Honeybee venom and melittin suppress growth factor receptor activation in HER2-enriched and triple-negative breast cancer

Ciara Duffy,Andrew Redfern,Kevin Pfleger,Kathleen Davern,K Swaminathan Iyer,Elizabeth Johnstone,Edina Wang,Boris Baer,Diwei Ho,Eleanor Woodward,Pilar Blancafort,Anabel Sorolla,Emily Golden

doi:10.1038/s41698-020-00129-0

Abstract

Despite decades of study, the molecular mechanisms and selectivity of the biomolecular components of honeybee (Apis mellifera) venom as anticancer agents remain largely unknown. Here, we demonstrate that honeybee venom and its major component melittin potently induce cell death, particularly in the aggressive triple-negative and HER2-enriched breast cancer subtypes. Honeybee venom and melittin suppress the activation of EGFR and HER2 by interfering with the phosphorylation of these receptors in the plasma membrane of breast carcinoma cells. Mutational studies reveal that a positively charged C-terminal melittin sequence mediates plasma membrane interaction and anticancer activity. Engineering of an RGD motif further enhances targeting of melittin to malignant cells with minimal toxicity to normal cells. Lastly, administration of melittin enhances the effect of docetaxel in suppressing breast tumor growth in an allograft model. Our work unveils a molecular mechanism underpinning the anticancer selectivity of melittin, and outlines treatment strategies to target aggressive breast cancers.

Highlights

The European honeybee (Apis mellifera) has been the source of a number of products used medicinally by humans, such as honey, propolis, and venom for thousands of years[1]
To assess anticancer efficacy and selectivity, venom from both European honeybees collected in Perth, Australia and melittin peptide were evaluated in dose–response assays in a panel of cell lines representative of the intrinsic breast cancer subtypes and in nontransformed cells (Fig. 1a)
Honeybee venom showed high anticancer selectivity, with a significantly higher potency in TNBC (e.g., SUM159 and SUM149) and in the HER2-enriched breast cancer cell lines (e.g., MDA-MB-453 and SKBR3), followed by luminal breast cancer cells, with the lowest impact on normal cells (primary dermal fibroblast cells alone inducing a higher level of apoptosis than honeybee venom at both 18 and 24 h post treatment (Fig. 2a, quantification in Supplementary Fig. 2)

Summary

Introduction

The European honeybee (Apis mellifera) has been the source of a number of products used medicinally by humans, such as honey, propolis, and venom for thousands of years[1]. Melittin is a positively charged, amphipathic 26-amino-acid peptide[5] that associates with the phospholipids of the membrane bilayer, causing cell death by forming ~4.4 nm-diameter transmembrane toroidal pores that may enable the internalization of additional small molecules with cytotoxic activities[4,6,7] Both honeybee venom and melittin have demonstrated antitumoral effects in melanoma[8], non-small-cell lung cancer[9], glioblastoma[10], leukemia[11], ovarian[12], cervical[13], and pancreatic cancers[14], with higher cytotoxic potency in cancer cells compared to nontransformed cells[8,11,14,15]. Honeybee venom and melittin induced apoptosis in MCF7 cells[20], and reduced cell viability and migration in MDA-MB-231 breast cancer cells[21,22]

Methods

Results

Conclusion