[Functional activity and expression of P-glycoprotein in chronic myeloid leukemia]. / Funktsional'naia aktivnost' i ékspressiia P-glikoproteina pri khronicheskom mieloleikoze.

AIM: To evaluate the prognostic significance of P-glycoprotein (Pgp) in chronic myeloid leukemia (CML). MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: These data suggest that active Pgp contributes to CML BC (presumably to patient's response to therapy) but this contribution is not decisive.

[Characteristics of drug resistance of tumor plasmocytes in vitro in patients with multiple myeloma differently responsive to chemotherapy]. / Kharakteristika lekarstvennoi ustoichivosti opukholevykh plazmotsitov in vitro u bol'nykh mnozhestvennoi mielomoi s razlichnym otvetom na khimioterapiiu.

AIM: To determine sensitivity of tumor plasmocytes in vitro to cytostatic drugs (prednisolone, alkeran belustin, vincristine, rubomycin, doxorubicin, cytarabin, methotrexate, cysplatin, etoposide). MATERIAL AND METHODS: The sensitivity was measured with DISC method in 12 patients with multiple myeloma (MM) in two groups: resistant and responsive to induction polychemotherapy (PCT). RESULTS: The groups appeared significantly different by lowering of pathological paraprotein concentration (PIg): by 7.4 +/- 2.5% and 32.5 +/- 3.7%, respectively (p < 0.05). The resistance to the drugs was higher in the resistant patients than in the responders (0.7 +/- 0.28 versus 0.4 +/- 0.02, p < 0.05). PCT schemes of resistant patients contained 65.0 +/- 2.3% of ineffective drugs. In the responders the percentage was 35.7 +/- 5.3% (p < 0.05). CONCLUSION: The relationship exists between resistance of tumor plasmocytes to drugs in vitro and clinical findings.

[Adaptation of reverse transcriptase polymerase chain reaction for clinical diagnosis of expression of MDR1 gene]. / Adaptatsiia metoda obratnotranskriptaznoi tsepnoi reaktsii dlia klinicheskoi diagnostiki ékspressii gena MDR1.

Chemotherapy of malignant tumors is ineffective usually because of tumor cell resistance to it. Two types of resistance are known: cell resistance to a certain drug and multiple drug resistance (MDR). MDR covers a wide spectrum of drugs with different chemical structure and mechanisms of action. The most frequent cause of MDR is hyperexpression in the plasma membrane of P glycoprotein cells, which is coded for by MDR1 gene realizing active release of many cytotoxic substances from cells (Pgp-MDR). Acquisition of MDR phenotype by patient's cells impedes therapy and is often a poor prognostic sign, and therefore testing of material from cancer patients for MDR phenotype is important for selecting tumor therapy. We adapted the reverse transcriptase polymerase chain reaction (RT-PCR) to evaluating the MDR1 gene expression in peripheral blood cells of patients with hemoblastosis, assessed its sensitivity and specificity, and carried out clinical trials with blood samples from patients with MDR. Comparison of the results of RT-PCR with the findings of other methods used for detection of Pg-MDR showed their good correlation in the majority of cases. These results recommend these method for clinical practice in patients with hemoblastosis.

Studies of some mechanisms of drug resistance in chronic myeloid leukemia (CML).

CML is the myeloproliferative disorder connected with the specific chromosome translocation (9;22) and occurrence of the fusion gene/protein BCR-ABL. BCR-ABL protein is believed to inhibit apoptosis and to cause drug resistance. We investigated the correlation of two different forms of BCR-ABL mRNA in 94 pts with their overall survival. It was found that b2a2 (but not b2a3) mRNA expression correlates with longer survival of patients treated with chemotherapy. We did not find an influence of different types of BCR/ABL mRNA on the survival of pts treated with interferon-alpha. FAS/APO-1 antigen was expressed by the cells of 34% of the pts in CML blast crisis (BC) and directly correlated with the the expression of CD34, CD13 and CD14 differentiation antigens. FAS/APO-1 non-expression correlated with higher rate of remissions in BC. We investigated P-glyco-protein (Pgp) expression and functional activity in 40 BC CML pts. 2-fold shorter survival was found in the pts with Pgp expression. Pgp expression strongly correlated with CD13 antigen. Consecutive studies of pts in BC CML show that Pgp expressing cells often do not multiply in the course of BC CML. We postulate that Pgp may be regarded as differentiation marker of the cells and the unfavorable prognostic factor in BC CML.

Distinct effects of various p53 mutants on differentiation and viability of human K562 leukemia cells.

Mutations of the p53 tumor suppressor are often observed in various human tumors, including blast crisis of chronic myelogenous leukemia (CML). The pattern of p53 mutations in CML shows some peculiarities compared with majority of other malignancies. In particular, the substitutions at codon 273, one of the most common p53 alterations in various tumors, are not characteristic of CML. To test whether the distinctions in the pattern of p53 mutations are connected with some peculiarities of the biological effects of different mutant proteins in leukemic cells, we obtained and analyzed a panel of human K562 cell sublines expressing various exogenous p53; human Pro156, His175, His194, Trp248, and His273, or murine temperature-sensitive (ts) Val135 that has properties of mutant protein at 37 degrees C, but shows activities of the wild-type (wt) p53 at 32 degrees C. We have found that expression of wt-p53 enhanced the dependence of cells on growth/survival factors. Incubation of sparse (< 10(5) cells per/ml) K562/Val135 cultures at 32 degrees C caused apoptosis. In media conditioned by cells of different origin (K562, colorectal carcinoma LIM1215, Rat1 fibroblasts) the p53-dependent apoptosis was inhibited. Under such conditions the expression of ts-wt-p53 was accompanied by dramatic increase in the number of cells producing specific markers of erythroid differentiation-GlycPhA and Ag-Eb. Unlike to the wt-p53, the majority of tumor-derived mutant p53 (Pro156, His175, His194) increased cell survival in low serum and decreased the number of cells expressing Glyc-PhA, CD9, CD15, and CD71 differentiation antigens. On the other hand, expression of His273-p53 caused significant augmentation in the number of CD9-positive cells and enhanced the dependence on growth/survival factors that are present in serum or conditioned media. The data obtained allow to suggest that an unusual pattern of p53 mutations in CML reflects some peculiarities of biological effects of certain mutant proteins on differentiation and viability of leukemic cells.

[The effect of the tumor suppressor p53 and its mutant forms on the differentiation and viability of K562 leukemic cells]. / Vliianie opukholevogo supressora p53 i ego mutantnykh form na differentsirovku i zhiznesposobnost' leikoznykh kletok K562.

Mutations of the p53 tumor suppressor are often observed in various human malignancies including blast crisis of chronic myelogenous leukaemia (CML). The pattern of p53 mutation in CML shows some peculiarities as compared with the majority of other neoplasias. In particular, the substitutions at codon 273, one of the most common p53 alteration in various tumors, are not characteristic of CML. To test whether distinction in the pattern of p53 mutation are associated with certain peculiarities of biological effects of different mutant proteins in myeloid cells, we obtained and analysed a panel of human K562 cell sublines expressing various exogenous p53: human Pro156, His175, His194, Trp248 and His 273, or murine temperature-sensitive (ts) Val135 that has properties of mutant protein at 37 degrees C, but shows activities of wild-type (wt) p53 at 32 degrees C. We have found that expression of wt-p53 enhanced the dependence of cells on growth/survival factors, incubation of sparse (< 10(5) cells per/ml) K562/Val135 cultures at 32 degrees C caused apoptosis. In media conditioned by cells of different origin (K562, colorectal carcinoma LIM 1215, Rat1 fibroblast) the p53-dependent apoptosis was inhibited. In conditions that do not lead to apoptosis, the expression of ts-wt-p53 was accompanied by dramatic increase in the number of cells containing glycophorin A (GlycPhA) and "antigen of erythroblasts"--specific markers of erythroid differentiation. Unlike the wt-p53, the majority of tumor-derived mutant p53 (Pro156, His175, His194, Trp248) increased cells survival in media with low serum content and decreased the number of cell expressing GlycPhA, CD9, CD15 and CD71 differentiation antigens. On the other hand, expression of His273-p53 caused a significant augmentation in the number of CD9-positive cells and enhanced the dependence on growth/survival factors that are present in serum or conditioned media. The data obtained are consistent with the idea that unusual pattern of p53 mutations in CML can reflect the peculiarities of the effects of some mutant proteins on differentiation and/or viability of leukemic cells.