Loughran O, Clark L J, Bond J, Baker A, Berry I J, Edington K G, Ly I S, Simmons R, Haw R, Black D M, Newbold R F, Parkinson E K
CRC Beatson Laboratories, Beatson Institute for Cancer Research, Garscube Estate, Bearsden, Glasgow, Scotland.
Oncogene. 1997 Apr 24;14(16):1955-64. doi: 10.1038/sj.onc.1201028.
Human keratinocyte immortality is genetically recessive to the normal phenotype of limited replicative lifespan and appears to require the dysfunction of p53 and the cyclin D-Cdk inhibitor p16. In order to test for the inactivation of other candidate replicative lifespan genes in the immortal cells of human tumors, we developed a series of mortal and immortal keratinocyte cultures derived from neoplastic lesions of the head and neck which were amenable to molecular genetic analysis by the loss of heterozygosity (LOH) technique. The results indicate that keratinocyte immortalization in head and neck squamous cell carcinoma (SCC-HN) development involves the inactivation of at least two further pathways to senescence and four in all. Chromosomes 1, 4 and 7 carry genes representing immortality complementation groups C, B and D respectively and immortal keratinocytes showed LOH at either 4q32-q34 between D4S1554 and D4S171 (group B) or 7q31 (group D) but never 1q25 (group C). These results tentatively suggest that the genes responsible for the immortality complementation groups encode proteins on the same pathway to senescence. In addition, all of the immortal keratinocyte lines possessed high levels of telomerase activity and a suppressor of telomerase activity has been mapped to the short arm of chromosome 3p. Five out of eight lines showed LOH at 3p21.2-p21.3, a region which may carry a gene capable of suppressing SCC-HN telomerase. However, alternative mechanisms of telomerase reactivation were also suggested by our results. None of the above genetic alterations were seen in seven senescent neoplastic keratinocyte cultures. Other loci harbouring antiproliferative genes implicated in replicative lifespan showed few or no alterations and any alterations seen were additional to those described above.
人类角质形成细胞的永生化在遗传上相对于有限复制寿命的正常表型是隐性的，并且似乎需要p53和细胞周期蛋白D - Cdk抑制剂p16功能失调。为了检测人类肿瘤永生细胞中其他候选复制寿命基因的失活情况，我们建立了一系列源自头颈部肿瘤病变的 mortal 和永生角质形成细胞培养物，这些培养物适合通过杂合性缺失（LOH）技术进行分子遗传学分析。结果表明，头颈部鳞状细胞癌（SCC - HN）发展过程中的角质形成细胞永生化涉及至少另外两条衰老途径的失活，总共四条。染色体1、4和7分别携带代表永生互补组C、B和D的基因，永生角质形成细胞在D4S1554和D4S171之间的4q32 - q34（B组）或7q31（D组）出现杂合性缺失，但在1q25（C组）从未出现。这些结果初步表明，负责永生互补组的基因在同一条衰老途径上编码蛋白质。此外，所有永生角质形成细胞系都具有高水平的端粒酶活性，并且端粒酶活性的一个抑制因子已被定位到染色体3p的短臂上。八个细胞系中有五个在3p21.2 - p21.3出现杂合性缺失，该区域可能携带一个能够抑制SCC - HN端粒酶的基因。然而，我们的结果也提示了端粒酶重新激活的其他机制。在七个衰老的肿瘤角质形成细胞培养物中未观察到上述任何基因改变。其他含有与复制寿命相关的抗增殖基因的位点很少或没有改变，并且所观察到的任何改变都是上述改变之外的。
