We report a highly useful pseudo-complementary G•C base pair based on electrostatic repulsion between preQ1 and G-clamp. While pseudo-complementary (pc) PNA oligomers containing preQ1•G-clamp base pairs suppressed PNA homoduplex formation, they formed very stable PNA-DNA heteroduplexes. We demonstrated that double-duplex invasion proceeded with 100% efficiency when less than 2 equivalents of pcPNAs were used under low salt conditions, and furthermore, an invasion efficiency of 97-100% was achieved under physiological salt conditions and at 37 °C by using a larger amount of pcPNAs.
A series of twenty-one 6-(2-hydroxybenzoyl)pyrazolo[1,5-a]pyrimidine-3‑carbonitrile derivatives (HBPs), incorporating a pyrazolo[1,5-a]pyrimidine scaffold with a Michael acceptor moiety, were designed and synthesized as novel reactive oxygen species (ROS)-generating anticancer agents. Following structural characterization via NMR and mass spectrometry, anti-proliferative screening in EGFR-mutant (L858R/T790M) H1975 non-small cell lung cancer cells identified HBP-10 as the hit compound. Molecular docking predicted favorable binding of HBP-10 to the active site of glutathione S-transferase P (GST-P). In order to evaluate the stability of the HBP-10-GST-P complex, molecular dynamics simulations were carried out. Mechanistic studies demonstrated that HBP-10 induces intracellular ROS accumulation, triggering endoplasmic reticulum stress, DNA damage, and caspase-dependent apoptosis. Notably, scavenging ROS with N-acetylcysteine markedly attenuated these cytotoxic effects, confirming ROS generation as the upstream mediator of cell death. In conclusion, these findings establish HBP-10 as a highly promising anticancer hit compound for the development of next-generation therapeutic agents, targeting ROS-mediated cellular stress in EGFR-mutant NSCLC.
The parent 15-mer peptide exhibited no activity against Pseudomonas aeruginosa. Previous studies demonstrated that neither all-hydrocarbon stapling (i, i + 4 octenyl bridge) nor divinylpyrimidine exogenous linker cyclization conferred anti-P. aeruginosa activity upon this sequence. In the present study, this peptide served as a template for computer-assisted truncation to a 13-mer (CSP0), followed by amino acid substitution and the introduction of an i, i + 7 lactam bridge on the predicted α-helical face to afford the cyclic peptide CSP2. CSP2 exhibited potent antibacterial activity, with MICs of 8 μg/mL against P. aeruginosa ATCC 27853 (>16-fold improvement over the linear precursor CSP1), 4 μg/mL against Acinetobacter baumannii BNCC 337173 (16-fold), and 4 μg/mL against Staphylococcus aureus (8-fold). Time-kill assays revealed rapid bactericidal kinetics against P. aeruginosa (bactericidal endpoint at 2× MIC within 2 h) and dose-dependent activity against S. aureus (up to 4 log10 reduction at 4× MIC within 4 h). The minimum hemolytic concentration (MHC) was 50 μg/mL, and the 50% hemolytic concentration (HC50) exceeded 100 μg/mL, affording a therapeutic index (TI = HC50/MIC) against A. baumannii of >25. N-terminal acylation of CSP2 further enhanced antibacterial activity, with CSP2-2 exhibiting particular potency against S. aureus ST9, achieving a MIC of 4 μg/mL-a 16-fold improvement over CSP2-and a MIC of 16 μg/mL against Listeria monocytogenes ATCC13932 (4-fold). However, this augmented efficacy was concomitant with significantly elevated hemolytic toxicity; consequently, the overall therapeutic indices of the acylated derivatives failed to surpass those of CSP2.
Aberrant epigenetic regulation of microRNAs and their targets contributes to colorectal cancer (CRC) progression. This study examined the methylation-dependent regulation of the miR-124-KITENIN axis and its clinical significance in CRC. Site‑specific hypermethylation within the KITENIN (VANGL1) locus, particularly at cg00819310, was associated with poorer patient survival. miR-124, a direct negative regulator of KITENIN, was frequently hypermethylated and transcriptionally silenced, leading to KITENIN upregulation. Treatment with 5-aza-2'-deoxycytidine restored miR-124 expression and reduced KITENIN levels in CRC cells. These results demonstrate that miR-124 silencing enhances KITENIN activation and CRC progression, supporting miR-124 methylation as a potential prognostic and therapeutic target.
Exosomes are nano-sized extracellular vesicles loaded with bioactive cargo that mediate intercellular communication. Their emerging role in tissue regeneration has garnered increasing attention, especially in the context of peripheral nerve injury (PNI), which poses a significant therapeutic challenge. Although many studies have explored exosome-based therapies for PNI, the findings are often fragmented and lack a comprehensive synthesis. This systematic review aims to synthesize the current evidence and elucidate the molecular mechanisms through which exosomes contribute to neural regeneration. This systematic review, conducted in accordance with PRISMA 2020 guidelines, included 33 eligible studies identified through Scopus, ScienceDirect, PubMed, and Google Scholar. Exosomes derived from diverse cellular sources were assessed for their capacity to enhance repair outcomes. Reported cargo, including miRNAs and neurotrophic factors, has been shown to activate key signaling pathways that promote neurite outgrowth, modulate Schwann cell and immune responses, stimulate angiogenesis, and activate perineurial cells. By orchestrating these processes, exosomes emerge as a promising therapeutic strategy to enhance nerve regeneration and functional recovery.
Cardiac fibrosis is a major driver of heart failure and a key therapeutic target. Here, we demonstrated the role of atonal homologue 8 (ATOH8) in the modulation of cardiac fibrosis in heart failure. The expression of ATOH8 was significantly reduced in patients with heart failure and in the left ventricular tissues of model mice. ATOH8 silencing resulted in the worsening of fibrosis, and adenovirus- induced overexpression of ATOH8 attenuated the progression of cardiac fibrosis under in vitro conditions. RNA sequencing analysis demonstrated that ATOH8 potentially influences cardiac fibrosis by modulating the TGF-/Smad signaling pathway. This was verified through ATOH8 silencing experiments, which showed a marked reduction in the expression of Smad7-a known inhibitor of fibrosis. Further investigation into the molecular mechanisms via immunoprecipitation mass spectrometry indicated that ATOH8 can directly bind to the transcription factor RUNX2, which was found to directly interact with the promoter region of Smad7 to suppress its expression. Accordingly, ATOH8 silencing was found to enhance RUNX2-mediated transcriptional repression of Smad7. The findings collectively imply that ATOH8 attenuates cardiac fibrosis through the RUNX2/Smad7 axis, although interactions with other fibrotic proteins need to be explored further. Through in vivo experiments in model mice of heart failure, we were able to demonstrate that the targeted overexpression of ATOH8 in fibroblasts via adeno-associated virus-9 carrying periostin significantly alleviated cardiac fibrosis and dysfunction induced by transverse aortic constriction surgery. Thus, the findings presented here indicate that ATOH8 potentially represents a novel biomarker and therapeutic target for the attenuation of cardiac fibrosis.
Peripheral nerve injury (PNI) causes rapid disruption of neuromuscular connectivity, leading to sarcopenia characterized by muscle wasting, mitochondrial dysfunction, and metabolic imbalance. Although calcium dysregulation and aberrant AMPK/mTOR signaling are known contributors, the molecular cascade linking nerve injury to muscle degeneration remains incompletely understood. This review explores pharmacological and molecular strategies to restore neuromuscular integrity after PNI. We focus on agents such as 4-aminopyridine (4-AP), a potassium channel blocker that enhances nerve conduction, and clemastine, an antihistamine that promotes Schwann cell-mediated remyelination. These compounds represent a potential dual approach to accelerating nerve repair while maintaining muscle viability. We also explore muscle-centered molecular strategies, focusing on pathways such as Forkhead box protein O (FOXO), Glycogen synthase kinase 3 beta (GSK-3β), signal transducer and activator of transcription 3 (STAT3), and TGF-β/Smad, which govern the balance between protein synthesis and degradation. Of note, most current studies suggest that phytochemicals derived from marine sources, including seaweed, may attenuate denervation-induced catabolism by modulating FOXO signaling and suppressing E3 ubiquitin ligase activity. Additionally, we highlight the critical crosstalk between motor neurons and skeletal muscle, mediated by neurotrophic factors such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and Neurotrophin-3 (NT-3), which support both neuromuscular junction stability and axonal regrowth. By integrating insights from nerve biology and muscle physiology, this review outlines a therapeutic framework that targets both nerve regeneration and muscle preservation, an approach that effectively addresses nerve injury-induced sarcopenia effectively.
Repeated morphine administration for managing persistent pain frequently induces both physical and psychological dependence, accompanied by alterations in cortical gene expression. To elucidate the molecular underpinnings of morphine dependence, gene expression in the frontal cortex of mice subjected to acute and chronic morphine treatment was profiled using microarray analysis and validated by semi-quantitative PCR. Genes including Drd2, Adora2a, Olfr767, Egr2, Gng7, and Gpr6 were upregulated following both acute and chronic morphine treatment. Gene ontology analysis revealed significant enrichment of differentially expressed genes in membrane components, GPCR signaling pathways, and neurological system processes, indicating integrated alterations in receptor-mediated signaling and downstream transcriptional regulation. Consistent with this, selective phosphorylation of CREB was observed during naloxone-precipitated withdrawal, highlighting CREB-dependent transcription as a key molecular correlate of cortical neuroadaptation. Behavioral assays confirmed robust physical and psychological dependence, supporting the functional relevance of these molecular changes. Collectively, these findings identify a GPCR-centered molecular framework in which coordinated regulation and functional interaction of receptors such as DRD2 and ADORA2A, along with associated signaling components, contribute to morphine-induced neuroplasticity and dependence. These insights may provide a foundation for the development of targeted therapeutic strategies to mitigate opioid dependence.
Maslinic acid, a triterpenoid isolated from Olea europaea L., has been reported to exert anti-tumor and anti-inflammatory effects. Previous studies have shown that maslinic acid promotes skeletal muscle hypertrophy via mTORC1 and TGR5 signaling. Here, we examined the effects of maslinic acid on obesity-associated skeletal muscle atrophic changes and adipose tissue dysfunction. Male C57BL/6 mice were fed a high-fat diet (HFD) to induce obesity and subsequently received maslinic acid via intraperitoneal injection. In parallel, differentiated C2C12 myotubes were exposed to palmitic acid to induce lipotoxic stress-associated atrophic changes and were treated with maslinic acid to examine related cellular responses. Maslinic acid increased gastrocnemius muscle weight and attenuated obesity-associated myofiber atrophic changes in HFD-fed mice. In skeletal muscle, maslinic acid treatment was associated with increased myosin IIa expression and AKT phosphorylation, reduced expression of the atrophy-related proteins MuRF1 and Atrogin-1, and changes in mitochondrial morphology and mitochondrial dynamics-related protein expression, including increased mitofusin-2 expression and decreased phosphorylation of dynamin-related protein 1 (DRP1). Consistently, in palmitic acid-treated C2C12 myotubes, maslinic acid treatment was associated with increased myosin IIa and mitofusin-2 levels and reduced MuRF1, Atrogin-1, and DRP1 phosphorylation. In addition, maslinic acid reduced epididymal fat mass in obese mice and altered macrophage-associated marker expression in epididymal adipose tissue. Collectively, these findings suggest that maslinic acid may ameliorate obesity-associated skeletal muscle atrophic changes and adipose tissue dysfunction, accompanied by reduced adiposity and treatment-associated changes in atrophy-related, mitochondrial dynamics-related, and macrophage-associated marker expression.
Citrus nippokoreana, a traditional Korean citrus species, is rich in flavonoids and polyphenols with antioxidant properties; however, its neuroprotective potential remains unclear. Neurodegeneration is closely associated with oxidative stress, neuronal apoptosis, and impaired synaptic signaling. In this study, we investigated the effects of C. nippokoreana peel extract (CNE, 30% ethanol) using in vitro and in vivo models. CNE significantly protected HT22 hippocampal neurons against glutamate-induced oxidative stress by reducing intracellular reactive oxygen species (ROS) and apoptosis, while regulating AKT/Nrf2-associated antioxidant pathways and enhancing BDNF/CREB signaling. In a scopolamine-induced mouse model, oral administration of CNE (50 or 100 mg/kg/day) improved cognitive performance in behavioral tests. CNE also restored the expression of BDNF, CREB, and HO-1, and reduced acetylcholinesterase activity in the hippocampus. Histological analysis confirmed reduced neuronal damage. Furthermore, serum metabolomics revealed modulation of tryptophan metabolism, phosphatidylcholine species, and redox-related pathways. To explore constituents potentially contributing to the neuroprotective effects of CNE, major compounds identified by phytochemical profiling were screened in glutamate-induced HT22 cells. Several phytochemicals exhibited protective effects, suggesting that the biological activity of CNE may result from the combined actions of multiple constituents rather than a single compound. These findings suggest that CNE attenuates oxidative stress-induced neuronal damage and improves cognitive function through coordinated regulation of antioxidant defense, neurotrophic signaling, and cholinergic function.
Plastics are globally recognized as widely used materials, but once discarded, they undergo physical and chemical decomposition, forming micro- and nano-sized particles that lead to adverse effects. Therefore, this study aimed to explore the impact of nanoplastics on immune cells and overall health. Experiments conducted with 100 nm polystyrene nanoparticles (PS-NPs) revealed a decrease in the proliferation of splenic CD4+ T cells, demonstrated by using the MTT assay, carboxyfluorescein succinimidyl ester dilution assay, Ki-67 staining, cell cycle analysis, and mTOR signaling pathway analysis. Furthermore, the differentiation of naïve CD4+ T cells into four CD4+ subsets (Th1, Th2, Th17, Treg cells) appeared to be reduced. PS-NPs were found to suppress the maturation of bone marrow-derived dendritic cells, as evidenced by a decrease in the expression of CD40, CD80, CD86, and major histocompatibility complex class II molecules, following lipopolysaccharide activation, which also reduced the division of T cells. PS-NPs interfered with the immune modulation of bone marrow-derived macrophages (BMDMs), which affected the differentiation of BMDMs into M1 or M2 macrophages. To investigate the in vivo effect of PS-NPs on immune cell development further, 3-week-old mice were administered water containing PS-NPs for 3 weeks. Subsequent analysis of various immune cells in the thymus, bone marrow, and spleen revealed a decrease in cell numbers in the spleen following PS-NP treatment, as well as changes in the composition of conventional dendritic cells, macrophages, and B cells. These findings suggest that PS-NPs can perturb immune cell-associated responses and homeostasis.
Hepatocellular carcinoma (HCC) is primarily caused by hepatitis B virus (HBV). The pyrimidine-salvage pathway (PSP) is crucial for tumor proliferation, but its prognostic and immunomodulatory roles in HBV-HCC are unclear. By using single-cell transcriptomics, we investigated PSP signatures and their link to clinical outcomes and immune modulation in HBV-HCC. Data from XENA and GEO databases were analyzed. Malignant cell subpopulations were identified, and single-cell PSP activity was quantified. HBV-specific malignant subpopulations were characterized using the Ro/e metric. Cell-cell communication was analyzed. A prognostic model was developed and validated using a training cohort, and a nomogram was constructed. Immune infiltration, drug sensitivity, and the functional role of ferritin light chain (FTL) were examined experimentally. Malignant cells were classified into HBV⁻ and HBV⁺ subpopulations. The HBV⁺ group showed low PSP gene (PSPG) expression. The six-gene prognostic model demonstrated high predictive accuracy for 1-, 3-, and 5-year survival. High-risk patients had shorter survival and increased infiltration of macrophages, Tregs, and activated dendritic cells. Drug sensitivity analysis identified potential agents. In vitro, FTL silencing suppressed HBV-HCC cell proliferation and migration. This investigation clarified the prognostic significance of PSPGs and their immunomodulatory roles in HBV-HCC, and established a prognostic model with predictive power. FTL, identified as a key gene, represented a potential therapeutic target for HBV-HCC. These findings provided a novel theoretical foundation for the treatment of HBV-HCC.
Thyroid cancer is one of the most prevalent malignancies of the endocrine system, comprising various subtypes such as papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), medullary thyroid carcinoma (MTC), and the aggressive anaplastic thyroid carcinoma (ATC). Despite a generally favorable prognosis for PTC, recurrence, metastasis, and resistance to conventional therapies continue to pose significant challenges. The pathogenesis of thyroid cancer involves genetic mutations in BRAF, RAS, and RET, as well as dysregulated molecular pathways such as MAPK, PI3K/Akt/mTOR, and NF-κB, all of which contribute to cancer progression and therapeutic resistance. This review highlights how Traditional Chinese Medicine (TCM), with its extensive history and a diverse range of bioactive compounds derived from natural sources, offers a complementary approach to thyroid cancer treatment. TCM has been shown to modulate various cellular mechanisms, including inhibiting tumor proliferation, inducing apoptosis, and regulating immune responses. Additionally, TCM can influence the tumor microenvironment (TME), reducing immune evasion and improving therapeutic sensitivity. Many TCM compounds have been identified for their ability to target critical oncogenic signaling pathways, offering a holistic approach to cancer treatment with fewer side effects than traditional chemotherapy. Furthermore, integrating TCM with modern medicine, including novel formulations and nanotechnology, offers the potential to improve efficacy and reduce side effects. The convergence of Artificial Intelligence (AI) and Systems Biology also holds great promise for optimizing personalized treatment regimens and advancing targeted therapies, ultimately improving patient outcomes in thyroid cancer management.
While chemoresistance in non-small cell lung cancer (NSCLC) cells has historically been attributed to permanent genetic mutations, emerging evidence highlights the role of nongenetic transcriptional plasticity and 'drug-tolerant persister' cells. To systematically map these epigenetic vulnerabilities, we utilized a genome-wide CRISPR interference library to screen wild-type TP53 NSCLC (A549) cells under carboplatin selection. Using the DrugZ algorithm and subsequent pathway enrichment analyses, this screen revealed that transcriptional suppression of interstrand crosslink DNA repair networks, including the Fanconi anemia pathway, markedly sensitized cells to carboplatin. Unexpectedly, transcriptional silencing of TP53 and its downstream target CDKN1A emerged as the strongest drivers of resistance, enabling cells to bypass therapy-induced senescence and maintain their proliferative potential later. To validate these findings in a clinically relevant context, we established a chronic carboplatin-resistant cell model (A549CarboR cells). A549CarboR exhibited a reduction in TP53 transcripts, along with decreased H3K27 acetylation and increased DNA hypermethylation on its promoter. Epigenetic remodeling using the DNA methyltransferase inhibitor (DNMTi) was associated with unblocking TP53 transcription, restored p53 signaling, and resensitization of resistant cells to carboplatin. Conversely, histone deacetylase inhibitors induced CDKN1A transcription to bypass TP53, indicating distinct epigenetic circuits. Collectively, the results demonstrate for the first time that TP53 expression is dynamically regulated at the transcriptional level through promoter methylation related to the drug tolerance. These insights emphasize that epigenetic silencing, rather than exclusive genetic loss-of-function, contribute to platinum resistance and underscore the therapeutic potential of pairing platinum regimens with DNMTi to target the transcriptomic plasticity of persistent cancer cell populations.
Colorectal cancer (CRC) remains a major cause of cancer-related mortality due to therapeutic resistance. Because colorectal cancer stem-like cells (CRCSCs) play a central role in tumor initiation and progression, therapeutic strategies addressing CSC-enriched populations are urgently needed. In this study, we investigated the anticancer effects of emodin, a natural anthraquinone, in CSC-enriched tumorsphere models. Emodin significantly suppressed the viability and self-renewal capacity of HCT116- and SW480-derived CSCs. It induced G0/G1 cell cycle arrest and markedly downregulated stemness-associated markers (CD44, CD133, ALDH1A1, SOX2, NANOG, and OCT4). Importantly, emodin-induced cell death was characterized by mitochondrial dysfunction, increased mitochondrial reactive oxygen species, loss of membrane potential, and nuclear translocation of apoptosis-inducing factor (AIF). This cytotoxicity was not rescued by the pan-caspase inhibitor Z-VAD-FMK, confirming caspase-independent apoptosis. Furthermore, network pharmacology and experimental validation identified GSK3β as a key target. Emodin reduced Wnt/β-catenin signaling by decreasing β-catenin stabilization and nuclear accumulation. Crucially, a rescue experiment utilizing LiCl confirmed that emodin's suppressive effects are mechanistically dependent on the GSK3β/Wnt/β-catenin axis. Collectively, emodin suppresses CRCSC characteristics in vitro by downregulating Wnt/β-catenin signaling and inducing AIF-associated caspase-independent apoptosis, highlighting its therapeutic potential against CRC.
Metabolic dysfunction-associated steatohepatitis (MASH) is characterized by lipotoxic hepatocellular injury, inflammation, and fibrosis, with excess hepatic cholesterol contributing to disease pathogenesis. While the SCAP-INSIG-SREBP2 pathway classically regulates cholesterol biosynthetic gene expression via sterol sensing at the endoplasmic reticulum, the epigenetic mechanisms coupling cellular sterol status to gene expression remain unclear. Here, we investigated the role of sirtuin 6 (SIRT6), a nuclear histone deacetylase, in sterol-induced feedback regulation of cholesterol biosynthetic genes in hepatocytes. In HepG2 and AML12 cells, 25-hydroxycholesterol (25-HC) reduced the expression of SREBP2 and downstream cholesterol biosynthetic genes, including HMGCR and HMGCS1. This repression was associated with SIRT6 activation, as evidenced by reduced acetylation of histone H3 lysine 9 and lysine 56. Pharmacological SIRT6 inhibition reversed the repression of cholesterol biosynthetic genes, whereas SIRT6 activators phenocopied the inhibitory effects of 25-HC on the SREBP2 pathway. Conversely, sterol depletion via lovastatin inhibited SIRT6 activity, leading to the compensatory upregulation of cholesterol biosynthetic genes. Notably, SIRT6 overexpression or pharmacological activation reversed lovastatin-induced upregulation of SREBP2 and its target genes. These findings establish SIRT6 as a sterol-responsive nuclear regulator that converts intracellular cholesterol status into epigenetic repression of the cholesterol biosynthetic program. This SIRT6-dependent pathway complements endoplasmic reticulum-based sterol sensing and provides a mechanistic insight into hepatic cholesterol dysregulation in MASH.
Alzheimer's disease (AD) is a neurodegenerative disorder with intricate pathogenic factors. Multi-target drug design offers a promising approach to address AD's complex pathogenesis. α-Mangostin (α-M), a natural product with multifunctional anti-AD potential, is limited by poor aqueous solubility and bioavailability. This work employed regioselective Williamson O-alkylation to semi-synthesize three novel α-M alkylamine derivatives (1-3), enabling tunable mono- and disubstitution. In silico predictions demonstrated that disubstituted compounds 2 and 3 exhibited markedly improved blood-brain barrier permeability and oral bioavailability. While, experimental results showed that monosubstitution optimally balanced intrinsic antioxidant activity with target binding properties. Compound 1 displayed potent AChE inhibition (IC50 = 0.11 μM) with high selectivity (SI = 59.27), effectively inhibited both self-induced and AChE-induced Aβ aggregation (53.8% and 57.3%, respectively), and exhibited excellent antioxidant capacity (·OH IC50 = 0.19 μM). Meanwhile, disubstitution achieved superior BuChE inhibition by occupying both sides of the expanded active site pocket. Furthermore, 1 significantly reduced ROS levels by ∼48% in C. elegans. These results highlight the potential of tunable α-M derivatives as promising anti-AD candidates.
A series of new C30-aminated lupane analogues was prepared from betulin in three straightforward steps and evaluated for inhibitory activity against Plasmodium falciparum. Taking advantage of the Meinwald rearrangement of the terminal C20/29 racemic epoxide in acidic conditions, reductive amination of the resulting aldehyde allowed the generation of C30-aminated analogues in good yields with a significant increase of hydrophilicity. The approach avoids the use of protecting groups and is compatible with a broad range of primary and secondary amines. Screening of the seventeen synthesized C30-aminated betulin derivatives for antimalarial activity revealed that the C30-tryptamine analogue 5g exhibited good inhibitory activity against P. falciparum 3D7 and the chloroquine-mefloquine-pyrimethamine multiresistant strain P. falciparum Dd2 with IC50 values of 0.62 μM and 0.24 μM, respectively. Moreover, the compound did not cause red blood cell lysis at concentrations up to 25 μM and displayed moderate cytotoxicity with an IC50 value of 4.2 μM against human keratinocytes HaCaT cells. These results highlight the great potential of the prop-1-en-2-yl moiety on lupane triterpenoids to improve biological and physicochemical properties and support the extension of the chemical diversity at the C30 position towards new bioactive antiprotozoal betulin analogues.
Triple-negative breast cancer (TNBC) is a highly aggressive malignancy lacking effective targeted therapies. While 5-Aminolevulinic acid (5-ALA) is an FDA-approved prodrug for photodynamic therapy (PDT), its clinical efficacy against TNBC is severely restricted by poor lipophilicity and the rapid metabolic clearance of its active photosensitizer, protoporphyrin IX (PpIX), into heme. To overcome these limitations, we designed and synthesized 28 novel prodrug conjugates by covalently linking 5-ALA with the iron chelator 3-hydroxypyridinone (HPO) via an ester bond, exploring both R and S stereochemical configurations. Biological evaluations revealed that these conjugates possessed significantly improved lipophilicity and negligible dark toxicity, while exhibiting significantly enhanced phototoxicity to free 5-ALA. Notably, the R-configuration conjugates 13a and 13d emerged as the most potent candidates against MDA-MB-231 TNBC cells, demonstrating IC50 values of 51.16 ± 1.93 μM and 49.65 ± 2.50 μM, respectively (vs. >100 μM for 5-ALA). Mechanistic studies suggested that these conjugates induced nearly 4-fold higher intracellular PpIX fluorescence than 5-ALA, which is hypothesized to correlate with HPO-mediated labile iron chelation and subsequent preservation of the intracellular PpIX pool against ferrochelatase-mediated clearance. These findings highlight the promise of 5-ALA-HPO conjugates as synergistic, dual-action photosensitizers for advancing PDT in aggressive TNBC models in vitro.
