Frequent silencing of DBC1 is by genetic or epigenetic mechanisms in non-small cell lung cancers

Genome-wide screening of DNA copy number aberrations in 27 cell lines derived from non-small cell lung cancers (NSCLCs), using a custom-made comparative genomic hybridization (CGH)-array, identified a homozygous deletion of the deleted in bladder cancer 1 gene (DBC1) in one cell line. Homozygous deletion of DBC1, located at 9q33.1, was also observed in two of 53 primary NSCLC tumors examined. Moreover, 21 of the other 26 cell lines showed complete loss of DBC1 expression, although normal lung tissues express this gene, and treatment with 5-aza-2'-deoxycytidine restored expression of DBC1. Hypermethylation in part of a CpG island around the exon 1 of DBC1 has been reported in urothelial cancers, but the potential association between methylation and expression status was never clarified in that disease. In our experiments, a different part of the same CpG island showed promoter activity in vitro and was frequently methylated in our cell lines and primary tumors of NSCLC, where methylation status correlated inversely with gene expression. Among our primary NSCLC cases, methylation of the DBC1 promoter occurred more frequently in men, elderly patients and smokers than in women, younger patients and nonsmokers respectively, but it was not correlated with tumor stage or histology. Exogenous overexpression of DBC1 in NSCLC cell lines lacking its expression inhibited cell growth. Our results provide the first evidence that DBC1 is a likely tumor suppressor for NSCLC; silencing of the gene through homozygous deletion or methylation of its promoter region may be associated with progression of this disease.     

Non-small cell lung cancers frequently express phosphorylated Akt; an immunohistochemical study

Mounting evidence suggests that the alterations of Akt/protein kinase B (PKB) play an important role in tumorigenesis. Phosphorylated Akt regulates many of the key effector molecules involved in apoptosis, angiogenesis, and cell cycle progression during tumorigenesis. The expression of phosphorylated Akt has been described in some human malignancies, but not in primary human lung cancer. In this study, to understand the role of Akt in lung tumorigenesis we analyzed the expression of phosphorylated Akt in 43 non-small cell lung cancers (NSCLCs) by immunohistochemistry. Phosphorylated Akt was detected either in the cytoplasm (23 cases) or nucleus (6 cases) in 29 of 43 NSCLCs (67.4%). Squamous cell carcinomas, adenocarcinomas, and bronchioloalveolar carcinomas expressed phosphorylated Akt in 68.2%, 61.5% and 75%, respectively. We also analyzed the phosphorylated Akt expression between primary NSCLCs and their corresponding nodal metastasis; the expression was not, however, different between the primary and metastatic lesions. Taken together, these results indicate that Akt 1 is frequently activated in NSCLCs, irrespective of the histological subtypes, and suggest that phosphorylated Akt may play a role in the development of NSCLC rather than in the progression of NSCLC.     

Identification of chromosome arm 9p as the most frequent target of homozygous deletions in lung cancer

Genome scanning at a 1-Mb resolution was undertaken in 29 lung cancer cell lines to clarify the distribution of homozygous (i.e., both allele) deletions along lung cancer genomes, using a high-resolution single nucleotide polymorphism array. Eighteen regions, including two known tumor suppressor loci, CDKN2A at 9p21 and FHIT at 3p14, were found homozygously deleted. Frequencies of deletions at the 18 regions were evaluated by genomic polymerase chain reaction in 78 lung cancer cell lines. Seven regions, 2q24, 3p14, 5q11, 9p21, 9p23, 11q14, and 21q21, were homozygously deleted in two or more cell lines. The CDKN2A locus at 9p21 was most frequently deleted (20/78, 26%), and the deletions were detected exclusively in non-small-cell lung carcinomas (NSCLCs). The PTPRD (protein tyrosine phosphatase receptor type D) locus at 9p23 was the second-most frequently deleted (8/78, 10%), and the deletions were detected in both small-cell lung carcinomas (SCLC) and NSCLC. In addition, the 9p24 region was deleted in a NSCLC. In total, 24 (31%) cell lines carried at least one deletion on chromosome arm 9p, while deletions on the remaining chromosome arms were observed at most in four (5%) cell lines. Deletions at 9p24, 9p23, and 9p21 were not contiguous with one another, and preferential co-occurrence or mutual exclusiveness for the deletions at these three loci was not observed. Thus, it was indicated that 9p is the most frequent target of homozygous deletions in lung cancer, suggesting that the arm contains multiple lung tumor suppressor genes and/or genomic features fragile during lung carcinogenesis.     

PTEN/MMAC1/TEP1在肺癌中的丢失和失活

目的 了解抑制癌基因ＰＴＥＮ／ＭＭＡＣ１／ＴＥＰ１（以下简称ＰＴＥＮ）在肺癌中的缺失和失活。方法 选用２４例具有正常对照的肺癌新鲜标本,１８例小细胞肺癌石蜡切片,用聚合酶链反应及杂合性丢失分析法检测ＰＴＥＮ的杂合笥丢失;并采用原位杂交法、免疫组化化学染色法、Ｗｅｓｔｅｍ ｂｌｏｔ法观察肺癌标本中ＰＴＥＮ ｍＲＮＡ和蛋白水平的表达。对１株肺腺癌和３株小细胞肺癌系进行ＰＴＥＮ的Ｓｏｕｔｈｅｒｎ、Ｎｏｒ     

Allelotyping demonstrates common and distinct patterns of chromosomal loss in human lung cancer types

Allelic loss is a hallmark of tumor suppressor gene (TSG) inactivation. We have allelotyped 29 paired lymphoblastoid and lung cancer cell lines derived from 11 patients with small cell (SCLC) and 18 patients with non-small cell lung carcinomas (NSCLC). Statistical analysis indicated that a threshold of 30% separated non-random allelic loss from the random genetic deletions of malignancy. We have identified non-random allelic loss at 42 of 54 (78%) specific chromosomal regions examined, with 22 regions (52%) common between the two major lung cancer histologic types. There were 3 regions (7%) with allelic loss specific for SCLC and 17 regions (41%) specific for NSCLC. Furthermore, there were significant differences in loss of heterozygosity (LOH) frequencies between NSCLC and SCLC at 13 regions on eight chromosome arms (3p, 5q, 6q, 9p, 10q, 11p, 13q, and 19p). Eight homozygous deletions were present in seven cell lines at four regions, 3p12, 3p14.2, 9p21, and 10q23–25. We have also identified novel sites of chromosomal deletions. In particular, there was frequent loss at 11p13 in SCLC and loss at 6p21.3 and 13q12.3 in NSCLC. In this study, we demonstrate that a) non-random allelic losses in lung cancer involve multiple regions; b) some losses are common to both NSCLC and SCLC subtypes, whereas others are subtype specific; c) there are genetic deletions at novel chromosomal regions; and d) several homozygous deletions have been noted. Our studies demonstrate the usefulness of continuous cell lines for detailed allelotyping, for comparing genetic abnormalities between SCLC and NSCLC, and for identifying homozygous deletions. Genes Chromosomes Cancer 21:308–319, 1998. © 1998 Wiley-Liss, Inc.     

Neuroendocrine differentiation in endocrine and nonendocrine lung carcinomas

Bronchial carcinoids and small cell lung cancer (SCLC) are currently recognized as neuroendocrine (NE) neoplasms. However, non-SCLC (NSCLC) may also express NE properties. Paraffin-embedded sections of a comprehensive panel of 113 lung carcinomas were analyzed for the expression of three general markers common to all NE cells, namely, chromogranin A, Leu-7 and neuron-specific enolase (NSE), five specific NE secretory products, and four other tumor markers by immunohistochemistry using the sensitive avidin-biotinylated peroxidase technique. The authors were able to demonstrate the following: (1) most, but not all carcinoids and SCLCs expressed multiple NE markers in a high percentage of tumor cells; (2) up to a half of NSCLC cases contained small subpopulations of cells expressing NE in a high percentage of tumor cells; (2) up to half of NSCLC cases contained small subpopulations of cells expressing NE markers; and (3) occasional NSCLCs showed staining patterns indistinguishable from SCLC. Specifically, 7 of 77 NSCLCs expressed four or more NE markers. NE markers in NSCLCs were more commonly expressed in adenocarcinomas and large cell carcinomas and rarely in squamous cell carcinomas. For comparison, the mean number of NE markers expressed by all cases of NSCLC was 1.5, carcinoids 6.0, and SCLCs 3.8. Individual "marker counts" were not useful in categorizing lung tumors as carcinoids and SCLC versus NSCLC. Instead, 95% of the tumors were correctly classified, applying a statistical model created from staining indices of the three general NE markers (chromogranin A, Leu-7, NSE) and three other tumor markers (carcinoembryonic antigen, keratin, vimentin). Because NSCLCs with NE features might have different clinical characteristics than other NSCLCs, immunohistochemistry provides an effective manner to identify this biologically interesting subset of NSCLCs in routine paraffin sections.     

Microsatellite alteration at chromosome 3p loci in neuroendocrine and non-neuroendocrine lung tumors. Histogenetic and clinical relevance.

Although chromosome 3p regions are the most frequent site for genetic alterations in small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC), the extent of such abnormality in carcinoid tumors remained to be investigated. Moreover, the histogenetic and biological implications of these findings in non-carcinoid lung tumors remain unclear. We studied eight microsatellite loci on chromosome 3p regions by multiplex polymerase chain reaction in paired normal and tumor DNA from 17 carcinoid tumors, 5 SCLCs, and 38 NSCLCs to determine the histogenetic and the clinical significance of their alterations in these neoplasms. Our results revealed a lack of microsatellite abnormalities at all loci tested in both typical and atypical carcinoid tumors. SCLCs and NSCLCs showed loss of heterozygosity in 100% (5/5) and 58.0% (22/38), respectively. Loss of heterozygosity at more than two loci correlated significantly with poor histological differentiation and were preponderantly found in high proliferative index and DNA aneuploid NSCLCs. Microsatellite instability was noted in only one (1.7%) of the lesions. Our study suggests that 1) the difference in chromosome 3p alterations between carcinoid tumors and SCLCs favors a stochastic rather than linear evolution of these tumors, 2) 3p alterations may constitute an initial event in the development of small cell carcinomas, and 3) loss of heterozygosity at 3p loci is associated with aggressive tumor characteristics in non-small-cell carcinomas.     

p53 expression in oat and non-oat small cell lung carcinomas: correlations with proliferating cell nuclear antigen.

AIMS--To investigate the immunohistochemical expression of p53 protein in small cell lung carcinoma (SCLC), comparing it with that in non-small cell carcinoma (NSCLC); and to evaluate the correlation between p53 and proliferating cell nuclear antigen (PCNA) expression as well as between p53 and PCNA expression and survival. METHODS--Paraffin wax embedded tissues from 61 cases of primary lung carcinoma were stained for p53 protein and PCNA using the monoclonal antibodies 1801 and PC-10, respectively, in a standard avidin-biotin immunoperoxidase method. RESULTS--Of the 61 lung carcinomas 35 (57%) were positive for p53 (range 1% to 90%). Ninety percent of the non-oat SCLC contained positive cells and the labelling index (LI) was significantly higher than that of the oat SCLC (p < 0.001). SLCC also displayed a higher p53 LI than NSCLC (p < 0.01); no difference was found between squamous carcinoma, adenocarcinoma, and oat cell carcinoma. A p53 LI of greater than 1% tended to be associated with nodal metastases (p < 0.05), and p53 expression in node positive tumours as well as in oat cell carcinomas was indicative of poorer survival (p < 0.01 and p < 0.1, respectively). A p53 Li of greater than 60% was a negative prognostic factor in non-oat SCLC (p < 0.05). PCNA LI was highest in non-oat SCLC and lowest in NSCLC; oat cell carcinomas had a mean LI intermediate between NSCLC and non-oat SCLC (NSCLC v oat cell carcinoma p < 0.05 and oat cell v non-oat cell carcinomas p < 0.01). A PCNA LI was not correlated with nodal metastases or survival, but there was a significant positive correlation between PCNA LI and p53 LI (rs = 0.484, p < 0.001). CONCLUSIONS--p53 and PCNA expression differ substantially among the various types of lung carcinomas. Substantial differences were also found between oat and non-oat types of SCLC, indicating that SCLC is heterogeneous as far as proliferation rate and altered p53 expression is concerned. p53 seems to be of some prognostic value. The relation between PCNA and p53 expression indicates that the PCNA gene is slightly upregulated by p53.     

Expression of p16 and lack of pRB in primary small cell lung cancer.

The retinoblastoma protein (pRB), p16, and cyclin D1 are major components of the RB pathway, which controls the G1 checkpoint of the cell cycle. Proper regulation of this pathway is crucial for normal cell proliferation. Abnormal forms of these proteins have been found in various types of malignant tumours. In the present report, immunohistochemical techniques were applied to study the expression of pRB, p16, and cyclin D1 in 161 samples of primary small cell lung cancer (SCLC) and 20 samples of non-small cell lung cancer (NSCLC). While pRB and cyclin D1 staining was negative in 161 specimens of SCLC, expression of p16 was observed in 153 samples. In contrast to SCLC, 16 out of 20 NSCLC cases exhibited pRB expression and 15 showed cyclin D1 expression, but only very weak p16 staining was found in five samples. These observations could provide additional criteria for the distinction between SCLC and NSCLC. Furthermore, these findings, based on primary tissues, implicate different mechanisms in the tumourigenesis of SCLC and NSCLC.     

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.     

Differential expression of RON in small and non-small cell lung cancers

RON is a MET related receptor tyrosine kinase (RTK) and its natural ligand is macrophage stimulating protein (MSP). RON plays a very important role in the regulation of inflammation. Several studies have previously reported overexpression of RON in a variety of cancers including lung and identified numerous RON alternate splice forms that very likely contribute to tumor growth and metastasis. Here, we have analyzed the expression of total RON protein as well as its kinase-active form (phospho-RON) in 175 archival lung tumor FFPE (formalin fixed paraffin embedded) samples that included non-small-cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and their metastatic forms. The frequency and intensity of RON protein expression was much higher in lung tumors of neuroendocrine origin such as SCLC and in secondary tumors that metastasized to brain. In addition, the majority of the expressed RON protein was phospho-RON. We also identified 62, and 30 kDa isoforms of RON (GenBank accession numbers are JN689381 and JN689382) using RNA isolated from pooled lung cancer cell lines and RT-PCR. A majority of the NSCLC cell lines expressed a 150 kDa band that corresponded to the RON β chain and 120 kDa band in the panel of SCLC cell lines tested. RON was expressed on the cell surface in NSCLC cell lines. Finally, knock down of RON expression resulted in a significant loss in viability as well as motility in lung cancer cells suggesting that RON is a potential therapeutic target.     

No evidence of microsatellite instability but frequent loss of heterozygosity in primary resected lung cancer

We examined microsatellite instability and loss of heterozygosity (LOH) in primary lung tumors from 93 cancer patients, using 16 microsatellite markers. The cases studied included 87 non-small-cell lung cancers (NSCLC) and six small-cell lung cancers (SCLC). All the patients except two were current or former smokers. The microsatellite markers were all dinucleotide repeat sequences from chromosomal locations 1p, 3p, 5q, 8p, 9p, 10p, 11p, 13q, and 17q. None of the tumors showed microsatellite instability (0/93). In NSCLC, 28% (24/87) of the cases showed LOH in at least one locus, whereas, in SCLC, 67% (4/6) had allelic losses. The frequency of LOH differed between the various cell types of NSCLC. The highest frequency was seen in large cell carcinoma (3/6, 50%) followed by squamous cell carcinoma (16/43, 37%) and adenocarcinoma (5/35, 14%). The most common site of LOH was 3p, where markers D3S1284, D3S659, D3S1289, D3S966, D3S647, and D3S1038 were studied. LOH, studied with 9p markers (D9S126, D9S171, D9S162), was less common. The present results, together with earlier reports, suggest that smoking-related primary lung cancers seldom show microsatellite instability but are characterized by frequent LOH. Environ. Mol. Mutagen. 30:217–223, 1997. © 1997 Wiley-Liss, Inc.     

Involvement of aryl hydrocarbon receptor signaling in the development of small cell lung cancer induced by HPV E6/E7 oncoproteins

Background  

Lung cancers consist of four major types that and for clinical-pathological reasons are often divided into two broad categories: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). All major histological types of lung cancer are associated with smoking, although the association is stronger for SCLC and squamous cell carcinoma than adenocarcinoma. To date, epidemiological studies have identified several environmental, genetic, hormonal and viral factors associated with lung cancer risk. It has been estimated that 15-25% of human cancers may have a viral etiology. The human papillomavirus (HPV) is a proven cause of most human cervical cancers, and might have a role in other malignancies including vulva, skin, oesophagus, head and neck cancer. HPV has also been speculated to have a role in the pathogenesis of lung cancer. To validate the hypothesis of HPV involvement in small cell lung cancer pathogenesis we performed a gene expression profile of transgenic mouse model of SCLC induced by HPV-16 E6/E7 oncoproteins.     

Cytoplasmic expression of c-erbB2 in non-small cell lung cancers

The aim of this study was to investigate the expression of c-erbB2 in non-small cell lung cancers (NSCLCs) with attention both to membranous and cytoplasmic reaction, and to try to elucidate the meaning of cytoplasmic expression of c-erbB2 in NSCLCs. Immunohistochemical c-erbB2 expression and related clinico-pathological features were examined in 312 surgically resected patient tissues of NSCLCs, including 175 cases of adenocarcinoma and 137 cases of squamous cell carcinoma. Immunostaining of inner- and ecto-domain of c-erbB2, mRNA expression and the quantitation of soluble c-erbB2 in cultured media were performed in five NSCLC cell lines. Cytoplasmic expression of c-erbB2 was observed more frequently than membranous, both in patient tissues and cell lines. Neither membranous nor cytoplasmic expression of c-erbB2 was significantly correlated with short outcome in NSCLCs. Membranous c-erbB2 was expressed by both inner and ecto-domain, while cytoplasmic c-erbB2 was expressed by either or both inner and ecto-domain. c-erbB2 mRNA was produced in most cell lines; however, the soluble form was only detectable in a cell line that only presented a membranous c-erbB2. In conclusion, cytoplasmic c-erbB2 of NSCLCs was not a full-length protein only expressed in cellular membrane, but reflected degenerated c-erbB2 fragments with less functional ability.