The in vitro activity of the tyrosine kinase inhibitor STI571 in BCR–ABL positive chronic myeloid leukaemia cells: synergistic interactions with anti-leukaemic agents

Abstract

Chronic myeloid leukaemia is typically characterised by the presence of dysregulated BCR -ABL tyrosine kinase activity, which is central to the oncogenic feature of being resistant to a wide range of cytotoxic agents. We have investigated whether the inhibition of this tyrosine kinase by the novel compound STI571 (formerly CGP57148B) would render K562, KU812 cell lines and chronic myeloid leukaemia-progenitor cells sensitive to induction of cell kill. Proliferation assays showed STI571 to be an effective cytotoxic agent in chronic myeloid leukaemia-derived cell lines (IC 50 on day 5 of 4.6 mg ml 71 and 3.4 mg ml 71 for K562 and KU812 respectively) and in leukaemic blast cells (per cent viability on day 3 at 4 mg ml 71 : 55.5+8.7 vs 96.4+3.7%). STI571 also appeared to specifically target bcr -abl expressing cells, as results from colony forming assays using the surviving cell fraction from STI571-treated peripheral CD34 + chronic myeloid leukaemia blast cells, indicated a reduction in the expansion of colonies of myeloid lineage, but no effect on normal colony formation. Our data also showed synergy between STI571 and other anti-leukaemic agents; as an example, there were significant increases in per cent cell kill in cell lines cultured with both STI571 and etoposide compared to the two alone (per cent cell kill on day 3: 73.7+11.3 vs 44.5+8.7 and 17.8+7.0% in cultures with STI571 and etoposide alone respectively; P50.001). This study confirms the central oncogenic role of BCR -ABL in the pathogenesis of chronic myeloid leukaemia, and highlights the role of targeting this tyrosine kinase as a useful tool in the clinical management of the disease.

Causative Factors Involved in Development of Resistance to Tyrosine Kinase Inhibition and Novel Strategies Designed to Override This Resistance

“…Alternatively, synergy may be explained by the ability of imatinib to increase the intracellular uptake and retention of nilotinib (and therefore its overall concentration), possibly through imatinib inhibition of ABCB1-mediated efflux of nilotinib (White et al, 2007). The demonstrated synergy between imatinib and nilotinib complements other published reports showing synergistic interaction between imatinib and the dual Src/Abl inhibitors, dasatinib and AP23848 (O'Hare et al, 2005), as well as synergistic interactions between imatinib and a panel of standard chemotherapeutic agents (Liu et al, 2002). In addition, combinations of dasatinib and imatinib have proven to be effective in diminishing the frequency of occurrence of drug-resistant BCR-ABL mutants, with the exception of T315I (Shah et al, 2004;Burgess et al, 2005;Bradeen et al, 2006;Talpaz et al, 2006).…”

Effect of haemopoietic growth factors on cancer cell lines and their role in chemosensitivity

“…HCT116 þ MEK cells exhibited increased MAPK levels and BCL-2 levels compared to the parental cell line (Figure 9b). HCT116 þ MEK cells were also less sensitive to the cytotoxic effects of cisplatin (day-3 IC 50 : 17.2 vs 9.1 mM -values generated as shown in Liu et al, 2002b) (Figure 9c). Similarly, HL60 cells were transfected with constitutively inactive MEK cDNA (HL60 ÀMEK ).…”

“…Similarly, the cytotoxic effect of this 3-day culture with cisplatin was also investigated in the cells precultured for 3 days with 10 IU/ml Epo and 100 ng/ml GM-CSF. The GF concentrations selected were optimal concentrations as established previously (Liu et al, 2002b). Cell parameters listed previously were then assessed on the final day (day 6).…”

Cannabis-induced cytotoxicity in leukemic cell lines: the role of the cannabinoid receptors and the MAPK pathway

“…17 Acquisition of data was performed within 1 hour using a FACSCalibur (BD Biosciences, Oxford, United Kingdom). Five thousand cells were analyzed for each data point, and the percentages of cells in sub-G 1 (apoptotic fraction, cells with a reduced DNA content but similar morphology), G 1 , S, and G 2 /M phases were determined using the cell cycle analysis program WinMDI v2.4 (http://facs.scripps.edu/software.html).…”

“…Although this simplistic approach to investigating synergy/hyperadditivity is limited and less powerful than the usual median-dose effect and isobologram methodologies, strong synergistic interactions would have been detected. 17 It would be interesting to see whether there would be any benefit of combining THC with common antileukemic agents, such as the anthracyclines and etoposide.Overall, these data reaffirm the complexity of the data that are currently available. A cytotoxic response to THC has been studied previously; however, these studies have only correlated cannabinoid receptor mRNA levels with this response.…”