Hsieh Yi-Hsien, Wu Trang-Tiau, Huang Chih-Yang, Hsieh Yih-Shou, Hwang Jin-Ming, Liu Jer-Yuh
Institute of Biochemistry and Biotechnology, School of Medicine, College of Medicine, Chung Shan Medical University, Taichung, Taiwan, Republic of China.
Cancer Res. 2007 May 1;67(9):4320-7. doi: 10.1158/0008-5472.CAN-06-2486.
Protein kinase Calpha (PKCalpha) has been suggested to play an important role in tumorigenesis, invasion, and metastasis. In this study, we investigated the signal pathways selectively activated by PKCalpha in human hepatocellular carcinoma (HCC) cells to determine the role of mitogen-activated protein kinases (MAPK) in PKCalpha-mediated HCC migration and invasion. A stable SK-Hep-1 cell clone (siPKCalpha-SK) expressing DNA-based small interfering RNA (siRNA) PKCalpha was established and was then characterized by cell growth, migration, and invasion. The expression of PKCalpha was decreased in siPKCalpha-SK, and cell growth, migration, and invasion were reduced. These changes were associated with the decrease in p38 MAPK phosphorylation level, but not in c-jun-NH(2)-kinase-1/2 (JNK-1/2) and extracellular signal-regulated kinase-1/2 (ERK-1/2). This phenomenon was confirmed in the SK-Hep-1 cells treated with antisense PKCalpha olignucleotide. The p38 MAPK inhibitor SB203580 or dominant negative p38 mutant plasmid (DN-p38) was used to evaluate the dependency of p38 MAPK in PKCalpha-regulated migration and invasion. Attenuation of cell migration and invasion was revealed in the SK-Hep-1 cells treated with the SB203580 or DN-p38, but not with ERK-1/2 inhibitor PD98059 or JNK-1/2 inhibitor SP600125. Overexpression of constitutively active MKK6 or PKCalpha may restore the inactivation of p38 and the attenuation of cell migration and invasion in siPKCalpha-SK. Similar findings were observed in the stable HA22T/VGH cell clone expressing siRNA PKCalpha. This study provides new insight into the role of p38 MAPK in PKCalpha-mediated malignant phenotypes, especially in PKCalpha-mediated cancer cell invasion, which may have valuable implications for developing new therapies for some PKCalpha-overexpressing cancers.
蛋白激酶Cα（PKCα）被认为在肿瘤发生、侵袭和转移中起重要作用。在本研究中，我们调查了PKCα在人肝癌（HCC）细胞中选择性激活的信号通路，以确定丝裂原活化蛋白激酶（MAPK）在PKCα介导的HCC迁移和侵袭中的作用。建立了表达基于DNA的小干扰RNA（siRNA）PKCα的稳定SK-Hep-1细胞克隆（siPKCα-SK），然后通过细胞生长、迁移和侵袭对其进行表征。PKCα在siPKCα-SK中的表达降低，细胞生长、迁移和侵袭减少。这些变化与p38 MAPK磷酸化水平的降低有关，但与c-jun-NH(2)-激酶-1/2（JNK-1/2）和细胞外信号调节激酶-1/2（ERK-1/2）无关。在用反义PKCα寡核苷酸处理的SK-Hep-1细胞中证实了这一现象。使用p38 MAPK抑制剂SB203580或显性负性p38突变体质粒（DN-p38）来评估p38 MAPK在PKCα调节的迁移和侵袭中的依赖性。在用SB203580或DN-p38处理的SK-Hep-1细胞中显示出细胞迁移和侵袭的减弱，但在用ERK-1/2抑制剂PD98059或JNK-1/2抑制剂SP600125处理的细胞中未显示。组成型活性MKK6或PKCα的过表达可能恢复siPKCα-SK中p38的失活以及细胞迁移和侵袭的减弱。在表达siRNA PKCα的稳定HA22T/VGH细胞克隆中观察到了类似的结果。本研究为p38 MAPK在PKCα介导的恶性表型中的作用提供了新的见解，特别是在PKCα介导的癌细胞侵袭中，这可能对开发针对某些PKCα过表达癌症的新疗法具有重要意义。
