Activating KRAS, NRAS, and BRAF mutants enhance proteasome capacity and reduce endoplasmic reticulum stress in multiple myeloma.
Proc Natl Acad Sci U S A
; 117(33): 20004-20014, 2020 08 18.
Article
en En
| MEDLINE
| ID: mdl-32747568
ABSTRACT
KRAS, NRAS, and BRAF mutations which activate p44/42 mitogen-activated protein kinase (MAPK) signaling are found in half of myeloma patients and contribute to proteasome inhibitor (PI) resistance, but the underlying mechanisms are not fully understood. We established myeloma cell lines expressing wild-type (WT), constitutively active (CA) (G12V/G13D/Q61H), or dominant-negative (DN) (S17N)-KRAS and -NRAS, or BRAF-V600E. Cells expressing CA mutants showed increased proteasome maturation protein (POMP) and nuclear factor (erythroid-derived 2)-like 2 (NRF2) expression. This correlated with an increase in catalytically active proteasome subunit ß (PSMB)-8, PSMB9, and PSMB10, which occurred in an ETS transcription factor-dependent manner. Proteasome chymotrypsin-like, trypsin-like, and caspase-like activities were increased, and this enhanced capacity reduced PI sensitivity, while DN-KRAS and DN-NRAS did the opposite. Pharmacologic RAF or MAPK kinase (MEK) inhibitors decreased proteasome activity, and sensitized myeloma cells to PIs. CA-KRAS, CA-NRAS, and CA-BRAF down-regulated expression of endoplasmic reticulum (ER) stress proteins, and reduced unfolded protein response activation, while DN mutations increased both. Finally, a bortezomib (BTZ)/MEK inhibitor combination showed enhanced activity in vivo specifically in CA-NRAS models. Taken together, the data support the hypothesis that activating MAPK pathway mutations enhance PI resistance by increasing proteasome capacity, and provide a rationale for targeting such patients with PI/RAF or PI/MEK inhibitor combinations. Moreover, they argue these mutations promote myeloma survival by reducing cellular stress, thereby distancing plasma cells from the apoptotic threshold, potentially explaining their high frequency in myeloma.
Palabras clave
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Proteínas Proto-Oncogénicas p21(ras)
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Complejo de la Endopetidasa Proteasomal
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Proteínas Proto-Oncogénicas B-raf
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Estrés del Retículo Endoplásmico
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GTP Fosfohidrolasas
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Proteínas de la Membrana
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Mieloma Múltiple
Tipo de estudio:
Prognostic_studies
Límite:
Humans
Idioma:
En
Año:
2020
Tipo del documento:
Article