UVA-induced cell cycle progression is mediated by a disintegrin and metalloprotease/epidermal growth factor receptor/AKT/Cyclin D1 pathways in keratinocytes

He YY, Council SE, Feng L, Chignell CF
Source: Cancer Res
Publication Date: (2008)
Issue: 68(10): 3752-8
Research Area:
Cancer Research/Cell Biology
Dermatology/Tissue Engineering
Cells used in publication:
Species: human
Tissue Origin: dermal
Nucleofector® I/II/2b
1 million HaCaT cells at 90 % confluency were nucleofected with 1.5 µg cyclin D1 or ADAM17 specific siRNA using Kit V, program U-020; knock-down of approx. 75 respectively 90 % was achieved. Cy3-labeled siRNA was used as control and transfection efficiency was determined as ~95 %.
UVA (315-400 nm), which constitutes approximately 95% of the UV irradiation in natural sunlight, represents a major environmental challenge to the skin and is clearly associated with human skin cancer. Here, we show that a low, nonlethal dose of UVA induces dose-dependent cell cycle progression in human HaCaT keratinocytes. We found that UVA induced cyclin D1 accumulation, whereas siRNA knockdown of cyclin D1 blocked the UVA-induced cell cycle progression, indicating that this process is mediated by cyclin D1. UVA irradiation also induced AKT activation; when cells were incubated with phosphatidylinositol-3-OH kinase/AKT inhibitor or infected with dominant-negative AKT, cyclin D1 up-regulation, cell cycle progression, and proliferation were inhibited, suggesting that AKT activation is required for UVA-induced cell cycle progression. In contrast, extracellular signal-regulated kinase (ERK) was not activated by UVA exposure; incubation with ERK/mitogen-activated protein kinase inhibitor had no effect on UVA-induced cyclin D1 up-regulation and cell cycle progression. Activation of epidermal growth factor receptor (EGFR) was observed after UVA exposure. EGFR kinase inhibitor AG attenuated the UVA-induced AKT/cyclin D1 pathway and cell cycle progression, indicating that EGFR is upstream of AKT/cyclin D1 pathway activation. Furthermore, metalloprotease inhibitor GM6001 blocked UVA-induced cell cycle progression, and siRNA knockdown of a disintegrin and metalloprotease (ADAM)17 had a similar inhibitory effect, demonstrating that ADAM17 mediates the EGFR/AKT/cyclin D1 pathway and cell cycle progression to the S phase induced by UVA radiation. Identification of these signaling pathways in UVA-induced cell proliferation will facilitate the development of efficient and safe chemopreventive and therapeutic strategies for skin cancer.