FoxO3a Mediates the Inhibitory Effects of the Antiepileptic Drug Lamotrigine on Breast Cancer Growth

Exposure to psychotropic drugs and breast cancer risk in patients with bipolar disorder and major depressive disorder: a nested case-control study

Breast cancer is one of the most prevalent and serious types of cancer globally. Previous literature has shown that women with mental illness may have an increased risk of breast cancer, however whether this risk is associated with the use of psychotropic drugs has yet to be elucidated. This study aimed to assess such risk among women with major depressive disorder (MDD) and bipolar disorder (BD). A nested case-control study design was used with data obtained from the Taiwan National Health Insurance Research Database. Logistic regression analysis with adjustments for demographic characteristics, medical and mental comorbidities, and all-cause clinical visits was performed to estimate the risk of breast cancer according to the cumulative defined daily dose (cDDD) of psychotropic drugs. The study included 1564 women with MDD or BD who had breast cancer, and 15,540 women with MDD or BD who did not have breast cancer. After adjusting for important confounders, the long-term use of valproic acid (odds ratio, 95% confidence interval: 0.58, 0.39-0.56, cDDD ≥ 365), citalopram (0.58, 0.37-0.91, cDDD 180-365), and sertraline (0.77, 0.61-0.91, cDDD ≥ 365) was associated with a lower risk of breast cancer compared to a cDDD < 30. The short-term use of fluvoxamine (0.82, 0.69-0.96, cDDD 30-180), olanzapine (0.54, 0.33-0.89, cDDD 30-179), risperidone (0.7, 0.51-0.98, cDDD 30-179), and chlorpromazine (0.48, 0.25-0.90, cDDD 30-179) was associated with a lower risk of breast cancer. We found no evidence of an increased risk of breast cancer in patients with MDD or BD receiving psychotropic drugs.

FoxO3a Drives the Metabolic Reprogramming in Tamoxifen-Resistant Breast Cancer Cells Restoring Tamoxifen Sensitivity

Tamoxifen-resistant breast cancer cells (TamR-BCCs) are characterized by an enhanced metabolic phenotype compared to tamoxifen-sensitive cells. FoxO3a is an important modulator of cell metabolism, and its deregulation has been involved in the acquisition of tamoxifen resistance. Therefore, tetracycline-inducible FoxO3a was overexpressed in TamR-BCCs (TamR/TetOn-AAA), which, together with their control cell line (TamR/TetOn-V), were subjected to seahorse metabolic assays and proteomic analysis. FoxO3a was able to counteract the increased oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) observed in TamR by reducing their energetic activity and glycolytic rate. FoxO3a caused glucose accumulation, very likely by reducing LDH activity and mitigated TamR biosynthetic needs by reducing G6PDH activity and hindering NADPH production via the pentose phosphate pathway (PPP). Proteomic analysis revealed a FoxO3a-dependent marked decrease in the expression of LDH as well as of several enzymes involved in carbohydrate metabolism (e.g., Aldolase A, LDHA and phosphofructokinase) and the analysis of cBioPortal datasets of BC patients evidenced a significant inverse correlation of these proteins and FoxO3a. Interestingly, FoxO3a also increased mitochondrial biogenesis despite reducing mitochondrial functionality by triggering ROS production. Based on these findings, FoxO3a inducing/activating drugs could represent promising tools to be exploited in the management of patients who are refractory to antiestrogen therapy.

Understanding Lamotrigine's Role in the CNS and Possible Future Evolution

The anti-epileptic drug lamotrigine (LTG) has been widely used to treat various neurological disorders, including epilepsy and bipolar disorder. However, its precise mechanism of action in the central nervous system (CNS) still needs to be determined. Recent studies have highlighted the involvement of LTG in modulating the activity of voltage-gated ion channels, particularly those related to the inhibition of neuronal excitability. Additionally, LTG has been found to have neuroprotective effects, potentially through the inhibition of glutamate release and the enhancement of GABAergic neurotransmission. LTG's unique mechanism of action compared to other anti-epileptic drugs has led to the investigation of its use in treating other CNS disorders, such as neuropathic pain, PTSD, and major depressive disorder. Furthermore, the drug has been combined with other anti-epileptic drugs and mood stabilizers, which may enhance its therapeutic effects. In conclusion, LTG's potential to modulate multiple neurotransmitters and ion channels in the CNS makes it a promising drug for treating various neurological disorders. As our understanding of its mechanism of action in the CNS continues to evolve, the potential for the drug to be used in new indications will also be explored.

Antitumor Potential of Antiepileptic Drugs in Human Glioblastoma: Pharmacological Targets and Clinical Benefits

Glioblastoma (GBM) is characterized by fast-growing cells, genetic and phenotypic heterogeneity, and radio-chemo-therapy resistance, contributing to its dismal prognosis. Various medical comorbidities are associated with the natural history of GBM. The most disabling and greatly affecting patients' quality of life are neurodegeneration, cognitive impairment, and GBM-related epilepsy (GRE). Hallmarks of GBM include molecular intrinsic mediators and pathways, but emerging evidence supports the key role of non-malignant cells within the tumor microenvironment in GBM aggressive behavior. In this context, hyper-excitability of neurons, mediated by glutamatergic and GABAergic imbalance, contributing to GBM growth strengthens the cancer-nervous system crosstalk. Pathogenic mechanisms, clinical features, and pharmacological management of GRE with antiepileptic drugs (AEDs) and their interactions are poorly explored, yet it is a potentially promising field of research in cancer neuroscience. The present review summarizes emerging cooperative mechanisms in oncogenesis and epileptogenesis, focusing on the neuron-to-glioma interface. The main effects and efficacy of selected AEDs used in the management of GRE are discussed in this paper, as well as their potential beneficial activity as antitumor treatment. Overall, although still many unclear processes overlapping in GBM growth and seizure onset need to be elucidated, this review focuses on the intriguing targeting of GBM-neuron mutual interactions to improve the outcome of the so challenging to treat GBM.

From HDAC to Voltage-Gated Ion Channels: What's Next? The Long Road of Antiepileptic Drugs Repositioning in Cancer

Simple Summary

Although in the last decades the clinical outcome of cancer patients considerably improved, the major drawbacks still associated with chemotherapy are the unwanted side effects and the development of drug resistance. Therefore, a continuous effort in trying to discover new tumor markers, possibly of diagnostic, prognostic and therapeutic value, is being made. This review is aimed at highlighting the anti-tumor activity that several antiepileptic drugs (AEDs) exert in breast, prostate and other types of cancers, mainly focusing on their ability to block the voltage-gated Na⁺ and Ca⁺⁺ channels, as well as to inhibit the activity of histone deacetylases (HDACs), all well-documented tumor markers and/or molecular targets. The existence of additional AEDs molecular targets is highly suspected. Therefore, the repurposing of already available drugs as adjuvants in cancer treatment would have several advantages, such as reductions in dose-related toxicity CVs will be sent in a separate mail to the indicated address of combined treatments, lower production costs, and faster approval for clinical use.

Abstract

Cancer is a major health burden worldwide. Although the plethora of molecular targets identified in the last decades and the deriving developed treatments, which significantly improved patients’ outcome, the occurrence of resistance to therapies remains the major cause of relapse and mortality. Thus, efforts in identifying new markers to be exploited as molecular targets in cancer therapy are needed. This review will first give a glance on the diagnostic and therapeutic significance of histone deacetylase (HDAC) and voltage gated ion channels (VGICs) in cancer. Nevertheless, HDAC and VGICs have also been reported as molecular targets through which antiepileptic drugs (AEDs) seem to exert their anticancer activity. This should be claimed as a great advantage. Indeed, due to the slowness of drug approval procedures, the attempt to turn to off-label use of already approved medicines would be highly preferable. Therefore, an updated and accurate overview of both preclinical and clinical data of commonly prescribed AEDs (mainly valproic acid, lamotrigine, carbamazepine, phenytoin and gabapentin) in breast, prostate, brain and other cancers will follow. Finally, a glance at the emerging attempt to administer AEDs by means of opportunely designed drug delivery systems (DDSs), so to limit toxicity and improve bioavailability, is also given.

Prognostic and therapeutic significance of XPO1 in T-cell lymphoma

T-cell lymphoma (TCL) is a highly heterogeneous group of invasive non-Hodgkin lymphoma with adverse prognosis and limited treatment options. The relationship between TCL and Exportin-1 (XPO1), a major nuclear export receptor, has not been established yet. We here investigated the prognostic role and therapeutic implication of XPO1 in TCL. We analyzed XPO1 expression in a cohort of 69 TCL tumors and found that XPO1 was over-expressed in 76.8% of TCL and correlated with decreased progression-free survival (PFS) and overall survival (OS). In vitro treatment of TCL cell lines with KPT-8602, the second-generation selective inhibitor of nuclear export (SINE), inhibited XPO1 expression and showed significant anti-proliferative, cell-cycle arrest and pro-apoptotic efficacy. In mechanism, KPT-8602 restored the localization of cytoplasmic FOXO3A, p27, p21, IκBα and PP2A into the nucleus, leading to AKT and NF-κB deactivation. Our data demonstrate for the first time that XPO1 could be an unfavorable prognostic factor for TCL, and provide a rationale for further investigation of the efficacy of KPT-8602 in TCL patients.

DHW-221, a Dual PI3K/mTOR Inhibitor, Overcomes Multidrug Resistance by Targeting P-Glycoprotein (P-gp/ABCB1) and Akt-Mediated FOXO3a Nuclear Translocation in Non-small Cell Lung Cancer

Multidrug resistance (MDR) is considered as a primary hindrance for paclitaxel failure in non-small cell lung cancer (NSCLC) patients, in which P-glycoprotein (P-gp) is overexpressed and the PI3K/Akt signaling pathway is dysregulated. Previously, we designed and synthesized DHW-221, a dual PI3K/mTOR inhibitor, which exerts a remarkable antitumor potency in NSCLC cells, but its effects and underlying mechanisms in resistant NSCLC cells remain unknown. Here, we reported for the first time that DHW-221 had favorable antiproliferative activity and suppressed cell migration and invasion in A549/Taxol cells in vitro and in vivo. Importantly, DHW-221 acted as a P-gp inhibitor via binding to P-gp, which resulted in decreased P-gp expression and function. A mechanistic study revealed that the DHW-221-induced FOXO3a nuclear translocation via Akt inhibition was involved in mitochondrial apoptosis and G0/G1 cell cycle arrest only in A549/Taxol cells and not in A549 cells. Interestingly, we observed that high-concentration DHW-221 reinforced the pro-paraptotic effect via stimulating endoplasmic reticulum (ER) stress and the mitogen-activated protein kinase (MAPK) pathway. Additionally, intragastrically administrated DHW-221 generated superior potency without obvious toxicity via FOXO3a nuclear translocation in an orthotopic A549/Taxol tumor mouse model. In conclusion, these results demonstrated that DHW-221, as a novel P-gp inhibitor, represents a prospective therapeutic candidate to overcome MDR in Taxol-resistant NSCLC treatment.

FoxO3a Inhibits Tamoxifen-Resistant Breast Cancer Progression by Inducing Integrin α5 Expression

Resistance to endocrine therapy is still a major clinical challenge in the management of estrogen receptor α-positive (ERα+) breast cancer (BC). Here, the role of the Forkhead box class O (FoxO)3a transcription factor in tumor progression has been evaluated in tamoxifen-resistant BC cells (TamR), expressing lower levels of FoxO3a compared to sensitive ones. FoxO3a re-expression reduces TamR motility (wound-healing and transmigration assays) and invasiveness (matrigel transwell invasion assays) through the mRNA (qRT-PCR) and protein (Western blot) induction of the integrin α5 subunit of the α5β1 fibronectin receptor, a well-known membrane heterodimer controlling cell adhesion and signaling. The induction occurs through FoxO3a binding to a specific Forkhead responsive core sequence located on the integrin α5 promoter (cloning, luciferase, and ChIP assays). Moreover, FoxO3a failed to inhibit migration and invasion in integrin α5 silenced (siRNA) cells, demonstrating integrin α5 involvement in both processes. Finally, using large-scale gene expression data sets, a strong positive correlation between FoxO3a and integrin α5 in ERα+, but not in ER-negative (ERα-), BC patients emerged. Altogether, our data show how the oncosuppressor FoxO3a, by increasing the expression of its novel transcriptional target integrin α5, reverts the phenotype of endocrine-resistant BC toward a lower aggressiveness.

Anti-cancer potential of some commonly used drugs

Cancer is a global concern leading to millions of deaths every year. A declining trend in new drug discovery and development is becoming one of the major issues among the pharmaceutical, biotechnology industries, and regulatory agencies. New drug development is proven to be a very lengthy and costly process. The launch of a new drug takes 8-12 years and huge investments. The success rate in oncology therapeutics is also low due to toxicities at the pre-clinical and clinical trial levels. Many oncological drugs get rejected at a very promising stage, showing adverse reactions on healthy cells. Thus, exploring new therapeutic benefits of the existing, shelved drugs for their anti-cancerous action could result in a therapeutic approach preventing the toxicities which occur during clinical trials. Drug repurposing has the potential to overcome the challenges faced via conventional way of drug discovery and is becoming an area of interest for researchers and scientists. However, very few in vivo studies are conducted to prove the anti-cancerous activity of the drugs. Insufficient in vivo animal studies and a lack of human clinical trials are the lacunae in the field of drug repurposing. This review focuses on an aspect of drug repurposing for cancer therapeutics. Various studies that show that drugs approved for clinical indications other than cancer have shown promising anti-cancer activities. Some of the commonly used drugs like Benzodiazepines (Diazepam, Midzolam), Antidepressants (Imipramine, Clomipramine, and Citalopram), Antiepileptic (Valporic acid, Phenytoin), Antidiabetics (metformin), etc. have been reported to show potential activity against the cancerous cells.

Triazine Derivative as Putative Candidate for the Reduction of Hormone-Positive Breast Tumor: In Silico, Pharmacological, and Toxicological Approach

Background and objectives: Breast cancer is a heterogeneous disease that poses the highest incidence of morbidity among women and presents many treatment challenges. In search of novel breast cancer therapies, several triazine derivatives have been developed for their potential chemotherapeutic activity. This study aims to evaluate the N-nitroso-N-methyl urea (NMU)-induced anti-mammary gland tumor activity of 2,4,6 (O-nitrophenyl amino) 1,3,5-triazine (O-NPAT). Methods: The in silico modeling and in vitro cytotoxicity assay were performed to strengthen the research hypothesis. For in vivo experimentation, 30 female rats were divided into five groups. Group I (normal control) received normal saline. Group II (disease control) received NMU (50 mg/kg). Group III (standard control) was treated with tamoxifen (5 mg/kg). Groups IV and V received O-NPAT at a dose level of 30 and 60 mg/kg, respectively. For tumor induction, 3 intraperitoneal doses of NMU were given at a 3-week interval, whereas all treatment compounds were administered orally for 14 consecutive days. Biochemical and oxidative stress markers were estimated for all experimental animals. DNA strand breakage alongside inflammatory markers was also measured for the analysis of inflammation. The hormonal profile of progesterone and estrogen was also estimated. Results: The test compound presented a significant reduction in organ weight and restored the hepatic and renal enzymes. O-NPAT treatments enhanced the antioxidant enzyme level of catalase (CAT), superoxide dismutase (SOD), and total sulfhydryl (TSH), with a highly significant reduction in lactate dehydrogenase (LDH) and lipid peroxidation. Also, the decrease in fragmented DNA, hormonal levels (estradiol and progesterone), and inflammatory cytokines (IL-6 and TNF-α) justified the dosage efficacy further supported by histopathological findings. Conclusion: All results indicated the anti-breast tumor activity of O-NPAT and presented its possibility of exploitation for beneficial effects in breast cancer treatment.

Schiff-Based Metal Complexes of Lamotrigine: Design, Synthesis, Characterization, and Biological Evaluation

In the current study, a series of Schiff base derivatives of lamotrigine are complexed with zinc, copper, silver, and tin and characterized by spectroscopic techniques and biological assays. Docking analyses revealed six complexes with favorable binding interactions, which were further subjected to in vitro anticancer activity. The complexes 6b and 6c displayed the most potent antiproliferative activity against MCF-7 cell lines with an IC₅₀ value of 11.9 ± 0.27 and 12.0 ± 0.14 μM, respectively, as compared with the standard doxorubicin with an IC₅₀ value of 0.90 ± 0.14 μM. In vivo anticonvulsant activities of the compounds were evaluated by the subcutaneous pentylenetetrazole model and neurotoxic activities by the minimal motor impairment model. The neurotoxicity of targeted compounds was measured using the rotating rod (ROT) method. Computational studies were carried out using the reported crystal structures of multidrug-resistant protein (PDB-ID: 2KAV) and dihydrofolate reductase (PDB-ID: 3GHW), indicating that the compound 6c showed significant interactions at the voltage-gated sodium ion channel in the brain and at dihydrofolate reductase enzyme in the breast. Certain metal complexes of Schiff base ligands (e.g., 6c) were found to possess the most potent anticancer, anticonvulsant, and neurotoxic potential than lamotrigine alone.

Targeting the pH Paradigm at the Bedside: A Practical Approach

The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but rather an essential process in the physiopathology of accelerated proliferation and invasion. From the over-simplification of increased lactate production as the cause of the paradigm, as initially proposed, basic science researchers have arrived at highly complex and far-reaching knowledge, that substantially modified that initial belief. These new developments show that the paradigm entails a different regulation of membrane transporters, electrolyte exchangers, cellular and membrane enzymes, water trafficking, specialized membrane structures, transcription factors, and metabolic changes that go far beyond fermentative glycolysis. This complex world of dysregulations is still shuttered behind the walls of experimental laboratories and has not yet reached bedside medicine. However, there are many known pharmaceuticals and nutraceuticals that are capable of targeting the pH paradigm. Most of these products are well known, have low toxicity, and are also inexpensive. They need to be repurposed, and this would entail shorter clinical studies and enormous cost savings if we compare them with the time and expense required for the development of a new molecule. Will targeting the pH paradigm solve the "cancer problem"? Absolutely not. However, reversing the pH inversion would strongly enhance standard treatments, rendering them more efficient, and in some cases permitting lower doses of toxic drugs. This article's goal is to describe how to reverse the pH gradient inversion with existing drugs and nutraceuticals that can easily be used in bedside medicine, without adding toxicity to established treatments. It also aims at increasing awareness among practicing physicians that targeting the pH paradigm would be able to improve the results of standard therapies. Some clinical cases will be presented as well, showing how the pH gradient inversion can be treated at the bedside in a simple manner with repurposed drugs.

Production of Plant-Derived Oleuropein Aglycone by a Combined Membrane Process and Evaluation of Its Breast Anticancer Properties

Natural products and herbal therapies represent a thriving field of research, but methods for the production of plant-derived compounds with a significative biological activity by synthetic methods are required. Conventional commercial production by chemical synthesis or solvent extraction is not yet sustainable and economical because toxic solvents are used, the process involves many steps, and there is generally a low amount of the product produced, which is often mixed with other or similar by-products. For this reason, alternative, sustainable, greener, and more efficient processes are required. Membrane processes are recognized worldwide as green technologies since they promote waste minimization, material diversity, efficient separation, energy saving, process intensification, and integration. This article describes the production, characterization, and utilization of bioactive compounds derived from renewable waste material (olive leaves) as drug candidates in breast cancer (BC) treatment. In particular, an integrated membrane process [composed by a membrane bioreactor (MBR) and a membrane emulsification (ME) system] was developed to produce a purified non-commercially available phytotherapic compound: the oleuropein aglycone (OLA). This method achieves a 93% conversion of the substrate (oleuropein) and enables the extraction of the compound of interest with 90% efficiency in sustainable conditions. The bioderived compound exercised pro-apoptotic and antiproliferative activities against MDA-MB-231 and Tamoxifen-resistant MCF-7 (MCF-7/TR) cells, suggesting it as a potential agent for the treatment of breast cancer including hormonal resistance therapies.

Targeting Ion Channels for Cancer Treatment: Current Progress and Future Challenges

Ion channels are key regulators of cancer cell pathophysiology. They contribute to a variety of processes such as maintenance of cellular osmolarity and membrane potential, motility (via interactions with the cytoskeleton), invasion, signal transduction, transcriptional activity and cell cycle progression, leading to tumour progression and metastasis. Ion channels thus represent promising targets for cancer therapy. Ion channels are attractive targets because many of them are expressed at the plasma membrane and a broad range of existing inhibitors are already in clinical use for other indications. However, many of the ion channels identified in cancer cells are also active in healthy normal cells, so there is a risk that certain blockers may have off-target effects on normal physiological function. This review describes recent research advances into ion channel inhibitors as anticancer therapeutics. A growing body of evidence suggests that a range of existing and novel Na⁺, K⁺, Ca²⁺ and Cl^- channel inhibitors may be effective for suppressing cancer cell proliferation, migration and invasion, as well as enhancing apoptosis, leading to suppression of tumour growth and metastasis, either alone or in combination with standard-of-care therapies. The majority of evidence to date is based on preclinical in vitro and in vivo studies, although there are several examples of ion channel-targeting strategies now reaching early phase clinical trials. Given the strong links between ion channel function and regulation of tumour growth, metastasis and chemotherapy resistance, it is likely that further work in this area will facilitate the development of new therapeutic approaches which will reach the clinic in the future.

Repurposing of drugs: An attractive pharmacological strategy for cancer therapeutics

Human malignancies are one of the major health-related issues though out the world and anticipated to rise in the future. The development of novel drugs/agents requires a huge amount of cost and time that represents a major challenge for drug discovery. In the last three decades, the number of FDA approved drugs has dropped down and this led to increasing interest in drug reposition or repurposing. The present review focuses on recent concepts and therapeutic opportunities for the utilization of antidiabetics, antibiotics, antifungal, anti-inflammatory, antipsychotic, PDE inhibitors and estrogen receptor antagonist, Antabuse, antiparasitic and cardiovascular agents/drugs as an alternative approach against human malignancies. The repurposing of approved non-cancerous drugs is an effective strategy to develop new therapeutic options for the treatment of cancer patients at an affordable cost in clinics. In the current scenario, most of the countries throughout the globe are unable to meet the medical needs of cancer patients because of the high cost of the available cancerous drugs. Some of these drugs displayed potential anti-cancer activity in preclinic and clinical studies by regulating several key molecular mechanisms and oncogenic pathways in human malignancies. The emerging pieces of evidence indicate that repurposing of drugs is crucial to the faster and cheaper discovery of anti-cancerous drugs.

Epileptogenesis and oncogenesis: An antineoplastic role for antiepileptic drugs in brain tumours?

The first description of epileptic seizures due to brain tumours occurred in 19th century. Nevertheless, after over one hundred years, scientific literature is still lacking on how epilepsy and its treatment can affect tumour burden, progression and clinical outcomes. In patients with brain tumours, epilepsy dramatically impacts their quality of life (QoL). Even antiepileptic therapy seems to affect tumor lesion development. Numerous studies suggest that certain actors involved in epileptogenesis (inflammatory changes, glutamate and its ionotropic and metabotropic receptors, GABA-A and its GABA-AR receptor, as well as certain ligand- and voltage-gated ion channel) may also contribute to tumorigenesis. Although some antiepileptic drugs (AEDs) are known operating on such mechanisms underlying epilepsy and tumor development, few preclinical and clinical studies have tried to investigate them as targets of pharmacological tools acting to control both phenomena. The primary aim of this review is to summarize known determinants and pathophysiological mechanisms of seizures, as well as of cell growth and spread, in patients with brain tumors. Therefore, a special focus will be provided on the anticancer effects of commonly prescribed AEDs (including levetiracetam, valproic acid, oxcarbazepine and others), with an overview of both preclinical and clinical data. Potential clinical applications of this finding are discussed.

Drug Repurposing in the Development of Anticancer Agents

BACKGROUND

Research into repositioning known drugs to treat cancer other than the originally intended disease continues to grow and develop, encouraged in part, by several recent success stories. Many of the studies in this article are geared towards repurposing generic drugs because additional clinical trials are relatively easy to perform and the drug safety profiles have previously been established.

OBJECTIVE

This review provides an overview of anticancer drug development strategies which is one of the important areas of drug restructuring.

METHODS

Repurposed drugs for cancer treatments are classified by their pharmacological effects. The successes and failures of important repurposed drugs as anticancer agents are evaluated in this review.

RESULTS AND CONCLUSION

Drugs could have many off-target effects, and can be intelligently repurposed if the off-target effects can be employed for therapeutic purposes. In cancer, due to the heterogeneity of the disease, often targets are quite diverse, hence a number of already known drugs that interfere with these targets could be deployed or repurposed with appropriate research and development.

FoxO3a as a Positive Prognostic Marker and a Therapeutic Target in Tamoxifen-Resistant Breast Cancer

Background: Resistance to endocrine treatments is a major clinical challenge in the management of estrogen receptor positive breast cancers. Although multiple mechanisms leading to endocrine resistance have been proposed, the poor outcome of this subgroup of patients demands additional studies. Methods: FoxO3a involvement in the acquisition and reversion of tamoxifen resistance was assessed in vitro in three parental ER+ breast cancer cells, MCF-7, T47D and ZR-75-1, in the deriving Tamoxifen resistant models (TamR) and in Tet-inducible TamR/FoxO3a stable cell lines, by growth curves, PLA, siRNA, RT-PCR, Western blot, Immunofluorescence, Transmission Electron Microscopy, TUNEL, cell cycle, proteomics analyses and animal models. FoxO3a clinical relevance was validated in silico by Kaplan–Meier survival curves. Results: Here, we show that tamoxifen resistant breast cancer cells (TamR) express low FoxO3a levels. The hyperactive growth factors signaling, characterizing these cells, leads to FoxO3a hyper-phosphorylation and subsequent proteasomal degradation. FoxO3a re-expression by using TamR tetracycline inducible cells or by treating TamR with the anticonvulsant lamotrigine (LTG), restored the sensitivity to the antiestrogen and strongly reduced tumor mass in TamR-derived mouse xenografts. Proteomics data unveiled novel potential mediators of FoxO3a anti-proliferative and pro-apoptotic activity, while the Kaplan–Meier analysis showed that FoxO3a is predictive of a positive response to tamoxifen therapy in Luminal A breast cancer patients. Conclusions: Altogether, our data indicate that FoxO3a is a key target to be exploited in endocrine-resistant tumors. In this context, LTG, being able to induce FoxO3a, might represent a valid candidate in combination therapy to prevent resistance to tamoxifen in patients at risk.