Down-Regulation of PDCD4 Promotes Proliferation, Angiogenesis and Tumorigenesis in Glioma Cells

Platycodin D suppresses proliferation, migration, and invasion of human glioblastoma cells through regulation of Skp2

BACKGROUND

Platycodin D (PD) is a major bioactive component of Platycodon grandiflorum, a medicinal herb that is widely used in China, and is effective against various human cancers, including glioblastoma multiforme (GBM). S phase kinase-related protein 2 (Skp2) is oncogenic and overexpressed in various human tumors. It is highly expressed in GBM and its expression is correlated with tumor growth, drug resistance and poor prognosis. In this study, we investigated whether inhibition of glioma progression by PD is mediated by decreasing expression of Skp2.

METHODS

Cell Counting Kit-8 (CCK-8) and Transwell assays were used to determine the effects of PD on GBM cell proliferation, migration, and invasion in vitro. mRNA and protein expression were determined by real time polymerase chain reaction (RT-PCR) and western blotting, respectively. The U87 xenograft model was used to verify the anti-glioma effect of PD in vivo. Expression levels of Skp2 protein were analyzed by immunofluorescence staining.

RESULTS

PD suppressed proliferation and motility of GBM cells in vitro. The expression of Skp2 in U87 and U251 cells was significantly reduced by PD. PD mainly decreased the cytoplasmic expression of Skp2 in glioma cells. Skp2 protein expression was downregulated by PD, resulting in upregulation of its downstream targets, p21and p27. The inhibitory effect of PD was enhanced by Skp2 knockdown in GBM cells and reversed in cells with Skp2 overexpression.

CONCLUSION

PD suppresses glioma development by regulation of Skp2 in GBM cells.

microRNAs (miRNAs) in Glioblastoma Multiforme (GBM)-Recent Literature Review

Glioblastoma multiforme (GBM) is the most common, malignant, poorly promising primary brain tumor. GBM is characterized by an infiltrating growth nature, abundant vascularization, and a rapid and aggressive clinical course. For many years, the standard treatment of gliomas has invariably been surgical treatment supported by radio- and chemotherapy. Due to the location and significant resistance of gliomas to conventional therapies, the prognosis of glioblastoma patients is very poor and the cure rate is low. The search for new therapy targets and effective therapeutic tools for cancer treatment is a current challenge for medicine and science. microRNAs (miRNAs) play a key role in many cellular processes, such as growth, differentiation, cell division, apoptosis, and cell signaling. Their discovery was a breakthrough in the diagnosis and prognosis of many diseases. Understanding the structure of miRNAs may contribute to the understanding of the mechanisms of cellular regulation dependent on miRNA and the pathogenesis of diseases underlying these short non-coding RNAs, including glial brain tumors. This paper provides a detailed review of the latest reports on the relationship between changes in the expression of individual microRNAs and the formation and development of gliomas. The use of miRNAs in the treatment of this cancer is also discussed.

Knockdown of PDCD4 ameliorates neural cell apoptosis and mitochondrial injury through activating the PI3K/AKT/mTOR signal in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a complex neurodegenerative disorder and hampers normal living. It has been reported that programmed cell death 4 (PDCD4) is associated with tumor suppression, inflammatory response, and apoptosis.

OBJECTIVE

The aim of this study was to investigate the role of PDCD4 in PD.

METHODS

The in vivo and in vitro PD models were established by MPTP-induced mice and MMP+ stimulated MN9D cells, respectively. The expression of PDCD4 was detected by western blot. The MN9D cell viability and apoptosis were determined by MTT and flow cytometry assay. Moreover, the MN9D cell mitochondrial injury was evaluated by JC-1 staining.

RESULTS

In this study, PDCD4 was highly expressed in brain tissue of MPTP-induced PD mouse model. In a loss-function experiments, knockdown of PDCD4 promoted MN9D cell viability and allayed MPP+-triggered MN9D cell apoptosis. Furthermore, knockdown of PDCD4 ameliorated MPP+-evoked MN9D cell mitochondrial injury. Mechanically, knockdown of PDCD4 abolished the effect of MMP+ stimulation via activating phosphoinositide 3-kinase(PI3K)/AKT/mammalian target of rapamycin (mTOR) signal. Notably, the protective effects of shPDCD4 on cell apoptosis and mitochondrial injury were suppressed by PI3K inhibitor LY294002.

CONCLUSION

In summary,knockdown of PDCD4 ameliorates neural cell apoptosis and mitochondrial injury through activating the PI3K/AKT/mTOR signal, providing a novel target for PD treatment.

AVAILABILITY OF DATA AND MATERIALS

All data generated or analyzed during this study are included in this published article.

Remodeling the tumor immune microenvironment with oncolytic viruses expressing miRNAs

MiRNAs (miRNA, miR) play important functions in the tumor microenvironment (TME) by silencing gene expression through RNA interference. They are involved in regulating both tumor progression and tumor suppression. The pathways involved in miRNA processing and the miRNAs themselves are dysregulated in cancer. Consequently, they have become attractive therapeutic targets as underscored by the plethora of miRNA-based therapies currently in pre-clinical and clinical studies. It has been shown that miRNAs can be used to improve oncolytic viruses (OVs) and enable superior viral oncolysis, tumor suppression and immune modulation. In these cases, miRNAs are empirically selected to improve viral oncolysis, which translates into decreased tumor growth in multiple murine models. While this infectious process is critical to OV therapy, optimal immunomodulation is crucial for the establishment of a targeted and durable effect, resulting in cancer eradication. Through numerous mechanisms, OVs elicit a strong antitumor immune response that can also be further improved by miRNAs. They are known to regulate components of the immune TME and promote effector functions, antigen presentation, phenotypical polarization, and varying levels of immunosuppression. Reciprocally, OVs have the power to overcome the limitations encountered in canonical miRNA-based therapies. They deliver therapeutic payloads directly into the TME and facilitate their amplification through selective tumoral tropism and abundant viral replication. This way, off-target effects can be minimized. This review will explore the ways in which miRNAs can synergistically enhance OV immunotherapy to provide the basis for future therapeutics based on this versatile combination platform.

Expression levels and network analysis of inflammamiRs in peripheral blood mononuclear cells exposed to DDE "in vitro"

Recent studies have demonstrated that dichlorodiphenyldichloroethylene (DDE) induced a pro-inflammatory condition in peripheral blood mononuclear cells (PBMC). However, the molecular mechanisms implicated in this condition are poorly understood. Therefore, this study aimed to evaluate miR-155, miR-126, and miR-21 expression levels in PBMC exposed "in vitro" to DDE. PBMC were dosed with increasing concentrations of DDE (10-80 µg mL^-1) at different treatment times (0-24 h). The results showed an up-regulation in the expression levels of assessed miRNAs (miR-155, miR-146, and miR-21) after PBMCs were exposed to DDE. Besides, bioinformatic analysis was performed to understand the biological roles of assessed miRNAs. The bioinformatic analysis shows that assessed miRNAs are associated with regulating signaling pathways involved in cancer, apoptosis, cell cycle, inflammation, metabolism, etc. These findings offer new insights into the molecular mechanisms related to the inflammatory processes and their regulation induced by DDE in PBMC exposed "in vitro".

Immunological classification of hepatitis B virus-positive hepatocellular carcinoma by transcriptome analysis

BACKGROUND

Hepatitis B virus (HBV) infection is a major factor responsible for HBV+ hepatocellular carcinoma (HCC).

AIM

An immunological classification of HBV+ HCC may provide both biological insights and clinical implications for this disease.

METHODS

Based on the enrichment of 23 immune signatures, we identified two immune-specific subtypes (Imm-H and Imm-L) of HBV+ HCC by unsupervised clustering. We showed that this subtyping method was reproducible and predictable by analyzing three different datasets.

RESULTS

Compared to Imm-L, Imm-H displayed stronger immunity, more stromal components, lower tumor purity, lower stemness and intratumor heterogeneity, lower-level copy number alterations, higher global methylation level, and better overall and disease-free survival prognosis. Besides immune-related pathways, stromal pathways (ECM receptor interaction, focal adhesion, and regulation of actin cytoskeleton) and neuro-related pathways (neuroactive ligand-receptor interaction, and prion diseases) were more highly enriched in Imm-H than in Imm-L. We identified nine proteins differentially expressed between Imm-H and Imm-L, of which MYH11, PDCD4, Dvl3, and Syk were upregulated in Imm-H, while PCNA, Acetyl-a-Tubulin-Lys40, ER-α_pS118, Cyclin E2, and β-Catenin were upregulated in Imm-L.

CONCLUSION

Our data suggest that “hot” tumors have a better prognosis than “cold” tumors in HBV+ HCC and that “hot” tumors respond better to immunotherapy.

PM2.5 induces pulmonary microvascular injury in COPD via METTL16-mediated m6A modification

Fine particulate matter (PM2.5) exposure is a significant cause of chronic obstructive pulmonary disease (COPD), but the detailed mechanisms involved in COPD remain unclear. In this study, we established PM2.5-induced COPD rat models and showed that PM2.5 induced pulmonary microvascular injury via accelerating vascular endothelial apoptosis, increasing vascular permeability, and reducing angiogenesis, thereby contributing to COPD development. Moreover, microvascular injury in COPD was validated by measurements of plasma endothelial microparticles (EMPs) and serum VEGF in COPD patients. We then performed m⁶A sequencing, which confirmed that altered N⁶-methyladenosine (m⁶A) modification was induced by PM2.5 exposure. The results of a series of experiments demonstrated that the expression of methyltransferase-like protein 16 (METTL16), an m⁶A regulator, was upregulated in PM2.5-induced COPD rats, while the expression of other regulators did not differ upon PM2.5-induction. To clarify the regulatory effect of METTL16-mediated m⁶A modification induced by PM2.5 on pulmonary microvascular injury, cell apoptosis, permeability, and tube formation, the m⁶A level in METTL16-knockdown pulmonary microvascular endothelial cells (PMVECs) was evaluated, and the target genes of METTL16 were identified from a set of the differentially expressed and m⁶A-methylated genes associated with vascular injury and containing predicted sites of METTL16 methylation. The results showed that Sulfatase 2 (Sulf2) and Cytohesin-1 (Cyth1) containing the predicted METTL16 methylation sites, exhibited higher m⁶A methylation and were downregulated after PM2.5 exposure. Further studies demonstrated that METTL16 may regulate Sulf2 expression via m⁶A modification and thereby contribute to PM2.5-induced microvascular injury. These findings not only provide a better understanding of the role played by m⁶A modification in PM2.5-induced microvascular injury, but also identify a new therapeutic target for COPD.

Exosomal and intracellular miR-320b promotes lymphatic metastasis in esophageal squamous cell carcinoma

Cancer-cell-released exosomal microRNAs (miRNAs) are important mediators of cell-cell communication in the tumor microenvironment. In this study, we sequenced serum exosome miRNAs from esophageal squamous cell carcinoma (ESCC) patients and identified high expression of miR-320b to be closely associated with peritumoral lymphangiogenesis and lymph node (LN) metastasis. Functionally, miR-320b could be enriched and transferred by ESCC-released exosomes directly to human lymphatic endothelial cells (HLECs), promoting tube formation and migration in vitro and facilitating lymphangiogenesis and LN metastasis in vivo as assessed by gain- and loss-of-function experiments. Furthermore, we found programmed cell death 4 (PDCD4) as a direct target of miR-320b through bioinformatic prediction and luciferase reporter assay. Re-expression of PDCD4 could rescue the effects induced by exosomal miR-320b. Notably, the miR-320b-PDCD4 axis activates the AKT pathway in HLECs independent of vascular endothelial growth factor-C (VEGF-C). Moreover, overexpression of miR-320b promotes the proliferation, migration, invasion, and epithelial-mesenchymal transition progression of ESCC cells. Finally, we demonstrate that METTL3 could interact with DGCR8 protein and positively modulate pri-miR-320b maturation process in an N6-methyladenosine (m6A)-dependent manner. Therefore, our findings uncover a VEGF-C-independent mechanism of exosomal and intracellular miR-320b-mediated LN metastasis and identify miR-320b as a novel predictive marker and therapeutic target for LN metastasis in ESCC.

The interaction between PDCD4 and YB1 is critical for cervical cancer stemness and cisplatin resistance

Cancer multidrug resistance (MDR) is existence in stem cell-like cancer cells characterized by stemness including high-proliferation and self-renewal. Programmed cell death 4 (PDCD4), as a proapoptotic gene, whether it engaged in cancer stemness and cisplatin resistance is still unknown. Here we showed that PDCD4 expressions in Hela/DDP (cisplatin resistance) cells were lower than in parental Hela cells. Moreover, the levels of drug resistance genes and typical stemness markers were markedly elevated in Hela/DDP cells. In vivo, xenograft tumor assay confirmed that knockdown of PDCD4 accelerated the grafted tumor growth. In vitro, colony formation and MTT assay demonstrated that PDCD4 overexpression inhibited cells proliferation in conditions with or without cisplatin. By contrast, PDCD4 deficiency provoked cell proliferation and cisplatin resistance. On mechanism, PDCD4 decreased the protein levels of pAKT and pYB1, accompanied by reduced MDR1 expression. Correspondingly, luciferase reporter assay showed PDCD4 regulated MDR1 promoter activity entirely relied on YB1. Furthermore, Ch-IP, GST-pulldown, and Co-IP assays provided novel evidence that PDCD4 could directly bind with YB1 by the nucleolar localization signal (NOLS) segment, causing the reduced YB1 binding into the MDR1 promoter region through blocking YB1 nucleus translocation, triggering the decreased MDR1 transcription. Taken together, PDCD4-pAKT-pYB1 forms the integrated molecular network to regulate MDR1 transcription during the process of stemness-associated cisplatin resistance.