Human β-Defensin 2 (HBD-2) Displays Oncolytic Activity but Does Not Affect Tumour Cell Migration

Abstract

Defensins form an integral part of the cationic host defence peptide (HDP) family, a key component of innate immunity. Apart from their antimicrobial and immunomodulatory activities, many HDPs exert multifaceted effects on tumour cells, notably direct oncolysis and/or inhibition of tumour cell migration. Therefore, HDPs have been explored as promising anticancer therapeutics. Human β-defensin 2 (HBD-2) represents a prominent member of human HDPs, being well-characterised for its potent pathogen-killing, wound-healing, cytokine-inducing and leukocyte-chemoattracting functions. However, its anticancer effects remain largely unknown. Recently, we demonstrated that HBD-2 binds strongly to phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2), a key mediator of defensin-induced cell death and an instructional messenger during cell migration. Hence, in this study, we sought to investigate the lytic and anti-migratory effects of HBD-2 on tumour cells. Using various cell biological assays and confocal microscopy, we showed that HBD-2 killed tumour cells via acute lytic cell death rather than apoptosis. In addition, our data suggested that, despite the reported PI(4,5)P2 interaction, HBD-2 does not affect cytoskeletal-dependent tumour cell migration. Together, our findings provide further insights into defensin biology and informs future defensin-based drug development.

From oncolytic peptides to oncolytic polymers: A new paradigm for oncotherapy

“…Although the underlying interaction mechanism between oncolytic peptides and plasma membrane is not fully elucidated, several techniques have been employed to characterize the mode of action of oncolytic peptides towards tumor cells, such as X-ray diffraction, surface plasmon resonance, attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy, confocal fluorescence microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), circular dichroism (CD) spectroscopy, flow cytometry and molecular dynamics simulation (MD simulation), etc. [ [64] , [65] , [66] , [67] , [68] , [69] , [70] ]. In general, the oncolytic peptides-mediated cancer cell killing can be roughly divided into four main stages: (1) oncolytic peptides are attracted to the cancer cell surface via electrostatic interaction between the negatively charged cytoplasmic membrane components and the positively charged peptides residues [ 65 ]; (2) additional hydrophobic interactions between the phospholipid hydrophobic tail and the residues of the non-polar peptide serve to facilitate the embedding of oncolytic peptides into tumor cells membranes via multiple theoretical models [ 38 ]; (3) the membrane curvature would be changed, subsequently, the structure and integrity of the cells membrane were disrupted (e.g., blebbing, pore formation, and vascularization) [ 71 ]; (4) tumor cells are lysed and the intracellular contents would be released [ 68 ].…”

Role of Defensins in Tumor Biology

“…Furthermore, hBD-2 and -3 were reported to contain an oncolytic motif that binds to phosphatidylinositol 4,5-bisphosphate. This interaction is critical for mediating cytolysis of tumor cells, and experiments with hBD-2 showed that the defensin killed tumor cells via acute lytic cell death instead of apoptosis [ 46 , 47 ]. Other research confirmed this, as A549 adenocarcinoma cells treated with hBD-3 displayed immediate cell membrane damage.…”

Structure–activity relationships of antibacterial peptides

“…While chemical synthesis has been used to produce most of the abovementioned molecules, the production cost for defensins is still too high, and synthetic defensins analogues are needed (Bindra et al, 2022 ). Some modifications were carried out in the N‐terminal amphipathic domain and in C‐terminal hydrophobic groups of cecropins.…”