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P-glycoprotein (P-170) is the phenotypic marker of tumoral cells that show the phenomenon of multidrug resistance (MDR). Using an immunocytochemical approach, we employed the monoclonal antibody C219 (which recognizes an epitope of such a glycoprotein) to evaluate in cytologic samples the expression of P-170 on neoplastic cells from 52 patients affected by different hematologic malignancies and its eventual correlation to clinical outcome. Longitudinal studies were also performed in 14 patients. Results obtained demonstrated that a) the so-called "MDR phenotype" may be heterogeneously represented (from less than 1 to 100% of positive cells) in hemopoietic tumors at diagnosis (without exposure to pharmacologic agents), as well as during the course of the disease, although a more substantial presence of P-170 occurred in treated patients. There was no correlation between neoplastic kinetic activity (such as expression of Ki 67 recognized nuclear proliferation-associated antigen) and P-170-positive cells. b) Percentage of positive cells as well as intensity of staining seemed to be important in determining MDR; in general, there was a strong correlation between expression of P-170 in more than 20% of neoplastic cells and a lack of response to chemotherapy. However, some false-positive and false-negative cases were observed. c) The detection of scattered P-170-positive cells may predict a pharmacologic selection of intrinsic or mutant-resistant clones.

Beta 2-microglobulin (B2m) was measured on serum samples in 274 patients with acute and chronic lymphoproliferative disorders (85 non-Hodgkin lymphomas-NHL, 30 Hodgkin lymphomas-HL, 34 B-cell chronic lymphocytic leukemias-B-CLL, 8 Waldenström macroglobulinemias-WM, 76 multiple myelomas-MM, 31 acute lymphoblastic leukemias-ALL, 10 hairy cell leukemias-HCL). Two hundred and four patients were studied at the time of diagnosis, and results were correlated to clinical stage, and histologic subtype in NHL, immunoglobulin type in MM, and immunologic phenotype in ALL. Moreover, B2m was tested during and after chemo- and/or radiotherapy, and results were correlated to response, progression or relapse. Elevated pretreatment B2m values were found in widespread forms of NHL and HL, in patients with B symptoms and in the unfavorable histologic subgroups of NHL. Rapid falls in levels followed therapy institution. In B-CLL and in MM a close relationship between B2m and cell mass was found. A significant B2m level reduction followed treatment, whereas its increase could detect a relapse. In ALL, serum B2m was only slightly above the normal range. B2m seems to reflect the total burden of malignant cells mainly in MM and B-CLL; in other lymphoproliferative disorders it provides less prognostic information.