Cutaneous chemical carcinogenesis is a complex biological process that may be divided into three distinct steps. Tumor initiation, the first stage, is characterized by genetic alterations. Tumor initiators require metabolic activation by cytochrome p450 1A1 (CYP1A1) to express their tumor initiating activity. Tumor promotion is the stage whereby initiated cells undergo clonal expansion resulting in papilloma formation. Promotion is characterized by a strong inflammatory response in the skin followed by increased DNA synthesis leading to epidermal cell proliferation and hyperplasia. In the final stage, progression, papillomas are converted to squamous cell carcinomas. Cytokines are a group of regulatory molecules which function as important mediators of numerous cell functions. In vitro studies have suggested that treatment of cultured keratinocytes with tumor initiators may upregulate certain cytokines. We hypothesize that treatment of the skin with chemical carcinogens upregulates cytokine production and that these increased cytokine levels lead to a dimunition of the resulting degree of tumorigenesis by protecting animals from the adverse effects of DMBA exposure. To test this hypothesis, CD1 mouse skin will be initiated with 7,12-dimethylbenz(a) anthracene (DMBA). To determine if initiation affects cytokine gene expression, we will determine the mRNA levels of interleukin-1 (IL-1)alpha and Beta, interleukin-6 (IL-6) and tumor necrosis factor (TNF) alpha in DMBA initiated mice by slot blotting. By pretreating with the anti-initiator, clotrimazole, prior to initiation with DMBA, we will determine whether the effects of DMBA on cytokine mRNA expression requires metabolism via cytochrome P450 dependent enzymes. We will evaluate whether the induction of cytokines serves to protect animals with antibodies that neutralize the biological activities of cytokines (IL-1a and B, IL-6) and TNF-alpha). We will examine their effects on initiation by determining DMBA-DNA adduct formation as well as their effects on DMBA/TPA induced skin tumorigenesis. These studies will elucidate the effects that tumor initiators have on cytokine expression in the skin and will expand our understanding of the potential regulatory role that these multifunctional molecules may play in cutaneous carcinogenesis. Furthermore, these studies may lead to insights relevant to the treatment of human non-melanoma skin cancers.
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