growth inhibition and cytotoxicity. PDGFRβ-upregulated, PLX4032-resistant (PPRM) cell lines show dual phospho (p)-ERK and p-AKT upregulation, and their growth inhibitory responses to specific small molecule inhibitors correlated with p-ERK, p-AKT, and p-p70S6K levels. Coordinate inhibition of (V600E)B-RAF inhibition and the RTK-PI3K-AKT-mTORC axis led to functionally significant rebound signaling, illustrating a robust and dynamic network connectivity. Combined B-RAF, phosphoinositide 3-kinase (PI3K), and mTORC1/2 inhibition suppressed both immediate early and delayed compensatory signaling, resulting in a highly synergistic growth inhibitory response but less efficient cytotoxic response. In contrast, the combination of MEK1/2, PI3K, and mTORC1/2 inhibitors consistently triggered apoptosis in a highly efficient manner. Together, our findings offer a rational strategy to guide clinical testing in preidentified subsets of patients who relapse during treatment with (V600E)B-RAF inhibitors.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Antineoplastic Agents / pharmacology*
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Antineoplastic Agents / therapeutic use
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Apoptosis / drug effects
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Drug Resistance, Neoplasm / drug effects*
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Drug Resistance, Neoplasm / physiology
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Drug Screening Assays, Antitumor
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Drug Synergism
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Humans
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Imidazoles / pharmacology*
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Indoles / pharmacology*
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MAP Kinase Kinase Kinases / antagonists & inhibitors
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Mechanistic Target of Rapamycin Complex 1
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Melanoma / drug therapy
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Melanoma / pathology*
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Morpholines / pharmacology*
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Multiprotein Complexes
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Neoplasm Proteins / antagonists & inhibitors
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Neoplasm Proteins / physiology*
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Phosphatidylinositol 3-Kinases / physiology
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Phosphoinositide-3 Kinase Inhibitors
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Point Mutation
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Proteins / antagonists & inhibitors
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Proteins / physiology
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Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
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Proto-Oncogene Proteins B-raf / genetics
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Proto-Oncogene Proteins c-akt / antagonists & inhibitors
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Proto-Oncogene Proteins c-akt / physiology
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Quinolines / pharmacology*
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Receptor, Platelet-Derived Growth Factor beta / antagonists & inhibitors
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Receptor, Platelet-Derived Growth Factor beta / genetics
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Receptor, Platelet-Derived Growth Factor beta / physiology*
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Recombinant Fusion Proteins / physiology
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Spheroids, Cellular / drug effects
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Sulfonamides / pharmacology*
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TOR Serine-Threonine Kinases
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Transcription Factors / antagonists & inhibitors
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Transcription Factors / physiology
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Vemurafenib
Substances
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Antineoplastic Agents
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CRTC2 protein, human
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Imidazoles
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Indoles
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Morpholines
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Multiprotein Complexes
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Neoplasm Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Proteins
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Quinolines
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Recombinant Fusion Proteins
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Sulfonamides
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Transcription Factors
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Vemurafenib
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(5-(2,4-bis((3S)-3-methylmorpholin-4-yl)pyrido(2,3-d)pyrimidin-7-yl)-2-methoxyphenyl)methanol
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Receptor, Platelet-Derived Growth Factor beta
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AKT1 protein, human
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BRAF protein, human
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Mechanistic Target of Rapamycin Complex 1
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Proto-Oncogene Proteins B-raf
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Proto-Oncogene Proteins c-akt
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TOR Serine-Threonine Kinases
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MAP Kinase Kinase Kinases
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dactolisib