Induction of apoptosis and down regulation of cell cycle proteins in mantle cell lymphoma by flavopiridol treatment

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 10 nmol/L induced apoptosis by 6 h 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.