Fitzsimmons S A, Ireland H, Barr N I, Cuthbert A P, Going J J, Newbold R F, Parkinson E K
Beatson Institute for Cancer Research, Cancer Research UK Beatson Laboratories, Glasgow, UK.
Oncogene. 2003 Mar 20;22(11):1737-46. doi: 10.1038/sj.onc.1206295.
Normal human keratinocytes possess a finite replicative lifespan. Most advanced squamous cell carcinomas (SCCs), however, are immortal, a phenotype that is associated with p53 and INK4A dysfunction, high levels of telomerase and loss of heterozygosity (LOH) at several genetic loci, suggestive of the dysfunction of other mortality genes. We show here that human chromosome 6 specifically reduces the proliferation or viability of a human SCC line, BICR31, possessing LOH across the chromosome. This was determined by an 88% reduction in colony yield (P<0.001), following the reintroduction of an intact normal chromosome 6 by monochromosome transfer. Deletion analysis of immortal segregants using polymorphic markers revealed the loss of a 2.9 Mbp interval, centred on marker D6S1045 at 6q14.3-q15, in 6/19 segregants. Crucially, allelic losses of this region were not identified in control hybrids constructed between chromosome 6 and the BICR6 SCC cell line that is heterozygous for chromosome 6 and which showed no reduction in colony formation relative to the control chromosome transfers. This indicates that the minimally deleted region at D6S1045 is not the result of fragile sites, a recombination hot spot, or a feature of the monochromosome transfer technique. LOH of D6S1045 was found in 2/9 immortal SCC lines and was part of a minimally deleted region of line BICR19. Furthermore, allelic imbalance, consistent with LOH, was detected in 3/17 advanced SCCs of the tongue. These results suggest the existence of a suppressor of SCC immortality and tumour development at chromosome 6q14.3-q15, which is important to a subset of human SCCs.
正常人类角质形成细胞具有有限的复制寿命。然而，大多数晚期鳞状细胞癌（SCC）是永生的，这种表型与p53和INK4A功能障碍、端粒酶水平升高以及几个基因位点的杂合性缺失（LOH）有关，提示其他死亡基因功能异常。我们在此表明，人类6号染色体特异性降低了具有全染色体LOH的人类SCC细胞系BICR31的增殖或活力。这是通过单染色体转移重新引入完整的正常6号染色体后，集落产量降低88%（P<0.001）确定的。使用多态性标记对永生分离株进行缺失分析，发现19个分离株中有6个缺失了一个2.9 Mbp的区间，该区间以6q14.3 - q15处的标记D6S1045为中心。至关重要的是，在由6号染色体与BICR6 SCC细胞系构建的对照杂种中未发现该区域的等位基因缺失，BICR6 SCC细胞系对6号染色体是杂合的，并且相对于对照染色体转移，其集落形成没有减少。这表明D6S1045处的最小缺失区域不是脆性位点、重组热点或单染色体转移技术的特征所致。在9个永生SCC细胞系中有2个发现了D6S1045的LOH，并且它是BICR19细胞系最小缺失区域的一部分。此外，在17个晚期舌SCC中有3个检测到与LOH一致的等位基因不平衡。这些结果表明在6号染色体q14.3 - q15处存在SCC永生和肿瘤发展的抑制因子，这对一部分人类SCC很重要。
