Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
J Cell Physiol. 2010 Jun;223(3):764-70. doi: 10.1002/jcp.22088.
Recently, we reported that reduction of intracellular Cl(-) concentration (Cl(-)) inhibited proliferation of MKN28 gastric cancer cells by diminishing the transition rate from G(1) to S cell-cycle phase through upregulation of p21, cyclin-dependent kinase inhibitor, in a p53-independent manner. However, it is still unknown how intracellular Cl(-) regulates p21 expression level. In this study, we demonstrate that mitogen-activated protein kinases (MAPKs) are involved in the p21 upregulation and cell-cycle arrest induced by reduction of Cl(-). Culture of MKN28 cells in a low Cl(-) medium significantly induced phosphorylation (activation) of MAPKs (ERK, p38, and JNK) and G(1)/S cell-cycle arrest. To clarify the involvement of MAPKs in p21 upregulation and cell growth inhibition in the low Cl(-) medium, we studied effects of specific MAPKs inhibitors on p21 upregulation and G(1)/S cell-cycle arrest in MKN28 cells. Treatment with an inhibitor of p38 or JNK significantly suppressed p21 upregulation caused by culture in a low Cl(-) medium and rescued MKN28 cells from the low Cl(-)-induced G(1) cell-cycle arrest, whereas treatment with an ERK inhibitor had no significant effect on p21 expression or the growth of MKN28 cells in the low Cl(-) medium. These results strongly suggest that the intracellular Cl(-) affects the cell proliferation via activation of p38 and/or JNK cascades through upregulation of the cyclin-dependent kinase inhibitor (p21) in a p53-independent manner in MKN28 cells.
最近，我们报道了通过降低细胞内氯离子浓度(Cl-)，通过上调细胞周期蛋白依赖性激酶抑制剂 p21，使 MKN28 胃癌细胞从 G1 期向 S 期的过渡率降低，从而抑制其增殖，这一过程不依赖于 p53。然而，细胞内氯离子如何调节 p21 的表达水平仍不清楚。在本研究中，我们证明丝裂原活化蛋白激酶（MAPKs）参与了氯离子减少诱导的 p21 上调和细胞周期阻滞。在低氯离子培养基中培养 MKN28 细胞可显著诱导 MAPKs（ERK、p38 和 JNK）的磷酸化（激活）和 G1/S 细胞周期阻滞。为了阐明 MAPKs 在低氯离子培养基中 p21 上调和细胞生长抑制中的作用，我们研究了 MAPKs 特异性抑制剂对 MKN28 细胞中 p21 上调和 G1/S 细胞周期阻滞的影响。用 p38 或 JNK 的抑制剂处理可显著抑制低氯离子培养引起的 p21 上调，并使 MKN28 细胞从低氯离子诱导的 G1 期细胞周期阻滞中恢复，而用 ERK 抑制剂处理对 MKN28 细胞在低氯离子中的 p21 表达或生长没有显著影响。这些结果强烈表明，细胞内氯离子通过激活 p38 和/或 JNK 级联反应，在 MKN28 细胞中以不依赖 p53 的方式上调细胞周期蛋白依赖性激酶抑制剂（p21），从而影响细胞增殖。
