Willow bark extract (BNO 1455) and its fractions promote apoptosis in human lung cancer cells irrespective their basal level of COX-2, p53 and Bcl-2 genes

Aim of this study was to examine effects of compounds (salicylalcohol derivates F1, flavonoids F2, proanthocyanidins F3), isolated from willow bark extract BNO 1455 on proliferation and apoptosis in human lung cancer cells. We used COX-2 proficient human non-small cell lung cancer (NSCLC) A549 cells with wild type p53 and low level Bcl-2 genes (6.5%) in opposite to small cell lung cancer (SCLC) SW2 cells with negligible COX-2 basal level (4%), mutation on p53 and high expression of Bcl-2 genes (93%). Cytotoxicity and growth inhibitory activity of BNO 1455 and its fractions were investigated after 72h exposure with propidium iodide uptake by flow cytometry and with WST-1 assay, respectively. Apoptosis induction was detected by Annexin V adherence and morphological changes in cell scatter characteristics using flow cytometry in cell lines at their established GI₅₀ concentrations. As controls acetylsalicylic acid (ASA), salicin (SAL) and quercetin were used. Dose dependent antiproliferative effects were observed on both cancer cell lines. Comparative studies indicate quantitative differences concerning the GI₅₀. The GI₅₀ (µg/ml) of BNO 1455 was 206.7 and 52.8 for A549 and SW2 cells, respectively. GI₅₀ values of ASA were comparable being between 2.2–3.4 mM. Fractions F1, F2 and F3 contributed to the inhibitory activity of BNO 1455 in an additive manner according to their amount as expressed in inhibitory units of 100mg substances. Apoptosis induction after 72h treatment of cells with all substances was confirmed by Annexin V adherence in both cell lines at GI₅₀. However, the F2 and F3 fractions were more potent inducers of apoptosis. Results of this study demonstrate antiproliferative and apoptosis-inducing effects of willow bark extract.