Vitamin D Combined with Aminolevulinate (ALA)-Mediated Photodynamic Therapy (PDT) for Human Psoriasis: A Proof-of-Principle Study

Recent Advances in Photodynamic Therapy for Vascular Abnormalities

Abstract Background: Photodynamic therapy (PDT) is a minimally invasive therapy that was gradually established as a first-line treatment for vascular abnormalities. Its action depends on the appropriate wavelength of light and photosensitizer to produce toxic oxygen species and cause cell death. Objective: Several new clinical improvements and trends in PDT have been described in recent years. The aim of this review is to provide an overview of the current data from clinical trials. Methods: In this review, we introduce and generalize the wavelength, duration, dose, strength, and photosensitizer of PDT for the treatment of vascular abnormalities, such as circumscribed choroidal hemangiomas (CCH), choroidal neovascularization (CNV) and capillary malformation (CM). Results: The systematic review findings indicate that the application of PDT is a safe effective method to treat CCH, CNV and CM. However, PDT also has early onset side effects and late onset side effects. Conclusions: Based on the discussion of the effectiveness of PDT, we conclude that PDT has great potential for clinical use, although PDT has possible side effects.

Treatment of nonmelanoma skin cancer with pro-differentiation agents and photodynamic therapy: Preclinical and clinical studies (Review)

Photodynamic therapy (PDT) is a nonscarring cancer treatment in which a pro-drug (5-aminolevulinic acid, ALA) is applied, converted into a photosensitizer (protoporphyrin IX, PpIX) which is then activated by visible light. ALA-PDT is now popular for treating nonmelanoma skin cancer (NMSC), but can be ineffective for larger skin tumors, mainly due to inadequate production of PpIX. Work over the past two decades has shown that differentiation-promoting agents, including methotrexate (MTX), 5-fluorouracil (5FU) and vitamin D (Vit D) can be combined with ALA-PDT as neoadjuvants to promote tumor-specific accumulation of PpIX, enhance tumor-selective cell death, and improve therapeutic outcome. In this review, we provide a historical perspective of how the combinations of differentiation-promoting agents with PDT (cPDT) evolved, including Initial discoveries, biochemical and molecular mechanisms, and clinical translation for the treatment of NMSCs. For added context, we also compare the differentiation-promoting neoadjuvants with some other clinical PDT combinations such as surgery, laser ablation, iron-chelating agents (CP94), and immunomodulators that do not induce differentiation. Although this review focuses mainly on the application of cPDT for NMSCs, the concepts and findings described here may be more broadly applicable towards improving the therapeutic outcomes of PDT treatment for other types of cancers.

Combination of vitamin D and photodynamic therapy enhances immune responses in murine models of squamous cell skin cancer

Improved treatment outcomes for non-melanoma skin cancers can be achieved if Vitamin D (Vit D) is used as a neoadjuvant prior to photodynamic therapy (PDT). However, the mechanisms for this effect are unclear. Vit D elevates protoporphyrin (PpIX) levels within tumor cells, but also exerts immune-modulatory effects. Here, two murine models, UVB-induced actinic keratoses (AK) and human squamous cell carcinoma (A431) xenografts, were used to analyze the time course of local and systemic immune responses after PDT ± Vit D. Fluorescence immunohistochemistry of tissues and flow analysis (FACS) of blood were employed. In tissue, damage-associated molecular patterns (DAMPs) were increased, and infiltration of neutrophils (Ly6G+), macrophages (F4/80+), and dendritic cells (CD11c+) were observed. In most cases, Vit D alone or PDT alone increased cell recruitment, but Vit D + PDT showed even greater recruitment effects. Similarly for T cells, increased infiltration of total (CD3+), cytotoxic (CD8+) and regulatory (FoxP3+) T-cells was observed after Vit D or PDT, but the increase was even greater with the combination. FACS analysis revealed a variety of interesting changes in circulating immune cell levels. In particular, neutrophils decreased in the blood after Vit D, consistent with migration of neutrophils into AK lesions. Levels of cells expressing the PD-1+ checkpoint receptor were reduced in AKs following Vit D, potentially counteracting PD-1+ elevations seen after PDT alone. In summary, Vit D and ALA-PDT, two treatments with individual immunogenic effects, may be advantageous in combination to improve treatment efficacy and management of AK in the dermatology clinic.

Time-gated luminescent probes for lysosomal singlet oxygen: Synthesis, characterizations and bioimaging applications

BACKGROUD

Single oxygen (1O2), the molecular oxygen at its excited state, plays a crucial role in the photodynamic therapy (PDT) of some diseases owing to its strong oxidizing property to destroy malignant cells. Although the fluorescent probe technique has proven its powerful application abilities for detection of 1O2 in biological systems, most of the reported fluorescent probes suffered from the interference of background autofluorescence of biological samples. It is clear that the real-time and in situ, background-free fluorescent detection of 1O2 generated in live cells, especially in some organelles, is of great significance for understanding the action mechanism of PDT drugs.

RESULTS

By introducing a lysosome-anchoring motif, a morpholine moiety, into a 1O2-specifically-reactive terpyridine polyacid ligand, [4'-(9-anthryl)-2,2':6',2″-terpyridine-6,6″-diyl] bis(methylenenitrilo) tetrakis (acetic acid) (ATTA), and chelating with lanthanide ions (Eu3+ or Tb3+), two lanthanide complex-based "turn-on" luminescent probes that can be used for the background-free time-gated luminescent (TGL) detection of lysosomal 1O2, Lyso-ATTA-Eu3+ and Lyso-ATTA-Tb3+, have been developed. The probes exhibit fast luminescence responses (within 2.5 min) towards 1O2 with high selectivity and sensitivity (<0.75 μM) in a wide pH range (4-11). And the excellent lysosome-localization performance of the probes allowed them to be used for the monitoring of endogenous 1O2 in lysosomes, which enabled the variability of lysosomal-1O2 concentrations induced by different photosensitizers to be successfully discriminated. Furthermore, by doping Lyso-ATTA-Eu3+ into the polyethylene glycol (PEG) hydrogel, the smart luminescent sensor film, PEG-Lyso-ATTA-Eu3+, was prepared, and successfully used for the detection of the on-site 1O2 production during the PDT process of psoriatic disease in model mice.

SIGNIFICANT

Two lysosome-targetable background-free TGL probes for 1O2 were firstly reported. The developed smart luminescent sensor film could be a powerful tool for the clinical monitoring of PDT on skin diseases without using sophisticated and expensive instruments.

Vitamin D and Vitamin D3 Supplementation during Photodynamic Therapy: A Review

Photodynamic therapy is an unconventional yet increasingly common method of treating dermatological diseases and cancer that is implemented more often in adults than in children. Current clinical uses include treatment of actinic keratosis, superficial basal cell carcinomas, and acne. Despite its high efficiency, photodynamic therapy support supplements have recently been reported in the literature, including calcitriol (1,25-dihydroxycholecalciferol), the active form of vitamin D, and vitamin D3 cholecalciferol. In clinical trials, photodynamic therapy enhanced with vitamin D or D3 supplementation has been reported for treatment of squamous cell skin cancers, actinic keratosis, and psoriasis. Experimental research on the effect of photodynamic therapy with vitamin D or D3 has also been carried out in breast cancer cell lines and in animal models. The aim of this review is to evaluate the usefulness and effectiveness of vitamin D and D3 as supports for photodynamic therapy. For this purpose, the Pubmed and Scopus literature databases were searched. The search keyword was: “vitamin D in photodynamic therapy”. In the analyzed articles (1979–2022), the authors found experimental evidence of a positive effect of vitamin D and D3 when used in conjunction with photodynamic therapy. An average of 6–30% (in one case, up to 10 times) increased response to photodynamic therapy was reported in combination with vitamin D and D3 as compared to photodynamic therapy alone. Implementing vitamin D and D3 as a supplement to photodynamic therapy is promising and may lead to further clinical trials and new clinical methodologies.

Combination of 5-Fluorouracil with Photodynamic Therapy: Enhancement of Innate and Adaptive Immune Responses in a Murine Model of Actinic Keratosis

We previously showed that a combination of differentiation-inducing agents (5-fluorouracil, vitamin D3, or methotrexate) and aminolevulinate-based photodynamic therapy (PDT) improves clinical responses by enhancing protoporphyrin IX (PpIX) photosensitizer levels and cell death. Here, we show that in addition to its previously known effects, 5-fluorouracil (5FU) enhances PDT-induced tumor-regressing immunity. Murine actinic keratoses (AK) were treated with topical 5FU or vehicle for three days prior to ALA application, followed by blue light illumination (~417 nm). Lesions were harvested for time-course analyses of innate immune cell recruitment into lesions, i.e., neutrophils (Ly6G+) and macrophages (F4/80+), which peaked at 72 hours and 1 week post PDT, respectively, and was greater in 5FU treated lesions. Enhanced infiltration of activated T cells (CD3+) throughout the time course, and of cytotoxic T cells (CD8+) at 1 - 2 weeks post PDT, also occurred in 5FU treated lesions. 5FU pretreatment reduced the presence of cells expressing the immune checkpoint marker PD-1 at ~72 hours post PDT, favoring cytotoxic T cell activity. A combination of 5FU and PDT, each individually known to induce long-term tumor-targeting immune responses in addition to their more immediate effects on cancer cells, may synergize to provide better management of squamous precancers.

An Update on Photodynamic Therapy of Psoriasis—Current Strategies and Nanotechnology as a Future Perspective

Psoriasis (PS) is an immune-mediated skin disease with substantial negative effects on patient quality of life. Despite significant progress in the development of novel treatment options over the past few decades, a high percentage of patients with psoriasis remain undertreated and require new medications with superior long-term efficacy and safety. One of the most promising treatment options against psoriatic lesions is a form of phototherapy known as photodynamic therapy (PDT), which involves either the systemic or local application of a cell-targeting photosensitizing compound, followed by selective illumination of the lesion with visible light. However, the effectiveness of clinically incorporated photosensitizers in psoriasis treatment is limited, and adverse effects such as pain or burning sensations are frequently reported. In this study, we performed a literature review and attempted to provide a pooled estimate of the efficacy and short-term safety of targeted PDT in the treatment of psoriasis. Despite some encouraging results, PDT remains clinically underutilized. This highlights the need for further studies that will aim to evaluate the efficacy of a wider spectrum of photosensitizers and the potential of nanotechnology in psoriasis treatment.

REAP (Rapid Elimination of Active Plasmodium): A photodynamic strategy exploiting intrinsic kinetics of the parasite to combat severe malaria

Plasmodium falciparum, the causative organism of Malaria is a mosquito-borne parasitic disease which infects red blood cells (RBCs), where it multiplies rapidly and goes through different stages of its life cycle. When the parasite load exceeds >3% in the blood, malaria transforms into severe malaria which requires immediate attention as death occurs within hours to days. The increase in people traveling to malaria-endemic areas and resistance/partial resistance to most known antimalarial drugs has put the current management scheme in jeopardy. To improve the patient outcome at this point, the physician may opt to perform exchange transfusions from another individual as an adjunct therapy to reduce parasitized RBCs, but the strategy has many drawbacks, including chances of infection. These limitations can be mitigated if the patient's own blood is withdrawn/extracted, sterilized from the parasitic load and then re-transfused almost similar to what is done in extracorporeal blood treatment for sepsis, poisoning and graft versus host disease. Thus, in the present study a light-based photochemical approach, Photodynamic Therapy (PDT) built on delta-aminolevulinic acid-protoporphyrin IX (ALA-PpIX) synthesis is exploited. This modality was effective at destruction of both resistant and susceptible strains of parasites, including at a high load mimicking severe drug resistant malaria. The current findings have set the stage for concept of an ALA-PpIX based PDT platform, "the REAP (Rapid Elimination of Active Plasmodium) strategy". This approach provides an additional tool towards the defense against multi-drug resistant severe malaria, and other intracellular blood pathogens, dependent on heme-synthesis.

Vitamin D and Other Differentiation-promoting Agents as Neoadjuvants for Photodynamic Therapy of Cancer

The efficacy of photodynamic therapy (PDT) using aminolevulinic acid (ALA), which is preferentially taken up by cancerous cells and converted to protoporphyrin IX (PpIX), can be substantially improved by pretreating the tumor cells with vitamin D (Vit D). Vit D is one of several "differentiation-promoting agents" that can promote the preferential accumulation of PpIX within the mitochondria of neoplastic cells, making them better targets for PDT. This article provides a historical overview of how the concept of using combination agents ("neoadjuvants") for PDT evolved, from initial discoveries about neoadjuvant effects of methotrexate and fluorouracil to later studies to determine how vitamin D and other agents actually work to augment PDT efficacy. While this review focuses mainly on skin cancer, it includes a discussion about how these concepts may be applied more broadly toward improving PDT outcomes in other types of cancer.

Adjuvants that Empower the Action of Photodynamic Therapy

Compounds have been devised whose supportive actions make them important adjuvants in the priming of photosensitization to selectively target cancer cells. Here, we highlight the paper by Maytin and Hasan in this issue of Photochemistry & Photobiology, which describes adjuvants methotrexate, 5-fluorouracil, vitamin D and its analogs leading to improved photodynamic therapy outcome. These small molecule adjuvants act by different mechanisms to enhance the cytotoxicity in tumor cells and the therapeutic effect in cancers. These findings add to the list of strategies for enhancement of photodynamic therapy.

Anticancer effect of LS-HB-mediated photodynamic therapy on hepatocellular carcinoma in vitro and in vivo

Photodynamic therapy (PDT) is a relatively safe way for disease diagnosis and treatment that is based on light and photosensitizers. LS-HB is a promising photosensitizer with a light absorption peak of 660 nm.

AIMS

The present study aimed to investigate the anticancer effects of LS-HB-PDT on hepatocellular carcinoma and its underlying molecular mechanism.

METHODS

In the present study, the MTT assay and xenograft tumor model experiment were used to evaluate its anticancer effects as well as its dark toxicity in hepatocellular carcinoma in vitro and in vivo. Reactive oxygen species assay kit was utilized to detect the reactive oxygen species production induced by LS-HB-PDT.

RESULTS

In vitro, the MTT assay results revealed that LS-HB-PDT exhibited significant cytotoxic effects both in a drug- and light dose-dependent manner. The IC₅₀ of LS-HB-PDT on hepatocellular carcinoma cells was 2.685 μg/ml. However, no dark cytotoxicity was observed at the LS-HB concentrations of 0-50 μg/ml, and no light-induced cytotoxicity was observed at the light (660 nm) dosages of 0-40 J/cm². Furthermore, reactive oxygen species could be induced after LS-HB-PDT in a drug- and light dose-dependent manner. In vivo experiment, the tumor inhibition ratio of tumor-bearing nude mice following LS-HB-PDT was enhanced with the drug and light dose increasing. Notably, tumors in 60.0% of mice disappeared after LS-HB-PDT (2 mg/kg; 100 J/cm²), and the tumor inhibition ratio reached 92.3%. Furthermore, the histological results revealed necrosis and thrombus in tumor tissue caused by LS-HB-PDT, which were not observed in the control, drug alone and light alone groups of mice.

CONCLUSIONS

The present study indicated that LS-HB was a promising photosensitizer with excellent anticancer effects and low side effects. LS-HB-PDT induced reactive oxygen species damage in the cells directly and destroyed tumor blood vessels, thus leading to tumor tissue necrosis.

Photodynamic Therapy and the Biophysics of the Tumor Microenvironment

Targeting the tumor microenvironment (TME) provides opportunities to modulate tumor physiology, enhance the delivery of therapeutic agents, impact immune response and overcome resistance. Photodynamic therapy (PDT) is a photochemistry-based, nonthermal modality that produces reactive molecular species at the site of light activation and is in the clinic for nononcologic and oncologic applications. The unique mechanisms and exquisite spatiotemporal control inherent to PDT enable selective modulation or destruction of the TME and cancer cells. Mechanical stress plays an important role in tumor growth and survival, with increasing implications for therapy design and drug delivery, but remains understudied in the context of PDT and PDT-based combinations. This review describes pharmacoengineering and bioengineering approaches in PDT to target cellular and noncellular components of the TME, as well as molecular targets on tumor and tumor-associated cells. Particular emphasis is placed on the role of mechanical stress in the context of targeted PDT regimens, and combinations, for primary and metastatic tumors.

Towards dosimetry for photodynamic diagnosis with the low-level dose of photosensitizer

BACKGROUND

Contemporary medicine does not concern the issue of dosimetry in photodynamic diagnosis (PDD) but follows the photosensitizer (PS) producers recommendation. Most preclinical and clinical PDD studies indicate a considerable variation in the possibility of visualization and treatment, as e.g. in case of cervix lesions. Although some of these variations can be caused by the different histological subtypes or various tumor geometries, the issue of varying PS concentration in the tumor tissue volume is definitely an important factor. Therefore, there is a need to establish the objective and systematic PDD dosimetry protocol regarding doses of light and photosensitizers.

METHODS

Four different irradiation sources investigated in PDD (literature) were used for PS excitation. The PS luminescence was examined by means of the non-imaging (spectroscopic) and imaging (wide- and narrow-field of view) techniques. The methodology for low-level intensity photoluminescence (PL) characterization and dedicated image processing algorithm for PS luminescence images analysis were proposed. Further, HeLa cells' cultures penetration by PS was studied by a confocal microscopy.

RESULTS

Reducing the PS dose with the choice of proper photoexcitation conditions decreases the PDD procedure costs and the side effects, not affecting the diagnostic efficiency. We determined in vitro the minimum incubation time and photosensitizer concentration of Photolon for diagnostic purposes, for which the Photolon PL can still be observed. It was demonstrated that quantification of PS concentration, choice of proper photoexcitation source, appropriate adjustment of light dose and PS penetration of cancer cells may improve the low-level luminescence photodynamic diagnostics performance.

CONCLUSIONS

Practical effectiveness of the PDD strongly depends on irradiation source parameters (bandwidth, maximum intensity, half-width) and their optimization is the main conditioning factor for low-level intensity and low-cost PDD.

Fluorouracil Enhances Photodynamic Therapy of Squamous Cell Carcinoma via a p53-Independent Mechanism that Increases Protoporphyrin IX levels and Tumor Cell Death

Photodynamic therapy (PDT), using 5-aminolevulinic acid (ALA) to drive synthesis of protoporphryin IX (PpIX) is a promising, scar-free alternative to surgery for skin cancers, including squamous cell carcinoma (SCC) and SCC precursors called actinic keratoses. In the United States, PDT is only FDA approved for treatment of actinic keratoses; this narrow range of indications could be broadened if PDT efficacy were improved. Toward that goal, we developed a mechanism-based combination approach using 5-fluorouracil (5-FU) as a neoadjuvant for ALA-based PDT. In mouse models of SCC (orthotopic UV-induced lesions, and subcutaneous A431 and 4T1 tumors), pretreatment with 5-FU for 3 days followed by ALA for 4 hours led to large, tumor-selective increases in PpIX levels, and enhanced cell death upon illumination. Several mechanisms were identified that might explain the relatively improved therapeutic response. First, the expression of key enzymes in the heme synthesis pathway was altered, including upregulated coproporphyrinogen oxidase and downregulated ferrochelatase. Second, a 3- to 6-fold induction of p53 in 5-FU-pretreated tumors was noted. The fact that A431 contains a mutant form p53 did not prevent the development of a neoadjuvantal 5-FU effect. Furthermore, 5-FU pretreatment of 4T1 tumors (cells that completely lack p53), still led to significant beneficial inductions, that is, 2.5-fold for both PpIX and PDT-induced cell death. Thus, neoadjuvantal 5-FU combined with PDT represents a new therapeutic approach that appears useful even for p53-mutant and p53-null tumors. Mol Cancer Ther; 16(6); 1092-101. ©2017 AACR.

Comparing desferrioxamine and light fractionation enhancement of ALA-PpIX photodynamic therapy in skin cancer

Background:

Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) provides selective uptake and conversion of ALA into protoporphyrin IX (PpIX) in actinic keratosis and squamous cell carcinoma, yet large response variations in effect are common between individuals. The aim of this study was to compare pre-treatment strategies that increase the therapeutic effect, including fractionated light delivery during PDT (fPDT) and use of iron chelator desferrioxamine (DFO), separately and combined.

Methods:

Optical measurements of fluorescence were used to quantify PpIX produced, and the total amount of PpIX photobleached as an implicit measure of the photodynamic dose. In addition, measurements of white light reflectance were used to quantify changes in vascular physiology throughout the PDT treatment.

Results:

fPDT produced both a replenishment of PpIX and vascular re-oxygenation during a 2 h dark interval between the first and second PDT light fractions. The absolute photodynamic dose was increased 57% by fPDT, DFO and their combination, as compared with PDT group (from 0.7 to 1.1). Despite that light fractionation increased oedema and scab formation during the week after treatment, no significant difference in long-term survival has been observed between treatment groups. However, outcomes stratified on the basis of measured photodynamic dose showed a significant difference in long-term survival.

Conclusions:

The assessment of implicit photodynamic dose was a more significant predictor of efficacy for ALA-PDT skin cancer treatments than prescription of an enhanced treatment strategy, likely because of high individual variation in response between subjects.

Current Advances in 5-Aminolevulinic Acid Mediated Photodynamic Therapy

Kennedy and Pottier discovered that photodynamic therapy (PDT) could be carried out using a procedure consisting of topical application of the porphyrin-precursor, 5-aminolevulinic acid (ALA) to the skin, followed after some time by illumination with various light parameters in the 1980s. Since then, ALA-PDT has expanded enormously and now covers most aspects of dermatological disease. The purpose of this review is to discuss a range of ingenious strategies that investigators have devised for improving the overall outcome (higher efficiency and lower side effects) of ALA-PDT. The big advance of using ALA esters instead of the free acid to improve skin penetration was conceived in the 1990s. A variety of more recent innovative approaches can be divided into three broad groups: (a) those relying on improving delivery or penetration of ALA into the skin; (b) those relying on ways to increase the synthesis of protoporphyrin IX inside the skin; (c) those relying on modification of the illumination parameters. In the first group, we have improved delivery of ALA with penetration-enhancing chemicals, iontophoresis, intracutaneous injection, or fractionated laser. There is also a large group of nanotechnology-related approaches with ALA being delivered using liposomes/ethosomes, ALA dendrimers, niosomes, mesoporous silica nanoparticles, conjugated gold nanoparticles, polymer nanoparticles, fullerene nanoparticles, and carbon nanotubes. In the second group, we can find the use of cellular differentiating agents, the use of iron chelators, and the effect of increasing the temperature. In the third group, we find methods designed to reduce pain as well as improve efficiency including fractionated light, daylight PDT, and wearable light sources for ambulatory PDT. This active area of research is expected to continue to provide a range of intriguing possibilities.

Photodynamic therapy for psoriasis

INTRODUCTION

Photodynamic therapy for psoriasis showed promise in the early 1990s with reports of plaque clearance following topical aminolevulinic acid - photodynamic therapy (ALA-PDT).

METHODS

In December 2013, we conducted a systematic search of the PubMed Medline database using the keywords "psoriasis" and "photodynamic therapy".

RESULTS

Numerous clinical studies have failed to demonstrate a consistent, efficacious response to topical ALA-PDT. Furthermore, severe pain and burning sensations were repeatedly reported, many cases being intolerable for patients.

DISCUSSION

The variability in clinical response and the painful side effects have made topical ALA-PDT an unsuitable treatment option for chronic plaque psoriasis. Nonetheless, early clinical studies of other modalities such as topical hypericin and methylene blue, as well as systemic ALA and verteporfin, have shown that these photosensitizers are efficacious and much better tolerated than topical ALA.

CONCLUSION

With the current landscape of phototherapy dominated by psoralen combined with ultraviolet A (PUVA) and narrow-band ultraviolet B (NB-UVB), an alternative light therapy utilizing the visible spectrum is certainly promising and a worthwhile endeavor to pursue.

Improve efficacy of topical ALA-PDT by calcipotriol through up-regulation of coproporphyrinogen oxidase

BACKGROUND

Topical 5-aminolevulinic acid-mediated photodynamic therapy (topical ALA-PDT) is effective for treating oral precancerous lesions. The aim of this in vivo and in vitro study was to examine whether the efficacy of topical ALA-PDT could be further improved by calcipotriol (CAL).

METHODS

Precancerous lesions in the buccal pouch of hamsters were induced by dimethylbenz(a)anthracene (DMBA). Lesions were treated with multiple topical ALA-PDT with or without CAL pretreatment. ALA-induced protoporphyrine IX (PpIX) was monitored by in situ fluorescence measurement. The effect of CAL on heme-related enzymes (CPOX, PPOX, and FECH) were examined in an in vitro model using human squamous cell carcinoma (SCC) cells (SCC4, SAS) using Western blots.

RESULTS

Fluorescence spectroscopy revealed that PpIX reached its peak level in precancerous epithelial cells of buccal pouch at 2.5 or 3.5h without or with CAL pretreatment, respectively. Both treatment regimens showed similar response rates, but the complete response was achieved after 5 times of ALA-PDT and 3 times of CAL-ALA-PDT (p<0.001). Pretreatment of SCC cells with 10(-8) or 10(-7)M CAL could result in a significant cell death (p<0.05) and an elevation of CPOX protein level.

CONCLUSION

Topical CAL can improve the efficacy of ALA-PDT in treating precancerous lesions, likely through the increase in CPOX level and in PpIX production.

Combination of oral vitamin D3 with photodynamic therapy enhances tumor cell death in a murine model of cutaneous squamous cell carcinoma

Photodynamic therapy (PDT), in which 5-ALA (a precursor for protoporphyrin IX, PpIX) is administered prior to exposure to light, is a nonscarring treatment for skin cancers. However, for deep tumors, ALA-PDT is not always effective due to inadequate production of PpIX. We previously developed and reported a combination approach in which the active form of vitamin D3 (calcitriol) is given systemically prior to PDT to improve PpIX accumulation and to enhance PDT-induced tumor cell death; calcitriol, however, poses a risk of hypercalcemia. Here, we tested a possible strategy to circumvent the problem of hypercalcemia by substituting natural dietary vitamin D3 (cholecalciferol; D3 ) for calcitriol. Oral D3 supplementation (10 days of a 10-fold elevated D3 diet) enhanced PpIX levels 3- to 4-fold, and PDT-mediated cell death 20-fold, in subcutaneous A431 tumors. PpIX levels and cell viability in normal tissues were not affected. Hydroxylated metabolic forms of D3 were only modestly elevated in serum, indicating minimal hypercalcemic risk. These results show that brief oral administration of cholecalciferol can serve as a safe neoadjuvant to ALA-PDT. We suggest a clinical study, using oral vitamin D3 prior to PDT, should be considered to evaluate this promising new approach to treating human skin cancer.

Synergistic apoptotic effect of Doxil ® and aminolevulinic acid-based photodynamic therapy on human breast adenocarcinoma cells

BACKGROUND

5-Aminolevulinic acid (ALA) is a natural heme precursor metabolized into protoporphyrin IX (PpIX). PpIX preferentially accumulates in tumor cells resulting in the formation of singlet oxygen upon exposure to visible light. Doxil(®), an active agent against breast and ovarian cancer, is a nano-formulation of doxorubicin. This study aimed to investigate in vitro synergistic cytotoxic effect of low doses of combined chemotherapy and ALA/PDT to human breast adenocarcinoma cells (MCF-7) compared to high doses of each individual therapy.

METHODS

MCF-7 cells were pretreated with Doxil(®) (48 h) followed by ALA/PDT (4h). The cell viability was evaluated by trypan blue assay and PpIX production was measured spectrofluorometrically. Alkaline phosphatase was determined as a marker for cellular differentiation. Apoptosis and necrosis were evaluated by fluorescence stains. The apoptosis cell death pathways were investigated: detection of mitochondrial membrane potential (ΔΨm) and percent of DNA fragmentation, malondialdehyde, histone deacetylase (HDAC) activity, caspase-3 and death receptors (DR4 and DR5). Vascular endothelial growth factor (VEGF) was determined by ELISA, as an angiogenic mediator.

RESULTS

There was a higher reduction in cell viability in Doxil(®)+ALA/PDT-treated cells compared with their individual effect. The combined therapy showed enhanced apoptosis with a significant increase in the loss of ΔΨm, DNA fragmentation %, caspase-3, DR4, DR5 and lipid peroxides and inhibited HDAC. Pretreatment with Doxil(®) resulted in a twofold increase in the intracellular PpIX, by increasing the PDT killing of MCF-7 cells.

CONCLUSION

The combined therapy using 50% of IC50 of ALA/PDT and Doxil(®) possessed a synergistic apoptotic effect on MCF-7 cells compared to 100% of IC50 of each therapy through enhancing both intrinsic and extrinsic apoptotic pathways, thus may minimize side effects of Doxil(®) and ALA.