Head And Neck Squamous Cell Carcinoma Carcinogenesis Research Articles

DNA ploidy and chromosomal alterations in head and neck squamous cell carcinoma.

In head and neck squamous cell carcinomas (HNSCC) the prognostic factors that are routinely considered when deciding therapeutic strategies are still stage and site of the primary tumour, and the presence of nodal or distant metastases. However, it is recognised that these clinical predictors are limited since they do not satisfactorily reflect the biological behaviour of the individual tumour. With the evolving understanding of the genetic and molecular basis of human malignancies, there are an increasing number of factors being claimed to provide prognostic information even in HNSCC. Here we review own and published data on DNA ploidy, karyotyping and molecular cytogenetic changes and its relevance in HNSCC carcinogenesis. The survey suggests that the induction of aneuploidy is a very early event in tumour development being detectable already in non-dysplastic leukoplakia and highly predictive for the subsequent development of a carcinoma. Moreover, specific chromosomal imbalances are associated with different stages of cancer progression and patient's survival, which we have compiled into a progression model of HNSCC.

Genomic gain of PIK3CA and increased expression of p110alpha are associated with progression of dysplasia into invasive squamous cell carcinoma.

PIK3CA, encoding the catalytic subunit p110alpha of phosphatidylinositol 3-kinase (PI3K), is activated in malignant diseases. However, the role of the PIK3CA gene aberrations for tumourigenesis of head and neck squamous cell carcinoma (HNSCC) is to date unclear. The present study was designed to determine the genomic aberration of PIK3CA in invasive HNSCC and dysplastic precursor lesions by fluorescence in situ hybridization (FISH) with a YAC probe, containing the PIK3CA gene, on isolated interphase nuclei from histomorphologically well-defined regions of formalin-fixed tissue sections and to compare these data with protein and mRNA expression of p110alpha. The mRNA and protein levels of p110alpha were assessed, respectively, by in situ hybridization and immunohistochemistry on consecutive tissue sections. Copy number gains at 3q26 were observed in one of six low-to-moderate dysplasias (17%) and in seven of nine high-grade dysplasias (78%), as well as in 11 carcinomas (100%). In addition, one of seven high-grade dysplasias (14%) and 6 of 11 carcinomas (55%) had amplifications of 3q26. The majority of cases with copy number gain in more than 50% of the cells and/or amplification in more than 10% of cells showed increased p110alpha mRNA and protein expression, whereas only two cases (18%) (one high-grade dysplasia and one carcinoma) with no gain or low-level gain displayed increased p110alpha protein expression. These data suggest that 3q26 copy number gain and amplification represent early genomic aberrations in HNSCC carcinogenesis. In addition, p110alpha mRNA and protein expression in HNSCC may be regulated by these genomic aberrations as well as by epigenetic events.

Nonmalignant Oral Keratinocytes from Patients with Head and Neck Squamous Cell Carcinoma Show Enhanced Metabolism of Retinoic Acid

Background and Objective: Retinoids show promise in the treatment of various (pre)malignancies, including head and neck squamous cell carcinoma (HNSCC). It has been shown that metabolic pathways of retinoids are important in their anticancer effect and that these pathways may change during HNSCC carcinogenesis. We have previously reported that HNSCC cells have a 17-fold greater turnover rate of retinoic acid (RA) than normal oral keratinocytes from noncancer controls, and that the formation of polar metabolites such as 4-oxo-RA and 4-hydroxy-RA is only seen in HNSCC cell lines. We aimed to establish whether this altered retinoid metabolism is an intrinsic characteristic of HNSCC patients. Methods: The normal mucosa of cancer and noncancer patients was the source of keratinocyte cultures. The cells were exposed to RA for various time periods, and the levels of various retinoids were measured in the culture medium and cell pellets with reverse-phase liquid chromatography. Results: Cells from cancer patients were morphologically normal and showed no genetic aberrations (i.e. loss of heterozygosity). The RA turnover rate in normal oral keratinocytes of cancer patients was 15 times higher (p = 0.003) than that in normal oral keratinocytes of noncancer controls, with average turnover rates of 218.6 and 14.8 pmol/mg protein/h, respectively. Specific profiles of RA metabolites were similar. Conclusion: The observed higher RA metabolism in noncancer cells of HNSCC patients suggests that individuals with a relatively high RA turnover have an increased risk of developing HNSCC.

Molecular characterization of head and neck tumors by analysis of telomerase activity and a panel of microsatellite markers

Head and neck cancer is a frequent malignancy with a complex, and up to now not clear etiology. The reactivation of telomerase activity and losses or gains of specific chromosomal regions, which point to deletions of tumor suppressor genes or amplification of oncogenes are supposed to be the molecular processes during the development and progression of head and neck cancer. Therefore, we analyzed telomerase activity and microsatellite markers using a genome wide panel of 28 microsatellite markers in 38 head and neck squamous-cell carcinomas (HNSCC). Our microsatellite marker set included distinct chromosomal areas that all likely harbor genes contributing to the carcinogenesis of HNSCC. DNA or protein lysates were obtained from primary tumors and compared to peripheral lymphocytes or corresponding normal tissue. At least one genomic alteration [loss of heterozygosity (LOH), or microsatellite instability (MSI)] was found in 31 of the 38 cases (82%). Most frequently we detected an LOH in the chromosomal region 9p12-21 where at least the tumor suppressor genes (TSG) p16INK4A, p14ARF and p15INKB are localized. The comparison between grade two and grade three tumors showed a highly changed frequency of LOH in the chromosomal region 7q31, where a putative TSG is predicted. Telomerase activity was present in 31/37 (83.8%) tumor samples independent of the histopathological staging and grading of the tumors. These molecular characterizations of HNSCC may be a further hint for the involvement of additional, so far unknown, TSGs in the tumor progression and will elucidate the regulation of telomerase.

Mutagen sensitivity and environmental exposures as contributing causes of chromosome 3p losses in head and neck cancers

The interaction between environmental exposures and host susceptibility may lead to specific mutational events within head and neck squamous cell carcinoma (HNSCC). Furthermore, this interplay may determine not only the probability of cancer development but also the biologic characteristics of the tumor once it occurs. To better understand the relationship of mutagen sensitivity and tobacco and/or alcohol consumption on HNSCC carcinogenesis, we examined loss of heterozygosity on chromosome 3p in 58 HNSCCs using 10 microsatellite markers. Mutagen sensitivity was determined in vitro by quantitating bleomycin-induced chromatid breaks utilizing peripheral blood lympocytes from respective patients. Forty-six of the 58 invasive cancers showed allelic loss at one or more loci. Consistent with previous investigations, three discrete regions of deletions were identified: 3p13-14.2, 3p21.1-21. 2, and 3p25.1-26.1. The frequency and types of deletions were dependent upon tobacco and alcohol exposures. The distal region of 3p but not the remaining two regions was most frequently influenced by tobacco exposure. In contrast, heavy alcohol use when combined with tobacco use was associated with whole-arm loss of 3p rather than identifiable site-specific damage. Furthermore, this combined influence of alcohol and tobacco exposures on whole-arm loss was most apparent in those patients who expressed mutagen-sensitivity; the odds ratio of whole-arm loss increasing from 2.67 (95% CI 0. 21-33.49) in those individuals who were mutagen resistant to 13.5 (95% CI 1.3-136.0; P = 0.02 by Fisher's exact test) in those who were mutagen sensitive. An assessment of clinical parameters in this population demonstrated that patients with whole-arm loss were more likely to present with cervical lymph node metastases and advanced stage disease than patients with partial losses. Results indicate that various environmental exposures as well as the expression of mutagen sensitivity will influence the types of chromosome 3p allelic losses in head and neck cancers as well as the behavior of disease once it develops.

Mutagen sensitivity and environmental exposures as contributing causes of chromosome 3p losses in head and neck cancers

The interaction between environmental exposures and host susceptibility may lead to specific mutational events within head and neck squamous cell carcinoma (HNSCC). Furthermore, this interplay may determine not only the probability of cancer development but also the biologic characteristics of the tumor once it occurs. To better understand the relationship of mutagen sensitivity and tobacco and/or alcohol consumption on HNSCC carcinogenesis, we examined loss of heterozygosity on chromosome 3p in 58 HNSCCs using 10 microsatellite markers. Mutagen sensitivity was determined in vitro by quantitating bleomycin-induced chromatid breaks utilizing peripheral blood lympocytes from respective patients. Forty-six of the 58 invasive cancers showed allelic loss at one or more loci. Consistent with previous investigations, three discrete regions of deletions were identified: 3p13–14.2, 3p21.1–21.2, and 3p25.1–26.1. The frequency and types of deletions were dependent upon tobacco and alcohol exposures. The distal region of 3p but not the remaining two regions was most frequently influenced by tobacco exposure. In contrast, heavy alcohol use when combined with tobacco use was associated with whole-arm loss of 3p rather than identifiable site-specific damage. Furthermore, this combined influence of alcohol and tobacco exposures on whole-arm loss was most apparent in those patients who expressed mutagen-sensitivity; the odds ratio of whole-arm loss increasing from 2.67 (95% CI 0.21–33.49) in those individuals who were mutagen resistant to 13.5 (95% CI 1.3–136.0; P = 0.02 by Fisher's exact test) in those who were mutagen sensitive. An assessment of clinical parameters in this population demonstrated that patients with whole-arm loss were more likely to present with cervical lymph node metastases and advanced stage disease than patients with partial losses. Results indicate that various environmental exposures as well as the expression of mutagen sensitivity will influence the types of chromosome 3p allelic losses in head and neck cancers as well as the behavior of disease once it develops.

9p21 deletion correlates with recurrence in head and neck cancer.

Deletion of 9p21 is a common event in many human tumors, including head and neck squamous cell carcinoma (HNSCC). The gene CDKN2, which encodes the protein p16, a cyclin-dependent kinase-4 inhibitor, maps to 9p21. The role of CDKN2 as the tumor suppressor gene in these neoplasms is unclear. The role of loss of heterozygosity (LOH) as a prognostic tool has not been described in HNSCC. We performed deletion mapping using Southern and PCR-based LOH analysis and prospective survival analysis. We demonstrate that LOH of 9p and, specifically, the interferon (IFN) gene cluster correlates with recurrence of HNSCC. We also demonstrate two separate areas of deletion on 9p, one centromeric to IFNbeta and telomeric to CDKN2 and the other centromeric to CDKN2 and telomeric to the polymorphic marker D9S19. All the deletions involve either the markers IFNalpha and/or D9S171 and D9S126 but not necessarily CDKN2. These results suggest another tumor suppressor gene (TSG) may be involved in HNSCC carcinogenesis and may play a role in aggressive disease as manifest by local, regional, or distant recurrence.

P53 overexpression in normal and dysplastic tissues adjacent to p53 negative squamous cell carcinomas of the head and neck

p53 overexpression was present in the normal or dysplastic epithelium, but absent in the adjacent invasive cancers of five patients with head and neck squamous cell carcinomas (HNSCC), when p53 immunostaining (IHC) was performed. In three of the five p53 immunoreactive dysplasias and adjacent p53 negative invasive cancers single stranded conformation polymorphism (SSCP) results from exon 7 and 8 were also obtained. Bandshifts in exon 7 were detected in two dysplasias, and bandshifts in exon 8 were found in a third. Sequencing of exon 7 in the first dysplasia with bandshift indicated a deletion of codon 241-242 (loss of CT) resulting in a frame shift. In the second dysplasia with bandshift a mutation was observed in codon 244 resulting in a Gly-->Arg substitution in the protein sequence. In the adjacent IHC p53 negative invasive cancer lesions, no bandshifts could be observed by SSCP, and sequencing did not reveal any mutated p53. WAF1/p21 (IHC) expression was assayed to study p53 function. Image cytometry (ICM) DNA analysis, estimating genetic instability, showed progress in DNA aberration for invasive cancer lesions as compared with the dysplasias. Human papillomavirus (HPV DNA) was not detected by a polymerase chain reaction (PCR) in any of the five cancers thus excluding possible p53 degradation caused by HPV protein. In conclusion, the finding of p53 mutations in mild, moderate, and severe dysplasia indicates that p53 mutation, not only p53 immunoreactivity, can be an early event in HNSCC carcinogenesis. The lack of p53 immunoreactivity in the invasive cancers adjacent to p53 positive dysplasias could possibly be attributed to loss of the mutant allele, or clonal heterogeneity.