Advances in Chibby' s inhibition in the Wnt/β-catenin singaling pathway

It is well known that canonical Wnt/β-catenin signaling pathway plays a key role in tumori-genesis. Recent studies show that Chibby as an antagonist of the Wnt/β-catenin signaling pathway is a kind of nuclear protein that has been conserved throughout evolution. Chibby inhibits Wnt/β-catenin pathway at least through two distinct molecular pathways. Thus Chibby could inhibit the progression of tumors whose Wnt/β-catenin pathway is abnormally activated. This provids a new perspective in tumor research.     

Wnt/β-catenin pathway in bone cancers

The Wnt signaling pathway regulates some of the crucial aspects of cellular processes. The beta-catenin dependent Wnt signaling (Wnt/β-catenin) pathway controls the expression of key developmental genes, and acts as an intracellular signal transducer. The association of Wnt/β-catenin pathway is often reported with different cancers. In this study, we have reviewed the association of Wnt/β-catenin pathway with bone cancers, focusing on carcinogenesis and therapeutic aspects. Wnt/β-catenin pathway is a highly complex and unique signaling pathway, which has ability to regulate gene expression, cell invasion, migration, proliferation, and differentiation for the initiation and progression of bone cancers, especially osteosarcoma. Association of Wnt/β-catenin pathway with chondrosarcoma, Ewing’s sarcoma and chondroma is also documented. Recently, targeting Wnt/β-catenin pathway has gained significant interests as a potential therapeutic application for the treatment of bone cancers. Small RNA technology to knockdown aberrant Wnt/β-catenin or inhibition of β-catenin expression by natural component has shown promising effects against bone cancers. Advances in understanding the mechanisms of Wnt signaling and new technologies have facilitated the discovery of agents that can target and regulate Wnt/β-catenin signaling pathway, and these may provide a basement for the innovative therapeutic approaches in the treatment of bone cancers.     

Jak/Stat pathway in Waldenström's macroglobulinemia

While high serum concentrations of immunoglobulin M (IgM) protein are responsible for much of the morbidity associated with Waldenström's macroglobulinemia (WM), the mechanisms controlling IgM secretion in this malignancy remain unknown. The Jak/Stat signaling pathway mediates the effects of most cytokines involved in stimulating immunoglobulin production in nonmalignant B cells. However, in many hematopoietic malignancies, cytokine-driven stimulation of the Jak/Stat pathway is hyperactive, promoting the expression of genes associated with proliferation and survival. Autocrine/paracrine signaling of cytokines present in the tumor microenvironment may lead to persistent Jak/Stat signal transduction in WM as well. Yet despite evidence implicating the Jak/Stat pathway in the pathogenesis of WM, the relationship between Jak/Stat-mediated cytokine signaling and IgM hypersecretion has not been defined. Through the use of targeted Jak/Stat inhibitors, it is now possible to examine the contribution of aberrant cytokine signaling to IgM production, potentially allowing for a more targeted approach to WM therapy.     

Post-imatinib surgery in advanced/metastatic GIST: is it worthwhile in all patients?

BackgroundSurgical indication for metastatic gastrointestinal stromal tumor (GIST) treated with imatinib is not yet established.Materials and methodsWe analyzed 80 patients who underwent surgery for metastatic GIST after imatinib therapy from July 2002 to October 2007. Patients were divided into those with surgery at best clinical response (group A, n = 49) and those with surgery at focal progression (group B, n = 31). Primary end points were progression-free survival (PFS) and disease-specific survival (DSS).ResultsTwo-year postoperative PFS was 64.4% in group A and 9.7% in group B (P < 0.01). In group A, median PFS was not reached; in group B, it was 8 months. Median DSS from the time of imatinib onset was not reached in either group. Five-year DSS was 82.9% in group A and 67.6% in group B (P < 0.01). Multivariate analysis confirmed a significantly shorter PFS and DSS in group B. Surgical morbidity occurred in 13 patients (16.3%).ConclusionsSurgery for focal progressive lesions could be considered as part of the second-line/third-line armamentarium in selected cases. Surgery of residual disease upon best clinical response seems associated with survival benefit compared with historical controls in similar patient collectives treated with imatinib alone. However, evidence from prospective randomized trials is needed to make definite recommendations.     

Regulation of neuroendocrine differentiation by AKT/hnRNPK/AR/β-catenin signaling in prostate cancer cells

Current diagnostic tools cannot predict clinical failure and androgen‐independent disease progression for patients with prostate cancer (PC). The survival signaling pathways of prostate cells play a central role in the progression of tumors to a neuroendocrine (NE) phenotype. NE cells demonstrate attributes that suggest that they are an integral part of the signaling cascade leading to castration‐resistant PC. In this study, making use of in vitro neuroendocrine differentiation (NED) of human LNCaP and mouse TRAMP‐C2 cells after androgen withdrawal, and of the transgenic adenocarcinoma of mouse prostate (TRAMP) model, we characterized a sequence of molecular events leading to NED and identified a number of markers that could be detectable by routine analyses not only in castration resistant PC but also in hormone naïve PC at the time of initial diagnosis. We found that NED associates with AKT activation that in turn regulates heterogeneous nuclear ribonucleoprotein K (hnRNP K), androgen receptor (AR) and β‐catenin levels. Addition of molecules targeting membrane‐bound receptors and protein kinases blocks NE differentiation in LNCaP and TRAMP‐C2 cells. The extent of AKT phosphorylation and hnRNP K, AR and β‐catenin levels may have a potential value as prognostic indicators discriminating between androgen‐responsive and unresponsive cells and could be used as molecular targets to monitor the anti‐tumor action of new therapeutic protocols based on antireceptor agents and/or neuroendocrine hormone antagonists.     

Expression of Toll-like Receptor 2/4 on Alveolar Macrophage in the Model of Total Hepatic Ischemia/Reperfusion Injury in Mice

Objective： To explore the expression and meaning of Toll-like receptor 2/4 in alveolar macrophage during the process of total hepatic ischemia in mice. Methods： BALB/c mice were used in a model of total hepatic ischemia/reperfusion. Alveolar Macrophage were collected at the time point of lh, 6h and 12h by the means of bronchoalveolar lavage （BAL）, and its TLR2/4 mRNA and protein were detected with Flow Cytometry and Real-time PCR. The level of TNF in BAL fluid were measured. The concentration of MPO, the ratio of wet/dry and lung histological scores were used to assess the degrees of lung injuries. Results： At the three time points of hepatic ischemia reperfusion, the expression of TLR2/4 protein of and mRNA were up-regulated and the level of TLR2 was on the rise continually. TLR4 at the time of 6 h reached the peak value （P〈0.01）. The level of TNF-2 in BAL fluid reached the highest point at the time of 6 h （P〈0.01）. The ratio of wet/dry rose continually during hepatic ischemia reperfusion. After 1 h, the level of MPO increased rapidly. Then it reached the peak value during the period of 6 h to 12 h. Conclusion： TLR2/4 on the mice of alveolar macrophage were activated in the process of hepatic ischemia/reperfusion and involved in the injury of lung.     

Expression of erB4/HER4 in Gastric Carcinoma

Objective： To explore the expression of HER4 in gastric carcinoma and elucidate the relationship between its overexpression and clinical pathology. Methods： A total of 68 samples of gastric carcinoma were examined for the expression of HER4 by immunohistochemical assay. Results： HER4 was overexpressed in 79.41% of gastric carcinoma. The overexpression of HER4 correlated only with lymph node metastasis and TNM staging. Conclusion： erbB4 is one of the genes to regulate the growth of gastric carcinoma and artificial interference the overexpression of HER4 may be an effective treatment of gastric carcinoma.     

Dickkopfs and Wnt/β-catenin signalling in liver cancer

Liver cancer is the fifth and seventh most common cause of cancer in men and women, respectively. Wnt/β-catenin signalling has emerged as a critical player in both the development of normal liver as well as an oncogenic driver in hepatocellular carcinoma (HCC). Based on the current understanding, this article summarizes the possible mechanisms for the aberrant activation of this pathway with specific focus on HCC. Furthermore, we will discuss the role of dickkopfs (DKKs) in regulating Wnt/β-catenin signalling, which is poorly understood and understudied. DKKs are a family of secreted proteins that comprise at least four members, namely DKK1-DKK4, which act as inhibitors of Wnt/β-catenin signalling. Nevertheless, not all members antagonize Wnt/β-catenin signalling. Their functional significance in hepatocarcinogenesis remains to be further characterized for which these studies should provide new insights into the regulatory role of DKKs in Wnt/β-catenin signalling in hepatic carcinogenesis. Because of the important oncogenic roles, there are an increasing number of therapeutic molecules targeting β-catenin and the Wnt/β-catenin pathway for potential therapy of HCC.     

Two novel variants in the 3′UTR of the BRCA1 gene in familial breast and/or ovarian cancer

For the majority of breast and/or ovarian cancer patients tested for BRCA1/2 genes, mutation screening of the coding regions remains negative. MicroRNAs which negatively regulate mRNA translation by binding to 3′ untranslated region (3′UTR) are implicated in cancer. Genetic changes in the 3′UTR of several genes were reported to be associated with higher susceptibility to particular tumor types. The aim of this study was to analyze the BRCA1 3′UTR in patients tested negative for BRCA1/2 deleterious mutations, in order to find variants implicated in the decrease of BRCA1 expression through modification of miRNA binding. Genotyping analyses were performed on genomic DNA of 70 BRCA negatives index cases, selected among patients with breast or ovarian cancer, less than 50 years old, with a strong family history. The co-occurrence of the identified variants with deleterious BRCA1 mutations was then determined in a control population of 210 patients. A luciferase gene reporter assay was used to investigate the impact of the variants on the BRCA1 gene expression. Two novel variants, c.*750A>G and c.*1286C>A, were identified in the 3′UTR of BRCA1 gene, in two patients. The former was found three times in the control population, whereas the latter was absent. The used functional assay did not reveal any effect on the luciferase expression. This study reveals a weak genomic variability in the 3′UTR of the BRCA1 gene. All together, the results led us to classify the variant c.*750A>G as probably neutral, the variant c.*1286C>A remaining unclassified.     

The anti-CD20 mAb LFB-R603 interrupts the dysregulated NF-κB/Snail/RKIP/PTEN resistance loop in B-NHL cells: role in sensitization to TRAIL apoptosis

LFB-R603 is a chimeric anti-CD20 mouse/human monoclonal antibody with a human IgG1 constant (Fc) region. In comparison to rituximab, LFB-R603 exhibits a high affinity to the Fcγ RIII (CD16) and a potent in vitro antibody-dependent cellular cytotoxicity (ADCC). We examined several experimental designs for the biological anti-tumor activity of LFB-R603 as well as its sensitizing activity to apoptosis in resistant non-Hodgin's B-cell lymphoma (B-NHL) in comparison to rituximab. Treatment of the B-NHL cell line Ramos with LFB-R603 was not toxic at the concentrations used and induced cell aggregation following culture at 24 and 48 h similarly to rituximab. Hence, we hypothesized that LFB-R603 may signal the tumor cells and modify intracellular survival/anti-apoptotic pathways. Treatment of Ramos cells with LFB-R603 inhibited the constitutively active NF-κB survival pathway, followed by significant potentiation of TRAIL-mediated apoptosis. We examined the underlying molecular mechanism by which the LFB-R603-mediated NF-κB inhibition results in the reversal of tumor cell resistance to TRAIL. We hypothesized that downstream gene products regulated by NF-κB that are involved in the resistance may be involved in LFB-R603-mediated sensitization. We found that LFB-R603 inhibited NF-κB activation and the anti-apoptotic factor Snail and induced the pro-apoptotic factor RKIP. The direct roles of Snail and RKIP modulation by LFB-R603 in the reversal of B-NHL resistance to TRAIL were examined by knocking down Snail and overexpressing RKIP in Ramos cells, respectively. Both approaches increased significantly the cell sensitivity to TRAIL apoptosis. In addition to changes observed in the expression levels of Snail and RKIP, Ramos cells treated with LFB-R603 induced the expression of PTEN along with inhibition of the PI3K-AKT activated pathway. PTEN silencing in Ramos cells pretreated with LFB-R603 and TRAIL inhibited TRAIL apoptosis; thus, demonstrating that PTEN induction by LFB-R603 has a direct role in tumor cell sensitization to TRAIL apoptosis. Several of the findings obtained in the experimental designs with LFB-R603 were superior to those obtained with rituximab. Overall, the findings demonstrate that LFB-R603 interferes with the dysregulated NF-κB/Snail/RKIP/PTEN/AKT resistance circuitry in B-NHL cells. Further, the findings suggest that LFB-R603 may sensitize tumor cells to various apoptotic stimuli including cytotoxic ligands such as TRAIL and chemotherapeutic drugs.     

LGR5 regulates pro-survival MEK/ERK and proliferative Wnt/β-catenin signalling in neuroblastoma

LGR5 is a marker of normal and cancer stem cells in various tissues where it functions as a receptor for R-spondins and increases canonical Wnt signalling amplitude. Here we report that LGR5 is also highly expressed in a subset of high grade neuroblastomas. Neuroblastoma is a clinically heterogenous paediatric cancer comprising a high proportion of poor prognosis cases (~40%) which are frequently lethal. Unlike many cancers, Wnt pathway mutations are not apparent in neuroblastoma, although previous microarray analyses have implicated deregulated Wnt signalling in high-risk neuroblastoma. We demonstrate that LGR5 facilitates high Wnt signalling in neuroblastoma cell lines treated with Wnt3a and R-spondins, with SK-N-BE(2)-C, SK-N-NAS and SH-SY5Y cell-lines all displaying strong Wnt induction. These lines represent MYCN-amplified, NRAS and ALK mutant neuroblastoma subtypes respectively. Wnt3a/R-Spondin treatment also promoted nuclear translocation of β-catenin, increased proliferation and activation of Wnt target genes. Strikingly, short-interfering RNA mediated knockdown of LGR5 induces dramatic Wnt-independent apoptosis in all three cell-lines, accompanied by greatly diminished phosphorylation of mitogen/extracellular signal-regulated kinases (MEK1/2) and extracellular signal-regulated kinases (ERK1/2), and an increase of BimEL, an apoptosis facilitator downstream of ERK. Akt signalling is also decreased by a Rictor dependent, PDK1-independent mechanism. LGR5 expression is cell cycle regulated and LGR5 depletion triggers G1 cell-cycle arrest, increased p27 and decreased phosphorylated retinoblastoma protein. Our study therefore characterises new cancer-associated pathways regulated by LGR5, and suggest that targeting of LGR5 may be of therapeutic benefit for neuroblastomas with diverse etiologies, as well as other cancers expressing high LGR5.