Epigenetic Regulation Implicates Hypoxia-resistance of Hepatoma Stem Cell Population.

终末生长停滞（TGA）和细胞凋亡在肝癌各种治疗后原癌细胞群的清除中起着重要作用。我们以前已经表明，STI 571（格列卫），一种选择性酪氨酸激酶抑制剂，通过选择性抑制c-Abl酪氨酸激酶活性，在体外和体内延缓甲状腺间变性癌（ATC）细胞系的生长。在本研究中，我们研究了格列卫在体外和体内调节肝癌细胞缺氧反应的能力。采用细胞生长试验、集落形成试验和异种移植模型研究Gleevec对肝癌细胞株HuH 7和HepG 2的缺氧增敏作用。应用流式细胞仪、免疫印迹和组织化学技术研究格列卫对放射反应的机制。克隆形成分析表明，格列卫减少缺氧应激后的细胞存活。在携带ATC异种移植物的小鼠中，与单独使用任一种治疗方式相比，格列卫联合放射治疗对肿瘤生长的抑制作用增强。我们研究了几种可能有助于增强辐射和/或缺氧反应的潜在机制。Gleevec促进照射后的ATC细胞中p21 cip 1的积累。Gleevec抑制辐射诱导的ARO细胞c-ABL激活，并显示诱导终末生长停滞。格列卫的抗肿瘤活性似乎是由于与衰老相关的终末生长停滞相关的增殖生长抑制。我们的研究表明，肝癌干细胞群体是耐缺氧的，c-Abl抑制是治疗高度恶性肝癌的关键。

Terminal growth arrest(TGA) as well as apoptosis plays important role in elimination of dongenic populations after various therapy for hepatoma. We have shown previously that STI571(Gleevec), a selective tyrosine kinase inhibitor, retarded the growth of anaplastic thyroid cancer(ATC) cell lines in vitro and in vivo through selective inhibition of c-Abl tyrosine kinase activity. In the present study, we investigated the ability of Gleevec to modulate the in vitro and in vivo hypoxia response of hepatoma cells. Cell growth assay, colony formation assay and xenograft models were used to quantify Gleevec hypoxiasensitizing effect for hepatoma cell lines HuH7 and HepG2. FACS, Western Blotting and histochemistry techniques were applied to study mechanisms radiation response after Gleevec exposure. Clonogenic analysis demonstrated that Gleevec reduced cell survival after hypoxia stress. Gleevec combined with radiation produced increase in the tumor growth inhibition when compared to treatment with either modality alone in mice bearing ATC xenografts. We investigated several potential mechanisms that may contribute to the enhanced radiation and/or hypoxia responses. Gleevec promoted p21cip 1 accumulation in irradiated ATC cells. Gleevec suppressed radiation-induced c-ABL activation in ARO cells and displayed the induction of terminal growth arrest. Antitumor activity of Gleevec appears to be due to the proliferative growth inhibition associated with the terminal growth arrest associated with senescence. Our study suggest that hepatoma stem cell population is hypoxia resistant and c-Abl suppression is critical for treatment of highly malignant hepatomas.