Abstract
Propolis from stingless bees is a natural resinous substance with diverse therapeutic properties, including anti-cancer activity. Despite increasing global interest, little is known about the bioactive potential of propolis from Southeast Asian stingless bees, particularly those native to Brunei Darussalam. Therefore, we investigated propolis extracts from five stingless bee species in Brunei and elucidated the underlying molecular mechanisms using transcriptomic and metabolomic profiling. Propolis extracts from Heterotrigona itama, Tetragonula melanoleuca, Tetrigona binghami, Geniotrigona thoracica, and Lepidotrigona canifrons were tested against lymphoma (U2932, HT, OCI-LY3), lung (H1975) and bladder (EJ) cancer cell lines. RNAseq and pathway enrichment analysis were performed to investigate the molecular mechanisms influenced by ethanol extracts from the three stingless bee species, H. itama, T. binghami, and T. melanoleuca on representative cell lines. Gas chromatography/mass spectrometer (GC-MS)-based metabolomics was performed for metabolite profiling of ethanol and ethyl acetate propolis extracts. Ethanol extracts elicited greater anticancer activity in general, as compared to ethyl acetate extracts. Ethanol propolis extracts from T. melanoleuca and H. itama were the most potent amongst the five stingless bee species, particularly on the lymphoma cell lines. Transcriptomic pathways involved in cell cycle progression, including E2F Targets and G2M Checkpoint, were downregulated in the EJ and H1975 cell lines, suggesting that the extracts may induce cell cycle arrest, particularly in adherent cells. MTORC1 signaling were downregulated across multiple cell lines. Interestingly, upregulation of several inflammation-related pathways, including TNFα signaling via NF-κB, Interferon Alpha Response, Interferon Gamma Response, and Inflammatory Response was observed. GC-MS analysis identified six major classes of compounds, including polyketides, phenolic acids and terpenoids, which were enriched in ethanol compared with ethyl acetate extracts. Propolis extracts from Brunei stingless bees demonstrate anti-cancer properties associated with pro-inflammatory and anti-oncogenic signalling activity. These findings support further investigation of their bioactive constituents as anti-cancer agents.
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Introduction
Stingless bee propolis is known to harbor antimicrobial, anti-inflammatory, and immune-boosting properties1. Due to their geographical distribution, stingless bee propolis is particularly utilized in tropical and subtropical regions such as Southeast Asia, Africa, and parts of Central and South America2. Indigenous cultures in these regions value stingless bee propolis for its potent medicinal properties, commonly applying it topically for wound healing and the treatment of skin infections including fungal conditions, and even snake bites3. Stingless bee propolis is also often consumed or infused in teas to support respiratory health, aid digestion, and boost general immunity4.
In recent years, a growing body of scientific research has corroborated these traditional uses, renewing interest in stingless bee propolis as a source of bioactive natural compounds and potential therapeutic agents. Among its pharmacological properties, the anti-cancer potential of stingless bee propolis is especially compelling. Campos et al. reviewed the anti-cancer potential of stingless bee propolis from Southeast Asian countries, including Thailand, Indonesia, Vietnam, India, Philippines and Malaysia, as well as other regions around the world, against multiple cancer cell lines, such as breast, lung, colon, liver, and gastric cancers5. Despite considerable research on stingless bee propolis, Brunei Darussalam remains an untapped region, particularly in cancer research1,6,7.
Here, we report the anticancer properties of propolis extracts from five stingless bee species native to Brunei Darussalam. Using transcriptomic and metabolomic profiling, we characterize the chemical composition and evaluate the anti-proliferative effects of both ethanol and ethyl acetate extracts. Our findings reveal species-specific anticancer activity, with diffuse large B-cell lymphoma (DLBCL) cell lines exhibiting the highest sensitivity, followed by lung and bladder cancer cell lines to a lesser extent.
Materials and methods
Propolis samples and extracts
Propolis samples were collected from Tasbee Meliponiculture Farm, which is a small scale stingless bee farm located in a forested village in Tutong, Brunei Darussalam (4° 49’ 2.164’’ N, 114° 45’ 49.065’’ E), specifically from five farmed stingless bee species: Heterotrigona itama, Tetrigona melanoleuca, Tetrigona binghami, Geniotrigona thoracica, and Lepidotrigona canifrons. To ensure robust metabolomic and transcriptomic analysis for each species, samples were collected from various hives. For solvent extraction, 5 g of dried propolis from each species was soaked in 50 mL of either 70% ethanol or ethyl acetate at room temperature for 48 h with constant stirring. The mixture was then filtered using Whatman No.1 filter paper, and the solvent was evaporated under reduced pressure at 40 °C using a rotary evaporator to obtain the concentrated extract. The ethanol and ethyl acetate propolis extracts were dissolved in dimethyl sulfoxide (DMSO) at a concentration of 100,000 µg/mL. The mixture was then subjected to sonication using a probe sonicator and heated at 50 °C for 30 min to ensure complete dissolution of the propolis extract. Both dissolved extracts were stored at 4 °C until further use in biological assays and chemical analyses.
Cell lines
DLBCL U2932 cell line (Catalog no. ACC 633, DSMZ, Germany) were maintained in modified RPMI supplemented with 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin-streptomycin. OCI-LY3 (Catalog no. ACC 761, DSMZ, Germany) and HT (Catalog no. CRL-2260, ATCC, VA, USA) DLBCL cell lines were maintained in modified RPMI supplemented with 20% fetal bovine serum, 1% L-glutamine, and 1% penicillin-streptomycin. Non-small cell lung cancer (NSCLC) H1975 cells (Catalog no. CRL-5908, ATCC, VA, USA) were maintained in modified RPMI supplemented with 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin-streptomycin. Bladder carcinoma EJ cells (Catalog no. 85061108, European Collection of Cell Cultures, UK) were maintained in modified RPMI supplemented with 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin-streptomycin. The cell lines were maintained in a 37 °C incubator with 5% CO2 and free from mycoplasma contamination. The cell lines were selected for initial screening for practical purposes as these were readily available in our lab.
Assessment of cell viability
5000 cells were seeded in 96-well plates. After 24 h, five varying dosages of propolis extracts (70 µg/mL, 50 µg/mL, 25 µg/mL, 10 µg/mL, 1 µg/mL) were added to the seeded cells. After 8 to 72 h of treatment, cell viability was determined using CellTiter-Glo® Luminescent Cell Viability Assay (Promega, WI, USA) as per the manufacturer’s instructions. Two cell lines H1975 and U2932 were treated with osimertinib and doxorubicin (Selleck Chemicals, USA), respectively, for 72 h. Peripheral blood mononuclear cells (PBMC) from a healthy individual were used to evaluate cytotoxicity of the propolis extracts. IC50 values were calculated using GraphPad Prism 9 (GraphPad, MA, USA). Three biological replicates were performed, as a balance between statistical power, resource constraints, and biological variability.
SDS-PAGE and Western blot
Whole cell lysates were subjected to separation using SDS-PAGE with 4–15% Mini-PROTEAN™ TGX Stain-Free™ Protein Gels (Bio-Rad Laboratories, Hercules, CA, USA) and then transferred onto 0.2 μm PVDF membranes (Bio-Rad Laboratories, Hercules, CA, USA). After blocking for 1 h with 5% non-fat dry milk (Bio-Rad Laboratories, Hercules, CA, USA) in TBST solution (50 mM Tris/HCl pH 7.4, 150 mM NaCl, 0.1% Tween-20), the membranes were exposed to primary antibodies: phospho-P53 S20 (ab157454, Abcam, UK), cleaved PARP (#5625, Cell Signaling, MA, USA), cleaved caspase-3 (#9661S, Cell Signaling, MA, USA), beta-actin (#4970, Cell Signaling, MA, USA) overnight at 4 °C with gentle shaking. Exposure to HRP-conjugated antibodies (Cytiva, Washington, DC, USA) were performed for 1 h and eventually subjected to chemiluminescence detection using the SuperSignal Substrate Western Blotting Kit (Thermo Fisher Scientific, MA, USA) and imaged with ChemiDoc™ XRS + System with Image Lab™ Software (Bio-Rad Laboratories, Hercules, CA, USA).
RNA extraction, whole transcriptomic sequencing and bioinformatics analysis
A total of 2 × 105 cells were seeded into each well of 6-well plates. After allowing the cells to adhere and grow for 24 h, the respective average IC50 dosage determined for the specific cell line was administered to the cells. The cells were harvested 72 h after treatment for transcriptomic profiling. RNA was extracted using TRIzol (Ambion, Thermo Fisher Scientific, MA, USA; Cat#15596018) to separate RNA aqueous phase and Qiagen RNeasy extraction kit (Qiagen, Hilden, Germany) according to the manufacturer’s instructions. RNA bioanalyzer (Agilent Technologies, CA, USA) was used to determine the RNA integrity (RIN) values and quantified using the Nanodrop 2000 Spectrophotometer. Approximately 20 µg of RNA with RIN values over 7.0 was sent for RNA library construction and sequencing using Illumina NovaSeq 6000 (PE150 configuration; NovogeneAIT, Singapore). Three biological replicates were prepared for each cell line under each treatment condition for practical reasons. For analysis, sequencing data was aligned to the GRCh38 transcriptome using STAR (v2.7.9a)8, and transcript abundance was subsequently counted using Salmon (v1.10.1)9. Differentially-expressed genes were identified using DESeq2 (v1.48.1)10 with thresholds of adjusted p-value < 0.05 and log2-fold change > 1. Pathway enrichment of the differentially expressed gene was performed using ClusterProfiler (v4.16.0)11 against the MSigDB Hallmark genesets.
Metabolic profiling using mass spectrometry
100 mg of propolis sample was immersed in 100 mL of solvent (either ethanol or ethyl acetate) and heated at 30 °C for 1 h. The mixture was then shaken at 150 rpm for 4 h and subsequently filtered using Whatman filter paper. The resulting filtrate was used for chemical identification by gas chromatography - mass spectrometer (GC-MS; Shimadzu QP-2010). Compounds were identified by comparing their GC-MS spectra with those in the NIST database.
Statistical analysis
Results are presented as mean ± standard deviation (SD) of data collected from triplicate experiments. Statistical analysis of mean values was performed through t-test with Bonferroni correction using MedCalc for Windows, version 19.0.7 (MedCalc Software, Ostend, Belgium). A p < 0.05 was considered to be significant.
Results
Comparative efficacy of ethanol and Ethyl acetate propolis extracts
Ethanol and ethyl acetate were used as solvents to extract compounds from propolis harvested from the hives of five stingless bee species (G. thoracica, L. canifrons, H. itama, T. binghami, and T. melanoleuca) (Fig. 1). Representative photographs of the bees alongside their corresponding hive structures and propolis deposits are shown in Fig. 2. In our initial screening, we evaluated the potential effect on cancer cell viability of the propolis extracts at a single dose (50 µg/mL), on three cancer cell lines (U2932, H1975, and EJ) at 72 h. Ethanol extracts from H. itama and G. thoracica propolis showed more potent effects than their ethyl acetate counterparts, particularly in the U2932 and H1975 cell lines (Fig. 3A). For H. itama, the ethanol extract significantly reduced cell viability, leaving only 2% of viable cells in U2932 and 15% in H1975. In contrast, the ethyl acetate extract left 51% of cells viable in both lines (p < 0.001). Similarly, G. thoracica ethanol extract reduced cell viability to 56% and 62% in U2932 and H1975, respectively, whereas the ethyl acetate extract was less effective, leaving 85% and 71% cells viable in the respective cell lines (p < 0.01).
Overview of study design. Propolis extracts from Geniotrigona thoracica, Lepidotrigona canifrons, Heterotrigona itama, Tetragonula binghami, and Tetragonula melanocephala were prepared using ethanol and ethyl acetate. Cancer cell lines were treated with the extracts for 72 h. RNA sequencing was performed to evaluate gene expression in the treated cells, and compound profiles were profiled using mass spectrometry.
Stingless bee species and their corresponding hive structures and propolis. Five stingless bee species (Geniotrigona thoracica, Heterotrigona itama, Tetragonula binghami, Lepidotrigona canifrons, and Tetragonula melanocephala) alongside their hive structures and propolis deposits. For the Lepidotrigona canifrons beehive, no photo was taken since this species is quite aggressive.
Preliminary single dose treatment (50 µg/mL) with stingless bee propolis extracts and its effect on cancer cell viability. (A) Comparison of the effects of ethanol and ethyl acetate extracts from five stingless bee species on the viability of three cancer cell lines (U2932, H1975, and EJ). Statistical significance is indicated. ***, p < 0.001; **, p < 0.01; *, p < 0.05; n.s., non-significant. (B) Comparison of the effects of ethanol propolis extracts (50 µg/mL) from five stingless bee species (H. itama, T. melanoleuca, T. binghami, G. thoracica, and L. canifrons) on the viability of five cancer cell lines (U2932, H1975, OCI-LY3, HT, and EJ). The heatmap represents post-treatment cell viability (%), where lower values (red) indicate stronger cytotoxic effects.
Evaluation of ethanol propolis extracts in additional cell lines
We further observed that ethanol-based propolis extracts of T. melanoleuca and T. binghami were highly active in the U2932 cell line, prompting us to evaluate the activity of the various propolis extracts (ethanol-based only) on two other lymphoma cell lines, HT and OCI-LY3 (Fig. 3B). Of all the ethanol extracts from the propolis of five stingless bee species, T. melanoleuca ranked highest in efficacy, with single-dose (50 µg/mL) treatment lowering average cell viability to 23.6% across all lines at 72 h. This species was the most potent in the lymphoma cell lines, U2932, HT and OCI-LY3 (3%, 14% and 18% post-treatment cell viability, respectively). H. itama was the second most potent of all ethanol extracts, reducing cell viability to an average of 42% across all lines. It was the most potent bee species on U2932 and H1975 (2% and 15% post-treatment cell viability, respectively). In contrast, G. thoracica and L. canifrons exhibited weaker anti-proliferative effects, with cell viability remaining above 55% across all four cell lines. L. canifrons was the least effective bee species.
IC50 comparisons
Dose-dependent treatment of the ethanol extracts resulted in T. melanoleuca and H. itama exhibiting the lowest IC50 values across all cell lines as well, particularly against U2932 (17 µg/mL and 27 µg/mL, respectively) and H1975 (28 µg/mL and 38 µg/mL, respectively) at 72 h (Fig. 4A). Comparatively, T. binghami, G. thoracica and L. canifrons were less potent, showing generally higher IC50 values across all cell lines. U2932 DLBCL is the most sensitive cell line to ethanol extracts from propolis. The extracts from T. melanoleuca and H. itama also demonstrated a time-dependent response in U2932 and H1975 cell lines. Comparatively, their effect was less pronounced on healthy PBMC (Fig. 4B). H1975 and U2932 cell lines were also treated with osimertinib and doxorubicin, respectively, as a reference control (Fig. 4C).
Dose-dependent and time-dependent response of stingless bee ethanol extracts on cancer cell lines. (A) Heatmap of IC50 values across cell lines (EJ, H1975, U2932, HT, and OCI-LY3) and bee species ethanol extracts (T. melanocephala, H. itama, L. canifrons, G. thoracica, and T. binghami). Lower IC50 values (represented by darker blue) indicate higher potency. (B) Time-dependent response to extracts from T. melanoleuca and H. itama in U2932 and H1975 cell lines, as well as healthy PBMC. (C) H1975 and U2932 cell lines treated with osimertinib and doxorubicin.
Metabolite profiling
The chemical composition of the propolis ethanol extracts was characterized using GC-MS, revealing distinct chemical signatures from the ethanol propolis extract of the stingless bee species. A total of 38 compounds were identified, with six major classes of compounds including: (1) Alkaloids, (2) Amino acids and Peptides, (3) Fatty acids, (4) Polyketides, (5) Shikimates and Phenylpropanoids, and (6) Terpenoids. The analysis revealed that ethanol extracts exhibit a broader range of chemical diversity, with higher proportions of alkaloids, polyketides, phenolic acids, and terpenoids (Fig. 5).
Heatmap of relative composition of compounds detected in stingless bee propolis extracts partitioned by ethanol and ethyl acetate solvents. Rows represent identified chemical classes grouped by their chemical pathways (colored annotation bar), while columns indicate propolis samples from different stingless bee species. Color intensity indicates % composition derived from GC-MS peak area integration. Ethanol and ethyl acetate extractions are displayed side by side to enable direct comparison of solvent-specific extraction profiles.
Among the three most potent species: ethanol extracts from T. binghami featured a notable composition of carbocyclic fatty acid (2-Cyclopentene-1-carboxylic acid, 26.73%), monoterpenoid (alpha-Pinene, 18.98%), L-Proline (17.81%), and Cycloartane triterpenoid (Lanostane-7,11-dione). Extracts from H. itama contain 1-Naphthacenecarboxylic acid, a compound from the anthraquinone class, alongside a substantial amount of alpha-Pinene (15.11%). Finally, the most potent extract from T. melanoleuca revealed a unique combination of alkaloids (Quinoxaline 4.63% and 1,3,5-triazine 4.39%) with Physodic acid (3.85%) and a high abundance of L-proline (22.97%). The higher chemical diversity of T. melanoleuca likely contributed to the cytotoxic potency in the cell line assays (Supplementary Table S1).
Transcriptomic pathway enrichment analysis
Pathway enrichment analysis was performed to investigate the molecular mechanisms influenced by ethanol extracts from the three stingless bee species, H. itama, T. binghami, and T. melanoleuca, based on their IC50 values. The analysis revealed significant modulation of key cancer-related pathways, particularly those related to inflammation, cell cycle regulation, cholesterol metabolism, and cellular stress responses (Supplementary Table S2). Pathways involved in cell cycle progression, including E2F Targets and G2M Checkpoint, were notably downregulated in the EJ and H1975 cell lines, suggesting that the extracts may induce cell cycle arrest, particularly in adherent cells. Cholesterol homeostasis was also downregulated in the EJ and HT cell lines, most prominently in response to T. melanoleuca and H. itama extracts. Pathway enrichment analysis revealed the upregulation of several inflammation-related pathways, including TNFα signaling via NF-κB, Interferon Gamma Response, and Inflammatory Response. This suggests that the ethanol extracts may induce pro-inflammatory signaling, which is often linked to immune system activation and potential anti-tumorigenic effects. Hypoxia pathways were also upregulated, indicating that the extracts may exert pro-hypoxic effects. Notably, the unfolded protein response (UPR) was significantly enriched in several cell lines, suggesting that the extracts induce cellular stress, which may lead to apoptosis, particularly under hypoxic conditions. Upregulation of p53 pathway was observed in EJ and H1975, but not in HT or U2932 (Figs. 6A-B). Western blot showed that phospho-p53 was increased following treatment with the selected extracts (H. itama and T. melanoleuca) in H1975 but not U2932 cell line, but induction of cleaved PARP and cleaved caspase-3 was observed in U2932 but not in H1975, supporting their differential effects in adherent and suspension cell lines (Fig. 6C and Supplementary Fig. 1).
Pathway enrichment following treatment of propolis ethanol extracts. Dot plots showing enriched cancer hallmark pathways based on differentially expressed genes following treatment with propolis ethanol extracts from three stingless bee species—H. itama, T. binghami, and T. melanoleuca. Dot size corresponds to the gene ratio, while color intensity represents the significance of enrichment (adjusted p-value). Pathways are grouped by cell line, illustrating upregulated (up) and downregulated (down) expression patterns across treatments. (A) Significant results shown for EJ, H1975, and HT cell lines. (B) Significant results shown for U2932 cell line. (C) Western blot showing corroborative evidence for p53 pathway activation in H1975 cell line, and apoptosis induction in U2932 cell line.
Discussion
Stingless bee propolis has been investigated to exhibit potential pharmacological activity, including antiproliferative effects against various types of cancer1,5. Notably, previous reports have suggested the anticancer potential of stingless bee propolis including cancers of the lung, colon, breast, stomach, pancreas, liver, and head and neck12,13,14,15,16,17,18,19,20,21. In our current study, we demonstrated the in vitro antiproliferative activity of stingless bee propolis from five species on bladder cancer, lung cancer, and lymphoma cell lines. Notably, ethanol extracts elicited greater anticancer activity in general, as compared to ethyl acetate extracts. Amongst the five bee species, ethanol-based propolis extract from T. melanoleuca was the most potent, particularly on the lymphoma cell lines. Similarly, ethanol extracted propolis from H. itama exhibited potent activity.
In this study, the comparative cell line assay and chemical analysis revealed the distinct chemical profiles of ethanol-based propolis extracts across the various stingless bee species. This highlights the impact of environmental adaptation and local foraging behavior on propolis composition. Propolis is a resinous material collected from local flora and serves as a key defence mechanism against threats such as pathogens, parasites and predators. Understanding the stingless bee’s species-specific chemical diversity is critical for evaluating its therapeutic potential.
The extraction efficiency of these molecules is therefore critical for harnessing the full therapeutic value of propolis. While studies on propolis extracts have explored a variety of solvents, including ethanol, ethyl acetate, methanol, and hexane, comparative analyses across multiple stingless bee species remain limited. For instance, Santos et al. reported that ethanolic extracts of H. itama propolis exhibited significantly higher antimicrobial activity against Staphylococcus spp. (72.67%) compared to ethyl acetate (56.49%) and hexane (10.29%) extracts22. Although the study focused on antimicrobial rather than anticancer effects, it highlights the effectiveness of ethanol in extracting biologically active compounds over ethyl acetate. In plant extraction studies, ethanol has also been shown to disrupt cell structures more effectively than non-polar solvents, facilitating the release of bioactive compounds23. A similar mechanism may apply to propolis, where ethanol may more effectively dissolve the resinous matrix of propolis, allowing the extraction of a broader range of compounds, including hydrophilic and moderately lipophilic molecules. Ethanol’s polarity likely plays a key role in its superior extraction efficiency of polar to moderately non-polar compounds, such as phenolics, flavonoids, alkaloids and terpenoids23. These findings are also supported by the GC-MS results in this study, which reveal that ethanol extracts contain a higher diversity of compound classes known for their diverse biological activities. Overall, 38 distinct compounds were identified across six major chemical classes. These findings reinforce the value of ethanol as an extraction solvent for the comprehensive recovery of bioactive compounds from propolis. Ethyl acetate, being less polar, may not efficiently extract hydrophilic components that are critical to the bioactivity of propolis. Terpenoids, typically non-polar or weakly polar, were found in higher proportions in the ethanol extracts as well. This may be due to the presence of polar functional groups (e.g., hydroxyl or carboxyl groups) in many terpenoids, particularly oxygenated terpenoids like monoterpenoids. Additionally, the composition of the propolis may favor these polar terpenoid subtypes, contributing to this extraction pattern. Future studies should focus on detailed structural characterization of the extracted terpenoids to confirm the prevalence of oxygenated or functionalized derivatives.
Studies of propolis from stingless bee species have identified a range of bioactive compounds, including flavonoids, phenolic acids, and terpenoids, which are believed to contribute significantly to their anticancer properties24,25,26. Species-specific profiling further highlighted distinct metabolite signatures among the three most potent extracts. T. binghami propolis featured carbocyclic fatty acid, monoterpenoid and triterpenoids. H. itama extracts were characterized by a unique anthraquinone-class compound and a notable abundance of alpha-Pinene. T. melanoleuca, which demonstrated the strongest anticancer activity, exhibited the highest chemical diversity with two unique alkaloids, depsidone and a high amino-acid content. The anticancer potential of terpenoids has been well-documented, including in hematological malignancies. Kamran et al. reviewed the activities of twenty-give terpenoids through mechanisms such as cell cycle arrest and the induction of apoptosis27. In particular, the monoterpenoid d-limonene was reported to inhibit several tumor types, including the HL-60 leukemia cell line by decreasing anti-apoptotic Bcl-2 and enhancing pro-apoptotic Bax28. Anticancer activity of artesunate, a sesquiterpenoid lactone, was also reported in several cancer types, including doxorubicin-resistant T leukemia by generation of reactive oxygen species and triggering apoptosis29.
Our results identified by T. melanoleuca and H. itama as the most potent among the five bee species evaluated. The anticancer properties of H. itama have been investigated in previous studies, demonstrating its potential against a range of cancer cell lines. Arung et al. tested the cytotoxic effects of ethanolic extracts of H. itama on human breast cancer (MCF-7), human cervical adenocarcinoma (HeLa), and human colon cancer (Caco-2) cells, reporting a weak reduction in cell viability only in Caco-2 at a concentration of 75 µg/mL30. Lim et al. demonstrated that H. itama propolis extracts significantly inhibited lung cancer cells (A549) while relatively sparing normal lung cells (MRC-5), highlighting its selective anticancer potential30. Abdullah et al. studied three stingless bee species that were also included in our work— G. thoracica, H. itama, and T. binghami. While their research focused on the phytochemical properties, chemical compositions, and biological activities of propolis instead of anti-cancer properties, they identified H. itama as exhibiting the highest antioxidant activity among the three species, attributed to its high phenolic and flavonoid content6. Though the anti-cancer properties of T. melanoleuca propolis has not been well studied, Sanpa et al. conducted a study on the chemical composition and bioactive properties of T. melanoleuca propolis25. The study revealed that the propolis of T. melanoleuca was rich in triterpenes such as ursolic and oleanolic acid derivatives, derived from plant resins. These triterpenes, often containing carboxylic acid groups, are known for their anti-inflammatory, antioxidant, and anticancer activities, making them key contributors to the bioactivity of T. melanoleuca extracts. Ursolic and oleanolic acid derivatives have been extensively reported to induce apoptosis, inhibit cell proliferation, and modulate cancer-related pathways, including NF-κB signaling and ROS generation. These mechanisms align closely with the pathway modulations observed in our study. These distinct metabolite profiles underscore species-specific chemical diversity and may help explain differences in observed anticancer potency. The rich chemical diversity of T. melanoleuca ethanol extract, which contains alkaloids and terpenoids, may play an indirect role in the potent anticancer activity exhibited by T. melanoleuca. These findings collectively support the therapeutic potential of T. melanoleuca propolis and underscore the importance of further studies to fully characterize its bioactive compounds.
Our current study is limited to the in vitro evaluation of the stingless bee propolis extracts and does not identify specific compounds for deep characterization. Additionally, the chemical diversity of the propolis is constrained by the local flora available for foraging, which may limit the generalizability of our findings to other geographic regions. The tumor cell lines were also selected based on practical availability, and may not necessarily reflect the optimal spectrum of anti-cancer activity of the propolis extracts. Nonetheless, it provides preliminary insight into the anticancer potential of T. melanoleuca and H. itama propolis extracts, particularly on lymphoma. Using whole transcriptomic analysis, our study also highlights that propolis extracts may induce pro-inflammatory signaling and regulates major cancer pathways such as MYC and MTORC1 signaling, supporting their potential anti-tumorigenic effects. In conclusion, we propose that stingless bee propolis may be developed as potential anticancer agents. Future studies will focus on identifying the specific active components for drug development and elucidation of underlying molecular mechanisms.
Data availability
RNA-Seq data were deposited into the NCBI’s Sequence Read Archive (SRA) database under BioProject accession number PRJNA1288749 (https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1288749).
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Acknowledgements
We thank the Brunei Forestry Department, Ministry of Primary Resources and Tourism for providing the export permit (JPH/HOB/TAD/51-239). We also express our gratitude to Mr Mitasby Mamit of Tasbee Meliponiculture Farm for allowing us to collect propolis samples.
Funding
This work was supported by the Singapore Ministry of Health’s National Medical Research Council Research Transition Award (TA21jun-0005), Clinician Scientist Individual Research Grant (CIRG25jan-0007), Large Collaborative Grant (OFLCG-23May0039), and TETRAD II Collaborative Centre Grant (CG21APR2002), the SingHealth Duke-NUS AM/ACP-Designated Philanthropic Fund Grant Award (08/FY2023/EX/27-A65), Verdant Foundation, Tanoto Foundation, NCCS Cancer fund, as well as the Khoo Bridge Funding Award provided by Duke-NUS Medical School and the “Estate of Tan Sri Khoo Teck Puat” (Duke-NUS-KBrFA/2025/0090). This work was also supported by Universiti Brunei Darussalam through research grants (UBD/RSCH/1.4/FICBF(b)/2023/056 & UBD/RSCH/1.13/FICBF(b)/2021/032).
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BYL, AHL, and JYC analysed the data and drafted the manuscript; ECYL, CHWT, CCYN, BTT, NZ, NNMS, AU, and NA contributed to study design and obtained data. BYL, HT and JYC designed the study, interpreted the results, and revised the manuscript; and all authors read and approved the final version of the manuscript.
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Lim, B.Y., Lim, A.H., Tay, C.H.W. et al. Anti-cancer activity of propolis extracts from stingless bees of Brunei Darussalam. Sci Rep 16, 2794 (2026). https://doi.org/10.1038/s41598-025-32628-0
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DOI: https://doi.org/10.1038/s41598-025-32628-0








