The eIF4F translation initiation complex plays a critical role in melanoma resistance to clinical BRAF and MEK inhibitors. In this study, we uncover a function of eIF4F in the negative regulation of the rat sarcoma (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling pathway. We demonstrate that eIF4F is essential for controlling ERK signaling intensity in treatment-naïve melanoma cells harboring BRAF or NRAS mutations. Specifically, the dual-specificity phosphatase DUSP6/MKP3, which acts as a negative feedback regulator of ERK activity, requires continuous production in an eIF4F-dependent manner to limit excessive ERK signaling driven by oncogenic RAF/RAS mutations. Treatment with small-molecule eIF4F inhibitors disrupts the negative feedback control of MAPK signaling, leading to ERK hyperactivation and EGR1 overexpression in melanoma cells in vitro and in vivo. Furthermore, our quantitative analyses reveal a high spare signaling capacity in the ERK pathway, suggesting that eIF4F-dependent feedback keeps the majority of ERK molecules inactive under normal conditions. Overall, our findings highlight the crucial role of eIF4F in regulating ERK signaling flux and suggest that pharmacological eIF4F inhibitors can disrupt the negative feedback control of MAPK activity in melanomas with BRAF and NRAS activating mutations.

• Klíčová slova
• DUSP6, ERK, MAP kinase, eIF4F, melanoma,
• MeSH
• eukaryotický iniciační faktor 4F * metabolismus   genetika   MeSH
• extracelulárním signálem regulované MAP kinasy metabolismus   MeSH
• fosfatasa 6 s dvojí specificitou metabolismus   genetika   MeSH
• GTP-fosfohydrolasy * metabolismus   genetika   MeSH
• lidé MeSH
• MAP kinasový signální systém * genetika   MeSH
• melanom * genetika   metabolismus   patologie   MeSH
• membránové proteiny * metabolismus   genetika   MeSH
• mutace * MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• protoonkogenní proteiny B-Raf * genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• BRAF protein, human MeSH Prohlížeč
• DUSP6 protein, human MeSH Prohlížeč
• EIF4E protein, human MeSH Prohlížeč
• eukaryotický iniciační faktor 4F * MeSH
• extracelulárním signálem regulované MAP kinasy MeSH
• fosfatasa 6 s dvojí specificitou MeSH
• GTP-fosfohydrolasy * MeSH
• membránové proteiny * MeSH
• NRAS protein, human MeSH Prohlížeč
• protoonkogenní proteiny B-Raf * MeSH

Inflammatory and oncogenic signaling, both known to challenge genome stability, are key drivers of BCR-ABL-positive chronic myeloid leukemia (CML) and JAK2 V617F-positive chronic myeloproliferative neoplasms (MPNs). Despite similarities in chronic inflammation and oncogene signaling, major differences in disease course exist. Although BCR-ABL has robust transformation potential, JAK2 V617F-positive polycythemia vera (PV) is characterized by a long and stable latent phase. These differences reflect increased genomic instability of BCR-ABL-positive CML, compared to genome-stable PV with rare cytogenetic abnormalities. Recent studies have implicated BCR-ABL in the development of a "mutator" phenotype fueled by high oxidative damage, deficiencies of DNA repair, and defective ATR-Chk1-dependent genome surveillance, providing a fertile ground for variants compromising the ATM-Chk2-p53 axis protecting chronic phase CML from blast crisis. Conversely, PV cells possess multiple JAK2 V617F-dependent protective mechanisms, which ameliorate replication stress, inflammation-mediated oxidative stress and stress-activated protein kinase signaling, all through up-regulation of RECQL5 helicase, reactive oxygen species buffering system, and DUSP1 actions. These attenuators of genome instability then protect myeloproliferative progenitors from DNA damage and create a barrier preventing cellular stress-associated myelofibrosis. Therefore, a better understanding of BCR-ABL and JAK2 V617F roles in the DNA damage response and disease pathophysiology can help to identify potential dependencies exploitable for therapeutic interventions.

• Klíčová slova
• ATM-Chk2 pathway, DNA damage response, chronic myeloid leukemia, polycythemia vera,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Inflammatory and oncogenic signaling converge in disease evolution of BCR-ABL-negative myeloproliferative neoplasms, clonal hematopoietic stem cell disorders characterized by gain-of-function mutation in JAK2 kinase (JAK2V617F), with highest prevalence in patients with polycythemia vera (PV). Despite the high risk, DNA-damaging inflammatory microenvironment, PV progenitors tend to preserve their genomic stability over decades until their progression to post-PV myelofibrosis/acute myeloid leukemia. Using induced pluripotent stem cells-derived CD34+ progenitor-enriched cultures from JAK2V617F+ PV patient and from JAK2 wild-type healthy control, CRISPR-modified HEL cells and patients' bone marrow sections from different disease stages, we demonstrate that JAK2V617F induces an intrinsic IFNγ- and NF-κB-associated inflammatory program, while suppressing inflammation-evoked DNA damage both in vitro and in vivo. We show that cells with JAK2V617F tightly regulate levels of inflammatory cytokines-induced reactive oxygen species, do not fully activate the ATM/p53/p21waf1 checkpoint and p38/JNK MAPK stress pathway signaling when exposed to inflammatory cytokines, suppress DNA single-strand break repair genes' expression yet overexpress the dual-specificity phosphatase (DUSP) 1. RNAi-mediated knock-down and pharmacological inhibition of DUSP1, involved in p38/JNK deactivation, in HEL cells reveals growth addiction to DUSP1, consistent with enhanced DNA damage response and apoptosis in DUSP1-inhibited parental JAK2V617F+ cells, but not in CRISPR-modified JAK2 wild-type cells. Our results indicate that the JAK2V617F+ PV progenitors utilize DUSP1 activity as a protection mechanism against DNA damage accumulation, promoting their proliferation and survival in the inflammatory microenvironment, identifying DUSP1 as a potential therapeutic target in PV.

• MeSH
• cytokiny genetika   metabolismus   MeSH
• fosfatasa 1 s dvojí specificitou genetika   MeSH
• hematopoetické kmenové buňky patologie   MeSH
• indukované pluripotentní kmenové buňky patologie   MeSH
• Janus kinasa 2 genetika   MeSH
• lidé MeSH
• mutace MeSH
• nádorové buněčné linie MeSH
• nádorové mikroprostředí MeSH
• oxidační stres * MeSH
• polycythaemia vera genetika   MeSH
• poškození DNA * MeSH
• proliferace buněk * MeSH
• reprodukovatelnost výsledků MeSH
• transkripční faktor STAT1 metabolismus   MeSH
• zánět metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokiny MeSH
• DUSP1 protein, human MeSH Prohlížeč
• fosfatasa 1 s dvojí specificitou MeSH
• JAK2 protein, human MeSH Prohlížeč
• Janus kinasa 2 MeSH
• STAT1 protein, human MeSH Prohlížeč
• transkripční faktor STAT1 MeSH