Differentiation induction subtraction hybridization (DISH): a strategy for cloning genes displaying differential expression during growth arrest and terminal differentiation.

Human cancers often display aberrant patterns of differentiation. By appropriate chemical manipulation, specific human cancers, such as human melanoma, leukemia and neuroblastoma, can be induced to lose growth potential irreversibly and terminally differentiate. Treatment of HO-1 human melanoma cells with a combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) results in irreversible growth arrest, a suppression in tumorigenic properties and terminal cell differentiation. A potential mechanism underlying these profound changes in cancer cell physiology is the activation of genes that can suppress the cancer phenotype and/or the inactivation of genes that promote the cancer state. To define the repertoire of genes modulated as a consequence of induction of growth arrest and terminal differentiation in human melanoma cells, we are using a differentiation induction subtraction hybridization (DISH) approach. A subtracted cDNA library, differentiation inducer treated cDNAs minus uninduced cDNAs, was constructed that uses temporally spaced mRNAs isolated from HO-1 cells treated with IFN-beta+MEZ. Approximately 400 random clones were isolated from the subtracted DISH library and analyzed by reverse Northern and Northern blotting approaches. These strategies resulted in the identification and cloning of both 30 known and 26 novel cDNAs displaying elevated expression in human melanoma cells induced to growth arrest and terminally differentiate by treatment with IFN-beta+MEZ. The DISH scheme and the genes presently identified using this approach should provide a framework for delineating the molecular basis of growth regulation, expression of the transformed phenotype and differentiation in melanoma and other cancers.