SummaryThe discovery of the chimeric tyrosine kinase breakpoint cluster region kinase-Abelson kinase (BCR-ABL)-targeted drug imatinib conceptually changed the treatment of chronic myelogenous leukemia (CML). However, some CML patients show drug resistance to imatinib. To address this issue, some artificial heterocyclic compounds have been identified as BCR-ABL inhibitors. Here we examined whether plant-derived pentacyclic triterpenoid gypsogenin and/or their derivatives show inhibitory activity against BCR-ABL. Among the three derivatives, benzyl 3-hydroxy-23-oxoolean-12-en-28-oate (1c) was found to be the most effective anticancer agent on the CML cell line K562, with an IC 50 value of 9.3 µM. In contrast, the IC 50 against normal peripheral blood mononuclear cells was 276.0 µM, showing better selectivity than imatinib. Compound 1c had in vitro inhibitory activity against Abelson kinase 1 (ABL1) (IC 50 =8.7 μM), the kinase component of BCR-ABL. In addition, compound 1c showed a different inhibitory profile against eight kinases compared with imatinib. The interaction between ATP binding site of ABL and 1c was examined by molecular docking study, and the binding mode was different from imatinib and newer generation inhibitors. Furthermore, 1c suppresses signaling downstream of BCR-ABL. This study suggests the possibility that plant extracts may be a source for CML treatment and offer a strategy to overcome drug resistance to known BCR-ABL inhibitors.
KeywordsGypsogenin, Abelson tyrosine-protein kinase 1, chronic myelogenous leukemia
Biological and Pharmaceutical Bulletin Advance PublicationCancer is a worldwide health problem, and despite intensive research efforts over the last several decades, an effective cure has not been identified.
1)However, the recent discovery of molecular targeted drugs against cancer at the end of the 20 th century has led to promising results. 1,2) Imatinib (Fig. 1), which targets the chimeric tyrosine kinase breakpoint cluster region kinase-Abelson kinase (BCR-ABL), [3][4][5][6] was discovered based on the findings that chronic myelogenous leukemia (CML) is caused by a chromosomal translocation that results in the constitutively expressed and active BCR-ABL. 7,8) While imatinib can be initially effective in treating CML, some patients have shown drug resistance to imatinib. [9][10][11] Several new generation drugs with a different binding mode to Abelson kinase (ABL) have thus been developed. 6,[12][13][14][15][16] These drugs are artificial heterocyclic compounds, however, if widely distributed natural products and/or their derivatives show the inhibitory activity against BCR-ABL, it would be more convenient to get.Pentacyclic triterpenoids, a category of natural compounds, can be extracted from a variety of plants and show various activities. 17,18) Some of these triterpenoids were reported to exhibit anti-tyrosine kinase activity. 19,20) Here we focused on a pentacyclic triterpenoid gypsogenin, 21,22) extracted from Gypsophila species, 23,24) which is widely distributed in the Eu...
