p53 mutations in squamous cell carcinoma of the head and neck predominate in a subgroup of former and present smokers with a low frequency of genetic instability.

We examined the p53 mutational profile of 65 squamous cell carcinomas of the head and neck (SCCHNs) from patients living in northwest England. Twenty-three p53 mutations were detected in 20 samples (31%). GC-->AT transitions were the predominant type of mutation. The p53 mutational profile of SCCHN tumors was similar to that of non-small cell lung tumors from patients within the same geographical area, supporting the idea of a common model for carcinogenesis in the upper respiratory tract. Statistical analysis showed that the incidence of p53 mutations among present and former smokers was significantly higher than that in nonsmokers (P < 0.02). In addition, p53 mutations were found to predominate in a group of SCCHN patients with low genetic damage, as indicated by the fractional allelic loss value. The above findings suggest an early initiating role for p53 and imply that at least two separate carcinogenic pathways may be involved in the development of SCCHN.

Synchronous oral carcinomas: independent or common clonal origin?

Second primary tumors in patients with head and neck cancer have a detrimental impact on long-term survival; at least 15% of patients develop additional tumors. Originally, it was hypothesized that multiple tumors developed independently after widespread epithelial exposure to carcinogens (the field cancerization theory), but recent molecular studies now support the alternative theory of a common clonal origin. If multiple tumors originate from the same clone, early genetic alterations in these cells should be common to all of the tumors. We have compared the pattern of allelic imbalance in paired tumors from five male patients with two synchronous oral squamous cell carcinomas and in peripheral dysplasia using microsatellite markers on chromosomes 3p, 9p, and 17p. Discordance, usually through loss of alternate alleles at the same microsatellite loci, was detected in two patients. The remaining three patients had identical alterations in their tumors. The changes identified occurred early in tumorigenesis, because, with only one exception, these were also present in the associated dysplasia. Thus, we provide evidence that synchronous oral squamous cell carcinomas are of independent origin in some patients but may be of common clonal origin in others.

Loss of heterozygosity on chromosomes 3, 9, 13, and 17, including the retinoblastoma locus, in uveal melanoma.

PURPOSE: To identify tumor-suppressor loci that may contribute to the pathogenesis of uveal melanoma. METHODS: Multiplex fluorescence microsatellite assays were performed on 27 uveal melanomas using markers at 3p25-p26, 3p14.2, 9p21-p23, 13q14, 13q12.3-q13, and 17p13, close to or within the von Hippel Lindau (VHL), fragile histidine triad (FHIT), p16/cyclin-dependent kinase inhibitor 2 (CDKN2A), retinoblastoma (RB1), breast cancer 2 (BRCA2), and p53 tumor suppressor loci, respectively. Further markers on chromosomes 3 and 9 were analyzed individually. RESULTS: Loss of heterozygosity (LOH) was identified in 63% of tumors, most frequently on chromosome 3 (52%), in association with epithelioid cells (P = 0.0002) and microvascular loops (P = 0.0008). In the majority of cases, LOH on chromosome 3 was detected at all informative markers. The second most common alteration was LOH at an RB1 intragenic marker (21% tumors), with retention of a more centromeric 13q marker (near BRCA2). The pattern of LOH on chromosome 9p was consistent with the involvement of a region telomeric to CDKN2A. LOH at TP53 was infrequent. CONCLUSIONS: In the majority of cases, chromosome 3 LOH involves an entire chromosome homologue, which hampers identification of the relevant suppressor loci. This LOH correlates with the presence of microvascular loops and epithelioid cells, two of the recognized histologic indicators of poor prognosis. Data for chromosomes 13 and 9 support a role for RB1 in the pathogenesis of uveal melanoma but also raise the possibility of the involvement of additional loci close to RB1 and CDKN2A.

Overexpression of epidermal growth factor receptor restricted to macrophages in uveal melanoma.

OBJECTIVE: To determine whether expression of the epidermal growth factor receptor (EGFR) is of prognostic value in uveal melanoma. METHODS: Thirty consecutive patients treated for primary posterior uveal melanoma by enucleation or local resection were studied. Tumors were examined for EGFR and CD68 expression by immunohistochemistry on formalin-fixed, paraffin-embedded sections. Extracted DNA from paired frozen tumor and blood samples was examined for loss of heterozygosity on chromosome 3 using polymerase chain reaction-based microsatellite analysis. Immunoreactivity for EGFR was correlated with clinicopathological, chromosome 3, and follow-up data. RESULTS: Immunoreactivity for EGFR was observed in 7 (23%) of 30 uveal melanomas, but was restricted to solitary or small groups of cells with macrophage-like morphology. Immunoreactive cells were confirmed as macrophages using an antibody to the macrophage marker CD68. Chromosome 3 loss, epithelioid cells, and microvascular loops were detected in 17 (57%), 22 (73%) and 19 (63%) of the 30 tumors, respectively. Metastatic disease was detected in 5 patients (17%). No correlation was found between any of these variables and EGFR positivity. CONCLUSIONS: The absence of EGFR immunoreactivity in tumor cells does not support the use of EGFR expression as a prognostic indicator in patients with uveal melanoma. Future EGFR studies in uveal melanoma should be interpreted with caution in view of our findings that tumor-associated macrophages can express this receptor.

Decreased endothelin receptor B expression in large primary uveal melanomas is associated with early clinical metastasis and short survival.

The most devastating aspect of cancer is the metastasis of tumour cells to organs distant from the original tumour site. The major problem facing oncologists treating uveal melanoma, the most common cancer of the eye, is metastatic disease. To lower mortality, it is necessary to increase our understanding of the molecular genetic alterations involved in this process. Using suppression subtractive hybridisation, we have analysed differential gene expression between four primary tumours from patients who have developed clinical metastasis and four primary tumours from patients with no evidence of metastasis to date. We have identified endothelin receptor type B as differentially expressed between these tumours and confirmed this observation using comparative multiplex RT-PCR. In a further 33 tumours, reduced endothelin receptor type B expression correlated with death from metastatic disease. Reduced expression also correlated with other known prognostic indicators, including the presence of epithelioid cells, chromosome 3 allelic imbalance and chromosome 8q allelic imbalance. Endothelin receptor type B expression was also reduced in four out of four primary small cell lung carcinomas compared to normal bronchial epithelium. We also show that the observed down-regulation of endothelin receptor type B in uveal melanoma was not due to gene deletion. Our findings suggest a role for endothelin receptor type B in the metastasis of uveal melanoma and, potentially, in the metastasis of other neural crest tumours.

Fractional allele loss indicates distinct genetic populations in the development of squamous cell carcinoma of the head and neck (SCCHN).

Loss of heterozygosity (LOH) had been widely used to assess genetic instability in tumours and a high LOH on chromosome arms 3p, 9p and 17p has been considered to be a common event in squamous cell carcinoma of the head and neck (SCCHN). We have investigated LOH in 52 SCCHN using a range of microsatellite markers. LOH was observed in 69% of individuals on 17p using seven markers, in 64% of individuals on 3p using 17 markers and in 61% of individuals on 9p using 11 markers. Fractional allele loss (FAL) has been calculated for each tumour (FAL is the number of chromosomal arms showing LOH divided by the number of informative chromosomal arms) and a median FAL value of 0.25 was obtained in the 52 SCCHN studied. The LOH data were examined on the basis of FAL scores: low FAL (LFAL), 0.00-0.19; medium FAL (MFAL), 0.20-0.32; high FAL (HFAL), 0.33-0.88. HFAL tumours demonstrated a significantly higher LOH on chromosome arms 3p, 9p and 17p, with 94% LOH on 3p, 94% on 9p and 100% on 17p compared with LFAL tumours. Six of the 16 patients in the LFAL group were found to have no LOH on 3p, 9p or 17p and of these four had LOH at other sites, on chromosomes 2p25-p24, 5q21-22, 7pter-p22, 8q13-q22.1, 11q23.3, 13q32, 17q, 18p11.21, 18q21.31 and 19q12-q13.1. These results indicate that LFAL patients form a subset of SCCHN tumours with distinct molecular initiating events which may represent a discrete genetic population.

p53 mutations in relation to human papillomavirus type 16 infection in squamous cell carcinomas of the head and neck.

The relationship between human papillomavirus (HPV) type 16 infection and p53 gene mutations was investigated in squamous cell carcinomas of the head and neck (SCCHN). HPV was detected by general primer-mediated and type-specific PCR. Alterations in the p53 gene were investigated using single-strand conformation polymorphism and sequence analysis in 27 SCCHN, of which 12 were HPV 16-positive and 15 were HPV-negative. Mutations were detected in 2/12 (16.7%) HPV 16-positive and 7/15 (46.7%) HPV-negative tumours; this difference was not statistically significant. The predominant mutations were deletions and C --> T transitions; G --> T transversions were found in only 2 tumours. Our results indicate that the presence of HPV 16 and p53 mutations is not mutually exclusive and detection of a p53 mutation does not exclude a potential role for HPV 16 in the pathogenesis of a subset of SCCHN.

Prevalence of mucosotropic human papillomaviruses in squamous-cell carcinoma of the head and neck.

The prevalence of mucosotropic human papillomavirus (HPV) DNA in 63 squamous-cell carcinomas (SCC) from different anatomic sites in the head and neck was determined by general primer-mediated polymerase chain reaction (GP-PCR). HPV DNA was detected in 20.6% of SCC. Additional type-specific PCR for HPV 6, 11, 16, 18, 31 and 33 demonstrated the presence of HPV 16 alone in these carcinomas. HPV 16 was also detected in normal epithelium from the resection margins of the majority of HPV-positive SCC. HPV status did not correlate with tumour site, whether primary or recurrent, TNM stage, metastases, degree of differentiation, smoking or alcohol history, fate or survival.