[Functional activity and expression of P-glycoprotein in chronic myeloid leukemia]

To evaluate the prognostic significance of P-glycoprotein (Pgp) in chronic myeloid leukemia (CML).

Functional activity (rhodamine 123 test) and expression of Pgp (binding of UIC2 monoclonal antibodies by cells) were evaluated by flow cytofluorometry. A total of 141 samples of peripheral blood from 121 patients with various stages of CML were examined.

The number of patients whose cells express functionally active Pgp increases during the blast crisis (BC) in comparison with the chronic phase (CP). Repeated testing of patients with BC and CP showed that Pgp-expressing cells can disappear from the peripheral blood of patients despite the treatment by Pgp preparations and substrates. However the number of cases with expression and functional activity of Pgp increases in the course of BC. Several patients in whom functionally active Pgp was not detected during diagnosis of BC had longer BC phase than patients with the active protein.

These data suggest that active Pgp contributes to CML BC (presumably to patient's response to therapy) but this contribution is not decisive.