Cytotoxic effect of different statins and thiazolidinediones on malignant glioma cells

Metabolic imbalance and brain tumors: The interlinking metabolic pathways and therapeutic actions of antidiabetic drugs

Brain tumors are complex, heterogeneous malignancies, often associated with significant morbidity and mortality. Emerging evidence suggests the important role of metabolic syndrome, such as that observed in diabetes mellitus, in the progression of brain tumors. Several studies indicated that hyperglycemia, insulin resistance, oxidative stress, and altered adipokine profiles influence tumor growth, proliferation, and treatment resistance. Intriguingly, antidiabetic drugs (e.g., metformin, sulfonylureas, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and thiazolidinediones) have shown promise as adjunctive or repurposed agents in managing brain tumors. Metformin can impair tumor cell proliferation, enhance treatment sensitivity, and modify the tumor microenvironment by activating AMP-activated protein kinase (AMPK) and inhibiting mammalian target of rapamycin (mTOR) signaling pathways. DPP-4 inhibitors and GLP-1 receptor agonists can target both metabolic and inflammatory aspects of brain tumors, while thiazolidinediones may induce apoptosis in tumor cells and synergize with other therapeutics. Consequently, further studies and clinical trials are needed to confirm the efficacy, safety, and utility of metabolic interventions in treating brain tumors. Here, we review the evidence for the metabolic interconnections between metabolic diseases and brain tumors and multiple actions of anti-diabetes drugs in brain tumors.

Statins, Allies against Antibiotic Resistance?

Due to the ever-increasing rate of antibacterial resistance, the search for effective antibacterial agents has become imperative. Researchers have investigated the potential antimicrobial properties of various classes of nonantibiotic drugs. Statins are a group of antihyperlipidemic drugs with several cholesterol-independent effects, including antiinflammatory, immune-modulating, antioxidant, and antibacterial effects. In vitro and in vivo studies have demonstrated the antibacterial properties of statins against various grampositive and gram-negative bacteria. Simvastatin and atorvastatin are the most potent members of the family. Their antibacterial effect can be attributed to several direct and indirect mechanisms. Bacterial invasion, growth, and virulence are affected by statins. However, since in vitro minimum inhibitory concentrations (MICs) are significantly higher than serum concentrations at the lipid-lowering dosage, indirect mechanisms have been suggested to explain the positive clinical results, including reducing inflammation and improving immune response capacity. Further, statins have shown promising results when combined with antibiotics and other antibacterial agents, such as triazenes and silver nanoparticles. Despite this, the controversial aspects of statins have cast doubt on their efficacy as a possible solution for antibacterial resistance, and further research is required. Consequently, this review will examine in detail the current clinical and in vitro findings and controversies regarding statins' antibacterial properties and their relevance to antibacterial resistance.

The effects of statin therapy on brain tumors, particularly glioma: a review

Brain tumors account for less than 2% of all malignancies. However, they are associated with the highest morbidity and mortality rates among all solid tumors. The most common malignant primary brain tumors are glioma or glioblastoma (GBM), which have a median survival time of about 14 months, often suffer from recurrence after a few months following treatment, and pose a therapeutic challenge. Despite recent therapeutic advances, the prognosis for glioma patients is poor when treated with modern therapies, including chemotherapy, surgery, radiation, or a combination of these. Therefore, discovering a new target to treat brain tumors, particularly glioma, might be advantageous in raising progression-free survival and overall survival (OS) rates. Statins, also known as competitive HMG-CoA reductase inhibitors, are effective medications for reducing cholesterol and cardiovascular risk. The use of statins prior to and during other cancer treatments appears to enhance patient outcomes according to preclinical studies. After surgical resection followed by concurrent radiation and treatment, OS for patients with GBM is only about a year. Statins have recently emerged as potential adjuvant medications for treating GBM due to their ability to inhibit cell growth, survival, migration, metastasis, inflammation, angiogenesis, and increase apoptosis in-vitro and in-vivo studies. Whether statins enhance clinical outcomes, such as patient survival in GBM, is still debatable. This study aimed to explore the effects of statin therapy in the context of cancer treatment, with a particular focus on GBM.

Potential Therapeutic Effects of PPAR Ligands in Glioblastoma

Glioblastoma (GB), also known as grade IV astrocytoma, represents the most aggressive form of brain tumor, characterized by extraordinary heterogeneity and high invasiveness and mortality. Thus, a great deal of interest is currently being directed to investigate a new therapeutic strategy and in recent years, the research has focused its attention on the evaluation of the anticancer effects of some drugs already in use for other diseases. This is the case of peroxisome proliferator-activated receptors (PPARs) ligands, which over the years have been revealed to possess anticancer properties. PPARs belong to the nuclear receptor superfamily and are divided into three main subtypes: PPAR-α, PPAR-β/δ, and PPAR-γ. These receptors, once activated by specific natural or synthetic ligands, translocate to the nucleus and dimerize with the retinoid X receptors (RXR), starting the signal transduction of numerous genes involved in many physiological processes. PPARs receptors are activated by specific ligands and participate principally in the preservation of homeostasis and in lipid and glucose metabolism. In fact, synthetic PPAR-α agonists, such as fibrates, are drugs currently in use for the clinical treatment of hypertriglyceridemia, while PPAR-γ agonists, including thiazolidinediones (TZDs), are known as insulin-sensitizing drugs. In this review, we will analyze the role of PPARs receptors in the progression of tumorigenesis and the action of PPARs agonists in promoting, or not, the induction of cell death in GB cells, highlighting the conflicting opinions present in the literature.

Nose-to-brain delivery of simvastatin mediated by chitosan-coated lipid-core nanocapsules allows for the treatment of glioblastoma in vivo

Glioblastoma is the most common and lethal malignant brain tumor. Despite simvastatin (SVT) showing potential anticancer properties, its antitumoral effect against glioblastoma appears limited when the conventional oral administration route is selected. As a consequence, nose-to-brain delivery has been proposed as an alternative route to deliver SVT into the brain. This study aimed to prepare chitosan-coated simvastatin-loaded lipid-core nanocapsules (LNC_SVT-chit) suitable for nose-to-brain delivery and capable of fostering antitumor effects against glioblastoma both in vitro and in vivo. Results showed that the nanocapsules present adequate particle size (mean diameter below 200 nm), narrow particle size distribution (PDI < 0.2), positive zeta potential and high encapsulation efficiency (nearly 100%). In vitro cytotoxicity of LNC_SVT-chit was comparable to non-encapsulated SVT in C6 rat glioma cells, whereas LNC_SVT-chit were more cytotoxic than non-encapsulated SVT after 72 h of incubation against U-138 MG human glioblastoma cell line. In studies carried out in rats, LNC_SVT-chit significantly enhanced the amount of drug in rat brain tissue after intranasal administration (2.4-fold) when compared with free SVT. Moreover, LNC_SVT-chit promoted a significant decrease in tumor growth and malignancy in glioma-bearing rats in comparison to control and free SVT groups. Additionally, LNC_SVT-chit did not cause any toxicity in treated rats. Considered overall, the results demonstrated that the nose-to-brain administration of LNC_SVT-chit represents a novel potential strategy for glioblastoma treatment.

Statins and Gliomas: A Systematic Review of the Preclinical Studies and Meta-Analysis of the Clinical Literature

BACKGROUND

Gliomas represent most common primary brain tumors. Glioblastoma (GBM) is the most common subtype and carries a poor prognosis. There is growing interest in the anti-glioma properties of statins. The aim of this study was to conduct a systematic review of the preclinical literature and to meta-analyze existing clinical studies to determine what benefit, if any, statins may confer in the context of glioma.

METHODS

The PubMed, Embase, Cochrane, and Web of Science libraries were queried in May 2021. Preclinical studies were included if they investigated the anti-cancer effects of statins in glioma in vitro and in vivo. Clinical studies were included if they reported incidence rates of glioma by statin use, or mortality outcomes among GBM patients by statin use. Pooled point estimates were calculated using a random-effects model.

RESULTS

In total, 64 publications, 51 preclinical and 13 clinical, were included. Preclinical studies indicated that statins inhibited glioma cell proliferation, migration, and invasion. These effects were time- and concentration-dependent. Synergistic anti-glioma effects were observed when statins were combined with other anti-cancer therapies. Clinical observational studies showed an inverse, albeit non-statistically significant, association between statin use and incidence rate of glioma (HR = 0.84, 95% CI 0.62-1.13, I² = 72%, p-heterogeneity = 0.003, 6 studies). Statin use was not associated with better overall survival following GBM surgery (HR = 1.05, 95% CI 0.85-1.30, I² = 30%, p-heterogeneity = 0.23, 4 studies).

CONCLUSION

Statins were potent anti-cancer drugs that suppressed glioma growth through various mechanisms in vitro; these effects have translated into the clinical realm, clinically but not statistically, in terms of glioma incidence but not GBM survival.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Activation of PPARγ intensified the effects of arsenic trioxide in acute promyelocytic leukemia through the suppression of PI3K/Akt pathway: Proposing a novel anticancer effect for pioglitazone

The indulgent success of arsenic trioxide (ATO) in the induction of complete remission in acute promyelocytic leukemia (APL) patients has accommodated this agent into the therapeutic protocols. However, the intrusion of unfavorable side effects had put an unanswered question on the way of the application of this agent; whether the benefits of ATO may outweigh its drawbacks. In this study, we found that when ATO is accompanied by an activator of peroxisome proliferator-activated receptors gamma (PPARγ), even the lower concentrations could induce significant inhibitory effects on the survival of NB4 through diminishing the ability of the cells to replicate DNA in the S phase of cell cycle. We also found that through suppression of the PI3K pathway, the combination of pioglitazone and ATO provided a signal through which the induction of apoptotic cell death was enhanced probably via the elevation of reactive oxygen species (ROS). With respect to the tight connection between PI3K pathway and autophagy system and given to the inhibitory effect of pioglitazone-plus-ATO on PI3K, we found that the combination of these agents not only suppressed the expression of autophagy-related genes, but also their efficacy was augmented when autophagy was inhibited in NB4; clarifying the encouraging role of autophagy in the survival maintenance of APL cells. In conclusion, given the significant efficacy as well as the safety profile of pioglitazone in potentiating the anticancer effects of chemotherapeutic drugs, the present study suggests it as a promising agent to be used in adjuvant strategy for the treatment of APL.

PPARγ Agonists in Combination Cancer Therapies

Peroxisome proliferator-activated receptor-gamma (PPARγ) is a nuclear receptor acting as a transcription factor involved in the regulation of energy metabolism, cell cycle, cell differentiation, and apoptosis. These unique properties constitute a strong therapeutic potential that place PPARγ agonists as one of the most interesting and widely studied anticancer molecules. Although PPARγ agonists exert significant, antiproliferative and tumoricidal activity in vitro, their anticancer efficacy in animal models is ambiguous, and their effectiveness in clinical trials in monotherapy is unsatisfactory. However, due to pleiotropic effects of PPARγ activation in normal and tumor cells, PPARγ ligands interact with many antitumor treatment modalities and synergistically potentiate their effectiveness. The most spectacular example is a combination of PPARγ ligands with tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). In this setting, PPARγ activation sensitizes leukemic stem cells, resistant to any previous form of treatment, to targeted therapy. Thus, this combination is believed to be the first pharmacological therapy able to cure CML patients. Within the last decade, a significant body of data confirming the benefits of the addition of PPARγ ligands to various antitumor therapies, including chemotherapy, hormonotherapy, targeted therapy, and immunotherapy, has been published. Although the majority of these studies have been carried out in vitro or animal tumor models, a few successful attempts to introduce PPARγ ligands into anticancer therapy in humans have been recently made. In this review, we aim to summarize shines and shadows of targeting PPARγ in antitumor therapies.

The Role of Metabolic Plasticity in Blood and Brain Stem Cell Pathophysiology

Our understanding of intratumoral heterogeneity in cancer continues to evolve, with current models incorporating single-cell signatures to explore cell-cell interactions and differentiation state. The transition between stem and differentiation states in nonneoplastic cells requires metabolic plasticity, and this plasticity is increasingly recognized to play a central role in cancer biology. The insights from hematopoietic and neural stem cell differentiation pathways were used to identify cancer stem cells in leukemia and gliomas. Similarly, defining metabolic heterogeneity and fuel-switching signals in nonneoplastic stem cells may also give important insights into the corresponding molecular mechanisms controlling metabolic plasticity in cancer. These advances are important, because metabolic adaptation to anticancer therapeutics is rooted in this inherent metabolic plasticity and is a therapeutic challenge to be overcome.

Lovastatin Enhances Cytotoxicity of Temozolomide via Impairing Autophagic Flux in Glioblastoma Cells

Drug resistance to temozolomide (TMZ) contributes to the majority of tumor recurrence and treatment failure in patients with glioblastoma multiforme (GBM). Autophagy has been reported to play a role in chemoresistance in various types of cancer, including GBM. The anticancer effect of statins is arousing great research interests and has been demonstrated to modulate autophagic function. In this study, we investigated the combinational effects of lovastatin and TMZ on treating U87 and U251 GBM cell lines. Cytotoxicity was measured by MTT and colony formation assays; apoptosis was measured by flow cytometry; the cellular autophagic function was detected by the EGFP-mRFP-LC3 reporter and western blot assay. The results showed that lovastatin might enhance the cytotoxicity of TMZ, increase the TMZ-induced cellular apoptosis, and impair the autophagic flux in GBM cells. Lovastatin triggered autophagy initiation possibly by inhibiting the Akt/mTOR signaling pathway. Moreover, lovastatin might impair the autophagosome-lysosome fusion machinery by suppressing LAMP2 and dynein. These results suggested that lovastatin could enhance the chemotherapy efficacy of TMZ in treating GBM cells. The mechanism may be associated with impaired autophagic flux and thereby the enhancement of cellular apoptosis. Combining TMZ with lovastatin could be a promising strategy for GBM treatment.

Epidemiologic Analysis Along the Mevalonate Pathway Reveals Improved Cancer Survival in Patients Who Receive Statins Alone and in Combination With Bisphosphonates

PURPOSE

Cohort studies report associations between statin use and improved survival in patients with cancer. We used pharmacoepidemiologic methods to evaluate the survival of patients with cancer who received statins alone or in ostensibly synergistic drug combinations.

MATERIALS AND METHODS

Patients with cancer who were diagnosed from 2010 to 2013 were identified in a large health care claims database. The rate of all-cause death up to 1 year after diagnosis was compared by Cox proportional hazard regression. Sensitivity analyses included age stratification, statin type and intensity, and comparison with or without bisphosphonates and dipyridamole.

RESULTS

Among 312,907 identified patients with cancer, treatment groups included statin users (n = 65,440), nonstatin users who received medications that block cholesterol absorption (n = 9,289), and nonusers (n = 226,007). Statin use before diagnosis was associated with improved overall survival compared with no treatment (hazard ratio [HR], 0.85; 95% CI, 0.80 to 0.91) and specifically in patients with leukemia, lung, or renal cancers. Nonstatin users had increased overall survival compared with no treatment (HR, 0.73; 95% CI, 0.62 to 0.85); when stratified, this difference held true only for pancreatic cancer and leukemia. No differences were observed between statin and nonstatin groups. Bisphosphonate use alone had no effect (n = 4,528), but patients who used both statins and bisphosphonates (n = 4,090) had increased survival compared with no treatment (HR, 0.60; 95% CI, 0.45 to 0.81). The effect of the combination of dipyridamole and statin use (n = 651) was not significant compared with no treatment.

CONCLUSION

This study suggests that the combination of statins with drugs that affect isoprenylation, such as bisphosphonates, improves survival in patients with cancer. Consideration of pathway-specific pharmacology allows for hypotheses testing with the pharmacoepidemiologic approach. Prospective evaluation of these findings warrants clinical investigation and preclinical mechanistic studies.

Statins: a new approach to combat temozolomide chemoresistance in glioblastoma

Patients with glioblastoma multiforme (GBM) have an average life expectancy of approximately 15 months. Recently, statins have emerged as a potential adjuvant cancer therapy due to their ability to inhibit cell proliferation and induce apoptosis in many types of cancer. The exact mechanisms that mediate the inhibitory actions of statins in cancer cells are largely unknown. The purpose of this proceeding paper is to discuss some of the known anticancer effects of statins, while focusing on GBM therapy that includes adjunct therapy of statins with chemotherapeutic agents.

Improved survival with continuation of statins in bacteremic patients

Objectives:

Varying statin exposures in bacteremic patients have different impacts on mortality. Among patients with adherent statin use, we sought to evaluate the impact of statin continuation on inpatient mortality in bacteremic patients.

Methods:

A retrospective cohort study was conducted using Optum Clinformatics^TM with matched Premier Hospital data (October 2009–March 2013). Patients with a primary diagnosis of bacteremia and 6 months of continuous enrollment prior to the admission, receiving antibiotics at least 2 days of antibiotics during the first 3 days of admission, were selected for inclusion. Furthermore, patients demonstrating adherent statin use based on 90 days of continuous therapy prior to admission were included. We then compared those continuing statin therapy for at least the first 5 days after admission and those not continuing during the admission.

Results:

Simvastatin (53.2%) and atorvastatin (33.8%) were the most commonly used statins among the 633 patients who met our inclusion and exclusion criteria. Propensity score adjusted Cox proportional hazards regression models demonstrated significantly lower inpatient mortality among those continuing statin therapy compared with those not continuing (n = 232 vs 401, adjusted hazard ratio 0.25, 95% confidence interval 0.08–0.79).

Conclusion:

Among patients adherent to their statin therapy prior to a bacteremia hospitalization, continued statin use after admission increased survival by 75% compared with those not continuing.

The Anti-Angiogenic Effect of Atorvastatin in Glioblastoma Spheroids Tumor Cultured in Fibrin Gel: in 3D in Vitro Model

Purpose:

Glioblastoma multiform (GBM) is the most aggressive glial neoplasm. Researchers have exploited the fact that GBMs are highly vascularized tumors. Anti-angiogenic strategies including those targeting VEGF pathway have been emerged for treatment of GBM. Previously, we reported the anti-inflammatory effect of atorvastatin on GBM cells. In this study, we investigated the anti-angiogenesis and apoptotic activity of atorvastatin on GBM cells.

Methods:

Different concentrations of atorvastatin (1, 5, 10µM) were used on engineered three-dimensional (3D) human tumor models using glioma spheroids and Human Umbilical Vein Endothelial cells (HUVECs) in fibrin gel as tumor models. To reach for these aims, angiogenesis as tube-like structures sprouting of HUVECs were observed after 24 hour treatment with different concentrations of atorvastatin into the 3-D fibrin matrix and we focused on it by angiogenesis antibody array. After 48 hours exposing with different concentrations of atorvastatin, cell migration of HUVECs were investigated. After 24 and 48 hours exposing with different concentrations of atorvastatin VEGF, CD31, caspase-3 and Bcl-2 genes expression by real time PCR were assayed.

Results:

The results showed that atorvastatin has potent anti-angiogenic effect and apoptosis inducing effect against glioma spheroids. Atorvastatin down-regulated the expression of VEGF, CD31 and Bcl-2, and induced the expression of caspase-3 especially at 10µM concentration. These effects are dose dependent.

Conclusion:

These results suggest that this biomimetic model with fibrin may provide a vastly applicable 3D culture system to study the effect of anti-cancer drugs such as atorvastatin on tumor malignancy in vitro and in vivo and atorvastatin could be used as agent for glioblastoma treatment.

Drug Repositioning in Glioblastoma: A Pathway Perspective

Glioblastoma multiforme (GBM) is the most malignant primary adult brain tumor. The current standard of care is surgical resection, radiation, and chemotherapy treatment, which extends life in most cases. Unfortunately, tumor recurrence is nearly universal and patients with recurrent glioblastoma typically survive <1 year. Therefore, new therapies and therapeutic combinations need to be developed that can be quickly approved for use in patients. However, in order to gain approval, therapies need to be safe as well as effective. One possible means of attaining rapid approval is repurposing FDA approved compounds for GBM therapy. However, candidate compounds must be able to penetrate the blood-brain barrier (BBB) and therefore a selection process has to be implemented to identify such compounds that can eliminate GBM tumor expansion. We review here psychiatric and non-psychiatric compounds that may be effective in GBM, as well as potential drugs targeting cell death pathways. We also discuss the potential of data-driven computational approaches to identify compounds that induce cell death in GBM cells, enabled by large reference databases such as the Library of Integrated Network Cell Signatures (LINCS). Finally, we argue that identifying pathways dysregulated in GBM in a patient specific manner is essential for effective repurposing in GBM and other gliomas.

Atorvastatin augments temozolomide's efficacy in glioblastoma via prenylation-dependent inhibition of Ras signaling

Ras signaling is often dysregulated and plays essential roles for the maintenance of glioblastoma. The proper function of Ras depends largely on the appropriate post-translational modification termed prenylation. Targeting protein prenylation therefore represents an alternative therapeutic strategy in glioblastoma. In this study, we demonstrate that prenylation inhibition by atorvastatin is active against glioblastoma. Atorvastatin alone dose-dependently inhibits growth and survival of multiple glioblastoma cell lines. Its combination with temozolomide significantly enhances temozolomide's efficacy in in vitro cultured cell system as well as in vivo xenograft glioblastoma tumor model. We further show that this is achieved by the inhibition of Ras prenylation, leading to decreased activation of Ras and its downstream signaling pathways, including Erk, rS6 and eIF4E. Our findings suggest that inhibition of Ras activity by atorvastatin effectively targets the MEK and other signaling pathways. Our study provides a fundamental evidence to repurpose atorvastatin for a potential treatment of glioblastoma.

Atorvastatin Promotes Cytotoxicity and Reduces Migration and Proliferation of Human A172 Glioma Cells

Malignant gliomas have resistance mechanisms to chemotherapy that enable tumor invasiveness and aggressiveness. Alternative therapies in cancer treatment, as statins, have been suggested to decrease proliferation, inhibit cell migration, and induce cell death. The aim of this study was to evaluate the effect of atorvastatin (ATOR) on cell viability, migration, proliferation, apoptosis, and autophagy in A172 human glioma cells. Temozolomide (TMZ), a chemotherapic used to glioma treatment, was tested as a comparison to cytotoxic effects on gliomas. Cell viability was also assessed in primary culture of cortical astrocytes. ATOR treatment (0.1 to 20 μM) did not alter astrocytic viability. However, in glioma cells, ATOR showed cytotoxic effect at 10 and 20 μM concentrations. TMZ (500 μM) reduced cell viability similarly to ATOR, and drug association did not show additive effect on cell viability. ATOR, TMZ, and their association decreased cell migration. ATOR also decreased glioma cell proliferation. ATOR increased apoptosis, and TMZ association showed a potentiation effect, enhancing it. ATOR and TMZ treatment increased acidic vesicular organelle (AVO) presence in A172 cells, an indicative of autophagy. ATOR effect of reducing A172 cell viability did not alter glutamate transport and glutamine synthetase activity, but it was partially prevented through antagonism of ionotropic and metabotropic glutamate receptors. Our data shows a cytotoxic effect of ATOR on glioma cells, whereas no toxicity was observed to astrocytes. ATOR showed similar cytotoxic effect as TMZ to glioma cells, and it may be a safer drug, regarding side effect induction, than chemotherapic agents.

A Metabolic Inhibitory Cocktail for Grave Cancers: Metformin, Pioglitazone and Lithium Combination in Treatment of Pancreatic Cancer and Glioblastoma Multiforme

Pancreatic cancer (PC) and glioblastoma multiforme (GBM) are among the human cancers with worst prognosis which require an urgent need for efficient therapies. Here, we propose to apply to treat both malignancies with a triple combination of drugs, which are already in use for different indications. Recent studies demonstrated a considerable link between risk of PC and diabetes. In experimental models, anti-diabetogenic agents suppress growth of PC, including metformin (M), pioglitazone (P) and lithium (L). L is used in psychiatric practice, yet also bears anti-diabetic potential and selectively inhibits glycogen synthase kinase-3 beta (GSK-3β). M, a biguanide class anti-diabetic agent shows anticancer activity via activating AMP-activated protein kinase (AMPK). Glitazones bind to PPAR-γ and inhibit NF-κB, triggering cell proliferation, apoptosis resistance and synthesis of inflammatory cytokines in cancer cells. Inhibition of inflammatory cytokines could simultaneously decrease tumor growth and alleviate cancer cachexia, having a major role in PC mortality. Furthermore, mutual synergistic interactions exist between PPAR-γ and GSK-3β, between AMPK and GSK-3β and between AMPK and PPAR-γ. In GBM, M blocks angiogenesis and migration in experimental models. Very noteworthy, among GBM patients with type 2 diabetes, usage of M significantly correlates with better survival while reverse is true for sulfonylureas. In experimental models, P synergies with ligands of RAR, RXR and statins in reducing growth of GBM. Further, usage of P was found to be lesser in anaplastic astrocytoma and GBM patients, indicating a protective effect of P against high-grade gliomas. L is accumulated in GBM cells faster and higher than in neuroblastoma cells, and its levels further increase with chronic exposure. Recent studies revealed anti-invasive potential of L in GBM cell lines. Here, we propose that a triple-agent regime including drugs already in clinical usage may provide a metabolic adjuvant therapy for PC and GBM.

Repurposing some older drugs that cross the blood-brain barrier and have potential anticancer activity to provide new treatment options for glioblastoma

Glioblastoma is a brain neoplasm with limited 5-year survival rates. Developments of new treatment regimens that improve patient survival in patients with glioblastoma are needed. It is likely that a number of existing drugs used in other conditions have potential anticancer effects that offer significant survival benefit to glioblastoma patients. Identification of such drugs could provide a novel treatment paradigm.

Chemotherapy and chemoprevention by thiazolidinediones

Thiazolidinediones (TZDs) are synthetic ligands of Peroxisome-Proliferator-Activated Receptor gamma (PPARγ). Troglitazone, rosiglitazone, and pioglitazone have been approved for treatment of diabetes mellitus type II. All three compounds, together with the first TZD ciglitazone, also showed an antitumor effect in preclinical studies and a beneficial effect in some clinical trials. This review summarizes hypotheses on the role of PPARγ in tumors, on cellular targets of TZDs, antitumor effects of monotherapy and of TZDs in combination with other compounds, with a focus on their role in the treatment of differentiated thyroid carcinoma. The results of chemopreventive effects of TZDs are also considered. Existing data suggest that the action of TZDs is highly complex and that actions do not correlate with cellular PPARγ expression status. Effects are cell-, species-, and compound-specific and concentration-dependent. Data from human trials suggest the efficacy of TZDs as monotherapy in prostate cancer and glioma and as chemopreventive agent in colon, lung, and breast cancer. TZDs in combination with other therapies might increase antitumor effects in thyroid cancer, soft tissue sarcoma, and melanoma.

Statins are potential anticancerous agents (review)

Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), which is a rate-limiting enzyme in the mevalonate pathway. The pleiotropic effects of statins may be mediated by the inhibition of downstream products such as small GTP-binding proteins, Rho, Ras and Rac whose localization and function are dependent on isoprenylation. Preclinical studies of statins in different cancer cell lines and animal models showed antiproliferative, pro‑apoptotic and anti-invasive effects. Notably, statins showed targeted action in cancerous cell lines compared to normal cells. Previous studies have also shown the synergistic effects of statins with chemotherapeutic agents and radiotherapy. This effect of statins was also observed in chemotherapeutic-resistant tumors. Statins were reported to sensitize the cells to radiation by arresting them in the late G1 phase of the cell cycle. Similarly, population-based studies also demonstrated a chemopreventive and survival benefit of statins in various types of cancers. However, this benefit has yet to be proven in clinical trials. The inter-individual variation in response to statins may be contributed to many genetic and non-genetic factors, including single-nucleotide polymorphisms in HMGCR gene and the overexpression of heterogeneous nuclear ribonucleoprotein A1, which was reported to reduce HMGCR enzyme activity. However, more studies with large phase III randomized controlled trials in cancer patients should be conducted to establish the effect of stains in cancer prevention and treatment.

Statin use and survival following glioblastoma multiforme

AIM

While some studies indicate a potential chemopreventive effect of statin use on the risk of glioma, the effect of statins on the prognosis of brain tumours has not yet been examined. We thus conducted a cohort study evaluating the influence of statin use on survival in patients with glioblastoma multiforme (GBM).

METHODS

We identified 1562 patients diagnosed with GBM during 2000-2009 from the Danish Cancer Registry and linked this cohort to Danish nationwide demographic and health registries. Within the GBM cohort, each patient recorded as using statins prior to diagnosis (defined as ≥ 2 redeemed prescriptions) was matched to two statin non-users (<2 redeemed prescriptions) by propensity scores based on age, gender, year of diagnosis, comorbidity, and use of selected drugs. Cox proportional hazard models were used to compute hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause death associated with prediagnostic statin use.

RESULTS

A total of 339 GBM patients were included in the analyses. Of these, 325 died during median follow-up of 6.9 months (interquartile range: 3.8-13.4 months). Prediagnostic statin use was associated with a reduced HR of death (0.79; 95% CI: 0.63-1.00). The HRs decreased with increasing duration or intensity of prediagnostic statin use [long-term (≥ 5 years) statin use: HR 0.75 (95% CI: 0.47-1.20); high-intensity statin use: HR 0.66 (95% CI: 0.44-0.98)]. Additional adjustment for oncotherapeutic modalities yielded similar results (overall HR 0.80, 95% CI: 0.63-1.01).

CONCLUSION

Long-term prediagnostic statin use may improve survival following GBM.

The Key to Unlocking the Chemotherapeutic Potential of PPARγ Ligands: Having the Right Combination

Despite extensive preclinical evidence that peroxisome proliferator-activated receptor (PPAR)γ activation protects against tumourigenesis, results from a few clinical trials using PPARγ ligands as monotherapy show modest success. In spite of this, several groups reported exciting results with therapeutic regimens that combine PPARγ ligands with other compounds: chemotherapeutic agents, retinoid x receptor (RXR)α agonists, statins, or cell-to-cell signaling molecules in preclinical cancer models and human trials. Here we have compiled an extensive review, consolidating the existing literature, which overwhelmingly supports a beneficial effect of treating with PPARγ ligands in combination with existing chemotherapies versus their monotherapy in cancer. There are many examples in which combination therapy resulted in synergistic/additive effects on apoptosis, differentiation, and the ability to reduce cell growth and tumour burden. There are also studies that indicate that PPARγ ligand pretreatment overcomes resistance and reduces toxicities. Several mechanisms are explored to explain these protective effects. This paper highlights each of these studies that, collectively, make a very strong case for the use of PPARγ ligands in combination with other agents in the treatment and management of several cancers.

Rosiglitazone suppresses glioma cell growth and cell cycle by blocking the transforming growth factor-beta mediated pathway

Glioma is one of the most malignant tumors in the central nervous system. As a peroxisome proliferator-activated receptor γ (PPAR-γ) activator, the thiazolidinediones (TZDs) induce growth arrest and cell death in a broad spectrum of tumor cells. In this study, we investigated the role of rosiglitazone in glioma cells. We found that rosiglitazone, a member of TZDs, suppresses growth of human glioma cell lines U87 and U251. Rosiglitazone also induces cell cycle arrest and apoptosis, which may be the mechanism of its anti-proliferation effect. Next, we found that rosiglitazone suppresses the expression of TGF-beta and its receptor TGF-betaR2, and suppresses phosphorylation of Smad3. Rosiglitazone also inhibits formation of the Smad3/Smad4 complex. Furthermore, Rosiglitazone affects the expression of Smad3/Smad4 associated regulators of gene expression, including p21 and c-Myc. These results suggest that rosiglitazone suppresses growth and cell cycle of human glioma cells by blocking the TGF-beta mediated pathway.

Antibacterial activity of statins: a comparative study of atorvastatin, simvastatin, and rosuvastatin

Background

Statins have several effects beyond their well-known antihyperlipidemic activity, which include immunomodulatory, antioxidative and anticoagulant effects. In this study, we have tested the possible antimicrobial activity of statins against a range of standard bacterial strains and bacterial clinical isolates.

Methods

Minimum inhibitory concentrations (MIC) values were evaluated and compared among three members of the statins drug (atorvastatin, simvastatin, and rosuvastatin).

Results

It was revealed that statins are able to induce variable degrees of antibacterial activity with atorvastatin, and simvastatin being the more potent than rosuvastatin. Methicillin-sensitive staphylococcus aureus (MSSA), methicillin-resistant staphylococcus aureus (MRSA), vancomycin-susceptible enterococci (VSE), vancomycin-resistant enterococcus (VRE), acinetobacter baumannii, staphylococcus epidermidis, and enterobacter aerogenes, were more sensitive to both atorvastatin, and simvastatin compared to rosuvastatin. On the other hand, escherichia coli, proteus mirabilis, and enterobacter cloacae were more sensitive to atorvastatin compared to both simvastatin and rosuvastatin. Furthermore, most clinical isolates were less sensitive to statins compared to their corresponding standard strains.

Conclusion

Our findings might raise the possibility of a potentially important antibacterial class effect for statins especially, atorvastatin and simvastatin.