Lan Mei, Shi Yongquan, Han Zheyi, Hao Zhiming, Pan Yanglin, Liu Na, Guo Changcun, Hong Liu, Wang Jun, Qiao Taidong, Fan Daiming
State Key Laboratory of Cancer Biology & Institute of Digestive Disease, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, China.
Cancer Biol Ther. 2005 Dec;4(12):1342-7. doi: 10.4161/cbt.4.12.2175. Epub 2005 Dec 14.
Voltage-gated potassium (Kv) channels have been reported to be involved in the proliferation of many types of cells, including tumor cells. The overexpression of the Kv channels and related channel activity are involved in the neoplastic process. Our previous study has shown the existence of delayed rectifier potassium (I(K)) current in gastric cancer cells SGC7901. However, the expression and function of most delayed rectifier potassium (K(D)) channel subunits in gastric cancer cells are not completely resolved. Here we examine expression of K(D) channel subunits in Kv1-Kv3 families in immortalized gastric epithelial cells GES and various gastric cancer cells (including AGS, KATOIII, MKN28, MKN45, MGC803, SGC7901, SGC7901/ADR and SGC7901/VCR), and their roles in cell proliferation. RT-PCR analysis reveals that all cell lines examined express Kv1.3, Kv1.5, Kv1.6, Kv2.1 and Kv2.2. However, Kv1.2 and Kv3.2 genes are barely detectable in any given cancer cell lines. Kv1.5 protein, high mRNA levels in all cell lines examined, is also expressed in some cancer cells lines and more frequently detected in gastric cancer tissues. Downregulation of the expression of Kv1.5 in SGC7901 with RNA interference significantly inhibited the proliferation and tumorigenicity of SGC7901 cells. Moreover, in Ca(2+)-containing rather than Ca(2+)-free medium, KCl (50mM) stimulated a rapid increase in the concentration of cytosolic calcium in empty vector transfected cells that was blocked by verapamil. Likewise, decrease the expression of Kv1.5 with short interfering RNA also blocked the depolarization-induced influx of Ca(2+). This finding suggests that more than one kind of K(D) channel subunits are expressed in various gastric cancer cell lines. Kv1.5 may be involved in tumor cells proliferation by controlling Ca(2+) entry, and the interference of K(D) channels expression and/or activity could provide a novel strategy to reverse the malignant phenotype of gastric cancer cells.
据报道，电压门控钾（Kv）通道参与包括肿瘤细胞在内的多种类型细胞的增殖。Kv通道的过表达及相关通道活性与肿瘤形成过程有关。我们之前的研究表明，胃癌细胞SGC7901中存在延迟整流钾电流（I(K)）。然而，胃癌细胞中大多数延迟整流钾（K(D)）通道亚基的表达和功能尚未完全明确。在此，我们检测了永生化胃上皮细胞GES和各种胃癌细胞（包括AGS、KATOIII、MKN28、MKN45、MGC803、SGC7901、SGC7901/ADR和SGC7901/VCR）中K(D)通道亚基在Kv1 - Kv3家族中的表达情况，以及它们在细胞增殖中的作用。逆转录聚合酶链反应（RT-PCR）分析显示，所有检测的细胞系均表达Kv1.3、Kv1.5、Kv1.6、Kv2.1和Kv2.2。然而，在任何给定的癌细胞系中几乎检测不到Kv1.2和Kv3.2基因。Kv1.5蛋白在所有检测的细胞系中mRNA水平都很高，在一些癌细胞系中也有表达，且在胃癌组织中更常被检测到。用RNA干扰下调SGC7901中Kv1.5的表达可显著抑制SGC7901细胞的增殖和致瘤性。此外，在含Ca(2+)而非无Ca(2+)的培养基中，50mM氯化钾刺激空载体转染细胞的胞质钙浓度迅速升高，这一过程被维拉帕米阻断。同样，用短干扰RNA降低Kv1.5的表达也能阻断去极化诱导的Ca(2+)内流。这一发现表明，多种K(D)通道亚基在各种胃癌细胞系中表达。Kv1.5可能通过控制Ca(2+)内流参与肿瘤细胞增殖，干扰K(D)通道的表达和/或活性可能为逆转胃癌细胞的恶性表型提供一种新策略。
