Autophagy regulation in cancer development and therapy

Autophagy is a cellular process to degrade long-lived or malfunctioning proteins and obsolete or damaged organelles. It maintains cellular homeostasis and helps cells survive stressful conditions. Tumor suppressors mostly positively regulate autophagy, whereas oncogene products usually inhibit autophagy. Alterations in key autophagy genes have also been shown to affect cancer development. However, the role of autophagy in cancer depends on the status of the cells and can either suppress or promote tumor growth. In the present review, we report on the current state of knowledge about the reciprocal regulation of autophagy and the potential role of autophagy played in cancer development and therapy.     

A polymorphism of the interleukin-1 beta gene influences survival in pancreatic cancer

Pro-inflammatory cytokines contribute to the cachexia associated with pancreatic cancer and stimulate the acute phase response which has been associated with shortened survival in such patients. Polymorphisms of cytokine genes may influence their production. The present study examined the effect of a polymorphism of the interleukin (IL)-1b gene upon the inflammatory state and survival in pancreatic cancer. Genomic DNA was obtained from 64 patients with pancreatic cancer and 101 healthy controls. Using the polymerase chain reaction and subsequent TaqI restriction enzyme digestion the subject's genotype for a diallelic polymorphism of the interleukin-1b gene was established. IL-1b production by peripheral blood mononuclear cells and serum C-reactive protein (CRP) levels from patients were also examined and survival noted. Patients homozygous for allele 2 of the IL-1b gene had significantly shorter survival than other groups (P = 0.0001). These patients also exhibited higher IL-1b production (P = 0.022). Possession of allele 2 was also associated with significantly shorter survival (median 144 vs 256 days, P = 0.034) and significantly higher CRP level (P = 0.0003). The possession of a genotype resulting in increased IL-1b production was associated with shortened survival and increased serum CRP level. This may reflect the role of IL-1b in inducing an acute phase protein response and cachexia in cancer or may be related to changes in tumour phenotype.     

Enhanced VEGF production and decreased immunogenicity induced by TGF-beta 1 promote liver metastasis of pancreatic cancer

TGF-betas are multifunctional polypeptides that regulate cell growth and differentiation, extracellular matrix deposition, cellular adhesion properties, angiogenesis and immune functions. In this study, we investigated the effect of TGF-beta1 on liver metastasis and its mechanism by using human pancreatic cancer cell lines Panc-1, Capan-2, and SW1990. Capan-2 and SW1990 cells demonstrated enhanced liver metastatic potential by in vivo splenic injection with TGF-beta1. Consequently, we examined the role of TGF-beta1 on in vitro angiogenesis and received cytotoxicity by peripheral blood mononuclear leukocytes (PBMLs). While TGF-beta1 slightly decreased cell proliferation, it also upregulated VEGF production in all cancer cells examined. The binding of PBMLs to cancer cells and cancer cell cytotoxicity during co-culture with PBMLs were remarkably decreased by treatment with TGF-beta1. Panc-1 cells revealed no liver metastasis despite their high immunogenetic and angiogenetic abilities, which was attributed to a lack of expression of the cell surface carbohydrates that induce attachment to endothelial cells. We concluded that the presence of TGF-beta1 in the microenvironment of tumour site might play an important role in enhancing liver metastasis of pancreatic cancer by modulating the capacity of angiogenesis and immunogenicity.     

Sulforaphane inhibited expression of hypoxia-inducible factor-1alpha in human tongue squamous cancer cells and prostate cancer cells

Previous studies show that a number of natural compounds from our diet have anticancer effects. Sulforaphane is the most characterized isothiocyanates (ITCs), which are identified in cruciferous vegetables. Sulforaphane is viewed as a conceptually promising agent in cancer prevention. Because of its ability to induce cancer cell apoptosis, it inhibits progression of benign tumors to malignant tumors and interrupts metastasis. However, the effect of sulforaphane on tongue cancer cell proliferation has not yet been reported, and the mechanisms that sulforaphane inhibits cancer development are still unclear. Hypoxia-inducible factor 1 (HIF-1) expression is associated with tumorigenesis and angiogenesis. It regulates the expression of many genes including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase, and lactate dehydrogenase A. In our study, we investigated the effects of sulforaphane on expression of hypoxia-inducible factor-1alpha (HIF-1alpha), which was overexpressed in many human malignant tumors, human tongue squamous cell carcinoma and prostate cancer DU145 cells. Sulforaphane inhibited hypoxia induced expression of HIF-1alpha via inhibiting synthesis of HIF-1alpha. Sulforaphane was also found to inhibit hypoxia induced HIF-1alpha expression through activating JNK and ERK signaling pathways, but not AKT pathway. Inhibition of HIF-1alpha by sulforaphane resulted in decreasing expression of VEGF. Taken together, these results suggest that sulforaphane is an effective chemopreventive compound against tongue cancers and prostate cell angiogenesis in vitro, and that the HIF-1alpha target provides a new sight into the mechanisms of sulforaphane's inhibition against tumor cell proliferation.     

Hypoxia-induced lncRNA CASC9 enhances glycolysis and the epithelial-mesenchymal transition of pancreatic cancer by a positive feedback loop with AKT/HIF-1α signaling

Increasing evidence indicates the dysregulations and pivotal roles of lncRNAs in the development and progression of various cancers, including pancreatic cancer. Enhanced glycolytic flux and epithelial-to-mesenchymal transition (EMT) have been considered as important factors in driving the malignance of pancreatic cancer. Here, we sought to evaluate the biological role and involved mechanism of lncRNA CASC9 (CASC9) in pancreatic cancer. Our present study showed that CASC9 was upregulated in various pancreatic cancer cell lines. Loss- and gain-of function of CASC9 demonstrated its critical roles in promoting the glycolysis and EMT phenotypes of pancreatic cancer. Moreover, knockdown of CASC9 inhibited the tumorigenicity and metastasis in vivo. Additionally, our findings showed that hypoxia induced the expression of CASC9 and enhanced the binding of HIF-1α to its promoter. We also demonstrated that the positive feedback loop of CASC9 and the AKT/HIF-1α signaling cascade partially mediated this biological process. Altogether, our results suggest that CASC9 promotes the glycolysis and EMT of pancreatic cancer by a positive feedback loop with AKT/HIF-1α signaling, which is synergistically enhanced by the tumor hypoxic niche. Our study will provide potential therapeutic targets for treating pancreatic cancer.     

Adiponectin promotes pancreatic cancer progression by inhibiting apoptosis via the activation of AMPK/Sirt1/PGC-1α signaling

Adiponectin is an adipocyte-secreted adipokine with pleiotropic actions. Clinical evidence has shown that serum adiponectin levels are increased and that adiponectin can protect pancreatic beta cells against apoptosis, which suggests that adiponectin may play an anti-apoptotic role in pancreatic cancer (PC). Here, we investigated the effects of adiponectin on PC development and elucidated the underlying molecular mechanisms. Adiponectin deficiency markedly attenuated pancreatic tumorigenesis in vivo. We found that adiponectin significantly inhibited the apoptosis of both human and mouse pancreatic cancer cells via adipoR1, but not adipoR2. Furthermore, adiponectin can increase AMP-activated protein kinase (AMPK) phosphorylation and NAD-dependent deacetylase sirtuin-1 (Sirt1) of PC cells. Knockdown of AMPK or Sirt1 can increase the apoptosis in PC cells. AMPK up-regulated Sirt1, and Sirt1 can inversely phosphorylate AMPK. Further studies have shown that Sirt1 can deacetylate peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which can increase the expression levels of mitochondrial genes. Thus, adiponectin exerts potent anti-apoptotic effects on PC cells via the activation of AMPK/Sirt1/PGC1α signaling. Finally, adiponectin can elevate β-catenin levels. Taken together, these novel findings reveal an unconventional role of adiponectin in promoting pancreatic cancers, and suggest that the effects of adiponectin on tumorigenesis are highly tissue-dependent.     

Changes in E-cadherin associated with cytoplasmic molecules in well and poorly differentiated endometrial cancer

E-cadherin function is thought to be impaired in epithelial cancer. To investigate the alterations in E-cadherin associated with cytoplasmic molecules including alpha-catenin, beta-catenin, gamma-catenin, p120CAS, and IQGAP1 in various endometrial cancers with different degree of differentiation, we examined the localization and expression of E-cadherin and cytoplasmic molecules in 30 cases of both well and poorly differentiated endometrioid adenocarcinomas, using immunofluorescence and immunoblotting techniques. E-cadherin and cytoplasmic molecules demonstrated linear staining at the cell boundaries in normal endometrium. In all 20 cases with well differentiated adenocarcinomas, alpha-catenin and IQGAP1 disappeared from the cell adhesive sites, but other cytoplasmic molecules were co-localized with E-cadherin along the cell boundaries. In all 10 cases with poorly differentiated adenocarcinomas, E-cadherin and cytoplasmic molecules accumulated as large aggregates along cell adhesive sites, and the localization of IQGAP1 differed from those of other cytoplasmic molecules. The expression of these molecules in all 20 cases with well differentiated adenocarcinomas decreased or was lost in Triton-insoluble fraction, in comparison with the findings for all cases with normal endometrium or poorly differentiated adenocarcinomas. These results suggested that each alteration in E-cadherin associated with cytoplasmic molecules may play a different role in E-cadherin dysfunction between well and poorly differentiated adenocarcinomas.     

MUC1 expression in primary and metastatic pancreatic cancer cells for in vitro treatment by (213)Bi-C595 radioimmunoconjugate

Control of micrometastatic pancreatic cancer remains a major objective in pancreatic cancer treatment. The overexpression of MUC1 mucin plays an important role in cancer metastasis. The aim of this study was to detect the expression of MUC1 in human primary tumour tissues and three pancreatic cancer cell lines (CAPAN-1, CFPAC-1 and PANC-1), and target MUC1-positive cancer cells in vitro using (213)Bi-C595 alpha-immunoconjugate (AIC). The expression of MUC1 on pancreatic tumour tissues and cancer cell lines was performed by immunohistochemistry and further confirmed by confocal microscope and flow cytometry analysis on the cell surface. Cytotoxicity of (213)Bi-C595 was tested by MTS assay. Apoptosis was documented using TUNEL assay. Overexpression of MUC1 was found in approximately 90% of tested tumour samples and the three pancreatic cancer cell lines. (213)Bi-C595 is specifically cytotoxic to pancreatic cancer cells in a concentration-dependent fashion. These results suggest that overexpression of MUC1 in pancreatic cancer is a useful target, and that the novel (213)Bi-C595 AIC selectively targets pancreatic cancer cells in vitro. (213)Bi-C595 may be a useful agent for the treatment of micrometastases or minimal residual disease (MRD) in pancreatic cancer patients with overexpression of MUC1 antigen.     

IL-17 in pancreatic disease: pathogenesis and pharmacotherapy

Increasing evidence highlights the role of the interleukin (IL)-17 family in pancreatic diseases. IL-17A induces acinar cell injury directly, recruits neutrophils, and cooperates with other inflammatory factors to exacerbate pancreatic inflammation. It also triggers islet β-cell apoptosis and nitric oxide-dependent cytotoxicity, thus aggravating islet inflammation. IL-17A seems to have different roles in pancreatic intraepithelial neoplasia (PanIN) and pancreatic cancer (PC). IL-17A participates in the progression of acinar-ductal metaplasia (ADM) and PanIN, but not related to the characteristics of PC stem cells and the overall survival of patients. Acting similar to IL-17A, IL-17B accelerates the invasion and metastasis of PC, and predicts prognosis of PC and the therapeutic effect of gemcitabine. Herein, we review the current understanding of the pathogenesis of IL-17 in pancreatitis, type 1 diabetes mellitus (T1DM), and PC, as well as potential pharmacotherapy targeting IL-17 and its receptors in pancreatic diseases. The findings summarized in this article are of considerable significance for understanding the essential role of IL-17 in pancreatic diseases.     

Curcumin inhibits pancreatic cancer cell proliferation by regulating Beclin1 expression and inhibiting the hypoxia-inducible factor-1α-mediated glycolytic pathway

BackgroundPancreatic cancer has a high degree of malignancy and high mortality. Understanding its biological status can provide more therapeutic targets for the future. The present study was to investigate whether curcumin can inhibit pancreatic cancer cell proliferation by regulating Beclin1 expression and inhibiting the hypoxia-inducible factor-1α (HIF-1α)-mediated glycolytic pathway.MethodsTwo pancreatic cancer cell lines, PANC-1 and SW1990, were treated with different concentrations of curcumin (0, 20, 40, and 60 µM). Cell viability was detected using the Cell Counting Kit-8 (CCK-8) assay and flow cytometry was performed to determine the apoptosis rate and cell cycle arrest of the pancreatic cancer cells. PANC-1 and SW1990 cells were treated with different concentrations of curcumin under hypoxic conditions for 48 hours to detect the relative expression of the Beclin1 protein. The co-immunoprecipitation (co-IP) method was used to determine whether curcumin could inhibit the interaction between Beclin1 and HIF-1α.ResultsThe proliferation inhibition rates of PANC-1 cells after exposure to 0, 20, 40, and 60 µM curcumin were 0%, 31.6%, 47.2%, and 63.9%, respectively, and that of SW1990 cells were 0%, 18.8%, 46.3%, and 63.5% respectively. Western blot analyses showed decreased expression of Beclin1 in cells treated with curcumin. The expression of Beclin1 in the nucleus and cytoplasm decreased with increasing concentrations of curcumin. Co-IP results demonstrated that curcumin inhibited the interaction between Beclin1 and HIF-1α. Treatment with the higher doses of curcumin (40 and 60 µM) significantly decreased the protein expression levels of HIF-1α. In addition, the expression levels of Kidney-Specific Cadherin (HSP70, HSP90, and von Hippel-Lindau protein (pVHL) were significantly decreased in pancreatic cancer cells while the expression of prolyl hydroxylase (PHD) and receptor of activated protein kinase C (RACK1) increased significantly. Furthermore, curcumin reduced cellular adenosine triphosphate (ATP) production in a dose-dependent manner. Compared with control pancreatic cancer cells, the expression levels of GLUT1, HK2, LDHA, and PDK1 gradually decreased with increasing curcumin concentrations.ConclusionsCurcumin can inhibit the expression of Beclin1 and HIF-1α in pancreatic cancer cells under anoxic conditions, thereby affecting the glycolysis pathway and inhibiting cell proliferation.     

Hypoxia induces a lipogenic cancer cell phenotype via HIF1α-dependent and -independent pathways

The biochemistry of cancer cells diverges significantly from normal cells as a result of a comprehensive reprogramming of metabolic pathways. A major factor influencing cancer metabolism is hypoxia, which is mediated by HIF1α and HIF2α. HIF1α represents one of the principal regulators of metabolism and energetic balance in cancer cells through its regulation of glycolysis, glycogen synthesis, Krebs cycle and the pentose phosphate shunt. However, less is known about the role of HIF1α in modulating lipid metabolism. Lipids serve cancer cells to provide molecules acting as oncogenic signals, energetic reserve, precursors for new membrane synthesis and to balance redox biological reactions. To study the role of HIF1α in these processes, we used HCT116 colorectal cancer cells expressing endogenous HIF1α and cells in which the hif1α gene was deleted to characterize HIF1α-dependent and independent effects on hypoxia regulated lipid metabolites. Untargeted metabolomics integrated with proteomics revealed that hypoxia induced many changes in lipids metabolites. Enzymatic steps in fatty acid synthesis and the Kennedy pathway were modified in a HIF1α-dependent fashion. Palmitate, stearate, PLD3 and PAFC16 were regulated in a HIF-independent manner. Our results demonstrate the impact of hypoxia on lipid metabolites, of which a distinct subset is regulated by HIF1α.     

Glycosylation of MUC6 by α1,4‐linked N‐acetylglucosamine enhances suppression of pancreatic cancer malignancy

Biomarkers for early diagnosis of pancreatic cancer are greatly needed, as the high fatality of this cancer is in part due to delayed detection. α1,4‐linked N‐acetylglucosamine (αGlcNAc), a unique O‐glycan specific to gastric gland mucus, is biosynthesized by α1,4‐N‐acetylglucosaminyltransferase (α4GnT) and primarily bound at the terminal glycosylated residue to scaffold protein MUC6. We previously reported that αGlcNAc expression decreases at early stages of neoplastic pancreatic lesions, followed by decreased MUC6 expression, although functional effects of these outcomes were unknown. Here, we ectopically expressed α4GnT, the αGlcNAc biosynthetic enzyme, together with MUC6 in the human pancreatic cancer cell lines MIA PaCa‐2 and PANC‐1, neither of which expresses α4GnT and MUC6. We observed significantly suppressed proliferation in both lines following coexpression of α4GnT and MUC6. Moreover, cellular motility decreased following MUC6 ectopic expression, an effect enhanced by cotransduction with α4GnT. MUC6 expression also attenuated invasiveness of both lines relative to controls, and this effect was also enhanced by additional α4GnT expression. We found αGlcNAc‐bound MUC6 formed a complex with trefoil factor 2. Furthermore, analysis of survival curves of patients with pancreatic ductal adenocarcinoma using a gene expression database showed that samples marked by higher A4GNT or MUC6 mRNA levels were associated with relatively favorable prognosis. These results strongly suggest that αGlcNAc and MUC6 function as tumor suppressors in pancreatic cancer and that decreased expression of both may serve as a biomarker of tumor progression to pancreatic cancer.     

Integrins: roles in cancer development and as treatment targets

The integrin family of cell adhesion proteins promotes the attachment and migration of cells on the surrounding extracellular matrix (ECM). Through signals transduced upon integrin ligation by ECM proteins or immunoglobulin superfamily molecules, this family of proteins plays key roles in regulating tumour growth and metastasis as well as tumour angiogenesis. Several integrins play key roles in promoting tumour angiogenesis and tumour metastasis. Antagonists of several integrins (alpha5beta1, alphavbeta3 and alphavbeta5) are now under evaluation in clinical trials to determine their potential as therapeutics for cancer and other diseases.