p53 inactivation in chewing tobacco-induced oral cancers and leukoplakias from India

The inactivation of p53 tumour suppressor gene vis-á-vis point mutation, overexpression and degradation due to Human Papilloma virus (HPV) 16/18 infection, was examined in chewing tobacco-associated oral cancers and oral leukoplakias from India. The analysis of mutations was assessed by polymerase chain reaction (PCR) with single strand conformation polymorphism (PCR-SSCP) of exons 5-9 on DNA from 83 oral cancer cases, and the mutations confirmed by direct nucleotide sequencing of the PCR products. p53 protein expression was evaluated by immunohistochemical analysis on paraffin-embedded sections of 62 representative oral cancer biopsies and 22 leukoplakias, using p53-specific monoclonal antibody DO-7. The presence of HPV16/18 was detected in the 83 oral cancer cases by PCR analysis using HPV L1 consensus sequences, followed by Southern hybridization with type-specific oligonucleotide probes. Forty-six per cent (38/83) of oral cancer tumours showed p53 alterations, with 17% (14/83) showing point mutations, 37% (23/62) with overexpression and 25% (21/83) with presence of HPV16 wherein the E6 HPV16 protein degrades p53. HPV18 was not detected in any of the samples. Ninety-two per cent concordance was observed between missense point mutations and overexpression of p53 protein. A significant correlation was not observed between p53 alterations in oral cancer and clinico-pathological profile of the patients. Twenty-seven per cent (6/22) of oral leukoplakias showed p53 overexpression. The overall p53 alterations in oral cancer tissues and oral lesions are comparable to data from the oral cancers reported in the Western countries with smoking and alcohol-associated oral cancers, and suggest a critical role for p53 gene in a significant proportion of oral cancers from India. The overexpression of p53 protein in leukoplakias may serve as a valuable biomarker for identifying individuals at high risk of transformation to malignant phenotype.     

Expression of bcl-2 and bax in chewing tobacco-induced oral cancers and oral lesions from India

Deregulation of oncogenes and tumor suppressor genes involved in apoptosis has been associated with tumor development and progression. To investigate the involvement of apoptosis regulating proteins in oral cancer in Indian patients, primarily associated with chewing tobacco habits, immunohistochemical expression of bcl-2 and bax was examined in 63 oral squamous cell carcinomas, and 31 putative premalignant lesions. Our studies revealed overexpression of tumor specific cytoplasmic bcl-2 in 56% and bax in 43% oral cancers. The oral cancers in the Indian patients are preceded by premalignant oral lesions; hence oral lesions were examined for bcl-2 and bax expression. We observed aberrant expression of bcl-2 in 16% oral lesions comprising leukoplakias and SMF and bax in 55% oral lesions. We have already reported, p53 expression in these oral cancers and lesions. It was noteworthy that 30% oral cancers demonstrated a p53+bcl2+ pattern, and 14% samples exhibited p53+bcl2+bax+ pattern. However, none of the oral lesions showed concurrent deregulation of p53 and bcl-2 or all the three genes. Interestingly 45% oral lesions were p53-bax+ as compared to 18% oral cancers; while 39% oral lesions were bcl2-bax+ as compared to 14% oral cancers, indicating overexpression of bax in oral lesions, in the absence of p53 and bcl-2 proteins. Significant correlation was observed between positive nodal status and bcl2+ (p=0.047) and p53+bcl-2+ (p=0.01) in oral cancers. Kaplan Meier survival analysis showed significantly (p=0.059) higher survival in patients with p53- oral tumors than with p53+ tumors. Our studies thus indicate frequent overexpression of apoptosis regulators bcl-2, bax and p53 proteins in oral cancers, and a subset of oral lesions, representing early events in oral car-cinogenesis. The aberrant bcl-2 expression and loss of p53 function observed, may play an important role in the tumorigenesis of oral cancers by allowing escape from apoptosis and enabling additional genetic alterations to accrue.     

Frequent loss of heterozygosity on chromosome 9 in Chinese esophageal squamous cell carcinomas

Multiple and extensive alterations in chromosome 9 were detected in thirty-four esophageal squamous cell carcinoma patients, using seventeen polymorphic markers localized to chromosome 9 to detect the loss of heterozygosity (LOH) by polymerase chain reaction techniques. The LOH rates detected in this study range from 42.9 to 80.0%. Three commonly deleted regions mapping to 9p23-p22, 9q13-q22.3, and 9q34 were observed. D9S1812 LOH at 9q22.1 was significantly associated with well- and moderately-differentiated tumors; LOH at D9S768, mapping to 9q13-21.3, indicated that drinking habits are not a significant risk factor for Chinese esophagus cancer. Interestingly, no case of microsatellite instability was observed.     

Use of complete coverage array comparative genomic hybridization to define copy number alterations on chromosome 3p in oral squamous cell carcinomas

Loss of 3p has been associated with oral cancer progression and is common in many cancers. However, regions of alteration on 3p are poorly defined. We have constructed a high-resolution chromosomal array using a tiling set of 535 human bacterial artificial chromosomes that provides near complete coverage of 3p. Array comparative genomic hybridization analysis of 20 microdissected oral squamous cell carcinomas showed multiple and recurrent segments of copy number changes. These include a deletion containing the FHIT gene; novel segments of copy decrease at 3p22, 3p24, and 3p26; and an unexpected approximately 0.7 Mbp segmental increase at 3p21. These data strongly support the value of using chromosomal array comparative genomic hybridization for detailed profiling of oral squamous cell carcinomas.     

c-Abl expression in oral squamous cell carcinomas

c-Abl is proto-oncogene product. c-Abl has roles in signal transduction, cell cycle regulation, and inhibition of apoptosis. There are many reports about c-Abl function in hematopoietic cells, but few are concerned with solid tumors. In the present study, biopsy specimens from 44 patients with oral squamous cell carcinomas were subjected to immunohistochemistry, and the expression levels of c-Abl were correlated with clinicopathological features. Statistical analyses revealed that c-Abl expression was significantly associated with T-category (p = 0.011), sex (p = 0.014), and differentiation (p = 0.007), but no significant difference was observed with N-category, age, primary tumor region, or the other histological gradings. The low c-Abl expression group included more T4, male, and poorly differentiated cases. There was a trend towards longer tendency survival in the high expression group, but the difference was not significant. We conclude that c-Abl is a good candidate for a tumor-expansion marker.     

Chemoprevention of oral squamous cell carcinomas

Among individuals with a history of head and neck cancer and tobacco abuse the risk of second primary cancers in the upper aerodigestive tract is high. Chemoprevention of oral squamous cell carcinomas is based on two conditions: Premalignant mucosa lesions are treated with chemopreventive agents in order to prevent malignant conversion (primary prevention). In secondary prevention of oral cancer, after curative therapy patients are treated by chemoprevention in order to reduce the rate of second primaries. This paper presents a comprehensive clinical review of oral cancer prevention studies, highlighting the agents mostly used, such as beta-carotene, alpha-tocopherol, ascorbic acid, and retinoids. Although most intervention trials showed good overall response with these substances, high relapse rates and serious side effects, in most cases related to the retinoid compounds were noticed. In addition, in all prospective randomized chemoprevention trials (CARET, ATBC and PHS) no significant evidence of benefit for supplementation with alpha-tocopherol, beta-carotene or retinyl palmitate was reported.     

Arsenic-related DNA copy-number alterations in lung squamous cell carcinomas

Background:

Lung squamous cell carcinomas (SqCCs) occur at higher rates following arsenic exposure. Somatic DNA copy-number alterations (CNAs) are understood to be critical drivers in several tumour types. We have assembled a rare panel of lung tumours from a population with chronic arsenic exposure, including SqCC tumours from patients with no smoking history.

Methods:

Fifty-two lung SqCCs were analysed by whole-genome tiling-set array comparative genomic hybridisation. Twenty-two were derived from arsenic-exposed patients from Northern Chile (10 never smokers and 12 smokers). Thirty additional cases were obtained for comparison from North American smokers without arsenic exposure. Twenty-two blood samples from healthy individuals from Northern Chile were examined to identify germline DNA copy-number variations (CNVs) that could be excluded from analysis.

Results:

We identified multiple CNAs associated with arsenic exposure. These alterations were not attributable to either smoking status or CNVs. DNA losses at chromosomes 1q21.1, 7p22.3, 9q12, and 19q13.31 represented the most recurrent events. An arsenic-associated gain at 19q13.33 contains genes previously identified as oncogene candidates.

Conclusions:

Our results provide a comprehensive approach to molecular characteristics of the arsenic-exposed lung cancer genome and the non-smoking lung SqCC genome. The distinct and recurrent arsenic-related alterations suggest that this group of tumours may be considered as a separate disease subclass.     

Microsatellite and chromosome instability in squamous cell laryngeal carcinoma.

Head-and neck squamous cell carcinoma (HNSCC) represents almost 5% of all malignancies in Europe. The aetiology of HNSCC is complex, with both genetic and mutagenic factors involved. The aim of the present study was to investigate the loss of heterozygosity (LOH), mainly at tumour suppressor loci (using markers D1S2883, D2S123, D3S1611, D5S346, D7S501, D8S254, TP53, NM23), microsatellite instability (BAT25, 26, 40) and (bleomycin test) in patients with squamous cell larynx cancer. In a group of 20 patients LOH was observed mainly at the loci 3p (64.7%), 8q (71.4%), 17q (M1-30.8%, M2-25%, M3-38.5%). Despite chromosomal instability detected by bleomycin no microsatellite instability was observed.     

Concurrent hypermethylation of multiple regulatory genes in chewing tobacco associated oral squamous cell carcinomas and adjacent normal tissues

The methylation pattern in the promoter region of p16, DAPK, MGMT and GSTP1 genes was investigated in oral cancer tissues and tumor associated adjacent tissues, using methylation specific PCR assay. The samples constituted 60 primary oral tumors and corresponding adjacent clinically and histopathologically normal mucosa, and buccal epithelial scrapings from 20 normal healthy individuals without any tobacco habits. The incidence of hypermethylation in oral tumor and adjacent mucosa for p16 gene was 66.7 and 50%, for DAPK was 68.3 and 60%, and MGMT gene was 51.7 and 26.7%, respectively. The overall hypermethylation in the three genes in the primary tumor was 86.7%, and corresponding adjacent normal mucosa tissues 76.7%. Hypermethylation was not observed in the promoter region of GSTP1 gene in either the primary tumors or the corresponding adjacent normal mucosa. Absence of aberrant methylation in the four genes was noted in buccal scrapings from normal healthy individuals with no tobacco habits. Thus, a high frequency of promoter region hypermethylation was observed in p16, DAPK and MGMT genes in oral cancer tissues as well as in corresponding adjacent normal mucosa. Our results indicate that epigenetic alteration of these genes is a frequent event in oral cancer, and is an early event observed in normal oral mucosa of the patients, indicating the critical importance of the epigenetic alteration in chewing tobacco associated oral carcinogenesis.     

Microsatellite alterations in esophageal dysplasia and squamous cell carcinoma from laser capture microdissected endoscopic biopsies

Esophageal squamous cell carcinoma (ESCC), with a 5 year survival below 15%, is one of the most common fatal cancers worldwide. Significant reduction in mortality may be achieved by detecting and treating asymptomatic precursor lesions and curable early cancers. To explore this possibility and look for potential early detection markers, we examined alterations in 16 microsatellite markers in laser capture microdissected (LCM) endoscopic biopsies from the esophagus, including 15 dysplasias and 22 ESCCs, in patients from Shanxi Province, a region in north-central China. We found a significant increase in the total frequency of allelic loss with increasing disease severity. Allelic loss was seen in 2% of the markers in patients with low grade dysplasia (LGD), 15% of the markers in patients with high grade dysplasia (HGD), and 35% of the markers in patients with ESCC. Ten different markers (D3S4513, D5S2501, D8S1106, D9S118, D9S910, D13S1493, D13S894, D13S796, D15S655, and D17S1303) showed allelic loss in one or more of the premalignant lesions tested. The frequency of microsatellite instability (MSI) also increased with histological severity, from 22% in LGD to 33% in HGD and 59% in ESCC. These results indicate that the development of ESCC is associated with genetic instability, that this instability can be detected in endoscopic biopsies of recognized precursor lesions in patients without invasive cancer, and that these markers may be useful as predictive markers in the early detection of ESCC. Finally, we also report methodologic/technical modifications that enhance the use of LCM for screening endoscopic biopsies.     

Histological malignancy grading of oral squamous cell carcinomas

A modification of Jakobsson's criteria that determines the mode of cancer invasion (Yamamoto, 1982) has been reported to be useful in predicting the prognosis in patients with an oral squamous cell carcinoma. In this retrospective study, a five-factorial grading system of the histological malignancy (+ the differentiations, the nuclear polymorphism, the mitoses, and the cellular response) was evaluated in relation to clinical course of each patient. Result: 75 cases were classified into four grades from Grade 1, the lowest malignancy, to Grade 4, the highest malignancy. The percentage metastases was 10, 24, 54, and 75% for each grade, respectively. The percentage of survival was 75, 75, 35, and 25% for each grade, respectively. From these results, this grading system was seen to have a close-correlation with the clinical course of each patient.     

Risk factors of metastasis in oral squamous cell carcinomas

Lymph node and distant metastasis were comparatively studied in 225 oral carcinomas, and factors predisposing toward metastasis were investigated using clinical and immunohistopathological approaches. Neither the sites of tumors nor T-stage was correlated with either type of metastasis. Tumor cell differentiation was weakly correlated with lymph node metastasis, and stromal reaction (the degree of cell infiltration) did not differ greatly between metastasis-positive and negative tumors, although natural killer (NK) activities were correlated with lymph node metastasis. However, the mode of tumor cell invasion was closely associated with both lymph node and distant metastases. In grade 4C and 4D tumors, distant and lymph node metastases were observed in 8 (16%) and 31 (62%) cases, respectively, while of 68 grade 1 and 2 tumors, distant metastasis was not observed in any, and lymph node metastasis occurred in only 15 (22. 1%). In addition, the expression of p53 protein was correlated with lymph node metastasis; of 70 tumors without p53 protein expression, 23 (32.9%) revealed lymph node metastasis, while it occurred in 54 out of 96 tumors positive for p53 protein. However, p53 protein expression was not associated with distant metastasis, and p24 protein, a cyclin-dependent kinase inhibitor, did not show any relationship with either type of metastasis. These results indicate that lymph node metastasis is correlated with multiple factors in the host and tumor cells, but distant metastasis is only correlated with the mode of tumor cell invasion, suggesting that the former can be highly accurately predicted by invasion mode, p53 protein expression and NK activity.     

Galectin 3 expression in primary oral squamous cell carcinomas

Background

Immunologic factors can promote the progression of oral squamous cell carcinomas (oscc). The phylogenetic highly conserved protein Galectin 3 (Gal3) contributes to cell differentiation and immune homeostasis. There is evidence that Gal3 is involved in the progression of oscc and influences the regulation of macrophage polarization. Macrophage polarization (M1 vs. M2) in solid malignancies like oscc contributes to tumor immune-escape. However, the relationship between macrophage polarization and Gal3 expression in oscc is not yet understood. The current study analyzes the association between histomorphologic parameters (T-, N-, L- Pn-status, grading) and Gal3 expression resp. the ratio between Gal3 expressing cells and CD68 positive macrophages in oscc specimens.

Methods

Preoperative diagnostic biopsies (n?=?26) and tumor resection specimens (n?=?34) of T1/T2 oscc patients were immunohistochemically analyzed for Gal3 and CD68 expression. The number of Gal3 expressing cells and the ratio between CD68 and Gal3 expressing cells was quantitatively assessed.

Results

In biopsy and tumor resection specimens, the number of Gal3 positive cells as well as the Gal3/CD68 ratio were significantly (p?<?0.05) higher in T2 oscc compared to T1 cases. In biopsy specimens, a significantly (p?<?0.05) increased Gal3 expression and Gal3/CD68 ratio was associated with the progression marker lymph vessel infiltration (L1). Tumor resection specimens of cases with lymph node metastases (N+) had a significantly (p?<?0.05) increased Gal3 expression. Additionally, a high Gal3/CD68 ratio correlated significantly (p?<?0.05) with higher grading (G3) in tumor resection specimens.

Conclusion

High Gal3 expression in oscc is associated with tumor size (T-status) and parameters of malignancy (N-, L-status, grading). Gal3 might contribute to M2 macrophage mediated local immune tolerance. Gal3 expression shows association with prognosis in oscc and represent a potential therapeutic target.

     

Characterization of novel cell lines established from three human oral squamous cell carcinomas

Human oral squamous cell carcinoma cell lines (KOSCC-11, -25A, -25B, -25C, -25D, -25E, -33A, and -33B) were established by explantation culture from these oral squamous cell carcinomas. The histopathology of the primary tumors, in vitro growth characteristics, epithelial origin, in vitro anchorage-independency, in vivo tumorigenicity, the frequency of human papillomavirus (HPV) infections, and the status of proto-oncogenes, tumor suppressor genes, DNA mismatch repair genes, and microsatellite instability were investigated in the cell lines. KOSCC-11 is a well-differentiated oral squamous cell carcinoma (OSCC) derived from mandibular gingiva. KOSCC-25A, -25B, -25C, -25D, and -25E cell lines were derived from the same OSCC. KOSCC-33A and -33B were established from the same tumor that originated from the maxillary sinus. All tumor lines studied grew as monolayers and showed: i) epithelial origin by the presence of desmosome and keratin; ii) in vitro anchorage-independent growth ability; and iii) tumorigenic potential in nude mice. The cancer cell lines did not contain HPV DNA and did not express viral genes. Northern blot analysis revealed: i) overexpression of EGFR in four cell lines, ii) overexpression of c-H-ras in four cell lines, iii) overexpression of c-myc in three cell lines, iv) decreased expression of TGF-alpha in seven cell lines, and v) decreased expression of c-jun in five cancer cell lines compared with normal human oral keratinocytes. In all KOSCC cell lines and their corresponding tumor tissues, mutations were identified in highly-conserved functional regions of the p53 gene. The KOSCC-11 cell line contained a frameshift mutation and the other cell lines harbored an identical p53 mutation at codon 175 from CGC (Arg) to CTC (Leu). In five cell lines, a significant reduction of p21WAF1/Cip1 protein was evident. Cancer cell lines expressed higher level of Rb protein than normal human oral keratinocytes. DCC, a tumor suppressor gene, was not detected in KOSCC-25C. The KOSCC-33A cell line displayed microsatellite instability and showed a loss of hMSH2 expression. These well-characterized human OSCC cell lines should serve as useful tools for understanding the biological characteristics of oral cancer.     

Microsatellite analysis of chromosome 3p region in sporadic renal cell carcinomas

The etiology and progression of renal carcinomas (RCC) is still poorly understood. RCC have been classified into several pathological entities. The most frequent type, clear cell carcinoma, accounts for about 80% of sporadic RCC and shows several chromosome abnormalities documented both by conventional cytogenetics, loss of eterozygosity (LOH) and replication error (RER) studies. In 10 clear cell type sporadic RCC we evaluated LOH and RER using a set of 10 microsatellite markers covering the chromosome 3p region, which has been suggested for interstitial deletions. Electrophoresis was performed by automated sequencer ABI Prism 377 and data were analyzed with Genescan and Genotyper 2.5 softwares. We revealed allelic loss in 48,7% of informative microsatellites and a single case of RER. We found the highest LOH frequency in 3p25-26 region where maps Von Hippel-Lindau (VHL) oncosuppressor gene. In addition, DNA hypermethylation, an alternative mechanism of VHL gene silencing, was evaluated by methylation-specific PCR. However hypermethylation status was not detected in any of our tumor samples.     

Genomic DNA copy number alterations from precursor oral lesions to oral squamous cell carcinoma

Oral cancer is a multifactorial disease in which both environmental and genetic factors contribute to the aetiopathogenesis. Oral cancer is the sixth most common cancer worldwide with a higher incidence among Melanesian and South Asian countries. More than 90% of oral cancers are oral squamous cell carcinoma (OSCC).The present study aimed to determine common genomic copy number alterations (CNAs) and their frequency by including 12 studies that have been conducted on OSCCs using array comparative genomic hybridization (aCGH). In addition, we reviewed the literature dealing with CNAs that drive oral precursor lesions to the invasive tumors. Results showed a sequential accumulation of genetic changes from oral precursor lesions to invasive tumors. With the disease progression, accumulation of genetic changes increases in terms of frequency, type and size of the abnormalities, even on different regions of the same chromosome. Gains in 3q (36.5%), 5p (23%), 7p (21%), 8q (47%), 11q (45%), 20q (31%) and losses in 3p (37%), 8p (18%), 9p (10%) and 18q (11%) were the most common observations among those studies. However, losses are less frequent than gains but it appears that they might be the primary clonal events in causing oral cancer.     

p73 gene alterations and expression in primary oral and laryngeal squamous carcinomas

p73, a recently identified gene, maps to chromosome region 1p36.3, which is frequently deleted in a variety of solid tumors. Although the gene shares sequence and functional homologies with p53, its suppressor function has not been proven. We investigated for the first time the genetic and expression status of the p73 gene and analyzed its flanking microsatellite loci on chromosome 1p36.3 in 67 primary oral and laryngeal squamous cell carcinomas to determine their association with these tumors. Our results reveal two missense mutations at codons 469 and 477 and a silent mutation at codon 349 in the C-terminal domain. Site-directed mutagenesis of p73 cDNA with these mutations and a p21 transactivation assay failed to show any significant functional consequences of these mutations. Microsatellite analysis of the flanking loci of p73 in region 1p36 showed overall alterations (loss of heterozygosity and instability) frequency of 39%, 16% at the proximal marker and 46% at the distal markers. Of the 21 cases for which we did protein expression analyses, 11 tumors had a >2-fold variation compared with matching histologically normal mucosa. Our study shows that: (i) intragenic alterations in this gene are rare and lack functional significance; (ii) its variable expression argues against a tumor suppressor function; (iii) this gene plays a minor role in head and neck squamous carcinoma; (iv) a distal site to this gene on 1p36 may harbor another suppressor gene.     

Genomic instability in oral squamous cell carcinoma: relationship to betel-quid chewing

Genomic instability in repeated DNA sequences is exhibited by a variety of cancer types, including oral squamous cell carcinoma. Exposure to carcinogenic compounds may further increase the instability. We have used Inter-Simple Sequence Repeat (Inter-SSR) PCR methodology to detect genetic alterations in 37 oral cancer patients who had chewed betel-quid. Thirty-eight percent of DNA from tumors had genomic alterations in the sequences flanked by (CA)(8) and (GT)(8) repeats. Patients with tumor DNAs harboring genomic alterations had a two-fold higher consumption of betel-quid than patients without alterations in tumor DNA. Matched normal and tumor DNAs were also screened for microsatellite instability where four patients (10.8%) showed alterations in at least one microsatellite marker but there was no relationship between this phenotype and betel-quid chewing. These data indicate that exposure to carcinogens present in the betel-quid may contribute to genomic instability detected by inter-SSR PCR in a subset of oral tumors.