Pristimerin, a quinonemethide
triterpenoid, has demonstrated anticancer activity against a number of types of
cancer, including
breast cancer. However, its mechanism of action remains unclear. The present study investigated the autophagy‑induced anticancer efficacy of
pristimerin on MDA‑MB‑231 human
breast cancer cells.
Pristimerin inhibited the growth of these cells in a concentration‑dependent manner. Treatment with
pristimerin dose‑dependently induced an increase of light chain 3B (LC3‑II), whereas autophagy inhibitor 3‑methyladenine (3‑MA) inhibited pristimerin‑induced LC3‑II accumulation and cytotoxic effects. Autophagy was also activated by
paclitaxel as observed by an elevated LC3‑II level. Although 24 µM
paclitaxel induced autophagy without cytotoxicity, combined with
pristimerin it additively induced cell growth inhibition and autophagy induction. Autophagy induction was measured with an autophagy detection kit and LC3‑II levels were monitored by western blot analysis. Treatment with 3‑MA inhibited LC3‑II accumulation and cell death induced by a combination of
paclitaxel and
pristimerin.
Pristimerin and
paclitaxel inhibited extracellular signal‑regulated
kinase (ERK)1/2/p90RSK signaling, consistent with autophagy indicators, namely p62 degradation and
beclin 1 expression. In addition, ERK activator
ceramide C6 treatment suppressed the LC3‑II levels induced by a combination of
paclitaxel and
pristimerin. These results suggested that exposure to
pristimerin induced autophagic cell death, whereas a combination treatment of
pristimerin and
paclitaxel resulted in an additive effect on ERK‑dependent autophagic cell death.