Kratzke R A, Shimizu E, Geradts J, Gerster J L, Segal S, Otterson G A, Kaye F J
NCI-Navy Medical Oncology Branch, National Cancer Institute, Bethesda, Maryland 20889.
Cell Growth Differ. 1993 Aug;4(8):629-35.
To examine whether the expression of retinoblastoma (RB) protein could mediate tumor suppression in a lung carcinoma cell line carrying multiple genetic defects, we transfected the Rb gene into a non-small cell lung cancer cell line with absent RB protein. We observed that the stable expression of a functional RB product was associated with a decreased efficiency of soft agar cloning and partial suppression of tumorigenicity in nude mice. The suppression of tumorigenicity was marked when 10(6) cells were injected into the flanks of nude mice but was less prominent when 10(7) cells were injected. RB-mediated tumor suppression, however, was consistently blocked by preincubation of the transfected cells with an extract enriched with an extracellular matrix (Matrigel). Analysis of tumors harvested from nude mice showed that they continued to express detectable levels of human RB protein which retained functional E1A binding activity and nuclear localization. RB-mediated inhibition of soft agar cloning was also blocked in a dose-dependent manner by the addition of Matrigel. These observations demonstrate that the expression of wild-type RB may suppress certain parameters of tumorigenicity in lung carcinoma cells that contain multiple genetic alterations. In addition, the reversal of tumor suppression by an extract enriched in basement membrane components may offer clues for further investigations into the mechanism of RB-mediated tumor suppression.
为了研究视网膜母细胞瘤（RB）蛋白的表达是否能在携带多种基因缺陷的肺癌细胞系中介导肿瘤抑制作用，我们将Rb基因转染到一种缺乏RB蛋白的非小细胞肺癌细胞系中。我们观察到，功能性RB产物的稳定表达与软琼脂克隆效率降低以及裸鼠致瘤性的部分抑制相关。当将10⁶个细胞注射到裸鼠侧腹时，致瘤性的抑制很明显，但当注射10⁷个细胞时则不太显著。然而，转染细胞与富含细胞外基质（基质胶）的提取物预孵育可持续阻断RB介导的肿瘤抑制作用。对从裸鼠收获的肿瘤进行分析表明，它们继续表达可检测水平的人RB蛋白，该蛋白保留了功能性E1A结合活性和核定位。添加基质胶也以剂量依赖性方式阻断了RB介导的软琼脂克隆抑制作用。这些观察结果表明，野生型RB的表达可能抑制含有多种基因改变的肺癌细胞中某些致瘤性参数。此外，富含基底膜成分的提取物对肿瘤抑制作用的逆转可能为进一步研究RB介导的肿瘤抑制机制提供线索。
