Department of Radiation Oncology, University of Virginia School of Medicine, P.O. Box 800383, Charlottesville, VA 22908.
Mol Cancer Res. 2014 Mar;12(3):348-58. doi: 10.1158/1541-7786.MCR-13-0485. Epub 2013 Dec 20.
Epithelial tumor cells express T-type Ca(2+) channels, which are thought to promote cell proliferation. This study investigated the cellular response to T-type Ca(2+) channel inhibition either by small-molecule antagonists or by RNAi-mediated knockdown. Selective T-type Ca(2+) channel antagonists caused growth inhibition and apoptosis more effectively in HCT116 cells expressing wild-type p53 (p53wt), than in HCT116 mutant p53(-/-) cells. These antagonists increased p53-dependent gene expression and increased genomic occupancy of p53 at specific target sequences. The knockdown of a single T-type Ca(2+) channel subunit (CACNA1G) reduced cell growth and induced caspase-3/7 activation in HCT116 p53wt cells as compared with HCT116 mutant p53(-/-) cells. Moreover, CaCo2 cells that do not express functional p53 were made more sensitive to CACNA1G knockdown when p53wt was stably expressed. Upon T-type Ca(2+) channel inhibition, p38-MAPK promoted phosphorylation at Ser392 of p53wt. Cells treated with the inhibitor SB203580 or specific RNAi targeting p38-MAPKα/β (MAPK14/MAPK11) showed resistance to T-type Ca(2+) channel inhibition. Finally, the decreased sensitivity to channel inhibition was associated with decreased accumulation of p53 and decreased expression of p53 target genes, p21Cip1 (CDKN1A) and BCL2-binding component 3 (BBC3/PUMA).
A novel pathway involving p53 and p38-MAPK is revealed and provides a rationale for antitumor therapies that target T-type Ca(2+) channels.
上皮肿瘤细胞表达 T 型钙 (Ca 2+ ) 通道，这些通道被认为能促进细胞增殖。本研究通过小分子拮抗剂或 RNAi 介导的敲低来研究 T 型 Ca 2+ 通道抑制对细胞的反应。在表达野生型 p53 (p53wt) 的 HCT116 细胞中，选择性 T 型 Ca 2+ 通道拮抗剂比在 HCT116 突变型 p53(-/-)细胞中更有效地引起生长抑制和细胞凋亡。这些拮抗剂增加了 p53 依赖性基因表达，并增加了 p53 在特定靶序列上的基因组结合。单个 T 型 Ca 2+ 通道亚基 (CACNA1G) 的敲低降低了 HCT116 p53wt 细胞的细胞生长，并诱导 caspase-3/7 激活，与 HCT116 突变型 p53(-/-)细胞相比。此外，当稳定表达 p53wt 时，不表达功能性 p53 的 CaCo2 细胞对 CACNA1G 敲低更为敏感。T 型 Ca 2+ 通道抑制后，p38-MAPK 促进 p53wt 的 Ser392 磷酸化。用抑制剂 SB203580 或针对 p38-MAPKα/β (MAPK14/MAPK11) 的特异性 RNAi 处理的细胞对 T 型 Ca 2+ 通道抑制表现出抗性。最后，对通道抑制的敏感性降低与 p53 积累减少和 p53 靶基因 p21Cip1 (CDKN1A) 和 BCL2 结合成分 3 (BBC3/PUMA) 的表达减少有关。
揭示了一条涉及 p53 和 p38-MAPK 的新途径，为靶向 T 型 Ca 2+ 通道的抗肿瘤治疗提供了依据。
