The chemokines, MGSA/GRO and IL-8, are constitutively expressed in melanoma and appear to play a causal role in melanoma tumor progression. Evidence to date points to a transcriptional deregulation of the MGSA/GRO chemokine, partly through an endogenous activation of the transcription factor, NF- kappaB. An immediate upstream regulatory region (IUR) is located adjacent to the NF-kappaB element and in CAT reporter assays, mutation of this element drastically decreases basal transcription. The IUR element, TCGAT, binds three proteins, approximately 100, 40 and 22kD, and the binding of these proteins cannot be eliminated or supershifted in electrophoretic mobility shift assay by antibodies to other potentially relevant transcription factors. Preliminary data point to a potential interaction between the NF-kappaB and the novel IUR binding proteins. There are four specific aims for this proposal: 1) to characterize the process by which NF-kappaB is constitutively activated in Hs294T melanoma cells and determine whether NF-kappaB activation contributes to the endogenous transcription of MGSA/GRO in melanoma; 2) to purify, sequence and clone the proteins which bind to the immediate upstream region (IUR) of the MGSA/GROalpha gene enhancer, and to determine if these factors contribute to MGSA deregulation in melanoma; 3) to characterize the prevalence or coordinate deregulation of CXC chemokines in malignant melanoma; and 4) to determine whether overexpression of the mouse homolog of MGSA in normal melanocytes is associated with tumor formation in vivo, a transgenic model will be developed. Expression of the mouse homolog of MGSA/GRO, MIP-2, will be directed by the tyrosinase promoter which will result in melanocyte specific expression. We will treat the transgenic mice with chemical carcinogens and uv irradiation to determine how continued expression of these chemokines effects melanocyte response to agents involved in tumor initiation/progression. These experiments should provide important new information about the mechanism by which deregulation of the expression of chemokines chemotactic occurs and this is key to understanding how to suppress these mediators of tumorigenesis and chronic inflammatory response.
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