Lentiviral vector neutral endopeptidase gene transfer suppresses prostate cancer tumor growth

Long-term neprilysin inhibition - implications for ARNIs

Neprilysin has a major role in both the generation and degradation of bioactive peptides. LCZ696 (valsartan/sacubitril, Entresto), the first of the new ARNI (dual-acting angiotensin-receptor-neprilysin inhibitor) drug class, contains equimolar amounts of valsartan, an angiotensin-receptor blocker, and sacubitril, a prodrug for the neprilysin inhibitor LBQ657. LCZ696 reduced blood pressure more than valsartan alone in patients with hypertension. In the PARADIGM-HF study, LCZ696 was superior to the angiotensin-converting enzyme inhibitor enalapril for the treatment of heart failure with reduced ejection fraction, and LCZ696 was approved by the FDA for this purpose in 2015. This approval was the first for chronic neprilysin inhibition. The many peptides metabolized by neprilysin suggest many potential consequences of chronic neprilysin inhibitor therapy, both beneficial and adverse. Moreover, LBQ657 might inhibit enzymes other than neprilysin. Chronic neprilysin inhibition might have an effect on angio-oedema, bronchial reactivity, inflammation, and cancer, and might predispose to polyneuropathy. Additionally, inhibition of neprilysin metabolism of amyloid-β peptides might have an effect on Alzheimer disease, age-related macular degeneration, and cerebral amyloid angiopathy. Much of the evidence for possible adverse consequences of chronic neprilysin inhibition comes from studies in animal models, and the relevance of this evidence to humans is unknown. This Review summarizes current knowledge of neprilysin function and possible consequences of chronic neprilysin inhibition that indicate a need for vigilance in the use of neprilysin inhibitor therapy.

miR-451a Inhibited Cell Proliferation and Enhanced Tamoxifen Sensitive in Breast Cancer via Macrophage Migration Inhibitory Factor

This study aims to investigate the regulative effects of microRNA-451a (miR-451a) on cell proliferation and sensitivity to tamoxifen in breast cancer cells. In cell culture experiments, the lentiviral vectors of pHBLV-miR-451a and pHBLV-miR-451a sponge were constructed and used to transfect MCF-7 and LCC2 cells. The transfection efficiency was tested by fluorescent observation, and cell lines with stable over- or downregulated expression of miR-451a were established. The expression of miR-451a and the target gene macrophage migration inhibitory factor (MIF) were detected by real-time reverse transcriptase polymerase chain reaction and/or western blot. Moreover, MTT assay, colony formation, and Transwell invasion assays were also performed. Data showed that the recombinant lentiviral vectors were constructed correctly, and the virus titer was 1 × 10(8) CFU/mL. The stable transfected cells were obtained. Overexpression of miR-451a downregulated MIF expression in mRNA and protein levels and inhibited cell proliferation, colony formation, and invasion of breast cancer cells. Downregulation of miR-451a upregulated MIF expression and increased breast cancer cell growth, invasion, and tamoxifen sensitivity. In summary, the miR-451a/MIF pathway may play important roles in the biological properties of breast cancer cells and may be a potential therapeutic target for breast cancer.

Engineered microenvironments provide new insights into ovarian and prostate cancer progression and drug responses

Tissue engineering technologies, which have originally been designed to reconstitute damaged tissue structure and function, can mimic not only tissue regeneration processes but also cancer development and progression. Bioengineered approaches allow cell biologists to develop sophisticated experimentally and physiologically relevant cancer models to recapitulate the complexity of the disease seen in patients. Tissue engineering tools enable three-dimensionality based on the design of biomaterials and scaffolds that re-create the geometry, chemistry, function and signalling milieu of the native tumour microenvironment. Three-dimensional (3D) microenvironments, including cell-derived matrices, biomaterial-based cell culture models and integrated co-cultures with engineered stromal components, are powerful tools to study dynamic processes like proteolytic functions associated with cancer progression, metastasis and resistance to therapeutics. In this review, we discuss how biomimetic strategies can reproduce a humanised niche for human cancer cells, such as peritoneal or bone-like microenvironments, addressing specific aspects of ovarian and prostate cancer progression and therapy response.

Submaxillary gland androgen-regulated protein 3A expression is an unfavorable risk factor for the survival of oropharyngeal squamous cell carcinoma patients after surgery

Recently, increased expression of the submaxillary gland androgen-regulated protein 3A (SMR3A) was found in recurrent tumors of an orthotopic floor-of-mouth mouse tumor model after surgery. However, SMR3A expression in the pathogenesis of human malignancy and its correlation with the clinical outcome have not been addressed so far. We analyzed tissue microarrays with specimens from oropharyngeal squamous cell carcinoma (OPSCC) patients (n = 157) by immunohistochemistry and compared SMR3A expression with clinical and pathological features by statistical analysis. Strong SMR3A expression was found in almost 36 % of all primary OPSCCs. Although, SMR3A protein levels were not associated with any clinical or histopathological feature tested, univariate Kaplan-Meier analysis revealed a significant correlation between high SMR3A protein expression and poor progression-free (p = 0.02) and overall survival (p = 0.03). Furthermore, high SMR3A expression was an independent marker for poor clinical outcome [HR (SMR3A(high) vs. SMR3(low)) = 2.32; 95 % CI = 1.03-5.23] concerning overall survival in a multivariate analysis of OPSCC patients with surgery as primary therapy (n = 100). Our data demonstrate for the first time increased SMR3A protein expression in the pathogenesis of OPSCC, which serves as an unfavorable risk factor for patient survival.

Adenoviral neutral endopeptidase gene delivery in combination with paclitaxel for the treatment of prostate cancer

Neutral endopeptidase (NEP) is a cell-surface peptidase that inhibits prostate cancer cell growth partly via inhibition of Akt kinase. We investigated the antitumor effects of an adenovirus gene delivery system (AdNEP) to restore NEP expression in DU145 prostate cancer cells in combination with paclitaxel chemotherapy. DU145 cells were infected with adenovirus expressing NEP or LacZ, treated with paclitaxel, and assessed for cell viability, Akt activation and induction of apoptosis. Athymic mice with established DU145 xenografts were injected intratumorally with AdNEP or AdLacZ and intraperitoneally with paclitaxel and monitored for tumor growth over 28 days. Compared to AdLacZ plus paclitaxel, AdNEP plus paclitaxel significantly inhibited DU145 cell growth and increased apoptosis as determined by increased caspase-3 and PARP-1 proteolytic fragments. In a xenograft model, tumor volume was reduced in mice treated with AdNEP plus paclitaxel (122.85±89.5 mm3; P<0.01) compared with mice treated with AdNEP plus saline (653.9±230.3 mm3), AdLacZ plus paclitaxel (575.9±176.6 mm3) or AdLacZ plus saline (920.2±238.2 mm3). In conclusion, these data suggest that NEP can augment taxane-induced apoptosis through inhibition of Akt/Bad signaling, and that the combination of NEP plus paclitaxel may be an effective strategy to inhibit castration-resistant prostate cancer growth.

Protease-activated drug development

In this extensive review, we elucidate the importance of proteases and their role in drug development in various diseases with an emphasis on cancer. First, key proteases are introduced along with their function in disease progression. Next, we link these proteases as targets for the development of prodrugs and provide clinical examples of protease-activatable prodrugs. Finally, we provide significant design considerations needed for the development of the next generation protease-targeted and protease-activatable prodrugs.

The impact of amyloid precursor protein signalling and histone deacetylase inhibition on neprilysin expression in human prostate cells

The zinc metallopeptidase, neprilysin (NEP), is an endothelin-1 degrading enzyme whose expression is extensively downregulated in prostate cancer. The expression of NEP in neuronal cells is regulated by intramembrane proteolysis of the amyloid precursor protein (APP) through its intracellular domain (AICD) facilitating histone acetylation of the NEP promoter and gene transcription. The present study has examined whether similar mechanisms operate in prostate cell lines. The expression of APP and its processing enzymes (β- and γ-secretases) was examined in a number of prostate cell lines, and the effect of γ-secretase inhibition was explored on NEP expression and activity. The potential interaction of AICD with the NEP promoter was examined by chromatin immunoprecipitation. Our results indicated that all key components involved in APP processing were expressed in prostate cancer cell lines but suppression of AICD production using a γ-secretase inhibitor did not decrease NEP expression and activity, and no direct AICD-NEP promoter interaction could be detected. However, histone deacetylase inhibitors (valproate and trichostatin A) caused a 2- to 3-fold increase in NEP expression in PC-3 cells, and combinatorial treatment with the DNA demethylating agent, AzaC, further increased NEP expression levels. Although AICD is detectable in prostate cell lines, it does not appear to regulate NEP by AICD-mediated signalling. Apart from promoter de-methylation, the data suggest that histone acetylation may facilitate partial re-activation of NEP expression in advanced prostate cancer cells. Upregulation of this tumour-suppressing protein may provide a novel therapeutic strategy in prostate cancer.

Inhibition of tumor growth and induction of apoptosis in prostate cancer cell lines by overexpression of tissue inhibitor of matrix metalloproteinase-3

The destruction of extracellular matrix by matrix metalloproteinases is a key event in cancer progression. The tissue inhibitors of metalloproteinases can restrain tumor growth by inhibiting these enzymes. We sought to determine whether overexpression of tissue inhibitor of metalloproteinase-3 (TIMP-3) could suppress the malignant phenotype of human prostate cancer cell line PC-3M. Stable overexpression of TIMP-3 inhibited cell proliferation significantly by MTT assay. Both early and late apoptosis were observed in TIMP-3 overexpressing cells, and flow cytometry analysis showed S-phase blocking of the cell cycle. Monolayer invasion assay and transwell invasion assay showed significantly decreased invasive potential in TIMP-3 overexpressing cells compared with control cells. Cell adhesion and motility were also lower after TIMP-3 was overexpressed. In vivo, cells stably overexpressing TIMP-3 completely lost the ability to form tumors after injection into nude mice. Transfection of TIMP-3 into established tumors by electroporation also had a significant antitumor effect. TIMP-3-treated tumor tissues had significant apoptosis by TUNEL assay. These results showed that overexpression of TIMP-3 inhibits invasion and proliferation of prostate cancer cells in vitro and inhibits tumor growth in vivo. The experiments suggest a potential use for TIMP-3 in the gene therapy of prostate cancer.

Targeting the endothelin system: novel therapeutic options in gynecological, urological and breast cancers

The endothelin system comprises the three peptide hormones endothelin (ET)-1, -2, -3, their G protein-coupled receptors, endothelin-A-receptor (ET(A)R) and endothelin-B-receptor (ET(B)R), and the enzymes of endothelin biosynthesis and degradation. In the past two decades, an impressive amount of data has been accumulated investigating the role of the endothelin system in a variety of malignancies. In many cancers, ET-1/ET(A)R interaction induces proliferation, angiogenesis, antiapoptosis and resistance to chemotherapy. Data indicate a pivotal role of the endothelin system in tumorigenesis, local progression and metastasis. Subsequently, novel drugs have been designed inhibiting ET-1 biosynthesis or ET(A)R interaction. A wide range of preclinical data is available on the role of ET(A)R antagonists in gynecological, urological and breast cancers providing evidence for their antiangiogenic, proapoptotic and growth inhibitory effects. Of particular interest is the anti-invasive and antimetastatic efficacy of ET(A)R antagonists and synergism when co-administered with established cancer therapies. Data indicate a future role of ET(A)R antagonists in oncologic therapies.