XB130, a novel adaptor protein, promotes thyroid tumor growth

High XB130 expression in renal cell carcinoma is strongly associated with poor prognosis

The aim of this study was to assess the prognostic value of XB130 expression in three major RCC subtypes, and its association with clinical outcomes and adverse clinicopathologic features. A total of 101 nephrectomy samples at Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Thailand, from 2007 to 2017 were included in the study. XB130 immunohistochemistry was performed on slides from a tissue microarray comprised of 71 clear cell RCCs, 23 papillary RCCs, and 7 chromophobe RCCs, and were scored using a Histoscore system on a 0-300 scale. High XB130 expression in clear cell RCC and papillary RCC patients was associated with poor prognosis (log-rank test, P = 0.013, and P = 0.001, respectively). WHO/ISUP grade (P = 0.001) and XB130 high expression (P = 0.019) were found to be independent risk factors for mortality in clear cell RCC using multivariate analysis. The high expression of XB130 in clear cell RCC patients was also associated with high WHO/ISUP grade (P = 0.011), distant metastasis (P = 0.036), TNM stage (P = 0.007), sarcomatoid/rhabdoid differentiation (P = 0.061), and urinary collecting system invasion (P = 0.002). Similarly, high XB130 expression (P = 0.038) was associated with poor prognosis among papillary RCC patients as well as with lymphovascular invasion (P = 0.022), TNM stage (P = 0.030), and sarcomatoid/rhabdoid differentiation (P = 0.044). Overall, our findings showed that high XB130 expression in clear cell RCC and papillary RCC patients are associated with a worse prognosis.

The 3'‑untranslated region of XB130 regulates its mRNA stability and translational efficiency in non‑small cell lung cancer cells

Silencing XB130 inhibits cell proliferation and epithelial-mesenchymal transition in non-small cell lung cancer (NSCLC), suggesting that downregulating XB130 expression may impede NSCLC progression. However, the molecular mechanism underlying the regulation of XB130 expression remains unclear. In the present study, the role of the 3'-untranslated region (3'-UTR) in the regulation of XB130 expression was investigated. Recombinant psiCHECK-2 vectors with wild-type, truncated, or mutant XB130 3'-UTR were constructed, and the effects of these insertions on reporter gene expression were examined using a dual-luciferase reporter assay and reverse transcription-quantitative PCR. Additionally, candidate proteins that regulated XB130 expression by binding to critical regions of the XB130 3'-UTR were screened for using an RNA pull-down assay, followed by mass spectrometry and western blotting. The results revealed that insertion of the entire XB130 3'-UTR (1,218 bp) enhanced reporter gene expression. Positive regulatory elements were primarily found in nucleotides 113-989 of the 3'-UTR, while negative regulatory elements were found in the 1-112 and 990-1,218 regions of the 3'-UTR. Deletion analyses identified nucleotides 113-230 and 503-660 of the 3'-UTR as two major fragments that likely promote XB130 expression by increasing mRNA stability and translation rate. Additionally, a U-rich element in the 970-1,053 region of the 3'-UTR was identified as a negative regulatory element that inhibited XB130 expression by suppressing translation. Furthermore, seven candidate proteins that potentially regulated XB130 expression by binding to the 113-230, 503-660, and 970-1,053 regions of the 3'-UTR were identified, shedding light on the regulatory mechanism of XB130 expression. Collectively, these results suggested that complex sequence integrations in the mRNA 3'-UTR variably affected XB130 expression in NSCLC cells.

Proteomics of immune cells from liver tumors reveals immunotherapy targets

Elucidating the mechanisms by which immune cells become dysfunctional in tumors is critical to developing next-generation immunotherapies. We profiled proteomes of cancer tissue as well as monocyte/macrophages, CD4⁺ and CD8⁺ T cells, and NK cells isolated from tumors, liver, and blood of 48 patients with hepatocellular carcinoma. We found that tumor macrophages induce the sphingosine-1-phospate-degrading enzyme SGPL1, which dampened their inflammatory phenotype and anti-tumor function in vivo. We further discovered that the signaling scaffold protein AFAP1L2, typically only found in activated NK cells, is also upregulated in chronically stimulated CD8⁺ T cells in tumors. Ablation of AFAP1L2 in CD8⁺ T cells increased their viability upon repeated stimulation and enhanced their anti-tumor activity synergistically with PD-L1 blockade in mouse models. Our data reveal new targets for immunotherapy and provide a resource on immune cell proteomes in liver cancer.

Pathogenesis of Multinodular Goiter in Elderly XB130-Deficient Mice: Alteration of Thyroperoxidase Affinity with Iodide and Hydrogen Peroxide

Background: Multinodular goiter (MNG) is the most common disorder of the thyroid gland. Aging and genetic mutations that impair thyroid hormone (TH) production have been implicated in the development of MNG. XB130 is an adaptor/scaffold protein predominantly expressed in the thyroid gland. XB130 deficiency leads to transient postnatal growth retardation in mice due to congenital hypothyroidism. We studied the formation of MNG and possible mechanisms in elderly mice. Methods: Thyroid glands of male and female Xb130-knockout (Xb130^-/-), heterozygous (Xb130^+/-), and wild-type (Xb130^+/+) mice at the ages of 12-20 months were harvested for visual examination, histopathological, and immunohistological analyses. Blood and thyroid samples were collected after feeding elderly mice with a low iodine diet for ¹²⁵I uptake and perchlorate discharge assay. The activity of thyroperoxidase (Tpo) was examined by spectrophotometric evaluation of iodide oxidation. Results: While moderate MNG was seen in Xb130^+/+ and Xb130^+/- mice, severe MNG, characterized by multiple nodules intermixed with dilated colloid-rich macrofollicles, was found only in Xb130^-/- mice at 18 months. Thyrocyte cytoskeletal structure and cell adhesion molecules were disorganized, and TH production was significantly reduced. Reduced iodide organification was seen in elderly Xb130^+/+ mice and further enhanced in Xb130^-/- mice. In Xb130^+/+ mice, Tpo shows high affinity with hydrogen peroxide (H₂O₂) throughout aging, but reduced affinity with iodide in an age-dependent manner. By contrast, in elderly Xb130^-/- mice, the affinity of Tpo for iodide remained high, but the affinity of Tpo for H₂O₂ was reduced. Conclusions: The pathophysiological features in the thyroid glands of aged Xb130^-/- mice closely resemble the features of MNG in humans. Moderate MNG in elderly mice was dramatically aggravated by XB130 deficiency. Reduced affinity of Tpo for H₂O₂ may contribute to MNG development via oxidative stress. This could be specific to XB130 deficiency but also could be a common mechanism in MNG. Its clinical relevance should be further investigated.

Thyroidal Transcriptomic Profiles of Pathoadaptive Responses to Congenital Hypothyroidism in XB130 Knockout Mice

Congenital hypothyroidism is a genetic condition in which the thyroid gland fails to produce sufficient thyroid hormone (TH), resulting in metabolic dysfunction and growth retardation. Xb130-/- mice exhibit perturbations of thyrocyte cytoskeleton and polarity, and develop postnatal transient growth retardation due to congenital hypothyroidism, leading ultimately to multinodular goiter. To determine the underlying mechanisms, we performed transcriptomic analyses on thyroid glands of mice at three age points: week 2 (W2, before visible growth retardation), W4 (at the nadir of growth); and W12 (immediately before full growth recovery). Using gene set enrichment analysis, we compared a defined set of thyroidal genes between Xb130+/+ and Xb130-/- mice to identify differentially enriched gene clusters. At the earliest postnatal stage (W2), the thyroid glands of Xb130-/- mice exhibited significantly downregulated gene clusters related to cellular metabolism, which continued to W4. Additionally, mutant thyroids at W4 and W12 showed upregulated gene clusters related to extracellular matrix, angiogenesis, and cell proliferation. At W12, despite nearly normal levels of serum TH and TSH and body size, a significantly large number of gene clusters related to inflammatory response were upregulated. Early postnatal TH deficiency may suppress cellular metabolism within the thyroid gland itself. Upregulation of genes related to extracellular matrix and angiogenesis may promote subsequent thyroid growth. Chronic inflammatory responses may contribute to the pathogenesis of multinodular goiter in later life. Some of the pathoadaptive responses of Xb130-/- mice may overlap with those from other mutations causing congenital hypothyroidism.

XB130 Plays an Essential Role in Folliculogenesis Through Mediating Interactions Between Microfilament and Microtubule Systems in Thyrocytes

Background: XB130 (actin filament-associated protein 1-like 2, AFAP1L2) is a thyroid-abundant adaptor/scaffold protein. Xb130^-/- mice exhibit transient growth retardation postnatally due to congenital hypothyroidism with diminished thyroglobulin iodination and release at both embryonic and early postnatal stages due to disorganized thyroid apical membrane structure and function. We hypothesized that XB130 is crucial for polarity and folliculogenesis by mediating proper cytoskeletal structure and function in thyrocytes. Methods: Primary thyrocytes isolated from thyroid glands of Xb130^-/- mice and their wild-type littermates at postnatal week 2 were cultured in 10% Matrigel for different time periods. Folliculogenesis was studied with immunofluorescence staining, followed by confocal microscopy. Cells were also transfected to express human XB130 fused Green Fluorescent Protein (XB130-GFP) or Green Fluorescent Protein (GFP) only before morphological analysis. Cytoskeletal structures from embryo and postnatal thyroid glands were also studied. Results: In three-dimensional cultures of thyrocytes, XB130, aligned with actin filaments, participated in defining the site of apical membrane formation and coalescence to form a thyroid follicle lumen. Xb130^-/- thyrocytes displayed delayed folliculogenesis, reduced recruitment of a microtubule (MT)-associated proteins, and disorganized acetylated tubulin under the apical membrane, resulting in delayed folliculogenesis with reduced efficiency in formation of the thyroid follicle lumen. Conclusions: XB130 critically regulates thyrocyte polarization by functioning as a link between the actin filament cortex and MT network at the apical membrane of thyrocytes. Defects of adaptor scaffold proteins may affect cellular polarity and cytoskeletal structure and function and result in disorders of epithelial function, such as congenital hypothyroidism.

Members of the miR-30 family inhibit the epithelial-to-mesenchymal transition of non-small-cell lung cancer cells by suppressing XB130 expression levels

MicroRNAs (miRs) are associated with cancer metastasis. Aberrant expression levels of members of the miR-30 family have been observed in non-small-cell lung cancer (NSCLC). However, the effects of miR-30 family members on the epithelial-to-mesenchymal transition (EMT) of NSCLC cells and the underlying molecular mechanisms have not yet been fully elucidated. The present study investigated the effects of miR-30 family members on EMT, migration and invasion of NSCLC cells and found that overexpression of these miRs inhibited EMT via decreasing the expression levels of N-cadherin, β-catenin and SNAI1, along with weakened migration and invasion abilities. Then, XB130 was identified as a downstream target of the miR-30 family members. XB130-knockdown also inhibited EMT of NSCLC cells, whereas ectopic overexpression of XB130 partly rescued the suppressive effects of miR-30c and miR-30d on EMT. In conclusion, miR-30 family members inhibited EMT of NSCLC cells, partially via suppressing XB130 expression levels.

XB130, regulated by miR-203, miR-219, and miR-4782-3p, mediates the proliferation and metastasis of non-small-cell lung cancer cells

XB130 is a novel adapter protein that behaves as a tumor promoter or suppressor mediating cell proliferation and metastasis in the development of different human tumors. Altered expression of XB130 has been verified in human non-small cell-lung cancer (NSCLC). However, the exact effect of XB130 on NSCLC is not well-understood. In this study, we investigated the biological function and posttranscriptional regulation of XB130 in NSCLC. First, the effects of XB130 silence on NSCLC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) were examined. Then the targeting relationship between XB130 and miR-203, miR-219, or miR-4782-3p was demonstrated by dual-luciferase reporter assay. Finally, the effects of miR-203, miR-219, and miR-4782-3p on NSCLC cell function were studied, respectively. We found that XB130 silence significantly inhibited cell growth, migration and invasion, and reversed EMT. Furthermore, XB130 was posttranscriptionally regulated by miR-203, miR-219, and miR-4782-3p. Overexpression of miR-203, miR-219, or miR-4782-3p inhibited cell growth, migration and invasion, and reversed EMT, just like the role of XB130 in NSCLC cells, whereas the suppressive effects of microRNA (miRNA) overexpression were weakened by miRNA inhibitors or ectopic expression of XB130 in NSCLC cells. These data demonstrate that XB130 is posttranscriptionally regulated by miR-203, miR-219, and miR-4782-3p and mediates the proliferation and metastasis of NSCLC cells.

XB130 deficiency enhances carcinogen-induced skin tumorigenesis

XB130 is an adaptor protein that functions as a mediator of multiple tyrosine kinases important for regulating cell proliferation, survival, migration and invasion. Formerly predicted as an oncogene, alterations of its expression are documented in various human cancers. However, the exact role of XB130 in tumorigenesis is unknown. To address its function in skin tumorigenesis, a two-stage dimethylbenzanthracene (DMBA)/12-O-tetradecanoylphorbol 13-acetate (TPA) study was performed on XB130 knockout (KO), heterozygous (HZ) and wild-type (WT) littermate mice. DMBA/TPA-treated XB130 KO and HZ males developed a significantly higher number of epidermal tumors that were notably larger in size than did WT mice. Interestingly, DMBA/TPA-treated female mice did not show any difference in tumor multiplicity regardless of the genotypes. The skin tumor lesions of XB130 KO males were more progressed with an increased frequency of keratoacanthoma. Deficiency of XB130 dramatically increased epidermal tumor cell proliferation. The responses to DMBA and TPA stimuli were also individually investigated to elucidate the mechanistic role of XB130 at different stages of tumorigenesis. DMBA-treated male XB130 KO mice showed compensatory p53-mediated stress response. TPA-treated XB130 KO males demonstrated more skin ulceration with more severe edema, enhanced cell proliferation, accumulation of infiltrating neutrophils and increased production of pro-inflammatory cytokine genes compared with WT mice. Enhanced activities of nuclear factor-kappa B pathway, increased protein expression of metalloproteinase-9 and ERK1/2 phosphorylation were found in these KO mice. These findings demonstrate that XB130 acts as a tumor suppressor in carcinogen-induced skin tumorigenesis that may be mediated through inhibiting inflammation.

Knockdown of XB130 restrains cancer stem cell-like phenotype through inhibition of Wnt/β-Catenin signaling in breast cancer

The cancer stem cells (CSCs) is a subset of cancer cells that possess stem cell properties, which plays a crucial role in the occurrence, metastasis, and recurrence of the tumor. XB130 is a novel adapter protein potentially serves as a functional factor in CSCs. To determine the role of CSCs in breast cancer, we focused on the study of XB130. In our study, we found that XB130 expression was significantly upregulated in breast cancer and was closely related to the clinicopathologic characteristics, overall survival and poor prognosis of breast cancer patients. Functionally, we found that knockdown of XB130 was not only played an important role in proliferation, epithelial-mesenchymal transition (EMT), and metastasis in breast cancer cells but also exhibited potent antitumor activity in animal tumor models. Moreover, we demonstrated that silencing endogenous XB130 regulated the cancer stem cell-like properties of breast cancer, including the formation of self-renewing spheres and the proportion of breast cancer SP⁺ cells. Mechanistically, our studies indicated that downregulation of XB130 restrained the EMT and Wnt/β-catenin signaling, so as to weaken the tumor-initiating cell-like phenotype of breast cancer cells. This study indicates that XB130 plays an important role in maintaining the EMT and stem cell-like characteristics of breast cancer cells, supporting the significance of XB130 as a new potential therapeutic target for early diagnosis and prognosis of breast cancer.

Systems Biology Approaches to Investigate Genetic and Epigenetic Molecular Progression Mechanisms for Identifying Gene Expression Signatures in Papillary Thyroid Cancer

Thyroid cancer is the most common endocrine cancer. Particularly, papillary thyroid cancer (PTC) accounts for the highest proportion of thyroid cancer. Up to now, there are few researches discussing the pathogenesis and progression mechanisms of PTC from the viewpoint of systems biology approaches. In this study, first we constructed the candidate genetic and epigenetic network (GEN) consisting of candidate protein–protein interaction network (PPIN) and candidate gene regulatory network (GRN) by big database mining. Secondly, system identification and system order detection methods were applied to prune candidate GEN via next-generation sequencing (NGS) and DNA methylation profiles to obtain the real GEN. After that, we extracted core GENs from real GENs by the principal network projection (PNP) method. To investigate the pathogenic and progression mechanisms in each stage of PTC, core GEN was denoted in respect of KEGG pathways. Finally, by comparing two successive core signaling pathways of PTC, we not only shed light on the causes of PTC progression, but also identified essential biomarkers with specific gene expression signature. Moreover, based on the identified gene expression signature, we suggested potential candidate drugs to prevent the progression of PTC with querying Connectivity Map (CMap).

XB130 Knockdown Inhibits the Proliferation, Invasiveness, and Metastasis of Hepatocellular Carcinoma Cells and Sensitizes them to TRAIL-Induced Apoptosis

Background

XB130 is a recently discovered adaptor protein that is highly expressed in many malignant tumors, but few studies have investigated its role in hepatocellular carcinoma (HCC). Therefore, this study explored the relationship between this protein and liver cancer and investigated its molecular mechanism of action.

Methods

The expression of XB130 between HCC tissues and adjacent nontumor tissues was compared by real-time polymerase chain reaction, immunochemistry, and Western blotting. XB130 silencing was performed using small hairpin RNA. The effect of silencing XB130 was examined using Cell Counting Kit-8, colony assay, wound healing assay, and cell cycle analysis.

Results

We found that XB130 was highly expressed in HCC tissues (cancer tissues vs. adjacent tissues: 0.23 ± 0.02 vs. 0.17 ± 0.02, P < 0.05) and liver cancer cell lines, particularly MHCC97H and HepG2 (MHCC97H and HepG2 vs. normal liver cell line LO-2: 2.35 ± 0.26 and 2.04 ± 0.04 vs. 1.00 ± 0.04, respectively, all P < 0.05). The Cell Counting Kit-8 assay, colony formation assay, and xenograft model in nude mice showed that silencing XB130 inhibited cell proliferative ability both in vivo and in vitro, with flow cytometry demonstrating that the cells were arrested in the G0/G1 phase in HepG2 (HepG2 XB130-silenced group [shA] vs. HepG2 scramble group [NA]: 74.32 ± 5.86% vs. 60.21 ± 3.07%, P < 0.05) and that the number of G2/M phase cells was decreased (HepG2 shA vs. HepG2 NA: 8.06 ± 2.41% vs. 18.36 ± 4.42%, P < 0.05). Furthermore, the cell invasion and migration abilities were impaired, and the levels of the epithelial-mesenchymal transition-related indicators vimentin and N-cadherin were decreased, although the level of E-cadherin was increased after silencing XB130. Western blotting showed that the levels of phosphorylated phosphoinositide 3-kinase (PI3K) and phospho-protein kinase B (p-Akt) also increased, although the level of phosphorylated phosphatase and tensin homolog increased, indicating that XB130 activated the PI3K/Akt pathway. Furthermore, we found that a reduction in XB130 increased liver cancer cell sensitivity to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis.

Conclusions

Our findings suggest that XB130 might be used as a predictor of liver cancer as well as one of the targets for its treatment.

XB130 is overexpressed in prostate cancer and involved in cell growth and invasion

XB130 is a cytosolic adaptor protein involved in various physiological processes and oncogenesis of certain malignancies, but its role in the development of prostate cancer remains unclear. In current study, we examined XB130 expression in prostate cancer tissues and found that XB130 expression was remarkably increased in prostate cancer tissues and significantly correlated with increased prostate specific antigen (PSA), free PSA (f-PSA), prostatic acid phosphatase (PAP) and T classification. Patients with highly expressed XB130 had significantly decreased survival, which suggested XB130 as a possible prognostic indicator for prostate cancer. In vitro experiments showed that reduced XB130 expression restrained tumor growth both in vitro and in vivo. Furthermore, XB130 knockdown hindered transition of G1 to S phase in prostate cancer cell line DU145 and LNCap, which might contribute to the inhibition of cellular proliferation. Results from transwell assay demonstrated that downregulation of XB130 may attenuate invasion and metastasis of prostate cancer. Semiquantitative analysis of Western blot suggested that decreased XB130 expression was accompanied by diminished Akt signaling and EMT process. Thus, above observations suggest that XB130 may be a novel molecular marker and potent therapeutic target for prostate cancer.

Actin Filament-Associated Protein 1-Like 1 Mediates Proliferation and Survival in Non-Small Cell Lung Cancer Cells

BACKGROUND The actin filament-associated protein (AFAP) family consists of 3 novel adaptor proteins: AFAP1, AFAP1L1, and AFAP1L2/XB130. Although evidence shows that AFAP1 and AFAP1L2 play an oncogenic role, the effect of AFAP1L1 on tumor cell behavior has not been fully elucidated, and it remains unknown whether AFAP1L1 could be a prognostic marker and/or therapeutic target of lung cancer. MATERIAL AND METHODS Human A549 non-small cell lung cancer (NSCLC) cells were used in this study. AFAP1L1 gene was knocked down by AFAP1L1 short hairpin RNA (shRNA) transfection. Cell proliferation was analyzed using Celigo image cytometry and MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay, cell cycle progression was assessed with flow cytometry, and cell apoptosis was determined by flow cytometry after annexin-n staining. The PathScan intracellular signaling array was used to investigate cancer-related signaling proteins influenced by knocking down AFAP1L1 in A549. RESULTS AFAP1L1 gene expression was successfully inhibited by the AFAP1L1-shRNA transfection. Cell proliferation was inhibited and cell proportions in G1 and G2/M phases were increased, and cell apoptosis was increased in the AFAP1L1-shRNA transfected cells as compared with negative control shRNA transfected cells. Using the PathScan intracellular signaling array, we found that downregulation of AFAP1L1 significantly activated P38 and caspase 3, and inhibited PRAS40 activation. CONCLUSIONS Our data show that AFAP1L1 promotes cell proliferation, accelerates cell cycle progression, and prevents cell apoptosis in lung cancer cells. Therefore, AFAP1L1 might play an oncogenic role in NSCLC.

XB130 deficiency enhances lipopolysaccharide-induced septic response and acute lung injury

XB130 is a novel oncoprotein that promotes cancer cell survival, proliferation and migration. Its physiological function in vivo is largely unknown. The objective of this study was to determine the role of XB130 in lipopolysaccharide (LPS)-induced septic responses and acute lung injury. LPS was intraperitoneally administrated to Xb130 knockout (KO) and wild type (WT) mice. There was a significant weight loss in KO mice at Day 2 and significantly higher disease scores during the 7 days of observation. The levels of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, interleukin-6 and interleukin-10 in the serum were significantly higher in KO mice at Day 2. In KO mice there were a significantly higher lung injury score, higher wet/dry lung weight ratio, more apoptotic cells and less proliferative cells in the lung. Macrophage infiltration was significantly elevated in the lung of KO mice. There was significantly increased number of p-GSK-3β positive cells in KO mice, which were mainly neutrophils and macrophages. XB130 is expressed in alveolar type I and type II cells in the lung. The expression in these cells was significantly reduced after LPS challenge. XB130 deficiency delayed the recovery from systemic septic responses, and the presence of XB130 in the alveolar epithelial cells may provide protective mechanisms by reducing cell death and promoting cell proliferation, and reducing pulmonary permeability.

Blockade of potassium ion transports enhances hypotonicity-induced cytocidal effects in gastric cancer

Background

Peritoneal lavage with distilled water has been used for surgeries of various cancers to reduce peritoneal recurrence. This study examined whether blockade of potassium ion transports enhances hypotonicity-induced cytocidal effects in gastric cancer (GC).

Results

A potassium channel blocker inhibited the occurrence of regulatory volume decrease (RVD) induced by mild hypotonic stimulation, and significantly enhanced cytocidal effects on GC cells. Incubating MKN45 cells with hypotonic solutions containing a potassium channel blocker significantly reduced the formation of peritoneal metastases in nude mice.

Methods

The three human GC cell lines (HGC-27, Kato III, and MKN45) were exposed to mild hypotonic solutions, and the effects of blockade of potassium ion transports during hypotonic stimulation on cell volume changes and cell viabilities were examined. In the in vivo study, MKN45 cells stimulated with mild hypotonic solutions were intraperitoneally injected into nude mice, and the effects of blockade of potassium ion transports during hypotonic stimulation on the formation of peritoneal metastases were evaluated.

Conclusions

Blockade of potassium ion transports enhances hypotonicity-induced cytocidal effects on GC cells, which may contribute to development of a novel lavage method for further reduction of peritoneal recurrence in GC.

LoTo: a graphlet based method for the comparison of local topology between gene regulatory networks

One of the main challenges of the post-genomic era is the understanding of how gene expression is controlled. Changes in gene expression lay behind diverse biological phenomena such as development, disease and the adaptation to different environmental conditions. Despite the availability of well-established methods to identify these changes, tools to discern how gene regulation is orchestrated are still required. The regulation of gene expression is usually depicted as a Gene Regulatory Network (GRN) where changes in the network structure (i.e., network topology) represent adjustments of gene regulation. Like other networks, GRNs are composed of basic building blocks; small induced subgraphs called graphlets. Here we present LoTo, a novel method that using Graphlet Based Metrics (GBMs) identifies topological variations between different states of a GRN. Under our approach, different states of a GRN are analyzed to determine the types of graphlet formed by all triplets of nodes in the network. Subsequently, graphlets occurring in a state of the network are compared to those formed by the same three nodes in another version of the network. Once the comparisons are performed, LoTo applies metrics from binary classification problems calculated on the existence and absence of graphlets to assess the topological similarity between both network states. Experiments performed on randomized networks demonstrate that GBMs are more sensitive to topological variation than the same metrics calculated on single edges. Additional comparisons with other common metrics demonstrate that our GBMs are capable to identify nodes whose local topology changes between different states of the network. Notably, due to the explicit use of graphlets, LoTo captures topological variations that are disregarded by other approaches. LoTo is freely available as an online web server at http://dlab.cl/loto.

XB130 promotes bronchioalveolar stem cell and Club cell proliferation in airway epithelial repair and regeneration

Proliferation of bronchioalveolar stem cells (BASCs) is essential for epithelial repair. XB130 is a novel adaptor protein involved in the regulation of epithelial cell survival, proliferation and migration through the PI3K/Akt pathway. To determine the role of XB130 in airway epithelial injury repair and regeneration, a naphthalene-induced airway epithelial injury model was used with XB130 knockout (KO) mice and their wild type (WT) littermates. In XB130 KO mice, at days 7 and 14, small airway epithelium repair was significantly delayed with fewer number of Club cells (previously called Clara cells). CCSP (Club cell secreted protein) mRNA expression was also significantly lower in KO mice at day 7. At day 5, there were significantly fewer proliferative epithelial cells in the KO group, and the number of BASCs significantly increased in WT mice but not in KO mice. At day 7, phosphorylation of Akt, GSK-3β, and the p85α subunit of PI3K was observed in airway epithelial cells in WT mice, but to a much lesser extent in KO mice. Microarray data also suggest that PI3K/Akt-related signals were regulated differently in KO and WT mice. An inhibitory mechanism for cell proliferation and cell cycle progression was suggested in KO mice. XB130 is involved in bronchioalveolar stem cell and Club cell proliferation, likely through the PI3K/Akt/GSK-3β pathway.

XB130: A novel adaptor protein in cancer signal transduction

Adaptor proteins are functional proteins that contain two or more protein-binding modules to link signaling proteins together, which affect cell growth and shape and have no enzymatic activity. The actin filament-associated protein (AFAP) family is an important member of the adaptor proteins, including AFAP1, AFAP1L1 and AFAP1L2/XB130. AFAP1 and AFAP1L1 share certain common characteristics and function as an actin-binding protein and a cSrc-activating protein. XB130 exhibits certain unique features in structure and function. The mRNA of XB130 is expressed in human spleen, thyroid, kidney, brain, lung, pancreas, liver, colon and stomach, and the most prominent disease associated with XB130 is cancer. XB130 has a controversial effect on cancer. Studies have shown that XB130 can promote cancer progression and downregulation of XB130-reduced growth of tumors derived from certain cell lines. A higher mRNA level of XB130 was shown to be associated with a better survival in non-small cell lung cancer. Previous studies have shown that XB130 can regulate cell growth, migration and invasion and possibly has the effect through the cAMP-cSrc-phosphoinositide 3-kinase/Akt pathway. Except for cancer, XB130 is also associated with other pathological or physiological procedures, such as airway repair and regeneration.

Phosphatidylinositol 3-Kinase-Associated Protein (PI3KAP)/XB130 Crosslinks Actin Filaments through Its Actin Binding and Multimerization Properties In Vitro and Enhances Endocytosis in HEK293 Cells

Actin-crosslinking proteins control actin filament networks and bundles and contribute to various cellular functions including regulation of cell migration, cell morphology, and endocytosis. Phosphatidylinositol 3-kinase-associated protein (PI3KAP)/XB130 has been reported to be localized to actin filaments (F-actin) and required for cell migration in thyroid carcinoma cells. Here, we show a role for PI3KAP/XB130 as an actin-crosslinking protein. First, we found that the carboxyl terminal region of PI3KAP/XB130 containing amino acid residues 830-840 was required and sufficient for localization to F-actin in NIH3T3 cells, and this region is directly bound to F-actin in vitro. Moreover, actin-crosslinking assay revealed that recombinant PI3KAP/XB130 crosslinked F-actin. In general, actin-crosslinking proteins often multimerize to assemble multiple actin-binding sites. We then investigated whether PI3KAP/XB130 could form a multimer. Blue native-PAGE analysis showed that recombinant PI3KAP/XB130 was detected at 250-1200 kDa although the molecular mass was approximately 125 kDa, suggesting that PI3KAP/XB130 formed multimers. Furthermore, we found that the amino terminal 40 amino acids were required for this multimerization by co-immunoprecipitation assay in HEK293T cells. Deletion mutants of PI3KAP/XB130 lacking the actin-binding region or the multimerizing region did not crosslink actin filaments, indicating that actin binding and multimerization of PI3KAP/XB130 were necessary to crosslink F-actin. Finally, we examined roles of PI3KAP/XB130 on endocytosis, an actin-related biological process. Overexpression of PI3KAP/XB130 enhanced dextran uptake in HEK 293 cells. However, most of the cells transfected with the deletion mutant lacking the actin-binding region incorporated dextran to a similar extent as control cells. Taken together, these results demonstrate that PI3KAP/XB130 crosslinks F-actin through both its actin-binding region and multimerizing region and plays an important role in endocytosis.

AFAP-1L2 influences proliferation and apoptosis of pancreatic cancer cells via PI3K/Akt pathway

AIM: To investigate the expression of actin filament-associated protein 1-like 2 (AFAP-1L2) in different pancreatic cancer cell lines, the effect of AFAP-1L2 on cell proliferation, cell cycle and apoptosis, and the possible mechanism.

METHODS: Western blot and real-time quantitative PCR (qRT-PCR) were used to detect the AFAP-1L2 protein and mRNA expression in PANC-1, MiaPaCa-2, Colo-357, BXPC-3, SW1990 and CFPAC-1 cell lines (having different differentiation degrees). siAFAP-1L2 plasmid was constructed and transfected into MiaPaCa-2 cell to downregulate the expression of AFAP-1L2. Proteins of the phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt) pathway were detected by Western blot and qRT-PCR after siAFAP-1L2 transfection. Proliferation was detected by MTT assay. Cell cycle and apoptosis were detected by flow cytometry.

RESULTS: Western blot and qRT-PCR analyses showed that AFAP-1L2 was correlated with differentiation degree, and the expression was higher in cell lines with low differentiation than in those with moderate or high differentiation. PI3KCA protein expression in the siAFAP-1L2 group was lower than that in the MOCK and siRNA control groups (F = 20.16, P = 0.0022). α-Akt mRNA expression in the siAFAP-1L2 group was higher than that in the MOCK and siRNA control groups (F = 7.719, P = 0.0219); α-pAkt protein expression in the siAFAP-1L2 group was lower than that in MOCK and siRNA control groups (F = 5.507, P = 0.0439). PI3KCA mRNA expression in the siAFAP-1L2 group was lower than that in the AFAP-1L2 and siRNA control groups (F = 20.16, P = 0.0022). α-Akt mRNA expression in the siAFAP-1L2 group was higher than that in the MOCK and siRNA control groups (F = 6.068, P = 0.0362); α-pAkt mRNA expression in the siAFAP-1L2 group was lower than that in the MOCK and siRNA control groups (F = 10.33, P = 0.0114). MTT assay showed that the proliferation of MiaPaCa-2 cells at 48 h, 72 h, and 96 h was inhibited after siAFAP-1L2 transfection (F = 3.924, P < 0.05; F = 6.812, P < 0.01; F = 7.003, P < 0.01). Flow cytometry showed that cells in G₁ phase were increased, but those in G₂ and S phases were decreased (F = 4.87, 5.26, 4.94, P < 0.05 for all). The apoptosis rate of MiaPaCa-2 cell was increased after siAFAP-1L2 transfection (F = 7.231, P < 0.01).

CONCLUSION: AFAP-1L2 expression is associated with cell differentiation. AFAP-1L2 modulates cell proliferation, cell cycle and apoptosis via the PI3K/Akt pathway. AFAP-1L2 is a target candidate for pancreatic cancer therapy.

XB130/Tks5 scaffold protein interaction regulates Src-mediated cell proliferation and survival

XB130 and Tks5 interact endogenously and form a complex with Src tyrosine kinase. Tks5, like XB130, plays a role in cell proliferation and cell survival, and the interaction between XB130 and Tks5 is critical for regulation of Src-mediated cell proliferation and survival.

The scaffold protein XB130 regulates cell growth, survival, and migration. Yeast two-hybrid screening suggests that XB130 interacts with another scaffold protein, Tks5. We hypothesized that XB130 and Tks5 form a macromolecular complex to mediate signal transduction cascades for the regulation of cell growth and survival. Coimmunoprecipitation demonstrated that XB130 and Tks5 interact endogenously and form a complex with Src tyrosine kinase. Structure–function studies showed that the fifth SH3 domain of Tks5 binds to the N-terminus of XB130, which contains polyproline-rich motifs. Cell growth and survival studies revealed that down-regulation of XB130 and/or Tks5 reduced cell proliferation, resulting in cell cycle inhibition at the G1 phase and increased caspase 3 activity and apoptosis. Moreover, cell proliferation and survival were increased by overexpression of XB130 or Tks5 but decreased when XB130/Tks5 binding was disrupted by overexpression of XB130 N-terminal deleted mutant and/or Tks5 fifth SH3 domain W1108A mutant. Furthermore, down-regulation of XB130 and/or Tks5 inhibited serum- and growth factor–induced Src activation and downstream phosphorylation of PI3K and Akt. Our results suggest that Tks5, similar to XB130, plays a role in cell proliferation and cell survival and that the interaction between XB130 and Tks5 appears to be critical for regulation of Src-mediated cellular homeostasis.

Expression of XB130 in human ductal breast cancer

OBJECTIVES

XB130 is involved in gene regulation, cell proliferation, cell survival, cell migration, and tumorigenesis. In the present study, we first evaluated the expression of the XB130 and its prognostic significance in breast cancer. Then we evaluated whether XB130 could be a target for therapy in breast cancer.

MATERIALS AND METHODS

Immunohistochemistry was used to assess the level of XB130 protein in surgically resected, formalin-fixed, paraffin-embedded breast cancer specimens. Associations between XB130 and the postoperative prognosis of patients with breast cancer were evaluated. We evaluated the effect of XB130 inhibited by RNA interference on proliferation, invasion and apoptosis in vitro in a metastatic subclone of MCF-7 breast cancer cell line (LM-MCF-7). The effect of XB130 silencing alone or in combination with gemcitabine on LM-MCF-7 cells apoptosis was also investigated.

RESULTS

XB130 protein was present in the cytoplasm of malignant cells, and not in the normal breast tissues. There was correlation between the presence of XB130 in tumour cells and lymph node status, tumor classification and clinical stage. XB130 expression level was significantly associated with recurrence-free and overall survival. Furthermore, multivariate Cox regression analyses revealed that positive XB130 was an independent risk factor for overall survival and recurrence free survival. XB130 silencing alone inhibits tumor growth and induces apoptosis in the LM-MCF-7 cells. Depletion of the XB130 in combination with gemcitabine resulted in marked apoptotic and necrotic cell death in LM-MCF-7 cells.

CONCLUSIONS

XB130 could be useful as a prognostic marker of recurrence-free and overall survival in invasive breast cancer, as well as for the response to chemotherapy.

Evaluation of the efficacy of peritoneal lavage with distilled water in colorectal cancer surgery: in vitro and in vivo study

BACKGROUND

Peritoneal lavage with distilled water has been performed during colorectal cancer surgery. This study investigated the cytocidal effects of hypotonic shock in vitro and in vivo in colorectal cancer cells.

METHODS

Three human colorectal cancer cell lines, DLD1, HT29, and CACO2, were exposed to distilled water, and morphological changes were observed under a differential interference contrast microscope connected to a high-speed digital video camera. Cell volume changes were assessed using a high-resolution flow cytometer. Re-incubation experiments were performed to investigate the cytocidal effects of distilled water. In the in vivo experiment, cancer cells after hypotonic shock were injected intraperitoneally into mice and the degree of established peritoneal metastasis was subsequently evaluated. The effects of the blockade of Cl(-) channels on these cells during hypotonic shock were also analyzed.

RESULTS

Morphological observations revealed a rapid cell swelling followed by cell rupture. Measurements of cell volume changes showed that mild hypotonic shock induced regulatory volume decrease (RVD) while severe hypotonic shock broke cells into fragments. Re-incubation experiments demonstrated the cytocidal effects of hypotonicity. In vivo experiments revealed the absence of peritoneal dissemination in mice in the distilled water group, and its presence in all mice in the control group. The blockade of Cl(-) channels increased cell volume by inhibiting RVD and enhanced cytocidal effects during mild hypotonic shock.

CONCLUSIONS

These results clearly support the efficacy of peritoneal lavage with distilled water during colorectal cancer surgery and suggest that regulating of Cl(-) transport may enhance the cytocidal effects of hypotonic shock.

XB130 expression in human osteosarcoma: a clinical and experimental study

Identifying prognostic factors for osteosarcoma (OS) aids in the selection of patients who require more aggressive management. XB130 is a newly characterized adaptor protein that was reported to be a prognostic factor of certain tumor types. However, the association between XB130 expression and the prognosis of OS remains unknown. In the present study, we investigated the association between XB130 expression and clinicopathologic features and prognosis in patients suffering OS, and further investigated its potential role on OS cells in vitro and vivo. A retrospective immunohistochemical study of XB130 was performed on archival formalin-fixed paraffin-embedded specimens from 60 pairs of osteosarcoma and noncancerous bone tissues, and compared the expression of XB130 with clinicopathological parameters. We then investigate the effect of XB130 sliencing on invasion in vitro and lung metastasis in vivo of the human OS cell line. Immunohistochemical assays revealed that XB130 expression in OS tissues was significantly higher than that in corresponding noncancerous bone tissues (P=0.001). In addition, high XB130 expression more frequently occurred in OS tissues with advanced clinical stage (P=0.002) and positive distant metastasis (P=0.001). Moreover, OS patients with high XB130 expression had significantly shorter overall survival and disease-free survival (both P<0.001) when compared with patients with the low expression of XB130. The univariate analysis and multivariate analysis shown that high XB130 expression and distant metastasis were the independent poor prognostic factor.We showed that XB130 depletion by RNA interference inhibited invasion of XB130-rich U2OS cells in vitro and lung metastasis in vivo. This is the first study to reveal that XB130 overexpression may be related to the prediction of metastasis potency and poor prognosis for OS patients, suggesting that XB130 may serve as a prognostic marker for the optimization of clinical treatments. Furthermore, XB130 is the potential molecular target for OS therapy.

XB130 deficiency affects tracheal epithelial differentiation during airway repair

The repair and regeneration of airway epithelium is important for maintaining homeostasis of the respiratory system. XB130 is an adaptor protein involved in the regulation of cell proliferation, survival and migration. In the human trachea, XB130 is expressed on the apical site of ciliated epithelial cells. We hypothesize that XB130 may play a role in epithelial repair and regeneration after injury. Xb130 knockout (KO) mice were generated, and a mouse isogenic tracheal transplantation model was used. Adult Xb130 KO mice did not show any significant anatomical and physiological phenotypes in comparison with their wild type (WT) littermates. The tracheal epithelium in Xb130 KO mice, however, was significantly thicker than that in WT mice. Severe ischemic epithelial injury was observed immediately after the tracheal transplantation, which was followed by epithelial cell flattening, proliferation and differentiation. No significant differences were observed in terms of initial airway injury and apoptosis. However, at Day 10 after transplantation, the epithelial layer was significantly thicker in Xb130 KO mice, and associated with greater proliferative (Ki67+) and basal (CK5+) cells, as well as thickening of the connective tissue and fibroblast layer between the epithelium and tracheal cartilages. These results suggest that XB130 is involved in the regulation of airway epithelial differentiation, especially during airway repair after injury.

Efficacy of a hypotonic treatment for peritoneal dissemination from gastric cancer cells: an in vivo evaluation

The aim of the present study was to determine the efficacy of a hypotonic treatment for peritoneal dissemination from gastric cancer cells using an in vivo model. We firstly evaluated the toxicity of a peritoneal injection of distilled water (DW) (2 mL for 3 days) in mice. Macroscopic and microscopic examinations revealed that the peritoneal injection of DW did not severely damage the abdominal organs of these mice. MKN45 gastric cancer cells preincubated with NaCl buffer or DW for 20 minutes in vitro were then intraperitoneally injected into nude mice, and the development of dissemination nodules was analyzed. The total number, weight, and volume of the dissemination nodules were significantly decreased by the DW preincubation. We then determined whether the peritoneal injection of DW inhibited the establishment of peritoneal dissemination. After a peritoneal injection of MKN45 cells into nude mice, NaCl buffer or DW was injected into the abdominal cavity for 3 days. The total volume of dissemination nodules was significantly lower in DW-injected mice than in NaCl-injected mice. In conclusion, we demonstrated the safeness of a peritoneal injection of DW. Furthermore, the development of dissemination nodules from gastric cancer cells was prevented by a preincubation with or peritoneal injection of DW.

XB130-A Novel Adaptor Protein: Gene, Function, and Roles in Tumorigenesis

Several adaptor proteins have previously been shown to play an important role in the promotion of tumourigenesis. XB130 (AFAP1L2) is an adaptor protein involved in many cellular functions, such as cell survival, cell proliferation, migration, and gene and miRNA expression. XB130's functional domains and motifs enable its interaction with a multitude of proteins involved in several different signaling pathways. As a tyrosine kinase substrate, tyrosine phosphorylated XB130 associates with the p85 α regulatory subunit of phosphoinositol-3-kinase (PI3K) and subsequently affects Akt activity and its downstream signalling. Tumourigenesis studies show that downregulation of XB130 expression by RNAi inhibits tumor growth in mouse xenograft models. Furthermore, XB130 affects tumor oncogenicity by regulating the expression of specific tumour suppressing miRNAs. The expression level and pattern of XB130 has been studied in various human tumors, such as thyroid, esophageal, and gastric cancers, as well as, soft tissue tumors. Studies show the significant effects of XB130 in tumourigenesis and suggest its potential as a diagnostic biomarker and therapeutic target for cancer treatments.

Prognostic significance of XB130 expression in surgically resected pancreatic ductal adenocarcinoma

Background

XB130 is a newly discovered adaptor protein for intracellular signal transduction; it is involved in gene regulation, cell proliferation, cell survival, cell migration, and tumorigenesis. However, its expression and role in pancreatic ductal adenocarcinoma (PDAC) have not been investigated. The present study was designed to clarify the prognostic significance of XB130 expression in PDAC.

Methods

A total of 76 consecutive patients with surgically resected PDAC were retrospectively reviewed. XB130 expression was detected by immunohistochemical analysis on the paraffin-embedded tumour sections. Correlation between the expression of XB130 and clinicopathological parameters was analyzed.

Results

XB130 expression was significantly upregulated in PDAC(56.5%, 43/76) compared to normal pancreas (0%, 0/15; P < 0.05). Increased XB130 expression was correlated with lymph node metastasis (P = 0.017), distant metastasis (P = 0.0024), high tumour-node-metastasis (TNM) stage (P =0.001), and high tumour grade (P = 0.013). The survival of 43 patients with high XB130 expression was significantly worse than that of the 33 patients with low XB130 expression (P = 0.001). Univariate analysis showed that high XB130 expression (P = 0.0045), tumour size (P = 0.024), distant metastasis (P = 0.003), TNM stage (P = 0.002) and lymphatic metastasis (P = 0.016) were independent prognostic factors of postoperative survival. Multivariate analysis using the Cox proportional hazards model showed that high XB130 expression and distant metastasis (P = 0.0239) were significant independent risk factors.

Conclusions

XB130 was overexpressed in the PDAC. XB130 is a promising pathological marker for the prediction of outcome in patients with PDAC.

GOLPH3 predicts survival of colorectal cancer patients treated with 5-fluorouracil-based adjuvant chemotherapy

Background

Golgi phosphoprotein 3 (GOLPH3) has been validated as a potent oncogene involved in the progression of many types of solid tumors, and its overexpression is associated with poor clinical outcome in many cancers. However, it is still unknown the association of GOLPH3 expression with the prognosis of colorectal cancer (CRC) patients who received 5-fluorouracil (5-FU)-based adjuvant chemotherapy.

Methods

The expression of GOLPH3 was determined by qRT-PCR and immunohistochemistry in colorectal tissues from CRC patients treated with 5-FU based adjuvant chemotherapy after surgery. The association of GOLPH3 with clinicopathologic features and prognosis was analysed. The effects of GOLPH3 on 5-FU sensitivity were examined in CRC cell lines.

Results

GOLPH3 expression was elevated in CRC tissues compared with matched adjacent noncancerous tissues. Kaplan-Meier survival curves indicated that high GOLPH3 expression was significantly associated with prolonged disease-free survival (DFS, P = 0.002) and overall survival (OS, P = 0.011) in patients who received 5-FU-based adjuvant chemotherapy. Moreover, multivariate analysis showed that GOLPH3 expression was an independent prognostic factor for DFS in CRC patients treated with 5-FU-based chemotherapy (HR, 0.468; 95%CI, 0.222-0.987; P = 0.046). In vitro, overexpression of GOLPH3 facilitated the 5-FU chemosensitivity in CRC cells; while siRNA-mediated knockdown of GOLPH3 reduced the sensitivity of CRC cells to 5-FU-induced apoptosis.

Conclusions

Our results suggest that GOLPH3 is associated with prognosis in CRC patients treated with postoperative 5-FU-based adjuvant chemotherapy, and may serve as a potential indicator to predict 5-FU chemosensitivity.

XB130 promotes proliferation and invasion of gastric cancer cells

Background

XB130 has been reported to be expressed by various types of cells such as thyroid cancer and esophageal cancer cells, and it promotes the proliferation and invasion of thyroid cancer cells. Our previous study demonstrated that XB130 is also expressed in gastric cancer (GC), and that its expression is associated with the prognosis, but the role of XB130 in GC has not been well characterized.

Methods

In this study, we investigated the influence of XB130 on gastric tumorigenesis and metastasis in vivo and in vitro using the MTT assay, clonogenic assay, BrdU incorporation assay, 3D culture, immunohistochemistry and immunofluorescence. Western blot analysis was also performed to identify the potential mechanisms involved.

Results

The proliferation, migration, and invasion of SGC7901 and MNK45 gastric adenocarcinoma cell lines were all significantly inhibited by knockdown of XB130 using small hairpin RNA. In a xenograft model, tumor growth was markedly inhibited after shXB130-transfected GC cells were implanted into nude mice. After XB130 knockdown, GC cells showed a more epithelial-like phenotype, suggesting an inhibition of the epithelial-mesenchymal transition (EMT) process. In addition, silencing of XB130 reduced the expression of p-Akt/Akt, upregulated expression of epithelial markers including E-cadherin, α-catenin and β-catenin, and downregulated mesenchymal markers including fibronectin and vimentin. Expression of oncoproteins related to tumor metastasis, such as MMP2, MMP9, and CD44, was also significantly reduced.

Conclusions

These findings indicate that XB130 enhances cell motility and invasiveness by modulating the EMT-like process, while silencing XB130 in GC suppresses tumorigenesis and metastasis, suggesting that it may be a potential therapeutic target.

XB130, a new adaptor protein, regulates expression of tumor suppressive microRNAs in cancer cells

XB130, a novel adaptor protein, promotes cell growth by controlling expression of many related genes. MicroRNAs (miRNAs), which are frequently mis-expressed in cancer cells, regulate expression of targeted genes. In this present study, we aimed to explore the oncogenic mechanism of XB130 through miRNAs regulation. We analyzed miRNA expression in XB130 short hairpin RNA (shRNA) stably transfected WRO thyroid cancer cells by a miRNA array assay, and 16 miRNAs were up-regulated and 22 miRNAs were down-regulated significantly in these cells, in comparison with non-transfected or negative control shRNA transfected cells. We chose three of the up-regulated miRNAs (miR-33a, miR-149 and miR-193a-3p) and validated them by real-time qRT-PCR. Ectopic overexpression of XB130 suppressed these 3 miRNAs in MRO cells, a cell line with very low expression of XB130. Furthermore, we transfected miR mimics of these 3 miRNAs into WRO cells. They negatively regulated expression of oncogenes (miR-33a: MYC, miR-149: FOSL1, miR-193a-3p: SLC7A5), by targeting their 3′ untranslated region, and reduced cell growth. Our results suggest that XB130 could promote growth of cancer cells by regulating expression of tumor suppressive miRNAs and their targeted genes.

MEK/ERK pathway mediates PKC activation-induced recruitment of PKCζ and MMP-9 to podosomes

Podosomes are adhesive structures on the ventral surface of cells that invade and degrade the extracellular matrix. Recently, we reported that phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) activator, induced podosome formation in normal human bronchial epithelial (NHBE) cells, and atypical PKCζ regulated MMP-9 recruitment to podosomes for its release and activation. The objective of this study was to explore signaling pathways that are involved in PKC activation-induced podosome formation and matrix degradation. Herein, we found that PDBu increased phosphorylation of PI3K p85, Akt, Src, ERK1/2, and JNK. Inhibitors for PI3K, Akt, and Src suppressed PDBu-induced podosome formation and matrix degradation. In contrast, blockers for MEK/ERK or JNK did not inhibit podosome formation but reduced proteolytic activity of podosomes. Inhibition of PKCζ activity with its pseudosubstrate peptide (PS)-inhibited PDBu-induced phosphorylation of MEK/ERK and JNK. On the other hand, inhibition of MEK/ERK or JNK pathway did not affect PKCζ phosphorylation, but reduced the recruitment of PKCζ and MMP-9 to podosomes. We conclude that PKCζ may regulate MEK/ERK and JNK phosphorylation and in turn activated MEK/ERK and JNK may regulate the proteolytic activity of PDBu-induced podosomes by influencing the recruitment of PKCζ and MMP-9 to podosomes.

Silencing of XB130 is associated with both the prognosis and chemosensitivity of gastric cancer

XB130 is a newly characterized adaptor protein that was reported to promote thyroid tumor growth, but its role in the progression of other kinds of cancer such as gastric cancer (GC) remains unknown. Accordingly, we investigated the association between XB130 expression and the prognosis of GC patients. The subjects were 411 patients with GC in stages I to IV. XB130 expression was examined in surgical specimens of GC. Kaplan-Meier analysis and the Cox proportional hazards model were used to assess the prognostic significance of XB130 for survival and recurrence. Moreover, GC cells stably transfected with XB130 short hairpin RNA were established to analyze the effect of XB130 on sensitivity of chemotherapy. The results show that both XB130 mRNA and protein expression were detectable in normal gastric tissues. The overall survival time of stage IV patients and the disease-free period after radical resection of GC in stage I–III patients were significantly shorter when immunohistochemical staining for XB130 was low than when staining was high (both p<0.05). XB130 expression also predicted tumor sensitivity to several chemotherapy agents. Viability of both XB130-silenced SGC7901 cells and wild-type cells was suppressed by 5-fluorouracil (5-FU), cisplatin, and irinotecan in a dose-dependent way, but cisplatin and irinotecan were more sensitive against sXB130-silenced GC cells and 5-FU showed higher sensitivity to wild-type cells. When treated by 5-FU, patients with high expression of XB130 tumors had a higher survival rate than those with low expression tumors. These findings indicate that reduced XB130 protein expression is a prognostic biomarker for shorter survival and a higher recurrence rate in patients with GC, as well as for the response to chemotherapy.

XB130 mediates cancer cell proliferation and survival through multiple signaling events downstream of Akt

XB130, a novel adaptor protein, mediates RET/PTC chromosome rearrangement-related thyroid cancer cell proliferation and survival through phosphatidyl-inositol-3-kinase (PI3K)/Akt pathway. Recently, XB130 was found in different cancer cells in the absence of RET/PTC. To determine whether RET/PTC is required of XB130-related cancer cell proliferation and survival, WRO thyroid cancer cells (with RET/PTC mutation) and A549 lung cancer cells (without RET/PTC) were treated with XB130 siRNA, and multiple Akt down-stream signals were examined. Knocking-down of XB130 inhibited G₁-S phase progression, and induced spontaneous apoptosis and enhanced intrinsic and extrinsic apoptotic stimulus-induced cell death. Knocking-down of XB130 reduced phosphorylation of p21Cip1/WAF1, p27Kip1, FOXO3a and GSK3β, increased p21Cip1/WAF1protein levels and cleavages of caspase-8 and-9. However, the phosphorylation of FOXO1 and the protein levels of p53 were not affected by XB130 siRNA. We also found XB130 can be phosphorylated by multiple protein tyrosine kinases. These results indicate that XB130 is a substrate of multiple protein tyrosine kinases, and it can regulate cell proliferation and survival through modulating selected down-stream signals of PI3K/Akt pathway. XB130 could be involved in growth and survival of different cancer cells.

XB130 as an independent prognostic factor in human esophageal squamous cell carcinoma

BACKGROUND

Adaptor proteins, with multimodular structures, can participate in the regulation of various cellular functions. A novel adaptor protein XB130 has been implicated as a substrate and regulator of tyrosine kinase-mediated signaling and in controlling cell proliferation and apoptosis in thyroid and lung cancer cells. However, its expression and role in gastrointestinal cancer have not been investigated. We sought to determine the role of XB130 in cell cycle progression of esophageal squamous cell carcinoma (ESCC) cells and to examine its expression and effects on the prognosis of patients with ESCC.

METHODS

Expression of XB130 in human ESCC cell lines was analyzed by Western blot testing and immunofluorescent staining. Knockdown experiments with XB130 small interfering RNA (siRNA) were conducted, and the effect on cell cycle progression was analyzed. Immunohistochemistry of XB130 for 52 primary tumor samples obtained from patients with ESCC undergoing esophagectomy was performed.

RESULTS

XB130 was highly expressed in TE2, TE5, and TE9 cells. In these cells, knockdown of XB130 with siRNA inhibited G1-S phase progression and increased the expression of p21, the cyclin-dependent kinase inhibitor. Immunohistochemistry showed that 71.2% of the patients expressed XB130 in the nuclei and/or cytoplasm of the ESCC cells. Further, nuclear expression of XB130 was an independent prognostic factor of postoperative survival.

CONCLUSIONS

These observations suggest that the expression of XB130 in ESCC cells may affect cell cycle progression and impact prognosis of patients with ESCC. A deeper understanding of XB130 as a mediator and/or biomarker in ESCC is needed.

Claudin 1 mediates TNFα-induced gene expression and cell migration in human lung carcinoma cells

Epithelial-mesenchymal transition (EMT) is an important mechanism in carcinogenesis. To determine the mechanisms that are involved in the regulation of EMT, it is crucial to develop new biomarkers and therapeutic targets towards cancers. In this study, when TGFβ1 and TNFα were used to induce EMT in human lung carcinoma A549 cells, we found an increase in an epithelial cell tight junction marker, Claudin 1. We further identified that it was the TNFα and not the TGFβ1 that induced the fibroblast-like morphology changes. TNFα also caused the increase in Claudin-1 gene expression and protein levels in Triton X-100 soluble cytoplasm fraction. Down-regulation of Claudin-1, using small interfering RNA (siRNA), inhibited 75% of TNFα-induced gene expression changes. Claudin-1 siRNA effectively blocked TNFα-induced molecular functional networks related to inflammation and cell movement. Claudin-1 siRNA was able to significantly reduce TNF-enhanced cell migration and fibroblast-like morphology. Furthermore, over expression of Claudin 1 with a Claudin 1-pcDNA3.1/V5-His vector enhanced cell migration. In conclusion, these observations indicate that Claudin 1 acts as a critical signal mediator in TNFα-induced gene expression and cell migration in human lung cancer cells. Further analyses of these cellular processes may be helpful in developing novel therapeutic strategies.

The actin-binding domain of actin filament-associated protein (AFAP) is involved in the regulation of cytoskeletal structure

Actin filament-associated protein (AFAP) plays a critical role in the regulation of actin filament integrity, formation and maintenance of the actin network, function of focal contacts, and cell migration. Here, we show that endogenous AFAP was present not only in the cytoskeletal but also in the cytosolic fraction. Depolymerization of actin filaments with cytochalasin D or latrunculin A increased AFAP in the cytosolic fraction. AFAP harbors an actin-binding domain (ABD) in its C-terminus. AFAPΔABD, an AFAP mutant with selective ABD deletion, was mainly in the cytosolic fraction when overexpressed in the cells, which was associated with a disorganized cytoskeleton with reduced stress fibers, accumulation of F-actin on cellular membrane, and formation of actin-rich small dots. Cortactin, a well-known podosome marker, was colocalized with AFAPΔABD in these small dots at the ventral surface of the cell, indicating that these small dots fulfill certain criteria of podosomes. However, these podosome-like small dots did not digest gelatin matrix. This may be due to the reduced interaction between AFAPΔABD and c-Src. When AFAPΔABD-transfected cells were stimulated with phorbol ester, they formed podosome-like structures with larger sizes, less numerous and longer life span, in comparison with wild-type AFAP-transfected cells. These results indicate that the association of AFAP with F-actin through ABD is crucial for AFAP to regulate cytoskeletal structures. The AFAPΔABD, as cytosolic proteins, may be more accessible to the cellular membrane, podosome-like structures, and thus be more interactive for the regulation of cellular functions.

Src tyrosine kinase inhibition prevents pulmonary ischemia-reperfusion-induced acute lung injury

PURPOSE

Pulmonary ischemia-reperfusion is a pathological process seen in several clinical conditions, including lung transplantation, cardiopulmonary bypass, resuscitation for circulatory arrest, atherosclerosis, and pulmonary embolism. A better understanding of its molecular mechanisms is very important.

METHODS

Rat left lung underwent in situ ischemia for 60 min, followed by 2 h of reperfusion. The gene expression profiles and Src protein tyrosine kinase (PTK) phosphorylation were studied over time, and PP2, an Src PTK inhibitor, was intravenously administered 10 min before lung ischemia to determine the role of Src PTK in lung injury.

RESULTS

Reperfusion following ischemia significantly changed the expression of 169 genes, with Mmp8, Mmp9, S100a9, and S100a8 being the most upregulated genes. Ischemia alone only affected expression of 9 genes in the lung. However, Src PTK phosphorylation (activation) was increased in the ischemic lung, mainly on the alveolar wall. Src PTK inhibitor pretreatment decreased phosphorylation of Src PTKs, total protein tyrosine phosphorylation, and STAT3 phosphorylation. It increased phosphorylation of the p85α subunit of PI3 kinase, a signal pathway that can inhibit coagulation and inflammation. PP2 reduced leukocyte infiltration in the lung, apoptotic cell death, fibrin deposition, and severity of acute lung injury after reperfusion. Src inhibition also significantly reduced CXCL1 (GRO/KI) and CCL2 (MCP-1) chemokine levels in the serum.

CONCLUSION

During pulmonary ischemia, Src PTK activation, rather than alteration in gene expression, may play a critical role in reperfusion-induced lung injury. Src PTK inhibition presents a new prophylactic treatment for pulmonary ischemia-reperfusion-induced acute lung injury.

Roles of XB130, a novel adaptor protein, in cancer

Adaptor proteins, with multi-modular structures, can participate in the regulation of various cellular functions. During molecular cloning process of actin filament associated protein, we have discovered a novel adaptor protein, referred to as XB130. The human xb130 gene is localized on chromosome 10q25.3, and encodes an 818 amino acid protein. The N-terminal region of XB130 includes several tyrosine phosphorylation sites and a proline-rich sequence that might interact with Src homology 2 and 3 domain-containing proteins, respectively. Our studies have indeed implicated XB130 as a likely substrate and regulator of tyrosine kinase-mediated signaling. Down-regulation of endogenous XB130 with small interfering RNA reduced c-Src activity, IL-8 production and phosphorylation of Akt in human lung epithelial cells. Further, XB130 binds the p85α subunit of phosphatidyl-inositol-3-kinase and subsequently mediates signaling through RET/PTC in thyroid cancer cells. Knockdown of XB130 using small interfering RNA inhibited G1-S phase progression, induced spontaneous apoptosis and enhanced intrinsic and extrinsic apoptotic stimulus-induced cell death in human lung and thyroid cancer cells. Growth of tumors in nude mice formed from XB130 short hairpin RNA stably transfected human thyroid cancer cells were significantly reduced, with decreased cell proliferation and increased apoptosis. Further, XB130 has a high affinity to lamellipodial F-actin meshwork and is involved in the motility and invasiveness of cancer cells. Gene expression profiling identified 246 genes significantly changed in XB130 short hairpin RNA transfected thyroid cancer cells. Among them, 57 genes are related to cell proliferation or survival, including many transcription regulators. Pathway analysis showed that the top ranked disease related to XB130 is Cancer, and the top molecular and cellular functions are Cellular Growth and Proliferation, and Cell Cycle. These observations suggest that the expression of XB130 may affect cell proliferation, survival, motility and invasion in various cancer cells. A deeper understanding of these mechanisms may lead to the discovery of XB130 as an important mediator in tumor development and as a novel therapeutic target for cancer.