Expressão da molecula do MHC classe I pelo tumor de Walker 256 durante sua conversão de variante A (agressiva) em variante AR (regressiva)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Novel tumor cell variants can be obtained by serially passaging tumor cells in different media and/or environments. In vivo environmental selective pressures usually account for this phenomenon, leading to tumor cell changes and/or clonal expansions. Serial intraperitoneal (ip) passages of the Walker 256 (W256) tumor A variant was followed in rats for studying the generation of its immunogenic AR variant. The MHC class I molecule expression was assessed by flow cytometry, since variations in this molecule, would explain changes in tumor cell immunogenicity. The AR variant was identified in every ip passage (20x106 tumor cells every 4-5 days) by an increase in red blood cell (RBC) osmotic fragility (OF) with marked spleen hypertrophy, whereas the A variant was identified by a decrease in RBC OF with moderate spleen hypertrophy. Within 25 ip passages, all serial repetitions shifted from A to AR variant. The number of ip passages required for the shift was variable. Subsequently, tumor cells were rejected in one experimental repetition and immunity against the AR and A variants was conferred. The relative fluorescence intensity was 1,6 times higher in the AR variant (n=15, 14.21±1.32) than in the A variant (n=10, 9.10±1.22) showing an increase in the number of MHC class I positive cells.These data provide evidence that the generation of the AR variant could result from factors present in the ip environment leading to an increase in the number of W256 MHC class I positive tumor cells, probably due to immune cell selection of MHC class I negative tumor cells

ASSUNTO(S)

cancer celulas cancerosas imunologia tumores

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