BCR-ABL nuclear entrapment kills human CML cells: ex vivo study on 35 patients with the combination of imatinib mesylate and leptomycin B

Imatinib and leptomycin B are effective in overcoming imatinib-resistance due to Bcr-Abl amplification and clonal evolution but not due to Bcr-Abl kinase domain mutation

“…In that study, a combination of 10 µM imatinib and 10 nM leptomycin B was used in colony forming assays using a different schedule. 18 In an MTT-based experiment, Aloisi et al have also shown that the combination is effective in inhibiting Bcr-Abl point mutant D276G but not Y253F and T315I. These data are in accordance with our observations in the T315I clone.…”

Reduction of apoptosis in Rb-deficient embryos via Abl knockout

“…Abl is also activated during amyloid-bpeptide induced neuronal cell death (Alvarez et al, 2004). The oncogenic BCR-ABL of chronic myelogenous leukemia (CML) can stimulate cell death when it is trapped in the nucleus of CML cells (Vigneri and Wang, 2001;Aloisi et al, 2006). The Abl tyrosine kinase can activate the apoptotic function of p53 and p73 (Agami et al, 1999;Gong et al, 1999;Sionov et al, 1999;Yuan et al, 1999;Goldberg et al, 2002;Vella et al, 2003).…”

Nuclear entrapment of BCR–ABL by combining imatinib mesylate with leptomycin B does not eliminate CD34+ chronic myeloid leukaemia cells

“…6 These data showed that this combination preferentially targeted BCR-ABL-expressing cells, by producing the greatest decrease in the number of Ph þ compared with Ph À colonies. In this study, we report the effect of IM and LMB directly on CML CD34 þ cells by evaluating the toxicity of this drug regime on these cells rather than the cytostatic effect studied in colony-forming assays by Aloisi et al 6 Exposure of total CD34 þ cells (obtained from leukapheresis material (495% CD34 þ ) from chronic phase (CP) CML patients with written informed consent) to the combination of IM with LMB failed to eliminate these cells (Figure 1c), despite the fact that nuclear localization of BCR-ABL was detected (Figure 1d). However, a 1-log reduction in total cell number, compared with input, resulted 3 days after drug washout (Figure 1c /ml in 3-ml cultures were treated with IM (10 mM), LMB (10 nM), or both drugs simultaneously, in duplicate wells for 72 h before drug washout with phosphate buffer saline (PBS).…”

“…produced a similar inhibitory effect to that of the drug combination on CML CD34 þ cell viability. 6 However, LMB also inhibited the proliferation of BCR-ABL À CD34 þ cells by three-to fivefold, showing a cytostatic effect with recovery 3 days after drug washout, demonstrating the non-specific toxicity of this drug (Figure 1e). This result suggests that CML CD34 þ cells seem to be more sensitive to inhibition of nuclear export than BCR-ABL À CD34 þ cells.…”