Comparison of in vitro antileukemic activity of obatoclax and ABT-737

Obatoclax and ABT-737 belong to a new class of anticancer agents known as BH3-mimetics. These agents antagonize the anti-apoptotic members of Bcl-2 family. The Bcl-2 proteins modulate sensitivity of many types of cancer cells to chemotherapy. Therefore, the objective of the present study was to examine and compare the antileukemic activity of obatoclax and ABT-737 applied alone, and in combination with anticancer agent, mafosfamide and daunorubicin. The in vitro cytotoxic effects of the tested agents on human leukemia cells were determined using the spectrophotometric MTT test, Coulter electrical impedance method, flow cytometry annexin V–fluorescein/propidium iodide assay, and light microscopy technique. The combination index analysis was used to quantify the extent of agent interactions. BH3 mimetics significantly decreased the leukemia cell viability and synergistically enhanced the cytotoxic effects induced by mafosfamide and daunorubicin. Obatoclax affected the cell viability to a greater degree than did ABT-737. In addition, various patterns of temporary changes in the cell volume and count, and in the frequency of leukemia cells undergoing apoptosis, were found 24 and 48 h after the tested agent application. ABT-737 combined with anticancer agents induced apoptosis more effectively than obatoclax when given in the same combination regimen. The results of the present study point to the different antileukemic activities of obatoclax and ABT-737, when applied alone, and in combination with anticancer agents. A better understanding of the exact mechanisms of BH3 mimetic action is of key importance for their optional use in cancer therapy

In vitro response of human pathological hematopoietic cells to fludarabine phosphate

The present study was undertaken to determine a possible influence of fludarabine (fludarabine phosphate, F-ara-AMP) on the cell viability and count. The experiments were performed in vitro on human acute lymphoblastic MOLT-4 cells, human acute myeloblastic ML-1 cells, and human histiocytic lymphoma U-937 cells. The research was conducted using the spectrophotometric and Beckman Coulter methods. The cell viability was analyzed using MTT assay. The cell count was detected using an electronic Z2 Coulter counter. Temporary changes in the cell viability and count were assessed at 24h and 48h after F-ara-AMP application. The in vitro activity of fludarabine phosphate against MOLT-4, ML-1, and U-937 cells was compared. F-ara-AMP applied at the four concentrations - 250 nM, 500 nM, 750 nM, and 1 μM - distinctly decreased the viability and count of the pathological hematopoietic cells. The effects of F-ara-AMP on MOLT-4, ML-1, and U-937 cells were dependent on the tested agent and its dose, the time intervals after the agent application, and the cell line used. ML-1 and U-937 cells appeared to be more resistant than MOLT-4 cells to the action of fludarabine phosphate. The in vitro response of the three human pathological hematopoietic cell lines to the F-ara-AMP action, was shown