Type II cGMP-dependent protein kinase inhibits activation of key members of the RTK family in gastric cancer cells

Prognostic biomarkers and molecular pathways mediating Helicobacter pylori–induced gastric cancer: a network-biology approach

Cancer of the stomach is the second most frequent cancer-related death worldwide. The survival rate of patients with gastric cancer (GC) remains fragile. There is a requirement to discover biomarkers for prognosis approaches. Helicobacter pylori in the stomach is closely associated with the progression of GC. We identified the genes associated with poor/favorable prognosis in H. pylori–induced GC. Multivariate statistical analysis was applied on the Gene Expression Omnibus (GEO) dataset GSE54397 to identify differentially expressed miRNAs (DEMs) in gastric tissues with H. pylori–induced cancer compared with the H. pylori–positive with non-cancerous tissue. A protein interaction map (PIM) was built and subjected to DEMs targets. The enriched pathways and biological processes within the PIM were identified based on substantial clusters. Thereafter, the most critical genes in the PIM were illustrated, and their prognostic impact in GC was investigated. Considering p-value less than 0.01 and |Log2 fold change| as >1, five microRNAs demonstrated significant changes among the two groups. Gene functional analysis revealed that the ubiquitination system, neddylation pathway, and ciliary process are primarily involved in H. pylori–induced GC. Survival analysis illustrated that the overexpression of DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, and TXNIP was associated with poor prognosis, while increased MRPS5 expression was related to a favorable prognosis in GC patients. DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, TXNIP, and MRPS5 may be considered prognostic biomarkers for H. pylori–induced GC. However, experimental validation is necessary in the future.

Molecular Mechanisms of Nitric Oxide in Cancer Progression, Signal Transduction, and Metabolism

SIGNIFICANCE

Cancer is a complex disease, which not only involves the tumor but its microenvironment comprising different immune cells as well. Nitric oxide (NO) plays specific roles within tumor cells and the microenvironment and determines the rate of cancer progression, therapy efficacy, and patient prognosis. Recent Advances: Key understanding of the processes leading to dysregulated NO flux within the tumor microenvironment over the past decade has provided better understanding of the dichotomous role of NO in cancer and its importance in shaping the immune landscape. It is becoming increasingly evident that nitric oxide synthase 2 (NOS2)-mediated NO/reactive nitrogen oxide species (RNS) are heavily involved in cancer progression and metastasis in different types of tumor. More recent studies have found that NO from NOS2+ macrophages is required for cancer immunotherapy to be effective.

CRITICAL ISSUES

NO/RNS, unlike other molecules, are unique in their ability to target a plethora of oncogenic pathways during cancer progression. In this review, we subcategorize the different levels of NO produced by cells and shed light on the context-dependent temporal effects on cancer signaling and metabolic shift in the tumor microenvironment.

FUTURE DIRECTIONS

Understanding the source of NO and its spaciotemporal profile within the tumor microenvironment could help improve efficacy of cancer immunotherapies by improving tumor infiltration of immune cells for better tumor clearance.

PKG II inhibits PDGF-BB triggered biological activities by phosphorylating PDGFRβ in gastric cancer cells

Previous studies revealed that type II cGMP-dependent protein kinase G (PKG II) could inhibit the activation of epidermal growth factor receptor (EGFR) which is a widely investigated RTK. PDGFR belongs to family of receptor tyrosine kinases (RTKs) too. However, the effect of PKG II on PDGFR activation is not clear yet. This study investigated potential regulatory effect of PKG II on activation of PDGFRβ and the downstream signaling transductions in gastric cancer. The results from CCK8 assay and Transwell assay indicated that PDGF-BB induced cell proliferation and migration. Activated PKG II reversed the above variations caused by PDGF-BB. Immunoprecipitation and Western blotting results showed that PKG II combined with PDGFRβ and phosphorylated this receptor, and thereby inhibited PDGF-BB induced activation of PDGFRβ, and MAPK/ERK and PI3K/Akt mediated signal transduction pathways. Based on the prediction by phosphorylation site software, Ser643 and Ser712 were mutated to alanine respectively which prevented phosphorylation at these sites. Mutation at Ser712 abolished the inhibitory function of PKG II on PDGFRβ activation but mutation of Ser643 had no such an effect, indicating that Ser712 was PKG II-specific phosphorylating site of PDGFRβ. In conclusion, PKG II inhibited PDGFRβ activation in gastric cancer via phosphorylating Ser712 of this RTK.

Cyclic Guanosine Monophosphate (cGMP)-Dependent Protein Kinase II Blocks Epidermal Growth Factor (EGF)/Epidermal Growth Factor Receptor (EGFR)-Induced Biological Effects on Osteosarcoma Cells

Background

The present work was performed to detect the potential inhibitory effect of cyclic guanosine monophosphate (cGMP)-dependent protein kinase II (PKG II) on epidermal growth factor (EGF) receptor-induced biological activity and related signal cascades in osteosarcoma cells.

Material/Methods

We transfected the osteosarcoma MG-63 cell line with an adenoviral vector encoding PKG II cDNA (Ad-PKGII) and incubated the transfected cells with 250 μM 8-pCPT-cGMP to activate the PKG II. We stimulated the MG-63 cells with100 ng/ml EGF, and then detected their proliferation using a CCK-8 assay. Transwell assay was used to examine MG-63 cell migration; and Western blot analysis was used to detect expression of matrix metalloproteinase 9 (MMP-9) and activation of ERK and Akt.

Results

Stimulating cells by 100 ng/ml EGF promoted MG-63 cell proliferation and migration, ERK and Akt phosphorylation, and MMP-9 expression. These effects of EGF were inhibited in MG-63 cells infected with Ad-PKGII and incubated with 8-pCPT-cGMP.

Conclusions

Our results demonstrate that Ad-PKGII infection significantly inhibited EGF-induced proliferation and migration, as well as the associated-signal cascades; which indicates that PKG II might be a potential anti-cancer factor.

PKG II reverses HGF-triggered cellular activities by phosphorylating serine 985 of c-Met in gastric cancer cells

Previous studies showed that type II cGMP-dependent protein kinase G (PKG II) could inhibit the activation of epidermal growth factor receptor (EGFR). Both c-Met and EGFR belong to family of receptor tyrosine kinases (RTKs) and have high molecular analogy. However, the effect of PKG II on c-Met activation is unclear. This study was designed to investigate the inhibitory effect of PKG II on the activation of c-Met and consequent biological activities. The results from CCK8 assay, Transwell assay and TUNEL assay showed that HGF enhanced cell proliferation and migration, and decreased cell apoptosis. Activated PKG II reversed the above changes caused by HGF. Immunoprecipitation and Western blotting results showed that PKG II could bind with c-Met and phosphorylate its Ser985, and thereby inhibited HGF-induced activation of c-Met and MAPK/ERK and PI3K/Akt/mTOR mediated signal transduction. When Ser985 of c-Met was mutated to Alanine for preventing phosphorylation of this site, the blocking effect of PKG II on c-Met activation was annulled. When Ser985 of c-Met was mutated to Aspartic acid for mimicking phosphorylation of this site, HGF-induced activation of c-Met was prevented. In conclusion, the results indicated that PKG II could block c-Met activation via phosphorylating Ser985 of this RTK.

Platelet-derived growth factor receptors (PDGFRs) fusion genes involvement in hematological malignancies

PURPOSE

To investigate oncogenic platelet-derived growth factor receptor(PDGFR) fusion genes involvement in hematological malignancies, the advances in the PDGFR fusion genes diagnosis and development of PDGFR fusions inhibitors.

METHODS

Literature search was done using terms "PDGFR and Fusion" or "PDGFR and Myeloid neoplasm" or 'PDGFR and Lymphoid neoplasm' or "PDGFR Fusion Diagnosis" or "PDGFR Fusion Targets" in databases including PubMed, ASCO.org, and Medscape.

RESULTS

Out of the 36 fusions detected, ETV6(TEL)-PDGFRB and FIP1L1-PDGFRA fusions were frequently detected, 33 are as a result of chromosomal translocation, FIP1L1-PDGFRA and EBF1-PDGFRB are the result of chromosomal deletion and CDK5RAP2- PDGFRΑ is the result of chromosomal insertion. Seven of the 34 rare fusions have detectable reciprocals.

CONCLUSION

RNA aptamers are promising therapeutic target of PDGFRs and diagnostic tools of PDGFRs fusion genes. Also, PDGFRs have variable prospective therapeutic strategies including small molecules, RNA aptamers, and interference therapeutics as well as development of adaptor protein Lnk mimetic drugs.

Platelet-derived growth factor receptor/platelet-derived growth factor (PDGFR/PDGF) system is a prognostic and treatment response biomarker with multifarious therapeutic targets in cancers

Progress in cancer biology has led to an increasing discovery of oncogenic alterations of the platelet-derived growth factor receptors (PDGFRs) in cancers. In addition, their overexpression in numerous cancers invariably makes PDGFRs and platelet-derived growth factors (PDGFs) prognostic and treatment markers in some cancers. The oncologic alterations of the PDGFR/PDGF system affect the extracellular, transmembrane and tyrosine kinase domains as well as the juxtamembrane segment of the receptor. The receptor is also involved in fusions with intracellular proteins and receptor tyrosine kinase. These discoveries undoubtedly make the system an attractive oncologic therapeutic target. This review covers elementary biology of PDGFR/PDGF system and its role as a prognostic and treatment marker in cancers. In addition, the multifarious therapeutic targets of PDGFR/PDGF system are discussed. Great potential exists in the role of PDGFR/PDGF system as a prognostic and treatment marker and for further exploration of its multifarious therapeutic targets in safe and efficacious management of cancer treatments.

The platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) are major players in oncogenesis, drug resistance, and attractive oncologic targets in cancer

The platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) play a key role in signaling pathways in oncogenesis. The overexpression of PDGFs and PDGFRs and the oncogenic alterations of these receptors have been implicated in human cancers and correlated significantly with poor outcomes. This review discusses the biology of the PDGF isoforms and receptors briefly, and their role in oncogenesis. Also, the attractiveness of targeting PDGFs and PDGFRs, based on a wide display of oncologic alterations in cancers, diverse therapeutic strategies, their roles in resistance to cancer treatments with prospects of overcoming drug resistance, and the extent to which validated biomarkers have been developed for effective PDGFs and PDGFRs-based cancer management are discussed.

Interaction of cCMP with the cGK, cAK and MAPK Kinases in Murine Tissues

cAMP and cGMP are well established second messengers that are essential for numerous (patho)physiological processes. These purine cyclic nucleotides activate cAK and cGK, respectively. Recently, the existence of cCMP was described, and a possible function for this cyclic nucleotide was investigated. It was postulated that cCMP plays a role as a second messenger. However, the functions regulated by cCMP are mostly unknown. To elucidate probable functions, cCMP-binding and -activated proteins were identified using different methods. We investigated the effect of cCMP on purified cyclic nucleotide-dependent protein kinases and lung and jejunum tissues of wild type (WT), cGKI-knockout (cGKI KO) and cGKII-knockout (cGKII KO) mice. The catalytic activity of protein kinases was measured by a (γ-³²P) ATP kinase assay. Cyclic nucleotide-dependent protein kinases (cAK, cGKI and cGKII) in WT tissue lysates were stimulated by cCMP. In contrast, there was no stimulation of phosphorylation in KO tissue lysates. Competitive binding assays identified cAK, cGKI, and cGKII as cCMP-binding proteins. An interaction between cCMP/MAPK and a protein-protein complex of MAPK/cGK were detected via cCMP affinity chromatography and co-immunoprecipitation, respectively. These complexes were abolished or reduced in jejunum tissues from cGKI KO or cGKII KO mice. In contrast, these complexes were observed in the lung tissues from WT, cGKI KO and cGKII KO mice. Moreover, cCMP was also able to stimulate the phosphorylation of MAPK. These results suggest that MAPK signaling is regulated by cGMP-dependent protein kinases upon activation by cCMP. Based on these results, we propose that additional cCMP-dependent protein kinases that are capable of modulating MAPK signaling could exist. Hence, cCMP could potentially act as a second messenger in the cAK/cGK and MAPK signaling pathways and play an important role in physiological processes of the jejunum and lung.

Knockdown of EGFR inhibits growth and invasion of gastric cancer cells

The epidermal growth factor receptor (EGFR) is an oncogenic trans-membranous receptor, which is overexpressed in multiple human cancers. However, the role of EGFR in gastric cancer (GC) is still elusive. In this study, we aimed to investigate the expression and molecular mechanisms of EGFR in GC cells. Forty cases of GC and the corresponding adjacent non-cancerous tissues (ANCT) were collected, and the expression of EGFR was assessed using immunohistochemistry in biopsy samples. Furthermore, EGFR signaling was blocked by constructed recombinant small hairpin RNA lentiviral vector (Lv-shRAGE) used to transfect into human GC SGC-7901 cells. The expression of AKT, proliferating cell nuclear antigen (PCNA) and matrix metallopeptidase-9 (MMP-9) was detected by real-time PCR and western blotting assays. Cell proliferative activities and invasive capability were, respectively, determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and Transwell assays. Cell apoptosis and cycle distribution were analyzed by flow cytometry. EGFR was found highly expressed in cancer tissues compared with the ANCT and correlated with lymph node metastases. Knockdown of EGFR reduced cell proliferation and invasion of GC with decreased expression of AKT, PCNA and MMP-9 and induced cell apoptosis and cycle arrest. Upregulation of EGFR expression is associated with lymph node metastases of GC, and blockade of EGFR signaling suppresses growth and invasion of GC cells through AKT pathway, suggesting that EGFR may represent a potential therapeutic target for this aggressive malignancy.