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Objectives: Malignant pleural mesothelioma (MPM) is a deadly disease with limited treatment options. Approaches to enhance patient immunity against MPM have been tested but shown variable results. Previously, we have demonstrated interesting vascular modulating properties of low-dose photodynamic therapy (L-PDT) on MPM. Here, we hypothesized that L-PDT vascular modulation could favour immune cell extravasation in MPM and improve tumour control in combination with immune checkpoint inhibitors., Methods: First, we assessed the impact of L-PDT on vascular endothelial E-selectin expression, a key molecule for immune cell extravasation, in vitro and in a syngeneic murine model of MPM. Second, we characterized the tumour immune cell infiltrate by 15-colour flow cytometry analysis 2 and 7 days after L-PDT treatment of the murine MPM model. Third, we determined how L-PDT combined with immune checkpoint inhibitor anti-CTLA4 affected tumour growth in a murine MPM model., Results: L-PDT significantly enhanced E-selectin expression by endothelial cells in vitro and in vivo. This correlated with increased CD8+ T cells and activated antigen-presenting cells (CD11b+ dendritic cells and macrophages) infiltration in MPM. Also, compared to anti-CTLA4 that only affects tumour growth, the combination of L-PDT with anti-CTLA4 caused complete MPM regression in 37.5% of animals., Conclusions: L-PDT enhances E-selectin expression in the MPM endothelium, which favours immune infiltration of tumours. The combination of L-PDT with immune checkpoint inhibitor anti-CTLA4 allows best tumour control and regression., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Vascular-targeted low-dose photodynamic therapy (L-PDT) was shown to improve chemotherapy distribution in malignant pleural tumors such as malignant pleural mesothelioma (MPM). However, the mechanisms triggered by L-PDT on the tumor vasculature are still debated. In pericyte and endothelial cell co-cultures, we show that pericytes exhibit enhanced sensitivity towards L-PDT compared to endothelial cells, displaying actin stress fibers and cellular contraction via Rho/ROCK kinase signaling myosin light chain and focal adhesion kinase phosphorylation (MLC-P, FAK-P). We then confirm, in two separate MPM models, in mice the phosphorylation of the MLC in pericytes specifically following L-PDT. Furthermore, while L-PDT does not affect tumor vascular density or diameter, we show that it enhances tumor vascular pericyte coverage, leads to a drop in tumor interstitial fluid pressure and enhances the transport of FITC-dextran throughout tumors. In conclusion, L-PDT has the potential to stabilize the tumor vascular bed which improves vascular transport. The mechanism described in the present study may help translate and optimize this approach in patients. Lasers Surg. Med. 51:550-561, 2019. © 2019 Wiley Periodicals, Inc., (© 2019 Wiley Periodicals, Inc.)

Background: Low-dose photodynamic therapy PDT (photoinduction) can modulate tumor vessels and enhance the uptake of liposomal cisplatin (Lipoplatin®) in pleural malignancies. However, the photo-induction conditions must be tightly controlled as overtreatment shuts down tumor vessels and enhances normal tissue drug uptake., Material and Methods: In a pleural sarcoma and adenocarcinoma rat model (n = 12/group), we applied photoinduction (0.0625 mg/kg Visudyne®, 10 J/cm 2 ) followed by intravenous Lipoplatin® (5 mg/kg) administration. Tumor and normal tissue IFP were assessed before and up to 1 hour following photoinduction. Lipoplatin® uptake was determined 60 minutes following photoinduction. We then treated the pleura of tumor-free minipigs with high dose photodynamic therapy (PDT) (0.0625 mg/kg Visudyne®, 30 J/cm 2 , n = 5) followed by Lipoplatin (5 mg/kg) administration., Results: In rodents, photoinduction resulted in a significant decrease of IFP (P < 0.05) in both tumor types but not in the surrounding normal lung, equally exposed to light. Also, photoinduction resulted in a significant increase of Lipoplatin® uptake in both tumor types (P < 0.05) but not in normal lung. Tumor IFP variation and Lipoplatin® uptake fitted an inverted parabola. In minipigs, high dose photodynamic treatment resulted in pleural IFP increase of some animals which predicted higher Lipoplatin® uptake levels., Conclusion: Normal and tumor vasculatures react differently to PDT. Continuous IFP monitoring in normal and tumor tissues is a promising biomarker of vessel photoinduction. Moderate drop in tumor with no change in normal tissue IFP are predictive of specific Lipoplatin® uptake by cancer following PDT. Lasers Surg. Med. 49:773-780, 2017. © 2017 Wiley Periodicals, Inc., (© 2017 Wiley Periodicals, Inc.)

Background: Low-dose, Visudyne®-mediated photodynamic therapy (photo-induction) was shown to selectively enhance tumor vessel transport causing increased uptake of systemically administered chemotherapy in various tumor types grown on rodent lungs. The present experiments explore the efficacy of photo-induced vessel modulation combined to intravenous (IV) liposomal cisplatin (Lipoplatin®) on rodent lung tumors and the feasibility/toxicity of this approach in porcine chest cavities., Material and Methods: Three groups of Fischer rats underwent orthotopic sarcoma (n = 14), mesothelioma (n = 14), or adenocarcinoma (n = 12) implantation on the left lung. Half of the animals of each group had photo-induction (0.0625 mg/kg Visudyne®, 10 J/cm(2) ) followed by IV administration of Lipoplatin® (5 mg/kg) and the other half received Lipoplatin® without photo-induction. Then, two groups of minipigs underwent intrapleural thoracoscopic (VATS) photo-induction (0.0625 mg/kg Visudyne®; 30 J/cm(2) hilum; 10 J/cm(2) apex/diaphragm) with in situ light dosimetry in combination with IV Lipoplatin® administration (5 mg/kg). Protocol I (n = 6) received Lipoplatin® immediately after light delivery and Protocol II (n = 9) 90 minutes before light delivery. Three additional animals received Lipoplatin® and VATS pleural biopsies but no photo-induction (controls). Lipoplatin® concentrations were analyzed in blood and tissues before and at regular intervals after photo-induction using inductively coupled plasma mass spectrometry., Results: Photo-induction selectively increased Lipoplatin® uptake in all orthotopic tumors. It significantly increased the ratio of tumor to lung Lipoplatin® concentration in sarcoma (P = 0.0008) and adenocarcinoma (P = 0.01) but not in mesothelioma, compared to IV drug application alone. In minipigs, intrapleural photo-induction combined to systemic Lipoplatin® was well tolerated with no toxicity at 7 days for both treatment protocols. The pleural Lipoplatin® concentrations were not significantly different at 10 and 30 J/cm(2) locations but they were significantly higher in protocol I compared to II (2.37 ± 0.7 vs. 1.37 ± 0.7 ng/mg, P  < 0.001)., Conclusion: Visudyne®-mediated photo-induction selectively enhances the uptake of IV administered Lipoplatin® in rodent lung tumors. Intrapleural VATS photo-induction with identical treatment conditions combined to IV Lipoplatin chemotherapy is feasible and well tolerated in a porcine model. Lasers Surg. Med. 47:807-816, 2015. © 2015 Wiley Periodicals, Inc., (© 2015 Wiley Periodicals, Inc.)

Background: The pre-conditioning of tumor vessels by low-dose photodynamic therapy (L-PDT) was shown to enhance the distribution of chemotherapy in different tumor types. However, how light dose affects drug distribution and tumor response is unknown. Here we determined the effect of L-PDT fluence on vascular transport in human mesothelioma xenografts. The best L-PDT conditions regarding drug transport were then combined with Lipoplatin(®) to determine tumor response., Methods: Nude mice bearing dorsal skinfold chambers were implanted with H-Meso1 cells. Tumors were treated by Visudyne(®) -mediated photodynamic therapy with 100 mW/cm(2) fluence rate and a variable fluence (5, 10, 30, and 50 J/cm(2) ). FITC-Dextran (FITC-D) distribution was assessed in real time in tumor and normal tissues. Tumor response was then determined with best L-PDT conditions combined to Lipoplatin(®) and compared to controls in luciferase expressing H-Meso1 tumors by size and whole body bioluminescence assessment (n = 7/group)., Results: Tumor uptake of FITC-D following L-PDT was significantly enhanced by 10-fold in the 10 J/cm(2) but not in the 5, 30, and 50 J/cm(2) groups compared to controls. Normal surrounding tissue uptake of FITC-D following L-PDT was significantly enhanced in the 30 J/cm(2) and 50 J/cm(2) groups compared to controls. Altogether, the FITC-D tumor to normal tissue ratio was significantly higher in the 10 J/cm(2) group compared others. Tumor growth was significantly delayed in animals treated by 10 J/cm2-L-PDT combined to Lipoplatin(®) compared to controls., Conclusions: Fluence of L-PDT is critical for the optimal distribution and effect of subsequently administered chemotherapy. These findings have an importance for the clinical translation of the vascular L-PDT concept in the clinics., (© 2015 Wiley Periodicals, Inc.)

Background: Visudyne®-mediated photodynamic therapy (PDT) at low drug/light conditions has shown to selectively enhance the uptake of liposomal doxorubicin in subpleural localized sarcoma tumors grown on rodent lungs without causing morphological alterations of the lung. The present experiments explore the impact of low-dose PDT on liposomal doxorubicin (Liporubicin™) uptake to different tumor types grown on rodent lungs., Material and Methods: Three groups of Fischer rats underwent subpleural generation of sarcoma, mesothelioma, or adenocarcinoma tumors on the left lung. At least five animals of each group (sarcoma, n = 5; mesothelioma, n = 7; adenocarcinoma, n = 5) underwent intraoperative low-dose (10 J/cm(2) at 35 mW/cm(2) ) PDT with 0.0625 mg/kg Visudyne® of the tumor and the lower lobe. This was followed by intravenous (IV) administration of 400 µg Liporubicin™. After a circulation time of 60 min, the tumor-bearing lung was processed for HPLC analyses. At least five animals per group underwent the same procedure but without PDT (sarcoma, n = 5; mesothelioma, n = 5; adenocarcinoma, n = 6). Five untreated animals per group underwent CD31 immunostaining of their tumors with histomorphometrical assessment of the tumor vascularization., Results: Low-dose PDT significantly enhanced Liporubicin™ uptake to all tumor types (sarcoma, P = 0.0007; mesothelioma, P = 0.001; adenocarcinoma, P = 0.02) but not to normal lung tissue compared to IV drug administration alone. PDT led to a significantly increased ratio of tumor to lung tissue drug uptake for all three tumor types (P < 0.05). However, the tumor drug uptake varied between tumor types and paralleled tumor vascular density. The vascular density was significantly higher in sarcoma than in adenocarcinoma (P < 0.001) and mesothelioma (P < 0.001), whereas there was no significant difference between adenocarcinoma and mesothelioma., Conclusion: Low-dose Visudyne®-mediated PDT selectively enhances the uptake of systemically administered liposomal doxorubicin in tumors without affecting the drug uptake to normal lung. However, drug uptake varied significantly between tumor types and paralleled tumor vascular density., (Copyright © 2012 Wiley Periodicals, Inc.)

Background and Objective: Photodynamic therapy (PDT) affects vascular barrier function and thus increases vessel permeability. This phenomenon may be exploited to facilitate targeted drug delivery and may lead to a new clinical application of photodynamic therapy. Here, we investigate the role of leukocyte recruitment for PDT-induced vascular permeabilization., Study Design/material and Methods: Fluorescein isothiocyanate dextran (FITC-D, 2,000 kDa) was injected intravenously 120 minutes after focal PDT on striated muscle in nude mice bearing dorsal skinfold chambers (Visudyne® 800 µg/kg, fluence rate 300 mW/cm2 , light dose of 200 J/cm2). Leukocyte interaction with endothelial cells was inhibited by antibodies functionally blocking adhesion molecules ("MABS-PDT" group, n = 5); control animals had PDT but no antibody injection (group "PDT", n = 7). By intravital microscopy, we monitored leukocyte rolling and sticking in real-time before, 90 and 180 minutes after PDT. The extravasation of FITC-D from striated muscle vessels into the interstitial space was determined in vivo during 45 minutes to assess treatment-induced alterations of vascular permeability., Results: PDT significantly increased the recruitment of leukocytes and enhanced the leakage of FITC-D. Neutralization of adhesion molecules before PDT suppressed the rolling of leukocytes along the venular endothelium and significantly reduced the extravasation of FITC-D as compared to control animals (156 ± 27 vs. 11 ± 2 (mean ± SEM, number of WBC/30 seconds mm vessel circumference; P < 0.05) at 90 minutes after PDT and 194 ± 21 vs. 14 ± 4 at 180 minutes after PDT). In contrast, leukocyte sticking was not downregulated by the antibody treatment., Conclusion: Leukocyte recruitment plays an essential role in the permeability-enhancing effect of PDT., (Copyright © 2011 Wiley-Liss, Inc.)

Background: In specific conditions, photodynamic therapy (PDT) can enhance the distribution of macromolecules across the endothelial barrier in solid tumors. It was recently postulated that tumor neovessels were more responsive to PDT than the normal vasculature. We hypothesized that Visudyne(R)-mediated PDT could selectively increase liposomal doxorubicin (Liporubicin) uptake in sarcoma tumors to rodent lungs while sparing the normal surrounding tissue., Materials and Methods: Sarcoma tumors were generated subpleurally in the left lower lung lobe of 66 Fischer rats. Ten days following sarcoma implantation, tumors underwent different pre-treatment schemes: no PDT (controls), low-dose PDT (0.0625 mg/kg Visudyne(R), 10 J/cm(2) and 35 mW/cm(2)) and high-dose PDT (0.125 mg/kg Visudyne(R), 10 J/cm(2) and 35 mW/cm(2)). Liporubicin was then administered and allowed to circulate for 1, 3, or 6 hours. At the end of each treatment scheme, we assessed the uptake of Liporubicin in tumor and lung tissues by high-performance liquid chromatography and fluorescence microscopy., Results: In all PDT-treated groups, there was a significant enhancement of Liporubicin uptake in tumors compared to controls after 3 and 6 hours of drug circulation. In addition, Liporubicin distribution within the normal lung tissue was not affected by PDT. Thus, PDT pre-treatment significantly enhanced the ratio of tumor-to-lung drug uptake compared to controls. Finally, fluorescence microscopy revealed a well-detectable Liporubicin signaling throughout PDT-treated tumors but not in controls., Conclusions: PDT is a tumor-specific enhancer of Liporubicin distribution in sarcoma lung tumors which may find a translation in clinics.

OBJECTIVES The pre-treatment of tumour neovessels by low-level photodynamic therapy (PDT) improves the distribution of concomitantly administered systemic chemotherapy. The mechanism by which PDT permeabilizes the tumour vessel wall is only partially known. We have recently shown that leukocyte–endothelial cell interaction is essential for photodynamic drug delivery to normal tissue. The present study investigates whether PDT enhances drug delivery in malignant mesothelioma and whether it involves comparable mechanisms of actions. METHODS Human mesothelioma xenografts (H-meso-1) were grown in the dorsal skinfold chambers of 28 nude mice. By intravital microscopy, the rolling and recruitment of leukocytes were assessed in tumour vessels following PDT (Visudyne® 400 μg/kg, fluence rate 200 mW/cm2 and fluence 60 J/cm2) using intravital microscopy. Likewise, the distribution of fluorescently labelled macromolecular dextran (FITC-dextran, MW 2000 kDa) was determined after PDT. Study groups included no PDT, PDT, PDT plus a functionally blocking anti-pan-selectin antibody cocktail and PDT plus isotype control antibody. RESULTS PDT significantly enhanced the extravascular accumulation of FITC-dextran in mesothelioma xenografts, but not in normal tissue. PDT significantly increased leukocyte–endothelial cell interaction in tumour. While PDT-induced leukocyte recruitment was significantly blunted by the anti-pan-selectin antibodies in the tumour xenograft, this manipulation did not affect the PDT-induced extravasation of FITC-dextran. CONCLUSIONS Low-level PDT pre-treatment selectively enhances the uptake of systemically circulating macromolecular drugs in malignant mesothelioma, but not in normal tissue. Leukocyte–endothelial cell interaction is not required for PDT-induced drug delivery to malignant mesothelioma. [ABSTRACT FROM AUTHOR]