Calpain 2 Regulates Akt-FoxO-p27Kip1 Protein Signaling Pathway in Mammary Carcinoma
Calpain 2 Regulates Akt-FoxO-p27Kip1 Protein Signaling Pathway in Mammary Carcinoma
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DOI：
10.1074/jbc.m112.349308
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发表时间：
2012-05-04
影响因子：
4.8
通讯作者：
Greer, Peter A.
中科院分区：
文献类型：
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作者：
Ho, Wai-chi;Pikor, Larissa;Greer, Peter A.
我们研究了广泛表达的钙蛋白酶2亚型在乳腺肿瘤细胞生长、迁移、信号传导和肿瘤发生中的作用。RNA干扰介导的capn 2转录物的敲低被用于操纵钙蛋白酶2的催化亚基在AC 2 M2小鼠乳腺癌细胞系中的表达。稳定敲除capn 2与体外增殖率、软琼脂集落形成效率和迁移率降低相关，表明钙蛋白酶2在有丝分裂、存活和运动发生中的作用。生化分析显示，在钙蛋白酶2缺陷细胞中，蛋白磷酸酶2A水平升高，激活Akt水平降低，这与FoxO 3a靶基因产物p27（Kip 1）水平升高相关，p27是细胞增殖的关键调节因子。AC 2 M2细胞中钙蛋白酶2缺乏与FoxO 3a的核定位增强相关，这与其处于能够调节转录靶点的去抑制状态一致。原位移植的钙蛋白酶2敲低AC 2 M2细胞产生的肿瘤生长速率降低，体内p27（Kip 1）表达增强。总之，钙蛋白酶2缺乏与Akt活性降低、蛋白磷酸酶2A水平升高、FoxO 3a去抑制和p27（Kip 1）肿瘤抑制因子表达增强相关。这些观察结果表明，钙蛋白酶2通过PI 3 K-Akt-FoxO-p27（Kip 1）信号级联在体外和体内促进肿瘤细胞生长。因此，抑制钙蛋白酶2可能在癌症治疗中提供治疗益处。
We investigated the role of the ubiquitously expressed calpain 2 isoform in breast tumor cell growth, migration, signaling, and tumorigenesis. RNAi-mediated knockdown of the capn2 transcript was used to manipulate expression of the catalytic subunit of calpain 2 in the AC2M2 mouse mammary carcinoma cell line. Stable knockdown of capn2 correlated with reduced in vitro proliferation rates, soft agar colony formation efficiency, and migration rates, indicating roles for calpain 2 in mitogenesis, survival, and motogenesis. Biochemical analysis showed increased levels of protein phosphatase 2A and reduced levels of activated Akt in calpain 2-deficient cells, and this correlated with increased levels of the FoxO3a target gene product p27(Kip1), a key regulator of cell proliferation. Calpain 2 deficiency in the AC2M2 cells correlated with enhanced nuclear localization of FoxO3a, consistent with it being in a derepressed state capable of regulating transcriptional targets. Orthotopically engrafted calpain 2 knockdown AC2M2 cells generated tumors with reduced growth rates and enhanced in vivo expression of p27(Kip1). In summary, calpain 2 deficiency correlated with reduced Akt activity, increased protein phosphatase 2A levels, derepression of FoxO3a, and enhanced expression of the p27(Kip1) tumor suppressor. These observations argue that calpain 2 promotes tumor cell growth both in vitro and in vivo through the PI3K-Akt-FoxO-p27(Kip1) signaling cascade. Inhibition of calpain 2 might therefore provide therapeutic benefits in the treatment of cancer.