Eduarda Ribeiro

Despite its established role as a cornerstone of chemotherapy for solid tumors, 5-Fluorouracil (5-FU) clinical efficacy remains limited by chemoresistance and heterogeneous drug response. Traditional explanations have focused on intracellular metabolism and genetic determinants; however, increasing evidence identifies the plasma membrane as a critical regulatory interface controlling drug availability, signaling integration, and cell fate. Here, we propose a membrane-centered framework in which compartmentalized cAMP/PKA signaling, modulated by repurposed vasoregulatory agents—levosimendan, milrinone, and terbutaline—enhances 5-FU response by functionally remodeling the cancer cell membrane. This remodeling may influence lipid raft organization, ENT1/SLC29A1 transporter trafficking, and the balance between drug influx and efflux, increasing intracellular 5-FU bioavailability and overcoming membrane-mediated pseudo-resistance. In parallel, cAMP-dependent signaling may modulate redox homeostasis, mitochondria-associated membranes, and apoptotic threshold regulation, shifting the cellular response toward irreversible cell death. Importantly, this framework is reconciled with canonical resistance mechanisms—including TYMS upregulation, DPD overexpression, and MMR deficiency—positioning membrane phenotype as a functionally upstream regulatory layer. Differential sensitivity observed experimentally in bladder versus prostate cancer models supports the concept of integrated membrane phenotype biomarkers. Clinical translation requires rigorous pharmacokinetic–pharmacodynamic validation and cardiovascular safety assessment. Redefining the plasma membrane as a dynamic therapeutic interface may provide a rationale for drug repurposing, patient stratification, and personalized combination strategies.

Background: Clotrimazole (CLZ) is an approved antifungal with reported pleiotropic effects. Beyond its antifungal use, CLZ can perturb glycolytic flux and ionic homeostasis, motivating its evaluation as a repurposing candidate in oncology. Objective: We aimed to evaluate CLZ and nitazoxanide (NTZ) as drug repurposing candidates for pancreatic ductal adenocarcinoma (PDAC) in comparison with standard chemotherapeutics gemcitabine (GEM) and 5-fluorouracil (5-FU). Methods: T3M4 PDAC cells were treated (0.1–100 µM; 48–72 h) with 5-FU, GEM, CLZ, and NTZ. Cell viability (MTT) and morphology were assessed, and CLZ-based combinations were analyzed by the Chou–Talalay method. In silico studies provided physicochemical descriptors and ADMET profiles, along with predicted interactions with relevant bioorganic targets (e.g., KCa3.1/KCNN4 ion channels). Results: CLZ produced marked cytotoxicity at 72 h (IC₅₀ ≈ 9 µM) and achieved a greater reduction in cell viability at higher concentrations compared to 5-FU and GEM under identical conditions, whereas NTZ showed modest and inconsistent effects. CLZ combinations with 5-FU or GEM were mainly antagonistic. In silico analyses indicated high membrane permeability and suggested potential interactions with KCa3.1, supporting a hypothesis-generating interpretation of the observed in vitro effects. Conclusions: Within a drug repurposing framework, CLZ exhibited consistent cytotoxic activity as a single agent in a PDAC cell model, whereas NTZ revealed limited effects and CLZ-based combinations were not beneficial under the tested conditions. These findings position CLZ as a monotherapy-oriented repurposing candidate for PDAC and motivate further mechanistic and translational studies to clarify the biological basis of its in vitro activity.

Background/Objectives: Repurposed cAMP-elevating agents may personalize fluoropyrimidine therapy by exploiting pathway-specific vulnerabilities. Methods: We tested the PDE3 inhibitor milrinone and the β2-agonist terbutaline alone or combined with 10 μM 5-fluorouracil (5-FU) in UM-UC-5 (bladder), A549 (lung), and PC-3 (prostate) cells. Viability, migration, clonogenicity, and intracellular ROS (DCFDA) were measured; drug interactions used Chou–Talalay/CompuSyn. Results: In UM-UC-5, both agents reduced viability, migration, and clonogenicity and synergized with 5-FU (CI < 1 across Fa ≈ 0.42–0.57). 5-FU increased ROS, whereas terbutaline consistently lowered ROS below baseline and blunted 5-FU-induced oxidative signals; milrinone showed a dose-dependent redox profile without consistent ROS suppression. A549 combinations did not outperform 5-FU; PC-3 was largely unresponsive. Conclusions: cAMP modulators selectively potentiate 5-FU in bladder cancer cells and modulate redox programs (notably with terbutaline), supporting a biomarker-guided combination strategy (e.g., β2-AR/PDE3/PI3K–Akt features) for personalized therapy in bladder cancer; mechanistic and in vivo validation are warranted.

Cancer remains a leading cause of mortality worldwide, necessitating innovative therapeutic strategies. Drug repurposing offers a cost-effective approach to cancer treatment by identifying new anticancer applications for existing drugs. Terbutaline, a β2-adrenergic receptor agonist, and Milrinone, a phosphodiesterase-3 inhibitor, are traditionally used as positive inotropic agents but have shown potential anticancer effects. This review explores their mechanisms of action in cancer, focusing on their roles in modulating cyclic adenosine monophosphate (cAMP) levels, oxidative stress, and the tumor microenvironment. Terbutaline influences β2-adrenergic signaling, impacting cell proliferation, angiogenesis, and immune evasion. Milrinone, through PDE3 inhibition, elevates cAMP, promoting apoptosis and reducing tumor growth. Both agents exhibit anti-inflammatory and anti-angiogenic properties, suggesting their potential as adjuvant therapies in oncology. Despite promising preclinical data, clinical validation is required to confirm their efficacy and safety in cancer patients. This review highlights the therapeutic promise of repurposing Terbutaline and Milrinone, emphasizing the need for further research to optimize their application in cancer therapy.

The therapeutic potential of combining 5-FU with repurposed drugs such as Sildenafil, Tezosentan, Levosimendan, and Resveratrol was investigated in lung cancer treatment using the A549 cell line. This study aimed to enhance 5-FU efficacy while mitigating side effects and overcoming drug resistance. The cytotoxic effects of 5-FU were assessed via MTT assay, with an IC₅₀ value of 5.03 µM for A549 cells. Subsequent experiments evaluated the impact of combining 5-FU with the aforementioned drugs on cell viability, clonogenic potential, and morphology. The results demonstrated that while Sildenafil and Tezosentan modestly improved 5-FU efficacy, Levosimendan reduced cell viability by 40% (p < 0.01) and Resveratrol by over 50% (p < 0.001), with clonogenicity reduced by up to 60% (p < 0.001). These findings suggest that combining 5-FU with Levosimendan or Resveratrol offers promising approaches for lung cancer therapy, potentially reducing the need for higher doses of 5-FU and minimizing associated toxicity. Future studies are warranted to elucidate the mechanisms underlying these interactions and assess their clinical relevance.

Resveratrol, a naturally occurring polyphenol found in grapes, berries, and peanuts, has garnered significant attention for its potential anti-cancer properties. This review provides a comprehensive analysis of its role in cancer therapy, both as a standalone treatment and in combination with other therapeutic approaches. This review explores the molecular mechanisms underlying resveratrol’s anti-cancer effects, including its antioxidant activity, modulation of cellular signaling pathways, antiproliferative properties, anti-inflammatory effects, and epigenetic influences. This review also examines in vitro and in vivo studies that highlight resveratrol’s efficacy against various cancer types. Furthermore, the synergistic effects of resveratrol when used in conjunction with conventional treatments like chemotherapy and radiotherapy, as well as targeted therapies and immunotherapies, are discussed. Despite promising preclinical results, this review addresses the challenges and limitations faced in translating these findings into clinical practice, including issues of bioavailability and toxicity. Finally, it outlines future research directions and the potential for resveratrol to enhance existing cancer treatment regimens. This review aims to provide a thorough understanding of resveratrol’s therapeutic potential and to identify areas for further investigation in the quest for effective cancer treatments.

Backgroung: The rising complexity and associated side effects of cancer treatments highlight the need for safer and more effective therapeutic agents. Carbon-based nanomaterials such as CDs have been gaining prominence for their unique characteristics, opening avenues for diverse applications such as fluorescence imaging, drug and gene transport, controlled drug delivery, medical diagnosis, and biosensing. Despite promising advancements in research, it remains imperative to scrutinize the properties and potential cytotoxicity of newly developed CDs, ensuring their viability for these applications. Methods: We synthesized four N-doped CDs through a hydrothermal method. Cell viability assays were conducted on A549 and UM-UC-5 cancer cells at a range of concentrations and incubation times, both individually and with the chemotherapeutic agent 5-fluorouracil (5-FU). Results: The obtained results suggest that the newly developed CDs exhibit suitability for applications such as bioimaging, as no significant impact on cell viability was observed for CDs alone.

Backgroud: This study investigates the potential of vasodilator drugs as additive therapy in the treatment of urological cancers, particularly in combination with the antineoplastic agent 5-fluorouracil (5-FU). Methods: The study evaluated the cytotoxic effects of sildenafil, tezosentan and levosimendan alone and in combination with 5-FU on urological cancer cell lines. The assessment included MTT assays, colony formation assays and wound healing assays to determine cell viability, proliferative capacity, and migratory behavior, respectively. Results: Sildenafil and tezosentan showed limited cytotoxic effects, while levosimendan demonstrated moderate anticancer activity. The combination of levosimendan and 5-FU exhibited an additive interaction, enhancing cytotoxicity against cancer cells while sparing normal cells. Levosimendan also inhibited cell migration and proliferation, potentially through mechanisms involving the modulation of cAMP levels and nitric oxide production. Conclusions: The findings suggest that levosimendan can be used in conjunction with 5-FU to reduce the required dose of 5-FU, thereby minimizing side effects without compromising therapeutic efficacy. This study offers a new perspective for enhancing therapeutic outcomes in patients with urological cancers.

Prostate and bladder cancer treatments have several challenges, including intense side effects and mechanisms of resistance. Thus, it is urgent to find drugs that can fill these gaps. For this purpose, Entecavir (ETV) was tested alone and in combination with 5-Fluorouracil (5-FU). Prior to this, a preliminary computational analysis was conducted to evaluate the combination of these two drugs. After exposing PC-3 and UM-UC-5 cells to the drugs, cell morphology was assessed using a microscope, while cell viability, proliferation, and cytotoxicity were evaluated using the MTT assay, and finally, the statistical analysis was performed. It was concluded that ETV showed significant cytotoxic effects in the PC-3 cells, and 5-FU, although not as effective as in other tumor types, it managed to inhibit the viability of the PC-3 cells. The combination of 5-FU with ETV after 72 h of exposure is an advantageous association, surpassing the results of each drug alone. In the UM-UC-5 cells, ETV alone did not produce the expected effect, neither did the combination. Nevertheless, repurposing ETV has proven to be an effective strategy in PC, especially through its combination with 5-FU.

Cancer remains a significant global health challenge despite advancements in diagnosis and treatment. Traditional cancer therapies often face limitations such as toxicity and drug resistance. Drug repurposing has emerged as a promising strategy to overcome these challenges by identifying new therapeutic uses for existing drugs. This review explores the potential of repurposing positive inotropic agents, which are traditionally used in cardiovascular medicine, for cancer therapy. Positive inotropic agents, including cardiac glycosides, β-agonists, phosphodiesterase inhibitors, and calcium sensitizers have shown preclinical evidence of anti-tumor activity through various mechanisms, such as modulation of the intracellular signaling pathways, increasing cyclic adenosine monophosphate (cAMP) levels, the production of nitric oxide, and decreasing reactive oxygen species levels. Despite the absence of specific clinical trials in this area, these findings suggest a promising avenue for further research and development of combination therapies to improve cancer treatment outcomes. However, challenges such as elucidating specific anti-tumor mechanisms, identifying predictive biomarkers, and optimizing safety profiles need to be addressed to fully realize the therapeutic potential of positive inotropic agents in oncology.