Objectives: CD49f is an adhesion molecule present on malignant lymphoblasts in B-cell
acute lymphoblastic leukemia; it is associated with a poor prognosis. CD49f expression
has been proposed as a marker for measurable residual disease (MRD) marker, but this
marker has yet to be implemented in clinical practice. Methods: In this study, we
used flow cytometry to detect CD49f expression by leukemic blasts in paired bone marrow
and cerebrospinal fluid samples at diagnosis and bone marrow at day 15 of treatment.
Results: At diagnosis, 93% of bone marrow and 100% of cerebrospinal fluid lymphoblasts
expressed CD49f. The intensity of CD49f expression statistically significantly increased
during treatment (P < .001). In MRD-negative end-of-treatment samples, only a small
population of hematogones expressed CD49f. Interestingly, the intensity of CD49f expression
varied among the different groups of recurrent genetic abnormalities. The ETV6::RUNX1
fusion and ETV6::RUNX1 combined with the high hyperdiploid group were associated with
increased expression, whereas the Philadelphia-like group showed low CD49f expression.
The lower CD49f expression at diagnosis predicted a lower MRD rate at day 15 of treatment.
Conclusions: We concluded that CD49f can be used as an MRD marker and possible prognostic
factor in B-cell acute lymphoblastic leukemia.
