Sabari Vallath

In vivo retargeting of adenovirus type 5 to alphavbeta6 integrin results in reduced hepatotoxicity and improved tumor uptake following systemic delivery.

ABSTRACT A key impediment to successful cancer therapy with adenoviral vectors is the inefficient transduction of malignant tissue in vivo. Compounding this problem is the lack of cancer-specific targets, coupled with a shortage of corresponding high-efficiency ligands, permitting selective retargeting. The epithelial cell-specific integrin αvβ6 represents an attractive target for directed therapy since it is generally not expressed on normal epithelium but is upregulated in numerous carcinomas, where it plays a role in tumor progression. We previously have characterized a high-affinity, αvβ6-selective peptide (A20FMDV2) derived from VP1 of foot-and-mouth disease virus. We generated recombinant adenovirus type 5 (Ad5) fiber knob, incorporating A20FMDV2 in the HI loop, for which we validated the selectivity of binding and functional inhibition of αvβ6. The corresponding αvβ6-retargeted virus Ad5-EGFPA20 exhibited up to 50-fold increases in coxsackievirus- and-adenovirus-receptor-independent transduction and up to 480-fold-increased cytotoxicity on a panel of αvβ6-positive human carcinoma lines compared with Ad5-EGFPWT. Using an αvβ6-positive (DX3-β6) xenograft model, we observed a ∼2-fold enhancement in tumor uptake over Ad5-EGFPWT following systemic delivery. Furthermore, ∼5-fold-fewer Ad5-EGFPA20 genomes were detected in the liver (P = 0.0002), correlating with reduced serum transaminase levels and E1A expression. Warfarin pretreatment, to deplete coagulation factors, did not improve tumor uptake significantly with either virus but did significantly reduce liver sequestration and hepatic toxicity. The ability of Ad5-EGFPA20 to improve delivery to αvβ6, combined with its reduced hepatic tropism and toxicity, highlights its potential as a prototype virus for future clinical investigation.

Targeting EGFR signalling in chronic lung disease: therapeutic challenges and opportunities

Chronic respiratory diseases, including pulmonary fibrosis, chronic obstructive pulmonary disease (COPD) and lung cancer, are the second leading cause of death among Europeans. Despite this, there have been only a few therapeutic advances in these conditions over the past 20 years. In this review we provide evidence that targeting the epidermal growth factor receptor (EGFR) signalling pathway may represent a novel therapeutic panacea for treating chronic lung disease. Using evidence from human patient samples, transgenic animal models, and cell and molecular biology studies we highlight the roles of this signalling pathway in lung development, homeostasis, repair, and disease ontogeny. We identify mechanisms underlying lung EGFR pathway regulation and suggest how targeting these mechanisms using new and existing therapies has the potential to improve future lung cancer, COPD and pulmonary fibrosis patient outcomes. Deregulated EGFR pathway signalling is a common event and an important therapeutic target for many chronic lung diseases http://ow.ly/rH74p

Therapeutic Targeting of Integrin αvβ6 in Breast Cancer

Background Integrin αvβ6 promotes migration, invasion, and survival of cancer cells; however, the relevance and role of αvβ6 has yet to be elucidated in breast cancer. Methods Protein expression of integrin subunit beta6 (β6) was measured in breast cancers by immunohistochemistry (n > 2000) and ITGB6 mRNA expression measured in the Molecular Taxonomy of Breast Cancer International Consortium dataset. Overall survival was assessed using Kaplan Meier curves, and bioinformatics statistical analyses were performed (Cox proportional hazards model, Wald test, and Chi-square test of association). Using antibody (264RAD) blockade and siRNA knockdown of β6 in breast cell lines, the role of αvβ6 in Human Epidermal Growth Factor Receptor 2 (HER2) biology (expression, proliferation, invasion, growth in vivo) was assessed by flow cytometry, MTT, Transwell invasion, proximity ligation assay, and xenografts (n ≥ 3), respectively. A student’s t-test was used for two variables; three-plus variables used one-way analysis of variance with Bonferroni’s Multiple Comparison Test. Xenograft growth was analyzed using linear mixed model analysis, followed by Wald testing and survival, analyzed using the Log-Rank test. All statistical tests were two sided. Results High expression of either the mRNA or protein for the integrin subunit β6 was associated with very poor survival (HR = 1.60, 95% CI = 1.19 to 2.15, P = .002) and increased metastases to distant sites. Co-expression of β6 and HER2 was associated with worse prognosis (HR = 1.97, 95% CI = 1.16 to 3.35, P = .01). Monotherapy with 264RAD or trastuzumab slowed growth of MCF-7/HER2-18 and BT-474 xenografts similarly (P < .001), but combining 264RAD with trastuzumab effectively stopped tumor growth, even in trastuzumab-resistant MCF-7/HER2-18 xenografts. Conclusions Targeting αvβ6 with 264RAD alone or in combination with trastuzumab may provide a novel therapy for treating high-risk and trastuzumab-resistant breast cancer patients.

Targeting of Aberrant αvβ6 Integrin Expression in Solid Tumors Using Chimeric Antigen Receptor-Engineered T Cells

Expression of the αvβ6 integrin is upregulated in several solid tumors. In contrast, physiologic expression of this epithelial-specific integrin is restricted to development and epithelial re-modeling. Here, we describe, for the first time, the development of a chimeric antigen receptor (CAR) that couples the recognition of this integrin to the delivery of potent therapeutic activity in a diverse repertoire of solid tumor models. Highly selective targeting αvβ6 was achieved using a foot and mouth disease virus-derived A20 peptide, coupled to a fused CD28+CD3 endodomain. To achieve selective expansion of CAR T cells ex vivo, an IL-4-responsive fusion gene (4αβ) was co-expressed, which delivers a selective mitogenic signal to engineered T cells only. In vivo efficacy was demonstrated in mice with established ovarian, breast, and pancreatic tumor xenografts, all of which express αvβ6 at intermediate to high levels. SCID beige mice were used for these studies because they are susceptible to cytokine release syndrome, unlike more immune-compromised strains. Nonetheless, although the CAR also engages mouse αvβ6, mild and reversible toxicity was only observed when supra-therapeutic doses of CAR T cells were administered parenterally. These data support the clinical evaluation of αvβ6 re-targeted CAR T cell immunotherapy in solid tumors that express this integrin.

Two-dimensional heteronuclear saturation transfer difference NMR reveals detailed integrin αvβ6 protein–peptide interactions

We report the first example of peptide-protein heteronuclear two-dimensional (2D) saturation transfer difference nuclear magnetic resonance (STD NMR). This method, resulting in dramatically reduced overlap, was applied to the interaction of the integrin αvβ6 with a known peptide ligand and highlights novel contact points between the substrate and target protein.

Combined fiber modifications both to target αvβ6 and detarget the coxsackievirus–adenovirus receptor improve virus toxicity profiles in vivo but fail to improve antitumoral efficacy relative to adenovirus serotype 5

Achieving high-efficiency tumor targeting after systemic delivery is a considerable challenge facing oncolytic gene therapists. Efficient retargeting should be combined with efforts to improve in vivo safety, reduce hepatotoxicity, minimize off-target interactions, and improve antitumoral potency and efficacy. We previously described the successful retargeting of adenovirus serotype 5 (Ad5) to α(v)β(6), an integrin that is highly overexpressed in numerous human carcinomas. In this study, we have further modified this construct by introducing mutations that ablate coxsackievirus-adenovirus receptor (CAR) binding and putative interactions with factor IX (FIX)/C4b-binding protein (C4BP). We have found that the resulting vector, Ad5-477dlTAYT(A20), displays a desirable in vivo safety profile. This vector does not agglutinate human erythrocytes, fails to cause thrombocytopenia after intravenous delivery, has limited induction of proinflammatory cytokines, and results in low-level toxicity (aspartate aminotransferase/alanine aminotransferase) when compared with Ad5-EGFP(WT). Furthermore, it has reduced accumulation in Kupffer cells (1 hr) and limited hepatocyte transduction at later time points (24 and 96 hr). The parental vector, Ad5-EGFP(A20), also displayed many of these desirable properties. As a result of the improved safety profile of both A20-modified vectors, we escalated the dose from 2×10(10) to 4×10(10) viral particles in an antitumoral efficacy study. We observed improvements in reducing percent tumor growth at early time points (96 hr) when compared with Ad5-EGFP(WT), although increasing the dose did not affect the therapeutic outcome beneficially. On completion of the experiment, we detected increased E1A staining in the tumors of all A20-treated groups and we determined that E1A expression was localized largely within α(v)β(6)(+) tumor cells. However, in spite of apparently efficient tumor transduction, this did not result in enhanced antitumoral efficacy as the virus failed to disseminate effectively throughout the tumor mass, presumably due to physical intratumoral restrictions. This highlights a remaining challenge that needs to be overcome before such vectors can be developed for future cancer gene therapy applications.

CADM1 inhibits squamous cell carcinoma progression by reducing STAT3 activity

Although squamous cell carcinomas (SqCCs) of the lungs, head and neck, oesophagus, and cervix account for up to 30% of cancer deaths, the mechanisms that regulate disease progression remain incompletely understood. Here, we use gene transduction and human tumor xenograft assays to establish that the tumour suppressor Cell adhesion molecule 1 (CADM1) inhibits SqCC proliferation and invasion, processes fundamental to disease progression. We determine that the extracellular domain of CADM1 mediates these effects by forming a complex with HER2 and integrin α6β4 at the cell surface that disrupts downstream STAT3 activity. We subsequently show that treating CADM1 null tumours with the JAK/STAT inhibitor ruxolitinib mimics CADM1 gene restoration in preventing SqCC growth and metastases. Overall, this study identifies a novel mechanism by which CADM1 prevents SqCC progression and suggests that screening tumours for loss of CADM1 expression will help identify those patients most likely to benefit from JAK/STAT targeted chemotherapies.

The integrin αvβ6: a novel target for CAR T-cell immunotherapy?

Immunotherapy of cancer using chimeric antigen receptor (CAR) T-cells is a rapidly expanding field. CARs are fusion molecules that couple the binding of a tumour-associated cell surface target to the delivery of a tailored T-cell activating signal. Re-infusion of such genetically engineered T-cells to patients with haematological disease has demonstrated unprecedented response rates in Phase I clinical trials. However, such successes have not yet been observed using CAR T-cells against solid malignancies and this is, in part, due to a lack of safe tumour-specific targets. The αvβ6 integrin is strongly up-regulated in multiple solid tumours including those derived from colon, lung, breast, cervix, ovaries/fallopian tube, pancreas and head and neck. It is associated with poorer prognosis in several cancers and exerts pro-tumorigenic activities including promotion of tumour growth, migration and invasion. By contrast, physiologic expression of αvβ6 is largely restricted to wound healing. These attributes render this epithelial-specific integrin a highly attractive candidate for targeting using immunotherapeutic strategies such as CAR T-cell adoptive immunotherapy. This mini-review will discuss the role and expression of αvβ6 in cancer, as well as its potential as a therapeutic target.

S130 Role of CADM1 in squamous cell carcinoma progression

Introduction Lung cancer is the second most common cancer in the UK with about 42,000 people being diagnosed in 2010 alone (Office of National Statistics, 2012). With a tendency to form invasive metastases coupled with its frequent late stage diagnosis, lung cancer attributes to the largest cause of cancer related mortality worldwide. Despite advances in treatment and care, the five-year mortality rate remains at 90%. There is a desperate need to improve patient survival, which can be achieved partly through improved screening techniques and more importantly by expanding our understanding of the molecular changes associated with lung cancer development and progression. We investigate the role of a tumour suppressor gene, first identified in lung cancer, tumour suppressor in lung cancer 1 (TSLC1) or cell adhesion molecule 1 (Cadm1) in regulating squamous cell carcinoma (SqCC) growth and metastases. Methods Cadm1 expression levels were examined using q-PCR analysis on human pre-invasive airway and normal lung tissue collected as part of an on-going UCL/CRUK longitudinal-tracking study (Lung-Surveillance and Lung-SEARCH trials). Cadm1 was introduced into an established SqCC cell line (A431) and in vitro functional assays performed to investigate its effect on tumour growth, progression and invasion. Pre-clinical mice models were used to study the effect of Cadm1 expression in tumour growth and metastatic potential. Results q-PCR analyses demonstrated that loss of Cadm1 expression is a frequent early event in pre-invasive human airway compared to normal tissue (p = 0.001). Functional assays using A431, with Cadm1 reintroduced, showed Cadm1 expression levels directly associated with a significant decrease in cell proliferation (p = 0.001) over 10 days and significant reduction in invasion (p = 0.001) over 72 hours compared to control A431 cells without Cadm1. Pre-clinical xenograft tumourigenecity experiments in mice showed that Cadm1 expression significantly inhibited tumour growth (p = 0.01) together with a significant reduction in the number of metastases observed (p = 0.01) when compared with the control group. Conclusion These data suggest that restoration of Cadm1 expression in human squamous cell carcinomas play an important role in regulation of tumour growth and metastasis. Understanding the mechanism through which Cadm1 expression is able to modulate cancer progression maybe therapeutically beneficial.

Cadm1 regulates airway stem cell growth and differentiation via modulation of Stat3 activity

Airway homeostasis, repair, and regeneration are imperfectly understood processes involving the proliferation and differentiation of endogenous lung stem cells. Here, we establish that epithelial Cell adhesion molecule 1 (Cadm1) regulates the growth and differentiation of airway basal cells, previously identified as lung stem cells. Immunohistochemistry and gene expression analysis reveals that Cadm1 is broadly expressed throughout the murine tracheobronchial epithelium, exhibits transient downregulation concomitant with airway injury, and is subsequently restored during basal cell differentiation. Using Cadm1 null (KO) and keratin 14 (K14)-specific Cadm1 overexpressing transgenic mice, we demonstrate that maintaining Cadm1 expression reduces basal stem cell proliferation after tracheal polidocanol injury, whereas Cadm1 deletion causes increased ciliated cell differentiation and sustained downstream Stat3 signalling. Altogether, this study defines a previously uncharacterised role for Cadm1 in directing airway basal cell homeostasis and repair via modulation of Stat3 activity.