Effect of justicidin B - a potent cytotoxic and pro-apoptotic arylnaphtalene lignan on human breast cancer-derived cell lines.

Justicidin B produced by genetically transformed cultures of Linum leonii was tested for cytotoxic activity and induction of apoptosis in MDA-MB-231 and MCF-7 breast cancer derived cell lines. The tested lignan evoked strong, concentration dependent cytotoxicity in both cell lines, whereby MCF-7 proved to be far more sensitive as compared to MDA-MB-231. The 24 h treatment of both cell lines increased the level of apoptotic DNA fragmentation; however the proapoptotic activity is completely inhibited if the cells are co-incubated with the non-selective pan-caspase inhibitor Boc-Asp(OMe)-fluoromethyl ketone (PCI), which implies that justicidin B, activates programmed cell death via caspase -dependent mechanisms. Exposure of MDA-MB-231 cells with justicidin B leads to concentration dependent decrease in the expression of NFkB; whereas the treatment of MCF-7, is consistent with strong increase in the expression of this transcription factor.