TNFSF4 and acute myeloid leukemia: Consistently, the interaction with either soluble or cell-bound OX40L might trigger the OX40 signaling, with OX40L being possibly provided by various cells of the immune system, but also by leukemic cells, even if no correlation between OX40 and OX40L expression on the very same AML blasts of a given patient was observed in our analysis.