Flavonoids and its derivatives are common components found in traditional Chinese medicine and food. Several studies indicated flavonoids could benefit in cancer prevention or therapy, but their structure-activity relationships (SAR) remain poorly defined. In order to further understand the SAR, a series of oxime-containing flavone derivatives were designed, synthesized and evaluated for their biological anti-cancer potential. The anti-proliferative ability of these compounds was measured by several human cancer cell lines from different origins including nasopiiaryngeal carcinoma, leukemia and lung carcinoma. Among over 30 different oxime-containing flavone derivatives, (Z)-6-[2-hydroxyimino-2-(4-methoxyphenyl ethoxy])- 2-phenyl-4H-l-benzopyran-4-one (WTC01) possessed most potent activity against human nasopharyngeal carcinoma cells growth with IC50 of 400 nM. As determined by flow cytometry, WTC01 treatment results in an accumulation of human nasopharyngeal carcinoma NPC-TW01 and HONE-1 cells in G2-M phase with time- and concentraton-dependent manner before cell death. Furthermore, Annexin-V/propidium iodide (PI) binding assay, Hoechst 33258/PI double staining, and PARP cleavage indicates that cell death proceed through an apoptotic pathway. Interestingly, WTC01 also causes mitochondrial transmembrane potential loss and activation of caspase-9 and caspase-3 without noticeable activation of the caspase-8. These results suggest that the WTC01-mediated apoptotic signaling pathway depends on the mitochondria and caspase-9/-3 cascades. Further studies showed that WTC01 inhibits tubulin assembly through binding to the colchicine-binding site of tubulin, this data suggests that tubulin may serve as the cellular target for WTC01. Notably, the in vivo study showed that WTC01 exhibits good pharmacokinetic properties and completely inhibits the growth of NPC-TW01 xenograft tumor at i.p. doeses of 25 and 50 mg/kg in nude mice. Taken together, these findings indicated that WTC01, a novel synthetic oxime-containing flavone, exhibits potent activity against cancer growth through the disruption of microtubule and has potential for management of nasopharyngeal malignancies.
