Induction of caspase-8 in human cells by the extracellular administration of peptides containing a C-terminal SLV sequence

Model Amphipathic Peptide Coupled with Tacrine to Improve Its Antiproliferative Activity

Drug repurposing and drug combination are two strategies that have been widely used to overcome the traditional development of new anticancer drugs. Several FDA-approved drugs for other indications have been tested and have demonstrated beneficial anticancer effects. In this connection, our research group recently reported that Tacrine, used to treat Alzheimer's Disease, inhibits the growth of breast cancer MCF-7 cells both alone and in combination with a reference drug. In this view, we have now coupled Tacrine with the model amphipathic cell-penetrating peptide (CPP) MAP, to ascertain whether coupling of the CPP might enhance the drug's antiproliferative properties. To this end, we synthesized MAP through solid-phase peptide synthesis, coupled it with Tacrine, and made a comparative evaluation of the parent drug, peptide, and the conjugate regarding their permeability across the blood-brain barrier (BBB), ability to inhibit acetylcholinesterase (AChE) in vitro, and antiproliferative activity on cancer cells. Both MAP and its Tacrine conjugate were highly toxic to MCF-7 and SH-SY5Y cells. In turn, BBB-permeability studies were inconclusive, and conjugation to the CPP led to a considerable loss of Tacrine function as an AChE inhibitor. Nonetheless, this work reinforces the potential of repurposing Tacrine for cancer and enhances the antiproliferative activity of this drug through its conjugation to a CPP.

Cell-penetrating peptides: A comparative membrane toxicity study

Cell-penetrating peptides (CPPs) constitute a new class of delivery vectors with high pharmaceutical potential. However, the abilities of these peptides to translocate through cell membranes can be accompanied by toxic effects resulting from membrane perturbation at higher peptide concentrations. Therefore, we investigated membrane toxicity of five peptides with well-documented cell-penetrating properties, pAntp(43-58), pTAT(48-60), pVEC(615-632), model amphipathic peptide (MAP), and transportan 10, on two human cancer cell lines, K562 (erythroleukemia) and MDA-MB-231 (breast cancer), as well as on immortalized aortic endothelial cells. We studied the effects of these five peptides on the leakage of lactate dehydrogenase and on the fluorescence of plasma membrane potentiometric dye bis-oxonol. In all cell lines, pAntp(43-58), pTAT(48-60), and pVEC(615-632) induced either no leakage or low leakage of lactate dehydrogenase, accompanied by modest changes in bis-oxonol fluorescence. MAP and transportan 10 caused significant leakage; in K562 and MDA-MB-231 cells, 40% of total lactate dehydrogenase leaked out during 10 min exposure to 10 microM of transportan 10 and MAP, accompanied by a significant increase in bis-oxonol fluorescence. However, none of the CPPs tested had a hemolytic effect on bovine erythrocytes comparable to mastoparan 7. The toxicity profiles presented in the current study are of importance when selecting CPPs for different applications.