Institute of General Pathology, Giovanni XXIII Cancer Research Center, Catholic University, Rome, Italy.
J Cell Physiol. 2010 Jul;224(1):234-41. doi: 10.1002/jcp.22124.
The CD133 molecule has been proposed as a surface marker of cancer stem cells in several human malignancies, including colon cancers. The function and the mechanisms regulating CD133 expression remain unknown. The HT29 human colon cancer cells undergo differentiation following treatment with various agents and represent a useful in vitro model of colon differentiation. This study evaluated the behavior of CD133 during sodium butyrate-induced differentiation of HT29 cells. Treatment with sodium butyrate induced a progressive decrease of CD133 expression, as assessed by flow cytometry using the AC133 monoclonal antibody. Indeed, expression of CD133, which was about 47% in untreated control cells, gradually decreased down to about 3% after 72 h in a time- and dose-dependent manner. No relationship was observed between CD133 protein evaluated by flow cytometry and mRNA expression level, and no changes were detected in the methylation status of the CD133 gene promoter during HT29 differentiation. Moreover, the expression of the CD133 protein, evaluated by Western blot analysis using a specific anti-CD133 antibody directed against the C-terminal intracytoplasmic region of human CD133 protein, did not correlate with flow cytometry results. Different results were also obtained using the two antibodies to analyze the expression of the CD133 molecule in human colon cancers. These findings demonstrate that membrane expression of the CD133 stem cell marker might undergo a complex regulation during differentiation of colon cells and suggest that HT29 cells are a useful in vitro model to study the mechanisms involved in this regulation which likely occurs at a post-transcriptional level.
CD133 分子已被提议作为几种人类恶性肿瘤，包括结肠癌中的癌症干细胞的表面标志物。CD133 表达的功能和调节机制仍不清楚。HT29 人结肠癌细胞在用各种试剂处理后经历分化，代表了结肠分化的有用的体外模型。本研究评估了 CD133 在 HT29 细胞的丁酸钠诱导分化过程中的行为。用丁酸钠处理诱导 CD133 表达的逐渐下降，如通过用 AC133 单克隆抗体进行流式细胞术评估。事实上，在未经处理的对照细胞中约为 47%的 CD133 表达逐渐下降，在 72 小时后以时间和剂量依赖性方式下降至约 3%。在 HT29 分化过程中，未观察到流式细胞术评估的 CD133 蛋白与 mRNA 表达水平之间存在关系，并且未检测到 CD133 基因启动子的甲基化状态发生变化。此外，用针对人 CD133 蛋白的 C 末端细胞内区的特异性抗 CD133 抗体通过 Western blot 分析评估的 CD133 蛋白表达与流式细胞术结果不相关。在用两种抗体分析人结肠癌中 CD133 分子的表达时也得到了不同的结果。这些发现表明，CD133 干细胞标志物的膜表达可能在结肠细胞分化过程中受到复杂的调节，并表明 HT29 细胞是研究这种调节所涉及的机制的有用的体外模型，这可能发生在转录后水平。
