PECAM1 and acute myeloid leukemia: Having demonstrated that TNFα secreted by the AML blasts contributes to loss of CD31+Sca-1high ECs, we then reasoned that cytoreductive therapy that eliminates TNFα-secreting blasts could reverse the depletion of CD31+Sca-1high EC-lined vessels (i.e., arterioles) as observed in the leukemic BM niche.