Combenefit: an interactive platform for the analysis and visualization of drug combinations

MOTIVATION

Many drug combinations are routinely assessed to identify synergistic interactions in the attempt to develop novel treatment strategies. Appropriate software is required to analyze the results of these studies.

RESULTS

We present Combenefit, new free software tool that enables the visualization, analysis and quantification of drug combination effects in terms of synergy and/or antagonism. Data from combinations assays can be processed using classical Synergy models (Loewe, Bliss, HSA), as single experiments or in batch for High Throughput Screens. This user-friendly tool provides laboratory scientists with an easy and systematic way to analyze their data. The companion package provides bioinformaticians with critical implementations of routines enabling the processing of combination data.

AVAILABILITY AND IMPLEMENTATION

Combenefit is provided as a Matlab package but also as standalone software for Windows (http://sourceforge.net/projects/combenefit/).

CONTACT

Giovanni.DiVeroli@cruk.cam.ac.uk

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Abstract 389: The dual mTOR inhibitor, AZD2014, and castration increase intra-tumoral immune cell infiltration and anti-tumour activity in a genetically engineered mouse model of prostate cancer

Background: Medical therapy for men with prostate cancer (PCa) is evolving, including recent evidence to support the use of chemotherapy for men with hormone sensitive disease. PI3K/AKT/mTOR pathway aberrations are common in patients with primary PCa and almost universal in metastatic tumours. The mTOR pathway acts as a central regulator of tumour cell metabolism, proliferation, cell cycle progression and immune regulation. The aim of this study was to investigate the effects of mTOR inhibitor AZD2014 on tumour growth and immune infiltration in a genetically engineered mouse model of PCa.

Methods: PtenL/L;PB-Cre4 mice, which developed invasive hormone-sensitive prostate tumours between 10-14 months of age, were enrolled (n = 13-15 per group) and treated with AZD2014 (15mg/Kg) or vehicle orally for 14 doses (QD 5/7) with or without castration. Tumour volumes were assessed by ultrasound imaging. Tumour samples were collected within 4 hours post 14th dose for histological and molecular analysis.

Results: AZD2014 was well tolerated, no overt toxicity was observed. Mean plasma concentrations of AZD2014 were 4.4±2.1μM at time of tumour sampling. AZD2014 alone or AZD2014+castration inhibited mTORC1 and mTORC2 activity as demonstrated by reduced p4EBP1(Thr37/46) 48%±27% (P<0.001) and 37%±11% (P<0.001), pS6(Ser235/236) 74%±43% (P<0.001) and 44%±13% (P<0.001), pAKT(Ser473) 36%±8% (P<0.001) and 20%±3% (P<0.01), respectively compared to vehicle-treated mice. Proliferation (Ki67+) was reduced in AZD2014-treated tumours by 70%±45% (P<0.001) and AZD2014+castration by 42%±16% (P<0.001). Apoptosis (CC3+) was increased in AZD2014 and AZD2014+castration groups by 3.3-fold (both, P<0.001) or castration only group by 2-fold (P<0.001). Tumour volumes were significantly reduced (54%, p<0.05) in AZD2014+castration group. Castration induced increased infiltration of T cells (CD3+, 2-fold, P<0.001) and macrophages (F4/80+, 1.6-fold, P<0.001) in the tumour tissues. These effects were more pronounced when combined with AZD2014 (CD3+, 2.8-fold, P<0.001; F4/80+, 2.3-fold, P<0.001). Multi-channel flow cytometry has confirmed increased proliferation of CD45+, CD3+ and CD8+ cells in tumours from the AZD2014+castration group.

Conclusion: These data confirm the anti cancer effect of AZD2014 in this PCa model. Furthermore, AZD2014+castration was more effective than either treatment as a single agent. The increased intra-tumoral T cell infiltration observed may have contributed to the anti-tumour effect. Further studies are ongoing to maximise this therapeutic effect and will inform current clinical studies in men with hormone sensitive, high risk prostate cancer.

Citation Format: Chiranjeevi Sandi, Antonio Ramos-Montoya, Sergio L. Filisbino, Adina Hughes, Suzanne Mosely, Michelle Morrow, Robert W. Wilkinson, Sarah Jurmeister, Karan Wadhwa, Frances M. Richards, Duncan I. Jodrell, Sabina Cosulich, Barry R. Davies, Simon Pacey. The dual mTOR inhibitor, AZD2014, and castration increase intra-tumoral immune cell infiltration and anti-tumour activity in a genetically engineered mouse model of prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 389.

Anti-stromal treatment together with chemotherapy targets multiple signalling pathways in pancreatic adenocarcinoma

Stromal targeting for pancreatic ductal adenocarcinoma (PDAC) is rapidly becoming an attractive option, due to the lack of efficacy of standard chemotherapy and increased knowledge about PDAC stroma. We postulated that the addition of stromal therapy may enhance the anti-tumour efficacy of chemotherapy. Gemcitabine and all-trans retinoic acid (ATRA) were combined in a clinically applicable regimen, to target cancer cells and pancreatic stellate cells (PSCs) respectively, in 3D organotypic culture models and genetically engineered mice (LSL-Kras(G12D) (/+) ;LSL-Trp53(R172H) (/+) ;Pdx-1-Cre: KPC mice) representing the spectrum of PDAC. In two distinct sets of organotypic models as well as KPC mice, we demonstrate a reduction in cancer cell proliferation and invasion together with enhanced cancer cell apoptosis when ATRA is combined with gemcitabine, compared to vehicle or either agent alone. Simultaneously, PSC activity (as measured by deposition of extracellular matrix proteins such as collagen and fibronectin) and PSC invasive ability were both diminished in response to combination therapy. These effects were mediated through a range of signalling cascades (Wnt, hedgehog, retinoid, and FGF) in cancer as well as stellate cells, affecting epithelial cellular functions such as epithelial-mesenchymal transition, cellular polarity, and lumen formation. At the tissue level, this resulted in enhanced tumour necrosis, increased vascularity, and diminished hypoxia. Consequently, there was an overall reduction in tumour size. The enhanced effect of stromal co-targeting (ATRA) alongside chemotherapy (gemcitabine) appears to be mediated by dampening multiple signalling cascades in the tumour-stroma cross-talk, rather than ablating stroma or targeting a single pathway. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Understanding the Complexity of Porous Graphitic Carbon (PGC) Chromatography: Modulation of Mobile-Stationary Phase Interactions Overcomes Loss of Retention and Reduces Variability

Porous graphitic carbon (PGC) is an important tool in a chromatographer's armory that retains polar compounds with mass spectrometry (MS)-compatible solvents. However, its applicability is severely limited by an unpredictable loss of retention, which can be attributed to contamination. The solutions offered fail to restore the original retention and our observations of retention time shifts of gemcitabine/metabolites on PGC are not consistent with contamination. The mobile phase affects the ionization state of analytes and the polarizable PGC surface that influences the strength of dispersive forces governing retention on the stationary phase. We hypothesized that failure to maintain the same PGC surface before and after running a gradient is a cause of the observed retention loss/variability on PGC. Herein, we optimize the choice of mobile phase solvent in a gradient program with three parts: a preparatory phase, which allows binding of analytes to column; an elution phase, which gives the required separation/peak shape; and a maintenance phase, to preserve the required retention capacity. Via liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis of gemcitabine and its metabolites extracted from tumor tissue, we demonstrate reproducible chromatography on three PGC columns of different ages. This approach simplifies use of the PGC to the same level as that of a C-18 column, removes the need for column regeneration, and minimizes run times, thus allowing PGC columns to be used to their full potential.

Abstract A123: Preclinical evaluation of dual mTOR inhibitor, AZD2014, in prostate cancer

Background: An estimated 220,800 cases and 27,540 deaths from prostate cancer (PCa) will occur in the USA during 2015. Altered PI3K/AKT/mTOR signalling contributes to prostate cancer progression and transition to androgen-independent disease, for example one study reported 42% of primary and 100% of metastatic PCa tumours exhibited mutations, altered expression or copy number variations within this pathway. First generation mTOR inhibitors (preferentially inhibit mTORC1), have had limited anti-cancer effect in patients with PCa, possibly due to negative feedback activation of the AKT pathway via mTORC2. The dual mTORC1/2 inhibitor, AZD2014, may overcome this liability. Using a genetically engineered PTEN conditional mouse model (Ptenloxp/loxp;PB-Cre4), we have investigated the effects of AZD2014. The studies complement a clinical trial (NCT02064608) of AZD2014, given to men before radical prostatectomy and are timed for when invasive prostate carcinomas develop in the model around 10-14 months prior to onset of resistance to castration through AKT pathway activation. AZD2014, 15mg/kg daily, oral (with or without castration) or vehicle were administered for 14 days.

Results: AZD2014 was well tolerated with no overt toxicity observed. Pharmacokinetic (PK) analysis revealed mean concentrations of 4.4±2.1μM of AZD2014 in the plasma samples collected 4 hours after day 14 dose. AZD2014 alone or combined with castration inhibited mTORC1 and mTORC2 measured by reductions in p4EBP1(Thr37/46) by approximately 48%±27% (p<0.001) and 37%±11% (p<0.001); pS6(Ser235/236) by 74%±43% (p<0.001) and 44%±13% (p<0.001) and pAKT(Ser473) by 36%±8% (p<0.001) and 20%±3% (p<0.01) as compared to vehicle-treated mice. AZD2014 treatment was anti-proliferative; Ki67 was significantly reduced in AZD2014-treated mice (70%±45%, p<0.001) or AZD2014 plus castration (42%±16%, p<0.001). Apoptosis was detected with cleaved caspase 3 and increased by 3.3-fold (p<0.001) in both AZD2014 or AZD2014 plus castration groups and 2-fold (p<0.001) in the castration only group, respectively. In all cases, 10 mice were used in each group and 80-120 randomly chosen images were analysed using Aperio automatic quantitative algorithms. Tumour volumes (ultrasound imaging) were reduced by 51% (p<0.05) comparing AZD2014 plus castration against control. HRMAS 1H NMR spectroscopy was used on tumour tissue to determine changes in metabolites following treatment and identified that the total choline to creatine ratio (t-Cho/Cr) was reduced by 40% in AZD2014-treated mice tumour samples (p<0.05) as compared to control-treated mice.

Conclusions: Short term (14 days) treatment with AZD2014 with or without castration was associated with both pharmacodynamic and anti-tumour effects. The t-Cho/Cr ratio, previously reported as positively correlated with Gleason score in PCa patients, might be, in addition to our standard mTOR PD markers, utilised as a non-invasive biomarker of AZD2014 activity. The primary and phenotypic biomarker effects of monotherapy with AZD2014 in this relevant genetically engineered mouse model of prostate cancer will be compared with paired biopsies from the ongoing exploratory window study in the prostate cancer patients prior to prostatectomy, and may inform potential novel combination approaches that are translatable to the clinic.

Citation Format: Chiranjeevi Sandi, Antonio Ramos-Montoya, Sergio L. Felisbino, Sarah Jurmeister, Basetti Madhu, Karan Wadhwa, John R. Griffiths, Frances M. Richards, Duncan I. Jodrell, David E. Neal, Sabina Cosulich, Barry Davies, Simon Pacey. Preclinical evaluation of dual mTOR inhibitor, AZD2014, in prostate cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A123.

An automated fitting procedure and software for dose-response curves with multiphasic features

In cancer pharmacology (and many other areas), most dose-response curves are satisfactorily described by a classical Hill equation (i.e. 4 parameters logistical). Nevertheless, there are instances where the marked presence of more than one point of inflection, or the presence of combined agonist and antagonist effects, prevents straight-forward modelling of the data via a standard Hill equation. Here we propose a modified model and automated fitting procedure to describe dose-response curves with multiphasic features. The resulting general model enables interpreting each phase of the dose-response as an independent dose-dependent process. We developed an algorithm which automatically generates and ranks dose-response models with varying degrees of multiphasic features. The algorithm was implemented in new freely available Dr Fit software (sourceforge.net/projects/drfit/). We show how our approach is successful in describing dose-response curves with multiphasic features. Additionally, we analysed a large cancer cell viability screen involving 11650 dose-response curves. Based on our algorithm, we found that 28% of cases were better described by a multiphasic model than by the Hill model. We thus provide a robust approach to fit dose-response curves with various degrees of complexity, which, together with the provided software implementation, should enable a wide audience to easily process their own data.

CHK1 Inhibition Synergizes with Gemcitabine Initially by Destabilizing the DNA Replication Apparatus

Combining cell-cycle checkpoint kinase inhibitors with the DNA-damaging chemotherapeutic agent gemcitabine offers clinical appeal, with a mechanistic rationale based chiefly on abrogation of gemcitabine-induced G2-M checkpoint activation. However, evidence supporting this mechanistic rationale from chemosensitization studies has not been consistent. Here we report a systematic definition of how pancreatic cancer cells harboring mutant p53 respond to this combination therapy, by combining mathematical models with large-scale quantitative biologic analyses of single cells and cell populations. Notably, we uncovered a dynamic range of mechanistic effects at different ratios of gemcitabine and CHK1 inhibitors. Remarkably, effective synergy was attained even where cells exhibited an apparently functional G2-M surveillance mechanism, as exemplified by a lack of both overt premature CDK1 activation and S-phase mitotic entry. Consistent with these findings, S-G2 duration was extended in treated cells, leading to a definable set of lineage-dependent catastrophic fates. At synergistic drug concentrations, global replication stress was a distinct indicator of chemosensitization as characterized molecularly by an accumulation of S-phase cells with high levels of hyperphosphorylated RPA-loaded single-stranded DNA. In a fraction of these cells, persistent genomic damage was observed, including chromosomal fragmentation with a loss of centromeric regions that prevented proper kinetochore-microtubule attachment. Together, our results suggested a "foot-in-the-door" mechanism for drug synergy where cells were destroyed not by frank G2-M phase abrogation but rather by initiating a cumulative genotoxicity that deregulated DNA synthesis.

Abstract 2540: A new mathematical model and software, to enable improved quantification and interpretation of combinatorial drug effects

Drug combinations are used commonly to treat patients with cancer. Combination studies are conducted in vitro, to support advancement to in vivo and/or clinical research. In order to interpret in vitro data, mathematical models and numerical methods are used to quantify degrees of drug synergism. Several traditional approaches exist but they have been questioned with regard to how resulting synergy or antagonism levels should be interpreted. Our aim was to develop a robust method to analyse in vitro drug combination data, avoiding the issues related to traditional models and methods. To facilitate its implementation, software to enable rigorous and systematic assessment of combinations in vitro was also developed. We have derived a new mathematical model to identify synergy distributions based on drug combination dose response surfaces. Our new model and the classical Bliss, Loewe and HSA models were incorporated into the newly developed Combenefit software. Combenefit enables systematic quantification of high-throughput screening data, incorporating statistical assessment, metrics to describe synergy distributions and advanced graphical visualisation. Using multiple simulations of combination data with expected outcomes, our approach showed that it always provided appropriate evaluation while classical models failed to do so. We showed how our new model is in principle better aligned with in vivo requirements of identifying combinations which provide improvements compared to single agents. We then proceeded to analyse a large high-throughput combination screen. We first demonstrated that dataset assessment is strongly model-sensitive. We then demonstrated that our new model identified the best combinations in terms of dose response, thus confirming our simulated cases. Therefore, we have developed a new mathematical model that solves fundamental issues of model relevance that are encountered with classical models in the context of drug combinations. The newly developed Combenefit software enables easily performing rigorous and systematic quantification of in vitro combinations based on this novel approach. (Combenefit is freely available on our institutional website http://www.cruk.cam.ac.uk/combenefit). The resulting procedure is robust and better aligned with our perception of in vivo requirements.

Citation Format: Giovanni Y. Di Veroli, Duncan I. Jodrell, Frances M. Richards, Ian Goldlust. A new mathematical model and software, to enable improved quantification and interpretation of combinatorial drug effects. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2540. doi:10.1158/1538-7445.AM2015-2540

Abstract 3497: Mechanism-based scheduling of triple therapy gemcitabine/CHK1i/WEE1i in pancreatic cancer at submaximal yet synergistic concentrations

Sensitization of cancer cells to gemcitabine has been shown with checkpoint kinase CHK1 and WEE1 inhibitors. To rationalize and optimize the concomitant use of these three agents, we first performed growth inhibition assays on MIA PaCa-2 pancreatic cancer cells using gemcitabine in combination with either CHIR-124 (CHK1 inhibitor) or MK-1775 (WEE1 inhibitor). In silico analysis with three mathematical models (Bliss Independence, Loewe and Highest Single Agent) identified synergistic growth inhibition at submaximal (i.e. <GI50) concentrations of the single agents (10nM gemcitabine, 20nM CHIR-124, 300nM MK-1775) in MIA PaCa-2 cells. At these concentrations of gemcitabine+CHIR-124, quantitative image-based cytometry demonstrated S-phase redistribution, with 31% of >8000 individual cells undergoing extensive fork collapse (compared to 0-1% with single agents) as evidenced by co-staining of yH2AX and hyper-phosphorylated RPA32. Conversely, submaximal gemcitabine+MK-1775 induced clear reduction of inhibitory CDK1 Y15 level compared to single agents. Consistent with this G2/M abrogation, in a Fucci-based CDT1/geminin-expressing MIA PaCa-2 stable cell line, gemcitabine+MK-1775 partially reversed the accumulation of the geminin-expressing (S/G2) population induced by gemcitabine alone. This was accompanied by an increase in the CDT1-expressing (G1) population, alongside aberrant mitotic cells with features of perturbed kinetochore-microtubule integrity. Based on these findings, we performed a series of long-term, kinetic live-cell imaging assays to determine the optimal scheduling for gemcitabine/CHK1i/WEE1i as a triplet at synergistic concentrations. In contrast to the widely proposed scheduling regimen, we found that delayed administration of CHK1i (at 24 hours), relative to gemcitabine, did not lead to synergy. However, concurrent administration yielded durable growth inhibition, even when the two agents were removed after 24 hours. This inhibition was further enhanced with the subsequent addition of WEE1i at 24 hours, but not continuation of a CHK1i. Together, our results illustrate differential mechanistic effects of CHK1 and WEE1 inhibitors with gemcitabine, when combined at sub-GI50 concentrations, and propose a novel triple agent schedule that will be evaluated in vivo.

Citation Format: Siang-Boon Koh, Frances M. Richards, Esther Rodriguez, Scott K. Lyons, Duncan I. Jodrell. Mechanism-based scheduling of triple therapy gemcitabine/CHK1i/WEE1i in pancreatic cancer at submaximal yet synergistic concentrations. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3497. doi:10.1158/1538-7445.AM2015-3497

The EGFR demonstrates linear signal transmission

Cells sense information encoded in extracellular ligand concentrations and process it using intracellular signalling cascades. Using mathematical modelling and high-throughput imaging of individual cells, we studied how a transient extracellular growth factor signal is sensed by the epidermal growth factor receptor system, processed by downstream signalling, and transmitted to the nucleus. We found that transient epidermal growth factor signals are linearly translated into an activated epidermal growth factor receptor integrated over time. This allows us to generate a simplified model of receptor signaling where the receptor acts as a perfect sensor of extracellular information, while the nonlinear input-output relationship of EGF-EGFR triggered signalling is a consequence of the downstream MAPK cascade alone.

Gemcitabine diphosphate choline is a major metabolite linked to the Kennedy pathway in pancreatic cancer models in vivo

BACKGROUND

The modest benefits of gemcitabine (dFdC) therapy in patients with pancreatic ductal adenocarcinoma (PDAC) are well documented, with drug delivery and metabolic lability cited as important contributing factors. We have used a mouse model of PDAC: KRAS(G12D); p53(R172H); pdx-Cre (KPC) that recapitulates the human disease to study dFdC intra-tumoural metabolism.

METHODS

LC-MS/MS and NMR were used to measure drug and physiological analytes. Cytotoxicity was assessed by the Sulphorhodamine B assay.

RESULTS

In KPC tumour tissue, we identified a new, Kennedy pathway-linked dFdC metabolite (gemcitabine diphosphate choline (GdPC)) present at equimolar amounts to its precursor, the accepted active metabolite gemcitabine triphosphate (dFdCTP). Utilising additional subcutaneous PDAC tumour models, we demonstrated an inverse correlation between GdPC/dFdCTP ratios and cytidine triphosphate (CTP). In tumour homogenates in vitro, CTP inhibited GdPC formation from dFdCTP, indicating competition between CTP and dFdCTP for CTP:phosphocholine cytidylyltransferase (CCT). As the structure of GdPC precludes entry into cells, potential cytotoxicity was assessed by stimulating CCT activity using linoleate in KPC cells in vitro, leading to increased GdPC concentration and synergistic growth inhibition after dFdC addition.

CONCLUSIONS

GdPC is an important element of the intra-tumoural dFdC metabolic pathway in vivo.

SPARC independent drug delivery and antitumour effects of nab-paclitaxel in genetically engineered mice

DESIGN

Pharmacokinetic and pharmacodynamic parameters of cremophor-paclitaxel, nab-paclitaxel (human-albumin-bound paclitaxel, Abraxane) and a novel mouse-albumin-bound paclitaxel (m-nab-paclitaxel) were evaluated in genetically engineered mouse models (GEMMs) by liquid chromatography-tandem mass spectrometry (LC-MS/MS), histological and biochemical analysis. Preclinical evaluation of m-nab-paclitaxel included assessment by three-dimensional high-resolution ultrasound and molecular analysis in a novel secreted protein acidic and rich in cysteine (SPARC)-deficient GEMM of pancreatic ductal adenocarcinoma (PDA).

RESULTS

nab-Paclitaxel exerted its antitumoural effects in a dose-dependent manner and was associated with less toxicity compared with cremophor-paclitaxel. SPARC nullizygosity in a GEMM of PDA, Kras(G12D);p53(flox/-);p48Cre (KPfC), resulted in desmoplastic ductal pancreas tumours with impaired collagen maturation. Paclitaxel concentrations were significantly decreased in SPARC null plasma samples and tissues when administered as low-dose m-nab-paclitaxel. At the maximally tolerated dose, SPARC deficiency did not affect the intratumoural paclitaxel concentration, stromal deposition and the immediate therapeutic response.

CONCLUSIONS

nab-Paclitaxel accumulates and acts in a dose-dependent manner. The interaction of plasma SPARC and albumin-bound drugs is observed at low doses of nab-paclitaxel but is saturated at therapeutic doses in murine tumours. Thus, this study provides important information for future preclinical and clinical trials in PDA using nab-paclitaxel in combination with novel experimental and targeted agents.

Abstract B96: Design, synthesis and biological evaluation of a novel allosteric inhibitor of HSET that damages cancer cells with supernumerary centrosomes

Almost a century ago Theodor Boveri suggested that tumor cells differ from normal cells in their high incidence of centrosome amplification. However, only recently have new therapeutic strategies been explored in an attempt to exploit these differences and the role of kinesins in mitosis. Intense interest in the field has led to development of KSP and CENP-E inhibitors that have been tested clinically as treatments for human cancer. Success has been limited because both motor proteins are essential to normal mitosis and inhibition leads to mitotic arrest and associated neutropenia toxicity in normal cells. In contrast HSET is essential for survival of cancer cells with centrosome amplification and has been shown to be dispensable in normal cells. Hence, HSET inhibition offers a unique opportunity to selectively damage malignant cells with supernumerary centrosomes without affecting normal cells. In keeping with these findings we report discovery of a novel allosteric inhibitor of HSET, CW069, that does not disrupt division in normal human fibroblast cells, or in MCF-7 cells with normal centrosome numbers. In fact, CW069 induces multipolar mitosis exclusively in cancer cells with extra centrosomes, causing apoptosis via catastrophic aneuploidy. The increased multipolar mitoses induced in N1E-115 cells by inhibitor CW069 recapitulates the phenotype described here, and by others, for siRNA depletion of HSET. The inhibitor also reduces cell growth and centrosome clustering in cancer cells with a lower incidence of centrosome amplification, including BT549 and MDA-MB-231 breast cancer cells. This is consistent with recent reports that depletion of HSET in DNA damage repair deficient cells may be lethal even to cancer cells with low-level centrosome amplification. Taken together, these data indicate that CW069 inhibition of HSET is not restricted to use in N1E-115 cells with high centrosome amplification, and could be broadly applicable to a range of human cancers. What is more, CW069 does not decrease the clonogenic capacity of primary adult human bone marrow cells, suggesting that it would not cause neutropenia toxicity in normal cells.

It is anticipated that HSET inhibition could have a greater therapeutic margin than KSP or CENP-E inhibition, and, to the best of our knowledge we have described the first allosteric inhibitor of HSET that reduces centrosome clustering but does not induce the mitotic phenotypes associated with inhibition of KSP or CENP-E. This selectivity for HSET is consistent with our computational model, which indicates that the HSET loop 5 displays dynamic conformational selection for CW069 that cannot be achieved by closely related KSP.

In summary, CW069 not only represents a substantial advance toward new cancer therapeutics, but also offers researchers a unique tool to unveil the full details of HSET function in mitosis.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B96.

Citation Format: Ciorsdaidh A. Watts, Frances M. Richards, Andreas Bender, Peter J. Bond, Oliver Korb, Oliver Kern, Michelle Riddick, Paul Owen, Rebecca M. Myers, Jordan Raff, Fanni Gergely, Duncan I. Jodrell, Steven V. Ley. Design, synthesis and biological evaluation of a novel allosteric inhibitor of HSET that damages cancer cells with supernumerary centrosomes. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B96.

Anti-tumour efficacy of capecitabine in a genetically engineered mouse model of pancreatic cancer

Capecitabine (CAP) is a 5-FU pro-drug approved for the treatment of several cancers and it is used in combination with gemcitabine (GEM) in the treatment of patients with pancreatic adenocarcinoma (PDAC). However, limited pre-clinical data of the effects of CAP in PDAC are available to support the use of the GEMCAP combination in clinic. Therefore, we investigated the pharmacokinetics and the efficacy of CAP as a single agent first and then in combination with GEM to assess the utility of the GEMCAP therapy in clinic. Using a model of spontaneous PDAC occurring in Kras(G12D); p53(R172H); Pdx1-Cre (KPC) mice and subcutaneous allografts of a KPC PDAC-derived cell line (K8484), we showed that CAP achieved tumour concentrations (∼25 µM) of 5-FU in both models, as a single agent, and induced survival similar to GEM in KPC mice, suggesting similar efficacy. In vitro studies performed in K8484 cells as well as in human pancreatic cell lines showed an additive effect of the GEMCAP combination however, it increased toxicity in vivo and no benefit of a tolerable GEMCAP combination was identified in the allograft model when compared to GEM alone. Our work provides pre-clinical evidence of 5-FU delivery to tumours and anti-tumour efficacy following oral CAP administration that was similar to effects of GEM. Nevertheless, the GEMCAP combination does not improve the therapeutic index compared to GEM alone. These data suggest that CAP could be considered as an alternative to GEM in future, rationally designed, combination treatment strategies for advanced pancreatic cancer.

Paclitaxel and CYC3, an aurora kinase A inhibitor, synergise in pancreatic cancer cells but not bone marrow precursor cells

BACKGROUND

Amplification of aurora kinase A (AK-A) overrides the mitotic spindle assembly checkpoint, inducing resistance to taxanes. RNA interference targeting AK-A in human pancreatic cancer cell lines enhanced taxane chemosensitivity. In this study, a novel AK-A inhibitor, CYC3, was investigated in pancreatic cancer cell lines, in combination with paclitaxel.

METHODS

Western blot, flow cytometry and immunostaining were used to investigate the specificity of CYC3. Sulforhodamine B staining, time-lapse microscopy and colony-formation assays were employed to evaluate the cytotoxic effect of CYC3 and paclitaxel. Human colony-forming unit of granulocyte and macrophage (CFU-GM) cells were used to compare the effect in tumour and normal tissue.

RESULTS

CYC3 was shown to be a specific AK-A inhibitor. Three nanomolar paclitaxel (growth inhibition 50% (GI(50)) 3 nM in PANC-1, 5.1 nM in MIA PaCa-2) in combination with 1 μM CYC3 (GI(50) 1.1 μM in MIA PaCa2 and 2 μM in PANC-1) was synergistic in inhibiting pancreatic cell growth and causing mitotic arrest, achieving similar effects to 10-fold higher concentrations of paclitaxel (30 nM). In CFU-GM cells, the effect of the combination was simply additive, displaying significantly less myelotoxicity compared with high concentrations of paclitaxel (30 nM; 60-70% vs 100% inhibition).

CONCLUSION

The combination of lower doses of paclitaxel and CYC3 merits further investigation with the potential for an improved therapeutic index in vivo.

Anti-tumour effects of a specific anti-ADAM17 antibody in an ovarian cancer model in vivo

ADAM 17 (TNF-α converting enzyme, TACE) is a potential target for cancer therapy, but the small molecule inhibitors reported to date are not specific to this ADAM family member. This membrane-bound metalloproteinase is responsible for ectodomain shedding of pathologically significant substrates including TNF-α and EGFR ligands. The aim of this study was to evaluate the pharmacokinetics, pharmacodynamics and anti-tumour efficacy of the first specific inhibitor, an anti-human ADAM17 IgG antibody, clone D1(A12). We used intraperitoneal xenografts of the human ovarian cancer cell line IGROV1-Luc in Balb/c nude mice, chosen because it was previously reported that growth of these xenografts is inhibited by knock-down of TNF-α. In vitro, 200 nM D1(A12) inhibited shedding of ADAM17 substrates TNF-α, TNFR1-α, TGF-α, amphiregulin (AREG), HB-EGF and IL-6Rα, from IGROV1-Luc cells, (4.7 nM IC(50) for TNF-α shedding). In IGROV1-Luc xenografts in vivo, D1(A12) IgG showed pharmacokinetic properties suitable for efficacy studies, with a single i.p. dose of 10 mg/kg D1(A12) sufficient to maintain IgG plasma and ascites fluid concentrations above 100 nM for more than 7 days. The plasma half life was 8.6 days. Next, an efficacy study was performed, dosing D1(A12) or anti-human TNF-α antibody infliximab at 10 mg/kg q7d, quantifying IGROV1-Luc tumour burden by bioluminescence. D1(A12) IgG showed a significant reduction in tumour growth (p = 0.005), 56% of vehicle control. Surprisingly, D1(A12) did not reduce the concentration of circulating human TNF-α, suggesting that another enzyme may compensate for inhibition of ADAM17 in vivo (but not in vitro). However, D1(A12) did show clear pharmacodynamic effects in the mice, with significant inhibition of shedding from tumour of ADAM17 substrates TNFR1-α, AREG, and TGF-α (4-15-fold reductions, p<0.0001 for all three). Thus, D1(A12) has anti-ADAM17 activity in vivo, inhibits shedding of EGFR ligands and has potential for use in EGF ligand-dependent tumours.

Abstract 2724: Activity of the specific anti-ADAM17 inhibitory IgG antibody (Ab), D1(A12) in an ovarian cancer model in vivo

ADAM17 (TNF-α converting enzyme, TACE) is a membrane-bound metalloproteinase responsible for ectodomain shedding of TNF-α, EGFR ligands and other pathologically significant proteins. ADAM17 overexpression is reported in many cancers, with roles in cancer cell proliferation, migration and drug resistance. Small molecule inhibitors of ADAM17 lack specificity, so we developed a specific human ADAM17 inhibitory IgG Ab, D1(A12), which inhibits the proteolysis of ADAM17 substrates (TNF-α, amphiregulin, etc.,) in cancer cells in vitro (C.J. Tape, et al., Proc Natl Acad Sci USA 108: 5578-83, 2011). We have now assessed the suitability of the D1(A12) Ab for therapeutic use, by investigating its pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumour efficacy in mice. The IGROV1-Luc xenograft model of intraperitoneal (i.p.) disseminated ovarian carcinoma in nude mice was used, as IGROV1-Luc cells secrete TNF-α and other ADAM17 products and knockdown of TNF-α expression inhibits tumour growth (H. Kulbe, et al., Cancer Res., 67: 585- 592, 2007). We investigated the PK of D1(A12) Ab using a single 10 mg/kg dose i.p., first in non-tumour-bearing (NTB) mice and then in mice bearing IGROV1-Luc tumours, measuring the concentration of D1(A12) IgG in plasma and ascitic fluid by ELISA. In NTB mice, plasma Cmax was 512 nM, half life 8.6 days. The concentrations in tumour-bearing mice were expected to be lower due to a larger volume of distribution due to the ascitic fluid, and in tumour-bearing mice the Cmax was 425 nM in plasma and 391 nM in ascitic fluid. The PK data suggest that weekly dosing with 10 mg/kg D1(A12) maintains therapeutically active concentrations of the IgG, so this regimen was used for an efficacy study comparing D1(A12) with vehicle. D1(A12) showed clear PD effects: Ascitic fluid concentrations of 3 ADAM17 products were reduced when compared to vehicle: AREG (55 +/− 19 vs 302 +/− 37 pg/ml, p &lt; 0.001), soluble hTNFR1α (479 +/− 100 vs 2108 +/− 204 pg/ml, p &lt; 0.001) and TGF-β (0.35 +/− 0.67 vs 5.2 +/− 2.2 pg/ml, p = 0.002), indicative of inhibition of ADAM17 activity in vivo. However, D1(A12) did not significantly reduce the concentration of TNF-α in ascitic fluid (109 +/− 21 vs 134 +/−32 pg/ml, p = 0.06), suggesting that in this system ADAM17 is not the only metalloproteinase with TACE activity. Tumour burden was quantified using bioluminescence generated from the luciferase expressing cells, measured using an IVIS xenogen 200 imager. There was decreased tumour growth in the D1(A12)-treated group (compared to vehicle), although this did not reach statistical significance (p=0.09). In conclusion we have shown that the anti-ADAM17 antibody has PK properties suitable for therapeutic studies and that it can inhibit shedding of ADAM17-dependent growth factors in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2724. doi:1538-7445.AM2012-2724

Abstract 3771: Capecitabine pharmacokinetics and efficacy in spontaneous tumors occurring in a genetically engineered mouse model (GEMM) of pancreatic cancer

Capecitabine (CAP) is an oral fluoropyrimidine, converted sequentially and selectively to 5-FU at the tumour site. It is used in the treatment of a number of cancers as a single agent and in patients with pancreatic cancer, in combination with gemcitabine. However, pre-clinical data in pancreatic cancer models are limited. In this study, we investigated the pharmacokinetics (PK) and efficacy of CAP in a GEMM of spontaneous pancreatic adenocarcinoma (PDA) occurring in KrasG12D; p53R172H; Pdx1-Cre (KPC) mice, compared to an allograft model of a cell line isolated from a PDA arising in the KPC mice. In the PK study, tumour was collected 2 hours after CAP treatment (755 mg/kg by oral gavage), homogenates were analysed using an LC-MS/MS assay developed to simultaneously detect capecitabine and its 3 metabolites DFCR, DFUR and 5-FU (modified from S.M.Guichard, et al., J. Chrom. B. 2005). Data were compared to our previously reported studies in an allograft model (Proc. AACR 2011 a 5446). After a QDx7 treatment, 5-FU concentrations of 27 ± 13 μM were achieved (compared to 23.0 ± 8.1 μM and 22.7 ± 7.7 μM in allograft tumours after 1 and 5 consecutive doses respectively), confirming adequate drug delivery to the in situ tumour following oral administration of CAP. Therefore we proceeded to efficacy studies in this model. In the allograft model we had identified a significant reduction of the tumour doubling time with 755 mg/kg CAP (5 days/week, 3 weeks), compared to control (7.5 ± 3.0 vs 3.5 ± 0.5 days; P&lt;0.001). In in situ tumours, a short term study over 7 days showed a reduction in tumour growth in CAP-treated KPC PDA tumours compared to control (199% ± 22% vs 121% ± 10%; P&lt;0.01). In a survival study in KPC mice, CAP (755 mg/kg, 5 days/week) was compared to the standard treatment for advanced pancreatic cancer, gemcitabine (GEM, 100 mg/kg, Q3D), and there was no difference in the median survival of mice with spontaneous PDA tumours (P=0.61) suggesting a similar efficacy of CAP to GEM. There is conflicting evidence regarding the utility of the combination of GEM and CAP in this disease, so we also investigated the combination in mice bearing allograft PDA tumours. Full doses of both drugs were not tolerated, but the combination of GEM (75 mg/kg Q3D, 2 weeks) plus CAP (539 mg/kg, 5 days/week, 2 weeks) was feasible. This regimen was associated with significant growth inhibition, but this was not superior to GEM alone (75 mg/kg) at the same dose (tumour doubling time: 8.6 ± 10.8 vs 7.2 ± 2.8 days respectively). In summary, orally administered CAP achieves active concentrations of 5-FU in PDA tumours. Similar effects on survival compared to GEM are seen in PDA tumours. Growth inhibition data in allograft tumours did not show any additional benefit for the GEMCAP combination, when compared to GEM alone. CAP could be considered as an alternative to GEM in future, rationally designed, combination treatment strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3771. doi:1538-7445.AM2012-3771

A novel method for quantification of gemcitabine and its metabolites 2',2'-difluorodeoxyuridine and gemcitabine triphosphate in tumour tissue by LC-MS/MS: comparison with (19)F NMR spectroscopy

PURPOSE

To develop a sensitive analytical method to quantify gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and its metabolites 2',2'-difluorodeoxyuridine (dFdU) and 2',2'-difluorodeoxycytidine-5'-triphosphate (dFdCTP) simultaneously from tumour tissue.

METHODS

Pancreatic ductal adenocarcinoma tumour tissue from genetically engineered mouse models of pancreatic cancer (KP ( FL/FL ) C and KP ( R172H/+) C) was collected after dosing the mice with gemcitabine. (19)F NMR spectroscopy and LC-MS/MS protocols were optimised to detect gemcitabine and its metabolites in homogenates of the tumour tissue.

RESULTS

A (19)F NMR protocol was developed, which was capable of distinguishing the three analytes in tumour homogenates. However, it required at least 100 mg of the tissue in question and a long acquisition time per sample, making it impractical for use in large PK/PD studies or clinical trials. The LC-MS/MS protocol was developed using porous graphitic carbon to separate the analytes, enabling simultaneous detection of all three analytes from as little as 10 mg of tissue, with a sensitivity for dFdCTP of 0.2 ng/mg tissue. Multiple pieces of tissue from single tumours were analysed, showing little intra-tumour variation in the concentrations of dFdC or dFdU (both intra- and extra-cellular). Intra-tumoural variation was observed in the concentration of dFdCTP, an intra-cellular metabolite, which may reflect regions of different cellularity within a tumour.

CONCLUSION

We have developed a sensitive LC-MS/MS method capable of quantifying gemcitabine, dFdU and dFdCTP in pancreatic tumour tissue. The requirement for only 10 mg of tissue enables this protocol to be used to analyse multiple areas from a single tumour and to spare tissue for additional pharmacodynamic assays.

Abstract 5446: The activity and pharmacokinetics of capecitabine in a mouse model (K8484) of pancreatic adenocarcinoma

The pharmacokinetics (PK) of the oral fluoropyrimidine capecitabine were investigated in a mouse model of pancreatic cancer. Allografts of a cell line (K8484) derived from a pancreatic adenocarcinoma which occurred in a KrasG12D; p53R172H; Pdx1-Cre (KPC) mouse (S. Hingorani, et al., Cancer Cell 2005) were grown subcutaneously in left and right flanks of syngeneic immunocompetent recipient mice. Mice were dosed with either a single dose or 5 daily doses of capecitabine at 755 mg/kg (2.1 mmol/kg/day) with tumour volumes of approximately 250 mm3. Plasma and tissue homogenates were analysed using an LC-MS/MS assay developed to simultaneously detect capecitabine and its 3 metabolites DFCR, DFUR and 5-FU (S.M.Guichard, et al., J. Chrom. B. 2005).

Forty minutes after a single dose the mean plasma concentrations (n=3) were 28 +/- 20 mg/ml capecitabine, 78 +/- 48 mg/ml DFCR, 41 +/- 17 mg/ml DFUR and 0.19 +/- 0.07 mg/ml (1.5 µM) 5-FU, with concentrations of all analytes falling at 2 and 4 hours. In the tumour tissue, mean concentrations at 40 mins were capecitabine: 37 +/- 19 ng/mg tissue, DFCR: 56 +/- 12 ng/mg; DFUR: 20 +/- 8 ng/mg and 5-FU: 3.3 +/- 0.7 ng/mg. At 2 and 4 hours the tumour 5-FU concentrations were 3.0 +/- 1.1 and 1.4 +/- 0.6 ng/mg respectively. In the liver, DFCR concentrations were higher than in the tumour from the same mice but DFUR concentrations were lower and 5-FU was below the limit of quantification (&lt;0.4 ng/mg) in most, consistent with the reported distribution of carboxylesterases, cytidine deaminase and thymidine phosphorylase in tissues (M. Miwa, et al., Eur. J. Cancer 1998). In animals dosed for 5 days, there was no evidence of accumulation of capecitabine or its metabolites in tumour tissue when compared to the single dose. The concentration of tumour 5-FU, ranging from 1.4 to 3.3 ng/mg, is estimated to be equivalent to 11 to 25 µM, more than 10-fold higher than the plasma concentration. The IC50 for 5-FU in K8484 cells, grown in vitro, was 1.4 +/- 0.8 µM suggesting that oral dosing with capecitabine delivers a therapeutically effective dose to the allograft. This was then confirmed in an efficacy study, treating tumour-bearing mice with oral capecitabine for 5 days per week for 3 weeks, which resulted in significant inhibition of tumour growth rate compared to the vehicle treated group, with mean tumour doubling time of 7.5 +/- 3.0 days for capecitabine compared to 3.5 +/- 0.5 days for the vehicle treated group (P &lt; 0.001).

Despite identical germline Kras and p53 genotypes, the KPC PDA and KPC allograft tumour types have previously shown differences in gemcitabine sensitivity in vivo, predicted to be due to differences in drug delivery (K. Olive, et al., Science 2009). Therefore, capecitabine PK and efficacy are now being investigated in the autochthonous tumours arising in the KPC model.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5446. doi:10.1158/1538-7445.AM2011-5446

Zebrafish based assays for the assessment of cardiac, visual and gut function--potential safety screens for early drug discovery

INTRODUCTION

Safety pharmacology is integral to the non-clinical safety assessment of new chemical entities prior to first administration to humans. The zebrafish is a well established model organism that has been shown to be relevant to the study of human diseases. The potential role of zebrafish in safety pharmacology was evaluated using reference compounds in three models assessing cardiac, visual and intestinal function.

METHODS

Compound toxicity was first established in zebrafish to determine the non toxic concentration of a blinded set of 16 compounds. In the cardiac assay, zebrafish larvae at 3 days post fertilisation (d.p.f.) were exposed to compounds for 3 h before measurement of the atrial and ventricular rates. To investigate visual function, the optomotor response was assessed in 8 d.p.f. larvae following a 5 day compound exposure. In the intestinal function assay, the number of gut contractions was measured in 7 d.p.f. larvae after a 1 h compound exposure. Finally, compound uptake was determined for 9 of the 16 compounds to measure the concentration of compound absorbed by the zebrafish larvae.

RESULTS

Seven compounds out of nine produced an expected effect that was statistically significant in the cardiac and visual functions assays. In the gut contraction assay, six out of ten compounds showed a statistically significant effect that was also the expected result whilst two displayed anticipated but non-significant effects. The compound uptake method was used to determine larval tissue concentrations and allowed the identification of false negatives when compound was poorly absorbed into the zebrafish.

DISCUSSION

Overall, results generated in three zebrafish larvae assays demonstrated a good correlation between the effects of compounds in zebrafish and the data available from other in vivo models or known clinical adverse effects. These results suggest that for the cardiac, intestinal and visual function, zebrafish assays have the potential to predict adverse drug effects and supports their possible role in early safety assessment of novel compounds.

Solvents, interfaces and protein structure

Mean packing densities in protein interiors are comparable to those of most organic solids but the variations between small regions may be substantial. Packing defects may be related to allowed structural fluctuations. Molecular surface areas can be correlated with free energies of transfer between different solvents. The proportionality factor will depend, in general, on the nature of the solute and both the solvents. The changes in solvent-protein interfacial area on chain folding are large and the implied changes in free energy from this solvent-squeezing effect are correspondingly large. The strong tendency to minimize surface area is reflected in the globular shape of most protein molecules or domains in larger structures. The formation of isolated units of secondary structure from an extended chain represents about one half of the eventual total area change. The tendencies of amino acids to form beta-sheets correlate well with the rank-ordered list based on non-polar area change for each residue type. The calculated area changes for helix and sheet formation are not identical in rank order. The rank-ordered list for alpha-helix formation correlates satisfactorily with the probability list prepared from actual structures if glutamic acid and tyrosine are removed. What special characteristics unrelated to surface area these two amino acids might have is not clear. Tertiary structure formation from preformed secondary structural units can be rank ordered on area change and possible nucleation sites can be identified. A prediction scheme for helix-helix interactions is proposed. The hydrophobic force begins to be felt when two helices are about 0.6 nm (6 A) from their final contact positions. Interfacial surface tension is a logical parameter to relate free energy and solvent contact area, but this macroscopic parameter must be used with great caution. It is suggested that water in the deep grooves, characteristic of the active sites of many enzymes, may have a substantially higher fugacity than bulk water as indicated, at least qualitatively, by the Kelvin equation based on surface curvature. Such water would be more easily displaced than its plane surface counterpart and could contribute significantly to ligand-binding energy. This factor would be in addition to the usual solvent entropic effects associated with surface area reduction on association.

GBR12909 Possesses Anticonvulsant Activity in Zebrafish and Rodent Models of Generalized Epilepsy but Cardiac Ion Channel Effects Limit Its Clinical Utility

BACKGROUND/AIMS

GBR12909 has been reported to possess anticonvulsant activity with focal brain perfusion to the hippocampus of pilocarpine, although an earlier publication suggested any anticonvulsant effects were only mild. Here we further explored the anticonvulsant potential of GBR12909 with a suite of anticonvulsant assays in both zebrafish and mammals and then explored whether it possessed any QT effects which might limit clinical utility.

METHODS

We assessed the anticonvulsant effects of GBR12909 in zebrafish pentylenetetrazole (PTZ), mammalian maximal electroshock and PTZ models of generalized epilepsy and a rodent hippocampal kindling model. Cardiac effects were assessed in zebrafish and man.

RESULTS

GBR12909 possesses anticonvulsant activity in zebrafish and rodent models of generalized epilepsy. However, phase 1 human data indicated potential QT effects. Subsequent testing in a zebrafish QT assay confirmed marked arrhythmogenic potential.

CONCLUSION

Further clinical development of GBR12909 in epilepsy was considered inappropriate because of insufficient window between the therapeutic effects and the cardiac arrhythmia problems identified in zebrafish assays. Any further development based on this mechanism of action should avoid the GBR12909 chemical scaffold, or involve structure-activity dissociation of its neurological and cardiac effects.

Identification of novel VHL targets that are associated with the development of renal cell carcinoma

von Hippel-Lindau (VHL) disease is a dominantly inherited family cancer syndrome characterized by the development of retinal and central nervous system haemangioblastomas, renal cell carcinoma (RCC) and phaeochromocytoma. Specific germline VHL mutations may predispose to haemangioblastomas, RCC and phaeochromocytoma to a varying extent. Although dysregulation of the hypoxia-inducible transcription factor-2 and JunB have been linked to the development of RCC and phaeochromocytoma, respectively, the precise basis for genotype-phenotype correlations in VHL disease have not been defined. To gain insights into the pathogenesis of RCC in VHL disease we compared gene expression microarray profiles in a RCC cell line expressing a Type 1 or Type 2B mutant pVHL (RCC-associated) to those of a Type 2A or 2C mutant (not associated with RCC). We identified 19 differentially expressed novel VHL target genes linked to RCC development. Eight targets were studied in detail by quantitative real-time polymerase chain reaction (three downregulated and five upregulated by wild-type VHL) and for six genes the effect of VHL inactivation was mimicked by hypoxia (but hypoxic-induction of smooth muscle alpha-actin 2 was specific for a RCC cell line). The potential role of four RCC-associated VHL target genes was assessed in vitro. NB thymosin beta (TMSNB) and proteinase-activated receptor 2 (PAR2) (both downregulated by wt pVHL) increased cell growth and motility in a RCC cell line, but aldehyde dehydrogenase (ALDH)1 and ALDH7 had no effect. These findings implicate TMSNB and PAR2 candidate oncogenes in the pathogenesis of VHL-associated RCC.