Abundant expression of fibronectin is a major feature of leukemic dendritic cells differentiated from patients with acute myeloid leukemia.

Dendritic cells (DCs) are the most potent antigen-presenting cells responsible for the initiation of primary immune responses, playing a key role in eliciting effective antitumor immune responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with DC features. In order to identify genes differentially expressed in leukemia-derived DCs (AML-DCs), a polymerase chain reaction (PCR)-based subtraction approach was applied using cDNA from AML-DCs and monocyte-derived DCs from healthy donors as competitors. In the 548 sequences analyzed, 80% corresponded to fibronectin (FN) gene fragments. Overexpression of FN in AML-DCs was demonstrated both by semiquantitative PCR analysis and by immunostaining. In addition, we could show that FN was secreted by AML-DCs. Indeed, FN overexpression was already detectable in AML blasts of M4 and M5 subtype, and was significantly induced during DC differentiation after culture. Although the molecular events leading to overexpression of FN and the in vivo relevance of this phenomenon remain to be resolved, leukemic DCs appear to have specific patterns of differentiation, warranting stringent biological and cellular monitoring for the development and testing of leukemic DC-based immunotherapeutic strategies.