GENE EXPRESSION PROFILE ASSOCIATED WITH RADIORESISTANCE AND MALIGNANCY IN MELANOMA

IBAÑEZ, IRENE L.; GARCÍA, FRANCISCO M.; BRACALENTE, CANDELARIA; ZUCCATO, CAMILA; NOTCOVICH, CINTIA; MOLINARI, BEATRIZ; DURÁN, HEBE

Buenos Aires

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

Sociedad Argentina de Radioprotección (SAR), Asociación Internacional de Protección Radiológica

The incidence of melanoma has substantially increased over the last decades. Melanomas respond poorly to treatments and no effective therapy exists to inhibit its metastatic spread. The aim of this study was to evaluate the association between radioresistance of melanoma cells and malignancy. A melanoma model developed in our laboratory from A375 human amelanotic melanoma cells was used. It consists in two catalase-overexpressing cell lines with the same genetic background, but with different phenotypes: A375-A7, melanotic and non-invasive and A375-G10, amelanotic and metastatic; and A375-PCDNA3 (transfected with empty plasmid) as control. Radiosensitivity was determined by clonogenic assay after irradiating these cells with a Cs137 gamma source. Survival curves were fitted to the linear-quadratic model and surviving fraction at 2 Gy (SF2) was calculated. Results showed that A375-G10 cells were significantly 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-A7 and A375-G10 respectively. Bioinformatic analysis of whole genome expression microarrays data (Affymetrix) from these cells was performed. A priori defined gene sets associated with cell cycle, apoptosis and MAPK signaling pathway were collected from KEGG (Kyoto Encyclopedia of Genes and Genomes) to evaluate significant differences in gene set expression between cells by GSEA (Gene Set Enrichment Analysis). A375-G10 showed significant decrease in the expression of genes related to DNA damage response (ATM, TP53BP1 and MRE11A) compared to A375-A7 and controls. Moreover, A375-G10 exhibited down-regulated gene sets that are involved in DNA repair, checkpoint and negative regulation of cell cycle and apoptosis. In conclusion, A375-G10 gene expression profile could be involved in radioresistance mechanisms of these cells. Thus, this expression profile suggests that A375-G10 could escape from DNA damage-induced apoptosis with the consequent progression in the cell cycle resulting in genomic instability and increase of malignancy.