Adachi J, Ookawa K, Shiseki M, Okazaki T, Tsuchida S, Morishita K, Yokota J
Biology Division, National Cancer Center Research Institute, Tokyo, Japan.
Cell Growth Differ. 1996 Jul;7(7):879-86.
Multiple genetic alterations, including inactivation of the p53 and RB genes and loss of heterozygosity on chromosome 3p, occur commonly in small cell lung carcinoma (SCLC). To assess the biological significance of p53 inactivation in the development of SCLC, tetracycline (Tc)-inducible p53 expression plasmids were introduced into a SCLC cell line, N417, in which the p53 gene as well as the RB gene was inactivated. In the absence (induced) of Tc, cells transfected with the wild-type p53 gene formed colonies in 29-58% of those with a mutant p53 gene. However, wild-type p53 genes were expressed in 0 of 43 transfectants, whereas mutant p53 genes were expressed in 75% (36/48) of the transfectants, suggesting that the growth of SCLC cells was suppressed by the expression of the wild-type p53 gene. Thus, wild-type p53-inducible clones were further established by transfection in the presence (repressed) of Tc. The in vitro growth was significantly suppressed by the induction of wild-type p53 expression, and apoptosis but not G1 arrest was observed within 24 h of p53 induction. These results strongly suggest that the restoration of the p53 function is sufficient to suppress the growth of SCLC cells in which other genetic alterations remain uncorrected, and that growth suppression by p53 is due to induction of apoptosis but not due to induction of G1 arrest through the RB pathway.
多种基因改变，包括p53和RB基因失活以及3号染色体短臂杂合性缺失，在小细胞肺癌（SCLC）中普遍存在。为了评估p53失活在SCLC发生发展中的生物学意义，将四环素（Tc）诱导型p53表达质粒导入p53基因和RB基因均失活的SCLC细胞系N417。在没有（诱导）Tc的情况下，转染野生型p53基因的细胞形成菌落的数量是转染突变型p53基因细胞的29% - 58%。然而，43个转染子中野生型p53基因均未表达，而75%（36/48）的转染子中突变型p53基因表达，这表明野生型p53基因的表达抑制了SCLC细胞的生长。因此，通过在有（抑制）Tc存在的情况下转染进一步建立了野生型p53诱导型克隆。野生型p53表达的诱导显著抑制了体外生长，并且在p53诱导后24小时内观察到细胞凋亡但未观察到G1期阻滞。这些结果强烈表明，p53功能的恢复足以抑制其他基因改变未得到纠正的SCLC细胞的生长，并且p53介导的生长抑制是由于诱导细胞凋亡而非通过RB途径诱导G1期阻滞。
