Modulation of CD13 expression during retinoic acid-induced differentiation of HL60 cells.

CD13/aminopeptidase-N, an enzyme expressed by myeloid cells, may be important in the regulation and signalling pathways that control myeloid growth and differentiation. In this study we have used the myeloid leukaemic cell line HL60, and its ability to differentiate when induced by all-trans-retinoic acid (ATRA), to study the regulation of CD13 molecules, and its associated aminopeptidase-N enzyme activity during the myeloid differentiation pathway. In addition, the effect of the growth factor granulocyte-macrophage colony stimulating factor (GM-CSF) on CD13 expression, by undifferentiated and differentiated HL60 cells, has been investigated. Our results show that CD13 expression, and its enzyme activity, is downregulated during differentiation of HL60 induced by ATRA, but not when using GM-CSF.