Screening human lung cancer with predictive models of serum magnetic resonance spectroscopy metabolomics.

The current high mortality of human lung cancer stems largely from the lack of feasible, early disease detection tools. An effective test with serum metabolomics predictive models able to suggest patients harboring disease could expedite triage patient to specialized imaging assessment. Here, using a training-validation-testing-cohort design, we establish our high-resolution magic angle spinning (HRMAS) magnetic resonance spectroscopy (MRS)-based metabolomics predictive models to indicate lung cancer presence and patient survival using serum samples collected prior to their disease diagnoses. Studied serum samples were collected from 79 patients before (within 5.0 y) and at lung cancer diagnosis. Disease predictive models were established by comparing serum metabolomic patterns between our training cohorts: patients with lung cancer at time of diagnosis, and matched healthy controls. These predictive models were then applied to evaluate serum samples of our validation and testing cohorts, all collected from patients before their lung cancer diagnosis. Our study found that the predictive model yielded values for prior-to-detection serum samples to be intermediate between values for patients at time of diagnosis and for healthy controls; these intermediate values significantly differed from both groups, with an F1 score = 0.628 for cancer prediction. Furthermore, values from metabolomics predictive model measured from prior-to-diagnosis sera could significantly predict 5-y survival for patients with localized disease.

13 C NMR quantification of polyamine syntheses in rat prostate.

Currently, many prostate cancer patients, detected through the prostate specific antigen test, harbor organ-confined indolent disease that cannot be differentiated from aggressive cancer according to clinically and pathologically known measures. Spermine has been considered as an endogenous inhibitor for prostate-confined cancer growth and its expression has shown correlation with prostate cancer growth rates. If established clinically, measurements of spermine bio-synthesis rates in prostates may predict prostate cancer growth and patient outcomes. Using rat models, we tested the feasibility of quantifying spermine bio-synthesis rates with 13 C NMR. Male Copenhagen rats (10 weeks, n = 6) were injected with uniformly 13 C-labeled L-ornithine HCl, and were sacrificed in pairs at 10, 30, and 60 min after injection. Another two rats were injected with saline and sacrificed at 30 min as controls. Prostates were harvested and extracted with perchloric acid and the neutralized solutions were examined by 13 C NMR at 600 MHz. 13 C NMR revealed measurable ornithine, as well as putrescine-spermidine-spermine syntheses in rat prostates, allowing polyamine bio-synthetic and ornithine bio-catabolic rates to be calculated. Our study demonstrated the feasibility of 13 C NMR for measuring bio-synthesis rates of ornithine to spermine enzymatic reactions in rat prostates. The current study established a foundation upon which future investigations of protocols that differentiate prostate cancer growth rates according to the measure of ornithine to spermine bio-synthetic rates may be developed.

Differentiation of patients with and without prostate cancer using urine 1 H NMR metabolomics.

Prostate cancer (PCa) is one of the most prevalent cancers in men worldwide. For its detection, serum prostate-specific antigen (PSA) screening is commonly used, despite its lack of specificity, high false positive rate, and inability to discriminate indolent from aggressive PCa. Following increases in serum PSA levels, clinicians often conduct prostate biopsies with or without advanced imaging. Nuclear magnetic resonance (NMR)-based metabolomics has proven to be promising for advancing early-detection and elucidation of disease progression, through the discovery and characterization of novel biomarkers. This retrospective study of urine-NMR samples, from prostate biopsy patients with and without PCa, identified several metabolites involved in energy metabolism, amino acid metabolism, and the hippuric acid pathway. Of note, lactate and hippurate-key metabolites involved in cellular proliferation and microbiome effects, respectively-were significantly altered, unveiling widespread metabolomic modifications associated with PCa development. These findings support urine metabolomics profiling as a promising strategy to identify new clinical biomarkers for PCa detection and diagnosis.

Metabolomic prostate cancer fields in HRMAS MRS-profiled histologically benign tissue vary with cancer status and distance from cancer.

In this article, we review the state of the field of high resolution magic angle spinning MRS (HRMAS MRS)-based cancer metabolomics since its beginning in 2004; discuss the concept of cancer metabolomic fields, where metabolomic profiles measured from histologically benign tissues reflect patient cancer status; and report our HRMAS MRS metabolomic results, which characterize metabolomic fields in prostatectomy-removed cancerous prostates. Three-dimensional mapping of cancer lesions throughout each prostate enabled multiple benign tissue samples per organ to be classified based on distance from and extent of the closest cancer lesion as well as the Gleason score (GS) of the entire prostate. Cross-validated partial least squares-discriminant analysis separations were achieved between cancer and benign tissue, and between cancer tissue from prostates with high (≥4 + 3) and low (≤3 + 4) GS. Metabolomic field effects enabled histologically benign tissue adjacent to cancer to distinguish the GS and extent of the cancer lesion itself. Benign samples close to either low GS cancer or extensive cancer lesions could be distinguished from those far from cancer. Furthermore, a successfully cross-validated multivariate model for three benign tissue groups with varying distances from cancer lesions within one prostate indicates the scale of prostate cancer metabolomic fields. While these findings could, at present, be potentially useful in the prostate cancer clinic for analysis of biopsy or surgical specimens to complement current diagnostics, the confirmation of metabolomic fields should encourage further examination of cancer fields and can also enhance understanding of the metabolomic characteristics of cancer in myriad organ systems. Our results together with the success of HRMAS MRS-based cancer metabolomics presented in our literature review demonstrate the potential of cancer metabolomics to provide supplementary information for cancer diagnosis, staging, and patient prognostication.

Applications of high-resolution magic angle spinning MRS in biomedical studies I-cell line and animal models.

High-resolution magic angle spinning (HRMAS) MRS allows for direct measurements of non-liquid tissue and cell specimens to present valuable insights into the cellular metabolisms of physiological and pathological processes. HRMAS produces high-resolution spectra comparable to those obtained from solutions of specimen extracts but without complex metabolite extraction processes, and preserves the tissue cellular structure in a form suitable for pathological examinations following spectroscopic analysis. The technique has been applied in a wide variety of biomedical and biochemical studies and become one of the major platforms of metabolomic studies. By quantifying single metabolites, metabolite ratios, or metabolic profiles in their entirety, HRMAS presents promising possibilities for diagnosis and prediction of clinical outcomes for various diseases, as well as deciphering of metabolic changes resulting from drug therapies or xenobiotic interactions. In this review, we evaluate HRMAS MRS results on animal models and cell lines reported in the literature, and present the diverse applications of the method for the understanding of pathological processes and the effectiveness of therapies, development of disease animal models, and new progress in HRMAS methodology.

Applications of high-resolution magic angle spinning MRS in biomedical studies II-Human diseases.

High-resolution magic angle spinning (HRMAS) MRS is a powerful method for gaining insight into the physiological and pathological processes of cellular metabolism. Given its ability to obtain high-resolution spectra of non-liquid biological samples, while preserving tissue architecture for subsequent histopathological analysis, the technique has become invaluable for biochemical and biomedical studies. Using HRMAS MRS, alterations in measured metabolites, metabolic ratios, and metabolomic profiles present the possibility to improve identification and prognostication of various diseases and decipher the metabolomic impact of drug therapies. In this review, we evaluate HRMAS MRS results on human tissue specimens from malignancies and non-localized diseases reported in the literature since the inception of the technique in 1996. We present the diverse applications of the technique in understanding pathological processes of different anatomical origins, correlations with in vivo imaging, effectiveness of therapies, and progress in the HRMAS methodology.

Extracellularly delivered single-stranded viral RNA causes neurodegeneration dependent on TLR7.

Innate immune receptors represent an evolutionarily ancient system that allows organisms to detect and rapidly respond to pathogen- and host-derived factors. TLRs are predominantly expressed in immune cells and mediate such a response. Although this class of pattern recognition receptors is involved in CNS disorders, the knowledge of ligands leading to activation of TLRs and to subsequent CNS damage is limited. We report in this study that ssRNA causes neurodegeneration and neuroinflammation dependent on TLR7 in the CNS. TLR7 is not only expressed in microglia, the major immune cells of the brain, but also in neurons of the CNS. Extracellularly delivered ssRNA40, an oligoribonucleotide derived from HIV and an established ligand of TLR7, induces neuronal cell death dependent on TLR7 and the central adapter molecule MyD88 in vitro. Activation of caspase-3 is involved in neuronal damage mediated by TLR7. This cell-autonomous neuronal cell death induced by ssRNA40 is amplified in the presence of microglia that mount an inflammatory response to ssRNA40 through TLR7. Intrathecal administration of ssRNA40 causes widespread neurodegeneration in wild-type but not in TLR7(-/-) mice, confirming that neuronal cell death induced by ssRNA40 through TLR7 occurs in vivo. Our results point to a possible mechanism through which extracellularly delivered ssRNA contributes to CNS damage and determine an obligatory role for TLR7 in this pathway.

High Resolution Magic Angle Spinning Proton NMR Study of Alzheimer's Disease with Mouse Models.

Alzheimer's disease (AD) is a crippling condition that affects millions of elderly adults each year, yet there remains a serious need for improved methods of diagnosis. Metabolomic analysis has been proposed as a potential methodology to better investigate and understand the progression of this disease; however, studies of human brain tissue metabolomics are challenging, due to sample limitations and ethical considerations. Comprehensive comparisons of imaging measurements in animal models to identify similarities and differences between aging- and AD-associated metabolic changes should thus be tested and validated for future human non-invasive studies. In this paper, we present the results of our highresolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) studies of AD and wild-type (WT) mouse models, based on animal age, brain regions, including cortex vs. hippocampus, and disease status. Our findings suggest the ability of HRMAS NMR to differentiate between AD and WT mice using brain metabolomics, which potentially can be implemented in in vivo evaluations.

Anticoagulation Practice in Patients with Cancer-Associated Thrombosis: Insights from GeCAT, a German Prospective Registry Study.

INTRODUCTION: Cancer-associated venous thrombosis (CAT) is a common and serious complication of active malignancies, increasing in frequency during systemic treatment and radiotherapy. Due to a high risk of recurrence and bleeding, the administration of anticoagulants for initial treatment and secondary prevention of CAT is challenging. We conducted a prospective registry study of patients with acute CAT to evaluate the way treatment is given to these patients in routine practice. METHODS: From May 2015 to May 2017, all consecutive patients with acute venous thromboembolism (VTE) admitted to specialty or emergency departments of the participating hospitals in Berlin, Germany, were entered into the registry. Patients with cancer underwent extensive baseline evaluation including the type and location of thrombosis and use of anticoagulant therapy. Follow-up assessments were made at discharge and by telephone interviews at 3 and 6 months. RESULTS: A total of 382 patients with acute CAT were enrolled in the study, representing 24.5% of all patients with thrombosis. 70.4% of CAT patients had deep vein thromboses (DVT), 48.2% had pulmonary embolism (PE), and 18.6% had concurrent PE and DVT. A significant proportion of VTE (27%) was asymptomatic and was diagnosed only incidentally. At baseline, 97.9% of the patients received anticoagulant therapy, predominantly with low-molecular-weight heparin (LMWH) (n = 334, 87.4%). Direct oral anticoagulants (DOACs) were given to 5.8% of patients, and vitamin K antagonists were rarely used (<2% of patients). Changes in the prescription of antithrombotic agents were seen at discharge from hospital and during follow-up. Overall, the use of LMWH declined during follow-up, while the proportion of patients treated with DOACs increased to 32.4% at 6 months. At baseline, the most frequently used LMWH were enoxaparin and nadroparin, but many patients were switched to once daily tinzaparin prior to discharge. Initially and after discharge, the majority of patients were treated by oncologists. Overall, 263 (68.8%) and 222 (58.1%) patients were still alive and could be contacted at 3 and 6 months of follow-up, respectively. Of these, 84.0% and 71.6% were still on anticoagulant therapy (58.6% and 36.5% on LMWH). CONCLUSION: In accordance with the guidelines, the majority of CAT patients received anticoagulation therapy for the recommended minimum duration of 3-6 months. LMWH remained the preferred option throughout the study, demonstrating good patient adherence. In deviation from guideline recommendations and available study results during the study period, more than a quarter of CAT patients were treated with DOACs. Only recently, DOACs have been established as another option for anticoagulation in CAT patients.

High-Resolution Magic Angle Spinning (HRMAS) NMR Methods in Metabolomics.

High-resolution magic angle spinning (HRMAS) NMR spectroscopy enables the evaluation of metabolite profiles of intact tissue with high spectral resolution. The ability to preserve the tissue after analysis permits subsequent histopathological examination and enables the analyses of correlations between tissue metabolites and pathologies, thus making HRMAS NMR spectroscopy a powerful tool in the metabolomics field. Improved methods for the elimination of spinning sidebands that appear at low spinning rates preserve the integrity of tissue structures better and allow measurement of delicate tissues, such as clinical biopsy core samples. In the metabolomics field, HRMAS NMR has been established as a valuable tool for both untargeted and targeted metabolite profiling. In this chapter, we present protocols to perform HRMAS NMR spectroscopy experiments, including sample preparation, acquisition procedures, measurement parameters, histopathological examination techniques, spectral processing, and metabolite quantification and statistical analyses.

Cancer metabolomic markers in urine: evidence, techniques and recommendations.

Urinary tests have been used as noninvasive, cost-effective tools for screening, diagnosis and monitoring of diseases since ancient times. As we progress through the 21st century, modern analytical platforms have enabled effective measurement of metabolites, with promising results for both a deeper understanding of cancer pathophysiology and, ultimately, clinical translation. The first study to measure metabolomic urinary cancer biomarkers using NMR and mass spectrometry (MS) was published in 2006 and, since then, these techniques have been used to detect cancers of the urological system (kidney, prostate and bladder) and nonurological tumours including those of the breast, ovary, lung, liver, gastrointestinal tract, pancreas, bone and blood. This growing field warrants an assessment of the current status of research developments and recommendations to help systematize future research.

Magnetic Resonance Spectroscopy-based Metabolomic Biomarkers for Typing, Staging, and Survival Estimation of Early-Stage Human Lung Cancer.

Low-dose CT has shown promise in detecting early stage lung cancer. However, concerns about the adverse health effects of radiation and high cost prevent its use as a population-wide screening tool. Effective and feasible screening methods to triage suspicious patients to CT are needed. We investigated human lung cancer metabolomics from 93 paired tissue-serum samples with magnetic resonance spectroscopy and identified tissue and serum metabolomic markers that can differentiate cancer types and stages. Most interestingly, we identified serum metabolomic profiles that can predict patient overall survival for all cases (p = 0.0076), and more importantly for Stage I cases alone (n = 58, p = 0.0100), a prediction which is significant for treatment strategies but currently cannot be achieved by any clinical method. Prolonged survival is associated with relative overexpression of glutamine, valine, and glycine, and relative suppression of glutamate and lipids in serum.

Prostate cancer diagnosis and characterization with mass spectrometry imaging.

BACKGROUND: Prostate cancer (PCa), the most common cancer and second leading cause of cancer death in American men, presents the clinical challenge of distinguishing between indolent and aggressive tumors for proper treatment. PCa presents significant alterations in metabolic pathways that can potentially be measured using techniques like mass spectrometry (MS) or MS imaging (MSI) and used to characterize PCa aggressiveness. MS quantifies metabolomic, proteomic, and lipidomic profiles of biological systems that can be further visualized for their spatial distributions through MSI. METHODS: PubMed was queried for all publications relating to MS and MSI in human PCa from April 2007 to April 2017. With the goal of reviewing the utility of MSI in diagnosis and prognostication of human PCa, MSI articles that reported investigations of PCa-specific metabolites or metabolites indicating PCa aggressiveness were selected for inclusion. Articles were included that covered MS and MSI principles, limitations, and applications in PCa. RESULTS: We identified nine key studies on MSI in intact human prostate tissue specimens that determined metabolites which could either differentiate between benign and malignant prostate tissue or indicate PCa aggressiveness. These MSI-detected biomarkers show promise in reliably identifying PCa and determining disease aggressiveness. CONCLUSIONS: MSI represents an innovative technique with the ability to interrogate cancer biomarkers in relation to tissue pathologies and investigate tumor aggressiveness. We propose MSI as a powerful adjuvant histopathology imaging tool for prostate tissue evaluations, where clinical translation of this ex vivo technique could make possible the use of MSI for personalized medicine in diagnosis and prognosis of PCa. Moreover, the knowledge provided from this technique can majorly contribute to the understanding of molecular pathogenesis of PCa and other malignant diseases.

Primary prevention and treatment of venous thromboembolic events in patients with gastrointestinal cancers - Review.

Venous thromboembolism event (VTE) is a common and morbid complication in cancer patients. Patients with gastrointestinal cancers often suffer from symptomatic or incidental splanchnic vein thrombosis, impaired liver function and/or thrombocytopenia. These characteristics require a thorough risk/benefit evaluation for individual patients. Considering the risk factors for the development of VTE and bleeding events in addition to recent study results may be helpful for correct initiation of primary pharmacological prevention and treatment of cancer-associated thrombosis (CAT), preferably with low molecular weight heparins (LMWH). Whereas thromboprophylaxis is most often recommended in hospitalized surgical and non-surgical patients with malignancy, there is less agreement as to its duration. With regard to ambulatory cancer patients, the lack of robust data results in low grade recommendations against routine use of anticoagulant drugs. Anticoagulation with LMWH for the first months is the evidence-based treatment for acute CAT, but duration of secondary prevention and the drug of choice are unclear. Based on published guidelines and literature, this review will focus on prevention and treatment strategies of VTE in patients with gastrointestinal cancers.

Cisplatin Plus Ifosfamide with/without Etoposide as Salvage Treatment in Heavily-pre-treated Patients with Metastatic Breast Cancer.

BACKGROUND: The efficacy of platinum- and ifosfamide-based chemotherapy regimens as salvage treatment in metastatic breast cancer (MBC) has not yet been sufficiently evaluated. PATIENTS AND METHODS: Patients with MBC treated with cisplatin plus ifosfamide with (PEI) and without (PI) etoposide in our clinic between 04/2005 and 04/2014 were retrospectively analyzed. RESULTS: A total of 20 patients (median four prior chemotherapies) treated with PEI/PI were identified, out of whom 18 were evaluable for objective response. Treatment with PEI/PI resulted in one complete remission, nine partial remissions and two cases of stable disease. The median (range) progression-free survival was 4 (0-18) months and median overall survival from therapy initiation was 8.5 (0-50) months. PEI/PI therapy caused grade 3/4 toxicities (mainly hematological) in 80% of patients. CONCLUSION: PEI/PI is an adequate salvage treatment for patients with MBC but cannot be generally recommended due to toxicity. However, comparison with platinum monotherapy trials suggests that PEI/PI might be a more effective treatment for patients with triple-negative breast cancer.

Targeting multiple tyrosine kinase receptors with Dovitinib blocks invasion and the interaction between tumor cells and cancer-associated fibroblasts in breast cancer.

A constitutive and dynamic interaction between tumor cells and their surrounding stroma is a prerequisite for tumor invasion and metastasis. Fibroblasts and myofibroblasts (collectively called cancer associated fibroblasts, CAFs) often represent the major cellular components of tumor stroma. Tumor cells secret different growth factors which induce CAFs proliferation and differentiation, and, consequently, CAFs secrete different chemokines, cytokines or growth factors which induce tumor cell invasion and metastasis. In this study we showed here that CAFs from breast cancer surgical specimens significantly induced the invasion of breast cancer cells in vitro. Most interestingly, the novel multiple tyrosine kinase inhibitor Dovitinib significantly blocked the CAFs-induced invasion of breast cancer cells by, at least in part, inhibition of the expression and secretion of CCL2, CCL5 and VEGF in CAFs. Inhibition of PI3K/Akt/mTOR signaling could be responsible for the effects of Dovitinib, since Dovitinib antagonized the promoted phosphorylated Akt after treatment with PDGF, FGF or breast cancer cell-conditioned media. Treatment with Dovitinib in combination with PI3K/Akt/mTOR signaling inhibitors Ly294002 or RAD001 resulted in additive inhibition of cell invasion. This is the first in vitro study to show that the multiple tyrosine kinase inhibitor has therapeutic activities against breast cancer metastasis by targeting both tumor cells and CAFs.

Linac-based stereotactic radiotherapy and radiosurgery in patients with meningioma.

BACKGROUND: It was our purpose to analyze long-term clinical outcome and to identify prognostic factors after Linac-based fractionated stereotactic radiotherapy (Linac-based FSRT) and stereotactic radiosurgery (SRS) in patients with intracranial meningiomas. MATERIALS AND METHODS: Between 10/1995 and 03/2009, 297 patients with a median age of 59 years were treated with FSRT for intracranial meningioma. 50 patients had a Grade I meningioma, 20 patients had a Grade II meningioma, 12 patients suffered from a Grade III tumor, and in 215 cases no histology was obtained (Grade 0). Of the 297 patients, 144 underwent FSRT as their primary treatment and 158 underwent postoperative FSRT. 179 patients received normofractionated radiotherapy (nFSRT), 92 patients received hypofractionated FSRT (hFSRT) and 26 patients underwent SRS. Patients with nFSRT received a mean total dose of 57.31 ± 5.82 Gy, patients with hFSRT received a mean total dose of 37.6 ± 4.4 Gy and patients who underwent SRS received a mean total dose of 17.31 ± 2.58 Gy. RESULTS: Median follow-up was 35 months. Overall progression free survival (PFS) was 92.3% at 3 years, 87% at 5 years and 84.1% at 10 years. Patients with adjuvant radiotherapy showed significantly better PFS-rates than patients who had been treated with primary radiotherapy. There was no significant difference between PFS-rates of nFSRT, hFSRT and SRS patients. PFS-rates were independent of tumor size. Patients who had received nFSRT showed less acute toxicity than those who had received hFSRT. In the Grade 0/I group the rate of radiologic focal reactions was significantly lower than in the atypical/malignant histology group. CONCLUSION: This large study showed that FSRT is an effective and safe treatment modality with high PFS-rates for intracranial meningioma. We identified "pathological grading" and and "prior surgery" as significant prognostic factors.

The multi-tyrosine kinase inhibitor TKI258, alone or in combination with RAD001, is effective for treatment of human leukemia with BCR-ABL translocation in vitro.

BACKGROUND/AIM: BCR-ABL-positive (BCR-ABL(+)) leukemia is very difficult to treat although much improvement has been achieved due to the clinical application of imatinib and the second-generation tyrosine kinase inhibitors (TKIs). This study aimed to evaluate for the first time the treatment value of the multiple tyrosine kinase inhibitor TKI258 in BCR-ABL(+) leukemia. MATERIALS AND METHODS: Proliferation of different BCR-ABL(+) leukemic cells was measured with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay; cell apoptosis with Annexin V/propidium iodide (PI) and flow cytometry. Gene expression at the protein level was determined by western blotting. RESULTS: This drug showed treatment efficacy in naïve and imatinib-resistant BCR-ABL(+) leukemia cells, particularly in cells harboring T315I-mutated BCR-ABL, for which no effective inhibitor is available to date. By combination with the mTOR inhibitor RAD001, a synergistic effect on cell proliferation was observed in these cell lines. CONCLUSION: TKI258 may become a potent therapeutic agent, either alone or in combination with RAD001, for treatment of BCR-ABL(+) leukemia.

TKI258, a multi-tyrosine kinase inhibitor is efficacious against human infant/childhood lymphoblastic leukemia in vitro.

BACKGROUND/AIM: The goal of the present study was to evaluate if the multiple tyrosine kinase inhibitor (TKI) TKI258 has any treatment value for infant/childhood acute lymphoblatic leukemia (ALL), especially those ALLs bearing the mixed lineage leukemia (MLL) genes. MATERIALS AND METHODS: Cell proliferation was measured with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay; cell apoptosis and cell-cycle distribution with flow cytometry. Gene expression at the protein level was determined by western blotting. RESULTS: These ALL cells were extremely sensitive to TKI258 treatment with a concentration for 50% inhibition of cell proliferation (IC50) values in the nanomolar range in vitro. By combination with mTOR inhibitor RAD001, a synergistic effect on cell death and cell proliferation was observed in these cells. CONCLUSION: TKI258 may become a potent therapeutic agent, either alone or in combination with RAD001, for treatment of ALL, especially the entity with MLL genes.

Metformin and the mTOR inhibitor everolimus (RAD001) sensitize breast cancer cells to the cytotoxic effect of chemotherapeutic drugs in vitro.

AIM: Metformin appears to interfere directly with cell proliferation and apoptosis in cancer cells in a non-insulin-mediated manner. One of the key mechanisms of metformin's action is the activation of adenosine monophosphate activated protein kinase (AMPK). AMPK is linked with the phosphatidylinositol 3-kinase (PI3K)/ phosphatase and tensin homolog (PTEN)/protein kinase B (AKT) pathway and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinases (ERK) cascades--all known for being frequently dysregulated in breast cancer. Therefore, simultaneously targeting AMPK through metformin and the PI3K/AKT/mTOR pathway by an mTOR inhibitor could become a therapeutic approach. The aim of this study was to evaluate the anticancer effect of metformin alone and in combination with chemotherapeutic drugs and the mTOR inhibitor RAD001. MATERIALS AND METHODS: The proliferation of breast cancer cells was measured with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay; and the cell apoptosis with enzyme-linked immunosorbent assay (ELISA). Gene expression at the protein level was determined by western blot. RESULTS: We tested metformin alone and in combination with RAD001 and/or chemotherapeutic agents (carboplatin, paclitaxel and doxorubicin, respectively) on several human breast cancer cell lines with respect to cell proliferation, apoptosis and autophagy. Metformin alone inhibited cell proliferation and induced apoptosis in different breast cancer cell lines (ERα-positive, HER2-positive, and triple-negative). The cytotoxic effect of metformin was more remarkable in triple-negative breast cancer cell lines than in other cell lines. The cell apoptosis induced by metformin is, at least partly, caspase-dependent and apoptosis inducing factor (AIF)-dependent. Interestingly, we demonstrated that metformin induced cell autophagy. Inhibiting autophagy with chloroquine, enhanced the treatment efficacy of metformin, indicating that autophagy induced by metformin may protect breast cancer cells from apoptosis. We further demonstrated that co-administration of metformin with chemotherapeutic agents and RAD001 intensified the inhibition of cell proliferation. The analysis of cell cycle-regulating proteins cyclin D, cyclin E and p27 by western blot indicated that the synergistic inhibition of G1 phase of the cell cycle by the combination treatment of metformin, chemotherapeutic drugs and/or RAD001 contributed to the synergistic inhibition of cell proliferation. CONCLUSION: Our investigation provides a rationale for the clinical application of metformin within treatment regimens for breast cancer.