Structural Bases for the Involvement of Phosphatidylinositol-4,5-bisphosphate in the Internalization of the Cell-Penetrating Peptide Penetratin.

Cell-penetrating peptides cross cell membranes through various parallel internalization pathways. Herein, we analyze the role of the negatively charged lipid phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) in the internalization of Penetratin. Contributions of both inner leaflet and outer leaflet pools of PI(4,5)P2 were revealed by quantifying the internalization of Penetratin in cells treated with PI(4,5)P2 binders. Studies on model systems showed that Penetratin has a strong affinity for PI(4,5)P2 and interacts selectively with this lipid, even in the presence of other negatively charged lipids, as demonstrated by affinity photo-crosslinking experiments. Differential scanning calorimetry experiments showed that Penetratin induces lateral segregation in PI(4,5)P2-containing liposomes, which was confirmed by coarse-grained molecular dynamics simulations. NMR experiments indicated that Penetratin adopts a stabilized helical conformation in the presence of PI(4,5)P2-containing membranes, with an orientation parallel to the bilayer plane, which was also confirmed by all-atom simulations. NMR and photo-crosslinking experiments also suggest a rather shallow insertion of the peptide in the membrane. Put together, our findings suggest that PI(4,5)P2 is a privileged interaction partner for Penetratin and that it plays an important role in Penetratin internalization.

[A five-year experience in conformational radiotherapy in the treatment of prostate cancer. Evaluation of acute toxicity in 131 patients]. / Radiothérapie conformationnelle dans le traitement du cancer de la prostate. Evaluation de la toxicité aiguë chez 131 patients.

PURPOSE: To evaluate the urinary and rectal toxicity secondary to 3D conformal radiotherapy for prostate cancer. MATERIAL AND METHODS: Between 1998 and 2003, 131 men with prostate cancer underwent 3D conformal radiotherapy with or without androgen deprivation. The different stages were: 2 T1b ; 40 T1c; 19 T2a; 16 T2b; 18 T2c; 33 T3a; 1 T3b and 2 T3c with Gleason score: 4-6 = 47%, 7 = 36% and 8-9 in 17% of the cases. The median patient age was 66 (48-87). Pretreatment PSA level was respectively < 10 ng/ml (41%). 10-20 ng/ml (30%) and > 20 ng/ml (29%). Of the 131 patients, 98 received androgen ablation therapy before radiation. The total radiation dose varied between 66 and 74 Gy, delivered with 18MV photons of the linear accelerator, the median follow up was 33 months (5-67). RESULTS: According to the RTOG grading (gr) for acute toxicity, we noticed 3gr 3 genitourinary (GU) toxicity and no gr3 gastro intestinal (GI) toxicity. There were 36 gr 1 and 12 gr 2 GI toxicity, 41 gr 1 and 22 gr 2 GU toxicity. The mean prostate volume was 41 cc for patients who received androgen ablation and 56 cc for the others (p < 0.002). The percentage of volume receiving more than 50 Gy (V50) was calculated, the median V50 was 32% (5-67) for the rectum and 35% (5-79) for the bladder CONCLUSION: The toxicity profile in this study is in the same range than those of the literature and of our previous study concerning our first 50 patients with prostate cancer treated with 3D conformal radiotherapy.