Flavopiridol Induces Cell Cycle Arrest and p53-independent Apoptosis in Non-Small Cell Lung Cancer Cell Lines (original) (raw)
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Cancer research, 2002
Flavopiridol is a potent inhibitor of cyclin-dependent kinases (cdks). In a large proportion of solid tumor cell lines, the initial response to flavopiridol is cell cycle arrest. NCI-H661 non-small cell lung cancer cells are representative of a subset of more sensitive cell lines in which apoptosis is observed during the first 24 h of drug exposure. Analysis of the apoptotic population indicates that cells in S-phase are preferentially dying. In addition, cells are sensitized to flavopiridol following recruitment to S-phase, whether accomplished by synchronization or by treatment with noncytotoxic concentrations of chemotherapy agents that impose an S-phase delay. Combinations of gemcitabine or cisplatin, followed by flavopiridol at concentrations that correlate with cdk inhibition, produce sequence-dependent cytotoxic synergy. A survey of paired cell lines, including WI38 diploid fibroblasts or normal human bronchial epithelial cells, along with their SV40-transformed counterparts,...
Journal of Clinical Investigation, 1998
Flavopiridol (HMR 1275) has been identified recently as a novel antineoplastic agent in the primary screen conducted by the Developmental Therapeutics Program, National Cancer Institute. Flavopiridol inhibits most cyclin-dependent kinases (cdks) and displays unique anticancer properties. Here, we investigated whether this compound was effective against head and neck squamous cell carcinomas (HNSCC). Exposure of HNSCC cells to flavopiridol diminished cdc2 and cdk2 activity and potently inhibited cell proliferation (IC 50 43-83 nM), which was concomitant with the appearance of cells with a sub-G 1 DNA content. Moreover,
Early induction of apoptosis in hematopoietic cell lines after exposure to flavopiridol
Blood, 1998
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% (...
Molecular Cancer …, 2002
The results of a phase I clinical trial of the topoisomerase I (Topo I) poison CPT-11 followed by the cyclin-dependent kinase inhibitor flavopiridol in patients with advanced solid tumors indicate that patients whose tumors were wild-type, but not mutant, for p53 obtained the most clinical benefit from this combination therapy. We elected to elucidate the mechanistic basis for this effect in isogenic-paired HCT116 colon cancer cells that were either wild-type (+/+) or null (À/À) for p53. With the combination therapy of SN-38 (the active metabolite of CPT-11) followed by flavopiridol, the induction of apoptosis was 5-fold greater in the p53+/+ cells compared with the p53À/À cells. This sequential treatment induced phosphorylation of p53 at Ser 15 , which interacted with Rad51, a DNA repair protein involved in homologous recombination. Rad51 bound to p53-Ser 15 within the first 5 hours of combination therapy, and then was transcriptionally suppressed at 24 hours by flavopiridol only in p53+/+ cells. Microarray analysis also revealed suppression of Rad51 in a p53-dependent manner. Depletion of Rad51 by small interfering RNA (siRNA) sensitized both p53+/+ and p53À/À cells to SN-38-induced apoptosis with increase of ;H2AX, a marker of DNA damage. Conversely, overexpression of Rad51 rescued p53+/+ cells from SN!F-induced apoptosis. Because flavopiridol inhibits Cdk9, we found that inhibition of Cdk9 by DRB or by siRNA could recapitulate the flavopiridol effects, with suppression of Rad51 and induction of apoptosis only in p53+/+ cells. In conclusion, after DNA damage by Topo I poisons, flavopiridol targets homologous recombination through a p53-dependent down-regulation of Rad51, resulting in enhancement of apoptosis.
Molecular Cancer Therapeutics, 2002
Interactions between the cyclin-dependent kinase inhibitor flavopiridol (FP) and the histone deacetylase inhibitor sodium butyrate (SB) have been examined in human leukemia cells (U937) in relation to differentiation and apoptosis. Whereas 1 mM of SB or 100 nM of FP minimally induced apoptosis (4% and 10%, respectively) at 24 h, simultaneous exposure of U937 cells to these agents dramatically increased cell death (e.g., ϳ60%), reflected by both morphological and Annexin/propidium iodide-staining features, procaspase 3 activation, and poly(ADP-ribose) polymerase cleavage. Similar interactions were observed in human promyelocytic (HL-60), Blymphoblastic (Raji), and T-lymphoblastic (Jurkat) leukemia cells. Coadministration of FP opposed SB-mediated accumulation of cells in G 0 G 1 and differentiation, reflected by reduced CD11b expression, but instead dramatically increased procaspase-3, procaspase-8, Bid, and poly(ADP-ribose) polymerase cleavage, as well as mitochondrial damage (e.g., loss of mitochondrial membrane potential and cytochrome c release). FP also blocked SB-related p21 WAF1-CIP1 induction through a caspase-independent mechanism and triggered the caspase-mediated cleavage of p27 KIP1 and retinoblastoma protein. The latter event was accompanied by a marked reduction in retinoblastoma protein/E2F1 complex formation. However, FP did not modify the extent of SBassociated acetylation of histones H3 and H4. Treatment of cells with FP/SB also resulted in the caspase-mediated cleavage of Bcl-2 and caspaseindependent down-regulation of Mcl-1. Levels of cyclins A, D 1 , and E, and X-linked inhibitor of apoptosis also declined in SB/FP-treated cells. Finally, FP/SB coexposure potently induced apoptosis in two primary acute myelogenous leukemia samples. Together, these findings demonstrate that FP, when combined with SB, induces multiple perturbations in cell cycle and apoptosis regulatory proteins, which oppose leukemic cell differentiation but instead promote mitochondrial damage and apoptosis.
Flavopiridol (L86 8275; NSC 649890), a new kinase inhibitor for tumor therapy
International Journal of Oncology, 1996
Flavopiridol is a new synthetic flavone, structurally related to a natural alkaloid, originally purified from Dysoxylum binectariferum, a plant indigenous to India and used in Indian folk medicine. Flavopiridol was detected by a tandem screening system consisting in inhibition of the EGF-receptor Tyrosine Phosphokinase and cytotoxicity. As a cytostatic mechanism, however, Flavopiridol strongly inhibits the cyclin-dependent kinases (cdkl, cdk2, cdk4, cdk7), with the potential to cause inhibition of cell cycle progression in G, and G 2 by multiple mechanisms relatable to cdk inhibition. In certain cell types, Flavopiridol induces apoptosis. The antitumor activity of that compound on human xenograft tumors is similar to standard cytostatic drugs and superior to them at least in prostate carcinoma. The dose limiting toxicity is diarrhea. Compared with other flavonoids or other kinase inhibitors Flavopiridol can be regarded as unique as no other compound is yet known that as specifically and potently inhibits nearly all the main cyclin dependent kinases and by that mechanisms can arrest cell cycle progression in G, as well as in G 2 and no other specific kinase inhibitor is known, which after i.v. or oral application reduces the growth of subcutaneous or subrenal xenografts of human tumors of different types. Initial results of a phase I study at the National Cancer Institute (NCI), USA, (Investigational New Drug Application no. 46211) provided some clinical and laboratory evidence for antineoplastic effect at nontoxic doses (no grade IV toxicities encountered). Thus, Flavopiridol is clearly in need of further clinical evaluation of its tumor therapeutic potential. In this review the chemical profile, tumorpharmacology (in vitro activity,
Anticancer research
Flavopiridol is a semi-synthetic flavone analog of the alkaloid, rohitukine, a compound from an Indian tree, Dysoxylum binectariferum. It has been shown to inhibit cyclin-dependent kinases (CDKs), causing cell cycle arrest and growth inhibition. Flavopiridol is reported to have cytotoxic activity against a wide range of cancer cell lines and has demonstrated its efficacy in several clinical trials. Flavopiridol seems a well-suited potential new agent for the treatment of bladder cancer. We, therefore, evaluated whether flavopiridol inhibits growth and induces apoptosis in bladder cancer cells and additionally examined the toxicity and efficacy of this drug in vivo in a rat bladder cancer model. The in vitro experiments showed an IC20 of 50-100 nM in all cell lines tested. However, there was a difference in the response with regard to the grading of the tumor cells at higher doses. The IC50 was found to be 150-350 nM in the well-differentiated RT4 and RTI12 cell lines after treatment...
Cancer research, 2003
Transformed cells are selectively sensitized to apoptosis induced by the cyclin-dependent kinase inhibitor flavopiridol after their recruitment to S phase. During S phase, cyclin A-dependent kinase activity neutralizes E2F-1 allowing orderly S phase progression. Inhibition of cyclin A-dependent kinase by flavopiridol could cause inappropriately persistent E2F-1 activity during S phase traversal and exit. Transformed cells, with high baseline levels of E2F-1 activity, may be particularly sensitive to cyclin A-dependent kinase inhibition, as the residual level of E2F-1 activity that persists may be sufficient to induce apoptosis. Here, we demonstrate that flavopiridol treatment during S phase traversal results in persistent expression of E2F-1. The phosphorylation of E2F-1 is markedly diminished, whereas that of the retinoblastoma protein is minimally affected, so that E2F-1/DP-1 heterodimers remain bound to DNA. In addition, manipulation of E2F-1 levels leads to predictable outcomes ...
Cancer Research, 2008
The results of a phase I clinical trial of the topoisomerase I (Topo I) poison CPT-11 followed by the cyclin-dependent kinase inhibitor flavopiridol in patients with advanced solid tumors indicate that patients whose tumors were wild-type, but not mutant, for p53 obtained the most clinical benefit from this combination therapy. We elected to elucidate the mechanistic basis for this effect in isogenic-paired HCT116 colon cancer cells that were either wild-type (+/+) or null (À/À) for p53. With the combination therapy of SN-38 (the active metabolite of CPT-11) followed by flavopiridol, the induction of apoptosis was 5-fold greater in the p53+/+ cells compared with the p53À/À cells. This sequential treatment induced phosphorylation of p53 at Ser 15 , which interacted with Rad51, a DNA repair protein involved in homologous recombination. Rad51 bound to p53-Ser 15 within the first 5 hours of combination therapy, and then was transcriptionally suppressed at 24 hours by flavopiridol only in p53+/+ cells. Microarray analysis also revealed suppression of Rad51 in a p53-dependent manner. Depletion of Rad51 by small interfering RNA (siRNA) sensitized both p53+/+ and p53À/À cells to SN-38-induced apoptosis with increase of ;H2AX, a marker of DNA damage. Conversely, overexpression of Rad51 rescued p53+/+ cells from SN!F-induced apoptosis. Because flavopiridol inhibits Cdk9, we found that inhibition of Cdk9 by DRB or by siRNA could recapitulate the flavopiridol effects, with suppression of Rad51 and induction of apoptosis only in p53+/+ cells. In conclusion, after DNA damage by Topo I poisons, flavopiridol targets homologous recombination through a p53-dependent down-regulation of Rad51, resulting in enhancement of apoptosis. [Cancer Res 2008;68 :2312-20]