Role of IkappaB kinase in tumorigenesis

Anti-Cancer Effect of Sulforaphane in Human Pancreatic Cancer Cells Mia PaCa-2

BACKGROUND

Pancreatic cancer is difficult to treat early as it has no early symptoms. The presence of sulforaphane (SFN) in cruciferous vegetables has been found to possess anti-cancer effects in gastric and colon cancers. Glycogen synthase kinase-3 beta (GSK-3β), a serine/threonine kinase, plays a significant role in pancreatic cancer progression, influencing tumor growth, metastasis, and treatment resistance. Targeting GSK-3β has shown potential to enhance the efficacy of chemotherapy. However, the mechanism underlying the anticancer effects of SFN on pancreatic cancer through GSK-3β is unclear.

AIMS

In this study, we examined the anticancer effects of SFN in human pancreatic cancer cell line Mia PaCa-2 and evaluated its molecular mechanisms with respect to the GSK-3β-related pathway.

METHODS AND RESULTS

SFN increased the protein expression of the phosphorylated form of GSK3β (Ser9). In the Wingless Int-1 homolog/β-catenin pathway, GSK3β induced apoptosis by phosphorylating β-catenin. However, in mutant Kirsten rat sarcoma viral oncogene homolog-like-dependent cells such as Mia PaCa-2, GSK3β was suppressed and the β-catenin level was increased, thus inducing apoptosis. Indeed, SFN increased the protein expression of β-catenin in the cytoplasm and nucleus. Subsequently, we measured the level of cMyc, the target gene of β-catenin. SFN decreased cMyc expression despite an increase in the β-catenin. We measured the expression of nuclear factor (NF)-κB, a downstream factor of GSK3β and an upstream factor of cMyc. SFN decreased the expression of NF-κB and cMyc, indicating that SFN inhibits cell proliferation by suppressing the GSK3β/NF-κB/cMyc pathway. As the suppression of NF-κB results in a decrease in B-cell lymphoma 2 (BCL-2) which is the anti-apoptotic gene, we tested the effect of SFN in the expression of BCL-2. SFN inhibited the expression of BCL-2 and increased the ratio of the apoptotic regulator gene BCL-2 associated X (BAX), where SFN induced the cleaved cysteine aspartase-3 and poly-adenosine diphosphate ribose polymerase.

CONCLUSION

These results indicate that SFN may have therapeutic potential in the inhibition of pancreatic cancer.

Transcriptomic Integration Analyses Uncover Common Bisphenol A Effects Across Species and Tissues Primarily Mediated by Disruption of JUN/FOS, EGFR, ER, PPARG, and P53 Pathways

Bisphenol A (BPA) is a common endocrine disruptor widely used in the production of electronic, sports, and medical equipment, as well as consumer products like milk bottles, dental sealants, and thermal paper. Despite its widespread use, current assessments of BPA exposure risks remain limited due to the lack of comprehensive cross-species comparative analyses. To address this gap, we conducted a study aimed at identifying genes and fundamental molecular processes consistently affected by BPA in various species and tissues, employing an effective data integration method and bioinformatic analyses. Our findings revealed that exposure to BPA led to significant changes in processes like lipid metabolism, proliferation, and apoptosis in the tissues/cells of mammals, fish, and nematodes. These processes were found to be commonly affected in adipose, liver, mammary, uterus, testes, and ovary tissues. Additionally, through an in-depth analysis of signaling pathways influenced by BPA in different species and tissues, we observed that the JUN/FOS, EGFR, ER, PPARG, and P53 pathways, along with their downstream key transcription factors and kinases, were all impacted by BPA. Our study provides compelling evidence that BPA indeed induces similar toxic effects across different species and tissues. Furthermore, our investigation sheds light on the underlying molecular mechanisms responsible for these toxic effects. By uncovering these mechanisms, we gain valuable insights into the potential health implications associated with BPA exposure, highlighting the importance of comprehensive assessments and awareness of this widespread endocrine disruptor.

The inflammatory kinase IKKα phosphorylates and stabilizes c-Myc and enhances its activity

BACKGROUND

The IκB kinase (IKK) complex, comprising the two enzymes IKKα and IKKβ, is the main activator of the inflammatory transcription factor NF-κB, which is constitutively active in many cancers. While several connections between NF-κB signaling and the oncogene c-Myc have been shown, functional links between the signaling molecules are still poorly studied.

METHODS

Molecular interactions were shown by co-immunoprecipitation and FRET microscopy. Phosphorylation of c-Myc was shown by kinases assays and its activity by improved reporter gene systems. CRISPR/Cas9-mediated gene knockout and chemical inhibition were used to block IKK activity. The turnover of c-Myc variants was determined by degradation in presence of cycloheximide and by optical pulse-chase experiments.. Immunofluorescence of mouse prostate tissue and bioinformatics of human datasets were applied to correlate IKKα- and c-Myc levels. Cell proliferation was assessed by EdU incorporation and apoptosis by flow cytometry.

RESULTS

We show that IKKα and IKKβ bind to c-Myc and phosphorylate it at serines 67/71 within a sequence that is highly conserved. Knockout of IKKα decreased c-Myc-activity and increased its T58-phosphorylation, the target site for GSK3β, triggering polyubiquitination and degradation. c-Myc-mutants mimicking IKK-mediated S67/S71-phosphorylation exhibited slower turnover, higher cell proliferation and lower apoptosis, while the opposite was observed for non-phosphorylatable A67/A71-mutants. A significant positive correlation of c-Myc and IKKα levels was noticed in the prostate epithelium of mice and in a variety of human cancers.

CONCLUSIONS

Our data imply that IKKα phosphorylates c-Myc on serines-67/71, thereby stabilizing it, leading to increased transcriptional activity, higher proliferation and decreased apoptosis.

Elevated NIBP/TRAPPC9 mediates tumorigenesis of cancer cells through NFκB signaling

Regulatory mechanisms underlying constitutive and inducible NFκB activation in cancer remain largely unknown. Here we investigated whether a novel NIK- and IKK2-binding protein (NIBP) is required for maintaining malignancy of cancer cells in an NFκB-dependent manner. Real-time polymerase chain reaction analysis of a human cancer survey tissue-scan cDNA array, immunostaining of a human frozen tumor tissue array and immunoblotting of a high-density reverse-phase cancer protein lysate array showed that NIBP is extensively expressed in most tumor tissues, particularly in breast and colon cancer. Lentivirus-mediated NIBP shRNA knockdown significantly inhibited the growth/proliferation, invasion/migration, colony formation and xenograft tumorigenesis of breast (MDA-MB-231) or colon (HCT116) cancer cells. NIBP overexpression in HCT116 cells promoted cell proliferation, migration and colony formation. Mechanistically, NIBP knockdown in cancer cells inhibited cytokine-induced activation of NFκB luciferase reporter, thus sensitizing the cells to TNFα-induced apoptosis. Endogenous NIBP bound specifically to the phosphorylated IKK2 in a TNFα-dependent manner. NIBP knockdown transiently attenuated TNFα-stimulated phosphorylation of IKK2/p65 and degradation of IκBα. In contrast, NIBP overexpression enhanced TNFα-induced NFκB activation, thus inhibiting constitutive and TNFα-induced apoptosis. Collectively, our data identified important roles of NIBP in promoting tumorigenesis via NFκΒ signaling, spotlighting NIBP as a promising target in cancer therapeutic intervention.

Platycodin D induces tumor growth arrest by activating FOXO3a expression in prostate cancer in vitro and in vivo

Platycodin D (PD), a major saponin derived from Platycodin grandiflorum, exerted cytotoxicity against prostate cancer cell lines (PC3, DU145 and LNCaP cells) with IC₅₀ values in the range of 11.17 to 26.13μmol/L, whereas RWPE-1cells (a non-malignant human prostate epithelial cell line) were not significantly affected. A further study in these cell lines showed that PD could potently affect cell proliferation (indicated by the bromodeoxyuridine assay), induce cell apoptosis (determined by Annexin V-FITC flow cytometry) and cause cell cycle arrest (indicated by PI staining). After being treated with PD for 48 hours, DU145 and LNCaP cells were arrested in the G0 /G1 phase, and PC3 cells were arrested in the G2/M phase. A Western blotting analysis indicated that PD increased the expression of the FOXO3a transcription factor, decreased the expression of p-FOXO3a and MDM2 and increased the expression of FOXO-responsive genes, p21 and p27. MDM2 silencing (transiently by siRNA-MDM2) increased the PD-induced FOXO3a protein expression, while MDM2 overexpression (in cells transiently transfected with a pcDNA3-MDM2 plasmid) decreased the PD-induced expression of the FOXO3a protein. Moreover, PD dose-dependently inhibited the growth of PC3 xenograft tumors in BALB/c nude mice. A Western blotting analysis of the excised xenograft tumors indicated that similar changes in protein expression also occurred in vivo. These results suggest that PD exhibits significant activity against prostate cancer in vitro and in vivo. The FOXO3a transcription factor appears to be involved in the activity of PD. Together, all of these findings provide a basis for the future development of this agent for human prostate cancer therapy.

Auranofin displays anticancer activity against ovarian cancer cells through FOXO3 activation independent of p53

Auranofin is a gold-containing compound classified by the World Health Organization as a clinically established rheumatoid arthritis therapeutic agent. Through drug screening for novel anticancer therapeutics, we unexpectedly identified auranofin as a potent anticancer agent against a p53-null ovarian carcinoma SKOV3 cell line. However, the molecular mechanism underlying auranofin-mediated anticancer activity in ovarian cancer cells is basically unknown. Here, we show that auranofin inhibits proliferation and survival of SKOV3 cells in a dose- and time-dependent manner. Auranofin treatment activates the pro-apoptotic caspase-3, increases protein levels of apoptosis-inducing proteins Bax and Bim and reduces the expression of the anti-apoptotic mediator Bcl-2 in SKOV3 cells. Moreover, auranofin downregulates IκB kinase (IKK)-β and promotes nuclear localization and the activation of FOXO3 tumor suppressor, leading to cellular apoptosis in SKOV3 cells. In contrast, silencing FOXO3 diminishes the pro-apoptotic signaling of auranofin in SKOV3 cells. These results suggest that auranofin may induce caspase-3-mediated apoptosis in a FOXO3-dependent manner. The observed upregulation of pro-apoptotic genes and apoptosis in cancer cells without p53 in response to auranofin suggests a novel p53-independent mechanism underlying auranofin-induced apoptosis in ovarian cancer cells.

Current overview of functions of FoxO proteins, with special regards to cellular homeostasis, cell response to stress, as well as inflammation and aging

FoxO transcription factors act at the interconnections between metabolic pathways inducible by many important signal transducers and mediators, such as p53, Ikk-β, NFKB, Akt, sirtuins, PTEN, and others. This may account for a crucial significance of disruptions in FoxO functions both in many kinds of diseases (including cancer, chronic inflammatory diseases, degenerative diseases, obesity, polymetabolic syndrome) and in some disease-like conditions (such as inflammaging, cachexia related to chronic inflammation, cancer-promotion by some chronic inflammatory responses, and the aging process itself). This paper reviews complex interactions between FoxOs and other signal transducers, trying to pinpoint how exactly disruptions of FoxO functions may occur, and how they may contribute to occurrence, development or complications of the conditions mentioned above.

Myeloid cell RelA/p65 promotes lung cancer proliferation through Wnt/β-catenin signaling in murine and human tumor cells

Smoking is the most important risk factor for both lung cancer (LC) and chronic obstructive pulmonary disease. The aim of this study was to investigate the role of myeloid cell nuclear factor-κB in the regulation of tumor cell growth signaling. We subjected mice lacking myeloid RelA/p65 (rela(Δ-/-)) to a metastatic LC model. Cigarette smoke (CS) exposure significantly increased the proliferation of Lewis lung carcinoma cell tumors in wild-type mice. In CS-exposed rela(Δ-/-) mice, the tumor growth was largely inhibited. Transcriptome and pathway analysis of cancer tissue revealed a fundamental impact of myeloid cells on various growth signaling pathways, including the Wnt/β-catenin pathway. In conclusion, myeloid RelA/p65 is necessary to link smoke-induced inflammation with LC growth and has a role in the activation of Wnt/β-catenin signaling in tumor cells.

Beyond NF-κB activation: nuclear functions of IκB kinase α

IκB kinase (IKK) complex, the master kinase for NF-κB activation, contains two kinase subunits, IKKα and IKKβ. In addition to mediating NF-κB signaling by phosphorylating IκB proteins during inflammatory and immune responses, the activation of the IKK complex also responds to various stimuli to regulate diverse functions independently of NF-κB. Although these two kinases share structural and biochemical similarities, different sub-cellular localization and phosphorylation targets between IKKα and IKKβ account for their distinct physiological and pathological roles. While IKKβ is predominantly cytoplasmic, IKKα has been found to shuttle between the cytoplasm and the nucleus. The nuclear-specific roles of IKKα have brought increasing complexity to its biological function. This review highlights major advances in the studies of the nuclear functions of IKKα and the mechanisms of IKKα nuclear translocation. Understanding the nuclear activity is essential for targeting IKKα for therapeutics.

Zerumbone suppresses IKKα, Akt, and FOXO1 activation, resulting in apoptosis of GBM 8401 cells

BACKGROUND

Zerumbone, a sesquiterpene compound isolated from subtropical ginger, Zingiber zerumbet Smith, has been documented to exert antitumoral and anti- inflammatory activities. In this study, we demonstrate that zerumbone induces apoptosis in human glioblastoma multiforme (GBM8401) cells and investigate the apoptotic mechanism.

METHODS

We added a caspase inhibitor and transfected wild-type (WT) IKK and Akt into GBM 8401 cells, and measured cell viability and apoptosis by MTT assay and flow cytometry. By western blotting, we evaluated activation of caspase-3, dephosphorylation of IKK, Akt, FOXO1 with time, and change of IKK, Akt, and FOXO1 phosphorylation after transfection of WT IKK and Akt.

RESULTS

Zerumbone (10~50 μM) induced death of GBM8401 cells in a dose-dependent manner. Flow cytometry studies showed that zerumbone increased the percentage of apoptotic GBM cells. Zerumbone also caused caspase-3 activation and poly (ADP-ribose) polymerase (PARP) production. N-benzyloxycarbonyl -Val-Ala-Asp- fluoromethylketone (zVAD-fmk), a broad-spectrum caspase inhibitor, hindered zerumbone-induced cell death. Transfection of GBM 8401 cells with WT IKKα inhibited zerumbone-induced apoptosis, and zerumbone significantly decreased IKKα phosphorylation levels in a time-dependent manner. Similarly, transfection of GBM8401 cells with Akt suppressed zerumbone-induced apoptosis, and zerumbone also diminished Akt phosphorylation levels remarkably and time-dependently. Moreover, transfection of GBM8401 cells with WT IKKα reduced the zerumbone-induced decrease in Akt and FOXO1 phosphorylation. However, transfection with WT Akt decreased FOXO1, but not IKKα, phosphorylation.

CONCLUSION

The results suggest that inactivation of IKKα, followed by Akt and FOXO1 phosphorylation and caspase-3 activation, contributes to zerumbone-induced GBM cell apoptosis.

Quercetin in cancer prevention and therapy

Quercetin is a plant-derived flavonoid known to possess anti-inflammatory property, but its use as a chemopreventive substance has been reviewed quite recently. A number of reports have assessed the pro-apoptotic action of quercetin in cancer cells, which contributes to the chemopreventive action of food, similar to many other flavonoids. Quercetin is a forthright inhibitor of PI3K, NF-B, and other kinases involved in intracellular signaling. However, a possible selective intracellular target for quercetin has still not been focused on. The challenge is to highlight an eligible target in order to address possible natural compounds, either in food extracts or as pharmaceuticals, as real drugs against cancer.

Gensenoside Rg3 inhibits hypoxia-induced VEGF expression in human cancer cells

AIMS

The ginsenoside Rg3 (Rg3) inhibits xenograft growth and angiogenesis in tumors mainly via down-regulates VEGF expression. This study was designed to investigate the mechanisms by which Rg3 down-regulates VEGF expression.

METHODS

MTT assay was performed to investigate the effect of Rg3 on the growth of human esophageal carcinoma cell line Eca-109 and 786-0 cells under normoxic and hypoxic conditions. ELISA was used to detect VEGF protein secreted by the cells under normoxic and hypoxic conditions. Real-time quantitative reverse transcriptase polymerase chain reaction and Western blotting were used to detect gene expression and protein synthesis.

RESULTS

Rg3 inhibited Eca-109 and 786-0 cell proliferation and induced a significant reduction in VEGF mRNA under hypoxia conditions. Rg3 treatment inhibited hypoxia-induced expression HIF-1α, COX-2 and NF-κB under normoxic and hypoxic conditions. Treatment with Rg3 reduced the hypoxia-induced phosphorylation of STAT3 in a dose-dependent manner in the both cell lines. Rg3 treatment also inhibited the phosphorylation of ERK1/2 and JNK induced by hypoxia.

CONCLUSIONS

Rg3 targets hypoxia-induced multiple signaling pathways to down-regulate VEGF expression in cancer cells. These actions may contribute to the overall efficacy of Rg3 against tumor angiogenesis and growth.

Genetics vs. entropy: longevity factors suppress the NF-kappaB-driven entropic aging process

Molecular studies in model organisms have identified potent longevity genes which can delay the aging process and extend the lifespan. Longevity factors promote stress resistance and cellular survival. It seems that the aging process itself is not genetically programmed but a random process involving the loss of molecular fidelity and subsequent accumulation of waste products. This age-related increase in cellular entropy is compatible with the disposable soma theory of aging. A large array of host defence systems has been linked to the NF-kappaB system which is an ancient signaling pathway specialized to host defence, e.g. functioning in immune system. Emerging evidence demonstrates that the NF-kappaB system is activated during aging. Oxidative stress and DNA damage increase with aging and elicit a sustained activation of the NF-kappaB system which has negative consequences, e.g. chronic inflammatory response, increase in apoptotic resistance, decline in autophagic cleansing, and tissue atrophy, i.e. processes that enhance the aging process. We will discuss the role of NF-kappaB system in the pro-aging signaling and will emphasize that several longevity factors seem to be inhibitors of NF-kappaB signaling and in that way they can suppress the NF-kappaB-driven entropic host defence catastrophe.

FoxO4 inhibits NF-kappaB and protects mice against colonic injury and inflammation

BACKGROUND & AIMS

FoxO4 is a member of the forkhead box transcription factor O (FoxO) subfamily. FoxO proteins are involved in diverse biological processes. In this study, we examine the role of FoxO4 in intestinal mucosal immunity and inflammatory bowel disease (IBD).

METHODS

Foxo4-null mice were subjected to trinitrobenzene sulfonic acid (TNBS) treatment. Microarray analysis and quantitative reverse transcription polymerase chain reaction were used to identify the cytokine transcripts that were altered by Foxo4 deletion. The effects of Foxo4 deficiency on the intestinal epithelial permeability and levels of tight junction proteins were examined by permeable fluorescent dye and Western blot. The molecular and cellular mechanisms by which FoxO4 regulates the mucosal immunity were explored through immunologic and biochemical analyses. The expression level of FoxO4 in intestinal epithelial cells of patients with IBD was examined with immunohistochemistry.

RESULTS

Foxo4-null mice were more susceptible to TNBS injury-induced colitis. The chemokine CCL5 is significantly up-regulated in the colonic epithelial cells of Foxo4-null mice, with increased recruitment of CD4(+) intraepithelial T cells and up-regulation of cytokines interferon-gamma and tumor necrosis factor-alpha in the colon. Foxo4 deficiency also resulted in an increase in intestinal epithelial permeability and down-regulation of the tight junction proteins ZO-1 and claudin-1. Mechanistically, FoxO4 inhibited the transcriptional activity of nuclear factor-kappaB (NF-kappaB), and Foxo4 deficiency is associated with increased NF-kappaB activity in vivo. FoxO4 transcription is transiently repressed in response to TNBS treatment and in patients with IBD.

CONCLUSION

These results indicate that FoxO4 is an endogenous inhibitor of NF-kappaB and identify a novel function of FoxO4 in the regulation of NF-kappaB-mediated mucosal immunity.

Induction of Akt activity by chemotherapy confers acquired resistance

Resistance to chemotherapy is a major cause of treatment failure in human cancer. Accumulating evidence has indicated that the acquisition of resistance to chemotherapeutic drugs involves the activation of the PI3K/Akt pathway. Modulating Akt activity in response to chemotherapy has been observed often in chemoresistant cancers. The potential molecular mechanisms by which chemotherapeutic agents activate the PI3K/Akt pathway are emerging. Activation of this pathway evades the cytotoxic effects of chemotherapeutic agents via regulation of essential cellular functions such as protein synthesis, antiapoptosis, survival and proliferation in cancer. How chemotherapeutic agents induce Akt activation and how activated Akt confers chemoresistance through regulation of signaling networks are discussed in this review. Combining PI3K/Akt inhibitors with standard chemotherapy has been successful in increasing the efficacy of chemotherapeutic agents both in vivo and in vitro. Several small molecules have been developed to specifically target PI3K/Akt and other components of this pathway, which in combination with chemotherapy may be a valid approach to overcome therapeutic resistance. We propose several feedback and feedforward regulatory mechanisms of signaling networks for maintenance of the Akt activity for cell survival. These regulatory mechanisms may limit the efficacy of PI3K/Akt-targeted therapy; therefore, disruption of these mechanisms may be an effective strategy for development of novel anti-cancer therapies.

Insulin acts through FOXO3a to activate transcription of plasminogen activator inhibitor type 1

Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of fibrinolysis. PAI-1 levels are elevated in type 2 diabetes, and this elevation correlates with macro- and microvascular complications of diabetes. However, the mechanistic link between insulin and up-regulation of PAI-1 is unclear. Here we demonstrate that overexpression of Forkhead-related transcription factor (Fox)O1, FoxO3a, and FoxC1 augment insulin's ability to activate the PAI-1 promoter. In addition, insulin treatment promotes the phosphorylation of nuclear and cytoplasmic Fox03a and an increase of cytoplasmic Fox03a. In contrast, insulin treatment led to the accumulation of phospho-Fox01 only in the cytoplasm. Furthermore, insulin also increased the ability of chimeric LexA-FoxO1, LexA-FoxO3a, and LexA-FoxC1 proteins to increase the activity of a LexA reporter, suggesting that the effect of insulin on FoxO3a was direct. Using small interfering RNA to specifically deplete each of the Fox transcription factors tested, we demonstrate that only reduction of FoxO3a inhibits insulin-increased PAI-1-Luc expression and PAI-1 mRNA accumulation. Finally, chromatin immunoprecipitation assays confirm the presence of FoxO3a on the PAI-1 promoter. These results suggest that FoxO3a mediates insulin-increased PAI-1 gene expression.

How ERK1/2 activation controls cell proliferation and cell death: Is subcellular localization the answer?

Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) are members of the mitogen-activated protein kinase super family that can mediate cell proliferation and apoptosis. The Ras-Raf-MEK-ERK signaling cascade controlling cell proliferation has been well studied but the mechanisms involved in ERK1/2-mediated cell death are largely unknown. This review focuses on recent papers that define ERK1/2 translocation to the nucleus and the proteins involved in the cytosolic retention of activated ERK1/2. Cytosolic retention of ERK1/2 denies access to the transcription factor substrates that are responsible for the mitogenic response. In addition, cytosolic ERK1/2, besides inhibiting survival and proliferative signals in the nucleus, potentiates the catalytic activity of some proapoptotic proteins such as DAP kinase in the cytoplasm. Studies that further define the function of cytosolic ERK1/2 and its cytosolic substrates that enhance cell death will be essential to harness this pathway for developing effective treatments for cancer and chronic inflammatory diseases.

Over-expression of adenine nucleotide translocase 1 (ANT1) induces apoptosis and tumor regression in vivo

Background

Adenine nucleotide translocase (ANT) is located in the inner mitochondrial membrane and catalyzes the exchange of mitochondrial ATP for cytosolic ADP. ANT has been known to be a major component of the permeability transition pore complex of mitochondria and contributes to mitochondria-mediated apoptosis. Human ANT has four isoforms (ANT1, ANT2, ANT3, and ANT4), and the expression of the ANT isoforms is variable depending on the tissue and cell type, developmental stage, and proliferation status. Among the isoforms, ANT1 is highly expressed in terminally-differentiated tissues, but expressed in low levels in proliferating cells, such as cancer cells. In particular, over-expression of ANT1 induces apoptosis in cultured tumor cells.

Methods

We applied an ANT1 gene transfer approach to induce apoptosis and to evaluate the anti-tumor effect of ANT1 in a nude mouse model.

Results

We demonstrated that ANT1 transfection induced apoptosis of MDA-MB-231 cells, inactivated NF-κB activity, and increased Bax expression. ANT1-inducing apoptosis was accompanied by the disruption of mitochondrial membrane potential, cytochrome c release and the activation of caspases-9 and -3. Moreover, ANT1 transfection significantly suppressed tumor growth in vivo.

Conclusion

Our results suggest that ANT1 transfection may be a useful therapeutic modality for the treatment of cancer.

Epothilones induce human colon cancer SW620 cell apoptosis via the tubulin polymerization independent activation of the nuclear factor-kappaB/IkappaB kinase signal pathway

Molecular mechanisms underlying epothilone-induced apoptotic cell death were investigated in SW620 human colon cancer cells. Treatment with epothilone B and D at different concentrations (1-100 nmol/L) dose-dependently inhibited cell growth and caused cell cycle arrest at G2-M, which was followed by apoptosis. Consistent with this induction of apoptotic cell death, epothilone B and D enhanced the constitutional activation of nuclear factor-kappaB (NF-kappaB) via IkappaB degradation through IkappaB kinase (IKKalpha and IKKbeta) activation, and this resulted in p50 and p65 translocation to the nucleus. Moreover, cells treated with sodium salicylic acid, an IKK inhibitor, or transiently transfected with mutant IKKalpha and beta did not show epothilone-induced cell growth inhibition or p50 translocation, although p65 was still translocated to the nucleus. Treatment with epothilone B and D also enhanced beta-tubulin polymerization and the formation of p50/beta-tubulin complex. However, beta-tubulin polymerization was not inhibited in the cells treated by sodium salicylic acid or transiently transfected with mutant IKKalpha and beta. Moreover, epothilone B and D increased the expressions of NF-kappaB-dependent apoptotic cell death regulatory genes, i.e., Bax, p53, and the active form of caspase-3, but reduced Bcl-2 expression, and these actions were partially reversed by salicylic acid. In addition, caspase-3 inhibitor reduced epothilone B-induced cell death and NF-kappaB activation. These findings suggest that the activation of NF-kappaB/IKK signals plays an important role in the epothilone-induced apoptotic cell death of SW620 colon cancer cells in a tubulin polymerization-independent manner.

ERK promotes tumorigenesis by inhibiting FOXO3a via MDM2-mediated degradation

The RAS-ERK pathway is known to play a pivotal role in differentiation, proliferation and tumour progression. Here, we show that Erk downregulates Forkhead box O 3a (FOXO3a) by directly interacting with and phosphorylating FOXO3a at Ser 294, Ser 344 and Ser 425, which consequently promotes cell proliferation and tumorigenesis. The ERK-phosphorylated FOXO3a degrades via an MDM2-mediated ubiquitin-proteasome pathway. However, the non-phosphorylated FOXO3a mutant is resistant to the interaction and degradation by murine double minute 2 (MDM2), thereby resulting in a strong inhibition of cell proliferation and tumorigenicity. Taken together, our study elucidates a novel pathway in cell growth and tumorigenesis through negative regulation of FOXO3a by RAS-ERK and MDM2.

Neural stem cells, inflammation and NF-kappaB: basic principle of maintenance and repair or origin of brain tumours?

Several recent reports suggest that inflammatory signals play a decisive role in the self-renewal, migration and differentiation of multipotent neural stem cells (NSCs). NSCs are believed to be able to ameliorate the symptoms of several brain pathologies through proliferation, migration into the area of the lesion and either differentiation into the appropriate cell type or secretion of anti-inflammatory cytokines. Although NSCs have beneficial roles, current evidence indicates that brain tumours, such as astrogliomas or ependymomas are also caused by tumour-initiating cells with stem-like properties. However, little is known about the cellular and molecular processes potentially generating tumours from NSCs. Most pro-inflammatory conditions are considered to activate the transcription factor NF-kappaB in various cell types. Strong inductive effects of NF-kappaB on proliferation and migration of NSCs have been described. Moreover, NF-kappaB is constitutively active in most tumour cells described so far. Chronic inflammation is also known to initiate cancer. Thus, NF-kappaB might provide a novel mechanistic link between chronic inflammation, stem cells and cancer. This review discusses the apparently ambivalent role of NF-kappaB: physiological maintenance and repair of the brain via NSCs, and a potential role in tumour initiation. Furthermore, it reveals a possible mechanism of brain tumour formation based on inflammation and NF-kappaB activity in NSCs.

Shotgun protein sequencing: assembly of peptide tandem mass spectra from mixtures of modified proteins

Despite significant advances in the identification of known proteins, the analysis of unknown proteins by MS/MS still remains a challenging open problem. Although Klaus Biemann recognized the potential of MS/MS for sequencing of unknown proteins in the 1980s, low throughput Edman degradation followed by cloning still remains the main method to sequence unknown proteins. The automated interpretation of MS/MS spectra has been limited by a focus on individual spectra and has not capitalized on the information contained in spectra of overlapping peptides. Indeed the powerful shotgun DNA sequencing strategies have not been extended to automated protein sequencing. We demonstrate, for the first time, the feasibility of automated shotgun protein sequencing of protein mixtures by utilizing MS/MS spectra of overlapping and possibly modified peptides generated via multiple proteases of different specificities. We validate this approach by generating highly accurate de novo reconstructions of multiple regions of various proteins in western diamondback rattlesnake venom. We further argue that shotgun protein sequencing has the potential to overcome the limitations of current protein sequencing approaches and thus catalyze the otherwise impractical applications of proteomics methodologies in studies of unknown proteins.

Helicobacter pylori-secreting protein Tipalpha is a potent inducer of chemokine gene expressions in stomach cancer cells

PURPOSE

Stomach cancer has a high mortality rate in East Asia, and is strongly associated with Helicobacter pylori (H. pylori) infection. H. pylori is known to express chemokine genes in the gastric mucosa, chemokines that are important host immune factors facilitating inflammation and tumor growth. To investigate the mechanism of carcinogenesis in the stomach, it is essential to determine which molecule of H. pylori is involved in induction of chemokines, but this has remained unclear. We previously reported that a tumor necrosis factor-alpha (TNF-alpha) inducing protein (Tipalpha) secreted from H. pylori acts as a tumor promoter in stomach cancer development, and thus started to investigate whether Tipalpha is involved in induction of chemokine genes.

METHODS

Comprehensive gene expression analysis was conducted using DNA microarray and KeyMolnet analyses. The gene expression was quantitatively analyzed by real-time RT-PCR.

RESULTS

Comprehensive and quantitative gene expression analyses revealed that Tipalpha induces gene expression of the chemokines Ccl2, Ccl7, Ccl20, Cxcl1, Cxcl2, Cxcl5 and Cxcl10 extensively and simultaneously in mouse stomach cancer cells, MGT-40. Tipalpha induced high levels of chemokine gene expression, whereas inactive deleted Tipalpha, del-Tipalpha, showed only marginal expression, suggesting a correlation between tumor promotion and chemokine gene expression by Tipalpha. MG-132, a proteasome inhibitor which represses NF-kappaB-activation, inhibited chemokine gene expressions.

CONCLUSION

We report here that Tipalpha of H. pylori gene product is a strong inducer of chemokine gene expressions, providing a new model for stomach cancer development.