Effects of arsenic and UVB radiation on induction of cyclin D1 in human keratinocytes.

Arsenic and Ultraviolet radiation B (UVB) are environmental toxins that have been linked to various epithelial cancers. Arsenic metabolism in humans leads to its collection in the skin, where it encounters and can act with known carcinogen UVB. Epidemiological evidence of the two toxins demonstrates their potential to affect signaling pathways, with various consequences. Here we employ an in vitro model system using Normal Human Epidermal Keratinocytes (NHEK) to identify the effect of arsenic and UVB on humans and whether they work synergistically. We find that although both cause induction of cyclin D1, culturing cells with both co-mutagens does not lead to a potentiated effect. Evidence from other systems indicates that both arsenic and UVB affect promoter activity in various ways, including methylation. We undertook to examine the effects of arsenite and UVB on activation of the cyclin D1 promoter related to changes in promoter methylation. While data had been inconclusive in identifying methylation as the cause of cyclin D1 induction, emerging trends seem to suggest an inverse relationship between methylation of the cyclin D1 promoter region and induction of cyclin D1. Finally, we aimed to create a reporter construct capable of directly demonstrating inductive effects of arsenic and UVB on the cyclin D1 promoter region through luciferase activity. Preliminary results demonstrate that arsenic led to a two-fold increase in luciferase activity, whereas UVB indicated that manipulation of the promoter region may not be the cause of induction