From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
the Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, and.
J Biol Chem. 2013 Jul 19;288(29):21197-21207. doi: 10.1074/jbc.M113.484576. Epub 2013 Jun 5.
Recently, we have shown that CXCL12/CXCR4 signaling plays an important role in gemcitabine resistance of pancreatic cancer (PC) cells. Here, we explored the effect of gemcitabine on this resistance mechanism. Our data demonstrate that gemcitabine induces CXCR4 expression in two PC cell lines (MiaPaCa and Colo357) in a dose- and time-dependent manner. Gemcitabine-induced CXCR4 expression is dependent on reactive oxygen species (ROS) generation because it is abrogated by pretreatment of PC cells with the free radical scavenger N-acetyl-L-cysteine. CXCR4 up-regulation by gemcitabine correlates with time-dependent accumulation of NF-κB and HIF-1α in the nucleus. Enhanced binding of NF-κB and HIF-1α to the CXCR4 promoter is observed in gemcitabine-treated PC cells, whereas their silencing by RNA interference causes suppression of gemcitabine-induced CXCR4 expression. ROS induction upon gemcitabine treatment precedes the nuclear accumulation of NF-κB and HIF-1α, and suppression of ROS diminishes these effects. The effect of ROS on NF-κB and HIF-1α is mediated through activation of ERK1/2 and Akt, and their pharmacological inhibition also suppresses gemcitabine-induced CXCR4 up-regulation. Interestingly, our data demonstrate that nuclear accumulation of NF-κB results from phosphorylation-induced degradation of IκBα, whereas HIF-1α up-regulation is NF-κB-dependent. Lastly, our data demonstrate that gemcitabine-treated PC cells are more motile and exhibit significantly greater invasiveness against a CXCL12 gradient. Together, these findings reinforce the role of CXCL12/CXCR4 signaling in gemcitabine resistance and point toward an unintended and undesired effect of chemotherapy.
最近，我们已经证实，CXCL12/CXCR4 信号在胰腺癌细胞（PC）对吉西他滨的耐药性中发挥着重要作用。在此，我们探索了吉西他滨对这一耐药机制的影响。我们的数据表明，吉西他滨以剂量和时间依赖的方式诱导两种 PC 细胞系（MiaPaCa 和 Colo357）中 CXCR4 的表达。吉西他滨诱导的 CXCR4 表达依赖于活性氧（ROS）的产生，因为 PC 细胞用自由基清除剂 N-乙酰-L-半胱氨酸预处理可消除其表达。吉西他滨诱导的 CXCR4 上调与核内 NF-κB 和 HIF-1α 的时间依赖性积累相关。在吉西他滨处理的 PC 细胞中观察到 NF-κB 和 HIF-1α 与 CXCR4 启动子的增强结合，而它们的 RNA 干扰沉默导致吉西他滨诱导的 CXCR4 表达受到抑制。吉西他滨处理后 ROS 的诱导先于 NF-κB 和 HIF-1α 的核内积累，而 ROS 的抑制作用则减弱了这些效应。ROS 对 NF-κB 和 HIF-1α 的影响是通过激活 ERK1/2 和 Akt 介导的，其药理学抑制也抑制了吉西他滨诱导的 CXCR4 上调。有趣的是，我们的数据表明，NF-κB 的核内积累是由于 IκBα 的磷酸化诱导降解所致，而 HIF-1α 的上调则依赖于 NF-κB。最后，我们的数据表明，吉西他滨处理的 PC 细胞更具迁移性，并且在 CXCL12 梯度下表现出显著更高的侵袭性。总之，这些发现强化了 CXCL12/CXCR4 信号在吉西他滨耐药中的作用，并指出了化疗的一种意外和不良影响。
