PDCD10-Deficiency Promotes Malignant Behaviors and Tumor Growth via Triggering EphB4 Kinase Activity in Glioblastoma

PDCD10 promotes the tumor-supporting functions of TGF-β in pancreatic cancer

The progression of pancreatic ductal adenocarcinoma (PDAC) is significantly affected by transforming growth factor (TGF)-β but targeting TGF-β can also compromize physiological effects in patients. Our study examined the functions of the ubiquitously expressed protein, PDCD10, as a modulator of TGF-β signaling in PDAC. Using in silico analyses we found that in patient samples, PDCD10 is significantly higher expressed in PDAC tumor tissue compared with normal pancreas and it is highly correlated with reduced survival. We created stable KO's of PDCD10 in two PDAC lines, PaTu 8902 (SMAD4 +/+) and PaTu 8988t (SMAD4 -/-), and found that KO lines are more sensitive to 5-FU and Gemcitabine treatment than their wild-type counterparts. Performing viability and wound closure assays we further found that PDCD10 promotes cell survival and proliferation by enhancing specifically the mitogenic functions of TGF-β. The molecular mechanism underlying this effect was further investigated using Western blots and with primary organoid lines derived from patient PDAC tissue samples. The data imply that PDCD10 mediates an increase in p-ERK through a non-SMAD4 pathway, leading to EMT promotion. Furthermore, PDCD10 facilitates deactivation of RB via a SMAD4-dependent pathway, thereby counter-acting the anti-proliferative actions of TGF-β. By performing proximity ligation assays (PLA) we found that PDCD10 associates with the kinase MST4, translocates it intracellularly and thereby facilitates phosphorylations of RB and ERK1/2. Our study indicates that PDCD10 promotes the proliferative function and EMT induction of TGF-β in pancreatic cancer cells. Therefore, targeting PDCD10 in PDAC patients could represent a promising new strategy to optimize TGF-β targeted therapies.

PDCD10 Is a Key Player in TMZ-Resistance and Tumor Cell Regrowth: Insights into Its Underlying Mechanism in Glioblastoma Cells

Overcoming temozolomide (TMZ)-resistance is a major challenge in glioblastoma therapy. Therefore, identifying the key molecular player in chemo-resistance becomes urgent. We previously reported the downregulation of PDCD10 in primary glioblastoma patients and its tumor suppressor-like function in glioblastoma cells. Here, we demonstrate that the loss of PDCD10 causes a significant TMZ-resistance during treatment and promotes a rapid regrowth of tumor cells after treatment. PDCD10 knockdown upregulated MGMT, a key enzyme mediating chemo-resistance in glioblastoma, accompanied by increased expression of DNA mismatch repair genes, and enabled tumor cells to evade TMZ-induced cell-cycle arrest. These findings were confirmed in independent models of PDCD10 overexpressing cells. Furthermore, PDCD10 downregulation led to the dedifferentiation of glioblastoma cells, as evidenced by increased clonogenic growth, the upregulation of glioblastoma stem cell (GSC) markers, and enhanced neurosphere formation capacity. GSCs derived from PDCD10 knockdown cells displayed stronger TMZ-resistance and regrowth potency, compared to their parental counterparts, indicating that PDCD10-induced stemness may independently contribute to tumor malignancy. These data provide evidence for a dual role of PDCD10 in tumor suppression by controlling both chemo-resistance and dedifferentiation, and highlight PDCD10 as a potential prognostic marker and target for combination therapy with TMZ in glioblastoma.

Protumorigenic role of the atypical cadherin FAT1 by the suppression of PDCD10 via RelA/miR221-3p/222-3p axis in glioblastoma

The atypical cadherin FAT1 function either as a pro or antitumorigenic in tumors of different tissue origins. Our group previously demonstrated the protumorigenic nature of FAT1 signaling in glioblastoma (GBM). In this study, we investigated how FAT1 influences the expression of clustered oncomiRs (miR-221-3p/miR-222-3p) and their downstream effects in GBM. Through several experiments involving the measurement of specific gene/microRNA expression, gene knockdowns, protein and cellular assays, we have demonstrated a novel oncogenic signaling pathway mediated by FAT1 in glioma. These results have been verified using antimiRs and miR-mimic assays. Initially, in glioma-derived cell lines (U87MG and LN229), we observed FAT1 as a novel up-regulator of the transcription factor NFκB-RelA. RelA then promotes the expression of the clustered-oncomiRs, miR-221-3p/miR-222-3p, which in turn suppresses the expression of the tumor suppressor gene (TSG), PDCD10 (Programmed cell death protein10). The suppression of PDCD10, and other known TSG targets (PTEN/PUMA), by miR-221-3p/miR-222-3p, leads to increased clonogenicity, migration, and invasion of glioma cells. Consistent with our in-vitro findings, we observed a positive expression correlation of FAT1 and miR-221-3p, and an inverse correlation of FAT1 and the miR-targets (PDCD10/PTEN/PUMA), in GBM tissue-samples. These findings were also supported by publicly available GBM databases (The Cancer Genome Atlas [TCGA] and The Repository of Molecular Brain Neoplasia Data [Rembrandt]). Patients with tumors displaying high levels of FAT1 and miR-221-3p expression (50% and 65% respectively) experienced shorter overall survival. Similar results were observed in the TCGA-GBM database. Thus, our findings show a novel FAT1/RelA/miR-221/miR-222 oncogenic-effector pathway that downregulates the TSG, PDCD10, in GBM, which could be targeted therapeutically in a specific manner.

Programmed cell death 10 increased blood-brain barrier permeability through HMGB1/TLR4 mediated downregulation of endothelial ZO-1 in glioblastoma

Dysfunction of blood brain barrier (BBB) contributes to the development of peritumoral edema (PTE) and GBM progression. Programmed cell death 10 (PDCD10) exerts various influence on cancers, especially in glioblastoma (GBM). We previously found that PDCD10 expression was positively correlated with PTE extent in GBM. Thus, the present study aims to investigate the emerging role of PDCD10 in regulating BBB permeability in GBM. Here we found that in vitro indirect co-culture of ECs with Pdcd10-overexpressed GL261 cells resulted in a significant increase of FITC-Dextran (MW, 4000) leakage by reducing endothelial zonula occluden-1 (ZO-1) and Claudin-5 expression in ECs respectively. Overexpression of Pdcd10 in GBM cells (GL261) triggered an increase of soluble high mobility group box 1 (HMGB1) release, which in turn activated endothelial toll like receptor 4 (TLR4) and downstream NF-κB, Erk1/2 and Akt signaling in ECs through a paracrine manner. Moreover, Pdcd10-overexpressed GL261 cells facilitated a formation of abnormal vasculature and increased the BBB permeability in vivo. Our present study demonstrates that upregulation of PDCD10 in GBM triggered HMGB1/TLR4 signaling in ECs and significantly decreased endothelial ZO-1 expression, which in turn dominantly increased BBB permeability and contributed to tumor progression in GBM.

The Dual Role of PDCD10 in Cancers: A Promising Therapeutic Target

Programmed cell death 10 (PDCD10) was initially considered as a protein associated with apoptosis. However, recent studies showed that PDCD10 is actually an adaptor protein. By interacting with multiple molecules, PDCD10 participates in various physiological processes, such as cell survival, migration, cell differentiation, vesicle trafficking, cellular senescence, neurovascular development, and gonadogenesis. Moreover, over the past few decades, accumulating evidence has demonstrated that the aberrant expression or mutation of PDCD10 is extremely common in various pathological processes, especially in cancers. The dysfunction of PDCD10 has been strongly implicated in oncogenesis and tumor progression. However, the updated data seem to indicate that PDCD10 has a dual role (either pro- or anti-tumor effects) in various cancer types, depending on cell/tissue specificity with different cellular interactors. In this review, we aimed to summarize the knowledge of the dual role of PDCD10 in cancers with a special focus on its cellular function and potential molecular mechanism. With these efforts, we hoped to provide new insight into the future development and application of PDCD10 as a clinical therapeutic target in cancers.

Small Extracellular Vesicles and Their Involvement in Cancer Resistance: An Up-to-Date Review

In recent years, tremendous progress has been made in understanding the roles of extracellular vesicles (EVs) in cancer. Thanks to advancements in molecular biology, it has been found that the fraction of EVs called exosomes or small EVs (sEVs) modulates the sensitivity of cancer cells to chemotherapeutic agents by delivering molecularly active non-coding RNAs (ncRNAs). An in-depth analysis shows that two main molecular mechanisms are involved in exosomal modified chemoresistance: (1) translational repression of anti-oncogenes by exosomal microRNAs (miRs) and (2) lack of translational repression of oncogenes by sponging of miRs through long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). At the cellular level, these processes increase the proliferation and survival of cancer cells and improve their ability to metastasize and resist apoptosis. In addition, studies in animal models have shown enhancing tumor size under the influence of exosomal ncRNAs. Ultimately, exosomal ncRNAs are responsible for clinically significant chemotherapy failures in patients with different types of cancer. Preliminary data have also revealed that exosomal ncRNAs can overcome chemotherapeutic agent resistance, but the results are thoroughly fragmented. This review presents how exosomes modulate the response of cancer cells to chemotherapeutic agents. Understanding how exosomes interfere with chemoresistance may become a milestone in developing new therapeutic options, but more data are still required.

PDCD10 promotes the aggressive behaviors of pituitary adenomas by up-regulating CXCR2 and activating downstream AKT/ERK signaling

As the second most common primary intracranial neoplasms, about 40% of pituitary adenomas (PAs) exhibit aggressive behaviors and resulting in poor patient prognosis. The molecular mechanisms underlying the aggressive behaviors of PAs are not yet fully understood. Biochemical studies have reported that programmed cell death 10 (PDCD10) is a component of the striatin-interacting phosphatase and kinase (STRIPAK) complex and plays a dual role in cancers in a tissue- or disease-specific manner. In the present study, we report for the first time that the role of PDCD10 in PAs. Cell proliferation, migration and invasion were either enhanced by overexpressing or inhibited by silencing PDCD10 in PA cells. Moreover, PDCD10 significantly promoted epithelial–mesenchymal transition (EMT) of pituitary adenoma cells. Mechanistically, we showed that the expression of CXCR2, together with phosphorylation levels of AKT and ERK1/2 were regulated by PDCD10. Activation of CXCR2 inversed inactivation of AKT/ERK signal pathways and the tumor-suppressive effects induced by PDCD10 silencing. Finally, the pro-oncogenic effect of PDCD10 was confirmed by in vivo tumor grafting. Taken together, we demonstrate for the first time that PDCD10 can induce aggressive behaviors of PAs by promoting cellular proliferation, migration, invasion and EMT through CXCR2-AKT/ERK signaling axis.

Programmed cell death 10 promotes metastasis and epithelial-mesenchymal transition of hepatocellular carcinoma via PP2Ac-mediated YAP activation

Tumour metastasis is the main cause of postoperative tumour recurrence and mortality in patients with hepatocellular carcinoma (HCC), but the underlying mechanism remains unclear. Accumulating evidence has demonstrated that programmed cell death 10 (PDCD10) plays an important role in many biological processes. However, the role of PDCD10 in HCC progression is still elusive. In this study, we aimed to explore the clinical significance and molecular function of PDCD10 in HCC. PDCD10 is significantly upregulated in HCC, which also correlates with aggressive clinicopathological characteristics and predicts poor prognosis of HCC patients after liver resection. High PDCD10 expression promotes HCC cell proliferation, migration, and invasion in vitro and tumour growth, metastasis in vivo. In addition, PDCD10 could facilitate epithelial-to-mesenchymal transition (EMT) of HCC cells. In terms of the mechanism, PDCD10 directly binds to the catalytic subunit of protein phosphatase 2A (PP2Ac) and increases its enzymatic activity, leading to the interaction of YAP and dephosphorylation of the YAP protein. This interaction contributes to YAP nuclear translocation and transcriptional activation. PP2Ac is necessary for PDCD10-mediated HCC progression. Knocking down PP2Ac abolished the tumour-promoting role of PDCD10 in the migration, invasion and EMT of HCC. Moreover, a PP2Ac inhibitor (LB100) could restrict tumour growth and metastasis of HCC with high PDCD10 expression. Collectively, PDCD10 promotes EMT and the progression of HCC by interacting with PP2Ac to promote YAP activation, which provides new insight into the mechanism of cancer metastasis. PDCD10 may be a potential prognostic biomarker and therapeutic target for HCC.

Overexpression of EphB4 promotes neurogenesis, but inhibits neuroinflammation in mice with acute ischemic stroke

Ischemic stroke is one of the most common diseases that has a high rate of mortality, and has become a burden to the healthcare system. Previous research has shown that EPH receptor B4 (EphB4) promotes neural stem cell proliferation and differentiation in vitro. However, little is known regarding its role in the neurogenesis of ischemic stroke in vivo. Thus, the present study aimed to verify whether EphB4 was a key regulator of neurogenesis in ischemic stroke in vivo. Cerebral ischemia was induced in C57BL/6J mice via middle cerebral artery occlusion (MCAO), followed by reperfusion. Immunofluorescence staining was performed to evaluate the effect of EphB4 on the neurogenesis in cerebral cortex. The levels of inflammatory cytokines were determined using an ELISA kit. The expression levels of ABL proto-oncogene 1, non-receptor tyrosine kinase (ABL1)/Cyclin D1 signaling pathway-related proteins were detected via western blotting. The current findings indicated that EphB4 expression was significantly increased in the cerebral cortex of MCAO model mice in comparison with sham-operated mice. Moreover, EphB4 appeared to be expressed in neural stem cells (Nestin⁺), and persisted as these cells became neuronal progenitors (Sox2⁺), neuroblasts [doublecortin (DCX)⁺], and eventually mature neurons [neuronal nuclei (NeuN)⁺]. Overexpression of EphB4 elevated the number of proliferating (bromodeoxyuridine⁺, Ki67⁺) and differentiated cells (Nestin⁺, Sox2⁺, DCX⁺ and NeuN⁺), indicating the promoting effect of EphB4 on the neurogenesis of ischemic stroke. Furthermore, EphB4 overexpression alleviated the inflammation injury in MCAO model mice. The expression levels of proteins-related to the ABL1/Cyclin D1 signaling pathway were significantly increased by the overexpression of EphB4, which suggested that restoration of EphB4 promoted the activation of the ABL1/Cyclin D1 signaling pathway. In conclusion, this study contributes to the current understanding of the mechanisms of EphB4 in exerting neurorestorative effects and may recommend a potential new strategy for ischemic stroke treatment.

Programmed Cell Death 10 Mediated CXCL2-CXCR2 Signaling in Regulating Tumor-Associated Microglia/Macrophages Recruitment in Glioblastoma

Background

Programmed cell death 10 (PDCD10) plays a crucial role in regulating tumor phenotyping, especially in glioblastoma (GBM). Glioma-associated microglia/macrophages (GAMs) in tumor pathological microenvironment contribute to GBM progression. We previously found that the infiltration of GAMs was associated with PDCD10 expression in GBM patients. The present study aims to further explore the regulation of PDCD10 on GAMs in GBM.

Methods

Overexpression of PDCD10 in human- and murine-GBM cells was established by lentiviral transduction. Cell behaviors and polarization of primary microglia, microglia- and macrophage-like cells were investigated through indirect co-culture with GBM cells in vitro respectively. The PDCD10-induced release of chemokines was identified by a chemokine protein array. The cross-talk between GBM and microglia as well as macrophages was further studied using selective antagonist SB225002. Finally, an orthotopic homograft mouse model was employed to verify the results of in vitro experiments.

Results

Indirect co-culture with PDCD10-overexpressed GBM cells promoted proliferation and migration of microglia- and macrophage-like cells, and stimulated pro-tumorigenic polarization of primary microglia, microglia- and macrophage-like cells. Pdcd10-upregulated GBM cells triggered a nearly 6-fold increase of CXC motif chemokine ligand 2 (CXCL2) release, which in turn activated CXC chemokine receptor 2 (CXCR2) and downstream Erk1/2 and Akt signaling in primary microglia, microglia- and macrophage-like cells. The blockage of CXCR2 signaling with specific inhibitor (SB225002) abolished microglia- and macrophage-like cell migration induced by PDCD10-upregulated GBM cells. Moreover, Pdcd10-upregulated GL261 cells promoted GAMs recruitment and tumor growth in vivo.

Conclusion

Our study demonstrates that overexpression of PDCD10 in GBM recruits and activates microglia/macrophages, which in turn promotes tumor progression. CXCL2-CXCR2 signaling mediated by PDCD10 is potentially involved in the crosstalk between GBM cells and GAMs.

YY1 regulated transcription-based stratification of gastric tumors and identification of potential therapeutic candidates

Gastric cancer is one of the leading causes of cancer-related death worldwide. The transcription factor YY1 regulates diverse biological processes, including cell proliferation, development, DNA damage responses, and carcinogenesis. This study was designed to explore the role of YY1 regulated transcription in gastric cancer. YY1 silencing in gastric cancer cells has resulted in the inhibition of Wnt/β-catenin, JNK/MAPK, ERK/MAPK, ER, and HIF-1α signaling pathways. Genome-wide mRNA profiling upon silencing the expression YY1 gene in gastric cancer cells and comparison with the previously identified YY1 regulated genes from other lineages revealed a moderate overlap among the YY1 regulated genes. Despite the differing genes, all the YY1 regulated gene sets were expressed in most of the intestinal subtype gastric tumors and a subset of diffuse subtype gastric tumors. Integrative functional genomic analysis of the YY1 gene sets revealed an association among the pathways Wnt/β-catenin, Rapamycin, Cyclin-D1, Myc, E2F, PDGF, and AKT. Further, the drugs capable of inhibiting YY1 mediated transcription were identified as suitable targeted therapeutic candidates for gastric tumors with activated YY1. The data emerging from the investigation would pave the way for the development of YY1-based targeted therapeutics for gastric cancer.