Author Correction: Delivery of acetylthevetin B, an antitumor cardiac glycoside, using polymeric micelles for enhanced therapeutic efficacy against lung cancer cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Design and synthesis of biotinylated cardiac glycosides for probing Nur77 protein inducting pathway.

The orphan nuclear receptor Nur77 (also known as TR3 or nerve growth factor-induced clone B NGFI-B) functions as a nuclear transcription factor in the regulation of target gene expression and plays a critical role in the regulation of differentiation, proliferation, apoptosis, and survival of many different cell types. Recent studies demonstrate that Nur77 also involves many important physiological and pathological processes including cancer, inflammation and immunity, cardiovascular diseases, and bone diseases. Our previous studies showed that cardiac glycosides could induce the expression of Nur77 protein and its translocation from the nucleus to the cytoplasm and subsequent targeting to mitochondria, leading to apoptosis of cancer cells. In order to probe the Nur77 protein inducting pathway, we designed and synthesized a series of novel biotinylated cardiac glycosides from ß-Antiarin and α-Antiarin, two typical cardiac glycosides from the plant of Antiaris toxicaria. The induction of Nur77 protein expression of these biotinylated cardiac glycosides and their inhibitory effects on NIH-H460 cancer cell proliferation were evaluated. Results displayed that some biotinylated cardiac glycosides could significantly induce the expression of Nur77 protein comparable with their parent compounds ß-Antiarin and α-Antiarin. Also, their streptavidin binding activities were evaluated. Among them, biotinylated cardiac glycosides P4b and P5a exhibited significant effect on the induction of Nur77 expression along with high binding capacity with streptavidin, suggesting that they can be used as probes for probing Nur77 protein inducting pathway.

Delivery of acetylthevetin B, an antitumor cardiac glycoside, using polymeric micelles for enhanced therapeutic efficacy against lung cancer cells.

Acetylthevetin B (ATB), a cardiac glycoside from the seed of Thevetia peruviana (Pers) K Schum (yellow oleander), exhibits not only antitumor activity but also potential cardiac toxicity. In the present study, we attempted to enhance its antitumor action and decrease its adverse effects via chitosan-Pluronic P123 (CP) micelle encapsulation. Two ATB-loaded CP micelles (ATB-CP1, ATB-CP2) were prepared using an emulsion/solvent evaporation technique. They were spherical in shape with a particle size of 40-50 nm, showed a neutral zeta potential, and had acceptable encapsulation efficiency (>90%). Compared to the free ATB (IC50=2.94 µmol/L), ATB-loaded CP micelles exerted much stronger cytotoxicity against human lung cancer A549 cells with lower IC50 values (0.76 and 1.44 µmol/L for ATB-CP1 and ATB-CP2, respectively). After administration of a single dose in mice, the accumulation of ATB-loaded CP1 micelles in the tumor and lungs, respectively, was 15.31-fold and 9.49-fold as high as that of free ATB. A549 xenograft tumor mice treated with ATB-loaded CP1 micelles for 21 d showed the smallest tumor volume (one-fourth of that in the control group) and the highest inhibition rate (85.6%) among all the treatment groups. After 21-d treatment, no significant pathological changes were observed in hearts and other main tissues. In summary, ATB may serve as a promising antitumor chemotherapeutic agent for lung cancer, and its antitumor efficacy was significantly improved by CP micelles, with lower adverse effects.

Cardiac glycosides from the seeds of Thevetia peruviana and their pro-apoptotic activity toward cancer cells.

Phytochemical investigation of the seeds of Thevetia peruviana resulted in the isolation of seven cardiac glycosides (1-7), including two new compounds (1 and 2). Cytotoxicity of them toward cancer cell lines P15 (human lung cancer cell), MGC-803 (human gastric cancer cells), SW1990 (human pancreatic cancer cells), and normal hepatocyte cell LO2 suggested that compound 1 could selectively inhibit the proliferation of cancer cell lines with IC50 from 0.05 to 0.15 µM. Pro-apoptotic activity revealed that it induced the apoptosis of MGC-803 cancer cells in a dose-dependent manner. Meanwhile, treatment of MGC-803 cancer cells with 1 resulted in diminution of pro-caspases 3 and 9 and activation of caspases 3 and 9, while it increased the Bax/Bcl-2 ratio in a dose-dependent manner. These meant that 1 induced the apoptosis of cancer cells by involving the intrinsic apoptotic pathway. In addition, the cell cycle distribution of MGC-803 cancer cells treated by 1 revealed that it could lead to cell cycle arrest at the G2/M phase. Altogether, this study suggested that compound 1 may exhibit anticancer activity by its capability of induction of intrinsic apoptosis and cell cycle arrest at G2/M phase.

Cardiac Glycosides from the Seeds of Thevetia peruviana.

Investigation of the seeds of Thevetia peruviana resulted in the isolation of 15 new (2-16) and 18 known (1 and 17-33) cardiac glycosides. Eight 19-nor-cardenolides (1-8), including two rare 19-nor-10-hydroperoxycardenolides, were obtained from T. peruviana for the first time. All the structures were characterized by NMR spectroscopy and chemical derivatization. The inhibitory effects of cardiac glycosides 1-33 against three cancer cell lines (human lung cancer cells, P15; human gastric cancer cells, MGC-803; and human pancreatic cancer cells, SW1990) and one normal hepatocyte cell line, LO2, were evaluated, and a preliminary structure-activity relationship is discussed. In addition, cardiac glycosides 1, 22, 26, and 28 were evaluated for their apoptosis-inducing activities in MGC-803 cells, showing IC50 values in the range 0.02-0.53 µM.