Therapeutic efficacy of the pan-cdk inhibitor PHA-793887 in vitro and in vivo in engraftment and high-burden leukemia models
Received 13 January 2010; received in revised form 8 February 2010; accepted 9 February 2010. published online 17 February 2010.
Objective
The aim of the work was to determine and characterize, in vitro and in vivo, the therapeutic activity of PHA-793887, a new potent pan-cdk inhibitor, in the context of hematopoietic neoplasms.
Materials and Methods
Thirteen leukemic cell lines bearing different cytogenetic abnormalities and normal hematopoietic cells were used in cytotoxicity and colony assays. The drug activity at the molecular level was analyzed by Western blotting. PHA-793887 was also tested in vivo in several leukemia xenograft models.
Results
PHA-793887 was cytotoxic for leukemic cell lines in vitro, with IC50 ranging from 0.3 to 7 μM (mean: 2.9 μM), regardless of any specific chromosomal aberration. At these doses, the drug was not cytotoxic for normal unstimulated peripheral blood mononuclear cells or CD34+ hematopoietic stem cells. Interestingly, in colony assays PHA-793887 showed very high activity against leukemia cell lines, with an IC50 <0.1 μM (mean: 0.08 μM), indicating that it has efficient and prolonged antiproliferative activity. PHA-793887 induced cell-cycle arrest, inhibited Rb and nucleophosmin phosphorylation, and modulated cyclin E and cdc6 expression at low doses (0.2−1 μM) and induced apoptosis at the highest dose (5 μM). It was also effective in vivo in both subcutaneous xenograft and primary leukemic disseminated models that better mimic naturally occurring human disease. Interestingly, in one disseminated model derived from a relapsed Philadelphia-positive acute lymphoid leukemia patient, PHA-793887 showed strong therapeutic activity also when treatment was started after establishment of high disease burden.
Conclusions
We conclude that PHA-793887 has promising therapeutic activity against acute leukemias in vitro and in vivo.
aNerviano Medical Sciences Srl, Business Unit Oncology, Nerviano, Italy
bLaboratory of Cellular Therapy “G. Lanzani,” USC Haematology, Ospedali Riuniti di Bergamo, Bergamo, Italy
Offprint requests to: Josée Golay, Ph.D., Laboratory of Cellular Therapy “G. Lanzani,” Ospedali Riuniti, c/o Presidio Matteo Rota, Via Garibaldi 11-13, 24128 Bergamo, Italy
This article is dedicated to the memory of our colleague, Valter Croci.
∗ Drs. Alzani and Pedrini contributed equally to this work.
ABSTRACT