Differential expression of human endogenous retrovirus K transcripts in primary human melanocytes and melanoma cell lines after UV irradiation.

Human endogenous retroviruses (HERVs) are discussed as causative agents of various diseases including cancers. Expression of endogenous retroviral sequences can be induced by ultraviolet (UV) light, which is also considered as a cofactor in the development of cutaneous melanoma. Therefore, we investigated whether ultraviolet C (UVC) induces HERV-K rec and np9 expression in normal human epidermal melanocytes (NHEM) and in melanoma cell lines. NHEM and four different melanoma cell lines were irradiated with 10 and 30 mJ/cm(2) UVC, respectively. Expression of the HERV-K transcripts rec and np9 was measured 0, 6, 12, and 24 h after UV exposure by quantitative real-time PCR. In NHEM, HERV-K rec expression was significantly induced 24 h after UV exposure with 10 mJ/cm(2) UVC, whereas np9 expression transiently increased 6 and 12 h after irradiation with both UV doses. In contrast, in melanoma cell lines MEWO, G-361 and GR-M rec, and np9 expression was downregulated or remained unchanged after UV treatment. UVC irradiation induced HERV-K rec and np9 expression in NHEM, which might be an indicator of a functional role of Rec and/or Np9 in melanoma formation.