Loss of heterozygosity of chromosome 3p markers in small-cell lung cancer

Frequent FHIT gene loss of heterozygosity in human papillomavirus-infected non-smoking female lung cancer in Taiwan

The fragile histidine triad (FHIT), located in chromosome region 3p14.2, had been reported to be a frequent allele with loss of heterozygosity (LOH) in smoking lung cancer and HPV-associated cervical cancer. Additionally, FHIT LOH may act as a tumor suppressor gene to involve in smoking-related lung tumorigenesis and HPV-related cervical tumorigenesis, respectively. In our previous report, a high prevalence of HPV 16/18 infection has been observed in non-smoking female lung cancer patients, and thus it was speculated that HPV 16/18 infection may increase the LOH frequency of FHIT in female cases to implicate in lung tumorigenesis. In this study, 157 lung cancer patients were enrolled and subjected to FHIT LOH analysis with three microsatellite markers. As expected, the frequency of FHIT LOH in males, smokers, and squamous cell carcinomas lung cancer patients was significantly higher than that of their corresponding counterpart (P=0.020 for gender, P<0.001 for smoking status, and P=0.038 for tumor type). Interestingly, a correlation between HPV 16 infection and FHIT LOH was observed in female lung cancer cases. To be more specifically, FHIT LOH frequency was remarkably increased from 18% (6 of 33) in HPV 16 non-infected female cases to 46% (11 of 24) in HPV 16 infected cases. The higher frequency of FHIT LOH observed in HPV 16-infected female lung tumors suggested that the involvement of HPV infection in lung tumorigenesis may, at least in part, be mediated through FHIT LOH.

The role of human papillomavirus type 16 and the fragile histidine triad gene in the outcome of cervical neoplastic lesions

The presence of high-risk human papillomavirus, loss of heterozygosity on chromosome 3p and fragile histidine triad gene expression were assessed as potential markers of cancer and CIN progression in 83 cervical cancers and 74 cervical intraepithelial neoplasia grade 1 lesions. Human papillomavirus type 16 was an indicator of vascular involvement in cancers. Loss of heterozygosity, especially in the fragile histidine triad gene intron 5, was an indicator of high-grade tumours, greater tumour depth and lymph node involvement. Abnormal fragile histidine triad gene expression was more frequent in cervical intraepithelial neoplasia grade 1 lesions with increased risk of disease progression.

Frequent inactivation of RASSF1A, BLU, and SEMA3B on 3p21.3 by promoter hypermethylation and allele loss in non-small cell lung cancer

Non-small cell lung cancer frequently shows loss of heterozygosity of the chromosome 3p21.3 region and several genes such as RASSF1A, BLU, and SEMA3B have been identified as candidate tumor suppressor genes at this region since their downregulation and hypermethylation at their promoter regions were frequently detected in lung cancer. To determine whether these three genes are simultaneously inactivated during lung cancer development, we studied 138 primary non-small cell lung cancers for the promoter methylation status of these genes and allelic loss of the chromosome 3p21.3 region. We found promoter hypermethylation at 32% in RASSF1A, 30% in BLU, and 47% in SEMA3B. Allelic loss of 3p21.3 was detected in 54 (58%) of 93 informative tumors. Despite the weak association of methylation status among these three genes, there was no correlation between the methylation status of each gene and loss of heterozygosity. We also studied possible genes downstream of RASSF1A in 16 primary non-small cell lung cancers and found that the expressions of SM22 and SPARC were significantly downregulated in RASSF1A-hypermethylated tumors. Our results showed that, while candidate tumor suppressor genes at this locus can be simultaneously inactivated by epigenetic alterations, loss of heterozygosity without any hypermethylation of the three genes can also occur in some cases, suggesting that just one allelic loss might also be sufficient for the inactivation of any of these genes for lung cancer development.

High-grade neuroendocrine carcinomas display unique cytogenetic aberrations

Neuroendocrine tumors represent a spectrum of tumor types with different biologic and clinical features. The morphologic types include the low-grade typical and atypical carcinoids and the high-grade small cell and large cell neuroendocrine carcinomas (NECs). Cytogenetic descriptions of high-grade NECs are rare. Complete karyotypic descriptions of 34 high-grade NECs are reviewed: 7 extrapulmonary small cell NECs, 3 metastatic NECs of unknown primary, and 24 small cell lung carcinomas (SCLCs). Chromosomal deletions are more frequent than gains and often involve the entire chromosome arm. Typical aberrations are deletions of chromosome 3p, 5q, 10q, and 17p and gains of 1q, 3q, and 5p occurring as isochromosomes. Non-small cell lung cancers (NSCLCs) have different cytogenetic aberrations, but those with a metastatic phenotype display the identical aberrations as SCLC, a tumor known for its metastatic phenotype at onset. A genetic classification of lung cancer that incorporates the pattern of recurrent chromosome aberrations may be a better predictor of clinical outcome than a morphologic classification.

Clinicopathological significance of aberrant methylation of RAR?2 at 3p24, RASSF1A at 3p21.3, and FHIT at 3p14.2 in patients with non-small cell lung cancer

We investigated the clinicopathological significance of aberrant methylation of the retinoic acid receptor-beta2 (RARbeta2), RAS association domain family 1A (RASSF1A) and fragile histidine triad (FHIT) genes located on choromosome 3p in 120 patients with primary non-small cell lung cancer (NSCLC) by a methylation-specific PCR method. Aberrant methylation of these was detected in 31 (26%), 35 (29%) and 43 (36%) tumors, respectively. There was no correlation with the methylation status of any of the genes. RARbeta2 methylation was more frequently observed in patients with a smoking history (19 of 61, 31%) than in patients without one (3 of 29, 10%, P = 0.0373). RARbeta2 methylation was also preferentially observed in advanced stage NSCLC (12 of 71 (17%) in stage I, 5 of 15 (33%) in stage II, 11 of 24 (46%) in stage III, and 3 of 8 (38%) in stage IV, P = 0.0057 (stage I versus II, III,and IV)). FHIT methylation was predominantly detected in tumors with vascular invasion (21 of 44, 48%, P = 0.0703) or lymphatic permeation (28 of 59, 47%, P = 0.0115). RASSF1A methylation was more frequently observed in adenocarcinomas (28 of 72, 39%) than in squamous cell carcinomas (6 of 45, 13%, P = 0.0033). These results indicate that aberrant methylation of the candidate tumor suppressor genes on 3p plays a respective role in the pathogenesis of NSCLC.

Alterations of the Dutt1/Robo1 gene in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

Abnormalities of tumor suppressor genes (TSGs) on chromosome 3p are known to be important for the development of human lung cancers. In the present study, we investigated alterations of the Dutt1/Robo1 gene, as a possible tumor suppressor in this region, in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). Male Wistar rats, 6-wk-old, were given 2000 ppm BHP in their drinking water for 12 wk and maintained without further treatment until killed at wk 25. A total of 12 lung adenocarcinomas were obtained and total RNAs were extracted from each for assessment of aberrant transcripts of the Dutt1/Robo1 gene by reverse transcription (RT)-polymerase chain reaction (PCR) analysis. Aberrant transcripts bearing deletions of nucleotides (nt) 55-4318, 89-4346, 605-4221, and 929-4318 were detected in four of 12 adenocarcinomas (33.3%). Loss or reduced expression of the Dutt1/Robo1 gene was not found in any of the adenocarcinomas. Genomic DNAs extracted from six adenocarcinomas for Southern blot analysis did not show any evidence of deletion or gross rearrangement of the Dutt1/Robo1 gene. These results suggest that alterations of the Dutt1/Robo1 gene may be involved in the development of some lung adenocarcinomas induced by BHP in rats.

A susceptibility locus at chromosome 3p21 linked to familial nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) poses one of the serious health problems in southern Chinese, with an incidence rate ranging from 15 to 50/100,000. Chromosome translocation t(1;3) and frequent loss of heterogeneity on short arms of chromosome 3 and 9 have been reported to be associated with NPC, and a genome-wide scan identified an NPC susceptibility locus on chromosome 4p15.1-q12 recently. In our study, we collected samples from 18 families at high risk of NPC from the Hunan province in southern China, genotyped with a panel of polymorphic markers on short arms of chromosomes 3, 9, and 4p15.1-q12. A locus on 3p21 was identified to link to NPC with a maximum logarithm of odds for linkage score of 4.18. Fine mapping located the locus to a 13.6-cM region on 3p21.31-21.2, where a tumor suppressor gene cluster resided. Our findings identified a novel locus for NPC and provided a map location for susceptibility genes candidates. In contrast to a recent study, no significant evidence for NPC linkage to chromosomes 4 and 9 was observed.

Small cell lung cancer: from molecular biology to novel therapeutics

Small cell lung cancer (SCLC) is an aggressive tumor which metastasizes early. Patients with this disease have a poor prognosis even with immediate treatment. Because of the aggressive nature of this disease, all aspects of this tumor are studied extensively. This review will provide an update of the biology of SCLC at both the molecular and cellular levels. Cellular pathways and their relationship to cellular function will also be discussed. Treatment of both primary limited- and extensive-stage diseases as well as recurrent disease will be discussed including chemotherapy, thoracic radiotherapy, and surgery. The role of novel therapeutics being investigated will also be addressed.

Transcription Factors NF-YA Regulate the Induction of Human OGG1 Following DNA-alkylating Agent Methylmethane Sulfonate (MMS) Treatment

A human 8-oxoguanine-DNA glycosylase (hOGG1) is the main enzyme that repairs 8-oxoG, which is a critical mutagenic lesion. There is a great deal of interest in the up- or down-regulation of OGG1 expression after DNA damage. In this study, we investigated the effect of a DNA-alkylating agent, methylmethane sulfonate (MMS), on hOGG1 expression level and found that MMS treatment resulted in an increase in the functional hOGG1 expression in HCT116 cells. A region between -121 and -61 of the hOGG1 promoter was found to be crucial for this induction by MMS. Site-directed mutations of the two inverted CCAAT motifs substantially abrogated the induction of the hOGG1 promoter as a result of MMS treatment. In addition, the NF-YA protein (binding to the inverted CCAAT box) was induced after exposing cells to MMS. Moreover, gel shift and supershift analyses with the nuclear extracts prepared from HCT116 cells identified NF-YA as the transcription factor interacting with the inverted CCAAT box. Mutations of the inverted CCAAT box either prevented the binding of this factor or abolished its activation as a result of MMS treatment. Finally, this study showed that hOGG1-expressing HCT116 cells exhibited increased hOGG1 repair activity and resistance to MMS. Overall, these results demonstrate that MMS can up-regulate hOGG1 expression through the induction of the transcription factor, NF-YA, and increased transcription level of the hOGG1 gene correlates with an increase in enzyme activity providing functional protection from MMS.

Reduced transcription of the RB2/p130 gene in human lung cancer

Reduced expression of the retinoblastoma gene (RB)2/p130 protein, as well as mutation of exons 19, 20, 21, and 22 of the same gene, has been reported in primary lung cancer. However, it has been suggested by other investigators that mutational inactivation and loss of the RB2/p130 gene and protein, respectively, are rare events in lung cancer. In order to determine the contribution and mechanisms of RB2/p130 gene inactivation to lung cancer development and progression, we quantified RB2/p130 mRNA expression levels in a range of human lung cancer cell lines (n = 13) by real-time reverse transcription (RT)-polymerase chain reaction (PCR) analysis. In comparison to normal lung tissue, reduced transcription of the RB2/p130 gene was found in all small cell lung cancer cell lines examined, along with six out of the eight nonsmall cell lung cancers tested, most of which had inactivation of RB/p16 pathway. On the basis of Western blot analysis, the expression of RB2/p130 protein was consistent with RNA expression levels in all lung cancer cell lines examined. In addition, the mutational status of the RB2/p130 gene (specifically, exons 19, 20, 21, and 22) was determined in 30 primary lung cancers (from patients with distant metastasis) and 30 lung cancer cell lines by PCR-single strand conformation polymorphism (SSCP) analysis and direct DNA sequencing. There was no evidence of somatic mutations within the RB2/p130 gene in the 60 lung cancer samples (both cell lines and tumors) assessed, including the 11 lung cancer cell lines that displayed reduced expression of the gene. Furthermore, hypermethylation of the RB2/p130 promoter was not found in any of the above-mentioned 11 cell lines, as determined by a DNA methylation assay, combined bisulfite restriction analysis (COBRA). The results of the present study suggest that the reduced RB2/p130 expression seen in lung cancer may be in part transcriptionally mediated, albeit not likely via a mechanism involving hypermethylation of the RB2/p130 promoter. The observed reduction in RB2/p130 gene expression may be due to histone deacetylation, altered mRNA stability, and/or other forms of transcriptional regulation.

Alterations in the Fhit gene in pancreatic duct adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters

Alteration of the Fhit gene was investigated in pancreatic duct adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine (BOP) in Syrian golden hamsters. The animals received 70 mg/kg BOP, followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine and then L-methionine and administration of 20 mg/kg BOP. A total of 15 pancreatic duct adenocarcinomas were obtained 10 wk after the beginning of the experiment, and total RNAs were extracted from each for assessment of aberrant transcription of the Fhit gene by reverse transcription-polymerase chain reaction analysis. Aberrant transcripts lacking nucleotides in the regions of nt -75 to 348, nt -15 to 348, or nt -75 to 178 were detected in 11 adenocarcinomas (73.3%). Southern blot analysis of eight tumors did not show any evidence of gross rearrangement or deletion. These results indicated that changes in the Fhit gene occurred frequently and thus may have played a role in the development of pancreatic duct adenocarcinomas induced by BOP in hamsters.

Molecular and cellular biology of small cell lung cancer

For any tumor to become cancerous, various genetic mutations and biologic alterations must occur in the cell that in combination render it a malignant neoplasm. Small cell lung cancer (SCLC) is a neoplasm associated with several molecular and cellular abnormalities. SCLC is associated with early and frequent metastasis as well as a poor ultimate response to chemotherapy. New and novel therapies based on understanding the mechanisms of transformation are needed. SCLC is associated with multiple chromosomal abnormalities, the most common of which is chromosome 3p deletion, as well as with abnormal oncogenes and tumor-suppressor genes. Along with the genetic alterations, SCLC has been shown to overexpress various cell surface receptors, including receptor tyrosine kinases (RTKs), G-protein-coupled receptors, integrins, and others. Some downstream molecules are also activated, such as phosphatidylinositol 3'-kinase, and would serve as good candidates for therapeutic strategies.

FHIT: from gene discovery to cancer treatment and prevention

Chromosomal abnormalities, including homozygous deletions and loss of heterozygosity, are among the most common features of human tumours. The short arm of human chromosome 3, particularly the region 3p14.2, is a major site of such rearrangements. The 3p14.2 region spans the most active common fragile site of the human genome, encompassing a familial-kidney-cancer-associated breakpoint and a papilloma virus integration site. 6 years ago, the FHIT gene was identified in this region. Subsequent studies have shown that FHIT is commonly the target of chromosomal aberrations involving the long arm of human chromosome 3 and is thereby inactivated in most of the common human malignant diseases, including cancers of the lung, oesophagus, stomach, breast, and kidney. During the past 5 years, evidence has accumulated in support of a tumour-suppressor function for FHIT. In this review, we describe the recent findings in the molecular biology of FHIT with particular focus on the opportunities for treatment and prevention of cancer that have emerged.

Chromosomal alterations in small cell lung cancer revealed by multicolour fluorescence in situ hybridization

Small cell lung cancer (SCLC) is a major cause of cancer related morbidity and mortality. Karyotypic studies have revealed numerous chromosomal aberrations in most SCLC however, classical G-banding analysis is unable to fully characterise complex marker chromosomes. Recent developments in molecular cytogenetics now allow accurate identification of the chromosomal components of complicated rearrangements. We have applied the technique of multicolour fluorescence in situ hybridization (M-FISH) in combination with comparative genomic hybridization (CGH) to the analysis of 5 SCLC cell lines and 1 primary tumour specimen to characterise the chromosomal abnormalities. CGH analysis identified many similarities between specimens, with frequent DNA copy number decreases on chromosomes 3p, 5q, 10, 16q, 17p and frequent gains on 3q, 1p, 1q and 14q. In contrast, M-FISH analysis revealed a large number of structural abnormalities, with each specimen demonstrating an individual pattern of chromosomal translocations. Forty different translocations were identified with the vast majority (39) being unbalanced. Chromosome 5 was the most frequently rearranged chromosome (9 translocations) followed by chromosomes 2, 10 and 16 (6 translocations each). Further investigation of these frequently involved chromosomes is warranted to establish whether consistent break points are involved in these translocations, causing dysregulation of specific genes that are crucial for tumour progression and secondly to identify the affected genes.

Chromosomal imbalances in human lung cancer

A wealth of cytogenetic data has demonstrated that numerous somatic genetic changes are involved in the pathogenesis of human lung cancer. Despite the complexity of the genomic changes observed in these neoplasms, recurrent chromosomal patterns have emerged. In this review, we summarize chromosomal alterations identified in small cell and non-small cell lung cancer, using classical and molecular cytogenetic techniques. These analyses have uncovered a set of chromosome regions implicated in lung cancer development and progression. However, many of the target genes remain unknown. Newer technology, such as array-CGH, when combined with cDNA microarrays and tissue microarrays, will facilitate the integration of genomic and gene expression data and pave the way toward a molecular classification of lung carcinomas. The molecular implications of consistent chromosome imbalances found in lung cancer to date are also discussed.

Scotin, a novel p53-inducible proapoptotic protein located in the ER and the nuclear membrane

p53 is a transcription factor that induces growth arrest or apoptosis in response to cellular stress. To identify new p53-inducible proapoptotic genes, we compared, by differential display, the expression of genes in spleen or thymus of normal and p53 nullizygote mice after gamma-irradiation of whole animals. We report the identification and characterization of human and mouse Scotin homologues, a novel gene directly transactivated by p53. The Scotin protein is localized to the ER and the nuclear membrane. Scotin can induce apoptosis in a caspase-dependent manner. Inhibition of endogenous Scotin expression increases resistance to p53-dependent apoptosis induced by DNA damage, suggesting that Scotin plays a role in p53-dependent apoptosis. The discovery of Scotin brings to light a role of the ER in p53-dependent apoptosis.

Direct correlation between FRA3B expression and cigarette smoking

Cytogenetic deletions and/or loss of heterozygosity (LOH) of the short arm of chromosome 3, often with a break at 3p14, are well documented in lung tumors. The coincidence of a chromosomal fragile site, FRA3B, at a common chromosomal breakpoint in lung cancer has suggested that fragility at this site may predispose to breakage that could contribute to multistep carcinogenesis. This idea is supported by the more recent finding that FRA3B maps within the FHIT (fragile histadine triad) gene, and that aberrant transcripts and genomic deletions of FHIT/FRA3B occur in a variety of tumors including lung tumors. To determine whether some individuals have increased fragility of FRA3B that might increase the risk for breakage or deletion in 3p14.2, fragile site expression was examined in smokers, nonsmokers, and small cell lung cancer (SCLC) patients. The data clearly show that active smokers exhibit a significantly higher frequency of fragile site expression, including FRA3B, compared to that of nonsmokers and patients diagnosed with SCLC who have stopped smoking. These results suggest that active tobacco exposure increases chromosome fragile site expression, and that this fragility is transient and reversible. The data support the hypothesis that exposure to tobacco carcinogens increases the potential for chromosome breakage at fragile sites.

Investigation of genetic susceptibility to non-small cell lung cancer by fragile site expression

Fragile sites are non-staining gaps and breaks in specific points of chromosomes that are inducible by various culture conditions. Previous studies have shown that various clastogenic agents increase expression of fragile sites. In this study, the expression of common fragile sites induced by aphidicolin was evaluated on prometaphase chromosomes obtained from peripheral blood lymphocytes. Chromosomal aberrations and fragile site expression of 60 individuals, including 20 patients with non-small cell lung cancer (NSCLC), 20 of their clinically healthy family members, and 20 age-matched normal healthy controls without history of any cancer type were studied. Both the proportion of damaged cells (P < 0.001) and the mean number of gaps and breaks per cell (P < 0.001) were significantly higher in both the patients and relatives' groups when compared with the control group. However, they were insignificant when the patients were compared to their relatives (P > 0.05). We determined four aphidicolin type common fragile sites in our study. These sites in patients with NSCLC and relatives were the following: 1p21, 2q33, 3p14, and 16q23. In these fragile sites, 2q33, 3p14, and 16q23 sites were statistically significant when compared with control group (P < 0.001, P < 0.0005, and P < 0.05, respectively). Consequently, we believe that fragile site studies may be helpful to detection of cancer risk.

Alterations of the Fhit gene in hepatocellular carcinomas induced by N-nitrosodiethylamine in rats

The present study was conducted to assess whether Fhit gene alterations are a feature of hepatocellular carcinomas (HCCs) induced by N-nitrosodiethylamine (DEN) in male Fischer 344 rats. Animals, 6 wk old, received a single intraperitoneal injection of DEN at a dose of 10 mg/kg body weight, followed by combined treatment with partial hepatectomy and colchicine to induce cell-cycle disturbance and a selection procedure, consisting of 2-acetylaminofluorene and carbon tetrachloride. Fourteen HCCs were obtained 42 wk after the beginning of the experiment; total RNA was extracted for the assessment of aberrant transcription of the Fhit gene by reverse transcriptase-polymerase chain reaction analysis. Aberrant transcripts were detected in nine of the 14 HCCs (64.3%). Sequence analysis showed that these resulted from the absence of nt -9 to 279, nt -9 to 348, nt -98 to 279, nt -26 to 365, or nt -98 to 348. Western blot analysis demonstrated reduced expression of Fhit protein in six of 10 HCCs (60.0%), with a perfect correlation with Fhit gene alterations. These results indicated that changes in the Fhit gene occur frequently and may thus play some role in the development of HCCs induced by DEN in rats.

Chromosomal fragile sites and relationship between genetic predisposition to small cell lung cancer

Fragile sites are non-staining gaps and breaks on mammalian chromosomes. Several investigators have pointed out that these sites may act as factors that predispose to specific chromosomal rearrangements that are present in some cancer cases. The expression of common fragile sites induced by aphidicolin (Apc) was evaluated on prometaphase chromosomes obtained from the peripheral blood lymphocytes of 15 patients with lung cancer, 20 of their clinically healthy family members, and 20 age-matched normal controls. As a result of cytogenetic evaluation carried out by the High Resolution Banding (HRB) technique, 1q21, 2q33, 3p14, 7q32, 13q13, 16q23, 17q21, and 22q12 are defined as fragile sites in patients and relatives. The rate of total fragile sites and 2q33, 3p14, and 16q23 are statistically significant in both patients and relatives when compared with the control group. Therefore, our results showed that common fragile sites might be unstable factors in the human genome and they can be used as suitable markers for genetic predisposition to lung cancer.

FHIT alterations in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

Alteration of the FHIT gene was investigated in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl) amine (BHP) in male Wistar rats. Animals at 6 weeks of age were given 2000 p.p.m. of BHP in drinking water for 12 weeks, then maintained without further treatment until killed at the end of week 25. A total of 25 lung adenocarcinomas were obtained and total RNAs were extracted from each for assessment of aberrant transcription of the FHIT gene by reverse transcription (RT)-polymerase chain reaction (PCR) analysis. Aberrant transcripts were detected in 15 adenocarcinomas (60%) as absence in the regions of nucleotides (nt) -9 to 279, -98 to 279, -98 to 348 or -98 to 447. Genomic DNAs were also extracted from all 25 adenocarcinomas and exons 5-9 were examined for mutations, using PCR-single strand conformation polymorphism (SSCP) analysis and sequencing. A mutation was detected in only one adenocarcinoma (4%), an ACC to ATC (Thr to IIe) transition at codon 76. Southern blot analysis of eight tumors did not show any evidence of gross rearrangement or deletion of the FHIT gene. Western blot analysis revealed reduced expression of Fhit protein in six out of 10 adenocarcinomas (60%). These results suggest that alteration of the FHIT gene may be involved in the development of lung adenocarcinomas induced by BHP in rats.

Overexpression of candidate tumor suppressor gene FUS1 isolated from the 3p21.3 homozygous deletion region leads to G1 arrest and growth inhibition of lung cancer cells

Recently we identified FUS1 as a candidate tumor suppressor gene (TSG) in the 120 kb 3p21.3 critical region contained in nested lung and breast cancer homozygous deletions. Mutation of FUS1 is infrequent in lung cancers which we have confirmed in 40 other primary lung cancers. In addition, we found no evidence for FUS1 promoter region methylation. Because haploinsufficiency or low expression of Fus1 may play a role in lung tumorigenesis, we tested the effect of exogenously induced overexpression of Fus1 protein and found 60-80% inhibition of colony formation for non-small cell lung cancer lines NCI-H1299 (showing allele loss for FUS1) and NCI-H322 (containing only a mutated FUS1 allele) in vitro. By contrast, a similar level of expression of a tumor-acquired mutant form of FUS1 protein did not significantly suppress colony formation. Also, induced expression of Fus1 under the control of an Ecdysone regulated promoter decreased colony formation 75%, increased the doubling time twofold, and arrested H1299 cells in G1. In conclusion, our data are consistent with the hypothesis that FUS1 may function as a 3p21.3 TSG, warranting further studies of its function in the pathogenesis of human cancers.

The contribution of endogenous sources of DNA damage to the multiple mutations in cancer

There is increasing evidence that most human cancers contain multiple mutations. By the time a tumor is clinically detectable it may have accumulated tens of thousands of mutations. In normal cells, mutations are rare events occurring at a rate of 10(-10) mutations per nucleotide per cell per generation. We have argued that the mutation rates exhibited by normal human cells are insufficient to account for the large number of mutations found in human cancers, and therefore, that an early event in tumorigenesis is the development of a mutator phenotype. In normal cells, spontaneous and induced DNA damage is balanced by multiple pathways for DNA repair, and most DNA damage is repaired without error. However, in tumor cells this balance may be shifted such that damage overwhelms the repair capacity, resulting in the accumulation of multiple mutations. Our hypothesis is that multiple random mutations occur during carcinogenesis. The sequential mutations that are observed in some human tumors result from selective events required for tumor progression. We consider the possibility that endogenous sources of DNA damage, in particular oxidative DNA damage, may contribute to genomic instability and to a mutator phenotype in some tumors. Endogenous and environmental sources of reactive oxygen species (ROS) are abundant. In tumor cells, antioxidant or DNA repair capacity may be insufficient to compensate for the production of ROS, and these endogenous ROS may be capable of damaging DNA and inducing mutations in critical DNA stability genes. The possibility that oxidative DNA damage could be a significant source of the genomic instability characteristic of human cancers is exciting, because it may be feasible to modulate the extent of oxidative damage through antioxidant therapy. The use of antioxidants to reduce the extent of molecular damage by ROS could delay the progression of cancer.

The CpG island of the novel tumor suppressor gene RASSF1A is intensely methylated in primary small cell lung carcinomas

Loss of heterozygosity at 3p21.3 occurs in more than 90% of small cell lung carcinomas (SCLCs). The Ras association domain family 1 (RASSF1) gene cloned from the lung tumor suppressor locus 3p21.3 consists of two major alternative transcripts, RASSF1A and RASSF1C. Epigenetic inactivation of isoform A (RASSF1A) was observed in 40% of primary non-small cell lung carcinomas and in several tumor cell lines. Transfection of RASSF1A suppressed the growth of lung cancer cells in vitro and in nude mice. Here we have analysed the methylation status of the CpG island promoters of RASSF1A and RASSF1C in primary SCLCs. In 22 of 28 SCLCs (=79%) the promoter of RASSF1A was highly methylated at all CpG sites analysed. None of the SCLCs showed evidence for methylation of the CpG island of RASSF1C. The results suggest that hypermethylation of the CpG island promoter of the RASSF1A gene is associated with SCLC pathogenesis.

Quantitative fluorescence in situ hybridization in lung cancer as a diagnostic marker

The diagnosis of lung cancer is quite often hampered by the existence of various cell types within samples such as biopsies or pleural effusions. We have established a new marker for image cytometry of interphase tumor cells of the lung by using the most recurrent and early cytogenetic event in lung cancer, the loss of the short arm of chromosome 3. The method is based on the detection of the imbalance between the long and the short arms of chromosome 3 by performing two-color fluorescence in situ hybridization on both arms. Fourteen tumors were analyzed after short-term culture and compared with the corresponding cytogenetic data obtained from metaphase analysis. Results on interphase nuclei and control experiments on metaphases were the same, with imbalance ratios ranging from 1.0 to 2.0 (mean value 1.6, median 1.5). To assess the clinical significance of this approach, three pleural effusions were analyzed. Data showed that normal cells within the sample could have been distinguished from the tumor cells based on different imbalance values between the long and the short arms. Thus, our method allows refined detection of lung tumor cells within samples containing heterogeneous cell populations.

Donor origin of neuroendocrine carcinoma in 2 transplant patients determined by molecular cytogenetics

Organ transplant recipients have an increased tumor incidence owing to their immunocompromised state. The origin of such tumors, whether donor or recipient, will have a clinical impact on decision-making concerning immunosuppressive therapy, retransplantation, and for recipients of other organs from the same donors. We report molecular cytogenetic determination of donor origin in 2 cases of small-cell neuroendocrine carcinoma developing in sex-mismatched transplant recipients (kidney and liver). Fluorescence in situ hybridization (FISH) analysis was performed on liver core needle biopsy material from the liver transplant patient and on liver fine needle aspiration cytopreparations from the kidney transplant patient. The results for the liver transplant patient were confirmed with microsatellite allelic analysis and with comparative genomic hybridization. In both cases, FISH showed the presence of only X chromosomes within the tumor cells, indicating the donor origin of the neoplasms. FISH is an excellent method to determine neoplastic origin in sex-mismatched transplant patients. HUM PATHOL 31:1425-1429.

Molecular genetic abnormalities in the pathogenesis of human lung cancer

In the past few years our knowledge of the molecular pathogenesis of lung cancer has significantly increased. There are several molecular mechanisms involved in the multistage carcinogenesis through which respiratory epithelial cells become preneoplastic and then invasive cancer. In this review we summarize some of these changes including, genomic alterations such as loss of heterozygosity and microsatellite alterations, autocrine-paracrine loops, alterations in oncogenes and tumor suppressor genes, tumor angiogenesis, aberrant promoter methylation and inherited predisposition to lung cancer. Translation of these findings to the clinic is also discussed.

Characterization of chromosomal aberrations in lung cancer cell lines by cross-species color banding

Using cross-species color banding (RxFISH) and chromosome painting techniques, chromosomal aberrations were investigated in six lung cancer cell lines (NCI-H524, H865, H522, H1373, H358, A549). Each cell line had a variable number of numerical and structural cytogenetic aberrations. While NCI-H524, -H865, and -H522 had near diploidy, NCI-H358, -H1373, and A549 had near triploidy. The origins of the marker chromosomes were further identified by RxFISH and chromosome painting: Nonrandom chromosomal rearrangements were seen on 1p, 3q, 5p10-p15, 6q13-q21, 7q22-q31, 9p32, 15q22-qter, 17p, 17q21-q25, and 21. These abnormal cytogenetic findings indicate that multiple genetic lesions are associated with the development of lung cancer, and thus, these might be possible candidate regions for the abnormal genes involved in lung cancer.

The age of cancer

A striking link exists between advanced age and increased incidence of cancer. Here I review how several of the age-related molecular and physiological changes might act in concert to promote cancer, and in particular epithelial carcinogenesis. Experimental data indicate that the aged, cancer-prone phenotype might represent the combined pathogenetic effects of mutation load, epigenetic regulation, telomere dysfunction and altered stromal milieu. Further verification of the role of these effects should in turn lead to the design of effective therapeutics for the treatment and prevention of cancer in the aged.

Loss-of-heterozygosity analysis of small-cell lung carcinomas using single-nucleotide polymorphism arrays

Human cancers arise by a combination of discrete mutations and chromosomal alterations. Loss of heterozygosity (LOH) of chromosomal regions bearing mutated tumor suppressor genes is a key event in the evolution of epithelial and mesenchymal tumors. Global patterns of LOH can be understood through allelotyping of tumors with polymorphic genetic markers. Simple sequence length polymorphisms (SSLPs, or microsatellites) are reliable genetic markers for studying LOH, but only a modest number of SSLPs are used in LOH studies because the genotyping procedure is rather tedious. Here, we report the use of a highly parallel approach to genotype large numbers of single-nucleotide polymorphisms (SNPs) for LOH, in which samples are genotyped for nearly 1,500 loci by performing 24 polymerase chain reactions (PCR), pooling the resulting amplification products and hybridizing the mixture to a high-density oligonucleotide array. We characterize the results of LOH analyses on human small-cell lung cancer (SCLC) and control DNA samples by hybridization. We show that the patterns of LOH are consistent with those obtained by analysis with both SSLPs and comparative genomic hybridization (CGH), whereas amplifications rarely are detected by the SNP array. The results validate the use of SNP array hybridization for tumor studies.

The expression frequency of common fragile sites and genetic predisposition to colon cancer

The expression frequency of common fragile sites induced by aphidicolin (Apc), bromodeoxyuridine (BrdU), and caffeine was evaluated on prometaphase chromosomes obtained from the peripheral blood lymphocytes of 32 patients with colon cancer, 30 of their clinically healthy family members and 30 age-matched normal controls. The proportion of damaged cells (P < 0.001), the mean number of chromosomal aberrations and the expression frequencies of fragile sites were significantly higher in the patient and relative groups compared to the control group. Our findings show an increased genetic instability in patients with colon cancer and their first-degree relatives. In addition, common fragile sites can be used as a suitable marker for determining genetic predisposition to cancer.

The expression of fragile sites in lymphocytes of patients with rectum cancer and their first-degree relatives

Fragile sites are non-staining gaps and breaks in specific points of chromosomes. These sites also include acentric fragments, triradial figures and several rearrangements. Although this issue has been controversial recently, they may be related to structural chromosomal rearrangement in some neoplasms. In this study, the expression of fragile sites induced by aphidicolin (Apc), 5-bromodeoxyuridine (BrdU) and caffeine was investigated on prometaphase chromosomes obtained from the peripheral blood lymphocytes of 36 patients with rectum cancer, 30 first-degree relatives and 30 normal healthy controls. The results of the structural chromosome aberrations determined in patients and their first-degree relatives were significantly higher than those in control subjects (P<0.001). We determined aphidicolin type common fragile sites (1p36, 1p31, 1p21, 1q21, 1q25, 1q44, 2p24, 2q21, 2q33, 2q37, 3p14, 5q21, 5q33, 13q13, 14q24, 16q23 and 18q21). When the rates of sites such as 1p21, 1q25, 2q33, 3p14, 5q21 and 14q24 in patients and in their first-degree relatives were compared with the control group, the difference was statistically significant. Our results indicated an increased genetic instability in patients with rectum cancer and their first-degree relatives. Therefore, the increase of fragile site expression may be an important marker showing genetic predisposition to rectum cancer.

The human OGG1 gene: structure, functions, and its implication in the process of carcinogenesis

A particularly important stress for all cells is the one produced by reactive oxygen species (ROS) that are formed as byproducts of cell metabolism. Among DNA damages induced by ROS, 8-hydroxyguanine (8-OH-G) is certainly the product that has retained most of the attention in the past few years. The biological relevance of 8-OH-G in DNA has been unveiled by the study of Escherichia coli and Saccharomyces cerevisiae genes involved in the neutralization of the mutagenic effects of 8-OH-G. These genes, fpg and mutY for E. coli and OGG1 for yeast, code for DNA glycosylases. Inactivation of any of those genes leads to a spontaneous mutator phenotype, characterized by the increase in GC to TA transversions. In yeast, the OGG1 gene encodes a DNA glycosylase/AP lyase that excises 8-OH-G from DNA. In human cells, the OGG1 gene is localized on chromosome 3p25 and encodes two forms of hOgg1 protein which result from an alternative splicing of a single messenger RNA. The alpha-hOgg1 protein has a nuclear localization whereas the beta-hOgg1 is targeted to the mitochondrion. Biochemical studies on the alpha-hOgg1 protein show that it is a DNA glycosylase/AP lyase that excises 8-OH-G and Fapy-G from gamma-irradiated DNA. Several approaches have been used to study the biological role of OGG1 in mammalian cells, ranging from its overexpression in cell lines to the generation of homozygous ogg1-/- null mice. Furthermore, to explore a possible role in the prevention of cancer, the cDNA coding for alpha-hOgg1 has been sequenced in human tumors. All these results point to 8-OH-G as an endogenous source of mutations in eukaryotes and to its likely involvement in the process of carcinogenesis. A review of the recent literature on the mammalian Ogg1 proteins, the main repair system involved in the elimination of this mutagenic lesion, is presented.

Isolation and characterization of the novel gene, TU3A, in a commonly deleted region on 3p14.3-->p14.2 in renal cell carcinoma

We previously identified a 700-kb region of common allelic loss on 3p14.3-->p14.2 in renal cell carcinoma (RCC). We further analyzed this region and constructed a sequence ready bacterial artificial chromosome (BAC) contig. This region was totally covered by six overlapping BAC clones and was roughly estimated to be 700 kb. Furthermore, we isolated a gene in this region that we termed TU3A. This gene encodes a protein consisting of 144 amino acids. Homology search did not show any significant similarities with known genes or proteins. Northern analysis with normal tissue identified a 3.0-kb transcript that was expressed ubiquitously. Although our mutation search using 37 primary RCCs as well as five RCC cell lines failed to detect any somatic alterations in the TU3A gene, two of five RCC cell lines had totally lost its expression. Considering the fact that we found no genetic alterations in TU3A, it is possible that some epigenetic alteration may have suppressed its expression.

Recurrent allelic deletions of chromosome arms 15q and 16q in human small cell lung carcinomas

The genetic lesions that lead to the development of small cell lung carcinoma (SCLC) remain incompletely defined. To identify recurrent allelic deletions in specific chromosomal regions that could serve as markers for tumor suppressor gene (TSG) inactivation in SCLC, we performed a comprehensive allelotype analysis of all 39 nonacrocentric autosomal arms. Alterations in 158 polymorphic microsatellite alleles were examined in 24 pairs of human SCLC tumor and normal control DNA samples. A total of 2,107 informative reactions were analyzed. This analysis revealed allelic losses of 100% on chromosome arm 3p, >85% loss within chromosome arms 13q and 17p, and >70% loss within chromosome arms 4q, 5q, 15q, and 16q. The allelic deletions on chromosome arms 15q and 16q have not been defined previously for SCLC and are candidate regions to harbor novel TSGs. Genes Chromosomes Cancer 27:323-331, 2000.

Replication status as a marker for predisposition for lymphoma in patients with chronic hepatitis C with and without cryoglobulinemia

OBJECTIVE

Essential mixed cryoglobulinemia (EMC) type II is associated with hepatitis C virus (HCV) in 90% of the patients with this disorder. A significant subset of these patients is at risk to develop non-Hodgkin lymphoma (NHL). The objective of this study was to examine whether the presence of EMC, a presumably premalignant step of lymphoproliferation, is associated with changes in the replication state of normal structural genes.

MATERIALS AND METHODS

The study group included three subgroups: (1) seven patients with HCV without EMC; (2) eight patients with HCV associated with EMC. 3. Seven patients with follicular lymphoma; and (3) six healthy individuals served as control group. Monocolor fluorescent in situ hybridization (FISH) with probes to p53, RB-1, and 21q22 was applied to leukocytes nuclei for the evaluation of replication timing.

RESULTS

Asynchronous replication (SD) rate was similar in patients with NHL and those with HCV associated with EMC and both are significantly higher when compared to patients with HCV without EMC and to normal controls (p < 0.01) for each comparison. This held true for all studied loci (21q22, RB-1, and p53). Patients infected by HCV (but without EMC) had a significantly higher rate of asynchronous pattern in comparison with healthy controls (p < 0.01).

CONCLUSIONS

Patients with a "premalignant" clinical condition HCV with EMC already demonstrate asynchronous type of replication which is similar to patients who already have an established malignant disease (i.e., NHL). In the future, replication may be used to assess the risk of malignant transformation in patients with "benign" proliferation.

Orphan receptor COUP-TF is required for induction of retinoic acid receptor beta, growth inhibition, and apoptosis by retinoic acid in cancer cells

Retinoic acid receptor beta (RARbeta) plays a critical role in mediating the anticancer effects of retinoids. Expression of RARbeta is highly induced by retinoic acid (RA) through a RA response element (betaRARE) that is activated by heterodimers of RARs and retinoid X receptors (RXRs). However, RARbeta induction is often lost in cancer cells despite expression of RARs and RXRs. In this study, we provide evidence that orphan receptor COUP-TF is required for induction of RARbeta expression, growth inhibition, and apoptosis by RA in cancer cells. Expression of COUP-TF correlates with RARbeta induction in a variety of cancer cell lines. In addition, stable expression of COUP-TF in COUP-TF-negative cancer cells restores induction of RARbeta expression, growth inhibition, and apoptosis by RA, whereas inhibition of COUP-TF by expression of COUP-TF antisense RNA represses the RA effects. In a transient transfection assay, COUP-TF strongly induced transcriptional activity of the RARbeta promoter in a RA- and RARalpha-dependent manner. By mutation analysis, we demonstrate that the effect of COUP-TF requires its binding to a DR-8 element present in the RARbeta promoter. The binding of COUP-TF to the DR-8 element synergistically increases the RA-dependent RARalpha transactivation function by enhancing the interaction of RARalpha with its coactivator CREB binding protein. These results demonstrate that COUP-TF, by serving as an accessory protein for RARalpha to induce RARbeta expression, plays a critical role in regulating the anticancer activities of retinoids.

The putative tumour suppressor Fus-2 is an N-acetyltransferase

Acetyltransferases are essential enzymes for a wide variety of cellular processes and mutations in acetyltransferase genes have been associated with the development of certain cancers. For this reason, we conducted a computerized sequence homology search for novel acetyltransferases. Here, we show that the putative tumour suppressor protein Fus-2 has homology to the catalytic domain of acetyltransferases. We demonstrate that Fus-2 can acetylate the N-terminus of proteins using a ping-pong mechanism and that it has a specificity for substrates. Consistent with other N-acetyltransferases, Fus-2 localizes to the cytoplasm, as shown by GFP-tag experiments. Since the Fus-2 gene maps to the chromosomal region 3p21.3, which contains at least one tumour suppressor gene, the N-acetyltransferase functions of Fus-2 may be relevant to its potential role in cancer.

Comparison of chromosomal imbalances in neuroendocrine and non-small-cell lung carcinomas

Lung carcinomas are represented by non-small-cell lung carcinomas (NSCLC) and neuroendocrine carcinomas (NE) which differ in their clinical presentation and prognosis. We used comparative genomic hybridization (CGH) to characterize and compare the chromosomal pattern of 11 NSCLC and 11 high-grade NE lung carcinomas. Overall, the total number of aberrations was higher in NSCLC than in high-grade NE lung tumors (p < 0.05) and gains predominated over losses in NSCLC (p < 0.0003). Gains common to both lung tumor phenotypes were detected in 1p, 1q, 3q, 5p, 6p, 8q, 12, 17q, 19p, 19q, 20p, 20q, and X, whereas common losses were found in 2q, 3p, 4p, 4q, 5q, 8p, 9p, 10p, 11p, 11q, 13q, and 17p. Major gains on 18q and losses on 2p and 16q were exclusively detected in high-grade NE lung tumors. On the other hand, major gains on 2p and 15q and losses on 21q were found only in NSCLC. Furthermore, gains within 22q11-q12 and 7p12-p15 were associated with NSCLC (p < 0.05). The differences in the pattern and distribution of genetic changes observed in NSCLC as opposed to high-grade NE lung carcinomas suggest the existence of distinct tumorigenic pathways between these two major classes of lung tumors.

A molecular cytogenetic study of chromosome 3 rearrangements in small cell lung cancer: consistent involvement of chromosome band 3q13.2

To more precisely determine the nature of chromosome 3 rearrangements in small cell lung carcinomas (SCLCs), we have applied molecular cytogenetic technologies to a newly characterized SCLC tumor and five SCLC cell lines. Fluorescent in situ hybridization, chromosome microdissection, and, on the previously uncharacterized tumor, spectral karyotyping was utilized to determine chromosome 3 rearrangements. In all cases, our studies were performed on previously G-banded chromosomes in a sequential manner to facilitate a direct comparison. A consistent breakpoint on the long arm of chromosome 3 at band 3q13.2 was identified in all six tumors. This breakpoint was commonly the result of complex chromosomal rearrangements. Loss of the entire short arm of a chromosome 3 was noted in all six tumor cultures. Two of these cell lines had two sublines, one of which contained a 3q13.2 rearrangement and the other of which contained a chromosome rearrangement that resulted in loss of a chromosome 3 short arm. This consistent rearrangement at chromosome band 3q13.2, as demonstrated by molecular cytogenetic methods, may indicate the location of a gene important in the tumorigenesis of SCLC.

Multi-step evolution of lung cancer

In an attempt to improve the poor survival rates for lung cancer, therapeutic strategies require a deeper understanding of the biological events contributing to the formation and progression of the disease. In particular, the importance of studying the different stages of lung cancer including early pre-neoplasia is being recognised and studies examining genetic changes in pre-invasive and invasive lesions are being used to identify key events in tumorigenesis.

Frequent loss of heterozygosity at chromosome 3p14.2-3p21 in human pancreatic islet cell tumours

OBJECTIVE

Pancreatic islet betacell tumours occur either sporadically or as part of inherited neoplastic syndromes, most commonly multiple endocrine neoplasia (MEN) type 1. Recently, a transgenic mouse model has been established in which the expression of the SV40 large T antigen was targeted to betacells by the rat insulin promoter, leading to the development of multiple pancreatic betacell tumours. In the advanced stages of tumour evolution, these tumours exhibited a high prevalence of loss of heterozygosity (LOH) on mouse chromosomes 9 and 16, at regions syntenic with regions 3q, 3p21, 6q12, 15q24 and 22q of the human genome.

DESIGN

Loss of heterozygosity in human islet cell tumours was analysed in a PCR based approach at regions of the human genome syntenic with the mouse loci linked to pancreatic betacell tumours as well as the MEN1 gene on chromosome 11q13. These included 35 microsatellite markers in the human chromosomal regions 3q, 3p21, 6q12, 11q13, 15q24 and 22q.

PATIENTS

21 patients diagnosed with insulinoma were analysed. Histologically, 16 tumours were benign, while 5 were malignant insulinomas.

RESULTS

Thirteen of 21 (62%) tumours were found to have loss of genetic material on chromosome 3. The shortest region of overlap implicated a deletion at 3p14.2-3p21 region, corresponding to the marker D3S1295. We did not detect a substantial frequency of LOH in the other syntenic regions, except for the region of MEN 1 gene on 11q13 found to be deleted in 6 (29%) cases, including 3 of 4 tumours from MEN 1 families. Deletions of 3p14. 2-3p21 were observed in 8 of 15 (53%) benign tumours, and in 5 of 6 (83%) malignant neoplasms.

CONCLUSIONS

These results indicate the high frequency of 3p14.2-3p21 deletions in human pancreatic betacell neoplasms. These finding suggest the presence of a tumour suppressor gene in this region, that may be important in the microevolution of these tumours towards malignancy.

Role of FHIT in human cancer

Through investigation of hemizygous and homozygous deletions in common human cancers, including lung cancer, we have cloned and characterized a gene at chromosome region 3p14.2, FHIT, that is inactivated in epithelial tumors, particularly in tumors resulting from exposure to environmental carcinogens. In some tumors, particularly those associated with environmental carcinogens, alterations in the FHIT gene occur quite early in the development of cancer. In other cancers, Fhit inactivation seems to be a later event, possibly associated with progression to more aggressive neoplasias. Thus, detection of Fhit expression by immunohistochemistry in premalignant and malignant tissues may provide important diagnostic and prognostic information.

Diagnostic relevance of chromosomal in-situ hybridization in Merkel cell carcinoma: targeted interphase cytogenetic tumour analyses

AIMS

To resolve the conflicting diagnoses of five pathologists (which included well-differentiated neuroendocrine carcinoma, malignant carcinoid, undifferentiated small-cell carcinoma, primitive neuroectodermal tumour, metastases of small-cell lung carcinoma (SCLC) and Merkel cell carcinoma (MCC)), and tumour-free lungs after necropsy, we investigated an alarmingly metastasizing MCC in a 32-year-old Caucasian man using chromosomal in-situ hybridization (CISH). Differences in incidence and course in males and females also prompted targeted analyses for chromosomes X and Y. The lesion was also analysed for p53 gene mutations.

METHODS AND RESULTS

Paraffin sections of the thorax, buccal lymph nodes and scalp tumours were stained with haematoxylin and eosin. Immunohistochemistry was performed with antibodies against pancytokeratin, keratin 20, neuron-specific enolase (NSE), chromogranin, neurofilaments and vimentin, among others. Sections (5-6 microm) of the tumours were analysed with alpha-satellite probes for chromosomes 1, 6, 7, 11, 12, 17, 18, X and Y using CrSH; and exons 5-9 of the p53 gene were examined by polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) methods. Although positive for pancytokeratin, keratin 20, chromogranin, NSE, synaptophysin and vimentin, the similarity in antigen profiles expressed by SCLC and MCC prevented a definitive tumour diagnosis. Chromosomal in-situ hybridization, however, revealed trisomies 1 and 11, two frequent aberrations in MCC, and trisomy 18. Moreover, 71% of the tumour cells had two to three copies of X, whereas 98% of the cell nuclei in the hair follicles and normal epidermis (purported Merkel cell origins) displayed one X chromosome. No mutations were detected in the five exons of the p53 gene examined.

CONCLUSIONS

Had CISH been performed earlier, treatment may have been tailored specifically to suit MCC, since MCC and SCLC have different therapeutic strategies. Finally, chromosome X may be of prognostic relevance in MCC, which apparently predominates in females and yet shows poorer prognosis in males, and hence be worthy of further investigation.

SZF1: a novel KRAB-zinc finger gene expressed in CD34+ stem/progenitor cells

The identification and study of genes expressed in hematopoietic stem/progenitor cells should further our understanding of hematopoiesis. Transcription factors in particular are likely to play important roles in maintaining the set of genes that define the stem/progenitor cell. We report here the identification of a putative KRAB-zinc finger gene (SZF1) from a cDNA library prepared from human bone marrow CD34+ cells. Characterization of SZF1 implicates its role in hematopoiesis. The predicted protein contains a highly conserved KRAB domain at the NH2 terminus and four zinc fingers of the C2H2 type at the COOH terminus. Two alternatively spliced products of SZF1 were isolated, which predict proteins of 421 (SZF1-1) and 361 (SZF1-2) amino acids, differing from each other only at the carboxy terminus. The two transcripts of SZF1 have different expression patterns. SZF1-2 is ubiquitously expressed, as indicated by Northern blot, RNase protection, and reverse transcriptase polymerase chain reaction. SZF1-1 expression, in contrast, was detected only in CD34+ cells. We recently isolated the promoter region for the stem/progenitor cell expressed FLT3/FLK-2/STK-1 gene and used this region to generate a reporter construct to test the effect of SZF1 expression. Cotransfection of the reporter construct with SZF1 constructs showed that SZF1-2 repressed transcription three- to fourfold, whereas SZF1-1 showed a lower level of repression. The expression pattern of SZF1 transcripts and the transcriptional repression of a CD34+-specific promoter demonstrate a possible role for SZF1 in hematopoietic stem/progenitor cell differentiation.