Combination of surgical resection and photodynamic therapy of 9L gliosarcoma in the nude rat

The objective of the present study was to investigate the treatment of 9L gliosarcoma brain tumor in the rat with the combination of surgical resection and photodynamic therapy (PDT). Nude rats with intracranial 7-day-old 9L gliomas were randomly subjected to no treatment, PDT alone (Photofrin: 2 mg kg(-1), optical: 80 J cm(-2)), surgical resection alone or resection combined with 2 mg kg(-1) Photofrin-mediated PDT at an optical dose of 80 J cm(-2). All animals were sacrificed 14 days after tumor implantation. Hematoxylin-and-eosin and immunohistochemical stainings were performed to assess the tumor volume and the expression of vascular endothelial growth factor (VEGF) in the brain adjacent to the tumor (BAT) as well as the tumor cell apoptosis and proliferation. Our data show that both surgical resection alone and PDT alone significantly decreased tumor volume, but furthermore, surgical resection combined with PDT significantly reduced the tumor volume and reduced local tumor infiltration compared to either surgical resection or PDT treatment alone. PDT treatment with or without resection increased tumor apoptosis, but resection alone did not alter the tumor cell apoptosis compared with a nontreatment control group. Both surgical resection alone and PDT alone induced a significant increase in VEGF expression in the BAT; however intraoperative PDT did not further increase VEGF expression, compared with surgery alone or PDT alone. No significant differences were found in tumor cell proliferation as indicated by Ki67 immunoreactivity among the four groups. Our results suggest that PDT enhances the efficacy of surgical resection in the management of malignant gliomas without increasing VEGF expression in the BAT.     

In vivo study of the inflammatory modulating effects of low-level laser therapy on iNOS expression using bioluminescence imaging

This study was designed to demonstrate that bioluminescence imaging (BLI) can be used as a new tool to evaluate the effects of low-level laser therapy (LLLT) during in vivo inflammatory process. Here, the efficacy of LLLT in modulating inducible nitric oxide synthase (iNOS) expression using different therapeutic wavelengths was determined using transgenic animals with the luciferase gene under control of the iNOS gene expression. Thirty transgenic mice, FVB/N-Tg(iNOS-luc)Xen, were allocated randomly to one of four experimental groups treated with different wavelengths (lambda = 635, 785, 808 and 905 nm) or a control group (nontreated). Inflammation was induced by intra-articular injection of zymosan A in both knee joints. Laser treatment (25 mW cm(-2), 200 s, 5 J cm(-2)) was applied to the knees 15 min after inflammation induction. Measurements of iNOS expression were performed at various times (0, 3, 5, 7, 9 and 24 h) by measuring the bioluminescence signal using a highly sensitive charge-coupled device (CCD) camera. The results showed a significant increase in BLI signal after irradiation with 635 nm laser when compared to the nonirradiated animals and the other LLLT-treated groups, indicating wavelength dependence of LLLT effects on iNOS expression during the inflammatory process, and thus demonstrating an action spectrum of iNOS gene expression following LLLT in vivo that can be detected by BLI. Histological analysis was also performed and demonstrated the presence of fewer inflammatory cells in the synovial joints of mice irradiated with 635 nm compared with nonirradiated knee joints.     

Prompt assessment of WST11-VTP outcome using luciferase transfected tumors enables second treatment and increase in overall therapeutic rate

Abstract This study hypothesized that success rate assessment of vascular targeted photodynamic therapy (VTP) of solid tumors 24 h post-treatment may allow prompt administration of a second treatment in case of failure, increasing the overall success rate. Here, we show that treatment of luciferase transfected CT26-luc mouse colon carcinoma tumors in BALB/c mice by VTP with WST11 (a Pd-bacteriochlorophyll-based photosensitizer) allows fast assessment of treatment success 24 h post-treatment, using bioluminescence imaging (BLI). WST11-VTP was found to abolish luciferin bioluminescence in the treated tumors resulting in two types of responses. One, comprising 75% of the mice, signified successful outcome, presenting neither BLI signal nor tumor regrowth (24 h-90 days post-VTP). The second (the remaining 25% of the mice) signified treatment failure, presenting various levels of BLI signal with subsequent tumor regrowth (24 h-90 days). Consequently, the mice that failed the first treatment were treated again. We show that treatment success rate in both VTP sessions was identical and that the cumulative success rate of the treatment increased from 75% to over 90%. These results therefore, present a fast method of assessing VTP outcome and support the feasibility of successive multiple treatments with these sensitizers in the clinical arena. The presented methodology can also be helpful in future preclinical studies, and expedite the development of VTP drugs.     

Photodynamic Therapy of 9L Gliosarcoma with Liposome-Delivered Photofrin

Abstract— The effect of Photofrin encapsulated in a liposome delivery vehicle for photodynamic therapy (PDT) of the 9L gliosarcoma and normal rat brain was tested. We hypothesized that the liposome vehicle enhances therapeutic efficacy, possibly by increasing tumor tissue concentration of Photofrin. Male Fisher rats bearing a 9L gliosarcoma were treated 16 days after intracerebral tumor implantation with either Photofrin in dextrose (n = 5) or Photofrin in liposome (n = 6). Nontumor-bearing animals were treated with Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle. Tissue concentrations of Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle were measured in tumor, brain adjacent to tumor and in normal brain tissue. Photofrin was administered (intraperitoneally) at a dose of 12.5 mg/kg and PDT (17 J/cm₂ of 632 nm light at 100 mW/cm₂) was performed 24 h after Photofrin administration. Brains were removed 24 h after PDT and stained with hematoxylin and eosin for analysis of cellular damage. The PDT using Photofrin in the liposome vehicle caused significantly more damage to the tumor ( P < 0.001) than did PDT with Photofrin in dextrose. The PDT of tumor with Photofrin delivered in liposomes caused a 22% volume of cellular necrosis, while PDT of tumor with Photofrin delivered in dextrose caused only scattered cellular damage. Photofrin concentration in tumors was significantly higher ( P = 0.021) using liposome (33.8 ± 18.9 μg/g) compared to dextrose delivery (5.5 ± 1.5 μg/g). Normal brain was affected similarly in both groups, with only scattered cellular necrosis. Our data suggest that the liposome vehicle enhances the therapeutic efficacy of PDT treatment of 9L tumors.     

Luminol Chemiluminescence Reports Photodynamic Therapy‐Generated Neutrophil Activity In Vivo and Serves as a Biomarker of Therapeutic Efficacy

Inflammatory cells, most especially neutrophils, can be a necessary component of the antitumor activity occurring after administration of photodynamic therapy. Generation of neutrophil responses has been suggested to be particularly important in instances when the delivered photodynamic therapy (PDT) dose is insufficient. In these cases, the release of neutrophil granules and engagement of antitumor immunity may play an important role in eliminating residual disease. Herein, we utilize in vivo imaging of luminol chemiluminescence to noninvasively monitor neutrophil activation after PDT administration. Studies were performed in the AB12 murine model of mesothelioma, treated with Photofrin‐PDT. Luminol‐generated chemiluminescence increased transiently 1 h after PDT, followed by a subsequent decrease at 4 h after PDT. The production of luminol signal was not associated with the influx of Ly6G⁺ cells, but was related to oxidative burst, as an indicator of neutrophil function. Most importantly, greater levels of luminol chemiluminescence 1 h after PDT were prognostic of a complete response at 90 days after PDT. Taken together, this research supports an important role for early activity by Ly6G⁺ cells in the generation of long‐term PDT responses in mesothelioma, and it points to luminol chemiluminescence as a potentially useful approach for preclinical monitoring of neutrophil activation by PDT.     

Metronomic Photodynamic Therapy as a New Paradigm for Photodynamic Therapy: Rationale and Preclinical Evaluation of Technical Feasibility for Treating Malignant Brain Tumors¶

The concept of metronomic photodynamic therapy (mPDT) is presented, in which both the photosensitizer and light are delivered continuously at low rates for extended periods of time to increase selective tumor cell kill through apoptosis. The focus of the present preclinical study is on mPDT treatment of malignant brain tumors, in which selectivity tumor cell killing versus damage to normal brain is critical. Previous studies have shown that low‐dose PDT using 5‐aminolevulinic acid (ALA)‐induced protoporphyrin IX(PpIX) can induce apoptosis in tumor cells without causing necrosis in either tumor or normal brain tissue or apoptosis in the latter. On the basis of the levels of apoptosis achieved and model calculations of brain tumor growth rates, metronomic delivery or multiple PDT treatments, such as hyperfractionation, are likely required to produce enough tumor cell kill to be an effective therapy. In vitro studies confirm that ALA‐mPDT induces a higher incidence of apoptotic (terminal deoxynucleotidyl transferase‐mediated 2′‐deoxyuridine 5′‐triphosphate, sodium salt nick‐end labeling positive) cells as compared with an acute, high‐dose regimen (ALA‐αPDT). In vivo, mPDT poses two substantial technical challenges: extended delivery of ALA and implantation of devices for extended light delivery while allowing unencumbered movement. In rat models, ALA administration via the drinking water has been accomplished at very high doses (up to 10 times therapeutic dose) for up to 10 days, and ex vivo spectro‐fluorimetry of tumor (9L gliosarcoma) and normal brain demonstrates a 3–4 fold increase in the tumor‐to‐brain ratio of PpIX concentration, without evidence of toxicity. After mPDT treatment, histological staining reveals extensive apoptosis within the tumor periphery and surrounding microinvading colonies that is not evident in normal brain or tumor before treatment. Prototype light sources and delivery devices were found to be practical, either using a laser diode or light‐emitting diode (LED) coupled to an implanted optical fiber in the rat model or a directly implanted LED using a rabbit model. The combined delivery of both drug and light during an extended period, without compromising survival of the animals, is demonstrated. Preliminary evidence of selective apoptosis of tumor under these conditions is presented.     

Fabrication of doxorubicin and chlorotoxin-linked Eu-Gd2O3 nanorods with dual-model imaging and targeted therapy of brain tumor

It is urgent to find a technology accurately to better diagnose and treat to brain tumor.Eu-doped Gd2 O3 nanorods(Eu-Gd2 O3 NRs)with paramagnetic and fluorescent properties were conjugated with doxorubicin(Dox)and chlorotoxin(CTX)via PEGylation,hydrazone bond and sulfur bond(named as CTXNRs-Dox),and these NRs could release more Dox in lower pH environment.The results of cell experiments indicated that CTX-NRs-Dox had obvious targeting and toxic effects on U251 cells,as well as good fluorescence imaging behavior.The orthotopic glioma-transplanted mice models were constructed via the intracranial injection of glioma cells(U87 MG).The result of experiments after the tail-vein injection of the prepared NRs suggested that CTX-NRs-Dox could target to brain tumors via the long-time blood circulation,leading to their obvious contrast enhancement of MR imaging of the intracranial tumor and their significant inhibitory effect on the growth and metastasis of brain tumors.A mechanism of synergistic effect of CTX-NRs-Dox on targeting and inhabiting the brain tumor was proposed.Our research suggested that CTX-NRs-Dox had potential application prospect in the detection and treatment of glioma.     

Monitoring photodynamic therapy of localized infections by bioluminescence imaging of genetically engineered bacteria

The increasing occurrence of multi-antibiotic resistant microbes has led to the search for alternative methods of killing pathogens and treating infections. Photodynamic therapy (PDT) uses the combination of non-toxic dyes and harmless visible light to produce reactive oxygen species that can kill mammalian and microbial cells. Although the photodynamic inactivation of bacteria has been known for over a hundred years, its use to treat infections has not been much developed. This may be partly due to the difficulty of monitoring the effectiveness of PDT in animal models of infection. In order to facilitate this monitoring process, we have developed a procedure that uses bioluminescent genetically engineered bacteria and a light sensitive imaging system to allow real-time visualization of infections. When these bacteria are treated with PDT in vitro, the loss of luminescence parallels the loss of colony-forming ability. We have developed several models of infections in wounds and soft-tissue abscesses in mice that can be followed by bioluminescence imaging. The size and intensity of the infection can be sequentially monitored in a non-invasive fashion in individual mice in real-time. When photosensitizers are introduced into the infected tissue followed by illumination with red light, a light-dose dependent loss of luminescence is seen. If the bacterium is invasive, the loss of luminescence correlates with increased survival of the mice, whilst animals in control groups die of sepsis within five days. Healing of the PDT treated wounds is not impaired and may actually be improved. This approach can allow many animal models of localized infections to be accurately monitored for efficacy of treatment by PDT.     

Magnetic Resonance Imaging Evaluation of Photodynamic Therapy-Induced Hemorrhagic Necrosis in the Murine M1 Tumor Model

Abstract— Proton magnetic resonance imaging (MRI) and histological methods were used to evaluate photodynamic therapy (PDT)-induced hemorrhagic necrosis in the murine Ml tumor within 72 h of treatment of male DBA/2 mice. The effects of three photosensitizing drugs were investigated: Photofrin (n = 4), Zn (II) phthalocyanine (n = 7) and benzoporphyrin derivative monoacid ring A (n = 11). As noted in previous studies of PDT using MRI, MRI makes possible serial, noninvasive, in vivo observation of tissue response to PDT. Our serial study of MRI and histological data confirms that tumors responded in the same way to PDT treatment using the three photosensitizing drugs: vascular damage followed by hemorrhagic necrosis. Most importantly and unlike previous MRI studies of PDT, we used a very high field magnet that enhanced the effect of magnetic susceptibility on image signal when blood is processed by the body after PDT-induced hemorrhagic necrosis. This last finding demonstrates the utility of high field magnets and the importance of localized, serial experiments in future magnetic resonance studies of PDT.     

Combination therapy with antiangiogenic treatment and photodynamic therapy for the nude mouse bearing U87 glioblastoma

The objective of this study was to evaluate the effects of combination therapy with photodynamic therapy (PDT) and a novel antiangiogenic regimen using monoclonal antibodies against both vascular endothelial growth factor receptors (VEGFR)-1 (MF1) and VEGFR-2 (DC101) on intracranial glioblastoma xenografts in nude mice. Nude mice bearing intracerebral U87 glioblastoma were treated with PDT and the antiangiogenic regimen (MF1 and DC101) either alone or in combination, while those left untreated served as tumor controls. Tumor volume and animal survival time were analyzed to evaluate the outcome of different treatment modalities. In addition, the immunohistochemical expression of VEGF in the brain adjacent to the tumor, von Willebrand factor (vWF), apoptotic, and proliferative markers in the tumor area were examined. PDT or MF1 + DC101 alone significantly reduced the tumor volume and prolonged the survival time of glioma-implanted animals. Combined therapy markedly reduced tumor volume and increased survival time with significantly better outcomes than both monotherapies. Both vWF and VEGF levels significantly increased after PDT while they both significantly decreased after antiangiogenic treatment, compared with no treatment. PDT plus antiangiogenic treatment led to significant decreases in both vWF and VEGF expression, compared with PDT alone. Either PDT or antiangiogenic treatment alone significantly increased tumor cell apoptosis compared with no treatment, while combination therapy resulted in further augmentation of apoptosis. Antiangiogenic treatment with or without PDT significantly decreased tumor cell proliferation, compared with either no treatment or PDT alone. In summary, we demonstrate both significant inhibition of tumor growth and extended survival of mice treated by the combination therapy with PDT and antiangiogenic agents, compared with each single treatment, suggesting that the combination therapy may be a promising strategy to improve clinical outcomes in glioblastoma.     

A Photodynamic System based on Endogenous Bioluminescence for in vitro Anticancer Studies

Photodynamic therapy (PDT) is becoming an important cancer treatment in recent years. However, at present, the therapeutic effect of PDT is limited due to insufficient penetration depth of light. In this study, a new photodynamic system (d ‐Lu)PCN‐224 is constructed by porphyrin‐based metal‐organic framework (MOF) PCN‐224 and bioluminescent molecule d ‐fluorescein (d ‐Lu). The bioluminescence (BL) spectrum of the reaction overlaps with the absorption spectrum of PCN‐224, so it is speculated that bioluminescence resonance energy transfer (BRET) between the MOF and d ‐Lu which indicates inner light can be gained and used for PDT. Confocal imaging analysis and cytotoxicity assays have demonstrated that (d ‐Lu)PCN‐224 can produce singlet oxygen and decrease the cell viability of SKOV‐3. This system provides a possibility of PDT for deep‐level organization without an external light source.     

IMPROVED SURVIVAL FROM INTRACAVITARY PHOTODYNAMIC THERAPY OF RAT GLIOMA

The effectiveness of intratumoral photoradiation in photodynamic therapy (PDT) using a polyporphyrin photosensitizer was studied in the RT-2 rat glioma model. One week after intracerebral implantation of RT-2 cells, experimental rats received a single i.p. injection of 2 mg/kg of Photofrin. After administration of the photosensitizer (48 h), the tumors were partially resected and the exposed cavity was irradiated with 15 J of laser light at a wavelength of 630 nm. Further treatment with a large craniectomy significantly enhanced rat survival. Control rats which received no photosensitizer but were treated with surgery, alone or in combination with laser irradiation, succumbed from early tumor recurrence. Photodynamic therapy without decompressive surgery resulted in hemorrhagic infarction of residual tumor and adjacent brain with focal cerebral edema which resulted in cerebral herniation and early death. Our results indicate that photodynamic therapy is effective in treating residual brain tumor but at the expense of brain tissue surrounding the tumor. Unless relieved, intracranial pressure from photodynamic therapy-associated cerebral edema in this animal model resulted in shortened survival.     

Role of the Immune System in Mediating the Antitumor Effect of Benzophenothiazine Photodynamic Therapy

The role of the host immune system in contributing to tumor regression following benzophenothiazine photodynamic therapy (PDT) was examined. Photodynamic therapy with 2-iodo-5-ethylamino-9-diethylaminobenzo[a]-phenothiazinium chloride (2I-EtNBS) eradicated EMT-6 mammary fibrosarcomas in 75-100% of treated mice. In contrast, PDT failed to inhibit tumor growth in T-cell-deficient nude mice. Furthermore, T-cell depletion studies with anti-CD8 antibody revealed that the CD8+ T-cell population was critical for an effective PDT response (tumor volume 14 days post-PDT: 262 mm3 vs 59 mm3 in controls; P < 0.01). Because anti-CD4 antibody inhibited tumor growth in the absence of PDT, the role of CD4+ T cells remains unclear. Depletion of natural killer (NK) cells in vivo with anti-asialo-GM1 antibody significantly reduced a suboptimal PDT effect relative to vehicle controls (tumor volume 13 days post-PDT: 513 mm3 vs 85 mm3, respectively; P < 0.001). However, splenic NK cells obtained from PDT-treated tumor-bearing mice were not cytotoxic in vitro against EMT-6 cells, suggesting that NK cells contribute to the PDT effect in vivo by an indirect mechanism. In addition, when mice with complete tumor regression following PDT were rechallenged 28 days later with 5 x 10(5) EMT-6 cells, tumor growth was significantly inhibited as compared to controls (tumor volume 40 days postrechallenge: 137 mm3 vs 833 mm3 in controls; P < 0.03; percent animals without tumor in five experiments: 67% vs 8% in controls). Collectively, these results demonstrate that CD8+ T cells are required to prevent tumor regrowth after 2I-EtNBS-PDT, NK cells contribute to this response and such PDT can elicit protective antitumor immunity.     

Chemical molecule-induced light-activated system for anticancer and antifungal activities

Except for chemotherapy, surgery, and radiotherapy, photodynamic therapy (PDT) as new therapy modality is already in wide clinic use for the treatment of various diseases. The major bottleneck of this technique is the requirement of outer light source, which always limits effective application of PDT to the lesions in deeper tissue. Here, we first report a new modality for treating cancer and microbial infections, which is activated by chemical molecules instead of outer light irradiation. In this system, in situ bioluminescence of luminol can be absorbed by a cationic oligo(p-phenylene vinylene) (OPV) that acts as the photosensitizer through bioluminescence resonance energy transfer (BRET) process. The excited OPV sensitizes oxygen molecule in the surroundings to produce reactive oxygen species (ROS) that kill the adjacent cancer cells in vitro and in vivo, and pathogenic microbes. By avoiding the use of light irradiation, this work opens a new therapy modality to tumor and pathogen infections.     

A pH-activatable and aniline-substituted photosensitizer for near-infrared cancer theranostics

This work reports a newly designed pH-activatable and aniline-substituted aza-boron-dipyrromethene as a trifunctional photosensitizer to achieve highly selective tumor imaging, efficient photodynamic therapy (PDT) and therapeutic self-monitoring through encapsulation in a cRGD-functionalized nanomicelle. The diethylaminophenyl is introduced in to the structure for pH-activatable near-infrared fluorescence and singlet oxygen (¹O₂) generation, and bromophenyl is imported to increase the ¹O₂ generation efficiency upon pH activation by virtue of its heavy atom effect. After encapsulation, the nanoprobe can target α_vβ₃ integrin-rich tumor cells via cRGD and is activated by physiologically acidic pH for cancer discrimination and PDT. The fascinating advantage of the nanoprobe is near-infrared implementation beyond 800 nm, which significantly improves the imaging sensitivity and increases the penetration depth of the PDT. By monitoring the fluorescence decrease in the tumor region after PDT, the therapeutic efficacy is demonstrated in situ and in real time, which provides a valuable and convenient self-feedback function for PDT efficacy tracking. Therefore, this rationally designed and carefully engineered nanoprobe offers a new paradigm for precise tumor theranostics and may provide novel opportunities for future clinical cancer treatment.     

Photodynamic Therapy of Human Glioma (U87) in the Nude Rat

Abstract— We measured the response of normal brain and the human U87 glioma implanted in the brain of rats (n = 65) to photodynamic therapy (PDT) using Photofrin as the sensitizer. Normal brain and U87 tumor implanted within brain of athymic (nude) rats were subjected to PDT (12.5 mg/kg of Photofrin) at increasing optical energy doses (35 J/cm², 140 J/cm², 280 J/cm²) of 632 nm light. Photofrin concentration in tumor, brain adjacent to tumor and normal brain were measured in a separate population of rats. Twenty-four hours after PDT, the brains were removed, sectioned, stained with hematoxylin and eosin (H&E), and the volumes of the PDT-induced lesion measured. Photofrin concentration in tumor greatly exceeded that of normal brain and brain adjacent to tumor (>20×). Both normal brain and U87 tumor exhibited superficial tissue damage with PDT at 35 J/cm². However, both normal and tumor-implanted brain exhibited tissue damage with increasing optical dose. A heterogeneous pattern of pannecrosis along with a uniform volume of pannecrosis was detected in the tumor. In contrast, normal brain exhibited a uniform sharply demarcated volume of necrosis. Our data indicate that the U87 human brain tumor model and the normal brain in the athymic rat are sensitive to PDT and Photofrin with an optical dose-dependent response to treatment.     

Angiogenesis induced by photodynamic therapy in normal rat brains

Angiogenesis promotes tumor growth and invasiveness in brain. Because brain injury often induces expression of angiogenic-promoting molecules, we hypothesize that oxidative insult induced by photodynamic therapy (PDT) could lead to an endogenous angiogenic response, possibly diminishing the efficacy of PDT treatment of tumors. Therefore, we sought to establish whether PDT induced an angiogenic response within the nontumored brain. PDT using Photofrin as a sensitizer at an optical dose of 140 J/cm2 was performed on normal rat brain (n = 30). Animals were sacrificed at 24 h, and 1, 2, 3 and 6 weeks after PDT treatment. Fluorescein isothiocyanatedextran perfusion was performed, and brains were fixed for immunohistological study. Immunostaining revealed that vascular endothelial growth factor (VEGF) expression increased within the PDT-treated hemisphere 1 week after treatment and remained elevated for 6 weeks. Three-dimensional morphologic analysis of vasculature within PDT-treated and contralateral brain demonstrated PDT-induced angiogenesis, as indicated by a significant increase in vessel connectivity (P < 0.001) concomitant with decreased (P < 0.05) mean segment length compared with vessels within the contralateral hemisphere. Volumetric measurement of angiogenic regions indicate that neovascular expansion continued for 4 weeks after PDT. These data demonstrate that PDT induces VEGF expression and neovascularization within normal brain. Because angiogenesis promotes growth and invasiveness of tumor, antagonizing this endogenous angiogenic response to PDT may present a practical means to enhance the efficacy of PDT.     

Outcome of mTHPC mediated photodynamic therapy is primarily determined by the vascular response

We have previously shown that the efficacy of photodynamic therapy (PDT) using the photosensitizer meso-tetra-hydroxyphenyl-chlorin (mTHPC) correlated with plasma drug levels at the time of illumination rather than drug levels in human tumor xenografts or mouse skin. These results suggested that vascular-mediated effects could be important determinants of PDT response in vivo. In the present study we further investigated the relationship between PDT response, mTHPC pharmacokinetics and the localization and extent of vascular damage induced in human squamous cell carcinoma xenografts (HNXOE). Plasma levels of mTHPC decreased exponentially with time after injection, whereas tumor drug levels remained maximal for at least 48 h. At 3 h after administration mTHPC was localized in the blood vessels, whereas at later times it was distributed throughout the whole tumor. Illumination at 3 h after mTHPC, which resulted in 100% long-term tumor cure, led to a marked reduction of vascular perfusion and increased tumor hypoxia at 1 h after treatment. Illumination at 48 h resulted in rapid regrowth of most tumors and only 10% cure. This protocol did not affect a significant decrease in vascular perfusion or increase in tumor hypoxia. These data show that optimal responses to mTHPC-mediated PDT were primarily dependent on the early vascular response, and that plasma drug levels at the time of illumination could predict this relationship.     

Induction of systemic neutrophil response in mice by photodynamic therapy of solid tumors.

Photodynamic therapy (PDT) of solid tumors elicits a strong, acute inflammatory response characterized by a rapid and massive infiltration of activated neutrophils into the tumor. The present study investigated the impact of PDT on the systemic and local (treatment site) kinetics of neutrophil trafficking and activity in mouse SCCVII and EMT6 tumor models. Differential leukocyte counts in the peripheral blood of treated mice revealed a pronounced neutrophilia developing rapidly after Photofrin porfimer sodium (Photofrin)- or tetra(m-tetrahydroxyphenyl)chlorin (mTHPC)-based PDT. Significant neutrophilia was also observed upon PDT treatment of normal dorsal skin but not on the footpad of tumor-free mice. The changes in circulating neutrophil numbers were accompanied by an efflux of these cells from the bone marrow. An increased proportion of cells with high L-selectin (CD62L antigen) expression was found among bone-marrow-residing neutrophils 6-24 h after PDT, and in neutrophils in the peripheral circulation and treated tumors 24 h after therapy. Complement inhibition completely prevented the development of PDT-induced neutrophilia. The results of the present study demonstrate that treatment of solid tumors by PDT induces a strong and protracted increase in systemic neutrophil numbers mediated by complement activation. This reaction reflects rapid and massive mobilization and activation of neutrophils for the destruction of PDT-treated tumor tissue.     

Photodynamic therapy with aluminum-chloro-phtalocyanine induces necrosis and vascular damage in mice tongue tumors

In this paper we describe the efficacy of the liposomal-AlClPc (aluminum-chloro-phthalocyanine) formulation in PDT study against Ehrlich tumor cells proliferation in immunocompetent swiss mice tongue. Experiments were conduced in sixteen tumor induced mice that were divided in three control groups: (1) tumor without treatment; (2) tumor with 100 J/cm² laser (670 nm) irradiation; and (3) tumor with AlClPc peritumoral injection; and a PDT experimental group when tumors received AlClPc injection followed by tumor irradiation. Control groups present similar macroscopically and histological patterns after treatments, while PDT treatment induced 90% of Ehrlich tumor necrosis after 24 h of one single application, showing the efficacy of liposome-AlClPc (aluminum-chloro-phthalocyanine) mediated PDT on the treatment of oral cancer.