Wnt signaling modulator DKK4 inhibits colorectal cancer metastasis through an AKT/Wnt/ß-catenin negative feedback pathway.

Aberrant activation of the Wnt/ß-catenin signaling pathway is implicated in most malignant cancers, especially in the initiation and progression of colorectal cancer (CRC). DKK4 is a classical inhibitory molecule of the Wnt/ß-catenin pathway, but its role in CRC is ambiguous, and the molecular mechanism remains unclear. Here, we determined DKK4 expression was significantly upregulated in 23 CRC cell lines and 229 CRC tissues when analyzed by quantitative PCR and immunohistochemistry, respectively. Our analysis of tissue samples indicated the survival time of CRC patients with high DKK4 expression was longer than that of patients with medium-low DKK4 expression. We examined the effects of DKK4 on cell proliferation and metastasis by cell counting kit-8 assays, transwell assays, and subcutaneous and metastatic mouse tumor models, and we discovered that DKK4 silencing promoted the metastasis of CRC cells both in vitro and in vivo. Our RNA-seq analysis revealed that AKT2, FZD6, and JUN, which play important roles in AKT and Wnt signaling, were significantly increased after DKK4 knockdown. DKK4 represses Wnt/ß-catenin signaling by repressing FZD6 and AKT2/s552 ß-catenin in CRC. Further experiments revealed recombinant Wnt3a and LiCl could induce DKK4 expression. Moreover, our bioinformatics analysis and luciferase reporter assays identified posttranscriptional regulators of DKK4 in CRC cells. In summary, DKK4 is elevated in CRC and inhibits cell metastasis by a novel negative feedback mechanism of the Wnt3a/DKK4/AKT/s552 ß-catenin regulatory axis to restrict overactivation of Wnt activity in CRC. Therefore, DKK4 restoration may be applied as a potential CRC therapeutic strategy.

Low Expression of Phosphodiesterase 2 (PDE2A) Promotes the Progression by Regulating Mitochondrial Morphology and ATP Content and Predicts Poor Prognosis in Hepatocellular Carcinoma.

Phosphodiesterase 2 (PDE2A) modulates the levels of cAMP/cGMP and was recently found to be involved in mitochondria function regulation, closely related to multiple types of tumor progression. This study aimed to estimate the prognostic significance and biological effects of PDE2A on hepatocellular carcinoma (HCC). We comprehensively analyzed the PDE2A mRNA expression in HCC based on The Cancer Genome Atlas (TCGA) database and investigated the effects of PDE2A on the proliferation and metastatic capacity of HCC cells. PDE2A was downregulated in 25 cancer types, including HCC. Lower PDE2A expression was a protective factor in HCC and was negatively associated with serum AFP levels, tumor status, vascular invasion, histologic grade, and pathologic stage of HCC. Moreover, tumors with low PDE2A expression displayed a decreased immune function. Then, the ROC curve was used to assess the diagnostic ability of PDE2A in HCC (AUC = 0.823 in TCGA and AUC = 0.901 in GSE76427). Patients with low PDE2A expression exhibited worse outcomes compared with those with high PDE2A expression. Additionally, GO functional annotations demonstrated the involvement of PDE2A in the ECM organization, systems development, and ERK-related pathways, indicating that PDE2A might regulate HCC growth and metastasis. The in vitro experiments confirmed that overexpression of PDE2A inhibited proliferation, colony formation, migration, and invasion in two HCC cell lines (HLF and SNU-368), while inhibition of PDE2A has the opposite results. The mechanism of PDE2A's effect on HCC cells is attributed to the change of mitochondrial morphology and ATP content. These data demonstrated that PDE2A closely participated in the regulation of HCC proliferation and metastasis and can be used as a predictive marker candidate and a potential therapeutic target for HCC.

Regulation of the small GTPase Ran by miR-802 modulates proliferation and metastasis in colorectal cancer cells.

BACKGROUND: The small GTPase Ran is upregulated in multiple cancers and fundamental for cancer cell survival and progression, but its significance and molecular mechanisms in colorectal cancer (CRC) remain elusive. METHODS: Ran expression was detected in CRC cell lines and tumour tissues. In vitro and in vivo functional assays were performed to examine the effects of Ran on cell proliferation and metastasis. The pathways and effectors regulated by Ran were explored by an unbiased screening. Bioinformatics prediction and experimental validation were used to identify the miRNA regulator for Ran. RESULTS: Ran expression was frequently increased in metastatic CRC cells and tissues, especially in metastatic tissues. The upregulation of Ran correlated with poor CRC patient prognosis. Ran silencing reduced proliferation and metastasis of CRC cells both in vitro and in vivo. Ran regulated the expression of EGFR and activation of ERK and AKT signalling pathways. miR-802 was identified as an upstream regulator of Ran and miR-802 overexpression resulted in antiproliferative and antimetastatic activities. CONCLUSION: Our study demonstrates the oncogenic roles and underlying mechanisms of Ran in CRC and the novel miR-802/Ran/EGFR regulatory axis may provide potential biomarkers for the treatment of CRC.

Hydrogen Sulfide Mediates K+ and Na+ Homeostasis in the Roots of Salt-Resistant and Salt-Sensitive Poplar Species Subjected to NaCl Stress.

Non-invasive micro-test techniques (NMT) were used to analyze NaCl-altered flux profiles of K+, Na+, and H+ in roots and effects of NaHS (a H2S donor) on root ion fluxes in two contrasting poplar species, Populus euphratica (salt-resistant) and Populus popularis (salt-sensitive). Both poplar species displayed a net K+ efflux after exposure to salt shock (100 mM NaCl), as well as after short-term (24 h), and long-term (LT) (5 days) saline treatment (50 mM NaCl, referred to as salt stress). NaHS (50 µM) restricted NaCl-induced K+ efflux in roots irrespective of the duration of salt exposure, but K+ efflux was not pronounced in data collected from the LT salt stress treatment of P. euphratica. The NaCl-induced K+ efflux was inhibited by a K+ channel blocker, tetraethylammonium chloride (TEA) in P. popularis root samples, but K+ loss increased with a specific inhibitor of plasma membrane (PM) H+-ATPase, sodium orthovanadate, in both poplar species under LT salt stress and NaHS treatment. This indicates that NaCl-induced K+ loss was through depolarization-activated K+ channels. NaHS caused increased Na+ efflux and a corresponding increase in H+ influx for poplar roots subjected to both the short- and LT salt stress. The NaHS-enhanced H+ influx was not significant in P. euphratica samples subjected to short term salt stress. Both sodium orthovanadate and amiloride (a Na+/H+ antiporter inhibitor) effectively inhibited the NaHS-augmented Na+ efflux, indicating that the H2S-enhanced Na+ efflux was due to active Na+ exclusion across the PM. We therefore conclude that the beneficial effects of H2S probably arise from upward regulation of the Na+/H+ antiport system (H+ pumps and Na+/H+ antiporters), which promote exchange of Na+ with H+ across the PM and simultaneously restricted the channel-mediated K+ loss that activated by membrane depolarization.

[Spectroscopic Studies on the Host Plant Selection Mechanism of Trabala vishnou gigantina Yang (Lepidoptera: Lasiocampidae)].

Trabala vishnou gigantina Yang (Lepidoptera: Lasiocampidae) is a polyphagous forestry pest whose periodic breaking out results in great economic damage including total crop failure to forestry and fruit production in China. In this study, in order to improve the understanding of the host plant selection mechanism of T. vishnou gigantina larvae, locust, caragana, willow, poplar, apricot and sea-buckthorn were used as potential host plants for the test. Two-way choice experiment method was used to study the T. vishnou gigantina Yang feeding preferences of the six kinds of plants. Moreover, the chemical component and physical structure of six plants were analyzed with Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Among the six plants, T. vishnou gigantina larvae showed a strong preference for sea-buckthorn, followed by, apricot, willow, poplar, locust, and caragana. The FTIR analysis displayed that those six plants presented similar characteristic on absorption peak position, peak amount, and shape. The targets (1 154/1 733, 1 154/898) by FTIR showed that lipids and polysaccharide were major nutriments to affect the host plant selection of T. vishnou gigantina larvae. The XRD results showed that crystallinity index (CrI) also could affect the host plant selection of T. vishnou gigantina larvae. In this research, spectroscopy technology was firstly applied to the study of interactive relationship between insect and host, which would blaze a trail for intensive study of host plant selection mechanism of insect at molecular level.

Effect of Four Types of Chemical Pretreatment on Enzymatic Hydrolysis by SEM, XRD and FTIR Analysis.

Catalpa sawdust was respectively pretreated by NaOH, Ca(OH)2, H2SO4 and HCl solution, and the enzymatic hydrolysis of catalpa sawdust was significantly enhanced by alkaline pretreatments. In order to investigate the mechanisms of pretreatment of catalpa sawdust, the characteristics of catalpa sawdust before and after pretreatments were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was found that the surface of catalpa sawdust was disrupted by four kinds of chemical pretreatment, and the pretreatment with Ca(OH)2 solution resulted in the most serious damage. The XRD results showed that part of amorphous regions was damaged by alkaline pretreatments, which led to a relative increase of crystallinity Index (CrI) of catalpa sawdust; while the CrI of catalpa sawdust was insignificantly influenced by acid pretreatments. The FTIR analysis displayed that the molecular structures of hemicellulose and lignin of catalpa sawdust were damaged in different degrees by four types of pretreatment. The significant improvement of enzymatic hydrolysis of catalpa sawdust after alkaline pretreatment might be attributed to the effective delignification of alkaline.