Background: Isorhamnetin (Iso), a novel and essential monomer derived from total flavones of Hippophaerhamnoides that has long been used as a traditional Chinese medicine for angina pectoris and acute myocardialinfarction, has also shown a spectrum of antitumor activity. However, little is known about the mechanisms ofaction Iso on cancer cells.
Objectives: To investigate the effects of Iso on A549 lung cancer cells and underlyingmechanisms. Materials and
Methods: A549 cells were treated with 10~320 μg/ml Iso. Their morphological andcellular characteristics were assessed by light and electronic microscopy. Growth inhibition was analyzed byMTT, clonogenic and growth curve assays. Apoptotic characteristics of cells were determined by flow cytometry(FCM), DNA fragmentation, single cell gel electrophoresis (comet) assay, immunocytochemistry and terminaldeoxynucleotidyl transferase nick end labeling (TUNEL) . Tumor models were setup by transplanting Lewislung carcinoma cells into C57BL/6 mice, and the weights and sizes of tumors were measured.
Results: Isomarkedly inhibited the growth of A549 cells with induction of apoptotic changes. Iso at 20 μg/ml, could induceA549 cell apoptosis, up-regulate the expression of apoptosis genes Bax, Caspase-3 and P53, and down-regulatethe expression of Bcl-2, cyclinD1 and PCNA protein. The tumors in tumor-bearing mice treated with Iso weresignificantly smaller than in the control group. The results of apoptosis-related genes, PCNA, cyclinD1 and otherprotein expression levels of transplanted Lewis cells were the same as those of A549 cells in vitro.
Conclusions:Iso, a natural single compound isolated from total flavones, has antiproliferative activity against lung cancer invitro and in vivo. Its mechanisms of action may involve apoptosis of cells induced by down-regulation of oncogenesand up-regulation of apoptotic genes.