DNA-PK, ATM and MDR proteins inhibitors in overcoming fludarabine resistance in CLL cells.

AIM: To perform the comparative study of the effects of DNA-dependent protein kinase (DNA-PK) inhibitors vanillin and NU7026, ataxia telangiectasia mutated kinase (ATM)/ ATM and Rad3 related (ATR) kinase inhibitor caffeine and multidrug resistance (MDR) protein modulator cyclosporine A (CsA) on fludarabine resistant and sensitive lymphocytes from chronic lymphocytic leukemia (CLL) patients. METHODS: Cells sensitivity in vitro was determined with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). DNA-PKs and ATM expression in CLL cells was evaluated using Western blotting. Multidrug tansporter protein expression and function was assessed by flow cytometry. Pro- or anti-apoptotic genes (BAX, LICE BCL-2, BCL-XS FLICE, FAS, TRAIL) expression on mRNA level was evaluated. RESULTS: Caffeine, vanillin, NU7026 and CsA increased fludarabine cytotoxicity against fludarabine-resistant CLL cells samples in comparison with sensitive cell samples. However, fludarabine-sensitive CLL samples were sensitized with inhibitors to a greater extent compared with resistant CLL samples. ATM expression increased in fludarabine-resistant CLL samples, but no apparent correlation between DNA-PKs level and fludarabine sensitivity in vitro or sensitization effect of DNA-PK inhibitors were observed. Fludarabine-resistant CLL lymphocytes showed tendency for depressed MDR efflux and decreased level of mRNA of pro-apoptotic gene BCL-XS. CONCLUSION: Absence of any definite conformity between fludarabine-resistant cell susceptibility to combined action of fludarabine and inhibitors, and molecular pathways that might be involved in this process does not exclude drugs synergy in fludarabine-resistant cells that could be used for overcoming resistance to nucleoside analogs in CLL.

Different Mechanisms of Resistance to Lymphokine-activated Killer (LAK) Cells in Leukemic Cell Sublines Selected by Etoposide or by LAK Cells.

Two models of in vitro induction of human IM-9 lymphoblastoid cell line resistance to LAK cell-mediated killing were compared. IM-9 cell line variants were selected in vitro by prolonged exposure to LAK cells or to etoposide. Sensitivity to killing by LAK cells or by etoposide, conjugation with LAK cells and surface marker patterns were compared. Both LAK-cell-selected cell subline (IM-9/SL-15) and etoposide-selected cell subline (IM-9/ER) have acquired resistance to LAK cell-mediated death. IM-9/ER cells, but not IM-9/SL-15 cells, were 3.2-fold less sensitive to etoposide as compared to parental IM-9 cells. IM-9/SL-15 cells revealed decreased conjugation with LAK cells and augmented CDlla/CD18 surface molecule expression as compared to IM-9 line. In contrast, IM-9/ER cells displayed a level of conjugation with LAK cells equal to IM-9 cells, but loss of CD11a/C18 expression. Our results suggest different mechanisms of acquired resistance to LAK cells are operative in etoposide- or LAK-selected sublines, involving deterioration of LFA-1 molecule expression and altered conjugation properties, respectively.

Hematological Effects of Chernobyl In Belarus: Do They Really Exist Ten Years Later?

While analysing exposure of the lymphohemopoietic system of the population of Belarus to ionizing radiation as a consequence of the Chernobyl nuclear accident it should be stated that the separation of the effect of low level radiation from the whole set of other Chernobyl factors including the socio-psychological and environmental situation is not reliable as currently these factors cannot be quantified fully. Structural, metabolic or functional changes of blood cells registered in exposed people which are believed to be deterministic but which are not unidirectional, and are based sometimes on inappropriately controlled clinical observations, may be of significance for the evaluation of certain non-hematological diseases, as the deviations of hematopoietic and immune cell behaviour patterns may influence natural defence mechanisms, the incidence of diseases and their clinical manifestations. The risk of non-deterministic effects of irradiation associated with the Chernobyl accident is too low now for leukemias to be statistically found but it could not be ruled out entirely in future assuming combined unfavourable action of all environmental factors.

Frequencies of unstable chromosome aberrations in peripheral blood lymphocytes of Chernobyl emergency accident workers.

On the basis of the investigation of unstable chromosome aberrations in peripheral blood lymphocytes of Chernobyl accident emergency workers, of residents of the contaminated areas, of patients with blood diseases and of donor's blood irradiated in vitro it is stated that presence of unstable chromosome aberrations such as dicentrics in lymphocytes of emergency workers and residents indicates that they have been overexposed. However, in the absence of the described aberrations in individuals involved in emergency work or in residents years after accident it is impossible to reject the overexposure.

Study of the effect of the state of reparative regeneration of normal hemopoietic tissue on the leukemic process.

On the basis of the investigation of transplanted leukemia development in mice with induced reparative restoration of hemopoietic tissue, of the antileukemic activity of various components isolated from regenerating blood forming organs and of the underlying mechanisms of this action, it has been suggested that some growth regulator molecules in recovering hemopoietic tissue are a part of the natural antileukemic defence of the body and may be of special significance in leukemia treatment especially for residual leukemic cell inhibition as a strategy.