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Biomedical subjects

M Osmak

Publications and source records attributed to M Osmak.

At least 37 records · Page 2Linked to original sources
PubMed1997

Ascorbic acid and 6-deoxy-6-chloro-ascorbic acid: potential anticancer drugs.

The role of ascorbic acid (AA) in prevention and suppression of carcinogenesis has been known for a long time. It was also found that AA may inhibit the growth of some tumor cells in vitro and in vivo. We examined the influence of ascorbic acid and 6-chloro-6-deoxy ascorbic acid (6-Cl-AA) on the growth of various human cell lines: lung fibroblasts (Hef), ovarian adenocarcinoma (OVCAR), colon adenocarcinoma (HT-29), laryngeal carcinoma (HEp2) cells, HEp2 cells resistant to vincristine (HEp2VA3), cervical carcinoma (HeLa) cells, HeLa cells resistant to cisplatin (Helacis), breast adenocarcinoma (SK-BR-3) cells, and SK-BR-3 resistant to doxorubicin (SK-BR-3-Dox), as well as mouse fibroblasts L929, mouse melanoma B16 (Mel B16) cells and Chinese hamster fibroblasts (V79). Both drugs arrested the growth of: HeLa, SK-BR-3, SK-BR-3-Dox, L929, and Mel B16 cells, but did not influence the growth of others: Hef, OVCAR, HEp2, HEp2VA3 and V79. 6-Cl-AA suppressed more the proliferation of HeLacis, SK-BR-3-Dox and Mel B16 cells than AA, while AA was active only against HT-29 cells. Inhibitory effect of 6-Cl-AA was confirmed by the in vivo experiments on solid melanoma B16 tumors. Our results indicate that AA and 6-Cl-AA could serve as potential antitumor agents, especially against some tumor cells resistant to chemotherapy.

Animals↗
PubMed1997

Characterization of human breast adenocarcinoma SK-BR-3 cells resistant to doxorubicin.

Doxorubicin shows a wide spectrum of activities in solid tumors, especially against breast carcinoma. The aim of this study was to examine if doxorubicin, when given at lower concentrations than applied in clinic, may induce changes in treated cells. With this purpose we developed human breast adenocarcinoma SK-BR-3 cell line resistant to doxorubicin. The sensitivity of these cells to doxorubicin and to some other cytostatics used in cancer treatment was determined by colorimetric MTT assay. Some parameters which may be of importance as prognostic factors in treatment of breast cancer were analyzed as well. The expression of genes involved in mitotic signal pathway (EGF, TGF alpha, EGF-R, erbB-2, erbB-3, c-myc and c-H-ras) was determined immunocytochemically. The concentrations of cathepsins were determined using quantitative immunoreactive assays (cathepsins B and L) or immunoradiometric assay (cathepsin D). The results revealed that even low doses of doxorubicin can induce numerous changes in treated cells: they become resistant to doxorubicin, and cross-resistant to several other cytostatics. The expression of the above mentioned genes involved in mitotic signal transduction, as well as cathepsins D and L, was similar in both parental and doxorubicin treated cells.

Adenocarcinoma↗
PubMed1997

Glutathione S-transferase activity as an early marker for malignant tumors of corpus uteri.

Glutathione (GSH) concentrations and glutathione S-transferase (GST) activities were determined in 30 paired malignant human corpus uteri tumor samples and in samples of adjacent normal tissues. For GSH concentrations no difference was found between normal (126.0 +/- 52.4 nmol/mg protein) and tumor tissues (110.1 +/- 46.4 nmol/min/mg protein; p = 0.219). The GST activities were significantly higher in tumor tissues (322.4 +/- 135.54 nmol/min/mg protein) than in corresponding normal tissues (224.6 +/- 95.64 nmol/min/mg protein; p = 0.005). This activities were independent on the pathohistological and clinical factors, except for positive lymphovascular invasion and myometrial invasion (over 50%), where significantly lower GST activities were found. For normal tissues the positive correlation between GSH concentrations and GST activities was found (correlation coefficient = 0.50, p = 0.005), but not for tumor tissue (correlation coefficient = 0.20, p = 0.281). The prognosis of patients (according to the well established prognostic factors, such as tumor type, myometrial invasion and grades) who had lower GSH concentration and GST activity in normal tissue was similar to those with higher GSH concentration and GST activity. In conclusion, higher GST activities found in tumor of corpus uteri suggest, that GST activity could be used as a tumor marker for the early stages of these malignant tumors.

Adult↗
PubMed1995

Modulation of resistance to cisplatin by amphotericin B and aphidicolin in human larynx carcinoma cells.

The aim of this study was to examine whether resistance to cisplatin [cis-diamminedichloroplatinum (II)] (CDDP) could be overcome by amphotericin B, cyclosporin A and aphidicolin in two sublines of human larynx carcinoma HEp2 cells. The sensitivity of parental and cisplatin-resistant CA3 and CK2 cells to amphotericin B, cyclosporin A and aphidicolin, and also the effects of these drugs (given in maximal nontoxic concentrations) on cisplatin sensitivity were determined by clonogenic survival assay. CA3 and CK2 cells were sensitive to amphotericin B, and resistant to cyclosporin A and aphidicolin, compared with their parental cells. Amphotericin B increased cisplatin toxicity 2-fold in CA3 cells and 2.7-fold in CK2 cells, while it had no effect in parental HEp2 cells. Cyclosporin A did not influence the sensitivity of examined cells to cisplatin. The sensitizing effect of aphidicolin was more obvious in cisplatin-resistant cells. Cisplatin toxicity was increased by aphidicolin: 1.5-fold in HEp2 cells, 2-fold in CA3 cells, and 1.9-fold in CK2 cells. Therefore, the resistance to cisplatin in human larynx carcinoma CA3 and CK2 cells can be partially reversed by amphotericin B and aphidicolin.

Amphotericin B↗
PubMed1995

Characterization of carboplatin-resistant sublines derived from human larynx carcinoma cells.

In human larynx carcinoma cells, resistance to carboplatin (CBDCA) was induced by continuous five-day exposure of parental lines to the increasing CBDCA concentrations in culture medium, reaching the clinical level of 9.23 micrograms/ml. Three clones were selected and characterized: CBP-3, CBP-6 and CBP-7, CBP-3 clone was 2.0-fold, CBP-6 2.1-fold, and CBP-7 2.9-fold more resistant to carboplatin. The response of these sublines to different cytostatics was compared to the response of the parental cell lines to the same drug. CBP-7 and CBP-6 clones exhibited cross-resistance to cisplatin (cis-DDP), CBP-7 clone became markedly more sensitive and CBP-3 slightly more sensitive to 5-fluorouracil (5-FU), CBP-6 became sensitive to etoposide (Et), CBP-6 became sensitive and CBP-7 resistant to vinblastine (VBL). Other clones did not change change their sensitivity to cis-DDP, 5-FU, Et or VBL. None of the three clones did alter the sensitivity to mitomycin C, doxorubicin (Dox) or vincristine (VCR). There was no change in the growth rate. Glutathione (GHS) levels were elevated in all three clones, but the increase was significant only for CBP-7 clone. Similarly, the activity of glutathione transferase (GST) was elevated in all clones, but this increase was not significant for CBP-7 clone. The analysis of the of c-myc, c-Ha-ras and c-fos genes reveal no change in the c-myc expression, induction of the c-Ha-ras oncogene in CBP-6 and CBP-7 cells, and biochemistry and oncogene expression indicate that the acquired resistance to carboplatin is a complex, multifactorial process in these cells.

Antineoplastic Agents↗
PubMed1994

Low doses of gamma-rays can induce the expression of mdr gene.

We reported earlier that human cervical carcinoma HeLa cells exposed to 30 fractions of 0.5 Gy gamma-rays became resistant to cisplatin, methotrexate and vincristine, but retained the same sensitivity to gamma-rays and ultraviolet light. The aim of this study was to examine whether a small number of gamma-ray fractions, with a lower daily dose, may also change the sensitivity of preirradiated cells to different cytotoxic drugs. Using the modified MTT staining procedure, we found that cells preirradiated with 5 or 10 daily fractions of only 0.17 Gy gamma-rays did not alter their sensitivity to mitomycin, cisplatin, methotrexate, 5-fluorouracil, etoposide and doxorubicin. However, 10 fractions of gamma-rays induced resistance to vincristine and vinblastine. Our immunocytochemical experiments using monoclonal antibody JSB-1 show that the plasma membrane P-glycoprotein is involved in the induced resistance to Vinca alkaloids.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Human larynx carcinoma cells resistant to cis-diamminedichloroplatinum(II): mechanisms involved in the resistance.

The aim of this study was to characterize two cis-diamminedichloroplatinum(II) (CDDP) resistant cell lines established from human larynx carcinoma HEp2 cells through repeated treatments with increased CDDP concentrations. CK2 cells obtained by continuous treatments were more resistant to CDDP than CA3 cells obtained by acute treatments. The examination of growth characteristics showed that both CDDP resistant cells had doubling times identical to that of the parental cells, but had lower plating efficiency. The possible involvement of glutathione (GSH), glutathione transferases (GST), metallothioneins, P-glycoprotein and drug accumulation in CDDP resistance was examined. Glutathione contents were elevated in both CDDP resistant lines. However, neither GSH nor GST were involved in CDDP resistance. This was demonstrated by simultaneous incubation of parental and CDDP resistant cells with CDDP and specific inhibitors of GSH and GST alpha and pi (buthionine sulfoximine and ethacrinic acid). Similarly, verapamil, an inhibitor of P-glycoprotein, did not influence the sensitivity of parental and resistant cells to CDDP. As compared to the parental cells, CK2 cells became resistant and CA3 cells became sensitive to cadmium, indicating increased level of metallothioneins in CK2 cells, and reduced level in CA3 cells. Measurements of platinum contents in parental and CDDP resistant cells after 1, 3 and 6 hours exposure to 70 mumol CDDP showed reduction in platinum accumulation after each exposure time in CK2 cells, and after 6 hours exposure in CA3 cells. This study identified decreased platinum accumulation as an important mechanism of CDDP resistance in human larynx carcinoma cells.

Buthionine Sulfoximine↗
PubMed1994

Human larynx carcinoma cells resistant to cis-diamminedichloroplatinum(II): cross-resistance patterns.

In our previous study we developed two lines of human larynx carcinoma HEp2 cells resistant to cis-diamminedichloroplatinum(II) (CDDP) due to acute (CA3 cells), or continuous (CK2 cells) treatments with increased CDDP concentrations. CA3 line was 2.3-fold resistant, and CK2 line 3.7-fold resistant to CDDP as compared to the parental cells. In this study the sensitivity of CDDP resistant and parental cells to several antitumor drugs was examined using clonogenic survival assay. CK2 cells were 1.7-fold more resistant to vincristine than parental cells, while CA3 cells exhibited resistance to vincristine only at higher concentrations of this drug. Verapamil, an inhibitor of P-glycoprotein, was not able to reverse the resistance of CK2 cells to vincristine, indicating that this cross-resistance did not involve P-glycoprotein. As compared to the parental cells, CK2 cells were 2.1-fold resistant, and CA3 cells 1.7-fold resistant to mitomycin C. CK2 cells were 2-fold more resistant to 5-fluorouracil than the parental cells, while CA3 cells did not exhibit any change in the sensitivity to this drug. CA3 cells were 0.4-fold sensitive to epoxide and 0.53-fold sensitive to doxorubicin, while CK2 cells had the same sensitivity to these drugs as the parental cells. Our results showed that treatment schedule determines the response of CDDP resistant human larynx carcinoma cells to additional drugs, suggesting the complexity of the judicious choice of the drugs in the combined modality treatments of cancer.

Antineoplastic Agents↗
PubMed1993

The characterization of two human cervical carcinoma HeLa sublines resistant to cisplatin.

Human cervical carcinoma HeLa cells were made resistant to cisplatin by one of two schedules; "acute" (cells repeatedly treated with cisplatin for 1 h in serum-free medium--CA cells) or "continuous" (cells treated repeatedly for 24 h in complete medium--CK cells). The sensitivity of CA and CK sublines to cisplatin and various other antineoplastic drugs was determined by the modified MTT staining procedure. The possible involvement of glutathione (GSH), glutathione S-transferases (GST) and metallothioneins (MT) in cisplatin resistance was examined. The results show that acutely treated CA cells became more resistant to cisplatin than CK cells. The resistance to cisplatin does not involve either glutathione or glutathione transferase. The increased levels of metallothioneins might be involved in the development of resistance. The sensitivity of CA and CK sublines to the selected drugs was different from that of the parent cells. Both sublines became cross-resistant to vincristine and methotrexate, but only CA cells exhibited cross resistance to etoposide doxorubicin and 5-fluorouracil. Thus, the development of resistance to cisplatin is a consequence of numerous intracellular alterations that are reflected in cell response to a variety of anticancer drugs. The response depends on the schedule of resistance development and on the nature of the secondary agent.

Antineoplastic Agents↗
PubMed1993

Resistance of human larynx carcinoma cells to cisplatin, gamma-irradiation and methotrexate does not involve overexpression of c-myc or c-Ki-ras oncogenes.

In our previous study, we achieved resistance to cisplatin or vincristine (VCR) by repeated treatments of human larynx carcinoma HEp2 cells with these drugs. Resistant cells were cloned and four clones were selected: CA3 and VA3 clones were selected from cells acutely treated with cisplatin or VCR, while CK2 and VK2 cells were selected from cells chronically treated with cisplatin and VCR, respectively. The aim of this study was to examine whether the development of resistance to cisplatin and vincristine changes the expression of c-myc and c-Ki-ras oncogenes and to determine whether there is a correlation between the expression of these oncogenes and the sensitivity of selected clones to cisplatin, methotrexate and gamma-rays. The cell sensitivity to cisplatin, methotrexate and gamma-rays was determined on the basis of the clonogenic survival assay. The expression of c-myc and c-Ki-ras oncogenes was examined by the use of RNA dot blot and Northern blot analyses. The results show that the development of resistance to selected drugs does not alter the expression of either c-myc or c-Ki-ras oncogene. CA3 and CK2 clones were resistant to cisplatin, while the vincristine resistant clones VA3 and VK2 became sensitive to this drug. The sensitivity of resistant clones to gamma-rays varied. CA3 cells were resistant, VA3 and VK2 cells sensitive, while CK2 cells exhibited the same sensitivity to gamma-rays as did the parental cells. All four clones tested became cross-resistant to methotrexate. We can conclude that development of resistance to cisplatin and vincristine does not alter the expression of c-myc or c-Ki-ras oncogene. We did not find any correlation between expression of these oncogenes and the sensitivity to cisplatin, methotrexate or gamma-rays.

Blotting, Northern↗
PubMed1993

Multifactorial molecular mechanisms are involved in resistance of preirradiated human cervix carcinoma cells to cis-dichlorodiammineplatinum (II) and vincristine.

We previously found that human cervix carcinoma HeLa cells irradiated with multiple fractions of gamma rays (0.5 Gy daily, five times per week over 6 weeks) become resistant to cis-dichlorodiammineplatinum(II) (cis-DDP), methotrexate (MTX) and vincristine (VCR), but retain the same sensitivity to gamma rays or UV light. In the present report attempts were made to elucidate the mechanisms by which these cells have acquired resistance to cis-DDP and VCR. The sensitivity to different drugs was measured by modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. Neither buthionine sulfoximine (BSO) nor ethacrinic acid were able to reverse the resistance of preirradiated cells to cis-DDP. Therefore, neither the increased levels of glutathione nor glutathione transferase seem to be involved in resistance to cis-DDP. Preirradiated cells did show resistance to cadmium, indicating the increased levels of metallothioneins in these cells. Resistance of preirradiated cells to vincristine was abolished by the addition of verapamil, indicating that resistance to this drug may depend on the increased expression of plasma membrane P-glycoprotein. It was concluded that mechanisms of resistance of preirradiated cells to cytostatics are multifactorial and involve at least the increased levels of metallothioneins and changes in the plasma membrane. Acquired resistance to cytotoxic drugs induced by preirradiation may be the reason for the reduced response to these drugs after radiation treatment of certain tumors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Multiple fractions of gamma rays do not induce overexpression of c-myc or c-Ki-ras oncogenes in human cervical carcinoma cells.

Multiple fractions of gamma rays (0.5 Gy daily, 30 fractions) had previously been found to change the sensitivity of human cervical carcinoma HeLa cells to anticancer drugs. Preirradiated cells became resistant to cisplatin, methotrexate and vincristine, but retained the same sensitivity to gamma rays and ultraviolet light. Some mechanisms involved in resistance of preirradiated cells to cisplatin and vincristine were determined, i.e. the increased levels of metallothioneins and increased expression of plasma membrane P glycoprotein. As recent reports indicated that the resistance to cisplatin and ionizing radiation may involve expression of oncogenes, we examined whether multiple fractions of gamma rays can change the expression of c-myc and c-Ki-ras oncogenes in HeLa cells and determined whether there is a correlation between expression of these oncogenes and sensitivity of preirradiated cells to cisplatin and gamma rays. The expression of c-myc and c-Ki-ras oncogenes were examined by the use of DNA dot blot, RNA dot blot and Northern blot analyses. The results show that preirradiation did not induce either amplification or elevated expression of c-myc or c-Ki-ras oncogenes. Further, there is no correlation between expression of c-myc and c-Ki-ras oncogenes and the acquired resistance to cisplatin.

Blotting, Northern↗
PubMed1992

Regulation of NK cell activity and the level of the intracellular cAMP in human peripheral blood lymphocytes by Met-enkephalin.

The effect of Met-enkephalin on natural killer (NK) activity and on intracellular cyclic adenosine monophosphate (cAMP) level in human peripheral blood lymphocytes was measured 1/4, 1, 2, and 24 h after incubation. Concentrations of Met-enkephalin ranged from 10(-12) to 10(-8) M. Cyclic changes in NK activity and in the intracellular cAMP level after treatment with Met-enkephalin were observed. Kinetics of changes caused by high (10(-9), 10(-8) M) and low concentrations (10(-12), 10(-11), 10(-10) M) of Met-enkephalin differed from each other. Early, nearly threefold increase in the level of intracellular cAMP was found 15 min after treating peripheral blood lymphocytes with 10(-12) M Met-enkephalin. By contrast, a nearly 75% decrease of intracellular cAMP level was found 2 h after treatment with 10(-9) M Met-enkephalin. Generally, early intensive changes in the cAMP level in peripheral blood lymphocytes, induced by Met-enkephalin, were followed by delayed, subtle changes in NK cell activity in the opposite direction.

Adolescent↗
PubMed1992

In vivo bidirectional regulation of mouse natural killer (NK) cell cytotoxic activities by Leu-enkephalin: reversibility by naloxone.

Intraperitoneal injection of Leu-enkephalin (LENK, 10 or 7.5 mg/kg) induced bidirectional modulation of natural cytotoxic activities in spleens of CBA mice (suppression followed by enhancement). NK-cytotoxic activity was more affected than the ADCC. Early suppression of NK activity could be reversed by 4 x M excess of naloxone injected 20 min before LENK, suggesting that the suppression was mediated by opioid receptors. Subsequent increase of NK activity could not be abrogated by naloxone, at least not completely. Naloxone itself decreased NK activity 12 hours after treatment, but enhanced ADCC at 24 and 48 hours. This increase was abrogated by LENK. In addition to functional alterations, LENK also induced phenotypic changes of spleen cells, i.e. a decrease in the percentage of asialo-GM-1+ cells 24 hours posttreatment. There was no correlation between LENK-induced alterations of cytotoxic function and the percentage of cells with NK phenotype (GM-1+). Thus, LENK modulates cytolytic functions and the phenotype of NK cells in vivo in a complex way, which besides opioid mechanisms may also include non-opioid ones.

Animals↗
PubMed1992

Alteration of NK- and ADCC-activities in rats genetically selected for low or high platelet serotonin level.

By selective breeding we have recently obtained two discrete sublines of rats that differ in serotonin content in their platelets. As both serotonin and platelets may influence, or even take part, in immune reactions, we tested in this work the natural cytotoxicity in rats with constitutionally different platelet serotonin levels (PSL). Rats with low platelet serotonin level (mean +/- SD, 1.26 +/- 0.14 micrograms 5HT/mg protein; 81% vs. controls) had significantly higher (P less than 0.001) natural killer (NK) activity (mean +/- SD, 9.1 +/- 3.9%) than control rats with average PSL (1.57 +/- 0.18 micrograms 5HT/mg protein). On the contrary, rats with constitutionally high PSL (2.42 +/- 0.21 micrograms 5HT/mg protein, 154% vs. controls) had somewhat lower (P less than 0.02) NK activity (4.1 +/- 1.7%) than control animals (5.7 +/- 1.9%). Antibody-dependent cellular cytotoxicity (ADCC) against nucleated targets of the RCH line, detecting lymphoid effectors, as well as ADCC against chicken red blood cells (CRBC), detecting predominantly non-lymphoid effectors, were also significantly higher (P less than 0.001) in rats with low PSL (19.6 +/- 6.8% vs. 6.6 +/- 3.1% in controls for lymphoid effectors, and 71.8 +/- 6.1% vs. 48.7 +/- 8.8% in control rats for non-lymphoid effectors). However, no significant alteration of either ADCC was determined in rats with high PSL. The results suggest in vivo regulation of natural cytotoxicity by serotonin.

Animals↗
PubMed1992

Chromosomal analysis of Chinese hamster V79 cells exposed to multiple gamma-ray fractions: induction of adaptive response to mitomycin C.

Chinese hamster V79 cells were irradiated daily with 0.3 Gy of gamma-rays 5 times per week for 12 weeks (total 18 Gy). These cells were challenged with an additional dose of 15. Gy gamma-rays or treated with 5 micrograms/ml of mitomycin C (MMC) for 2 h. In spite of the high total accumulated dose of gamma-rays, the number of chromosomal aberrations and sister-chromatid exchanges (SCEs) did not significantly increase in the preirradiated cells, as compared to control cells. If preirradiated cells were challenged with an additional 1.5 Gy of gamma-rays, an insignificant decrease in the yield of chromatid aberrations was observed. In contrast, preirradiated cells became significantly more resistant to the induction of chromosomal damage when challenged with mitomycin C. Our results suggest that multiple fractions of gamma-rays can induce the adaptive response to mitomycin C in preirradiated cells.

Adaptation, Physiological↗
PubMed1992

Collateral resistance or sensitivity of human larynx carcinoma HEp2 cells resistant to cis-dichlorodiammineplatinum (II) or vincristine sulfate.

Human larynx carcinoma HEp2 cells in tissue culture were repeatedly treated with two chemotherapeutic agents which exhibit distinct mechanisms of action and which differ in mechanisms underlying resistance: cis-dichlorodiammineplatinum (II) (cis-DDP) and vincristine sulfate (VCR). Two schedules of resistance development were used: Acute (cells repeatedly treated with drug for 1 hour in serum-free medium: CA15 and VA15 cells), and continuous (repeatedly treated for 24 hours in complete medium: CK15 and VK15 cells). The sensitivity of cis-DDP resistant (CA15 and CK15 cells) and VCR resistant (VA15 and VK15 cells) sublines to cis-DDP VCR, methotrexate (MTX) and gamma rays was determined by survival assay. The results showed that all sublines became resistant to MTX. Cis-DDP resistant cells became cross-resistant to VCR too. Of VCR resistant sublines, only VK15 cells changed (increased) their sensitivity to cis-DDP. Resistant sublines (except CA15) became sensitive to gamma rays. The degree of resistance or collateral resistance/sensitivity depended on the chemotherapeutic agent used for selection and on the schedule of resistance development. The present data support the idea of complexity of resistance phenomenon. They also emphasize the difficulty and importance of judicious choice of agents that should be given in combined therapy of tumors.

Cell Survival↗