ALA Dipeptides Derivatives for Their Use in Photodynamic Therapy

VALLECORSA, P; DI VENOSA, GABRIELA; MAMONE, LEANDRO; GIUNTINI, F; GANDARA, LAUTARO; BATLLE ALCIRA; ROSSETTI, MARIA VICTORIA; MACROBERT, ALEXANDER; EGGLESTON, L; CASAS, ADRIANA

Lucerna

Congreso; INTERNATIONAL CONGRESS ON PORPHYRINS AND PORPHYRIAS 2013; 2013

Swiss Society of Clinical Chemistry

Photodynamic Therapy (PDT) is a non-thermal technique for inducingtissue damage with light following administration of a lightactivatedphotosensitising drug which can be selectively retained inmalignant or diseased lesions relative to normal adjacent tissueIn last years, 5-aminolaevulinic acid (ALA)-mediated PDT hasbecome one of the most promising fields in PDT research. ALA is thepro-drug of the photosensitiser Protoporphyrin IX (PpIX). The efficacyof ALA-PDT is somewhat limited by the hydrophilic nature ofthe molecule, leading to poor penetration through certain tissues.An attractive way to obtain ALA prodrugs that have both improvedphysicochemical properties and can selectively release ALA in specificcell lines is to incorporate ALA into a short peptide derivative.The aim of this work was test two novel ALA dipeptides,AcLeuALAMe and AcPheALAMe in different cell lines.The cell lines employed were F3II and LM3 mammary carcinomas,PAM212 normal keratinocytes, and B16 melanoma, andPpIX was evaluated fluorimetrically after chemical extraction andexpressed as fluorescence units (FU).PpIX synthesised from ALA was as follows:PAM212 > LM3 > F3II, > B16. And porphyrins from ALA reached plateauvalues employing 0.4-0.6 mM concentrations in all the cell lines,PAM212: 30 FU/105 cells, LM3; 15 FU/105 cells, F3II: 10 FU/105 cellsand B16: 5 FU/105 cells. On the other hand, PpIX plateaux werereached employing 0.001 mM and 0.05 mM from Phe-ALA andLeu-ALA respectively, in the four cell lines, whereas maximal PpIXsynthesis reached was similar to ALA. This shows that 2 orders ofmagnitude lower concentrations are needed as compared to ALA tosynthesise plateau porphyrin values in tumour and non-tumour celllines.Application of PDT treatment employing 0.05 mM of derivativesnot always led to lethal doses 50 (LD50) proportional to porphyrinsynthesis: PAM212: 34,2 mJ/cm2 (Phe-ALA and Leu-ALA), F3II: 24.7mJ/cm2 (Phe-ALA and Leu-ALA), LM3: 20 mJ/cm2 (Phe-ALA and Leu-ALA), B16: 13.3 and 17.1 mJ/cm2 for Phe-ALA and Leu-ALA respectively.Employing equimolar doses, ALA did not induce any PDT damage inany of the cell lines. It is worth to note that PAM212, which is thebest PpIX producer, is the most resistant to ALA dipetides treatment,showing that cell type is a keypoint in resistance to photodamage.Mice skin explants exposed to either 0.1 and 1 mM ALA and ALApeptides,induced equal porphyrin synthesis, thus showing that invitro penetration of the ALA derivatives through the skin is differentin vivo as compared to in vitro models