Alterations of P16 (MTS1) in node-positive non-small cell lung carcinomas

The status of the P16 gene was investigated by Southern blot, polymerase chain reaction–single strand conformational polymorphism (PCR–SSCP), and DNA sequencing analyses in 30 primary resected non-small cell lung carcinomas (NSCLCs) with metastatic involvement of thoracic lymph nodes and 33 NSCLCs without node metastases. Direct sequencing of tumour DNA samples scored positive by PCR–SSCP showed five somatic mutations of the P16 gene: four nonsense and one frameshift. The Southern blot analysis revealed the presence of a homozygous deletion of the P16 locus in one tumour. All of the six NSCLCs with somatic aberrations of the P16 gene belonged to the series of tumours with metastatic diffusion to thoracic lymph nodes. In each of these six cases, the genetic aberration was seen in both the primary tumour and the node metastasis. No P16 alteration was found in tumours without metastatic lymph nodes. This difference was statistically significant (P=0·02). No correlation was present between P16 alterations and other clinicopathological parameters including age of patients, tumour size, histological type, and grade. In three tumours with genetic aberration of P16, there was a concomitant alteration of the p53 gene. Our results indicate that the P16 gene is infrequently mutated (10 per cent of the cases examined) in primary resected NSCLC. However, since P16 mutations were found only in metastatic tumours, they may be important events in late phases of tumour progression and could represent useful markers of tumour aggressiveness in NSCLC. © 1997 John Wiley & Sons, Ltd.     

Association of CDKN2A (p16)/CDKN2B (p15) alterations and homozygous chromosome arm 9p deletions in human lung carcinoma

To elucidate the possibility of the existence of multiple tumor suppressor genes on chromosome arm 9p, we performed genetic and epigenetic analyses of the CDKN2A/p16/MTS1 and CDKN2B/p15/MTS2 genes as well as homozygous deletion mapping of 9p in human lung carcinoma. To avoid overlooking genetic alterations due to contamination of noncancerous cells, we examined 32 non-small cell lung carcinoma (NSCLC) and 16 small cell lung carcinoma (SCLC) cell lines. CDKN2A was mutated or homozygously deleted in 20 (63%) of 32 NSCLC cell lines, and methylation of the CpG island in the CDKN2A gene was detected in six of the 12 cell lines carrying the wild-type CDKN2A gene. Although homozygous deletions of the CDKN2B gene were also detected in NSCLC cell lines with CDKN2A deletions, mutation and methylation in the CDKN2B gene were infrequent. Thus, it was indicated that the CDKN2A gene rather than the CDKN2B gene plays a critical role as a tumor suppressor gene in NSCLC. Homozygous deletions on 9p were detected in 14 (44%) NSCLC cell lines. It is of note that two common regions of homozygous deletions were mapped proximal to the CDKN2A and CDKN2B loci, suggesting that tumor suppressor genes other than CDKN2A are present on 9p. In contrast to NSCLC, homozygous deletions on 9p as well as CDKN2A and CDKN2B alterations were infrequent in SCLC. Therefore, the pathogenetic significance of 9p alterations is likely to differ between SCLC and NSCLC. Genes Chromosomes Cancer 22:232–240, 1998. © 1998 Wiley-Liss, Inc.     

肺癌组织CDKN2/p16基因点突变的分析

目的 研究我国肺癌组织中CDKN2／p16基因点突变的发生情况。方法 采用聚合酶链反应－单链构象多态性和序列分析的方法，对89例肺癌组织中CDKN2／p16基因第2外显子的点突变进行了研究。结果 在未发生第2外显子缺失的69例肺癌组织中，发现CDKN2／p16基因第2外显子变异或可疑变异者16例；对该16例进行序列分析，共发现有9例存在不同类型的基因点突变。结论 点突变是CDKN2／p16基因失活的一种形式，但不是主要形式。由点突变引起的CDKN2／p16基因失活在肺癌的发生发展中起一定的作用。     

A common variant of CDKN2A (p16) predisposes to breast cancer

Background: A common missense variant of the CDKN2A gene (A148T) predisposes to malignant melanoma in Poland. An association between malignant melanoma and breast cancer has been reported in several families with CDKN2A mutations, Objective: To determine whether this variant also predisposes to breast cancer. Methods: Genotyping was undertaken in 4209 cases of breast cancer, unselected for family history, from 18 hospitals throughout Poland and in 3000 controls. Results: The odds ratio (OR) associated with the CDKN2A allele for women diagnosed with breast cancer before the age of 50 was 1.5 (p = 0.002) and after age 50 it was 1.3 (p = 0.2). The effect was particularly strong for patients diagnosed at or before the age of 30 (OR = 3.8; p = 0.0002). Conclusions: CDKN2A appears to be a low penetrance breast cancer susceptibility gene in Poland. The association should be confirmed in other populations.     

非小细胞肺癌p16基因异常与临床病理相关性研究

目的　探讨抑癌基因p16在非小细胞肺癌中的失活方式、mRNA和p16蛋白表达与临床病理因素的相关性。方法　应用对比性多重聚合酶链式反应检测 6 4例非小细胞肺癌中p16基因启动子的甲基化状况 ,同时应用原位杂交和免疫组织化学方法 [链霉素抗生物素蛋白 过氧化物酶 (SP)法 ]检测p16基因的mRNA和蛋白表达水平 ,并将上述结果与非小细胞肺癌之临床病理因素进行了相关性研究。结果　 5 6 3% (36 / 6 4 )的肺癌标本被检出有p16基因启动子甲基化 ,且甲基化与p16蛋白表达呈负相关 (P <0 0 5 ) ;免疫组织化学检测结果显示 ,5 7 8% (37/ 6 4 )的标本呈现p16蛋白表达缺失 ;原位杂交检测有 2 0 3% (13/ 6 4 )的标本被检出p16mRNA表达 ,且这 13例阳性者的p16蛋白也表达。同时具有p16基因启动子甲基化和蛋白表达缺失的非小细胞肺癌患者淋巴结转移率明显增高 ,术后生存期明显降低 (P <0 0 5 )。结论　启动子甲基化是导致非小细胞肺癌p16基因失活的主要方式 ,同时具有p16基因启动子甲基化及p16蛋白表达异常的患者预后不良     

p16 (CDKN2) is a major deletion target at 9p21 in bladder cancer

The p16 gene has been identified as a candidate tumour suppressorgene at 9p21, a region commonly deleted in bladder cancer. Wescreened 140 bladder tumours and 16 cell lines for deletionsand sequence variants of p16. Eight cell lines showed homozygousdeletion of p16 and two had small sequence variations. All 13tumours with small defined deletions of 9p21, 18/31 (58%) oftumours with monosomy 9 and 9/91 (10%) of tumours with no chromosome9 loss of heterozygosity had homozygous deletion of p16. Notumour-specific sequence variants were identified. Deletionmapping revealed a nested set of deletions focused on p16. Sixdeletions involved p16 but not the related and adjacent genep15 and one tumour had an intragenic deletion of p16. All otherdeletions involved both p16 and p15. We conclude that p16 representsthe major target for deletion at 9p21 in bladder cancer.     

肺癌CDKN2/p16基因纯合缺失的研究

目的　研究 Ｃ Ｄ Ｋ Ｎ２／ｐ１６ 基因的缺失与肺癌发生、发展的关系。方法　采用多重聚合酶链反应技术,对８９ 例肺癌进行了 Ｃ Ｄ Ｋ Ｎ２／ｐ１６ 基因第１ 、２ 外显子纯合缺失的分析研究。结果　标本取材方法的改良提高了聚合酶链反应技术对基因缺失的检出率,８９ 例肺癌中检出第１ 外显子缺失率１９ ．１ ％ （１７／８９） ,第２ 外显子缺失率２２ ．５ ％ （２０／８９） ,有１４ 例第１ 、２ 外显子共同缺失,第１ 或（ 和） 第２ 外显子总缺失率为２５８ ％ （２３／８９） 。 Ｃ Ｄ Ｋ Ｎ２／ｐ１６ 基因的缺失集中发生于非小细胞肺癌, 并与转移和分期有关。结论 Ｃ Ｄ Ｋ Ｎ２／ｐ１６ 基因的缺失是非小细胞肺癌的遗传易感因素,并在其恶性进展中起一定作用。     

Selective p38 activation in human non-small cell lung cancer

The mitogen-activated protein kinase (MAPK) pathways transmit signals from the cell membrane to the nucleus. Activation of MAPK cascades may play a role in malignant transformation. We hypothesized that enhanced expression of one or more of these pathways would occur in human lung cancers. Using Western blot analysis of tissue homogenates from resected non- small cell lung cancers and matched non-neoplastic lung tissue, we determined that only activated p38 was consistently increased in tumor compared with normal tissue. In vitro kinase assays confirmed that the levels of activated MAPK correlated with the activity of the enzymes, and immunohistochemical analysis confirmed the cellular localization of the activated MAPKs. We incubated a lung cancer cell line in a hypoxic chamber to simulate the hypoxic environment in solid lung tumors, but found no increase in p38 activation. Contrary to our expectations, ERK and JNK, the MAPK pathways traditionally associated with cell growth and perhaps malignant transformation, were not consistently activated in the human lung tumor samples. However, p38, a MAPK usually associated with stress responses, growth arrest, and apoptosis, was activated in all of the human lung cancer samples, suggesting an additional role for this pathway in malignant cell growth or transformation.     

非小细胞肺癌survivin、p53和COX-2蛋白的表达

目的探讨非小细胞肺癌组织中survivin、p53和环氧合酶-2（COX-2）蛋白表达及其在肺癌发生、分化程度、淋巴结转移以及预后评估中的意义。方法采用SP法免疫组化技术检测70例非小细胞肺癌组织中的survivin、p53和COX-2表达情况。结果survivin和COX-2阳性表达与肺非小细胞癌组织的分化程度、有无淋巴结转移及临床TNM分期有关（P〈0．01）;p53阳性表达与非小细胞肺癌组织的分化程度有关（P〈0．01）。同时发现,survivin、p53和COX-2（＋＋＋～＋＋＋＋）阳性表达率明显高于（＋～＋＋）,差异有显著性（P〈0．01）。这3种抗体中在非小细胞肺癌中的阳性表达占76％。结论survivin、p53和COX-2的表达在非小细胞肺癌组织的浸润、转移和发展中具有重要意义,有助于对非小细胞肺癌的诊断及预后的评价。     

Mechanisms of p185HER2 expression in human non-small cell lung cancer cell lines.

To identify mechanisms that allow p185HER2 expression in lung cancer, we performed Western, Southern, and Northern blot analyses of 14 cell lines derived from human non-small cell lung carcinomas and one cell line derived from a human mesothelioma. Human bronchiole epithelial cells and rat type II pneumocytes were found to express p185HER2 at low to undetectable levels by Western blot technique. In contrast, 13 lung cancer cell lines expressed p185HER2, and eight of these 13 expressed p185HER2 at levels at least 2-fold higher than that found in normal bronchiole epithelial cells or type II pneumocytes. Genomic Southern analysis showed that amplification of the HER2 gene was present in only one of the eight cell lines that expressed p185HER2 at these higher levels. Increased levels of steady-state HER2 mRNA occurred in the remaining seven cell lines. We conclude that in human non-small cell lung carcinoma cell lines the most common mechanism resulting in increased p185HER2 expression is due to mechanisms that increase HER2 mRNA levels, with HER2 gene amplification occurring less commonly.     

Two p16 (CDKN2A) germline mutations in 30 Israeli melanoma families

Germline mutations in the p16 (CDKN2A) tumour suppressor gene have been linked to inherited predisposition to malignant melanoma (MM). Variable frequencies of p16 germline mutations were reported in different collections of melanoma families but it can be as high as 50%. Here we describe the results of p16 mutation screening in 30 melanoma kindreds in Israel. The entire coding region of the p16 gene, including exons 1, 2 and 3, flanking exon/intron junctions, and a portion of the 3' untranslated (UTR) region of the gene were examined by single-stranded conformation polymorphism (SSCP) analysis and direct sequencing. Two p16 germline mutations were identified: G101W, which has been previously observed in a number of melanoma kindreds, and G122V, a novel missense mutation. Thus, the frequency of mutations identified in this collection of Israeli families was 7%. Functional analysis indicated that the novel G122V variant retained some capacity to interact with cyclin dependent kinases (CDKs) in vitro, yet it was significantly impaired in its ability to cause a G1 cell cycle arrest in human diploid fibroblasts. This partial loss of function is consistent with the predicted impact of G122V substitution on the 3-dimensional structure of the p16 protein.     

CDKN2A (p16INK4A) somatic and germline mutations

The cell cycle is composed of a series of steps that can be negatively or positively regulated by various factors. A group of low-molecular-weight proteins have recently been identified that specifically inhibit the function of cyclin-dependent kinases in mammalian cells. Inactivation of the CDKN2A gene (also known as p16^INK4A and MTS1) attracted considerable interest after it was mapped to 9p21, a locus for familial melanoma. In an effort to standardize the information regarding human CDKN2A mutations detected in cancers, a database with information of 146 point mutations has been created. Cancer type, origin of cells, specific mutation, amino acid change, literature citation, and other data are provided for each mutation entry. Studies of biochemical and biological functions of both wild-type and mutant proteins are central to our understanding of the role of p16^INK4a mutations in tumorigenesis, a summary of these studies is also included in the present update. © 1996 Wiley-Liss, Inc.     

人非小细胞肺癌细胞中端粒酶活性的检测与研究

目的 研究非小细胞肺癌细胞癌组织中端粒酶活性表达,探讨端粒酶生表达与非小细胞肺癌发生发展的关系。方法 收集经手术及病理证实的非小细胞肺癌４８例标本,１２例肺癌癌旁肺组织、７例非肿瘤病例所取正常肺组织作对照。用端粒酶检测试剂盒检测组织本端粒酶活性。结果 ７５．００％（３６／４８）非小细胞肺癌组织标本检出端粒酶活性,８．３３％（１／１２）癌旁肺组织检出端粒酶活笥,７例非肿瘤标本所取的正常肺组织均未检出     

Characterization of CDKN2A(p16) methylation and impact in colorectal cancer: systematic analysis using pyrosequencing

ABSTRACT: BACKGROUND: The aim of this study is to analyse CDKN2A methylation using pyrosequencing on a large cohort of colorectal cancers and corresponding non-neoplastic tissues. In a second step, the effect of methylation on clinical outcome is addressed. METHODS: Primary colorectal cancers and matched non-neoplastic tissues from 432 patients underwent CDKN2A methylation analysis by pyrosequencing (PyroMarkQ96). Methylation was then related to clinical outcome, microsatellite instability (MSI), and BRAF and KRAS mutation. Different amplification conditions (35 to 50 PCR cycles) using a range of 0-100% methylated DNA were tested. RESULTS: Background methylation was at most 10% with [greater than or equal to]35 PCR cycles. Correlation of observed and expected values was high, even at low methylation levels (0.02%, 0.6%, 2%). Accuracy of detection was optimal with 45 PCR cycles. Methylation in normal mucosa ranged from 0 to >90% in some cases. Based on the maximum value of 10% background, positivity was defined as a [greater than or equal to]20% difference in methylation between tumor and normal tissue, which occurred in 87 cases. CDKN2A methylation positivity was associated with MSI (p = 0.025), BRAF mutation (p < 0.0001), higher tumor grade (p < 0.0001), mucinous histology (p = 0.0209) but not with KRAS mutation. CDKN2A methylation had an independent adverse effect (p = 0.0058) on prognosis. CONCLUSION: The non-negligible CDKN2A methylation of normal colorectal mucosa may confound the assessment of tumor-specific hypermethylation, suggesting that corresponding non-neoplastic tissue should be used as a control. CDKN2A methylation is robustly detected by pyrosequencing, even at low levels, suggesting that this unfavorable prognostic biomarker warrants investigation in prospective studies.     

CDKN2A Gene Deletions and Loss of p16 Expression Occur in Osteosarcomas That Lack RB Alterations

Osteosarcomas often suffer mutations of the RB (retinoblastoma) gene, with resultant inactivation of the pRb protein. pRb is one component in a cell-cycle control pathway that includes the p16 (encoded by the CDKN2A gene) and cyclin-dependent kinase 4 (cdk4, encoded by the CDK4 gene) proteins. We therefore sought to determine whether the CDKN2A and CDK4 genes were altered in those osteosarcomas that lacked RB inactivation. Twenty-one osteosarcomas (2 low-grade and 19 high-grade) were evaluated for homozygous deletion of the CDKN2A gene, CDK4 amplification, and allelic loss of the RB gene, as well as for expression of p16 and pRb proteins. Five high-grade osteosarcomas showed loss of p16 expression; four of these had homozygous CDKN2A deletions, and the fifth had a probable deletion obscured by numerous nonneoplastic, p16-immunopositive multinucleated giant cells. Thus, p16 immunohistochemistry may provide a sensitive means for assessing CDKN2A status. Twelve tumors (including the two low-grade osteosarcomas) were immunopositive for pRb, and nine tumors were immunonegative for pRb. Of the five cases with CDKN2A/p16 alterations, none had allelic loss of the RB gene and all expressed pRb, suggesting that each of these tumors had an intact RB gene. None of the tumors showed CDK4 amplification. No alterations were detected in the two low-grade osteosarcomas. This study suggests that CDKN2A is a tumor suppressor inactivated in osteosarcomas that lack RB mutations and that the p16-pRb cell-cycle control pathway is deregulated in a large number of high-grade osteosarcomas.     

CDKN 2/p16基因甲基化失活与肺癌关系的研究

目的 研究ＣＤＫＮ２／ｐ１６基因５’端调控序列区ＣｐＧ岛甲基化的状态与肺癌发展的关系。方法 采用甲基化敏感性核酸酶切基因组ＤＮＡ的方法,对８９例肺癌的ＣＤＳＮ２／ｐ１６基因进行了Ｓｏｕｔｈｅｒｎ杂交分析。结果 ８９例肺癌发现该基因甲基化２１例,甲基化频率为２３．６％（２１／８９）,其中１７例发生于４２例Ｐ１６蛋白 阴性表达的患者。结论 ＣＤＫＮ２ｐ／１６基因５’端ＣｐＧ岛甲基化可能是该基因失活的重     

P53 and P16 gene mutations in non-small cell lung cancer

The aim of this study was to assess prospectively the occurrence of p53 and p16 mutations (considered separately and together) in NSCLC in terms of their clinical and prognostic relevance. Study group included 87 patients who underwent pulmonary resection for cure. p53 and p16 mutations were found in 22 (25%) and 14 (16%) cases, respectively. In eight patients (9%) both mutations were present, and the tendency for their common occurrence was significant (p = 0.02). There was no relation between mutation and clinical characteristics. Median survival in the entire group was 17 months and the 3-year survival probability--41%. There was no correlation between the occurrence of any mutation (considered separately or together) and survival. These results indicate that p53 and p16 gene mutations tend to occur together in NSCLC, however these alterations seem not to have noteworthy clinical and prognostic significance.     

Tumor suppressor gene p16 (CDKN2A) mutation status and promoter inactivation in head and neck cancer.

The p16INK4A (CDKN2A/MTS1) putative tumor suppressor gene encodes a cyclin dependent kinase inhibitor which plays an important role in the regulation of the G1/S phase cell cycle checkpoint. A high frequency of various p16 gene alterations were consequently observed in many primary tumors. P16 can be inactivated by different mechanisms: i) homozygous deletion, ii) methylation of the promoter region or iii) point mutation. In order to investigate p16 alterations in head and neck cancer (HNC) we analyzed 70 primary tumors of the larynx, pharynx and oral cavity including their corresponding normal mucosa for mutation inactivation by direct sequencing exon 2. We detected only one so far undescribed transversion G to T at position 322 (Asp108Tyr) and a known polymorphism (Ala148Thr) in five cases. The methylation status of the p16 promoter region was analyzed by an improved highly sensitive methylation-specific PCR protocol. P16 methylation inactivation was found in 16 of 55 cases (29%). Our data indicate that p16 point mutations in HNC are less frequent, but inactivation by methylation of the promoter region could be involved in genesis and progression of HNC.