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ST 1.3 –
Efectos biológicos de las radiaciones ionizantes y Dosimetría biológica
GENE EXPRESSION PROFILE ASSOCIATED WITH
RADIORESISTANCE AND MALIGNANCY IN MELANOMA
Ibañez, Irene L.
1,2
; García, Francisco M.
3
; Bracalente, Candelaria
2
;
Zuccato, Camila F.
4
; Notcovich, Cintia
1
; Molinari, Beatriz
1
; Durán, Hebe
1,2,3
*
1
Comisión Nacional de Energía Atómica (CNEA). Argentina.
2
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Argentina.
3
Universidad Nacional de San Martín (UNSAM). Argentina.
4
Universidad Argentina de la Empresa (UADE)
* Responsible author, email: hduran@cnea.gov.a
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-over expressing celllines 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.