Mortal and Immortal Molecular Phenotypes in HNSCC In-Vivo

Objectives: Investigation of molecular markers in head and neck squamous cell carcinoma (HNSCC) has demonstrated alterations in genes related to proliferation, differentiation, adhesion and others including those which control invasion and metastasis. Some of these may be useful markers of poor prognosis and recurrence. Methods: To further investigate the molecular phenotype associated with HNSCC development, we used gene-expression profiling of a panel of mortal and immortal cell cultures derived from HNSCCs, using Affymetrix U133A/B genechips. This was followed by validation of selected molecular markers by western blotting in the cultures and immunohistochemistry in the original tissue. Results: This showed that mortal HNSCC cells express markers associated with motility and invasion, as well as several chemokines, whereas immortal HNSCC cells show elevated expression of cell-cycle markers and loss of differentiation markers. The distinctive mortal and immortal gene expression signatures were found in the tumours from which the cultures were derived, but those which gave rise to mortal cultures exhibited significant heterogeneity of gene expression pattern. Conclusions: These patterns of gene expression may reflect the differing origin of these cell populations. Mortal neoplastic keratinocytes lack telomerase when cultured in vitro, have WT p53, are more stable genetically and display a gene expression profile which has features of a stem cell origin. In contrast, immortal HNSCCs display characteristics expected in differentiated cells that have reactivated telomerase in response to telomeric erosion triggering p53 mutations and genetic instability. Our previous publications have demonstrated these features in vitro and others have reported similar findings in other cancer models. There is also evidence that tumours with the characteristics of the mortal class have a better prognosis in vivo, whereas the immortal phenotype is associated with poorer outcome. These surrogate markers of immortality could be valuable for prognosis and therapy if confirmed in larger in vivo studies.