Keratinocytes tumor promoter

Tumor promoters convert some basal keratinocytes to an embryonic phenotype similar to the dark cells thereby supplying a positive environment for the dark cells to expand in number. 

Hennings, H. et al.. Activity of diverse tumor promoters in a keratinocyte co-culture model of initiated epidermis. Carcinogenesis, 13, 2145, 1992. 

PTX (1) also caused a significant reduction in the actin cytoskeleton as with other polyol and polyether toxins such as pectenotoxin-6 and maitotoxin [33]. Thus, the cytoskeleton is suggested to be an early target for the toxic effect of such toxins. Furthermore, the skin tumor promoter activity of palytoxin has gathered attention. Notably, palytoxin did not activate protein kinase C but extracellular signal-regulated kinase (ERK) through a mechanism that involves inactivation of an ERK phosphatase in keratinocytes derived from initiated mouse skin [34]. 

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