Loss of heterozygosity at 5q21-22 (adenomatous polyposis coli gene region) in oral squamous cell carcinoma is common and correlated with advanced disease

A Forward Genetic Approach to Mapping a P-Element Second Site Mutation Identifies DCP2 as a Novel Tumor Suppressor in Drosophila melanogaster

The use of transposons to create mutations has been the cornerstone of Drosophila genetics in the past few decades. Second-site mutations caused by transpositions are often devoid of transposons and thereby affect subsequent analyses. In a P-element mutagenesis screen, a second site mutation was identified on chromosome 3, wherein the homozygous mutants exhibit classic hallmarks of tumor suppressor mutants, including brain tumor and lethality; hence the mutant line was initially named as lethal (3) tumorous brain [l(3)tb]. Classical genetic approaches relying on meiotic recombination and subsequent complementation with chromosomal deletions and gene mutations mapped the mutation to CG6169, the mRNA decapping protein 2 (DCP2), on the left arm of the third chromosome (3L). Thus the mutation was renamed as DCP2l(3)tb Fine mapping of the mutation further identified the presence of a Gypsy-LTR like sequence in the 5'UTR coding region of DCP2, along with the expansion of the adjacent upstream intergenic AT-rich sequence. The mutant phenotypes are rescued by the introduction of a functional copy of DCP2 in the mutant background, thereby establishing the causal role of the mutation and providing a genetic validation of the allelism. With the increasing repertoire of genes being associated with tumor biology, this is the first instance of mRNA decapping protein being implicated in Drosophila tumorigenesis. Our findings, therefore, imply a plausible role for the mRNA degradation pathway in tumorigenesis and identify DCP2 as a potential candidate for future explorations of cell cycle regulatory mechanisms.

Genetic gains and losses in oral squamous cell carcinoma: impact on clinical management

PURPOSE

The identification of genetic markers associated with oral cancer is considered essential to improve the diagnosis, prognosis, early tumor and relapse detection and, ultimately, to delineate individualized therapeutic approaches. Here, we aimed at identifying such markers.

METHODS

Multiplex Ligation-dependent Probe Amplification (MLPA) analyses encompassing 133 cancer-related genes were performed on a panel of primary oral tumor samples and its corresponding resection margins (macroscopically tumor-free tissue) allowing, in both types of tissue, the detection of a wide arrange of copy number imbalances on various human chromosomes.

RESULTS

We found that in tumor tissue, from the 133 cancer-related genes included in this study, those that most frequently exhibited copy number gains were located on chromosomal arms 3q, 6p, 8q, 11q, 16p, 16q, 17p, 17q and 19q, whereas those most frequently exhibiting copy number losses were located on chromosomal arms 2q, 3p, 4q, 5q, 8p, 9p, 11q and 18q. Several imbalances were highlighted, i.e., losses of ERBB4, CTNNB1, NFKB1, IL2, IL12B, TUSC3, CDKN2A, CASP1, and gains of MME, BCL6, VEGF, PTK2, PTP4A3, RNF139, CCND1, FGF3, CTTN, MVP, CDH1, BRCA1, CDKN2D, BAX, as well as exon 4 of TP53. Comparisons between tumor and matched macroscopically tumor-free tissues allowed us to build a logistic regression model to predict the tissue type (benign versus malignant). In this model, the TUSC3 gene showed statistical significance, indicating that loss of this gene may serve as a good indicator of malignancy.

CONCLUSIONS

Our results point towards relevance of the above mentioned cancer-related genes as putative genetic markers for oral cancer. For practical clinical purposes, these genetic markers should be validated in additional studies.

Gene expression in uninvolved oral mucosa of OSCC patients facilitates identification of markers predictive of OSCC outcomes

Oral and oropharyngeal squamous cell carcinomas (OSCC) are among the most common cancers worldwide, with approximately 60% 5-yr survival rate. To identify potential markers for disease progression, we used Affymetrix U133 plus 2.0 arrays to examine the gene expression profiles of 167 primary tumor samples from OSCC patients, 58 uninvolved oral mucosae from OSCC patients and 45 normal oral mucosae from patients without oral cancer, all enrolled at one of the three University of Washington-affiliated medical centers between 2003 to 2008. We found 2,596 probe sets differentially expressed between 167 tumor samples and 45 normal samples. Among 2,596 probe sets, 71 were significantly and consistently up- or down-regulated in the comparison between normal samples and uninvolved oral samples and between uninvolved oral samples and tumor samples. Cox regression analyses showed that 20 of the 71 probe sets were significantly associated with progression-free survival. The risk score for each patient was calculated from coefficients of a Cox model incorporating these 20 probe sets. The hazard ratio (HR) associated with each unit change in the risk score adjusting for age, gender, tumor stage, and high-risk HPV status was 2.7 (95% CI: 2.0–3.8, p = 8.8E-10). The risk scores in an independent dataset of 74 OSCC patients from the MD Anderson Cancer Center was also significantly associated with progression-free survival independent of age, gender, and tumor stage (HR 1.6, 95% CI: 1.1–2.2, p = 0.008). Gene Set Enrichment Analysis showed that the most prominent biological pathway represented by the 71 probe sets was the Integrin cell surface interactions pathway. In conclusion, we identified 71 probe sets in which dysregulation occurred in both uninvolved oral mucosal and cancer samples. Dysregulation of 20 of the 71 probe sets was associated with progression-free survival and was validated in an independent dataset.

The role of the adenomatous polyposis coli (APC) in oral squamous cell carcinoma

The main cause of death in oral squamous cell carcinomas (OSCC) is metastasis. Intercellular adhesion is mediated by a family of glycoproteins called cadherins and other molecules like catenins and APC (adenomatous polyposis coli) among other. The WNT (wingless-type) gene family is a group of genes, key signaling pathway for embryonic development and oncogenesis. The goal of this paper is to describe the role of the APC gene, and its derivatives, in the carcinogenicity pathway of WNT-1, identifying its role as a tumor suppressor gene in OSCC, while describing the genetic (loss of heterozygosity and mutations) and epigenetic alterations that modulate its expression and evaluate its relationship with the clinicopathological parameters of this type of tumors. As for APC, its activity as a tumor suppressor gene appears muted on a relatively frequent basis in these tumors, either by LOH, mutations or epigenetic control mechanisms, thus resulting in a low degree of agreement between the results of different studies.

Loss of heterozygosity of the APC gene in oral squamous cell carcinoma

The aim of this study was to investigate loss of heterozygosity (LOH) of the APC tumor suppressor gene loci, using restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) in 40 cases of oral squamous cell carcinoma (OSCC). Observed informativity was 72.5% for APC exon 11 and 82.5% for APC exon 15. LOH at APC exon 11 was observed in 2 (6.9%) of 29 informative cases, and no LOH was observed for APC exon 15. Our results suggest that inactivation of the APC gene plays a minor role in the carcinogenesis of OSCC.

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.

Identification of target genes in laryngeal squamous cell carcinoma by high-resolution copy number and gene expression microarray analyses

Molecular mechanisms contributing to initiation and progression of head and neck squamous cell carcinoma are still poorly known. Numerous genetic alterations have been described, but molecular consequences of such alterations in most cases remain unclear. Here, we performed an integrated high-resolution microarray analysis of gene copy number and expression in 20 laryngeal cancer cell lines and primary tumors. Our aim was to identify genetic alterations that play a key role in disease pathogenesis and pinpoint genes whose expression is directly impacted by these events. Integration of DNA level data from array-based comparative genomic hybridization with RNA level information from oligonucleotide microarrays was achieved with custom-developed bioinformatic methods. High-level amplifications had a clear impact on gene expression. Across the genome, overexpression of 739 genes could be attributed to gene amplification events in cell lines, with 325 genes showing the same phenomenon in primary tumors including FADD and PPFIA1 at 11q13. The analysis of gene ontology and pathway distributions further pinpointed genes that may identify potential targets of therapeutic intervention. Our data highlight genes that may be critically important to laryngeal cancer progression and offer potential therapeutic targets.

Unraveling the chromosomal aberrations of head and neck squamous cell carcinoma: a review

Information from the genetic analysis of head and neck cancer has grown enormously in the last 20 years. The advent of high-resolution genetic analysis techniques such as microarray technology will further expand this field in the future. Here we review the data on chromosomal aberrations of head and neck squamous cell carcinoma, focusing on the data generated by comparative genomic hybridization analysis, and suggest how such findings will be taken forward over the next decade. With the search engine PUBMED, the key words "comparative genomic hybridisation," "head and neck," "oral," "hypopharyngeal," "laryngeal," and "squamous cell carcinoma" were used. Publications unavailable in English were excluded.

Cytoplasmic expression of E-cadherin and beta-Catenin correlated with LOH and hypermethylation of the APC gene in oral squamous cell carcinomas

BACKGROUND

Inactivation of the adenomatous polyposis coli (APC) gene results in accumulation and translocation of beta-Catenin, which are important for malignant development. The aim of the present study is to investigate the possible role of APC/beta-Catenin pathway in oral squamous cell carcinomas.

METHODS

The DNA from 34 patients was examined for loss of heterozygosity (LOH) at two markers surrounding the APC, and for hypermethylation of the APC promoter by using methylation-specific polymerase chain reaction (MS-PCR). Fifteen of 34 samples were stained immunohistochemically to show the expression of E-cadherin and beta-Catenin.

RESULTS

We found that cytoplasmic rather than membrane staining of E-cadherin and beta-Catenin was a prominent aberrant tumour-related alteration, and that this expression was mainly present in moderately and poorly differentiated tumours. LOH and hypermethylation of the APC promoter was found in four of 31 and five of 34 carcinoma samples, respectively. Four of five cases presenting LOH/hypermethylation showed cytoplasmic expression of E-cadherin and beta-Catenin by immunohistochemical (IHC) staining.

CONCLUSION

The present results indicate that LOH at the APC locus or hypermethylation of the APC promoter 1a may lead to free beta-Catenin accumulation in cytoplasm of oral carcinoma cells and thereby to oral malignant progression.

Bioinformatics in Otolaryngology

This article reviews the recent literature on microarray analysis, bioinformatics techniques, and genomics in relation to the study of carcinogenesis of head and neck cancers.

Expression of adenomatous polyposis coli (APC) in tumorigenesis of human oral squamous cell carcinoma

The product of the adenomatous polyposis coli (APC) tumor suppressor gene has been observed to regulate the Wnt signaling pathway through beta-catenin. In the present study, we attempted to clarify the relation between APC and the canceration of oral squamous epithelium. Each target tissue of normal squamous epithelium, epithelial dysplasia, and squamous cell carcinoma (SCC) was recovered the oral SCC case by laser microdissection. In recovered cells, we examined the change in expression of APC and beta-catenin gene transcription products, as well as the existence of mutations in APC gene. We analyzed the localization of each protein of APC and beta-catenin by immunohistochemical study. We found a clear change in the expression level of the gene transcription product of APC in canceration of oral squamous epithelium and the differentiation of oral SCC. In addition, there was some change in the localization of the APC protein in canceration. It was not clear, however, whether the APC was mutated. A change was also observed in the expression level of the beta-catenin gene transcription product during the differentiation of oral SCC. Our results suggest that the changes in the expression level and the intracellular localization of APC are related to the canceration of oral squamous epithelium, and in malignant characterization of oral SCC. Mutations of the APC gene might not be indispensable, however, in canceration of oral squamous epithelium.

Loss of heterozygosity at APC and MCC genes of oral cancer and leukoplakia tissues from Indian tobacco chewers

BACKGROUND

Loss of heterozygosity (LOH) at tumor suppressor genes, such as adenomatous polyposis coli (APC) and mutated in colon cancer (MCC) genes, is one of the early events in carcinogenesis of oral tissue in Caucasian and Chinese patients. We wanted to check whether it is also true in Indian oral pre-cancer and cancer patients.

METHODS

Loss of heterozygosity at APC and MCC genes was investigated in 57 and 40 unrelated primary oral leukoplakia (a pre-cancerous lesion) and squamous cell carcinomas (SCC), respectively, by polymerase chain reaction.

RESULTS

In these samples, most of the leukoplakia patients had tobacco smoking habit whereas majority of cancer patients had tobacco chewing habit. LOH at APC gene was observed in 4 of 16 (25%) and 1 of 29 (3%) informative tumor and leukoplakia DNAs from tobacco chewers, respectively. LOH at MCC gene was not detected either in tumor or in leukoplakia DNAs.

CONCLUSION

This infrequent LOH at APC gene of pre-cancer and cancer tissues suggests that it may not be an early event in oral carcinogenesis in these patients.

Comparative study of HPV prevalence in Japanese and North-east Chinese oral carcinoma

BACKGROUND

Human papillomavirus (HPV) plays a role in the development of oral carcinoma. However, the reported prevalence of HPV in oral carcinoma has varied widely.

METHODS

The prevalence of HPV 16, 18 and 33 was investigated in Japanese and North-east Chinese oral squamous cell carcinomas (OSCCs) with polymerase chain reaction (PCR). The expression of p53 protein was examined immunohistochemically.

RESULTS

HPV 16 and 18 were detected in 7 (23.3%) and 10 (33.3%) of 30 Japanese and 11 (36.7%) and 5 (16.7%) of 30 Chinese samples, respectively. HPV 16 and 18 coinfection was detected in 3/30 Japanese and 2/30 Chinese samples. HPV 33 was not detected. There was no significant correlation between HPV 16 and 18 and the sites, gender, age and histological grade. The prevalence of both HPV 16 and 18 was similar and higher in the Japanese and North-east Chinese samples (46.7% each). HPV 16 or/and 18 infection or/and p53 overexpression were in 22 (73.3%) of 30 Japanese samples and 24 (80.0%) of 30 North-east Chinese samples, respectively.

CONCLUSIONS

HPV 16/18 infection or/and p53 overexpression may play an important role in developing some OSCCs. and the presence of HPV sequences and mutant p53 are not necessarily mutually exclusive.

Oral cancer: reviewing the present understanding of its molecular mechanism and exploring the future directions for its effective management

The present review aims to analyze the information available regarding the molecular mechanisms of Oral Carcinogenesis and explore the future directions where the field of Cancer Biology is venturing. Oncologists have excellently followed the proverb "Necessity is the mother of Invention". The desire to be more precise and comprehensive in their studies has led to the invention of some of the most innovative techniques like laser capture microdissection, comparative genomic hybridization, microarrays, and protein chips etc. Various Biotech companies and Cancer Institutes are on a hunt for anti-cancer drugs and molecular markers for cancers. These revolutionary approaches and the new breed of Oncologists have made the field very exciting and have generated the hope that finally the war against cancer would be won. In the end it is urged that the lead taken in other cancers like colon, breast, leukemia will be emulated in oral cancer. This is expected to provide a molecular blueprint for HNSCC, thus helping to identify suitable markers for the early detection of pre-neoplastic lesions, as well as novel targets for its pharmacological intervention.

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.

Genetic susceptibility to oral cancer and the expression of common fragile sites. a study of 100 patients

The expression of bleomycin-induced fragile sites (FS) in the blood lymphocytes of 150 individuals (100 oral cancer patients and 50 age and sex matched controls) is described. FS expression frequencies in oral cancer patients were significantly higher when compared with controls. FS expression was site specific in oral cancer patients. Chromosome 5 was the most affected, with four of its FS expressing in high frequencies. Enhanced expression of FS at the centromeric region was observed in the patient group. This study emphasizes the role of FS in the genetic susceptibility to oral cancer.

Mutations of the adenomatous polyposis coli gene in areca quid and tobacco-associated oral squamous cell carcinomas in Taiwan

BACKGROUND

Adenomatous polyposis coli (APC) gene mutations have been demonstrated not only in colorectal tumors but also in a variety of human cancers.

METHODS

To elucidate the possible roles of APC gene mutations in oral squamous cell carcinomas (OSCCs), we examined 40 untreated human primary OSCCs using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing assays.

RESULTS

By screening nearly one-half of the coding region (codons 279-1673, including the MCR) of the APC gene, five missense mutations and a 1-base pair deletion were detected in five (12.5%) tumors, resulting in five amino-acid substitutions or a truncation of the APC protein. All patients with APC mutations were both areca quid chewers and tobacco smokers (P = 0.049).

CONCLUSIONS

These results suggest that APC mutations may also contribute to the carcinogenesis of at least some OSCCs in Taiwan, especially for the users of areca quid and tobacco.

Comparative genomic hybridization of esophageal squamous cell carcinoma: correlations between chromosomal aberrations and disease progression/prognosis

BACKGROUND

Esophageal carcinoma is a major cause of cancer-related deaths among males in Taiwan. However, to date, the genetic alterations that accompany this lethal disease are not understood.

METHODS

Chromosomal aberrations of 46 samples of esophageal squamous cell carcinoma (EC-SCC) were analyzed by comparative genomic hybridization (CGH), and their correlations with pathologic staging and prognosis were analyzed statistically.

RESULTS

In total, 321 gains and 252 losses were found in 46 tumor samples; thus, the average gains and losses per patient were 6.98 and 5.47, respectively. Frequent gain abnormalities were found on chromosome arms 1q, 2q, 3q, 5p, 7p, 7q, 8q, 11q, 12p, 12q, 14q, 17q, 20q, and Xq. Frequent deletions were found on chromosome arms 1p, 3p, 4p, 5q, 8p, 9p, 9q, 11q, 13q, 16p, 17p, 18q, 19p, and 19q. It was found that deletions of 4p and 13q12-q14 and gain of 5p were significantly correlated with pathologic staging. Losses of 8p22-pter and 9p also were found more frequently in patients with advanced disease. Gain of 8q24-qter was seen more frequently in patients with Grade 3 tumors. A univariate analysis found that pathologic staging; gains of 5p and 7q; and deletions of 4p, 9p, and 11q were significant prognostic factors. However, pathologic staging became the only significant factor in a multivariate analysis.

CONCLUSIONS

CGH not only revealed novel chromosomal aberrations in EC-SCC, but also found possible genotypic changes associated with disease progression. Despite all of the possible associations of chromosomal aberrations with disease progression, the most important prognostic factor for patients with EC-SCC was pathologic staging.

A novel nuclear protein, 5qNCA (LOC51780) is a candidate for the myeloid leukemia tumor suppressor gene on chromosome 5 band q31

Interstitial deletion or loss of chromosome 5, del(5q) or -5, is a frequent finding in myeloid leukemias and myelodysplasias, suggesting the presence of a tumor suppressor gene within the deleted region. In our search for this gene, we identified a candidate, 5qNCA (LOC51780), which lies within a consistently-deleted segment of 5q31. 5qNCA expresses a 7.2-kb transcript with a 5286-bp open reading frame which is present at high levels in heart, skeletal muscle, kidney, placenta, and liver as well as CD34+ cells and AML cell lines. 5qNCA encodes a 191-kD nuclear protein which contains a highly-conserved C-terminus containing a zinc finger with the unique spacing Cys-X2-Cys-X7-His-X2-Cys-X2-Cys-X4-Cys-X2-Cys and a jmjC domain, which is often found in proteins that regulate chromatin remodeling. Expression of 5qNCA in a del(5q) cell line results in suppression of clonogenic growth. Preliminary sequence results in AML and MDS samples and cell lines has revealed a possible mutation in the KG-1 cell line resulting in a THR to ALA substitution that has not been found in over 100 normal alleles to date. We propose 5qNCA is a good candidate for the del(5q) tumor suppressor gene based on its predicted function and growth suppressive activities, and suggest that further mutational and functional study of this interesting gene is warranted.

Loss of heterozygosity and HIV infection in patients with anal squamous-cell carcinoma

PURPOSE

This study was designed to determine whether loss of heterozygosity and/or microsatellite instability correlate with HIV infection and tumor recurrence after chemoradiation therapy in patients with squamous-cell carcinoma of the anus.

BACKGROUND

The molecular mechanisms leading to the progression of HIV-related squamous-cell carcinoma of the anus are poorly understood. In particular, genetic alterations responsible for resistance to chemoradiation have important clinical and functional implications.

METHODS

In a case-control study, we analyzed normal and tumor DNA samples of four patients with squamous-cell carcinoma of the anus who were successfully treated with chemoradiotherapy and four patients with radio-resistant squamous-cell carcinoma of the anus who required abdominoperineal resection for local recurrence. To determine the presence of microsatellite instability, we used the reference panel of five pairs of microsatellite primers recommended for colorectal cancer specimens. These include the microsatellite markers BAT25, BAT26, D5S346 (APC), D2S123 (hMSH2), and D17S250 (P53). In addition, we used microsatellite markers for loss of heterozygosity analyses that were tightly linked to tumor suppressor genes. These included D3S1611 (hMLH1), D17S513 (P53), D18S46 and 18qTA (DCC/SMAD4), D5S107 (APC), and CA5 (hMSH2).

RESULTS

There were two HIV-positive and two HIV-negative patients in each group. Three HIV-positive patients (one in the chemoradiotherapy group and two in the nonchemoradiotherapy group) demonstrated loss of heterozygosity. In the chemoradiotherapy group, one HIV-positive patient demonstrated loss of heterozygosity at the hMLH1 locus. In the nonchemoradiotherapy group, two HIV-positive patients exhibited a total of four instances of loss of heterozygosity. One tumor had loss of heterozygosity at hMSH2 and DCC/SMAD4; another tumor demonstrated loss of heterozygosity at hMSH2 and APC. Microsatellite instability-low was found in two HIV-positive patients. No instances of loss of heterozygosity and microsatellite instability were detected in HIV-negative patients.

CONCLUSION

Loss of heterozygosity and microsatellite instability, which reflect inactivation of tumor-suppressor genes and genomic instability, occur with increased frequency in HIV-associated squamous-cell carcinoma. These data demonstrate for the first time evidence of loss of heterozygosity at the APC and DCC/SMAD4 gene loci in anal carcinoma. Although the findings presented here need to be expanded in a larger study, the recurrent loss of heterozygosity at D2S123, which was demonstrated in HIV-positive patients with radio-resistant squamous-cell carcinoma of the anus, is notable.

Detection of HPV in Japanese and Chinese oral carcinomas by in situ PCR

Human papillomavirus (HPV) is established as the cause of almost 100% of cervical carcinomas. However, the association of HPV with oral squamous cell carcinomas (SCCs) is less well understood. We examined the prevalence of HPV in oral SCCs in samples of Japanese and Chinese populations. Using in situ polymerase chain reaction (PCR) analysis (MY09 and MY11 consensus primers), HPV was detected in the nucleus of epithelia and tumor cells in oral lesions. Analysis revealed the specific presence of HPV DNA in all cases of SCC in our Japanese (10/10) and Chinese (10/10) population samples. These results suggest that HPV infection could be one of several risk factors contributing to oral SCC in Japanese and Chinese.

A review of inherited cancer syndromes and their relevance to oral squamous cell carcinoma

This paper examines the genetic defects associated with inherited cancer syndromes and their relevance to oral cancer. Tumour suppressor genes are now thought of as either gatekeepers or caretakers according to whether they control cell growth directly by inhibiting cell proliferation and/or promoting cell death (gatekeepers) or whether they maintain the integrity of the genome by DNA repair mechanisms (caretakers). In disorders such as xeroderma pigmentosum, ataxia telangiectasia, Bloom syndrome and Fanconi's anaemia, where there are defective caretaker genes, there is an increased incidence of second primary malignancies, including oral cancer. By contrast, with the exception of Li Fraumeni syndrome, abnormalities of gatekeeper genes do not predispose to oral cancer. Not only do Li Fraumeni patients develop second primary malignancies, but defects of the p53 pathway (p53 mutation, MDM2 over-expression, CDKN2A deletion) appear to be a ubiquitous feature of sporadic oral cancer as it occurs in the West. The findings suggest that genetic instability is of fundamental importance in the pathogenesis of oral cancer.

Genome-wide screening for radiation response factors in head and neck cancer

INTRODUCTION

Radiation therapy is an integral part of the treatment of head and neck cancer. Factors predicting radiation response are ill defined. The aim of this study was to identify genetic aberrations associated with radiation response in cell lines derived from head and neck squamous cell carcinomas (HNSCC) using comparative genomic hybridization (CGH) for genome-wide screening.

METHODS

Five cell lines derived from HNSCC were subjected to a single course of radiation (400 cGy) in parallel with a similarly handled, untreated control. Cellular response to radiation was determined on posttreatment days 1, 2, 3, 4, and 5 using a cell viability assay (MTT assay). Radiation response was defined as 35% or greater decrease in cell survival relative to control. Tumor doubling time was determined by cell counts performed at day 0 and 1 for each cell line. All experiments were done in quadruplicate. CGH analysis was performed by differentially labeling DNA from tumor and normal tissue with fluorescent agents. The labeled DNAs were simultaneously hybridized to normal metaphase chromosomes. Image analysis for fluorescence intensity along the entire length of each metaphase chromosome allowed generation of a color ratio, which was used to detect copy number changes.

RESULTS

Radioresistance was identified in two of five cell lines. The tumor doubling time was not a predictor of radiation response. CGH identified a complex pattern of aberrations, with gain of 3q common to all cell lines. The number of genetic aberration was higher in radiation-sensitive cell lines than in radiation-resistant ones. No recurrent aberrations were unique to the radiation-resistant cell lines. Recurrent gains at 7p and 17q and losses at 5q, 7q, and 18q were unique to the radiation-sensitive cell lines.

CONCLUSIONS

The number of aberrations identified by CGH analysis may be a predictor of radiation response. A large study of primary tumors is warranted to confirm this association and identify specific genetic aberrations associated with radiation response.

Distinct pattern of expression of differentiation and growth-related genes in squamous cell carcinomas of the head and neck revealed by the use of laser capture microdissection and cDNA arrays

Although risk factors for squamous cell carcinomas of the head and neck (HNSCC) are well recognized, very little is known about the molecular mechanisms responsible for this malignancy. Furthermore, the ability to investigate gene expression profiles at different stages of tumor progression is usually limited by the remarkable heterogeneity of these neoplastic lesions. Here, we show the successful use of laser capture microdissection (LCM) to procure specific cell populations. The 5000 cells from representative sets of HNSCC and their matching normal tissues are sufficient to extract RNA of high integrity for the synthesis of labeled amplified cDNA probes which can then be hybridized to these membranes arrayed with known human cancer-related cDNAs. Furthermore, when compared to normal tissues, we demonstrate a consistent decrease in expression of differentiation markers such as cytokeratins, and an increase in the expression of a number of signal transducing and cell cycle regulatory molecules, as well as growth and angiogenic factors and tissue degrading proteases. Unexpectedly, we also found that most HNSCC overexpress members of the wnt and notch growth and differentiation regulatory system, thus suggesting that the wnt and notch pathways may contribute in squamous cell carcinogenesis. This experimental approach may facilitate the identification candidate markers for the early detection of preneoplastic lesions, as well as novel targets for pharmacological intervention in this disease.

Loss of heterozygosity of adenomatous polyposis coli gene in cutaneous tumors as determined by using polymerase chain reaction and paraffin section preparations

It has been suggested that an alteration in the adenomatous polyposis coli (APC) gene, which is a tumor suppressor gene, is one of the earlier events in carcinogenesis of some adenocarcinomas. We undertook this study to determine the prevalence of loss of heterozygosity (LOH) of the APC gene in several kinds of cutaneous tumors. Fifty-seven unrelated Japanese patients were examined for analysis of the APC gene. The 57 cases consisted of extramammary Paget's disease, squamous cell carcinoma (SCC), eccrine poroma and porocarcinoma, metastatic tumor of rectal adenocarcinoma and malignant melanoma. DNA was extracted from the tumor and normal portions dissected from the formalin-fixed paraffin-embedding sections and amplified with the use of the PCR. The amplified DNA was examined for LOH in the APC gene. Seven samples of 32 heterozygous persons of APC gene (three out of seven eccrine poromas, two eccrine porocarcinomas and two metastatic tumors of rectal adenocarcinoma) showed for LOH in the APC gene. None of the heterozygous samples from the extramammary Paget's disease (11), SCC (five) and melanoma (five) showed LOH. These results suggest that tumor or tumor suppressor genes, other than the APC gene, may be responsible for extramammary Paget's disease and SCC and that LOH involving APC may have some relevance to the formation and progression of eccrine tumors as in rectal tumors.

Gains of 8q23-qter and 20q and loss of 11q22-qter in esophageal squamous cell carcinoma associated with lymph node metastasis

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is associated with poor prognosis and lymph node metastasis is one of the critical prognostic factors. Although it is important to elucidate the genetic aberrations underlying its lymph node metastasis, to the authors' knowledge little is known regarding alterations in the primary ESCC that are linked with ESCC metastasis to the lymph nodes.

METHODS

To elucidate genetic aberrations involved in the lymph node metastasis of ESCC, comparative genomic hybridization analysis was applied to 36 ESCC specimens, from 12 cases with no lymph node metastasis and 24 cases with lymph node metastasis.

RESULTS

Copy number gains frequently were detected at 3q (75%), 8q23-qter (50%), 11q13 (44%), 5p14-pter (25%), 20q (25%), 7q (22%), 2p (19%), 12p (17%), and 20p (17%) and losses were detected at 18q (58%), 3p (50%), 9p (44%), 5q14-23 (39%), 4q (33%), 13q (22%), and 11q22-qter (19%). DNA amplifications were detected at four loci: 11q13, 2q12, 7q21, and 20q11.2 It is interesting to note that the gains of 8q23-qter (P < 0.0005) and 20q (P < 0.02) and loss of 11q22-qter (P < 0.05) were observed in tumors metastatic to the lymph nodes. The gains of 3q and 11q13 and losses of 18q, 3p, 9p, 5q14-23, and 4q were detected in both early and advanced stage ESCCs.

CONCLUSIONS

These observations suggest that gains of 8q23-qter and 20q and loss of 11q22-qter allow the prediction of lymph node metastasis, and that gains of 3q and 11q13 and losses of 18q, 3p, 9p, 5q14-23, and 4q are associated with the development of ESCC.

Loss of heterozygosity in human skin

Loss of heterozygosity (LOH) is a genetic mechanism by which a heterozygous somatic cell becomes either homozygous or hemizygous because the corresponding wild-type allele is lost. LOH has today been recognized as a major cause of malignant growth. This article gives a comprehensive review of skin disorders in which an origin from LOH has been either documented at the molecular level or postulated on the basis of clinical evidence. LOH has been shown to cause basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, but this mechanism can likewise be taken as an important model to explain the origin of many other skin diseases such as benign hamartomas; type 2 segmental manifestation of autosomal dominant skin disorders; a pronounced segmental manifestation of acquired skin disorders with a polygenic background, superimposed on symmetric lesions of the usual type; paired mutant patches in the form of either allelic or nonallelic twin spotting; and the exceptional familial occurrence of some nevi, reflecting paradominant transmission. completion of this learning activity, readers should be familiar with the mechanism of LOH and its general significance for the biology of plants, animals, and humans. Participants should understand that this mechanism plays a crucial role not only in cutaneous malignant growth but also in the development of benign skin disorders, and they should be able to examine such diseases with a prepared mind to gain a better understanding of their origin.