RESUMEN
Cushing's disease is a rare but devastating and difficult to manage condition. The somatostatin analogue pasireotide is the only pituitary-targeting pharmaceutical approved for the treatment of Cushing's disease but is accompanied by varying efficacy and potentially severe side effects. Finding means to predict which patients are more likely to benefit from this treatment may improve their management. More than half of corticotroph tumours harbour mutations in the USP8 gene, and there is evidence of higher somatostatin receptor 5 (SSTR5) expression in the USP8-mutant tumours. Pasireotide has a high affinity for SSTR5, indicating that these tumours may be more sensitive to treatment. To test this hypothesis, we examined the inhibitory action of pasireotide on adrenocorticotrophic hormone synthesis in primary cultures of human corticotroph tumour with assessed USP8 mutational status and in immortalized murine corticotroph tumour cells overexpressing human USP8 mutants frequent in Cushing's disease. Our in vitro results demonstrate that pasireotide exerts a higher antisecretory response in USP8-mutant corticotroph tumours. Overexpressing USP8 mutants in a murine corticotroph tumour cell model increased endogenous somatostatin receptor 5 (Sstr5) transcription. The murine Sstr5 promoter has two binding sites for the activating protein 1 (AP-1) and USP8 mutants possibly to mediate their action by stimulating AP-1 transcriptional activity. Our data corroborate the USP8 mutational status as a potential marker of pasireotide response and describe a potential mechanism through which USP8 mutants may regulate SSTR5 gene expression.
Asunto(s)
Neoplasias , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT) , Animales , Corticotrofos/metabolismo , Endopeptidasas/genética , Endopeptidasas/metabolismo , Complejos de Clasificación Endosomal Requeridos para el Transporte/genética , Humanos , Ratones , Neoplasias/metabolismo , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/tratamiento farmacológico , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/genética , Somatostatina/análogos & derivados , Somatostatina/farmacología , Factor de Transcripción AP-1/metabolismo , Factor de Transcripción AP-1/uso terapéutico , Ubiquitina Tiolesterasa/genética , Ubiquitina Tiolesterasa/metabolismoRESUMEN
Metastasis is a complex process by which cancer cells escape from the primary tumor to colonize distant organs. RAC1 is a member of the RHO family of small guanosine triphosphatases that plays an important role in cancer migration, invasion, angiogenesis and metastasis. RAC1 activation has been related to most cancers, such as cutaneous melanoma, breast, lung, and pancreatic cancer. RAC1P29S driver mutation appears in a significant number of cutaneous melanoma cases. Likewise, RAC1 is overexpressed or hyperactivated via signaling through oncogenic cell surface receptors. Thus, targeting RAC1 represents a promising strategy for cutaneous melanoma therapy, as well as for inhibition of other signaling activation that promotes resistance to targeted therapies. In this review, we focus on the role of RAC1 in metastatic cutaneous melanoma emphasizing the anti-metastatic potential of RAC1- targeting drugs.
Asunto(s)
Melanoma , Neoplasias Cutáneas , Línea Celular Tumoral , Movimiento Celular , Humanos , Transducción de Señal , Melanoma Cutáneo MalignoRESUMEN
RHO GTPases are key regulators of the cytoskeletal architecture, which impact a broad range of biological processes in malignant cells including motility, invasion, and metastasis, thereby affecting tumor progression. One of the constraints during cell migration is the diameter of the pores through which cells pass. In this respect, the size and shape of the nucleus pose a major limitation. Therefore, enhanced nuclear plasticity can promote cell migration. Nuclear morphology is determined in part through the cytoskeleton, which connects to the nucleoskeleton through the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Here, we unravel the role of RAC1 as an orchestrator of nuclear morphology in melanoma cells. We demonstrate that activated RAC1 promotes nuclear alterations through its effector PAK1 and the tubulin cytoskeleton, thereby enhancing migration and intravasation of melanoma cells. Disruption of the LINC complex prevented RAC1-induced nuclear alterations and the invasive properties of melanoma cells. Thus, RAC1 induces nuclear morphology alterations through microtubules and the LINC complex to promote an invasive phenotype in melanoma cells.
Asunto(s)
Núcleo Celular/metabolismo , Melanoma/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Animales , Línea Celular Tumoral , Movimiento Celular/genética , Forma del Núcleo Celular/fisiología , Embrión de Pollo , Citoesqueleto/metabolismo , Humanos , Proteínas de la Membrana/metabolismo , Microtúbulos/metabolismo , Invasividad Neoplásica/genética , Matriz Nuclear/metabolismo , Proteínas Nucleares/metabolismo , Quinasas p21 Activadas/metabolismo , Proteína de Unión al GTP rac1/fisiología , Proteínas de Unión al GTP rho/metabolismoRESUMEN
RAS GTPases are frequently mutated in human cancer. H- and NRAS isoforms are distributed over both plasma-membrane and endomembranes, including the Golgi complex, but how this organizational context contributes to cellular transformation is unknown. Here we show that RAS at the Golgi is selectively activated by apoptogenic stimuli and antagonizes cell survival by suppressing ERK activity through the induction of PTPRκ, which targets CRAF for dephosphorylation. Consistently, in contrast to what occurs at the plasma-membrane, RAS at the Golgi cannot induce melanoma in zebrafish. Inactivation of PTPRκ, which occurs frequently in human melanoma, often coincident with TP53 inactivation, accelerates RAS-ERK pathway-driven melanomagenesis in zebrafish. Likewise, tp53 disruption in zebrafish facilitates oncogenesis driven by RAS from the Golgi complex. Thus, RAS oncogenic potential is strictly dependent on its sublocalization, with Golgi complex-located RAS antagonizing tumor development.
Asunto(s)
Transformación Celular Neoplásica/patología , Aparato de Golgi/metabolismo , Melanoma/patología , Proteínas Tirosina Fosfatasas Clase 2 Similares a Receptores/metabolismo , Proteínas ras/metabolismo , Animales , Línea Celular Tumoral , Modelos Animales de Enfermedad , Técnicas de Silenciamiento del Gen , Humanos , Sistema de Señalización de MAP Quinasas/fisiología , Ratones , Células 3T3 NIH , ARN Interferente Pequeño/metabolismo , Proteínas Tirosina Fosfatasas Clase 2 Similares a Receptores/genética , Pez Cebra , Proteínas de Pez Cebra/metabolismoRESUMEN
OBJECTIVE: Almost half of the cases of Cushing's disease (CD) tumours carry recurrent activating somatic mutations in the ubiquitin-specific protease eight gene (USP8). The USP8 mutational status could predict remission in patients with CD, so our objective was to correlate the presence of somatic USP8 mutations with the rate of recurrence after transsphenoidal surgery (TSS) retrospectively. DESIGN: Biochemical, radiological and clinical data were retrospectively assessed in 48 patients. USP8 mutational status was determined from corticotroph tumour samples. Association between USP8 mutational status, remission and recurrence was investigated. PATIENTS: Patients with Cushing's disease from a single-centre cohort who underwent TSS between 1991 and 2012. MEASUREMENTS: Long-term remission and recurrence rate after TSS with at least 6 months follow-up. Biochemical, radiological and clinical data, including sex, age at diagnosis, tumour size and pre-operative hormonal levels. USP8 mutational status. RESULTS: Patients with USP8 mutant corticotroph tumours (18 of 48; 37%) were diagnosed significantly earlier (mean ± SD 46 ± 10 years vs 53 ± 11 years; P = 0.028) and presented with higher pre-operative 24-hour urinary-free cortisol levels (median IQR µg/24 hours 1174.0, 1184.5 vs 480.0, 405.3; P = 0.045). The incidence of recurrence in a 10-year follow-up was significantly higher in patients with USP8 mutant tumours after the initial remission (58% vs 18% P = 0.026). Recurrence appeared significantly earlier in these patients (months 70, 44-97 95% CI vs 102, 86-119 95% CI; P = 0.019). CONCLUSION: Recurrence appears to be more frequent and earlier after TSS in patients with USP8 mutant corticotroph tumours.
RESUMEN
Signals conveyed through the RAS-ERK pathway are essential for the determination of cell fate. It is well established that signal variability is achieved in the different microenvironments in which signals unfold. It is also known that signal duration is critical for decisions concerning cell commitment. However, it is unclear how RAS-ERK signals integrate time and space in order to elicit a given biological response. To investigate this, we used MCF-7 cells, in which EGF-induced transient ERK activation triggers proliferation, whereas sustained ERK activation in response to heregulin leads to adipocytic differentiation. We found that both proliferative and differentiating signals emanate exclusively from plasma membrane-disordered microdomains. Of interest, the EGF signal can be transformed into a differentiating stimulus by HRAS overexpression, which prolongs ERK activation, but only if HRAS localizes at disordered membrane. On the other hand, HRAS signals emanating from the Golgi complex induce apoptosis and can prevent heregulin-induced differentiation. Our results indicate that within the same cellular context, RAS can exert different, even antagonistic, effects, depending on its sublocalization. Thus cell destiny is defined by the ability of a stimulus to activate RAS at the appropriate sublocalization for an adequate period while avoiding switching on opposing RAS signals.
Asunto(s)
Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Sistema de Señalización de MAP Quinasas/fisiología , Proteínas ras/metabolismo , Apoptosis/fisiología , Diferenciación Celular/efectos de los fármacos , Factor de Crecimiento Epidérmico/metabolismo , Genes ras , Humanos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Células MCF-7/metabolismo , Glándulas Mamarias Humanas/metabolismo , Quinasas de Proteína Quinasa Activadas por Mitógenos , Neurregulina-1 , Proteínas Proto-Oncogénicas p21(ras)/metabolismo , Transducción de Señal/efectos de los fármacos , Análisis Espacio-TemporalRESUMEN
Nearly 50% of human malignancies exhibit unregulated RAS-ERK signaling; inhibiting it is a valid strategy for antineoplastic intervention. Upon activation, ERK dimerize, which is essential for ERK extranuclear, but not for nuclear, signaling. Here, we describe a small molecule inhibitor for ERK dimerization that, without affecting ERK phosphorylation, forestalls tumorigenesis driven by RAS-ERK pathway oncogenes. This compound is unaffected by resistance mechanisms that hamper classical RAS-ERK pathway inhibitors. Thus, ERK dimerization inhibitors provide the proof of principle for two understudied concepts in cancer therapy: (1) the blockade of sub-localization-specific sub-signals, rather than total signals, as a means of impeding oncogenic RAS-ERK signaling and (2) targeting regulatory protein-protein interactions, rather than catalytic activities, as an approach for producing effective antitumor agents.
Asunto(s)
Carcinogénesis/efectos de los fármacos , Proteína Quinasa 1 Activada por Mitógenos/antagonistas & inhibidores , Multimerización de Proteína/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Bibliotecas de Moléculas Pequeñas/farmacología , Proteínas ras/metabolismo , Animales , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Embrión de Pollo , Femenino , Células HEK293 , Humanos , Immunoblotting , Indoles/química , Indoles/metabolismo , Indoles/farmacología , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Desnudos , Ratones SCID , Proteína Quinasa 1 Activada por Mitógenos/química , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Modelos Moleculares , Estructura Molecular , Unión Proteica/efectos de los fármacos , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Estructura Terciaria de Proteína , Bibliotecas de Moléculas Pequeñas/química , Bibliotecas de Moléculas Pequeñas/metabolismo , Ensayos Antitumor por Modelo de Xenoinjerto/métodos , Pez CebraRESUMEN
Lysine methylation has been traditionally associated with histones and epigenetics. Recently, lysine methyltransferases and demethylases - which are involved in methylation of non-histone substrates - have been frequently found deregulated in human tumours. In this realm, a new discovery has unveiled the methyltransferase SMYD3 as an enhancer of Ras-driven cancer. SMYD3 is up-regulated in different types of tumours. SMYD3-mediated methylation of MAP3K2 increases mutant K-Ras-induced activation of ERK1/2. Methylation of MAP3K2 prevents it from binding to the phosphatase PP2A, thereby impeding the impact of this negative regulator on Ras-ERK1/2 signals, leading to the formation of lung and pancreatic adenocarcinomas. Furthermore, depletion of SMYD3 synergises with a MEK inhibitor, currently in clinical trials, to block Ras-driven pancreatic neoplasia. These results underscore the importance of lysine methylation in the regulation of signalling pathways relevant for tumourigenesis and endorse the development of drugs targeting unregulated lysine methylation as therapeutic agents in the struggle against cancer.