[Can Analysis of Cellular Lipidome Contribute to Discrimination of Tumour and Non-tumour Colon Cells?]

BACKGROUNDS

Colon cancer development is often characterized by abnormalities in lipid synthesis and metabolism, which may influence energetic balance, structure and function of biological membranes, or production of specific mediators and cell signalling. The changes in lipid profile and metabolism (lipidome) may significantly affect cell behaviour and response to therapy. Permanent epithelial cell lines at various stages of cancer development are used for better understanding of this topic on cellular and molecular levels. In our study, we hypothesized that detailed analyses of colon cancer cell line lipidomes may help to identify major alterations in the amount and profile of specific lipid classes/species, which can contribute to their different response to various stimuli.

MATERIAL AND METHODS

Cellular lipids were isolated from six human epithelial cell lines derived from tissues at various stages of tumour development. Liquid chromatography coupled with tandem mass spectometry analyses were performed in order to determine amount and mass profiles of all phospholipid (PL), lysophospholipid (lysoPL) and sphingolipid classes. The data was statistically evaluated (cluster and discrimination analyses) with respect to mutual comparison of cell lines and to significantly discriminating lipid types.

RESULTS

The results of cluster analysis arranged cell lines in order corresponding to their level of transformation (normal cells, adenoma, carcinoma and lymph node metastasis). The results of discrimination analyses revealed the most discriminating lipid types and distinction in PL: lysoPL ratios. Particularly, significant correlation of the amount and profiles of both specific lysoPL and sphingolipid classes with cell transformation level were observed. Similar approaches are now applied to compare lipidomes of colon epithelial cells isolated from tumour vs. non-tumour samples of colon cancer patients.

CONCLUSION

Our results indicate that a) selected cancer cell lines are suitable model for lipidomic studies that can serve as a basis for subsequent clinical research, b) cellular lipidome analyses may help to discriminate tumour and non-tumour cells in clinical samples, where specific types of lipids could serve as biomarkers.Key words: colon cancer - cell lines - liquid chromatography - mass spektrometry - phospholipids - sphingolipids - bioinformatics The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. This work was supported by Czech Health Research Council, grant No. AZV 15-30585A.Submitted: 19. 3. 2018Accepted: 18. 4. 2018.

Higher anti-tumour efficacy of platinum(IV) complex LA-12 is associated with its ability to bypass M-phase entry block induced in oxaliplatin-treated human colon cancer cells

OBJECTIVES

Therapeutic potential of conventionally used platinum-based drugs in treatment of colorectal tumours has been limited due to high incidence of tumour resistance to them and to their severe side effects. This evokes a search for more suitable anti-cancer drugs. We have compared ability of oxaliplatin and a novel platinum(IV) complex, LA-12, to modulate the cell cycle and induce apoptosis in human colon adenocarcinoma HCT116 wt and p53/p21 null cells, and have investigated molecular mechanisms involved.

MATERIALS AND METHODS

Cell cycle-related changes were analysed by flow cytometry (bromodeoxyuridine/propidium iodide staining, histone H3 phosphorylation). Apoptosis was detected using flow cytometry (assays monitoring caspase activity) and fluorescence microscopy (nuclear morphology). Changes in levels of genes/proteins involved in cell cycle and apoptosis regulation were examined by RT-PCR and western blotting.

RESULTS

Our results highlight the outstanding ability of LA-12 to induce effective elimination of colon cancer cells independently of p53/p21, and in significantly lower doses compared to oxaliplatin. While oxaliplatin induced p53- and p21-dependent G2 -phase arrest associated with downregulation of cyclin B1 and Cdk1, LA-12 allowed cells to enter M-phase of the cell cycle regardless of p53/p21 status.

CONCLUSIONS

Higher malignant cell toxicity and ability to bypass cell cycle arrest important for the cell damage repair suggest LA-12 to be a more effective candidate for elimination of colon tumours from a variety of genetic backgrounds, compared with oxaliplatin.

Post-translational modifications regulate signalling by Ror1

AIM

In this study, we analysed the post-translational modification of receptor tyrosine kinase-like orphan receptor (Ror1). Ror1 is highly upregulated in B cells of patients with chronic lymphocytic leukaemia (CLL). Molecularly, Ror1 acts as the Wnt receptor in the non-canonical Wnt pathway.

METHODS

The level of Ror1 glycosylation in HEK293 cells and in primary human CLL cells was analysed by treatment of inhibitors interfering with different steps of glycosylation process and by direct treatment of cell lysates with N-glycosidase. Ror1 ubiquitination was determined by ubiquitination assay. Functional consequences of post-translational modifications were analysed by immunohistochemistry and by analysis of cell surface proteins. Differences in Ror1 glycosylation were confirmed by analysis of 14 samples of B cells from CLL patients.

RESULTS

We demonstrate that Ror1 is extensively modified by N-linked glycosylation. Glycosylation produces several variants of Ror1 with electrophoretic migration of approx. 100, 115 and 130 kDa. Inhibition of glycosylation interferes with cell surface localization of the 130-kDa variant of Ror1 and prevents Ror1-induced formation of filopodia. Moreover, we show that 130-kDa Ror1 is mono-ubiquitinated. Furthermore, individual CLL patients show striking differences in the electrophoretic migration of Ror1, which correspond to the level of glycosylation.

CONCLUSION

Our data show that Ror1 undergoes complex post-translational modifications by glycosylation and mono-ubiquitination. These modifications regulate Ror1 localization and signalling, and are highly variable among individual CLL patients. These may suggest that Ror1 signals only in a subset of CLL patients despite Ror1 levels are ubiquitously high in all CLL patients.

Non-dioxin-like polychlorinated biphenyls induce a release of arachidonic acid in liver epithelial cells: a partial role of cytosolic phospholipase A(2) and extracellular signal-regulated kinases 1/2 signalling

Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) have been shown to act as tumor promoters in liver; however, the exact mechanisms of their action are still only partially understood. One of the interesting effects of NDL-PCBs is the acute inhibition of gap junctional intercellular communication (GJIC), an effect, which has been often found to be associated with tumor promotion. As previous studies have suggested that NDL-PCB-induced disruption of lipid signalling pathways might correspond with GJIC inhibition, we investigated effects of PCBs on the release of arachidonic acid (AA) in the rat liver epithelial WB-F344 cell line, a well-established model of liver progenitor cells. We found that both 2,2',4,4'-tetrachlorobiphenyl (PCB 47) and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), but not the dioxin-like, non-ortho-substituted, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), induce a massive release of AA. The AA release, induced by PCB 153, was partially inhibited by extracellular signal-regulated kinases 1/2 (ERK1/2) signalling inhibitor, U0126, and by cytosolic phospholipase A(2) (cPLA(2)) inhibitor, AACOCF(3). Although PCB 153 induced both ERK1/2 and p38 activation, the specific p38 kinase inhibitor, SB203580, had no effect on AA release. Inhibitors of other phospholipases, including phosphatidylcholine-specific phospholipase C or phosphatidylinositol-specific phospholipase C, were also without effect. Taken together, our findings suggest that the AA release, induced by non-dioxin-like PCBs in liver progenitor cell line, is partially mediated by cytosolic PLA(2) and regulated by ERK1/2 kinases. Our results suggest that more attention should be paid to cell signalling pathways regulated by AA or eicosanoids after PCB exposure, which might be involved in their toxic effects.

Dibenzanthracenes and benzochrysenes elicit both genotoxic and nongenotoxic events in rat liver ‘stem-like’ cells

Polycyclic aromatic hydrocarbons (PAHs) with molecular weight 278 are a group of PAHs that are mostly not covered by the current monitoring programs, despite their relative abundance in environmental samples and possible carcinogenicity. Although benzo[g]chrysene (BgChry) and dibenz[a,h]anthracene (DBahA) have been for a long time studied as genotoxic, tumour-initiating compounds, little is known about the potential tumour-promoting effects of this group of PAHs. In the present study, we investigated their impact on activation of the aryl hydrocarbon receptor (AhR), induction of enzymes involved in metabolic activation of PAHs, disruption of cell cycle control in confluent cell population and inhibition of gap junctional intercellular communication (GJIC), using the rat liver epithelial cell line WB-F344 as a model of liver progenitor cells. We found that BgChry was the weakest inducer of the AhR-mediated activity, while relative potencies of benzo[b]chrysene (BbChry) and benzo[c]chrysene (BcChry) were comparable to the previously reported values for dibenzanthracenes. All compounds increased expression of cytochromes P450 1A1 and 1B1, and aldo-keto reductase 1C9. BgChry was found to induce high amounts of DNA adducts, which corresponded with induction of p53 phosphorylation at Ser15, apoptosis and accumulation of cells in S-phase of cell cycle, leading to a decrease in cell numbers. All other compounds were found to stimulate cell proliferation in contact-inhibited WB-F344 cells in a dose-dependent manner. We found that only BgChry, and to a lesser extent also BcChry, inhibited GJIC at high concentrations. Taken together, dibenzanthracenes and benzochrysenes, with exception of BgChry, seem to act primarily through deregulation of cell proliferation in liver epithelial cells, which is related to their relatively high AhR-mediated activity. The disruption of cell cycle control might contribute to their carcinogenic effects, as well as to carcinogenicity of complex environmental mixtures containing high levels of PAHs with molecular weight 278.

Hsp90 inhibitor geldanamycin increases the sensitivity of resistant ovarian adenocarcinoma cell line A2780cis to cisplatin

Ovarian carcinoma is the leading cause of death among gynecological neoplasms in the world. The chemoresistance is a major obstacle in the effective treatment of ovarian and other cancers. We evaluated the effects of Hsp90 inhibitor geldanamycin (GEL) alone and in combination with cisplatin in cisplatin resistant ovarian adenocarcinoma cell line. Our results showed Akt depletion and S-phase arrest of A2780cis cells after GEL treatment. Combined exposure of A2780cis cells to GEL and cisplatin resulted in greater than additive cytotoxic effect.

Neural differentiation potentiated by the leukaemia inhibitory factor through STAT3 signalling in mouse embryonal carcinoma cells

LIF is a cytokine playing a key role in the regulation of self-renewal and maintenance of undifferentiated state in mouse ES cells. The response of pluripotent cells to LIF is mediated mainly by the STAT3 and ERK signalling pathways. Recently, we have shown that LIF potentiated retinoic acid-induced neural differentiation of pluripotent mouse embryonal carcinoma P19 cells. Here we demonstrate that pro-neural effects of LIF and partially also of retinoic acid are abolished by inhibition of the JAK2->STAT3 signalling pathway. In contrast, inhibition of the MEK1->ERK signalling pathway does not exhibit any effect. These results suggest that in neurogenic regions, cooperative action of LIF and other neuro-differentiation-inducing factors, such as retinoic acid, may be mediated by the STAT3 signalling pathway.

Meloxicam, a cyclooxygenase 2 inhibitor, supports hematopoietic recovery in gamma-irradiated mice

Meloxicam, a selective inhibitor of cyclooxygenase 2, a nonsteroidal anti-inflammatory drug with an improved side-effects profile in terms of gastrointestinal toxicity, has been found to stimulate hematopoiesis in whole-body gamma-irradiated mice. A distinct corroboration of this positive action of meloxicam is an enhancement of the recovery of hematopoietic progenitor cells committed to granulocyte-macrophage and erythroid development, which has been demonstrated in sublethally irradiated animals treated with meloxicam at a dose of 20 mg/kg administered intraperitoneally either singly 1 h before irradiation or repeatedly after radiation exposure. The results suggest that meloxicam can be added to the list of biological response modifiers that can be used in the treatment of hematopoietic damage induced by ionizing radiation.

The effects of parenteral lipid emulsions on cancer and normal human colon epithelial cells in vitro

Differences in lipid metabolism of tumor and normal tissues suggest a distinct response to available lipid compounds. In this study, the in vitro effects of five types of commercial parenteral lipid emulsions were investigated on human cell lines derived from normal fetal colon (FHC) or colon adenocarcinoma (HT-29). Changes of the cellular lipid fatty acid content, cell oxidative response, and the cell growth and death rates were evaluated after 48 h. No effects of any type of emulsions were detected on cell proliferation and viability. Compared to the controls, supplementation with lipid emulsions resulted in a multiple increase of linoleic and linolenic acids in total cell lipids, but the content of arachidonic, eicosapentaenoic, and docosahexaenoic acids decreased particularly in HT-29 cells. The concentration of emulsions which did not affected HT-29 cells increased the percentage of floating and subG0/G1 FHC cells probably due to their higher reactive oxygen species production and lipid peroxidation. Co-treatment of cells with antioxidant Trolox reduced the observed effects. Our results imply that lipid emulsions can differently affect the response of colon cells of distinct origin.

The effects of parenteral lipid emulsions on cancer and normal human colon epithelial cells in vitro

Differences in lipid metabolism of tumor and normal tissues suggest a distinct response to available lipid compounds. In this study, the in vitro effects of five types of commercial parenteral lipid emulsions were investigated on human cell lines derived from normal fetal colon (FHC) or colon adenocarcinoma (HT-29). Changes of the cellular lipid fatty acid content, cell oxidative response, and the cell growth and death rates were evaluated after 48 h. No effects of any type of emulsions were detected on cell proliferation and viability. Compared to the controls, supplementation with lipid emulsions resulted in a multiple increase of linoleic and linolenic acids in total cell lipids, but the content of arachidonic, eicosapentaenoic, and docosahexaenoic acids decreased particularly in HT-29 cells. The concentration of emulsions which did not affected HT-29 cells increased the percentage of floating and subG0/G1 FHC cells probably due to their higher reactive oxygen species production and lipid peroxidation. Co-treatment of cells with antioxidant Trolox reduced the observed effects. Our results imply that lipid emulsions can differently affect the response of colon cells of distinct origin.

Lipoxygenase inhibitors suppress proliferation of G5:113 fibrosarcoma cells in vitro but they have no anticancer activity in vivo

Nordihydroguaiaretic acid (NDGA) and esculetin, both nonspecific inhibitors of lipoxygenases (LOX), were found to suppress expressively the in vitro proliferation of fibrosarcoma cells G5:113 in concentrations ranging from 10 to 50 microM. Subsequent flow-cytometric analysis of the cell cycle showed that both these drugs significantly decreased the percentage proportion of cells in the G0/G1-phase and simultaneously increased significantly this proportion in the S-phase. No apoptosis was detected in the whole range of concentrations studied, from 2.5 to 50 mM. On the contrary, in experiments in vivo, neither NDGA nor esculetin had any curative effect if they were repeatedly injected intraperitoneally (i.p.) into mice bearing tumors growing from subcutaneously (s.c.) transplanted G5:113 cells. Pretreatment of the fibrosarcoma cells with NDGA or esculetin in vitro preceding their s.c. transplantation into mice did not result in suppression of the tumor growth, either. Finally, if G5:113 cells were injected intravenously and the mice were subsequently treated repeatedly with i.p. injections of NDGA, decreased survival and increased number of surface lung metastases were observed in the NDGA-treated group. Thus the suppressive action of inhibitors of LOX on the growth of fibrosarcoma cells in vitro was not reflected in their anti-tumor effects in vivo.

Conditions for gene transfection into the HL-60 human leukaemia cell line by electroporation

Electroporation represents a powerful technique for cell transfection; however, its efficiency in haemopoietic cells (approximately 1%) is largely unsatisfactory. Biological processes in haemopoietic cells are often studied using leukaemia cell line HL-60. For this reason we developed conditions for efficiently introducing plasmids to HL-60 cells by electroporation, as an alternative to other techniques. This technique employs the electric pulse (250-270 V; 1000 microF) followed by separation of living cells on a Ficoll-Paque discontinuous gradient. Using 10-20 micrograms of plasmid, we routinely achieve 12-14% of transfectants.

Lipoxygenase inhibitors induce arrest of tumor cells in S-phase of the cell cycle

Inhibitors of the lipoxygenase pathway of arachidonic acid metabolism represent a potential anti-tumor drugs. These compounds have been found to inhibit the growth and induce the apoptosis of various tumor cells both in vitro and in vivo. In this study, the effects of the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid (NDGA) on the progression of the cell cycle were investigated in eight mammalian cell lines of different origin. Flow cytometric analyses of cell cycle distribution after staining of DNA with propidium iodide or 7-aminoactinomycin D and DNA synthesis using incorporation of 5-bromo-2'-deoxy-uridine showed that both esculetin and NDGA suppress cell growth by interrupting the progression of cells through S-phase that results in their accumulation in this phase of the cell cycle. The possible mechanisms of these effects and the significance of the findings for the improvement of anticancer therapy targeted on cell cycle is discussed.

Inhibitors of arachidonic acid metabolism potentiate tumour necrosis factor-alpha-induced apoptosis in HL-60 cells

We investigated whether and how could various modulators of arachidonic acid metabolism affect apoptosis induced by tumour necrosis factor-alpha (TNF-alpha) in human myeloid leukaemia HL-60 cells. These included arachinonyltrifluoromethyl ketone (AACOCF3; cytosolic phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor), MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethyl propanoic acid; 5-lipoxygenase-activating protein inhibitor), nordihydroguaiaretic acid (general lipoxygenase inhibitor), and arachidonic acid itself. Incubation of HL-60 cells with nordihydroguaiaretic acid resulted in apoptosis and it was characterised by mitochondria membrane depolarisation, release of cytochrome c from mitochondria into cytosol and activation of caspase-3. Indomethacin and nordihydroguaiaretic acid synergistically potentiated TNF-alpha-induced apoptosis, while arachidonic acid, AACOCF3 and MK-886 did not modulate its effects. Furthermore, indomethacin potentiated apoptosis in cells treated with a differentiating agent, all-trans retinoic acid, which induces resistance to TNF-alpha. However, the observed effects were probably not associated either with the cyclooxygenase- or lipoxygenase-dependent activities of indomethacin and nordihydroguaiaretic acid, respectively. Since indomethacin may reportedly activate peroxisome proliferator-activated receptors (PPARs), the effects of specific ligands of PPARs on apoptosis were studied as well. It was found that selective PPARs ligands had no effects on TNF-alpha-induced apoptosis. The findings suggest that arachidonic acid metabolism does not play a key role in regulation of apoptosis induced by TNF-alpha in the present model. Nevertheless, our data raise the possibility that indomethacin could potentially be used to improve the treatment of human myeloid leukaemia.

Monitoring river sediments contaminated predominantly with polyaromatic hydrocarbons by chemical and in vitro bioassay techniques

Extracts of sediment samples collected from the Morava River and its tributaries (Czech Republic) were examined for mutagenic, dioxin-like, and estrogenic activities. Moreover, the human leukemic HL-60 cell line was tested as a potential model for the detection of effects of environmental contaminants on cell proliferation and differentiation processes. Analytical data indicate that the sediments were contaminated predominantly with polycyclic aromatic hydrocarbons (PAHs) and phthalate esters. The sums of concentrations of 16 U.S. Environmental Protection Agency priority PAHs ranged from 0.8 to 13.2 micrograms/g and those of phthalates reached up to 3,000 ng/g, while only low levels of chlorinated hydrocarbons were found. The main goal of the present study was to determine effects of PAH prevalence on in vitro bioassays, with special emphasis on dioxin-like activity. The dioxin-like activity was tested using a reporter gene assay based on chemical-activated luciferase expression (the CALUX assay). Significant dioxin-like activity (2.6-40.1 micrograms/g benzo[a]pyrene equivalents and 5.9-48.2 ng/g 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents) was detected in all samples, and the results obtained with various exposure times or with both crude and PAH-deprived extracts indicate that the response was probably caused almost exclusively by the presence of high concentrations of PAHs. This corresponds with results of chemical analyses and indicates that various exposure times would allow a discrimination between dioxin-like activities of persistent compounds and easily metabolized aryl hydrocarbon (Ah) receptor inducers. Only sediment extracts containing the highest concentrations of PAHs were mutagenic, as determined by the umu assay. Estrogenic activity was found in several samples (4.75-22.61 pg/g estradiol equivalents) using cells stably transfected with an estrogen-responsive element linked to a luciferase promoter. Noncytotoxic doses of extracts had no effects on HL-60 cell proliferation, while two of the tested crude extracts significantly enhanced their all-trans retinoic acid-induced differentiation. These activities were not associated with phthalate esters and/or PAHs. Our results indicate that cellular and biochemical in vitro assays based on various specific modes of action may yield data complementary to results of mutagenicity tests and that they could be useful in environmental risk assessment. High levels of PAHs are apparently associated with dioxin-like and mutagenic activities rather than with estrogenic activity.

Modulation of death receptor-mediated apoptosis in differentiating human myeloid leukemia HL-60 cells

Differentiating myeloid cells may become resistant to various apoptotic stimuli. In the present study, dimethyl sulfoxide (DMSO) and all-trans retinoic acid (ATRA) were found to modulate the sensitivity of HL-60 cells to death receptor-mediated apoptosis in a time-dependent manner. During the early stages of differentiation, DMSO treatment increased the response of HL-60 cells to tumor necrosis factor alpha; (TNF-alpha), but enhanced responsiveness was lost during later differentiation stages. In contrast, ATRA treatment induced resistance to TNF-alpha-induced apoptosis. HL-60 cells were resistant to Fas-mediated apoptosis but were sensitized by culturing in serum-free conditions. Similar to its effect on TNF-alpha sensitivity, DMSO pretreatment augmented the response to Fas-mediated signaling, which coincided with increased expression of Fas on DMSO-pretreated cells. However, during the later stages of DMSO-induced differentiation, sensitivity to anti-Fas antibody-induced apoptosis declined significantly, although Fas expression was still elevated. The reduced sensitivity to anti-Fas treatment partially correlated with increased Fas-associated phosphatase-1 mRNA expression. Thus, regardless of either Fas up-regulation or potentiation of TNF-alpha-mediated apoptosis during early DMSO-induced differentiation, a slow increase in resistance to apoptosis mediated through these death receptors occurs during DMSO-induced differentiation, which contrasts with the rapid induction of resistance following treatment with ATRA.

Transforming growth factor-beta1 induces junB mRNA accumulation, G1-phase arrest, and pRb dephosphorylation in human leukemia HL-60 cells

Although TGF-beta1 unambiguously functions as a regulator of hematopoietic differentiation, its significance for the development of myeloid lineage is still questionable. In this study three components of early response to TGF-beta1 treatment were investigated in human promyelocytic leukemia HL-60 cells. Changes in junB mRNA accumulation and pRb dephosphorylation were accompained by accumulation of cells in G1 phase of the cell cycle. Time dependence of these changes may implicate mutual cooperation of the pRb and junB in the cell cycle control. It can be concluded that, although myeloid HL-60 cells are known to require rather complex cytokine stimulation to fully differentiate, they clearly possess the ability to respond to TGF-beta1.

Inhibition of the cytochrome P-450 modulates all-trans-retinoic acid-induced differentiation and apoptosis of HL-60 cells

We studied the effects of inhibition of cytochrome P-450 by proadifen (SKF525A) on the processes induced in myeloid leukemia HL-60 cells by all-trans-retinoic acid (ATRA). The parameters reflecting cell proliferation, differentiation, and apoptosis were detected by flow cytometry as the principal method at selected time intervals (24-96 hours). Changes in the expression of Bcl-2 protein were detected by Western blotting. The majority of experiments were designed as a factorial combination of the treatment and assessed for significance of the interactions. Proadifen was demonstrated synergistically (1) to potentiate the antiproliferative and differentiation effects of ATRA, and (2) to increase cell viability and prevent ATRA-induced apoptosis. Moreover, proadifen weakened ATRA-induced downregulation of the Bcl-2 protein. Our results may be of practical importance because cytochrome P-450 inhibitors are used clinically in treating cancer patients. Assuming that effects on the leukemic cells in vivo would be similar, this type of combined therapy could help to achieve better results even with lower doses of ATRA.

Epigenetic mechanisms of the carcinogenic effects of xenobiotics and in vitro methods of their detection

Carcinogenesis is associated with various epigenetic mechanisms, which can alter intra- and intercellular communication and gene expression and thus affect cytokinetics, i.e. regulation of cell proliferation, differentiation, and apoptosis. These processes lead to a loss of homeostatic control. In addition to "classical" epigenetic events such as DNA methylation and histone acetylation, the major mechanisms include changes in concentrations of signal molecules (hormones, growth factors, fatty acids, etc.), modulation of cell receptors and drug-, hormone- and fatty acid-metabolizing enzymes, oxidative stress, and interference with intracellular signal transduction pathways. Multidisciplinary and multibiomarker approach is necessary for setting up a battery of specific biochemical, molecular, and cellular in vitro methods detecting the epigenetic carcinogenic potential of individual chemicals or their environmental mixtures. This approach is based on studies of modes of action of xenobiotics at various levels, including the molecular mechanisms and modulations of cytokinetics, each of them having its specific predictive value.

TNF-alpha modulates the differentiation induced by butyrate in the HT-29 human colon adenocarcinoma cell line

The aim of this study was to determine whether and how tumour necrosis factor alpha (TNF-alpha) modulates butyrate effects. After the treatment of human colon adenocarcinoma HT-29 cells with sodium butyrate (NaBt), TNF-alpha or with their combinations we detected cell cycle (flow cytometry), cell proliferation (amidoblack and MTT assays), the amount of dead (floating) and apoptotic cells (flow cytometry and fluorescence microscopy), and the level of differentiation by alkaline phosphatase (ALP) activity (spectrophotometry), relative F-actin content (confocal laser scanning microscopy analysis) and E-cadherin expression (Western blot analysis). Both TNF-alpha and NaBt decreased cell growth in a dose-dependent manner. After combined treatment of the cells with both agents used, either none or additive effects were observed as compared with NaBt treatment alone. The level of dead and apoptotic cells was dose-dependently increased after this combined treatment. In contrast, TNF-alpha suppressed ALP activity and F-actin accumulation induced by NaBt. The results suggest that TNF-alpha does not influence significantly the antiproliferative effects of NaBt but, contrary to its potentiation of apoptosis, it markedly reduces NaBt-induced differentiation of HT-29 colon adenocarcinoma cells.

Retinoid X receptor suppresses transformation by the v-myb oncogene

The v-myb oncogene of avian myeloblastosis virus causes acute monoblastic leukemia in vivo and transforms myelomonocytic cells in culture. Retinoids are potent regulators of proliferation and differentiation in various cell types, and they can initiate differentiation in certain types of leukemic cells. However, the BM2 v-myb-transformed chicken monoblastic cell line is resistant to retinoic acid treatment. We found that overexpression of the retinoid X receptor confers sensitivity of BM2 cells to retinoic acid, resulting in induction of growth arrest and terminal differentiation. In contrast, the frequency of apoptosis was not affected by the retinoid X receptor in this cell type. We also demonstrated that suppression of transformation by v-Myb results from the negative effect of retinoid X receptor on v-Myb transactivation function, similar to that previously described for the retinoic acid receptor. The retinoid X receptor-induced inhibition of transactivation by v-Myb seems to be enhanced by a cell type-specific factor(s), which is not required by retinoic acid receptor.

Inhibitors of lipoxygenase metabolism exert synergistic effects with retinoic acid on differentiation of human leukemia HL-60 cells

The interaction between drugs suppressing the production of arachidonic acid metabolites and inducers of granulocytic differentiation, i.e., all-trans retinoic acid and dimethyl sulphoxide (DMSO) was investigated using the human myeloid leukemia HL-60 cell line. The experiments were designed as a complete factorial combination of treatments and used chemiluminescence as a marker of cell oxidative burst (level of differentiation). It was clearly demonstrated that two structurally different inhibitors of 5-lipoxygenase metabolism, i.e., 3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-di methyl propanoic acid (MK-886) and esculetin, significantly potentiated the HL-60 cell differentiation induced by retinoic acid or DMSO. Detailed mathematical evaluation of the results revealed the synergistic character of the interaction. The most significant effects were achieved with a combination of 5-lipoxygenase inhibitors and low doses of retinoic acid. These results were confirmed by analysis of cell morphology and expression of cell surface antigen CD11b after treatment of the cells with selected concentrations of agents. In contrast to those on differentiation, no additional effects of MK-886 or esculetin on cell proliferation (cell number and cell cycle parameters) and apoptosis were observed. An inhibitor of cyclooxygenases, indomethacin, affected neither cell proliferation nor differentiation of cells. The results implied that either modulation of 5-lipoxygenase metabolism or a certain type of imbalance in arachidonic acid metabolism could modulate the effects of retinoic acid or DMSO on myeloid cell differentiation.

5-Lipoxygenase inhibitors potentiate effects of TGF-beta 1 on the differentiation of human leukemia HL-60 cells

It was clearly demonstrated that two structurally different inhibitors of 5-lipoxygenase (5-LPO) metabolism (leukotriene synthesis), i.e. MK-886 and esculetin, when combined with transforming growth factor-beta 1 (TGF-beta 1), significantly enhanced the differentiation but did not change proliferation (i.e. cell number and cell cycle parameters) of human leukemia HL-60 cells in vitro. Although cell morphology and measurement of cell surface antigens (CD11b, CD14, and CD66b) after 48 h of combined treatment with MK-886 and TGF-beta 1 suggested a shift of the HL-60 cell population into more differentiated stages of myelopoiesis, cells with a fully mature phenotype were not observed. The effects on differentiation were better distinguished in the functional parameters of differentiation, i.e. oxidative burst of cells as detected by chemiluminescence and the nitroblue tetrazolium reduction test. Detailed statistical analysis of these data proved a significant synergistic interaction between TGF-beta 1 and inhibitors of 5-LPO metabolism. The differentiation effects of TGF-beta 1 alone and especially of its combination with MK-886 were most pronounced when the cells were pretreated with dimethyl sulfoxide or all-trans-retinoic acid. The results imply that either the lack of 5-LPO metabolites or a certain type of mis-balance in arachidonic acid metabolism can modulate the TGF-beta 1 effect on myeloid differentiation.

Eicosanoid inhibitors enhance synergistically the effect of transforming growth factor beta 1 on CCL 64 cell proliferation

The interactions between drugs suppressing the production of arachidonic acid metabolites-eicosanoids and transforming growth factor beta 1 (TGF-beta 1) were investigated using CCL64 cells. These experiments, designed as complete factorial combination of treatments, demonstrated that both esculetin and eicosatetraynoic acid significantly potentiated the inhibitory effect of TGF-beta 1 on [3H]thymidine incorporation. The expression of overadditive effects depended both on the type and concentration of combined factors. These results corresponded with cell cycle analysis data (increased cell number in G1 and decreased cell number in S and G2/M phases) and with the results monitoring cell number following treatment with eicosatetraynoic acid, esculetin, 3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-di methyl propanoic acid (MK-886) and indomethacin. Summarizing, the degree of significance of combined effects supports the hypothesis of synergistic potentiation of TGF-beta 1 effects caused by eicosanoid inhibitors. The results indicate that either the lack of some eicosanoids or a certain type of misbalance in the metabolism of arachidonic acid leading to its abundance might modulate TGF-beta 1 effects on the cell cycle and proliferation in CCL64 cells.

Suppression of human cancer cell proliferation by lipoxygenase inhibitors and gamma-radiation in vitro

The effects of inhibitors of arachidonic acid oxidative metabolism, gamma-radiation and/or their combinations on proliferation and cell cycle were studied in human breast carcinoma HS578T and monoblastoid U937 cell lines. While piroxicam an inhibitor of cyclooxygenase pathway, had no significant effects on cell proliferation, inhibitors of lipoxygenase pathway, nordihydroguaiaretic acid and esculetin, suppressed [3H]-thymidine incorporation and cell growth. The latter agents also differed in their modulation of cell cycle parameters depending on the cell line and the time of treatment. When the cells were preirradiated with gamma radiation (5 Gy) and treated with the drugs (at concentrations 50 mumol/l and higher) the effects on cell proliferation were mostly additive. On the other hand, the results suggest that antiproliferative effects could be significantly strengthened when lower doses (25 mumol/l) of lipoxygenase inhibitors were combined with a low dose (1 Gy) of gamma-radiation. Experiments monitoring the reversibility of the effects after single or combined treatment with the agents showed that irradiation suppressed the ability of U937 cells to restore cell proliferation, and that these effects may be strenghtened by esculetin. In conclusion, our results (1) suggest that the lipoxygenase pathway plays a significant role in proliferation of cancer HS578T and U937 cells in vitro, and (2) implicate the possibility of more effective antiproliferative effects after combined treatment of cells with gamma-radiation and lipoxygenase inhibitors.

Effects of drugs inhibiting prostaglandin or leukotriene biosynthesis on postirradiation haematopoiesis in mouse

Two non-steroidal anti-inflammatory drugs, i.e. indomethacin (INDO), an inhibitor of prostaglandin production, and esculetin (ESCUL), an inhibitor of leukotriene production, were tested for their ability to modify haematopoiesis in three experimental systems: (a) in vitro clonal proliferation of marrow GM-CFC from the irradiated mouse was found to be augmented by addition of INDO at a low concentration, and inhibited by ESCUL in a dose-dependent manner; (b) in the lethally irradiated and bone marrow-transplanted mice treated with the drugs in the postirradiation period, stimulatory effects of INDO on CFU-S and GM-CFC populations and an inhibitory effect of ESCUL on GM-CFC were observed; and (c) when the drugs were administered i.p. to mice 1 h before 5-Gy irradiation, INDO enhanced the postirradiation recovery of haematopoietic indices such the numbers of CFU-S, GM-CFC, peripheral blood granulocytes, and nucleated bone marrow cells, while ESCUL had no effect or even inhibited the recovery of these indices. Survival curves for CFU-S and GM-CFC showed that altered haematopoietic recovery in the INDO- and ESCUL-pretreated mice was not due to changes of intrinsic radiosensitivity of pluripotent (CFU-S) or committed (GM-CFC) stem cell populations. These results confirm earlier findings suggesting an inhibitory role of prostaglandins on haematopoiesis, and provide evidence that endogenous leukotrienes might play a positive role in the regulation of haematopoietic functions in an irradiated organism.

Effects of nordihydroguaiaretic acid on the chemiluminescence of murine phagocytes

Antioxidative effects of nordihydroguaiaretic acid (NDGA) on murine bone marrow phagocytes were studied using luminol- and lucigenin-amplified chemiluminescence (CL). NDGA applied in vitro strongly suppressed the opsonized zymosan particles stimulated CL response in a dose-dependent manner (in concentrations of 0.3-30 micrograms NDGA/ml), thus confirming its antioxidant activity. However, no effects were observed in mice and their serum samples when investigated one minute to one hour after an i.p. administration of NDGA. These differences suggest that NDGA may undergo a rapid metabolism in vivo.

The effect of nordihydroguaiaretic acid, an inhibitor of prostaglandin and leukotriene biosynthesis, on hematopoiesis of gamma-irradiated mice

The effects of the inhibition of the cyclooxygenase and lipoxygenase metabolic pathways of arachidonic acid on the postirradiation recovery of hematopoietic functions in mice were investigated. Nordihydroguaiaretic acid (NDGA), an inhibitor of prostaglandin (PG) and leukotriene (LT) production, was given to animals in single doses (0.015 to 0.75 mg/mouse) 1 hour before 5 Gy of total-body gamma-irradiation. Enhanced hematopoietic recovery in terms of exogenous and endogenous spleen colonies, femoral granulocyte-macrophage colony-forming cells and peripheral blood granulocyte levels was observed at higher doses of NDGA. The treatment used influenced neither lymphocyte nor erythrocyte postirradiational levels or hemoglobin concentration. A comparison of the effects induced by a high dose of NDGA (0.3 mg per mouse) with those observed after an isomolar dose of indomethacin (an inhibitor of PG production) indicated only slight differences between these two drugs. An isomolar dose of esculetin (an inhibitor of LT production) had no effect on the postirradiation behavior of hematopoiesis. The results suggest that the inhibition of PG production plays the main role in the mechanism of NDGA action. Inhibition of LT production seems to be of less importance for hematopoiesis in these in vivo conditions.

Possibilities of the combined use of non-steroidal anti-inflammatory drugs and sulfhydryl compounds in radioprotection

The combined preirradiation administration of indomethacin and cystamine was found to enhance synergistically the recovery of hemopoiesis in sublethally gamma-irradiated mice. This effect can be explained by a common operation of two mechanisms of radioprotection, i.e. of an increased survival of hemopoietic stem cells due to cystamine action and of stimulatory effects of indomethacin on the proliferation of surviving cells, mediated by the inhibition of prostaglandin synthesis. Attempts to prove such enhancement of protective effects on irradiated mice in terms of postirradiation lethality were unsuccessful. The reason seems to be the influence of toxic effects of the indomethacin-cystamine combination on the gastrointestinal tract. When using the less toxic combination, i.e. diclofenac and WR-2721, the additivity of protective effects is manifested even in the survival of lethally irradiated mice. The results suggest that under suitable conditions avoiding the unfavourable toxic effects, non-steroidal anti-inflammatory drugs can be successfully used with the aim to enhance the efficiency of sulfhydryl radioprotectors.

Effect of indomethacin, diclofenac sodium and sodium salicylate on peripheral blood cell counts in sublethally gamma-irradiated mice

Treatment with indomethacin and diclofenac sodium was found to increase granulocyte counts in the blood of sublethally gamma-irradiated mice. Treatment with sodium salicylate was ineffective in this respect, administration of sodium salicylate together with indomethacin even decreased the indomethacin-induced effects. The results suggest that the hemopoiesis-stimulating effects of non-steroidal anti-inflammatory drugs cannot be correlated with the anti-inflammatory activity but rather with the side effects of these compounds, including the action on gastro-intestinal prostanoid production. This conclusion doubts on the possibility of the usefulness of non-steroidal anti-inflammatory drugs in conditions of the radiation syndrome.

In vivo studies of the relationship between the activation of lipid metabolism, postirradiation bone marrow cell proliferation and radioresistance of mice

The effect of adaptation to intermittent feeding on the in vivo biosynthesis of fatty acids and total lipids in the epididymal adipose tissue, the liver and the bone marrow was studied in adult male mice (CBA/JPh x C57BL@10 ScSnPh)F1. At the same time the effects of the same experimental stimulus on the rate of regeneration (proliferation) of bone marrow cells after sublethal irradiation of animals and on the overall radioresistance of mice expressed as 30 days survival after whole-body gamma irradiation were determined. Intermittent feeding in mice has been shown to have a significant effect on the biosynthesis of fatty acids and total lipids in all the tissues studied, including bone marrow cells, the intensity of the effect being closely dependent on the duration of the experimental stimulus. Maximum stimulation of lipogenesis during realimentation was observed approximately within 1 week of adaptation, with a reduction of the metabolic responses thereafter. The intensity of bone marrow cell proliferation in mice irradiated in the realimentation phase was inversely proportional to the preirradiation degree of biosynthesis of fatty acids and total lipids: in a period of lower lipogenetic capacity of cells in the tissue studied (around the weeks 2-5 of adaptation) an increase in the regeneration potential of bone marrow cells was observed together with increased radioresistance of the mice. During the 1-week of adaptation the opposite proved to be the case. Attention is drawn to the possible participation of prostaglandins and lipid peroxides in the responses observed.

The fall in the incorporation of labelled iron into the bone marrow during enhanced erythropoiesis: this paradox explained by changes in ferrokinetics and cytokinetics using the model of mice affected by thyroid hormones

Using the model of mice affected by thyroid hormones, a ferrokinetic analysis was made of the repeatedly observed paradoxical fall in the incorporation of labelled iron into the bone marrow under conditions of the overall stimulation of erythrocyte formation.

Enhancement of hemopoietic recovery by indomethacin after sublethal whole-body gamma irradiation

The effect of the non-steroid anti-inflammatory drug, indomethacin, a potent prostaglandin synthesis inhibitor, on the recovery of hemopoiesis was investigated in sublethally gamma irradiated mice. Treatment with indomethacin after irradiation was found to increase the granulocyte and lymphocyte counts in peripheral blood. Furthermore, an increased rate of the restitution of bone marrow cellularity and of the spleen weight was observed. Using the method of 125iodo-deoxyuridine uptake in the spleen, the ability of indomethacin to potentiate cell proliferation was demonstrated.

Intermittent feeding as a factor enhancing hemopoietic stem cell proliferation and spleen colony formation in irradiated mice

The influence of metabolic stimulation induced by a 3 weeks' adaptation of the animals to intermittent food intake on hemopoietic stem cells was investigated in mice. The methods used included transplantation of bone marrow to lethally irradiated recipients, assay of CFUs number, seeding efficiency, and incorporation of 125iododeoxyuridine into the DNA of spleen cells. A stimulatory effect of the metabolically influenced hemopoietic environment on the proliferative activity in stem cell compartments and on the recovery of hemopoietic organs was demonstrated. These stimulatory effects were most marked when the bone marrow of metabolically influenced donors was transplanted to similarly influenced recipients.

Stimulatory effect of intermittent feeding on hemopoietic recovery in sublethally gamma-irradiated mice

The effect of three-week adaptation to intermittent feeding on the recovery of the hemopoietic functions of mice after sublethal gamma irradiation was investigated. Measurement of oxygen consumption, carbon dioxide output and the respiratory quotient demonstrated an increased metabolic rate in the intermittently fed animals and an accentuation of lipogenic processes. This metabolic state persisted even after irradiation. An improvement in the recovery of hemopoietic functions after irradiation was demonstrated in adapted animals, which was reflected by the increased proliferative activity of the hemopoietic cell populations (more intensive incorporation of 125I-UdR into the DNA of cells of the spleen, thymus and femoral bone marrow), by more rapid renewal of spleen weight, more rapid recovery of the femoral bone marrow cellularity and increased levels of granulocytes in peripheral blood.

Protective effect of intermittent fasting on the mortality of gamma-irradiated mice

The effect of 1 to 6 weeks' adaptation to intermittent fasting (alternating periods of 24 h fasting and subsequent 24 h feeding) on the manifestations of radioresistance of mice subjected to whole-body gamma-irradiation was studied. A favourable effect of this feeding regimen on the survival of irradiated animals was observed. The optimal radioprotective effect was achieved in mice adapted to intermittent fasting for 2 to 3 weeks and irradiated after 24 h of food intake. Furthermore, it was shown that the radioresistance of the adapted organism depends on the momentary state of food intake. After renewal of the normal ad libitum feeding the adaptively induced radioresistance decreases.

Comparison of cell proliferation in the regenerating bone marrow and spleen of irradiated mice with the use of 125I-iododeoxyuridine

The method of 125IUdR labelling of hemopoietic cell populations was used to estimate differences of repopulation kinetics in the femoral bone marrow and spleen of sublethally irradiated mice. In regenerating bone marrow the cellularity and proliferation index, as measured by 6 h 125IUdR incorporation, were found to be inversely related. In the spleen the proliferation index increased parallelly with the increase in cellularity and indicates an ineffectiveness of a change in the set point of local cellularity control. Experiments with measuring the retention of 125IUdR in hemopoietic organs revealed, in the spleen of irradiated animals, phases of increased cell losses as well as immigration of labelled cells into this organ.