Reactive Oxygen Species Produced by 5-Aminolevulinic Acid Photodynamic Therapy in the Treatment of Cancer

Roles of the ABCG2 Transporter in Protoporphyrin IX Distribution and Toxicity

ATP-binding cassette transporter subfamily G member 2 (ABCG2) is a membrane-bound transporter responsible for the efflux of various xenobiotics and endobiotics, including protoporphyrin IX (PPIX), an intermediate in the heme biosynthesis pathway. Certain genetic mutations and chemicals impair the conversion of PPIX to heme and/or increase PPIX production, leading to PPIX accumulation and toxicity. In mice, deficiency of ABCG2 protects against PPIX-mediated phototoxicity and hepatotoxicity by modulating PPIX distribution. In addition, in vitro studies revealed that ABCG2 inhibition increases the efficacy of PPIX-based photodynamic therapy by retaining PPIX inside target cells. In this review, we discuss the roles of ABCG2 in modulating the tissue distribution of PPIX, PPIX-mediated toxicity, and PPIX-based photodynamic therapy. SIGNIFICANCE STATEMENT: This review summarized the roles of ABCG2 in modulating PPIX distribution and highlighted the therapeutic potential of ABCG2 inhibitors for the management of PPIX-mediated toxicity.

Optimization of the Treatment of Squamous Cell Carcinoma Cells by Combining Photodynamic Therapy with Cold Atmospheric Plasma

Actinic keratosis (AK) is characterized by a reddish or occasionally skin-toned rough patch on sun-damaged skin, and it is regarded as a precursor to squamous cell carcinoma (SCC). Photodynamic therapy (PDT), utilizing 5-aminolevulinic acid (ALA) along with red light, is a recognized treatment option for AK that is limited by the penetration depth of light and the distribution of the photosensitizer into the skin. Cold atmospheric plasma (CAP) is a partially ionized gas with permeability-enhancing and anti-cancer properties. This study analyzed, in vitro, whether a combined treatment of CAP and ALA-PDT may improve the efficacy of the treatment. In addition, the effect of the application sequence of ALA and CAP was investigated using in vitro assays and the molecular characterization of human oral SCC cell lines (SCC-9, SCC-15, SCC-111), human cutaneous SCC cell lines (SCL-1, SCL-2, A431), and normal human epidermal keratinocytes (HEKn). The anti-tumor effect was determined by migration, invasion, and apoptosis assays and supported the improved efficacy of ALA-PDT in combination with CAP. However, the application sequence ALA-CAP-red light seems to be more efficacious than CAP-ALA-red light, which is probably due to increased intracellular ROS levels when ALA is applied first, followed by CAP and red light treatment. Furthermore, the expression of apoptosis- and senescence-related molecules (caspase-3, -6, -9, p16INK4a, p21CIP1) was increased, and different genes of the junctional network (ZO-1, CX31, CLDN1, CTNNB1) were induced after the combined treatment of CAP plus ALA-PDT. HEKn, however, were much less affected than SCC cells. Overall, the results show that CAP may improve the anti-tumor effects of conventional ALA-PDT on SCC cells. Whether this combined application is successful in treating AK in vivo has to be carefully examined in follow-up studies.

A hyaluronic acid-based dissolving microneedle patch loaded with 5-aminolevulinic acid for improved oral leukoplakia treatment

INTRODUCTION

A local microneedle patch loaded with 5-aminolevulinic acid (ALA) was constructed to improve the efficiency of ALA photodynamic treatment of oral leukoplakia, reduce local photosensitivity reactions, and promote the healing of lesions.

METHODS

The microneedle patch loaded with ALA was constructed with the hyaluronic acid (HA) solution (ALA-HAMN), and its morphology, strength, mucosal penetration, and biocompatibility were tested.

RESULTS

In vivo safety and permeability tests confirmed that ALA-HAMN had good biocompatibility and could penetrate the mucosal barrier and quickly dissolve and release ALA for in situ transdermal administration. The 4-nitroquinoline oxide (NQO) rat model experiment showed that ALA-HAMN can significantly improve photodynamic therapy (PDT) efficiency and has no damage to mucosal tissue compared with the commonly used ALA cotton ball dressing.

CONCLUSIONS

The ALA-loaded microneedle patch was successfully constructed for the photodynamic treatment of oral leukoplakia, and the photodynamic efficiency and comfort of oral leukoplakia were improved, which provided an effective delivery mode to improve clinical ALA-PDT treatment of oral leukoplakia (OLK).

Enhancing 5-ALA-PDT efficacy against resistant tumor cells: Strategies and advances

As a precursor of protoporphyrin IX (PpIX), an endogenous pro-apoptotic and fluorescent molecule, 5-Aminolevulinic acid (5-ALA) has gained substantial attention for its potential in fluorescence-guided surgery as well as photodynamic therapy (PDT). Moreover, 5-ALA-PDT has been suggested as a promising chemo-radio sensitization therapy for various cancers. However, insufficient 5-ALA-induced PpIX fluorescence and the induction of multiple resistance mechanisms may hinder the 5-ALA-PDT clinical outcome. Reduced efficacy and resistance to 5-ALA-PDT can result from genomic alterations, tumor heterogeneity, hypoxia, activation of pathways related to cell surveillance, production of nitric oxide, and most importantly, deregulated 5-ALA transporter proteins and heme biosynthesis enzymes. Understanding the resistance regulatory mechanisms of 5-ALA-PDT may allow the development of effective personalized cancer therapy. Here, we described the mechanisms underlying resistance to 5-ALA-PTD across various tumor types and explored potential strategies to overcome this resistance. Furthermore, we discussed future approaches that may enhance the efficacy of treatments using 5-ALA-PDT.

Harnessing Porphyrin Accumulation in Liver Cancer: Combining Genomic Data and Drug Targeting

The liver, a pivotal organ in human metabolism, serves as a primary site for heme biosynthesis, alongside bone marrow. Maintaining precise control over heme production is paramount in healthy livers to meet high metabolic demands while averting potential toxicity from intermediate metabolites, notably protoporphyrin IX. Intriguingly, our recent research uncovers a disrupted heme biosynthesis process termed 'porphyrin overdrive' in cancers that fosters the accumulation of heme intermediates, potentially bolstering tumor survival. Here, we investigate heme and porphyrin metabolism in both healthy and oncogenic human livers, utilizing primary human liver transcriptomics and single-cell RNA sequencing (scRNAseq). Our investigations unveil robust gene expression patterns in heme biosynthesis in healthy livers, supporting electron transport chain (ETC) and cytochrome P450 function without intermediate accumulation. Conversely, liver cancers exhibit rewired heme biosynthesis and a massive downregulation of cytochrome P450 gene expression. Notably, despite diminished drug metabolism, gene expression analysis shows that heme supply to the ETC remains largely unaltered or even elevated with patient cancer progression, suggesting a metabolic priority shift. Liver cancers selectively accumulate intermediates, which are absent in normal tissues, implicating their role in disease advancement as inferred by expression analysis. Furthermore, our findings in genomics establish a link between the aberrant gene expression of porphyrin metabolism and inferior overall survival in aggressive cancers, indicating potential targets for clinical therapy development. We provide in vitro proof-of-concept data on targeting porphyrin overdrive with a drug synergy strategy.

Uncovering Porphyrin Accumulation in the Tumor Microenvironment

Heme, an iron-containing tetrapyrrole, is essential in almost all organisms. Heme biosynthesis needs to be precisely regulated particularly given the potential cytotoxicity of protoporphyrin IX, the intermediate preceding heme formation. Here, we report on the porphyrin intermediate accumulation within the tumor microenvironment (TME), which we propose to result from dysregulation of heme biosynthesis concomitant with an enhanced cancer survival dependence on mid-step genes, a process we recently termed "Porphyrin Overdrive". Specifically, porphyrins build up in both lung cancer cells and stromal cells in the TME. Within the TME's stromal cells, evidence supports cancer-associated fibroblasts (CAFs) actively producing porphyrins through an imbalanced pathway. Conversely, normal tissues exhibit no porphyrin accumulation, and CAFs deprived of tumor cease porphyrin overproduction, indicating that both cancer and tumor-stromal porphyrin overproduction is confined to the cancer-specific tissue niche. The clinical relevance of our findings is implied by establishing a correlation between imbalanced porphyrin production and overall poorer survival in more aggressive cancers. These findings illuminate the anomalous porphyrin dynamics specifically within the tumor microenvironment, suggesting a potential target for therapeutic intervention.

Photodynamic Therapeutic Effect during 5-Aminolevulinic Acid-Mediated Photodynamic Diagnosis-Assisted Transurethral Resection of Bladder Tumors

Background

Photodynamic diagnosis-assisted transurethral resection of bladder tumors (PDD-TURBT) enhances detection of elusive lesions compared to standard white light-transurethral resection of bladder tumors (WL-TURBT). If minimal light exposure during PDD-TURBT induces the accumulation of reactive oxygen species (ROS), potentially resulting in phototoxicity in small lesions, apoptosis may be triggered in residual small tumors, allowing them to escape resection. We investigated the hypothesis of a potential photodynamic therapeutic effect during PDD-TURBT.

Methods and Materials

Our study, conducted between January 2016 and December 2020 at Nara Medical University Hospital, focused on a specific emphasis on ROS production. Immunohistochemical analysis for thymidine glycol and N ε -hexanoyl-lysine was performed on 69 patients who underwent 5-aminolevulinic acid-mediated PDD-TURBT and 28 patients who underwent WL-TURBT. Additionally, we incrementally applied the minimal irradiation energy to T24 and UM-UC-3 cells treated with 5-aminolevulinic acid using instruments similar to those used in PDD-TURBT and evaluated intracellular ROS production and phototoxicity.

Results

Immunohistochemical analysis revealed a significant increase in production of thymidine glycol and N ε -hexanoyl-lysine within the PDD-TURBT group. In T24 and UM-UC-3 cells treated with 5-aminolevulinic acid and light exposure, immunofluorescent staining demonstrated a dose-dependent increase in intracellular ROS production. In addition, higher irradiation energy levels were associated with a greater increase in ROS production and phototoxicity, as well as more significant decrease in mitochondrial membrane potential.

Conclusion

Although the irradiation energy used in PDD-TURBT did not reach the levels commonly used in photodynamic therapy, our findings support the presence of a potential cytotoxic effect on bladder lesions during PDD-TURBT.

Cascade Nanoreactor Employs Mitochondrial-Directed Chemodynamic and δ-ALA-Mediated Photodynamic Synergy for Deep-Seated Oral Cancer Therapy

The management of oral squamous cell carcinoma (OSCC) poses significant challenges, leading to organ impairment and ineffective treatment of deep-seated tumors, adversely affecting patient prognosis. A cascade nanoreactor that integrates photodynamic therapy (PDT) and chemodynamic therapy (CDT) for comprehensive multimodal OSCC treatment is introduced. Utilizing iron oxide and mesoporous silica, the FMMSH drug delivery system, encapsulating the photosensitizer prodrug δ-aminolevulinic acid (δ-ALA), is developed. Triphenylphosphine (TPP) modification facilitates mitochondrial targeting, while tumor cell membrane (TCM) coating provides homotypic targeting. The dual-targeting δ-ALA@FMMSH-TPP-TCM demonstrate efficacy in eradicating both superficial and deep tumors through synergistic PDT/CDT. Esterase overexpression in OSCC cells triggers δ-ALA release, and excessive hydrogen peroxide in tumor mitochondria undergoes Fenton chemistry for CDT. The synergistic interaction of PDT and CDT increases cytotoxic ROS levels, intensifying oxidative stress and enhancing apoptotic mechanisms, ultimately leading to tumor cell death. PDT/CDT-induced apoptosis generates δ-ALA-containing apoptotic bodies, enhancing antitumor efficacy in deep tumor cells. The anatomical accessibility of oral cancer emphasizes the potential of intratumoral injection for precise and localized treatment delivery, ensuring focused therapeutic agent delivery to maximize efficacy while minimizing side effects. Thus, δ-ALA@FMMSH-TPP-TCM, tailored for intratumoral injection, emerges as a transformative modality in OSCC treatment.

Effect of 5-Aminolevulinic Acid (5-ALA) in "ALADENT" Gel Formulation and Photodynamic Therapy (PDT) against Human Oral and Pancreatic Cancers

Oral squamous-cell and pancreatic carcinomas are aggressive cancers with a poor outcome. Photodynamic therapy (PDT) consists of the use of photosensitizer-induced cell and tissue damage that is activated by exposure to visible light. PDT selectively acts on cancer cells, which have an accumulation of photosensitizer superior to that of the normal surrounding tissues. 5-aminolevulinic acid (5-ALA) induces the production of protoporphyrin IX (PpIX), an endogenous photosensitizer activated in PDT. This study aimed to test the effect of a new gel containing 5% v/v 5-ALA (ALAD-PDT) on human oral CAL-27 and pancreatic CAPAN-2 cancer cell lines. The cell lines were incubated in low concentrations of ALAD-PDT (0.05%, 0.10%, 0.20%, 0.40%, 0.75%, 1.0%) for 4 h or 8 h, and then irradiated for 7 min with 630 nm RED light. The cytotoxic effects of ALAD-PDT were measured using the MTS assay. Apoptosis, cell cycle, and ROS assays were performed using flow cytometry. PpIX accumulation was measured using a spectrofluorometer after 10 min and 24 and 48 h of treatment. The viability was extremely reduced at all concentrations, at 4 h for CAPAN-2 and at 8 h for CAL-27. ALAD-PDT induced marked apoptosis rates in both oral and pancreatic cancer cells. Elevated ROS production and appreciable levels of PpIX were detected in both cell lines. The use of ALA-PDT as a topical or intralesional therapy would permit the use of very low doses to achieve effective results and minimize side effects. ALAD-PDT has the potential to play a significant role in complex oral and pancreatic anticancer therapies.

Comparative Study of 5-Aminolevulinic Acid-Mediated Photodynamic Therapy and the Loop Electrosurgical Excision Procedure for the Treatment of Cervical High-Grade Squamous Intraepithelial Lesions

The loop electrosurgical excision procedure (LEEP) is a common treatment for cervical intraepithelial neoplasia (CIN). Photodynamic therapy (PDT) mediated by 5-aminolevulinic acid (ALA) is a non-invasive modality that has been used for treating precancerous diseases and HPV infections. This comparative study evaluated the efficacy and safety of ALA PDT and the LEEP in the treatment of cervical high-grade squamous intraepithelial lesions (HSILs). Patient records were reviewed and HSIL patients with HPV infections (24-51 years old) who underwent PDT or LEEP treatment were selected. Efficacy was analyzed blindly based on HPV-DNA, cytology, and colposcopy-directed biopsy obtained at 6 months after treatment. Treatment-related discomfort and side effects were also analyzed. Cure rates of 88.1% and 70.0% were achieved for the PDT group and LEEP group (p < 0.05), respectively. HPV-negative conversion rates of 81.0% and 62.0% were achieved for the PDT group and LEEP group (p < 0.05), respectively. The overall lesion remission rate of the PDT group was 19% higher than that of the LEEP group. The incidence of side effects was much lower in the PDT group. These results show that ALA PDT is a feasible non-invasive treatment for cervical HSIL.

Successful treatment of epidermodysplasia verruciformis with a combination of 5-aminolevulinic acid photodynamic therapy and surgery

Epidermodysplasia verruciformis (EV) is a rare inherited immune disease characterized by pityriasis versicolor-like macules, hyperpigmented or hypopigmented warty papules and irregular reddish-brown plaques, mainly on the face, neck and extremities. Some therapeutic options include medications, lifestyle changes, ALA-PDT, surgery and so on. But there is no cure for EV and thus the clinical management is challenging. We report a case of EV that was refractory to multiple therapies and achieved an encouraging result with a combination therapy of surgery and 5-aminolevulinic acid photodynamic therapy (ALA-PDT).

Unleashing the power of porphyrin photosensitizers: Illuminating breakthroughs in photodynamic therapy

This comprehensive review provides the current trends and recent developments of porphyrin-based photosensitizers. We discuss their evolution from first-generation to third-generation compounds, including cutting-edge nanoparticle-integrated derivatives, and explores their pivotal role in advancing photodynamic therapy (PDT) for enhanced cancer treatment. Integrating porphyrins with nanoparticles represents a promising avenue, offering improved selectivity, reduced toxicity, and heightened biocompatibility. By elucidating recent breakthroughs, innovative methodologies, and emerging applications, this review provides a panoramic snapshot of the dynamic field, addressing challenges and charting prospects. With a focus on harnessing reactive oxygen species (ROS) through light activation, PDT serves as a minimally invasive therapeutic approach. This article offers a valuable resource for researchers, clinicians, and PDT enthusiasts, highlighting the potential of porphyrin photosensitizers to improve the future of cancer therapy.