Medicago SativaDefensin 1 (MsDef1), A Natural Tumor Targeted Sensitizer for Improving Chemotherapy: Translation from Anti-Fungal Agent to Potential Anti-Cancer Agent

Abstract

Introduction: MsDef1, a 45-amino acid cysteine-rich peptide from the seed of Medicago sativa is an antifungal defensin small protein. It exhibits broad-spectrum antifungal activity against fungal pathogens of plants at low micromolar concentrations. The common vulnerability of fungal and cancer cells determines the utility of MsDef1 as a potential anti-tumor agent. Results: The solution dynamics of 15N-labeled MsDef1, 15N longitudinal relaxation (T1) and 15N-1H Nuclear Overhauser Effect (NOE) shows that GlcCer binds at two sites on the peptide molecule, i.e., Asp36-Cys39 and amino acids between 12-20 and 33-40. MsDef1 interacts with drug resistant breast cancer MCF-7R cells, permeates GlcCer-rich plasma membrane and releases apoptotic ceramide. This results in the activation of ceramide pathway involving interaction of the peptide with intracellular thioredoxin (Trx), another tumor specific biomarker. MsDef1 oxidizes Trx through four S-S bonds and in the process, gets reduced to thiols. Oxidation of Trx is correlated with the activation of Apoptosis Stimulating Kinase 1 (ASK1) which is known to sensitize cancer cells to chemotherapeutics including front-line drug Doxorubicin. A combination of MsDef1 and Doxorubicin exhibits 5-10-fold greater apoptosis in vitro in MDR triple negative breast cancer (TNBC) cells compared to either MsDef1 or Doxorubicin alone. Conclusion: An antifungal plant defensin MsDef1 is shown to be a cell permeating peptide (CPP) for MDR cancer cells targeted to two tumor specific targets activating two cell death pathways. That makes MsDef1, potentially a tumor targeted sensitizer neoadjuvant to cancer therapy.

Defensin–lipid interactions in membrane targeting: mechanisms of action and opportunities for the development of antimicrobial and anticancer therapeutics

“…An example of this approach was reported for the defensin MsDef1 and doxorubicin against triple-negative breast cancer cells (MDA-MB-231R) and oestrogen receptor-positive cells (MCF-7R). In this study, defensin treatment synergistically improved doxorubicin effectiveness [ 96 ]. Furthermore, defensins could be used to aid in protection against opportunistic infections by ‘supplementing’ components of the innate immune system during chemotherapeutic treatment [ 97 ].…”

Overview of Host Defense Peptides with Promising Anti-Breast Cancer Activity

“…Targeting the cancer cell adhesion might be a possible strategy to prevent metastatic spreading. Peptide MsDef1, from the seed of Medicago sativa, is an anti-fungal defensin which have the ability to bind glucosylceramide (GlcCer) (64). MsDef1 induces sphingomyelinase activity and enhances GlcCer levels in the resistant triple negative breast cancer cells (64).…”

“…Peptide MsDef1, from the seed of Medicago sativa, is an anti-fungal defensin which have the ability to bind glucosylceramide (GlcCer) (64). MsDef1 induces sphingomyelinase activity and enhances GlcCer levels in the resistant triple negative breast cancer cells (64). MsDef1 also releases ceramide which have the ability to modulate the biochemical and cellular processes that will lead to apoptosis (64).…”

“…MsDef1 induces sphingomyelinase activity and enhances GlcCer levels in the resistant triple negative breast cancer cells (64). MsDef1 also releases ceramide which have the ability to modulate the biochemical and cellular processes that will lead to apoptosis (64). Addition of MsDef1 to the conventional chemotherapy with high dose of doxorubicin, exerts cumulative effects on cancer cell death (64).…”

“…MsDef1 also releases ceramide which have the ability to modulate the biochemical and cellular processes that will lead to apoptosis (64). Addition of MsDef1 to the conventional chemotherapy with high dose of doxorubicin, exerts cumulative effects on cancer cell death (64). MsDef1 targets cancer specific thioredoxin (Trx) system and activates the apoptosis signal regulating kinase-1 (ASK1) pathway.…”