PDT Effect Research Articles

The effects of PDT in primary malignant brain tumours could be improved by intraoperative radiotherapy

GBM has a poor survival despite surgery and chemoradiotherapy. Cytoreduction and PDT have postulated to afford better local GBM-control. However, the interaction of PDT with newer novel therapies had not been fully investigated. This study reviewed the impact of PDT in conjunction with intraoperative radiotherapy. Case note review of prospectively collected data of GBMs treated surgically by the senior author (SE). Patients received standard therapy (ST), ST+PDT or ST+PDT+IORT. ST involved maximum safe resection, PDT involved intracavity 100 J/cm² 630 nm laser and IORT involved intracavity 10-15 Gys using the PRS400®. Patients were followed up clinically and radiologically till death. There were 73 patients included in this analysis (42 males). The average age was 59years. Thirty received PDT and 43 did not. The mean survival of PDT-patients was significantly longer than those had ST alone (62.9 weeks vs. 20.6 weeks) (p=0.001). Patients < 65 year of age survived longer than those ≥ 65 year (p=0.033). IORT on its own did not make a significant difference to survival (p=0.111). However the average survival for patients who received PDT+IORT was substantially higher than those who received PDT alone (79 weeks vs. 39.7 weeks). Using a Cox regression covariant analysis, demonstrated that PDT was the only therapy to make a statistically significant difference to survival (p=0.018). PDT in high grade glioma was statistically significant therapeutic modality and its effects were further improved by IORT.

Molecular determinants of photodynamic therapy for lung cancers

PDT induces apoptosis, inflammatory reactions, immune reactions, and damage to the microvasculature around the tumors. The mechanisms responsible for the anticancer effects of Photofrin-PDT and NPe6-PDT differ somewhat. To select a photosensitizer for lung cancer treatment and to improve the efficacy of PDT, the mechanisms of action for PDT using Photofrin or NPe6 must be elucidated and the phenomena validated by analyzing molecular determinants from clinical samples. We examined the role of immunological reactions in the anti-tumor effects of PDT using cytokine-overexpressing cells and investigated whether the anti-apoptotic protein Bcl-2 may be a molecular target. Moreover, we investigated the association between ATP-binding cassette transporter proteins such as breast cancer-resistant protein (BCRP), which can pump out some types of photosensitizer, and the efficacy of PDT using clinical samples from 81 early lung cancer lesions treated with PDT between 1998 and 2006 at the Tokyo Medical University Hospital. Photofrin-PDT damaged Bcl-2 and rapidly induced apoptosis, but NPe6-PDT did not damage Bc-2 nor did it induce morphologically typical apoptosis. However, NPe6-PDT exerted a strong anti-tumor effect, regardless of the overexpression of Bcl-2. By analyzing the BCRP-overexpressing cells, Photofrin, but not NPe6, was found to be a substrate of BCRP. All 81 lung cancer lesions were BCRP-positive; as Photofrin was found to be a substrate of BCRP, the expression of BCRP significantly affected the efficacy of Photofrin-PDT. However, NPe6-PDT exerted a strong antitumor effect regardless of BCRP expression, and the complete response rate after NPe6-PDT was much higher than that after Photofrin-PDT. Our translational research suggests that NPe6-PDT may be superior to Photofrin-PDT for the treatment of lung caner, and individualized approaches to PDT based on the expression status of Bcl-2 and/or BCRP may improve the efficacy of PDT in patients with lung cancers.

PDT effect on Pythiosis—In vitro and in vivo investigation

PDT effect on Pythiosis—In vitro and in vivo investigation

Hexvix ® mediated rat bladder photodynamic therapy: The impact of fluence rate on normal bladder preservation

Bladder PDT, the first FDA indication, has been abandoned in favour of photodiagnosis with ALA or derivatives. Major drawback of this treatment modality is prolonged and severe irritative bladder symptoms, due to lack of selectivity of the drug and generalized urothelial necrosis. Low fluence rates are known to potentiate therapeutic efficacy due to an oxygen sparing regime. We have evaluated the effect of low fluence rate PDT on therapeutic outcome and side effects in rat tumor bearing bladders. Bladders were instilled with 8 mM hexylaminolevulinate and illuminated with 635 nm light to a total light dose of 20 or 15 J/cm2 at 100 or 15 mW/cm2, 5 rats per group. Fluence rates of 15 mW/cm2 did not provoke enhancement of cardiac and respiratory rhythms as opposed to 100 mW/cm2, neither was hematuria observed post treatment. Macroscopic aspects of bladders at 100 mW/cm2 show thickened bladders with hemorrhagic areas whereas 15 J/cm2 does not alter macroscopic features. Pathology revealed the absence of viable superficial tumors, irrespective of irradiation conditions. Inflammatory volume was calculated to be 96 a.u. for high fluence high light dose, reduced to 18 a.u. when reducing the light dose and 12 a.u. for the low fluence rates, irrespective of the light dose. Normal urothelial is preserved over the total bladder in case of 15 mW/cm2, whereas major portions of the bladder show absence of reduction of cell layers at 100 mW/cm2. Low fluence rate PDT does not hamper therapeutic efficacy and minimizes local side effects in rats.

Therapeutic effects of systemic PDT in a leukemia animal model using A20 cell lines

Therapeutic effects of systemic PDT in a leukemia animal model using A20 cell lines

Antiviral and antimycotic effects of PDT with ALAsense

Antiviral and antimycotic effects of PDT with ALAsense

Photodynamic inactivation of bacteria using polyethylenimine–chlorin(e6) conjugates: Effect of polymer molecular weight, substitution ratio of chlorin(e6) and pH

Antimicrobial photodynamic therapy (APDT) is a novel technique to treat local infections. Previously we reported that the attachment of chlorin(e6) to polyethylenimine (PEI) polymers to form PEI-ce6 conjugates is an effective way to improve ce6 PDT activity against bacteria. The aim of this work was to explore how the polymer molecular weight, substitution ratio (SR) of ce6 and pH value affect the PDT efficacy. We have synthesized PEI-ce6(10) (MW = 60,000, SR = 1) and PEI-ce6(11) (MW = 60,000, SR = 5) and compared these with the previous PEI-ce6(9) (MW = 10,000, SR = 1). We tested the PDT efficacy of these three conjugates against Gram-negative E. coli and Gram-positive bacteria (S. aureus and E. fecalis) at three different pH values (5.0, 7.4, 10.0) that may affect the charge on both the bacterial cells and on the conjugate (that has both basic and acidic groups). PEI-ce6(9) and PEI-ce6(10) were the most effective against these tested bacteria. The PDT effect of all three conjugates depended on pH values. The effective order was pH = 10.0 > pH = 7.4 > pH = 5.0 on E. coli. For S. aureus and E. fecalis the order was pH = 5.0 > pH = 10.0 > pH = 7.4. PEI-ce6(11) PDT activity was worse than PEI-ce6(10) activity which is probably connected to the fact that ce6 molecules are self-quenched within the PEI-ce6(11) molecule. Ce6 quenching within the PEI-ce6 molecules was proved by analyzing fluorescence spectra of PEI-ce6 conjugates at different pH values. There were no differences in bacterial uptake between different pH values in three PEI-ce6 conjugates. We assume high pH (rather than low pH as was hypothesized) disaggregates the conjugates, so the higher pH was more effective than the lower pH against E. coli. But for Gram-positive bacteria, low pH was more effective possibly due to more overall positive charge on the conjugate.

Schiff base oxovanadium(IV) complexes of phenanthroline bases showing DNA photocleavage activity at near-IR light and photocytotoxicity

Oxovanadium(IV) complexes [VO(L)(B)](ClO 4) ( 1– 3) of N-2-pyridylmethylidine-2-hydroxyphenylamine (HL) Schiff base and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2- d:2′,3′- f]quinoxaline (dpq in 2) or dipyrido[3,2- a:2′,3′- c]phenazine (dppz in 3), were prepared, characterized and their DNA binding property, photo-induced DNA cleavage activity and photocytotoxicity in HeLa cells studied. The crystal structure of 1 shows the presence of a VO 2+ moiety in VO 2N 4 coordination geometry. The complexes show a d– d band at ∼830 nm in DMF. The complexes display an oxidative V(V)–V(IV) response near 0.5 V versus SCE and a reductive V(IV)/V(III) response near −0.65 V in DMF −0.1 M TBAP. The complexes that are avid binders to CT DNA giving K b values within 7.1 × 10 4 to 3.2 × 10 5 M −1, do not show any significant chemical nuclease activity in presence of 3-mercaptopropionic acid or glutathione. The dpq and dppz complexes are photocleavers of pUC19 DNA in UV-A light of 365 nm forming both 1O 2 and ·OH radicals and in near-IR light of 785 nm forming ·OH radicals. The dppz complex exhibits photocytotoxicity in visible light in HeLa cells (IC 50 = 6.8 μM). Flow-cytometric study on this complex shows a high sub-G1 phase in light compared to dark indicating PDT effect.

Effect of ALA-mediated photodynamic therapy in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on bladder cancer cells.

IntroductionPhotodynamic therapy (PDT), an alternative treatment modality for superficial bladder tumors is based on the interaction of a photosensitizer with light. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising candidate for anticancer therapy due to its ability to selectively induce apoptosis in cancer cells. However, not all tumor cells are sensitive to TRAIL. TRAIL-resistant cancer cells can be sensitized to TRAIL induced apoptosis by anticancer agents.ObjectiveWe investigated the combined cytotoxic effect of TRAIL and PDT with 5-aminolevulinic acid (ALA) on bladder cancer cells.Materials and methodsThree human bladder transitional cancer cell lines: T24, 647V, and SW780 were treated with TRAIL and/or ALA-mediated PDT. Cytotoxicity was determined by MTT and LDH assay.ResultsOur study confirmed that T24 and 647V bladder cancer cells were resistant to TRAIL, whereas SW780 cells were sensitive to TRAIL. We therefore examined the cytotoxic effect of TRAIL in combination with ALA-mediated PDT on bladder cancer cells. We showed for the first time that pretreatment with low dose of PDT significantly sensitizes bladder cancer cells to TRAIL induced cytotoxicity.ConclusionALA-mediated PDT augments the cytotoxic effect of TRAIL on transitional cancer cells of bladder. The obtained results suggest that combined treatment of TRAIL and PDT may provide the basis for a new strategy to induce cytotoxicity in bladder cancer cells.

Photodynamic Therapy with Boronated Chlorin as a Photosensitizer

The purpose of this work was to study the efficiency of photodynamic therapy with boronated chlorin as a photosensitizer for treating experimental tumors such as ?-1 sarcoma and ?-16 melanoma. PDT of ?-1 sarcoma with laser radiation energy density of 300 J/cm2 and power density of 0.42 W/cm2 resulted in complete tumor regression at all three doses of the photosensitizer. Photodynamic therapy of ?-16 melanoma appeared to be the most effective when boronated chlorin at a dose of 10.0 mg/kg and laser radiation energy density of 150 J/cm2 and power density of 0.25 W/cm2 were used. A satisfactory effect of PDT on the tumor was achieved when a dose of 5.0 mg/kg, energy density of 300 J/cm2 and power density of 0.25 W/cm2 were used. At 10 - 21 days after PDT with use of other studied parameters, some animals showed continued tumor growth. Nevertheless, by the end of observation (at day 21), no lung metastases were found in animals. In control, they were detected in up to 43.4 % of cases.

Impact of metal on the DNA photocleavage activity and cytotoxicity of ferrocenyl terpyridine 3d metal complexes

Ferrocenyl terpyridine 3d metal complexes and their analogues, viz. [M(Fc-tpy)(2)](ClO(4))(2) (1-4), [Zn(Ph-tpy)(2)](ClO(4))(2) (5) and [Zn(Fc-dpa)(2)]X(2) (X = ClO(4), 6; PF(6), 6a), where M = Fe(II) in 1, Co(II) in 2, Cu(II) in 3 and Zn(II) in 4, Fc-tpy is 4'-ferrocenyl-2,2':6',2''-terpyridine, Ph-tpy is 4'-phenyl-2,2':6',2''-terpyridine and Fc-dpa is ferrocenyl-N,N-dipicolylmethanamine, are prepared and their DNA binding and photocleavage activity in visible light studied. Complexes 2, 4, 5 and 6a that are structurally characterized by X-ray crystallography show distorted octahedral geometry with the terpyridyl ligands binding to the metal in a meridional fashion, with Fc-dpa in 6a showing a facial binding mode. The Fc-tpy complexes display a charge transfer band in the visible region. The ferrocenyl (Fc) complexes show a quasi-reversible Fc(+)-Fc redox couple within 0.48 to 0.66 V vs. SCE in DMF-0.1 M TBAP. The DNA binding constants of the complexes are ∼10(4) M(-1). Thermal denaturation and viscometric data suggest DNA surface binding through electrostatic interaction by the positively charged complexes. Barring the Cu(II) complex 3, the complexes do not show any chemical nuclease activity in the presence of glutathione. Complexes 1-4 exhibit significant plasmid DNA photocleavage activity in visible light via a photoredox pathway. Complex 5, without the Fc moiety, does not show any DNA photocleavage activity. The Zn(II) complex 4 shows a significant PDT effect in HeLa cancer cells giving an IC(50) value of 7.5 μM in visible light, while being less toxic in the dark (IC(50) = 49 μM).

Efficient Synthesis and in vitro PDT Effect of Purpurin-18-N-Aminoimides

A simple and efficient synthetic route for making purpurin-18-N-aminoimides is described. The purpurin-18-Naminoimides are obtained by treatment of purpurin-18 methyl ester with various amines. These new compounds have long wavelength absorptions in the range of 706 - 711 nm. In preliminary screening, the purpurin-18-N-aminoimides have shown promising photosensitizing activity for the cancer cell by in vitro study in photodynamic therapy.

Hypocrellin B-encapsulated nanoparticle-mediated rev-caspase-3 gene transfection and photodynamic therapy on tumor cells

Gene therapy and photodynamic therapy are two kinds of important therapeutic strategies for treating malignant tumors. In order to explore the combined effects of gene therapy and PDT on tumor cells, rev-caspase-3 gene was transfected into the tumor model CNE2 cells using hypocrellin B-encapsulated nanoparticle (nano-HB) as a carrier. The transfected CNE2 cells were then irradiated by light from a LED source and the survival rate was investigated 18 h after PDT. Apoptosis was analyzed by a flow cytometer with propidium iodine (PI) staining and the active caspase-3 expression was measured using flow cytometry with phycoerythrin (PE)-conjugated anti-active caspase-3 antibody. The result from the flow cytometer showed that the level of the activated caspase-3 significantly increased up to 63.10% in the transfected CNE2 cells. The survival rate 18 h after gene transfection alone and nano-HB-mediated PDT was 96.6 ± 2.07%, 72.6 ± 4.15%, respectively. However, the survival rate of the transfected CNE2 cells 18 h after LED exposure significantly decreased to 50.6 ± 5.98% under the light energy of 4 J/cm 2. Apoptotic rate 18 h after the combination of gene transfection and PDT increased up to 24.65%. Our findings demonstrated that nano-HB could significantly enhance the tranfection efficiency of rev-caspase-3 gene in the CNE2 cells. LED irradiation could effectively kill the treated CNE2 cells and induce apoptosis, suggesting hypocrellin B-encapsulated nanoparticle as an efficient gene carrier and a novel photosensitizer. The combination of gene therapy and PDT using nanoparticle as a mediator can be developed for treating nasopharyngeal carcinoma.

Targeting tissue factor on tumour cells and angiogenic vascular endothelial cells by factor VII-targeted verteporfin photodynamic therapy for breast cancer in vitro and in vivoin mice

BackgroundThe objective of this study was to develop a ligand-targeted photodynamic therapy (tPDT) by conjugating factor VII (fVII) protein with photosensitiser verteporfin in order to overcome the poor selectivity and enhance the effect of non-targeted PDT (ntPDT) for cancer. fVII is a natural ligand for receptor tissue factor (TF) with high affinity and specificity. The reason for targeting receptor TF for the development of tPDT is that TF is a common but specific target on angiogenic tumour vascular endothelial cells (VEC) and many types of tumour cells, including solid tumours and leukaemia.MethodsMurine factor VII protein (mfVII) containing a mutation (Lys341Ala) was covalently conjugated via a cross linker EDC with Veterporfin (VP) that was extracted from liposomal Visudyne, and then free VP was separated by Sephadex G50 spin columns. fVII-tPDT using mfVII-VP conjugate, compared to ntPDT, was tested in vitro for the killing of breast cancer cells and VEGF-stimulated VEC and in vivo for inhibiting the tumour growth of breast tumours in a mouse xenograft model.ResultsWe showed that: (i) fVII protein could be conjugated with VP without affecting its binding activity; (ii) fVII-tPDT could selectively kill TF-expressing breast cancer cells and VEGF-stimulated angiogenic HUVECs but had no side effects on non-TF expressing unstimulated HUVEC, CHO-K1 and 293 cells; (iii) fVII targeting enhanced the effect of VP PDT by three to four fold; (iii) fVII-tPDT induced significantly stronger levels of apoptosis and necrosis than ntPDT; and (iv) fVII-tPDT had a significantly stronger effect on inhibiting breast tumour growth in mice than ntPDT.ConclusionsWe conclude that the fVII-targeted VP PDT that we report here is a novel and effective therapeutic with improved selectivity for the treatment of breast cancer. Since TF is expressed on many types of cancer cells including leukaemic cells and selectively on angiogenic tumour VECs, fVII-tPDT could have broad therapeutic applications for other solid cancers and leukaemia.

Abstract 496: Enhance efficacy of photodynamic therapy in combination with selenium in TC-1 animal model

Abstract Photodynamic therapy (PDT) is a promising cancer treatment modality that involves the interaction of the photosensitizer, molecular oxygen and light of specific wavelength to destroy tumor cells. To improve efficacy of PDT, the efforts are underway to develop combination protocols. Selenium is an essential trace element and has anticarcinogenic properties on a various human cancer model. The aim of this study was to investigate the synergetic anti-tumor effects of PDT plus selenium in vitro and in vivo. To compare the anti-proliferative effects by PDT, Selenium, or PDT plus selenium, MTT assay, microscopic observation and FACS analysis were performed. Apoptosis signaling pathways were analyzed using mouse signal transduction pathwayRT profiler PCR array (Superarray). For the vivo study, when tumor size was approximately 8 to 10 mm, Radachlorin (10mg/kg b.w.) was injected in to the tail vein at 3 hrs before irradiation with 100 J/cm2 of light and then selenium (1ug/kg b.w) was administrated daily during 20 days. Our results demonstrate that combination of selenium with PDT strongly inhibits growth of TC-1 cell and tumor in TC-1 cell implanted mice when compared to the other groups. Moreover, PDT and selenium treatment in TC-1 cells had apoptosis features in microscope and FACS analysis. Increased apoptosis was associated with tumor inhibition in the combination therapy group. In signal transduction pathway Superarray, genes closely relate to NFkB, p53, and phopholipase C pathway such as vcam1, mdm2, and fos were very significantly down-regulated at least 10 fold in TC-1 cell following co-treatment of PDT and selenium. Furthermore, anti-apoptosis related genes and tumor-promoting genes, birc2, birc3, hk2, ccl2, ptgs2, wisp1, mmp10 and wisp1 were also significantly down-regulated. Up-regulated genes by co-treatment of PDT and selenium had relatively low ranges of fold change than fold range of down-regulated genes and were related with cell survival and proliferation mechanism. These data indicate that combination therapy of selenium and PDT could more effectively induce tumor suppression response compared to PDT or Selenium alone. We suggest that combination therapy using PDT and selenium can be a useful to for inducing synergistic anticancer effect. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 496.

Author’s reply to comment on “The effect of photodynamic therapy on tumor angiogenesis. Cellular and Molecular Life Sciences, 66, 2275–2283”

The comments by Nowak-Slieinska et al. are an extensionof our review article. We agree with the authors that vas-cular normalization is an important event that decides theoutcome of anti-angiogenesis therapies. As reported byJain RK et al. [1], antiangiogenic agents can normalize theabnormal structure and function of tumor vasculature tomake it more efficient for oxygen and drug delivery.Therefore, induction of vascular normalization caused byanti-angiogenic agents provides a novel means of effectivedelivery of chemotherapeutic drugs. Our report was basedon the effective use of anti-angiogenesis therapy toimprove therapeutic efficacy of PDT. The authors agreethat the use of anti-angiogenesis agents before PDT toinduce vascular normalization and increase the homoge-nous effect of oxygen-dependent PDT is an interestinghypothesis that is worth pursuing.Reference

Oxovanadium(iv) complexes of phenanthroline bases: the dipyridophenazine complex as a near-IR photocytotoxic agent

Oxovanadium(iv) complexes [VOCl(B)(2)]Cl (1-3) of phenanthroline bases (B), viz. 1,10-phenanthroline (phen in ), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in ) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in ), have been prepared, characterized and their DNA and protein binding, photo-induced DNA and protein cleavage activity and photocytotoxicity have been studied. Complex , structurally characterized by X-ray crystallography, shows the presence of a vanadyl group in VOClN(4) coordination geometry. The dpq ligand displays a chelating mode of binding with a N-donor site trans to the oxo-group. The chloride ligand is cis to the oxo-group. The one-electron paramagnetic complexes show a d-d band near 715 nm in 15% DMF-Tris-HCl buffer. The complexes are redox active exhibiting a V(iv)/V(iii) redox couple within -0.5 to -0.7 V vs. SCE in 20% DMF-Tris-HCl/0.1 M KCl. The complexes bind to calf thymus (CT) DNA in the order: (dppz) > (dpq) > (phen). The binding data reveal the groove and/or partial intercalative DNA binding nature of the complexes. The complexes show "chemical nuclease" activity in the dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide via a hydroxyl radical pathway. The dpq and dppz complexes are efficient photocleavers of DNA in UV-A light of 365 nm forming reactive singlet oxygen ((1)O(2)) and hydroxyl radical ( OH) species. Complexes and also show DNA cleavage activity in red light (>750 nm) by an exclusive OH pathway. The complexes display a binding propensity to bovine serum albumin (BSA) protein giving K(BSA) values in the range of 7.1 x 10(4)-1.8 x 10(5) M(-1). The dppz complex shows BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via OH pathway. The dppz complex exhibits significant PDT effect in human cervical cancer HeLa cells giving IC(50) values of 1.0 microM and 12.0 microM in UV-A and visible light, respectively (IC(50) = >100 microM in the dark).

Targeting EGFR with photodynamic therapy in combination with Erbitux enhances in vivo bladder tumor response

BackgroundPhotodynamic therapy (PDT) is a promising cancer treatment modality that involves the interaction of the photosensitizer, molecular oxygen and light of specific wavelength to destroy tumor cells. Treatment induced hypoxia is one of the main side effects of PDT and efforts are underway to optimize PDT protocols for improved efficacy. The aim of this study was to investigate the anti-tumor effects of PDT plus Erbitux, an angiogenesis inhibitor that targets epidermal growth factor receptor (EGFR), on human bladder cancer model. Tumor-bearing nude mice were assigned to four groups that included control, PDT, Erbitux and PDT plus Erbitux and tumor volume was charted over 90-day period.ResultsOur results demonstrate that combination of Erbitux with PDT strongly inhibits tumor growth in the bladder tumor xenograft model when compared to the other groups. Downregulation of EGFR was detected using immunohistochemistry, immunofluorescence and western blotting. Increased apoptosis was associated with tumor inhibition in the combination therapy group. In addition, we identified the dephosphorylation of ErbB4 at tyrosine 1284 site to play a major role in tumor inhibition. Also, at the RNA level downregulation of EGFR target genes cyclin D1 and c-myc was observed in tumors treated with PDT plus Erbitux.ConclusionThe combination therapy of PDT and Erbitux effectively inhibits tumor growth and is a promising therapeutic approach in the treatment of bladder tumors.

Topical photodynamic therapy is immunosuppressive in humans

Visible light irradiation after application of a photosensitizer (topical photodynamic therapy; PDT) is increasingly used to treat nonmelanoma skin cancers and premalignant actinic keratoses. PDT can provide a cosmetically superior alternative to surgery, but carries failure rates of 10-40%. While some murine studies have suggested immune enhancement by PDT, others reported immunosuppressive effects, which may indicate impaired antitumour immunity and thus compromised tumour clearance. This study aimed to determine the in vivo immune effects of PDT in humans. Using healthy, Mantoux-positive volunteers, we irradiated discrete areas of the back with narrowband red light (630 nm; 37 J cm(-2)), with and without prior application of 5-aminolaevulinic acid (ALA) or methyl aminolaevulinate (MAL). Adjacent, untreated areas served as immunologically intact control sites. Delayed-type hypersensitivity responses to tuberculin purified protein derivative (Mantoux reactions) were then elicited in each of the irradiated, unirradiated and control sites, and the intensity of the reactions was quantitated with an erythema meter and by measurement of Mantoux diameter. By comparing Mantoux intensity at treated and control sites, immunosuppression was determined in each volunteer for each intervention. We found that both MAL-PDT and ALA-PDT significantly suppressed Mantoux erythema (by 30% and 50%, respectively) and diameter (41% and 38%). Red light alone significantly suppressed diameter (22%) but not erythema (13%). Topical PDT induced significant immune suppression, which could impair local antitumour immune responses and may thus contribute to treatment failure.

Hypericin- and mTHPC-mediated photodynamic therapy for the treatment of cariogenic bacteria

Abstract Objective Dental caries is one of the most common diseases in Western countries. Its pathoetiology is multifactorial, however, bacteria including Streptococcus mutans and the closely related Streptococcus sobrinus are regarded as key factors involved in this process. The fact that therapeutic approaches to eradicate these microorganisms are still limited prompted us to investigate the treatment potential of photodynamic therapy with the photoactive compounds hypericin (HYP) and meso-tetra(hydroxyphenyl)chlorin (mTHPC) in vitro. Material and methods S. mutans and S. sobrinus were cultivated under standard conditions and incubated with HYP (Invitrogen, Basel, Switzerland), the liposomal mTHPC derivative Foslipos (FOS, Biolitec, Jena, Germany), or a mixture of both at concentrations ranging between 0.625 and 10 μg/ml for various time points. Following a thorough washing step, bacteria were irradiated with a dental polymerization instrument (400–505 nm). All samples were subjected to serial dilutions and spiral plating on blood agar plates. Viable colony counts were determined after 48 h in culture. Photosensitizer fluorescence of bacteria was visualized by confocal microscopic techniques. Results One hundred percent of S. sobrinus could be killed by a 15 min incubation with as little as 2.5 μg/ml HYP, 5 μg/ml FOS or a mixture of 1.25 μg/ml of each photosensitizer followed by light activation of 120 s. In contrast to S. sobrinus, S. mutans displayed a significant dark toxicity for FOS (10–1.25 μg/ml) and no relevant PDT effects using HYP (10–0.625 μg/ml) under these conditions. HYP-mediated PDT effects (10 μg/ml) could be enhanced to more than 99.9% by prolonging photosensitizer incubation to 30 min and fractional illumination (2×120 s). Complete eradication of S. mutans was achieved by incubation for 15 min with a mixture of 0.625 μg/ml each of FOS and HYP and illumination for 120 s. Conclusion For both S. mutans and S. sobrinus, short PDT protocols with FOS and/or HYP could be established that completely eradicated these cariogenic bacteria in suspension. Our study, however, indicated that careful optimization of PDT conditions may be necessary for successful treatment of even closely related bacterial species. In multispecies microbial populations, the application of photosensitizer combinations for PDT may be useful.