Mcl-1 confers protection of Her2-positive breast cancer cells to hypoxia: therapeutic implications

作者：Muhammad Hasan Bashari, Fengjuan Fan, Sonia Vallet, Martin Sattler, M. Arn, Claudia Luckner‐Minden, Henning Schulze‐Bergkamen, Inka Zörnig, Frederik Marmé, Andreas Schneeweiß, Michael H. Cardone, Joseph T. Opferman, Dirk Jäger, Klaus Podar · 发表于：Breast Cancer Research · 年份：2016 · DOI：10.1186/s13058-016-0686-4 · 被引用次数：38 · 研究领域：Cell death mechanisms and regulation、Phagocytosis and Immune Regulation、Cancer, Hypoxia, and Metabolism

BACKGROUND: Molecular mechanisms leading to the adaptation of breast cancer (BC) cells to hypoxia are largely unknown. The anti-apoptotic Bcl-2 family member myeloid cell leukemia-1 (Mcl-1) is frequently amplified in BC; and elevated Mcl-1 levels have been correlated with poor prognosis. Here we investigated the pathophysiologic role of Mcl-1 in Her2-positive BC cells under hypoxic conditions. METHODS: RNA interference and a novel small molecule inhibitor, EU-5346, were used to examine the role of Mcl-1 in Her2-positive BC cell lines and primary BC cells (sensitive or intrinsically resistant to Her2 inhibitors) under hypoxic conditions (using a hypoxic incubation chamber). Mechanisms-of-action were investigated by RT-PCR, mitochondrial isolation, as well as immunoprecipitation/blotting analysis, and microscopy. The specificity against Mcl-1 of the novel small molecule inhibitor EU5346 was verified in Mcl-1(Δ/null) versus Mcl-1(wt/wt) Murine Embryonic Fibroblasts (MEFs). Proliferation, survival, and spheroid formation were assessed in response to Mcl-1 and Her2 inhibition. RESULTS: We demonstrate for a strong correlation between high Mcl-1 protein levels and hypoxia, predominantly in Her2-positive BC cells. Surprisingly, genetic depletion of Mcl-1 decreased Her2 and Hif-1α levels followed by inhibition of BC cell survival. In contrast, Mcl-1 protein levels were not downregulated after genetic depletion of Her2 indicating a regulatory role of Mcl-1 upstream of Her2. Indeed, Mcl...