Genetic Alterations in Lung Cancer

肺癌是男性和女性癌症相关死亡的主要原因，并且仍然是一个主要的健康问题。明年将有超过15.9万人死于肺癌，超过乳腺癌、前列腺癌和结肠癌的总和。大多数肺癌病例可归因于吸烟，在某些情况下还可归因于其他环境风险因素。虽然戒烟者患肺癌的相对风险大幅下降，但前吸烟者仍有患肺癌的风险。最近的几项研究表明，超过50%的新诊断的肺癌发生在以前的吸烟者中。据估计，在美国，吸烟者和前吸烟者的人数大致相同。由于戒烟是一项重大的公共卫生举措，因此前吸烟者在肺癌病例中所占的比例将越来越高。因此，存在两个肺癌高危人群，改善疾病管理对当前和以前的吸烟者都有益。 染色体9 p的遗传改变经常发生，通常包括p16/CDKN 2位点。然而，我们确定了一个区域的纯合性缺失的短臂上的染色体9 p的标记D9 S126，并提出了一个肿瘤抑制基因的存在，在肺肿瘤的发生在这一地区。我们通过分析30个非小细胞肺癌和12个小细胞肺癌细胞系，用55个遗传标记筛选，以确定染色体9 p上纯合缺失的新区域，从而改进了缺失区域。检测到三个新的非连续同源性缺失区域。在D9 S126的这些区域之一导致鉴定为TUSC 1的基因的鉴定。多重PCR和Southern印迹证实了TUSC 1的纯合性缺失，TUSC 1的北方印迹分析证实了可能由备选多聚腺苷酸化信号产生的约2和1.5 kb的两个转录物。这两种转录物在几种人体组织中表达，并且共享编码209个氨基酸的肽的开放阅读框。分析肺癌细胞系的RNA和蛋白质表达表明，TUSC 1在几种细胞系中下调，进一步表明TUSC 1可能在肿瘤发生中发挥作用。使用稳定转染有TUSC 1的肺肿瘤细胞系的研究显示体外增殖减少和体内肿瘤形成减少。总之，这些数据表明，染色体9 p可能含有其他重要的肿瘤抑制基因在肺肿瘤的发生和TUSC 1可能是一个候选的TSG。最近的研究利用酵母双杂交协议，并确定了潜在的蛋白质结合伴侣TUSC 1。这些相互作用正在使用免疫沉淀进行验证，并将导致有关TUSC 1相互作用的途径的信息。TUSC 1的抗体开发也将导致对多种人类肿瘤的检查，以检测原发性肿瘤中的表达水平。然后可以将表达水平与临床结果进行比较，以进一步确定TUSC 1作为肿瘤抑制基因。我们的实验室还分析了一组原发性肺肿瘤，并有证据表明TUSC 1表达失调。随后的临床结果分析应产生关于TUSC 1在肿瘤发生中的作用的重要信息。

Lung cancer is the leading cause of cancer related mortality in both men and women and continues to be a major health issue. More than 159,000 individuals will die from lung cancer in the coming year, more than breast, prostate and colon cancer combined. The majority of lung cancer cases is attributable to tobacco smoking and in some cases other environmental risk factors. Although the relative risk of developing lung cancer declines dramatically in smokers who quit, former smokers remain at risk for the disease. Several recent studies show that greater than 50% of newly diagnosed lung cancers occur in former smokers. It is estimated that there are approximately equal numbers of smokers and former smokers in the United States. Since smoking cessation is a major public health initiative, former smokers will increasingly account for a higher percentage of lung cancer cases. Thus, two high-risk population groups exist for lung cancer and improved disease management can be beneficial to both current and former smokers. Chromosome 9p genetic alterations occur frequently and often include the p16/CDKN2 locus. However, we identified a region of homozygous deletion on the short arm of chromosome 9p at the marker D9S126 and proposed the existence of a tumor suppressor gene important in lung tumorigenesis in this region. We refined the region of deletion by analyzing 30 non-small cell lung cancer and 12 small cell lung cancer cell lines by screening with 55 genetic markers to identify new regions of homozygous deletion on chromosome 9p. Three novel non-contiguous homozygously deleted regions were detected. One of these regions at D9S126 led to the identification of a gene identified as TUSC1. Multiplex PCR and Southern blot confirmed the homozygous deletion of TUSC1 and Northern blot analysis of TUSC1 demonstrated two transcripts of approximately 2 and 1.5 kb that are likely generated by alternative polyadenylation signals. Both transcripts are expressed in several human tissues and share an open reading frame encoding a peptide of 209 amino acids. Analyzing lung cancer cell lines for RNA and protein expression demonstrated down regulation of TUSC1 in several cell lines further suggesting TUSC1 may play a role in tumorigenesis. Studies using lung tumor cell lines stably transfected with TUSC1 show reduced proliferation in vitro and reduced tumor formation in vivo. Taken together, these data suggest that chromosome 9p may contain other tumor suppressor genes important in lung tumorigenesis and that TUSC1 may be a candidate TSG. Recent studies utilized yeast two hybrid protocols and identified potential protein binding partners for TUSC1. These interactions are being validated using immunoprecipitation and will lead to information concerning the pathways in which TUSC1 interacts. Antibody development for TUSC1 will also lead to the examination of multiple human tumors to detect expression levels in the primary tumors. The expression levels can then be compared to clinical outcome to further establish TUSC1 as a tumor suppressor gene. Our laboratory has also analyzed a set of primary lung tumors and has evidence for the dysregulation of TUSC1 expression. Subsequent analysis of clinical outcomes should yield important information concerning the role of TUSC1 in tumorigenesis.