Combination treatment of cancer cells with pan-Akt and pan-mTOR inhibitors: effects on cell cycle distribution, p-Akt expression level and radiolabelled-choline incorporation.

Signal transduction pathways, which regulate cell growth and survival, are up-regulated in many cancers and there is considerable interest in their pharmaceutical modulation for cancer treatment. However inhibitors of single pathway components induce feedback mechanisms that overcome the growth moderating effect of the inhibitor. Combination treatments have been proposed to provide a more complete pathway inhibition. Here the effect of dual treatment of cancer cells with a pan-Akt and a pan-mTOR inhibitor was explored. Breast (SKBr3 and MDA-MB-468) and colorectal (HCT8) cancer cells were treated with the pan-Akt inhibitor MK2206 and pan-mTOR inhibitor AZD8055. Cytotoxic effect of the two drugs were determined using the MTT assay and the Combination Index and isobolomic analysis used to determine the nature of the interaction of the two drugs. Flow cytometry and western blot were employed to demonstrate drug effects on cell cycle distribution and phosph-Aktser473 expression. Radiolabelled ([methyl-3H]) Choline uptake was measured in control and drug-treated cells to determine the modulatory effects of the drugs on choline incorporation. The two drugs acted synergistically to inhibit the growth rate of each cancer cell line. Flow cytometry demonstrated G0/G1 blockade with MK2206 and AZD8055 which was greater when cells were treated with both drugs. The incorporation of [methyl-3H] choline was found be decreased to a greater extent in cells treated with both drugs compared with cells treated with either drug alone. Conclusions Pan-mTOR and pan-Akt inhibition may be highly effective in cancer treatment and measuring changes in choline uptake could be useful in detecting efficacious drug combinations.

Early changes in [18F]FDG incorporation by breast cancer cells treated with trastuzumab in normoxic conditions: role of the Akt-pathway, glucose transport and HIF-1α.

HER-2 overexpression does not guarantee response to HER2-targeting drugs such as trastuzumab, which is cardiotoxic and expensive, so early detection of response status is crucial. Factors influencing [(18)F]FDG incorporation in the timeframe of cell signalling down-regulation subsequent to trastuzumab treatment are investigated to provide a better understanding of the relationship between growth response and modulation of [(18)F]FDG incorporation. HER-2-overexpressing breast tumour cell lines, MDA-MB-453, SKBr3 and BT474 and MDA-MB-468 (HER2 non-over-expressor) were treated with trastuzumab (4 h) and probed for AKT, pAKT, ERK1/2, pERK1/2 and HIF-1α to determine early signalling pathway inhibitory effects of trastuzumab. Cells incubated with trastuzumab and/or PI3K inhibitor LY294002 and ERK1/2 inhibitor U0126 and glucose transport and [(18)F]FDG incorporation measured. Cell lines expressed AKT, pAKT, ERK1/2 and pERK1/2 but not HIF-1α. Trastuzumab treatment decreased pAkt but not pERK1/2 levels. Trastuzumab did not further inhibit AKT when maximally inhibited with LY294002. Treatment with LY294002 and trastuzumab for 4 h decreased [(18)F]FDG incorporation in BT474 and MDA-MB-453 but not SKBr3 cells. LY294002 inhibited glucose transport by each cell line, but the glucose transport rate was tenfold higher by SKBr3 cells than BT474 and MDA-MB-453 cells. AKT-induced uptake of [(18)F]FDG was found to be HIF-1α independent in breast cancer cell lines. AKT inhibition level and tumour cell glucose transport rate can influence whether or not PI3K inhibitors affect [(18)F]FDG incorporation which may account for the variation in preclinical and clinical findings associated with [(18)F]FDG-PET in response to trastuzumab and other HER-2 targeting drugs.

Gene Abnormalities and Modulated Gene Expression Associated with Radionuclide Treatment: Towards Predictive Biomarkers of Response.

Molecular radiotherapy (MRT), also known as radioimmunotherapy or targeted radiotherapy, is the delivery of radionuclides to tumours by targeting receptors overexpressed on the cancer cell. Currently it is used in the treatment of a few cancer types including lymphoma, neuroendocrine, and prostate cancer. Recently reported outcomes demonstrating improvements in patient survival have led to an upsurge in interest in MRT particularly for the treatment of prostate cancer. Unfortunately, between 30% and 40% of patients do not respond. Further normal tissue exposure, especially kidney and salivary gland due to receptor expression, result in toxicity, including dry mouth. Predictive biomarkers to select patients who will benefit from MRT are crucial. Whilst pre-treatment imaging with imaging versions of the therapeutic agents is useful in demonstrating tumour binding and potentially organ toxicity, they do not necessarily predict patient benefit, which is dependent on tumour radiosensitivity. Transcript-based biomarkers have proven useful in tailoring external beam radiotherapy and adjuvant treatment. However, few studies have attempted to derive signatures for MRT response prediction. Here, transcriptomic studies that have identified genes associated with clinical radionuclide exposure have been reviewed. These studies will provide potential features for seeding multi-component biomarkers of MRT response.

CRISPR-Cas9 potential for identifying novel therapeutic targets in muscle-invasive bladder cancer.

Gene editing technologies help identify the genetic perturbations driving tumour initiation, growth, metastasis and resistance to therapeutics. This wealth of information highlights tumour complexity and is driving cancer research towards precision medicine approaches based on an individual's tumour genetics. Bladder cancer is the 11th most common cancer in the UK, with high rates of relapse and low survival rates in patients with muscle-invasive bladder cancer (MIBC). MIBC is highly heterogeneous and encompasses multiple molecular subtypes, each with different responses to therapeutics. This evidence highlights the need to identify innovative therapeutic targets to address the challenges posed by this heterogeneity. CRISPR-Cas9 technologies have been used to advance our understanding of MIBC and determine novel drug targets through the identification of drug resistance mechanisms, targetable cell-cycle regulators, and novel tumour suppressor and oncogenes. However, the use of these technologies in the clinic remains a substantial challenge and will require careful consideration of dosage, safety and ethics. CRISPR-Cas9 offers considerable potential for revolutionizing bladder cancer therapies, but substantial research is required for validation before these technologies can be used in the clinical setting.

Implementation of Oxygen Enhanced Magnetic Resonance Imaging (OE-MRI) and a Pilot Genomic Study of Hypoxia in Bladder Cancer Xenografts.

BACKGROUND/AIM: Patients with hypoxic bladder cancer benefit from hypoxia modification added to radiotherapy, but no biomarkers exist to identify patients with hypoxic tumours. We, herein, aimed to implement oxygen-enhanced MRI (OE-MRI) in xenografts derived from muscle-invasive bladder cancer (MIBC) for future hypoxia biomarker discovery work; and generate gene expression data for future biomarker discovery. MATERIALS AND METHODS: The flanks of female CD-1 nude mice inoculated with HT1376 MIBC cells. Mice with small (300 mm3) or large (700 mm3) tumours were imaged, breathing air then 100% O2, 1 h post injection with pimonidazole in an Agilant 7T 16cm bore magnet interfaced to a Bruker Avance III console with a T2-TurboRARE sequence using a dynamic MPRAGE acquisition. Dynamic Spoiled Gradient Recalled Echo images were acquired for 5 min, with 0.1mmol/kg Gd-DOTA (Dotarem, Guerbet, UK) injected after 60 s (1 ml/min). Voxel size and field of view of dynamic contrast enhanced (DCE)-MRI and OE-MRI scans were matched. The voxels considered as perfused with significant post-contrast enhancement (p<0.05) in DCE-MRI scans and tissue were further split into pOxyE (normoxic) and pOxyR (hypoxic) regions. Tumours harvested in liquid N2, sectioned, RNA was extracted and transcriptomes analysed using Clariom S microarrays. RESULTS: Imaged hypoxic regions were greater in the larger versus smaller tumour. Expression of known hypoxia-inducible genes and a 24 gene bladder cancer hypoxia score were higher in pimonidazole-high versus -low regions: CA9 (p=0.012) and SLC2A1 (p=0.012) demonstrating expected transcriptomic behaviour. CONCLUSION: OE-MRI was successfully implemented in MIBC-derived xenografts. Transcriptomic data derived from hypoxic and non-hypoxic xenograft regions will be useful for future studies.

A hypoxia biomarker does not predict benefit from giving chemotherapy with radiotherapy in the BC2001 randomised controlled trial.

BACKGROUND: BC2001 showed combining chemotherapy (5-FU + mitomycin-C) with radiotherapy improves loco-regional disease-free survival in patients with muscle-invasive bladder cancer (MIBC). We previously showed a 24-gene hypoxia-associated signature predicted benefit from hypoxia-modifying radiosensitisation in BCON and hypothesised that only patients with low hypoxia scores (HSs) would benefit from chemotherapy in BC2001. BC2001 allowed conventional (64Gy/32 fractions) or hypofractionated (55Gy/20 fractions) radiotherapy. An exploratory analysis tested an additional hypothesis that hypofractionation reduces reoxygenation and would be detrimental for patients with hypoxic tumours. METHODS: RNA was extracted from pre-treatment biopsies (298 BC2001 patients), transcriptomic data generated (Affymetrix Clariom-S arrays), HSs calculated (median expression of 24-signature genes) and patients stratified as hypoxia-high or -low (cut-off: cohort median). PRIMARY ENDPOINT: invasive loco-regional control (ILRC); secondary overall survival. FINDINGS: Hypoxia affected overall survival (HR = 1.30; 95% CI 0.99-1.70; p = 0.062): more uncertainty for ILRC (HR = 1.29; 95% CI 0.82-2.03; p = 0.264). Benefit from chemotherapy was similar for patients with high or low HSs, with no interaction between HS and treatment arm. High HS associated with poor ILRC following hypofractionated (n = 90, HR 1.69; 95% CI 0.99-2.89 p = 0.057) but not conventional (n = 207, HR 0.70; 95% CI 0.28-1.80, p = 0.461) radiotherapy. The finding was confirmed in an independent cohort (BCON) where hypoxia associated with a poor prognosis for patients receiving hypofractionated (n = 51; HR 14.2; 95% CI 1.7-119; p = 0.015) but not conventional (n = 24, HR 1.04; 95% CI 0.07-15.5, p = 0.978) radiotherapy. INTERPRETATION: Tumour hypoxia status does not affect benefit from BC2001 chemotherapy. Hypoxia appears to affect fractionation sensitivity. Use of HSs to personalise treatment needs testing in a biomarker-stratified trial. FUNDING: Cancer Research UK, NIHR, MRC.

Comparison of multiple gene expression platforms for measuring a bladder cancer hypoxia signature.

Tumour hypoxia status provides prognostic information and predicts response to hypoxia­modifying treatments. A previous study by our group derived a 24­gene signature to assess hypoxia in bladder cancer. The objectives of the present study were to compare platforms for generating signature scores, identify cut­off values for prospective studies, assess intra­tumour heterogeneity and confirm hypoxia relevance. Briefly, RNA was extracted from prospectively collected diagnostic biopsies of muscle invasive bladder cancer (51 patients), and gene expression was measured using customised Taqman Low Density Array (TLDA) cards, NanoString and Clariom S arrays. Cross­platform transferability of the gene signature was assessed using regression and concordance analysis. The cut­off values were the cohort median expression values. Intra­ and inter­tumour variability were determined in a retrospective patient cohort (n=51) with multiple blocks (2­18) from the same tumour. To demonstrate relevance, bladder cancer cell lines were exposed to hypoxia (0.1% oxygen, 24 h), and extracted RNA was run on custom TLDA cards. Hypoxia scores (HS) values showed good agreement between platforms: Clariom S vs. TLDA (r=0.72, P<0.0001; concordance 73%); Clariom S vs. NanoString (r=0.84, P<0.0001; 78%); TLDA vs. NanoString (r=0.80, P<0.0001; 78%). Cut­off values were 0.047 (TLDA), 7.328 (NanoString) and 6.667 (Clariom S). Intra­tumour heterogeneity in gene expression and HS (coefficient of variation 3.9%) was less than inter­tumour (7.9%) variability. HS values were higher in bladder cancer cells exposed to hypoxia compared with normoxia (P<0.02). In conclusion, the present study revealed that application of the 24­gene bladder cancer hypoxia signature was platform agnostic, cut­off values determined prospectively can be used in a clinical trial, intra­tumour heterogeneity was low and the signature was sensitive to changes in oxygen levels in vitro.

Selection of endogenous control genes for normalising gene expression data derived from formalin-fixed paraffin-embedded tumour tissue.

Quantitative real time polymerase chain reaction (qPCR) data are normalised using endogenous control genes. We aimed to: (1) demonstrate a pathway to identify endogenous control genes for qPCR analysis of formalin-fixed paraffin-embedded (FFPE) tissue using bladder cancer as an exemplar; and (2) examine the influence of probe length and sample age on PCR amplification and co-expression of candidate genes on apparent expression stability. RNA was extracted from prospective and retrospective samples and subject to qPCR using TaqMan human endogenous control arrays or single tube assays. Gene stability ranking was assessed using coefficient of variation (CoV), GeNorm and NormFinder. Co-expressed genes were identified from The Cancer Genome Atlas (TCGA) using the on-line gene regression analysis tool GRACE. Cycle threshold (Ct) values were lower for prospective (19.49 ± 2.53) vs retrospective (23.8 ± 3.32) tissues (p < 0.001) and shorter vs longer probes. Co-expressed genes ranked as the most stable genes in the TCGA cohort by GeNorm when analysed together but ranked lower when analysed individually omitting co-expressed genes indicating bias. Stability values were < 1.5 for the 20 candidate genes in the prospective cohort. As they consistently ranked in the top ten by CoV, GeNorm and Normfinder, UBC, RPLP0, HMBS, GUSB, and TBP are the most suitable endogenous control genes for bladder cancer qPCR.

Use of an imaging station for rapid colony counting in radiobiology studies.

Colony counting by eye is time consuming and subjective. Here comparison between the measurements of proliferative growth inhibition in plates of radiation-treated cells by an imaging station correlated highly significantly with counts determined by eye. This would suggest that an imaging station could be a viable alternative for colony counting for doses over 200KBq.

Colorectal tumor cells treated with 5-FU, oxaliplatin, irinotecan, and cetuximab exhibit changes in 18F-FDG incorporation corresponding to hexokinase activity and glucose transport.

UNLABELLED: The purpose of this study was to determine therapy-induced changes in 18F-FDG incorporation at the colorectal tumor cell level in response to conventional and novel chemotherapy agents and examine how these changes relate to factors involved in 18F-FDG incorporation. METHODS: SW620 cells were treated with inhibitory concentration of 50% (IC50) doses (determined by MTT) of 5-fluorouracil (5-FU), oxaliplatin, and irinotecan; HCT-8 cells were treated with IC50 doses of irinotecan, cetuximab, and irinotecan plus cetuximab. 18F-FDG incorporation, glucose transport, hexokinase (HK) activity, adenosine triphosphate (ATP) content, annexin V binding, and cell cycle distribution were determined after 24-, 48-, and 72-h treatments. Eight-hour treatments with and without subsequent incubation in drug-free medium were also examined. A clonogenic assay was used to determine the tumor-forming ability of treated cells. RESULTS: Apoptosis was evident in SW620 cells, especially after treatment with irinotecan and 5-FU. 18F-FDG incorporation was increased in SW620 cells after 24- or 48-h treatments with some agents and in HCT-8 cells after irinotecan treatment but was decreased in all 72-h treatments or cell-line combinations including cetuximab. Treatment of SW620 cells for 8 h followed by 64 h in drug-free medium also resulted in decreased 18F-FDG incorporation. Decreased 18F-FDG incorporation broadly corresponded to glucose transport in HCT-8 cells and to HK activity in SW620 cells. Inhibition of glucose transport decreased 18F-FDG incorporation into HCT-8 but not into SW620 cells. ATP levels were decreased by oxaliplatin treatment and increased at 48 or 72 h after irinotecan treatment. CONCLUSION: 18F-FDG incorporation is modulated by therapy-induced changes in both glucose transport and HK activity depending on the tumor cell. Colorectal cells treated with IC50 doses of cetuximab also exhibit decreased 18F-FDG.

Physicochemical Tools: Toward a Detailed Understanding of the Architecture of Targeted Radiotherapy Nanoparticles.

Targeted radiotherapy is proving to be an effective alternative to external beam radiotherapy for cancer treatment. Gold nanoparticles are biocompatible, commercially available, and readily functionalized, which makes them perfect candidates for the delivery of cytotoxic radionuclides labeled with antibodies to proteins abnormally expressed on cancer tissue. However, there is a lack of information regarding the efficacy of the successive modification steps involved in the functionalization process, as well as of the actual final state of the nanoparticles prior to preclinical tests, which results in a very inefficient screening and that will further impact on biological barriers, such as half-life interactions with serum proteins. Here, gold nanoparticles (15 nm diameter) were functionalized with linkers for antibody and radionuclide conjugation, following a well-stablished method. Successful coating of the gold nanoparticles was demonstrated using state-of-the-art physicochemical techniques, which include AF4-UV-ICPMS-MALS, Raman spectroscopy, and force-distance spectroscopy, which have led to an accurate description of the hydrodynamic diameter of the functionalized NPs and also about the adhesion energy and elastic properties of the modified NPs. Successive steps involved in the coating led to an organic shell of 12 nm diameter and no nanoparticle aggregation was observed. This may be a consequence of a decrease (or even the total absence) in water adsorption on the metal surface and/or of the organic labeling, that decreases the surface tension of the particles as estimated from the atomic force microscopy force-distance curves. Radiolabeling of gold nanoparticles prescreened using these physicochemical tools with 177Lu resulted in >75% efficiency.

Treatment of breast tumor cells in vitro with the mitochondrial membrane potential dissipater valinomycin increases 18F-FDG incorporation.

UNLABELLED: Mitochondrial membrane potential is essential for adenosine triphosphate (ATP) synthesis by oxidative phosphorylation, and its abolition is an early event during apoptosis, a type of cell death commonly exhibited by tumor cells responding to treatment. Dissipation of mitochondrial membrane potential can be specifically induced using the K+ ion channel-opening agent valinomycin and has been used in this study to determine how the loss of mitochondrial membrane potential could influence 18F-FDG incorporation. METHODS: MCF-7 cells were treated with valinomycin for 30 min, inducing loss of mitochondrial membrane potential as determined using flow cytometry with the JC-1 probe. 18F-FDG incorporation, the initial rate of O-methyl-D-glucose incorporation (a measure of glucose transport), hexokinase activity and subcellular distribution, ATP content using bioluminescence, and lactate production were determined on control and valinomycin-treated cells. RESULTS: A 30-min treatment of MCF-7 cells with 1 micromol of valinomycin per liter resulted in absence of red fluorescence from JC-1, indicative of dissipation of mitochondrial membrane potential. 18F-FDG incorporation was significantly increased by 30 min of treatment with valinomycin and was still apparent after 3.5 h of incubation. Hexokinase activity and subcellular distribution were not significantly different between control cells and cells treated for 30 min with valinomycin. Glucose transport was moderately though significantly increased, and lactate production was also increased. CONCLUSION: Loss of mitochondrial membrane potential is associated with increased 18F-FDG incorporation, glucose transport, and lactate production.

Decreased [18F]fluoro-2-deoxy-d-glucose incorporation and increased glucose transport are associated with resistance to 5FU in MCF7 cells in vitro.

INTRODUCTION: Tumor refractoriness to chemotherapy is frequently due to the acquisition of resistance. Resistant cells selected by exposure to chemotherapy agents may exhibit differences in [18F]fluoro-2-deoxy-d-glucose (FDG) incorporation, as compared with sensitive cells. METHODS: FDG incorporation, hexokinase (HK) activity, glucose transport and ATP content were determined in clones of 5-fluorouracil (5FU)-resistant MCF7 cells, established by long-term exposure to increasing 5FU concentrations, and in parental MCF7 cells. RESULTS: FDG incorporation was decreased in MCF7 cells resistant to 5FU; HK activity was similar in the resistant and sensitive cells, while glucose transport was increased, as compared with sensitive cells. Treatment of cells with the glucose efflux inhibitor phloretin increased FDG incorporation to similar levels in the resistant and sensitive cells. Analysis of microarray data demonstrated the expression of GLUT1, 8 and 10 transporters in MCF7 cells. GLUT8 and 10 expression was decreased in the resistant cells, while GLUT1 was only increased in cells resistant to the lowest 5FU concentration. CONCLUSION: FDG incorporation in 5FU-resistant MCF7 cells is decreased, as compared with sensitive cells. Our findings also suggest that this may be due to high rates of membrane glucose transport in the resistant cells resulting in enhanced efflux of FDG. We believe that this is the first demonstration that facilitative glucose transporters can actually decrease the incorporation of FDG.

Response Detection of Castrate-Resistant Prostate Cancer to Clinically Utilised and Novel Treatments by Monitoring Phospholipid Metabolism.

Androgen receptor (AR) activation is the primary driving factor in prostate cancer which is initially responsive to castration but then becomes resistant (castration-resistant prostate cancer (CRPC)). CRPC cells still retain the functioning AR which can be targeted by other therapies. A recent promising development is the use of inhibitors (Epi-1) of protein-protein interaction to inhibit AR-activated signalling. Translating novel therapies into the clinic requires sensitive early response indicators. Here potential response markers are explored. Growth inhibition of prostate cancer cells with flutamide, paclitaxel, and Epi-1 was measured using the MTT assay. To simulate choline-PET scans, pulse-chase experiments were carried out with [3H-methyl]choline and proportion of phosphorylated activity was determined after treatment with growth inhibitory concentrations of each drug. Extracts from treated cells were also subject to 31P-NMR spectroscopy. Cells treated with flutamide demonstrated decreased [3H-methyl]choline phosphorylation, whilst the proportion of phosphorylated [3H-methyl]choline that was present in the lipid fraction was increased in Epi-1-treated cells. Phospholipid breakdown products, glycerophosphorylcholine and glycerophosphoethanolamine levels, were shown by 31P-NMR spectroscopy to be decreased to undetectable levels in cells treated with Epi-1. LNCaP cells responding to treatment with novel protein-protein interaction inhibitors suggest that 31P-NMR spectroscopy may be useful in detecting response to this promising therapy.

Tumor 18F-FDG incorporation is enhanced by attenuation of P53 function in breast cancer cells in vitro.

UNLABELLED: Mutations in the p53 gene, often resulting in loss of wild-type (WT) p53 expression, are found at high frequencies in several cancer types. High uptake of (18)F-FDG detected using (18)F-FDG PET has been associated with a poor prognosis. To determine whether high (18)F-FDG uptake may be related to decreased expression of WT p53, we examined (18)F-FDG uptake in cells transfected with dominant negative p53 constructs that abrogate WT p53 function. METHODS: Two clones of MCF-7 breast cancer cells were stably transfected with a dominant negative p53 construct. (18)F-FDG uptake, hexokinase (HK) activity, and glucose transport were measured in each clone and in the control WT cells from which the clones had been derived. The expression of glucose transporters, HKs, and glucose-6-phosphatase was determined using microarray technology. RESULTS: Microarray experiments revealed that glucose transporters 1, 8, and 10 were expressed in MCF-7 cells, whereas glucose-6-phosphatase was absent. HK I was the principal HK in MCF-7 cells but was not differentially expressed at the messenger RNA level in the dominant negative p53 clones, compared with WT cells. However, increased HK activity was observed in both dominant negative p53 clones, compared with WT MCF-7. (18)F-FDG uptake was increased in both clones expressing the dominant negative p53 constructs. CONCLUSION: These data suggest that abrogation of p53 in breast cancer is associated with specific changes in glucose metabolism detected by PET.

Metformin Decouples Phospholipid Metabolism in Breast Cancer Cells.

INTRODUCTION: The antidiabetic drug metformin, currently undergoing trials for cancer treatment, modulates lipid and glucose metabolism both crucial in phospholipid synthesis. Here the effect of treatment of breast tumour cells with metformin on phosphatidylcholine (PtdCho) metabolism which plays a key role in membrane synthesis and intracellular signalling has been examined. METHODS: MDA-MB-468, BT474 and SKBr3 breast cancer cell lines were treated with metformin and [3H-methyl]choline and [14C(U)]glucose incorporation and lipid accumulation determined in the presence and absence of lipase inhibitors. Activities of choline kinase (CK), CTP:phosphocholine cytidylyl transferase (CCT) and PtdCho-phospholipase C (PLC) were also measured. [3H] Radiolabelled metabolites were determined using thin layer chromatography. RESULTS: Metformin-treated cells exhibited decreased formation of [3H]phosphocholine but increased accumulation of [3H]choline by PtdCho. CK and PLC activities were decreased and CCT activity increased by metformin-treatment. [14C] incorporation into fatty acids was decreased and into glycerol was increased in breast cancer cells treated with metformin incubated with [14C(U)]glucose. CONCLUSION: This is the first study to show that treatment of breast cancer cells with metformin induces profound changes in phospholipid metabolism.

Effects of Administered Cardioprotective Drugs on Treatment Response of Breast Cancer Cells.

BACKGROUND: Anticancer drug treatment, particularly with anthracyclines, is frequently associated with cardiotoxicity, an effect exacerbated by trastuzumab. Several compounds are in use clinically to attenuate the cardiac-damaging effects of chemotherapy drugs, including angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, the anti-diabetic drug metformin, and dexrazoxane. However, there is concern that the cardiac-preserving mechanisms of these drugs may also limit the anticancer efficacy of the chemotherapeutic agents. MATERIALS AND METHODS: Herein two breast cancer cell lines, SKBr3 and BT474, overexpressing human epithelial receptor 2 (HER2), the target of the humanised antibody trastuzumab, were treated with a range of concentrations (20-2000 nM) of doxorubicin with and without trastuzumab in the presence of clinically relevant doses of the ACE inhibitor enalapril, the beta-blocker carvedilol, metformin or dexrazoxane, and cell survival determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. RESULTS: None of the drugs reduced the anticancer effect of doxorubicin or trastuzumab (nor of the two drugs combined). Using Chou and Talalay's combination index, dexrazoxane and doxorubicin were found to act synergistically on the SKBr3 cells. (18)F-Fluoro-2-deoxy-D-glucose ((18)F-FDG) incorporation was reduced by treatment of SKBr3 cells with doxorubicin and this was shown to be due to reduced phosphorylation of (18)F-FDG in doxorubicin-treated cells. Treatment of SKBr3 cells with doxorubicin and dexrazoxane further reduced (18)F-FDG incorporation, indicating that the synergy in the cytotoxicity of these two drugs was reflected in their combined effect on (18)F-FDG incorporation. CONCLUSION: Commonly administered cardioprotective drugs do not interfere with anticancer activity of doxorubicin or tratsuzumab. Further studies to establish the effect of cardioprotective drugs on anticancer drug efficacy would be beneficial.

Probing the PI3K/Akt/mTor pathway using 31P-NMR spectroscopy: routes to glycogen synthase kinase 3.

Akt is an intracellular signalling pathway that serves as an essential link between cell surface receptors and cellular processes including proliferation, development and survival. The pathway has many downstream targets including glycogen synthase kinase3 which is a major regulatory kinase for cell cycle transit as well as controlling glycogen synthase activity. The Akt pathway is frequently up-regulated in cancer due to overexpression of receptors such as the epidermal growth factor receptor, or mutation of signalling pathway kinases resulting in inappropriate survival and proliferation. Consequently anticancer drugs have been developed that target this pathway. MDA-MB-468 breast and HCT8 colorectal cancer cells were treated with inhibitors including LY294002, MK2206, rapamycin, AZD8055 targeting key kinases in/associated with Akt pathway and the consistency of changes in 31P-NMR-detecatable metabolite content of tumour cells was examined. Treatment with the Akt inhibitor MK2206 reduced phosphocholine levels in MDA-MB-468 cells. Treatment with either the phosphoinositide-3-kinase inhibitor, LY294002 and pan-mTOR inhibitor, AZD8055 but not pan-Akt inhibitor MK2206 increased uridine-5'-diphosphate-hexose cell content which was suppressed by co-treatment with glycogen synthase kinase 3 inhibitor SB216763. This suggests that there is an Akt-independent link between phosphoinositol-3-kinase and glycogen synthase kinase3 and demonstrates the potential of 31P-NMR to probe intracellular signalling pathways.

Changes in [18F]Fluoro-2-deoxy-D-glucose incorporation induced by doxorubicin and anti-HER antibodies by breast cancer cells modulated by co-treatment with metformin and its effects on intracellular signalling.

PURPOSES: Metformin, currently undergoing clinical trials as an adjuvant for the treatment of breast cancer, modulates the activity of key intracellular signalling molecules which affect 2-[(18)F]Fluoro-2-deoxy-D-glucose ([(18)F]FDG) incorporation. Here, we investigate the effect of drugs used in the treatment of breast cancer combined with metformin on [(18)F]FDG incorporation in HER2- or HER1-overexpressing breast cancer cells to determine whether or not metformin may obscure changes in [(18)F]FDG incorporation induced by clinically utilised anticancer drugs in the treatment of breast cancer. METHODS: Three breast cancer cell lines expressing HER2 and one HER2 negative but HER1 positive were exposed to metformin, doxorubicin and trastuzumab or cetuximab. Cytotoxicity was measured by the MTT assay. Expression of active (phospho-) AMPK, PKB (Akt) and ERK was determined by Western blotting. [(18)F]FDG incorporation by cells exposed to drug combinations with metformin was determined. Glucose transport was assessed by measuring the initial rate of uptake of [(3)H]O-methyl-D-glucose ([(3)H]OMG). Phosphorylation of [(18)F]FDG was determined in intact cells after exposure to [(18)F]FDG. RESULTS: Phospho-AMPK was increased by metformin in all cell lines whilst phospho-Akt and phospho-ERK expressions were decreased in two. Metformin treatment increased [(18)F]FDG incorporation in all cell lines, and treatment with anti-HER antibodies or doxorubicin only produced minor modulations in the increase induced by metformin alone. Glucose transport was increased in BT474 cells and decreased in SKBr3 and MDA-MB-468 cells after treatment with metformin. The fraction of phosphorylated [(18)F]FDG was increased in metformin-treated cells compared with controls, suggesting that hexokinase efficiency was increased by metformin. CONCLUSION: This is the first study to show that increased [(18)F]FDG incorporation by breast cancer cells induced by metformin overwhelms the effect of doxorubicin and anti-HER treatments on [(18)F]FDG incorporation. Metformin-induced increased [(18)F]FDG incorporation was consistently associated with enhanced [(18)F]FDG phosphorylation.

99mTc-labelled human serum transferrin for tumour imaging: an in vitro and in vivo study of the complex.

This pilot study reports the uptake of 99mTc-transferrin by MCF7 cells and the biodistribution of the complex in mice bearing MCF7 tumours. Human serum holo-transferrin was labelled with 99mTc using pre-reduction with 2-mercaptoethanol. The uptake of the complex by MCF7 breast tumour cells, which was found to be competitively inhibited by the presence of unlabelled transferrin, reached a plateau within 30 min. Two groups of xenografted mice with small and large tumours, respectively, were injected with the complex, and the uptake was followed for up to 24 h post-administration using a dedicated gamma camera. The mean tumour uptake values, determined after dissection, in the two groups of mice were 6% (small tumours) and 1.7% (large tumours) of the injected dose per gram of tissue, with mean tumour/blood ratios of 2.7 and 1.7, respectively.