RESUMO
PURPOSE: Chronic lymphocytic leukemia (CLL) is currently incurable with standard chemotherapeutic agents, highlighting the need for novel therapies. Overcoming proliferative and cytoprotective signals generated within the microenvironment of lymphoid organs is essential for limiting CLL progression and ultimately developing a cure. EXPERIMENTAL DESIGN: We assessed the potency of cyclin-dependent kinase (CDK) inhibitor CR8, a roscovitine analog, to induce apoptosis in primary CLL from distinct prognostic subsets using flow cytometry-based assays. CLL cells were cultured in in vitro prosurvival and proproliferative conditions to mimic microenvironmental signals in the lymphoid organs, to elucidate the mechanism of action of CR8 in quiescent and proliferating CLL cells using flow cytometry, Western blotting, and quantitative real-time PCR. RESULTS: CR8 was 100-fold more potent at inducing apoptosis in primary CLL cells than roscovitine, both in isolated culture and stromal-coculture conditions. Importantly, CR8 induced apoptosis in CD40-ligated CLL cells and preferentially targeted actively proliferating cells within these cultures. CR8 treatment induced downregulation of the antiapoptotic proteins Mcl-1 and XIAP, through inhibition of RNA polymerase II, and inhibition of NF-κB signaling at the transcriptional level and through inhibition of the inhibitor of IκB kinase (IKK) complex, resulting in stabilization of IκBα expression. CONCLUSIONS: CR8 is a potent CDK inhibitor that subverts pivotal prosurvival and proproliferative signals present in the tumor microenvironment of CLL patient lymphoid organs. Our data support the clinical development of selective CDK inhibitors as novel therapies for CLL.
Assuntos
Antineoplásicos/farmacologia , Apoptose , Sobrevivência Celular/efeitos dos fármacos , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , NF-kappa B/metabolismo , Purinas/farmacologia , Piridinas/farmacologia , Adulto , Idoso , Ligante de CD40/fisiologia , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Proliferação de Células , Quinases Ciclina-Dependentes/antagonistas & inibidores , Quinases Ciclina-Dependentes/metabolismo , Avaliação Pré-Clínica de Medicamentos , Feminino , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , Interleucina-4/fisiologia , Masculino , Pessoa de Meia-Idade , Proteína de Sequência 1 de Leucemia de Células Mieloides , NF-kappa B/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Polimerase II/antagonistas & inibidores , Roscovitina , Transdução de Sinais/efeitos dos fármacos , Células Tumorais Cultivadas/efeitos dos fármacos , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/genética , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismoRESUMO
The dual specificity tyrosine-phosphorylation-regulated kinase DYRK1A possesses diverse roles in neuronal development and adult brain physiology, and increased activity has been linked to neurodegenerative diseases. Very few inhibitors of this kinase have been reported up to now. Screening of a library of > 900 plant and fungal extracts afforded 25 extracts with IC50s < 10 µg/mL against DYRK1A. To identify the active constituents, the extracts were submitted to a process integrating physicochemical data with biological information, referred to as HPLC-based activity profiling. Follow-up investigation of four extracts led to the targeted isolation of harmine (1, IC50 0.022 µM) from Peganum harmala, emodin (3, IC50 4.2 µM) from Cassia nigricans, kaempferol (4, IC50 0.91 µM) from Cuscuta chinensis, and 3,8-di-O-methylherbacetin (11, IC50 8.6 µM), 3,3',4'-tri-O-methylmyricetin (12, IC50 7.1 µM) and ombuin (15, IC50 1.7 µM) from Larrea tridentata as the active constituents. Active extracts and compounds were also tested on the closely related cdc2-like kinase CLK1. Finally, the selectivity profile of compounds was evaluated by including other members of the DYRKs and CLKs families. While the flavonoids and emodin did not show significant differences in the potency of their activities, harmine (1) was most active against DYRK1A, CLK1, and CLK4, and less potent against the other kinases, with selectivity ranging from 2- to 20-fold.