RESUMEN
BET inhibitors (BETi), which target transcription of key oncogenic genes, are currently being evaluated in early-phase clinical trials. However, because BETis show limited single-agent activity, there is increasing interest in identifying signaling pathways to enhance the efficacy of BETis. Here, we demonstrate increased MNK kinase-dependent eIF4E phosphorylation following treatment with BETis, indicating activation of a prosurvival feedback mechanism in response to BETis. BET PROTACs, which promote degradation of BET proteins, also induced eIF4E phosphorylation in cancer cells. Mechanistically, we show that the effect of BETis on MNK-eIF4E phosphorylation was mediated by p38 MAPKs. We also show that BETis suppressed RacGAP1 to induce Rac signaling-mediated eIF4E phosphorylation. Significantly, MNK inhibitors and MNK1/2 knockdown enhanced the efficacy of BETis in suppressing proliferation of cancer cells in vitro and in a syngeneic mouse model. Together, these results demonstrate a novel prosurvival feedback signaling induced by BETis, providing a mechanistic rationale for combination therapy with BET and MNK inhibitors for synergistic inhibition of cancer cells.
Asunto(s)
Acetanilidas/administración & dosificación , Compuestos de Anilina/administración & dosificación , Azepinas/administración & dosificación , Factor 4E Eucariótico de Iniciación/metabolismo , Compuestos Heterocíclicos con 3 Anillos/administración & dosificación , Proteínas Serina-Treonina Quinasas/metabolismo , Purinas/administración & dosificación , Neoplasias de la Tiroides/tratamiento farmacológico , Triazoles/administración & dosificación , Acetanilidas/farmacología , Compuestos de Anilina/farmacología , Animales , Azepinas/farmacología , Técnicas de Cultivo de Célula , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Sinergismo Farmacológico , Factor 4E Eucariótico de Iniciación/antagonistas & inhibidores , Compuestos Heterocíclicos con 3 Anillos/farmacología , Humanos , Ratones , Fosforilación/efectos de los fármacos , Purinas/farmacología , Transducción de Señal , Neoplasias de la Tiroides/metabolismo , Triazoles/farmacología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The fibrotic reaction is a characteristic feature of human pancreatic ductal adenocarcinoma (PDAC) tumors. It is associated with activation and proliferation of pancreatic stellate cells (PSCs), which are key regulators of fibrosis in vivo. While there is increasing interest in the regulation of PD-L1 expression in cancer and immune cells, the expression and regulation of PD-L1 in other stromal cells, such as PSCs, has not been fully evaluated. Here we show that PSCs in vitro express higher PD-L1 mRNA and protein levels compared to the levels present in PDAC cells. We show that inhibitors targeting bromodomain and extra-terminal (BET) proteins and BRD4 knockdown decrease interferon-γ (IFN-γ)-induced PD-L1 expression in PSCs. We also show that c-MYC, one of the well-established targets of BET inhibitors, does not mediate IFN-γ-regulated PD-L1 expression in PSCs. Instead we show that interferon regulatory factor 1 (IRF1) mediates IFN-γ-induced PD-L1 expression in PSCs. Finally, while we show that BET inhibitors do not regulate IFN-γ-induced IRF1 expression in PSCs, BET inhibitors decrease binding of IRF1 and BRD4 to the PD-L1 promoter. Together, these results demonstrate the interplay between IRF1 and BRD4 in the regulation of PD-L1 in PSCs.
Asunto(s)
Antígeno B7-H1/metabolismo , Carcinoma Ductal Pancreático/metabolismo , Factor 1 Regulador del Interferón/metabolismo , Proteínas Nucleares/metabolismo , Neoplasias Pancreáticas/metabolismo , Células Estrelladas Pancreáticas/metabolismo , Factores de Transcripción/metabolismo , Antígeno B7-H1/genética , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/patología , Proteínas de Ciclo Celular , Línea Celular Tumoral , Regulación Neoplásica de la Expresión Génica , Humanos , Factor 1 Regulador del Interferón/genética , Proteínas Nucleares/genética , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patología , Células Estrelladas Pancreáticas/patología , Factores de Transcripción/genética , Neoplasias PancreáticasRESUMEN
The fibrotic reaction, which can account for over 70%-80% of the tumor mass, is a characteristic feature of human pancreatic ductal adenocarcinoma (PDAC) tumors. It is associated with activation and proliferation of pancreatic stellate cells (PSCs), which are key regulators of collagen I production and fibrosis in vivo. In this report, we show that members of the bromodomain and extraterminal (BET) family of proteins are expressed in primary PSCs isolated from human PDAC tumors, with BRD4 positively regulating, and BRD2 and BRD3 negatively regulating, collagen I expression in primary cancer-associated PSCs. We show that the inhibitory effect of pan-BET inhibitors on collagen I expression in primary cancer-associated PSCs is through blocking of BRD4 function. Importantly, we show that FOSL1 is repressed by BRD4 in primary cancer-associated PSCs and negatively regulates collagen I expression. While BET inhibitors do not affect viability or induce PSC apoptosis or senescence, BET inhibitors induce primary cancer-associated PSCs to become quiescent. Finally, we show that BET inhibitors attenuate stellate cell activation, fibrosis, and collagen I production in the EL-KrasG12D transgenic mouse model of pancreatic tumorigenesis. Our results demonstrate that BET inhibitors regulate fibrosis by modulating the activation and function of cancer-associated PSCs.
Asunto(s)
Azepinas/administración & dosificación , Carcinoma Ductal Pancreático/tratamiento farmacológico , Colágeno Tipo I/metabolismo , Compuestos Heterocíclicos de 4 o más Anillos/administración & dosificación , Proteínas Nucleares/metabolismo , Neoplasias Pancreáticas/tratamiento farmacológico , Células Estrelladas Pancreáticas/efectos de los fármacos , Factores de Transcripción/metabolismo , Triazoles/administración & dosificación , Animales , Azepinas/farmacología , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/metabolismo , Proteínas de Ciclo Celular , Línea Celular Tumoral , Colágeno Tipo I/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Compuestos Heterocíclicos de 4 o más Anillos/farmacología , Humanos , Ratones , Proteínas Nucleares/antagonistas & inhibidores , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/metabolismo , Células Estrelladas Pancreáticas/citología , Células Estrelladas Pancreáticas/metabolismo , Células Estrelladas Pancreáticas/patología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-fos/metabolismo , Proteínas Proto-Oncogénicas p21(ras)/genética , Proteínas de Unión al ARN/antagonistas & inhibidores , Proteínas de Unión al ARN/metabolismo , Factores de Transcripción/antagonistas & inhibidores , Triazoles/farmacología , Ensayos Antitumor por Modelo de Xenoinjerto , Neoplasias PancreáticasRESUMEN
Cells in the pancreas that have undergone acinar-ductal metaplasia (ADM) can transform into premalignant cells that can eventually become cancerous. Although the epithelial-mesenchymal transition regulator Snail (Snai1) can cooperate with Kras in acinar cells to enhance ADM development, the contribution of Snail-related protein Slug (Snai2) to ADM development is not known. Thus, transgenic mice expressing Slug and Kras in acinar cells were generated. Surprisingly, Slug attenuated Kras-induced ADM development, ERK1/2 phosphorylation and proliferation. Co-expression of Slug with Kras also attenuated chronic pancreatitis-induced changes in ADM development and fibrosis. In addition, Slug attenuated TGF-α-induced acinar cell metaplasia to ductal structures and TGF-α-induced expression of ductal markers in ex vivo acinar explant cultures. Significantly, blocking the Rho-associated protein kinase ROCK1/2 in the ex vivo cultures induced expression of ductal markers and reversed the effects of Slug by inducing ductal structures. In addition, blocking ROCK1/2 activity in Slug-expressing Kras mice reversed the inhibitory effects of Slug on ADM, ERK1/2 phosphorylation, proliferation and fibrosis. Overall, these results increase our understanding of the role of Slug in ADM, an early event that can eventually lead to pancreatic cancer development.
Asunto(s)
Metaplasia/genética , Neoplasias Pancreáticas/genética , Proteínas Proto-Oncogénicas p21(ras)/genética , Factores de Transcripción de la Familia Snail/genética , Células Acinares/patología , Animales , Transformación Celular Neoplásica/genética , Modelos Animales de Enfermedad , Transición Epitelial-Mesenquimal/genética , Humanos , Metaplasia/patología , Ratones , Ratones Transgénicos , Conductos Pancreáticos/metabolismo , Conductos Pancreáticos/patología , Neoplasias Pancreáticas/patología , Pancreatitis Crónica/genética , Pancreatitis Crónica/patología , Transducción de Señal/genéticaRESUMEN
The study of pancreatic cancer has prompted the development of numerous mouse models that aim to recapitulate the phenotypic and mechanistic features of this deadly malignancy. This review accomplishes two tasks. First, it provides an overview of the models that have been used as representations of both the neoplastic and carcinoma phenotypes. Second, it presents new modeling schemes that ultimately will serve to more faithfully capture the temporal and spatial progression of the human disease, providing platforms for improved understanding of the role of non-epithelial compartments in disease etiology as well as evaluating therapeutic approaches.