Angiotensin II type 2 receptor gene deficiency attenuates susceptibility to tobacco-specific nitrosamine-induced lung tumorigenesis: involvement of transforming growth factor-beta-dependent cell growth attenuation

The potential role of renin angiotensin system in acute leukemia: a narrative review

Acute leukemias (ALs) are the most common cancers in pediatric population. There are two types of ALs: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Some studies suggest that the Renin Angiotensin System (RAS) has a role in ALs. RAS signaling modulates, directly and indirectly, cellular activity in different cancers, affecting tumor cells and angiogenesis. Our review aimed to summarize the role of RAS in ALs and to explore future perspectives for the treatment of these hematological malignancies by modulating RAS molecules. The database including Pubmed, Scopus, Cochrane Library, and Scielo were searched to find articles about RAS molecules in ALL and in pediatric patients. The search terms were "RAS", "Acute Leukemia", "ALL", "Angiotensin-(1-7)", "Pediatric", "Cancer", "Angiotensin II", "AML". In the bone marrow, RAS has been found to play a key role in blood cell formation, affecting several processes including apoptosis, cell proliferation, mobilization, intracellular signaling, angiogenesis, fibrosis, and inflammation. Local tissue RAS modulates tumor growth and metastasis through autocrine and paracrine actions. RAS mainly acts via two molecules, Angiotensin II (Ang II) and Angiotensin (1-7) [Ang-(1-7)]. While Ang II promotes tumor cell growth and stimulates angiogenesis, Ang-(1-7) inhibits the proliferation of neoplastic cells and the angiogenesis, suggesting a potential therapeutic role of this molecule in ALL. The interaction between ALs and RAS reveals a complex network of molecules that can affect the hematopoiesis and the development of hematological cancers. Understanding these interactions could pave the way for innovative therapeutic approaches targeting RAS components.

The tobacco-specific carcinogen NNK induces pulmonary tumorigenesis via nAChR/Src/STAT3-mediated activation of the renin-angiotensin system and IGF-1R signaling

The renin-angiotensin (RA) system has been implicated in lung tumorigenesis without detailed mechanistic elucidation. Here, we demonstrate that exposure to the representative tobacco-specific carcinogen nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) promotes lung tumorigenesis through deregulation of the pulmonary RA system. Mechanistically, NNK binding to the nicotinic acetylcholine receptor (nAChR) induces Src-mediated signal transducer and activator of transcription 3 (STAT3) activation, resulting in transcriptional upregulation of angiotensinogen (AGT) and subsequent induction of the angiotensin II (AngII) receptor type 1 (AGTR1) signaling pathway. In parallel, NNK concurrently increases insulin-like growth factor 2 (IGF2) production and activation of IGF-1R/insulin receptor (IR) signaling via a two-step pathway involving transcriptional upregulation of IGF2 through STAT3 activation and enhanced secretion from intracellular storage through AngII/AGTR1/PLC-intervened calcium release. NNK-mediated crosstalk between IGF-1R/IR and AGTR1 signaling promoted tumorigenic activity in lung epithelial and stromal cells. Lung tumorigenesis caused by NNK exposure or alveolar type 2 cell-specific Src activation was suppressed by heterozygous Agt knockout or clinically available inhibitors of the nAChR/Src or AngII/AGTR1 pathways. These results demonstrate that NNK-induced stimulation of the lung RA system leads to IGF2-mediated IGF-1R/IR signaling activation in lung epithelial and stromal cells, resulting in lung tumorigenesis in smokers.

Euglena gracilis Extract Protects From Tobacco Smoke Carcinogen-Induced Lung Cancer by Altering Gut Microbiota Metabolome

Extracts from Euglena gracilis have been shown to prevent cancer growth in mouse models. However, the molecular mechanism of this anti-cancer activity has not been determined nor has the effect of Euglena extracts on tobacco smoke carcinogen-induced carcinogenesis. Here, we investigate the hypothesis that this anti-cancer activity is a result of changes in the intestinal microbiota induced by oral administration of the extract. We found that a Euglena gracilis water extract prevents lung tumorigenesis induced by a tobacco smoke-specific carcinogen (NNK) in mice treated either 2 weeks before or 10 weeks after NNK injection. Both of these treatment regimens are associated with significant increases in 27 microbiota metabolites found in the mouse feces, including large increases in triethanolamine, salicylate, desaminotyrosine, N-acetylserine, glycolate, and aspartate. Increases in the short-chain fatty acids (SCFAs) including acetate, propionate and butyrate are also observed. We also detected a significant attenuation of lung carcinoma cell growth through the induction of cell cycle arrest and apoptosis caused by low levels of SCFAs. This study provides strong evidence of anti-cancer activity in Euglena gracilis extracts against tobacco smoke carcinogen-induced tumorigenesis and demonstrates that this activity is linked to increased production of specific gut microbiota metabolites and the resultant induction of cell cycle arrest and apoptosis of lung carcinoma cells.

Effects of Antihypertensive Drugs Use on Risk and Prognosis of Colorectal Cancer: A Meta-Analysis of 37 Observational Studies

Background: Antihypertensive drugs might play a key role in the risk and poor prognosis of colorectal cancer. However, current epidemiologic evidence remains inconsistent. The aim of this study is to quantify the association between antihypertensive drugs and colorectal cancer. Methods: To identify available studies, we systematically searched electronic databases: PubMed, Web of Science, Embase, Cochrane Library. The risk estimates and their corresponding 95% confidence intervals (CIs) were collected and analyzed by using random-effects models. Heterogeneity test and sensitivity analysis were also performed. Results: Overall, 37 observational studies were included in this analysis (26 studies with cohort design, three studies with nested case-control design, and 8 studies with case-control design). Antihypertensive drugs did not present a significant effect on the risk or overall survival of patients with colorectal cancer [Risk ratio (RR) = 1.00, 95% CI: 0.95-1.04; Hazard ratio (HR) = 0.93, 95% CI: 0.84-1.02]. In the subgroup analysis, diuretics use was significantly associated with a worse overall survival of patients with colorectal cancer (HR = 1.27; 95% CI: 1.14-1.40). However, use of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers was associated with improved progression-free survival of patients who suffered from colorectal cancer (HR = 0.83; 95% CI: 0.72-0.95). Conclusion: Antihypertensive drug usage did not influence the risk and overall survival of patients with colorectal cancer in general. Further investigation reminded us that diuretics use might reduce the overall survival time in colorectal cancer patients, whereas those who took Angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers had a longer progression-free survival.

Antihypertensive drugs and the risk of cancer: a critical review of available evidence and perspective

: The issue of a potential danger of antihypertensive drugs related to cancer susceptibility is currently generating a major debate in the scientific community, concerns in the public and emphasized interest from the media. The present article is a thorough review of what is known on the various classes of antihypertensive drugs concerning the risk of developing different neoplasms and about the suggested pathophysiological mechanisms, whenever available. The main limitations of evidence derived from studies currently available in this setting are also discussed, high-lightening the need for newly developed approaches to generate more accurate recommendations and informed advice for physicians.

Beta-1,3 Oligoglucans Specifically Bind to Immune Receptor CD28 and May Enhance T Cell Activation

Beta glucans are known to have immunomodulatory effects that mediated by a variety of mechanisms. In this article, we describe experiments and simulations suggesting that beta-1,3 glucans may promote activation of T cells by a previously unknown mechanism. First, we find that treatment of a T lymphoblast cell line with beta-1,3 oligoglucan significantly increases mRNA levels of T cell activation-associated cytokines, especially in the presence of the agonistic anti-CD3 antibody. This immunostimulatory activity was observed in the absence of dectin-1, a known receptor for beta-1,3 glucans. To clarify the molecular mechanism underlying this activity, we performed a series of molecular dynamics simulations and free-energy calculations to explore the interaction of beta-1,3 oligoglucans with potential immune receptors. While the simulations reveal little association between beta-1,3 oligoglucan and the immune receptor CD3, we find that beta-1,3 oligoglucans bind to CD28 near the region identified as the binding site for its natural ligands CD80 and CD86. Using a rigorous absolute binding free-energy technique, we calculate a dissociation constant in the low millimolar range for binding of 8-mer beta-1,3 oligoglucan to this site on CD28. The simulations show this binding to be specific, as no such association is computed for alpha-1,4 oligoglucan. This study suggests that beta-1,3 glucans bind to CD28 and may stimulate T cell activation collaboratively with T cell receptor activation, thereby stimulating immune function.

Prognostic and Immunological Value of Angiotensin-Converting Enzyme 2 in Pan-Cancer

Angiotensin-converting enzyme 2 (ACE2) plays a pivotal role in the renin–angiotensin system and is closely related to coronavirus disease of 2019. However, the role of ACE2 in cancers remains unclear. We explored the pan-cancer expression patterns and prognostic value of ACE2 across multiple databases, including Oncomine, PrognoScan, Gene Expression Profiling Interactive Analysis, and Kaplan–Meier Plotter. Then, we investigated the correlations between ACE2 expression and immune infiltration in cancers. We found that tumor tissues had higher expression levels of ACE2 compared with normal tissue in the kidney and the liver and lower expression levels in the lung. High expression levels of ACE2 were beneficial to survival in ovarian serous cystadenocarcinoma, liver hepatocellular carcinoma, kidney renal papillary cell carcinoma, and kidney renal clear cell carcinoma, although this was not the case in lung squamous cell carcinoma. For those with a better prognosis, there were significant positive correlations between ACE2 expression and immune infiltrates, including B cells, CD8 + T cells, CD4 + T cells, neutrophils, macrophages, and dendritic cells. In conclusion, ACE2 could serve as a pan-cancer prognostic biomarker and is correlated with immune infiltrates.

A robust signature associated with patient prognosis and tumor immune microenvironment based on immune-related genes in lung squamous cell carcinoma

BACKGROUND

Lung squamous cell carcinoma (LUSC) is one common type of lung cancer. Immune-related genes (IRGs) are closely associated with cancer prognosis. This study aims to screen the key genes associated with LUSC and establish an immune-related prognostic model.

METHODS

Based on the Cancer Genome Atlas (TCGA) database, we screened the differentially expressed genes (DEGs) between LUSC and normal samples. Intersecting the DEGs with the immune-related genes (IRGs), we obtained the differentially expressed IRGs (DEIRGs). Univariate as well as multivariate Cox regression analyses were performed to identify the survival-associated IRGs and establish an immune-related prognostic model. The relationship between the prognostic model and tumor-infiltrating immune cells was analyzed by TIMER and CIBERSORT.

RESULTS

A total of 229 DEIRGs were screened, and 14 IRGs associated with survival were identified using univariate Cox analysis. Among the 14 IRGs, six genes were selected out using Lasso and multivariate Cox analyses, and they were used to build the prognostic model. Further analysis indicated that overall survival (OS) of high-risk groups was lower than that of low-risk groups. High risk score was independently related to worse OS. Moreover, the risk score was positively correlated with several immune infiltration cells. Finally, the efficacy of the prognostic model was validated by another independent cohort GSE73403.

CONCLUSION

The DEIRGs described in the study may have the potential to be the prognostic molecular markers for LUSC. In addition, the risk score model could predict the OS and provides more information for the immunotherapy of patients with LUSC.

Renin-angiotensin system inhibitor use and colorectal cancer risk and mortality: A dose-response meta analysis

OBJECTIVE

This study was undertaken to determine whether use of the renin-angiotensin system (RAS) inhibitors would increase colorectal cancer morbidity and mortality.

METHODS

Databases were electronically searched to collect data of RAS use and colorectal cancer morbidity and mortality from inception to October 2018. Stata 12.0 software was used to perform a meta-analysis.

RESULTS

A total of 16 publications involving 2,847,597 participants were included. RAS inhibitor use was related to colorectal cancer risk (relative risk (RR): 0.86; 95% confidence interval (CI): 0.78-0.93) and mortality (RR: 0.80; 95% CI: 0.66-0.98) decrement. Subgroup analysis showed angiotensin-converting enzyme inhibitor (ACEI)/angiotensin II receptor blocker (ARB) (RR: 0.82; 95% CI: 0.69-0.96) or ARB (RR: 0.86; 95% CI: 0.73-0.98) or ACEI (RR: 0.81; 95% CI: 0.70-0.92) were related to colorectal cancer risk decrement. Furthermore, RAS inhibitor use was related to colorectal cancer risk decrement in Caucasians (RR: 0.88; 95% CI: 0.80-0.96) and Asians (RR: 0.72; 95% CI: 0.61-0.85). Additionally, dose-response showed that per one year duration of RAS inhibitor use incremental increase was related to 6% colorectal cancer risk decrement (RR: 0.94; 95% CI: 0.90-0.97).

CONCLUSION

According to the evidence, RAS inhibitor use was associated with colorectal cancer risk and mortality decrement.

ACE2 inhibits breast cancer angiogenesis via suppressing the VEGFa/VEGFR2/ERK pathway

BACKGROUND

Breast cancer angiogenesis is key for metastasis and predicts a poor prognosis. Angiotensin-converting enzyme 2 (ACE2), as a member of the renin-angiotensin system (RAS), was reported to restrain the progression of hepatocellular carcinoma (HCC) and non-small cell lung cancer (NSCLC) through inhibiting angiogenesis. However, the relationship between ACE2 and breast cancer angiogenesis remains unclear.

METHODS

The prognosis and relative gene selection were analysed using the GEPIA, GEO, TCGA and STRING databases. ACE2 expression in breast cancer tissue was estimated by reverse transcription-quantitative polymerase chain reaction (qPCR). Breast cancer cell migration, proliferation and angiogenesis were assessed by Transwell migration, proliferation, tube formation, and wound healing assays. The expression of vascular endothelial growth factor A (VEGFa) was detected by qPCR and Western blotting. The phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2), mitogen-activated protein kinase 1/2 (MEK1/2), and extracellular signal-regulated protein kinase 1/2 (ERK1/2) was examined by Western blotting. Breast cancer metastasis and angiogenesis in vivo were measured using a zebrafish model.

RESULTS

ACE2 was downregulated in breast cancer patients. Patients with higher ACE2 expression had longer relapse-free survival (RFS). In vitro, ACE2 inhibited breast cancer migration. Meanwhile, ACE2 in breast cancer cells inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, tube formation and migration. In the zebrafish model, ACE2 inhibited breast cancer cell metastasis, as demonstrated by analyses of the number of disseminated foci and the metastatic distance. Neo-angiogenesis was also decreased by ACE2. ACE2 downregulated the expression of VEGFa in breast cancer cells. Furthermore, ACE2 in breast cancer cells inactivated the phosphorylation of VEGFR2, MEK1/2, and ERK1/2 in HUVECs.

CONCLUSIONS

Our findings suggest that ACE2, as a potential resister to breast cancer, might inhibit breast cancer angiogenesis through the VEGFa/VEGFR2/ERK pathway.

TRIAL REGISTRATION

Retrospectively registered.

Angiotensin II type 2 receptor promotes apoptosis and inhibits angiogenesis in bladder cancer

Background

Bladder cancer (BCa) is the ninth most common form of cancer in the world. There is a continuing need not only for improving the accuracy of diagnostic markers but also for the development of new treatment strategies. Recent studies have shown that the renin-angiotensin system (RAS), which include the angiotensin type 1 (AT1R), type 2(AT2R), and Mas receptors, play an important role in tumorigenesis and may guide us in meeting those needs.

Results

In this study, we first observed that AT1R and Mas expression levels were significantly upregulated in BCa specimens while AT2R was significantly downregulated. Viral vector mediated overexpression of AT2R induced apoptosis and dramatically suppressed BCa cell proliferation in vitro, suggesting a therapeutic effect. Investigation into the mechanism revealed that the overexpression of AT2R increases the expression levels of caspase-3, caspase-8, and p38 and decreases the expression level of pErk. AT2R overexpression also leads to upregulation of 2 apoptosis-related genes (BCL2A1, TNFSF25) and downregulation of 8 apoptosis-related genes (CASP 6, CASP 9, DFFA, IGF1R, PYCARD, TNF, TNFRSF21, TNFSF10, NAIP) in transduced EJ cells as determined by PCR Array analysis. In vivo, we observed that AT2R overexpression caused significant reduction in xenograft tumors sizes by downregulation VEGF and induction of apoptosis.

Conclusions

Taken together, the data suggest that AT1R, AT2R or Mas could be used as a diagnostic marker of BCa and AT2R is a promising novel target gene for BCa gene therapy.

Angiotensin II Receptor Blockers and Cancer Risk: A Meta-Analysis of Randomized Controlled Trials

Angiotensin II receptor blockers (ARB) are widely used drugs that are proven to reduce cardiovascular disease events; however, several recent meta-analyses yielded conflicting conclusions regarding the relationship between ARB and cancer incidence, especially when ARB are combined with angiotensin-converting enzyme inhibitors (ACEI).We investigated the risk of cancer associated with ARB at different background ACEI levels.Search of PubMed and EMBASE (1966 to December 17, 2015) without language restriction.Randomized, controlled trials (RCTs) had at least 12 months of follow-up data and reported cancer incidence was included.Study characteristics, quality, and risk of bias were assessed by 2 reviewers independently.Nineteen RCTs including 148,334 patients were included in this study. Random-effects model meta-analyses were used to estimate the risk ratio (RR) of cancer risk. No excessive cancer risk was observed in our analyses of ARB alone versus placebo alone without background ACEI use (risk ratio [RR] 1.08, 95% confidence interval [CI] 1.00-1.18, P = 0.05); ARB alone versus ACEI alone (RR 1.03, 95%CI 0.94-1.14, P = 0.50); ARB plus partial use of ACEI versus placebo plus partial use of ACEI (RR 0.97, 95%CI 0.90-1.04, P = 0.33); and ARB plus ACEI versus ACEI (RR 0.99, 95%CI 0.79-1.24, P = 0.95).Lack of long-term data, inadequate reporting of safety data, significant heterogeneity in underlying study populations, and treatment regimens.ARB have a neutral effect on cancer incidence in randomized trials. We observed no significant differences in cancer incidence when we compared ARB alone with placebo alone, ARB alone with ACEI alone, ARB plus partial use of ACEI with placebo plus partial use of ACEI, or ARB plus ACEI combination with ACEI.

Adenovirus-Mediated Angiotensin II Type 2 Receptor Overexpression Inhibits Tumor Growth of Prostate Cancer In Vivo

The renin-angiotensin system (RAS) plays important roles in tumorigenesis and is involved with several hallmarks of cancer. Evidence shows that angiotensin II (AngII) type 1 receptor (AT1R) blockers may be associated with improved outcome in prostate cancer patients. Furthermore, our previous studies indicate that increased expression of Ang II type 2 receptor (AT2R) alone induced apoptosis in human prostate cancer lines, an effect that did not require Ang II. This study aimed to investigate the effects of AT2R on tumor growth in vivo and we hypothesized that AT2R over-expression would inhibit proliferation and induce apoptosis in vivo. Human prostate cancer DU145 xenograft mouse model was used to assess the effect of AT2R on tumor growth in vivo. Mice bearing a palpable tumor were chosen and divided randomly into three treatment groups: AT2R, GFP, and PBS. Then we directly injected into the xenograft tumors of the mice every three days with recombinant adenoviruses encoding AT2R (Ad5-CMV-AT2R-EGFP), EGFP (Ad5-CMV-EGFP) and PBS, respectively. The tumor sizes of the tumor bearing mice were then measured. Immunohistochemical Ki-67 staining and TUNEL assay were performed to examine the inhibitory effect of AT2R on tumor cell proliferation. The results showed that AT2R overexpression can inhibit tumor growth of prostate cancer in vivo by inhibiting proliferation and inducing apoptosis of tumor cells. GADD45A is involved in the AT2R-induced antitumor activity. This suggests that AT2R is a potentially useful gene for prostate gene therapy.

Effects of angiotensin II type 2 receptor overexpression on the growth of hepatocellular carcinoma cells in vitro and in vivo

Increasing evidence suggests that the renin-angiotensin system (RAS) plays an important role in tumorigenesis. The interaction between Angiotensin II (AngII) and angiotensin type 1 receptor (AT1R) may have a pivotal role in hepatocellular carcinoma (HCC) and therefore, AT1R blocker and angiotensin I-converting enzyme (ACE) inhibitors may have therapeutic potential in the treatment of hepatic cancer. Although the involvement of AT1R has been well explored, the role of the angiotensin II Type 2 receptor (AT2R) in HCC progression remains poorly understood. Thus, the aim of this study was to explore the effects of AT2R overexpression on HCC cells in vitro and in mouse models of human HCC. An AT2R recombinant adenoviral vector (Ad-G-AT2R-EGFP) was transduced into HCC cell lines and orthotopic tumor grafts. The results indicate that the high dose of Ad-G-AT2R-EGFP–induced overexpression of AT2R in transduced HCC cell lines produced apoptosis. AT2R overexpression in SMMC7721 cells inhibited cell proliferation with a significant reduction of S-phase cells and an enrichment of G1-phase cells through changing expression of CDK4 and cyclinD1. The data also indicate that overexpression of AT2R led to apoptosis via cell death signaling pathway that is dependent on activation of p38 MAPK, pJNK, caspase-8 and caspase-3 and inactivation of pp42/44 MAPK (Erk1/2). Finally, we demonstrated that moderately increasing AT2R expression could increase the growth of HCC tumors and the proliferation of HCC cells in vivo. Our findings suggest that AT2R overexpression regulates proliferation of hepatocellular carcinoma cells in vitro and in vivo, and the precise mechanisms of this phenomenon are yet to be fully determined.

Lowered cancer risk with ACE inhibitors/ARBs: a population-based cohort study

There are conflicting reports on cancer risk associated with angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers (ARBs). This retrospective cohort study was conducted to analyze the risk of cancer development in patients who received ACE inhibitors/ARBs as treatment for essential hypertension. Using the Taiwan National Health Insurance Research Database, 297,688 eligible study patients with essential hypertension were identified. According to their antihypertensive prescriptions, the study patients were stratified into an ACE inhibitor group, an ARB group, or a control group. After matching, participants were observed for the occurrence of cancer. In the ACE inhibitor group compared with the control group, the hazard ratio was 0.51 (95% confidence interval, 0.39-0.68). In the ARB group compared with the control group, the hazard ratio was 0.8 (95% confidence interval, 0.65-0.97). Regular use of ACE inhibitors/ARBs was not associated with an increased risk of cancer development and was actually found to decrease overall cancer risk in this study.

Inhaled gene therapy in lung cancer: proof-of-concept for nano-oncology and nanobiotechnology in the management of lung cancer

Lung cancer still remains one of the leading causes of death among cancer patients. Although novel targeted therapies have been established in everyday treatment practice, and conventional platinum-based doublets have demonstrated effective results regarding overall and progression-free survival, we have still failed to achieve long-term survival. Therefore, several strategies of applying locoregional therapy are under investigation. Aerosol chemotherapy is already under investigation and, taking this a step further, aerosol gene therapies with multiple delivery systems are being developed. Several efforts have demonstrated its efficiency and effectiveness, but there are still multiple factors that have to be considered and combined to achieve an overall more effective multifunctional treatment. In the current review, we present data regarding aerosol delivery systems, transporters, carriers, vectors, genes, toxicity, efficiency, specificity, lung microenvironment and delivery gene therapy systems. Finally, we present current studies and future perspectives.

Angiotensin-converting enzyme 2 attenuates the metastasis of non-small cell lung cancer through inhibition of epithelial-mesenchymal transition

Angiotensin-converting enzyme 2 (ACE2) is a key enzyme of the renin-angiotensin system (RAS). ACE2 plays a critical counterbalancing role by degrading angiotensin II (Ang II) to Ang 1-7. Recent studies suggest that RAS influences tumor growth and development by its paracrine effects on the tumor microenvironment. Epithelial‑mesenchymal transition (EMT) is now thought to be a process that plays a fundamental role in tumor progression and metastasis. In the present study, we investigated the role of ACE2 in lung cancer metastasis and the mechanism of EMT. This is the first study to elucidate the mechanism through which the overexpression of ACE2 in the A549 lung cancer cell line decreases metastasis formation in vivo and upregulates the expression of E-cadherin both in vitro and in vivo. We also observed the downregulation of vimentin, which supports a role of ACE2 in influencing EMT in lung cancer. Further analysis indicated that ACE2 abrogated the upregulation of TGF-β1-induced EMT markers, such as vimentin and α-smooth muscle actin (αSMA) in vitro in A549 cells. Finally, exposing A549 cells stably expressing ACE2 to DX600, an inhibitor of ACE2, recovered the sensitivity of lung cancer cells to TGF-β1-mediated induction of EMT. Our study demonstrated that ACE2 attenuated the metastasis of lung cancer and may serve as a target for new strategies to inhibit EMT in cancer cells.

Vectors for inhaled gene therapy in lung cancer. Application for nano oncology and safety of bio nanotechnology

Novel aerosol therapeutic modalities have been investigated for lung cancer. Inhaled gene therapy has presented safety and effectiveness previously in cystic fibrosis. However, safety concerns have been raised regarding the safety of non-viral vectors for inhaled gene therapy in lung cancer, and therefore small steps have been made towards this multifunctional treatment modality. During the last decade, numerous new nanocomplexes have been created and investigated as a safe gene delivery nano-vehicle. These formulations are multifunctional; they can be used as either local therapy or carrier for an effective inhaled gene therapy for lung cancer. Herein, we present current and future perspectives of nanocomplexes for inhaled gene therapy treatment in lung cancer.

Intratracheal administration of a nanoparticle-based therapy with the angiotensin II type 2 receptor gene attenuates lung cancer growth

Targeted gene delivery, transfection efficiency, and toxicity concerns remain a challenge for effective gene therapy. In this study, we dimerized the HIV-1 TAT peptide and formulated a nanoparticle vector (dTAT NP) to leverage the efficiency of this cell-penetrating strategy for tumor-targeted gene delivery in the setting of intratracheal administration. Expression efficiency for dTAT NP-encapsulated luciferase or angiotensin II type 2 receptor (AT2R) plasmid DNA (pDNA) was evaluated in Lewis lung carcinoma (LLC) cells cultured in vitro or in vivo in orthotopic tumor grafts in syngeneic mice. In cell culture, dTAT NP was an effective pDNA transfection vector with negligible cytotoxicity. Transfection efficiency was further increased by addition of calcium and glucose to dTAT/pDNA NP. In orthotopic tumor grafts, immunohistochemical analysis confirmed that dTAT NP successfully delivered pDNA to the tumor, where it was expressed primarily in tumor cells along with the bronchial epithelium. Notably, gene expression in tumor tissues persisted at least 14 days after intratracheal administration. Moreover, bolus administration of dTAT NP-encapsulated AT2R or TNF-related apoptosis-inducing ligand (TRAIL) pDNA markedly attenuated tumor growth. Taken together, our findings offer a preclinical proof-of-concept for a novel gene delivery system that offers an effective intratracheal strategy for administering lung cancer gene therapy.

A current evaluation of the safety of angiotensin receptor blockers and direct renin inhibitors

The safety of angiotensin II receptor blockers (ARBs) for the treatment of hypertension and cardiovascular and renal diseases has been well documented in numerous randomized clinical trials involving thousands of patients. However, recent concerns have surfaced about possible links between ARBs and increased risks of myocardial infarction and cancer. Less is known about the safety of the direct renin inhibitor aliskiren, which was approved as an antihypertensive in 2007. This article provides a detailed review of the safety of ARBs and aliskiren, with an emphasis on the risks of cancer and myocardial infarction associated with ARBs. Safety data were identified by searching PubMed and Food and Drug Administration (FDA) Web sites through April 2011. ARBs are generally well tolerated, with no known class-specific adverse events. The possibility of an increased risk of myocardial infarction associated with ARBs was suggested predominantly because the Valsartan Antihypertensive Long-Term Use Evaluation (VALUE) trial reported a statistically significant increase in the incidence of myocardial infarction with valsartan compared with amlodipine. However, no large-scale, randomized clinical trials published after the VALUE study have shown a statistically significant increase in the incidence of myocardial infarction associated with ARBs compared with placebo or non-ARBs. Meta-analyses examining the risk of cancer associated with ARBs have produced conflicting results, most likely due to the inherent limitations of analyzing heterogeneous data and a lack of published cancer data. An ongoing safety investigation by the FDA has not concluded that ARBs increase the risk of cancer. Pooled safety results from clinical trials indicate that aliskiren is well tolerated, with a safety profile similar to that of placebo. ARBs and aliskiren are well tolerated in patients with hypertension and certain cardiovascular and renal conditions; their benefits outweigh possible safety concerns.

NNK-Induced Lung Tumors: A Review of Animal Model

The incidence of lung adenocarcinoma has been remarkably increasing in recent years due to the introduction of filter cigarettes and secondary-hand smoking because the people are more exposed to higher amounts of nitrogen oxides, especially 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK), which is widely applied in animal model of lung tumors. In NNK-induced lung tumors, genetic mutation, chromosome instability, gene methylation, and activation of oncogenes have been found so as to disrupt the expression profiles of some proteins or enzymes in various cellular signal pathways. Transgenic animal with specific alteration of lung cancer-related molecules have also been introduced to clarify the molecular mechanisms of NNK in the pathogenesis and development of lung tumors. Based on these animal models, many antioxidant ingredients and antitumor chemotherapeutic agents have been proved to suppress the NNK-induced lung carcinogenesis. In the future, it is necessary to delineate the most potent biomarkers of NNK-induced lung tumorigenesis, and to develop efficient methods to fight against NNK-associated lung cancer using animal models.

Deficiency or blockade of angiotensin II type 2 receptor delays tumorigenesis by inhibiting malignant cell proliferation and angiogenesis

Despite significant expression level in cancer cells, the role of the angiotensin II Type 2 receptor (AT2R) in cancer progression remains poorly understood. We aimed to investigate the involvement of AT2R in tumorigenesis, hypothesizing a role in tumor cell proliferation and/or tumor angiogenesis. Two animal tumor models were used: fibrosarcoma induced by 3-methylcholanthrene (3-MCA) in FVB/N mice invalidated for AT2R (AT2R-KO) and carcinoma LL/2 cells injected in C57BL/6N mice treated with AT2R antagonist PD123,319. Tumor growth was monitored, microvascular density (MVD) evaluated by CD31 staining. Proliferation index of LL/2 and 3-MCA tumor cells was evaluated by expression of Ki-67. Angiogenesis was assessed by aorta ring assay and angiogenic mediators' expression by real-time RT-PCR. Tumor induction by 3-MCA was significantly delayed in AT2R-KO compared to wild-type mice (56 days vs. 28 days). Tumorigenesis following LL/2 cell injection in mice was also significantly reduced by early administration of the antagonist PD123,319. In vitro, inactivation or invalidation of AT2R inhibited proliferation of LL/2 and 3-MCA tumor cells, respectively. Tumor MVD was reduced in mice treated early with PD123,319. Ex vivo experiments revealed a significant decrease in angiogenesis after PD123,319 treatment or in AT2R-KO mice. Finally, we identified vascular endothelial growth factor (VEGF) as a soluble proangiogenic factor produced by LL/2 cells and we showed that in LL/2 and 3-MCA tumor cells, inhibition or deficiency of AT2R was associated with impaired production of proangiogenic factors included VEGF. This study uncovered novel mechanisms by which AT2R would promote tumor development, favoring both malignant cell proliferation and tumor angiogenesis.

Angiotensin II type 2 receptor signaling significantly attenuates growth of murine pancreatic carcinoma grafts in syngeneic mice

Background

Pancreatic cancer is one of the most aggressive human malignancies, with a very poor prognosis. To evaluate the effect of angiotensin II (Ang II) type 2 receptor (AT₂) expression in the host's body on the growth of pancreatic carcinoma, we have investigated the growth of mouse pancreatic ductal carcinoma grafts in syngeneic wild type and AT₂ receptor-deficient (AT₂-KO) mice.

Methods

The role of AT₂ receptor-signaling in stromal cells on the growth of murine pancreatic carcinoma cells (PAN02) was studied using various in vitro and in vivo assays. In vivo cell proliferation, apoptosis, and vasculature in tumors were monitored by Ki-67 immunostaining, TUNEL assay, and von Willebrand factor immunostaining, respectively. In the co-culture study, cell proliferation was measured by MTT cell viability assay. All the data were analyzed using t-test and data were treated as significant when p < 0.05.

Results

Our results show that the growth of subcutaneously transplanted syngeneic xenografts of PAN02 cells, mouse pancreatic ductal carcinoma cells derived from the C57/BL6 strain, was significantly faster in AT₂-KO mice compared to control wild type mice. Immunohistochemical analysis of tumor tissue revealed significantly more Ki-67 positive cells in xenografts grown in AT₂-KO mice than in wild type mice. The index of apoptosis is slightly higher in wild type mice than in AT₂-KO mice as evaluated by TUNEL assay. Tumor vasculature number was significantly higher in AT₂-KO mice than in wild type mice. In vitro co-culture studies revealed that the growth of PAN02 cells was significantly decreased when grown with AT₂ receptor gene transfected wild type and AT₂-KO mouse-derived fibroblasts. Faster tumor growth in AT₂-KO mice may be associated with higher VEGF production in stromal cells.

Conclusions

These results suggest that Ang II regulates the growth of pancreatic carcinoma cells through modulating functions of host stromal cells; Moreover, Ang II AT₂ receptor signaling is a negative regulator in the growth of pancreatic carcinoma cells. These findings indicate that the AT₂ receptor in stromal fibroblasts is a potentially important target for chemotherapy for pancreatic cancer.

Over-expression of angiotensin II type 2 receptor gene induces cell death in lung adenocarcinoma cells

The endogenous angiotensin II (Ang II) type 2 receptor (AT 2) has been shown to mediate apoptosis in cardiovascular tissues. Thus, the aim of this study was to explore the anti-cancer effect of AT 2 over-expression on lung adenocarcinoma cells in vitro using adenoviral (Ad), FuGENE, and nanoparticle vectors. All three gene transfection methods efficiently transfected AT 2 cDNA into lung cancer cells but caused minimal gene transfection in normal lung epithelial cells. Ad-AT 2 significantly attenuated multiple human lung cancer cell growth (A549 and H358) as compared to the control viral vector, Ad-LacZ, when cell viability was examined by direct cell count. Examination of annexin V by flow cytometry revealed the activation of the apoptotic pathway via AT 2 over-expression. Western Blot analysis confirmed the activation of caspase-3. Similarly, poly (lactide-co-glycolic acid) (PLGA) biodegradable nanoparticles encapsulated AT 2 plasmid DNA were shown to be effectively taken up into the lung cancer cell. Nanoparticle-based AT 2 gene transfection markedly increased AT 2 expression and resultant cell death in A549 cells. These results indicate that AT 2 over-expression effectively attenuates growth of lung adenocarcinoma cells through intrinsic apoptosis. Our results also suggest that PLGA nanoparticles can be used as an efficient gene delivery vector for lung adenocarcinoma targeted therapy.

Angiotensin II bi-directionally regulates cyclooxygenase-2 expression in intestinal epithelial cells

We previously demonstrated that angiotensin II (Ang II) receptor signaling is involved in azoxymethane-induced mouse colon tumorigenesis. In order to clarify the role of Ang II in COX-2 expression in the intestinal epithelium, the receptor subtype-specific effect on COX-2 expression in a rat intestinal epithelial cell line (RIE-1) has been investigated. Ang II dose- and time-dependently increased the expression of COX-2, but not COX-1 mRNA and protein. This stimulation was completely blocked by the AT(1) receptor antagonist but not the AT(2) receptor antagonist. Ang II and lipopolysaccharide (LPS) additively induced COX-2 protein in RIE-1 cells, whereas the LPS-induced COX-2 expression was significantly attenuated by low concentrations of Ang II or the AT(2) agonistic peptide CGP-42112A only in AT(2) over-expressed cells. These data indicate that Ang II bi-directionally regulates COX-2 expression via both AT(1) and AT(2) receptors. Control of COX-2 expression through Ang II signaling may have significance in cytokine-induced COX-2 induction and colon tumorigenesis.

Specific single chain variable fragment (ScFv) antibodies to angiotensin II AT(2) receptor: evaluation of the angiotensin II receptor expression in normal and tumor-bearing mouse lung

To gain insight into the mechanism by which angiotensin II type 2 receptor (AT(2)) regulates carcinogen-induced lung tumorigenesis, we have newly developed anti-AT(2) single chain variable fragment (ScFv) antibodies using a rodent phage-displayed recombinant antibody library with various peptide fragments of the receptor protein, and investigated the expression of the AT(2) receptor protein. The specificity of the antibodies was verified using AT(2) over-expressing COS-7 cells and AT(2) naturally expressing PC12W cells. In control wild type mouse lung, a stronger immunoreactivity was observed in bronchial epithelial cells. A moderate immunoreactivity was detected in pulmonary vascular walls and vascular endothelial cells. In the lungs possessing tobacco-specific nitrosamine (NNK)-induced tumors, significantly increased AT(2) and AT(1 )immunostaining was observed in adenomatous lesions. These data suggest that the increase in both receptors' expression in the alveolar epithelial cells may be accompanied with the onset of NNK-induced tumorigenesis and hence play important roles in lung tumorigenesis.