Podocalyxin is expressed in normal and leukemic monocytes

We have investigated the expression of podocalyxin in primary cultures of leukemic blast cells from 73 patients with acute myeloid leukemia. Podocalyxin was expressed at moderate levels in 15 patients and at high levels in 13 patients. The analysis of membrane markers showed that Podocalyxin expression in leukemic blasts was associated with a monocytic immunophenotype. Cases of podocalyxin-positive acute myelogenous leukemia had high blast cell counts at diagnosis and elevated CD123, CD135, VLA-4 and CXCR4 expression, features associated with poor prognosis. Podocalyxin expression in leukemic blasts was coupled with the concomitant expression of VEGF-R1, -R2, -R3 and Tie-2, the capacity to release VEGF-A and angiopoietin1 and the ability to differentiate into endothelial cells under appropriate culture conditions. These findings show that podocalyxin is a marker of acute myeloid leukemia with a monocytic phenotype and suggest that podocalyxin-positive cases of acute myeloid leukemia originate from the malignant transformation of progenitors common to the myeloid and endothelial lineages. These observations suggest a possible relationship between the monocytic lineage and podocytes.