Photosensitization of malignant tumors

Features of third generation photosensitizers used in anticancer photodynamic therapy: Review

Cancer remains a main public health issue and the second cause of mortality worldwide. Photodynamic therapy is a clinically approved therapeutic option. Effective photodynamic therapy induces cancer damage and death through a multifactorial manner including reactive oxygen species-mediated damage and killing, vasculature damage, and immune defense activation. Anticancer efficiency depends on the improvement of photosensitizers drugs used in photodynamic therapy, their selectivity, enhanced photoproduction of reactive species, absorption at near-infrared spectrum, and drug-delivery strategies. Both experimental and clinical studies using first- and second-generation photosensitizers had pointed out the need for developing improved photosensitizers for photodynamic applications and achieving better therapeutic outcomes. Bioconjugation and encapsulation with targeting moieties appear as a main strategies for the development of photosensitizers from their precursors. Factors influencing cellular biodistribution and uptake are briefly discussed, as well as their roles as cancer diagnostic and therapeutic (theranostics) agents. The two-photon photodynamic approach using third-generation photosensitizers is present as an attempt in treating deeper tumors. Although significant advances had been made over the last decade, the development of next-generation photosensitizers is still mainly in the developmental stage.

Enhanced Malignant Phenotypes of Glioblastoma Cells Surviving NPe6-Mediated Photodynamic Therapy are Regulated via ERK1/2 Activation

To manage refractory and invasive glioblastomas (GBM)s, photodynamic therapy (PDT) using talaporfin sodium (NPe6) (NPe6-PDT) was recently approved in clinical practice. However, the molecular machineries regulating resistance against NPe6-PDT in GBMs and mechanisms underlying the changes in GBM phenotypes following NPe6-PDT remain unknown. Herein, we established an in vitro NPe6-mediated PDT model using human GBM cell lines. NPe6-PDT induced GBM cell death in a NPe6 dose-dependent manner. However, this NPe6-PDT-induced GBM cell death was not completely blocked by the pan-caspase inhibitor, suggesting NPe6-PDT induces both caspase-dependent and -independent cell death. Moreover, treatment with poly (ADP-ribose) polymerase inhibitor blocked NPe6-PDT-triggered caspase-independent GBM cell death. Next, it was also revealed resistance to re-NPe6-PDT of GBM cells and GBM stem cells survived following NPe6-PDT (NPe6-PDT-R cells), as well as migration and invasion of NPe6-PDT-R cells were enhanced. Immunoblotting of NPe6-PDT-R cells to assess the behavior of the proteins that are known to be stress-induced revealed that only ERK1/2 activation exhibited the same trend as migration. Importantly, treatment with the MEK1/2 inhibitor trametinib reversed resistance against re-NPe6-PDT and suppressed the enhanced migration and invasion of NPe6-PDT-R cells. Overall, enhanced ERK1/2 activation is suggested as a key regulator of elevated malignant phenotypes of GBM cells surviving NPe6-PDT and is therefore considered as a potential therapeutic target against GBM.

Long-term Outcomes of Small Pigmented Choroidal Melanoma Treated with Primary Photodynamic Therapy

PURPOSE

To report the long-term outcomes of patients with small, pigmented, posteriorly located choroidal melanoma undergoing primary treatment using photodynamic therapy (PDT) with verteporfin at the London Ocular Oncology Service.

DESIGN

Retrospective, interventional, consecutive case series.

PARTICIPANTS

All patients undergoing primary treatment using PDT with verteporfin from April 2014 to December 2015 and followed until December 2019.

METHODS

This is a long-term follow-up study of the same cohort of patients previously reported by our group in 2017 and 2018.

MAIN OUTCOME MEASURES

Local tumor control, visual outcomes, and metastasis-free survival.

RESULTS

Twenty-six patients were included with a mean (± standard deviation) age and tumor thickness of 62 ± 14 years and 1.3 ± 0.5 mm, respectively. Tumors were posteriorly located (mean distance to optic nerve and fovea = 2.0 ± 2.2 mm and 1.6 ± 1.5 mm, respectively), and the majority were fully pigmented (73%). Overall, patients were followed for a median (interquartile range [IQR], range) of 49.5 (15.3, 7.0-66.0) months from first PDT to last follow-up. Over the course of this study, 14 of 26 (54%) have developed a local recurrence at a median of 20.0 months (20.5, 4.7-60.9 months). The most common pattern of recurrence was an isolated increase in basal dimensions (9/14; 64%). Median (IQR) final logarithm of the minimum angle of resolution visual acuity of the whole cohort was 0.2 (0.5). The only statistically significant difference in baseline and outcome characteristics between treatment failures and nonfailures was the distance to the fovea (median [IQR], 0.5 [1.3] vs. 2.5 [2.8]; P = 0.002) and final logarithm of the minimum angle of resolution visual acuity (median [IQR], 0.50 [0.80] vs. 0.00 [0.14]; P = 0.002), respectively.

CONCLUSIONS

Although treatment of small pigmented posterior choroidal melanoma with PDT effectively preserves visual acuity, 5-year treatment-success calculated by Kaplan-Meier analysis was only 38.4%. Recurrences after PDT tend to occur along the tumor edges, often with minimal increase in thickness. Given the substantial risk of treatment failure, primary PDT with vertepofrin is recommended in exceptional cases of choroidal melanoma, for which other treatments with greater tumor control are not a feasible option.

Recurrence after surgery in esophago-gastric junction adenocarcinoma: Current management and future perspectives

Recurrent esophago-gastric junction adenocarcinoma is not a rare event and its correct management is still debated. Many approaches for the treatment of these patients exist, but only few studies compare the different techniques. Most of the studies are retrospectives series and describe the experiences of single institutions in the treatment of recurrent esophageal and esophago-gastric junction cancers. Nowadays surgery is still the main and only curative treatment. Other alternative palliative therapies could be endoscopic stent placement and balloon dilation, photodynamic therapy, thermal tumor ablation (laser photoablation and Argon plasma coagulation), radiation therapy and brachytherapy, and chemotherapy. The aim of this review is to investigate the different rates, patterns and timings of recurrence of this tumor, and to explain the various approaches used for the treatment of recurrent esophago-gastric junction cancer.

Nanomedicine as an innovative therapeutic strategy for pediatric cancer

Childhood cancer is the leading cause of mortality in children between 1 and 14 years of age. Malignancy accounts for 18 % of overall childhood mortality. Therapeutic advances in the field of pediatric oncology have helped to increase survival. Nanotechnology is the modification of materials at a nanoscale and can be used to deliver therapeutic agents. Examples of nanotechnology applications are organic self-assembled amphiphilic polymers, non-organic nanocarriers such as nanotubes and quantum dots. Each of these has their own utility in different settings. Application of nanotechnology in medicine has been extensively studied. Examples of pediatric tumors that received special attention are: neuroblastoma, retinoblastoma, central nervous system tumors and musculoskeletal tumors. This review will summarize the application of nanomedicine as an innovative management strategy in pediatric oncology.

Dual Functioning Thieno-Pyrrole Fused BODIPY Dyes for NIR Optical Imaging and Photodynamic Therapy: Singlet Oxygen Generation without Heavy Halogen Atom Assistance

We discovered a rare phenomenon wherein a thieno-pyrrole fused BODIPY dye (SBDPiR690) generates singlet oxygen without heavy halogen atom substituents. SBDPiR690 generates both singlet oxygen and fluorescence. To our knowledge, this is the first example of such a finding. To establish a structure-photophysical property relationship, we prepared SBDPiR analogs with electron-withdrawing groups at the para-position of the phenyl groups. The electron-withdrawing groups increased the HOMO-LUMO energy gap and singlet oxygen generation. Among the analogs, SBDPiR688, a CF3 analog, had an excellent dual functionality of brightness (82290 m(-1)  cm(-1) ) and phototoxic power (99170 m(-1)  cm(-1) ) comparable to those of Pc 4, due to a high extinction coefficient (211 000 m(-1)  cm(-1) ) and balanced decay (Φflu =0.39 and ΦΔ =0.47). The dual functionality of the lead compound SBDPiR690 was successfully applied to preclinical optical imaging and for PDT to effectively control a subcutaneous tumor.

Treatment of amelanotic choroidal melanoma with photodynamic therapy

PURPOSE

To evaluate the effect of photodynamic therapy on amelanotic choroidal melanoma.

METHODS

Nine patients with posteriorly located amelanotic choroidal melanomas, one with a pigmented portion, underwent photodynamic therapy using verteporfin as the photosensitizing agent. The basal diameters ranged from 4 mm to 16 mm and the heights from 1.3 mm to 5.7 mm. Treatment was repeated until the melanoma was completely flat or its height had reached a stable end point. Tumor response was assessed by clinical examination, photography, and ultrasonography. Annual screening for hepatic metastases was performed.

RESULTS

Eight tumors demonstrated apparent complete regression over 1 month to 14 months. The amelanotic portion of the mixed tumor flattened, whereas the height of the pigmented part remained stable at 2 mm. In 8 patients there has been no recurrence during follow-up of between 34 months and 81 months. One case developed 2 separate local recurrences at 21 months and 34 months. There were no serious complications, no patient lost vision after treatment, and none developed metastatic disease.

CONCLUSION

In this series photodynamic therapy was highly effective in causing regression of posteriorly located amelanotic choroidal melanomas, without a detrimental effect on vision. While the short-term results are encouraging, there is some uncertainty regarding complete tumor destruction and long-term efficacy.

Biomodulatory approaches to photodynamic therapy for solid tumors

Photodynamic Therapy (PDT) uses a photosensitizing drug in combination with visible light to kill cancer cells. PDT has an advantage over surgery or ionizing radiation because PDT can eliminate tumors without causing fibrosis or scarring. Disadvantages include the dual need for drug and light, and a generally lower efficacy for PDT vs. surgery. This minireview describes basic principles of PDT, photosensitizers available, and aspects of tumor biology that may provide further opportunities for treatment optimization. An emerging biomodulatory approach, using methotrexate or Vitamin D in combination with aminolevulinate-based PDT, is described. Finally, current clinical uses of PDT for solid malignancies are reviewed.

Oncologic photodynamic therapy photosensitizers: a clinical review

A myriad of naturally occurring and synthetic structures are capable of transferring the energy of light. Few, however, allow for this energy transfer to enable a type II photochemical reaction which, as currently practiced, is a fundamental component of photodynamic therapy. Even fewer of these agents, aptly termed photosensitizers, have found success in the treatment of patients. This review will focus on the oncologic photosensitizers that have come to clinical trial with outcomes published in peer reviewed journals. Based on a clinical orientation the qualities of successful photosensitizers will be examined, how current drugs fare and potential future options explored.

Porphyrin and nonporphyrin photosensitizers in oncology: preclinical and clinical advances in photodynamic therapy

Photodynamic therapy (PDT) is now a well-recognized modality for the treatment of cancer. While PDT has developed progressively over the last century, great advances have been observed in the field in recent years. The concept of dual selectivity of PDT agents is now widely accepted due to the relative specificity and selectivity of PDT along with the absence of harmful side effects often encountered with chemotherapy or radiotherapy. Traditionally, porphyrin-based photosensitizers have dominated the PDT field but these first generation photosensitizers have several disadvantages, with poor light absorption and cutaneous photosensitivity being the predominant side effects. As a result, the requirement for new photosensitizers, including second generation porphyrins and porphyrin derivatives as well as third generation photosensitizers has arisen, with the aim of alleviating the problems encountered with first generation porphyrins and improving the efficacy of PDT. The investigation of nonporphyrin photosensitizers for the development of novel PDT agents has been considerably less extensive than porphyrin-based compounds; however, structural modification of nonporphyrin photosensitizers has allowed for manipulation of the photochemotherapeutic properties. The aim of this review is to provide an insight into PDT photosensitizers clinically approved for application in oncology, as well as those which show significant potential in ongoing preclinical studies.

Enhanced visualization of histological samples with an adjustable RGB contrast system with application for tissue used in photodynamic therapy

The analysis of histological sections has long been a valuable tool in the pathological studies. The interpretation of tissue conditions, however, relies directly on visual evaluation of tissue slides, which may be difficult to interpret because of poor contrast or poor color differentiation. The Chromatic Contrast Visualization System (CCV) combines an optical microscope with electronically controlled light-emitting diodes (LEDs) in order to generate adjustable intensities of RGB channels for sample illumination. While most image enhancement techniques rely on software post-processing of an image acquired under standard illumination conditions, CCV produces real-time variations in the color composition of the light source itself. The possibility of covering the entire RGB chromatic range, combined with the optical properties of the different tissues, allows for a substantial enhancement in image details. Traditional image acquisition methods do not exploit these visual enhancements which results in poorer visual distinction among tissue structures. Photodynamic therapy (PDT) procedures are of increasing interest in the treatment of several forms of cancer. This study uses histological slides of rat liver samples that were induced to necrosis after being exposed to PDT. Results show that visualization of tissue structures could be improved by changing colors and intensities of the microscope light source. PDT-necrosed tissue samples are better differentiated when illuminated with different color wavelengths, leading to an improved differentiation of cells in the necrosis area. Due to the potential benefits it can bring to interpretation and diagnosis, further research in this field could make CCV an attractive technique for medical applications.

Photodynamic diagnosis in urology: state-of-the-art

OBJECTIVES

To provide an overview on the methodology and clinical relevance of fluorescence diagnosis with exogenous fluorochromes or fluorochrome prodrugs in urology.

METHODS

The methodology is summarised on the basis of our experience and the relevant literature. Clinical results and perspectives are reported and concluded after we scanned and evaluated sources from PubMed. Search items were "aminolev*" or "hypericin" or "photodyn*" or "porphyrin" or "fluorescence" or "autofluorescence" and "bladder" or "prostate" or "kidney" or "peni*" or "condylo*". Some literature was also obtained from journals not indexed.

RESULTS

A large number of clinical trials have shown that photodynamic diagnosis (PDD) improves the ability to detect inconspicuous urothelial carcinoma of the bladder. Fluorescence diagnosis has recently been approved in Europe for the detection of bladder cancer after instillation of a hexaminolevulinate (Hexvix) solution. PDD is recommended by the European Association of Urology for the diagnosis of carcinoma in situ of the bladder. To date, the major weakness of PDD for the detection of bladder cancer is its relatively low specificity. Initial results with PDD for the detection of penile carcinoma, prostate cancer, kidney tumours, and urethral condylomata are promising.

CONCLUSIONS

To determine the actual impact of PDD on recurrence and progression rates of bladder cancer, further long-term observational studies are necessary. These studies also will clarify whether PDD is cost efficient.

Photodynamic therapy: light delivery and dosage for second-generation photosensitizers

With the development of new photosensitizers that have enhanced photoactivation at longer wavelengths than haematoporphyrin derivative, new considerations arise in the light source and delivery systems and in the techniques for physical dosimetry and in vivo optical measurements in photodynamic therapy. The limitations and future potential of solid-state laser sources are presented. The relationships between photosensitizer photoactivation characteristics and the effective photodynamic treatment volume are developed and discussed quantitatively. The problems in defining and measuring the photodynamic dose are examined, and potential techniques for measuring the factors involved in this are evaluated with emphasis on noninvasive approaches which may be used clinically.

Topical treatment strategies for non-melanoma skin cancer and precursor lesions

The ability to manage non-melanoma skin cancers and pre-malignant lesions with topical pharmacologic agents is highly compelling. This article examines currently available products and discusses their emerging roles and limitations. These include fluorouracil, diclofenac sodium, imiquimod, and photodynamic therapy.

Breast cancer with chest wall progression: treatment with photodynamic therapy

BACKGROUND

Chest wall progression of breast carcinoma affects up to 5% of breast cancer patients and is a major source of their pain. Treatment options are limited or may not be offered to these patients. Low-dose Photofrin-induced photodynamic therapy (PDT) offers an excellent clinical response with minimal morbidity. We report our continued experience with PDT in this setting.

METHODS

Fourteen patients with more than 500 truncal metastases were treated with PDT. All received off-label Photofrin (.8 mg/kg) i.v. and light treatment at 630 nm from a diode laser with a microlens at a fluence of 1800 mW and a total light dose of 150 to 200 J/cm2 at 48 hours. One patient required re-treatment because of extensive disease.

RESULTS

Follow-up was at least 6 months, and several extended to >24 months. All patients demonstrated tumor necrosis, with 9 of 14 complete responses, including with lesions >2 cm in thickness. Disease progression occurred outside of the treatment field. Several patients had initial regression of untreated lesions. Wound care, especially with disease in the deep tissues, was an issue.

CONCLUSIONS

Low-dose Photofrin-induced PDT offers patients with chest wall progression a treatment option with an excellent clinical response. To date, the response is prolonged and offers good local control. Surgical oncologists have an active role in this treatment option.

Physiological parameters and biodistribution of 5,10,15,20-tetra (4-methoxyphenyl) porphyrin in rats

Physiological parameters on hepatic and renal functionality and biodistribution, accumulation and elimination, in different organs of the 5,10,15,20-tetra (4-methoxyphenyl) porphyrin (TMP) were determined in Wistar rats. The transport of TMP by low-density (LDL) and high-density lipoproteins (HDL) was also investigated. The photosensitizer is accumulated in the spleen, where its concentration is significantly increased 21 d post-injection; it also accumulates in the liver and in a lower proportion, in the duodenum, and poorly in brain and muscle. The urine and serum biochemical parameters reached normal values both in control and treated groups. The glomerular filtrate rate was not affected by the TMP treatment in any of the studied times. These results would indicate that the sensitizer does not modify the renal glomerular function. TMP is mainly eliminated from the organism via the bile-gut pathway. Considering the total amount of porphyrin bound to both lipoproteins (LDL and HDL) in comparison with the total value of the TMP in serum, it can be inferred that a large amount of the agent is transported by lipoproteins in the plasma. This study proves information about the behavior of TMP in vivo under dark conditions. The results can be used to design photodynamic treatments using this porphyrin model as the sensitizer.

Electric magnetic resonance and spectrophotometry evidence on the photodynamic activity of a new perylenequinonoid pigment

Di-cysteine substituted hypocrellin B (DCHB) is a new water-soluble photosensitizer with significantly enhanced red absorption at wavelengths longer than 600 nm over the parent compound hypocrellin B (HB). The photosensitizing properties (Type I and/or Type II mechanisms) of DCHB have been investigated in dimethylsulfoxide (DMSO) and aqueous solution (pH 7.4) using electron paramagnetic resonance (EPR) and spectrophotometric methods. In anaerobic DMSO solution, the semiquinone anion radical of DCHB (DCHB-) is predominantly photoproduced via self-electron transfer between excited- and ground-state DCHB species. The presence of an electron donor significantly promotes the formation of the reduced form of DCHB. When a deoxygenated aqueous solution of DCHB and an electron door are irradiated with 532 nm light, the hydroquinone of DCHB (DCHBH2) is formed via the disproportionation of the first-formed DCHB- and second electron transfer to DCHB- and second electron transfer to DCHB- from the electron donor. When oxygen is present, singlet oxygen (1 O2), superoxide anion radical (O2-) and hydroxyl radical (OH) are produced. The quantum yield of 1 O2 generation by DCHB photosensitization is estimated to be 0.54 using Rose Bengal as a reference, a little lower than that of HB (0.76). The superoxide anion radical is also significantly enhanced by the presence of electron donors. Moreover, O2- upon disproportionation generated H2O2 and ultimately the highly reactive OH via the Haber-Weiss reaction pathway. The efficiency of O2- generation by DCHB is obviously enhanced over that of HB. These findings suggest that the photodynamic actions of DCHB may proceed via type I and Type II mechanisms and that this new photosensitizer retains photosensitizing activity after photodynamic therapy-oriented chemical modification.

Delta-aminolevulinic acid-mediated photosensitization of prostate cell lines: implication for photodynamic therapy of prostate cancer

BACKGROUND

Delta-aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) is currently being investigated for the treatment of prostate diseases. In this study, we evaluate 1) the in vitro production of protoporphyrin IX (PPIX) (the active photosensitizing agent of ALA-mediated PDT) by two different prostate cancer cell lines (LNCaP and PC-3) and a benign, modified, prostatic cell line (TP-2), and 2) the extent of PDT-induced cell injury, as determined by electron microscopy (EM) and cell survival.

METHODS

The cell lines were assigned into four treatment groups: group 1, control, no ALA and no light irradiation; group 2, dark control, ALA only; group 3, light control, radiation only; and group 4, PDT, ALA followed by irradiation (630 nm, 3 joules/cm2). The experiments were performed in triplicate. ALA concentration was 50 microg/ml of media in all instances.

RESULTS

Following incubation with ALA, PPIX production was significantly increased in the three cell lines studied, and more notably in the PC-3 cell line. Compared to controls, EM and cell survival studies demonstrated significant mitochondrial damage and decreased survival, respectively, in the cells treated with PDT. This was also more evident in the PC-3 cell line.

CONCLUSIONS

Our results demonstrate that prostate cells differ in their response to ALA-mediated PDT. This response appears to depend on the intracellular production of PPIX and the cell type, i.e., on the functional and structural characteristics of the cell mitochondria. In addition, our results suggest that PDT might be effective at killing prostate cancer cells.

In vitro and in vivo effects of photodynamic therapy on murine malignant melanoma

BACKGROUND

The role of photodynamic therapy (PDT) in the treatment of malignant melanoma is not well defined, nor is it known whether the dark melanoma cells absorb the light used in PDT.

METHODS

IN VITRO STUDIES

2 x 10(5) B16 murine melanoma cells were incubated with aluminum phthalocyanine (AlpcS4, 2.5 mg/kg) and were then subjected to photoradiation (50, 100 or 200 J/cm2). Viability was then assessed. In vivo studies:

HISTOLOGY

C57/B1 mice received 2 x 10(5) B16 cells subcutaneously and were randomized into study (PDT) and three control groups. AlpcS4 2.5 mg/kg was injected intraperitoneally and the mice were exposed to light (100 J/cm2). After 24 hours they were sacrificed and underwent autopsies. Survival: 40 mice were randomized into PDT (40 J/cm2) and control groups and were monitored for 50 days. Tumor growth: 40 mice were randomized into one control and three treatment groups (PDT on day 3, 6, or 12 after injection with B16 cells), and were monitored for 50 days. Temperature: Tumor temperatures before and at the end of PDT were recorded.

RESULTS

IN VITRO STUDIES

PDT caused a decrease in cell viability to 15.5 +/- 0.7%, 11.5 +/- 2.1%, and 1.5 +/- 0.7% (at 50, 100, and 200 J/cm2, respectively; P < .001). A significant reduction in thymidine incorporation was noted at all energy levels. In vivo studies:

HISTOLOGY

PDT caused massive tumor necrosis. Survival: PDT prolonged the survival of mice (41 +/- 13.4 days) compared to controls (15.8 +/- 3.8 days, P < .001). Tumor growth: 31 days after injection with B16 cells, the tumor size was 2.6 +/- 0.3 cm in the control group and 1.6 +/- 0.2, 0.9 +/- 0.3, and 1.0 +/- 0.4 cm in the PDT groups (days 3, 6 and 12, respectively; P < .01). Temperature: PDT increased skin temperature to 42.8 degrees C +/- 1.3 degrees C, 45.3 degrees C +/- 3.5 degrees C, and 51.7 degrees C +/- 2.7 degrees C at 40, 60, and 100 J/cm2, respectively (P < .01).

CONCLUSIONS

Photodynamic therapy was found to have significant effects in experimental melanoma in mice. The role of PDT in human melanoma remains to be studied.

5-Aminolevulinic acid-based photodynamic therapy. Clinical research and future challenges

BACKGROUND

Photodynamic therapy (PDT) for cancer patients has developed into an important new clinical treatment modality in the past 25-years. PDT involves administration of a tumor-localizing photosensitizer or photosensitizer prodrug (5-aminolevulinic acid [ALA], a precursor in the heme biosynthetic pathway) and the subsequent activation of the photosensitizer by light. Although several photosensitizers other than ALA-derived protoprophyrin IX (PpIX) have been used in clinical PDT, ALA-based PDT has been the most active area of clinical PDT research during the past 5 years. Studies have shown that a higher accumulation of ALA-derived PpIX in rapidly proliferating cells may provide a biologic rationale for clinical use of ALA-based PDT and diagnosis. However, no review updating the clinical data has appeared so far.

METHODS

A review of recently published data on clinical ALA-based PDT and diagnosis was conducted.

RESULTS

Several individual studies in which patients with primary nonmelanoma cutaneous tumors received topical ALA-based PDT have reported promising results, including outstanding cosmetic results. However, the modality with present protocols does not in general, appear to be superior to conventional therapies with respect to initial complete response rates and long term recurrence rates, particularly in the treatment of nodular skin tumors. Topical ALA-PDT does have the following advantages over conventional treatments: it is noninvasive; it produces excellent cosmetic results; it is well tolerated by patients; it can be used to treat multiple superficial lesions in short treatment sessions; it can be applied to patients who refuse surgery or have pacemakers and bleeding tendency; it can be used to treat lesions in specific locations, such as the oral mucosa or the genital area; it can be used as a palliative treatment; and it can be applied repeatedly without cumulative toxicity. Topical ALA-PDT also has potential as a treatment for nonneoplastic skin diseases. Systemic administration of ALA does not seem to be severely toxic, but the advantage of using this approach for PDT of superficial lesions of internal hollow organs is still uncertain. The ALA-derived porphyrin fluorescence technique would be useful in the diagnosis of superficial lesions of internal hollow organs.

CONCLUSIONS

Promising results of ALA-based clinical PDT and diagnosis have been obtained. The modality has advantages over conventional treatments. However, some improvements need to be made, such as optimization of parameters of ALA-based PDT and diagnosis; increased tumor selectivity of ALA-derived PpIX; better understanding of light distribution in tissue: improvement of light dosimetry procedure; and development of simpler, cheaper, and more efficient light delivery systems.

Supramolecular cationic tetraruthenated porphyrin induces single-strand breaks and 8-oxo-7,8-dihydro-2'-deoxyguanosine formation in DNA in the presence of light

The aim of this investigation is the evaluation of DNA interaction of with tetraruthenated porphyrin (TRP) and of DNA damage in the presence of light. Direct-fluorescence and electronic absorption measurements after incubation of DNA with TRP indicate strong binding between pBR322 DNA or calf thymus DNA with the modified porphyrin. Exposure of pBR322 DNA to TRP (up to 3 microM) and light leads to single-strand break formation as determined by the conversion of the supercoiled form (form I) of the plasmid into the nicked circular form (form II). Oxidative DNA base damage was evaluated by the detection of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) after irradiation of calf thymus DNA in the presence of the TRP. The data demonstrated a dose and time dependence with each type of DNA damage. These data indicate (1) a specificity of the binding mode and (2) type I and II photoinduced mechanisms leading to strand scission activity and 8-oxodGuo formation. Accordingly, singlet molecular oxygen formation, after TRP excitation, was confirmed by near-infrared emission. From these investigations a potential application of TRP in photodynamic therapy is proposed.

Lasers in dermatology

The use of dermatologic laser therapy is rapidly expanding. Thirty years of experience has produced advances in the technology, techniques, and therapeutic efficacy of dermatologic lasers. The original lasers have been improved and modified, and new types of lasers have expanded the dermatologist's therapeutic repertoire. Extensive research has provided a greater understanding of the skin's clinical and histologic response to laser treatment. This has allowed dermatologists to expand their therapeutic options and techniques and to improve clinical outcome.

Photodynamic therapy in a cell culture model of human intimal hyperplasia

OBJECTIVE

To investigate the effectiveness of photodynamic therapy (PDT) in eliminating proliferating vascular smooth muscle cells (VSMCs). This may have a potential role in reducing restenosis rates clinically.

MATERIALS AND METHODS

Human VSMCs were successfully cultured from 15 long saphenous veins (SV) and seven restenotic lesions (RL) removed during revision coronary and peripheral vein graft surgery. Cultured VSMCs were incubated with photofrin at doses of 0-5 micrograms/ml for 48 h, and then exposed to 4 J/cm2 of polychromatic light. Cell destruction was quantified by a colorimetric assay using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

RESULTS

Results are expressed as a mean percentage survival +/- standard error. Cells were minimally affected by either photofrin alone (SV: 95.5% +/- 5.3; RL: 119.8 +/- 4.8) or light alone (SV: 75.38% +/- 3.99; RL: 100.1 +/- 11.0). The combination of 2 micrograms/ml of photofrin and 4 J/cm2 of polychromatic light energy, i.e. PDT, was severely toxic to cells derived from saphenous veins (5.52% +/- 0.85) as well as cells derived from restenotic lesions (9.6 +/- 2.3). These doses are comparable to doses that can be achieved in vivo.

CONCLUSION

PDT in the appropriate drug and light doses can eliminate human VSMCs, including those responsible for vascular restenosis.

Long-term survival after photodynamic therapy for esophageal cancer

BACKGROUND/AIMS

Photodynamic therapy (PDT) has been adapted to the endoscopic treatment of digestive cancer, but its indications and efficacy remain uncertain. The aim of this study was to assess its feasibility in the curative treatment of small esophageal tumors.

METHODS

From 1983 to 1991, PDT was used to treat 123 patients with esophageal cancer who were recommended for nonsurgical treatment of squamous cell carcinoma (n = 104) and adenocarcinoma (n = 19). Endoscopic ultrasonography (EUS) was performed in 88 patients; 61 were staged uT1 and 27 were staged uT2. A hematoporphyrin derivative was injected 72 hours before laser irradiation with a 630-nm dye laser. PDT was applied alone in 56 patients and as part of a multimodal protocol in the 67 others.

RESULTS

The complete response rate at 6 months was 87%. The 5-year survival rate was 25% +/- 6%, and the 5-year disease-specific survival rate was 74% +/- 5%. The complete response rate and survival rate were not different (1) between the PDT alone and the PDT multimodal treatment groups, (2) between the adenocarcinoma and squamous cell carcinoma groups, and (3) between the uT1 and uT2 EUS groups. PDT-related complications were esophageal stenosis (n = 43) and cutaneous photosensitization (n = 16).

CONCLUSIONS

In patients with small esophageal tumors who pose high surgical risk, photodynamic therapy is an effective treatment.

Immediate changes in subcellular structures of transplanted tumors following photodynamic and laser hyperthermic therapy

BACKGROUND AND OBJECTIVE

To further understand the precise process of the tumor cell degeneration after photodynamic therapy (PDT), laser hyperthermic therapy (LH), and combined treatments using an Nd:YAG laser. It is important to examine initial morphological alteration of tumor cells after these treatments.

STUDY DESIGN/MATERIALS AND METHODS

In this study, nude mice bearing HeLa cell tumors were treated with PDT, LH, and combined treatments of the two. Tumor tissues obtained immediately after these treatments were analyzed using electron microscopy and morphometry.

RESULTS

In the combined treatments, which produced more severe effects on tumor cells, morphological features of apoptosis such as cytoplasmic condensation, blebs, and apoptotic bodies appeared in the cells, although the typical alteration in the nuclear chromatin was not seen.

CONCLUSION

Cytoplasmic alterations may proceed more rapidly than nuclear alterations in the cellular degeneration induced by the single or combined treatments of PDT and LH.

The effect of hypothermia and hyperthermia on photodynamic therapy of normal brain

The effect of whole body hyperthermia and hypothermia in conjunction with photodynamic therapy (PDT) was determined on normal rat brain. Hyperthermia animals (Group I, n = 18) were warmed until their core body temperature reached 40 degrees C, (brain temperature, 39.7 +/- 0.5 degree C) and maintained at 40 +/- 1 degree C for 30 minutes prior to and after PDT. Hypothermia (Group II, n = 31) animals were cooled to 30 +/- 1 degree C (brain temperature, 29.3 +/- 0.4 degree C) for 1 hour. PDT treatment was performed, and the body temperature of the animals was maintained at 30 degrees C for 2 hours post-PDT. A population of animals was subjected to PDT under normothermic (Group III, n = 16; body temperature, 37 +/- 1 degree C; brain temperature, 36.7 +/- 0.8 degree C) conditions and treated in a manner identical to that of hyperthermic animals. PDT was performed with 17 J/cm2, 35 J/cm2, or 70 J/cm2 (100 mW/cm2). Photofrin (Quadralogic Technologies Ltd., Vancouver, Canada) (12.5 mg/kg) was injected intraperitoneally 48 hours prior to laser treatment on all three groups. Wet-dry weight measurements were obtained on a separate set of all three groups of animals (n = 27). Cortical lesion depths were measured, and pathological evaluation was made at 24 hours post-PDT. No difference in the wet-dry weight measurements or histopathology was present between the three groups of animals. Lesion depths for Group I animals did not significantly differ from Group III animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical applications of photodynamic therapy

This is a review of photodynamic therapy, which is a classic binary system involving the use of a photosensitizer and light of very specific wavelength, consistent with the absorption characteristics of that sensitizer. As a binary system, its effects are almost entirely limited to tumour cells, but the major drawback is its limited penetration because it utilizes physical light within the visible spectrum. For Photofrin II, which is the only approved sensitizer for clinical use in this country, the effects are limited to approximately 0.5 cm or less, depending on the tissue and the amount of blood, etc. Newer sensitizers offer more penetration and the opportunity to repeat treatments, because the newer sensitizers do not have the very long (up to 10 weeks) period of enhanced skin sensitivity to sunlight. A summary of the results of photodynamic therapy by individual sites is included. The use of newer sensitizers, which represent much purer substances than Photofrin II, should give an opportunity for repeated treatments, which should eventually make this form of treatment far more important than it has been up to now.

Photodynamic therapy in psoriasis: suppression of cytokine production in vitro and recording of fluorescence modification during treatment in vivo

Photodynamic therapy (PDT) consists of the combination of photosensitizers absorbing light mainly in the red spectral region and irradiation with light of corresponding wavelengths. We analysed its effects on the cytokine secretion (IL-1 beta, TNF alpha, IL-6) of freshly isolated peripheral mononuclear cells from six patients with chronic plaque-stage psoriasis in comparison with PUVA. PUVA treatment resulted in a decreased production of all three cytokines, but most pronounced in the case of IL-6. PDT caused a similar change in the cytokine pattern, but its effectiveness was lower. In vivo fluorescence recordings were performed on psoriatic plaque lesions after topical application of the photosensitizer Photosan-3. Under irradiation, progressive photobleaching was noted with increasing radiation dosage. This is the first reported study of photochemical reactions using on-line fluorescence recordings during PDT of psoriatic lesions in vivo. Our results demonstrate the capacity of PDT to cause immunomodulatory effects similar to PUVA, thus indicating its potential application to the treatment of this common disease.

Minimally invasive surgery. Future developments

The rapid development of minimally invasive surgery means that there will be fundamental changes in interventional treatment. Technological advances will allow new minimally invasive procedures to be developed. Application of robotics will allow some procedures to be done automatically, and coupling of slave robotic instruments with virtual reality images will allow surgeons to perform operations by remote control. Miniature motors and instruments designed by microengineering could be introduced into body cavities to perform operations that are currently impossible. New materials will allow changes in instrument construction, such as use of memory metals to make heat activated scissors or forceps. With the reduced trauma associated with minimally invasive surgery, fewer operations will require long hospital stays. Traditional surgical wards will become largely redundant, and hospitals will need to cope with increased through-put of patients. Operating theatres will have to be equipped with complex high technology equipment, and hospital staff will need to be trained to manage it. Conventional nursing care will be carried out more in the community. Many traditional specialties will be merged, and surgical training will need fundamental revision to ensure that surgeons are competent to carry out the new procedures.

Photodynamic therapy for cancers: a clinical trial of porfimer sodium in Japan

Photodynamic therapy utilizing Photofrin has proven to be an effective modality that can be used in the treatment of a wide variety of solid tumors and luminal cancers. An argon pumped dye laser or excimer dye laser was used to deliver 630 nm light via quartz fibers passed through the biopsy channel subsequent to i.v. injection of photosensitizer. In this study, 64 patients with superficial cancers were treated in this manner but only 58 patients, including 21 with roentgenographically occult lung cancer, 8 with stage I lung cancer, 5 with esophageal cancer, 12 with gastric cancer, 8 with cervical cancer and 4 with bladder cancer were evaluable. Complete remission was obtained in 48 out of 58 cases (82.8%). There was no serious complication except skin photosensitivity, which was seen in 13 patients. We conclude that photodynamic therapy is efficacious in the treatment of superficial cancers where complete remission may be achieved.