Topoisomerase IIalpha and IIbeta expression in childhood acute lymphoblastic leukaemia: relation to prognostic factors and clinical outcome

Background/Aims—Many regimens used in the treatment of childhood acute lymphoblastic leukaemia (ALL) include Daunorubicin or Etoposide, which act as topoisomerase poisons. It has been suggested that there may be a relation between topoisomerase expression and response to topoisomerase poisons, based mainly on results from in vitro studies. Therefore, the aim of this study was to investigate this relation in a clinical setting and determine whether topoisomerase IIα and IIβ might be of predictive value in ALL. Methods—Cellular expression of topoisomerases IIα and IIβ was assessed in 177 cases of ALL by immunohistochemistry using monoclonal antibodies to the two enzymes. The percentages of cell nuclei showing positive staining for topoisomerase IIα and IIβ expression were assessed. Results—Taking the series as a whole, a clear separation of survival curves was seen with the established prognostic markers white blood cell (WBC) count, CD10 status, and sex. However, topoisomerase IIα and IIβ expression showed no relation to survival. No association was found between the topoisomerases and the prognostic markers CD10 and WBC count; however, topoisomerase IIα expression was found to be related to sex, with expression being lower in girls (p = 0.002). Conclusions—These results suggest that the response to topoisomerase poisons cannot be predicted by the assessment of topoisomerase IIα and IIβ expression as defined by immunohistochemistry.