Triple-negative breast cancers (TNBCs) are clinically aggressive forms associated with a poor prognosis. We evaluated the cytotoxic effect exerted on triple-negative MDA-MB231
breast cancer cells both by
parthenolide and its soluble analogue
dimethylamino parthenolide (DMAPT) and explored the underlying molecular mechanism. The drugs induced a dose- and time-dependent decrement in cell viability, which was not prevented by the
caspase inhibitor
z-VAD-fmk. In particular in the first hours of treatment (1-3 h),
parthenolide and DMAPT strongly stimulated
reactive oxygen species (ROS) generation. The drugs induced production of
superoxide anion by activating
NADPH oxidase. ROS generation caused depletion of
thiol groups and
glutathione, activation of
c-Jun N-terminal kinase (JNK) and downregulation of nuclear factor kB (
NF-kB). During this first phase,
parthenolide and DMAPT also stimulated autophagic process, as suggested by the enhanced expression of
beclin-1, the conversion of
microtubule-associated protein light chain 3-I (LC3-I) to LC3-II and the increase in the number of cells positive to
monodansylcadaverine. Finally, the drugs increased RIP-1 expression. This effect was accompanied by a decrement of
pro-caspase 8, while its cleaved form was not detected and the expression of c-FLIPS markedly increased. Prolonging the treatment (5-20 h) ROS generation favoured dissipation of mitochondrial membrane potential and the appearance of necrotic events, as suggested by the increased number of cells positive to
propidium iodide staining. The administration of DMAPT in nude mice bearing xenografts of MDA-MB231 cells resulted in a significant inhibition of tumour growth, an increment of animal survival and a marked reduction of the lung area invaded by
metastasis. Immunohistochemistry data revealed that treatment with DMAPT reduced the levels of
NF-kB, metalloproteinase-2 and -9 and
vascular endothelial growth factor, while induced upregulation of phosphorylated JNK. Taken together, our data suggest a possible use of
parthenolide for the treatment of TNBCs.