Smad4 sensitizes colorectal cancer to 5-fluorouracil through cell cycle arrest by inhibiting the PI3K/Akt/CDC2/survivin cascade
Smad4 sensitizes colorectal cancer to 5-fluorouracil through cell cycle arrest by inhibiting the PI3K/Akt/CDC2/survivin cascade
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Smad4 通过抑制 PI3K/Akt/CDC2/survivin 级联，通过细胞周期停滞使结直肠癌对 5-氟尿嘧啶敏感
DOI：
10.3892/or.2015.4479
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发表时间：
2016-03-01
期刊：
影响因子：
4.2
通讯作者：
Chen, Xiaoping
中科院分区：
文献类型：
--
作者：
Zhang, Binhao;Leng, Chao;Chen, Xiaoping
5-氟尿嘧啶（5-FU）是一种细胞周期特异性抗代谢药物，是治疗结直肠癌（CRC）最常用的化疗药物之一。然而，对以5-FU为基础的化疗的耐药性仍然是治疗这种恶性肿瘤的障碍。Smad4基因突变或缺失是大肠癌耐药的关键。然而，Smad4调节CRC化疗敏感性的机制仍不清楚。在本研究中，我们研究了Smad4在CRC对5-FU的化疗敏感性中的作用，以及Smad4调节的细胞周期阻滞是否参与5-FU化疗耐药。我们使用表达Smad4的CT26和Smad4缺失的SW620细胞系作为实验模型，通过敲低或转基因过表达。用5-FU处理细胞或肿瘤以通过细胞生长、致瘤性测定和小鼠模型确定化学敏感性。流式细胞仪检测细胞周期分布，Western blotting检测细胞周期相关蛋白。CT 26和SW 620细胞中的Smad 4缺陷在体外和体内均诱导对5-FU的化疗耐药性。Smad4缺陷可通过激活PI3K/Akt/CDC2/Survivin信号通路而减弱G1或G2期细胞阻滞。PI3K抑制剂LY294002逆转了Smad4缺陷细胞中Akt/CDC 2/Survivin级联反应的激活，而对Smad4高表达的细胞几乎没有影响。总之，我们发现了一种由Smad 4介导的新机制，通过抑制PI 3 K/Akt/CDC 2/生存素级联反应，通过细胞周期停滞来触发5-FU化疗敏感性。本研究还表明，LY294002具有潜在的治疗价值，以扭转化疗敏感性与Smad4低表达的大肠癌。
5-Fluorouracil (5-FU), a cell cycle-specific antimetabolite, is one of the most commonly used chemotherapeutic agents for colorectal cancer (CRC). Yet, resistance to 5-FU-based chemotherapy is still an obstacle to the treatment of this malignancy. Mutation or loss of Smad4 in CRC is pivotal for chemoresistance. However, the mechanism by which Smad4 regulates the chemosensitivity of CRC remains unclear. In the present study, we investigated the role of Smad4 in the chemosensitivity of CRC to 5-FU, and whether Smad4-regulated cell cycle arrest is involved in 5-FU chemoresistance. We used Smad4-expressing CT26 and Smad4-null SW620 cell lines as experimental models, by knockdown or transgenic overexpression. Cells or tumors were treated with 5-FU to determine chemosensitivity by cell growth, tumorigenicity assay and a mouse model. Cell cycle distribution was examined with flow cytometric analysis, and cell cycle-related proteins were examined by western blotting. Smad4 deficiency in CT26 and SW620 cells induced chemoresistance to 5-FU both in vitro and in vivo. Smad4 deficiency attenuated G1 or G2 cell cycle arrest by activating the PI3K/Akt/CDC2/survivin pathway. The PI3K inhibitor, LY294002, reversed the activation of the Akt/CDC2/survivin cascade in the Smad4-deficient cells, while it had little effect on cells with high Smad4 expression. In conclusion, we discovered a novel mechanism mediated by Smad4 to trigger 5-FU chemosensitivity through cell cycle arrest by inhibiting the PI3K/Akt/CDC2/survivin cascade. The present study also implies that LY294002 has potential therapeutic value to reverse the chemosensitivity of CRC with low Smad4 expression.