Cancer: Lung, colorectal, leukemia
Action: Apoptosis-inducing, cytostatic effect
Apoptosis
The anti-tumor component of Cortex periplocae is periplocin. Periplocin is one of the cardenolides isolated from cortex periplocae which is used for treatment of rheumatoid arthritis and reinforcement of bones and tendons in traditional medicine.
Periplocin has been reported to inhibit many cell lines, including MCF-7, TE-13, QG-56, SMMC-7721, T24, Hela, K562, TE-13 and Eca-109 cells. Studies have shown that periplocin reduces the expression of survivin, an inhibitor of apoptosis. It also releases caspases-3 and -7 from complexes and thereby increases their activities, ultimately inducing tumor cell apoptosis (Zhao et al., 2009).
Lung Cancer
The anti-tumor activity of periplocin was investigated in lung cancer cells both in vitro and in vivo, and its anti-cancer mechanism was explored. Periplocin inhibited the growth of lung cancer cells and induced their apoptosis in a time- and dose-dependent manner by cell-cycle arrest in G0/G1 phase. Periplocin exhibited anti-tumor activity both in human (A549) and mouse (LL/2) lung cancer xenograft models. Immunohistochemical analysis revealed that intratumoral angiogenesis was significantly suppressed.
Furthermore, anti-cancer activity mediated by periplocin was associated with decreased level of phosphorylated AKT and ERK both in vitro and in vivo, which are important for cell growth and survival. Moreover, periplocin induced apoptosis by down-regulating Bcl-2 and up-regulating Bax, leading to activation of caspase-3 and caspase-9.
These findings suggest that periplocin could inhibit the growth of lung cancer both in vitro and in vivo, which could be attributed to the inhibition of proliferation and the induction of apoptosis signaling pathways, such as AKT and ERK. These observations provide further evidence on the anti-tumor effect of periplocin, and it may be of importance to further explore its potential role as a therapeutic agent for cancer (Lu et al., 2010).
Colorectal Carcinomas
The Wnt/beta-catenin signaling pathway plays an important role in the development and progression of human cancers, especially in colorectal carcinomas. Periplocin extracted from cortex periplocae (CPP) significantly inhibited the proliferation of SW480 cells in a time-and dose-dependent manner (P<0.01). CPP (0.5 microg/mL) also caused G0/G1 cell-cycle arrest of SW480 cells and induced cell apoptosis (P<0.05). Compared to untreated control cells, after the treatment with CPP, the protein levels of beta-catenin in total cell lysates, cytosolic extracts, and nuclear extracts were reduced (P<0.01); the binding activity of the TCF complex in nucleus to its specific DNA binding site was suppressed; mRNAs of the downstream target genes survivin, c-myc and cyclin D1 were decreased (P<0.01) while beta-catenin mRNA remained unchanged.
CPP could significantly inhibit the proliferation of SW480 cells, which may be through down-regulating the Wnt/beta-catenin signaling pathway (Du et al., 2009).
Pro-apoptotic and Cytostatic Effect/Leukemia
Cardenoliddes are steroid glycosides which are known to exert cardiotonic effects by inhibiting the Na(+)/K(+)-ATPase. Several of these compounds have been shown also to possess anti-tumor potential. The aim of the present work was the characterization of the tumor cell growth inhibition activity of four cardenolides, isolated from Periploca graeca L., and the mechanisms underlying such an effect.
The pro-apoptotic and cytostatic effect of the compounds was tested in U937 (monocytic leukemia) and PC3 (prostate adenocarcinoma). Characterization of apoptosis and cell-cycle impairment was obtained by cytofluorimetry and WB. Periplocymarin and periplocin were the most active compounds, periplocymarin being more effective than the reference compound ouabain. The reduction of cell number by these two cardenolides was due in PC3 cells mainly to the activation of caspase-dependent apoptotic pathways, while in U937 cells to the induction of cell-cycle impairment without extensive cell death. Interestingly, periplocymarin, at cytostatic but non-cytotoxic doses, was shown to sensitize U937 cells to TRAIL. Taken together, these data outline that cardiac glycosides are promising anti-cancer drugs and contribute to the identification of new natural cardiac glycosides to obtain chemically modified non-cardioactive/low toxic derivatives with enhanced anti-cancer potency (Bloise et al., 2009).
References
Zhao LM, Ai J, Zhang Q, et al. (2009). Periplocin (a sort of ethanol from Cortex periplocae) induces apoptosis of esophageal carcinoma cells by influencing expression of related genes. Tumor (Chin), 29:1025-1030.