RACK1 suppresses gastric tumorigenesis by stabilizing the β-catenin destruction complex

RACK1 facilitates breast cancer progression by competitively inhibiting the binding of β-catenin to PSMD2 and enhancing the stability of β-catenin

The receptor for activated C kinase 1 (RACK1) is a key scaffolding protein with multifunctional and multifaceted properties. By mediating protein-protein interactions, RACK1 integrates multiple intracellular signals involved in the regulation of various physiological and pathological processes. Dysregulation of RACK1 has been implicated in the initiation and progression of many tumors. However, the exact function of RACK1 in cancer cellular processes, especially in proliferation, remains controversial. Here, we show that RACK1 is required for breast cancer cell proliferation in vitro and tumor growth in vivo. This effect of RACK1 is associated with its ability to enhance β-catenin stability and activate the canonical WNT signaling pathway in breast cancer cells. We identified PSMD2, a key component of the proteasome, as a novel binding partner for RACK1 and β-catenin. Interestingly, although there is no interaction between RACK1 and β-catenin, RACK1 binds PSMD2 competitively with β-catenin. Moreover, RACK1 prevents ubiquitinated β-catenin from binding to PSMD2, thereby protecting β-catenin from proteasomal degradation. Collectively, our findings uncover a novel mechanism by which RACK1 increases β-catenin stability and promotes breast cancer proliferation.

TRIM26 inhibited osteosarcoma progression through destabilizing RACK1 and thus inactivation of MEK/ERK signaling

Osteosarcoma is a highly aggressive malignant tumor that is common in the pediatric population and has a high rate of disability and mortality. Recent studies have suggested that the tripartite motif-containing family genes (TRIMs) play critical roles in oncogenesis in several cancers. TRIM26, one of the TRIMs family genes, was more frequently reported to exert a tumor-suppressive role, while its detailed functional roles in the osteosarcoma progression were still unknown and require further investigation. Herein, we found that TRIM26 was markedly downregulated in osteosarcoma tissues and cells. Survival analysis revealed that higher expression of TRIM26 was associated with better prognosis and its expression was an independent protective factor in osteosarcoma. Functional analysis demonstrated that overexpression of TRIM26 inhibited osteosarcoma cell proliferation and invasion via inhibiting the EMT process and MEK/ERK signaling. In contrast, the silence of TRIM26 caused the opposite effect. RACK1, a member of the Trp-Asp repeat protein family, was identified as a novel target of TRIM26. TRIM26 could interact with RACK1 and accelerate the degradation of RACK1, thus inactivation of MEK/ERK signaling. Overexpression of RACK1 could attenuate the inhibitory effect of TRIM26 overexpression on p-MEK1/2 and p-ERK1/2, and silence of RACK1 could partly impair the effect of TRIM26 knockdown-induced upregulation of p-MEK1/2 and p-ERK1/2. Further, a series of gain- and loss-of-function experiments showed that decreased malignant behaviors including cell proliferation and invasion in TRIM26-upregulated cells were reversed when RACK1 was overexpressed, whereas RACK1 knockdown diminished the increased malignant phenotypes in TRIM26-silenced osteosarcoma cells. In conclusion, our study indicated that TRIM26 inhibited osteosarcoma progression via promoting proteasomal degradation of RACK1, thereby resulting in inactivation of MEK/ERK signaling, and impeding the EMT process.

Ribosome Heterogeneity in Development and Disease

The functional ribosome is composed of ∼80 ribosome proteins. With the intensity-based absolute quantification (iBAQ) value, we calculate the stoichiometry ratio of each ribosome protein. We analyze the ribosome ratio-omics (Ribosome R ), which reflects the holistic signature of ribosome composition, in various biological samples with distinct functions, developmental stages, and pathological outcomes. The Ribosome R reveals significant ribosome heterogeneity among different tissues of fat, spleen, liver, kidney, heart, and skeletal muscles. During tissue development, testes at various stages of spermatogenesis show distinct Ribosome R signatures. During in vitro neuronal maturation, the Ribosome R changes reveal functional association with certain molecular aspects of neurodevelopment. Regarding ribosome heterogeneity associated with pathological conditions, the Ribosome R signature of gastric tumors is functionally linked to pathways associated with tumorigenesis. Moreover, the Ribosome R undergoes dynamic changes in macrophages following immune challenges. Taken together, with the examination of a broad spectrum of biological samples, the Ribosome R barcode reveals ribosome heterogeneity and specialization in cell function, development, and disease.

One-Sentence Summary

Ratio-omics signature of ribosome deciphers functionally relevant heterogeneity in development and disease.

B-lymphoid tyrosine kinase-mediated FAM83A phosphorylation elevates pancreatic tumorigenesis through interacting with β-catenin

Abnormal activation of Wnt/β-catenin-mediated transcription is closely associated with the malignancy of pancreatic cancer. Family with sequence similarity 83 member A (FAM83A) was shown recently to have oncogenic effects in a variety of cancer types, but the biological roles and molecular mechanisms of FAM83A in pancreatic cancer need further investigation. Here, we newly discovered that FAM83A binds directly to β-catenin and inhibits the assembly of the cytoplasmic destruction complex thus inhibiting the subsequent phosphorylation and degradation. FAM83A is mainly phosphorylated by the SRC non-receptor kinase family member BLK (B-lymphoid tyrosine kinase) at tyrosine 138 residue within the DUF1669 domain that mediates the FAM83A-β-catenin interaction. Moreover, FAM83A tyrosine 138 phosphorylation enhances oncogenic Wnt/β-catenin-mediated transcription through promoting β-catenin-TCF4 interaction and showed an elevated nucleus translocation, which inhibits the recruitment of histone deacetylases by TCF4. We also showed that FAM83A is a direct downstream target of Wnt/β-catenin signaling and correlates with the levels of Wnt target genes in human clinical pancreatic cancer tissues. Notably, the inhibitory peptides that target the FAM83A-β-catenin interaction significantly suppressed pancreatic cancer growth and metastasis in vitro and in vivo. Our results revealed that blocking the FAM83A cascade signaling defines a therapeutic target in human pancreatic cancer.

3,3'-Diindolylmethane Augments 5-Fluorouracil-InducedGrowth Suppression in Gastric Cancer Cells through Suppression of the Akt/GSK-3β and WNT/Beta-Catenin

Gastric cancer (GC) is one of the most lethal cancers in South Korea, and it is a cancer of concern worldwide. 5-fluorouracil (5-Fu) is commonly used as the first-line therapy for advanced GC; however, its side effects often limit the dosage range and impair patients' quality of life. Due to the limitations of current chemotherapy, new anticancer therapies are urgently needed. 3,3'-diindolylmethane (DIM) has been reported to have the ability to protect against various types of cancer. Our study aimed to elucidate the anticancer effect of DIM in GC when treated with the chemotherapeutic agent 5-Fu. In our results, combined treatment with DIM and 5-Fu resulted in higher apoptosis and lower cell proliferation than treatment with 5-Fu in SNU484 and SNU638 cell lines. Furthermore, when DIM and 5-Fu were administered together, cell invasion was diminished by mediated E-cadherin, MMP-9, and uPA; p-Akt and p-GSK-3β levels were reduced more significantly than when 5-Fu was administered alone. Moreover, in the Wnt signaling pathway, combined treatment of DIM and 5-Fu diminished β-catenin levels in the nucleus and inhibited cyclin D1and c-Myc protein levels. The Akt inhibitor, wortmannin, further inhibited the levels of β-catenin and c-Myc that were inhibited by DIM and 5-Fu. Furthermore, an animal xenograft model demonstrated that DIM combined with 5-Fu considerably reduced tumor growth without any toxic effects by regulating the Akt/GSK-3β and β-catenin levels. Our findings suggest that DIM significantly potentiates the anticancer effects of 5-Fu by targeting the Akt/GSK-3β and WNT/β-catenin because the combination therapy is more effective than 5-Fu alone, thereby offering an innovative potential therapy for patients with GC.

PPDPF Promotes the Development of Mutant KRAS-Driven Pancreatic Ductal Adenocarcinoma by Regulating the GEF Activity of SOS1

The guanine nucleotide exchange factor (GEF) SOS1 catalyzes the exchange of GDP for GTP on RAS. However, regulation of the GEF activity remains elusive. Here, the authors report that PPDPF functions as an important regulator of SOS1. The expression of PPDPF is significantly increased in pancreatic ductal adenocarcinoma (PDAC), associated with poor prognosis and recurrence of PDAC patients. Overexpression of PPDPF promotes PDAC cell growth in vitro and in vivo, while PPDPF knockout exerts opposite effects. Pancreatic-specific deletion of PPDPF profoundly inhibits tumor development in KRASG12D -driven genetic mouse models of PDAC. PPDPF can bind GTP and transfer GTP to SOS1. Mutations of the GTP-binding sites severely impair the tumor-promoting effect of PPDPF. Consistently, mutations of the critical amino acids mediating SOS1-PPDPF interaction significantly impair the GEF activity of SOS1. Therefore, this study demonstrates a novel model of KRAS activation via PPDPF-SOS1 axis, and provides a promising therapeutic target for PDAC.

Asparagine synthetase regulates lung-cancer metastasis by stabilizing the β-catenin complex and modulating mitochondrial response

The availability of asparagine is the limitation of cell growth and metastasis. Asparagine synthetase (ASNS) was an essential enzyme for endogenous asparagine products. In our study, ASNS-induced asparagine products were essential to maintain tumor growth and colony formations in vitro. But mutated ASNS which defected endogenous asparagine products still upregulated cell invasiveness, which indicated that ASNS promoted invasiveness by alternative pathways. Mechanically, ASNS modulated Wnt signal transduction by promoting GSK3β phosphorylation on ser9 and stabilizing the β-catenin complex, as result, ASNS could promote more β-catenin translocation into nucleus independent of endogenous asparagine. At the same time, ASNS modulated mitochondrial response to Wnt stimuli with increased mitochondrial potential and membrane fusion. In summary, ASNS promoted metastasis depending on Wnt pathway and mitochondrial functions even without endogenous asparagine products.

Rack1 regulates pro-inflammatory cytokines by NF-κB in diabetic nephropathy

Diabetic nephropathy (DN) is one of the chronic microvascular diseases of diabetes. Studies revealed that inflammation is involved in the development of DN. However, its mechanisms are not fully clear. Here, we screened DN-related mRNAs by RNA sequencing in the renal tissues of db/db DN mice and normal control mice. The Swiss-Model, ZDOCK 3.0.2 and PyMOL 2.3.2 were applied for bioinformatics analysis. In total, we obtained 6,820 mRNAs that were dysexpressed in DN. Among them, Receptor for Activated C Kinase 1 (Rack1) was focused on for its high fold changes and high values of fragments per kilobase million (FPKM) in both two groups (FPKM >100). Moreover, Rack1 was highly expressed in DN in vivo and in vitro. Results displayed that the expressions of pro-inflammatory cytokines Mcp-1 and Tnf-α were increased when Rack1 was overexpressed in cells cultured with low glucose while the expressions of Mcp-1 and Tnf-α were decreased when Rack1 was silenced in cells cultured with high glucose. Furthermore, results showed that the established DN inflammatory factor nuclear factor NF-kappa-B (NF-κB) was regulated by Rack1 via the direct interaction between Rack1 and NF-κB subunits P50 and P65. In summary, this identified Rack1 could play an important role in the inflammation of DN via NF-κB, which can provide new insight for DN research.

Roles of RACK1 in centrosome regulation and carcinogenesis

Receptor for activated C kinase 1 (RACK1) regulates various cellular functions and signaling pathways by interacting with different proteins. Recently, we showed that RACK1 interacts with breast cancer gene 1 (BRCA1), which regulates centrosome duplication. RACK1 localizes to centrosomes and spindle poles and is involved in the proper centrosomal localization of BRCA1. The interaction between RACK1 and BRCA1 is critical for the regulation of centrosome number. In addition, RACK1 contributes to centriole duplication by regulating polo-like kinase 1 (PLK1) activity in S phase. RACK1 binds directly to PLK1 and Aurora A, promoting the phosphorylation of PLK1 and activating the Aurora A/PLK1 signaling axis. Overexpression of RACK1 causes centrosome amplification, especially in mammary gland epithelial cells, inducing overactivation of PLK1 followed by premature centriole disengagement and centriole re-duplication. Other proteins, including hypoxia-inducible factor α, von Hippel-Lindau protein, heat-shock protein 90, β-catenin, and glycogen synthase kinase-3β, interact with RACK1 and play roles in centrosome regulation. In this review, we focus on the roles and underlying molecular mechanisms of RACK1 in centrosome regulation mediated by its interaction with different proteins and the modulation of their functions.

Inhibition of Fam114A1 protects melanocytes from apoptosis through higher RACK1 expression

Fam114A1 is a gene closely related to the development of nerve cells, melanocytes, and nerve cells that originate from the neural crest of the embryonic ectoderm. Recent studies showed that Fam114A1 has a role in the occurrence of ankylosing myelitis spondylitis and autoimmune enteritis; still, its cellular function remains poorly understood. In this study, we investigated the effect of Fam114A1 on the biological activity of melanocytes. We found that the expression of Fam114A1 in vitiligo melanocytes (MCV-L, MCV-N, PI3V) was higher than that in normal melanocytes, and the biological function of melanocytes was significantly affected when the Fam114A1 gene was silenced. Inhibition of Fam114A1 increased proliferation, migration, and melanin synthesis proteins, decreased apoptosis, while its overexpression reversed this process. Mechanistically, we discovered that RACK1 is a target protein of Fam114A1 and that RACK1 can be negatively regulated by Fam114A1. Further study showed that Fam114A1 inhibition could not protect melanocytes from apoptosis once the expression of RACK1 protein was silenced. In summary, Fam114A1 is an effective regulatory protein for regulating the function of melanocytes. Inhibition Fam114A1 protects melanocytes from apoptosis through increasing RACK1.

GNA14's interaction with RACK1 inhibits hepatocellular carcinoma progression through reducing MAPK/JNK and PI3K/AKT signaling pathway

Gαq subfamily proteins play critical roles in many biological functions including cardiovascular development, angiogenesis, and tumorigenesis of melanoma. However, the understanding of G Protein Subunit Alpha 14 (GNA14) in diseases, especially in cancers is limited. Here, we revealed that GNA14 was significantly low expression in Human hepatocellular carcinoma (HCC) samples. Low GNA14 expression was correlated with aggressive clinicopathological features. Moreover, the overall survival (OS) and disease-free survival (DFS) of high GNA14 expression HCC patients were much better than low GNA14 expression group. Lentivirus-mediated GNA14 knockdown significantly promoted the growth of liver cancer in vitro and in vivo. However, opposing results were observed when GNA14 is upregulated. Mechanistically, We identified receptor for activated C kinase 1 (RACK1) as a binding partner of GNA14 by co-immunoprecipitation and mass spectrometry (MS). Glutathione-S-transferase (GST) pull-down assay further verified the direct interaction between GNA14 and RACK1. RNA-Seq and loss- and gain-of-function assays also confirmed that GNA14 reduced the activity of both MAPK/JNK and PI3K/AKT signaling pathways through RACK1. GNA14 synergized with U73122 (PLC inhibitor) to enhance this effect. Further studies suggested that GNA14 potentially competed with protein kinase C (PKC) to bind with RACK1, consequently reducing the stability of PKC. Moreover, we also showed that GNA14’supression of p-AKT protein level depended on sufficient RACK1 expression. In conclusion, we indicated a different role of GNA14, which acted as a suppressor inhibiting liver cancer progression through MAPK/JNK and PI3K/AKT signaling pathways. Due to this, GNA14 served as a potentially valuable prognostic biomarker for liver cancer.

Aberrant expression of SFRP1, SFRP3, DVL2 and DVL3 Wnt signaling pathway components in diffuse gastric carcinoma

Diffuse gastric carcinoma (DGC) is characterized by poorly cohesive cells, highly invasive growth patterns, poor prognosis and resistance to the majority of available systemic therapeutic strategies. It has been previously reported that the Wnt/β-catenin signaling pathway serves a prominent role in the tumorigenesis of gastric carcinoma. However, the mechanism underlying the dysregulation of this pathway in DGC has not been fully elucidated. Therefore, the present study aimed to investigate the expression profiles of Wnt antagonists, secreted frizzled-related protein 1 (SFRP1) and secreted frizzled-related protein 3 (SFRP3), and dishevelled protein family members, dishevelled segment polarity protein 2 (DVL2) and dishevelled segment polarity protein 3 (DVL3), in DGC tissues. The association between the expression levels of these factors and the clinicopathological parameters of the patients was determined. Protein and mRNA expression levels in 62 DGC tumor tissues and 62 normal gastric mucosal tissues obtained from patients with non-malignant disease were measured using immunohistochemical and reverse transcription-quantitative PCR (RT-qPCR) analysis. Significantly lower protein expression levels of SFRP1 (P<0.001) and SFRP3 (P<0.001), but significantly higher protein expression levels of DVL2 (P<0.001) and DVL3 (P<0.001) were observed in DGC tissues compared with in control tissues by immunohistochemistry. In addition, significantly lower expression levels of SFRP1 (P<0.05) and higher expression levels of DVL3 (P<0.05) were found in in DGC tissues compared with those in normal gastric mucosal tissues using RT-qPCR. According to correlation analysis between the SFRP1, SFRP3, DVL2 and DVL3 protein expression levels and the clinicopathological characteristics of patients with DGC, a statistically significant correlation was found between the SFRP3 volume density and T stage (r=0.304; P=0.017) and between the SFRP3 volume density and clinical stage (r=0.336; P=0.008). In conclusion, the findings of the present study suggested that the Wnt signaling pathway components SFRP1, SFRP3, DVL2 and DVL3 may be aberrantly expressed in DGC tissues, implicating their possible role in the development of this malignant disease. The present data also revealed a positive relationship between SFRP3 protein expression and the clinical and T stage of DGC.

Expression of LOX Suggests Poor Prognosis in Gastric Cancer

Background: Lysyl oxidase (LOX) is a key enzyme for the cross-linking of collagen and elastin in the extracellular matrix. This study evaluated the prognostic role of LOX in gastric cancer (GC) by analyzing the data of The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) dataset. Methods: The Wilcoxon rank-sum test was used to calculate the expression difference of LOX gene in gastric cancer and normal tissues. Western blot and immunohistochemical staining were used to evaluate the expression level of LOX protein in gastric cancer. Kaplan-Meier analysis was used to calculate the survival difference between the high expression group and the low expression group in gastric cancer. The relationship between statistical clinicopathological characteristics and LOX gene expression was analyzed by Wilcoxon or Kruskal-Wallis test and logistic regression. Univariate and multivariate Cox regression analysis was used to find independent risk factors affecting the prognosis of GC patients. Gene set enrichment analysis (GSEA) was used to screen the possible mechanisms of LOX and GC. The CIBERSORT calculation method was used to evaluate the distribution of tumor-infiltrating immune cell (TIC) abundance. Results: LOX is highly expressed in gastric cancer tissues and is significantly related to poor overall survival. Wilcoxon or Kruskal-Wallis test and Logistic regression analysis showed, LOX overexpression is significantly correlated with T-stage progression in gastric cancer. Multivariate Cox regression analysis on TCGA and GEO data found that LOX (all p < 0.05) is an independent factor for poor GC prognosis. GSEA showed that high LOX expression is related to ECM receptor interaction, cancer, Hedgehog, TGF-beta, JAK-STAT, MAPK, Wnt, and mTOR signaling pathways. The expression level of LOX affects the immune activity of the tumor microenvironment in gastric cancer. Conclusion: High expression of LOX is a potential molecular indicator for poor prognosis of gastric cancer.

Interleukin-20 inhibits the osteogenic differentiation of MC3T3-E1 cells via the GSK3β/β-catenin signalling pathway

OBJECTIVE

To investigate the effects of interleukin-20 (IL-20) on the osteogenic differentiation of MC3T3-E1 cells.

METHODS

The pre-osteoblast line MC3T3-E1 was treated with different concentrations of IL-20 (0, 2, 20 and 100 ng/mL), and the cell viability was detected by the CCK8 assay. To assess the influence of IL-20 on osteogenic differentiation, alkaline phosphatase (ALP) activity and Alizarin red staining were performed at predetermined times. The expression levels of Runt-related transcription factor 2 (RUNX2), Osterix (Osx), glycogen synthase kinase-3β (GSK-3β) and β-catenin were detected by qRT-PCR and Western blotting analyses. 5 nmol/L lithium chloride (LiCl) was used as GSK-3β inhibitor.

RESULTS

IL-20 promoted cell proliferation but decreased ALP activity and mineralization. Moreover, IL-20 downregulated the expression of RUNX2, Osx and β-catenin but upregulated the level of GSK-3β.

CONCLUSIONS

The results suggest that IL-20 could inhibit the osteogenic differentiation of MC3T3-E1 cells via the GSK3β/β-catenin signalling pathway.

A novel UBE2T inhibitor suppresses Wnt/β-catenin signaling hyperactivation and gastric cancer progression by blocking RACK1 ubiquitination

Dysregulation of the Wnt/β-catenin signaling pathway is critically involved in gastric cancer (GC) progression. However, current Wnt pathway inhibitors being studied in preclinical or clinical settings for other cancers such as colorectal and pancreatic cancers are either too cytotoxic or insufficiently efficacious for GC. Thus, we screened new potent targets from β-catenin destruction complex associated with GC progression from clinical samples, and found that scaffolding protein RACK1 deficiency plays a significant role in GC progression, but not APC, AXIN, and GSK3β. Then, we identified its upstream regulator UBE2T which promotes GC progression via hyperactivating the Wnt/β-catenin signaling pathway through the ubiquitination and degradation of RACK1 at the lysine K172, K225, and K257 residues independent of an E3 ligase. Indeed, UBE2T protein level is negatively associated with prognosis in GC patients, suggesting that UBE2T is a promising target for GC therapy. Furthermore, we identified a novel UBE2T inhibitor, M435-1279, and suggested that M435-1279 acts inhibit the Wnt/β-catenin signaling pathway hyperactivation through blocking UBE2T-mediated degradation of RACK1, resulting in suppression of GC progression with lower cytotoxicity in the meantime. Overall, we found that increased UBE2T levels promote GC progression via the ubiquitination of RACK1 and identified a novel potent inhibitor providing a balance between growth inhibition and cytotoxicity as well, which offer a new opportunity for the specific GC patients with aberrant Wnt/β-catenin signaling.

Biological information and functional analysis reveal the role of discoidin domain receptor 1 in oral squamous cell carcinoma

OBJECTIVES

This study aimed to establish a framework for the role of discoidin domain receptor 1 (DDR1) in oral squamous cell carcinoma (OSCC) through biological data and functional analysis.

STUDY DESIGN

The GSE31056 series of the Gene Expression Omnibus database and UALCAN website were used to assess DDR1 expression in head and neck squamous cell carcinoma (HNSCC) and OSCC. DDR1 RNA sequencing data for 260 HNSCC samples from The Cancer Genome Atlas were overlaid to evaluate its association with tumor progression and prognosis. To identify the function of DDR1 in OSCC, 38 patients with OSCC were followed for 8 years and immunohistochemical analysis, western blotting, Cell Counting Kit-8, and colony formation assays were conducted on OSCC cell lines to reveal DDR1 expression and function.

RESULTS

DDR1 was overexpressed in HNSCC and OSCC tumor specimens and its expression correlated with overall survival and T-stage classification (P = .049, P = .0316). Furthermore, DDR1 was related to OSCC tumor growth because its expression increased with the T-stage level (P = .0071) but not N-stage level, histologic stage, or recurrence (P > .05). DDR1 was highly expressed in OSCC cell lines and promoted cell proliferation, which was repressed by nilotinib (P < .05).

CONCLUSIONS

DDR1 has an oncogenic role in OSCC and might be a novel target for anti-OSCC therapy.

YTHDF1 Promotes Gastric Carcinogenesis by Controlling Translation of FZD7

N⁶-methyladenosine (m⁶A) is the most prevalent internal RNA modification in mammals that regulates homeostasis and function of modified RNA transcripts. Here, we aimed to investigate the role of YTH m⁶A RNA-binding protein 1 (YTHDF1), a key regulator of m⁶A methylation in gastric cancer tumorigenesis. Multiple bioinformatic analyses of different human cancer databases identified key m⁶A-associated genetic mutations that regulated gastric tumorigenesis. YTHDF1 was mutated in about 7% of patients with gastric cancer, and high expression of YTHDF1 was associated with more aggressive tumor progression and poor overall survival. Inhibition of YTHDF1 attenuated gastric cancer cell proliferation and tumorigenesis in vitro and in vivo. Mechanistically, YTHDF1 promoted the translation of a key Wnt receptor frizzled7 (FZD7) in an m⁶A-dependent manner, and mutated YTHDF1 enhanced expression of FZD7, leading to hyperactivation of the Wnt/β-catenin pathway and promotion of gastric carcinogenesis. Our results demonstrate the oncogenic role of YTHDF1 and its m⁶A-mediated regulation of Wnt/β-catenin signaling in gastric cancer, providing a novel approach of targeting such epigenetic regulators in this disease. SIGNIFICANCE: This study provides a rationale for controlling translation of key oncogenic drivers in cancer by manipulating epigenetic regulators, representing a novel and efficient strategy for anticancer treatment. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/10/2651/F1.large.jpg.

Dual functions of Rack1 in regulating Hedgehog pathway

Hedgehog (Hh) pathway plays multiple roles in many physiological processes and its dysregulation leads to congenital disorders and cancers. Hh regulates the cellular localization of Smoothened (Smo) and the stability of Cubitus interruptus (Ci) to fine-tune the signal outputs. However, the underlying mechanisms are still unclear. Here, we show that the scaffold protein Rack1 plays dual roles in Hh signaling. In the absence of Hh, Rack1 promotes Ci and Cos2 to form a Ci–Rack1–Cos2 complex, culminating in Slimb-mediated Ci proteolysis. In the presence of Hh, Rack1 dissociates from Ci–Rack1–Cos2 complex and forms a trimeric complex with Smo and Usp8, leading to Smo deubiquitination and cell surface accumulation. Furthermore, we find the regulation of Rack1 on Hh pathway is conserved from Drosophila to mammalian cells. Our findings demonstrate that Rack1 plays dual roles during Hh signal transduction and provide Rack1 as a potential drug target for Hh-related diseases.

PCDHGA9 represses epithelial-mesenchymal transition and metastatic potential in gastric cancer cells by reducing β-catenin transcriptional activity

Gastric cancer (GC) has a high mortality rate, and metastasis is the main reason for treatment failure. It is important to study the mechanism of tumour invasion and metastasis based on the regulation of key genes. In a previous study comparing the expression differences between GES-1 and SGC-7901 cells, PCDHGA9 was selected for further research. In vitro and in vivo experiments showed that PCDHGA9 inhibited invasion and metastasis. A cluster analysis suggested that PCDHGA9 inhibited epithelial-mesenchymal transition (EMT) through the Wnt/β-catenin and TGF-β pathways. Laser confocal techniques and western blotting revealed that PCDHGA9 inhibited the nuclear translocation of β-catenin, regulated T cell factor (TCF)/ /lymphoid enhancer factor (LEF) transcriptional activity, directly impacted the signal transmission of the TGF-β/Smad2/3 pathway, strengthened the adhesion complex, weakened the effects of TGF-β, and blocked the activation of the Wnt pathway. In addition, PCDHGA9 expression was regulated by methylation, which was closely related to poor clinical prognosis. The aim of this study was to elucidate the molecular mechanism by which PCDHGA9 inhibits EMT and metastasis in GC to provide a new theoretical basis for identifying GC metastasis and a new target for improving the outcome of metastatic GC.

Epithelial V-like antigen 1 promotes hepatocellular carcinoma growth and metastasis via the ERBB-PI3K-AKT pathway

The role of epithelial V‐like antigen 1 (EVA1) has been well studied in thymic development and homostasis; however, its putative relationship with cancer remains largely unknown. Therefore, here we investigated the role of EVA1 in hepatocellular carcinoma. Interestingly, EVA1 expression was significantly increased in hepatocellular carcinoma (HCC) and was also associated with a poor prognosis and recurrence in HCC patients. Overexpression of EVA1 promoted cell growth, invasion and migration in vitro. Consistently, knockdown of EVA1 expression inhibited proliferation and migration in vitro, while repressing metastasis of HCC cells in vivo. RNA‐seq analysis indicated that EVA1 is able to upregulate the expression of genes in the ERBB3‐PI3K pathway. Accordingly, an increased level of AKT phosphorylation was detected in HCC cells after EVA1 overexpression. LY294002, a PI3K inhibitor, inhibited AKT phosphorylation and rescued the tumor‐promoting effect of EVA1 overexpression. Altogether, the present study has revealed the oncogenic role of EVA1 during HCC progression and metastasis through the ERBB‐PI3K‐AKT signaling pathway, reiterating the potential use of EVA1 as a therapeutic target and/or prognostic marker for HCC.

The hallmarks of GSK-3 in morphogenesis and embryonic development metabolism in arthropods

Several research groups around the world have studied diverse aspects of energy metabolism in arthropod disease vectors, with the aim of discovering potential control targets. As in all oviparous organisms, arthropod embryonic development is characterized by the mobilization of maternally-derived metabolites for the formation of new tissues and organs. Glycogen synthase kinase-3 (GSK-3) is a serine-threonine kinase described as an important regulator of metabolism and development in a wide range of organisms. GSK-3 was first identified based on its action upon glycogen synthase, a central enzyme in glycogen biosynthesis. Currently, it is recognized as a key component of multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, cell migration, and immune response. The present review will describe the current knowledge on GSK-3 activation and its role in morphogenesis and embryonic metabolism in arthropods. Altogether, the information discussed here can spark new approaches and strategies for further studies, enhancing our understanding of these important arthropod vectors and strengthening the resources in the search for novel control methods.

Zic1 suppresses gastric cancer metastasis by regulating Wnt/β-catenin signaling and epithelial-mesenchymal transition

Gastric cancer (GC) patients with metastasis had limited treatment options and dismal outcome. We have previously reported the aberrant expression of Zic family member 1 (Zic1) in GC. However, the functional roles and underlying mechanism of Zic1 in GC metastasis remain unknown. Here, we demonstrate that lower expression of Zic1 was correlated with more lymph node metastasis and poor outcome of GC patients. Ectopic expression of Zic1 suppressed both lung metastasis and peritoneal tumor dissemination of GC in mice. The metastatic suppressing ability of Zic1 was mediated by regulating the process of cell invasion, adhesion and epithelial-mesenchymal transition (EMT). Mechanistically, Zic1 could downregulate Wnt targets including c-Myc and Cyclin D1 by inhibiting LEF transcriptional activity in GC cells. Notably, Zic1 was inversely related to the expression of Cyclin D1 in GC tissues tested. In addition, Zic1 could physically interact with β-catenin/transcription factor 4 (TCF4) and disrupt their complex formation, while not affecting β-catenin nuclear localization. Collectively, our study indicated that Zic1 suppressed GC metastasis through attenuating Wnt/β-catenin signaling and the EMT process. Our work may provide novel therapeutic strategies for the metastasis of GC.

Overexpression of RACK1 Predicts Poor Prognosis in Melanoma

Melanoma is a highly malignant skin cancer with limited treatment options, the mechanism of the occurrence and development of melanoma is still unclear till now. Receptor for activated C kinase 1 (RACK1) is a scaffolding protein that mediates multiple signaling pathways; it interconnects distinct signaling pathways to control essential cellular processes. RACK1 was reported as an oncogene in human tumorigenesis, but little is known about its role in melanoma. This study aimed to investigate the expression of RACK1 in patients with melanoma and to reveal its possible functions in melanoma cells. The expression profiles of RACK1 detected in tumor tissues from melanoma patients showed that RACK1 was higher in tumor tissues, and its expression level was well associated with the clinical progression of melanoma (TNM stage, P=0.009). Furthermore, RNA interfering (RNAi) knockdown of RACK1 could efficiently suppress the proliferation, migration and invasion of A375 and A875 cells and promote their apoptosis. Taken together, these results suggest that RACK1 may be a poor prognostic factor in human melanoma, and it may be a new therapeutic target for melanoma treatment.

DUBs, Hypoxia, and Cancer

Alterations in protein ubiquitylation and hypoxia are commonly associated with cancer. Ubiquitylation is carried out by three sequentially acting ubiquitylating enzymes and can be opposed by deubiquitinases (DUBs), which have emerged as promising drug targets. Apart from protein localization and activity, ubiquitylation regulates degradation of proteins, among them hypoxia-inducible factors (HIFs). Thereby, various E3 ubiquitin ligases and DUBs regulate HIF abundance. Conversely, several E3s and DUBs are regulated by hypoxia. While hypoxia is a powerful HIF regulator, less is known about hypoxia-regulated DUBs and their impact on HIFs. Here, we review current knowledge about the relationship of E3s, DUBs, and hypoxia signaling. We also discuss the reciprocal regulation of DUBs by hypoxia and use of DUB-specific drugs in cancer.

UFM1 suppresses invasive activities of gastric cancer cells by attenuating the expres7sion of PDK1 through PI3K/AKT signaling

BACKGROUND

UFM1 has been found to be involved in the regulation of tumor development. This study aims to clarify the role and potential molecular mechanisms of UFM1 in the invasion and metastasis of gastric cancer.

METHODS

Expression of UFM1 in gastric tumor and paired adjacent noncancerous tissues from 437 patients was analyzed by Western blotting, immunohistochemistry, and realtime PCR. Its correlation with the clinicopathological characteristics and prognosis of gastric cancer patients was analyzed. The effects of UFM1 on the invasion and migration of gastric cancer cells were determined by the wound and trans-well assays, and the effect of UFM1 on subcutaneous tumor formation was verified in nude mice. The potential downstream targets of UFM1 and related molecular mechanisms were clarified by the human protein kinase assay and co-immunoprecipitation technique.

RESULTS

Compared with the corresponding adjacent tissues, the transcription level and protein expression level of UFM1 in gastric cancer tissues were significantly downregulated (P < 0.05). The 5-year survival rate of gastric cancer patients with low UFM1 expression was significantly lower than the patients with high UFM1 expression (42.1% vs 63.0%, P < 0.05). The invasion and migration abilities of gastric cancer cells with stable UFM1 overexpression were significantly decreased, and the gastric cancer cells with UFM1 stable knockdown showed the opposite results; similar results were also obtained in the nude mouse model. Further studies have revealed that UFM1 could increase the ubiquitination level of PDK1 and decrease the expression of PDK1 at protein level, thereby inhibiting the phosphorylation level of AKT at Ser473. Additionally, the effect of UFM1 on gastric cancer cell function is dependent on the expression of PDK1. The expression level of UFM1 can improve the poor prognosis of PDK1 in patients with gastric cancer.

CONCLUSION

UFM1 suppresses the invasion and metastasis of gastric cancer by increasing the ubiquitination of PDK1 through negatively regulating PI3K/AKT signaling.

PRMT1 promotes pancreatic cancer growth and predicts poor prognosis

BACKGROUND

Protein arginine methyltransferase 1 (PRMT1) is the founding member of the PRMT family of proteins, whose members catalyze methylation of arginine residues in various proteins. Although several studies have reported upregulation of PRMT1 in various cancer types, the expression pattern and the underlying mechanism of PRMT1 action in pancreatic ductal adenocarcinoma (PDAC) are still unclear.

METHODS

Immunohistochemistry staining as well as RT-PCR was used to determine the expression pattern of PRMT1 in clinical PDAC samples. Lentivirus packaging and transfection were employed to construct cell lines with PRMT1 overexpression or knockdown. MTT and crystal violet assays were used to determine the proliferation rates of PDAC cells. β-catenin transcription activity was measured using a TOPFlash assay. PRMT1 binding to the promoter region of CTNNB1 was determined by ChIP-qPCR assay.

RESULTS

Elevated PRMT1 expression was found in PDAC tissue samples compared to noncancerous normal tissues in 41 patients using a real-time PCR assay and in 90 patients using a tissue microarray (TMA) in conjunction with immunohistochemistry. Analysis of the PRMT1 expression data and PDAC clinical features revealed that PRMT1 expression was significantly correlated with PDAC tumor size and prognosis in postoperative patients. Additional functional experiments revealed that PRMT1 expression promoted the growth of pancreatic cancer-derived cells, both in vitro and in vivo. Mechanistically, we found that PRMT1 increased the cellular β-catenin level. We also found that PRMT1 and β-catenin were co-expressed in TCGA and GTEx datasets containing 370 samples.

CONCLUSIONS

Collectively, our study provides novel insight into the expression and function of PRMT1 in PDAC and indicates that PRMT1 may serve as a therapeutic target for treating patients with pancreatic ductal adenocarcinoma.

Fibulin-2 inhibits development of gastric cancer by downregulating β-catenin

The aim of the present study was to investigate the expression of fibulin-2 and β-catenin in gastric cancer tissues and the association to mutual regulation. Forty-nine cases of gastric cancer specimens obtained via surgical resection in the Pathology Department of Heping Hospital Affiliated to Changzhi Medical College from March 2013 to August 2017 were collected. The expression levels of fibulin-2 and β-catenin in 49 cases of gastric cancer and para-carcinoma tissues were detected via quantitative polymerase chain reaction and immunohistochemistry. The correlation of expression of fibulin-2 and β-catenin proteins in gastric cancer was detected via Spearman's analysis. The correlation of fibulin-2 and β-catenin protein expression with clinicopathological indexes of patients was also analyzed. Moreover, the fibulin-2 overexpression plasmid was constructed and transfected into human gastric cancer AGS and SGC-790 cell lines, so as to observe changes in β-catenin and its downstream indexes. Fibulin-2 messenger ribonucleic acid (mRNA) level in gastric cancer tissues was significantly lower than that in para-carcinoma tissues, while β-catenin mRNA level was significantly increased (P<0.05). The positive rate of fibulin-2 protein was 73.47% (36/49) in gastric cancer tissues and 16.33% (8/49) in para-carcinoma tissues, while that of β-catenin was 77.55% (38/49) in gastric cancer tissues and 28.57% (14/49) in para-carcinoma tissues, indicating that fibulin-2 protein is significantly deleted in gastric cancer tissues, and β-catenin protein is significantly upregulated (P<0.001). Fibulin-2 and β-catenin had a negative correlation (r=−0.361, P=0.003), but was closely correlated with the tumor size and lymph node metastasis (P<0.05). After overexpression of fibulin-2, expression of β-catenin, cyclin D1 and c-Myc protein was obviously downregulated (P<0.05). The tumor suppressor gene, fibulin-2, is significantly deleted in gastric cancer tissues, while β-catenin is remarkably enriched. Overexpression of fibulin-2 can inhibit the development of gastric cancer by downregulating β-catenin.

YAP-Induced Endothelial-Mesenchymal Transition in Oral Submucous Fibrosis

Oral submucous fibrosis (OSF) is a potentially malignant disorder. Current studies have shown that chewing areca nut is considered the main cause of OSF, and endothelial-mesenchymal transformation (EndMT) participates in the occurrence and development of the fibrotic lesion. However, the specific molecular mechanisms and treatments remain unclear. Here, we report the mechanism of arecoline-induced EndMT and the importance of this mechanism in OSF, and we also identify potential therapeutics for decreasing OSF incidence. We demonstrate the overexpression of Yes-associated protein (YAP) in human samples and that it was significantly associated with OSF pathologic stage. Arecoline activated YAP by increasing reactive oxygen species levels and inducing the PERK pathway (eukaryotic translation initiation factor 2 alpha kinase 3), resulting in the initiation of EndMT and leading to OSF. Verteporfin, a YAP–TEA domain pathway inhibitor, suppressed EndMT and decreased collagen accumulation, resulting in the alleviation of OSF in mice. These data indicate that arecoline regulates the activity of YAP and highlight an alternative method for treating OSF.

Upregulated RACK1 attenuates gastric cancer cell growth and epithelial-mesenchymal transition via suppressing Wnt/β-catenin signaling

Purpose: As there have been few studies on the effects of the receptor for activated C kinase 1 (RACK1) on gastric cancer (GC), we aimed to explore such effects and the mechanism that may be involved.

Patients and methods: Normal gastric epithelial cells and six GC cell lines were used to detect the mRNA expression of RACK1. Overexpressing RACK1 was transfected in HGC27 and MGC803 cells. The effects of overexpressing RACK1 on cell viability, migration, and invasion were determined by cell counting kit-8, wound scratch, and Transwell assay, respectively. The expressions of epithelial–mesenchymal transition (EMT) and Wnt/β-catenin signaling related genes were detected using quantitative real-time PCR or Western blot. Wnt pathway agonist LiCl was added into RACK1 overexpressing GC cells, and then cell viability, migration, and invasion were also detected.

Results: RACK1 was downregulated in GC cell lines. Under the circumstance that overexpressing RACK1 was successfully transfected in the two lowest RACK1-expressing GC cells, significant inhibition of cell viability, migration, and invasion, promotion to the mRNA and protein expression of E-cadherin, as well as a decrease in the N-cadherin and Snail expressions could be observed. Overexpressing RACK1 also enhanced the protein level of phosphorylation-β-catenin/β-catenin and attenuated c-Jun protein expression. Additionally, LiCl could partially reverse the inhibitory effects of cell viability, migration and invasion by overexpressing RACK.

Conclusion: We found RACK1 possibly inhibited epithelial–mesenchymal transition of GC cells through limitation of the Wnt/β-catenin pathway, thereby suppressing cell migration and invasion; RACK1 could also suppress cell growth.

Involvement of E3 Ligases and Deubiquitinases in the Control of HIF-α Subunit Abundance

The ubiquitin and hypoxia-inducible factor (HIF) pathways are cellular processes involved in the regulation of a variety of cellular functions. Enzymes called ubiquitin E3 ligases perform protein ubiquitylation. The action of these enzymes can be counteracted by another group of enzymes called deubiquitinases (DUBs), which remove ubiquitin from target proteins. The balanced action of these enzymes allows cells to adapt their protein content to a variety of cellular and environmental stress factors, including hypoxia. While hypoxia appears to be a powerful regulator of the ubiquitylation process, much less is known about the impact of DUBs on the HIF system and hypoxia-regulated DUBs. Moreover, hypoxia and DUBs play crucial roles in many diseases, such as cancer. Hence, DUBs are considered to be promising targets for cancer cell-specific treatment. Here, we review the current knowledge about the role DUBs play in the control of HIFs, the regulation of DUBs by hypoxia, and their implication in cancer progression.

Rack1 mediates tyrosine phosphorylation of Anxa2 by Src and promotes invasion and metastasis in drug-resistant breast cancer cells

Background

Acquirement of resistance is always associated with a highly aggressive phenotype of tumor cells. Recent studies have revealed that Annexin A2 (Anxa2) is a key protein that links drug resistance and cancer metastasis. A high level of Anxa2 in cancer tissues is correlated to a highly aggressive phenotype. Increased Anxa2 expression appears to be specific in many drug-resistant cancer cells. The functional activity of Anxa2 is regulated by tyrosine phosphorylation at the Tyr23 site. Nevertheless, the accurate molecular mechanisms underlying the regulation of Anxa2 tyrosine phosphorylation and whether phosphorylation is necessary for the enhanced invasive phenotype of drug-resistant cells remain unknown.

Methods

Small interfering RNAs, small molecule inhibitors, overexpression, loss of function or gain of function, rescue experiments, Western blot, wound healing assays, transwell assays, and in vivo metastasis mice models were used to investigate the functional effects of Rack1 and Src on the tyrosine phosphorylation of Anxa2 and the invasion and metastatic potential of drug-resistant breast cancer cells. The interaction among Rack1, Src, and Anxa2 in drug-resistant cells was verified by co-immunoprecipitation assay.

Results

We demonstrated that Anxa2 Tyr23 phosphorylation is necessary for multidrug-resistant breast cancer invasion and metastasis. Rack1 is required for the invasive and metastatic potential of drug-resistant breast cancer cells through modulating Anxa2 phosphorylation. We provided evidence that Rack1 acts as a signal hub and mediates the interaction between Src and Anxa2, thereby facilitating Anxa2 phosphorylation by Src kinase.

Conclusions

Our findings suggest a convergence point role of Rack1/Src/Anxa2 complex in the crosstalk between drug resistance and cancer aggressiveness. The interaction between Anxa2 and Rack1/Src is responsible for the association between drug resistance and invasive/metastatic potential in breast cancer cells. Thus, our findings provide novel insights on the mechanism underlying the functional linkage between drug resistance and cancer aggressiveness.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1147-7) contains supplementary material, which is available to authorized users.

Rack1 mediates Src binding to drug transporter P-glycoprotein and modulates its activity through regulating Caveolin-1 phosphorylation in breast cancer cells

The failure of chemotherapy and the emergence of multidrug resistance (MDR) are the major obstacles for effective therapy in locally advanced and metastatic breast cancer. Overexpression of the drug transporter P-glycoprotein (P-gp) in cancer cells is one of the main causes of MDR due to its ability to efflux anticancer drugs out of cells. Although the signaling node that regulates the expression of P-gp has been intensively investigated; the regulatory mechanism underlying P-gp transport activity remains obscure. Herein, we reported that Rack1 and tyrosine kinase Src confer drug resistance through modulating the transport function of P-gp without altering its protein level. We provide evidences that Rack1 and Src regulate P-gp activity by modulating caveolin-1 (Cav1) phosphorylation. Importantly, Rack1 acts as a signaling hub and mediates Src binding to P-gp, thereby facilitating the phosphorylation of Cav1 by Src and abolishing the inhibitory effect of Cav1 on P-gp. Taken together, our results demonstrate the pivotal roles of Rack1 and Src in modulating P-gp activity in drug-resistant cells. Our findings also provide novel insights into the mechanism regulating P-gp transport activity. Rack1 may represent a new target for the development of effective therapies for reversing drug resistance.

Distinct notch signaling expression patterns between nucleoside and nucleotide analogues treatment for hepatitis B virus infection

Nucleos(t)ide analogues therapies are currently approved for the treatment of chronic hepatitis B virus (HBV) infection, which effectively suppress HBV replication and correlate with the anti-HBV-specific immune response. Notch signaling serves pleiotropic roles in the immune system that also contribute to virus-specific immunity. In this study, we assessed Notch signal-related gene expression after administrating nucleoside or nucleotide analogues to HBV-replicating cells and clinical liver tissues. We found distinct Notch signaling expression patterns under nucleos(t)ide analogues therapies, with high expression for nucleotide analogues (adefovir pivoxil or tenofovir disoproxil fumarate) and low expression for nucleoside analogues (lamivudine or entecavir) in the presence of HBV infection. Furthermore, activation of mammalian target of rapamycin (mTOR)-Akt (Ser473) phosphorylation was also observed after nucleotide analogue treatment. In conclusion, nucleoside and nucleotide analogues displayed different patterns of Notch signaling activity under HBV infection, and the induction of mTORC2-Akt (Ser473) phosphorylation may contribute to nucleotide analogues-mediated Notch signaling activation.

CALB1 enhances the interaction between p53 and MDM2, and inhibits the senescence of ovarian cancer cells

Numerous studies have demonstrated the association between senescence and cancer. However, the molecular mechanism regulating senescence in ovarian cancer remains unknown. In the present study, the protein expression level of calbindin 1 (CALB1) in ovarian cancer was examined using western blot and immunohistochemistry. The function of CALB1 in ovarian cancer cells was examined using MTT assay, anchorage‑independent growth assay and senescence assay. The molecular mechanisms underlying CALB1 function were investigated using immunoprecipitation and pull‑down assays. In the present study, the expression of CALB1 was found to be increased in ovarian cancer. Overexpression of CALB1 promoted the proliferation and colony formation of ovarian cancer cells and inhibited senescence by modulating the expression levels of p21 and p27. Knockdown of CALB1 inhibited the proliferation and colony formation of ovarian cancer cells. Mechanistically, co‑immunoprecipitation assays revealed that CALB1 interacts with MDM2 proto‑oncogene (MDM2) and promoted the interaction between p53 and MDM2. Collectively, the present study suggested that CALB1 may act as an oncogene in ovarian cancer by inhibiting the p53 pathway.

Downregulation of tumor suppressor RACK1 by Helicobacter pylori infection promotes gastric carcinogenesis through the integrin β-1/NF-κB signaling pathway

Receptor of activated protein kinase C 1 (RACK1) is downregulated in gastric cancer and is involved in modulating NF-κB signaling pathway activity. However, the underlying molecular mechanisms regulating RACK1 expression are unclear. In this study, we demonstrated that downregulated expression of RACK1 was observed in gastric cancer tissue compared to adjacent normal tissue and was correlated with poor prognosis in patients. Helicobacter pylori (H. pylori) infection downregulated RACK1 expression in concert with canonical NF-κB signaling pathway activation in vivo and in vitro. RACK1 overexpression suppressed NF-κB signaling pathway activation as well as the release of downstream proinflammatory cytokines. In addition, RACK1 downregulation increased integrin β-1 expression, while integrin β-1 silencing decreased NF-κB signaling activation. Moreover, H. pylori infection downregulated RACK1 but upregulated integrin β-1 expression at the precancerous lesion stages in human subjects. Our data indicate that H. pylori infection promotes the upregulation of integrin β-1 expression via downregulation of RACK1 expression, which subsequently leads to the elevated activation of the NF-κB signaling pathway, an essential step in H. pylori-induced carcinogenesis.

Pancreatic progenitor cell differentiation and proliferation factor predicts poor prognosis in heptaocellular carcinoma

The aim of this study is to investigate the expression of pancreatic progenitor cell differentiation and proliferation factor (PPDPF) and its relationship with clinicopathological factors in hepatocellular carcinoma (HCC).A total of 135 patients diagnosed with HCC who underwent curative surgery were enrolled in this study. The expression of PPDPF was examined by real time-polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry. The prognostic value for each sample was explored.Both RT-PCR and western blot revealed PPDPF expression was upregulated in HCC. Higher PPDPF expression was also observed in HCC (54.07%) detected by immunohistochemistry (IHC), which was significantly associated with tumors size (P = .003), Edmondson-Steiner Grading (P = .021), recurrence (P = .010), and Diolame complete (P = .023). Patients with higher PPDPF expression had increased cancer progression and poorer prognosis than those with lower expression (P = .043). Multivariate analysis indicated PPDPF as an independent prognostic factor (P = .014).Aberrance PPDPF expression might be a useful predictor and could serve as a potential therapeutic target for HCC.

Liver cancer: WISP3 suppresses hepatocellular carcinoma progression by negative regulation of β-catenin/TCF/LEF signalling

Objectives

Wnt1‐inducible signalling pathway protein 3 (WISP3/CCN6) belongs to the CCN (CYR61/CTGF/NOV) family of proteins, dysregulation of this family contributed to the tumorigenicity of various tumours. In this study, we need to explore its role in hepatocellular carcinoma that remains largely elusive.

Materials and Methods

The expression of WISP3/CCN6 was analysed by qRT‐PCR and Western blotting. Effects of WISP3 on proliferation and metastasis of HCC cells were examined, respectively, by MTT assay and Boyden Chamber. Roles of WISP3 on HCC tumour growth and metastatic ability in vivo were detected in nude mice. Related mechanism study was confirmed by immunofluorescence and Western blotting.

Results

The expression of WISP3 was significantly downregulated in HCC clinical samples and cell lines, and reversely correlated with the tumour size. Forced expression of WISP3 in HCC cells significantly suppressed cell growth and migration in vitro as well as tumour growth and metastatic seeding in vivo. In contrast, downregulation of WISP3 accelerated cell proliferation and migration, and promoted in vivo metastasis. Further study revealed that WISP3 inhibited the translocation of β‐catenin to the nucleus by activating glycogen synthase kinase‐3β (GSK3β). Moreover, constitutively active β‐catenin blocked the suppressive effects of WISP3 on HCC.

Conclusions

Our study showed that WISP3 suppressed the progression of HCC by negative regulation of β‐catenin/TCF/LEF signalling, providing WISP3 as a potential therapeutic candidate for HCC.

Opposite regulation of Wnt/β-catenin and Shh signaling pathways by Rack1 controls mammalian cerebellar development

The development of the cerebellum depends on intricate processes of neurogenesis, migration, and differentiation of neural stem cells (NSCs) and progenitor cells. Defective cerebellar development often results in motor dysfunctions and psychiatric disorders. Understanding the molecular mechanisms that underlie the complex development of the cerebellum will facilitate the development of novel treatment options. Here, we report that the receptor for activated C kinase (Rack1), a multifaceted signaling adaptor protein, regulates mammalian cerebellar development in a cell type-specific manner. Selective deletion of Rack1 in mouse NSCs or granule neuron progenitors (GNPs), but not Bergmann glial cells (BGs), causes severe defects in cerebellar morphogenesis, including impaired folia and fissure formation. NSCs and GNPs lacking Rack1 exhibit enhanced Wnt/β-catenin signaling but reduced Sonic hedgehog (Shh) signaling. Simultaneous deletion of β-catenin in NSCs, but not GNPs, significantly rescues the Rack1 mutant phenotype. Interestingly, Rack1 controls the activation of Shh signaling by regulating the ubiquitylation and stability of histone deacetylase 1 (HDAC1)/HDAC2. Suppression of HDAC1/HDAC2 activity in the developing cerebellum phenocopies the Rack1 mutant. Together, these results reveal a previously unknown role of Rack1 in controlling mammalian cerebellar development by opposite regulation of Wnt/β-catenin and Shh signaling pathways.

Downregulated expression of RACK1 results in pancreatic cancer growth and metastasis

Background

The expression and function of the Receptor for Activated C Kinase 1 (RACK1) in cancer growth and metastasis are confused in different cancers, especially in pancreatic ductal adenocarcinoma (PDAC).

Methods

One-hundred and eighty-two PDAC tissue specimens (95 males and 87 females) including pancreatic cancer tissue and para-carcinoma tissue were collected for analysis between 2005 to 2012. Blood phenotypic parameters using cell count and capillary electrophoresis were investigated. HE staining, real time PCR, Western blot analysis, and soft agar assays were performed to determine the role of RACK1.

Purpose

In this study, we aim to determine the specific role of RACK1 in the untility of PDAC.

Results

We found that RACK1 expression was significantly lower in pancreatic cancer tissue than in para-carcinoma normal pancreatic tissue both in clinic and mice with pancreatic cancer at the early stage. Our results suggested that RACK1 silence could significantly promote cell growth and metastasis of pancreatic cancer cells. But we found that the overexpression of RACK1 has the opposite effect in vitro. In vivo MIAPaca-2 cells overexpressing RACK1, the results demonstrated lower metastatic ability than MIAPaca-2 cells. RACK1 overexpression could decrease the NF-κB transactivation activity of MIAPaca-2 cells, which was consistent with the inhibitory effect of RACK1 overexpression on the pro-migration and pro-invasive target gene of NF-κB, while which could be increased by RACK1 silence. RACK1 silence also enhanced protein expression of pro-migration and pro-invasive NF-κB target genes, which on the contrary, could be reversed by IκBα. Besides, RACK1 expression was significantly associated with lymph node metastasis, vessels metastasis, invasion of nerves as well as TNM staging. The 3-year survival rate of patients with high RACK1 expression was significantly higher than those patients with low RACK1 expression. However, RACK1 expression was not an independent risk factor for of the long-term postoperative survival of patients with pancreatic cancer.

Conclusion

The obtained results in our study suggested that the low expression of RACK1 was associated with cancer cell growth and metastasis in pancreatic cancer through the activation of the NF-κB pathway. RACK1 could be a potential therapeutic drug target to pancreatic cancer and metastasis.

RACK1 Promotes Self-Renewal and Chemoresistance of Cancer Stem Cells in Human Hepatocellular Carcinoma through Stabilizing Nanog

Targeting cancer stem cells (CSCs) has been proposed as a new strategy to eradicate malignancies, including hepatocellular carcinoma (HCC). However, the mechanisms by which CSCs sustain their self-renewal and chemoresistance remain elusive. Nanog is a master transcriptional regulator of stemness, especially in CSCs. Its expression is tightly regulated by the ubiquitin-proteasome system in embryonic stem cells (ESCs). Whether the suppression of Nanog ubiquitination contributes to its over-expression in CSCs has not been explored. In addition, the role of receptor for activated C kinase 1 (RACK1), an adaptor protein implicated in HCC growth, in liver CSC-like traits remains to be determined.

Methods: In vitro and in vivo assays were performed to investigate the role of RACK1 in liver CSC-like phenotype and murine ESC function. How RACK1 regulates Nanog expression was explored by immunoblotting and immunohistochemistry. The interaction of RACK1 with Nanog and the consequent effects on Nanog ubiquitination and stemness were then analyzed.

Results: RACK1 promotes self-renewal and chemoresistance of human liver CSCs and maintains murine ESC function. Consistently, RACK1 enhances the expression of Nanog in human HCC cells and murine ESCs. The protein levels of RACK1 in clinical HCC tissues positively correlate with those of Nanog. Further exploration indicates that RACK1 directly binds to Nanog, which prevents its recruitment of E3 ubiquitin ligase FBXW8 and ubiquitin-dependent degradation. The interaction with Nanog is essential for RACK1 to promote stemness.

Conclusions: Our data provide novel insights into the regulation of Nanog protein levels, as well the key role of RACK1 to enhance self-renewal and chemoresistance of CSCs in human HCC.

Cyclin G2 suppresses Wnt/β-catenin signaling and inhibits gastric cancer cell growth and migration through Dapper1

BACKGROUND

Gastric cancer is one of the most common malignant tumors. Cyclin G2 has been shown to be associated with the development of multiple types of tumors, but its underlying mechanisms in gastric tumors is not well-understood. The aim of this study is to investigate the role and the underlying mechanisms of cyclin G2 on Wnt/β-catenin signaling in gastric cancer.

METHODS

Real-time PCR, immunohistochemistry and in silico assay were used to determine the expression of cyclin G2 in gastric cancer. TCGA datasets were used to evaluate the association between cyclin G2 expression and the prognostic landscape of gastric cancers. The effects of ectopic and endogenous cyclin G2 on the proliferation and migration of gastric cancer cells were assessed using the MTS assay, colony formation assay, cell cycle assay, wound healing assay and transwell assay. Moreover, a xenograft model and a metastasis model of nude mice was used to determine the influence of cyclin G2 on gastric tumor growth and migration in vivo. The effects of cyclin G2 expression on Wnt/β-catenin signaling were explored using a TOPFlash luciferase reporter assay, and the molecular mechanisms involved were investigated using immunoblots assay, yeast two-hybrid screening, immunoprecipitation and Duolink in situ PLA. Ccng2-/- mice were generated to further confirm the inhibitory effect of cyclin G2 on Wnt/β-catenin signaling in vivo. Furthermore, GSK-3β inhibitors were utilized to explore the role of Wnt/β-catenin signaling in the suppression effect of cyclin G2 on gastric cancer cell proliferation and migration.

RESULTS

We found that cyclin G2 levels were decreased in gastric cancer tissues and were associated with tumor size, migration and poor differentiation status. Moreover, overexpression of cyclin G2 attenuated tumor growth and metastasis both in vitro and in vivo. Dpr1 was identified as a cyclin G2-interacting protein which was required for the cyclin G2-mediated inhibition of β-catenin expression. Mechanically, cyclin G2 impacted the activity of CKI to phosphorylate Dpr1, which has been proved to be a protein that acts as a suppressor of Wnt/β-catenin signaling when unphosphorylated. Furthermore, GSK-3β inhibitors abolished the cyclin G2-induced suppression of cell proliferation and migration.

CONCLUSIONS

This study demonstrates that cyclin G2 suppresses Wnt/β-catenin signaling and inhibits gastric cancer cell growth and migration through Dapper1.

EPH receptor A2 governs a feedback loop that activates Wnt/β-catenin signaling in gastric cancer

The erythropoietin-producing hepatoma (EPH) receptor A2 (EphA2) belongs to the Eph family of receptor tyrosine kinases. EphA2 is highly correlated with the formation of many solid tumors and has been linked to the dysregulation of signaling pathways that promote tumor cell proliferation, migration, and invasion as well as angiogenesis. Deregulation of Wnt signaling is implicated in many forms of human disease including gastric cancer. We previously reported that EphA2 promotes the epithelial–mesenchymal transition through Wnt/β-catenin signaling in gastric cancer. Herein, we present a novel mechanism by which EphA2 regulates Wnt/β-catenin signaling. EphA2 acts as a receptor for Wnt ligands and recruits Axin1 to the plasma membrane by directly binding Dvl2. The EphA2-Dvl2/Axin1 interaction was enhanced by Wnt3a treatment, suggesting that EphA2 acts as a functional receptor for the Wnt/β-catenin pathway and plays a vital role in downstream signaling. We showed that Dvl2 mediates the EphA2-Axin1 interaction by binding to the tyrosine kinase domain of EphA2. We propose that EphA2/Dvl2/Axin1 forms a complex that destabilizes the β-catenin destruction complex and allows β-catenin to translocate to the nucleus and initiate the transcription of c-MYC, the primary Wnt signaling target gene. Intriguingly, c-MYC could bind directly to the EphA2 and Wnt1 promoter to enhance their transcription. The entire process formed an EphA2-mediated feed-forward loop. A small molecular inhibitor of EphA2 potently inhibited the proliferation of gastric cancer in vitro and in vivo, including gastric cancer patient–derived xenografts. Thus, our data identify EphA2 as an excellent candidate for gastric cancer therapy.

Krüppel-like factor 9 suppressed tumorigenicity of the pancreatic ductal adenocarcinoma by negatively regulating frizzled-5

Krüppel-like factor 9 (KLF9) has been implicated in mediating a diverse range of biological processes. However, the expression pattern and biological functions of KLF9 in pancreatic ductal adenocarcinoma (PDAC) are still unknown. Here, we evaluated the role of KLF9 in pancreatic ductal adenocarcinoma (PDAC). Overexpression of KLF9 significantly inhibited proliferation and clone formation in PDAC cells, while silencing KLF9 expression dramatically promoted this effect in vitro. Knocking down the expression of KLF9 also promoted the tumorigenesis in the PDAC mouse xneograft model. In in vitro mechanism study, KLF9 negatively regulated the activity of wnt/beta-catenin pathway in Top/Fop reporter assay. Frizzled-5, a key component involving in this pathway, was sharp inhibited by KLF9 both in mRNA and protein level. Furthermore, a KLF9-binding site (BTE) was identified in the promoter region of Frizzled-5. Mutation or deletion of this BTE strongly disrupted the KLF9's regulatory effect on Frizzled-5. More importantly, the expression level of KLF9 was significantly lower in clinical PDAC tissue compared to matched normal tissues and inversely associated with survival of the patients. Together, our findings indicated that KLF9 suppressed tumorigenicity of the pancreatic ductal adenocarcinoma by negatively regulating frizzled-5.

RACK1 is indispensable for porcine reproductive and respiratory syndrome virus replication and NF-κB activation in Marc-145 cells

Porcine reproductive and respiratory syndrome virus (PRRSV) causes porcine reproductive and respiratory syndrome (PRRS), which is currently insufficiently controlled. RACK1 (receptor of activated protein C kinase 1) was first identified as a receptor for protein kinase C, with increasing evidence showing that the functionally conserved RACK1 plays important roles in cancer development, NF-κB activation and various virus infections. However, the roles of RACK1 during PRRSV infection in Marc-145 cells have not been described yet. Here we demonstrated that infection of Marc-145 cells with the highly pathogenic PRRSV strain YN-1 from our lab led to activation of NF-κB and upregulation of RACK1 expression. The siRNA knockdown of RACK1 inhibited PRRSV replication in Marc-145 cells, abrogated NF-κB activation induced by PRRSV infection and reduced the viral titer. Furthermore, knockdown of RACK1 could inhibit an ongoing PRRSV infection. We found that RACK1 is highly conserved across different species based on the phylogenetic analysis of mRNA and deduced amino acid sequences. Taken together, RACK1 plays an indispensable role for PRRSV replication in Marc-145 cells and NF-κB activation. The results would advance our further understanding of the molecular mechanisms underlying PRRSV infection in swine and indicate RACK1 as a promising potential therapeutic target.

Rack1 function in intestinal epithelia: regulating crypt cell proliferation and regeneration and promoting differentiation and apoptosis

Previously, we showed that receptor for activated C kinase 1 (Rack1) regulates growth of colon cells in vitro, partly by suppressing Src kinase activity at key cell cycle checkpoints, in apoptotic and cell survival pathways and at cell-cell adhesions. Here, we generated mouse models of Rack1 deficiency to assess Rack1's function in intestinal epithelia in vivo. Intestinal Rack1 deficiency resulted in proliferation of crypt cells, diminished differentiation of crypt cells into enterocyte, goblet, and enteroendocrine cell lineages, and expansion of Paneth cell populations. Following radiation injury, the morphology of Rack1-deleted small bowel was strikingly abnormal with development of large polypoid structures that contained many partly formed villi, numerous back-to-back elongated and regenerating crypts, and high-grade dysplasia in surface epithelia. These abnormalities were not observed in Rack1-expressing areas of intestine or in control mice. Following irradiation, apoptosis of enterocytes was strikingly reduced in Rack1-deleted epithelia. These novel findings reveal key functions for Rack1 in regulating growth of intestinal epithelia: suppressing crypt cell proliferation and regeneration, promoting differentiation and apoptosis, and repressing development of neoplasia. NEW & NOTEWORTHY Our findings reveal novel functions for receptor for activated C kinase 1 (Rack1) in regulating growth of intestinal epithelia: suppressing crypt cell proliferation and regeneration, promoting differentiation and apoptosis, and repressing development of neoplasia.

High expression of RACK1 is associated with poor prognosis in patients with pancreatic ductal adenocarcinoma

Receptor for activated C kinase 1 (RACK1) is associated with certain aspects of cancer biology and signaling pathways, but its function in pancreatic ductal adenocarcinoma (PDAC) remains unknown. In the present study, 157 patients with PDAC were enrolled. RACK1 mRNA and protein expression levels were analyzed in PDAC tissues and matched adjacent noncancerous tissues by reverse transcription-quantitative polymerase chain reaction and western blotting. RACK1 expression levels in paraffin-embedded PDAC tissues were determined by immunohistochemistry. The associations between RACK1 expression and clinical data were evaluated using χ² analysis. The relationship between RACK1 expression and the survival data of patients was analyzed using Kaplan-Meier and log rank tests. RACK1 mRNA and protein were revealed to be overexpressed in PDAC tumor tissues compared with adjacent noncancerous tissues. RACK1 expression was associated with clinical stage (P=0.001), lymph node invasion (P=0.003) and liver metastasis (P=0.001). Furthermore, patients with PDAC and high RACK1 expression demonstrated shorter overall survival times compared with patients with low RACK1 expression (P=0.002). Multivariate analysis indicated that RACK1 overexpression was an independent prognostic factor for patients with PDAC. Overexpression of RACK1 may contribute to tumor progression, and may be a potential prognostic biomarker for patients with PDAC.

Novel role of STRAP in progression and metastasis of colorectal cancer through Wnt/β-catenin signaling

Serine-Threonine Kinase Receptor-Associated Protein (STRAP) interacts with a variety of proteins and influences a wide range of cellular processes. Aberrant activation of Wnt/β-catenin signaling has been implicated in the development of colorectal cancer (CRC). Here, we show the molecular mechanism by which STRAP induces CRC metastasis by promoting β-catenin signaling through its stabilization. We have genetically engineered a series of murine and human CRC and lung cancer cell lines to investigate the effects of STRAP on cell migration and invasion in vitro, and on tumorigenicity and metastasis in vivo. Downregulation of STRAP inhibits invasion, tumorigenicity, and metastasis of CRC cells. Mechanistically, STRAP binds with GSK-3β and reduces the phosphorylation, ubiquitylation, and degradation of β-catenin through preventing its binding to the destruction complex. This leads to an inhibition of Wnt/β-catenin signaling and reduction in the expression of downstream targets, such as Cyclin D1, matrix metalloproteinases 2 and 9, and ß-TrCP. In human CRC specimens, higher STRAP expression correlates significantly with β-catenin expression with increased nuclear levels (R =0.696, p < .0001, n =128). Together, these results suggest that STRAP increases invasion and metastasis of CRC partly through inhibiting ubiquitin-dependent degradation of β-catenin and promoting Wnt/β-catenin signaling.

The receptor for activated protein kinase C promotes cell growth, invasion and migration in cervical cancer

Cervical cancer is one of the most common malignant tumors in women all over the world. However, the exact etiology of cervical cancer remains unclear. The receptor for activated protein kinase C (RACK1) is reported to be involved in tumorigenesis and tumor progression. Besides, the prognostic value of RACK1 in several kinds of tumors has been identified. However, there are limited studies on the functional role of RACK1 in cervical cancer. In this study, we tested the expression level of RACK1 by immunohistochemistry and western blot technologies and find that it is upregulated in cervical cancer. Colony formation and CCK8 assays indicate that RACK1 promotes cell proliferation in CaSki cervical cancer cells. While the silence of RACK1 decreases the cell proliferation in CCK8 analysis. β-galactosidase staining suggests that RACK1 decreases cell senescence in cervical cancer cells. Invasion and migration assay show that RACK1 promotes the invasion and migration of cervical cancer cells. Also, when RACK1 was silenced, it exerts the opposite result. Furthermore, the mRNA expression levels of MMP‑3, MMP‑9 and MMP‑10 were upregulated in RACK1‑overexpressed CaSki cells by qPCR analysis. RACK1 also induces S phase accumulation in cell cycle analysis and suppresses cell apoptosis in cervical cancer cells. Flow cytometry analysis of mitochondria functions suggests that RACK1 increases the mitochondrial membrane potential (Δψm) levels to prevent mitochondrial apoptosis in cervical cancer cells. To explore the possible mechanism of RACK1, we tested and found that RACK1 upregulates the expression of NF-κB, cyclin D1 and CDK4 and downregulates the expression of p53, p38, p21 and STAT1 in cervical cancer cells. These results suggest that RACK1 promotes cell growth and invasion and inhibits the senescence and apoptosis in cervical cancer cells probably by affecting the p53 pathway.

GNB2L1 and its O-GlcNAcylation regulates metastasis via modulating epithelial-mesenchymal transition in the chemoresistance of gastric cancer

GNB2L1 and its O-GlcNAcylation has been reported to play roles in gastric cancer metastasis. However, the roles of GNB2L1 in chemoresistance of gastric cancer has never been determined. In the present study, we found that GNB2L1 was downregulated in chemoresistant patients of gastric cancer, and observed the decrease of GNB2L1 in protein levels instead of mRNA levels in different chemoresistant gastric cancer cell lines. Further we proved that this downregulation of GNB2L1 was resulted from its elevated O-GlcNAcylation catalyzed by OGT in both cell lines and patients. Next, we investigate the function of GNB2L1 and its O-GlcNAcylation on gastric cancer metastasis during chemoresistance, and confirmed Ser124 as the major O-GlcNAcylation site on GNB2L1 that regulated its function on metastasis. Furthermore, our data demonstrated that GNB2L1 modulated EMT via regulating the translation of EMT-related proteins in the process of chemoresistance. In summary, this study indicated that GNB2L1 and its O-GlcNAcylation regulated metastasis via modulating the translation of EMT-related proteins in the chemoresistance of gastric cancer.