Functional cooperation between JunD and NF-kappaB in rat hepatocytes

GSK3β inhibition attenuates LPS-induced IL-6 expression in porcine adipocytes

IL-6 is not only a proinflammatory cytokine associated with inflammatory responses but also a regulator on the energy and glucose metabolism in adipose tissue. Glycogen synthase kinase 3β (GSK3β) has fundamental roles in the regulation of pro- and anti-inflammatory cytokines production. However, the regulatory role for GSK3β in the pig inflammatory response in adipocytes remains unknown. We show here that SB216763 and LPS increased the phosphorylation of GSK3β (Ser9), and decreased the phosphorylation of GS (Ser641) in adipocytes. The activity of porcine GSK3β was inhibited by SB216763, an inhibitor of GSK3β, attenuated the production of IL-6 in LPS-stimulated adipocytes. Additionally, the essential core region of the pig IL-6 promoter located at -191 bp to -59 bp, and an NF-κBp65 element in this region was responsible for IL-6 promoter activity. The transcription activity of NF-κBp65 was activated by LPS stimulation, and the GSK3β inhibition repressed LPS-induced luciferase activity of the IL-6 promoter. Furthermore, LPS increased p65 binding to the NF-κB site, and GSK3β inhibition had no effect on the association of NF-κBp65 with IL-6 gene promoter after LPS treatment. These results demonstrate that GSK3β has important regulatory roles in the LPS-induced inflammatory response of IL-6 production in pig adipocytes.

A c-Jun N-terminal kinase inhibitor, JNK-IN-8, sensitizes triple negative breast cancer cells to lapatinib

Triple negative breast cancers (TNBC) have poor prognosis compared to other breast cancer subtypes and represent 15-20% of breast cancers diagnosed. Unique targets and new molecularly-targeted therapies are urgently needed for this subtype. Despite high expression of Epidermal Growth Factor Receptor, inhibitors such as lapatinib have not shown therapeutic efficacy in TNBC patients. Herein, we report that treatment with the covalent JNK inhibitor, JNK-IN-8, synergizes with lapatinib to cause cell death, while these compounds as single agents have little effect. The combination significantly increases survival of mice bearing xenografts of MDA-MB-231 human TNBC cells. Our studies demonstrate that lapatinib treatment increases c-Jun and JNK phosphorylation indicating a mechanism of resistance. Combined, these compounds significantly reduce transcriptional activity of Nuclear Factor kappa B, Activating Protein 1, and Nuclear factor erythroid 2-Related Factor 2. As master regulators of antioxidant response, their decreased activity induces a 10-fold increase in reactive oxygen species that is cytotoxic, and is rescued by addition of exogenous antioxidants. Over expression of p65 or Nrf2 also significantly rescues viability during JNK-IN-8 and lapatinib treatment. Further studies combining JNK-IN-8 and lapatinib may reveal a benefit for patients with TNBC, fulfilling a critical medical need.

An initial phase of JNK activation inhibits cell death early in the endoplasmic reticulum stress response

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) activates the unfolded protein response (UPR). In mammalian cells, UPR signals generated by several ER-membrane-resident proteins, including the bifunctional protein kinase endoribonuclease IRE1α, control cell survival and the decision to execute apoptosis. Processing of XBP1 mRNA by the RNase domain of IRE1α promotes survival of ER stress, whereas activation of the mitogen-activated protein kinase JNK family by IRE1α late in the ER stress response promotes apoptosis. Here, we show that activation of JNK in the ER stress response precedes activation of XBP1. This activation of JNK is dependent on IRE1α and TRAF2 and coincides with JNK-dependent induction of expression of several antiapoptotic genes, including cIap1 (also known as Birc2), cIap2 (also known as Birc3), Xiap and Birc6 ER-stressed Jnk1(-/-) Jnk2(-/-) (Mapk8(-/-) Mapk9(-/-)) mouse embryonic fibroblasts (MEFs) display more pronounced mitochondrial permeability transition and increased caspase 3/7 activity compared to wild-type MEFs. Caspase 3/7 activity is also elevated in ER-stressed cIap1(-/-) cIap2(-/-) and Xiap(-/-) MEFs. These observations suggest that JNK-dependent transcriptional induction of several inhibitors of apoptosis contributes to inhibiting apoptosis early in the ER stress response.

Pooled ChIP-Seq Links Variation in Transcription Factor Binding to Complex Disease Risk

Cis-regulatory elements such as transcription factor (TF) binding sites can be identified genome-wide, but it remains far more challenging to pinpoint genetic variants affecting TF binding. Here, we introduce a pooling-based approach to mapping quantitative trait loci (QTLs) for molecular-level traits. Applying this to five TFs and a histone modification, we mapped thousands of cis-acting QTLs, with over 25-fold lower cost compared to standard QTL mapping. We found that single genetic variants frequently affect binding of multiple TFs, and CTCF can recruit all five TFs to its binding sites. These QTLs often affect local chromatin and transcription but can also influence long-range chromosomal contacts, demonstrating a role for natural genetic variation in chromosomal architecture. Thousands of these QTLs have been implicated in genome-wide association studies, providing candidate molecular mechanisms for many disease risk loci and suggesting that TF binding variation may underlie a large fraction of human phenotypic variation.

Apurinic/apyrimidinic endonuclease/redox effector factor-1(APE/Ref-1): a unique target for the prevention and treatment of human melanoma

Management of melanoma is a growing and challenging public health issue requiring novel and multidisciplinary approaches to achieve more efficient prevention and therapeutic benefits. The aim of this article is to show the critical role of APE/Ref-1 on melanomagenesis and progression. APE/Ref-1 serves as a redox-sensitive node of convergence of various signals as well as a DNA-repair enzyme, and its activation protects melanocytes and melanoma cells from chronic oxidative stress and promotes cell survival via mediation of downstream pathways. APE/Ref-1 is a strong candidate as a potential drug-treatable target for the prevention and treatment of human melanoma. Lead compounds exhibiting inhibitory effects on APE/Ref-1 are also reviewed. We anticipate potential clinical benefit in the future through inhibition of APE/Ref-1 and/or Ref-1-mediated signaling.

PI3K limits TNF-alpha production in CD16-activated monocytes

IgG complexes bind to Fc receptor family members FcgammaRI (CD64), FcgammaRII (CD32) and FcgammaRIII (CD16), activating cell MAPK and PI3K resulting in increased cytokine production from particular leukocytes. The signaling molecules involved in cytokine production after cross-linking CD16 have not been determined in monocytes. To address this question, TNF-alpha, IL-1beta and IL-6 were measured in activated monocytes after inhibiting MEK1/2, PI3K and glycogen synthase kinase-beta (GSK-3beta). The roles of GSK-3beta and NF-kappaB were then determined using reporter assays and siRNA treatment. The data suggested that an MAPK pathway stimulated TNF-alpha release but that active PI3K limited TNF-alpha, IL-1beta and IL-6 cytokine production after cross-linking CD16. PI3K was also shown to limit nuclear translocation of NF-kappaB. The limiting effect of PI3K on TNF-alpha production from activated monocytes depended on the decrease of GSK-3beta activity, which significantly reduced the transactivation of NF-kappaB. Moreover, the TNF-alpha production induced by CD16 cross-linking was reduced in monocytes after treatment with siRNA against NF-kappaB, implying that this transcription factor functioned in TNF-alpha production. The results suggest that CD16 cross-linking activated PI3K and that active PI3K limited TNF-alpha production by inhibiting GSK-3beta activity, that blocked the action of NF-kappaB.

JunD mediates androgen-induced oxidative stress in androgen dependent LNCaP human prostate cancer cells

BACKGROUND

Numerous and compelling evidence shows that high level of reactive oxygen species (ROS) plays a key role in prostate cancer occurrence, recurrence and progression. The molecular mechanism of ROS overproduction in the prostate gland, however, remains mostly unknown. Unique AP-1 transcription factor JunD has been shown to inhibit cell proliferation, promote differentiation and mediate stress responses in a variety of eukaryotic cells. We previously reported that androgen-androgen receptor induced ROS production in androgen-dependent LNCaP human prostate cancer cells is associated with increased JunD level/AP-1 transcriptional activity.

METHODS

LNCaP cells constitutively overexpressing a functionally inactive form of JunD (JunDDeltaTA) or stably transfected with JunD siRNA (siJunD) to suppress JunD protein expression were established. Overexpression of JunD in LNCaP cells using transient transfection method was applied to assess the induction of ROS production in LNCaP cells. DCF assay was used to measure the ROS concentrations in the transfected as well as non-transfected control cells. RT-PCR and Western blot analyses were used to confirm silencing or overexpression of JunD in the transfected cells.

RESULTS

In the absence of androgen, LNCaP cells transiently transfected with a JunD overexpressing vector have relatively enhanced cellular ROS levels as compared to LNCaP cells transfected with a vector control. LNCaP cells that fail to express functional JunD (JunDDeltaTA or siJunD) do not exhibit any increase in ROS production in response to androgen.

CONCLUSION

Based on these data, we conclude that JunD is an essential mediator of the androgen-induced increase in ROS levels in LNCaP cells.

Ultraviolet B regulation of transcription factor families: roles of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) in UVB-induced skin carcinogenesis

Prolonged and repeated exposure of the skin to ultraviolet light (UV) leads not only to aging of the skin but also increases the incidence of non-melanoma skin cancer (NMSC). Damage of cells induced by ultraviolet B (UVB) light both at the DNA level and molecular level initiates the activation of transcription factor pathways, which in turn regulate the expression of a number of genes termed the "UV response genes". Two such transcription factor families that are activated in this way are those of the nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) families. These two transcription factor families have been identified to be involved in the processes of cell proliferation, cell differentiation and cell survival and therefore play important roles in tumorigenesis. The study of these two transcription factor pathways and the cross-talk between them in response to UVB exposure may help with the development of new chemopreventive strategies for the prevention of UVB-induced skin carcinogenesis.

Gene expression profile analysis of the spontaneous reversal of rat hepatic fibrosis by cDNA microarray

Our aim was to gain insight into the gene expression profile during hepatic fibrosis autoreversal. Spontaneous recovery from hepatic fibrosis was created in SD rats by CCl(4) exposure for 8 weeks and then withdrawal for 6 weeks. Then differentially expressed genes during regression of fibrosis were analyzed using cDNA microarray. Results obtained were further subjected to hierarchical clustering and validated by semiquantitative RT-PCR. Expression of Mapk1 and Rps6ka1, which are critical members of the mitogen-activated protein kinase (MAPK) signaling pathway, was also investigated by Northern blot and immunohistochemistry. Microarray hybridization identified 254 genes differentially expressed throughout resolution of fibrosis. Being verified by RT-PCR, up- or down-regulated genes were classified into various groups according to clustering and function: (1) metabolic enzymes, (2) facilitated diffusion proteins/transporters/symporters, (3) gastrointestinal hormones/receptors, (4) lipoproteins/fatty acid binding proteins, (5) transcription factors/nuclear factors, and (6) the MAPK signaling pathway. The mRNA level of Mapk1 increased greatly as hepatic fibrosis reversed. Meanwhile Mapk1 and Rps6ka1 were proven to be expressed in hepatocytes and absent from mesenchymal cells. Six groups of genes exhibit a close relation to the recovery of CCl(4)-induced hepatic fibrosis. The MAPK signaling-dependent pathway, representing one of the gene groups, may contribute to the reversal of hepatic fibrosis.

Physical and functional cooperation between AP-1 and beta-catenin for the regulation of TCF-dependent genes

Stabilization of cytoplasmic beta-catenin is a hallmark of a variety of cancers. The stabilized beta-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. beta-Catenin may cross-talk with many signalling cascades to activate target genes. Whether beta-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that beta-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of beta-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of beta-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two beta-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/beta-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing beta-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.

JunD is a profibrogenic transcription factor regulated by Jun N-terminal kinase-independent phosphorylation

JunD is implicated in the regulation of hepatic stellate cell (HSC) activation and liver fibrosis via its transcriptional regulation of the tissue inhibitor of metalloproteinases-1 (TIMP-1) gene. In the present study we found in vivo evidence of a role for JunD in fibrogenesis. Expression of JunD was demonstrated in alpha-SMA-positive activated HSCs of fibrotic rodents and human livers. The junD-/- mice were protected from carbon tetrachloride-induced fibrosis. The livers of injured junD-/- mice displayed significantly reduced formation of fibrotic crosslinked collagen and a smaller number of alpha-SMA-positive HSCs compared with those of wild-type (wt) mice. Hepatic TIMP-1 mRNA expression in injured junD-/- mice was 78% lower and in culture activated junD-/- HSCs was 50%-80% lower than that in wt mice. In examining the signal transduction mechanisms that regulate JunD-dependent TIMP-1 expression, we found a role for phosphorylation of the Ser100 residue of JunD but ruled out JNK as a mediator of this event, suggesting ERK1/2 is utilized. In conclusion, a signaling pathway for the development of fibrosis involves the regulation of TIMP-1 expression by phosphorylated JunD.

Glycogen synthase kinase 3beta functions to specify gene-specific, NF-kappaB-dependent transcription

Loss of glycogen synthase kinase 3beta (GSK-3beta) in mice results in embryonic lethality via hepatocyte apoptosis. Consistent with this result, cells from these mice have diminished nuclear factor kappaB (NF-kappaB) activity, implying a functional role for GSK-3beta in regulating NF-kappaB. Here, we have explored mechanisms by which GSK-3beta may control NF-kappaB function. We show that cytokine-induced IkappaB kinase activity and subsequent phosphorylation of IkappaBalpha, p105, and p65 are not affected by the absence of GSK-3beta activity. Furthermore, nuclear accumulation of p65 following tumor necrosis factor treatment is unaffected by the loss of GSK-3beta. However, NF-kappaB DNA binding activity is reduced in GSK-3beta null cells and in cells treated with a pharmacological inhibitor of GSK-3. Expression of certain NF-kappaB-regulated genes, such as IkappaBalpha and macrophage inflammatory protein 2, is minimally affected by the absence of GSK-3beta. Conversely, we have identified a subset of NF-kappaB-regulated genes, including those for interleukin-6 and monocyte chemoattractant protein 1, that require GSK-3beta for efficient expression. We show that efficient localization of p65 to the promoter regions of the interleukin-6 and monocyte chemoattractant protein 1 genes following tumor necrosis factor alpha treatment requires GSK-3beta. Therefore, GSK-3beta has profound effects on transcription in a gene-specific manner through a mechanism involving control of promoter-specific recruitment of NF-kappaB.

Differential inhibition of UVB-induced AP-1 and NF-kappaB transactivation by components of the jun bZIP domain

Potential targets for chemoprevention of nonmelanoma skin cancer include UV-induced nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1) activation in keratinocytes. Inhibition of both these ultraviolet light B (UVB)-induced transcription factors has been shown with the dominant-negative c-jun mutant, TAM67; however, its mechanism of action has not yet been determined. Here we demonstrated that transient transfection of a mouse keratinocyte cell line (308) with a dominant-negative phosphorylation mutant of c-Jun before exposure to 250 J/m(2) UVB inhibits transactivation mediated by both AP-1 and NF-kappaB transcription factors to levels below those of UVB exposed controls. Through the utilization of immunoprecipitation techniques, protein-protein interactions between NF-kappaB family members IkappaBalpha, IkappaBbeta, p50, and p65 (Rel-A) were identified with an Xpress tagged dominant-negative c-Jun (TAM67) protein. Expression of the leucine zipper domain of the TAM67 protein inhibited UVB-induced NF-kappaB transactivation but not AP-1 transactivation. Expression of the bZIP domain of the TAM67 protein was able to inhibit transactivation mediated by both transcription factors. These data demonstrate that TAM67 is able to inhibit two significant UVB-induced molecular targets AP-1 and NF-kappaB, and that the inhibition of these two transcription factor families is potentially due to protein-protein interactions between different regions of the dominant-negative c-Jun protein.

Role of NF-kappaB signaling in hepatocyte growth factor/scatter factor-mediated cell protection

The cytokine scatter factor/hepatocyte growth factor (HGF/SF) protects epithelial, carcinoma, and other cell types against cytotoxicity and apoptosis induced by DNA-damaging agents such as ionizing radiation and adriamycin (ADR, a topoisomerase IIalpha inhibitor). We investigated the role of nuclear factor kappa B (NF-kappaB) signaling in HGF/SF-mediated protection of human prostate cancer (DU-145) and Madin-Darby canine kidney (MDCK) epithelial cells against ADR. HGF/SF caused the rapid nuclear translocation of the p65 (RelA) subunit of NF-kappaB associated with the transient loss of the inhibitory subunit IkappaB-alpha. Exposure to HGF/SF caused the activation of an NF-kappaB luciferase reporter that was blocked or attenuated by the expression of a mutant 'super-repressor' IkappaB-alpha. Electrophoretic mobility shift assay supershift assays revealed that HGF/SF treatment induced the transient binding of various NF-kappaB family proteins (p65, p50, c-Rel, and RelB) with radiolabeled NF-kappaB-binding oligonucleotides. The HGF/SF-mediated protection of DU-145 and MDCK cells against ADR (demonstrated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays) was abrogated by the IkappaB-alpha super-repressor. The ability of HGF/SF to activate NF-kappaB signaling was dependent on c-Akt --> Pak1 (p21-associated kinase-1) signaling (with Pak1 downstream of c-Akt) and was inhibited by the tumor suppressor PTEN (phosphatase and tensin homolog). Inhibitors of phosphatidylinositol-3'-kinase and Src family kinases significantly inhibited HGF/SF-mediated activation of NF-kappaB, while inhibitors of MEK, protein kinase C, and p70 S6 kinase had a modest effect or no effect on NF-kappaB activity. HGF/SF induced the expression of several known NF-kappaB target genes (cIAP-1 (cellular inhibitor of apoptosis-1), cIAP-2, and TRAF-2 (TNF receptor-associated factor-2)) in an NF-kappaB-dependent manner; HGF/SF blocked the inhibition of expression of these genes by ADR. Experimental manipulation of expression of these genes suggests that they (particularly TRAF-2 and cIAP-2) contribute to the protection against ADR by HGF/SF. These findings suggest that HGF/SF activates NF-kappaB through a c-Akt --> Pak1 signaling pathway that is also dependent on Src, and that NF-kappaB contributes to HGF/SF-mediated protection against ADR.

Global gene expression in neuroendocrine tumors from patients with the MEN1 syndrome

Background

Multiple Endocrine Neoplasia type 1 (MEN1, OMIM 131100) is an autosomal dominant disorder characterized by endocrine tumors of the parathyroids, pancreatic islets and pituitary. The disease is caused by the functional loss of the tumor suppressor protein menin, coded by the MEN1 gene. The protein sequence has no significant homology to known consensus motifs. In vitro studies have shown menin binding to JunD, Pem, Smad3, NF-kappaB, nm23H1, and RPA2 proteins. However, none of these binding studies have led to a convincing theory of how loss-of-menin leads to neoplasia.

Results

Global gene expression studies on eight neuroendocrine tumors from MEN1 patients and 4 normal islet controls was performed utilizing Affymetrix U95Av2 chips. Overall hierarchical clustering placed all tumors in one group separate from the group of normal islets. Within the group of tumors, those of the same type were mostly clustered together. The clustering analysis also revealed 19 apoptosis-related genes that were under-expressed in the group of tumors. There were 193 genes that were increased/decreased by at least 2-fold in the tumors relative to the normal islets and that had a t-test significance value of p < = 0.005. Forty-five of these genes were increased and 148 were decreased in the tumors relative to the controls. One hundred and four of the genes could be classified as being involved in cell growth, cell death, or signal transduction. The results from 11 genes were selected for validation by quantitative RT-PCR. The average correlation coefficient was 0.655 (range 0.235–0.964).

Conclusion

This is the first analysis of global gene expression in MEN1-associated neuroendocrine tumors. Many genes were identified which were differentially expressed in neuroendocrine tumors arising in patients with the MEN1 syndrome, as compared with normal human islet cells. The expression of a group of apoptosis-related genes was significantly suppressed, suggesting that these genes may play crucial roles in tumorigenesis in this syndrome. We identified a number of genes which are attractive candidates for further investigation into the mechanisms by which menin loss causes tumors in pancreatic islets. Of particular interest are: FGF9 which may stimulate the growth of prostate cancer, brain cancer and endometrium; and IER3 (IEX-1), PHLDA2 (TSS3), IAPP (amylin), and SST, all of which may play roles in apoptosis.

Cotreatment with Suberanoylanilide Hydroxamic Acid and 17-Allylamino 17-demethoxygeldanamycin Synergistically Induces Apoptosis in Bcr-Abl+Cells Sensitive and Resistant to STI571 (Imatinib Mesylate) in Association with Down-Regulation of Bcr-Abl, Abrogation of Signal Transducer and Activator of Transcription 5 Activity, and Bax Conformational Change

Interactions between the histone deacetylase (HDAC) inhibitors suberanoylanilide hydroxamic acid (SAHA) and sodium butyrate (SB) and the heat shock protein (Hsp) 90 antagonist 17-allylamino 17-demethoxygeldanamycin (17-AAG) have been examined in Bcr-Abl(+) human leukemia cells (K562 and LAMA84), including those sensitive and resistant to STI571 (imatinib mesylate). Cotreatment with 17-AAG and SAHA or SB synergistically induced mitochondrial dysfunction (cytochrome c and apoptosis-inducing factor release), caspase-3 and -8 activation, apoptosis, and growth inhibition. Similar effects were observed in LAMA84 cells and K562 cells resistant to STI571, as well as in CD34(+) cells isolated from the bone marrows of three patients with chronic myelogenous leukemia. These events were associated with increased binding of Bcr-Abl, Raf-1, and Akt to Hsp70, and inactivation of extracellular signal-regulated kinase 1/2 and Akt. In addition, 17-AAG/SAHA abrogated the DNA binding and the transcriptional activities of signal transducer and activator of transcription (STAT) 5 in K562 cells, including those ectopically expressing a constitutively active STAT5A construct. Cotreatment with 17-AAG and SAHA also induced down-regulation of Mcl-1, Bcl-xL, and B-Raf; up-regulation of Bak; cleavage of 14-3-3 proteins; and a profound conformational change in Bax accompanied by translocation to the membrane fraction. Moreover, ectopic expression of Bcl-2 attenuated cell death induced by this regimen, implicating mitochondrial injury in the lethality observed. Together, these findings raise the possibility that combining HDAC inhibitors with the Hsp90 antagonist 17-AAG may represent a novel strategy against Bcr-Abl(+) leukemias, including those resistant to STI571.

Interruption of the NF-κB pathway by Bay 11-7082 promotes UCN-01-mediated mitochondrial dysfunction and apoptosis in human multiple myeloma cells

Interactions between pharmacologic NF-κB inhibitors (eg, Bay 11-7082, SN-50) and the checkpoint abrogator UCN-01 have been examined in human multiple myeloma (MM) cells. Exposure of U266 cells to Bay 11-7082 (Bay) in combination with UCN-01 resulted in the abrogation of NF-κB/DNA binding activity and the synergistic induction of apoptosis. Comparable synergism was observed in other MM cell lines and patient-derived CD138+ cells and between an inhibitory peptide of NF-κB (SN50) and UCN-01. Bay/UCN-01-mediated lethality involved mitochondrial dysfunction, caspase cleavage, and poly adenosine diphosphate-ribose polymerase (PARP) degradation. Although Bay modestly blocked UCN-01-induced extracellular signal-regulated kinase (ERK) phosphorylation, coadministration activated c-Jun N-terminal kinase (JNK) and cdc2/cdk1 and down-regulated Mcl-1, XIAP, and Bcl-xL. Transfection with a constitutively activated mitogen-activated protein kinase kinase (MEK1)/green fluorescent protein (GFP) construct failed to block apoptosis induced by Bay/UCN-01 but significantly attenuated MEK inhibitor (U0126)/UCN-01-induced lethality. Inhibiting JNK activation with SP600125 or D-JNKI1 peptide markedly reduced Bay/UCN-01-mediated mitochondrial dysfunction and apoptosis and the down-regulation of Mcl-1, XIAP, and Bcl-xL but not of cdc2/cdk1 activation. Stable transfection of cells with dominant-negative caspase-9 dramatically diminished Bay/UCN-01 lethality without altering JNK or cdc2/cdk1 activation. Neither interleukin-6 (IL-6)- nor fibronectin-mediated adherence conferred resistance to Bay/UCN-01-induced apoptosis. Together, these findings suggest that a strategy combining UCN-01 with disruption of the IκB kinase (IKK)/IκB/NF-κB pathway warrants attention in MM. (Blood. 2004;103:2761-2770)

Bortezomib and flavopiridol interact synergistically to induce apoptosis in chronic myeloid leukemia cells resistant to imatinib mesylate through both Bcr/Abl-dependent and -independent mechanisms

Interactions between the cyclin-dependent kinase (CDK) inhibitor flavopiridol and the proteasome inhibitor bortezomib were examined in Bcr/Abl(+) human leukemia cells. Coexposure of K562 or LAMA84 cells to subtoxic concentration of flavopiridol (150-200 nM) and bortezomib (5-8 nM) resulted in a synergistic increase in mitochondrial dysfunction and apoptosis. These events were associated with a marked diminution in nuclear factor kappaB (NF-kappaB)/DNA binding activity; enhanced phosphorylation of SEK1/MKK4 (stress-activated protein kinase/extracellular signal-related kinase 1/mitogen-activated protein kinase kinase 4), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK); down-regulation of Bcr/Abl; and a marked reduction in signal transducer and activator of transcription 3 (STAT3) and STAT5 activity. In imatinib mesylate-resistant K562 cells displaying increased Bcr/Abl expression, bortezomib/flavopiridol treatment markedly increased apoptosis in association with down-regulation of Bcr/Abl and BclxL, and diminished phosphorylation of Lyn, Hck, CrkL, and Akt. Parallel studies were performed in imatinib mesylate-resistant LAMA84 cells exhibiting reduced expression of Bcr/Abl but a marked increase in expression/activation of Lyn and Hck. Flavopiridol/bortezomib effectively induced apoptosis in these cells in association with Lyn and Hck inactivation. The capacity of flavopiridol to promote bortezomib-mediated Bcr/Abl down-regulation and apoptosis was mimicked by the positive transcription elongation factor-b (P-TEFb) inhibitor DRB (5,6-dichloro 1-beta-d-ribofuranosylbenzinida-sole). Finally, the bortezomib/flavopiridol regimen also potently induced apoptosis in Bcr/Abl(-) human leukemia cells. Collectively, these findings suggest that a strategy combining flavopiridol and bortezomib warrants further examination in chronic myelogenous leukemia and related hematologic malignancies.

Transcriptional switch by activating transcription factor 2-derived peptide sensitizes melanoma cells to apoptosis and inhibits their tumorigenicity

The notorious resistance of melanoma cells to drug treatment can be overcome by expression of a 50-aa peptide derived from activating transcription factor 2 (ATF2(50-100)). Here we demonstrate that ATF2(50-100) induced apoptosis by sequestering ATF2 to the cytoplasm, thereby inhibiting its transcriptional activities. Furthermore, ATF2(50-100) binds to c-Jun N-terminal kinase (JNK) and increases its activity. Mutation within ATF2(50-100) that impairs association with JNK and the inhibition of JNK or c-Jun expression by RNA interference (RNAi) reduces the degree of ATF2(50-100)-induced apoptosis. In contrast, TAM67, a dominant negative of the Jun family of transcription factors, or JunD RNAi attenuates sensitization of melanoma cells expressing ATF2(50-100) to apoptosis after treatment with anisomycin, which is used as a model drug. Mutations within the JNK binding region of ATF2(50-100) or expression of TAM67 or JunD RNAi attenuates inhibition of melanoma's tumorigenicity by ATF2(50-100). We conclude that inhibition of ATF2 in concert with increased JNK/Jun and JunD activities is central for the sensitization of melanoma cells to apoptosis and inhibition of their tumorigenicity.

The proteasome inhibitor bortezomib interacts synergistically with histone deacetylase inhibitors to induce apoptosis in Bcr/Abl+ cells sensitive and resistant to STI571

Interactions between the proteasome inhibitor bortezomib and histone deacetylase inhibitors (HDIs) have been examined in Bcr/Abl+ human leukemia cells (K562 and LAMA 84). Coexposure of cells (24-48 hours) to minimally toxic concentrations of bortezomib + either suberoylanilide hydroxamic acid (SAHA) or sodium butyrate (SB) resulted in a striking increase in mitochondrial injury, caspase activation, and apoptosis, reflected by caspases-3 and -8 cleavage and poly(adenosine diphosphate-ribose) polymerase (PARP) degradation. These events were accompanied by down-regulation of the Raf-1/mitogen-induced extracellular kinase (MEK)/extracellular signal-related kinase (ERK) pathway as well as diminished expression of Bcr/Abl and cyclin D1, cleavage of p21CIP1 and phosphorylation of the retinoblastoma protein (pRb), and induction of the stress-related kinases Jun kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Transient transfection of cells with a constitutively active MEK construct significantly protected them from bortezomib/SAHA-mediated lethality. Coadministration of bortezomib and SAHA resulted in increased reactive oxygen species (ROS) generation and diminished nuclear factor kappa B (NF-kappa B) activation; moreover, the free radical scavenger L-N-acetylcyteine (LNAC) blocked bortezomib/SAHA-related ROS generation, induction of JNK and p21CIP1, and apoptosis. Lastly, this regimen potently induced apoptosis in STI571 (imatinib mesylate)-resistant K562 cells and CD34+ mononuclear cells obtained from a patient with STI571-resistant disease, as well as in Bcr/Abl- leukemia cells (eg, HL-60, U937, Jurkat). Together, these findings raise the possibility that combined proteasome/histone deacetylase inhibition may represent a novel strategy in leukemia, including apoptosis-resistant Bcr/Abl+ hematologic malignancies.

Transfection of K-rasAsp12 cDNA markedly elevates IL-1β- and lipopolysaccharide-mediated inducible nitric oxide synthase expression in rat intestinal epithelial cells

Activating mutations of K-ras are frequent in colon tumors and aberrant crypt foci, and may play important roles in colon carcinogenesis. Here, we investigated the effects of a K-ras codon 12 mutation on inducible nitric oxide synthase (iNOS) expression. When rat intestinal epithelial cells (IEC-6) were transfected with K-rasAsp12 cDNA, the iNOS expression linked to interleukin-1beta (IL-1beta) or lipopolysaccharide (LPS) treatment was markedly increased and prolonged. In contrast, it was only very faint and transient in cells transfected with the control vector or K-rasWT. Electrophoretic mobility-shift assays demonstrated that NF-kappaB binding activity induced by IL-1beta or LPS was also increased in K-rasAsp12-transfected cells, along with the binding of CREB-1, CREM-1, ATF-1, ATF-2, and Jun D to a cAMP-responsive element (CRE)-like site and the binding of C/EBPbeta to a C/EBP-binding consensus site. Furthermore, the anchorage-independent growth of K-rasAsp12-transfected cells was markedly increased by IL-1beta or LPS treatment, and decreased by ONO-1714, an iNOS inhibitor. In addition, tumor growth in nude mice injected with K-rasAsp12-transfected cells was significantly suppressed by NOS inhibition with 50 p.p.m. ONO-1714 or 100 p.p.m. L-NG-nitroarginine methyl ester. These results suggest that an activating mutation of K-ras can markedly enhance the iNOS expression mediated by IL-1beta or LPS, through the activation of promoters on NF-kappaB, C/EBP, and CRE-like sites, and that nitric oxide contributes to the colony formation and tumor growth of K-ras-transformed cells.

Proteasome inhibitors potentiate leukemic cell apoptosis induced by the cyclin-dependent kinase inhibitor flavopiridol through a SAPK/JNK- and NF-κB-dependent process

Interactions between proteasome and cyclin-dependent kinase inhibitors have been examined in human leukemia cells in relation to induction of apoptosis. Simultaneous exposure (24 h) of U937 myelomonocytic leukemia cells to 100 nM flavopiridol and 300 nM MG-132 resulted in a marked increase in mitochondrial injury (cytochrome c, Smac/DIABLO release, loss of deltaPsi(m)), caspase activation, and synergistic induction of cell death, accompanied by a marked decrease in clonogenic potential. Similar effects were observed with other proteasome inhibitors (e.g., Bortezomib (VELCADE trade mark bortezomib or injection), lactacystin, LLnL) and cyclin-dependent kinase inhibitors (e.g., roscovitine), as well as other leukemia cell types (e.g., HL-60, Jurkat, Raji). In U937 cells, synergistic interactions between MG-132 and flavopiridol were associated with multiple perturbations in expression/activation of signaling- and survival-related proteins, including downregulation of XIAP and Mcl-1, activation of JNK and p34(cdc2), and diminished expression of p21(CIP1). The lethal effects of MG-132/flavopiridol were not reduced in leukemic cells ectopically expressing Bcl-2, but were partially attenuated in cells ectopically expressing dominant-negative caspase-8 or CrmA. Flavopiridol/proteasome inhibitor-mediated lethality was also significantly diminished by agents and siRNA blocking JNK activation. Lastly, coadministration of MG-132 with flavopiridol resulted in diminished DNA binding of NF-kappaB. Notably, pharmacologic interruption of the NF-kappaB pathway (e.g., by BAY 11-7082, PDTC, or SN-50) or molecular dysregulation of NF-kappaB (i.e., in cells ectopically expressing an IkappaBalpha super-repressor) mimicked the actions of proteasome inhibitors in promoting flavopiridol-induced mitochondrial injury, JNK activation, and apoptosis. Together, these findings indicate that proteasome inhibitors strikingly lower the apoptotic threshold of leukemic cells exposed to pharmacologic CDK inhibitors, and suggest that interruption of the NF-kappaB cytoprotective pathway and JNK activation both play key roles in this phenomenon. They also raise the possibility that combining proteasome and CDK inhibitors could represent a novel antileukemic strategy.

Altered expression of immune modulator and structural genes in neonatal unilateral ureteral obstruction

BACKGROUND

Congenital obstructive nephropathy is a condition characterized by hydronephrosis, tubular dilatation, apoptosis, and atrophy, as well as interstitial cellular infiltration and progressive interstitial fibrosis. The renal consequences of chronic unilateral ureteral obstruction (UUO) in the neonatal rat are similar to those of clinical congenital obstructive nephropathy.

METHODS

To define alterations in renal gene expression induced by chronic neonatal UUO, Sprague-Dawley rats were subjected to UUO or sham operation within the first 2 days of life, and kidneys were harvested after 12 days.

RESULTS

Microarray analysis revealed that the mRNA expression of multiple immune modulators, including krox24, interferon-gamma regulating factor-1 (IRF-1), monocyte chemoattractant protein-1 (MCP-1), interleukin-1beta (IL-1beta), CCAAT/enhancer binding protein (C/EBP), p21, c-fos, c-jun, and pJunB, was significantly increased in obstructed compared to sham-operated kidneys (all P < 0.05). Western blot analysis revealed significant changes in immune modulator protein abundance in the obstructed versus sham-operated kidney for krox24 (P = 0.0004), IRF-1 (P = 0.005), MCP-1 (P = 0.01), and JunD (P = 0.0008). Alternatively, the abundance of all of the immune modulator proteins was similar in sham-operated and obstructed kidneys in rats subjected to acute (4 days) neonatal UUO. Microarray analysis studies also reveal that structural genes that comprise the cytoskeleton and cell matrix are significantly up-regulated by chronic neonatal UUO, including calponin, desmin, dynamin, and lumican (all P < 0.05).

CONCLUSION

Multiple genes are aberrantly expressed in the kidney of rats subjected to chronic neonatal UUO. Elucidation of these genes involved in neonatal UUO may lead to new insight about congenital obstructive nephropathy.

JunD mediates survival signaling by the JNK signal transduction pathway

The c-Jun NH(2)-terminal kinase (JNK) can cause cell death by activating the mitochondrial apoptosis pathway. However, JNK is also capable of signaling cell survival. The mechanism that accounts for the dual role of JNK in apoptosis and survival signaling has not been established. Here we demonstrate that JNK-stimulated survival signaling can be mediated by JunD. The JNK/JunD pathway can collaborate with NF-kappaB to increase antiapoptotic gene expression. This observation accounts for the ability of JNK to cause either survival or apoptosis in different cellular contexts. Furthermore, these data illustrate the general principal that signal transduction pathway integration is critical for the ability of cells to mount an appropriate biological response to a specific challenge.

Menin interacting proteins as clues toward the understanding of multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is a familial cancer syndrome characterized mostly by tumors of the parathyroids, pancreas and anterior pituitary. The gene responsible, MEN1, encodes Menin, a 610 aminoacid nuclear protein with no sequence homology to other proteins. Although a mouse knock-out model is available, the function of Menin is still elusive. Proteins of known function are shown to interact with Menin: JunD, nuclear factor-KappaB, Smad3, Pem, Nm23H1, glial fibrillary acidic protein, Vimentin, and probably P53. Their partnership with Menin may correspond to a regulation of their activity, but their relevance to the various traits of MEN1 pathogenicity is not established. This raises fundamental issues on the regulation pathways implicated in this complex endocrine disease.

JunD stabilization results in inhibition of normal intestinal epithelial cell growth through P21 after polyamine depletion

BACKGROUND & AIMS

Normal intestinal mucosal growth requires cellular polyamines that regulate expression of various genes involved in cell proliferation, growth arrest, and apoptosis. We have recently shown that growth inhibition after polyamine depletion is associated with an increase in JunD/AP-1 activity in normal intestinal epithelial cells (IEC-6 line). The current study tests the hypothesis that polyamine depletion-induced JunD/activator protein 1 (AP-1) activity results from the activation of junD gene expression and plays a critical role in regulation of intestinal epithelial cell growth.

METHODS

The junD gene transcription was examined by nuclear run-on assays, and messenger RNA (mRNA) stability was measured by determination of JunD mRNA half-life. Functions of JunD were investigated by using JunD antisense oligodeoxyribonucleotides and transient transfection with the junD-expressing vector.

RESULTS

Depletion of cellular polyamines by DL-alpha-difluoromethylornithine (DFMO) induced levels of JunD mRNA and protein, which was associated with an increase in G(1) phase growth arrest. Polyamine depletion did not increase the rate of junD gene transcription but significantly increased the stability of JunD mRNA. Decreasing JunD protein by using JunD antisense oligomers promoted cell growth in polyamine-deficient cells. Growth arrest following polyamine depletion also was accompanied by increases in both p21 expression and its promoter activity. Treatment with JunD antisense oligomers inhibited the p21 promoter and prevented the increase in p21 expression in the presence of DFMO. Ectopic expression of the wild-type junD increased p21-promoter activity and inhibited epithelial cell growth.

CONCLUSIONS

Polyamines negatively regulate junD gene expression posttranscriptionally, and increased JunD/AP-1 inhibits intestinal epithelial cell proliferation at least partially through the activation of p21 promoter.

Identification of alternatively spliced Act1 and implications for its roles in oncogenesis

Act1 (also called CIKS) is a recently identified molecule, which activates NF-kappaB and AP-1. Here, we identified alternatively spliced Act1 that lacked the exon 2 encoding the first nine amino acids in the amino terminus of the protein. Compared to full-length Act1, this truncated Act1 appeared to be equally active. We demonstrated further that only the spliced Act1 was detected in cDNA libraries derived from human fetal brain, liver, leukocytes, and bone marrow. In contrast, both the spliced and full-length Act1 templates were detected in a variety of human cancer cell lines. The expression of both the spliced and full-length transcripts was detected at 4-h time point, following the treatment of endothelial cells with tumor necrosis factor-alpha, interleukin-1beta or bacterial endotoxin. Notably, the dominant amounts of the spliced Act1 over the full-length Act1 were amplified from both the cancer cell mRNAs and the stimulated endothelial cell mRNAs. Taken together with the act1 chromosome localization at the 6q21 subregion, our findings indicate that the newly identified alternatively spliced Act1 is a major transcript of the molecule and that Act1 may play important roles in oncogenesis.

Induction of tissue factor expression in human endothelial cells by CD40 ligand is mediated via activator protein 1, nuclear factor kappa B, and Egr-1

Induction of tissue factor expression in endothelial cells via ligation of CD40 probably figures prominently in the pathogenesis of prevalent inflammatory diseases, including atherosclerosis. However, the molecular mechanisms of tissue factor gene expression triggered by CD40 ligand (CD40L) in this cell type remain unknown. We demonstrate here that the tissue factor promoter region -278 bp to +121 bp contains the CD40L-responsive elements, consisting of activator protein 1 (AP-1)+/-, nuclear factor (NF) kappaB-, and Egr-1-binding sites. Mutations of either the AP-1- or NF-kappaB-binding sites markedly reduced the CD40L-dependent promoter activation. The AP-1 and NF-kappaB sites displayed constitutive and CD40L-enhanceable DNA binding activity, respectively. Of note, mutation of the Egr-1-binding sites, previously not associated with CD40 signaling, impaired activation of the tissue factor promoter. Accordingly, CD40L strongly induced Egr-1 protein expression and DNA binding activity to all three bindings sites. In contrast to CD40L, other established inducers of tissue factor in endothelial cells, interleukin-1beta or tumor necrosis factor alpha, did not increase the expression of Egr-1. In conclusion, induction of tissue factor gene expression in human endothelial cells by CD40L involves AP-1 and NF-kappaB as well as Egr-1, a pathway previously not implicated in CD40 signaling and distinct from that employed by certain other proinflammatory cytokines.

Activator protein-1 activation in acute lung injury

The role of activator protein-1 (AP-1) in inflammation is primarily unknown. AP-1 was evaluated in nuclear extracts from alveolar macrophages and whole lung nuclear extracts during acute lung injury after deposition of IgG immune complexes. AP-1 activation occurred in macrophages and in whole lung extracts, but with distinctly different time courses. Low levels of constitutive AP-1 were observed in normal rat lung as determined by the electrophoretic mobility shift assay. Increased AP-1 was detected 2 hours after initiation of the inflammatory response in lung with a further increase by 4 hours, while AP-1 activation was found in alveolar macrophages 0.5 hour after onset of the inflammatory response. mRNAs and proteins for c-fos, c-jun, jun-B, and jun-D were all up-regulated in whole lung tissues and in alveolar macrophages during acute lung injury induced by IgG immune complex deposition. Depletion of lung macrophages sharply reduced AP-1 activation, as did anti-tumor necrosis factor-alpha, whereas complement depletion showed no effect on lung AP-1 activation. The data suggest that activation of AP-1 occurs in both alveolar macrophages and in the lung, and this activation process is macrophage- and tumor necrosis factor-alpha-dependent.

Effects of pharmacologic antagonists of epidermal growth factor receptor, PI3K and MEK signal kinases on NF-kappaB and AP-1 activation and IL-8 and VEGF expression in human head and neck squamous cell carcinoma lines

We previously reported that expression of angiogenesis factors interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) is promoted by coactivation of transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) by interleukin-1alpha in human head and neck squamous cell carcinomas (HNSCC). However, expression of IL-1 receptor antagonist incompletely blocked reporter gene activity and cytokine expression, suggesting that other upstream signals may contribute to activation. Overexpression and autocrine activation of epidermal growth factor receptor (EGFR) is detected in 90% of HNSCC, and EGFR inhibitors have been reported to inhibit IL-8 and VEGF expression, but the intermediary signal pathways and transcription factors by which EGFR modulates proangiogenic factors is unknown. EGFR can activate the phosphotidylinositol-3 kinase (PI3K) and mitogen-activated/extracellular signal-regulated kinase (MEK) pathways, which can potentially modulate activation of NF-kappaB and AP-1, respectively. In our study, we examined the effect of EGF and antagonists of EGFR, PI3K and MEK on NF-kappaB and AP-1 activation and IL-8 and VEGF expression in HNSCC cell lines UM-SCC-9 and 11B in which EGFR is overexpressed and activated. Recombinant EGF induced EGFR phosphorylation, activation of NF-kappaB and AP-1 reporter genes and IL-8 and VEGF expression, indicating that EGFR can mediate coactivation of both transcription factors and cytokine genes in HNSCC. EGFR antagonist PD153035 and anti-EGFR antibody C225 completely inhibited EGF-induced reporter activity and cytokine expression, but only partially inhibited constitutive activity. MEK inhibitor U0126 preferentially blocked AP-1 activity and expression of both IL-8 and VEGF, while PI3K inhibitor LY-294002 or a dominant negative inhibitor-kappaB preferentially blocked NF-kappaB activation and expression of IL-8 but not VEGF. EGFR, PI3K and MEK antagonists inhibited growth of HNSCC. We conclude that antagonists of EGFR, PI3K and MEK signal pathways have inhibitory activity against EGFR-induced NF-kappaB and AP-1 activation, IL-8 and VEGF expression and growth by HNSCC. Published 2002 Wiley-Liss, Inc.

Luteinizing hormone-releasing hormone induces JunD-DNA binding and extends cell cycle in human ovarian cancer cells

Expression of luteinizing hormone-releasing hormone (LHRH) and its receptor as part of an autocrine regulatory system of cell proliferation has been demonstrated in a number of human malignant tumors, including cancers of the ovary. This study was conducted to investigate whether LHRH induces activation of JunD and affects cell cycle regulation and DNA synthesis. Treatment of primary human ovarian cancer cells and human ovarian cancer cell lines EFO-21 and EFO-27 with LHRH agonist triptorelin (100 nM) resulted in an increase in G(0/1) phase and a decrease in G(2/S) phase of cell cycle. Treatment of quiescent EFO-21 or EFO-27 cells with triptorelin (100 nM) resulted in a 46.7 or 44.2-fold increase of AP-1 activation, respectively (p<0.001). Maximal binding of JunD on DNA consensus sequence was found after 4 h of treatment of quiescent EFO-21 or EFO-27 cells with triptorelin (100 nM). DNA synthesis was significantly decreased to 45.5+/-11.4% (day 0=control=100%; p<0.001) after 3 days of triptorelin (1 nM) treatment. These results suggest that LHRH agonist triptorelin induces JunD-DNA binding, resulting in reduced proliferation as indicated by increased G(0/1) phase of cell cycle and decreased DNA synthesis. Since LHRH activates nucleus factor kappa B (NF kappa B) and protects ovarian cancer cells from doxorubicin-induced apoptosis and JunD is shown to decrease cell cycle and cell proliferation, we propose that JunD activated by LHRH acts as a modulator of cell proliferation and cooperates with the anti-apoptotic and anti-mitogenic functions of LHRH.

NO sensitizes rat hepatocytes to proliferation by modifying S-adenosylmethionine levels

BACKGROUND & AIMS

Liver regeneration is a fundamental response of this organ to injury. Hepatocyte proliferation is triggered by growth factors, such as hepatocyte growth factor. However, hepatocytes need to be primed to react to mitogenic signals. It is known that nitrous oxide (NO), generated after partial hepatectomy, plays an important role in hepatocyte growth. Nevertheless, the molecular mechanisms behind this priming event are not completely known. S-adenosylmethionine (AdoMet) synthesis by methionine adenosyltransferase is the first step in methionine metabolism, and NO regulates hepatocyte S-adenosylmethionine levels through specific inhibition of this enzyme. We have studied the modulation of hepatocyte growth factor-induced proliferation by NO through the regulation of S-adenosylmethionine levels.

METHODS

Studies were conducted in cultured rat hepatocytes isolated by collagenase perfusion, which triggers NO synthesis.

RESULTS

The mitogenic response to hepatocyte growth factor was blunted when inducible NO synthase was inhibited; this process was overcome by the addition of an NO donor. This effect was dependent on methionine concentration in culture medium and intracellular S-adenosylmethionine levels. Accordingly, we found that S-adenosylmethionine inhibits hepatocyte growth factor-induced cyclin D1 and D2 expression, activator protein 1 induction, and hepatocyte proliferation.

CONCLUSIONS

Together our findings indicate that NO may switch hepatocytes into a hepatocyte growth factor-responsive state through the down-regulation of S-adenosylmethionine levels.