Spatial characterization of redox processes and speciation of Ru(III) anticancer complexes by 19F magnetic resonance imaging

The application of CF₃-labeled Ru(III) anticancer complexes to magnetic resonance (MR) imaging of tumour tissues is demonstrated. By combining anatomical chemical-shift selective (CHESS) imaging with ¹⁹F chemical-shift imaging (CSI) MR methods, we show that oxidation states and ligand-exchange processes of the complexes can be spatially encoded. Measurements on different tissue models, including a human breast adenocarcinoma tumour, validate the application of these complexes as MR theranostics for the sensing and targeting of hypoxia.

Ferrocene-appended anthraquinone and coumarin as redox-active cytotoxins

Appending of ferrocene (Fc) to biologically-active organic backbones can generate novel multi-functional species for targeting bacteria and cancer. In this work Fc was linked to coumarin and anthraquinone with the goal of harnessing the redox-active Fc centre to generate new compounds that exhibit cytoxicity through the generation of toxic reactive oxygen species (ROS). A Cu(I)-catalyzed azide-alkyne cycloaddition "click" reaction was used to connect the organic and Fc components via a triazole linker. Cyclic voltammetry shows that the Fc potentials are suitable for oxidation by biological hydrogen peroxide to give reactive ferrocenium (Fc⁺) species, which can then generate hydroxyl radicals. The ability of the compounds to generate hydroxyl radicals in the presence of hydrogen peroxide was shown directly using EPR spin-trapping experiments. Furthermore, in vitro studies in MCF-7 breast cancer cells show significant increases in ROS following incubation with the Fc-functionalized compounds. Screening for antibacterial activity produced negative results for all of the Fc compounds, consitent with low levels of hydrogen peroxide typically found in bacteria. By contrast, Fc-coumarin showed cytotoxicity against A549 lung cancer and SKOV3 ovarian cancer cell lines, whereas the parent compound was inactive. This is consistent both with the cytoxic potential of the Fc group and the elevated hydrogen peroxide levels found in many cancers. Interestingly, the anthraquinone compounds showed the opposite effect with the parent compounds showing modest activity against A549 cells, but the Fc compounds being inactive. This demonstrates other potential negative impacts of including Fc, such as significantly increased lipophilicity.

Inter-Metastatic Heterogeneity of Tumor Marker Expression and Microenvironment Architecture in a Preclinical Cancer Model

BACKGROUND

Preclinical drug development studies rarely consider the impact of a candidate drug on established metastatic disease. This may explain why agents that are successful in subcutaneous and even orthotopic preclinical models often fail to demonstrate efficacy in clinical trials. It is reasonable to anticipate that sites of metastasis will be phenotypically unique, as each tumor will have evolved heterogeneously with respect to gene expression as well as the associated phenotypic outcome of that expression. The objective for the studies described here was to gain an understanding of the tumor heterogeneity that exists in established metastatic disease and use this information to define a preclinical model that is more predictive of treatment outcome when testing novel drug candidates clinically.

METHODS

Female NCr nude mice were inoculated with fluorescent (mKate), Her2/neu-positive human breast cancer cells (JIMT-mKate), either in the mammary fat pad (orthotopic; OT) to replicate a primary tumor, or directly into the left ventricle (intracardiac; IC), where cells eventually localize in multiple sites to create a model of established metastasis. Tumor development was monitored by in vivo fluorescence imaging (IVFI). Subsequently, animals were sacrificed, and tumor tissues were isolated and imaged ex vivo. Tumors within organ tissues were further analyzed via multiplex immunohistochemistry (mIHC) for Her2/neu expression, blood vessels (CD31), as well as a nuclear marker (Hoechst) and fluorescence (mKate) expressed by the tumor cells.

RESULTS

Following IC injection, JIMT-1mKate cells consistently formed tumors in the lung, liver, brain, kidney, ovaries, and adrenal glands. Disseminated tumors were highly variable when assessing vessel density (CD31) and tumor marker expression (mkate, Her2/neu). Interestingly, tumors which developed within an organ did not adopt a vessel microarchitecture that mimicked the organ where growth occurred, nor did the vessel microarchitecture appear comparable to the primary tumor. Rather, metastatic lesions showed considerable variability, suggesting that each secondary tumor is a distinct disease entity from a microenvironmental perspective.

CONCLUSIONS

The data indicate that more phenotypic heterogeneity in the tumor microenvironment exists in models of metastatic disease than has been previously appreciated, and this heterogeneity may better reflect the metastatic cancer in patients typically enrolled in early-stage Phase I/II clinical trials. Similar to the suggestion of others in the past, the use of models of established metastasis preclinically should be required as part of the anticancer drug candidate development process, and this may be particularly important for targeted therapeutics and/or nanotherapeutics.

Preparation of parenteral nanocrystal suspensions of etoposide from the excipient free dry state of the drug to enhance in vivo antitumoral properties

Nanoparticle technology in cancer chemotherapy is a promising approach to enhance active ingredient pharmacology and pharmacodynamics. Indeed, drug nanoparticles display various assets such as extended blood lifespan, high drug loading and reduced cytotoxicity leading to better drug compliance. In this context, organic nanocrystal suspensions for pharmaceutical use have been developed in the past ten years. Nanocrystals offer new possibilities by combining the nanoformulation features with the properties of solid dispersed therapeutic ingredients including (i) high loading of the active ingredient, (ii) its bioavailability improvement, and (iii) reduced drug systemic cytotoxicity. However, surprisingly, no antitumoral drug has been marketed as a nanocrystal suspension until now. Etoposide, which is largely used as an anti-cancerous agent against testicular, ovarian, small cell lung, colon and breast cancer in its liquid dosage form, has been selected to develop injectable nanocrystal suspensions designed to be transferred to the clinic. The aim of the present work is to provide optimized formulations for nanostructured etoposide solutions and validate by means of in vitro and in vivo evaluations the efficiency of this multiphase system. Indeed, the etoposide formulated as a nanosuspension by a bottom-up approach showed higher blood life span, reduced tumor growth and higher tolerance in a murine carcinoma cancer model. The results obtained are promising for future clinical evaluation of these etoposide nanosuspensions.

Concomitant Chemoradiation Therapy with Gold Nanoparticles and Platinum Drugs Co-Encapsulated in Liposomes

A liposomal formulation of gold nanoparticles (GNPs) and carboplatin, named LipoGold, was produced with the staggered herringbone microfluidic method. The radiosensitizing potential of LipoGold and similar concentrations of non-liposomal GNPs, carboplatin and oxaliplatin was evaluated in vitro with the human colorectal cancer cell line HCT116 in a clonogenic assay. Progression of HCT116 tumor implanted subcutaneously in NU/NU mice was monitored after an irradiation of 10 Gy combined with either LipoGold, GNPs or carboplatin injected directly into the tumor by convection-enhanced delivery. Radiosensitization by GNPs alone or carboplatin alone was observed only at high concentrations of these compounds. Furthermore, low doses of carboplatin alone or a combination of carboplatin and GNPs did not engender radiosensitization. However, the same low doses of carboplatin and GNPs administered simultaneously by encapsulation in liposomal nanocarriers (LipoGold) led to radiosensitization and efficient control of cell proliferation. Our study shows that the radiosensitizing effect of a combination of carboplatin and GNPs is remarkably more efficient when both compounds are simultaneously delivered to the tumor cells using a liposomal carrier.

Abstract 3480: TMEM30A loss-of-function mutations drive lymphomagenesis and confer therapeutically exploitable vulnerability in B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype worldwide, accounting for 40% of all non-Hodgkin lymphomas. DLBCL presents as an aggressive disease requiring immediate treatment. Although significant improvement in outcome has been achieved, ~40% of patients still experience treatment failure. Here, we characterized the recurrent genetic alterations and transcriptomic signatures in diagnostic biopsies from a population registry-based cohort of 347 patients with de novo DLBCL uniformly treated with R-CHOP. This analysis revealed bi-allelic loss of function mutations of TMEM30A that were associated with favorable treatment outcome. TMEM30A is a chaperone protein, involved in maintaining the asymmetric distribution of phosphatidylethanolamine and phosphatidylserine, an integral component of the plasma membrane and “eat-me” signal recognized by macrophages. Using TMEM30A knockout systems by CRISPR genome editing techniques, we have functionally characterized this loss-of-function mutation in representative human and mouse DLBCL cell line models. We have discovered that TMEM30A loss is associated with increased B-cell signaling following antigen stimulation, including a two-fold increase in the diffusion rate of B-cell receptor (BCR) clustering, using high resolution Single Particle Tracking (SPT) technology. In addition, we have measured three-fold increase in chemotherapeutic drug accumulation in both knockout cell lines and randomly selected patient biopsies with TMEM30A biallelic loss. This observation was validated in a xenograft mouse model, which presented improved survival and limited tumor growth following vincristine treatment in mice injected with TMEM30A null DLBCL cell lines compared with native cell lines. This phenotype explains the improved prognosis observed in DLBCL patients following R-CHOP treatment. Furthermore, we have observed over two fold higher numbers of tumor-associated macrophages in B-cell lymphoma syngeneic mouse models with Tmem30a loss-of-function, prior to any form of treatment, suggesting the existence of “hot” and primed tumors. Our data highlight a multi-faceted role for TMEM30A and plasma membrane physiology in B-cell lymphomagenesis, and characterize intrinsic and extrinsic vulnerabilities of cancer cells that can be therapeutically exploited. Characterization of these mechanisms will address a missing link in the cancer field as related insights in lymphoma will outline therapeutic approaches that can be extended to cancer therapy in general.

Citation Format: Shannon Healy, Daisuke Ennishi, Ali Bashashati, Saeed Saberi, Christoffer Hother, Anja Mottok, Fong Chun Chan, Lauren Chong, Robert Kridel, Merrill Boyle, Barbara Meissner, Tomohiro Aoki, Katsuyoshi Takata, Bruce W. Woolcock, Elena Vigano, Libin Abraham, Michael Gold, Adele Telenius, Pedro Farinha, Graham Slack, Susana Ben-Neriah, Daniel Lai, Allen W. Zhang, Sohrab Salehi, Hennady P. Shulha, Derek S. Chiu, Sara Mostafavi, Alina S. Gerrie, Diego Villa, Laurie H. Sehn, Kerry J. J. Savage, Andrew J. J. Mungall, Andrew P. Weng, Marcel Bally, Ryan D. Morin, Gabriela V. Cohen Freue, Joseph M. Connors, Marco A. Marra, Sohrab P. Shah, Randy D. Gascoyne1, David W. Scott, Christian Steidl, Ulrich Steidl. TMEM30A loss-of-function mutations drive lymphomagenesis and confer therapeutically exploitable vulnerability in B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3480.

A new quinoline-based chemical probe inhibits the autophagy-related cysteine protease ATG4B

The cysteine protease ATG4B is a key component of the autophagy machinery, acting to proteolytically prime and recycle its substrate MAP1LC3B. The roles of ATG4B in cancer and other diseases appear to be context dependent but are still not well understood. To help further explore ATG4B functions and potential therapeutic applications, we employed a chemical biology approach to identify ATG4B inhibitors. Here, we describe the discovery of 4-28, a styrylquinoline identified by a combined computational modeling, in silico screening, high content cell-based screening and biochemical assay approach. A structure-activity relationship study led to the development of a more stable and potent compound LV-320. We demonstrated that LV-320 inhibits ATG4B enzymatic activity, blocks autophagic flux in cells, and is stable, non-toxic and active in vivo. These findings suggest that LV-320 will serve as a relevant chemical tool to study the various roles of ATG4B in cancer and other contexts.

Regional and local environmental conditions do not shape the response to warming of a marine habitat-forming species

The differential response of marine populations to climate change remains poorly understood. Here, we combine common garden thermotolerance experiments in aquaria and population genetics to disentangle the factors driving the population response to thermal stress in a temperate habitat-forming species: the octocoral Paramuricea clavata. Using eight populations separated from tens of meters to hundreds of kilometers, which were differentially impacted by recent mortality events, we identify 25 °C as a critical thermal threshold. After one week of exposure at this temperature, seven of the eight populations were affected by tissue necrosis and after 30 days of exposure at this temperature, the mean % of affected colonies increased gradually from 3 to 97%. We then demonstrate the weak relation between the observed differential phenotypic responses and the local temperature regimes experienced by each population. A significant correlation was observed between these responses and the extent of genetic drift impacting each population. Local adaptation may thus be hindered by genetic drift, which seems to be the main driver of the differential response. Accordingly, conservation measures should promote connectivity and control density erosion in order to limit the impact of genetic drift on marine populations facing climate change.

The cyanobacterial metabolite nocuolin a is a natural oxadiazine that triggers apoptosis in human cancer cells

Oxadiazines are heterocyclic compounds containing N-N-O or N-N-C-O system within a six membered ring. These structures have been up to now exclusively prepared via organic synthesis. Here, we report the discovery of a natural oxadiazine nocuolin A (NoA) that has a unique structure based on 1,2,3-oxadiazine. We have identified this compound in three independent cyanobacterial strains of genera Nostoc, Nodularia, and Anabaena and recognized the putative gene clusters for NoA biosynthesis in their genomes. Its structure was characterized using a combination of NMR, HRMS and FTIR methods. The compound was first isolated as a positive hit during screening for apoptotic inducers in crude cyanobacterial extracts. We demonstrated that NoA-induced cell death has attributes of caspase-dependent apoptosis. Moreover, NoA exhibits a potent anti-proliferative activity (0.7-4.5 μM) against several human cancer lines, with p53-mutated cell lines being even more sensitive. Since cancers bearing p53 mutations are resistant to several conventional anti-cancer drugs, NoA may offer a new scaffold for the development of drugs that have the potential to target tumor cells independent of their p53 status. As no analogous type of compound was previously described in the nature, NoA establishes a novel class of bioactive secondary metabolites.

Predictors of nonresponse to fluid restriction in hyponatraemia due to the syndrome of inappropriate antidiuresis

BACKGROUND

Fluid restriction (FR), the first-line treatment for hyponatraemia due to the syndrome of inappropriate antidiuresis (SIAD), often does not lead to successful correction of hyponatraemia. Therefore, predictive markers of treatment response are desirable. We evaluated routinely measured serum (s) and urine (u) parameters, s-copeptin and s-mid-regional pro-atrial natriuretic peptide (s-MR-proANP), as possible predictors of FR response.

METHODS

In this prospective observational study, we included patients with profound hyponatraemia (s-sodium <125 mmol L^-1 ) due to SIAD. Patients were classified as FR responders (increase in s-sodium concentration of >3 mmol L^-1 within 24 h) or nonresponders (increase of ≤3 mmol L^-1 within 24 h). Initial laboratory parameters were compared between groups with logistic regression analysis.

RESULTS

Of 106 SIAD patients analysed, 82 underwent treatment with FR; 48 (59%) patients showed a successful response to FR and 34 (41%) were considered nonresponders. High levels of u-sodium and u-osmolality were significantly associated with nonresponse to FR [odds ratio (OR) 15.0, 95% confidence interval (CI) 2.4-95.8, P = 0.004 and OR 34.8, 95% CI 1.2-1038.8, P = 0.041, respectively). The association of u-sodium and nonresponse remained significant also after adjustment for diuretic use. Lower levels of s-MR-proANP were associated with nonresponse (OR 0.03, 95% CI 0.003-0.3, P = 0.004), whereas s-copeptin was not significantly associated with response to FR.

CONCLUSION

Easily measured laboratory parameters, especially u-sodium, correlate with therapeutic response and identify patients most likely to fail to respond to FR. Measurement of these parameters may facilitate early treatment choice in patients with SIAD.

Precision autophagy: Will the next wave of selective autophagy markers and specific autophagy inhibitors feed clinical pipelines?

Research presented at the Vancouver Autophagy Symposium (VAS) 2014 suggests that autophagy's influence on health and disease depends on tight regulation and precision targeting of substrates. Discussions recognized a pressing need for robust biomarkers that accurately assess the clinical utility of modulating autophagy in disease contexts. Biomarker discovery could flow from investigations of context-dependent triggers, sensors, and adaptors that tailor the autophagy machinery to achieve target specificity. In his keynote address, Dr. Vojo Deretic (University of New Mexico) described the discovery of a cargo receptor family that utilizes peptide motif-based cargo recognition, a mechanism that may be more precise than generic substrate tagging. The keynote by Dr. Alec Kimmelman (Harvard Medical School) emphasized that unbiased screens for novel selective autophagy factors may accelerate the development of autophagy-based therapies. Using a quantitative proteomics screen for de novo identification of autophagosome substrates in pancreatic cancer, Kimmelman's group discovered a new type of selective autophagy that regulates bioavailable iron. Additional presentations revealed novel autophagy regulators and receptors in metabolic diseases, proteinopathies, and cancer, and outlined the development of specific autophagy inhibitors and treatment regimens that combine autophagy modulation with anticancer therapies. VAS 2014 stimulated interdisciplinary discussions focused on the development of biomarkers, drugs, and preclinical models to facilitate clinical translation of key autophagy discoveries.

Abstract B36: Developing circRNA signatures as a biomarker for the early diagnosis of pancreatic carcinoma

Background: At the time of diagnosis, pancreatic ductal adenocarcinoma (PDAC) is typically already advanced and incurable. Current research has concentrated on finding tumor markers for early detection while the cancer is still localized and amenable to therapy, however, these markers remain elusive. The studies described focus on developing exonic circular RNAs (circRNA) as a novel set of diagnostic/prognostic biomarkers for PDAC. CircRNAs found in mammalian cells, are backsplice variants of transcripts that are derived from approximately 15% of actively transcribed genes. The prevalence, stability and cell-specific expression patterns of circRNAs suggest that they could be exploited as an indirect or surrogate readout of transcriptional activity in normal and diseased states. Both coding and non-coding RNAs are encapsulated within cytoplasmic endosomes, which are subsequently released as extracellular or circulating microvesicles called exosomes. Exosomes have become a promising research focus as a source for biomarkers. Objective: We are interested in elucidating whether aberrantly expressed genes in PDAC produce different types of circRNAs that become enriched in tumor-secreted exosomes. Hypothesis: Exosomal circRNA (exo-circRNA) expression patterns are potentially specific to different stages/types of PDAC and therefore can be used in disease sub-typing and prognosis. Methods: Exosomes were isolated from a normal pancreatic exocrine cell line (htert-HPNE) as well as three PDAC cell lines ranging from well to poorly differentiated, including PANC-1, BxPC3and MIAPaCa-2. The size and relative abundance of exosomes was quantified by transmission electron microscopy (TEM). The expression of common exosomal markers (CD63, CD9, CD81, and HSP70) and the PDAC exosomal marker glypican-1 (GPC-1) was evaluated by flow cytometry. RNA was purified from exosomes (exo-RNA) and the rRNA depleted samples were subject to circular RNA isolation. Exo-circRNA was used to construct RNA-Seq libraries. Sequencing of the generated libraries was performed on the Illumina Nextseq platform using 2x100 reads V1 chemistry at a targeted depth of 25 million paired end reads per library. The four read libraries were mapped to the human reference genome GRCh38.p3 using BWA-MEM, and analyzed using two bioinformatics platforms, “CIRI” and “find_circ”. Comparison of membership and expression levels was made between a normal cell line and well-, moderately- and poorly differentiated, PDAC cell lines. Results: Exosome size ranged from 20nm to 80nm. These structures demonstrated some diversity in size and marker expression when comparing cell lines. The smallest structures were observed from BxPC3 cell. Here, we show for the first time the presence of circRNAs in exosomes collected from PDAC cell lines. RNA-seq analyses revealed a number of interesting circRNA species that show cell line specificity. Preliminary examination of PANC-1 RNA-seq libraries from the ENCODE database identified over 800 circRNA isoforms from total cellular transcriptome. The number of circRNA isoforms for PANC-1 cells decreased when using an enriched exo-circRNA library for alignment to approximately 19 putative circRNA markers. Furthermore, circRNA isoforms for each of the cell lines examined were distinct. Interestingly, no circRNAs of genes known to be overexpressed in PDAC (such as K-RAS) were found in the fraction of exo-cricRNA for any of the cell lines tested. Impact: The studies described demonstrate that specific circRNAs can be readily extracted from the exosomes of conditioned media. We hope that this novel tool can be further developed to help to diagnose pancreatic carcinoma when it is amenable to surgical resection and/or chemotherapy, thereby reducing the mortality associated with this disease.

Citation Format: Jessica Kalra, Keith Laderoute, Daniel Renouf, David Shaeffer, Marcel Bally. Developing circRNA signatures as a biomarker for the early diagnosis of pancreatic carcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B36.

Abstract B54: Location of tumor burden influences tumor and vascular architecture, necrosis, and nanoparticle delivery

The gene and protein expression profile of a metastatic lesion can vary from the primary tumor. As a result, behavior of a secondary lesion can differ in the context of drug uptake and sensitivity as compared to the parent tumor. A better understanding of phenotypic variations that arise as a result of location of disease burden may be able to shed light on why widely used subcutaneous and orthotopic preclinical models fail to predict clinical success of drug candidates evaluated in the metastatic setting. These data can be used as a guide for preclinical study design in drug discovery. Our objective was to examine metastatic lesions from a wide range of organs in order to establish patterns of microarchitecture that may influence drug biodistribution and therefore drug efficacy in vivo. We hypothesize that metastatic lesions are phenotypically unique tumors with heterogeneous microenvironments which results in variable drug delivery and therefore drug efficacy. The investigations described compare tumor and vascular architecture of an orthotopic tumor with metastatic lesions. To study this, female NCr nude mice were inoculated with Her2/neu positive human breast cancer cells (JIMT-1) transfected with a fluorescence protein (mkate). Animals were inoculated either in the mammary fat pad (o.t.) to replicate a primary tumor, or directly into the left ventricle (i.c.) to establish systemic disease. Tumor development was monitored using in vivo fluorescence imaging (IVFI). Once metastases were established, animals were dosed with a custom formulated fluorescent labelled liposome (LipoDiR). The distribution of LipoDiR was imaged using IVFI. Subsequently, animals were sacrificed, mammary fat pad tumors and organs with metastatic lesions were excised and imaged ex vivo for mkate and LipoDiR. Tumors within organ tissues were further analyzed via multiplex immunohistochemical staining. Tumor sections were stained with antibodies against Her2/neu, smooth muscle actin (SMA), Collagen IV (CIV), a blood vessel marker (CD31), and a marker of hypoxia (CAIX) in order to examine the variability of tumor and vascular architecture. JIMT-1mKate cells proved to be a valuable Her2/neu positive cell line with the ability to form consistent systemic disease in the lung, liver, brain, kidney, ovaries, and adrenal glands after i.c. inoculation. LipoDiR, was successfully used to image distribution of nanoparticles in vivo, ex vivo and in tissue sections at the microscopic level. Although LipoDiR pharmacokinetics were comparable between the two models (o.t. and i.c.), orthotopic tumors showed a significant enhanced permeability and retention (EPR) effect while most organ tumors were unable to accumulate drug over a 24 hours. When comparing the tumors collected from the mammary fat pad to disseminated tumors, vessel density (CD31), vessel maturity (CIV), vessel perfusion (DiR), hypoxia (CAIX) and tumor marker expression (Her2/neu) were highly variable. Interestingly, tumors seeded within an organ did not take on the organ architecture, nor did they appear similar to the primary tumor. Rather, metastatic lesions showed considerable variability suggesting that each secondary tumor is a distinct disease entity. Our data suggests that more heterogeneity in tumor architecture and protein expression exists in metastatic lesions than has been previously appreciated. This variability is fairly profound even between tumors found in the same organ and leads to a significant impact on nanoparticle distribution. These studies highlight a need to investigate candidate drugs in multiple disease models that recapitulate the most aggressive disease. Not only will this improve the ability of preclinical studies to predict clinical success of experimental drugs, it will also help to concentrate research efforts on those drugs with the ability to engender better outcomes for patients with the most refractory disease.

Citation Format: Jessica Kalra, Jennifer Baker, Alastair Kyle, Andrew Minchinton, Marcel Bally. Location of tumor burden influences tumor and vascular architecture, necrosis, and nanoparticle delivery. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B54.

Abstract 2902: The effectiveness of autophagy inhibition in sensitizing triple-negative breast cancer cells to chemotherapy

Introduction: High recurrence rates, drug resistance after initial response to chemotherapy, and overall poor prognosis along with the limited treatment options make triple-negative breast cancers (TNBCs) a major clinical challenge. Autophagy, an evolutionary conserved degradation and recycling process, has been shown to function as an adaptive survival response to chemotherapy. Previous studies have indicated higher expression of autophagy markers in TNBCs compared to other breast cancer subtypes, as well as their dependence on autophagy for survival. Our laboratory has also shown in xenograft models an enhanced effectiveness of chemotherapy for the treatment of TNBC when given in combination with autophagy inhibition (AI). These results support TNBCs as a good candidate for AI to improve efficacy of existing therapeutic regimens. However, currently available agents for AI in cancer patients have limited effectiveness, and development of more potent autophagy inhibitors (AIs) is underway.

Objective: Develop and test new tools for more potent AI in vivo.

Experimental Design: We are employing in vitro models using TNBC lines MDA-MB-231 and SUM159PT, as well as their derivatives R8 and R75, resistant to Epirubicin (EPI) and other anthracyclines. We are evaluating effects of various AIs, including lysosomotropic agents HCQ and lys05, siRNAs and shRNAs targeting autophagy-related (Atg) proteins, and small molecule inhibitors (under development) of ATG4B protein. In vivo xenograft mouse models of MDA-MB-231 and R8 are being used to evaluate the effects of combinatorial therapy with EPI and AI.

Methods: For the assessment of autophagy levels before and after AI we used autophagy flux (degradative completion of autophagy) assays. We evaluated the effects of chemotherapy alone and in combination with AIs on parent and resistant sub-lines by assessing their proliferation. For in vivo studies, TNBC cells are injected subcutaneously in Rag2M mice. Treatment with EPI, AI, or their combination is administered after tumor formation. Treatment efficacy is evaluated by tumor volume measurements; tumors are also assessed for the expression of autophagy markers.

Results: Our in vitro experiments showed enhanced cytotoxicity of lys05 compared to HCQ either alone or in combination with EPI. However, the use of lys05 in vivo gives contradictory results and requires further evaluation. AI targeting ATG4B, using shRNA-inducible monoclonal cell lines derived from MDA-MB-231 cells and novel small molecule inhibitors of ATG4B, significantly affected cancer cell proliferation in vitro, and is currently being investigated in vivo.

Conclusion: Novel approaches to AI may serve as useful tools to assess the effects of AI in vitro and in vivo. Our preliminary results suggest that more potent AIs may improve the effectiveness of treatment of TNBC.

Supported by CIHR GPG102167 and CIHR/AVON OBC127216.

Citation Format: Svetlana Bortnik, Suganthi Chittaranjan, Jing Xu, Wieslawa H. Dragowska, Jianghong An, Adrienne Kyle, Nancy E. Go, Lubomir Vezenkov, Courtney Choutka, Amy Leung, Suzana Kovacic, Damien Bosc, Karen Gelmon, Marcel Bally, Steven Jones, Robert Young, Sharon Gorski. The effectiveness of autophagy inhibition in sensitizing triple-negative breast cancer cells to chemotherapy. [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 2902. doi:10.1158/1538-7445.AM2015-2902

Mid-regional pro-atrial natriuretic peptide and the assessment of volaemic status and differential diagnosis of profound hyponatraemia

BACKGROUND

Hyponatraemia is common and its differential diagnosis and consequent therapy management is challenging. The differential diagnosis is mainly based on the routine clinical assessment of volume status, which is often misleading. Mid-regional pro-atrial natriuretic peptide (MR-proANP) is associated with extracellular and cardiac fluid volume.

METHODS

A total of 227 consecutive patients admitted to the emergency department with profound hypo-osmolar hyponatraemia (Na < 125 mmol L(-1) ) were included in this prospective multicentre observational study conducted in two tertiary centres in Switzerland. A standardized diagnostic evaluation of the underlying cause of hyponatraemia was performed, and an expert panel carefully evaluated volaemic status using clinical criteria. MR-proANP levels were compared between patients with hyponatraemia of different aetiologies and for assessment of volume status.

RESULTS

MR-proANP levels were higher in patients with hypervolaemic hyponatraemia compared to patients with hypovolaemic or euvolaemic hyponatraemia (P = 0.0002). The area under the curve (AUC) to predict an excess of extracellular fluid volume, compared to euvolaemia, was 0.73 [95% confidence interval (CI) 0.62-0.84]. Additionally, in multivariate analysis, MR-proANP remained an independent predictor of excess extracellular fluid volume after adjustment for congestive heart failure (P = 0.012). MR-proANP predicted the syndrome of inappropriate antidiuresis (SIAD) versus hypovolaemic and hypervolaemic hyponatraemia with an AUC of 0.77 (95% CI 0.69-0.84).

CONCLUSION

MR-proANP is associated with extracellular fluid volume in patients with hyponatraemia and remains an independent predictor of hypervolaemia after adjustment for congestive heart failure. MR-proANP may be a marker for discrimination between the SIAD and hypovolaemic or hypervolaemic hyponatraemia.

Abstract B11: The early autophagy inhibitor verteporfin moderately enhances the antitumor activity of gemcitabine in a pancreatic ductal adenocarcinoma model

Autophagy, a cellular self-eating process that is activated by several cancer drugs and appears to function as a protective mechanism, is a promising therapeutic target. Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to chemotherapy, and has been described as requiring elevated autophagy for growth. To date, all preclinical reports and clinical trials investigating pharmacological inhibition of autophagy have used chloroquine or hydroxychloroquine, which block autophagy at a late stage. Verteporfin is a newly discovered autophagy inhibitor that blocks autophagy at an early stage by inhibiting autophagosome formation. Here, we report that PDAC cell lines show variable sensitivity to verteporfin in vitro and that verteporfin inhibits autophagy stimulated by gemcitabine, the current standard treatment for PDAC. Pharmacokinetic and efficacy studies in a BxPC-3 xenograft mouse model demonstrate that verteporfin accumulated in tumors at autophagy-inhibiting levels but did not reduce tumor volume or increase survival as a single agent. However, in combination with gemcitabine, verteporfin moderately reduced tumor growth and enhanced survival compared to gemcitabine alone. Our results do not agree with the premise that autophagy inhibition is effective against PDAC as a single-modality treatment, but they support autophagy inhibition as an approach to sensitize PDAC to gemcitabine.

Citation Format: Elizabeth Donohue, Anitha Thomas, Norbert Maurer, Irina Manisali, Magali Zeisser-Labouebe, Natalia Zisman, Hilary J. Anderson, Murray Webb, Marcel Bally, and Michel Roberge. The early autophagy inhibitor verteporfin moderately enhances the antitumor activity of gemcitabine in a pancreatic ductal adenocarcinoma model. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B11.

The autophagy inhibitor verteporfin moderately enhances the antitumor activity of gemcitabine in a pancreatic ductal adenocarcinoma model

Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to chemotherapy. It has been described as requiring elevated autophagy for growth and inhibiting autophagy has been proposed as a treatment strategy. To date, all preclinical reports and clinical trials investigating pharmacological inhibition of autophagy have used chloroquine or hydroxychloroquine, which interfere with lysosomal function and block autophagy at a late stage. Verteporfin is a newly discovered autophagy inhibitor that blocks autophagy at an early stage by inhibiting autophagosome formation. Here we report that PDAC cell lines show variable sensitivity to verteporfin in vitro, suggesting cell-line specific autophagy dependence. Using image-based and molecular analyses, we show that verteporfin inhibits autophagy stimulated by gemcitabine, the current standard treatment for PDAC. Pharmacokinetic and efficacy studies in a BxPC-3 xenograft mouse model demonstrated that verteporfin accumulated in tumors at autophagy-inhibiting levels and inhibited autophagy in vivo, but did not reduce tumor volume or increase survival as a single agent. In combination with gemcitabine verteporfin moderately reduced tumor growth and enhanced survival compared to gemcitabine alone. While our results do not uphold the premise that autophagy inhibition might be widely effective against PDAC as a single-modality treatment, they do support autophagy inhibition as an approach to sensitize PDAC to gemcitabine.

Abstract 1684: Autophagy inhibition as an effective strategy for sensitizing triple-negative breast cancer cells to chemotherapy

Introduction: Triple-negative breast cancer (TNBC), defined by a lack of expression of the estrogen, progesterone and HER-2 receptors, remains a major clinical challenge due to higher recurrence rates and poorer prognosis compared to other subtypes of breast cancer. Tumors that initially respond to chemotherapy - the core treatment option for the patients with an advanced disease - eventually develop resistance. New therapeutic options are urgently required for TNBC. Autophagy, a lysosome-mediated degradation and recycling process, has been shown to function as an adaptive survival response during chemotherapy. Previous studies in other cancer subtypes have indicated that autophagy inhibition can restore chemotherapeutic sensitivity and enhance treatment response.

Objective: Generate proof-of-principle evidence for autophagy inhibition as an effective treatment strategy for TNBC.

Experimental Design: We are employing in vitro models using TNBC lines MDA-MB-231 and SUM159PT, as well as their derivative lines (R8 and R75, respectively) resistant to Epirubicin (EPI) and other anthracyclines. In vivo xenograft mouse models of MDA-MB-231 and R8 are being used to evaluate the effects of combinatorial therapy with EPI and autophagy inhibitor hydroxychloroquine (HCQ).

Methods: We assessed levels of autophagy in TNBC cell lines treated with EPI, developed EPI- resistant sub-lines, and compared basal autophagy levels in parental and resistant lines, using autophagy flux (degradative completion of autophagy) assays. We evaluated the effects of chemotherapy alone and in combination with autophagy inhibitors (HCQ or siRNAs targeting autophagy-related (Atg) proteins) on both parent and resistant sub-lines by assessing their viability. For in vivo studies, MDA-MB-231 cells were injected subcutaneously in Rag2M mice. After tumor formation, mice were treated with EPI, HCQ or their combination, and treatment efficacy was evaluated by tumor volume measurements. Autophagy levels in tumors were also assessed.

Results: TNBC cells demonstrated increased autophagy in response to EPI treatment in vitro and in vivo. EPI- resistant lines showed at least 1.5 fold increased basal autophagy levels compared to their parental lines suggesting a possible adaptive role for autophagy in development of chemoresistance. Knock-down of Atg proteins by siRNA dramatically reduced the viability of EPI-resistant sub-lines, which indicates dependence of drug-resistant cells on autophagy for survival. Resistance of MDA-MB-231-R8 cells to EPI was reverted by autophagy inhibition in vitro. Combination of EPI with HCQ in vivo showed an enhanced tumor response to treatment compared to monotherapy with EPI. Additional in vivo studies are in progress.

Conclusion: Our preliminary results suggest that autophagy inhibition may be an effective strategy for the treatment of chemo-refractory TNBC cells.

Citation Format: Svetlana Bortnik, Suganthi Chittaranjan, Wieslawa H. Dragowska, Namal Abeysundara, Amy Chen, Lindsay DeVorkin, Nancy Dos Santos, Nancy Erro Go, Amy Leung, Dana Masin, Maria Rizza, Dita Strutt, Sherry Weppler, Jing Xu, Hong Yan, Karen Gelmon, Donald Yapp, Marcel Bally, Sharon M. Gorski. Autophagy inhibition as an effective strategy for sensitizing triple-negative breast cancer cells to chemotherapy. [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 1684. doi:10.1158/1538-7445.AM2013-1684

Characterization of long-circulating cationic nanoparticle formulations consisting of a two-stage PEGylation step for the delivery of siRNA in a breast cancer tumor model

Polyethylene glycol (PEG) has been used widely in liposomal formulations as a strategy to inhibit opsonization by plasma proteins and to prolong liposome plasma circulation time. PEG can be incorporated onto the surface of liposomes either during the spontaneous self-assembling process or inserted after vesicle formation. The advantages of employing the PEG postinsertion method include improved drug encapsulation efficiency and the ability to incorporate PEG conjugates for enhanced cell binding and uptake. In this study, we propose to evaluate a cationic lipid nanoparticle formulation containing two PEGylation steps: pre- and post-siRNA insertion. Our results indicate that formulations consisting of the extra PEG post-insertion step significantly increased siRNA circulation in the plasma by two-folds in comparison with the formulations consisting of only the single PEGylation step. Moreover, this formulation was able to efficiently carry siRNA to the tumor site, increase siRNA stability and significantly downregulate luciferase mRNA expression by >50% when compared with the controls in an intraperitoneal and subcutaneous breast cancer tumor model. Overall, our cationic lipid nanoparticle formulation displayed enhanced plasma circulation, reduced liver accumulation, enhanced tumor targeting, and effective gene knockdown--demonstrating excellent utility for the delivery of siRNA.

Interaction of virions with membrane glycolipids

Cellular membranes contain various lipids including glycolipids (GLs). The hydrophilic head groups of GLs extend from the membrane into the aqueous environment outside the cell where they act as recognition sites for specific interactions. The first steps of interaction of virions with cells often include contacts with GLs. To clarify the details of such contacts, we have used the total internal reflection fluorescence microscopy to explore the interaction of individual unlabelled virus-like particles (or, more specifically, norovirus protein capsids), which are firmly bound to a lipid bilayer, and fluorescent vesicles containing glycosphingolipids (these lipids form a subclass of GLs). The corresponding binding kinetics were earlier found to be kinetically limited, while the detachment kinetics were logarithmic over a wide range of time. Here, the detachment rate is observed to dramatically decrease with increasing concentration of glycosphingolipids from 1% to 8%. This effect has been analytically explained by using a generic model describing the statistics of bonds in the contact area between a virion and a lipid membrane. Among other factors, the model takes the formation of GL domains into account. Our analysis indicates that in the system under consideration, such domains, if present, have a characteristic size smaller than the contact area between the vesicle and the virus-like particle.

Interaction of single viruslike particles with vesicles containing glycosphingolipids

Glycosphingolipids are involved in the first steps of virus-cell interaction, where they mediate specific recognition of the host cell membrane. We have employed total-internal-reflection fluorescence microscopy to explore the interaction kinetics between individual unlabeled noroviruslike particles, which are attached to a glycosphingolipid-containing lipid bilayer, and fluorescent vesicles containing different types and concentrations of glycosphingolipids. Under association equilibrium, the vesicle-binding rate is found to be kinetically limited, yielding information on the corresponding activation energy. The dissociation kinetics are logarithmic over a wide range of time. The latter is explained by the vesicle-size-related distribution of the dissociation activation energy. The biological, pharmaceutical, and diagnostic relevance of the study is briefly discussed.

Targeting tumor hypoxia: suppression of breast tumor growth and metastasis by novel carbonic anhydrase IX inhibitors

Carbonic anhydrase IX (CAIX) is a hypoxia and HIF-1-inducible protein that regulates intra- and extracellular pH under hypoxic conditions and promotes tumor cell survival and invasion in hypoxic microenvironments. Interrogation of 3,630 human breast cancers provided definitive evidence of CAIX as an independent poor prognostic biomarker for distant metastases and survival. shRNA-mediated depletion of CAIX expression in 4T1 mouse metastatic breast cancer cells capable of inducing CAIX in hypoxia resulted in regression of orthotopic mammary tumors and inhibition of spontaneous lung metastasis formation. Stable depletion of CAIX in MDA-MB-231 human breast cancer xenografts also resulted in attenuation of primary tumor growth. CAIX depletion in the 4T1 cells led to caspase-independent cell death and reversal of extracellular acidosis under hypoxic conditions in vitro. Treatment of mice harboring CAIX-positive 4T1 mammary tumors with novel CAIX-specific small molecule inhibitors that mimicked the effects of CAIX depletion in vitro resulted in significant inhibition of tumor growth and metastasis formation in both spontaneous and experimental models of metastasis, without inhibitory effects on CAIX-negative tumors. Similar inhibitory effects on primary tumor growth were observed in mice harboring orthotopic tumors comprised of lung metatstatic MDA-MB-231 LM2-4(Luc+) cells. Our findings show that CAIX is vital for growth and metastasis of hypoxic breast tumors and is a specific, targetable biomarker for breast cancer metastasis.

Abstract 3661: Vascular changes and potentiating secondary drug delivery in colorectal cancer with Irinophore C

Introduction: Colorectal cancer is the third most common cancer in the world. The predominant chemotherapeutic treatment in CRC is a combination of 5-fluorouracil (5-FU) and irinotecan (CPT-11). However, the combination is limited by toxicity and resistance. We now report on the effects of 5-FU in combination with a liposomal formulation of CPT-11, Irinophore C, that is more efficacious and less toxic than free CPT-11.

Materials and Methods: 5-FU was used singly and in combination with Irinophore C in a subcutaneous model of colorectal cancer, HT-29, to assess therapeutic efficacy and toxic effects. 5-FU and Irinophore C (40mg/kg) were injected intravenously on a Q7Dx3 schedule, and tumor growth delay was measured. In a subsequent study, a single bolus injection of 14C-spiked 5-FU was delivered at different timepoints during Irinophore C (tritium-labeled) or saline treatment (Q7Dx3), and the accumulation of 5-FU in tumor tissue measured with scintigraphy. Tumors were also harvested and snap-frozen at early (days 1 - 7) and late (days 14 and 21) time points following Irinophore C treatment. Cryosections were subsequently examined for perfusion using the fluorescent dye Hoechst 33342, stained for apoptosis (TUNEL), CD31, CD105, Collagen IV and with H&E to examine changes in vascular function and tissue morphology.

Results: Irinophore C significantly reduced tumour growth (p&lt;0.001) with little or no toxicity compared to saline controls, 5-FU alone and free CPT-11 plus 5-FU. In some cases, tumour growth was completely abolished. When used in combination with 5-FU, there was a slight increase in growth delay. Treatment of the tumours with Irinophore C increased the accumulation of the active lactone form of the drug in the tumour, and also significantly increased the tissue accumulation of a single bolus injection of 5-FU after two (∼50% increase, p&lt;0.001) and three weeks (∼66% increase, p&lt;0.001). Following treatment with Irinophore C, the density of tumor tissue was decreased, and the vascular coverage was increased, leading to increased total perfusion. In addition, apoptotic activity was increased following 1 to 2 weeks of treatment with Irinophore C, compared to controls.

Conclusions: Irinophore C is more efficacious, and less toxic, than free CPT-11. This novel formulation of CPT-11 appears to have a bimodal mechanism of action wherein both endothelial and cancer cells are targeted, and which may improve the delivery of a second drug. We further believe that the dose of Irinophore C used in the combination studies is with 5-FU is overly efficacious and masks the effects of 5-FU. Clinically, Irinophore C with its low toxicity and high efficacy could have advantages over the use of free CPT-11.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3661.

Abstract 455: Hypoxia induced carbonic anhydrase IX is essential for the growth and metastasis of breast tumors

Metastasis of primary malignancies is a multi-step process and remains the principal cause of cancer deaths. Carbonic anhydrase IX (CAIX) is a hypoxia inducible protein and a poor prognostic marker for several types of cancer, including breast cancer. However, the functional role of CAIX in the metastatic progression of breast cancer is unclear. Here, we have investigated its role in the growth and metastasis of breast tumors. Orthotopic mouse mammary tumors derived from metastatic 4T1 and 66cl4 cells or non-metastatic 67NR cells were examined for levels of proliferation (BrdU), hypoxia, (pimonidazole), perfusion (DiOC7), vasculature (CD31), apoptosis (TUNEL) and lymphangiogenesis (LYVE-1). Metastatic 4T1 and 66cl4 tumors expressed a hypoxia gene signature and were characterized as being poorly vascularized, with high levels of hypoxia. Large numbers of apoptotic cells and well developed intratumoral lymphatic vessels were also evident. Inhibition of expression of CAIX in the metastatic 4T1 cells by stable expression of short hairpin RNA (shRNA) resulted in cell death and reversal of extracellular acidosis in hypoxia in vitro, dramatic regression of tumors in vivo, and inhibition of metastasis. These properties were rescued by constitutive expression of human CAIX. Treatment of mice harboring 4T1 tumors with a novel CAIX-specific inhibitor resulted in significant inhibition of tumor growth. Interrogation by immunohistochemistry of a large (3992 patient samples) primary breast tumor tissue microarray showed that CAIX expression was significantly associated with worse distant relapse free survival (p&lt;10−16) and was most prominent in the basal breast cancers (51%). Our data show that CAIX-mediated function is required for the survival and metastasis of hypoxic breast tumors, and suggest that CAIX is a promising therapeutic target for metastatic breast cancer.

This work was supported by the Canadian Breast Cancer Research Alliance, with special funding from the Canadian Breast Cancer Foundation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 455.

QLT0267, a small molecule inhibitor targeting integrin-linked kinase (ILK), and docetaxel can combine to produce synergistic interactions linked to enhanced cytotoxicity, reductions in P-AKT levels, altered F-actin architecture and improved treatment outcomes in an orthotopic breast cancer model

Introduction

Substantial preclinical evidence has indicated that inhibition of integrin linked-kinase (ILK) correlates with cytotoxic/cytostatic cellular effects, delayed tumor growth in animal models of cancer, and inhibition of angiogenesis. Widely anticipated to represent a very promising therapeutic target in several cancer indications, it is increasingly evident that optimal therapeutic benefits obtained using ILK targeting strategies will only be achieved in combination settings. The purpose of this study was to investigate the therapeutic potential of the ILK small molecule inhibitor, QLT0267 (267), alone or in combination with chemotherapies commonly used to treat breast cancer patients.

Methods

A single end-point metabolic assay was used as an initial screen for 267 interactions with selected chemotherapeutic agents. These in vitro assays were completed with seven breast cancer cell lines including several which over-expressed human epidermal growth factor receptor 2 (Her2). One agent, docetaxel (Dt), consistently produced synergistic interactions when combined with 267. Dt/267 interactions were further characterized by measuring therapeutic endpoints linked to phosphorylated protein kinase B (P-AKT) suppression, inhibition of vascular endothelial growth factor (VEGF) secretion and changes in cytoarchitecture. In vivo efficacy studies were completed in mice bearing orthotopic xenografts where tumor growth was assessed by bioluminescence and calliper methods.

Results

The combination of 267 and Dt resulted in increased cytotoxic activity, as determined using an assay of metabolic activity. Combinations of cisplatin, doxorubicin, vinorelbine, paclitaxel, and trastuzumab produced antagonistic interactions. Further endpoint analysis in cell lines with low Her2 levels revealed that the 267/Dt combinations resulted in: a three-fold decrease in concentration (dose) of 267 required to achieve 50% inhibition of P-AKT; and a dramatic disruption of normal filamentous-actin cellular architecture. In contrast to Her2-positive cell lines, three-fold higher concentrations of 267 were required to achieve 50% inhibition of P-AKT when the drug was used in combination with Dt. In vivo studies focusing on low Her2-expressing breast cancer cells (LCC6) implanted orthotopically demonstrated that treatment with 267/Dt engendered improved therapeutic effects when compared with mice treated with either agent alone.

Conclusions

The findings indicate that the 267/Dt drug combination confers increased (synergistic) therapeutic efficacy towards human breast cancer cells that express low levels of Her2.

Silencing Bcl-2 in models of mantle cell lymphoma is associated with decreases in cyclin D1, nuclear factor-kappaB, p53, bax, and p27 levels

Molecular mechanisms responsible for lymphoma resistance to apoptosis often involve the bcl-2 pathway. In this study, we investigated the cell signaling pathways activated in bcl-2-overexpressing human mantle cell lymphoma cell lines (JVM-2 and Z-138) that have been treated with oblimersen, a molecular gene silencing strategy that effectively suppresses bcl-2 in vitro and in vivo. Z-138 cells expressed higher levels of bcl-2 and were more sensitive to the effects of bcl-2 silencing, mediated by oblimersen or bcl-2 small interfering RNA, in vitro. Tumors derived following injection of Z-138 cells were sensitive to oblimersen as judged by decreases in tumor growth rate and decreases in cell proliferation (as measured by Ki-67). Immunohistochemistry and Western blot analysis of oblimersen-treated Z-138 tumors revealed a dose-dependent decrease in bcl-2 levels and an associated increase in the proapoptotic proteins caspase-3 and caspase-9. Silencing bcl-2 in Z-138 xenografts revealed an associated dose-dependent suppression of bax, a decrease in nuclear factor-kappaB and phospho-nuclear factor-kappaB, and transient loss of p53 levels. Coimmunoprecipitation studies suggest that the latter observation is mediated by an association between bcl-2 and phospho-mdm2. Bcl-2 silencing also led to p27 down-regulation and coimmunoprecipitation studies point to a role for bcl-2 in regulation of p27 localization/degradation. Bcl-2 silencing was also correlated with loss of cyclin D1a protein levels but not cyclin D1b levels. Coimmunoprecipitation studies indicate that bcl-2 may mediate its effects on cyclin D1a via interaction with p38 mitogen-activated protein kinase as well as a previously unreported interaction between bcl-2 and cyclin D1a.

A novel liposomal irinotecan formulation with significant anti-tumour activity: use of the divalent cation ionophore A23187 and copper-containing liposomes to improve drug retention

We determined whether the method used to encapsulate irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 degrees C). Following a single intravenous injection (100mg/kg irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of irinotecan release of 44.4h; a >or=4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50mg/kg irinotecan) mediated an 18-fold increase in median T-C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar. Improved irinotecan retention was associated with increased therapeutic activity.

The Phosphoinositide-Dependent Kinase-1 Inhibitor 2-Amino-N-[4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]phenyl]-acetamide (OSU-03012) Prevents Y-Box Binding Protein-1 from Inducing Epidermal Growth Factor Receptor

The epidermal growth factor receptor (EGFR) is integral to basal-like and human epidermal growth factor receptor-2 (Her-2)-overexpressing breast cancers. Such tumors are associated with poor prognosis, the majority of which express high levels of EGFR. We reported that EGFR expression is induced by the oncogenic transcription factor Y-box binding protein-1 (YB-1) that occurs in a manner dependent on phosphorylation by Akt. Herein, we questioned whether blocking Akt with 2-amino-N-[4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]phenyl]-acetamide (OSU-03012), a phosphoinositide-dependent protein kinase-1 (PDK-1) small-molecule inhibitor, could prevent YB-1 from binding to the EGFR promoter. MDA-MB-468 and SUM 149 are basal-like breast cancer (BLBC) cells that were used for our studies because they express high levels of activated PDK-1, YB-1, and EGFR compared with the immortalized breast epithelial cell line 184htrt. In these cell lines, YB-1 preferentially bound to the -1 kilobase of the EGFR promoter, whereas this did not occur in the 184htrt cells based on chromatin immunoprecipitation. When the cells were exposed to OSU-03012 for 6 h, YB-1/EGFR promoter binding was significantly attenuated. To further confirm this observation, gel-shift assays showed that the drug inhibits YB-1/EGFR promoter binding. The inhibitory effect of OSU-03012 on EGFR was also observed at the mRNA and protein levels. OSU-03012 ultimately inhibited the growth of BLBC in monolayer and soft agar coordinate with the induction of apoptosis using an Array-Scan VTI high-content screening system. Furthermore, OSU-03012 inhibited the expression of EGFR by 48% in tumor xenografts derived from MDA-MB-435/Her-2 cells. This correlated with loss of YB-1 binding to the EGFR promoter. Hence, we find that OSU-03012 inhibits YB-1 resulting in a loss of EGFR expression in vitro and in vivo.

Transition Metal-Mediated Liposomal Encapsulation of Irinotecan (CPT-11) Stabilizes the Drug in the Therapeutically Active Lactone Conformation

PURPOSE

To determine whether entrapped transition metals could mediate the active encapsulation of the anticancer drug irinotecan into preformed liposomes. Further, to establish that metal complexation could stabilize liposomal irinotecan in the therapeutically active lactone conformation.

MATERIALS AND METHODS

Irinotecan was added to preformed 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/chol) liposomes prepared in CuSO4, ZnSO4, MnSO4, or CoSO4 solutions, and drug encapsulation was determined over time. The roles of the transmembrane pH gradient and internal pH were evaluated. TLC and HPLC were used to monitor drug stability and liposome morphology was assessed by cryo-TEM.

RESULTS

Irinotecan was rapidly and efficiently loaded into preformed liposomes prepared in unbuffered (approximately pH 3.5) 300 mM CuSO4 or ZnSO4. For Cu-containing liposomes, results suggested that irinotecan loading occurred when the interior pH and the exterior pH were matched; however, addition of nigericin to collapse any residual transmembrane pH gradient inhibited irinotecan loading. Greater than 90% of the encapsulated drug was in its active lactone form and cryo-TEM analysis indicated dark intravesicular electron-dense spots.

CONCLUSION

Irinotecan is stably entrapped in the active lactone conformation within preformed copper-containing liposomes as a result of metal-drug complexation.

Irinotecan-cisplatin interactions assessed in cell-based screening assays: cytotoxicity, drug accumulation and DNA adduct formation in an NSCLC cell line

PURPOSE

The use of in vitro drug cytotoxicity assays for the assessment of drug-drug interactions that lead to synergy may not take into account the many cellular determinants responsible for combination effects. Administration of the anticancer drug CPT-11, for example, is associated with rapid conversion of drug from its active lactone form to the inactive carboxylate form. Thus it is difficult to model, in vitro, the behavior of this drug when used as a single agent and when used in a combination setting, this factor may contribute to the interactions measured. Therefore, the objective of this study was to examine the influence of CPT-11 lactone ratio on the cellular accumulation of CPT-11 when used as a single agent and under conditions where it is used in combination with cisplatin.

METHODS

A fixed ratio experimental design was used and drug ratios of CPT-11 and cisplatin were judged to be antagonistic, additive, or synergistic to the non-small cell lung cancer cell line, H460, on the basis of the median effect analysis methodology of Chou and Talalay. The influence of extracellular pH on CPT-11 accumulation was evaluated at pH 7.4 and pH 6.6 when the drug was added immediately to the cells or first pre-equilibrated at the indicated pH. These studies were completed in the presence and absence of cisplatin.

RESULTS

When CPT-11 was added as a single agent to cells in pH = 7.4 media, the drug underwent hydrolysis to the carboxylate form; however, there was a rapid accumulation of the CPT-11 lactone form which peaked at 3,800 pmol/mg protein by 30 min and drops to 570 pmol/mg protein by 24 h. In pH = 6.6 media, accumulation of CPT-11 lactone was substantially lower over a 60 min timecourse; however, the cellular uptake measured at 24 h was comparable to that observed when the drug was added into pH 7.4 media. When evaluating CPT-11 lactone accumulation in a combination setting with cisplatin no significant difference in either CPT-11 lactone accumulation or cisplatin accumulation was observed, suggesting that drug interactions that led to synergy were mechanistically based. Results are presented which suggest that when cisplatin and CPT-11 are used in combination, there was a significant prolongation of platinum association with DNA compared to results obtained when cisplatin was used alone.

CONCLUSION

These results suggest that the CPT-11 lactone to carboxylate ratio does not influence the accumulation of the active CPT-11 lactone form in H460 cells and that CPT-11 does not influence cisplatin uptake when used in combination. It is argued, therefore, that the improved cytotoxicity between CPT-11 and cisplatin, as determined using cell-based assay, has the potential to be preserved in vivo assuming the optimal drug-drug ratio and concentration can be effectively delivered to the tumor.

Four human t(11;14)(q13;q32)-containing cell lines having classic and variant features of Mantle Cell Lymphoma

The objectives of this study were foremost to further characterize pre-existing cell lines containing the t(11;14)(q13;q32) translocation. This translocation along with cyclin D1 overexpression is characteristic of Mantle Cell Lymphoma (MCL), an aggressive B cell neoplasm. Considerable variation in the abundance of cyclin D1 expression was observed. mRNA levels were examined by RT-PCR as differences in cyclin D1 mRNA abundance have been shown to synergize with INK4A/Arf deletions to dictate proliferation rate and survival in MCL patient samples. In this study, the cell lines, Z-138 and HBL-2, which exhibited the fastest growth rates and the shortest survival times in Rag2-M mice, had high expression of either one or both cyclin D1 mRNA isoforms and had negligible expression of p16. On the other hand, NCEB-1 and JVM-2 had low expression of both mRNA isoforms, retained p16 expression, and had slower growth rates and exhibited longer survival times in Rag2-M mice. Furthermore, JVM-2, which was found to have the lowest expression of cyclin D1, was the only cell line that expressed cyclin D2. The results of the characterization of Z-138, HBL-2, NCEB-1 and JVM-2 reveal that this group of cell lines represents both classic and variant features of MCL.

Synergistic Cytotoxicity of Pyrazoloacridine with Doxorubicin, Etoposide, and Topotecan in Drug-Resistant Tumor Cells

Pyrazoloacridine (NSC 366140, PD115934, PZA) is a new class of acridine anticancer agents under investigation in Phase II clinical trials in patients with advanced cancers. Although poor responses in patients to the treatment with PZA alone have been observed, this class of agents remains of interest because of its distinct mechanism of action from other topoisomerase poisons. Therefore, the combination of PZA with conventional anticancer agents presents an attractive approach to treat drug-resistant human tumors. In the present study, the cytotoxic effects of PZA combined with doxorubicin, topotecan, and etoposide were determined using paired parental and doxorubicin-resistant human colon carcinoma (SW-620 and SW620/AD-300) and breast cancer cell lines (MCF-7 and MCF-7/TH). Cytotoxicity was measured by soft agar clonogenic assays. Dose effect and combination effects were analyzed by the method of Chou and Talalay. The combination of PZA with doxorubicin, topotecan, and etoposide in fixed ratios demonstrated synergistic cytotoxicity on both SW-620 and SW620/AD-300 cell lines. The combination of PZA with doxorubicin also exhibited synergistic cytotoxicity against both MCF-7 and MCF-7/TH cell lines. The mechanism of synergism appeared independent of topoisomerase I and II inhibition, and interference with protein-DNA complexes. Strategies to define optimal drug combinations are proving to be of significant value when considering potential clinical applications of new and established agents.

Inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase enhances chemotherapeutic effects on H460 human non-small cell lung cancer cells through activation of apoptosis

The effects of Dox (Dox), paclitaxel (Taxol), and serum starvation on the regulation of XIAP (X-linked inhibitor of apoptosis), Bcl-2 phosphorylation, and apoptosis were evaluated in human H460 non-small cell lung cancer cells. Protein kinases that responded to these treatments as prosurvival elements in signal transduction were identified by simultaneously screening phosphorylation of protein kinases in H460 cells cultured in serum-free medium or treated with Dox. We demonstrated that Dox and Taxol induced apoptosis through down-regulation of XIAP and phosphorylation of Bcl-2 in a concentration-dependent manner without changing expression of Bcl-xL in H460 cells. These effects were paralleled by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase protein. We identified that serum starvation and Dox reduced phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK), protein kinase C (PKC) alpha/beta and c-Jun NH(2)-terminal kinase. The MEK-specific inhibitor U0126 or PKC inhibitor staurosporine (STP) also down-regulated XIAP expression and induced apoptosis. Thus, our data suggest that apoptosis and down-regulation of XIAP induced by Dox exposure or serum starvation may be mediated through inactivation of the MEK/ERK and PKCalpha/beta pathways. In support of this we demonstrated that the cytotoxic effects of Dox when combined with U0126 or STP were enhanced, i.e., synergistic cytotoxic activities were demonstrated. The synergistic interaction of U0126 or STP with Dox was sequence- and concentration-dependent.

Assessment of the involvement of CYP3A in the vitro metabolism of a new modulator of MDR in cancer chemotherapy, OC144-193, by human liver microsomes

The novel substituted imidazole compound, OC144-093 exhibits potent biological activity in vitro and in vivo for reversal of P-glycoprotein (PgP) based resistance to cancer chemotherapy. Its mechanism of action relies upon its inhibitory interaction with the mdr1 gene product, a known mediator of multidrug resistance (MDR). Overlapping substrate specificities and tissue distribution of cytochrome P450 3A (CYP3A) and PgP indicate the potential for drug-drug interactions when modulator and anticancer agent are co-administered. We have examined the metabolism of OC144-093 in vitro using human liver microsomes to determine if CYP3A is involved. Our results show that OC144-093 is converted to one major metabolite (M1) in human liver microsomes which was identified by LCMS to be the O-deethylated derivative. Km and Vmax for O-deethylation were determined as 3.96+/-0.67 microM and 32.08+/-9.73 pmol/mg protein/min, respectively (n=3). Correlation studies conducted in a panel of human livers phenotyped for specific P450 enzyme activity showed a significant relationship between M1 formation and the activity of CYP2C9, CYP2B6, CYP2E1 and CYP3A4. Treatment of microsomes with carbon monoxide gas inhibited M1 formation and diethyldithiocarbamate and ketoconazole (>3 microM), non-specific CYP inhibitors, gave IC50 values of 124.4+/-21.6 microM and 25.3+/-3.2 microM respectively for the inhibition of O-deethylation, also implicating the involvement of CYP enzymes. Specific CYP inhibitors of CYP3A4 were essentially non-inhibitory to M1 formation. We can conclude therefore that OC144-093 is not extensively metabolised in human liver microsomes although conversion to its O-deethylated derivative does occur. Our data indicates that this conversion is not mediated by CYP3A4.

Characterization of hybrid CTL epitope delivery systems consisting of the Antennapedia homeodomain peptide vector formulated in liposomes

Peptide carriers, such the homeodomain of Antennapedia molecule (AntpHD), which spontaneously cross cellular membranes, have been exploited to deliver antigenic peptide Cw3 to the major histocompatibility complex (MHC) class-I presentation pathway and to prime cytotoxic T cells (CTL). However, the in vivo use of AntpHD recombinant peptide has been limited because CTLs can only be primed in the presence of sodium dodecyl sulfate (SDS) as adjuvant. In this report, we have exploited liposomes to protect the AntpHD-Cw3 from serum degradation and to facilitate the delivery of the recombinant peptide into the MHC class-I pathway of antigen-presenting cells. We have demonstrated that AntpHD recombinant peptide spontaneously associates with liposomes and this association is stable in vitro. However, exchange studies assessing the transfer of the peptide to model membranes or cells in vitro indicates that approximately 50% of the liposome-associated peptide is readily exchangeable. This is consistent with trypsin-protection assays, which have shown that approximately 40% of the liposome-associated peptide is protected from hydrolysis. Importantly, macrophages and dendritic cells are able to internalize AntpHD recombinant peptide associated with liposomes resulting in efficient delivery of the CTL peptide into the cytosol. These studies have demonstrated that dendritic cells treated with AntpHD-Cw3 in liposomes sensitize CTL clones to lyse syngeneic target cells expressing Cw3 epitope. This strategy, which combines liposomes and a peptide vector, provides a new approach for introducing molecules into the MHC class-I antigen presentation pathway of dendritic cells.

Liposomal encapsulation of topotecan enhances anticancer efficacy in murine and human xenograft models

Topotecan was encapsulated in sphingomyelin/cholesterol liposomes using an ionophore-generated proton gradient. After i.v. injection, liposomal topotecan was eliminated from the plasma much more slowly than free drug, resulting in a 400-fold increase in plasma area under the curve. Further, high-performance liquid chromatography analysis of plasma samples demonstrated that topotecan was protected from hydrolysis within the liposomal carrier with >80% of the drug remaining as the active, lactone species up to 24 h. The improved pharmacokinetics observed with liposomal topotecan correlated with increased efficacy in both murine and human tumor models. In the L1210 ascitic tumor model, optimal doses of liposomal topotecan resulted in a 60-day survival rate of 60-80%, whereas in a L1210 liver metastasis model, 100% long-term survival (>60 days) was achieved. In contrast, long-term survivors were rarely seen after treatment with free topotecan. Further, in a human breast carcinoma model (MDA 435/LCC6), liposomal topotecan provided greatly improved increase in life span relative to the free drug. These results suggest that liposomal encapsulation can significantly enhance the therapeutic activity of topotecan.

Assembly of XcpR in the cytoplasmic membrane is required for extracellular protein secretion in Pseudomonas aeruginosa

A broad range of extracellular proteins secreted by Pseudomonas aeruginosa use the type II or general secretory pathway (GSP) to reach the medium. This pathway requires the expression of at least 12 xcp gene products. XcpR, a putative nucleotide-binding protein, is essential for the secretion process across the outer membrane even though the protein contains no hydrophobic sequence that could target or anchor it to the bacterial envelope. For a better understanding of the relationship between XcpR and the other Xcp proteins which are located in the envelope, we have studied its subcellular localization. In a wild-type P. aeruginosa strain, XcpR was found associated with the cytoplasmic membrane. This association depends on the presence of the XcpY protein, which also appears to be necessary for XcpR stability. Functional complementation of an xcpY mutant required the XcpY protein to be expressed at a low level. Higher expression precluded the complementing activity of XcpY, although membrane association of XcpR was restored. This behavior suggested that an excess of free XcpY might interfere with the secretion by formation of inactive XcpR-XcpY complexes which cannot properly interact with their natural partners in the secretion machinery. These data show that a precise stoichiometric ratio between several components may be crucial for the functioning of the GSP.