Liu T J, el-Naggar A K, McDonnell T J, Steck K D, Wang M, Taylor D L, Clayman G L
Department of Head and Neck Surgery, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Cancer Res. 1995 Jul 15;55(14):3117-22.
Cancer gene therapy strategies for inducing apoptosis in solid tumors may allow contemporary medicine to reassess its management of these cancers. We demonstrated previously that overexpression of the wild-type p53 gene in squamous cell carcinoma of the head and neck cell lines via adenovirus-mediated gene transfer suppressed growth both in vitro and in vivo. Here, we characterize the mechanism of the growth suppression by the exogenous p53 gene as a consequence of programmed cell death (apoptosis). One of the cell lines used in this study, Tu-138, harbors a mutated p53 gene, whereas the other cell line, MDA 686LN, possesses a wild-type p53 gene. DNA fragmentation was detected by electrophoresis in both cell lines after infection with the wild-type p53 adenovirus, Ad5CMV-p53. With the use of the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling method, 4.4% of the remaining viable Tu-138 cell population was identified as apoptotic as early as 15 h after inoculation with Ad5CMV-p53. The percentage of apoptotic cells increased to 31% at 22 h. In contrast, only 10% of the viable MDA 686LN cells (wt-p53) had undergone apoptosis 30 h after Ad5CMV-p53 infection, although the percentage of apoptotic cells rapidly increased to 60% at 48 h after infection. For in vivo analysis of apoptosis, nude mice in which squamous cell carcinoma of the head and neck cell lines had been implanted s.c. had exogenous wt-p53 transiently introduced to the tumor cells via Ad5CMV-p53 2 days later. In situ end labeling clearly illustrated apoptosis in the tumor cells. These results suggest that wt-p53 plays an important role in the induction of apoptosis in human head and neck cancer cell lines and that selective induction of apoptosis in cancer cells can be further explored as a strategy for cancer gene therapy.
诱导实体瘤细胞凋亡的癌症基因治疗策略可能会促使当代医学重新评估对这些癌症的治疗方法。我们之前曾证明，通过腺病毒介导的基因转移，在头颈部鳞状细胞癌细胞系中野生型p53基因的过表达在体外和体内均能抑制生长。在此，我们将外源性p53基因导致生长抑制的机制确定为程序性细胞死亡（凋亡）。本研究中使用的一种细胞系Tu - 138含有突变的p53基因，而另一种细胞系MDA 686LN则拥有野生型p53基因。在用野生型p53腺病毒Ad5CMV - p53感染后，通过电泳在两种细胞系中均检测到了DNA片段化。使用末端脱氧核苷酸转移酶介导的dUTP - 生物素缺口末端标记法，早在接种Ad5CMV - p53后15小时，剩余存活的Tu - 138细胞群体中就有4.4%被鉴定为凋亡细胞。在22小时时，凋亡细胞的百分比增加到31%。相比之下，在Ad5CMV - p53感染后30小时，仅有10%的存活MDA 686LN细胞（野生型p53）发生凋亡，不过在感染后48小时，凋亡细胞的百分比迅速增加到60%。为了对凋亡进行体内分析，将已皮下植入头颈部鳞状细胞癌细胞系的裸鼠在两天后通过Ad5CMV - p53将外源性野生型p53短暂导入肿瘤细胞。原位末端标记清楚地显示了肿瘤细胞中的凋亡现象。这些结果表明，野生型p53在诱导人头颈部癌细胞系凋亡中起重要作用，并且癌细胞凋亡的选择性诱导可作为癌症基因治疗的一种策略进一步探索。
