Tumour-infiltrating neutrophils counteract anti-VEGF therapy in metastatic colorectal cancer.

BACKGROUND: Immune infiltration is implicated in the development of acquired resistance to anti-angiogenic cancer therapy. We therefore investigated the correlation between neutrophil infiltration in metastasis of colorectal cancer (CRC) patients and survival after treatment with bevacizumab. Our study identifies CD177+ tumour neutrophil infiltration as an adverse prognostic factor for bevacizumab treatment. We further demonstrate that a novel anti-VEGF/anti-Ang2 compound (BI-880) can overcome resistance to VEGF inhibition in experimental tumour models. METHODS: A total of 85 metastatic CRC patients were stratified into cohorts that had either received chemotherapy alone (n = 39) or combined with bevacizumab (n = 46). Tumour CD177+ neutrophil infiltration was correlated to clinical outcome. The impact of neutrophil infiltration on anti-VEGF or anti-VEGF/anti-Ang2 therapy was studied in both xenograft and syngeneic tumour models by immunohistochemistry. RESULTS: The survival of bevacizumab-treated CRC patients in the presence of CD177+ infiltrates was significantly reduced compared to patients harbouring CD177- metastases. BI-880 treatment reduced the development of hypoxia associated with bevacizumab treatment and improved vascular normalisation in xenografts. Furthermore, neutrophil depletion or BI-880 treatment restored treatment sensitivity in a syngeneic tumour model of anti-VEGF resistance. CONCLUSIONS: Our findings implicate CD177 as a biomarker for bevacizumab and suggest VEGF/Ang2 inhibition as a strategy to overcome neutrophil associated resistance to anti-angiogenic treatment.

Evaluation of Angiopoietin-2 as a biomarker in gastric cancer: results from the randomised phase III AVAGAST trial.

BACKGROUND: In the phase III AVAGAST trial, the addition of bevacizumab to chemotherapy improved progression-free survival (PFS) but not overall survival (OS) in patients with advanced gastric cancer. We studied the role of Angiopoietin-2 (Ang-2), a key driver of tumour angiogenesis, metastasis and resistance to antiangiogenic treatment, as a biomarker. METHODS: Previously untreated, advanced gastric cancer patients were randomly assigned to receive bevacizumab (n=387) or placebo (n=387) in combination with chemotherapy. Plasma collected at baseline and at progression was analysed by ELISA. The role of Ang-2 as a prognostic and a predictive biomarker of bevacizumab efficacy was studied using a Cox proportional hazards model. Logistic regression analysis was applied for correlations with metastasis. RESULTS: Median baseline plasma Ang-2 levels were lower in Asian (2143 pg ml(-1)) vs non-Asian patients (3193 pg ml(-1)), P<0.0001. Baseline plasma Ang-2 was identified as an independent prognostic marker for OS but did not predict bevacizumab efficacy alone or in combination with baseline VEGF. Baseline plasma Ang-2 correlated with the frequency of liver metastasis (LM) at any time: Odds ratio per 1000 pg ml(-1) increase: 1.19; 95% CI 1.10-1.29; P<0.0001 (non-Asians) and 1.37; 95% CI 1.13-1.64; P=0.0010 (Asians). CONCLUSIONS: Baseline plasma Ang-2 is a novel prognostic biomarker for OS in advanced gastric cancer strongly associated with LM. Differences in Ang-2 mediated vascular response may, in part, account for outcome differences between Asian and non-Asian patients; however, data have to be further validated. Ang-2 is a promising drug target in gastric cancer.

IAP antagonization promotes inflammatory destruction of vascular endothelium.

In this study, we show for the first time that the therapeutic antagonization of inhibitor of apoptosis proteins (IAPs) inhibits B16 melanoma growth by disrupting tumor vasculature. Specifically, the treatment of mice bearing B16 melanoma with an IAP antagonist compound A (Comp A) inhibits tumor growth not by inducing direct cytotoxicity against B16 cells but rather by a hitherto unrecognized antiangiogenic activity against tumor vessels. Our detailed analysis showed that Comp A treatment induces NF-κB activity in B16 tumor cells and facilitates the production of TNF. In the presence of Comp A, endothelial cells (ECs) become highly susceptible to TNF and undergo apoptotic cell death. Accordingly, the antiangiogenic and growth-attenuating effects of Comp A treatment were completely abolished in TNF-R knockout mice. This novel targeting approach could be of clinical value in controlling pathological neoangiogenesis under inflammatory condition while sparing blood vessels under normal condition.

BID-dependent release of mitochondrial SMAC dampens XIAP-mediated immunity against Shigella.

The X-linked inhibitor of apoptosis protein (XIAP) is a potent caspase inhibitor, best known for its anti-apoptotic function in cancer. During apoptosis, XIAP is antagonized by SMAC, which is released from the mitochondria upon caspase-mediated activation of BID. Recent studies suggest that XIAP is involved in immune signaling. Here, we explore XIAP as an important mediator of an immune response against the enteroinvasive bacterium Shigella flexneri, both in vitro and in vivo. Our data demonstrate for the first time that Shigella evades the XIAP-mediated immune response by inducing the BID-dependent release of SMAC from the mitochondria. Unlike apoptotic stimuli, Shigella activates the calpain-dependent cleavage of BID to trigger the release of SMAC, which antagonizes the inflammatory action of XIAP without inducing apoptosis. Our results demonstrate how the cellular death machinery can be subverted by an invasive pathogen to ensure bacterial colonization.

Embelin inhibits endothelial mitochondrial respiration and impairs neoangiogenesis during tumor growth and wound healing.

In the normal quiescent vasculature, only 0.01% of endothelial cells (ECs) are proliferating. However, this proportion increases dramatically following the angiogenic switch during tumor growth or wound healing. Recent evidence suggests that this angiogenic switch is accompanied by a metabolic switch. Here, we show that proliferating ECs increasingly depend on mitochondrial oxidative phosphorylation (OxPhos) for their increased energy demand. Under growth conditions, ECs consume three times more oxygen than quiescent ECs and work close to their respiratory limit. The increased utilization of the proton motif force leads to a reduced mitochondrial membrane potential in proliferating ECs and sensitizes to mitochondrial uncoupling. The benzoquinone embelin is a weak mitochondrial uncoupler that prevents neoangiogenesis during tumor growth and wound healing by exhausting the low respiratory reserve of proliferating ECs without adversely affecting quiescent ECs. We demonstrate that this can be exploited therapeutically by attenuating tumor growth in syngenic and xenograft mouse models. This novel metabolic targeting approach might be clinically valuable in controlling pathological neoangiogenesis while sparing normal vasculature and complementing cytostatic drugs in cancer treatment.

Ubiquitin C-terminal hydrolase-L1 potentiates cancer chemosensitivity by stabilizing NOXA.

The BH3-only protein NOXA represents one of the critical mediators of DNA-damage-induced cell death. In particular, its involvement in cellular responses to cancer chemotherapy is increasingly evident. Here, we identify a strategy of cancer cells to escape genotoxic chemotherapy by increasing proteasomal degradation of NOXA. We show that the deubiquitylating enzyme UCH-L1 is a key regulator of NOXA turnover, which protects NOXA from proteasomal degradation by removing Lys(48)-linked polyubiquitin chains. In the majority of tumors from patients with melanoma or colorectal cancer suffering from high rates of chemoresistance, NOXA fails to accumulate because UCH-L1 expression is epigenetically silenced. Whereas UCH-L1/NOXA-positive tumor samples exhibit increased sensitivity to genotoxic chemotherapy, downregulation of UCH-L1 or inhibition of its deubiquitylase activity resulted in reduced NOXA stability and resistance to genotoxic chemotherapy in both human and C. elegans cells. Our data identify the UCH-L1/NOXA interaction as a therapeutic target for overcoming cancer chemoresistance.

Analysis of Tie2-expressing monocytes (TEM) in patients with colorectal cancer.

Tie2-expressing monocytes (TEM) promote tumor angiogenesis and growth in experimental cancer models. The role of TEM in cancer patients is unknown. We studied TEM in healthy volunteers and colorectal cancer (CRC) patients. Although TEM were detectable in the blood and tumor lesions of CRC patients, their frequency and functional phenotype showed no correlation with levels of angiopoietin-2 or vascular endothelial growth factor, microvessel density, tumor markers, tumor stage, or outcome of antiangiogenic therapy. These unexpected findings are at odds with murine tumor models and question the diagnostic or therapeutic value of TEM in human cancer.

Hepatocyte growth factor (HGF) inhibits collagen I and IV synthesis in hepatic stellate cells by miRNA-29 induction.

BACKGROUND: In chronic liver disease, hepatic stellate cells (HSC) transdifferentiate into myofibroblasts, promoting extracellular matrix (ECM) synthesis and deposition. Stimulation of HSC by transforming growth factor-ß (TGF-ß) is a crucial event in liver fibrogenesis due to its impact on myofibroblastic transition and ECM induction. In contrast, hepatocyte growth factor (HGF), exerts antifibrotic activities. Recently, miR-29 has been reported to be involved in ECM synthesis. We therefore studied the influence of HGF and TGF-ß on the miR-29 collagen axis in HSC. METHODOLOGY: HSC, isolated from rats, were characterized for HGF and Met receptor expression by Real-Time PCR and Western blotting during culture induced myofibroblastic transition. Then, the levels of TGF-ß, HGF, collagen-I and -IV mRNA, in addition to miR-29a and miR-29b were determined after HGF and TGF-ß stimulation of HSC or after experimental fibrosis induced by bile-duct obstruction in rats. The interaction of miR-29 with 3'-untranslated mRNA regions (UTR) was analyzed by reporter assays. The repressive effect of miR-29 on collagen synthesis was studied in HSC treated with miR-29-mimicks by Real-Time PCR and immunoblotting. PRINCIPAL FINDINGS: The 3'-UTR of the collagen-1 and -4 subtypes were identified to bind miR-29. Hence, miR-29a/b overexpression in HSC resulted in a marked reduction of collagen-I and -IV synthesis. Conversely, a decrease in miR-29 levels is observed during collagen accumulation upon experimental fibrosis, in vivo, and after TGF-ß stimulation of HSC, in vitro. Finally, we show that during myofibroblastic transition and TGF-ß exposure the HGF-receptor, Met, is upregulated in HSC. Thus, whereas TGF-ß stimulation leads to a reduction in miR-29 expression and de-repression of collagen synthesis, stimulation with HGF was definitely associated with highly elevated miR-29 levels and markedly repressed collagen-I and -IV synthesis. CONCLUSIONS: Upregulation of miRNA-29 by HGF and downregulation by TGF-ß take part in the anti- or profibrogenic response of HSC, respectively.

Intrinsic phospholipase A2 activity of adeno-associated virus is involved in endosomal escape of incoming particles.

The unique region of the VP1 capsid protein of adeno-associated viruses (AAV) in common with autonomously replicating parvoviruses comprises a secreted phospholipase A2 (sPLA2) homology domain. While the sPLA2 domain of Minute Virus of Mice has recently been shown to mediate endosomal escape by lipolytic pore formation, experimental evidence for a similar function in AAV infection is still lacking. Here, we explored the function of the sPLA2 domain of AAV by making use of the serotype 2 mutant (76)HD/AN. The sPLA2 defect in (76)HD/AN, which severely impairs AAV's infectivity, could be complemented in trans by co-infection with wild-type AAV2. Furthermore, co-infection with endosomolytically active, but not with inactive adenoviral variants partially rescued (76)HD/AN, providing the first evidence for a function of this domain in endosomal escape of incoming AAV particles.

Combined paracrine and endocrine AAV9 mediated expression of hepatocyte growth factor for the treatment of renal fibrosis.

In chronic renal disease, tubulointerstitial fibrosis is a leading cause of renal failure. Here, we made use of one of the most promising gene therapy vector platforms, the adeno-associated viral (AAV) vector system, and the COL4A3-deficient mice, a genetic mouse model of renal tubulointerstitial fibrosis, to develop a novel bidirectional treatment strategy to prevent renal fibrosis. By comparing different AAV serotypes in reporter studies, we identified AAV9 as the most suitable delivery vector to simultaneously target liver parenchyma for endocrine and renal tubular epithelium for paracrine therapeutic expression of the antifibrogenic cytokine human hepatocyte growth factor (hHGF). We used transcriptional targeting to drive hHGF expression from the newly developed CMV-enhancer-Ksp-cadherin-promoter (CMV-Ksp) in renal and hepatic tissue following tail vein injection of rAAV9-CMV-Ksp-hHGF into COL4A3-deficient mice. The therapeutic efficiency of our approach was demonstrated by a remarkable attenuation of tubulointerstitial fibrosis and repression of fibrotic markers such as collagen1alpha1 (Col1A1), platelet-derived growth factor receptor-beta (PDGFR-beta), and alpha-smooth muscle actin (SMA). Taken together, our results show the great potential of rAAV9 as an intravenously applicable vector for the combined paracrine and endocrine expression of antifibrogenic factors in the treatment of renal failure caused by tubulointerstitial fibrosis.

The proteasome inhibitor bortezomib sensitizes melanoma cells toward adoptive CTL attack.

Adoptive transfer of tumor-specific cytolytic T lymphocytes (CTL) results in target cell lysis by activating the intrinsic apoptotic cell death program. Not surprisingly, deregulation of the apoptotic machinery is one of the central mechanisms by which tumor cells escape immune destruction despite specific CTL recognition. Here we show that treatment with the proteasome inhibitor bortezomib sensitizes previously resistant tumor cells for cytolytic T-cell attack. Human T cells were redirected toward melanoma cells by engineered expression of an immunoreceptor with binding specificity for high molecular weight-melanoma-associated antigen. Established melanoma cell lines as well as primary melanoma cells from tumor biopsies, which are notoriously resistant toward T-cell lysis, became sensitive upon bortezomib treatment. Detailed analysis of the underlying molecular mechanism revealed that bortezomib treatment induced mitochondrial accumulation of NOXA, which potentiated the release of mitochondrial second mitochondria-derived activator of caspase (SMAC) in response to CTL effector functions, including caspase-8 and granzyme B. Our data indicate that proteasome inhibition increases the sensitivity of tumor cells toward cytolytic T-cell attack by NOXA-mediated enhancement of mitochondrial SMAC release.

Complete remission in a colon cancer patient with a large, irresectable liver metastasis after XELOX/cetuximab/bevacizumab treatment.

BACKGROUND: Stage IV colorectal cancer is usually an incurable disease. However, patients with resectable metastases have 5-year disease-free survival rates of up to 30%. Even with primarily irresectable disease, cure can be achieved in patients who become operable after neoadjuvant treatment. To improve the prognosis of these patients, highly effective neoadjuvant regimens need to be developed. CASE REPORT: Here, we report the case of a 62-year-old male patient who had been diagnosed with International Union against Cancer (UICC) stage III colon cancer 7 years previously and now presented with a large, irresectable liver metastasis and enlarged perihepatic lymph nodes. After neoadjuvant treatment with cetuximab, bevacizumab and XELOX, the patient showed a complete remission and underwent surgery. Histopathologically, the resected tissue and lymph nodes were free of residual tumor. CONCLUSION: To our knowledge, this is the first report of a complete pathological response in a patient with irresectable colorectal cancer after intensive chemotherapy/anti-EGFR/ VEGF antibody therapy. This combination regimen may help to improve the survival rates for patients with irresectable disease.

Recent developments in adeno-associated virus vector technology.

Adeno-associated virus (AAV), a single-stranded DNA parvovirus, is emerging as one of the leading gene therapy vectors owing to its nonpathogenicity and low immunogenicity, stability and the potential to integrate site-specifically without known side-effects. A portfolio of recombinant AAV vector types has been developed with the aim of optimizing efficiency, specificity and thereby also the safety of in vitro and in vivo gene transfer. More and more information is now becoming available about the mechanism of AAV/host cell interaction improving the efficacy of recombinant AAV vector (rAAV) mediated gene delivery. This review summarizes the current knowledge of the infectious biology of AAV, provides an overview of the latest developments in the field of AAV vector technology and discusses remaining challenges.