FLT1 and cancer: Further functional, immunophenotypic, biochemical and molecular studies (e.g., inhibition of T-cell proliferation, reactive oxygen species production or expression of Arginase 1, Lox-1 or VEGFR1) (32, 79, 80) in e.g. PB from cancer patients are required to determine the degree of overlap between these populations and which additional markers would potentially be required to differentiate them.