Adhesion properties, intermediate filaments and malignant behaviour of head and neck squamous cell carcinoma cells in vitro.

This study compared phenotype and behaviour of seven head and neck squamous cell carcinoma (HNSCC) cell lines and normal epithelial cells. Indications were found that in HNSCC cells: 1) loss of the cell-cell adhesion molecule E-cadherin was correlated with loss of epithelioid cell morphology but not with loss of cell-cell cohesion; 2) reduced expression of the cell-cell adhesion molecule desmoglein was unrelated to cell shape or motility; 3) high expression of the cell-substrate adhesion molecule alpha 6 beta 4, a receptor for laminin, corresponded with epithelioid colony formation while, in our adhesion assay, low expression of alpha 6 beta 4 paradoxically coincided with an increased adhesion to laminin; 4) presence of vimentin intermediate filaments coincided with loss of anchorage dependency. We propose that by simultaneous downregulation of E-cadherin, replacement of alpha 6 beta 4 by an aberrant laminin receptor and co-expression of vimentin a malignant phenotype arises of spindle-shaped, motile, anchorage-independent HNSCC cells with enhanced laminin-binding capacity.

Characterization of a rat oral squamous cell carcinoma cell line UHG-RaC '93 induced by 4-nitroquinoline-1-oxide in vivo.

This study describes several characteristics of a cell line, UHG-RaC '93 derived from rat oral squamous cell carcinoma induced by the carcinogen 4-nitroquinoline-1-oxide (4NQO). The cell line was established from explant cultures without support of fibroblast feeder cells and continued for > 30 passages. UHG-RaC '93 had a high mitotic rate with a population doubling time of 25 h and a high rate of squame production. The first passage had a low colony-forming efficiency in agarose gel, whereas later passages did not grow at all in semi-solid medium. Phenotype selection was furthermore apparent from a gradual increase of the trypsin-detachment time. Cytogenetic analysis showed that UHG-RaC '93 was hypotetraploid with an average of 74 chromosomes. Abnormalities compared to the normal karyotype were assessed and consisted mainly of breakpoints at (1)(q5?3), (3)(p1), (3)(q11q23), (11)(p?11), (13)(p13) and a derivative (12)t(12;13)(q10;q10). The karyotype remained stable for at least 26 passages. The expression of typical epithelioid markers like cytokeratins and desmoglein corresponded with normal rat oral keratinocytes. However expression of alpha 6 beta 4-integrin was altered. Squame production, immunophenotype and anchorage dependency indicated that UHG-RaC '93 had the same features of a well-differentiated carcinoma with a low degree of agressiveness as the original tumour. The stable karyotype of this cell line provides a basis for further analysis of the effect of 4NQO on the genotype, phenotype and behaviour of rat oral keratinocytes.

Characterization of human larynx carcinoma cell lines HLaC'79 and HLaC'82: a common origin but diverged malignancies.

As part of a study on the relationship of tumour phenotype and behaviour, we have characterized two head and neck squamous cell carcinoma cell lines, derived from human laryngeal carcinomas and designated HLaC'79 and HLaC'82. Cytogenetic analysis revealed that HLaC'79 and HLaC'82 shared 10 major chromosome rearrangements indicating that the cell lines had a common origin. In the extremely complex chromosomal patterns, abnormalities were found in chromosomes 1, 3 (surplus 3q) and 5 (i(5p) x 2). Both cell lines displayed constitutive expression of vimentin and were capable of anchorage-independent growth in agarose gels. However, in spite of their common origin specific differences were found. Cells of HLaC'79 were spindle shaped and formed tumours in athymic mice. In contrast, cells of HLaC'82 had a compact morphology, contained less vimentin, were more contact inhibited and were not tumorigenic. These results indicate that malignant transformation in HLaC'82 was partially reversed.

Use of cultured mucosal grafts to cover defects caused by vestibuloplasty: an in vivo study.

PURPOSE: In oral and maxillofacial surgery palatal mucosal grafts are routinely used to cover mucosal defects caused by vestibuloplasty. However, the quantity of palatal mucosa is a limiting factor in more extensive operations. This study investigated whether autologous cultured sheets of mucosa can serve as a dressing for these wounds. MATERIALS AND METHODS: Punch biopsies (diameter, 4 mm) were taken from the hard palate of eight patients (five men, three women; mean age 43 years). Epithelial cells were enzymatically dissociated from these tissue specimens and grown in vitro in the presence of a fibroblast feeder layer. Within 3 weeks, a transplantable epithelial sheet of about 20 cm2 was obtained. The sheet was detached from the culture flask by enzyme treatment and fixed to a carrier of Vaseline (Cheeseborough Ponds Inc, Greenwich, CT) gauze. Using a split-mouth technique, the sheet was placed on half of a mucosal defect created by vestibuloplasty, while the other half of the defect was covered by a conventional split-thickness palatal graft. Both the cultured and conventional graft were held in place by the patient's relined denture fixed with perimandibular sutures. One week postsurgery, the denture and Vaseline gauze were removed. Three months after vestibuloplasty, biopsy specimens of each grafted site were taken and processed for light and transmission electron microscopy (LM, TEM). RESULTS: Three months postsurgery, the grafted mucosa of both sites bore close resemblance to palatal mucosa. Both the cultured and split-thickness grafts were vascularized, did not evoke a homograft reaction, and showed a smooth graft/lip mucosal junction and minimal wound contraction. LM and TEM revealed that both types of grafts formed a fully differentiated keratinizing mucosa with a well-developed basement membrane and rete ridges, comparable with the histology and ultrastructure of palatal mucosa in situ. CONCLUSION: It was concluded from this study that cultured mucosa can serve as a proper dressing for mucosal defects after vestibuloplasty.

The effect of detachment of cultured epithelial sheets on cellular ultrastructure and organisation.

In this morphological study the (ultra)structural changes that lead to contraction of detached cultured epithelium were investigated. Keratinocytes, isolated from human skin and oral mucosa, were grown to form stratified cell sheets. The multilayers were examined with light and electron microscopy before, during and after detachment from the culture vessel. Attached epithelium had a stretched morphology with flattened cells and nuclei. Evidence is provided that after enzymatical detachment with dispase (1) basal cells became columnar by contraction of actin bundles in the basal cortex, which was accompanied by blebbing of the basal cell membrane; (2) in all cell layers cytokeratin bundles contracted resulting in displacement of desmosomes and a spherical shape of the cells and nuclei. By slow dispase-detachment at 4 degrees C or by quick mechanical detachment, shrinkage of the sheet was partly suppressed but contraction of cytokeratin and related events occurred indicating that these were the result of the spontaneous reassembly of the intermediate filament system. The results suggested that the shape and ultrastructure of all cells in an epithelial multilayer are dependent on the interaction of the basal cells with the underlying extracellular matrix.

Cellular Interactions during the Mating Process in Chlamydomonas eugametos.

A method to determine the mating competence of Chlamydomonas eugametos was developed. The contribution of each mating type in the pair formation was investigated using asymmetric gamete mixtures. It was established that pair formation is not mediated by a pheromonal attraction mechanism between partner gametes, but depends on collision chances. On the other hand, it was demonstrated that during transient contacts between partner gametes the flagellar agglutinability of both partners is stimulated, evidently to prepare a successful mating. The plus mating type was generally less agglutinable than the minus mating type and was a rate-limiting factor in the mating process.