[The clinical significance of the expression of the multiple-drug resistance protein P-glycoprotein in chronic myeloleukemia]. / Klinicheskoe znachenie ékspressii belka mnozhestvennoi lekarstvennoi ustoichivosti P-glikoproteina pri khronicheskom mieloleikoze.

Cell resistance to pharmaceutical agents arises among other causes because of multiple drug resistance induced by P-glycoprotein (P-gp). The analysis of expression of P-gp and differentiation antigens of hemopoietic cells has been made on myeloid cells from 14 patients in CML chronic phase and 25 with CML acceleration and in blast crisis. Surface antigen expression was evaluated at flow cytofluorimetry (FACScan unit). Fluorescent dye rodomin (Rh123) helped examine P-gp functional activity. A close relationship is shown between P-gp expression and CD34 (r = 0.69. p = 0.0004), this giving evidence of these antigens expression on the same cells. In chronic phase P-gp is expressed on a few cells in some patients, its activity being low or absent. The appearance of UIC-2+ cells was unrelated to previous chemotherapy and brought no resistance to treatment. In terminal stage P-gp is expressed in 50% of cases. Functional tests identified the active protein in blast populations with a large number of UIC-2+ cells and in some patients with a small number of cells expressing P-gp. Therefore, comprehensive clinical investigations are needed of multiple drug resistance, though in half of the resistant patients in AML blast crisis P-gp+ cells were not identified suggesting the existence of other mechanisms responsible for resistance to treatment.

[A "primitive" variant of the blast crisis in chronic myeloleukemia]. / "Primitivnyi" variant blastnogo kriza khronicheskogo mieloleikoza.

While immunotyping blast cells from 45 patients with CML blast crisis, we detected 5 cases with immunologically primitive blast cells. The immunological phenotype of these cells corresponded to that of primitive stem cells which are characterized by expression of CD34 and HLA-DR antigens in the absence of other immunological markers. We suggest that blast cells from these patients may undergo differentiation similar to that of primitive stem cells that implies the existence of a new immunological variant of CML blast crisis, a primitive variant. Morphologically, blast cells in 3 cases could be classified as myeloid, in 2 cases precise identification was impossible. Cytochemically, this type of cells can be defined as mixed. The patients with CD34+ phenotype do not differ clinically or hematologically from those with CML blast crisis. Blast cells with membrane marker CD34 are likely to arise in any CML phase either as a component of overall leukemic population or predominant, single subclone.