Hepatocyte growth factor signal coupling to various transcription factors depends on triggering of Met receptor and protein kinase transducers in human hepatoma cells HepG2

A novel third generation bisphosphonate, minodronate (YM529), prevented proliferation and migration of hepatocellular carcinoma cells through inhibition of mevalonate pathway

AIM

Skeletal metastases and bone metasitasis are a common occurrence in patients with advanced hepatocellular carcinoma (HCC). Bisphosphonates (BPs), which are used for the treatment of osteoporosis and tumor-associated hypercalcemia, have recently been reported to decrease skeletal morbidity in patients with metastatic bone disease. Several studies revealed that nitrogen-containing BPs (N-BPs) could inhibit tumor growth and migration, indicating the possibility that N-BPs have direct inhibitory effects. We aimed to determine the effects of novel a N-BP (YM529) on human HCC cells in vitro.

METHODS

HCC cells were treated with various concentrations of YM529 and the growth inhibition rate was determined. Apoptosis was evaluated by caspase-3/7 assay and caspase-9 cleavage detection. The effects of YM529 on the migration of HCC cells induced by hepatocyte growth factor (HGF) were determined by cell migration assay. To evaluate the involvement of the mevalonate pathway, farnesol (FOH) and geranylgeraniol (GGOH) were added.

RESULTS

YM529 inhibited the proliferation of HCC cells in a dose-dependent manner. The activation of caspase-3/7 and cleavage of caspase-9 demonstrated the involvement of apoptosis in cytotoxicity. GGOH reduced the growth inhibitory effect of YM529 and suppressed the induction of caspase-3/7 activities by YM529 on HCC cells. YM529 inhibited tumor cell migration induced by HGF and this effect was reduced by co-treatment with GGOH.

CONCLUSION

YM529 inhibited the cell proliferation and migration of HCC cells, implicating the involvement of the mevalonate pathway. These results suggest that N-BPs are potential agents for the treatment of HCC skeletal metastases.

Inhibitory effect of HGF on invasiveness of aggressive MDA-MB231 breast carcinoma cells, and role of HDACs

Hepatocyte growth factor (HGF), through Met receptor binding, fulfils numerous functions in invasive tumour growth (survival/proliferation, motility, apoptosis), but epigenetic control of gene expression in this process is poorly understood. In HGF-treated breast cancer cells we studied (a) the chemoinvasion towards CXCL12 (ligand of the chemokine-receptor CXCR4) and (b) the mechanistic basis, that is, the transduction pathways that regulate CXCR4-mediated invasion, and the role played by histone deacetylases (HDACs) after blockade with trichostatin A (TSA). In highly invasive and metastatic MDA-MB231 cells HGF had a dual inhibitory effect, reducing spontaneous migration and specific chemoinvasion towards CXCL12, the latter by decreasing CXCR4 transactivation and protein level. After HGF the levels of phosphorylated (therefore active) c-Src and Akt persistently increased, indicating a role of these signal transducers in the HGF-dependent cellular and molecular effects. c-Src wild-type expression vector (Srcwt) increased active c-Src and mimicked the HGF-dependent inhibition of CXCR4 transactivation. Our findings indicate that HDACs participated in the HGF-inhibitory effects. In fact, blockade of HDACs hindered the HGF- and Srcwt-dependent reductions of CXCR4 transactivation and invasiveness, while inhibition of endogenous c-Src was additive with HGF, further reducing specific chemoinvasion. In conclusion, in MDA-MB231 cells HDAC blockade with TSA partly counteracted the HGF-dependent effects through molecular events that included enhancement of the expression of the genes for invasiveness Met and CXCR4 (depending on serum conditions), reduction of endogenous phospho-c-Src/c-Src and phosphoAkt/Akt ratios and triggering of apoptosis. The potential therapeutic use of TSA should take into account the variable aggressiveness of breast carcinoma cells and microenvironment signals such as HGF at the secondary growth site of the tumour. It was interesting that HGF reduced motility and CXCR4 functionality only of MDA-MB231 cells, and not of low-invasive MCF-7 cells, suggesting a mechanism implicated in metastatic cell homing.

Regulation of polyamine synthesis in human hepatocytes by hepatotrophic factor augmenter of liver regeneration

Different stages of liver regeneration are regulated by a variety of factors such as the liver growth associated protein ALR, augmenter of liver regeneration. Furthermore, small molecules like polyamines were proven to be essential for hepatic growth and regeneration. Therefore, using primary human hepatocytes in vitro we investigated the effect of ALR on the biosynthesis of polyamines. We demonstrated by HPLC analysis that recombinant ALR enhanced intracellular hepatic putrescine, spermidine, and spermine levels within 9-12h. The activation of polyamine biosynthesis was dose dependent with putrescine showing the strongest increase. Additionally, ALR treatment induced mRNA expression of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase, both key enzymes of polyamine biosynthesis. Further, ALR induced c-myc mRNA expression, a regulator of ODC expression, and therefore we assume that ALR exerts its liver regeneration augmenting effects through stimulation of its signalling pathway leading in part to enhanced polyamine synthesis.

Chemosensitization and radiosensitization of tumors by plant polyphenols

The treatment of cancer with chemotherapeutic agents and radiation has two major problems: time-dependent development of tumor resistance to therapy (chemoresistance and radioresistance) and nonspecific toxicity toward normal cells. Many plant-derived polyphenols have been studied intently for their potential chemopreventive properties and are pharmacologically safe. These compounds include genistein, curcumin, resveratrol, silymarin, caffeic acid phenethyl ester, flavopiridol, emodin, green tea polyphenols, piperine, oleandrin, ursolic acid, and betulinic acid. Recent research has suggested that these plant polyphenols might be used to sensitize tumor cells to chemotherapeutic agents and radiation therapy by inhibiting pathways that lead to treatment resistance. These agents have also been found to be protective from therapy-associated toxicities. How these polyphenols protect normal cells and sensitize tumor cells to treatment is discussed in this review.

Differential activation of NF kappa B/RelA-p50 and NF kappa B/p50-p50 in control and alcohol-drinking rats subjected to carrageenin-induced pleurisy

BACKGROUND

Carrageenin (CAR) injection into the pleural cavity causes local inflammation called carrageenin-induced pleurisy (CAR-IP). Inflammation onset is characterized by an activation of pro-inflammatory NFkappaB, RelA-p50, while inflammation resolution is characterized by an activation of an anti-inflammatory NFkappaB, p50-p50, that re-establishes homeostasis, an essential process for an organism's survival. Although chronic alcohol intake disrupts inflammation, the mechanism behind the development of inflammatory disorder in alcoholics is not yet known. Therefore, the aim of this investigation was to study the effects of ethanol intake on CAR-IP and NFkappaB activation in pleural fluid neutrophils in P rats.

METHODS

Alcohol-preferring, P rats were given free choice of alcohol (15% ethanol) and water or water alone (for control) for 15 days. Then, each rat was injected with 0.2 ml of 2% CAR into the pleural cavity under light ether anesthesia. At different time intervals after the CAR injection, rats were anesthetized and their blood and pleural fluid samples were collected. Pleural fluid inflammatory cells were identified with Turk's or Wright-Giemsa staining. Different cell types were sorted using a fluorescence-activated cell sorter. Pleural fluid neutrophils were examined for apoptosis and activation of the two NFkappaB subspecies.

RESULTS

In control rats, fluid began to accumulate in the pleural cavity 0.5 h after, which peaked 24 h after, CAR injection. Then, the values declined gradually. The increase in pleural fluid correlated with RelA-p50 activation, while the decline in pleural fluid correlated with p50-p50 activation and apoptosis in neutrophils. In alcohol-drinking rats, pleural fluid remained elevated for up to 6 days after CAR injection. Neutrophils from alcohol-drinking rats exhibited suppressed apoptosis, augmented RelA-p50 activation, and suppressed p50-p50 activation.

CONCLUSIONS

Alcohol intake prolonged inflammation in P rats. An alcohol-induced upregulation of RelA-p50 activation and downregulation of p50-p50 activation may be causally related to the alcohol-induced inflammation dysregulation.

Transcription factors in the cellular signaling network as prime targets of chemopreventive phytochemicals

Accumulating evidence from epidemiologic and laboratory studies support an inverse relationship between a regular consumption of fruits and vegetables and the risk of specific cancers. Numerous phytochemicals derived from edible plants have been reported to possess ability to interfere with a specific stage of carcinogenic process. Multiple mechanisms have been proposed to account for the anti-carcinogenic actions of dietary constituents, but more attention has recently focussed on intracellular signaling cascades as common molecular targets of a wide variety of chemopreventive phytochemicals.

Hepatocyte growth factor-induced proliferation of hepatic stem-like cells depends on activation of NF-kappaB

BACKGROUND/AIMS

Hepatocyte growth factor (HGF) regulates proliferation of hepatic stem cells. Transcription factor nuclear factor kappa B (NF-kappaB) has been demonstrated as a key mediator for cell growth regulation. We investigated the role of NF-kappaB in HGF-mediated cellular proliferation responses in a rat liver-derived hepatic stem-like cell line WB-F344.

METHODS

Cell proliferation was determined by incorporation of [3H]thymidine. Phosphorylation of ERK1/2, p38 MAPK, Akt and IkappaBalpha by HGF stimulation was detected by Western blotting. NF-kappaB activation was determined by electrophoretic mobility shift assay and NF-kappaB-mediated SEAP reporter assay. NF-kappaB activation was inhibited by treatment with an IkappaBalpha dominant-negative vector or inhibitor BAY-11-7082.

RESULTS

We found that stimulation of WB-F344 cells with HGF promoted cell proliferation and effectively protected WB-F344 cells from apoptosis induced by TNF-alpha. We also observed activation of ERK1/2, p38 MAPK, Akt and NF-kappaB signaling pathways by HGF in WB-F344 cells. HGF-induced cell proliferation was partly blocked by pre-treatment of the cells with inhibitors against MEK1 or p38 MAPK, and completely blocked using an inhibitor for NF-kappaB activity. Furthermore, it was demonstrated that IkappaB mutant that suppressed NF-kappaB activity completely blocked HGF-induced cell proliferation.

CONCLUSIONS

NF-kappaB activity is required for HGF-induced proliferation in hepatic stem-like cell line WB-F344, and this activity requires ERK1/2 and p38 MAPK pathways.

Cancer chemoprevention with dietary phytochemicals

Chemoprevention refers to the use of agents to inhibit, reverse or retard tumorigenesis. Numerous phytochemicals derived from edible plants have been reported to interfere with a specific stage of the carcinogenic process. Many mechanisms have been shown to account for the anticarcinogenic actions of dietary constituents, but attention has recently been focused on intracellular-signalling cascades as common molecular targets for various chemopreventive phytochemicals.

Expressive characteristic and biological significance of oncogenes during rat hepatocarcinogenesis

AIM

To explore the expressive characteristic and biological significance of oncogenes during experimental hepatocarcinogenesis in rat.

METHODS

A rat model of liver carcinoma was induced with carcinogen 3-Me-DAB. The hepatic expressive characteristic of Ha-ras, c-myc and Ki-ras rats in varied stages in induction of cancer were examined with in situ hybridization and RNA slot blot hybridization.

RESULTS

The hepatic expression and distribution of Ha-ras and c-myc were similar in different periods of cancer induction. In early stage of carcinoma induction, there were more positive cells of Ha-ras and c-myc but little Ki-ras positive cells. In late stage of carcinoma induced, the number of positive cells of three oncogenes was decreased; On the 17th week of induction of cancer, the signals of three oncogenes in all the cancer nodules were negative or weak but stronger in hepatic peri-cancer tissues.

CONCLUSION

Oncogenes Ha-ras and c-myc were activated and had synergistic effect on the malignant transformation of cells in early stage of hepatocarcinogenesis. Ki-ras might be activated in late stage of hepatocarcinogenesis and associated with malignant transformation of hepatocytes.

Hepatocyte growth factor induces apoptosis through the extrinsic pathway in hepatoma cells: favouring role of hypoxia-inducible factor-1 deficiency

Two hepatocarcinoma cell lines, the Hepa-1 wild-type (c1c7) and the beta-subunit mutated (c4) lacking hypoxia-inducible factor-1 (HIF-1) activity, were differentially susceptible to apoptosis by hepatocyte growth factor (HGF). The c4 cells were 40% apoptotic 48 h after HGF treatment. On the contrary, the wild-type c1c7 cells showed modest signs of apoptosis only at 72 h. The revertant vT[2] cells, consisting of c4 cells stably transfected with HIF-1beta expression vector, behaved as the parental cells. To understand the mechanisms of this different sensitivity, we examined a panel of genes involved in apoptosis: ornithine decarboxylase, c-Myc and p53 protein levels progressively decreased while JNK1, caspase 8 and 3 activities persistently increased in c4 cells undergoing apoptosis. Distinct time-related events in c1c7 cells were the transient activations of JNK1 and caspase 8 followed by the accumulation of ODC and c-Myc proteins. The proapoptotic effect of HGF in c4 hepatocarcinoma cells seems to be related to HIF-1 deficiency with loss of cytoprotective and signalling functions. This may contribute to the triggering of the extrinsic pathway consisting in caspase 8 activation, which in turn causes BID cleavage and cytochrome c release. The effector caspase 3 is also activated.

Heparanase expression correlates with invasion and poor prognosis in gastric cancers

Degradation of basement membrane and extracellular matrix structures are important features of the metastatic process of malignant tumors. Human heparanase degrades heparan sulfate proteoglycans, which represent the main components of basement membranes and the extracellular matrix. Because of the role of heparanase in tumor invasion and metastasis, we examined heparanase expression in primary gastric cancers and in cell lines derived from gastric cancers by immunohistochemistry and RT-PCR, respectively. Four of seven gastric cancer cell lines showed heparanase mRNA expression by RT-PCR. Heparanase protein was detected in both the cytoplasm and the nucleus of heparanase mRNA-positive cells by immunohistochemical staining. Heparanase expression was confirmed in 35 (79.5%) of 44 gastric tumor samples by immunohistochemical staining. However, no or weak heparanase expression was detected in normal gastric mucosa. In situ hybridization showed that the mRNA expression pattern of heparanase was similar to that of the protein, suggesting that increased expression of the heparanase protein at the invasive front was caused by an increase of heparanase mRNA in tumor cells. Analysis of the clinicopathologic features showed stronger heparanase expression in cases of huge growing tumors, extensive invasion to lymph vessels, and regional lymph node metastasis. In gastric cancer, patients with heparanase expression showed significantly poorer prognosis than those without such expression (p = 0.006). In conclusion, our findings suggest that high expression of heparanase in gastric cancer is a strong predictor of poor survival.

Contribution of spermidine to stimulation by hepatocyte growth factor in repair after damage of rabbit gastric mucosal cells in primary culture

Wound-healing of the gastric mucosa is suggested to be stimulated by hepatocyte growth factor (HGF). Polyamines are shown to contribute to repair after damage in the gastric mucosa. The present study was designed to elucidate whether HGF can stimulate wound-healing of the gastric mucosa via polyamine production, using rabbit gastric mucosal cells in primary culture. A wound was made as a round cell-free area in the cell sheet of confluent cultured cells. When HGF was added to the culture medium, such denuded area was significantly reduced in size compared with the control, but the reduction was inhibited by addition of D,L-alpha-difluoromethylornithine (DFMO), an inhibitor of a rate-limiting enzyme (ornithine decarboxylase) of polyamine biosynthesis, to the culture medium. However, the inhibitory effect by DFMO was reversed by pretreatment with spermidine, but not with putrescine. Intracellular levels of polyamines in the whole confluent cells including the cells around the denuded area were not changed by addition of HGF, but putrescine and spermidine levels were decreased by further addition of DFMO. We conclude that spermidine may be involved in stimulation by HGF in the repair after damage of gastric mucosal cells.

A cluster region of AP-1 responsive elements is required for transcriptional activity of mouse ODC gene by hepatocyte growth factor

Ornithine decarboxylase (ODC) activity is regulated by a variety of mechanisms including transcription, translation, and RNA and protein half-life. Since in mouse B16-F1 melanoma cells an early and remarkable (about 6-fold) increase in steady state mRNA levels was observed after hepatocyte growth factor (HGF) treatment, we investigated the transcriptional regulation of mouse ODC promoter. Transient transfection of various ODC-luciferase promoter constructs into the B16-Fl cells in combination with electrophoretic mobility shift assays identified the HGF-responsive element as a cluster of three AP-1 binding sites (-1660 to -1572). Even if each site differs from the canonical TPA responsive element for one nucleotide, only the first two AP-1 consensus sequences seemed to be functional since allowed DNA-binding activity of nuclear proteins after HGF treatment. Comparison of the results of transfection assays with the pOD2.5-luc (2.5 kb gene fragment) and with the construct deprived of the AP-1 cluster pOD-B-luc showed that this 50 bp region was required for ODC transactivating activity in response to HGF. Since in B16-F1 cells HGF increased AP-1 activity and the mRNA expression of various AP-1 subunits, we may conclude that HGF-induced transcription of mouse ODC was largely due to triggering of AP-1 pathway.

Aspirin and NS-398 inhibit hepatocyte growth factor-induced invasiveness of human hepatoma cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) activity and are considered to exert antitumor actions in a variety of cancer cells, although the effects are unlikely entirely due to COX inhibition. Because clinical observations suggest that hepatocyte growth factor (HGF) can promote metastasis of hepatoma cells while stimulating tumor invasiveness, we investigated the effect of aspirin and NS-398, a selective COX-2 inhibitor, on HGF-mediated invasiveness of HepG2 human hepatoma cells. HGF stimulated the invasiveness of HepG2 cells in Matrigel cell invasion assay, together with increased expression of matrix metalloproteinase (MMP) 9. Addition of aspirin or NS-398, similar to PD98059, which acts as a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK), an upstream kinase regulating extracellular signal-regulated kinase (ERK)1/2, abrogated such actions of HGF without affecting cell viability. Aspirin and NS-398, in contrast to PD98059, did not suppress ERK1/2 phosphorylation induced by HGF. However, both agents inhibited the kinase activity of ERK1/2 induced by HGF and repressed HGF-induced phosphorylation of 90-kd ribosomal S6 kinase (RSK) and Elk-1, key downstream substrates of ERK1/2, resulting in the suppression of transcriptional activity of Elk-1 as well as nuclear factor kappaB (NF-kappaB) and AP-1, which are involved in MMP-9 gene regulation. In conclusion, our results suggest that aspirin and NS-398 inhibit HGF-induced invasiveness of HepG2 human hepatoma cells through ERK1/2.

Scatter factor/hepatocyte growth factor stimulation of glioblastoma cell cycle progression through G(1) is c-Myc dependent and independent of p27 suppression, Cdk2 activation, or E2F1-dependent transcription

Scatter factor/hepatocyte growth factor (SF/HGF) expression has been linked to malignant progression in glial neoplasms. Using two glioma cell lines, U373MG and SNB-19, we have demonstrated that SF/HGF stimulation allows cells to escape G(1)/G(0) arrest induced by contact inhibition or serum withdrawal. SF/HGF induced effects on two mechanisms of cell cycle regulation: suppression of the cyclin-dependent kinase inhibitor p27 and induction of the transcription factor c-Myc. Regulation of p27 by SF/HGF was posttranslational and is associated with p27 nuclear export. Transient transfections of U373MG and SNB-19 with wild-type p27 and a degradation-resistant p27T187A mutant were insufficient to induce cell cycle arrest, and SF/HGF downregulation of p27 was not necessary for cell cycle reentry. Analysis of Cdk2 kinase activity and p27 binding to cyclin E complexes in the presence of exogenous wild-type p27 or p27T187A demonstrated that Cdk2 activity was not necessary for SF/HGF-mediated G(1)/S transition. Similarly, overexpression of dominant-negative forms of Cdk2 did not block SF/HGF-triggered cell cycle progression. In contrast, SF/HGF transcriptionally upregulated c-Myc, and overexpression of c-Myc was able to prevent G(1)/G(0) arrest in the absence of SF/HGF. Transient overexpression of MadMyc, a dominant-negative chimera for c-Myc, caused G(1)/G(0) arrest in logarithmically growing cells and blocked SF/HGF-mediated G(1)/S transition. c-Myc did not exert its effects through p27 downregulation in these cell lines. SF/HGF induced E2F1-dependent transcription, the inhibition of which did not block SF/HGF-induced cell cycle progression. We conclude that SF/HGF prevents G(1)/G(0) arrest in glioma cell lines by a c-myc-dependent mechanism that is independent of p27, Cdk2, or E2F1.

Wheat germ extract decreases glucose uptake and RNA ribose formation but increases fatty acid synthesis in MIA pancreatic adenocarcinoma cells

The fermented wheat germ extract with standardized benzoquinone composition has potent tumor propagation inhibitory properties. The authors show that this extract induces profound metabolic changes in cultured MIA pancreatic adenocarcinoma cells when the [1,2-13C2]glucose isotope is used as the single tracer with biologic gas chromatography-mass spectrometry. MIA cells treated with 0.1, 1, and 10 mg/mL wheat germ extract showed a dose-dependent decrease in cell glucose consumption. uptake of isotope into ribosomal RNA (2.4%, 9.4%, and 28.0%), and release of 13CO2. Conversely, direct glucose oxidation and ribose recycling in the pentose cycle showed a dose-dependent increase of 1.2%, 20.7%, and 93.4%. The newly synthesized fraction of cell palmitate and the 13C enrichment of acetyl units were also significantly increased with all doses of wheat germ extract. The fermented wheat germ extract controls tumor propagation primarily by regulating glucose carbon redistribution between cell proliferation-related and cell differentiation-related macromolecules. Wheat germ extract treatment is likely associated with the phosphorylation and transcriptional regulation of metabolic enzymes that are involved in glucose carbon redistribution between cell proliferation-related structural and functional macromolecules (RNA, DNA) and the direct oxidative degradation of glucose, which have devastating consequences for the proliferation and survival of pancreatic adenocarcinoma cells in culture.

Hepatocyte growth factor induces pro-apoptotic genes in HepG2 hepatoma but not in B16-F1 melanoma cells

Hepatocyte growth factor (HGF) exerts a cytostatic effect on HepG2 and B16-F1 cell lines. To evaluate the possible involvement of the apoptotic process in this effect, we performed studies at cellular and molecular levels. HGF induced apoptosis only in HepG2 hepatoma cells at day 3 in about 20% of the cells undergoing growth inhibition, while hallmarks of apoptosis did not occur in B16-F1 melanoma cells. During the first 24 h after HGF treatment, enhanced expression of the pro-apoptotic genes bax and c-Myc was observed at level of mRNA and protein. Concomitant induction of antizyme (AZ) might lower ornithine decarboxylase (ODC) protein level though a huge increase in ODC mRNA level took place. This was suggested as a signal for apoptosis decisional phase. The levels of the proteins examined except that of AZ fell down thereafter when HepG2 cells underwent apoptosis. In B16-F1 cells, only ODC and AZ protein levels were elevated probably in relation to the initial elevated growth rate and the absence of apoptosis involvement in the following cytostatic effect of HGF in melanoma cells. Consistent with this hypothesis, bax mRNA and protein levels were unchanged or even lower relative to control values.

Influence of proteasome and redox state on heat shock-induced activation of stress kinases, AP-1 and HSF

We studied the pattern of activation of stress kinases and of transcription factors activator protein-1 (AP-1) and heat shock factor (HSF) in FAO cells by combining two treatments, i.e. heating (42 degrees C for 1 h) and proteasome inhibition, each known to cause cellular heat shock response. The co-treatment heat shock (HS) and proteasome inhibitor (a peptidyl aldehyde or lactacystin) showed cumulative effects on the intensity and duration of activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) at the end of the HS period and during recovery. Similarly, the thiol-reducing agents N-(2-mercaptoethyl)-1,3-diaminopropane and dithiothreitol strongly activated both JNK and p38 MAPK in cells undergoing HS. AP-1 DNA binding activity in response to proteasome inhibitors was so strong that it shadowed the stimulatory effect of HS in the combined treatment, but lactacystin, which is the most potent and specific proteasome inhibitor, decreased the binding late during recovery from HS. Thiol-reducing agents prevented AP-1 DNA binding induced by HS. The combined HS/proteasome inhibitors or HS/thiol-reducing agents treatments cooperatively activated HSF DNA binding. Expression of collagenase I and hsp 70 mRNAs reflects the different behavior of AP-1 and HSF transcription factors in cells exposed to HS and proteasome inhibition. The data seem to indicate that JNK and p38 MAPK activations are not necessarily coupled to DNA binding of AP-1, which can be either increased or inhibited when these kinases are activated. AP-1 and HSF show opposite patterns of response to HS in the presence of proteasome inhibitors or reducing agents.

Cross-talk between steroid-receptor-mediated and cell-membrane-receptor-mediated signalling pathways results in the in vivo modulation of c-Met and ornithine decarboxylase gene expression in mouse kidney

The cross-talk in vivo between two signalling pathways activated by testosterone via intracellular androgen receptor, and induced by damage to renal tubules evoked by anti-folate [N(10)-propargyl-5,8-dideazafolic acid (CB 3717)] or folate is reported. We show that CB 3717/folate induces the expression of the hepatocyte growth factor (HGF)/c-Met signalling system in injured kidneys in which a significant, but transient, elevation of the HGF mRNA level occurs. It is followed by a severalfold increase in the c-Met transmembrane receptor message that persists for up to 24 h. The c-Met expression is also positively controlled by testosterone, which induces a significant increase in its mRNA level that is abolished by an anti-androgen, casodex. However, when testosterone and anti-folate/folate are administered sequentially, a substantial (3.5-4.0-fold) decrease in the increase of c-Met expression caused by CB 3717/folate alone occurs. Similarly, testosterone-induced ornithine decarboxylase (ODC) mRNA level and activity are decreased 2.8-7.7-fold when the androgen is applied together with CB 3717. Antagonism between these pathways is also visible under physiological conditions in the kidneys of male mice in which, owing to elevated endogenous testosterone levels, neither the ODC activity nor the mRNA level is induced by anti-folate/folate, whereas the c-Met message response to these drugs is significantly decreased. Our results document a substantial negative regulation of c-Met and ODC gene expression as a result of the cross-talk between testosterone-activated and HGF-activated pathways and suggest a sex-differentiated response to injury of mouse kidneys.

Genistein inhibits nonoxidative ribose synthesis in MIA pancreatic adenocarcinoma cells: a new mechanism of controlling tumor growth

Genistein is a plant isoflavonoid bearing potent tumor growth-regulating characteristics. This effect of genistein has been attributed partially to its tyrosine kinase-regulating properties, resulting in cell-cycle arrest and limited angiogenesis. Genistein has been used in chemotherapy-resistant cases of advanced leukemia with promising results. Here we demonstrate that genistein primarily affects nucleic acid synthesis and glucose oxidation in tumor cells using the [1,2-(13)C2]glucose isotope as the single tracer and gas chromatography/mass spectrometry to follow various intracellular glucose metabolites. The ribose fraction of RNA demonstrated a rapid 4.6%, 16.4%, and 46.3% decrease in isotope uptake through the nonoxidative branch of the pentose cycle and a sharp 4.8%. 24.6%, and 48% decrease in 13CO2 release from glucose after 2, 20, and 200 micromol/L genistein treatment, respectively. Fatty acid synthesis and the 13C enrichment of acetyl units were not significantly affected by genistein treatment. De novo glycogen synthesis from media glucose was not detected in cultured MIA cells. It can be concluded from these studies that genistein controls tumor growth primarily through the regulation of glucose metabolism, specifically targeting glucose carbon incorporation into nucleic acid ribose through the nonoxidative steps of the pentose cycle, which represents a new paradigm for the antiproliferative action of a plant phytochemical.