Early Induction of Apoptosis in Hematopoietic Cell Lines After Exposure to Flavopiridol

Abstract

Flavopiridol (NSC 649890; Behringwerke L86-8275, Marburg, Germany), is a potent inhibitor of cyclin dependent kinases (CDKs) 1, 2, and 4. It has potent antiproliferative effects in vitro and is active in tumor models in vivo. While surveying the effect of flavopiridol on cell cycle progression in different cell types, we discovered that hematopoietic cell lines, including SUDHL4, SUDHL6 (B-cell lines), Jurkat, and MOLT4 (T-cell lines), and HL60 (myeloid), displayed notable sensitivity to flavopiridol-induced apoptosis. For example, after 100 nmol/L for 12 hours, SUDHL4 cells displayed a similar degree of DNA fragmentation to that shown by the apoptosis-resistant PC3 prostate carcinoma cells only after 3,000 nmol/L for 48 hours. After exposure to 1,000 nmol/L flavopiridol for 12 hours, typical apoptotic morphology was observed in SUDHL4 cells, but not in PC3 prostate carcinoma cells despite comparable potency (SUDHL4:120 nmol/L; PC3: 203 nmol/L) in causing growth inhibition by 50% (IC50). Flavopiridol did not induce topoisomerase I or II cleavable complex activity. A relation of p53, bcl2, or bax protein levels to apoptosis in SUDHL4 was not appreciated. While flavopiridol caused cell cycle arrest with decline in CDK1 activity in PC3 cells, apoptosis of SUDHL4 cells occurred without evidence of cell cycle arrest. These results suggest that antiproliferative activity of flavopiridol (manifest by cell cycle arrest) may be separated in different cell types from a capacity to induce apoptosis. Cells from hematopoietic neoplasms appear in this limited sample to be very susceptible to flavopiridol-induced apoptosis and therefore clinical trials in hematopoietic neoplasms should be of high priority.

The cell cycle: a review of regulation, deregulation and therapeutic targets in cancer

“…Flavopiridol was first discovered as a potent growth inhibitor of several breast and lung cancer cell lines (Kaur et al 1992). Different studies have shown that flavopiridol has the potential to inhibit the proliferation of a broad range of different types of cell lines, human tumours, leukaemias and lymphomas (Drees et al 1997;Parker et al 1998). Several phase I and phase II clinical trials with different regimens have been completed.…”

Characterization of molecular and cellular functions of the cyclin‐dependent kinase CDK9 using a novel specific inhibitor

“…( Figure 2D), a modification that is an integral event in the induction of p53 by a diverse range of stimuli (Cox and Meek, 2010). Various cell lines, in particular of haematopoietic origin, show pronounced sensitivity to flavopiridol-and/or DRBinduced apoptosis (Konig et al, 1997;Parker et al, 1998;Te Poele et al, 1999). Due to its pro-apoptotic effects, flavopiridol is currently under investigation in phase II clinical trials as a therapeutic agent in acute myelogenous leukaemia (AML) (Karp et al, 2012).…”

Flavopiridol Pharmacogenetics: Clinical and Functional Evidence for the Role of SLCO1B1/OATP1B1 in Flavopiridol Disposition

“…Flavopiridol (Alvocidib, NSC 649890), is a serine/threonine kinase inhibitor that broadly targets cyclin-dependent kinases (CDKs), including the cyclin 9/cyclin T complex (pTEF-b), preventing activation of RNA polymerase II [1] – [2] . Flavopiridol initiates cell cycle arrest [3] , [4] and p53-independent apoptosis [5] – [6] through down-regulation of Mcl-1 and X-linked inactivator of apoptosis (XIAP) [7] , [8] [9] . These preclinical characteristics provided the rationale for clinical investigation of flavopiridol in chronic lymphocytic leukemia (CLL), as advanced CLL is commonly associated with elevated Mcl-1 and dysfunctional p53, rendering standard treatments such as alkylating agents, fludarabine and rituximab ineffective [10] .…”