IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Plasticity in Melanoma-associated-Antigens in human melanoma clonogenic cells
Autor/es:
M ARIS; JM ARRIAGA; A I BRAVO; M BIANCHINI; MM BARRIO; J MORDOH
Lugar:
Ciudad Autónoma de Buenos Aires
Reunión:
Congreso; Primer Congreso Franco Argentino de Inmunología (FAIC, French-Argentine Immunology Congress); 2010
Institución organizadora:
Sociedad de Inmunología Argentina - Sociedad de Inmunología Francesa
Resumen:
Cutaneous melanoma (CM) is the neoplasia with the fastest growing incidence. It expresses immunogenic Melanoma Associated Antigens (MAA) such as MART-1, gp100, and the cancer testis Ag NY-ESO-1. Since CM tends to down-regulate MAA expression, it is important to investigate if such down regulation affects cell proliferation. We studied anchorage-independent growing clonogenic cells (CC) of two human CM cell lines (MEL-XY1 and MEL-XY3) as a model of in vitro proliferation. Two growth stages were analyzed: an early stage, after 7 days, with colonies of about 100 cells, and a late stage, after 14 days, with colonies of several thousand cells, many of them with apoptotic/necrotic cores. We analyzed MART-1, gp100 and NY-ESO-1 Ags and the proliferation marker Ki-67 by IHQ. At 7 days, MEL-XY3 only had MART-1/gp100+ colonies, whereas MEL-XY1 colonies were either positive (49%), negative (21%) or mixed (30%). Since every colony was Ki-67+, it is concluded that the expression of MAA does not interfere with the proliferative potential. These observations were in accordance with MAA expression in biopsies and source lines. Lysis by specific CTL clones for MART-1 and gp100 on heterogeneous CC revealed that only positive cells were lysed (0.3% survived). By 14-days, the proportion of positive colonies for MART-1 and gp100 expression decreased, and mixed colonies increased (p<0,05). Both cell lines were uniformly NY-ESO-1+ in 7 and 14-day colonies. Then, NY-ESO-1 expression appears necessary to CC proliferation. Another objective was to elucidate intrinsic mechanisms governing MAA expression. We studied CpG methylation in MART-1 promoter by MSP, and found that the MEL-XY1 CC promoter was 60 fold more methylated than the MEL-XY3 CC one. Thus, Methylation of MART-1 promoter would be involved in MART-1 heterogeneity. Therefore, melanoma CC showed plasticity for MAA expression in time, and immunotherapeutic strategies should take this into account.