Stabilization of HIPK2 by escape from proteasomal degradation mediated by the E3 ubiquitin ligase Siah1

Homeodomain-interacting protein kinase 2 (HIPK2) induces apoptosis and, thus, is maintained at a low level via ubiquitin-mediated proteolysis. In a yeast two-hybrid screen, we identified Siah1, a RING finger E3 ubiquitin ligase, as an interacting protein of HIPK2. Siah1 targeted HIPK2 for poly-ubiquitination-mediated proteasomal degradation. Degradation of HIPK2 by Siah1 was blocked by forced expression of either Mixed Lineage Kinase-3 or Epstein-Barr viral protein LMP-1, as well as by DNA damaging stimuli. These findings effectively illustrate the regulatory mechanisms underlying HIPK2 stabilization by escape from Siah1-mediated degradation, and that Siah1 is an integration target for several internal or external stimuli for HIPK2 stabilization.     

Protein kinase D2 promotes the proliferation of glioma cells by regulating Golgi phosphoprotein 3

Protein kinase D2 (PKD2) has been demonstrated to promote tumorigenesis in many types of cancers. However, how PKD2 regulates cancer cell growth is largely unknown. In this study, we found that over-expression of PKD2 promoted glioma cell growth but down-regulation of PKD2 inhibited it. Further investigation indicated that PKD2 down-regulation decreased the protein level of Golgi phosphoprotein 3(GOLPH3) as well as p-AKT level. On the contrary, over-expression of PKD2 increased the protein level of GOLPH3 and p-AKT. In addition, GOLPH3 exhibited similar effect on glioma cell growth to that of PKD2. Importantly, GOLPH3 down-regulation partially abolished glioma cell proliferation induced by PKD2 over-expression, while over-expression of GOLPH3 also partially rescued the inhibition effect of PKD2 down-regulation on glioma cell growth. Interestingly, the level of PKD2 and GOLPH3 significantly increased and was positively correlated in a cohort of glioma patients, as well as in patients from TCGA database. Taken together, these results reveal that PKD2 promotes glioma cell proliferation by regulating GOLPH3 and then AKT activation. Our findings indicate that both PKD2 and GOLPH3 play important roles in the progression of human gliomas and PKD2-GOLPH3-AKT signaling pathway might be a potential glioma therapeutic target.     

PGK1-coupled HSP90 stabilizes GSK3β expression to regulate the stemness of breast cancer stem cells

Objective: Glycogen synthase kinase-3β(GSK3β) has been recognized as a suppressor of Wnt/β-catenin signaling, which is critical for the stemness maintenance of breast cancer stem cells. However, the regulatory mechanisms of GSK3β protein expression remain elusive.Methods: Co-immunoprecipitation and mass spectral assays were performed to identify molecules binding to GSK3β, and to characterize the interactions of GSK3β, heat shock protein 90(Hsp90), and co-chaperones. The role of PGK1 in Hsp90 ch...     

ATM and LKB1 dependent activation of AMPK sensitizes cancer cells to etoposide-induced apoptosis

The present study aims to determine the effect of AMPK on etoposide-induced apoptosis of cancer cells. Our results revealed that etoposide induced AMPK activation in prostate C4-2 cancer cells, an event that was attenuated by ATM siRNA. In A549 cells that lack LKB1, AMPK was unable to be activated by etoposide, which was restored by introduction of LKB1. Likewise, silencing LKB1 in C4-2 cells impaired AMPK activation. Finally, etoposide displayed a potent pro-apoptotic effect in cancer cells with functional LKB1 and AMPK. Thus, our results establish a linear relationship of ATM, LKB1 and AMPK in response to the DNA damage drug.     

Transcriptional down-regulation of IGFBP-3 in human hepatocellular carcinoma cells is mediated by the binding of TIA-1 to its AT-rich element in the 3′-untranslated region

Insulin-like growth factor binding protein-3 (IGFBP-3) plays key roles in regulating cell growth, differentiation, and apoptosis in a variety of cellular systems. We have observed significant down-regulation of IGFBP-3 expression in primary human hepatocellular carcinoma (HCC) tissues when compared to adjacent histologically normal tissues. In this study, we functionally mapped the entire 3′-UTR of the IGFBP-3 mRNA, spanning 1471nt and identified a 210 bp fragment consisting of AT-rich elements at the distal downstream region preceding the consensus pre-mRNA polyadenylation signal that provide high affinity binding for TIA-1 to mediate the specific suppression of IGFBP-3 expression in human HCC cells.     

Recombinant viral capsid protein VP1 suppresses migration and invasion of human cervical cancer by modulating phosphorylated prohibitin in lipid rafts

Recombinant capsid protein VP1 (rVP1) of foot-and-mouth disease virus inhibits invasion/metastasis of cancer cells. Here we studied its mechanism of action on human cervical cancer cells. The inhibition of cell invasion by rVP1 was accompanied with reduction in phosphatidylinositol (3,4,5)-triphosphate (PIP3), phospho-Akt S473, phosphorylated prohibitin (phospho-PHB) T258 in lipid rafts, dissociation of phospho-PHB T258 with Raf-1 and the inactivation of Raf-1/ERK. Addition of PIP3 or overexpression of constitutively active Akt and raft-anchored PHB T258 but not PHB T258I mutant protein reversed the inhibitory effects of rVP1. rVP1 inhibited cervical tumor growth and metastasis, and prolonged survival in xenograft mouse models. These results suggest that rVP1 inhibits cancer metastasis via de-phosphorylation of Akt and PHB T258 in lipid rafts to downregulate Raf/ERK signaling.     

Chemopreventive effects of dietary phytochemicals against cancer invasion and metastasis: phenolic acids, monophenol, polyphenol, and their derivatives

Cancer metastasis is the major cause of cancer-related death, and chemoprevention is defined as the use of natural or synthetic substances to prevent cancer formation or cancer progress. Evidence that phenolic compounds may have a potential inhibitory effect on cancer invasion and metastasis is increasingly being reported in the scientific literature. Curcumin, resveratrol, and their related derivatives are the most studied compounds in this topic so far; gallic acid, chlorogenic acid, caffeic acid, carnosol, capsaicin, 6-shogaol, 6-gingerol, and their corresponding derivatives are also suggested to be the active members of the phenolic family on anti-invasion and anti-metastasis. Because metastasis occurs through a multistep process, these bioactives might act on a variety of stages of the metastatic process to prevent tumor cells from metastasizing. This review summarizes the common protein targets and signaling pathways for the inhibition of invasion and metastasis as well as past publications on the in vitro and in vivo effects and molecular mechanisms of phenolic acids, monophenol, polyphenol, and their derivatives, except flavonoids, on cancer invasion and metastasis. Based on these data, we conclude that the daily consumption of natural dietary components that are rich in phenolics could be beneficial for the prevention of cancer metastasis.     

Glycine-extended gastrin induces matrix metalloproteinase-1- and -3-mediated invasion of human colon cancer cells through type I collagen gel and Matrigel

The effects of glycine-extended gastrin (G-Gly) on the invasion by colon cancer cells through stromal extracellular matrix and the role of metalloproteinases (MMPs) in this invasion were investigated. We found that 10(-9)-10(-6) M G-Gly significantly increased the invasiveness of 2 human colon cancer cell lines, LoVo and HT-29, both expressing the G-Gly-specific binding site but little gastrin/CCK-B receptor (gastrin receptor). LoVo cells expressed MMP-1, -2, -3 and -9. An amount of 10(-7) M G-Gly enhanced collagenase MMP-1 expression. Overexpression of enhanced green fluorescent protein (EGFP)-fused MMP-1 in LoVo cells, by cDNA transfection, enhanced invasiveness through type I collagen gel. Immunofluorescence study revealed that G-Gly increased the number of cytoplasmic vesicles containing MMP-1, some vesicles being released from the cells. The MMP-1 vesicles contained one of the ubiquitous coat proteins, Golgi-localized, gamma-adaptin ear-containing, ARF-binding proteins-2 (GGA-2). MMP-1 also colocalized with CD147 (EMMPRIN, an extracellular matrix metalloproteinase inducer in adjacent stromal cells). It was suggested that G-Gly increased the number of vesicles containing MMP-1 and that MMP-1 interacted with CD147 to increase invasion. G-Gly significantly enhanced the production of MMP-3, an activator of MMP-1 and -9, as well as gelatinase MMP-9 activity. The G-Gly-mediated MMP-9 increase was inhibited by treatment with anti-MMP-3 IgG and MMP-3 siRNA. Furthermore, G-Gly increased the proMMP-2 level, although no activated MMP-2 was found in conditioned medium in either the presence or the absence of G-Gly. By contrast, gastrin (10(-7) M) had no effect on the levels of these MMPs or the invasiveness of colon cancer cells in type I collagen gel and Matrigel. These effects of G-Gly on the activity and expression of MMPs and the invasiveness of colon cancer cells were inhibited by treating the cells with a broad-spectrum metalloproteinase inhibitor (CGS27023A) and nonselective gastrin/CCK receptor antagonists (proglumide and benzotript). But a gastrin/CCK-B receptor antagonist (YM022) did not inhibit the increased invasion by G-Gly. Together, these results demonstrate that G-Gly renders colon cancer cells more invasive by increasing MMP-1 and MMP-3 expressions via the putative G-Gly receptor and would thus be a good molecular target in a clinical setting.     

Development of ferret as a human lung cancer model by injecting 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

Objective

Development of new animal lung cancer models that are relevant to human lung carcinogenesis is important for lung cancer research. Previously we have shown the induction of lung tumor in ferrets (Mustela putorius furo) exposed to both tobacco smoke and a tobacco carcinogen (4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, NNK). In the present study, we investigated whether NNK treatment alone induces both preneoplastic and neoplastic lesions in the lungs of ferrets.

Methods

We exposed ferrets to NNK by i.p. injection of NNK (50 mg/kg BW) once a month for four consecutive months and then followed up for 24, 26 and 32 weeks. The incidences of pulmonary preneoplastic and neoplastic lesions were assessed by histopathological examination. The expressions of α7 nicotinic acetylcholine receptor (α7 nAChR, which has been shown to promote lung carcinogenesis) and its related molecular biomarkers in lungs were examined by immunohistochemistry and/or Western blotting analysis.

Results

Ferrets exposed to NNK alone developed both preneoplastic lesions (squamous metaplasia, dysplasia and atypical adenomatous hyperplasia) and tumors (squamous cell carcinoma, adenocarcinoma and adenosquamous carcinoma), which are commonly seen in humans. The incidence of tumor induced by NNK was time-dependent in the ferrets (16.7%, 40.0% and 66.7% for 24, 26 and 32 weeks, respectively). α7 nAChR is highly expressed in the ferret bronchial/bronchiolar epithelial cells, and alveolar macrophages in ferrets exposed to NNK, and in both squamous cell carcinoma and adenocarcinoma of the ferrets. In addition, we observed the tendency for an increase in phospho-ERK and cyclin D1 protein levels (p = 0.081 and 0.080, respectively) in the lungs of ferrets exposed to NNK.

Conclusion

The development of both preneoplastic and neoplastic lesions in ferret lungs by injecting NNK alone provides a simple and highly relevant non-rodent model for studying biomarkers/molecular targets for the prevention, detection and treatment of lung carcinogenesis in humans.     

Mechanisms of breast cancer bone metastasis

Bone, as well as liver and lung, is one of the most preferential metastatic target sites for cancers including breast, prostate, and lung cancers and the consequences are always devastating. Like other metastasis, breast cancer bone metastasis consists of several steps from the escape of primary site to the colonization in target site. This review focuses on several key steps including: 1. Invasion and escape from primary tumor site. 2. Target migration toward bone. 3. Specific adhesion and arrest in bone. 4. Establishment of metastasis in bone. The factors involved in this process will provide good targets for therapy.     

Targeted abrogation of diverse signal transduction cascades by emodin for the treatment of inflammatory disorders and cancer

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is a natural occurring anthraquinone derivative isolated from roots and barks of numerous plants, molds, and lichens. It is found as an active ingredient in different Chinese herbs including Rheum palmatum and Polygonam multiflorum, and has diuretic, vasorelaxant, anti-bacterial, anti-viral, anti-ulcerogenic, anti-inflammatory, and anti-cancer effects. The anti-inflammatory effects of emodin have been exhibited in various in vitro as well as in vivo models of inflammation including pancreatitis, arthritis, asthma, atherosclerosis and glomerulonephritis. As an anti-cancer agent, emodin has been shown to suppress the growth of various tumor cell lines including hepatocellular carcinoma, pancreatic, breast, colorectal, leukemia, and lung cancers. Emodin is a pleiotropic molecule capable of interacting with several major molecular targets including NF-κB, casein kinase II, HER2/neu, HIF-1α, AKT/mTOR, STAT3, CXCR4, topoisomerase II, p53, p21, and androgen receptors which are involved in inflammation and cancer. This review summarizes reported anti-inflammatory and anti-cancer effects of emodin, and re-emphasizes its potential therapeutic role in the treatment of inflammatory diseases and cancer.     

Mucins and toll-like receptors: kith and kin in infection and cancer

Inflammation is underlying biological phenomenon common in infection and cancer. Mucins are glycoproteins which establish a physical barrier for undesirable entry of foreign materials through epithelial surfaces. A deregulated expression and an anomalous glycosylation pattern of mucins are known in large number of cancers. TLRs are class of receptors which recognize the molecular patterns of invading pathogens and activate complex inflammatory pathways to clear them. Aberrant expression of TLRs is observed in many cancers. A highly orchestrated action of mucins and TLRs is well evolved host defence mechanism; however, a link between the two in other non-infectious conditions has received less attention. Here we present an overview as to how mucins and TLRs give protection to the host and are deregulated during carcinogenesis. Further, we propose the possible mechanisms of cross-regulation between them in pathogenesis of cancer. As both mucins and TLRs are therapeutically important class of molecules, an understanding of the underlying molecular mechanisms connecting the two will open new avenues for the therapeutic targeting of cancer.     

The stromal compartments in pancreatic cancer: Are there any therapeutic targets?

Pancreatic ductal adenocarcinoma (PDAC) is characterised by an abundant stromal response also known as a desmoplastic reaction. Pancreatic Stellate Cells have been identified as playing a key role in pancreatic cancer desmoplasia. There is accumulating evidence that the stroma contributes to tumour progression and to the low therapeutic response of PDAC patients. In this review we described the main actors of the desmoplastic reaction within PDAC and novel therapeutic approaches that are being tested to block the detrimental function of the stroma.