Hung Chih-Chang, Chien Chen-Yu, Chiang Wei-Fan, Lin Chang-Shen, Hour Tzyh-Chyuan, Chen Hau-Ren, Wang Ling-Feng, Ko Jenq-Yuh, Chang Chi-Hua, Chen Jeff Yi-Fu
Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Department of Biotechnology, Kaohsiung Medical University, Kaohsiung, Taiwan.
Oncotarget. 2015 Feb 28;6(6):4110-25. doi: 10.18632/oncotarget.2893.
Cisplatin (CDDP) is a potent chemotherapeutic agent but resistance to the drug remains a major challenge in cancer treatment. To evaluate the efficacy of CDDP in oral squamous cell carcinoma (OSCC), we found that p22phox was highly expressed in CDDP-resistant OSCC specimens. Knockdown of p22phox sensitized OSCC cell lines to CDDP (P < 0.05). Stable overexpression of p22phox augmented CDDP resistance, as evidenced by the significantly higher IC50 values. This cytoprotective effect was attributed to the abrogation of CDDP-induced apoptosis. Akt phosphorylation was increased in p22phox stable lines. However, blocking PI3K/Akt pathway only partially restored CDDP-induced apoptosis. In addition, the overexpressed p22phox in OSCC cells exhibited cytoplasmic localization with enhanced perinuclear expression, consistent with the localization pattern in OSCC specimens. Remarkably, CDDP entry into the nucleus was severely impaired in p22phox-overexpressing cells (P < 0.001), and cytoplasmically accumulated CDDP was co-localized with overexpressed p22phox. This was supported by decreased CDDP-DNA adduct formation and delayed chk1-p53 signaling activation. Together, overexpression of p22phox sequestered CDDP and caused defective CDDP entry into the nucleus, significantly attenuating CDDP-induced apoptosis. Such diminished apoptosis was further abolished by p22phox-activating PI3K/Akt pathway. Our work has suggested a novel biomarker and insight into the mechanism of CDDP resistance.
顺铂（CDDP）是一种有效的化疗药物，但对该药物的耐药性仍然是癌症治疗中的一个主要挑战。为了评估CDDP在口腔鳞状细胞癌（OSCC）中的疗效，我们发现p22phox在耐CDDP的OSCC标本中高表达。敲低p22phox可使OSCC细胞系对CDDP敏感（P < 0.05）。p22phox的稳定过表达增强了对CDDP的耐药性，IC50值显著升高证明了这一点。这种细胞保护作用归因于CDDP诱导的凋亡被消除。p22phox稳定细胞系中Akt磷酸化增加。然而，阻断PI3K/Akt通路仅部分恢复了CDDP诱导的凋亡。此外，OSCC细胞中过表达的p22phox表现出细胞质定位，核周表达增强，这与OSCC标本中的定位模式一致。值得注意的是，在过表达p22phox的细胞中，CDDP进入细胞核严重受损（P < 0.001），细胞质中积累的CDDP与过表达的p22phox共定位。这得到了CDDP-DNA加合物形成减少和chk1-p53信号激活延迟的支持。总之，p22phox的过表达隔离了CDDP并导致CDDP进入细胞核存在缺陷，显著减弱了CDDP诱导的凋亡。p22phox激活PI3K/Akt通路进一步消除了这种凋亡减少的情况。我们的工作提出了一种新的生物标志物，并深入了解了CDDP耐药的机制。
