RESUMEN
Met tyrosine kinase, a receptor for a hepatocyte growth factor (HGF), plays a critical role in tumor growth, metastasis, and drug resistance. Mitochondria are highly dynamic and undergo fission and fusion to maintain a functional mitochondrial network. Dysregulated mitochondrial dynamics are responsible for the progression and metastasis of many cancers. Here, using structured illumination microscopy (SIM) and high spatial and temporal resolution live cell imaging, we identified mitochondrial trafficking of receptor tyrosine kinase Met. The contacts between activated Met kinase and mitochondria formed dramatically, and an intact HGF/Met axis was necessary for dysregulated mitochondrial fission and cancer cell movements. Mechanically, we found that Met directly phosphorylated outer mitochondrial membrane protein Fis1 at Tyr38 (Fis1 pY38). Fis1 pY38 promoted mitochondrial fission by recruiting the mitochondrial fission GTPase dynamin-related protein-1 (Drp1) to mitochondria. Fragmented mitochondria fueled actin filament remodeling and lamellipodia or invadopodia formation to facilitate cell metastasis in hepatocellular carcinoma (HCC) cells both in vitro and in vivo. These findings reveal a novel and noncanonical pathway of Met receptor tyrosine kinase in the regulation of mitochondrial activities, which may provide a therapeutic target for metastatic HCC.
Asunto(s)
Carcinoma Hepatocelular/metabolismo , Neoplasias Hepáticas/metabolismo , Proteínas de la Membrana/metabolismo , Mitocondrias Hepáticas/metabolismo , Dinámicas Mitocondriales , Proteínas Mitocondriales/metabolismo , Proteínas Proto-Oncogénicas c-met/metabolismo , Carcinoma Hepatocelular/genética , Células HeLa , Humanos , Neoplasias Hepáticas/genética , Proteínas de la Membrana/genética , Mitocondrias Hepáticas/genética , Proteínas Mitocondriales/genética , Fosforilación , Proteínas Proto-Oncogénicas c-met/genéticaRESUMEN
Polycomb repressor complex 1 (PRC1) is linked to the regulation of gene expression and histone ubiquitylation conformation, which contributes to carcinogenesis. However, the upstream regulators of PRC1 biogenesis machinery remain obscure. Here, we report that the polycomb group-related mammalian gene Mel18 is a target of the protein kinase AKT. AKT phosphorylates Mel18 at T334 to disrupt the interaction between Mel18 and other PRC1 members, leading to attenuated PRC1-dependent ubiquitylation of histone H2A at Lys119. As such, PRC1 target genes, many of which are known oncogenes, are derepressed upon T334-Mel18 phosphorylation, which promotes malignant behaviours, including cell proliferation, tumour formation, migration and invasion, bone and brain metastatic lesion formation. Notably, a positive correlation between AKT activity and pT334-Mel18 is observed, and prognostic models based on p-AKT and pT334-Mel18 that predicted overall survival and distant metastasis-free survival in breast cancer patients are established. These findings have implications for understanding the role of AKT and its associated proteins in chromatin ubiquitylation, and also indicate the AKT-Mel18-H2AK119ub axis as a novel prognostic biomarker and therapeutic target for cancer patients.
Asunto(s)
Neoplasias de la Mama/genética , Carcinogénesis/genética , Proteínas de Ciclo Celular/genética , Complejo Represivo Polycomb 1/genética , Proteínas Proto-Oncogénicas c-akt/genética , Adulto , Anciano , Neoplasias de la Mama/patología , Proliferación Celular , Cromatina , Femenino , Regulación Neoplásica de la Expresión Génica/genética , Histonas/genética , Humanos , Estimación de Kaplan-Meier , Persona de Mediana Edad , Metástasis de la Neoplasia , Supervivencia sin Progresión , Ubiquitinación/genéticaRESUMEN
Rationale: Advanced nasopharyngeal carcinoma (NPC) is an aggressive disease with no targeted therapies and poor outcomes. New innovative targets are urgently needed. KLF4 has been extensively studied in the context of tumors, and current data suggest that it can act as either a tissue-specific tumor-inhibiting or a tumor-promoting gene. Here, we found that KLF4 played as a tumor-promoting gene in NPC, and could be mediated by PLK1. Methods: Tissue immunohistochemistry (IHC) assay was performed to identify the role of KLF4 in NPC. Global gene expression experiments were performed to explore the molecular mechanisms underlying KLF4-dependent tumorigenesis. Small-molecule kinase inhibitor screening was performed to identify potential upstream kinases of KLF4. The pharmacologic activity of polo-like kinase inhibitor volasertib (BI6727) in vitro and in vivo was determined. Result: Our investigation showed that high expression of KLF4 was correlated with poor prognosis in NPC. Moreover, genome-wide profiling revealed that KLF4 directly activated oncogenic programmes, including gene sets associated with KRAS, VEGF, and MYC signalling. We further found that inhibition of polo-like kinase 1 could downregulate the expression of KLF4 and that PLK1 directly phosphorylated KLF4 at Ser234. Notably, phosphorylation of KLF4 by PLK1 caused the recruitment and binding of the E3 ligase TRAF6, which resulted in KLF4 K32 K63-linked ubiquitination and stabilization. Moreover, KLF4 could enhance TRAF6 expression at the transcriptional level, thus initiating a KLF4-TRAF6 feed-forward loop. Treatment with the PLK1 inhibitor volasertib (BI6727) significantly inhibited tumor growth in nude mice. Conclusion: Our study unveiled a new PLK1-TRAF6-KLF4 feed-forward loop. The resulting increase in KLF4 ubiquitination leads to stabilization and upregulation of KLF4, which leads to tumorigenesis in NPC. These results expand our understanding of the role of KLF4 in NPC and validate PLK1 inhibitors as potential therapeutic agents for NPC, especially cancer patients with KLF4 overexpression.