Department of Surgery, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan.
Carcinogenesis. 2013 Jun;34(6):1232-43. doi: 10.1093/carcin/bgt057. Epub 2013 Feb 6.
Protein kinase Cα (PKCα) is highly expressed in pancreatic cancer. However, the effects of PKCα on Snail and claudin-1, which play crucial roles in epithelial cell polarity during epithelial-mesenchymal transition (EMT), remain unclear. In this study, we investigated the mechanisms of regulation of Snail and claudin-1 via a PKCα signal pathway during EMT in pancreatic cancer cells and in normal human pancreatic duct epithelial cells (HPDEs). By immunostaining, overexpression of PKCα and downregulation of claudin-1 were observed in poorly differentiated human pancreatic cancer tissues and the pancreatic cancer cell line PANC-1. Treatment with the PKCα inhibitor Gö6976 transcriptionally decreased Snail and increased claudin-1 in PANC-1 cells. The PKCα inhibitor prevented upregulation of Snail and downregulation of claudin-1 during EMT induced by transforming growth factor-β1 (TGF-β1) treatment and under hypoxia in PANC-1 cells. The effects of the PKCα inhibitor were in part regulated via an extracellular signal-regulated kinase (ERK) signaling pathway. The PKCα inhibitor also prevented downregulation of the barrier function and fence function during EMT in well-differentiated pancreatic cancer cell line HPAC. In normal HPDEs, the PKCα inhibitor transcriptionally induced not only claudin-1 but also claudin-4, -7 and occludin without a change of Snail. Treatment with the PKCα inhibitor in normal HPDEs prevented downregulation of claudin-1 and occludin by TGF-β1 treatment and enhanced upregulation of claudin-1, -4, -7 and occludin under hypoxia. These findings suggest that PKCα regulates claudin-1 via Snail- and mitogen-activated protein kinase/ERK-dependent pathways during EMT in pancreatic cancer. Thus, PKCα inhibitors may be potential therapeutic agents against the malignancy of human pancreatic cancer cells.
蛋白激酶 Cα（PKCα）在胰腺癌中高度表达。然而，PKCα 对上皮细胞极性在上皮间质转化（EMT）过程中起关键作用的 Snail 和 Claudin-1 的影响尚不清楚。在这项研究中，我们研究了 PKCα 信号通路在胰腺癌细胞和正常人类胰腺导管上皮细胞（HPDEs）中的 EMT 过程中调节 Snail 和 Claudin-1 的机制。通过免疫染色，在分化不良的人类胰腺癌组织和胰腺癌细胞系 PANC-1 中观察到 PKCα 的过表达和 Claudin-1 的下调。PKCα 抑制剂 Gö6976 处理可使 PANC-1 细胞中转录下调 Snail 并上调 Claudin-1。PKCα 抑制剂可防止 TGF-β1 处理和缺氧诱导的 PANC-1 细胞 EMT 中 Snail 的上调和 Claudin-1 的下调。PKCα 抑制剂的作用部分通过细胞外信号调节激酶（ERK）信号通路调节。PKCα 抑制剂还可防止 EMT 过程中分化良好的胰腺癌细胞系 HPAC 中屏障功能和围栏功能的下调。在正常的 HPDEs 中，PKCα 抑制剂不仅转录诱导 Claudin-1，还转录诱导 Claudin-4、-7 和 Occludin，而 Snail 没有变化。在正常的 HPDEs 中用 PKCα 抑制剂处理可防止 TGF-β1 处理下调 Claudin-1 和 Occludin，并增强缺氧时 Claudin-1、-4、-7 和 Occludin 的上调。这些发现表明，PKCα 通过 EMT 过程中 Snail 和丝裂原活化蛋白激酶/ERK 依赖性途径调节 Claudin-1。因此，PKCα 抑制剂可能是针对人类胰腺癌细胞恶性的潜在治疗剂。
