Chronic myeloid leukemia (CML) and
acute lymphoblastic leukemia (ALL) are caused by a
fusion protein, BCR-ABL, which induces cellular transformation by activating the signaling molecules, STAT5 and Akt. The specific BCR-ABL inhibitors including
imatinib,
nilotinib, and
dasatinib, are clinically utilized in the treatment with CML and ALL patients. Although these BCR-ABL inhibitors are initially successful in the treatment of
leukemia, many patients develop drug resistance due to the appearance of the gatekeeper mutation of BCR-ABL, T315I. Recently, we found that
taxodione, a
quinone methide diterpene isolated from a conifer, Taxodium distichum, significantly induced apoptosis in human
myelogenous leukemia-derived K562 cells, which is positive for the bcr-abl gene.
Taxodione reduced the activities of mitochondrial respiratory chain
complex III, leading to the production of
reactive oxygen species (ROS). An
antioxidant agent,
N-acetylcysteine (NAC), canceled
taxodione-induced ROS production and apoptotic cell death, suggesting that
taxodione induced apoptosis through ROS accumulation. Furthermore, in K562 cells treated with
taxodione, BCR-ABL, STAT5 and Akt were sequestered in mitochondrial fraction, and their localization changes decrease their abilities to stimulate cell proliferation. Strikingly, NAC canceled these
taxodione-caused inhibition of BCR-ABL, STAT5 and Akt. In addition,
taxodione significantly induced apoptosis in transformed Ba/F3 cells by not only BCR-ABL but also T315I-mutated BCR-ABL through the generation of ROS, suggesting that
taxodione has potential as anti-
tumor drug with high efficacy to overcome BCR-ABL T315I mutation-mediated resistance in
leukemia cells. It's also expected that these knowledge becomes an important clue in the development of anti-
cancer drugs against the broad range of
tumors.