In vitro sensitivities to UVA of lymphocytes from patients with colon and melanoma cancers and precancerous states in the micronucleus and the Comet assays.

To use lymphocytes as surrogate cells to investigate their in vitro sensitivities to ultraviolet (UV) treatment in different cancers and precancerous states by comparison with lymphocytes from healthy control individuals was the main aim of this research. UV light induces precise cellular and genomic mutations. In this study, the effect of ultraviolet A (UVA) (320-400 nm) was used as a generic mutagen to evaluate in vitro different sensitivities from lymphocytes of patients with suspected melanoma (SM), malignant melanoma (MM), polyposis coli (PC) and colorectal cancer (CRC). DNA damage was evaluated by two different methods: the micronucleus (MN) assay and the Comet assay. The baseline frequency of MNs was significantly increased in lymphocytes from all patients (SM, MM, PC and CRC) when compared to healthy individuals. After UV irradiation, MN frequencies were significantly increased in lymphocytes of all groups, both patients and healthy individuals. However, the MN frequency in all patient groups was significantly higher than in the healthy individual group. Similar results for the induction of genomic DNA damage were obtained for the Comet assay. Also for the Comet assay, UVA-induced DNA damage for all four patient groups was significantly increased when compared to healthy individuals (SM, MM, PC and CRC groups: P < 0.001). Conclusively, peripheral lymphocytes from patients with cancers MM and CRC or precancerous states SM and PC are more sensitive to a generic mutagen such as UVA than lymphocytes from healthy individuals. This feature may be used as an essential biomarker to screen and diagnose precancerous states and cancers in early stages.