RESUMO
Typical mantle cell lymphoma (MCL) is a distinct B-cell non-Hodgkin's lymphoma associated with over-expression of cyclin D1 related to translocation between the IgH and BCL-1 genes. Due to the important functional interaction between cyclin D1 and cyclin dependent kinases, cyclin dependent kinase inhibitors such as flavopiridol are under consideration for treatment of patients with MCL. The present study investigated the in vitro effects of flavopiridol on the MCL cell line (JeKo-1). Flavopiridol at a dose of 10nmol/L induced apoptosis by 6h of treatment as noted by flow cytometric analysis, morphologic examination and Western blotting. The cleavage of procaspase-3 and PARP and the decrease of flavopiridol-induced apoptosis by pan-caspase inhibition suggested that the caspase pathway serves an important role in the apoptotic process. Furthermore, MCL cells exposed to flavopiridol showed down regulation of key cell cycle proteins acting at the restriction point control between the G1 and S phases. The onset of flavopiridol-induced apoptosis also coincided with the down regulation of Mcl-1, anti-apoptotic protein. Collectively, our data indicates that flavopiridol may have significant therapeutic potential in the context of MCL.
Assuntos
Apoptose/efeitos dos fármacos , Proteínas de Ciclo Celular/metabolismo , Regulação para Baixo/efeitos dos fármacos , Flavonoides/farmacologia , Linfoma de Célula do Manto/tratamento farmacológico , Linfoma de Célula do Manto/metabolismo , Piperidinas/farmacologia , Caspase 3/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Ciclina D1/metabolismo , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Inibidor de Quinase Dependente de Ciclina p27/metabolismo , Humanos , Linfoma de Célula do Manto/patologia , Proteína de Sequência 1 de Leucemia de Células Mieloides , Proteínas de Neoplasias/metabolismo , Poli(ADP-Ribose) Polimerases/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteína do Retinoblastoma/metabolismo , Fatores de TempoRESUMO
Recent studies have suggested that protein kinase C (PKC) activation plays an important role in survival of chronic lymphocytic leukemia (CLL). In order to characterize the role of PKC in CLL, we investigated the expression pattern of PKC isoforms in CLL cells (7 cases) and evaluated the effect of PKC inhibition on the survival of CLL cells (20 cases). Expression of the classical PKC isoforms beta and gamma, the novel isoform delta and the atypical isoform zeta was seen in all analyzed patient samples by Western blot analysis. Expression of the PKC isoforms alpha, epsilon, and iota was variable. Following incubation with the PKC inhibitor, safingol, CLL cells underwent marked apoptosis in all cases. In order to characterize the molecular events associated with the apoptotic effect of PKC inhibition, gene expression patterns in CLL cells were evaluated by cDNA-microarray analysis. Following safingol treatment, several genes showed marked downregulation and PKC-related proteins demonstrated decreased hybridization signals. Among these proteins, CREB and Daxx were further studied by using Western blotting, nuclear binding assay and confocal immunofluorescent microscopy. These studies showed significant inhibition of these proteins, consistent with the results of microarray gene analysis. Overall, these findings suggest that PKC activation is important for CLL cell survival and that inhibitors of PKC may have a role in the treatment of patients with CLL.
