Pterostilbene and its emerging antineoplastic effects: a prospective treatment option for systemic malignancies

Potent anti-cancer effect of 3'-hydroxypterostilbene in human colon xenograft tumors

Here we report that 3′-hydroxypterostilbene (HPSB), a natural pterostilbene analogue, was more potent than pterostilbene against the growth of human cancer cells (COLO 205, HCT-116, and HT-29) with measured IC₅₀ values of 9.0, 40.2, and 70.9 µM, respectively. We found that HPSB effectively inhibited the growth of human colon cancer cells by inducing apoptosis and autophagy. Autophagy occurred at an early stage and was observed through the formation of acidic vesicular organelles and microtubule-associated protein 1 light chain 3-II production. At the molecular levels, the results from western blot analysis showed that HPSB significantly down-regulated phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinases (MAPKs) signalings including decreased the phosphorylation of mammalian target of rapamycin (mTOR). Significant therapeutic effects were demonstrated in vivo by treating nude mice bearing COLO 205 tumor xenografts with HPSB (10 mg/kg i.p.). These inhibitory effects were accompanied by mechanistic down-regulation of the protein levels of cyclooxygenase-2 (COX-2), matrix metallopeptidase-9 (MMP-9), vascular endothelial growth factor (VEGF), and cyclin D1, as well as by the induction of apoptosis in colon tumors. Our findings suggest that HPSB could serve as a novel promising agent for colon cancer treatment.

Pharmacokinetics and tissue distribution of pterostilbene in the rat

SCOPE

Pterostilbene (Pt) is emerging as an important health-promoting natural compound. Pharmacokinetic studies so far have focused on plasma levels, while Pt distribution in tissues is most relevant for biological action. This study determined tissue distribution of Pt and its major metabolite, pterostilbene-4'-sulfate (Pt-S), in rats after oral administration.

METHODS AND RESULTS

Upon intravenous (iv) administration (88 μmol/kg), Pt was cleared from blood with a half-life of 1.8 ± 0.3 h. Oral administration (same dose) resulted in moderate Pt bioavailability (∼35%) and in an increased abundance of Pt-S in blood (AUC(Pt)/AUC(Pt-S) ∼0.75 and ∼0.05 after iv or oral administration, respectively). Pt-S was the major species in all organs except the brain, where intact Pt was predominant (AUC(Pt)/AUC(Pt-S) ∼5). Both Pt and Pt-S peaked in all tissues at approximately 2 h. The highest levels (∼200 nmoles/g for Pt-S and 40 nmoles/g for Pt) were measured in the liver, the lowest (≤7 nmol/g) in skeletal muscles and testes.

CONCLUSION

AUC(Pt) was ∼2- to ∼25-fold higher in tissues than in blood; this may explain its bioactivity despite barely detectable blood levels. Of particular interest is the high fraction of nonmetabolized Pt in the brain, given the reports of its activity at the level of the central nervous system.

The novel pterostilbene derivative ANK-199 induces autophagic cell death through regulating PI3 kinase class III/beclin 1/Atg‑related proteins in cisplatin‑resistant CAR human oral cancer cells

Pterostilbene is an effective chemopreventive agent against multiple types of cancer cells. A novel pterostilbene derivative, ANK-199, was designed and synthesized by our group. Its antitumor activity and mechanism in cisplatin-resistant CAR human oral cancer cells were investigated in this study. Our results show that ANK-199 has an extremely low toxicity in normal oral cell lines. The formation of autophagic vacuoles and acidic vesicular organelles (AVOs) was observed in the ANK-199-treated CAR cells by monodansylcadaverine (MDC) and acridine orange (AO) staining, suggesting that ANK-199 is able to induce autophagic cell death in CAR cells. Neither DNA fragmentation nor DNA condensation was observed, which means that ANK-199-induced cell death is not triggered by apoptosis. In accordance with morphological observation, 3-MA, a specific inhibitor of PI3K kinase class III, can inhibit the autophagic vesicle formation induced by ANK-199. In addition, ANK-199 is also able to enhance the protein levels of autophagic proteins, Atg complex, beclin 1, PI3K class III and LC3-II, and mRNA expression of autophagic genes Atg7, Atg12, beclin 1 and LC3-II in the ANK-199-treated CAR cells. A molecular signaling pathway induced by ANK-199 was therefore summarized. Results presented in this study show that ANK-199 may become a novel therapeutic reagent for the treatment of oral cancer in the near future (patent pending).