Tetrandrine Induces Early G1 Arrest in Human Colon Carcinoma Cells by Down-Regulating the Activity and Inducing the Degradation of G1-S–Specific Cyclin-Dependent Kinases and by Inducing p53 and p21Cip1

Abstract

Tetrandrine is an antitumor alkaloid isolated from the root of Stephania tetrandra. We find that micromolar concentrations of tetrandrine irreversibly inhibit the proliferation of human colon carcinoma cells in MTT and clonogenic assays by arresting cells in G 1 . Tetrandrine induces G 1 arrest before the restriction point in nocodazole-and serum-starved synchronized HT29 cells, without affecting the G 1 -S transition in aphidicolin-synchronized cells. Tetrandrine-induced G 1 arrest is followed by apoptosis as shown by fluorescence-activated cell sorting, terminal deoxynucleotidyl transferase-mediated nick end labeling, and annexin V staining assays. Tetrandrine-induced early G 1 arrest is mediated by at least three different mechanisms. First, tetrandrine inhibits purified cyclin-dependent kinase 2 (CDK2)/cyclin E and CDK4 without affecting significantly CDK2/cyclin A, CDK1/cyclin B, and CDK6. Second, tetrandrine induces the proteasome-dependent degradation of CDK4, CDK6, cyclin D1, and E2F1. Third, tetrandrine increases the expression of p53 and p21Cip1 in wild-type p53 HCT116 cells. Collectively, these results show that tetrandrine arrests cells in G 1 by convergent mechanisms, including down-regulation of E2F1 and up-regulation of p53/p21Cip1 .

Tetrandrine citrate eliminates imatinib-resistant chronic myeloid leukemia cells in vitro and in vivo by inhibiting Bcr-Abl/β-catenin axis

“…Indeed, our results indicate that this compound can effectively ablate the primitive LSCs (CD34 + leukemia cells), which are exceptionally refractory to be killed by the TKIs or conventional chemotherapeutic agents (Holyoake et al, 1999;Elrick et al, 2005;Holtz et al, 2005;Barnes and Melo, 2006). Additionally, we found that tetrandrine induced G 1 arrest in CML cells, which is consistent with Meng's observations that tetrandrine causes G 1 arrest in colon cancer cells (Meng et al, 2004).…”

“…Tetrandrine is a natural bisbenzylisoquinoline and has been shown to be active against a variety of tumors, such as colon cancer (Meng et al, 2004), glioma (Chen and Tseng, 2010), ovarian cancer , and hepatocellular carcinoma (Liu et al, 2011). Notably, tetrandrine inhibits Wnt/β-catenin signaling and suppresses tumor growth of human colorectal cancer (He et al, 2011).…”

Tetrandrine induces apoptosis by activating reactive oxygen species and repressing Akt activity in human hepatocellular carcinoma

“…It was reported that tetrandrine mediated apoptosis in human leukemic cells and colon cancer cells. 18,19 To determine whether tetrandrine induces apoptosis of human HCC cells, dose-dependent response and time-course experiments of tetrandrine treatment were performed. Cell viability assay showed that tetrandrine induced Huh7, HepG2 and BEL7402 cell death in a concentration-dependent and dynamic manner, and Huh7 cells were more sensitive to tetrandrine treatment than HepG2 and BEL7402 cells (Figs.…”

Dose–response transition from cell cycle arrest to apoptosis with selective degradation of Mdm2 and p21WAF1/CIP1 in response to the novel anticancer agent, aminoflavone (NSC 686288)

“…Immunoprecipitation assays (Meng et al, 2004) were performed with 1 mg monoclonal antip21 WAF1/CIP1 or anti-Mdm2. The Protein A/G agarose was recovered and washed with lysis buffer.…”