Indirubin, an active component in the
traditional Chinese medicine formula Danggui Longhui Wan, shows promising anticancer effects.
Meisoindigo is an analog derived from
indirubin, which is less toxic and appears to be even more potent against
cancer. In considering
meisoindigo as a structural template for the development of new drugs, we designed and synthesized a series of 3-ylideneoxindole
acetamides as novel
anticancer agents. The
acetamides were then evaluated for in vitro and in vivo anticancer activities. The 3-ylideneoxindole
acetamides were found to have better anticancer activity than was indirubin-3'-oxime in several
cancer cell lines and also displayed a spectrum of activity similar to that of the
drug candidate
roscovitine, a CDK inhibitor. Among the 3-ylideneoxindole
acetamides, compound 10 showed particularly good efficacy. Cell cycle analysis further revealed that compound 10 arrested cells in the G1 phase and caused an increase in the sub-G1 population, indicating that the apoptosis pathway had been induced. In addition, exposure of cells to compound 10 led to the upregulation of the cell-cycle regulator
cyclin D1, which was sustained at a high level. In contrast, the same compound induced a short-term elevation in the level of
cyclin E, which was followed by a rapid decrease and the attenuation of Rb phosphorylation. Furthermore, a docking model suggests that compound 10 binds to the active site of CDK4. In testing the therapeutic potency of compound 10 on CT26-xenografted BALB/c mice, a significant reduction in
tumor size comparable to that of
cisplatin was found when administrated via the i.p. route. The mice presented no loss of
body weight, indicating that this compound possesses low toxicity. In the future, we are planning in vivo investigations of these new active
anticancer agents to better elucidate active mechanisms at the cellular level and thus benefit the development of anticancer
therapies.