Yao Kangshen, Shida Seiichiro, Selvakumaran Muthu, Zimmerman Robert, Simon Ephraim, Schick Jonathan, Haas Naomi B, Balke Marge, Ross Howard, Johnson Steven W, O'Dwyer Peter J
University of Pennsylvania, Philadelphia, PA 19104, USA.
Clin Cancer Res. 2005 Oct 15;11(20):7264-72. doi: 10.1158/1078-0432.CCR-05-0135.
Hypoxia contributes to cytotoxic chemotherapy and radiation resistance and may play a role in the efficacy of antiangiogenesis cancer therapy. We have generated a series of cell lines derived from the colon adenocarcinoma models HT29 and HCT116 by exposing cells in vitro to repeated sublethal periods of profound hypoxia. These cell lines have altered sensitivity to hypoxia-induced apoptosis: those derived from HT29 are resistant, whereas those from HCT116 are more susceptible. We used cDNA selected subtractive hybridization to identify novel genes mediating sensitivity to hypoxia-induced apoptosis and isolated macrophage migration inhibitory factor (MIF) from the hypoxia-conditioned cell lines. MIF expression correlates with susceptibility of the cell lines to apoptosis. In hypoxia-resistant cells, the induction of apoptosis by hypoxia can be restored by the addition of exogenous recombinant MIF protein, suggesting that resistance may result in part from down-regulation of MIF production possibly through an autocrine loop. Inhibition of MIF using small interfering RNA in the susceptible lines conferred resistance to hypoxia-induced cell death. The relative expression of MIF in the hypoxia-conditioned cells implanted s.c. in severe combined immunodeficient mice in vivo was similar to that observed in vitro. In an analysis of 12 unrelated colon tumor cell lines, MIF expression and response to hypoxia varied widely. Cell lines in which MIF was inducible by hypoxia were more sensitive to oxaliplatin. In human colon tumor specimens analyzed by immunohistochemistry, MIF expression was similarly variable. There was no detectable expression of MIF in normal colon mucosa or adenoma but positive staining in all carcinomas tested. Taken together, these data indicate that MIF may be a determinant of hypoxia-induced apoptosis in vitro and that its variable expression in human colon cancers may indicate a functional role in vivo. We suggest that MIF expression in colorectal cancer may be a marker of susceptibility to therapies that may depend on induction of hypoxia, possibly including antiangiogenic therapy.
缺氧会导致细胞毒性化疗和放疗耐药，并且可能在抗血管生成癌症治疗的疗效中发挥作用。我们通过在体外将细胞暴露于反复的亚致死性深度缺氧期，从结肠腺癌模型HT29和HCT116中生成了一系列细胞系。这些细胞系对缺氧诱导的凋亡敏感性发生了改变：源自HT29的细胞系具有抗性，而源自HCT116的细胞系更易感性。我们使用cDNA选择消减杂交来鉴定介导对缺氧诱导凋亡敏感性的新基因，并从缺氧条件下的细胞系中分离出巨噬细胞迁移抑制因子（MIF）。MIF表达与细胞系对凋亡的易感性相关。在缺氧抗性细胞中，通过添加外源性重组MIF蛋白可以恢复缺氧诱导的凋亡，这表明抗性可能部分是由于MIF产生的下调，可能是通过自分泌环。在易感细胞系中使用小干扰RNA抑制MIF可赋予对缺氧诱导细胞死亡的抗性。在严重联合免疫缺陷小鼠体内皮下植入的缺氧条件下细胞中，MIF的相对表达与体外观察到的相似。在对12个无关结肠肿瘤细胞系的分析中，MIF表达和对缺氧的反应差异很大。缺氧可诱导MIF的细胞系对奥沙利铂更敏感。在通过免疫组织化学分析的人结肠肿瘤标本中，MIF表达同样存在差异。在正常结肠黏膜或腺瘤中未检测到MIF表达，但在所有测试的癌组织中均呈阳性染色。综上所述，这些数据表明MIF可能是体外缺氧诱导凋亡的决定因素，并且其在人类结肠癌中的可变表达可能表明在体内具有功能作用。我们认为，结直肠癌中MIF的表达可能是对可能依赖于缺氧诱导的治疗（可能包括抗血管生成治疗）易感性的标志物。
