Designing effective anticancer-radiopeptides. A Molecular Dynamics study of their interaction with model tumor and healthy cell membranes.

One of the greatest merit of the use of radiopeptides in oncology is their selectivity which, however, brings about the drawback that each radiopeptide is specific for a given tumor type. To overcome this problem the direction currently taken in drug design is that of radiolabelling peptide hormones (or their analogues), relying on their intrinsic ability to bind to specific receptors in precise areas of the human body, at the cost, however, of a poor selectivity against healthy cells. We present here an extensive Molecular Dynamics study of a promising alternative inspired by the mechanism through which antimicrobial peptides interact with the negatively charged bacterial membranes. Appropriately modifying the human antimicrobial peptide, LL-37, we designed a functionalized radionuclide carrier capable of binding more strongly to the negatively charged (model) tumor membranes than to the neutral healthy ones. The mechanism behind this behaviour relies on the fact that at the slight acidic pH surrounding tumor tissues the histidines belonging to the peptide get protonated thus making it positively charged. We have investigated by an extended numerical study the way in which this artificial peptide interacts with models of tumor and healthy cell membranes, proving by Potential Mean Force calculations that the affinity of the peptide to model tumor membranes is significantly larger than to healthy ones. These features (high affinity and generic tumor selectivity) recommend antimicrobial derived customized carriers as promising theranostic constructs in cancer diagnostic and therapy.