Model cell culture system for defining the molecular and biochemical events mediating terminal differentiation of human melanoma cells.

Cancer cells are commonly less differentiated than their normal progenitors; a phenotype that correlates with loss of specialized functions and an increased capability to self-renew. Melanoma is an ideal model to analyze cancer progression and differentiation since a well-characterized process of step-wise tumor progression has been defined. Our lab previously described a combinatorial in vitro treatment protocol to induce terminal differentiation of human melanoma cells using a low dose of the PKC activator Mezerein (Mez) combined with interferon-beta (IFN-beta), which also activates IFN-stimulated gene expression in addition to the re-differentiation program. In principle, using an alternate way to induce terminal differentiation not including IFN-beta would be more compatible with gene expression profiling. A higher concentration of Mez alone induced terminal differentiation of HO-1 human melanoma cells as measured by morphological, growth and biochemical assays. Pre-treatment with the PKC inhibitor GF109203x blocked changes associated with differentiation and inhibited the ability of Mez to force irreversible/terminal differentiation. By combining this efficient method of inducing terminal differentiation with microarray analyses we now identify potential regulators of this process and demonstrate utility of this novel in vitro model in which to study the molecular determinants and mechanisms of human melanoma differentiation.