The anti-inflammatory TIPE2 is an inhibitor of the oncogenic Ras

Genome-wide analysis reveals TNFAIP8L2 as an immune checkpoint regulator of inflammation and metabolism

The interplay between inflammation and metabolism is widely recognized, yet the underlying molecular mechanisms remain poorly characterized. Using experimental database mining and genome-wide gene expression profiling methods, we found that in contrast to other TNFAIP8 family members, TNFAIP8L2 (TIPE2) was preferentially expressed in human myeloid cell types. In addition, Tnfaip8l2 expression drastically decreased in lipopolysaccharide (LPS)-stimulated macrophages. Consequently, Tnfaip8l2 deficiency led to heightened expression of genes that were enriched for leukocyte activation and lipid biosynthesis pathways. Furthermore, mitochondrial respiration rate was increased in Tnfaip8l2-deficient macrophages, as measured by Seahorse metabolic analyzer. Taken together, these results indicate that Tnfaip8l2 serves as a "brake" for immunometabolism, which needs to be released for optimized metabolic reprogramming as well as mounting effective inflammatory responses. The unique anti-inflammatory and metabolic-modulatory function of TNFAIP8L2 renders it a novel therapeutic target for cardiovascular diseases and cancer.

TIPE3 protein promotes breast cancer metastasis through activating AKT and NF-κB signaling pathways

TIPE3 (TNFAIP8L3) is the transfer protein of phosphoinositide second messengers that promote cancer. Its role in breast cancer has not been evaluated. We report here that TIPE3 protein was significantly upregulated in human breast cancer tissues as compared with adjacent non-tumor tissues from the same patients. The level of TIPE3 protein in invasive ductal carcinoma was significant higher than that in ductal carcinoma in situ (DCIS), and the level of TIPE3 in lymphatic metastasized carcinoma was higher than that in invasive ductal carcinoma from the same patients. Additionally, the level of TIPE3 protein was positively correlated with the level of human epidermal growth factor receptor 2 (HER-2), and TIPE3 expression was significantly higher in high-invasive breast cancer cell lines than that in low-invasive cell lines. Importantly, TIPE3 knockdown in breast cancer cells inhibited cell proliferation, migration, and invasion in vitro, whereas TIPE3 overexpression had the opposite effect. In mice, TIPE3 expression significantly promoted the metastasis of breast cancer cells. TIPE3 expression also increased the level of MMP2 and uPA, and the activation of the AKT and NF-κB signaling pathways. These results demonstrate that TIPE3 may promote breast cancer growth and metastasis through AKT and NF-κB, and may serve as a potential biomarker for breast cancer metastasis.

TIPE2 suppresses progression and tumorigenesis of esophageal carcinoma via inhibition of the Wnt/β-catenin pathway

BACKGROUND

Esophageal carcinoma is the eighth prevalent malignancy and ranks the sixth in carcinoma-related death worldwide. Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) has been identified as a tumor suppressor in multiple carcinomas. However, its roles and molecular mechanisms underlying esophageal carcinoma progression are still undefined till now.

METHODS

RT-qPCR assay was employed to detect the expression of TIPE2 mRNA. TIPE2 protein expression was measured by using western blot assay. Ad-V and Ad-TIPE2 adenoviruses were constructed to overexpress TIPE2. The effects of TIPE2 overexpression on cell proliferation, invasion and apoptosis were assessed by MTT and Edu incorporation assays, transwell invasion assay and flow cytometry analysis, respectively. The effect of TIPE2 overexpression on xenograft tumor growth was determined by measuring tumor volume and weight, together with immunohistochemistry assay. The effect of TIPE2 overexpression on the Wnt/β-catenin signaling pathway was evaluated by detecting the protein levels of β-catenin, c-Myc and cyclinD1 in EC9076 cells and xenograft tumors of esophageal carcinoma.

RESULTS

TIPE2 expression was downregulated in esophageal carcinoma tissues and cells. Adenovirus-mediated TIPE2 overexpression suppressed cell proliferation and invasion, and induced apoptosis in esophageal carcinoma cells. Enforced expression of TIPE2 inhibited tumor growth in vivo, as evidenced by the reduced tumor volume, tumor weight and proliferating cell nuclear antigen expression. Overexpression of TIPE2 inhibited the Wnt/β-catenin signaling pathway in esophageal carcinoma in vitro and in vivo.

CONCLUSIONS

These results suggest that TIPE2 suppressed progression and tumorigenesis of esophageal carcinoma via inhibition of the Wnt/β-catenin pathway.

Direction of leukocyte polarization and migration by the phosphoinositide-transfer protein TIPE2

Leukocyte polarization toward chemoattractants is essential for directed leukocyte migration, or chemotaxis. How leukocytes acquire polarity upon encountering chemical gradients is not well understood. We report here that leukocyte polarity is generated by TIPE2 (TNFAIP8L2), a transfer protein of phosphoinositide second messengers. TIPE2 functioned as a local enhancer of phosphoinositide-dependent signaling and cytoskeleton remodeling, promoting leading edge formation. Conversely, TIPE2 acted as an inhibitor of the GTPase Rac, promoting trailing edge polarization. Consequently, TIPE2-deficient leukocytes were defective in polarization and chemotaxis, and TIPE2-deficient mice were resistant to leukocyte-mediated neural inflammation. Thus, the leukocyte polarizer is a dual-role phosphoinositide transfer protein, and a potential therapeutic target for treating inflammatory diseases.

TIPE1 suppresses invasion and migration through down-regulating Wnt/β-catenin pathway in gastric cancer

Epithelial–mesenchymal transition (EMT) plays an important role in the invasiveness and metastasis of gastric cancer. Therefore, identifying key molecules involved in EMT will provide new therapeutic strategy for treating patients with gastric cancer. TIPE1 is a newly identified member of the TIPE (TNFAIP8) family, and its contributions to progression and metastasis have not been evaluated. In this study, we found that the levels of TIPE1 were significantly reduced and inversely correlated with differentiation status and distant metastasis in primary gastric cancer tissues. We further observed overexpression of TIPE1 in aggressive gastric cancer cell lines decreased their metastatic properties both in vitro and in vivo as demonstrated by markedly inhibiting EMT and metastasis of gastric cancer cells in nude mice. Consistently, gene silencing of TIPE1 in well‐differentiated gastric cancer cell line (AGS) inhibited these processes. Mechanistically, we found that TIPE1‐medicated Wnt/β‐catenin signalling was one of the critical signal transduction pathways that link TIPE1 to EMT inhibition. Importantly, TIPE1 dramatically restrained the expression and activities of MMP2 and MMP9 which are demonstrated to promote tumour progression and are implicated in EMT. Collectively, these findings provide new evidence for a better understanding of the biological activities of TIPE1 in progression and metastasis of gastric cancer and suggest that TIPE1 may be an innovative diagnostic and therapeutic target of gastric cancer.

The decreased expression of TIPE2 protein in the decidua of patients with missed abortion and possible significance

BACKGROUND

Missed abortion is a common occurrence for otherwise healthy women. Immunological factor is one of the most important reasons. Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) is a novel negative immune regulator related to several human diseases. However, the expression level and clinical significance of TIPE2 in missed abortion remain unclear.

METHODS

The expression of TIPE2 mRNA and protein in decidua and chorion from 36 missed abortion patients and 36 healthy controls was detected using quantitative real-time PCR, western blot and immunohistochemistry. In addition, serum TNF-ɑ and IL-10 levels were measured using flow cytometry. Serum estradiol and progesterone levels were measured by radioimmunoassay test. The correlations of TIPE2 protein levels with TNF-ɑ, IL-10, estradiol and progesterone were further analyzed.

RESULTS

TIPE2 protein levels were significantly lower in decidual tissues of missed abortion patients than those in healthy controls. The patients with missed abortion had significantly higher levels of serum TNF-ɑ, and lower levels of serum IL-10, estradiol and progesterone compared with healthy controls. The TIPE2 protein levels were positively related to serum IL-10 levels.

CONCLUSION

Our data indicate TIPE2 could play important roles in maintaining the maternal-fetal tolerance and decreased TIPE2 expression in the decidua may be related to the development of missed abortion.

Stable silencing of TIPE2 reduced the Poly I:C‑induced apoptosis in THP‑1 cells

The present study aimed to determine the underlying mechanism of toll‑like receptor (TLR) agonist polyinosinic:polycytidylic acid (Poly I:C)‑induced apoptosis in THP‑1 cells following silencing the expression of tumor necrosis factor α‑induced protein 8‑like 2 (TIPE2). THP‑1 cells were incubated with different concentrations of the TLR agonist. Following incubation, reverse transcription‑quantitative polymerase chain reaction was performed to quantify the mRNA expression of TIPE2. Lentiviral technology was used to silence the expression of TIPE2. MTT assay was performed to assess cell proliferation, Annexin V/PI double staining was used to evaluate the apoptosis and western blotting was used to determine the expression levels of caspase‑8 following TIPE2 silencing. The TLRs agonist Poly I:C increased the expression level of TIPE2. During the incubation, Poly I:C also inhibited the proliferation of THP‑1 cells and induced apoptosis. Following silencing of TIPE2 in THP‑1 cells, the Poly I:C‑induced TIPE2 expression was significantly downregulated. Additionally, the Poly I:C‑induced proliferation inhibition and apoptosis in THP‑1 cells were significantly reduced following silencing of TIPE2. The findings of the western blot analysis indicated that the active form of caspase‑8, p18, was downregulated following silencing of TIPE2. In conclusion, the expression of TIPE2 in THP‑1 cells may be upregulated by Poly I:C, which may also inhibit cell proliferation and induce apoptosis. Following the downregulation of TIPE2 the aforementioned effect of Poly I:C treatment was reversed and may be associated with the reduced activity of caspase‑8 that was observed in the TIPE2 silenced group.

Evolutionary divergence of the vertebrate TNFAIP8 gene family: Applying the spotted gar orthology bridge to understand ohnolog loss in teleosts

Comparative functional genomic studies require the proper identification of gene orthologs to properly exploit animal biomedical research models. To identify gene orthologs, comprehensive, conserved gene synteny analyses are necessary to unwind gene histories that are convoluted by two rounds of early vertebrate genome duplication, and in the case of the teleosts, a third round, the teleost genome duplication (TGD). Recently, the genome of the spotted gar, a holostean outgroup to the teleosts that did not undergo this third genome duplication, was sequenced and applied as an orthology bridge to facilitate the identification of teleost orthologs to human genes and to enhance the power of teleosts as biomedical models. In this study, we apply the spotted gar orthology bridge to help describe the gene history of the vertebrate TNFAIP8 family. Members of the TNFAIP8 gene family have been linked to regulation of immune function and homeostasis and the development of multiple cancer types. Through a conserved gene synteny analysis, we identified zebrafish orthologs to human TNFAIP8L1 and TNFAIP8L3 genes and two co-orthologs to human TNFAIP8L2, but failed to identify an ortholog to human TNFAIP8. Through the application of the orthology bridge, we determined that teleost orthologs to human TNFAIP8 genes were likely lost in a genome inversion event after their divergence from their common ancestor with spotted gar. These findings demonstrate the value of this enhanced approach to gene history analysis and support the development of teleost models to study complex questions related to an array of biomedical issues, including immunity and cancer.

Clinical Significance of TIPE2 Protein Upregulation in Non-Hodgkin's Lymphoma

Non-Hodgkin's lymphoma (NHL), which includes diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma, is a refractory malignant tumor originated from the lymphatic system. TNFAIP8L2 (TIPE2 or tumor necrosis-alpha-induced protein-8 like 2) is a negative regulator for inflammation and an inhibitor for carcinogenesis. However, whether TIPE2 plays a role in lymphomagenesis is unknown. In this study, we determined TIPE2 expression in NHL by immunohistochemistry and investigated its clinicopathological significance in DLBCL. We found that TIPE2 expression was upregulated in both DLBCL and peripheral T-cell lymphoma. But the expression of TIPE2 in T lymphomas was weaker than that in DLBCL. Interestingly, among DLBCL, TIPE2 expression was significantly stronger in the germinal center B-cell (GCB) type than in the non-GCB type. These results suggest that the expression of TIPE2 protein could be a predictor of better prognosis for DLBCL.

TIPE2 Overexpression Suppresses the Proliferation, Migration, and Invasion in Prostate Cancer Cells by Inhibiting PI3K/Akt Signaling Pathway

Tumor necrosis factor-α (TNF-α)-induced protein 8-like 2 (TNFAIP8L2, TIPE2) is involved in the invasion and metastasis of human tumors. However, the functional role of TIPE2 in prostate cancer remains unclear. In the present study, we explored the role of TIPE2 in prostate cancer and cancer progression including the molecular mechanism that drives TIPE2-mediated oncogenesis. Our results showed that TIPE2 was lowly expressed in human prostate cancer tissues and cell lines. In addition, restored TIPE2 obviously inhibits proliferation in prostate cancer cells. TIPE2 overexpression also suppresses the epithelial–mesenchymal transition (EMT) process and migration/invasion in prostate cancer cells. Mechanistically, TIPE2 overexpression obviously inhibits the phosphorylation levels of phosphatidylinositol 3-kinase (PI3K) and Akt in prostate cancer cells. In conclusion, for the first time we demonstrated that TIPE2 overexpression may suppress proliferation, migration, and invasion in prostate cancer cells by inhibiting the PI3K/Akt signaling pathway. Therefore, TIPE2 might serve as a potential therapeutic target for human prostate cancer.

Gene delivery of TIPE2 inhibits breast cancer development and metastasis via CD8+ T and NK cell-mediated antitumor responses

Breast cancer is the second leading cause of cancer-related deaths in the female patients which was mainly caused by metastasis. Development of target gene therapy for breast cancer to suppress tumor progress and metastasis will improve the therapeutic options and be of great benefit to the patients. Tumor necrosis factor-alpha-induced protein 8-like 2 is a novel molecule for maintaining immune homeostasis and is involved in cancer development. In the present study, we overexpressed TIPE2 in breast cancer cells to investigate the role of TIPE2 in the development of breast cancer. Our results showed that overexpression of TIPE2 significantly inhibited the proliferation of 4T1 cells in vitro and in vivo. We constructed a non-viral targeted gene therapeutic system by using the minicircle plasmids expressing TIPE2. We found that the growth and metastasis of breast cancer was significantly inhibited by hydrodynamic gene delivery of TIPE2 plasmids in vivo. Mechanistically, TIPE2 increased T and NK cells, and decreased MDSCs. Gene delivery of TIPE2 up-regulated the production of IFN-γ and TNF-α by CD8⁺ T and NK cells in spleens and tumor microenvironment, and enhanced the cytotoxic activity of CD8⁺ T and NK cells. Taken together, TIPE2 inhibited breast cancer development and metastasis possibly via promoting CD8⁺ T and NK cell-mediated antitumor immune responses. Thus, the results indicate that TIPE2 may be a potential therapeutic target for breast cancer therapy.

TIPE2 Inhibits Hypoxia-Induced Wnt/β-Catenin Pathway Activation and EMT in Glioma Cells

Hypoxia-induced epithelial-to-mesenchymal transition (EMT) could facilitate tumor progression. TIPE2, the tumor necrosis factor-α (TNF-α)-induced protein 8-like 2 (also known as TNFAIP8L2), is a member of the TNF-α-induced protein 8 (TNFAIP8, TIPE) family and has been involved in the development and progression of several tumors. However, the effects of TIPE2 on the EMT process in glioma cells and the underlying mechanisms of these effects have not been previously reported. In our study, we assessed the roles of TIPE2 in the EMT process in glioma cells in response to hypoxia. Our results indicated that TIPE2 expression was significantly decreased in human glioma cell lines. TIPE2 overexpression significantly inhibited hypoxia-induced migration and invasion, as well as suppressed the EMT process in glioma cells. Furthermore, TIPE2 overexpression prevented hypoxia-induced expression of β-catenin, cyclin D1, and c-myc in human glioma cells. In summary, these data suggest that TIPE2 overexpression inhibited hypoxia-induced Wnt/β-catenin pathway activation and EMT in glioma cells.

Regulation of inflammation and tumorigenesis by the TIPE family of phospholipid transfer proteins

The TIPE (tumor necrosis factor-α-induced protein 8-like) family are newly described regulators of immunity and tumorigenesis consisting of four highly homologous mammalian proteins: TNFAIP8 (tumor necrosis factor-α-induced protein 8), TIPE1 (TNFAIP8-like 1, or TNFAIP8L1), TIPE2 (TNFAIP8L2) and TIPE3 (TNFAIP8L3). They are the only known transfer proteins of the lipid secondary messengers PIP2 (phosphatidylinositol 4,5-bisphosphate) and PIP3 (phosphatidylinositol 3,4,5-trisphosphate). Cell-surface receptors, such as G-protein-coupled receptors and receptor tyrosine kinases, regulate inflammation and cancer via several signaling pathways, including the nuclear factor (NF)-κB and phosphoinositide-3 kinase (PI3K) pathways, the latter of which is upstream of both Akt and STAT3 activation. An expression analysis in humans demonstrated that the TIPE family is dysregulated in cancer and inflammation, and studies both in mice and in vitro have demonstrated that this family of proteins plays a critical role in tumorigenesis and inflammatory responses. In this review, we summarize the current literature for all four family members, with a special focus on the phenotypic manifestations present in the various knockout murine strains, as well as the related cell signaling that has been elucidated to date.

Adenovirus-mediated TIPE2 overexpression inhibits gastric cancer metastasis via reversal of epithelial-mesenchymal transition

Tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TNFAIP8L2; also termed TIPE2) has been shown to be involved in both the immune-negative modulation and cancer. We previously found that TIPE2 is lost in human gastric cancer, and TIPE2 restoration suppresses gastric cancer growth by induction of apoptosis and impairment of protein kinase B (PKB/AKT) and extracellular signal-regulated kinase-1/2 (ERK1/2) signaling. However, its correlation with epithelial-mesenchymal transition (EMT) in gastric cancer is largely elusive. In the present report, we carried out a gain-of-function study in AGS and HGC-27 human gastric cancer cells by adenovirus-mediated human TIPE2 gene transfer (AdVTIPE2). We then examined the effects of AdVTIPE2 on in vitro migration and invasion of AGS and HGC-27 tumor cells by wound-healing assay and Transwell invasion assay, respectively. We also investigated the effects of AdVTIPE2 on in vivo lung metastasis of AGS and HGC-27 tumor cells by intravenous (i.v.) injection in athymic BALB/c nude mice. We demonstrated that AdVTIPE2 remarkably suppressed the migratory, invasive and metastatic potential of AGS and HGC-27 tumor cells in vitro and in vivo in BALB/c nude mouse model. Mechanistically, AdVTIPE2 obviously upregulated E-cadherin epithelial marker in AGS and HGC-27 tumor cells, whereas it downregulated N-cadherin and Vimentin mesenchymal markers, Snail1, Snail2/Slug and Zeb1 EMT-inducing transcription factors (EMT-TFs), and tripartite motif-containing 29 (TRIM29) and phosphatase regenerating liver 3 (PRL-3) gastric cancer-specific metastasis markers. Importantly, glycogen synthase kinase-3β (GSK-3β) inhibitor VIII and 26S proteasome inhibitor MG132 assays revealed that TIPE2 downregulated Snail1 and Snail2/Slug in a GSK-3β- and proteasome-dependent manner possibly by impairing AKT signaling. Our data provided the first evidence that TIPE2 inhibits gastric cancer cell migration, invasion and metastasis very probably via reversal of EMT, revealing that TIPE2 may be a novel therapeutic target for human gastric cancer EMT and metastasis.

Negative Immune Regulator TIPE2 Promotes M2 Macrophage Differentiation through the Activation of PI3K-AKT Signaling Pathway

Macrophages play important roles in the regulation of the innate and adaptive immune responses. Classically activated macrophages and alternatively activated macrophages are the two major forms of macrophages and have opposing functionalities. Tumor necrosis factor-α-induced protein 8-2 is expressed primarily by immune cells and negatively regulates type 1 innate and adaptive immune responses to maintain immune tolerance. While previous studies indicate that TIPE2 promotes M2 but inhibits M1 macrophage differentiation, the underlying molecular mechanism by which TIPE2 promotes M2 macrophage differentiation remains unclear. Our current study shows that TIPE2-deficient bone-marrow cells are defective in IL-4 induced M2 macrophage differentiation in vitro. Mechanistic studies revealed that TIPE2 promotes phosphoinositide metabolism and the activation of the down-stream AKT signaling pathway, which in turn leads to the expression of markers specific for M2 macrophages. In addition, our results showed that Tipe2-deficiency does not affect the activation of the JAK-STAT6 signaling pathway that also plays an important role during M2 macrophage differentiation. Taken together, these results indicate that TIPE2 promotes M2 macrophage differentiation through the activation of PI3K-AKT signaling pathway, and may play an important role during the resolution of inflammation, parasite control, as well as tissue repair.

Expression and roles of TIPE2 in autoimmune hepatitis

Tumor necrosis factor, alpha-induced protein 8-like 2 (TIPE2) is associated with the development of hepatic inflammatory diseases. However, to date, the possible role of TIPE2 in autoimmune hepatitis (AIH) has not been reported. The present study aimed to investigate the expression of TIPE2 in peripheral blood mononuclear cells (PBMCs) of mice with AIH. Furthermore, the liver function, pro-inflammatory cytokine production and hepatic histopathology were examined in TIPE2-deficient mice in order to evaluate whether TIPE2 is involved in the pathogenesis of AIH. A murine model of AIH was induced by treatment with concanavalin A (ConA). The expression of TIPE family members in the PBMCs was examined using reverse-transcription quantitative polymerase chain reaction analysis, while the protein expression of TIPE2 was additionally detected by western blot analysis. The activity of alanine amiotransferase (ALT) and aspartate aminotransferase (AST) in the serum was measured on an automated chemical analyzer to assess liver function. The serum levels of tumor necrosis factor-α, interleukin (IL)-6 and IL-12 were measured using commercial ELISA kits. Hematoxylin and eosin staining was performed to assess hepatic histopathology. The results showed that the expression of TIPE2 was significantly decreased in the mice with AIH. Following ConA-induced AIH, TIPE2-deficient mice had significantly increased serum ALT and AST levels, enhanced production of pro-inflammatory cytokines, as well as more severe hepatic inflammation compared with the wild-type mice. In conclusion, the present study demonstrated, for the first time, that TIPE2 is involved in the pathogenesis of AIH. TIPE2 prevents liver dysfunction and inhibits deleterious inflammatory immune responses after AIH and may therefore serve as a novel agent for the treatment of AIH.

Transcriptome and Proteome Analyses of TNFAIP8 Knockdown Cancer Cells Reveal New Insights into Molecular Determinants of Cell Survival and Tumor Progression

Tumor necrosis factor-α-inducible protein 8 (TNFAIP8) is the first discovered oncogenic and an anti-apoptotic member of a conserved TNFAIP8 or TIPE family of proteins. TNFAIP8 mRNA is induced by NF-kB, and overexpression of TNFAIP8 has been correlated with poor prognosis in many cancers. Downregulation of TNFAIP8 expression has been associated with decreased pulmonary colonization of human tumor cells, and enhanced sensitivities of tumor xenografts to radiation and docetaxel. Here we have investigated the effects of depletion of TNFAIP8 on the mRNA, microRNA and protein expression profiles in prostate and breast cancers and melanoma. Depending on the tumor cell type, knockdown of TNFAIP8 was found to be associated with increased mRNA expression of several antiproliferative and apoptotic genes (e.g., IL-24, FAT3, LPHN2, EPHA3) and fatty acid oxidation gene ACADL, and decreased mRNA levels of oncogenes (e.g., NFAT5, MALAT1, MET, FOXA1, KRAS, S100P, OSTF1) and glutamate transporter gene SLC1A1. TNFAIP8 knockdown cells also exhibited decreased expression of multiple onco-proteins (e.g., PIK3CA, SRC, EGFR, IL5, ABL1, GAP43), and increased expression of the orphan nuclear receptor NR4A1 and alpha 1 adaptin subunit of the adaptor-related protein complex 2 AP2 critical to clathrin-mediated endocytosis. TNFAIP8-centric molecules were found to be predominately implicated in the hypoxia-inducible factor-1α (HIF-1α) signaling pathway, and cancer and development signaling networks. Thus TNFAIP8 seems to regulate the cell survival and cancer progression processes in a multifaceted manner. Future validation of the molecules identified in this study is likely to lead to new subset of molecules and functional determinants of cancer cell survival and progression.

Tyrosine phosphorylation of RalGDS by c-Met receptor blocks its interaction with Ras

RalGDS is a guanine nucleotide exchange factor that promotes the active GTP-bound form of Ral GTPases, RalA and RalB. GTP-bound Ras has the capacity to activate Ral GTPases at least in part by binding to the C-terminal Ras-binding domain (RBD) of RalGDS and directing the protein to Ral GTPases in the plasma membrane. In many cases, activation of Ral proteins complements other Ras effector pathways to carry out a cell function, but in others it opposes them. Moreover, in many cases activation of Ral proteins contributes to the oncogenic potential of Ras. However, in some cell types Ral proteins suppresses tumor formation, suggesting oncogenic stimuli that function through Ras may need to suppress Ral activation in order to transform cells. In this paper, we demonstrate a potential biochemical mechanism for such phenomena by showing that c-Met receptors promote the tyrosine phosphorylation of RalGDS at Y752 in its RBD, which blocks the binding of Ras to RalGDS.

Hepatitis C virus promotes hepatocellular carcinogenesis by targeting TIPE2, a new regulator of DNA damage response

Infection of hepatitis C virus (HCV) is associated with primary hepatocellular carcinoma (HCC). However, its underlying molecular mechanisms remain enigmatic. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2), a new negative regulator of immunity, plays significant roles in modulating inflammation and tumorigenesis. We hypothesized that TIPE2 might be involved in the development of HCV-induced HCC. To test this hypothesis, the expression of TIPE2 was determined by Western blot in the tumor and pericarcinomatous tissues collected from ten HCV-positive HCC patients; the interaction between TIPE2 and HCV-encoded non-structural proteins was analyzed by immunoprecipitation and immunofluorescence assays, and tumorigenesis and its mechanisms were studied in cell models and nude mice. Our results demonstrated that the expression of TIPE2 was significantly reduced in HCC tissues compared to that in the paracarcinoma tissues. HCV-encoded non-structural protein NS5A could specifically interact with TIPE2 and induce its degradation. Downregulation of TIPE2 by shRNA in cell lines increased genomic DNA damage and promoted cell colony formation in vitro and tumorigenesis in nude mice. In contrast, overexpression of TIPE2 had an opposite effect. Downregulation of TIPE2 by NS5A is associated with genomic DNA instability and HCV-induced HCC development. Thus, TIPE2 may be a new therapeutic target for the treatment of HCV-associated HCC.

Protective effect of Xuebijing injection on D-galactosamine- and lipopolysaccharide-induced acute liver injury in rats through the regulation of p38 MAPK, MMP-9 and HO-1 expression by increasing TIPE2 expression

Xuebijing injection (XBJ) has long been used to treat infectious diseases in China. The therapeutic effect of XBJ is probably associated with anti-inflammatory effects. However, the precise mechanisms responsible for the effects of XBJ remain unknown. The present study was conducted in order to evaluate the protective effects of XBJ in a rat model of D-galactosamine (D-Gal)- and lipopolysaccharide (LPS)-induced acute liver injury. In the present study, the rats were injected with D-Gal and LPS intraperitoneally to induce acute liver injury. Two hours prior to D-Gal and LPS administration, the treatment group was administered XBJ by intravenous infusion. The effects of XBJ on D-Gal- and LPS-induced expression of tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TIPE2), nuclear factor-κB (NF-κB), matrix metalloproteinase-9 (MMP-9) and heme oxygenase-1 (HO-1) as well as mitogen-activated protein kinase (MAPK) signaling was examined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot analysis, immunofluorescence, as well as by analysing the serum levels of pro-inflammatory cytokines and the transaminases, alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Myeloperoxidase (MPO), malondialdehyde (MDA) and superoxide dismutase (SOD) levels in the rat liver tissues were also measured. For histological analysis, hematoxylin and eosin (H&E)-stained liver samples were evaluated. The results showed that XBJ upregulated TIPE2 and HO-1 expression, reduced the expression of NF-κB65 and MMP-9, inhibited the LPS-induced gene expression of c-jun N-terminal kinase (JNK) and p38 MAPK, decreased the generation of pro-inflammatory cytokines [interleukin (IL)-6, IL-13 and TNF-α], inhibited ALT and AST activity, and ameliorated D-Gal- and LPS-induced liver injury. The histological results also demonstrated that XBJ attenuated D-Gal- and LPS-induced liver inflammation. It was found that XBJ may prevent LPS-induced pro-inflammatory gene expression through inhibiting the NF-κB and MAPK signaling pathways by upregulating TIPE2 expression, thereby attenuating LPS-induced liver injury in rats. The marked protective effects of XBJ suggest that it has the potential to be used in the treatment of LPS-induced liver injury.

TIPE2 (Tumor Necrosis Factor α-induced Protein 8-like 2) Is a Novel Negative Regulator of TAK1 Signal

TIPE2 (TNF-α-induced protein 8-like 2) is a novel death effector domain protein and is a negative regulator of the innate and adaptive immune response. Although it has been demonstrated that caspase-8 contributes to the negative regulation of TIPE2, the negative regulatory mechanism is not entirely understood. Here, we demonstrate that TIPE2 interacts with TGF-β-activated kinase 1 (TAK1), a crucial regulatory molecule of inflammatory and immune signals, and consequently acts as a powerful negative regulator of TAK1. The interaction between endogenous TIPE2 and TAK1 was observed in RAW264.7 macrophage-like cells and mouse primary cells derived from spleen and thymus. The TIPE2 amino acid 101-140 region interacted with TAK1 by binding to the amino acid 200-291 region of the internal kinase domain of TAK1. TIPE2 interfered with the formation of the TAK1-TAB1-TAB2 complex and subsequently inhibited activation of TAK1 and its downstream molecules. Importantly, silencing TIPE2 through RNA interference attenuated the inhibitory action of TIPE2 on LPS- and TNF-α-stimulated TAK1 activity. Exogenous TIPE2 101-140, the region that interacts with TAK1, also inhibited LPS- and TNF-α-stimulated NF-κB reporter activity. Interestingly, cell-permeable TIPE2 protein maintained its binding ability with TAK1 and exhibited the same inhibitory action of native TIPE2 on TLR4 signaling in vitro Thus, cell-permeable TIPE2 protein is a potential candidate for intracellular protein therapy for TAK1-related diseases. The present study demonstrates that TIPE2 acts as a novel negative regulator of inflammatory and immune responses through TAK1 signaling.

Tumor necrosis factor α-induced protein 8-like 1 promotes apoptosis by regulating B-cell leukemia/lymphoma-2 family proteins in RAW264.7 cells

Although the newly identified protein tumor necrosis factor α-induced protein 8-like 1 (TNFAIP8L1), also known as TIPE1, has been reported to be able to induce apoptosis in human hepatocellular carcinoma cells, the involvement of TIPE1 in apoptosis remains to be elucidated. The present study investigated the pro-apoptotic effect of TIPE1 in an murine macrophage cell line, RAW264.7. The cell apoptosis rate was detected by flow cytometry. The results revealed that overexpressed TIPE1 could directly enhance the apoptosis and the cisplatin-induced cell death of RAW264.7 cells in vitro. Meanwhile, TIPE1 overexpression could suppress tumor growth in vivo. Furthermore, western blotting revealed that overexpressed TIPE1 could upregulate the expression of B-cell leukemia/lymphoma (Bcl)-2 associated X protein (Bax), Bcl-2 interacting killer (Bik) and p53 upregulated modulator of apoptosis (Puma), and activate the mitogen activated protein kinases (MAPKs) signaling pathway. However, western blotting demonstrated that inhibitors of the MAPKs pathway could not decrease the expression of Bax, Bik or Puma. These results indicated that TIPE1 could promote the apoptosis of RAW264.7 cells by upregulating the pro-apoptotic members of the Bcl-2 family of proteins, and that the MAPKs signaling pathway was not involved in the pro-apoptotic effect of TIPE1.

Adenovirus-directed expression of TIPE2 suppresses gastric cancer growth via induction of apoptosis and inhibition of AKT and ERK1/2 signaling

Tumor necrosis factor (TNF)-α-induced protein 8-like 2 (TNFAIP8L2/TIPE2) as a novel anti-inflammatory factor plays an important role in maintaining immune homeostasis. Recently, TIPE2 has been shown to inhibit hepatocarcinoma growth and metastasis through targeting Ras and Rac1. However, its effects in human cancers are poorly understood. In the present study, we analyzed TIPE2 mRNA expression in a panel of human gastric cancer cells (AGS, HGC-27 and SGC-7901) and then examined the cell-autonomous effects of adenovirus-mediated human TIPE2 gene transfer (AdVTIPE2) on AGS and HGC-27 human gastric cancer cells. We found that compared with the GES-1 normal human gastric mucous epithelial cells, human TIPE2 was lost in the AGS, HGC-27 and SGC-7901 gastric cancer cells. Adenovirus-mediated human TIPE2 overexpression significantly inhibited AGS and HGC-27 gastric cancer cell growth and induced AGS and HGC-27 tumor cell apoptosis in vitro. Furthermore, AdVTIPE2 treatment obviously suppressed the growth of AGS gastric cancer subcutaneously xenografted tumors implanted in athymic BALB/c nude mice in vivo. Mechanistically, AdVTIPE2 exhibited marked effects on the upregulation of Bax, cleaved Caspase-9, cleaved Caspase-3, cleaved poly ADP ribose polymerase as well as the downregulation of B-cell lymphoma (Bcl)-XL, phosphorylated-protein kinase B (p-PKB/AKT), phosphorylated-extracellular signal-regulated kinase 1/2 (p-ERK1/2) in AGS gastric cancer cells in vitro and in vivo. Collectively, AdVTIPE2 suppressed gastric cancer growth very possibly by the activation of intrinsic apoptotic pathway and the attenuation of AKT and ERK1/2 signaling. Thus, our data indicated that TIPE2 may be a novel potential therapeutic target for human gastric cancer.

The pro-apoptotic effects of TIPE2 on AA rat fibroblast-like synoviocytes via regulation of the DR5-caspase-NF-κB pathway in vitro

TIPE2, also known as TNFAIP8L2, a member of the tumor necrosis factor-alpha-induced protein-8 (TNFAIP8) family, is known as an inhibitor in inflammation and cancer, and its overexpression induces cell death. We examined the role of TIPE2 with respect to adjuvant arthritis (AA)-associated pathogenesis by analyzing the TIPE2 regulation of death receptor (DR5)-mediated apoptosis in vitro. The results showed that TIPE2 was detected in normal fibroblast-like synoviocytes (FLSs), but scarcely observed in AA-FLSs. Therefore, recombinant MIGR1/TIPE2^+/+ and control MIGR1 lentivirus vectors were transfected to AA-FLSs, which were denoted as TIPE2^+/+-FLSs and MIGR1-FLSs, respectively. Our results showed that TIPE2^+/+-FLSs were highly susceptible to ZF1-mediated apoptosis, and ZF1 was our own purification of an anti-DR5 single chain variable fragment antibody. Under the presence of TIPE2, the expression of DR5 was significantly increased compared with that of the MIGR1-FLS group. In contrast, the level of phosphorylated nuclear factor-kappa B (pNF-κB) was lower in the TIPE2^+/+-FLS group treated with ZF1, whereas the activity of caspase was higher. Moreover, the rate of apoptosis in the TIPE2^+/+-FLS group, which was pretreated with caspase inhibitor Z-VAD-FMK, was significantly decreased. In contrast, the apoptosis occurrence in the MIGR1-FLS group increased significantly with the pretreatment of the NF-κB inhibitor Bay. These results indicated that TIPE2 increased the apoptosis of AA-FLSs by enhancing DR5 expression levels, thereby promoting the activation of caspase and inhibiting the activation of NF-κB in AA-FLSs. TIPE2 might potentially act as a therapeutic target for rheumatoid arthritis.

TIPE2 functions as a metastasis suppressor via negatively regulating β-catenin through activating GSK3β in gastric cancer

Tumor necrosis factor (TNF)-α-induced protein 8-like 2 (TNFAIP8L2, TIPE2) is a novel anti-inflammatory factor involved in maintaining immune homeostasis. Accumulating evidence has also shown that TIPE2 displays tumor-suppressive effects in several tumor types. Previous studies revealed that TIPE2 inhibits hepatocellular carcinoma metastasis by repressing Ral and Rac1 GTPases. However, its antimetastatic activity and underlying mechanism in other human cancers is largely unknown. We investigated TIPE2 in AGS, HGC-27 and SGC-7901 human gastric cancer cells compared with GES-1 normal human gastric mucous epithelial cells. We demonstrated that TIPE2 was expressed in GES-1 gastric mucous epithelial cells but lost in all three types of gastric cancer cells. We then performed a gain-of-function study by adenovirus-mediated TIPE2 overexpression (AdVTIPE2) and investigated the effects of TIPE2 on migration and invasion of AGS human gastric cancer cells. Wound healing and Transwell invasion assays showed that forced expression of TIPE2 markedly suppressed the gastric cancer cell migration and invasion in vitro. Mechanistically, TIPE2 remarkably reduced the total levels of pAKT, pGSK3β and β-catenin as well as the nuclear level of β-catenin in gastric cancer cells. The TIPE2-elicited antimetastatic effect in gastric cancer was closely associated with the inhibition of AKT signaling and enhancement of GSK3β activity followed by the degradation and decreased translocation to nucleus of β-catenin. These results provide the first compelling evidence that TIPE2 suppresses gastric cancer metastasis via downregulating β-catenin signaling through inhibiting AKT and activating GSK3β, indicating that TIPE2 is a promising therapeutic target for human gastric cancer metastasis.

MiR-21: an environmental driver of malignant melanoma?

Since the mid-1950’s, melanoma incidence has been rising steadily in industrialized Caucasian populations, thereby pointing to the pivotal involvement of environmental factors in melanomagenesis. Recent evidence underlines the crucial role of microRNA (miR) signaling in cancer initiation and progression. Increased miR-21 expression has been observed during the transition from a benign melanocytic lesion to malignant melanoma, exhibiting highest expression of miR-21. Notably, common BRAF and NRAS mutations in cutaneous melanoma are associated with increased miR-21 expression. MiR-21 is an oncomiR that affects critical target genes of malignant melanoma, resulting in sustained proliferation (PTEN, PI3K, Sprouty, PDCD4, FOXO1, TIPE2, p53, cyclin D1), evasion from apoptosis (FOXO1, FBXO11, APAF1, TIMP3, TIPE2), genetic instability (MSH2, FBXO11, hTERT), increased oxidative stress (FOXO1), angiogenesis (PTEN, HIF1α, TIMP3), invasion and metastasis (APAF1, PTEN, PDCD4, TIMP3). The purpose of this review is to provide translational evidence for major environmental and individual factors that increase the risk of melanoma, such as UV irradiation, chemical noxes, air pollution, smoking, chronic inflammation, Western nutrition, obesity, sedentary lifestyle and higher age, which are associated with increased miR-21 signaling. Exosomal miR-21 induced by extrinsic and intrinsic stimuli may be superimposed on mutation-induced miR-21 pathways of melanoma cells. Thus, oncogenic miR-21 signaling may be the converging point of intrinsic and extrinsic stimuli driving melanomagenesis. Future strategies of melanoma treatment and prevention should thus aim at reducing the burden of miR-21 signal transduction.

Rhodiola rosea suppresses thymus T-lymphocyte apoptosis by downregulating tumor necrosis factor-α-induced protein 8-like-2 in septic rats

In recent years, several studies have shown that Rhodiola rosea can enhance cellular immunity and humoral immune function in mice, and thus, it has become a research hotspot. However, its underlying mechanism of action has remained elusive. The present study investigated whether Rhodiola rosea was able to downregulate the expression of tumor necrosis factor-α-inducible protein 8-like 2 (TIPE2), thereby inhibiting the expression of apoptotic genes, attenuating T-lymphocyte apoptosis and improving immunity in septic mice. A mouse model of caecal ligation and puncture (CLP)-induced sepsis was established, and animals in the treatment group were pre-treated with an intraperitoneal injection of Rhodiola rosea extract, while animals in the control group and sham-operated group were injected with an equivalent amount of normal saline. TIPE2, B-cell lymphoma 2 (Bcl-2), Fas and Fas ligand (FasL) mRNA and protein levels in thymic T cells were determined using reverse transcription quantitative polymerase chain reaction and western blot analysis, respectively. Furthermore, the thymus T-lymphocyte apoptosis rate, thymus T-lymphocyte count and thymus T-lymphocyte sub-sets were assessed using flow cytometry. Levels of T-helper cell type 1 (Th1) cytokines [Interleukin (IL)-2, IL-12 and interferon (IFN)-γ] and Th2 cytokines (IL-4 and IL-10) were determined using ELISA. The results showed that, compared to that in the CLP group, the expression of TIPE2, Fas and FasL in the treatment group was significantly decreased, while the expression of Bcl-2 was increased (P<0.05). The thymus lymphocyte count in the CLP group was significantly higher compared with that in the treatment group (P<0.05). Furthermore, the apoptotic rate of thymus T-lymphocytes in the treatment group was significantly lower than that in the CLP group (P<0.05). In addition, treatment with Rhodiola rosea rescued decreased in the counts of the CD3⁺ T and CD4⁺ T sub-sets of thymus T lymphocytes in the CLP group (P<0.05), while not affecting the increased levels of Th2 cytokines (IL-4 and IL-10) in the CLP group compared with those in the control groups. In addition, the Th1 cytokines (IL-12, IL-2 and IFN-γ) were significantly increased (P<0.05) in the CLP group, and treatment with Rhodiola rosea led to further increases. The thymus index of septic mice treated with Rhodiola rosea as well as their survival rate were improved as compared with those in the CLP group. These findings suggested that Rhodiola rosea has protective effects against sepsis by decreasing apoptosis, increasing Th1 cytokines and enhancing the host’s immunity via the regulation of TIPE2 expression.

TIPE2 Inhibits Lung Cancer Growth Attributing to Promotion of Apoptosis by Regulating Some Apoptotic Molecules Expression

Recent studies found that TIPE2 was involved in cancer development. However, little is known about TIPE2 in lung cancer. Our study aims to clarify the role of TIPE2 in lung carcinogenesis. We examined the expression of TIPE2 in lung squamous cancer (LSC), small cell lung cancer and lung adenocarcinoma (AdC) tissues and found that TIPE2 expression was lost in small cell lung cancer, compared with adjacent non-tumor tissues. Overexpression of TIPE2 significantly inhibited the growth of lung cancer cell H446 in vitro and even suppressed tumor formation in vivo. Flow cytometry analysis found TIPE2 overexpression promoted apoptosis of H446. In TIPE2 over-expression cells, caspase-3, caspase-9, and Bax were significantly up-regulated while Bcl-2 was down-regulated. Moreover, coincident results were shown by immunohistochemistry in tumors from nude mice. TIPE2 inhibited the phosphorylation of Akt, while promoting the phosphorylation of P38, but had no effect on IκBα and ERK pathway. Taken together, TIPE2 promoted lung cancer cell apoptosis through affecting apoptosis-related molecules caspase-3, caspase-9, Bcl-2 and Bax, possibly via regulating P38 and Akt pathways, indicating that TIPE2 might be a novel marker for lung cancer diagnosis and therapy.

Downregulated TIPE2 is associated with poor prognosis and promotes cell proliferation in non-small cell lung cancer

The present study aims to investigate the expression pattern of TIPE2 protein and its clinical significance in human non-small cell lung cancer (NSCLC). We investigated the expression levels of TIPE2 in 96 NSCLC tumor samples by immunohistochemistry and then analyzed its clinical significance. Furthermore, the role of TIPE2 on the biological properties of the NSCLC cell line H1299 and A549 was experimentally tested in vitro and in vivo. We found that the expression level of TIPE2 was significantly higher in normal lung tissues compared with NSCLC tissues (P<0.001), and TIPE2 downregulation was significantly correlated with advanced TNM stage (P=0.006). TIPE2 expression was lower in lung cancer cell lines than normal bronchial cell line HBE. Transfection of TIPE2 plasmid was performed in H1299 and A549 cells. TIPE2 overexpression inhibited lung cancer cell proliferation, colony formation and cell invasive in vitro, and prevented lung tumor growth in vivo. In addition, TIPE2 transfection reduced the anti-apoptotic Bcl-XL protein and mesenchymal marker N-cadherin expression. Taken together, our results demonstrate that TIPE2 might serve as a tumor suppressor in NSCLC progression.

A multifunctional drug combination shows highly potent therapeutic efficacy against human cancer xenografts in athymic mice

The tumor microenvironment plays a crucial role during tumor development. Integrated combination of drugs that target tumor microenvironment is a promising approach to anticancer therapy. Here, we report a multifunctional combination of low-cytotoxic drugs composed of dipyridamole, bestatin and dexamethasone (DBDx) which mainly acts on the tumor microenvironment shows highly potent antitumor efficacy in vivo. In mouse hepatoma H22 model, the triple drug combination showed synergistic and highly potent antitumor efficacy. The combination indices of various combinations of the triple drugs were between 0.2 and 0.5. DBDx inhibited the growth of a panel of human tumor xenografts and showed no obvious systemic toxicity. At tolerated doses, DBDx suppressed the growth of human hepatocellular carcinoma BEL-7402, HepG2, and lung adenocarcinoma A549 xenografts by 94.5%, 93.7% and 96.9%, respectively. Clonogenic assay demonstrated that DBDx showed weak cytotoxicity. Western blot showed that Flk1 and Nos3 were down-regulated in the DBDx-treated group. Proteomic analysis showed that DBDx mainly affected the metabolic process and immune system process; in addition, the angiogenesis and VEGF signaling pathway were also affected. Conclusively, DBDx, a multifunctional drug combination of three low-cytotoxic drugs, shows synergistic and highly potent antitumor efficacy evidently mediated by the modulation of tumor microenvironment. Based on its low-cytotoxic attributes and its broad-spectrum antitumor therapeutic efficacy, this multifunctional combination might be useful in the treatment of cancers, especially those refractory to conventional chemotherapeutics.

Identical expression profiling of human and murine TIPE3 protein reveals links to its functions

Tumor necrosis factor-alpha-induced protein-8 like-3 (TNFAIP8L3, TIPE3) is a newly discovered member of TNFAIP8 family and regarded as a lipid second messenger transfer protein that promotes cancer. Yet the nature of the cells and tissues that express TIPE3 protein has not been determined. In this study, we examined TIPE3 expression in various murine and human tissues by immunohistochemistry and quantitative PCR. We found that TIPE3 expression was almost identical in most organs from human and mice. TIPE3 is a cytoplasmic protein expressed preferentially in epithelial-derived cells with secretory functions. Furthermore, TIPE3 protein is highly expressed in most human carcinoma cell lines. These results suggest that TIPE3 may play important roles in carcinogenesis and cell secretion.

Effect of Melilotus extract on lung injury via the upregulation of tumor necrosis factor-α-induced protein-8-like 2 in septic mice

As a Traditional Chinese Medicine, Melilotus extracts have been reported to function as an anti-inflammatory agent, antioxidant and inhibitor of capillary permeability. The present study aimed to identify the mechanisms by which Melilotus interferes with inflammation-associated and oxidative stress pathways during sepsis. An animal model of cecal ligation-perforation (CLP)-induced sepsis was established. Two hours prior to surgery, animals in the treatment group were administered 25 mg/kg Melilotus extract tablets and subsequently every 8 h. At 24 h post-administration, pathological modifications in lung tissue and expression levels of tumor necrosis factor-α-induced protein-8-like 2 (TIPE2) expression, nuclear factor (NF)-κB, toll-like receptor 4 (TLR4), heme oxygenase-1 (HO-1), inhibitor of κB kinase (IκB), pro-inflammatory mediators (interleukin-6 and tumor necrosis factor-α), myeloperoxidase (MPO), malondialdehyde (MDA) and superoxide dismutase (SOD), were examined. The results showed that Melilotus extract had a marked effect on the pathological manifestation of lung tissue and lung inflammatory response, the upregulation of TIPE2, HO-1 and IκB expression, and the inhibition of TLR4 and NF-κB activities. In addition, following treatment with Melilotus extract, the model animals demonstrated decreased levels of MPO and MDA as well as increased levels of SOD. In conclusion, these results indicated that Melilotus extract may be a potential therapeutic agent for the treatment of CLP-induced lung injury, the mechanism of which proceeded via inflammation- and oxidation-associated pathways by increasing TIPE2 expression.

Survivin-targeting Artificial MicroRNAs Mediated by Adenovirus Suppress Tumor Activity in Cancer Cells and Xenograft Models

Survivin is highly expressed in most human tumors and fetal tissue, and absent in terminally differentiated cells. It promotes tumor cell proliferation by negatively regulating cell apoptosis and facilitating cell division. Survivin's selective expression pattern suggests that it might be a suitable target for cancer therapy, which would promote death of transformed but not normal cells. This was tested using artificial microRNAs (amiRNAs) targeting survivin. After screening, two effective amiRNAs, which knocked down survivin expression, were identified and cloned into a replication-defective adenoviral vector. Tumor cells infected with the recombinant vector downregulated expression of survivin and underwent apoptotic cell death. Further studies showed that apoptosis was associated with increases in caspase 3 and cleaved Poly (ADP-ribose) polymerase, and activation of the p53 signaling pathway. Furthermore, amiRNA treatment caused blockade of mitosis and cell cycle arrest at the G2/M phase. In vivo, survivin-targeting amiRNAs expressed by adenoviral vectors effectively delayed growth of hepatocellular and cervical carcinomas in mouse xenograft models. These results indicate that silencing of survivin by amiRNA has potential for treatment of cancer.

TIPE2 inhibits TNF-α-induced hepatocellular carcinoma cell metastasis via Erk1/2 downregulation and NF-κB activation

Tumor necrosis factor-α-induced protein 8-like 2 (TNFAIP8L2, TIPE2), which belongs to the TNF-α-induced protein 8 family, is a negative regulator of immune homeostasis. Although pro-inflammatory cytokines such as TNF-α have been reported to be involved in liver carcinoma metastasis, the effect of TIPE2 on hepatocellular carcinoma metastasis remains unknown. We demonstrate that TNF-α clearly augments MMP-13/MMP-3 expression and promotes cell migration in HepG2 cells through activation of the Erk1/2-NF-κB pathways. Interestingly, in addition to human PBLs, macrophages and fibroblasts, liver cancer cells specifically express TNF-α following LPS treatment. Most importantly, TIPE2 overexpression efficiently abrogates the effects of LPS on TNF-α secretion and abolishes the effects of TNF-α on MMP-13/MMP-3 upregulation, cell migration and Erk1/2-NF-κB activation. Taken together, these findings demonstrate that TIPE2 was able to suppress TNF-α-induced hepatocellular carcinoma metastasis by inhibiting Erk1/2 and NF-κB activation, indicating that both TNF-α and TIPE2 might be potential targets for the treatment of HCC metastasis.

A new TIPE of phosphoinositide regulator in cancer

Specific phosphoinositide lipids promote cell growth and cancer. In this issue of Cancer Cell, Fayngerts and colleagues demonstrate that the TIPE3 protein enhances PtdIns(4,5)P2 and PtdIns(3,4,5)P3, is overexpressed in certain cancers, and promotes tumorigenesis. TIPE3 can act as a lipid transfer protein and may constitute a novel phosphoinositide metabolism regulator.

TIPE3 is the transfer protein of lipid second messengers that promote cancer

More than half of human cancers have aberrantly upregulated phosphoinositide signals; yet how phospholipid signals are controlled during tumorigenesis is not fully understood. We report here that TIPE3 (TNFAIP8L3) is the transfer protein of phosphoinositide second messengers that promote cancer. High-resolution crystal structure of TIPE3 shows a large hydrophobic cavity that is occupied by a phospholipid-like molecule. TIPE3 preferentially captures and shuttles two lipid second messengers, i.e., phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate, and increases their levels in the plasma membrane. Notably, human cancers have markedly upregulated TIPE3 expression. Knocking out TIPE3 diminishes tumorigenesis, whereas enforced TIPE3 expression enhances it in vivo. Thus, the function and metabolism of phosphoinositide second messengers are controlled by a specific transfer protein during tumorigenesis.

Hepatic transcriptome profiles differ among maturing beef heifers supplemented with inorganic, organic, or mixed (50% inorganic:50% organic) forms of dietary selenium

Selenium (Se) is an important trace mineral that, due to deficiencies in the soil in many parts of the USA, must be supplemented directly to the diet of foraging cattle. Both organic and inorganic forms of dietary Se supplements are available and commonly used, and it is known that Se form affects tissue assimilation, bioavailability, and physiological responses. However, little is known about the effects of form of dietary Se supplements on gene expression profiles, which ostensibly account for Se form-dependent physiological processes. To determine if hepatic transcriptomes of growing beef (Angus-cross) heifers (0.5 kg gain/day) was altered by form of dietary supplemental Se, none (Control), or 3 mg Se/day as inorganic Se (ISe, sodium selenite), organic (OSe, Sel-Plex®), or a blend of ISe and OSe (1.5 mg:1.5 mg, Mix) Se was fed for 168 days, and the RNA expression profiles from biopsied liver tissues was compared by microarray analysis. The relative abundance of 139 RNA transcripts was affected by Se treatment, with 86 of these with complete gene annotations. Statistical and bioinformatic analysis of the annotated RNA transcripts revealed clear differences among the four Se treatment groups in their hepatic expression profiles, including (1) solely and commonly affected transcripts; (2) Control and OSe profiles being more similar than Mix and ISe treatments; (3) distinct OSe-, Mix-, and ISe-Se treatment-induced "phenotypes" that possessed both common and unique predicted physiological capacities; and (4) expression of three microRNAs were uniquely sensitive to OSe, ISe, or Mix treatments, including increased capacity for redox potential induced by OSe and Mix Se treatments resulting from decreased expression of MiR2300b messenger RNA. These findings indicate that the form of supplemental dietary Se consumed by cattle will affect the composition of liver transcriptomes resulting, presumably, in different physiological capacities.

TIPE1 induces apoptosis by negatively regulating Rac1 activation in hepatocellular carcinoma cells

TIPE1 (tumor necrosis factor-α-induced protein 8-like 1 or TNFAIP8L1) is a newly identified member of the TIPE (TNFAIP8) family, which play roles in regulating cell death. However, the biologic functions of TIPE1 in physiologic and pathologic conditions are largely unknown. Here, we report the roles of TIPE1 in hepatocellular carcinoma (HCC). Evaluated by immunohistochemical staining, HCC tissues showed significantly downregulated TIPE1 expression compared with adjacent non-tumor tissues, which positively correlated with tumor pathologic grades and patient survival. Using a homograft tumor model in Balb/c mice, we discovered that TIPE1 significantly diminished the growth and tumor weight of murine liver cancer homografts. Consistently, TIPE1 inhibited both cell growth and colony formation ability of cultured HCC cell lines, which was further identified to be due to TIPE1-inducing apoptosis in a caspase-independent, necrostatin-1 (Nec-1)-insensitive manner. Furthermore, mechanistic investigations revealed that TIPE1 interacted with Rac1, and inhibited the activation of Rac1 and its downstream p65 and c-Jun N-terminal kinase pathway. Moreover, overexpression of constitutively active Rac1 partially rescued the apoptosis induced by TIPE1, and Rac1 knockdown significantly restored the deregulated cell growth induced by TIPE1 small interfering RNA. Our findings revealed that TIPE1 induced apoptosis in HCC cells by negatively regulating Rac1 pathway, and loss of TIPE1 might be a new prognostic indicator for HCC patients.

Critical roles of TIPE2 protein in murine experimental colitis

Both commensal bacteria and infiltrating inflammatory cells play essential roles in the pathogenesis of inflammatory bowel disease. The molecular mechanisms whereby these pathogenic factors are regulated during the disease are not fully understood. We report in this article that a member of the TNF-α-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) plays a crucial role in regulating commensal bacteria dissemination and inflammatory cell function in experimental colitis induced by dextran sodium sulfate (DSS). Following DSS treatment, TIPE2-deficient mice, or chimeric mice that are deficient in TIPE2 only in their hematopoietic cells, lost less body weight and survived longer than wild-type controls. Consistent with this clinical observation, TIPE2-deficient mice exhibited significantly less severe colitis and colonic damage. This was associated with a marked reduction in the colonic expression of inflammatory cytokines, such as TNF-α, IL-6, and IL-12. Importantly, the ameliorated DSS-induced colitis in TIPE2(-/-) mice also was associated with reduced local dissemination of commensal bacteria and a weaker systemic inflammatory response. Combined with our previous report that TIPE2 is a negative regulator of antibacterial immunity, these results indicate that TIPE2 promotes colitis by inhibiting mucosal immunity to commensal bacteria.

TIPE2 negatively regulates inflammation by switching arginine metabolism from nitric oxide synthase to arginase

TIPE2, the tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TNFAIP8L2), plays an essential role in maintaining immune homeostasis. It is highly expressed in macrophages and negatively regulates inflammation through inhibiting Toll-like receptor signaling. In this paper, we utilized RAW264.7 cells stably transfected with a TIPE2 expression plasmid, as well as TIPE2-deficient macrophages to study the roles of TIPE2 in LPS-induced nitric oxide (NO) and urea production. The results showed that TIPE2-deficiency significantly upregulated the levels of iNOS expression and NO production in LPS-stimulated macrophages, but decreased mRNA levels of arginase I and urea production. However, TIPE2 overexpression in macrophages was capable of downregulating protein levels of LPS-induced iNOS and NO, but generated greater levels of arginase I and urea production. Furthermore, TIPE2^−/− mice had higher iNOS protein levels in lung and liver and higher plasma NO concentrations, but lower levels of liver arginase I compared to LPS-treated WT controls. Interestingly, significant increases in IκB degradation and phosphorylation of JNK, p38, and IκB were observed in TIPE2-deficient macrophages following LPS challenge. These results strongly suggest that TIPE2 plays an important role in shifting L-arginase metabolism from production of NO to urea, during host inflammatory response.

MicroRNA-21 regulates T-cell apoptosis by directly targeting the tumor suppressor gene Tipe2

MicroRNAs (MiRs) are short noncoding RNAs that can regulate gene expression. It has been reported that miR-21 suppresses apoptosis in activated T cells, but the molecular mechanism remains undefined. Tumor suppressor Tipe2 (or tumor necrosis factor-α-induced protein 8 (TNFAIP8)-like 2 (TNFAIP8L2)) is a newly identified anti-inflammatory protein of the TNFAIP8 family that is essential for maintaining immune homeostasis. We report here that miR-21 is a direct target of nuclear factor-κB and could regulate Tipe2 expression in a Tipe2 coding region-dependent manner. In activated T cells and macrophages, Tipe2 expression was markedly downregulated, whereas miR-21 expression was upregulated. Importantly, Tipe2-deficient T cells were significantly less sensitive to apoptosis. Conversely, overexpression of Tipe2 in EL-4 T cells increased their susceptibility to activation-induced apoptosis. Therefore, Tipe2 provides a molecular bridge between miR-21 and cell apoptosis; miR-21 suppresses apoptosis in activated T cells at least in part through directly targeting tumor suppressor gene Tipe2.

Kras as a key oncogene and therapeutic target in pancreatic cancer

Pancreatic cancer is one of the deadliest human malignancies and little progress has been achieved in its treatment over the past decades. Advances in our understanding of the biology of this disease provide new potential opportunities for treatment. Pancreatic cancer is preceded by precursor lesions, the most common of which are known as Pancreatic Intraepithelial Neoplasia (PanIN). PanIN lesions, which are the focus of this review, have a high incidence of Kras mutations, and Kras mutations are a hallmark of the late-stage disease. We now know from genetically engineered mouse models that oncogenic Kras is not only driving the formation of pancreatic cancer precursor lesions, but it is also required for their progression, and for the maintenance of invasive and metastatic disease. Thus, an enormous effort is being placed in generating Kras inhibitors for clinical use. Additionally, alternative approaches, including understanding the role of Kras effector pathways at different stages of the disease progression, are being devised to target Kras effector pathways therapeutically. In particular, efforts have focused on the MAPK pathway and the PI3K pathway, for which inhibitors are widely available. Finally, recent studies have highlighted the need for oncogenic Kras to establish feedback mechanisms that maintain its levels of activity; the latter might constitute alternative ways to target Kras in pancreatic cancer. Here, we will review recent basic research and discuss potential therapeutic applications.

Elevated expression of tumour necrosis factor-α-induced protein 8 (TNFAIP8)-like 2 mRNA in peripheral blood mononuclear cells is associated with disease progression of acute-on-chronic hepatitis B liver failure

Aberrant immunity response contributes to the pathogenesis of acute-on-chronic hepatitis B liver failure. Tumour necrosis factor-α-induced protein-8 like-2 (TIPE2) is a recently identified molecular to maintain immune homoeostasis, but its role in acute-on-chronic hepatitis B liver failure (ACHBLF) is unknown. We detected TIPE2 mRNA levels in peripheral blood mononuclear cells (PBMCs) from 56 patients with ACHBLF, 60 chronic hepatitis B patients, 24 healthy controls and analysed its role in disease severity and prognosis. TIPE2 mRNA expression in patients with ACHBLF was higher than that of patients with chronic infection or healthy controls. In patients with ACHBLF, TIPE2 mRNA level was positively correlated with serum total bilirubin, international normalized ratio and model for end-stage liver disease scores. Furthermore, the level of TIPE2 mRNA was significantly higher in nonsurvivors than survivors in patients with ACHBLF. The mRNA level of TIPE2 gradually decreased week by week in survivors accompanied by recovery from patients with ACHBLF, while its expression sustained at high levels in nonsurvivors. TIPE2 mRNA level after lipopolysaccharide (LPS) stimulation ex vivo in patients with ACHBLF was higher compared with controls and patients with chronic infection. Meanwhile, cytokines ex vivo secreted were measured as a marker of immune activation. After LPS stimulation, interleukin (IL)-6 and tumour necrosis factor (TNF)-α mRNA expression were reduced in patients with ACHBLF, and a significantly negative correlation was found between TIPE2 and TNF-α mRNA levels. In conclusion, our results identified the potential role of TIPE2 in predicting disease progression and prognosis in patients with ACHBLF by negative regulating of cell-mediated immunity.