C6 ceramide dramatically enhances docetaxel-induced growth inhibition and apoptosis in cultured breast cancer cells: A mechanism study

Here we reported that co-administration of docetaxel and a cell-permeable short-chain ceramide (C6) resulted in a striking increase in growth inhibition and apoptosis in primary and transformed breast cells (MCF-7 and MDA-231), which were associated with mitochondrial permeability transition pore (mPTP) opening, a significant reactive oxygen species (ROS) production and the pro-apoptotic AMP-Protein Kinase (AMPK) as well as c-Jun N-terminal kinases (JNK) activations. Contrarily, the mPTP blocker sanglifehrin A (SfA) or the ROS scavenger N-acetyl-L-cysteine (NAC) largely inhibited co-administration-induced cytotoxicity. Further, cyclosporin A (CsA), the inhibitor of cyclophilin-D (Cyp-D, the key mPTP component), as well as Cyp-D RNA silencing also suppressed breast cancer cell death by the co-treatment, while cells overexpressing Cyp-D showed hypersensitivity to docetaxel. Meanwhile, JNK and AMPK inhibition alleviated cell death induced by the co-administration in cultured breast cancer cells. Significantly, C6 ceramide plus docetaxel caused dramatic human epidermal growth factor receptor (HER)-1/-2 degradation and downstream Akt/Erk inhibition in HER-2 expressing MDA-231 cells. These in vitro findings provide confidence in support of further development of C6 ceramide as an adjunct of docetaxel for the treatment of the metastatic breast cancer. (C) 2015 Elsevier Inc. All rights reserved.