Isorhamnetin is one member of
flavonoid components which has been used in the treatment of
heart disease. Recently the in vitro anti-
cancer effect of
isorhamnetin on human esophageal
squamous carcinoma cell line Eca-109 was investigated in our lab. When Eca-109 cells were in vitro exposed to the graded doses of
isorhamnetin (0-80 microg/ml) for 48 h, respectively,
isorhamnetin exhibited
cytostatic effect on the treated cells, with an IC(50) of 40+/-0.08 microg/ml as estimated by MTT assay. Inhibition on proliferation by
isorhamnetin was detected by
trypan blue exclusion assay, clone formation test, immunocytochemical assay of
PCNA and (3)H-thymidine uptake analysis. Cell cycle distribution was measured by FCM. It was found that the viability of Eca-109 cells was significantly hampered by
isorhamnetin. Compared with the negative control group, the treated group which was exposed to
isorhamnetin had increased population in G(0)/G(1) phase from 74.6 to 84 while had a significant reduction in G(2)/M phase from 11.9 to 5.8. In addition to its
cytostatic effect,
isorhamnetin also showed stimulatory effect on apoptosis. Typical apoptotic morphology such as condensation and fragmentation of nuclei and blebbing membrane of the apoptotic cells could be observed through transmission electron microscope. Moreover, the sharp increase in apoptosis rate between the control and treated group were detected by FCM from 6.3 to 16.3. To explore the possible molecular mechanisms that underlie the growth inhibition and apoptosis stimulatory effects of
isorhamnetin, the expressions of six proliferation- and death-related genes were detected by FCM. Expressions of bcl-2, c-myc and H-ras were downregulated whereas Bax, c-fos and p53 were upregulated. However, the in vivo experiments were required to further confirm the anti-
cancer effects of
isorhamnetin. In conclusion,
isorhamnetin appears to be a potent drug against
esophageal cancer due to its in vitro potential to not only inhibit proliferation but also induce apoptosis of Eca-109 cells.