Discovery of Highly Selective Inhibitors of Calmodulin-Dependent Kinases That Restore Insulin Sensitivity in the Diet-Induced Obesity in Vivo Mouse Model

Polymorphisms in the region of the calmodulin-dependent kinase isoform D (CaMK1D) gene are associated with increased incidence of diabetes, with the most common polymorphism resulting in increased recognition by transcription factors and increased protein expression. While reducing CaMK1D expression has a potentially beneficial effect on glucose processing in human hepatocytes, there are no known selective inhibitors of CaMK1 kinases that can be used to validate or translate these findings. Here we describe the development of a series of potent, selective, and drug-like CaMK1 inhibitors that are able to provide significant free target cover in mouse models and are therefore useful as in vivo tool compounds. Our results show that a lead compound from this series improves insulin sensitivity and glucose control in the diet-induced obesity mouse model after both acute and chronic administration, providing the first in vivo validation of CaMK1D as a target for diabetes therapeutics.

Sonic Hedgehog Ligand: A Role in Formation of a Mesenchymal Niche in Human Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterised by desmoplasia, thought to support progression and chemotherapeutic resistance. The Hedgehog pathway is known to play an important role in this cancer. While the upregulation of Sonic hedgehog (Shh) in the epithelium of PDAC is known, we investigated its expression in the tumour microenvironment in order to find new targets for new chemotherapeutical approaches. Immunohistochemistry was used for the investigation of Shh and Vimentin in primary human pancreatic tissues. Gene (qRT-PCR) and protein (immunofluorescence) expression of Shh, αSMA (a marker of the mesenchymal phenotype) and periostin (a marker of mesenchymal cells within a mixed population) were investigated in in vitro cell models. Shh expression was significantly upregulated in the stromal and epithelial compartments of poorly-differentiated PDAC samples, with a strong correlation with the amount of stroma present. Characterisation of stromal cells showed that there was expression of Shh ligand in a mixed population comprising αSMA+ myofibroblasts and αSMA- mesenchymal stem cells. Moreover, we demonstrated the interaction between these cell lines by showing a higher rate of mesenchymal cell proliferation and the upregulation of periostin. Therefore, targeting stromal Shh could affect the equilibrium of the tumour microenvironment and its contribution to tumour growth.

Water-soluble substituted chitosan derivatives as technology platform for inhalation delivery of siRNA

Despite research efforts full potential of siRNA-based therapeutics has not yet been fully realized due to a need for suitable, effective delivery formulations. Here, we examine a potential of a new class of water-soluble chitosans as siRNA platform for pulmonary delivery. The system is based on piperazine-substituted chitosans, a material designed to integrate established, safe application of chitosan for mucosal administration with novel properties: the piperazine-substituted chitosans are freely water-soluble at physiological pH, possess low cytotoxicity (no significant reduction in cell viability up to 0.1 mg/ml), and provide efficient incorporation of siRNA into sub-300 nm colloidal complexes (at relatively low polymer/siRNA ratio of 5:1). In vitro, the complexes achieved silencing of a model gene at a level of 40–80%, when tested in a panel of lung epithelial cells. Considering the formulation ‘developability’, there were no significant changes in the complexes’ size and integrity on aerosolisation by microsprayer (PenCentury™) device. Following intratracheal aerolisation, the complexes deposited throughout the lung, although relatively inhomogeneously, as judged from IVIS imaging of the isolated mouse lung (visualizing DY647-siRNA). In vivo data illustrate absence of adverse effects on repeated administration of complexes and significant tumor reduction in atopical lung cancer model in mice. Altogether, the data illustrates potential of substituted chitosan derivatives to be utilized as a safe system for inhalation delivery of siRNA.

Individual patient oesophageal cancer 3D models for tailored treatment

Background

A model to predict chemotherapy response would provide a marked clinical benefit, enabling tailored treatment of oesophageal cancer, where less than half of patients respond to the routinely administered chemotherapy.

Methods

Cancer cells were established from tumour biopsies taken from individual patients about to undergo neoadjuvant chemotherapy. A 3D-tumour growth assay (3D-TGA) was developed, in which cancer cells were grown with or without supporting mesenchymal cells, then subjected to chemo-sensitivity testing using the standard chemotherapy administered in clinic, and a novel emerging HDAC inhibitor, Panobinostat.

RESULTS

Individual patients cancer cells could be expanded and screened within a clinically applicable timescale of 3 weeks. Incorporating mesenchymal support within the 3D-TGA significantly enhanced both the growth and drug resistance profiles of the patients cancer cells. The ex vivo drug response in the presence, but not absence, of mesenchymal cells accurately reflected clinical chemo-sensitivity, as measured by tumour regression grade. Combination with Panobinostat enhanced response and proved efficacious in otherwise chemo-resistant tumours.

Conclusions

This novel method of establishing individual patient oesophageal cancers in the laboratory, from small endoscopic biopsies, enables clinically-relevant chemo-sensitivity testing, and reduces use of animals by providing more refined in vitro models for pre-screening of drugs. The 3D-TGA accurately predicted chemo-sensitivity in patients, and could be developed to guide tailored patient treatment. The incorporation of mesenchymal cells as the stromal cell component of the tumour micro-environment had a significant effect upon enhancing chemotherapy drug resistance in oesophageal cancer, and could prove a useful target for future drug development.

Multicomponent analysis of the tumour microenvironment reveals low CD8 T cell number, low stromal caveolin-1 and high tenascin-C and their combination as significant prognostic markers in non-small cell lung cancer

The complex interplay of the tumour microenvironment (TME) and its role in disease progression and response to therapy is poorly understood. The majority of studies to date focus on individual components or molecules within the TME and so lack the power correlative analysis. Here we have performed a multi-parameter analysis of the TME in 62 resectable non-small cell lung cancer (NSCLC) specimens detailing number and location of immune infiltrate, assessing markers of cancer-associated fibroblasts, caveolin-1 and tenascin-C, and correlating with clinicopathological details, as well as markers of disease progression such as epithelial-to-mesenchymal transition (EMT). The influence of individual parameters on overall survival was determined in univariate and multivariate analysis and the combination of risk factors and interplay between components analysed. Low numbers of CD8 T cells, low stromal levels of caveolin-1 or high levels of tenascin-C were significant prognostic markers of decreased overall survival in both univariate and multivariate analysis. Patients with two or more risk factors had dramatically reduced overall survival and those with all three a median survival of just 7.5 months. In addition, low levels of tumour E-cadherin correlated with reduced immune infiltrate into the tumour nests, possibly linking EMT to the avoidance of CD8 T cell control. The multicomponent approach has allowed identification of the dominant influences on overall survival, and exploration of the interplay between different components of the TME in NSCLC.

Spheroid arrays for high-throughput single-cell analysis of spatial patterns and biomarker expression in 3D

We describe and share a device, methodology and image analysis algorithms, which allow up to 66 spheroids to be arranged into a gel-based array directly from a culture plate for downstream processing and analysis. Compared to processing individual samples, the technique uses 11-fold less reagents, saves time and enables automated imaging. To illustrate the power of the technology, we showcase applications of the methodology for investigating 3D spheroid morphology and marker expression and for in vitro safety and efficacy screens. First, spheroid arrays of 11 cell-lines were rapidly assessed for differences in spheroid morphology. Second, highly-positive (SOX-2), moderately-positive (Ki-67) and weakly-positive (βIII-tubulin) protein targets were detected and quantified. Third, the arrays enabled screening of ten media compositions for inducing differentiation in human neurospheres. Last, the application of spheroid microarrays for spheroid-based drug screens was demonstrated by quantifying the dose-dependent drop in proliferation and increase in differentiation in etoposide-treated neurospheres.

High-Throughput Spheroid Screens Using Volume, Resazurin Reduction, and Acid Phosphatase Activity

Mainstream adoption of physiologically relevant three-dimensional models has been slow in the last 50 years due to long, manual protocols with poor reproducibility, high price, and closed commercial platforms. This chapter describes high-throughput, low-cost, open methods for spheroid viability assessment which use readily available reagents and open-source software to analyze spheroid volume, metabolism, and enzymatic activity. We provide two ImageJ macros for automated spheroid size determination-for both single images and images in stacks. We also share an Excel template spreadsheet allowing users to rapidly process spheroid size data, analyze plate uniformity (such as edge effects and systematic seeding errors), detect outliers, and calculate dose-response. The methods would be useful to researchers in preclinical and translational research planning to move away from simplistic monolayer studies and explore 3D spheroid screens for drug safety and efficacy without substantial investment in money or time.

Data on the number and frequency of scientific literature citations for established medulloblastoma cell lines

This article collates information about the number of scientific articles mentioning each of the established medulloblastoma cell lines, derived through a systematic search of Web of Science, Scopus and Google Scholar in 2016. The data for each cell line have been presented as raw number of citations, percentage share of the total citations for each search engine and as an average percentage between the three search engines. In order to correct for the time since each cell line has been in use, the raw citation data have also been divided by the number of years since the derivation of each cell line. This is a supporting article for a review of in vitro models of medulloblastoma published in “in vitro models of medulloblastoma: choosing the right tool for the job” (D.P. Ivanov, D.A. Walker, B. Coyle, A.M. Grabowska, 2016) [1].

Separating chemotherapy-related developmental neurotoxicity from cytotoxicity in monolayer and neurosphere cultures of human fetal brain cells

Chemotherapy-induced neurotoxicity can reduce the quality of life of patients by affecting their intelligence, senses and mobility. Ten percent of safety-related late-stage clinical failures are due to neurological side effects. Animal models are poor in predicting human neurotoxicity due to interspecies differences and most in vitro assays cannot distinguish neurotoxicity from general cytotoxicity for chemotherapeutics. We developed in vitro assays capable of quantifying the paediatric neurotoxic potential for cytotoxic drugs. Mixed cultures of human fetal brain cells were differentiated in monolayers and as 3D-neurospheres in the presence of non-neurotoxic chemotherapeutics (etoposide, teniposide) or neurotoxicants (methylmercury). The cytotoxic potency towards dividing progenitors versus differentiated neurons and astrocytes was compared using: (1) immunohistochemistry staining and cell counts in monolayers; (2) through quantitative Western blots in neurospheres; and (3) neurosphere migration assays. Etoposide and teniposide, were 5-10 times less toxic to differentiated neurons compared to the mix of all cells in monolayer cultures. In contrast, the neurotoxicant methylmercury did not exhibit selectivity and killed all cells with the same potency. In 3D neurospheres, etoposide and teniposide were 24 to 10 times less active against neurons compared to all cells. These assays can be used prioritise drugs for local drug delivery to brain tumours.

In vitro models of medulloblastoma: Choosing the right tool for the job

The recently-defined four molecular subgroups of medulloblastoma have required updating of our understanding of in vitro models to include molecular classification and risk stratification features from clinical practice. This review seeks to build a more comprehensive picture of the in vitro systems available for modelling medulloblastoma. The subtype classification and molecular characterisation for over 40 medulloblastoma cell-lines has been compiled, making it possible to identify the strengths and weaknesses in current model systems. Less than half (18/44) of established medulloblastoma cell-lines have been subgrouped. The majority of the subgrouped cell-lines (11/18) are Group 3 with MYC-amplification. SHH cell-lines are the next most common (4/18), half of which exhibit TP53 mutation. WNT and Group 4 subgroups, accounting for 50% of patients, remain underrepresented with 1 and 2 cell-lines respectively. In vitro modelling relies not only on incorporating appropriate tumour cells, but also on using systems with the relevant tissue architecture and phenotype as well as normal tissues. Novel ways of improving the clinical relevance of in vitro models are reviewed, focusing on 3D cell culture, extracellular matrix, co-cultures with normal cells and organotypic slices. This paper champions the establishment of a collaborative online-database and linked cell-bank to catalyse preclinical medulloblastoma research.

3-Dimensional Patient-Derived Lung Cancer Assays Reveal Resistance to Standards-of-Care Promoted by Stromal Cells but Sensitivity to Histone Deacetylase Inhibitors

There is a growing recognition that current preclinical models do not reflect the tumor microenvironment in cellular, biological, and biophysical content and this may have a profound effect on drug efficacy testing, especially in the era of molecular-targeted agents. Here, we describe a method to directly embed low-passage patient tumor-derived tissue into basement membrane extract, ensuring a low proportion of cell death to anoikis and growth complementation by coculture with patient-derived cancer-associated fibroblasts (CAF). A range of solid tumors proved amenable to growth and pharmacologic testing in this 3D assay. A study of 30 early-stage non-small cell lung cancer (NSCLC) specimens revealed high levels of de novo resistance to a large range of standard-of-care agents, while histone deacetylase (HDAC) inhibitors and their combination with antineoplastic drugs displayed high levels of efficacy. Increased resistance was seen in the presence of patient-derived CAFs for many agents, highlighting the utility of the assay for tumor microenvironment-educated drug testing. Standard-of-care agents showed similar responses in the 3D ex vivo and patient-matched in vivo models validating the 3D-Tumor Growth Assay (3D-TGA) as a high-throughput screen for close-to-patient tumors using significantly reduced animal numbers. Mol Cancer Ther; 15(4); 753-63. ©2016 AACR.

Systemic in vivo delivery of siRNA to tumours using combination of polyethyleneimine and transferrin–polyethyleneimine conjugates

Materials for delivery of oligonucleotides need to be simple to produce and formulate yet effectivein vivoto be considered for clinical applications.

Camptothecin prodrug block copolymer micelles with high drug loading and target specificity

The effects of a novel functional reducible camptothecin (CPT) block copolymer conjugate, targeting luteinizing hormone releasing hormone receptor (LHRHR) were evaluated against differing LHRHR expressing tumour cell lines and immune populations.

Abstract 3397: Validation of targets involved in supporting the stem cell niche in glioblastoma multiforme

Introduction: Glioblastoma multiforme (GBM) is a cytologically malignant tumour of the central nervous system, associated with poor prognosis and fatal outcome (5 year survival, <6%). GBM cancer stem cells (CSCs), which can be identified using the immunocytochemical marker CD133, are associated with poor prognosis. The gastrin receptor, CCK2R, is also expressed in glioblastoma cell-lines and promotes cancer progression. In this study we investigated the functional role of these two molecules in GBM to elucidate any potential therapeutic benefits.

Materials and methods: A panel of glioblastoma cells was grown either as monolayers, or, to provide a 3D in vitro tumour model, as neurospheres, which enrich for the cancer stem cell phenotype. Quantitative RT-PCR was used to quantify CD133 and CCK-2R gene expression over time in these cultures, and flow cytometry (FACS) to investigate expression at the protein level. CD133 and CCK-2R promoter reporters were constructed in pGL4 and promoter activity quantified using luciferase assays. Gene knockdown or specific inhibitors were used to investigate the role of these genes in glioblastoma cell tumorigenicity in vitro (using MTT, wound-healing, and neurosphere formation) and in an in vivo xenograft model.

Results: CD133 and CCK-2R gene and protein expression were higher in the more tumorigenic glioblastoma cell-line, U251, compared with the less tumorigenic line, U373. For both markers, higher gene expression correlated with higher promoter activity and FACS demonstrated the presence of a small population of positively-stained cells. Expression of both genes was upregulated during neurosphere formation, which was accelerated in hypoxia. Knockdown of CD133 and CCK-2R inhibition in cell line U251 reduced neurosphere-forming potential (p<0.05). Knockdown of CD133 also significantly reduced migration (p<0.001) and increased susceptibility to the chemotherapeutic agent etoposide (p<0.05).

Conclusions: CD133 and CCK-2R expression correlate with tumorigenic potential of GBM cells and are upregulated during neurosphere formation, which enriches for cancer stem cells. CD133 knockdown and CCK-2R inhibition reduced neurosphere formation. In addition, CD133 knockdown reduced GBM invasive capacity, and increased resistance to chemotherapeutic drugs. Therefore, use of CD133 and CCK-2R-targeted therapies, in combination with established standard of care may improve GBM patient outcome.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3397. doi:10.1158/1538-7445.AM2011-3397

Abstract 4280: Differential influence of naïve & tumour-conditioned mesenchymal stem cells on the growth of human epithelial cells in in vitro monolayer co-cultures & 3D hollow fibre systems

Background: Tumour cell behaviour is altered by the non-neoplastic portion of the stroma composed of fibroblasts, mesenchymal stem cells (MSC), pericytes, endothelial and inflammatory cells actively intertwined with the tumour parenchyma. Epithelial to mesenchymal transition (EMT) is a key phenotypic change involved in carcinoma progression, resulting in profound phenotypic changes to malignant cells e.g. loss of cell-cell adhesion, loss of cell polarity and acquisition of migratory and invasive properties. Human MSC can give rise to endothelial-like or pericyte-like cells, and are also capable of differentiating into carcinoma associated fibroblasts (CAFs) when exposed to soluble factors produced by tumour cells, which support the malignant epithelial cells resulting in overall enhanced tumour growth and survival in vitro and in vivo. EMT is common within primary tumours and may be further promoted by associated CAFs.

Objectives: The objectives of our current research are to recapitulate the human tumour micro-environment within the hollow fibre model (HF) and apply a real-time bio-imaging component to enable the non-invasive analysis of biological parameters associated with tumour progression.

Results: Using tumour cells stably expressing a bioluminescent reporter gene, we have investigated tumour growth in the presence and absence of naive (MSC) and tumour-conditioned (tcMSC) human mesenchymal stem cells both within in vitro cell cultures and the HF model. Real-time imaging of bioluminescent tumour cells demonstrated that these cells can actively proliferate within the HFs; and the presence of MSC or tcMSC significantly enhances tumour growth compared with tumour cells alone. Immuno-staining analysis revealed that a stromal network is established around the periphery of the fibre and that with prolonged culture, MSCs acquire a ‘myofibroblastic’ phenotype (elevated expression of αSMA and FSP1) resulting in growth promoting effects similar to CAFs. Here, we also demonstrate downregulation of E-Cadherin – a hallmark of EMT- and upregulation of genes of the EMT trascriptome, in both direct and indirect co-cultures.Conclusions: Here we provide experimental evidence that naive MSC or tcMSC may provide a tumour cell-protective setting and alter tumour behaviour both in vitro and in the hollow fibre model. Real-time PCR data obtained from direct and indirect co-cultures also provide an insight in the co-evolution of the carcinoma and surrounding stroma with the overall microenvironment. Finally, this recapitulation of the human tumour micro-environment provides a relevant model by which to identify and characterise novel anti-cancer compounds.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4280. doi:10.1158/1538-7445.AM2011-4280

Helicobacter pylori potentiates epithelial:mesenchymal transition in gastric cancer: links to soluble HB-EGF, gastrin and matrix metalloproteinase-7

BACKGROUND AND AIMS

Helicobacter pylori (H pylori) infection is a major risk factor in the development of distal gastric adenocarcinoma. Development of the invasive phenotype is associated with the phenomenon of epithelial:mesenchymal transition (EMT). Soluble heparin-binding epidermal growth factor (HB-EGF) has been implicated in this process. A study was undertaken to investigate the possibility that matrix metalloproteinase (MMP)-7 is upregulated in H pylori infection as a result of hypergastrinaemia, which may enhance shedding of HB-EGF and contribute towards EMT in gastric adenocarcinoma cell lines.

METHODS

Three gastric epithelial cell lines (AGS, MGLVA1 and ST16) were co-cultured with the pathogenic H pylori strain 60190 and non-pathogenic strain Tx30a in an in vitro infection model. Gene expression was quantified by real-time PCR, HB-EGF shedding by ELISA and protein expression by immunofluorescence or immunohistochemistry. The INS-GAS mouse, a transgenic mouse model of gastric carcinogenesis which overexpresses amidated gastrin, was used to investigate the in vivo relationship between HB-EGF, MMP-7, gastrin and EMT.

RESULTS

The pathogenic strain of H pylori significantly upregulated EMT-associated genes Snail, Slug and vimentin in all three gastric cell lines to a greater degree than the non-pathogenic strain. Pathogenic H pylori also upregulated HB-EGF shedding, a factor implicated in EMT, which was partially dependent on both gastrin and MMP-7 expression. Gastrin and MMP-7 siRNAs and MMP-7 neutralising antibody significantly reduced upregulation of HB-EGF shedding in H pylori infected gastric cell lines and reduced EMT gene expression. The effect of H pylori on EMT was also reversed by gastrin siRNA. Neutralisation of gastrin in the INS-GAS mouse model reduced expression of MMP-7, HB-EGF and key EMT proteins.

CONCLUSION

The upregulation of MMP-7 by pathogenic H pylori is partially dependent on gastrin and may have a role in the development of gastric cancer, potentially through EMT, by indirectly increasing levels of soluble HB-EGF.

Abstract 3954: A role for the cholecystokinin 2 receptor (CCK-2R) in promoting cancer progression

Background and aims: The gastrointestinal (GI) hormone, gastrin, promotes cancer progression and its down-regulation has been linked to reduced cancer stem cell numbers. Gastrin acts through the cholecystokinin 2 receptor (CCK-2R) and its biological effects are blocked by CCK-2R inhibitors. We investigated a potential role for CCK-2R in promoting survival of cancer stem cells using RNAi combined with a sensitive method to detect CCK-2R mRNA.

Materials and methods: A panel of cancer cell-lines was used, including GI, glioblastoma and small cell lung cancer (SCLC), with CCK-2R-transfected cells as a positive control. Linear-after-the-Exponential (LATE)-PCR was used to quantify CCK-2R gene expression and its sensitivity compared with a Taqman-based assay. Flow cytometry was used to investigate receptor protein expression. The activity of CCK-2R promoter reporters constructed in pGL4, using between 250 and 2000bp of DNA upstream of the CCK-2R start codon, was quantified using luciferase assays.

Results: LATE-PCR for CCK-2R gene expression is 1000-fold more sensitive than the Taqman-based assay. Cell-lines from the panel, including HCT116 (colorectal) and H209 (SCLC), in which CCK-2R mRNA was not detectable by the Taqman assay, were positive using the LATE-PCR. CCK-2R siRNAs resulted in up to 86% knockdown of the receptor in CCK-2R-transfected AGS cells, confirming the specificity of the LATE-PCR. FACS analysis for the CCK-2R protein suggests the presence of a small population of cells within HCT116 (colorectal) and AGS (gastric) cell-lines that express CCK-2R very highly. CCK-2R expression was enriched when cells were grown as colospheres and RNAi demonstrated a role for the CCK2R in promoting cell survival. The CCK-2R promoter constructs were active in cancer cell-lines, indicating that the 250bp proximal to the CCK-2R start codon are most crucial for transcription. However, transcriptional activity did not always correlate with gene expression.

Conclusions: LATE-PCR provides a highly sensitive method for detection of genes such as CCK-2R which have important biological functions but low expression. An element just upstream of the CCK-2R transcriptional start site appears to be controlling transcription in cell-lines showing low levels of endogenous expression of the CCK-2R genes, but lack of correlation between the RNA levels and transcriptional activity suggests possible post-transcriptional regulation of this gene. CCK-2R protein expression is elevated in a subset of cells, and may play a role in promoting survival of cancer stem cells.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

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 3954.

Abstract 752: In vivo pharmaceutical targets screening using lentiviral inducible-knockdown shRNA system

Background and Aims: Small interfering RNAs (shRNAs) are able to suppress gene expression through the endogenous cellular process of RNA interference pathway. Given the ability to knock-down essentially any gene, shRNAs have been used in many studies to screen for therapeutic targets in various pathological conditions. However, most of these studies have been carried out in vitro and the results cannot always be translated into an in vivo environment. In this project, we aimed to develop an efficient in vivo cancer target validation method using a lentiviral inducible-knockdown shRNA. To verify our approach, we used an essential cell-cycle protein polo-like kinase 1 (PLK1) as a proof of concept target.

Methods: TRIPZ inducible shRNAmir construct (Open Biosystems) carrying shRNA against PLK1 was transfected into the colon carcinoma cell line SW620 using lentiviral transduction. PLK1 gene knock-down following induction with doxycycline was quantified by real-time PCR. Inducible shRNAmir expression (detected by turboRFP) was monitored by fluorescence microscopy and quantified using Flow-cytometry or a fluorescence microplate reader.

Nude mouse xenografts were established by subcutaneous injection of 5×106 PLK1 shRNA transfected SW620 cells into the left flank of female nude mice. Doxycycline treatment (80mg/kilogram daily via oral gavage) was initiated when the mean tumour volume reached 500mm3. Mice were sacrificed 3 weeks following treatment and tumours were collected. PLK1 gene expression was assessed by RT-PCR and protein levels investigated using immunohistochemistry. Assessment of angiogenesis (micro-vessel density) was carried out using CD34 staining.

Results:

Following doxycycline induction in vitro, PLK1 inducible-knockdown SW620 cells showed dose and time-dependent PLK1 down-regulation, which was consistent with shRNAmir expression as marked by turboRFP. Flow-cytometry analysis showed about 95% of cells expressed the shRNAmir, 72 hours after induction.

In the in vivo model, the doxycycline-treated group showed significantly lower PLK1 gene expression compared with untreated control (60% reduction, p<0.003). The doxycycline-treated group also showed significantly lower PLK1 protein expression compared with the untreated control (p<0.001).

There was a decline in tumour growth rate in the treated group compared with the control group, which confirmed that knock-down of PLK1 slowed down tumour growth.

We also observed that, within the tumours from the doxycycline-treated group, there appeared to be reduced PLK1 expression in areas adjacent to the blood vessels compared with other areas of the tumour.

Conclusion: The results support the anti-tumour effects of PLK1 down-regulation and confirm an efficient methodology for cancer target screening using a lentiviral inducible-knockdown shRNA system.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

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 752.

Abstract A21: Cancer stem cell in multi-drug-resistant prostate cancer and green tea polyphenols restore drug sensitivity by reversal of epithelial mesenchymal transition

Background: Prostate cancer (PC) is the most common cause of cancer death in men. In advanced PC, many patients suffer chemo-resistance therefore; establishment of a drug-resistant cell model to study the mechanism of action of drug resistance and increase in drug sensitivity is urgently needed. Recently, cancer stem cells (CSCs), and epithelial mesenchymal transition (EMT) have been suggested to play important roles in drug resistance in various cancer types.

Green tea polyphenols, particularly the major component epigallocatechin-3-gallate (EGCG), have been shown to have chemopreventive properties in the malignant setting and recent studies have suggested that green tea catechins may enhance the chemo-sensitivity of drug-resistant cancer cells, such as breast cancer, although the mechanism of action is still unclear.

Aims: (1) To establish a multi-drug-resistant prostate cancer cell line enriched for CSCs and (2) To investigate whether EGCG can restore drug sensitivity by limiting CSC expansion and/or by reversal of EMT.

Experimental procedures: Chemo-resistant (CR) PC3M cells were developed by growth in increasing concentrations of a chemotherapeutic agent. Drug resistance was confirmed using increasing concentrations of doxorubicin (Dox), Taxotere (Tax), 5-fluorouracil (5FU) and cisplatin in fluorometric cell viability assays on resistant and wild-type (WT) cells. Immunofluorescent (IF) staining and flow cytometry were used to identify CSCs. Gene expression was assessed using quantitative real time-PCR. Cell morphology was observed using Nikon invert microscopy.

Results: A chemo-resistant variant of WT-PC3M was derived by long-term culture in increasing concentrations of the chemotherapeutic, 5FU. As a result, the IC50 for WT PC3M to 5FU was 30μM as compared to >500μM for CR PC3M. In addition, the CR cells were also shown to be resistant to other chemotherapeutics including Dox and Tax, but not cisplatin.

Enrichment for cells with CSC properties was determined in WT and CR cells. In comparison to WT PC3M, gene expression of both CD133 and ATP-binding cassette subfamily G2 (ABCG2), which have been reported as CSC markers in various cancer including prostate cancer, were significantly up-regulated by 10 and 2-folds, respectively in drug resistant cells (p<0.01). Protein expression of both CSC markers was confirmed to be elevated in CR PC3M by IF staining. Data from flow cytometry showed that there were 10–15% double-positive CD133/ABCG2 cells within CR cells whereas the percentage is <2% in WT PC3M cells. In addition, CD133 expression was confirmed to be down-regulated by EGCG.

When EGCG was combined with 5FU, the IC50 of 5FU in CR PC3M decreased from 500μM to 100μM in CR PC3M, but it did not show a significant effect in WT PC3M, suggesting that EGCG had restored drug sensitivity in CR cells.

It was noted that chemo-resistant PC3M had a more mesenchymal appearance when compared to WT PC3M. The expression of key EMT transcriptional regulator genes such as twist, snail, slug and zeb-1, were up-regulated whereas the epithelial marker gene E-cadherin was down-regulated in CR PC3M. After 48hours treatment with EGCG, all four EMT regulatory genes were significantly down-regulated by up to 3-folds whereas expression of E-cadherin was elevated.

Conclusion: Green tea polyphenols restore drug sensitivity in chemo-resistant prostate cancer by reversal of EMT.

Citation Information: Clin Cancer Res 2010;16(7 Suppl):A21