Molecular alterations in head and neck squamous cell carcinoma

Angiogenesis in the development of head and neck cancer and its inhibition by chemopreventive agents

Squamous cell carcinoma is an aggressive malignancy that often develops as multiple independent lesions throughout the mucosa of the upper aerodigestive tract. Therefore, the comprehensive treatment of this disease must not only address the initial primary neoplasm, but also prevent the progression of the premalignant lesions lurking throughout the rest of the mucosal surfaces. The need to treat these lesions has resulted in a search for chemopreventive agents that can halt or even reverse their malignant progression. The biologic and molecular mechanisms by which most chemopreventive agents act have remained unclear and controversial. Recent work from several laboratories has demonstrated that some drugs may act in part by inhibiting the ability of tumors to induce blood vessel growth. Angiogenesis, the growth of new blood vessels from pre-existing ones, is absolutely required for solid neoplasms to grow beyond 2-3 mm in diameter. Therefore, chemopreventive agents that act to inhibit angiogenesis may provide a very powerful modality by which one may limit the growth of both pre-malignant lesions and small nests of tumor cells. This review will outline the basic changes that occur in tumor cells that result in the switch from an anti-angiogenic to an angiogenic phenotype. In addition, it will discuss the mechanisms by which some chemopreventive agents, presently under clinical investigation, inhibit tumor angiogenesis. Finally, this paper will present a rationale for the use of multiple anti-angiogenic agents as a means of developing new chemopreventive protocols that result in reduced patient toxicity while maintaining similar clinical efficacies.

Differentially expressed genes in head and neck cancer

Carcinogenesis is considered a multistep process. To further elucidate involved genetic changes, the differential display method was applied to compare gene expression of head and neck carcinoma cells and normal keratinocytes from the upper aerodigestive tract. Total RNA was extracted from cultured squamous carcinoma cells and keratinocytes. mRNA was reverse transcribed into cDNA, amplified by PCR, and separated on a gel. Currently three DNA transcripts were identified with a length of 191 to 336 base pairs (bp) that were either expressed only by the keratinocytes or by the malignant cells. Differentially expressed DNA fragments of the carcinoma cells and the keratinocytes were cloned and sequenced. A gene bank database search identified one fragment expressed by the carcinoma cells as an unknown gene, another one found in the keratinocytes as probably a part of the human cell attachment domain, and the third one with homology to the mRNA of the human epidermal growth factor receptor (EGFR). Northern blot analysis confirmed the differential expression in the malignant cells or the keratinocytes. Differential display seems to confirm the well-known overexpression and up-regulation of the EGFR, the differential expression of the cell attachment domain may play a role as a cofactor in carcinogenesis of head and neck cancer, and the third unknown fragment is still under investigation to elucidate the role in carcinogenesis.

Expression of a novel mRNA in human head and neck squamous cell carcinoma cells

AIMS

The differential display reverse transcription polymerase chain reaction (DDRT-PCR) technique was used to search for differences between the mRNA expression profiles of squamous cell carcinoma (SCC) cell lines established from head and neck tumours and normal keratinocytes from the mucosa of the upper aerodigestive tract.

METHODS

Total RNA prepared from both cell types was reverse transcribed into cDNA then amplified in a PCR mixture. To compare the electrophoretic patterns, mRNAs were amplified by nested PCR using specific oligonucleotides. Additionally, using labelled cDNA probes, northern hybridisation was carried out on three cancer cell lines of different origin, a biopsy from a parotid gland pleomorphic adenoma, healthy mucosa, and keratinocytes.

RESULTS

Comparison of the separated bands revealed a fragment with a differential expression pattern in the SCC cells. This cloned sequence of a 336 base pair mRNA fragment exhibited no significant homology with known transcripts. Additionally, after amplification and sequencing of the 3' end of the fragment no homology with a known human gene sequence was found. However, low homology with a genomic sequence of a nematode was found. Northern hybridisation confirmed the selective expression of this fragment in SCC cells versus the cancer cell lines of different origin, the biopsy of the pleomorphic adenoma, keratinocytes, and healthy mucosa.

CONCLUSIONS

This is the first differentially expressed human genome transcript of squamous cell carcinoma of the head and neck identified by DDRT-PCR. It may prove useful, in the future, to characterise this tumour type.

Epidermal growth factor receptor, c-erbB-2 and p53 overexpressions in epithelial hyperplastic lesions of the larynx

An immunohistochemical analysis of overexpression of epidermal growth factor receptor (EGFR), c-erbB-2, and p53 proteins was performed on 43 biopsies of laryngeal epithelial hyperplastic lesions (EHLL), classified according to the Kambic-Lenart classification, and in 11 cases of laryngeal carcinoma (SCCL). The aim of the present study was to determine whether there is a correlation between the staining patterns of these proteins and different grades of EHLL, and to reveal their possible prognostic value. We compared the staining patterns of atypical hyperplasia adjacent to cancer with the same type of lesions which have not turned malignant. p53 and EGFR overexpressions were detected in 28/54 (52%) and 33/54 cases (61%), respectively, and tend to increase with the degree of epithelial changes. The intensity of staining in various grades of EHLL adjacent to cancer was more pronounced than the same type of lesions which have not progressed to cancer. c-erbB-2 was weakly positive in the majority of cases, and changed from predominantly membranous in simple hyperplasia to cytoplasmic staining in abnormal and atypical hyperplasias. There was no significant statistic correlation between the amount of positive cells for all proteins and the grade of epithelial abnormalities. We conclude that the overexpression of each biomarker itself adds little predictive value over routine histomorphology, and cannot be regarded as a reliable prognostic factor for EHLL. However, the histologic characteristics of atypical hyperplasia together with the immunostaining patterns of EGFR and p53 up to two-thirds or more of the epithelial thickness could be considered a reliable pattern which correlates with the progression to cancer.