Alantolactone, an allergenic
sesquiterpene lactone, has recently been found to have significant antitumor effects on malignant
tumor cells. Here, we investigated the potential effect of
alantolactone on Bcr/Abl+
imatinib-sensitive and -resistant cells.
Alantolactone treatment resulted in obvious apoptosis in both
imatinib-sensitive and -resistant K562 cells, as shown by the increase in
Annexin V-positive cells,
caspase-3 activation,
poly(ADP-ribose) polymerase-1 (PARP-1) cleavage and mitochondrial membrane potential collapse.
Alantolactone significantly inhibited NF-κB-dependent reporter gene activity, decreased the
DNA-binding activity of NF-ОκB, and blocked TNF-α-induced IκBα phosphorylation. Of interest, the oncogenic
Bcr/Abl fusion protein but not its
mRNA levels were quickly reduced upon
alantolactone exposure in
imatinib-sensitive and -resistant K562 cells. Bcr/Abl knockdown enhanced the apoptosis driven by
alantolactone. Bcr/Abl
protein reduction could not be reversed by the addition of
proteasome or
caspase-3 inhibitors. The overexpression of p65 inhibited
alantolactone-induced apoptosis, whereas p65 or Bcr/Abl silencing enhanced its apoptotic-inducing effect. Furthermore, Bcr/Abl-transfected 32D cells showed more sensitivity to
alantolactone than vector-transfected control cells, and the Bcr/Abl
protein was depleted, as observed in K562 cells. Finally,
alantolactone-induced apoptosis was also observed in primary CD34+ CML leukemic cells. Collectively, these findings suggest that
alantolactone is a promising potent agent to fight against CML cells via the inhibition of the NF-κB signaling pathway and depletion of the Bcr/Abl
protein.