Prevention of TGF-beta-induced apoptosis by interlukin-4 through Akt activation and p70S6K survival signaling pathways

IL-4 and IL-13 Receptor Signaling From 4PS to Insulin Receptor Substrate 2: There and Back Again, a Historical View

In this historical perspective, written in honor of Dr. William E. Paul, we describe the initial discovery of one of the dominant substrates for tyrosine phosphorylation stimulated by IL-4. We further describe how this “IL-4-induced phosphorylated substrate” (4PS) was characterized as a member of the insulin receptor substrate (IRS) family of large adaptor proteins that link IL-4 and insulin receptors to activation of the phosphatidyl-inositol 3′ kinase pathway as well as other downstream signaling pathways. The relative contribution of the 4PS/IRS pathway to the early models of IL-4-induced proliferation and suppression of apoptosis are compared to our more recent understanding of the complex interplay between positive and negative regulatory pathways emanating from members of the IRS family that impact allergic responses.

High expression of IL-4R enhances proliferation and invasion of hepatocellular carcinoma cells

OBJECTIVE

In this study, we aimed to investigate the expression and function of interleukin-4 receptor (IL-4R) in hepatocellular carcinoma (HCC).

METHODS

We collected 40 pairs of human HCC and adjacent normal tissue specimens and examined the expression levels of IL-4R. After IL-4R knockdown in HCC cell lines, cell proliferation and invasion ability were examined. Cell cycle and apoptosis were analyzed by flow cytometry. The activity of multiple signaling pathways was examined by Western blot.

RESULTS

IL-4R was overexpressed in HCC tumors compared with adjacent normal control tissues and was associated with tumor differentiation status. IL-4R knockdown resulted in enhanced apoptosis, impaired proliferation and reduced invasion of HCC cells. Furthermore, IL-4R knockdown abolished IL-4-induced activation of the Janus Kinase 1 (JAK1)/signal transducer and activator of transcription 6 (STAT6) and JUN N-terminal kinase (JNK)/extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways.

CONCLUSIONS

IL-4R plays an important role in regulating HCC cell survival and metastasis, and regulates the activity of the JAK1/STAT6 and JNK/ERK1/2 signaling pathways. We therefore suggest that IL-4/IL-4R may be a new therapeutic target for HCC.

Rapamycin can restore the negative regulatory function of transforming growth factor beta 1 in high grade lymphomas

TGF-β1 (transforming growth factor beta 1) is a negative regulator of lymphocytes, inhibiting proliferation and switching on the apoptotic program in normal lymphoid cells. Lymphoma cells often lose their sensitivity to proapoptotic/anti-proliferative regulators such as TGF-β1. Rapamycin can influence both mTOR (mammalian target of rapamycin) and TGF-β signaling, and through these pathways it is able to enhance TGF-β induced anti-proliferative and apoptotic responses. In the present work we investigated the effect of rapamycin and TGF-β1 combination on cell growth and on TGF-β and mTOR signalling events in lymphoma cells. Rapamycin, an inhibitor of mTORC1 (mTOR complex 1) did not elicit apoptosis in lymphoma cells; however, the combination of rapamycin with exogenous TGF-β1 induced apoptosis and restored TGF-β1 dependent apoptotic machinery in several lymphoma cell lines with reduced TGF-β sensitivity in vitro. In parallel, the phosphorylation of p70 ribosomal S6 kinase (p70S6K) and ribosomal S6 protein, targets of mTORC1, was completely eliminated. Knockdown of Smad signalling by Smad4 siRNA had no influence on apoptosis induced by the rapamycin+TGF-β1, suggesting that this effect is independent of Smad signalling. However, apoptosis induction was dependent on early protein phosphatase 2A (PP2A) activity, and in part on caspases. Rapamycin+TGF-β1 induced apoptosis was not completely eliminated by a caspase inhibitor. These results suggest that high mTOR activity contributes to TGF-β resistance and lowering mTORC1 kinase activity may provide a tool in high grade B-cell lymphoma therapy by restoring the sensitivity to normally available regulators such as TGF-β1.

TGF-β induced TMEPAI/PMEPA1 inhibits canonical Smad signaling through R-Smad sequestration and promotes non-canonical PI3K/Akt signaling by reducing PTEN in triple negative breast cancer

TMEPAI (transmembrane prostate androgen-induced) is amplified at genomic, transcript and protein levels in triple-negative breast cancers and promotes TGF-β dependent growth, motility and invasion. Tumor promotion by TMEPAI depends on two different but related actions on TGF-β signaling. Firstly, TMEPAI binds and sequesters regulatory Smads2/3 and thereby decreases growth suppressive signaling by TGF-β. Secondly, increased expression of TMEPAI decreases PTEN (phosphatase and tensin homolog) abundance, and thereby increases TGF-β dependent tumor promotive PI3K/Akt signaling. These actions of TMEPAI give rise to increased cell proliferation and motility. Moreover, signaling alterations produced by high TMEPAI were associated with oncogenic Snail expression and lung metastases. Finally, an inverse correlation between TMEPAI and PTEN levels was confirmed in triple negative breast cancer tumor samples. Together, our findings suggest that TMEPAI has dually critical roles to promote TGF-β dependent cancer cell growth and metastasis. Thus, redirected TGF-β signaling through TMEPAI may play a pivotal role in TGF-β mediated tumor promotion.

Transactivation of the TIEG1 confers growth inhibition of transforming growth factor-β-susceptible hepatocellular carcinoma cells

AIM: To investigate the role of transforming growth factor (TGF)-β-inducible early gene 1 (TIEG1) in TGF-β-induced growth inhibition in hepatocellular carcinoma (HCC) cells.

METHODS: Human hepatocyte and HCC cell lines with varied susceptibilities to TGF-β1 were tested by methylthiazoletetrazolium (MTT) assay. The expression changes of Smad2, Smad3, Smad4, Smad7, TIEG1 and TIEG2 gene following treatment with TGF-β1 in a TGF-β-sensitive hepatocyte cell line (MIHA), a TGF-β-sensitive hepatoma cell line (Hep3B) and two TGF-β-insensitive hepatoma cell lines (HepG2 and Bel7404) were examined. SiRNA targeting TIEG1 was transfected into Hep3B cells and the sensitivity of cells to TGF-β1 was examined. Overexpression of TIEG1 was induced by lentiviral-mediated transduction in TGF-β1-resistant hepatoma cell lines (Bel7404 and HepG2). MTT assay and 4’,6-Diamidino-2-phenylindole staining were used to identify cell viability and apoptosis, respectively. The expression level of stathmin was measured by reverse transcriptase polymerase chain reaction and Western-blotting analysis, and stathmin promoter activity by TIEG1 was monitored by a luciferase reporter gene system.

RESULTS: TIEG1 was significantly upregulated by TGF-β1 in the TGF-β1-sensitive HCC cell line, Hep3B, but not in the resistant cell lines. The suppression of TIEG1 by siRNAs decreased the sensitivity of Hep3B cells to TGF-β1, whereas the overexpression of TIEG1 mediated growth inhibition and apoptosis in TGF-β1-resistant HCC cell lines, which resembled those of TGF-β1-sensitive HCC cells treated with TGF-β1. Our data further suggested that stathmin was a direct target of TIEG1, as stathmin was significantly downregulated by TIEG1 overexpression, and stathmin promoter activity was inhibited by TIEG1 in a dose-dependent manner.

CONCLUSION: Our data suggest that transactivation of TIEG1 conferred growth inhibition of TGF-β-susceptible human HCC cells.

Transforming growth factor-β and the hallmarks of cancer

Tumorigenesis is in many respects a process of dysregulated cellular evolution that drives malignant cells to acquire six phenotypic hallmarks of cancer, including their ability to proliferate and replicate autonomously, to resist cytostatic and apoptotic signals, and to induce tissue invasion, metastasis, and angiogenesis. Transforming growth factor-β (TGF-β) is a potent pleiotropic cytokine that functions as a formidable barrier to the development of cancer hallmarks in normal cells and tissues. Paradoxically, tumorigenesis counteracts the tumor suppressing activities of TGF-β, thus enabling TGF-β to stimulate cancer invasion and metastasis. Fundamental gaps exist in our knowledge of how malignant cells overcome the cytostatic actions of TGF-β, and of how TGF-β stimulates the acquisition of cancer hallmarks by developing and progressing human cancers. Here we review the molecular and cellular mechanisms that underlie the ability of TGF-β to mediate tumor suppression in normal cells, and conversely, to facilitate cancer progression and disease dissemination in malignant cells.

T cells expressing constitutively active Akt resist multiple tumor-associated inhibitory mechanisms

Adoptive transfer of antigen-specific cytotoxic T lymphocytes has shown promise for the therapy of cancer. However, tumor-specific T cells are susceptible to diverse inhibitory signals from the tumor microenvironment. The Akt/protein kinase B plays a central role in T-cell proliferation, function, and survival and we hypothesized that expression of constitutively active Akt (caAkt) in T cells could provide resistance to many of these tumor-associated inhibitory mechanisms. caAkt expression in activated human T cells increased proliferation and cytokine production, a likely result of their sustained expression of nuclear factor-κB (NF-κB) and provided resistance to apoptosis by upregulating antiapoptotic molecules. caAkt expressing T cells (caAkt-T-cells) were also relatively resistant to suppression by and conversion into regulatory T cells (Tregs). These characteristics provided a survival advantage to T cells cocultured with tumor cells in vitro; CD3/28-stimulated T cells expressing a chimeric antigen receptor (CAR) specific for disialoganglioside (GD2) that redirected their activity to the immunosuppressive, GD2-expressing neuroblastoma cell line, LAN-1, resisted tumor-induced apoptosis when co-expressing transgenic caAkt. In conclusion, caAkt-transduced T cells showed resistance to several evasion strategies employed by tumors and may therefore enhance the antitumor activity of adoptively transferred T lymphocytes.

CNS expression of anti-inflammatory cytokine interleukin-4 attenuates Alzheimer's disease-like pathogenesis in APP+PS1 bigenic mice

Cytokines play an emerging role as neurotransmitters, neuromodulators, and neurohormones in the brain. This paradigm shift in cytokine function offers a new framework to understand their roles in ameliorating neurodegenerative disorders, such as Alzheimer's disease (AD). Molecular adjuvant therapy of AD animal models with glatiramer acetate induces anti-inflammatory responses and therapeutic effects. Although these effects are potentially mediated through anti-inflammatory cytokine signaling, the exact molecular identities and pathways are poorly understood. Here, we show that virus-mediated expression of the mouse interleukin (IL)-4 gene in beta-amyloid precursor protein + presenilin-1 (APP+PS1) bigenic mice attenuates AD pathogenesis. Introduction of an adeno-associated viral (AAV) vector encoding IL-4 into the hippocampus resulted in sustained expression of IL-4, reduced astro/microgliosis, amyloid-beta peptide (Abeta) oligomerization and deposition, and enhanced neurogenesis. Moreover, increased levels of IL-4 improved spatial learning, promoted phosphorylation of N-methyl-D-aspartate receptor subunit 2B at Tyr 1472, and enhanced its cell surface retention both in vivo and in vitro. Our data suggest that neuronal anti-inflammatory cytokine signaling may be a potential alternative target for non-Abeta-mediated treatment of AD.

Activation of PI 3-kinase/Akt/NF-kappaB and Stat3 signaling by avian reovirus S1133 in the early stages of infection results in an inflammatory response and delayed apoptosis

Avian reovirus (ARV) strain S1133 causes apoptosis in host cells in the middle to late stages of infection. This study investigated the early-stage biological response and intracellular signaling in ARV S1133-infected Vero and chicken cells. Treatment with conditioned medium from ARV S1133-infected cells increased the chemotactic activity of U937 cells. Neutralizing antibodies against IL-1beta and IL-6 showed that both cytokines contribute to viral-induced inflammation but neither affect cell survival. Inhibition of Akt, NF-kappaB, and Stat3 released the chemotactic activity and anti-apoptotic effect elicited by ARV S1133. ARV S1133 activated PI 3-kinase-dependent Akt/NF-kappaB and p70 S6 kinase, as well as Stat3; however, p70 S6 kinase was not involved in ARV S1133-mediated effects. DF1 cells over-expressing constitutively active PI 3-kinase and Stat3 showed association with enhancement of anti-apoptotic activity. In conclusion, in the early stages of ARV S1133 infection, activation of cell survival signals contributes to virus-induced inflammation and anti-apoptotic response.

Dominant role of antigen dose in CD4+Foxp3+ regulatory T cell induction and expansion

The definitions of tolerogenic vs immunogenic dendritic cells (DC) remain controversial. Immature DC have been shown to induce T regulatory cells (Treg) specific for foreign and allogeneic Ags. However, we have previously reported that mature DC (mDC) prevented the onset of autoimmune diabetes, whereas immature DC (iDC) were therapeutically ineffective. In this study, islet-specific CD4(+) T cells from BDC2.5 TCR-transgenic mice were stimulated in the absence of exogenous cytokine with iDC or mDC pulsed with high- or low-affinity antigenic peptides and examined for Treg induction. Both iDC and mDC presenting low peptide doses induced weak TCR signaling via the Akt/mammalian target of rapamycin (mTOR) pathway, resulting in significant expansion of Foxp3(+) Treg. Furthermore, unpulsed mDC, but not iDC, also induced Treg. High peptide doses induced strong Akt/mTOR signaling and favored the expansion of Foxp3(neg) Th cells. The inverse correlation of Foxp3 and Akt/mTOR signaling was also observed in DO11.10 and OT-II TCR-transgenic T cells and was recapitulated with anti-CD3/CD28 stimulation in the absence of DC. IL-6 production in these cultures correlated positively with Ag dose and inversely with Treg expansion. Studies with T cells or DC from IL-6(-/-) mice revealed that IL-6 production by T cells was more important in the inhibition of Treg induction at low Ag doses. These studies indicate that the strength of Akt/mTOR signaling, a critical T cell-intrinsic determinant for Treg vs Th induction, can be controlled by adjusting the dose of antigenic peptide. Furthermore, this operates in a dominant fashion over DC phenotype and cytokine production.

Human cholangiocarcinoma development is associated with dysregulation of opioidergic modulation of cholangiocyte growth

BACKGROUND/AIMS

Incidence of cholangiocarcinoma is increasing worldwide, yet remaining highly aggressive and with poor prognosis. The mechanisms that drive cholangiocyte transition towards malignant phenotype are obscure. Cholangiocyte benign proliferation is subjected to a self-limiting mechanism based on the autocrine release of endogenous opioid peptides. Despite the presence of both, ligands interact with delta opioid receptor (OR), but not with microOR, with the consequent inhibition of cell growth. We aimed to verify whether cholangiocarcinoma growth is associated with failure of opioidergic regulation of growth control.

METHODS

We evaluated the effects of OR selective agonists on cholangiocarcinoma cell proliferation, migration and apoptosis. Intracellular signals were also characterised.

RESULTS

Activation of microOR, but not deltaOR, increases cholangiocarcinoma cell growth. Such an effect is mediated by ERK1/2, PI3K and Ca(2+)-CamKIIalpha cascades, but not by cAMP/PKA and PKCalpha. microOR activation also enhances cholangiocarcinoma cell migration and reduces death by apoptosis. The anti-apoptotic effect of microOR was PI3K dependent.

CONCLUSIONS

Our data indicate that cholangiocarcinoma growth is associated with altered opioidergic regulation of cholangiocyte biology, thus opening new scenarios for future surveillance or early diagnostic strategies for cholangiocarcinoma.

The TGF-beta paradox in human cancer: an update

TGF-beta plays an essential role in maintaining tissue homeostasis through its ability to induce cell cycle arrest, differentiation and apoptosis, and to preserve genomic stability. Thus, TGF-beta is a potent anticancer agent that prohibits the uncontrolled proliferation of epithelial, endothelial and hematopoietic cells. Interestingly, tumorigenesis typically elicits aberrations in the TGF-beta signaling pathway that engenders resistance to the cytostatic activities of TGF-beta, thereby enhancing the development and progression of human malignancies. Moreover, these genetic and epigenetic events conspire to convert TGF-beta from a suppressor of tumor formation to a promoter of their growth, invasion and metastasis. The dichotomous nature of TGF-beta during tumorigenesis is known as the 'TGF-beta paradox', which remains the most critical and mysterious question concerning the physiopathological role of this multifunctional cytokine. Here we review recent findings that directly impact our understanding of the TGF-beta paradox and discuss their importance to targeting the oncogenic activities of TGF-beta in developing and progressing neoplasms.

Neuroprotective effect of sodium ferulate and signal transduction mechanisms in the aged rat hippocampus

AIM

To investigate whether the age-related increase in interleukin-1beta (IL-1beta) and c-Jun N-terminal kinases (JNK) pathway was coupled with a decrease in cell survival signaling pathways and whether sodium ferulate (SF) treatment was effective in preventing these age-associated changes.

METHODS

Groups of young and aged rats were fed for 4 weeks on a diet enriched in SF (100 mg/kg and 200 mg/kg per day). At the end of the period of dietary manipulation, Western blotting analysis was used to determine the expressions of IL-1beta, phosphorylated mitogen-activated protein kinase kinase (MKK)4, phospho-JNK, phospho-c-Jun, phosphorylated extracellular signal-regulated kinase (ERK1/2), phospho-MEK, phospho-Akt, phosphorylated ribosomal protein S6 protein kinase (p70S6K), and activated caspase-3 and caspase-7. Nissl staining was used to observe the morphological change in hippocampal CA1 regions. Immunohistochemical techniques for glial fibrillary acidic protein (GFAP) and integrin alphaM (OX-42) were used to determine the astrocyte and microglia activation.

RESULTS

IL-1beta protein levels, and phospho-MKK4, phospho-JNK1/2, and phospho-c-Jun were significantly enhanced in hippocampus prepared from age-matched control rats. Increased IL-1beta production and JNK1/2 activation was accompanied by downregulation of MEK/ERK1/2 pathway and Akt/p70S6K pathway, leading to cell apoptosis assessed by activation of caspase-3. Significantly, treatment of aged rats with SF (100 mg/kg and 200 mg/kg per day) for 4 weeks prevented the agerelated increase in IL-1beta and IL-1beta-induced JNK signaling pathway and also the age-related changes in ERK and Akt kinase.

CONCLUSION

SF plays neuroprotective roles through suppression of IL-1beta and IL-1beta-induced JNK signaling and upregulation of MEK/ERK1/2 and Akt/p70S6K survival pathways.