Gene expression profile associated with radioresistance and malignancy in melanoma

IBAÑEZ IL; GARCIA, FM; BRACALENTE C; ZUCCATO CF; NOTCOVICH C; MOLINARI B; DURAN H

Buenos Aires

Congreso; X Congreso Regional Latinoamericano IRPA de Protección y Seguridad Radiológica; 2015

The incidence ofmelanoma has substantially increased over the last decades. Melanomas respondpoorly to treatments and no effective therapy exists to inhibit its metastaticspread. The aim of this study was to evaluate the association betweenradioresistance of melanoma cells and malignancy. A melanoma model developed inour laboratory from A375 human amelanotic melanoma cells was used. It consistsin two catalase-overexpressing cell lines with the same genetic background, butwith different phenotypes: A375-A7, melanotic and non-invasive and A375-G10,amelanotic and metastatic; and A375-PCDNA3 (transfected with empty plasmid) ascontrol.Radiosensitivity wasdetermined by clonogenic assay after irradiating these cells with a Cs137gamma source. Survival curves were fitted to the linear-quadratic model and survivingfraction at 2 Gy (SF2) was calculated. Results showed that A375-G10 cells weresignificantly more radioresistant than both A375-A7 and control cells,demonstrated by SF2 and α parameter of survival curves: SF2=0.32±0.03, 0.43±0.16 and 0.89±0.05 and α=0.45±0.05, 0.20±0.05 and 0 for A375-PCDNA3, A375-A7and A375-G10 respectively.Bioinformaticanalysis of whole genome expression microarrays data (Affymetrix) from thesecells was performed. A priori defined gene sets associated with cell cycle,apoptosis and MAPK signaling pathway were collected from KEGG (KyotoEncyclopedia of Genes and Genomes) to evaluate significant differences in gene setexpression between cells by GSEA (Gene Set Enrichment Analysis). A375-G10showed significant decrease in the expression of genes related to DNA damageresponse (ATM, TP53BP1 and MRE11A) compared to A375-A7 and controls. Moreover, A375-G10exhibited down-regulated gene sets that are involved in DNA repair, checkpointand negative regulation of cell cycle and apoptosis. In conclusion, A375-G10gene expression profile could be involved in radioresistance mechanisms ofthese cells. Thus, this expression profile suggests that A375-G10 could escapefrom DNA damage-induced apoptosis with the consequent progression in the cellcycle resulting in genomic instability and increase of malignancy.