For example, we did not observe diminished keratohyalin granules, filaggrin, and involucrin expression in adult epidermis and we did observe an uncoupling of involucrin and loricrin expression in adult epidermis.
Hypoxia inhibits differentiation in some cell lines (Sahai et al, 1997) and possibly in breast carcinomas (Helczynska et al, 2003), but the association between hypoxia and involucrin expression indicates that this might not be true for squamous cell carcinomas.
Squamoid features and involucrin expression, detected in 22% and 27% of cases respectively, correlated with each other and were associated with high-grade atypia, a solid-nest pattern, cancer cell necrosis on histology and negative oestrogen receptor status.
However, both pimonidazole binding and involucrin are easily detected within 2 h of hypoxic exposure in vitro making this explanation less likely.
Thus, by the criteria of increased clonal growth ability and reduced involucrin expression [9] the SCC lines appear to contain a higher proportion of stem cells than primary keratinocytes.
Immunostaining of postconfluent SCC9 cell cultures showed punctate patterns for both involucrin expression and pimonidazole binding.
Figure 4 shows representative examples of immunostaining for involucrin expression and pimonidazole binding in contiguous sections taken from squamous cell carcinomas of the head neck.
While we did not examine inter-clonal differences within the SCC lines [2], the overall increase in colony forming efficiency and decrease in involucrin expression would indicate an expansion of the stem cell compartment.
Likewise, S100A16-H357 xenografts were found to be more differentiated and less proliferative, both histologically and at the molecular level as evidenced by the higher involucrin expression and lower expression of Ki67 and Bmi-1 (Fig. 6c– j).
38 Cornified envelope formation, involucrin expression and transglutaminase activity are increased in keratinocytes treated with cell permeable ceramides.
