Senescent cardiomyocytes contribute to cardiac dysfunction following myocardial infarction

Myocardial infarction is a leading cause of morbidity and mortality. While reperfusion is now standard therapy, pathological remodelling leading to heart failure remains a clinical problem. Cellular senescence has been shown to contribute to disease pathophysiology and treatment with the senolytic navitoclax attenuates inflammation, reduces adverse myocardial remodelling and results in improved functional recovery. However, it remains unclear which senescent cell populations contribute to these processes. To identify whether senescent cardiomyocytes contribute to disease pathophysiology post-myocardial infarction, we established a transgenic model in which p16 (CDKN2A) expression was specifically knocked-out in the cardiomyocyte population. Following myocardial infarction, mice lacking cardiomyocyte p16 expression demonstrated no difference in cardiomyocyte hypertrophy but exhibited improved cardiac function and significantly reduced scar size in comparison to control animals. This data demonstrates that senescent cardiomyocytes participate in pathological myocardial remodelling. Importantly, inhibition of cardiomyocyte senescence led to reduced senescence-associated inflammation and decreased senescence-associated markers within other myocardial lineages, consistent with the hypothesis that cardiomyocytes promote pathological remodelling by spreading senescence to other cell-types. Collectively this study presents the demonstration that senescent cardiomyocytes are major contributors to myocardial remodelling and dysfunction following a myocardial infarction. Therefore, to maximise the potential for clinical translation, it is important to further understand the mechanisms underlying cardiomyocyte senescence and how to optimise senolytic strategies to target this cell lineage.

Potential for cardiac toxicity with methylimidazolium ionic liquids

Methylimidazolium ionic liquids (MILs) are solvent chemicals used in industry. Recent work suggests that MILs are beginning to contaminate the environment and lead to exposure in the general population. In this study, the potential for MILs to cause cardiac toxicity has been examined. The effects of 5 chloride MIL salts possessing increasing alkyl chain lengths (2 C, EMI; 4 C, BMI; 6 C; HMI, 8 C, M8OI; 10 C, DMI) on rat neonatal cardiomyocyte beat rate, beat amplitude and cell survival were initially examined. Increasing alkyl chain length resulted in increasing adverse effects, with effects seen at 10^-5 M at all endpoints with M8OI and DMI, the lowest concentration tested. A limited sub-acute toxicity study in rats identified potential cardiotoxic effects with longer chain MILs (HMI, M8OI and DMI) based on clinical chemistry. A 5 month oral/drinking water study with these MILs confirmed cardiotoxicity based on histopathology and clinical chemistry endpoints. Since previous studies in mice did not identify the heart as a target organ, the likely cause of the species difference was investigated. qRT-PCR and Western blotting identified a marked higher expression of p-glycoprotein-3 (also known as ABCB4 or MDR2) and the breast cancer related protein transporter BCRP (also known as ABCG2) in mouse, compared to rat heart. Addition of the BCRP inhibitor Ko143 - but not the p-glycoproteins inhibitor cyclosporin A - increased mouse cardiomyocyte HL-1 cell sensitivity to longer chain MILs to a limited extent. MILs therefore have a potential for cardiotoxicity in rats. Mice may be less sensitive to cardiotoxicity from MILs due in part, to increased excretion via higher levels of cardiac BCRP expression and/or function. MILs alone, therefore may represent a hazard in man in the future, particularly if use levels increase. The impact that MILs exposure has on sensitivity to cardiotoxic drugs, heart disease and other chronic diseases is unknown.

Anthracycline-induced cardiotoxicity and senescence

Cancer continues to place a heavy burden on healthcare systems around the world. Although cancer survivorship continues to improve, cardiotoxicity leading to cardiomyopathy and heart failure as a consequence of cancer therapy is rising, and yesterday's cancer survivors are fast becoming today's heart failure patients. Although the mechanisms driving cardiotoxicity are complex, cellular senescence is gaining attention as a major contributor to chemotherapy-induced cardiotoxicity and, therefore, may also represent a novel therapeutic target to prevent this disease. Cellular senescence is a well-recognized response to clinical doses of chemotherapies, including anthracyclines, and is defined by cell cycle exit, phenotypic alterations which include mitochondrial dysfunction, and the expression of the pro-senescent, pro-fibrotic, and pro-inflammatory senescence-associated phenotype. Senescence has an established involvement in promoting myocardial remodeling during aging, and studies have demonstrated that the elimination of senescence can attenuate the pathophysiology of several cardiovascular diseases. Most recently, pharmacology-mediated elimination of senescence, using a class of drugs termed senolytics, has been demonstrated to prevent myocardial dysfunction in preclinical models of chemotherapy-induced cardiotoxicity. In this review, we will discuss the evidence that anthracycline-induced senescence causes the long-term cardiotoxicity of anticancer chemotherapies, consider how the senescent phenotype may promote myocardial dysfunction, and examine the exciting possibility that targeting senescence may prove a therapeutic strategy to prevent or even reverse chemotherapy-induced cardiac dysfunction.

Baseline blood pressure and development of cardiotoxicity in patients treated with anthracyclines: A systematic review

Aims

Anthracyclines, a mainstay of cancer treatment, are associated with significant life-threatening cardiotoxicity. As cancer survivorship improves, there is a growing need to identify patients most at risk and strategies to mitigate anthracycline-associated cardiotoxicity. Elevated baseline blood pressure (bBP) is a possible risk factor for cardiotoxicity. The aim of this systematic review was to summarise the literature and evaluate relationships between bBP and anthracycline-associated cardiotoxicity.

Methods and results

Systematic searches were conducted, limited to English language but without restrictions on study type or country of origin. All studies fulfilled the PRISMA statement and relevant studies reviewed and narratively synthesised. A total of 1330 papers were screened, with 12 included in the qualitative synthesis. Eight papers indicated elevated bBP was associated with significantly higher risk of developing cardiotoxicity. Four papers noted significant relationships between left ventricular ejection fraction (LVEF) decline and elevated bBP. Of the four papers that failed to show an association, one noted increased risk of developing chronic heart failure. A relationship between baseline diastolic and systolic BP and anthracycline-associated cardiotoxicity is also noted.

Conclusions

This study indicates adult patients with elevated bBP have increased vulnerability to anthracycline-associated cardiotoxicity, with those with pre-hypertension or raised systolic versus diastolic pressure potentially an overlooked population. Recommendations for inclusion of bBP, incorporating individual systolic versus diastolic pressures, in cardio-oncology risk prediction models to guide clinical decision-making are thus warranted.

The role of angiotensin signalling in anthracycline-induced cardiotoxicity

 

Anthracyclines (e.g. epirubicin, doxorubicin, daunorubicin) are widely used for the treatment of adult and paediatric cancers. Despite their therapeutic efficacy, anthracyclines are associated with both acute and late-onset cardiac toxicities. Meta-analyses report an overt cardiotoxicity incidence of 6.3%, whilst sub-clinical cardiotoxicity incidence is 17.9% (1). Angiotensin converting enzyme (ACE) inhibitors are used to treat anthracycline-induced cardiotoxicity (AIC) (2) and despite their efficacy being well studied for the treatment of heart failure, hypertension and post-acute coronary syndromes, their mechanism(s) for treating and preventing AIC remain unknown.

Using in vitro cardiomyocytes, we evaluated the angiotensin signalling mechanisms stimulated by doxorubicin chemotherapy, applying quantitative PCR, immunofluorescence and real-time cell analysis technologies.

In vitro adult human ventricular cardiomyocytes (AC10 cell line) treated with clinically relevant sub-toxic concentrations of doxorubicin, demonstrate a dose and time-dependent increase in angiotensin II type-1 receptor (AT1R) gene expression. Maximal AT1R expression was observed after 24 hours' exposure at 250 nanomolar (nM), with qPCR recording up to 13-fold increases in expression relative to control (figure 1). Consistent with gene expression studies, doxorubicin also induced expression of AT1R at the protein level, with immunofluorescence imaging displaying up-regulation of AT1R in association with doxorubicin concentrations up to 500nM (figure 2). Western blot results also support the induction of AT1R, however no relationship was observed between either doxorubicin concentration or drug exposure time.

Cellular growth and morphological changes of cardiomyocytes in response to clinically relevant doses of doxorubicin treatment were evaluated with real-time cell analysis using impedance-based xCELLigence technology. During the early phases of doxorubicin exposure, an increase in cell size was observed, whilst experiments modelling the pharmacokinetics and serial half-lives of doxorubicin demonstrated reversibility of doxorubicin-induced cardiomyocyte injury following drug elimination.

These data support the mechanistic hypothesis that a relationship exists between AIC and modulation of the angiotensin signalling pathway in cardiomyocytes. We demonstrate that cardiomyocyte exposure to doxorubicin induces AT1R gene and protein expression, whilst doxorubicin-induced cardiomyocyte injury displays reversibility following drug elimination. Genetic polymorphisms within the ACE gene have been associated with cardiomyopathy and left ventricular hypertrophy. Our research now provides the platform to ascertain whether the ACE genotype contributes to heart failure from AIC, and whether an elevation in pro-hypertrophic angiotensin II levels could exacerbate anthracycline-induced hypertrophy and promote the development of late-onset anthracycline-induced heart failure.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Cancer Research UK PhD research grant

Identification of Substituted Amino Acid Hydrazides as Novel Anti-Tubercular Agents, Using a Scaffold Hopping Approach

Discovery and development of new therapeutic options for the treatment of Mycobacterium tuberculosis (Mtb) infection, particularly drug-resistant strains, are urgently required to tackle the global burden of this disease. Herein, we reported the synthesis of a novel series of N-substituted amino acid hydrazides, utilising a scaffold hopping approach within a library of anti-tubercular agents. Efficacy and selectivity were evaluated against three strains of Mtb (wild-type, isoniazid-resistant and rifampicin-resistant), and cytotoxicity against macrophages in vitro. The antibacterial activity and therapeutic index of these molecules were significantly affected by modifications with the N-substituents. Introduction of a 3,5-dinitroaryl moiety demonstrated enhanced antibacterial activity against all three strains of Mtb. In contrast, the inclusion of an imidazo [1,2-a]pyridine-3-carboxy moiety resulted in enhanced activity towards isoniazid mono-resistant Mtb relative to wild-type Mtb. Consequently, this scaffold hopping approach showed significant promise for exemplification of novel molecules with specific activity profiles against drug-resistant tuberculosis.

Trichostatin A blocks aldosterone-induced Na+ transport and control of serum- and glucocorticoid-inducible kinase 1 in cortical collecting duct cells

BACKGROUND AND PURPOSE

Aldosterone stimulates epithelial Na⁺ channel (ENaC)-dependent Na⁺ retention in the cortical collecting duct (CCD) of the kidney by activating mineralocorticoid receptors that promote expression of serum and glucocorticoid-inducible kinase 1 (SGK1). This response is critical to BP homeostasis. It has previously been suggested that inhibiting lysine deacetylases (KDACs) can post-transcriptionally disrupt this response by promoting acetylation of the mineralocorticoid receptor. The present study critically evaluates this hypothesis.

EXPERIMENTAL APPROACH

Electrometric and molecular methods were used to define the effects of a pan-KDAC inhibitor, trichostatin A, on the responses to a physiologically relevant concentration of aldosterone (3 nM) in murine mCCD_cl1 cells.

KEY RESULTS

Aldosterone augmented ENaC-induced Na⁺ absorption and increased SGK1 activity and abundance, as expected. In the presence of trichostatin A, these responses were suppressed. Trichostatin A-induced inhibition of KDAC was confirmed by increased acetylation of histone H3, H4, and α-tubulin. Trichostatin A did not block the electrometric response to insulin, a hormone that activates SGK1 independently of increased transcription, indicating that trichostatin A has no direct effect upon the SGK1/ENaC pathway.

CONCLUSIONS AND IMPLICATIONS

Inhibition of lysine de-acetylation suppresses aldosterone-dependent control over the SGK1-ENaC pathway but does not perturb post-transcriptional signalling, providing a physiological basis for the anti-hypertensive action of KDAC inhibition seen in vivo.

Collaboration, competition and publication in toxicology: views of British Toxicology Society members

BTS members offer their opinions and interesting suggestions for improvement around resourcing, collaboration, competition, infrastructure and peer review in toxicology.

To ascertain attitudes to resourcing, collaboration and publication in toxicology, a survey was developed and distributed to British Toxicology Society (BTS) members. The survey comprised 14 questions with 5 response options (strongly agree; agree; conflicted; disagree; strongly disagree) and a free text box. One hundred completed surveys were received by the cut-off date for data analysis. Unsurprisingly, 60% of participants disagreed or strongly disagreed that toxicology research is adequately funded in the UK; only 12% agreed with this statement. A similar proportion of participants (53%) disagreed with the statement that funding councils give equal opportunity to toxicology whereas 31% were conflicted on this point. An overwhelming 97% of respondents agreed that collaboration is important in driving toxicology research whereas only 38% agreed that competition is important. When this question was broadened out beyond the discipline of toxicology, a similar profile was seen suggesting that participants held similar views on toxicology versus other types of research. Many respondents were conflicted regarding the role of competition both in toxicology and in other research disciplines. Free text comments suggested that some competition is good to drive quality but can be counterproductive when competing for limited resources. Most participants were in favour of making toxicology research data openly available (86%) and in favour of open access publication (89%) although there were reservations about the cost of open access. Many (60%) thought the current system of peer review is fair but 65% also supported the idea of double-blind peer review (where both reviewer and author are anonymized). Others suggested a step in the opposite direction towards increased transparency (revealing and holding reviewers to account) would be preferable. Overall, there was a broad theme in free text responses that the need for experienced toxicologists has increased at a time when training and investment in the discipline has declined. However, not all respondents held that view with some noting that toxicology both as a research and as an applied discipline is strong within the UK scientific community.

Vascular Disrupting Agents in cancer treatment: Cardiovascular toxicity and implications for co-administration with other cancer chemotherapeutics

Destruction of the established tumour vasculature by a class of compound termed Vascular Disrupting Agents (VDAs) is showing considerable promise as a viable approach for the management of solid tumours. VDAs induce a rapid shutdown and collapse of tumour blood vessels, leading to ischaemia and consequent necrosis of the tumour mass. Their efficacy is hindered by the persistence of a viable rim of tumour cells, supported by the peripheral normal vasculature, necessitating their co-administration with additional chemotherapeutics for maximal therapeutic benefit. However, a major limitation for the use of many cancer therapeutics is the development of life-threatening cardiovascular toxicities, with significant consequences for treatment response and the patient's quality of life. The aim of this review is to outline VDAs as a cancer therapeutic approach and define the mechanistic basis of cardiovascular toxicities of current chemotherapeutics, with the overall objective of discussing whether VDA combinations with specific chemotherapeutic classes would be good or bad in terms of cardiovascular toxicity.

Human Cardiac-Mesenchymal Stem Cell-Like Cells, a Novel Cell Population with Therapeutic Potential

Cardiac stem/progenitors are being used in the clinic to treat patients with a range of cardiac pathologies. However, improvements in heart function following treatment have been reported to be variable, with some showing no response. This discrepancy in response remains unresolved. Mesenchymal stem cells (MSCs) have been highlighted as a regenerative tool as these cells display both immunomodulatory and proregenerative activities. The purpose of this study was to derive a cardiac MSC population to provide an alternative/support to current therapies. We derived human cardiac-mesenchymal stem cell-like cells (CMSCLC), so named as they share some MSC characteristics. However, CMSCLC lack the MSC trilineage differentiation capacity, being capable of only rare adipogenic differentiation and demonstrating low/no osteogenic or chondrogenic potential, a phenotype that may have advantages following transplantation. Furthermore, CMSCLC expressed low levels of p16, high levels of MHCI, and low levels of MHCII. A lack of senescent cells would also be advantageous for cells to be used therapeutically, as would the ability to modulate the immune response. Crucially, CMSCLC display a transcriptional profile that includes genes associated with cardioprotective/cardiobeneficial effects. CMSCLC are also secretory and multipotent, giving rise to cardiomyocytes and endothelial cells. Our findings support CMSCLC as a novel cell population suitable for use for transplantation.

Pyridylphosphinate metal complexes: synthesis, structural characterisation and biological activity

For the first time, a series of 25 pseudo-octahedral pyridylphosphinate metal complexes (Ru, Os, Rh, Ir) has been synthesised and assessed in biological systems. Each metal complex incorporates a pyridylphosphinate ligand, a monodentate halide and a capping η(6)-bound aromatic ligand. Solid- and solution-state analyses of two complexes reveal a structural preference for one of a possible two diastereomers. The metal chlorides hydrolyse rapidly in D2O to form a 1 : 1 equilibrium ratio between the aqua and chloride adducts. The pKa of the aqua adduct depends upon the pyridyl substituent and the metal but has little dependence upon the phosphinate R' group. Toxicity was measured in vitro against non-small cell lung carcinoma H460 cells, with the most potent complexes reporting IC50 values around 50 μM. Binding studies with selected amino acids and nucleobases provide a rationale for the variation in toxicity observed within the series. Finally, an investigation into the ability of the chelating amino acid l-His to displace the phosphinate O-metal bond shows the potential for phosphinate complexes to act as prodrugs that can be activated in the intracellular environment.

Rationalized Computer-Aided Design of Matrix-Metalloprotease-Selective Prodrugs

Matrix metalloproteinases (MMPs) are central to cancer development and metastasis. They are highly active in the tumor environment and absent or inactive in normal tissues; therefore they represent viable targets for cancer drug discovery. In this study we evaluated in silico docking to develop MMP-subtype-selective tumor-activated prodrugs. Proof of principle for this therapeutic approach was demonstrated in vitro against an aggressive human glioma model, with involvement of MMPs confirmed using pharmacological inhibition.

Abstract 2054: Improved delivery of paclitaxel to prostate tumors: a membrane-type matrix metalloproteinase (MT-MMP)-targeted approach

Introduction : Membrane-type matrix metalloproteinases (MT-MMPs) are highly active in prostate tumours, but absent or inactive in normal tissues. MT-MMPs are also known to be elevated in the majority of solid human tumours and to be central to tumor invasion and angiogenesis. Our objective has been to design inactive prodrugs of paclitaxel that are converted to the active drug by selected MMPs within the prostate tumor microenvironment.

Methods and Results : We report the synthesis and biological evaluation of a new series of peptide-based conjugates of paclitaxel designed to be selectively cleaved by MT-MMPs in the tumour microenvironment. Paclitaxel is conjugated to the peptide C-terminus via a self-immolative linker, while the N-terminus is protected from non-specific exopeptidase cleavage through the use of a masking group.

The relative importance of individual amino acids within the MT-MMP peptide recognition sequence has been investigated following extensive ex vivo metabolic studies. These studies employed tissue homogenates to assess activation of prodrug conjugates in tumour (PC-3) tissues and stability in normal tissues (liver kidney lung). ICTTax5 emerged as our lead agent, demonstrating in vitro stability in normal tissue with differential release of free paclitaxel in tumour tissue.

Further in vivo murine pharmacokinetic studies monitoring paclitaxel release in liver, lung, kidney heart and plasma revealed a substantial increase in tumour exposure to paclitaxel following ICTTax5 prodrug administration (20mg/kg) compared to the molar equivalent dose of paclitaxel alone (7mg/kg). AUC (uM.h) ratios of paclitaxel released from ICTTax5 compared to paclitaxel administered alone were 16.2 for tumour and in the range of 0.05-0.99 for normal tissues. Similar highly significant changes in Cmax were demonstrated with a 10-fold (9.77) increase in tumour concentrations and a substantially decreased Cmax ratio (0.02 - 0.19) in other tissues when administered as ICTTax5.

Anti-tumour efficacy studies (PC3 xenografts) resulted in a highly significant growth delay following single dose administration of ICTTax5 [20mg/kg] with paclitaxel alone (7mg/kg; the molar equivalent dose to the paclitaxel released from ICTTax5) having no significant anti-tumour effect.

Conclusion : A series of peptide-based prodrug conjugates of paclitaxel were synthesized. ICTTax5 was identified as the lead molecule, enabling selective delivery of active paclitaxel to PC3 prostate tumours resulting in superior pharmacokinetics and efficacy when compared to delivery of paclitaxel alone.

Citation Format: Paul M. Loadman, Javier Giménez-Warren, Andrew Mitchell, Amanda D. Race, Jade A. Spencer, Steve D. Shnyder, Jason H. Gill, Robert A. Falconer. Improved delivery of paclitaxel to prostate tumors: a membrane-type matrix metalloproteinase (MT-MMP)-targeted approach. [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 2054.

Non-invasive molecular imaging for preclinical cancer therapeutic development

Molecular and non-invasive imaging are rapidly emerging fields in preclinical cancer drug discovery. This is driven by the need to develop more efficacious and safer treatments, the advent of molecular-targeted therapeutics, and the requirements to reduce and refine current preclinical in vivo models. Such bioimaging strategies include MRI, PET, single positron emission computed tomography, ultrasound, and optical approaches such as bioluminescence and fluorescence imaging. These molecular imaging modalities have several advantages over traditional screening methods, not least the ability to quantitatively monitor pharmacodynamic changes at the cellular and molecular level in living animals non-invasively in real time. This review aims to provide an overview of non-invasive molecular imaging techniques, highlighting the strengths, limitations and versatility of these approaches in preclinical cancer drug discovery and development.

Abstract 5391: MT-MMP cleavage profiling using rapid endopeptidase profiling library (REPLi)

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that are associated with the metastatic process. Relative to non-diseased tissue, the increased expression and activity of Membrane-type matrix metalloproteinases (MT-MMPs) such as MMP-15 within the prostate tumour microenvironment can be exploited in order to selectively activate highly toxic chemotherapeutics. The main advantage to such a targeted drug delivery system is a significant reduction of systemic toxicity, resulting in a highly efficacious and successful treatment for prostate cancer.

We have screened 3375 peptides with a variety of residue combinations using Rapid Endopeptidase Profiling Library (REPLi). A ‘small but smart’ design, the REPLi library template: MCA-Gly-Gly-Gly-Xaa-Xaa-Xaa-Gly-Gly-DPA-Lys-Lys contains a donor (MCA) and quenching acceptor (DPA) FRET pair. No fluorescence indicates the molecules within the pools are intact, however, upon cleavage, the tri-variable cores can be assessed via auto fluorescence of the MCA molecule.

By analysing the 512 distinct substrate pools we have identified combinations of Phe/Tyr and Asn/Gln residues as having a greater MMP-15 cleavage bias over MMP-14, with the opposite being true for variable cores with Ile/Leu and Lys/Arg combinations. Since most known substrates show little (if any) MMP selectivity this is a novel finding, and as such, provides us with insights that are essential for designing prodrugs targeted to specific MMPs.

Through detailed metabolic studies, this information is being utilised in a bid to maximise the successful development of novel MMP-15 targeted paclitaxel conjugated prostate cancer prodrugs.

Citation Format: Andrew Mitchell, Javier Giménez-Warren, Steven D. Shnyder, Jason H. Gill, Robert A. Falconer, Paul M. Loadman. MT-MMP cleavage profiling using rapid endopeptidase profiling library (REPLi). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5391. doi:10.1158/1538-7445.AM2014-5391

Tumor-targeted prodrug ICT2588 demonstrates therapeutic activity against solid tumors and reduced potential for cardiovascular toxicity

Development of therapeutic strategies for tumor-selective delivery of therapeutics through exploitation of the proteolytic tumor phenotype has significant scope for improvement of cancer treatment. ICT2588 is a peptide-conjugated prodrug of the vascular disrupting agent (VDA) azademethylcolchicine developed to be selectively hydrolyzed by matrix metalloproteinase-14 (MMP-14) within the tumor. In this report, we extend our previous proof-of-concept studies and demonstrate the therapeutic potential of this agent against models of human colorectal, lung, breast, and prostate cancer. In all tumor types, ICT2588 was superior to azademethylcolchicine and was greater or comparable to standard clinically used agents for the respective tumor type. Prodrug activation in clinical human lung tumor homogenates relative to stability in human plasma and liver was observed, supporting clinical translation potential. A major limiting factor to the clinical value of VDAs is their inherent cardiovascular toxicity. No increase in plasma von Willebrand factor (vWF) levels, an indicator of systemic vascular dysfunction and acute cardiovascular toxicity, was detected with ICT2588, thereby supporting the tumor-selective activation and reduced potential of ICT2588 to cause cardiovascular toxicity. Our findings reinforce the improved therapeutic index and tumor-selective approach offered by ICT2588 and this nanotherapeutic approach.

Development of novel tumor-targeted theranostic nanoparticles activated by membrane-type matrix metalloproteinases for combined cancer magnetic resonance imaging and therapy

A major drawback with current cancer therapy is the prevalence of unrequired dose-limiting toxicity to non-cancerous tissues and organs, which is further compounded by a limited ability to rapidly and easily monitor drug delivery, pharmacodynamics and therapeutic response. In this report, the design and characterization of novel multifunctional "theranostic" nanoparticles (TNPs) is described for enzyme-specific drug activation at tumor sites and simultaneous in vivo magnetic resonance imaging (MRI) of drug delivery. TNPs are synthesized by conjugation of FDA-approved iron oxide nanoparticles ferumoxytol to an MMP-activatable peptide conjugate of azademethylcolchicine (ICT), creating CLIO-ICTs (TNPs). Significant cell death is observed in TNP-treated MMP-14 positive MMTV-PyMT breast cancer cells in vitro, but not MMP-14 negative fibroblasts or cells treated with ferumoxytol alone. Intravenous administration of TNPs to MMTV-PyMT tumor-bearing mice and subsequent MRI demonstrates significant tumor selective accumulation of the TNP, an observation confirmed by histopathology. Treatment with CLIO-ICTs induces a significant antitumor effect and tumor necrosis, a response not observed with ferumoxytol. Furthermore, no toxicity or cell death is observed in normal tissues following treatment with CLIO-ICTs, ICT, or ferumoxytol. These findings demonstrate proof of concept for a new nanotemplate that integrates tumor specificity, drug delivery and in vivo imaging into a single TNP entity through attachment of enzyme-activated prodrugs onto magnetic nanoparticles. This novel approach holds the potential to significantly improve targeted cancer therapies, and ultimately enable personalized therapy regimens.

Abstract 5669: Design and synthesis of membrane type matrix metalloproteinase (MT-MMP) targeted anti-tumor agents

Design and synthesis of membrane type matrix metalloproteinase (MT-MMP) targeted anti-tumor agents

Membrane-type matrix metalloproteinases (MT-MMPs) are highly active in tumors, but absent or inactive in normal tissues. MT-MMPs are known to be elevated in the majority of human tumors and to be central to tumor invasion and angiogenesis. Our objective has been to design inactive prodrugs that are converted to a potent drug by selected MMPs within the tumor microenvironment.

We report the design and synthesis of a series of peptide-based conjugates of azademethylcolchicine (a potent colchicine analogue) designed to be selectively cleaved by MT-MMPs in the tumor microenvironment. Azademethylcolchicine was attached to the peptide C-terminus, while the N-terminus is protected from non-specific cleavage by exopeptidases through a masking group. A series of N-terminal masking groups, including unnatural amino acids, substituted aromatic groups, alkyl spacers and more complex endcaps was employed. Insights have been gained into the MT-MMP peptide recognition sequence and the relative importance of individual amino acids with regards MMP-selectivity. The P2’ position in particular has been extensively studied through substitution by both natural amino acid and unnatural amino acids.

We have investigated the efficiency of hydrolytic cleavage of these conjugates to release the active agent in both tumor and normal tissues. Results indicate significant effects of P2’ amino acid substitution upon stability and conversely activation in tumor and normal tissues (liver, kidney, lung, plasma), with half-lives of hydrolysis ranging from 2-60 min in tumor and 3-300 min in normal tissues.

In conclusion, a series of peptide-based prodrug conjugates of azademethylcolchicine was synthesized. Hydrolytic activation of these prodrugs in tumor tissue was rapid compared to liver and other normal tissues. From this screen, ICT-2588, which includes tyrosine at the P2’ position, emerged as the agent with a hydrolytic cleavage rate most suited for further evaluation as a tumour activated peptide-based conjugate.

Citation Format: Robert A. Falconer, Ahmed M. Youssef, Javier Gimenez Warren, Goreti R. Morais, Andrew Mitchell, Steve D. Shnyder, Jason H. Gill, Laurence H. Patterson, Paul M. Loadman. Design and synthesis of membrane type matrix metalloproteinase (MT-MMP) targeted anti-tumor agents. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5669. doi:10.1158/1538-7445.AM2013-5669

Induction of differentiation and apoptosis in leukaemic cell lines by the novel benzamide family histone deacetylase 2 and 3 inhibitor MI-192

Histone deacetylase inhibitors (HDACIs) are in advanced clinical development as cancer therapeutic agents. However, first generation HDACIs such as butyrate and valproate are simple short chain aliphatic compounds with moieties resembling acetyl groups, and have a broad spectrum of activity against HDACs. More complex second generation HDACIs undergoing clinical trials, such as the benzamide group compounds MS-275 and MGCD0103, are specific primarily for HDAC1 and HDAC2. To expand the repertoire of available HDACIs and HDAC specificities we created a novel benzamide-based compound named MI-192. When tested against purified recombinant HDACs, MI-192 had marked selectivity for the class I enzymes, HDAC2 and HDAC3. Screening in the NCI60 screen demonstrated that MI-192 had greatly enhanced efficacy against cells of leukaemic origin. When tested in culture against the acute myeloid leukaemic cell lines U937, HL60 and Kasumi-1, MI-192 induced differentiation and was cytotoxic through promotion of apoptosis. MI-192 therefore justifies further investigation and development as a potential therapeutic agent for use in leukaemia.

Development of a novel tumor-targeted vascular disrupting agent activated by membrane-type matrix metalloproteinases

Vascular disrupting agents (VDA) offer a strategy to starve solid tumors of nutrients and oxygen concomitant with tumor shrinkage. Several VDAs have progressed into early clinical trials, but their therapeutic value seems to be compromised by systemic toxicity. In this report, we describe the design and characterization of a novel VDA, ICT2588, that is nontoxic until activated specifically in the tumor by membrane-type 1 matrix metalloproteinase (MT1-MMP). HT1080 cancer cells expressing MT1-MMP were selectively chemosensitive to ICT2588, whereas MCF7 cells that did not express MT1-MMP were nonresponsive. Preferential hydrolysis of ICT2588 to its active metabolite (ICT2552) was observed in tumor homogenates of HT1080 relative to MCF7 homogenates, mouse plasma, and liver homogenate. ICT2588 activation was inhibited by the MMP inhibitor ilomastat. In HT1080 tumor-bearing mice, ICT2588 administration resulted in the formation of the active metabolite, diminution of tumor vasculature, and hemorrhagic necrosis of the tumor. The antitumor activity of ICT2588 was superior to its active metabolite, exhibiting reduced toxicity, improved therapeutic index, enhanced pharmacodynamic effect, and greater efficacy. Coadministration of ICT2588 with doxorubicin resulted in a significant antitumor response (22.6 d growth delay), which was superior to the administration of ICT2588 or doxorubicin as a single agent, including complete tumor regressions. Our findings support the clinical development of ICT2588, which achieves selective VDA targeting based on MT-MMP activation in the tumor microenvironment.

Micro-RNA-31 controls hair cycle-associated changes in gene expression programs of the skin and hair follicle

The hair follicle is a cyclic biological system that progresses through stages of growth, regression, and quiescence, which involves dynamic changes in a program of gene regulation. Micro-RNAs (miRNAs) are critically important for the control of gene expression and silencing. Here, we show that global miRNA expression in the skin markedly changes during distinct stages of the hair cycle in mice. Furthermore, we show that expression of miR-31 markedly increases during anagen and decreases during catagen and telogen. Administration of antisense miR-31 inhibitor into mouse skin during the early- and midanagen phases of the hair cycle results in accelerated anagen development, and altered differentiation of hair matrix keratinocytes and hair shaft formation. Microarray, qRT-PCR and Western blot analyses revealed that miR-31 negatively regulates expression of Fgf10, the components of Wnt and BMP signaling pathways Sclerostin and BAMBI, and Dlx3 transcription factor, as well as selected keratin genes, both in vitro and in vivo. Using luciferase reporter assay, we show that Krt16, Krt17, Dlx3, and Fgf10 serve as direct miR-31 targets. Thus, by targeting a number of growth regulatory molecules and cytoskeletal proteins, miR-31 is involved in establishing an optimal balance of gene expression in the hair follicle required for its proper growth and hair fiber formation.