Zhang Xiaochun, Komaki Ritsuko, Wang Li, Fang Bingliang, Chang Joe Y
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Clin Cancer Res. 2008 May 1;14(9):2813-23. doi: 10.1158/1078-0432.CCR-07-1528.
Radioresistance may be caused by cancer stem cells (CSC). Because CSCs require telomerase to proliferate, a telomerase-specific oncolytic adenoviral vector carrying apoptotic tumor necrosis factor-related apoptosis-inducing ligand and E1A gene (Ad/TRAIL-E1) may preferentially target CSCs.
We established two pairs of parental and radioresistant (R) esophageal carcinoma cell lines (Seg-1, Seg-1R and TE-2, TE-2R) by fractionated irradiation. Stem cell markers were measured by Western blotting and flow cytometry. Serial sorting was used to enrich stem-like side population cells. Telomerase activity, transgene expression, antitumor activity, apoptosis induction, and viral replication were determined in vitro and/or in vivo.
Expression of the stem cell markers beta-catenin, Oct3/4, and beta(1) integrin in Seg-1R cells was 29.4%, 27.5%, and 97.3%, respectively, compared with 4.8%, 14.9%, and 45.3% in Seg-1 cells (P < 0.05). SP levels in Seg-1R and TE-2R cells were 14.6% and 2.7%, respectively, compared with 3.4% and 0.3% in Seg-1 and TE-2 cells. Serial sorting of Seg-1R SP cells showed enrichment of the SP cells. Telomerase activities in Seg-1R, Seg-1R SP, and TE-2R cells were significantly higher than in Seg-1, Seg-1R non-SP, and TE-2 cells, respectively (P < 0.05). Seg-1R and TE-2R cells were more sensitive to Ad/TRAIL-E1 than parental cells. Increased Coxsackie-adenovirus receptor and elevated transgene expressions were found in the radioresistant cells. Ad/TRAIL-E1 resulted in significant tumor growth suppression and longer survival in Seg-1R-bearing mice (P < 0.05) with no significant toxicity.
Radioresistant cells established by fractionated irradiation display CSC-like cell properties. Ad/TRAIL-E1 preferentially targets radioresistant CSC-like cells.
癌症干细胞（CSC）可能导致放射抗性。由于CSC增殖需要端粒酶，携带凋亡肿瘤坏死因子相关凋亡诱导配体和E1A基因的端粒酶特异性溶瘤腺病毒载体（Ad/TRAIL-E1）可能优先靶向CSC。
我们通过分次照射建立了两对亲本和放射抗性（R）食管癌细胞系（Seg-1、Seg-1R和TE-2、TE-2R）。通过蛋白质免疫印迹法和流式细胞术检测干细胞标志物。采用连续分选法富集干细胞样侧群细胞。在体外和/或体内测定端粒酶活性、转基因表达、抗肿瘤活性、凋亡诱导和病毒复制。
与Seg-1细胞中的4.8%、14.9%和45.3%相比，Seg-1R细胞中干细胞标志物β-连环蛋白、Oct3/4和β1整合素的表达分别为29.4%、27.5%和97.3%（P<0.05）。与Seg-1和TE-2细胞中的3.4%和0.3%相比，Seg-1R和TE-2R细胞中的SP水平分别为14.6%和2.7%。Seg-1R SP细胞的连续分选显示SP细胞得到富集。Seg-1R、Seg-1R SP和TE-2R细胞中的端粒酶活性分别显著高于Seg-1、Seg-非SP和TE-2细胞（P<0.05）。Seg-1R和TE-2R细胞比亲本细胞对Ad/TRAIL-E1更敏感。在放射抗性细胞中发现柯萨奇腺病毒受体增加和转基因表达升高。Ad/TRAIL-E1导致携带Seg-1R的小鼠肿瘤生长显著受抑制且生存期延长（P<0.05），且无明显毒性。
通过分次照射建立的放射抗性细胞表现出CSC样细胞特性。Ad/TRAIL-E1优先靶向放射抗性CSC样细胞。
