Heterologous epidermal growth factor receptor (EGF-R) expression in larynx cancer cell lines: evidence for the existence of structurally modified receptors

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Expression of EGF, EGFR and PCNA in laryngeal lesions

The expression of EGF/EGFR in 47 laryngeal surgical specimens from 44 patients was examined. PCNA analysis as an index of proliferating cells was also performed in 32 cases of laryngeal cancer, six cases of pre-cancerous lesions and nine cases of normal laryngeal mucosa. EGFR failed to show a significant correlation with tumour behaviour, but EGF expression was statistically significantly higher in malignant (SCC) than in non-malignant tissues (pre-cancerous and normal tissues) (p < 0.006), and PCNA also showed a statistically significant difference (p < 0.016) between the two. In malignant tissues when EGF/EGFR in 'double-positive' and 'double-negative' cases was compared, a statistically significant difference in PCNA was found (p < 0.029); but this was not seen in non-malignant tissues. Our results support the hypothesis that an autocrime mechanism exists in laryngeal cancer and in this mechanism EGF may play an important role in tumour progression, especially when EGFR is overexpressed.