A Novel Emodin Derivative Inhibited Imatinib-Resistant Chronic Myelogenous Leukemia Cells.

Abstract 2774

Chronic myelogenous leukaemia (CML) is caused by fusion gene of bcr-abl, a constitutively active tyrosine kinase that is the result of the reciprocal translocation between chromosome 9 and 22, t (9;22). The majority of CML patients are diagnosed in the chronic phase that could be treated with tyrosine kinase inhibitor, imatinib (IM). However, some patients acquire resistance to imatinib and progress to a more aggressive phase of disease termed the accelerated phase and eventually the blast crisis with poor prognosis. Emodin, a natural anthraquinone compound extracted from traditional Chinese medicine, has been shown to have multiple biological activities. Our previous research results have shown that emodin has anti-leukemic effects in various leukemia cell lines. Based on these results, we designed and synthesized 28 kinds of derivatives. Among them, the derivative E35 was more potential in anti-leukemia. Here we focused on the investigation of the effects of E35 on IM-sensitive CML cell line K562 and IM- resistant CML cell line K562/G01, and K562 cell xenograft model in nude mice. The results showed E35 inhibited growth in K562 and K562/G01 cells in time- dependent and dose-dependent manners. E35 inhibited K562 cell proliferation with an average IC50 value of 2.8±0.4μmol/L, similar to that of the K562/G01 cells (average IC50=3.1±0.3μmol/L). E35 inhibited K562/G01 clone formation, yielding an average IC50 of 0.28μmol/L. This compound could induce apoptosis in K562 and K562/G01 cells in a dose-dependent way. It down-regulated the expressions of proliferation- and apoptosis-related proteins, such as bcl-2, PARP, Procaspase-3, Procaspase-8 and Procaspase-9, and up-regulated the molecules, such as bax, cleaved Caspase-3, cleaved Caspase-9 and spliced PARP, which lead to the induction of apoptosis. The expressions of Bcr-Abl were also inhibited in K562 and K562/G01 cells. E35 inhibited phosphorylation of P210Bcr-Abl, Akt, mTOR, 4E-BP1, p70S6k, ERK1/2 and other molecules in P210,PI3K/Akt/mTOR and MAPK signaling pathways. Anti-leukemic effects of E35 in K562 xenograft model in nude mice was observed. The tumor growth in K562 xenograft mice was significantly inhibited by E35 in a dose-dependent fashion. The treatment with 12mg/kg E35 and 100mg/kg IM presented the best inhibition effects in K562 xenograft. Western Blot showed that the protein expressions of Bcl-2 and signal molecules, such as p-P210^Bcr-Abl, p-Akt, p-mTOR, p-ERK1/2, were down-regulated in K562 xenograft cell. The E35 administration was well tolerated by the nude mice, and there were no significant adverse effects in blood counts and histopathological examination. Kaplan-Meier survival curves show that E35 raised the survival rates of mice with K562 xenograft and significantly prolonged the survival time in mice models. It could be concluded that the novel compound E35-Emodin derivatives had enhanced growth suppression and apoptosis induction of leukemia cell in vitro and in vivo.