Abstract 5572: Breastin a natural product from Nerium Oleander exhibits high activity in a panel of human tumor cell lines.

Background: More than half of all registered anticancer agents were originally derived from natural sources. We isolated and screened >2.000 pure compounds, and purified extracts from microorganisms and plants in a panel of human tumor cell lines (Kelter et al. ENA 2008). Here we report on the activity of Breastin, a defined extract isolated from the plant Nerium Oleander in 63 human cell lines. The mode of action was elucidated by comparing the activity profile with that of known anticancer agents with defined mechanism.

Methods: Breastin was isolated as cold extract from the leaves of the plant Nerium Oleander. It contains defined amounts of glycosides, flavonoides and polysaccharides. In-vitro activity was determined in 63 human tumor cell lines in a monolayer assay. 4 to 10,000 cells were seeded in 96 well plates; one day later Breastin was added at 5 concentrations and incubated with the cells for 4 days. The read-out was propidium iodide-based fluorescence. Based on IC₅₀ and IC₇₀ values tumor selectivity was analyzed. In the Compare Analysis the IC₅₀ and IC₇₀ pattern of Breastin was compared with the corresponding patterns of 180 known substances using Spearman Correlations.

Results: Breastin showed a dose-dependent antitumor activity, the mean IC₅₀ and IC₇₀ were 1.1 and 2.7 μg/ml, respectively. It was the most potent and selective preparation out of a series of 36 extracts that were obtained with different extraction procedures. 31 / 63 cell lines investigated showed IC₅₀ < 1.14 μg/ml. Breastin had a higher potency than several anticancer agents used in the clinic, e.g. Cisplatin, 5-Fluoruracil and Cyclophosphamide. The highest activity was seen in bladder, CNS, colon and NSC lung cancer cell lines as well as in pancreas and prostate models. In systematic combination studies Breastin increased the effect of the tubuline binders Paclitaxel, and Docetaxel in 4/6 cell lines, the alkylating agents Cyclophamide and Mitomycin, adriamycin and alimta.

The Compare Analyses showed no similarity with 180 known anticancer agents, the coefficients of correlation were < 0.6 in all cases. Therefore Breastin has probably a different mechanism of action. In previous studies components of Breastin acted as specific inhibitors of the membrane Na+/K+ ATPase. This type of compounds is not included in the reference data base. Analyses of predictive biomarkers and gene patterns are ongoing.

In former studies in-vivo activity was determined in murine models: B16 melanoma and Lewis-Lung-carcinoma were sensitive, leukemias L1210 and P388 were resistant.

Conclusion: The evaluation of 36 extracts from Nerium Oleander identified the cold extract called Breastin as most promising anticancer agent with selective in-vitro activity found in bladder, CNS, colon and NSC lung cancer cell lines as well as in pancreas and prostate models. Moreover, in combination studies Breastin showed synergism with severall cytotoxic drugs.

Citation Format: Heinz H. Fiebig, Gerhard Kelter, Armin Maier, Thomas Metz, Luay J. Rashan. Breastin a natural product from Nerium Oleander exhibits high activity in a panel of human tumor cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5572. doi:10.1158/1538-7445.AM2013-5572