[The peptide toxin components and nucleotide metabolites in Macrothele raveni venom synergistically inhibit cancer cell proliferation by activating the pro-apoptotic pathways].

Abstract

Objectives: To evaluate the inhibitory effect of Macrothele raveni crude venom against proliferation of different cancer cells and identify the active components in the venom.

Methods: Different cancer cell lines were treated with different concentrations of Macrothele raveni venom for 48 h, and cell proliferation and the half-maximal inhibitory concentrations (IC₅₀) of the venom were assessed with CCK-8 assay. The apoptosis rate of breast cancer MCF7 cells following the treatment was analyzed with flow cytometry, and the changes in cellular caspase-8 and caspase-9 expressions were detected. The crude venom was separated into protein, peptide, and small-molecule compound fractions using gel filtration chromatography and high-performance liquid chromatography (HPLC). The protein and peptide components were identified using proteomics analysis, and small-molecule compounds were structurally characterized using nuclear magnetic resonance (NMR), mass spectrometry (MS), and HPLC.

Results: The crude venom exhibited strong concentration-dependent inhibitory effects on proliferation of MCF7 cells and nasopharyngeal carcinoma SUNE1 and HONE1 cells (IC₅₀ of 2.14±0.29, 1.57±0.14, and 2.85±0.15 µg/mL, respectively), with less potent inhibitory effects in gastric cancer HGC27 cells and colorectal cancer SW620 cells (IC₅₀ of 3.02±0.27 and 3.02±0.28 µg/mL, respectively). The crude venom significantly promoted MCF7 cell apoptosis likely via the caspase 8 signaling pathway. The protein fraction from the crude venom showed a weak inhibitory effect in MCF7 cells, whereas the peptide fraction exhibited a much stronger inhibitory effect (IC₅₀ of 6.41±0.31 µg/mL). The peptides in the peptide fraction, with relative molecular mass around 10 000, were homologous to those found in Macrothele gigas venom. The small-molecule fraction consisted mainly of nucleotide metabolites without obvious inhibitory effects in MCF7 cells, but its combination with the peptide fraction showed significantly enhanced inhibitory activity. Conclusion The inhibitory effects of Macrothele raveni venom, which vary significantly across different cancer cell lines, are attributed primarily to its peptide components, which may act synergistically with the nucleotide metabolites.