Inhibition of autophagy exerts anti-colon cancer effects via apoptosis induced by p53 activation and ER stress.
Inhibition of autophagy exerts anti-colon cancer effects via apoptosis induced by p53 activation and ER stress.
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DOI：
10.1186/s12885-015-1789-5
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发表时间：
2015-10-24
期刊：
影响因子：
3.8
通讯作者：
Koike K
中科院分区：
文献类型：
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作者：
Sakitani K;Hirata Y;Hikiba Y;Hayakawa Y;Ihara S;Suzuki H;Suzuki N;Serizawa T;Kinoshita H;Sakamoto K;Nakagawa H;Tateishi K;Maeda S;Ikenoue T;Kawazu S;Koike K
虽然一些治疗结直肠癌的分子靶向药物已在临床上使用，并有助于改善预后，但目前晚期结直肠癌患者的中位生存期是不够的。自噬是细胞内氨基酸循环介导的一种基本的细胞生存机制，在癌症中起着重要的作用。最近，自噬被认为是一个很有前途的新分子靶点。据报道，未折叠蛋白反应(UPR)在肠道内稳态中与自噬以互补的方式发挥作用。然而，UPR在自噬抑制下在结肠癌中的作用仍有待阐明。我们的目的是阐明自噬对结肠癌的抑制作用。我们将K19CreERT小鼠和Atg5Flox/FLOX小鼠杂交，产生了Atg5FLOX/FLOX/K19CreERT小鼠。用偶氮甲烷/葡聚糖硫酸钠处理Atg5Flox/FLOX/K19CreERT小鼠，然后注射他莫昔芬抑制CK19阳性上皮细胞的自噬。为了研究自噬抑制的抗癌机制，我们使用了具有不同p53基因状态的结肠癌细胞株，以及针对ATG5和免疫球蛋白重链结合蛋白(Bip)的小干扰RNA(SiRNAs)，免疫球蛋白重链结合蛋白(Bip)是帮助折叠未折叠蛋白质的伴侣。ATG5FLOX/FLOX/K19CreERT小鼠结肠肿瘤自噬功能丧失，肿瘤体积缩小(对照组肿瘤总直径为28.1 mm，Atg5flx/FLOX/K19CreERT小鼠肿瘤总直径为20.7 mm，p = 0.036)。我们发现P53和UPR/内质网(ER)应激相关蛋白，如裂解的caspase 3和CAAT/增强子结合蛋白同源蛋白，在Atg5Flox/FLOX/K19CreERT小鼠的结肠癌中上调。虽然ATG5沉默和Bip沉默分别增加了野生型p53细胞的凋亡，但单独沉默ATG5对突变型p53细胞的凋亡没有同样的影响。然而，ATG5和Bip siRNAs共转染可增加突变型p53细胞的凋亡率。阻断自噬可能通过P53和内质网应激诱导细胞凋亡来治疗结肠癌，抑制UPR通路是克服自噬抑制抵抗的有效策略。
Although some molecularly targeted drugs for colorectal cancer are used clinically and contribute to a better prognosis, the current median survival of advanced colorectal cancer patients is not sufficient. Autophagy, a basic cell survival mechanism mediated by recycling of cellular amino acids, plays an important role in cancer. Recently, autophagy has been highlighted as a promising new molecular target. The unfolded protein response (UPR) reportedly act in complementary fashion with autophagy in intestinal homeostasis. However, the roles of UPR in colon cancer under autophagic inhibition remain to be elucidated. We aim to clarify the inhibitory effect of autophagy on colon cancer. We crossed K19CreERT and Atg5flox/flox mice to generate Atg5flox/flox/K19CreERT mice. Atg5flox/flox/K19CreERT mice were first treated with azoxymethane/dextran sodium sulfate and then injected with tamoxifen to inhibit autophagy in CK19-positive epithelial cells. To examine the anti-cancer mechanisms of autophagic inhibition, we used colon cancer cell lines harboring different p53 gene statuses, as well as small interfering RNAs (siRNAs) targeting Atg5 and immunoglobulin heavy-chain binding protein (BiP), a chaperone to aid folding of unfolded proteins. Colon tumors in Atg5flox/flox/K19CreERT mice showed loss of autophagic activity and decreased tumor size (the total tumor diameter was 28.1 mm in the control and 20.7 mm in Atg5flox/flox/K19CreERT mice, p = 0.036). We found that p53 and UPR/endoplasmic reticulum (ER) stress-related proteins, such as cleaved caspase 3, and CAAT/enhancer-binding protein homologous protein, are up-regulated in colon tumors of Atg5flox/flox/K19CreERT mice. Although Atg5 and BiP silencing, respectively, increased apoptosis in p53 wild type cells, Atg5 silencing alone did not show the same effect on apoptosis in p53 mutant cells. However, co-transfection of Atg5 and BiP siRNAs led to increased apoptosis in p53 mutant cells. Blocking autophagy has potential in the treatment of colon cancer by inducing apoptosis via p53 and ER stress, and suppressing the UPR pathway is a valid strategy to overcome resistance to autophagic inhibition.