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

Anthracycline cardiotoxicity: current methods of diagnosis and possible role of 18F-FDG PET/CT as a new biomarker

Despite advances in chemotherapy, the drugs used in cancer treatment remain rather harmful to the cardiovascular system, causing structural and functional cardiotoxic changes. Positron-emission tomography associated with computed tomography (PET/CT) has emerged like a promising technique in the early diagnosis of these adverse drug effects as the myocardial tissue uptake of fluorodeoxyglucose labeled with fluorine-18 (¹⁸F-FDG), a glucose analog, is increased after their use. Among these drugs, anthracyclines are the most frequently associated with cardiotoxicity because they promote heart damage through DNA breaks, and induction of an oxidative, proinflammatory, and toxic environment. This review aimed to present the scientific evidence available so far regarding the use of ¹⁸F-FDG PET/CT as an early biomarker of anthracycline-related cardiotoxicity. Thus, it discusses the physiological basis for its uptake, hypotheses to justify its increase in the myocardium affected by anthracyclines, importance of ¹⁸F-FDG PET/CT findings for cardio-oncology, and primary challenges of incorporating this technique in standard clinical oncology practice.

Molecular sensors for detection of tumor-stroma crosstalk

In most solid tumors, malignant cells coexist with non-cancerous host tissue comprised of a variety of extracellular matrix components and cell types, notably fibroblasts, immune cells, and endothelial cells. It is becoming increasingly evident that the non-cancerous host tissue, often referred to as the tumor stroma or the tumor microenvironment, wields tremendous influence in the proliferation, survival, and metastatic ability of cancer cells. The tumor stroma has an active biological role in the transmission of signals, such as growth factors and chemokines that activate oncogenic signaling pathways by autocrine and paracrine mechanisms. Moreover, the constituents of the stroma define the mechanical properties and the physical features of solid tumors, which influence cancer progression and response to therapy. Inspired by the emerging importance of tumor-stroma crosstalk and oncogenic physical forces, numerous biosensors, or advanced imaging and analysis techniques have been developed and applied to investigate complex and challenging questions in cancer research. These techniques facilitate measurements and biological readouts at scales ranging from subcellular to tissue-level with unprecedented level of spatial and temporal precision. Here we examine the application of biosensor technology for studying the complex and dynamic multiscale interactions of the tumor-host system.

Hyperglycemia and Chemoresistance in Breast Cancer: From Cellular Mechanisms to Treatment Response

Female breast cancer is a complex, multifactorial disease. Studies have shown that hyperglycemia is one of the most important contributing factors to increasing the risk of breast cancer that also has a major impact on the efficacy of chemotherapy. At the cellular level, hyperglycemia can promote the proliferation, invasion, and migration of breast cancer cells and can also induce anti-apoptotic responses to enhance the chemoresistance of tumors via abnormal glucose metabolism. In this article, we focus on the latest progress in defining the mechanisms of chemotherapy resistance in hyperglycemic patients including the abnormal behaviors of cancer cells in the hyperglycemic microenvironment and the impact of abnormal glucose metabolism on key signaling pathways. To better understand the advantages and challenges of breast cancer treatments, we explore the causes of drug resistance in hyperglycemic patients that may help to better inform the development of effective treatments.

Hypoxia PET Imaging with [18F]-HX4-A Promising Next-Generation Tracer

Hypoxia—a common feature of the majority of solid tumors—is a negative prognostic factor, as it is associated with invasion, metastasis and therapy resistance. To date, a variety of methods are available for the assessment of tumor hypoxia, including the use of positron emission tomography (PET). A plethora of hypoxia PET tracers, each with its own strengths and limitations, has been developed and successfully validated, thereby providing useful prognostic or predictive information. The current review focusses on [18F]-HX4, a promising next-generation hypoxia PET tracer. After a brief history of its development, we discuss and compare its characteristics with other hypoxia PET tracers and provide an update on its progression into the clinic. Lastly, we address the potential applications of assessing tumor hypoxia using [18F]-HX4, with a focus on improving patient-tailored therapies.

Effect of IDH3a on glucose uptake in lung adenocarcinoma: A pilot study based on [18 F]FDG

Subunit of isocitrate dehydrogenase 3 (IDH3a) as upstream of the hypoxia-inducible factor was reported highly expressed in malignant tumors, playing an important role in glucose metabolism reprogramming. As one of rate-limiting enzyme in the Krebs cycle, whether high expression of IDH3a affects glucose uptake in tumors has not been elucidated. This study was aimed to investigate the relationship between IDH3a expression and tumor glucose uptake. Sixty-five patients who underwent 2-[18 F]-2-deoxy-D-glucose ([18 F]-FDG) positron emission tomography/computed tomography (PET/CT) imaging before surgery and pathologically diagnosed as lung adenocarcinoma were included. All patients were divided into high (n = 31) and low (n = 34) groups according IDH3a expression by immunohistochemistry. Comparatively higher [18 F]-FDG uptake was found in high IDH3a expression group. Glucose transporter 1 (GLUT1) level was demonstrated to correlate with IDH3a expression, but not for hexokinase 2 (HK2). Furthermore, A549 and H1299 cells experiment showed, the expression of p-AKT and GLUT1 were significantly downregulated after IDH3a interference. The cellular uptake of [18 F]-FDG and lactate production were significantly reduced in treatment group. In summary, high expression of IDH3a in lung adenocarcinoma patients is associated with higher glucose uptake. IDH3a targets AKT-GLUT1 pathway to affect glucose uptake and metabolites in lung adenocarcinoma.

CDP-choline accumulation in breast and colorectal cancer cells treated with a GSK-3-targeting inhibitor

Purpose

Glycogen synthase kinase 3 (GSK3) is a key controlling element of many cellular processes including cell-cycle progression and recent studies suggest that GSK3 is a potential anticancer target. Changes in glucose metabolism associated with GSK3 inhibition may impact on lipid synthesis, whilst lipid metabolites can act as molecular response markers.

Methods

Here, SKBr3 breast and HCT8 colorectal cancer cells were treated with the GSK3 inhibitor SB216763, and [¹⁴C (U)] glucose and [³H] choline incorporation into lipids was determined. Cell extracts from treated cells were subject to ³¹P NMR spectroscopy.

Results

SB216763 treatment decreased choline incorporation into lipids and caused an accumulation of CDP-choline which was accompanied by decreased conversion of glucose into lipid components.

Conclusion

SB216763 profoundly inhibits phospholipid synthesis in cancer cells which demonstrate accumulation of CDP-choline detectable by ³¹P NMR spectroscopy. Metabolic changes in lipid metabolism present potential response markers to drugs targeting GSK3.

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-Akt^ser473 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.

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.

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.

Imaging Diagnostic and Therapeutic Targets: Human Epidermal Growth Factor Receptor 2

Since the approval of trastuzumab, a humanized monoclonal antibody against the extracellular domain of human epidermal growth factor receptor 2 (HER2), 3 other HER2-targeting agents have gained regulatory approval: lapatinib, pertuzumab, and trastuzumab-emtansine. These agents have revolutionized the management of HER2-positive breast cancer, highlighting the concept that targeted therapies are successful when patients exhibit tumor-selective expression of a molecular target-in this case, HER2. However, response prediction and innate or acquired resistance remain serious concerns. Predictive biomarkers of a response-which could help in the selection of patients who might benefit from a selected targeted therapy-are currently lacking. Molecular imaging with anti-HER2 probes allows the noninvasive, whole-body assessment of HER2 tumor burden and has the potential to improve patient selection, optimize the dose and schedule, and rationalize assessment of the response to anti-HER2 therapies. Furthermore, unlike biopsy-based HER2 assessment, this approach can reveal inter- or intratumoral heterogeneity as well as variations in HER2 expression over time. This review summarizes the available literature and the current status of molecular imaging as a tool for the assessment of HER2 (target) expression or the prediction of an early treatment response in early and advanced HER2-positive breast cancer.

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.

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.

Bisabolane Sesquiterpenoids from the Plant Endophytic Fungus Paraconiothyrium brasiliense

Brasilamides E-J (1-6), the bisabolane sesquiterpenoids with the 3-cyclohexylfuran (1 and 2) and 3-cyclohexylfuranone (3-6) skeletons, were isolated from the scale-up fermentation cultures of the plant endophytic fungus Paraconiothynium brasiliense Verkley. Although brasilamide E (1) is a known metabolite, its structure elucidation has yet to be described. The structures of 1-6 were elucidated primarily by NMR experiments. Compounds 3-6 were found to be racemic, and 3 was further separated into enantiomers 3a and 3b on a chiral HPLC column. The absolute configurations of 3a and 3b were assigned by electronic circular dichroism calculations. Compound 1 selectively inhibited the proliferation of the breast (MCF-7) and gastric (MGC) cancer cell lines, with IC50 values of 8.4 and 14.7 μM, respectively. Initial mechanistic investigation revealed that compound 1 inhibited the expression of a key energy metabolic enzyme, hexokinase II (HK2), in MCF-7 cells, which resulted in dysfunction of glucose metabolism and ATP depletion and eventually inhibited the proliferation of the breast cancer cells.