This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Melanoma is a common human malignancy of increasing incidence and mortality in people over the age of 45. It is also increasing rapidly in the population under age 35. Overexpression and mislocalization of B-catenin, a cell adhesion and signaling molecule, has been shown to correlate with severity of melanoma and other malignancies. This occurs through down-regulation of its adhesive function and an increase in its transcriptional activation function, leading to unregulated proliferation. Retinoic acid (RA) is known to inhibit the growth rate and invasiveness of melanoma cell lines. Retinoids have been shown to regulate B-catenin signaling during development and can alter its function in breast cancer cell lines to produce a less malignant phenotype. The interaction of RA and B-catenin in melanoma has not been investigated. Our hypothesis is that B-catenin transcriptional activity is enhanced in melanoma and that RA will inhibit this activity. The hypothesis will be tested by characterizing 13-catenin expression and function in mouse B 16 melanoma cells, nonmalignant mouse melanocytes and in human melanoma cell lines derived from progressively more malignant tumors. The effect of RA on Bcatenin expression/function will be determined, including 13-catenin RNA and protein expression, cytoskeletal attachment, intracellular localization and reporter gene transactivation. It is expected that even if retinoic acid does not directly affect these measures, there will be important basic information derived on the status of g-catenin in melanoma compared to non-malignant melanocytes. To examine a functional link between 13-catenin action and the melanoma phenotype, constructs expressing constitutively active or dominant negative 13-catenin signaling proteins will b e used. Non-malignant cells will be transfected with active 13-catenin and tested for malignant transformation. Melanoma cells will be transfected with 13-catenin inhibitory proteins and examined for loss of the malignant phenotype. If it is determined t h at gene transactivation by 13-catenin drives a malignant phenotype in melanocytes, analysis by eDNA microarrays will be used to determine the population and pattern of genes induced. The physical interaction of 13- catenin and retinoic acid receptors w i ll be examined. These studies will provide the basis for future investigations of mechanisms by which 13-catenin function affects the development and progression of melanoma.dd%
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