Timed sequential therapy of acute leukemia with flavopiridol: in vitro model for a phase I clinical trial.
OBJECTIVE
The survival of adults with acute leukemias remains unsatisfactory and requires new treatment approaches. Flavopiridol modulates cell cycle progression, inhibits transcription, and induces apoptosis. We designed an in vitro model of timed sequential therapy for acute leukemia to determine whether flavopiridol can: (a). trigger apoptosis in fresh acute leukemia; and (b). recruit surviving leukemic cells to a proliferative state, thereby priming such cells for the S-phase-related cytotoxicity of 1-beta-D-arabinofuranosylcytosine (ara-C).


METHODS
Bone marrow cells from 20 adults with relapsed and refractory acute leukemias were enriched for blasts by Ficoll Hypaque sedimentation. Blasts were cultured on day 0 in flavopiridol 250 nM for 24 h, removed from flavopiridol for 24 h, and then cultured in ara-C 1 microM for an additional 72 h (F(250)A(1)). Apoptosis and cell cycle phase distribution were estimated from cells stained with propidium iodide. Cell survival was determined after the 72 h ara-C exposure by double cytofluorescence assay with fluorescein diacetate and propidium iodide.


RESULTS
Flavopiridol induced a 4.3-fold increase in apoptosis in human leukemia samples within the first 24 h of culture. Subsequent removal of flavopiridol led to a 1.7-fold increase in the proportion of cells in S phase by day 2. Mean survival in F(250)A(1) cultures after 72 h exposure to ara-C was 35.6% compared with flavopiridol alone (F(250)A(0), 56.1%; P = 0.0003) and ara-C alone (F(0)A(1), 65.2%; P < 0.00001).


CONCLUSIONS
Flavopiridol induces apoptosis in marrow blasts from patients with refractory acute leukemias. Furthermore, flavopiridol pretreatment increases the proapoptotic and cytotoxic effects of ara-C. The advantage of sequential FP(250)A(1) over either agent alone is seen for both acute myelogenous leukemia and acute lymphoblastic leukemia. These findings support a clinical trial of timed sequential therapy where flavopiridol is given for cytoreduction and subsequent priming of remaining leukemic cells for enhanced cycle-dependent drug cytotoxicity.
Karp
Judith E
JE
University of Maryland Greenebaum Cancer Center, Baltimore, Maryland 2120, USA. jkarp2@jhmi.edu
Ross
Douglas D
DD
Yang
Weidong
W
Tidwell
Michael L
ML
Wei
Yuetong
Y
Greer
Jacqueline
J
Mann
Dean L
DL
Nakanishi
Takeo
T
Wright
John J
JJ
Colevas
A Dmitri
AD
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001854:Bone Marrow Cells / Q000378:metabolism; D002455:Cell Division; D002470:Cell Survival; D004396:Coloring Agents / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000627:therapeutic use*; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D010880:Piperidines / Q000627:therapeutic use*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy*; D011419:Propidium / Q000494:pharmacology; D016196:S Phase; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004396:Coloring Agents; D005419:Flavonoids; D010880:Piperidines; D011419:Propidium; C077990:alvocidib