Anti-cancer activity of propolis extracts from stingless bees of Brunei Darussalam

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.