5-Fluorouracil Enhances Protoporphyrin IX Accumulation and Lesion Clearance during Photodynamic Therapy of Actinic Keratoses: A Mechanism-Based Clinical Trial

The use of photodynamic therapy in medical practice

Cancer therapy, especially for tumors near sensitive areas, demands precise treatment. This review explores photodynamic therapy (PDT), a method leveraging photosensitizers (PS), specific wavelength light, and oxygen to target cancer effectively. Recent advancements affirm PDT's efficacy, utilizing ROS generation to induce cancer cell death. With a history spanning over decades, PDT's dynamic evolution has expanded its application across dermatology, oncology, and dentistry. This review aims to dissect PDT's principles, from its inception to contemporary medical applications, highlighting its role in modern cancer treatment strategies.

Diagnosis and therapy of actinic keratosis

Actinic keratosis (AK) is considered a chronic and recurring in situ skin neoplasia, with a possible transformation into invasive squamous cell carcinoma (SCC). Among others, predominant risk factors for development of AK are UV-light exposure and immunosuppression. Basal epidermal keratinocyte atypia (AK I) and proliferation (PRO score) seem to drive malignant transformation, rather than clinical appearance of AK (Olsen I-III). Due to the invasiveness of punch biopsy, those histological criteria are not regularly assessed. Non-invasive imaging techniques, such as optical coherence tomography (OCT), reflectance confocal microscopy (RCM) and line-field confocal OCT (LC-OCT) are helpful to distinguish complex cases of AK, Bowen's disease, and SCC. Moreover, LC-OCT can visualize the epidermis and the papillary dermis at cellular resolution, allowing real-time PRO score assessment. The decision-making for implementation of therapy is still based on clinical risk factors, ranging from lesion- to field-targeted and ablative to non-ablative regimens, but in approximately 85% of the cases a recurrence of AK can be observed after a 1-year follow-up. The possible beneficial use of imaging techniques for a non-invasive follow-up of AK to detect recurrence or invasive progression early on should be subject to critical evaluation in further studies.

Field Cancerization Therapies for the Management of Actinic Keratosis: An Updated Review

Field cancerization theory highlights that the skin surrounding actinic keratoses (AK) is also at increased risk for possible malignant transformation; thus, field-directed treatments may both reduce the risk of AK recurrence and potentially reduce the risk of development of cutaneous squamous cell carcinoma (cSCC). Photodynamic therapy (PDT) with either aminolevulinic acid (ALA) or methylaminolevulinate (MAL), as well as topical treatments such as 5-fluorouracil (5-FU), diclofenac gel, piroxicam, imiquimod, and ingenol mebutate, have all shown higher efficacy than vehicle treatments. PDT is widely recognized for its high efficacy; however, concerns for associated pain have driven new studies to begin using alternative illumination and pretreatment techniques, including lasers. Among topical treatments, a combination of 5-FU and salicylic acid (5-FU-SA) has shown to be the most effective but also causes the most adverse reactions. Tirbanibulin, a new topical agent approved for use in 2020, boasts a favorable safety profile in comparison with imiquimod, 5-FU, and diclofenac. Meanwhile, ingenol mebutate is no longer recommended for the treatment of AKs due to concerns for increased risk of cSCC development. Moving forward, an increasing number of studies push for standardization of outcome measures to better predict risk of future cSCC and use of more effective measures of cost to better guide patients. Here, we present an updated and comprehensive narrative review both confirming the efficacy of previously mentioned therapies as well as highlighting new approaches to PDT and discussing the use of lasers and novel topical treatments for treatment of AK.

Diagnose und Therapie aktinischer Keratosen

Actinic keratosis (AK) is considered a chronic and recurring in situ skin neoplasia, with a possible transformation into invasive squamous cell carcinoma (SCC). Among others, predominant risk factors for development of AK are UV-light exposure and immunosuppression. Basal epidermal keratinocyte atypia (AK I) and proliferation (PRO Score) seem to drive malignant turnover, rather than clinical appearance of AK (Olsen I-III). Due to the invasiveness of punch biopsy, those histological criteria are not regularly assessed. Non-invasive imaging techniques, such as optical coherence tomography (OCT), reflectance confocal microscopy (RCM) and line-field confocal OCT (LC-OCT) are helpful to distinguish complex cases of AK, Bowen's disease and SCC. Moreover, LC-OCT can visualize the epidermis and the papillary dermis at cellular resolution, allowing real-time PRO Score assessment. The decision-making for implementation of therapy is still based on clinical risk factors, ranging from lesion- to field-targeted and ablative to non-ablative regimes, but in approximately 85% of the cases a recurrence of AK can be observed after a 1-year follow-up. The possible beneficial use of imaging techniques for a non-invasive follow-up of AK to detect recurrence or invasive progression early on should be subject to critical evaluation in further studies.

Chlorin Conjugates in Photodynamic Chemotherapy for Triple-Negative Breast Cancer

Breast cancer (BC) is the most common type of cancer in women and the number of new cases in the US is still increasing each year. Triple-negative breast cancer (TNBC), which comprises 15-20% of all breast cancer, is a heterogeneous disease and is considered the most aggressive type of breast cancer due to the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expressions for treatments. Traditional chemotherapy is the standard protocol for the treatment of TNBC. Toxicity and multidrug resistance are major drawbacks to chemotherapy. The lack of molecular targets and poor prognosis for TNBC prompts an urgent need to discover novel therapeutic strategies to improve clinical outcomes and quality of life for patients. Photodynamic therapy (PDT) or light treatment is a binary anti-cancer procedure that uses a photosensitizer (PS) that, upon light activation, produces cytotoxic oxygen species, destroying tumor cells. PDT is minimally invasive and can be repeated a few times without accumulating significant toxicity in the surrounding tissues. The primary goal of this study was to investigate in vitro photodynamic chemotherapy as a ternary combination therapy using our synthesized photosensitizers (chlorin-vitamin conjugates and their corresponding indium complexes) co-treated with known chemotherapeutic agents (taxol, doxorubicin, cisplatin, fluorouracil, or methotrexate) in the presence of light and determine the optimum conditions as a pre-clinical study of an enhanced tumoricidal effect against TNBC. Our results indicated that the best combination for an effective chemophotodynamic effect involves a ternary treatment of the indium complex of the chlorin-lipoic acid conjugate (InCLA) co-treated with taxol, which exhibited strong synergism at the nanomolar concentration when combined in the presence of visible light irradiation. Other ternary combinations containing taxol with a synergistic anti-tumor effect against TNBC include chlorin-pantothenic acid (CPA) and chlorin-biotin (CBTN) conjugates. Several other ternary combinations containing InCLA, CBTN, and CPA with either cisplatin, fluorouracil, or methotrexate were identified to generate a synergistic or additive effect. The light dosage remained constant, but the dosages of photosensitizers and chemotherapy drugs were varied to obtain the lowest possible concentration for the desired effect. The synergistic, additive or antagonistic effects of the drug combinations were determined based on the Chou-Talalay method, with InCLA-taxol having the lowest combination index (CI) of 0.25. Fluorescence and transmission electron microscopy (TEM) images provided evidence of apoptosis as the preferred mode of cell death. Our study demonstrated the combination of PDT and chemotherapy as a potential treatment option for TNBC patients.

Pre-treatment with topical 5-fluorouracil increases the efficacy of daylight photodynamic therapy for actinic keratoses - A randomized controlled trial

BACKGROUND

Daylight photodynamic therapy (dPDT) and topical 5-fluorouracil (5-FU) are each effective treatments for thin grade I actinic keratosis (AKs), but less so for thicker grade II-III AKs. Prolonged topical treatment regimens can be associated with severe skin reactions and low compliance. This study compares the efficacy of sequential 4 % 5-FU and dPDT with dPDT monotherapy for multiple actinic keratoses.

METHODS

Sixty patients with a total of 1547 AKs (grade I: 1278; grade II: 246; grade III: 23) were treated in two symmetrical areas (mean size 75 cm2) of the face or scalp, which were randomized to (i) 4% 5-FU creme twice daily for 7 days before a single dPDT procedure and (ii) dPDT monotherapy. Daylight exposure was either outdoor or indoor daylight.

RESULTS

Twelve weeks after treatment 87 % of all AKs cleared after 5-FU+dPDT compared to 74 % after dPDT alone (p<0.0001). For grade II AKs, the lesion response rate increased from 55 % with dPDT monotherapy to 79 % after 5-FU+dPDT (p<0.0056). Moderate/severe erythema was seen in 88 % 5-FU+dPDT areas compared to 41 % of dPDT areas two days after dPDT. Twelve weeks after treatment 75 % of the patients were very satisfied with both treatments.

CONCLUSIONS

Sequential 5-FU and dPDT was more effective than dPDT monotherapy in the treatment of AKs, especially for grade II AKs. Local skin reactions were more pronounced after combination treatment, but no patients discontinued the treatment. The combination of 5-FU and dPDT is an effective treatment of large treatment areas with high compliance and satisfaction.

Comparative response to PDT with methyl-aminolevulinate and temoporfin in cutaneous and oral squamous cell carcinoma cells

Cutaneous and Head and Neck squamous cell carcinoma (CSCC, HNSCC) are among the most prevalent cancers. Both types of cancer can be treated with photodynamic therapy (PDT) by using the photosensitizer Temoporfin in HNSCC and the prodrug methyl-aminolevulinate (MAL) in CSCC. However, PDT is not always effective. Therefore, it is mandatory to correctly approach the therapy according to the characteristics of the tumour cells. For this reason, we have used cell lines of CSCC (A431 and SCC13) and HNSCC (HN5 and SCC9). The results obtained indicated that the better response to MAL-PDT was related to its localization in the plasma membrane (A431 and HN5 cells). However, with Temoporfin all cell lines showed lysosome localization, even the most sensitive ones (HN5). The expression of mesenchymal markers and migratory capacity was greater in HNSCC lines compared to CSCC, but no correlation with PDT response was observed. The translocation to the nucleus of β-catenin and GSK3β and the activation of NF-κβ is related to the poor response to PDT in the HNSCC lines. Therefore, we propose that intracellular localization of GSK3β could be a good marker of response to PDT in HNSCC. Although the molecular mechanism of response to PDT needs further elucidation, this work shows that the most MAL-resistant line of CSCC is more sensitive to Temoporfin.

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.

Photodynamic Therapy for Field Cancerization in the Skin: Where Do We Stand?

INTRODUCTION

Photodynamic therapy (PDT) with a photosensitizer is available for the treatment of multiple actinic keratoses (AKs) in a restricted skin area or, as it is established, for the field-cancerized skin.

OBJECTIVES

Our review aims to present the up-to-date literature on skin field cancerization using PDT employing different topical photosensitizers, modified light delivery protocols and combination treatments to obtain excellent efficacy and safety in everyday clinical practice.

METHODS

We sought PubMed, MEDLINE, Scopus, OVID, Embase, Science Direct, Cochrane Library, Research Gate and Google Scholar for [(aminolevulinic acid OR aminolevulinate) AND photodynamic therapy] with (field-directed OR field cancerization, (actinic keratosis), and (efficacy OR effectiveness OR pain OR tolerability) for studies published until February 2023.

RESULTS

Advantages of PDT compared to the other field treatments, including imiquimod, 5-fluorouracil, ingenol mebutate gel and diclofenac, reported better cosmetic outcomes and greater patient satisfaction. On the other hand, some drawbacks of field PDT include pain and treatment duration. Alternate illumination methods have also been investigated, including daylight as a light source. Pretreating the affected area may enhance photosensitizer absorption leading to better therapeutic results, while combinational treatments have also been tested. Patients prefer daylight PDT to traditional light sources since it is more well-tolerated and equally effective. Even as a preventive treatment, field PDT yields promising outcomes, especially for high-risk individuals, including organ transplant recipients.

CONCLUSIONS

This review provides a thorough display of the field of PDT on cancerized skin, which will facilitate physicians in applying PDT more efficiently and intuitively.

Improving the efficacy of photodynamic therapy for actinic keratosis: A comprehensive review of pharmacological pretreatment strategies

BACKGROUND

Photodynamic therapy (PDT) is approved for treatment of actinic keratoses (AKs) and field-cancerisation. Pretreatment with pharmacological compounds holds potential to improve PDT efficacy, through direct interaction with PpIX formation or through an independent response, both of which may improve PDT treatment.

OBJECTIVE

To present the currently available clinical evidence of pharmacological pretreatments prior to PDT and to associate potential clinical benefits with the pharmacological mechanisms of action of the individual compounds.

METHODS

A comprehensive search on the Embase, MEDLINE, and Web of Science databases was performed.

RESULTS

In total, 16 studies investigated 6 pretreatment compounds: 5-fluorouracil (5-FU), diclofenac, retinoids, salicylic acid, urea, and vitamin D. Two of these, 5-FU and vitamin D, robustly increased the efficacy of PDT across multiple studies, illustrated by mean increases in clearance rates of 21.88% and 12.4%, respectively. Regarding their mechanisms, 5-FU and vitamin D both increased PpIX accumulation, while 5-FU also induced a separate anticarcinogenic response. Pretreatment with diclofenac for four weeks improved the clearance rate in one study (24.9%), administration of retinoids had a significant effect in one of two studies (16.25%), while salicylic acid and urea did not lead to improved PDT efficacy. Diclofenac and retinoids demonstrated independent cytotoxic responses, whereas salicylic acid and urea acted as penetration enhancers to increase PpIX formation.

CONCLUSION

5-FU and vitamin D are well-tested, promising candidates for pharmacological pretreatment prior to PDT. Both compounds affect the haem biosynthesis, providing a target for potential pretreatment candidates.

KEY WORDS

Photodynamic Therapy, Actinic Keratosis,Pre-tretment,Review,enhancement.

Spotlight on porphyrins: Classifications, mechanisms and medical applications

Photodynamic therapy (PDT) and sonodynamic therapy (SDT) are non-invasive treatment methods with obvious inhibitory effect on tumors and have few side effects, which have been widely concerned and explored by researchers. Sensitizer is the main factor in determining the therapeutic effect of PDT and SDT. Porphyrins, a group of organic compounds widespread in nature, can be activated by light or ultrasound and produce reactive oxygen species. Therefore, porphyrins as sensitizers in PDT have been widely explored and investigated for many years. Herein, we summarize the classical porphyrin compounds and their applications and mechanisms in PDT and SDT. The application of porphyrin in clinical diagnosis and imaging is also discussed. In conclusion, porphyrins have good application prospects in disease treatment as an important part of PDT or SDT, and in clinical diagnosis and imaging.

Equivalent efficacy of indoor daylight and lamp‐based 5‐aminolevulinic acid photodynamic therapy for treatment of actinic keratosis

Background

Photodynamic therapy (PDT) is widely used as a treatment for actinic keratoses (AK), with new sunlight-based regimens proposed as alternatives to lamp-based treatments. Prescribing indoor daylight activation could help address the seasonal temperature, clinical supervision, and access variability associated with outdoor treatments.

Objective

To compare the AK lesion clearance efficacy of indoor daylight PDT treatment (30 min of 5-aminolevulinic acid (ALA) pre-incubation, followed by 2 h of indoor sunlight) versus a lamp-based PDT treatment (30 min of ALA preincubation, followed by 10 min of red light).

Methods

A prospective clinical trial was conducted with 41 patients. Topical 10% ALA was applied to the entire treatment site (face, forehead, scalp). Patients were assigned to either the lamp-based or indoor daylight treatment. Actinic keratosis lesion counts were determined by clinical examination and recorded for pre-treatment, 1-month, and 6-month follow-up visits.

Results

There was no statistical difference in the efficacy of AK lesion clearance between the red-lamp (1-month clearance = 57 ± 17%, 6-month clearance = 57 ± 20%) and indoor daylight treatment (1-month clearance = 61 ± 19%, 6-month clearance = 67 ± 20%). A 95% confidence interval of the difference of the means was measured between -4.4% and 13.4% for 1-month, and -2.2% and +23.6% for 6-month timepoints when comparing the indoor daylight to the red-lamp treatment, with a priori interval of equivalence of ±20%.

Limitations

Ensuring an equivalent dose between the indoor and lamp treatment cohorts limited randomisation since it required performing indoor daylight treatments only during sunny days.

Conclusion

Indoor-daylight PDT provided equivalent AK treatment efficacy to a lamp-based regimen while overcoming temperature limitations and UV-block sunscreen issues associated with outdoor sunlight treatments in the winter.

Clinical trial registration

Clinicaltrials.gov listing: NCT03805737.

Global Trends and Research Progress of Photodynamic Therapy in Skin Cancer: A Bibliometric Analysis and Literature Review

Background

Based on photochemical reactions through the combined use of light and photosensitizers, photodynamic therapy (PDT) is gaining popularity for the treatment of skin cancer. Various photosensitizers and treatment regimens are continuously being developed for enhancing the efficacy of PDT on skin cancer. Reviewing the development history of PDT on skin cancer, and summarizing its development direction and research status, is conducive to the further research.

Methods

To evaluate the research trends and map knowledge structure, all publications covering PDT on skin cancer were retrieved and extracted from Web of Science database. We applied VOSviewer and CiteSpace softwares to evaluate and visualize the countries, institutes, authors, keywords and research trends. Literature review was performed for the analysis of the research status of PDT on skin cancer.

Results

A total of 2662 publications were identified. The elements, mechanism, pros and cons, representative molecular photosensitizers, current challenges and research progress of PDT on skin cancer were reviewed and summarized.

Conclusion

This study provides a comprehensive display of the field of PDT on skin cancer, which will help researchers further explore the mechanism and application of PDT more effectively and intuitively.

Sandpaper curettage: A simple method to improve PDT outcomes for actinic keratosis

INTRODUCTION

Photodynamic therapy (PDT) is a non-scarring, repeatable, and safe treatment for actinic keratosis (AK), but improvements in efficacy are still needed.

BACKGROUND

Devices such as steel blades, needle rollers, and lasers are currently used to remove hypertrophic stratum corneum on AKs to improve PDT outcomes. However, curettage with fine sandpaper could be a gentler, effective alternative.

METHODS

A retrospective study was designed to compare PDT with or without sandpaper curettage. Patients were selected from a database registry of patients with face and scalp AKs (ClinicalTrials.gov NCT03319251). Patients in Group 1 underwent PDT alone (20% ALA, 15 min; blue light 417 nm, 30 min). Patients in Group 2 were pretreated with gentle sandpaper curettage prior to ALA and illumination. The two groups were compared using multivariate matching, normalizing for age, sex, initial AK counts, and time to follow-up.

RESULTS

Sixty-six patients were selected for matching analysis (n=38, PDT only; n=28, PDT+curettage). Demographics between the groups were similar (mean ± SD), including age (71.0 ± 8.3 vs. 71.0 ± 8.0 years), baseline AK count (53 ± 39 vs. 44± 32), and time to post-PDT follow-up (111 ± 28 vs. 113 ± 32 days). At follow-up, patients who received curettage showed an overall 55% improvement in scalp AK clearance compared to patients who did not receive curettage, adjusting for sex, age, time to follow-up, and baseline AK count (p = 0.0322, multivariable linear regression).

DISCUSSION

Sandpaper curettage before PDT treatment is an easy and inexpensive method to significantly improve AK clearance rates.

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.

Combination-Based Strategies for the Treatment of Actinic Keratoses with Photodynamic Therapy: An Evidence-Based Review

Photodynamic therapy (PDT) is a highly effective and widely adopted treatment strategy for many skin diseases, particularly for multiple actinic keratoses (AKs). However, PDT is ineffective in some cases, especially if AKs occur in the acral part of the body. Several methods to improve the efficacy of PDT without significantly increasing the risks of side effects have been proposed. In this study, we reviewed the combination-based PDT treatments described in the literature for treating AKs; both post-treatment and pretreatment were considered including topical (i.e., diclofenac, imiquimod, adapalene, 5-fluorouracil, and calcitriol), systemic (i.e., acitretin, methotrexate, and polypodium leucotomos), and mechanical–physical (i.e., radiofrequency, thermomechanical fractional injury, microneedling, microdermabrasion, and laser) treatment strategies. Topical pretreatments with imiquimod, adapalene, 5-fluorouracil, and calcipotriol were more successful than PDT alone in treating AKs, while the effect of diclofenac gel was less clear. Both mechanical laser treatment with CO2 and Er:YAG (Erbium:Yttrium–Aluminum–Garnet) as well as systemic treatment with Polypodium leucotomos were also effective. Different approaches were relatively more effective in particular situations such as in immunosuppressed patients, AKs in the extremities, or thicker AKs. Conclusions: Several studies showed that a combination-based approach enhanced the effectiveness of PDT. However, more studies are needed to further understand the effectiveness of combination therapy in clinical practice and to investigate the role of acitretin, methotrexate, vitamin D, thermomechanical fractional injury, and microdermabrasion in humans.

In vitro 5-Fluorouracil resistance produces enhanced photodynamic therapy damage in SCC and tumor resistance in BCC

Non-melanoma skin cancer (NMSC) is the most common malignancy worldwide, with rising incidence in the recent years. It includes basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Several non-invasive therapies have been developed for its treatment such as topical 5-Fluorouracil (5FU) and photodynamic therapy (PDT), among others. Despite both are appropriated for NMSC treatment, recurrence cases have been reported. To prevent this, in this work we explore the potential of the combination of PDT and 5FU to treat SCC and BCC. First we evaluate the efficacy of PDT in cells resistant to 5FU. For this purpose, we use SCC-13 and CSZ-1 cells, obtained from a human SCC and a murine BCC, respectively. We first induced 5FU resistance in these cell lines by repeated treatments with the drug and then, the efficacy to PDT was evaluated. The results obtained indicated that SCC-5FU resistant cells were sensible to PDT administration, whereas BCC-5FU resistant cells were also resistant to PDT. The observed responses in both cell lines are in concordance to Protoporphyrin IX (PpIX) and reactive oxygen species (ROS) levels produced after the incubation with MAL and subsequent light exposure. The obtained data support the fact that PDT seems to be an appropriate therapeutic option to be administered after 5FU resistance in SCC. However, PDT would not be a choice therapy for resistant BCC cells to 5FU.

Identification and pharmacological modification of resistance mechanisms to protoporphyrin-mediated photodynamic therapy in human cutaneous squamous cell carcinoma cell lines

BACKGROUND

Photodynamic therapy (PDT) is clinically approved to treat neoplastic skin diseases such as precursors of cutaneous squamous cell carcinoma (cSCC). In PDT, 5-aminolevulinic acid (5-ALA) drives the selective formation of the endogenous photosensitizer protoporphyrin IX (PpIX). Although 5-ALA PDT is clinically highly effective, resistance might occur due to decreased accumulation of PpIX in certain tumors. Such resistance may be caused by any fundamental step of PpIX accumulation: 5-ALA uptake, PpIX synthesis and PpIX efflux.

METHODS

We investigated PpIX accumulation and photodynamically induced cell death in PDT refractory SCC-13, PDT susceptible A431, and normal human epidermal keratinocytes (NHEK). Expression of genes associated with cellular PpIX kinetics was investigated on mRNA and protein level. PpIX accumulation and cell death upon illumination were pharmacologically manipulated using drugs targeting 5-ALA uptake, PpIX synthesis or efflux.

RESULTS

The experiments indicate that taurine transporter (SLC6A6) is the major pathway for 5-ALA uptake in cSCC cells, while being less important in NHEK. Downregulation of PpIX synthesis enzymes in SCC-13 was counteracted by methotrexate (MTX) treatment, which restored PpIX formation and cell death. PpIX efflux inhibitors targeting ABC transporters led to significantly increased PpIX accumulation in SCC-13, thereby fully overcoming resistance.

CONCLUSIONS

The results indicate a conserved threshold for PpIX accumulation with respect to PDT-resistance. Cells showed increased viability after PDT at PpIX concentrations below 1.5 nM. Selective uptake of 5-ALA via taurine transporter SLC6A6 in cutaneous tumor cells is novel but unrelated to resistance. MTX can partially abrogate resistance by PpIX synthesis enzyme induction, while efflux mechanisms via ABC transporters seem the main driving force and promising drug targets.

Significant improvement of facial actinic keratoses after blue light photodynamic therapy with oral vitamin D pretreatment: An interventional cohort-controlled trial

BACKGROUND

In mouse models of skin cancer, high-dose oral vitamin D3 (VD3; cholecalciferol) combined with photodynamic therapy (PDT) can improve the clearance of squamous precancers (actinic keratoses [AKs]).

OBJECTIVE

To determine whether oral VD3 can improve the clinical efficacy of a painless PDT regimen in humans with AK.

METHODS

The baseline lesion counts and serum 25-hydroxyvitamin D₃ levels were determined. In group 1, 29 patients underwent gentle debridement and 15-minute aminolevulinic acid preincubation with blue light (30 minutes; 20 J/cm²). In group 2, 29 patients took oral VD3 (10,000 IU daily for 5 or 14 days) prior to debridement and PDT. Lesion clearance was assessed at 3 to 6 months.

RESULTS

In group 1, the mean clearance rates of facial AK were lower in patients with VD3 deficiency (25-hydroxyvitamin D₃ level < 31 ng/dL; clearance rate, 40.9% ± 42%) than in patients with normal 25-hydroxyvitamin D₃ levels (62.6% ± 14.2%). High-dose VD3 supplementation (group 2) significantly improved the overall AK lesion response (72.5% ± 13.6%) compared with that in group 1 (54.4% ± 22.8%). No differences in side effects were noted.

LIMITATIONS

Nonrandomized trial design (interventional cohort matched to registry-based controls).

CONCLUSIONS

Oral VD3 pretreatment significantly improves AK clinical responses to PDT. The regimen appears promising and well tolerated.

Actinic keratosis (review of literature)

Actinic keratosis is an important medical and social problem, the correct diagnosis and treatment of which will help to avoid the development of invasive forms of cutaneous squamous cell carcinoma. With the further development of the early diagnosis of cancer, including skin cancer, the increase in human life expectancy, and the popularization of travel to exotic countries, the number of cases of actinic keratosis among the population will continue to grow. In this regard, it is important to discuss the causes and pathogenesis of the disease, the varied clinical picture of the disease, methods of non-invasive diagnostics, as well as methods of treatment, of which there are a great many in the treatment of actinic keratosis today. However, each of the methods has both advantages and disadvantages, and in the global trend towards a personalized approach to treatment, it is important to choose from the standpoint of evidence-based medicine the most suitable for each individual patient. Moreover, after treatment of actinic keratosis, relapses often occur, which are the result of insufficient diagnosis and the development of incorrect treatment tactics. The review article provides the clinical picture of actinic keratosis, diagnostic and therapeutic methods, and their comparison with each other in terms of efficacy and safety

Mitochondrion as a Selective Target for the Treatment of Atherosclerosis: Role of Mitochondrial DNA Mutations and Defective Mitophagy in the Pathogenesis of Atherosclerosis and Chronic Inflammation

BACKGROUND

Atherosclerosis is a chronic inflammatory condition that affects different arteries in the human body and often leads to severe neurological complications, such as stroke and its sequelae. Affected blood vessels develop atherosclerotic lesions in the form of focal thickening of the intimal layer, so called atherosclerotic plaques.

OBJECTIVES

Despite the high priority of atherosclerosis research for global health and the numerous preclinical and clinical studies conducted, currently, there is no effective pharmacological treatment that directly impacts atherosclerotic plaques. Many knowledge gaps exist in our understanding of the mechanisms of plaque formation. In this review, we discuss the role of mitochondria in different cell types involved in atherogenesis and provide information about mtDNA mutations associated with the disease.

RESULTS

Mitochondria of blood and arterial wall cells appear to be one of the important factors in disease initiation and development. Significant experimental evidence connects oxidative stress associated with mitochondrial dysfunction and vascular disease. Moreover, mitochondrial DNA (mtDNA) deletions and mutations are being considered as potential disease markers. Further study of mtDNA damage and associated dysfunction may open new perspectives for atherosclerosis treatment.

CONCLUSION

Mitochondria can be considered as important disease-modifying factors in several chronic pathologies. Deletions and mutations of mtDNA may be used as potential disease markers. Mitochondria-targeting antioxidant therapies appear to be promising for the development of treatment of atherosclerosis and other diseases associated with oxidative stress and chronic inflammation.

A photoactivatable antibody-Chlorin e6 conjugate enabling singlet oxygen production for tumor-targeting photodynamic therapy

Photodynamic therapy is a new technology for disease diagnosis and treatment in modern medical clinics. The main advantages of photodynamic therapy are low toxicity and side effects, a wide range of applications, no drug resistance, and no obvious trauma in the treatment process. However, to achieve effective photodynamic therapy, new photosensitizer carriers need to be constructed, which can selectively deliver photosensitizers into tumor tissues. In this work, a photoactivatable antibody-Chlorin e6 conjugate with a dual-function to target tumor tissue and realize cancer photodynamic therapy is constructed. Bothin vitroandin vivoexperiments indicate that the antibody-Chlorin e6 conjugate has the ability to target tumors rapidly and efficiently, and has the ability to generate reactive oxygen species and kill tumor cells. Overall, this photoactivable antibody-Chlorin e6 conjugate may provide a promising strategy to address the current challenges of cancer photodynamic therapy.

A Singlet Oxygen Priming Mechanism: Disentangling of Photooxidative and Downstream Dark Effects

Airborne singlet oxygen obtained from photosensitization of triplet dioxygen is shown to react with an alkene surfactant (8-methylnon-7-ene-1 sulfonate) leading to "ene" hydroperoxides that in the dark inactivate planktonic Escherichia coli (E. coli). The "ene" hydroperoxide photoproducts are not toxic on their own, but they become toxic after the bacteria are pretreated with singlet oxygen. The total quenching rate constant (k_T) of singlet oxygen of the alkene surfactant was measured to be 1.1 × 10⁶ M^-1 s^-1 at the air/liquid interface. Through a new mechanism called singlet oxygen priming (SOP), the singlet oxygen leads to hydroperoxides then to peroxyl radicals, tetraoxides, and decomposition products, which also promote disinfection, and therefore offer a "one-two" punch. This offers a strong secondary toxic effect in an otherwise indiscernible dark reaction. The results provide an insight into assisted killing by an exogenous alkene with dark toxicity effects following exposure to singlet oxygen.

Photodynamic Diagnosis and Therapy for Peritoneal Carcinomatosis: Emerging Perspectives

Simple Summary

Peritoneal carcinomatosis, the formation of wide-spread metastases throughout the abdominal cavity, remains challenging to diagnose and treat. Photodynamic diagnosis and photodynamic therapy are promising approaches for the diagnosis and treatment of peritoneal carcinomatosis, which use photosensitizers for fluorescence detection or photochemical treatment of (micro) metastases. With the aim of highlighting the potential of this theranostic approach, this review outlines the clinical state of the art in the use of photodynamic diagnosis and therapy for peritoneal carcinomatosis, identifies the major challenges, and provides emerging perspectives from preclinical studies to address these challenges. We conclude that the development of novel illumination strategies and targeted photonanomedicines may aid in achieving more efficient cytoreductive surgery. In addition to combination treatments with chemo-, and radiotherapy, such approaches hold significant promise to improve the outlook of patients with peritoneal carcinomatosis.

Abstract

Peritoneal carcinomatosis occurs frequently in patients with advanced stage gastrointestinal and gynecological cancers. The wide-spread peritoneal micrometastases indicate a poor outlook, as the tumors are difficult to diagnose and challenging to completely eradicate with cytoreductive surgery and chemotherapeutics. Photodynamic diagnosis (PDD) and therapy (PDT), modalities that use photosensitizers for fluorescence detection or photochemical treatment of cancer, are promising theranostic approaches for peritoneal carcinomatosis. This review discusses the leading clinical trials, identifies the major challenges, and presents potential solutions to advance the use of PDD and PDT for the treatment of peritoneal carcinomatosis. While PDD for fluorescence-guided surgery is practically feasible and has achieved clinical success, large randomized trials are required to better evaluate the survival benefits. Although PDT is feasible and combines well with clinically used chemotherapeutics, poor tumor specificity has been associated with severe morbidity. The major challenges for both modalities are to increase the tumor specificity of the photosensitizers, to efficiently treat peritoneal microtumors regardless of their phenotypes, and to improve the ability of the excitation light to reach the cancer tissues. Substantial progress has been achieved in (1) the development of targeted photosensitizers and nanocarriers to improve tumor selectivity, (2) the design of biomodulation strategies to reduce treatment heterogeneity, and (3) the development of novel light application strategies. The use of X-ray-activated PDT during whole abdomen radiotherapy may also be considered to overcome the limited tissue penetration of light. Integrated approaches that take advantage of PDD, cytoreductive surgery, chemotherapies, PDT, and potentially radiotherapy, are likely to achieve the most effective improvement in the management of peritoneal carcinomatosis.

Field cancerization: Treatment

The goal of field cancerization treatment is to reduce the risk of developing keratinocyte carcinoma. Selecting the appropriate therapy depends on the degree of field cancerization and the number of invasive cutaneous squamous cell carcinomas. Other considerations include treatment efficacy, cost, side effects, and patient preference. Field therapies are preferred because they address clinically visible disease and subclinical atypia. However, lesion-directed therapies are useful for lesions that are more difficult to treat or those where a histologic diagnosis is required. Patients with extensive field cancerization benefit from a combination of field-directed and lesion-directed treatments. The second article in this continuing medical education series provides a framework to guide evidence-based decision making for field cancerization treatment.

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.

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.

Probe-based fluorescence dosimetry of an antibody-dye conjugate to identify head and neck cancer as a first step to fluorescence-guided tissue preselection for pathological assessment

BACKGROUND

Despite the rapid growth of fluorescence imaging, accurate sampling of tissue sections remains challenging. Development of novel technologies to improve intraoperative assessment of tissue is needed.

METHODS

A novel contact probe-based fluorescence dosimeter device, optimized for IRDye800CW quantification, was developed. After evaluation of the device in a phantom setup, its clinical value was defined ex vivo in patients with head and neck squamous cell carcinoma who received panitumumab-IRDye800CW.

RESULTS

Ten patients were enrolled with a total of 216 data points obtained. Final histopathology showed tumor in 119 spots and normal tissue in 97 spots. Fluorescence-to-excitation ratios in tumor tissue were more than three times higher than those in normal tissue. The area under the curve was 0.86 (95% CI: 0.81-0.91) for tumor detection.

CONCLUSIONS

Fluorescence-guided tissue preselection using a fluorescence dosimeter could have substantial impact on tissue sampling for frozen section analysis and potentially reduce sampling errors.

A regimen to minimize pain during blue light photodynamic therapy of actinic keratoses: Bilaterally controlled, randomized trial of simultaneous versus conventional illumination

BACKGROUND

Blue light photodynamic therapy (PDT) is effective for actinic keratosis, but many patients experience stinging pain during illumination.

OBJECTIVE

To compare a conventional regimen (1 hour of 5-aminolevulinic acid [ALA] preincubation, followed by blue light) versus a new modified regimen in which blue light is started immediately after ALA application.

METHODS

A clinical trial with a bilaterally controlled, intrapatient study design was conducted with 23 patients. Topical 20% ALA was applied to the entire face and/or scalp. On 1 side of the body, blue light was started immediately and continued for either 30, 45, or 60 minutes (simultaneous PDT). On the contralateral side, the blue light began 1 hour after ALA application and lasted 1000 seconds (conventional PDT). Pain was evaluated on a scale from 0 to 10. Actinic keratosis lesion counts were determined by clinical examination and photography.

RESULTS

All patients experienced significantly less pain during simultaneous illumination than during the conventional regimen. At 3 months after treatment, lesion clearance was nearly identical on the 2 sides, as determined by statistical testing of noninferiority ± 15% margin.

LIMITATIONS

Although bilaterally controlled, the study was relatively small. Additional studies are recommended.

CONCLUSION

The modified PDT regimen is essentially painless, yet it provides treatment efficacy similar to a conventional regimen.

In order for the light to shine so brightly, the darkness must be present-why do cancers fluoresce with 5-aminolaevulinic acid?

Photodynamic diagnosis and therapy have emerged as a promising tool in oncology. Using the visible fluorescence from photosensitisers excited by light, clinicians can both identify and treat tumour cells in situ. Protoporphyrin IX, produced in the penultimate step of the haem synthesis pathway, is a naturally occurring photosensitiser that visibly fluoresces when exposed to light. This fluorescence is enhanced considerably by the exogenous administration of the substrate 5-aminolaevulinic acid (5-ALA). Significantly, 5-ALA-induced protoporphyrin IX accumulates preferentially in cancer cells, and this enhanced fluorescence has been harnessed for the detection and photodynamic treatment of brain, skin and bladder tumours. However, surprisingly little is known about the mechanistic basis for this phenomenon. This review focuses on alterations in the haem pathway in cancer and considers the unique features of the cancer environment, such as altered glucose metabolism, oncogenic mutations and hypoxia, and their potential effects on the protoporphyrin IX phenomenon. A better understanding of why cancer cells fluoresce with 5-ALA would improve its use in cancer diagnostics and therapies.

Verteporfin-loaded mesoporous silica nanoparticles inhibit mouse melanoma proliferation in vitro and in vivo

Melanoma is one of the most lethal tumors among the skin cancers, arising from complex genetic mutations in melanocyte. Melanoma microenvironment is very heterogeneous, showing complex vascular networks and immunogenicity, as well as induced acquired resistance to treatments by upregulation of multidrug resistance (MDR) mechanisms. Different studies have showed that Photodynamic Therapy (PDT) could be considered a new potential approach for melanoma treatment. PDT combines a light with a specific wavelength and a photosensitizer: when these two elements interact reactive oxygen species (ROS) are generated leading to tumor cell destruction. In this study verteporfin (Ver), a second-generation photosensitizer, has been conjugated with mesoporous silica nanoparticles (MSNs): the resulting Ver-MSNs are an efficient nanoplatforms used to enhance cargo capacity and cellular uptake. Our in vitro and in vivo studies investigated whether Ver-MSNs were able to reduce or inhibit melanoma growth. In vitro experiments performed using B16F10 mouse melanoma cells showed that Ver-MSNs stimulated by red light (693 nm) significantly decreased in vitro cells proliferation in a range of concentration between 0.1 μg/ml to 10 μg/ml. When Ver-MSNs (5 μg/ml in glycerol) were topically administrated to melanoma tumor mass developed in mice and stimulated by red light for four times in 16 days, they were able to reduce the tumor mass of 50.2 ± 6,6% compared to the untreated (only glycerol) mice. In the light of this information, PDT performed using Ver-MSNs could be considered a new promising and potential approach to treat melanoma.

A non-toxic approach for treatment of breast cancer and its metastases: capecitabine enhanced photodynamic therapy in a murine breast tumor model

Aim:

Breast cancer (BCA) in women is a leading cause of mortality and morbidity; distant metastases occur in ~40% of cases. Here, as an alternative to ionizing radiation therapy and chemotherapy and their associated side effects, we explored a new combination approach using capecitabine (CPBN) and aminolevulinate-based photodynamic therapy (PDT). We had previously developed a combination PDT approach in which 5-fluorouracil (5FU), a differentiation-promoting agent, increases the levels of protoporphyrin IX (PpIX) in cancer cells when given as a neoadjuvant prior to aminolevulinic acid (ALA). However, 5FU can be toxic when administered systemically at high levels. We reasoned that CPBN, a known chemotherapeutic for BCA and less toxic than 5FU (because CPBN is metabolized to 5FU specifically within tumor tissues), might work equally well as a PDT neoadjuvant.

Methods:

Murine 4T1 BCA cells harboring a luciferase transgene were injected into breast fat pads of female nude mice. CPBN (600 mg/kg/day) was administered by oral gavage for 3 days followed by intraperitoneal ALA administration and PDT with red light (633 nm) on day 4. Tumor growth and regression were monitored in vivo using bioluminescence imaging. Histological changes in primary tumors and metastases were assessed by immunohistochemistry after necropsy.

Results:

CPBN pretreatment of 4T1 tumors increased cellular differentiation, reduced proliferation, raised PpIX levels, enhanced tumor cell death, and reduced metastatic spread of 4T1 cells post-PDT, relative to vehicle-only controls.

Conclusion:

The use of CPBN as a non-toxic PDT neoadjuvant for treatment of BCA represents a novel approach with significant potential for translation into the clinic.