Localization of a putative tumor suppressor gene in the sub-telomeric region of chromosome 8p

Low BIN3 Expression is an Independent Predictor of Unfavorable Survival in Patients With Primary Colorectal Cancer

This study aimed to explore the mechanisms of bridging integrator-3 dysregulation, its prognostic value, and related signaling pathways in colorectal cancer . Bioinformatic analysis was performed based on the data from The Cancer Genome Atlas–colorectal cancer and Human Protein Atlas. Colorectal cancer cell lines, LoVo and HT29 cells, were used as in vitro cell model to assess the effect of demethylation on bridging integrator-3 expression. Results showed that bridging integrator-3 was downregulated in colorectal cancer tissues compared to normal colon and rectum tissues. Heatmap of bridging integrator-3 messenger RNA expression, exon expression, and DNA methylation indicated a negative correlation between bridging integrator-3 expression and methylation of some CpG sites within the coding sequence. Demethylation treatment significantly increased bridging integrator-3 expression in LoVo and HT29 cells. Low bridging integrator-3 messenger RNA and exon expression were associated with significantly worse overall survival (P = .015 and .013, respectively). Multivariate analysis confirmed that low bridging integrator-3 messenger RNA expression was an independent prognostic factor of unfavorable overall survival (Hazard Ratio (HR) = 1.596, 95% confidence interval: 1.024-2.486; P = .039). High bridging integrator-3 DNA methylation was also associated with significantly worse overall survival (P = .013). Kyoto Encyclopedia of Genes and Genomes analysis indicated that the genes correlated with bridging integrator-3 (absolute Pearson r ≥ 0.3, n = 121) were enriched in sphingolipid signaling pathway, natural killer cell-mediated cytotoxicity, p53 signaling pathway, and apoptosis. Based on these findings, we infer that DNA hypermethylation might be an important mechanism of suppressed bridging integrator-3 expression in colorectal cancer . Its low expression is an independent predictor of unfavorable survival in patients with primary colorectal cancer . Bridging integrator-3 might act as a tumor suppressor via modulating natural killer cell-mediated cytotoxicity, p53 signaling pathway, and apoptosis.

Chromosomal aberrations and prognosis in patients with concomitant chemoradiotherapy for resected head and neck cancer

Although concomitant chemoradiotherapy (CCRT) has recently become a mainstay of a primary treatment modality in advanced head and neck squamous cell carcinoma (HNSCC), some of the patients experience CCRT failure. If we can predict the CCRT outcomes, we can reduce unnecessary CCRT avoiding risk of CCRT‑related complication. We aimed to identify genetic alteration markers related to treatment failure in HNSCC patients who underwent radical surgery and CCRT. Genome‑wide copy number alterations (CNAs) were analyzed in 18 HNSCC patients with (n=9) or without (n=9) recurrence using oligoarray‑comparative genomic hybridization and candidate CNAs were validated by quantitative RT‑PCR. A total of 15 recurrently altered regions (RARs) were identified in the 18 HNSCC cases. Among them, two RARs were significantly associated with CCRT‑failure: copy number gained RARs of 7p11.2 harboring EGFR (P=0.029) and 18p11.32 harboring TYMS gene (P=0.029). Three RARs (7p11.2, 9p21.3 and 18p11.32) were significantly associated with poor disease‑specific survival in univariate analysis, and 7p11.2 was consistently significant in the multivariate analysis (HR 40.68, P=0.003). In conclusion, we defined novel genomic alterations associated with CCRT‑failure: 7p11.2 (EGFR) and 18p11.32 (TYMS). Our results provide useful clues for the elucidation of the molecular pathogenesis of HNSCC and to predict CCRT‑failure.

PinX1: a sought-after major tumor suppressor at human chromosome 8p23

Human chromosome 8p23 is a region that has the most frequent heterozygosity in common human adult epithelial malignancies, but its major tumor suppressor gene(s) remain to be identified. Telomerase is activated in most human cancers and is critical for cancer cell growth. However, little is known about the significance of telomerase activation in chromosome instability and cancer initiation. The gene encoding the potent and highly conserved endogenous telomerase inhibitor PinX1 is located at human chromosome 8p23. However, the role of PinX1 in telomerase regulation and cancer development is not clear. Recent works from our group indicate that PinX1 is critical for maintaining telomere length at the optimal length. Furthermore, PinX1 is reduced in a large subset of human breast cancer tissues and cells. Significantly, PinX1 inhibition activates telomerase, and elongates telomeres, eventually leading to chromosome instability, all of which are abrogated by telomerase knockdown or knockout. Moreover, PinX1 allele loss causes majority of mice to develop a variety of epithelial cancers, which display chromosome instability and recapitulate to 8p23 allele loss in humans. These results indicate that PinX1 is a sought-after major tumor suppressor at human chromosome 8p23 that is essential for regulating telomerase activity and maintaining chromosome stability. These results suggest that inhibition of telomerase using PinX1 especially its telomerase inhibitory fragment or other methods might be used to treat cancers that have telomerase activation.

The molecular biology of head and neck cancer

Head and neck squamous cell carcinomas (HNSCCs) are caused by tobacco and alcohol consumption and by infection with high-risk types of human papillomavirus (HPV). Tumours often develop within preneoplastic fields of genetically altered cells. The persistence of these fields after treatment presents a major challenge, because it might lead to local recurrences and second primary tumours that are responsible for a large proportion of deaths. Aberrant signalling pathways have been identified in HNSCCs and inhibition of epidermal growth factor receptor (EGFR) has proved a successful therapeutic strategy. In this Review, we discuss the recent literature on tumour heterogeneity, field cancerization, molecular pathogenesis and the underlying causative cancer genes that can be exploited for novel and personalized treatments of patients with HNSCC.

The molecular biology of head and neck cancer

Head and neck squamous cell carcinomas (HNSCCs) are caused by tobacco and alcohol consumption and by infection with high-risk types of human papillomavirus (HPV). Tumours often develop within preneoplastic fields of genetically altered cells. The persistence of these fields after treatment presents a major challenge, because it might lead to local recurrences and second primary tumours that are responsible for a large proportion of deaths. Aberrant signalling pathways have been identified in HNSCCs and inhibition of epidermal growth factor receptor (EGFR) has proved a successful therapeutic strategy. In this Review, we discuss the recent literature on tumour heterogeneity, field cancerization, molecular pathogenesis and the underlying causative cancer genes that can be exploited for novel and personalized treatments of patients with HNSCC.

Correlation of EGFR mutations with chromosomal alterations and expression of EGFR, ErbB3 and VEGF in tumor samples of lung adenocarcinoma patients

INTRODUCTION

Mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) are frequently detected in lung adenocarcinomas with bronchioloalveolar (BAC) differentiation and have been associated with increased response to small molecule EGFR inhibitors in some clinical studies. However, further molecular characterization of tumor cells carrying EGFR mutations (EGFR-mut) is warranted.

METHODS

By DNA sequencing, 120 patients with lung adenocarcinomas (70 tumors with BAC components) were screened for EGFR mutations within exons 18-21. Performing comparative genomic hybridization (CGH) and immunohistochemistry, chromosomal imbalances and protein expression levels of EGFR, ErbB3 and VEGF (vascular endothelial growth factor) were analyzed, respectively.

RESULTS

EGFR mutations were detected in 20/120 tumors. Tumors with BAC components carried more frequently EGFR mutations compared to adenocarcinomas without BAC histology (17/70=24% vs 3/50=6.0%; p=0.012). In a subsequent matched-pair analysis, CGH-analysis demonstrated similar mean numbers of chromosomal imbalances for EGFR mutated and wild-type tumors (8.6 vs 7.8 gains; 2.4 vs 2.7 losses), respectively. Furthermore, tumors with mutated EGFR demonstrated gains in chromosomes 7p, 16p and 20q and losses in chromosome 8p. Interestingly, EGFR mutated tumors showed higher VEGF expression (p=0.03) while differences in EGFR expression were not statistically significant.

CONCLUSION

EGFR gene mutations are frequently seen in lung adenocarcinomas with BAC differentiation and can be linked to chromosomal imbalances and increased VEGF expression.

Genome-wide tracking of unmethylated DNA Alu repeats in normal and cancer cells

Methylation of the cytosine is the most frequent epigenetic modification of DNA in mammalian cells. In humans, most of the methylated cytosines are found in CpG-rich sequences within tandem and interspersed repeats that make up to 45% of the human genome, being Alu repeats the most common family. Demethylation of Alu elements occurs in aging and cancer processes and has been associated with gene reactivation and genomic instability. By targeting the unmethylated SmaI site within the Alu sequence as a surrogate marker, we have quantified and identified unmethylated Alu elements on the genomic scale. Normal colon epithelial cells contain in average 25 486 ± 10 157 unmethylated Alu's per haploid genome, while in tumor cells this figure is 41 995 ± 17 187 (P = 0.004). There is an inverse relationship in Alu families with respect to their age and methylation status: the youngest elements exhibit the highest prevalence of the SmaI site (AluY: 42%; AluS: 18%, AluJ: 5%) but the lower rates of unmethylation (AluY: 1.65%; AluS: 3.1%, AluJ: 12%). Data are consistent with a stronger silencing pressure on the youngest repetitive elements, which are closer to genes. Further insights into the functional implications of atypical unmethylation states in Alu elements will surely contribute to decipher genomic organization and gene regulation in complex organisms.

The role of chromosomal aberrations in premalignant and malignant lesions in head and neck squamous cell carcinoma

The objectives of this study are to uncover the molecular mechanisms involved in head and neck squamous cell carcinoma (HNSCC) pathogenesis by studying the chromosomal aberrations in both premalignant and malignant patients and to highlight the genotype of HNSCC in Upper Egypt. From March 2001 to December 2003, prospective study was conducted in 41 patients with precancerous, 79 patients with cancerous laryngeal, oesophageal, nasopharyngeal, nasal, and oral lesions and 50 controls in ENT department, Sohag Faculty of Medicine, Sohag, Egypt. Samples taken by punch biopsy were frozen and stored at -80 degrees C and were subjected to histopathological examination. Metaphase cells were digitally imaged and karyotyped. Karyotypes have been analysed via anatomical image capture and compared with standard human chromosome ideograms. In precancerous lesions, there were 41% 3p loss, 51% 3q gain, 29% 8q gain, and 22% 11q13 gain. In malignant lesions, there were 63% 3p13-p24 loss, 59.5% 5q12-23 loss, 49.5% 8p22-p23 loss, 45.5% 9p21-p24 loss, 40.5% 18q22-q23 loss, 66% 3q gain, 39% 8q gain, and 16% 11q13 gain. In conclusion, early diagnosis of HNSCC can be achieved by DNA extraction from suspicious lesions in high-risk groups (smokers and alcoholics) and examination of chromosomal aberrations of 3p, 3q, 8q, and 11q13. If there are high percent of chromosomal aberrations in these chromosomes, active intervention should be done (chemoprevention and regular follow-up of head and neck examination for very early detection and management).

Advances in the biology of oral cancer

The incidence of oral cancer remains high and is associated with many deaths in both Western and Asian countries. Several risk factors for the development of oral cancer are now well known, including smoking, drinking and consumption of smokeless tobacco products. Genetic predisposition to oral cancer has been found in certain cases but its components are not yet entirely clear. In accordance with the multi-step theory of carcinogenesis, the natural history of oral cancer seems to gradually evolve through transitional precursor lesions from normal epithelium to a full-blown metastatic phenotype. A number of genomic lesions accompany this transformation and a wealth of related results has appeared in recent literature and is being summarized here. Furthermore, several key genes have been implicated, especially well-known tumor suppressors like the cyclin-dependent kinase inhibitors, TP53 and RB1 and oncogenes like the cyclin family, EGFR and ras. Viral infections, particularly with oncogenic HPV subtypes and EBV, can have a tumorigenic effect on oral epithelia and their role is discussed, along with potential therapeutic interventions. A brief explanatory theoretical model of oral carcinogenesis is provided and potential avenues for further research are highlighted.

Mutation analysis of the 8p22 candidate tumor suppressor gene ATIP/MTUS1 in hepatocellular carcinoma

A high frequency of allelic loss affecting chromosome 8p and a minimal region of deletion at p21-22 have been previously reported in hepatocellular carcinoma (HCC), suggesting that at least one tumor suppressor gene is present in this region. In this study, we assessed whether the angiotensin II AT2 receptor interacting protein (ATIP)/mitochondrial tumor suppressor gene (MTUS1), a gene newly identified at position 8p22, may be a candidate tumor suppressor gene mutated in HCC. We searched for alterations in the 17 coding exons of ATIP/MTUS1 by means of denaturating high-performance liquid chromatography and sequencing, in 51 HCC tumors and 58 cell lines for which loss of heterozygosity status was known. Five major nucleotide substitutions were identified, all located in exons used by the ATIP3 transcript which is the only ATIP transcript variant expressed in liver. These nucleotide variations result in amino-acid substitution or deletion of conserved structural motifs (nuclear localisation signal, polyproline motif, leucine zipper) and also affect exonic splicing enhancer motifs and physiological splice sites, suggesting potential deleterious effects on ATIP3 function and/or expression.

Mutation and expression analysis of LZTS1 in ovarian cancer

LZTS1 has been shown to have tumour suppressor activities against prostate and breast cancer and is located within a region of frequent loss of heterozygosity (LOH) at 8p22 in ovarian cancer. We have analysed the expression of LZTS1 in ovarian cancer and found no evidence of loss of expression relative to normal ovarian surface epithelial cells. We have also analysed the coding region of the LZTS1 gene in 87 primary ovarian adenocarcinomas by DHPLC and detected a single silent somatic mutation. These data indicate that LZTS1 is not the target of LOH at 8p22 in ovarian cancer.

Frequent allelic imbalances at 8p and 11q22 in oral and oropharyngeal epithelial dysplastic lesions

Allelic imbalance is characteristic of oral squamous cell carcinoma (SCC) and contributes to the tumorigenesis of this disease. Our previous studies suggest that chromosome regions 8p and 11q22.2 approximately q22.3 are frequent sites of loss of heterozygosity (LOH) in head and neck SCC. Here, we explored the allelic imbalance pattern of these regions in 27 cases of oral epithelial dysplastic lesions. A previously reported frequent LOH (9p21) in head and neck dysplasia was also examined. Laser capture microdissection (LCM) technology was utilized to harvest homogenous cell populations from archived clinical tissues and thus greatly enhancing the sensitivity, accuracy and reliability of genetic assessment. The allelic imbalance (LOH and microsatellite instability) on 8p, 11q22.2 approximately q22.3, and 9p21 were observed at one or more loci in 66.7%, 63.0%, and 63.0% of cases, respectively. Our results demonstrate that 8p, 11q22.2 approximately q22.3, and 9p21 are frequent allelic imbalance regions in oral premalignant dysplasia and suggest the presence of tumor suppressor genes in these regions.

Epigenetic inactivation and aberrant transcription of CSMD1 in squamous cell carcinoma cell lines

Background

The p23.2 region of human chromosome 8 is frequently deleted in several types of epithelial cancer and those deletions appear to be associated with poor prognosis. Cub and Sushi Multiple Domains 1 (CSMD1) was positionally cloned as a candidate for the 8p23 suppressor but point mutations in this gene are rare relative to the frequency of allelic loss. In an effort to identify alternative mechanisms of inactivation, we have characterized CSMD1 expression and epigenetic modifications in head and neck squamous cell carcinoma cell lines.

Results

Only one of the 20 cell lines examined appears to express a structurally normal CSMD1 transcript. The rest express transcripts which either lack internal exons, terminate abnormally or initiate at cryptic promoters. None of these truncated transcripts is predicted to encode a functional CSMD1 protein. Cell lines that express little or no CSMD1 RNA exhibit DNA methylation of a specific region of the CpG island surrounding CSMD1's first exon.

Conclusion

Correlating methylation patterns and expression suggests that it is modification of the genomic DNA preceding the first exon that is associated with gene silencing and that methylation of CpG dinucleotides further 3' does not contribute to inactivation of the gene. Taken together, the cell line data suggest that epigenetic silencing and aberrant splicing rather than point mutations may be contributing to the reduction in CSMD1 expression in squamous cancers. These mechanisms can now serve as a focus for further analysis of primary squamous cancers.

DLC1 is unlikely to be a primary target for deletions on chromosome arm 8p22 in head and neck squamous cell carcinoma

Allelic imbalance on chromosome arm 8p is common in head and neck squamous cell carcinoma (HNSCC). DLC1, a tumour suppressor gene inactivated in liver carcinogenesis and encoding a Rho GTPase activating protein (RhoGAP) maps to one of the deleted regions (8p21.3-22). In order to determine whether inactivation of DLC1 is involved in HNSCC, we have screened tumour cell lines for DLC1 mutations and expression. Pathological mutations were not identified in any of the 17 cell lines tested. Seven polymorphisms were identified; 13 of the 17 of cell lines were homozygous for all seven polymorphisms compared to only 2 of 17 controls suggesting a loss of heterozygosity in a majority of the cell lines. DLC1 expression was observed in all 11 HNSCC cell lines tested, thus excluding the possibility of transcriptional silencing of DLC1 by promoter hypermethylation. Overall, our data suggest that hemizygous deletions of the DLC1 locus are frequent in HNSCCs but this gene is unlikely to be primary target for inactivation on this chromosomal arm.

Deletions of chromosome 8p and loss of sFRP1 expression are progression markers of papillary bladder cancer

Many molecular alterations are known to occur in urothelial carcinoma of the bladder, but their significance for tumor progression is poorly understood. Deletions of chromosome 8p are frequently found in several tumor types and are often associated with progressive disease. In all, 99 bladder tumors were screened for deletions at 8p using loss of heterozygosity (LOH) and multicolor fluorescence in situ hybridization FISH analyses. Allelic loss on chromosome 8p in at least one marker was found in 25/99 (25%) tumors. There was a significant correlation of 8p deletions with invasive tumor growth and a highly significant association with papillary growth pattern in patients with invasive disease. cDNA array analyses revealed that secreted Frizzled-related protein 1 (sFRP1), an antagonist of Frizzled receptors and Wnt pathway activation on chromosome 8p12-11.1, is frequently downregulated in bladder cancer. To investigate sFRP1 as a candidate for a putative progression-related gene on 8p, urothelial cell lines and primary urothelial carcinomas were screened for sFRP1 expression using quantitative real-time PCR, Northern blot, immunofluorescence and immunohistochemistry (IHC). Of the investigated bladder cancers, 38% showed loss of sFRP1 expression by quantitative RT-PCR. Evaluation of the protein expression by IHC using tissue microarrays containing 776 bladder cancers revealed loss or strong reduction of sFRP1 expression in 66% of cases. SFRP1 loss was associated with higher tumor stage and grade and shorter overall survival. In addition, loss of sFRP1 was an independent indicator of poor survival in patients with papillary but not with muscle invasive bladder cancer. There were neither mutations in the coding region of sFRP1 nor homozygous deletions at 8p12-11.21. However, promoter methylation was detected using methylation-specific PCR in 29% of cases. In conclusion, we could show a close correlation of chromosome 8p deletions and progression of papillary bladder tumors. The sFRP1 gene on chromosome 8p12-11.1 could be a candidate gene for the predicted, progression-related tumor suppressor gene in bladder cancer and could contribute to urothelial carcinogenesis.

Genome-wide analyses on loss of heterozygosity in head and neck squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) is a frequent malignancy with a poor survival rate. Identifying the tumor suppressor gene (TSG) loci by genomic studies is an important step to uncover the molecular mechanisms involved in HNSCC pathogenesis. We therefore performed comprehensive analyses on loss of heterozygosity (LOH) using a genome-wide panel of 191 microsatellite markers in 22 HNSCC samples. We found 53 markers with significantly high LOH (>30%) on 21 chromosomal arms; the highest values of those were observed on 3p, 9p, 13q, 15q, and 17p, corresponding to D3S2432 (67%), D9S921-D9S925 (67%) and GATA62F03 (86%), D13S1493 (60%), D15S211 (62%), and D17S1353 (88%), respectively. Fifteen hot spots of LOH were defined in 13 chromosomal arms: 2q22-23, 4p15.2, 4q24-25, 5q31, 8p23, 9p23-24, 9q31.3, 9q34.2, 10q21, 11q21-22.3, 14q11-13, 14q22.3, 17p13, 18q11, and 19q12 as loci reported previously in HNSCCs. Furthermore, we identified five novel hot spots of LOH on three chromosomal arms in HNSCC at 2q33 (D2S1384), 2q37 (D2S125), 8q12-13 (D8S1136), 8q24 (D8S1128), and 15q21 (D15S211). In conclusion, our comprehensive allelotype analyses have unveiled and confirmed a total of 20 possible TSG loci that could be involved in the development of HNSCC. These results provide useful clues for identification of putative TSGs involved in HNSCC by fine mapping of the suspected regions and subsequent analysis for functional genes.

Multicolor-FISH analysis of a natural killer cell line (NK-92)

Relatively little is known about the cytogenetics of natural killer (NK) neoplasms, and the emergence of recurrent structural alterations involving specific chromosomal breakpoints is still in its infancy. This gap has doubtless hampered identification of the oncogene alterations posited to underly NK tumors. We describe in detail the cytogenetic rearrangements present in a cytotoxic NK cell line (NK-92) established from a patient with large granular lymphocyte (LGL) lymphoma. The NK-92 cell line is one of very few cytotoxic NK cell lines described and the first to be used clinically. Cytogenetic analysis was performed independently using two multicolor-fluorescence in situ hybridization (M-FISH) systems, the first M-FISH study of a cell line derived from a NK neoplasm. Several non-random cytogenetic features previously reported in NK cells were, thus, identified, including rearrangements of chromosomes 7 and 17, along with breakpoints at 11q23, 12q12 and 8p22/23. FISH revealed that NK-92 cells carry multiple rearrangements with distinct breakpoints at 8p resembling those previously described in NK lymphoma. Our data strengthen the claim of NK-92 to model NK neoplasms and highlight this cell line as a potential resource for mining relevant oncogenic changes therein.

Chromosomal changes in incidental prostatic carcinomas detected by comparative genomic hybridization

OBJECTIVES

The genetic changes underlying the development and progression of prostate cancer are poorly understood. To identify chromosomal regions in incidental prostatic carcinoma (T1a and T1b) was the primary aim of this study.

MATERIALS AND METHODS

We used comparative genomic hybridization (CGH) to search for DNA sequence copy number changes on a series of 48 T1 prostate cancer diagnosed by transurethral resection (TURP) and by adenomectomy. Incidental prostatic carcinomas have not been studied by CGH previously.

RESULTS

CGH analysis indicated that 14 cases (29.2%) of incidental prostatic carcinoma showed chromosome alterations. The most frequent alterations were chromosomal losses of 8p (10.4%), 13q (6.3%), 5q (4.2%) and 18q (4.2%), and gains of 17p (10.4%), 17q (10.4%), 9q (6.3%) and 7q (4.2%). Minimal overlapping chromosomal regions of loss, indicative for the presence of tumor suppressor genes (TSGs), were mapped to 8p22 and 13q14.1-q21.3, and minimal overlapping regions of gain, indicative for the presence of oncogenes, were found at 9q34.2-qter, 17p12 and 17q24-qter. The statistical analysis displayed a significant association between chromosomal aberration detected by CGH and high Gleason score (P < 0.005) as well as between tumor categories T1a and T1b and chromosomal imbalance (P = 0.041).

CONCLUSIONS

Studies directed at incidental prostatic carcinomas allow discovery of chromosomal changes in small and highly malignant tumors. Our results suggest that loss or gain of DNA in these regions are important in prostate cancer. This is the first study, which documents the spectrum of chromosomal changes in incidental prostatic carcinomas.

Identification of a region of homozygous deletion on 8p22-23.1 in medulloblastoma

To identify critical tumor suppressor loci that are associated with the development of medulloblastoma, we performed a comprehensive genome-wide allelotype analysis in a series of 12 medulloblastomas. Non-random allelic imbalances were identified on chromosomes 7q (58.3%), 8p (66.7%), 16q (58.3%), 17p (58.3%) and 17q (66.7%). Comparative genomic hybridization analysis confirmed that allelic imbalances on 8p, 16q and 17p were due to loss of genetic materials. Finer deletion mapping in an expanded series of 23 medulloblastomas localized the common deletion region on 8p to an interval of 18.14 cM on 8p22-23.2. We then searched within the region of loss on 8p for loci that might contain homozygous deletion using comparative duplex PCR. An overlapping homozygous deletion region was identified in a 1.8 cM interval on 8p22-23.1, between markers D8S520 and D8S1130, in two medulloblastomas. This region of homozygous deletion also encompasses the 1.4 cM minimal deletion region detected on 8p in ductal carcinoma in situ of breast. In conclusion, we reported for the first time a detailed deletion mapping on 8p in medulloblastoma and have identified a region of homozygous deletion on 8p22-23.1 that is likely to contain a critical tumor suppressor gene involved in the development of medulloblastoma.

Loss of a novel tumor suppressor gene locus at chromosome 8p is associated with leukemic mantle cell lymphoma

Patients with mantle cell lymphoma (MCL) may present with either nodal or leukemic disease. The molecular determinants underlying this different biologic behavior are not known. This study compared the pattern of genetic abnormalities in patients with nodal and leukemic phases of MCL using comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) for specific gene loci. Although both leukemic and nodal MCL showed similar genomic patterns of losses (involving 6q, 11q22-q23, 13q14, and 17p13) and gains (affecting 3q and 8q), genomic loss of chromosome 8p occurred more frequently in patients with leukemic disease (79% versus 11%, P <.001). Subsequent CGH analysis confirmed the genomic loss of 8p21-p23 in 6 of 8 MCL cell lines. Interestingly, MYC gene amplification was restricted to cases with 8p deletion. These data indicate the presence of a novel tumor suppressor gene locus on 8p, whose deletion may be associated with leukemic dissemination and poor prognosis in patients with MCL.

Cytogenetic and fluorescence in situ hybridization characterization of chromosome 8 rearrangements in head and neck squamous cell carcinomas

Structural rearrangements of chromosome 8 are frequently encountered in squamous cell carcinomas of the head and neck (HNSCC). These aberrations often affect the centromeric region, resulting in the formation of isochromosome i(8q) and whole arm translocations. Some tumors may display structural rearrangements of 8p23. To characterize further the localization of the breakpoints in such rearrangements, 12 HNSCC known to carry pericentromeric rearrangements of chromosome 8 and 8p23 abnormalities were investigated with fluorescence in situ hybridization (FISH) by the use of 15 YAC clones spanning 8p23 and 8p11 to 8q11. FISH confirmed that all, except one, aberrations cytogenetically interpreted to be i(8q) were true, monocentric i(8q). Similarly, all whole-arm translocations appeared as centric fusions. It could thus be concluded that the essential outcome of these rearrangements is genomic imbalances and not rearrangement of genes in the pericentromeric region. By the use of five YAC clones mapping to 8p23, different breakpoints at the molecular level were disclosed in cases with cytogenetically identical 8p23 rearrangements. An evaluation of the genomic imbalances detected in the present series revealed that overrepresentation of 8q material was present in 11 of the 12 tumors. The most commonly gained segment was 8q22 approximately qter, found in all cases with 8q overrepresentation. Loss of parts of or the entire 8p was seen in 10 tumors. The smallest overlapping deleted region was localized to the subtelomeric region of 8p.

Transcript map of the 8p23 putative tumor suppressor region

Cancers of the head and neck, prostate, liver, and bladder exhibit minimal regions of deletion within chromosomal band 8p23 that either overlap or map very close to one another. We previously refined a minimal region of deletion in squamous cell carcinomas to a 112-kb interval within 8p23. There seems to be only a single gene within this region that is expressed in normal upper aerodigestive tract epithelium. This candidate for the squamous cancer suppressor, CUB and sushi multiple domains-1 (CSMD1), extends into the minimal regions of deletions defined for the other types of cancer with 8p23 deletions. RT-PCR and EST data indicate that CSMD1 is also expressed in those organs,making this gene a candidate for a suppressor of multiple types of cancer. Both the sequence of the gene and the organization of the protein are highly conserved in the mouse.

High density deletion mapping of bladder cancer localizes the putative tumor suppressor gene between loci D8S504 and D8S264 at chromosome 8p23.3

Deletion of chromosome 8p is associated with the progression of bladder cancer. To identify the putative tumor suppressor gene locus we have analyzed 145 bladder cancers with 12 microsatellite markers for allelic changes at the chromosome 8p23.3 region. We mapped the smallest overlapping deletion to approximately 0.7 cM genetic distance between loci D8S504 and D8S264. Allelic changes at this region occurred in 75 (52%) of the 145 tumors. We found a significant correlation between alterations at chromosome 8p23.3 and the tumor grade. The correlation between genetic changes and tumor stage reflected the distribution of tumors of different grades in each pathologic stage.

Homozygous deletions define a region of 8p23.2 containing a putative tumor suppressor gene

Loss of heterozygosity at microsatellite loci in chromosomal band 8p23.2 is a frequent event in squamous cell carcinomas of the head and neck, suggesting that this region contains a putative tumor suppressor. Allelic loss studies on laryngeal and oral/oropharyngeal tumors have restricted the size of this region to approximately 1 cM. A similar pattern of deletions is also observed in prostatic and ovarian adenocarcinomas. As part of an effort to identify this gene by positional cloning, we developed a physical contig consisting of 12 overlapping bacterial artificial chromosome (BAC) clones spanning this interval. We developed sequence-tagged sites from the ends of these BACs and used them, along with seven microsatellite loci, to detect and map homozygous deletions in four head and neck squamous cancer cell lines. Our mapping analysis further restricted the consensus minimal region of deletion to a <191-kb interval.

Multiple regions of deletion on chromosome arm 13q in head-and-neck squamous-cell carcinoma

Several lines of evidence suggest that the progression of head-and-neck squamous-cell carcinoma (HNSCC) involves inactivation of at least one and possibly several tumor-suppressor genes on the long arm of chromosome 13. The fact that neither Rb1 nor BRCA2 appears to be inactivated in the majority of head-and-neck cancers suggests that novel tumor-suppressor genes are involved. We have used microsatellite repeat polymorphisms and PCR to detect several distinct minimal regions of deletion on 13q in supraglottic and oral squamous-cell carcinomas. One region maps to 13q34, the second to 13q14.3 and a potential third region, not reported in previous studies, maps to 13q12.1. Overall, 69% of the 145 tumors examined demonstrated allelic loss at one or more loci on 13q. We investigated whether a novel suppressor candidate mapping to 13q14. 3-q21, leukemia-associated gene 1, might also be involved in the progression of squamous-cell carcinomas. Multiplexed PCR revealed homozygous deletion of leu1 in one oral cavity tumor. This suggests that this gene or one nearby may be the actual target of deletions in this region of the chromosome arm.