Repurposing serotonergic drugs for gastric cancer: induction of apoptosis in vitro

Gastric adenocarcinoma remains a highly aggressive malignancy characterized by significant molecular heterogeneity and poor patient outcomes globally. Prior research has shown that serotonin signaling pathways often undergo dysregulation within various solid tumors, influencing cellular proliferation and survival through complex autocrine or paracrine loops. Conventional chemotherapy frequently fails to address the complex resistance mechanisms inherent in these heterogeneous gastric cell populations, leading to high recurrence rates. Identifying existing pharmacological agents with established safety profiles provides an accelerated pathway for developing novel oncological interventions via drug repurposing. Current literature suggests that modulating specific neurotransmitter receptors might trigger programmed cell death in non-neuronal tissues by altering intracellular signaling cascades. The biological role of 5-Hydroxytryptamine (5-HT) in the gastrointestinal tract extends beyond motility to include the regulation of mucosal integrity and potentially oncogenic transformation. This absence of evidence motivated the current investigation into how specific serotonergic modulators impact the viability of specialized gastric cancer lineages.

This investigation evaluates the potential of several serotonergic compounds to induce programmed cell death within the MKN-45 gastric cancer cell line. Researchers sought to determine the half-maximal inhibitory concentration (IC50) for agents including Tropisetron, Imipramine, Ketanserin, Citalopram, and Cyproheptadine to establish their relative cytotoxic potencies. The project aimed to characterize the specific molecular shifts in gene expression related to serotonin receptors and transporters following drug exposure to identify potential therapeutic targets. Quantifying the ratio between pro-apoptotic and anti-apoptotic markers served as a primary objective for assessing the therapeutic efficacy of these repurposed agents. Scientists intended to validate whether these medications could suppress the expression of Proliferating Cell Nuclear Antigen (PCNA), a vital marker for DNA replication and cell cycle progression. Understanding the intersection between neurotransmitter signaling and tumor cell survival provides a novel perspective on managing aggressive gastrointestinal malignancies. Establishing a foundation for personalized gastric cancer management through the identification of effective serotonergic candidates guided every stage of the experimental design.

The experimental protocol used the MKN-45 cell line as a robust model for studying aggressive gastric malignancy in a controlled in vitro environment. Cellular viability was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to establish precise half-maximal inhibitory concentration (IC50) values for each serotonergic compound. Morphological changes indicative of programmed cell death were visualized through Acridine Orange/Ethidium Bromide (AO/EB) dual staining techniques under fluorescence microscopy. Annexin V/Propionate Iodide (Annexin V/PI) flow cytometry provided a quantitative assessment of early and late apoptotic populations by detecting phosphatidylserine externalization. Real-time Polymerase Chain Reaction (RT-PCR) measured the transcript levels of 5-Hydroxytryptamine Receptor (HTR) subtypes, specifically HTR2A, HTR2B, and HTR3A, alongside the Serotonin Transporter (SLC6A4). Expression levels of B-cell Lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were analyzed to confirm the mitochondrial pathway of apoptosis. The researchers also monitored the expression of Proliferating Cell Nuclear Antigen (PCNA) to evaluate the anti-proliferative capacity of the selected pharmacological treatments.

Tropisetron, Imipramine, Ketanserin, and Cyproheptadine showed statistically significant induction of apoptosis in MKN-45 cells compared to untreated control groups. Quantitative analysis revealed that these four compounds markedly reduced the expression of the anti-apoptotic regulator B-cell Lymphoma 2 (Bcl-2) while simultaneously suppressing the Proliferating Cell Nuclear Antigen (PCNA). Pro-apoptotic Bcl-2-associated X protein (Bax) expression levels increased significantly following treatment, yielding a p-value of less than 0.05 across the effective drug panels, which shifted the Bax/Bcl-2 ratio toward cell death. Tropisetron and Imipramine emerged as the most potent candidates, exhibiting superior apoptotic effects and lower IC50 values relative to the other tested serotonergic agents. Citalopram did not show the same level of significant apoptotic activity as the other four repurposed medications in this specific gastric cancer cell model. The study confirmed that the observed cell death correlated with specific alterations in 5-Hydroxytryptamine Receptor 2A (HTR2A), HTR2B, and HTR3A receptor gene expression patterns within the treated cell populations. These results provide clear evidence that modulating serotonin receptors can effectively inhibit the growth of aggressive gastric adenocarcinoma cells in vitro.

These findings indicate that specific serotonergic modulators represent viable candidates for drug repurposing strategies in the context of gastric cancer therapy. The observed induction of programmed cell death suggests that serotonin signaling pathways are essential regulatory nodes for future pharmacological development in oncology. Tropisetron and Imipramine warrant prioritized attention in subsequent preclinical models due to their robust inhibitory effects on gastric cell proliferation and survival. Integrating these existing medications into oncology protocols could potentially enhance the efficacy of current treatment regimens for aggressive malignancies while reducing development costs. Future investigations should focus on the clinical safety, optimal dosing, and in vivo performance of these compounds within diverse patient populations. This research provides a preliminary framework for developing personalized therapeutic interventions based on the molecular profile of individual gastric tumors and their receptor expression. Ultimately, the study highlights the untapped potential of neurotransmitter-targeting drugs to serve as adjuvant or primary treatments for gastrointestinal cancers.