Type II cGMP-dependent protein kinase inhibits EGF-induced JAK/STAT signaling in gastric cancer cells

Genistein Directly Represses the Phosphorylation of STAT5 in Lactating Mammary Epithelial Cells

Genistein is a soy isoflavone and shows various physiological activities, such as affinities for estrogen receptors (ERs) and inhibitory effects on the epidermal growth factor receptor (EGFR) pathway. A previous study reported that genistein downregulates milk production ability in mammary epithelial cells (MECs) while decreasing the phosphorylation of STAT5. The ER and EGFR pathways indirectly regulate STAT5. In this study, the repressing mechanism of genistein against the phosphorylation of STAT5 was investigated using a culture model of mouse MECs with milk production ability. The results revealed that genistein did not influence the behavior of ERα and ERβ, whereas genistein immediately repressed the phosphorylation of ERK1/2. However, the decrease in phosphorylated STAT5 occurred independent of the phosphorylation of EGFR. Genistein repressed new phosphorylation of STAT5 by prolactin without influencing the phosphorylation of JAK2. In conclusion, this study indicates that genistein directly inhibits the phosphorylation of STAT5 in lactating MECs.

Active PKG II inhibited the growth and migration of ovarian cancer cells through blocking Raf/MEK and PI3K/Akt signaling pathways

Despite advances in chemotherapy, ovarian cancer (OC) is still the most lethal gynecologic malignancy. So, it is imperative to explore its mechanism and find novel targets to improve the outcome. Type II cyclic guanosine 3′,5′-monophosphate (cGMP)-dependent protein kinase (PKG II) has been recently reported to inhibit proliferation and metastasis in several tumors. The present study is to clarify the effect of PKG II combined with l-arginine (l-Arg) on OC cells. SKOV3 and A2780 cells were infected with adenovirus coding cDNA of PKG II to increase PKG II expression and l-Arg was applied to activate this kinase. CCK8 assay, Transwell migration and TUNEL assay were applied to detect the proliferation, migration and apoptosis of the OC cells, respectively. Western blotting was used to detect the level of total and phosphorylated proteins. Our results showed that co-treatment with PKG II and l-Arg inhibited EGF-induced proliferation and the expression of Proliferating Cell Nuclear Antigen (PCNA), Cyclin E and N-Cadherin, whereas up-regulated the expression of E-Cadherin, abolished the anti-apoptotic effect of EGF, prevented the process of epithelial-to-mesenchymal transition (EMT) as well as blocked EGF-triggered Raf-MEK and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways. Our results suggested that PKG II activated by l-Arg could inhibit proliferation and migration and promote the apoptosis of OC cells. Based on the above results and our previous data, it is speculated that PKG II is an inhibitor of cancer with extensive effects.

Therapeutic opportunities in colon cancer: Focus on phosphodiesterase inhibitors

Despite novel technologies, colon cancer remains undiagnosed and 25% of patients are diagnosed with metastatic colon cancer. Resistant to chemotherapeutic agents is one of the major problems associated with treating colon cancer which creates the need to develop novel agents targeting towards newer targets. A phosphodiesterase is a group of isoenzyme, which, hydrolyze cyclic nucleotides and thereby lowers intracellular levels of cAMP and cGMP leading to tumorigenic effects. Many in vitro and in vivo studies have confirmed increased PDE expression in different types of cancers including colon cancer. cAMP-specific PDE inhibitors increase intracellular cAMP that leads to activation of effector molecules-cAMP-dependent protein kinase A, exchange protein activated by cAMP and cAMP gated ion channels. These molecules regulate cellular responses and exert its anticancer role through different mechanisms including apoptosis, inhibition of angiogenesis, upregulating tumor suppressor genes and suppressing oncogenes. On the other hand, cGMP specific PDE inhibitors exhibit anticancer effects through cGMP dependent protein kinase and cGMP dependent cation channels. Elevation in cGMP works through activation of caspases, suppression of Wnt/b-catenin pathway and TCF transcription leading to inhibition of CDK and survivin. These studies point out towards the fact that PDE inhibition is associated with anti-proliferative, anti-apoptotic and anti-angiogenic pathways involved in its anticancer effects in colon cancer. Thus, inhibition of PDE enzymes can be used as a novel approach to treat colon cancer. This review will focus on cAMP and cGMP signaling pathways leading to tumorigenesis and the use of PDE inhibitors in colon cancer.

Resveratrol provides neuroprotection by regulating the JAK2/STAT3/PI3K/AKT/mTOR pathway after stroke in rats

Ischemic stroke is a common disease with high mortality and morbidity worldwide. One of the important pathophysiological effects of ischemic stroke is apoptosis. A neuroprotective effect is defined as the inhibition of neuronal apoptosis to rescue or delay the infarction in the surviving ischemic penumbra. Resveratrol is a natural polyphenol that reportedly prevents cerebral ischemia injury by regulating the expression of PI3K/AKT/mTOR. Therefore, this study aimed to elucidate the neuroprotective effect of resveratrol on cerebral ischemia/reperfusion injury and to investigate the signaling pathways and mechanisms through which resveratrol regulates apoptosis in the ischemic penumbra. Rats were subjected to middle cerebral artery occlusion for 2 h followed by 24 h reperfusion. Cerebral infarct volume was measured using 2% TTC staining. TUNEL staining was conducted to evaluate neuronal apoptosis. Western blotting and immunohistochemistry were used to detect the proteins involved in the JAK2/STAT3/PI3K/AKT/mTOR pathway. The results suggested that resveratrol significantly improved neurological function, reduced cerebral infarct volume, decreased neuronal damage, and markedly attenuated neuronal apoptosis; these effects were attenuated by the inhibition of PI3K/AKT with LY294002 and JAK2/STAT3 with AG490. We also found that resveratrol significantly upregulated the expression of p-JAK2, p-STAT3, p-AKT, p-mTOR, and BCL-2 and downregulated expression of cleaved caspase-3 and BAX, which was partially reversed by LY294002 and AG490. These results suggested that resveratrol provides a neuroprotective effect against cerebral ischemia/reperfusion injury, which is partially mediated by the activation of JAK2/STAT3 and PI3K/AKT/mTOR. Resveratrol may indirectly upregulate the PI3K/AKT/mTOR pathway by activating JAK2/STAT3.

Protein Kinases Type II (PKG II) Combined with L-Arginine Significantly Ameliorated Xenograft Tumor Development: Is L-Arginine a Potential Alternative in PKG II Activation?

BACKGROUND The mammalian cyclic guanosine monophosphate (cGMP)-dependent protein kinases type II (PKG II) plays critical physiological or pathological functions in different tissues. However, the biological effects of PKG II are dependent on cGMP. Published data indicated that L-arginine (L-Arg) promoted NO production, NO can activate soluble guanylate cyclase (sGC), and catalyzes guanosine triphosphate (GTP) into cGMP, which suggested L-Arg could activate PKG II. Therefore, the present work was performed to address: (i) whether L-Arg could be a potential alternative in PKG II activation, and (ii) whether L-Arg also contributes to PKG II against cancer. MATERIAL AND METHODS Nude BALB/c mice were inoculated with human MCF-7, HepG2, and SW480 cell lines via subcutaneous (s.c.) injecting. After 7 days of inoculation, Ad-PKG II was injected into the cancer tissues every 4 days, and the next day 10 μmol/mouse L-Arg was administered. Western blotting and immunohistochemistry were used to assess protein expression. RESULTS Our results demonstrated that L-Arg significantly activated PKG II and effectively ameliorated xenograft tumor development through inhibiting cancer growth, angiogenesis, and metastasis, which was partially dependent on blocking of epidermal growth factor receptor (EGFR) activity, as well as downstream signaling pathways such as Erk1/2. CONCLUSIONS Our results provide an exciting new insight: L-Arg is a potential alternative to PKG II activation.

The constitutively active PKG II mutant effectively inhibits gastric cancer development via a blockade of EGF/EGFR-associated signalling cascades

Type II cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG II) is a membrane-anchored enzyme expressed mainly in the intestinal mucosa and the brain, and is associated with various physiological or pathological processes. Upregulation of PKG II is known to induce apoptosis and inhibit proliferation and metastasis of cancer cells. The inhibitory effect of PKG II has been shown to be dependent on the inhibition of the activation of epidermal growth factor receptor (EGFR) and blockade of EGFR downstream signal transduction in vitro. However, it remains unclear whether similar phenomena/mechanisms exist in vivo and whether these effects are independent of cGMP or cGMP analogues. In the present work, nude mice with transplanted orthotopic tumours were infected with adenovirus encoding cDNA of constitutively active PKG II mutant (Ad-a-PKG II) and the effect of constitutively active PKG II (a-PKG II) on tumour development was detected. The results showed that a-PKG II effectively ameliorated gastric tumour development through delaying the growth, inducing the apoptosis, and inhibiting the metastasis and angiogenesis. The effect was related to blockade of EGFR activation and abrogation of the downstream signalling cascades. These findings provide novel insight which will benefit the development of new cancer therapies.

Identification of potential tissue-specific cancer biomarkers and development of cancer versus normal genomic classifiers

Machine learning techniques for cancer prediction and biomarker discovery can hasten cancer detection and significantly improve prognosis. Recent “OMICS” studies which include a variety of cancer and normal tissue samples along with machine learning approaches have the potential to further accelerate such discovery. To demonstrate this potential, 2,175 gene expression samples from nine tissue types were obtained to identify gene sets whose expression is characteristic of each cancer class. Using random forests classification and ten-fold cross-validation, we developed nine single-tissue classifiers, two multi-tissue cancer-versus-normal classifiers, and one multi-tissue normal classifier. Given a sample of a specified tissue type, the single-tissue models classified samples as cancer or normal with a testing accuracy between 85.29% and 100%. Given a sample of non-specific tissue type, the multi-tissue bi-class model classified the sample as cancer versus normal with a testing accuracy of 97.89%. Given a sample of non-specific tissue type, the multi-tissue multi-class model classified the sample as cancer versus normal and as a specific tissue type with a testing accuracy of 97.43%. Given a normal sample of any of the nine tissue types, the multi-tissue normal model classified the sample as a particular tissue type with a testing accuracy of 97.35%. The machine learning classifiers developed in this study identify potential cancer biomarkers with sensitivity and specificity that exceed those of existing biomarkers and pointed to pathways that are critical to tissue-specific tumor development. This study demonstrates the feasibility of predicting the tissue origin of carcinoma in the context of multiple cancer classes.

STAT1 Inhibits MiR-181a Expression to Suppress Colorectal Cancer Cell Proliferation Through PTEN/Akt

Signal transducers and activators of transcription 1 (STAT1) exhibits tumor-suppressor properties by inhibiting oncogenic pathways and promoting tumor immunosurveillance. MicroRNAs, a group of non-coding endogenous ones, may regulate gene expression and plays specific roles in tumorigenesis. Recently, miR-181a has been reported to be associated with poor prognosis of colorectal cancer (CRC). Using human colorectal cancer cell lines, we demonstrated that STAT1 suppresses both LoVo and SW480 cell growth by down-regulating miR-181a. STAT1 regulates the expression of miR-181a through binding to the elements in the miR-181a's promoter region. Further, we revealed that miR-181a accelerates CRC cell proliferation through phosphatase and tensin homolog on chromosome ten (PTEN). In addition, PTEN protein was upregulated in response to STAT1 overexpression or miR-181a inhibition, downregulated in response to STAT1 knockdown or miR-181a overexpression. Without changes on the AKT protein level, p-AKT was downregulated by STAT1 overexpression or miR-181a inhibition while upregulated by STAT1 knockdown or miR-181a overexpression, indicating PTEN/Akt pathway activated in STAT1/miR-181a regulation of CRC cell proliferation. Taken together, our findings shed new light on the STAT1/miR-181a/PTEN pathway in colorectal cancer and add new insight regarding the carcinogenesis of colorectal cancer. J. Cell. Biochem. 118: 3435-3443, 2017. © 2017 Wiley Periodicals, Inc.