Addition of PTK787/ZK 222584 Can Lower the Dosage of Amsacrine To Achieve Equal Amounts of AML Cell Death.

Acute myeloid leukemia (AML) is a disease with a poor prognosis. At this moment conventional chemotherapy is the gold standard for the treatment of AML. It is demonstrated that AML cells express VEGFA and VEGFC as well as KDR (VEGFR2), the main receptor for downstream effects, resulting in an autocrine pathway for cell survival. The present study investigates the role of PTK787/ZK 222584, a potent inhibitor of VEGF receptor tyrosine kinases, upon leukemic cell death, and the possibility of an additional effect upon cell death achieved by a conventional chemotherapeutic drug Amsacrine. In 3 AML-cell lines and 33 pediatric AML patient samples we performed total cell kill assays to determine the percentage of cell death achieved by PTK787/ZK 222584 (5–100 μM) and/or Amsacrine (0.001–2 μg/ml). Both drugs induced AML cell death. The LC50 values (drug concentration needed to kill 50% of the leukemic cells) for HL-60, TF-1 and THP-1 were 27 μM, 49 μM and 24 μM respectively. An excellent survival was seen on a KDR-negative cell line demonstrating that the cell death induced by PTK787/ZK 222584 is not a toxic effect. The primary blasts were overall 5–10 times more sensitive to PTK787/ZK 222584 than the cell lines, with a median LC50 value of 5.1 μM. Patient samples with a LC50 value below the median did not differ from patients above the median regarding age, sex, FAB classification or WBC count. With a response surface analysis we investigated the additional effect of PTK787/ZK 222584 upon cell death achieved by Amsacrine; we estimated the concentration combinations resulting in the same cell survival. We could show that, in cell lines as well as in primary AML blasts, the concentration of Amsacrine can be lowered and replaced for a certain dose of the potentially less toxic VEGFR inhibitor to achieve the same percentage of leukemic cell death. This study shows that PTK787/ZK 222584 might have more clinical potential in AML when combined with chemotherapy, e.g. Amsacrine. In addition, it is known from literature that topoisomerase inhibitors, e.g. Amsacrine, can cause treatment related AMLs. Moreover, many survivors of childhood or adolescent cancer experience treatment related cardiovascular complications that can impair their quality of life years after treatment. Therefore, reduction of complications and long-term effects of chemotherapy is warranted and might be achieved by lowering dosages of Amsacrine and replace it by other drugs with a lower toxicity profile, such as PTK787/ZK 222584.