Wang G L, Lo K W, Tsang K S, Chung N Y, Tsang Y S, Cheung S T, Lee J C, Huang D P
Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin.
Br J Cancer. 1999 Dec;81(7):1122-6. doi: 10.1038/sj.bjc.6690818.
The p16 gene, encodes a key checkpoint protein p16 in the cell cycle, has been reported inactivation in a wide variety of human cancers. We have previously demonstrated high frequency of p16 alterations in primary nasopharyngeal carcinoma (NPC), xenografts and cell lines. The finding implied that inactivation of the p16 gene may play an important role in the NPC development. To investigate the tumour suppressor function of p16 in NPC, we transfected p16-deficient NPC cell line, NPC/HK-1, with a wild-type p16 expression construct, and evaluated growth and tumorigenic properties of the clones stably expressing exogenous p16. Expression of the exogenous wild-type p16 significantly inhibited cell growth by more than 70% when compared to that of the parental and empty vector-transfected cells. This growth inhibition was attributable to a significant proportion of p16-expressing cells arrested at G1 phase in the cell cycle as revealed by flow cytometric analysis. By anchorage-independent colony forming assay, we found that the ability to form colonies in soft agar was highly reduced in cells expressing p16. NPC/HK1 cells expressing functional p16 also showed suppressed tumorigenicity in athymic nude mice. Taken together, our results provide strong evidence for a tumour suppressor role of p16 in NPC.
p16基因编码细胞周期中的关键检查点蛋白p16，已有报道称其在多种人类癌症中失活。我们之前已经证明，在原发性鼻咽癌（NPC）、异种移植瘤和细胞系中，p16改变的频率很高。这一发现表明，p16基因的失活可能在NPC的发展中起重要作用。为了研究p16在NPC中的肿瘤抑制功能，我们用野生型p16表达构建体转染p16缺陷的NPC细胞系NPC/HK-1，并评估稳定表达外源性p16的克隆的生长和致瘤特性。与亲本细胞和空载体转染细胞相比，外源性野生型p16的表达显著抑制细胞生长超过70%。流式细胞术分析显示，这种生长抑制归因于相当一部分表达p16的细胞在细胞周期的G1期停滞。通过非锚定依赖性集落形成试验，我们发现表达p16的细胞在软琼脂中形成集落的能力大大降低。表达功能性p16的NPC/HK1细胞在无胸腺裸鼠中也表现出致瘤性受到抑制。综上所述，我们的结果为p16在NPC中的肿瘤抑制作用提供了有力证据。
