Photosensitizers for Photodynamic Therapy of Brain Cancers-A Review

Exploring the GSTP1 inhibition potential of photosensitizer compounds for enhanced cancer treatment in photodynamic therapy

Photodynamic therapy (PDT) has gained considerable attention in cancer treatment due to its non-invasive nature and the ability of photosensitizers to generate reactive oxygen species upon light activation, leading to tumor destruction. Glutathione S-transferase P1 (GSTP1) is a key enzyme in chemotherapy resistance, often overexpressed in various cancers, and its inhibition of GSTP1 presents a promising strategy to enhance cancer treatment. This study is aimed at assessing the potential of prominent photosensitizers as GSTP1 inhibitors through molecular docking analysis to strengthen the efficacy of PDT. The photosensitizers were docked into the active site of GSTP1, and their binding affinities, inhibition constants (Ki), and molecular interactions were assessed. Among the tested photosensitizers, zinc phthalocyanine, hypericin, and temoporfin emerged as the top candidates, exhibiting binding energies of - 10.8, - 10.2, and - 9.8 kcal/mol, along with Ki values of 0.012, 0.033, and 0.064 µM, respectively. These compounds outperformed the reference inhibitor ethacrynic acid, which had a binding energy of - 6.6 kcal/mol and a Ki of 14.35 µM. These findings suggest that the dual action of these photosensitizers provides a promising strategy for combating cancer and overcoming treatment resistance.

Synthesis, Molecular Docking, and Biological Activity of New EGFR-Targeted Photosensitizers Based on Cationic Porphyrins Encapsulated into Pluronic F127 Micelles

The development of new effective photosensitizers (PS) for photodynamic therapy (PDT) is one of the important tasks in medical and organic chemistry. PSs inhibiting epidermal growth factor receptors (EGFR) overexpressed in cancer cells are of particular importance. In this work, we proposed the design and molecular docking of novel hybrid photosensitizers based on meso-aryl-substituted porphyrins and the Erlotinib molecule, a clinically approved tyrosine kinase inhibitor. The spacer length between the macrocycles and Erlotinib, hydrophilicity, and hydrophobicity of the porphyrin ring substituents were varied in the obtained compounds to evaluate structure-activity relationships (SAR). Photophysical and photochemical characteristics were studied for all of the received compounds in the presence of solubilizers suitable for the creation of dosage forms. Nanomicelles based on Pluronic F127 were obtained and characterized for the received compounds. In vitro biological tests on three cancer cell lines, MCF-7 (breast carcinoma), A431 (epidermoid carcinoma), MDA-MB-231 (breast adenocarcinoma), and normal NKE cells (human kidney epithelial cells) were performed, which showed low dark toxicity as well as light-induced activity of conjugates in the nanomolar range. Confocal microscopy experiments showed preferred accumulation of UB-2 and a lower accumulation of UB-3 PSs. In the case of UB-3, we observed a pronounced colocalization with early endosome antigen (EEA1). Also, cell apoptosis and inhibition of phosphorylation of EGFR were demonstrated for the UB-3 compound. Thus, the proposed design of targeting PS containing cationic pyridyl moieties and a linker between the porphyrin macrocycle and Erlotinib can contribute to antitumor PDT.

Metabolic imbalance and brain tumors: The interlinking metabolic pathways and therapeutic actions of antidiabetic drugs

Brain tumors are complex, heterogeneous malignancies, often associated with significant morbidity and mortality. Emerging evidence suggests the important role of metabolic syndrome, such as that observed in diabetes mellitus, in the progression of brain tumors. Several studies indicated that hyperglycemia, insulin resistance, oxidative stress, and altered adipokine profiles influence tumor growth, proliferation, and treatment resistance. Intriguingly, antidiabetic drugs (e.g., metformin, sulfonylureas, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and thiazolidinediones) have shown promise as adjunctive or repurposed agents in managing brain tumors. Metformin can impair tumor cell proliferation, enhance treatment sensitivity, and modify the tumor microenvironment by activating AMP-activated protein kinase (AMPK) and inhibiting mammalian target of rapamycin (mTOR) signaling pathways. DPP-4 inhibitors and GLP-1 receptor agonists can target both metabolic and inflammatory aspects of brain tumors, while thiazolidinediones may induce apoptosis in tumor cells and synergize with other therapeutics. Consequently, further studies and clinical trials are needed to confirm the efficacy, safety, and utility of metabolic interventions in treating brain tumors. Here, we review the evidence for the metabolic interconnections between metabolic diseases and brain tumors and multiple actions of anti-diabetes drugs in brain tumors.

Photodynamic and sonodynamic therapy synergy: mechanistic insights and cellular responses against glioblastoma multiforme

Glioblastoma multiforme (GBM), the most aggressive form of brain cancer, poses substantial challenges to effective treatment due to its complex and infiltrative nature, making it difficult to manage. Photodynamic therapy (PDT) and sonodynamic therapy (SDT), have emerged as promising individual treatment options against GBM due to their least-invasive approach. However, both PDT and SDT have drawbacks that require careful consideration. A combination therapy using light and sound waves has gained attention, offering new avenues to overcome challenges from individual therapies. Sono-photodynamic therapy (SPDT) has been used against various tumours. Researchers are considering SPDT as a favourable alternative to the conventional therapies for GBM. SPDT offers complementary mechanisms of action, including the production of ROS, disruption of cellular structures, and induction of apoptosis, leading to enhanced tumour cell death. This review gives an insight about PDT/SDT and their limitations in GBM treatment and the need for combination therapy. We try to unveil the process of SPDT and explore the mechanism behind improved SPDT-meditated cell death in GBM cells by focusing on the ROS-mediated cell response occurring as a result of SPDT and discussing current modifications in the existing sensitisers for their optimal use in SPDT for GBM therapy.

Efficient Photosensitizer Delivery by Neutrophils for Targeted Photodynamic Therapy of Glioblastoma

Background/Objectives: Glioblastoma (GBM) is the deadliest type of brain tumor and photodynamic therapy (PDT) is a promising treatment modality of GBM. However, insufficient photosensitizer distribution in the GBM critically limits the success of PDT. To address this obstacle, we propose tumoritropic neutrophils (NE) as active carriers for photosensitizer delivery to achieve GBM-targeted PDT. Methods: Isolated mouse NE were loaded with functionalized hexagonal boron nitride nanoparticles carrying the photosensitizer chlorin e6 (BNPD-Ce6). In vitro experiments were conducted to determine drug release from the loaded NE (BNPD-Ce6@NE) to mouse GBM cells and consequential photo-cytotoxicity. In vivo experiments were performed on mice bearing intracranial graft GBMs to demonstrate GBM-targeted drug delivery and the efficacy of anti-GBM PDT mediated by BNPD-Ce6@NE. Results: BNPD-Ce6@NE displayed good viability and migration ability, and rapidly released BNPD-Ce6 to co-cultured mouse GBM cells, which then exhibited marked reactive oxygen species (ROS) generation and cytotoxicity following 808 nm laser irradiation (LI). In the in vivo study, a single intravenous bolus injection of BNPD-Ce6@NE resulted in pronounced Ce6 distribution in intracranial graft GBMs 4 h post injection, which peaked around 8 h post injection. A PDT regimen consisting of multiple intravenous BNPD-Ce6@NE injections each followed by one extracranial tumor-directed LI 8 h post injection significantly slowed the growth of intracranial graft GBMs and markedly improved the survival of host animals. Histological analysis revealed massive tumor cell damage and NE infiltration in the PDT-treated GBMs. Conclusions: NE are efficient carriers for GBM-targeted photosensitizer delivery to achieve efficacious anti-GBM PDT.

The Activity of 1,8-Dihydroanthraquinone Derivatives in Nervous System Cancers

Primary and metastatic tumors of the nervous system represent a diverse group of neoplasms, each characterized by distinct biological features, prognostic outcomes, and therapeutic approaches. Due to their molecular complexity and heterogeneity, nervous system cancers (NSCs) pose significant clinical challenges. For decades, plants and their natural products with established anticancer properties have played a pivotal role in the treatment of various medical conditions, including cancers. Anthraquinone derivatives, a class of tricyclic secondary metabolites, are found in several botanical families, such as Fabaceae, Polygonaceae, Rhamnaceae, and Rubiaceae. In a comprehensive review, recent advancements in the anticancer properties of 1,8-dihydroanthraquinone derivatives-such as emodin, aloe-emodin, hypericin, chrysophanol, rhein, and physcion-were analyzed. These compounds have been studied extensively, both used individually and in combination with other chemotherapeutic agents, using in vitro and in vivo models of nervous system tumors. It was demonstrated that 1,8-dihydroanthraquinone derivatives induce apoptosis and necrosis in cancerous cells, intercalate into DNA, disrupting transcription and replication in rapidly dividing cells, and alter ROS levels, leading to oxidative stress that damages tumor cells. Additionally, they can influence signaling pathways involved in oncogenesis, such as MAPK, PI3K/Akt, or others crucial for the survival and the proliferation of NSC cells. The exploration of 1,8-dihydroanthraquinone derivatives aims to develop novel therapies that could overcome resistance and improve cancer patients' outcomes.

Preclinical Photodynamic Therapy Targeting Blood Vessels with AGuIX® Theranostic Nanoparticles

Background: Glioblastoma multiforme (GBM) is the most common highly aggressive, primary malignant brain tumor in adults. Current experimental strategies include photodynamic therapy (PDT) and new drug delivery technologies such as nanoparticles, which could play a key role in the treatment, diagnosis, and imaging of brain tumors. Objectives: The purpose of this study was to test the efficacy of PDT using AGuIX-TPP, a polysiloxane-based nanoparticle (AGuIX) that contains TPP (5,10,15,20-tetraphenyl-21H,23H-porphine), in biological models of glioblastoma multiforme and to investigate the vascular mechanisms of action at multiple complexity levels. Methods: PDT effects were studied in monolayer and spheroid cell culture, as well as tumors in chicken chorioallantoic membranes (CAMs) and in mice were studied. Results: Treatment was effective in both endothelial ECRF and glioma U87 cells, as well as in the inhibition of growth of the glioma spheroids. PDT using AGuIX-TPP inhibited U87 tumors growing in CAM and destroyed their vascularization. The U87 tumors were also grown in nude mice. Their vascular network, as well as oxygen partial pressure, were assessed using ultrasound and EPR oximetry. The treatment damaged tumor vessels and slightly decreased oxygen levels. Conclusions: PDT with AGuIX-TPP was effective against glioma cells, spheroids, and tumors; however, in mice, its efficacy appeared to be strongly related to the presence of blood vessels in the tumor before the treatment.

Viral-Porphyrin Combo: Photodynamic and Oncolytic Viral Therapy for Potent Glioblastoma Treatment

Combined viral and photodynamic therapy for oncological diseases has great potential to treat aggressive tumors such as glioblastomas. A conjugate of vesicular stomatitis virus (VSV) with protoporphyrin IX was prepared, and its oncolytic effects were studied and compared to the effects of the individual components. The VSV showed an oncolytic effect on glioblastoma cell lines T98G and LN229 at a virus titer of 105 TCID50/mL. A VSV titer of 104 TCID50/mL was sufficient for neuroblastoma cell death. A study of the effect of VSV in tumor 3D cell modeling found that VSV had a clear viral cytopathic effect on spheroids of T98G and LN229 cells. Conjugation with the porphyrin significantly reduced the viral titer, but when irradiated, lysis of cells was observed. Photodynamic treatment of T98G and LN229 cells and spheroids with protoporphyrin IX as a photosensitizer also had a cytotoxic effect on cells and, to a lesser extent, on the tumoroids, as complete cell death was not achieved for the tumoroids. The combination therapy, which involved sequential photodynamic therapy using protoporphyrin IX as a photosensitizer and treatment with VSV, was shown to significantly enhance efficacy, resulting in complete cell death of both T98G and LN229 cells and tumoroids. The combination treatment allowed for the use of a lower viral titer (103-104 TCID50/mL) and a lower porphyrin concentration (0.5 μg/mL) to achieve a significant cytotoxic effect. As a result, the implementation of this combination therapy would likely lead to fewer side effects from the treatment. This study clearly demonstrated the excellent perspectives of combination therapy for the treatment of highly aggressive tumors such as glioblastomas.

Ferroptosis in glioma therapy: advancements in sensitizing strategies and the complex tumor-promoting roles

Ferroptosis, an iron-dependent form of non-apoptotic regulated cell death, is induced by the accumulation of lipid peroxides on cellular membranes. Over the past decade, ferroptosis has emerged as a crucial process implicated in various physiological and pathological systems. Positioned as an alternative modality of cell death, ferroptosis holds promise for eliminating cancer cells that have developed resistance to apoptosis induced by conventional therapeutics. This has led to a growing interest in leveraging ferroptosis for cancer therapy across diverse malignancies. Gliomas are tumors arising from glial or precursor cells, with glioblastoma (GBM) being the most common malignant primary brain tumor that is associated with a dismal prognosis. This review provides a summary of recent advancements in the exploration of ferroptosis-sensitizing methods, with a specific focus on their potential application in enhancing the treatment of gliomas. In addition to summarizing the therapeutic potential, this review also discusses the intricate interplay of ferroptosis and its potential tumor-promoting roles within gliomas. Recognizing these dual roles is essential, as they could potentially complicate the therapeutic benefits of ferroptosis. Exploring strategies aimed at circumventing these tumor-promoting roles could enhance the overall therapeutic efficacy of ferroptosis in the context of glioma treatment.

Photodynamic Therapy in the Treatment of Cancer-The Selection of Synthetic Photosensitizers

Photodynamic therapy (PDT) is a promising cancer treatment method that uses photosensitizing (PS) compounds to selectively destroy tumor cells using laser light. This review discusses the main advantages of PDT, such as its low invasiveness, minimal systemic toxicity and low risk of complications. Special attention is paid to photosensitizers obtained by chemical synthesis. Three generations of photosensitizers are presented, starting with the first, based on porphyrins, through the second generation, including modified porphyrins, chlorins, 5-aminolevulinic acid (ALA) and its derivative hexyl aminolevulinate (HAL), to the third generation, which is based on the use of nanotechnology to increase the selectivity of therapy. In addition, current research trends are highlighted, including the search for new photosensitizers that can overcome the limitations of existing therapies, such as heavy-atom-free nonporphyrinoid photosensitizers, antibody-drug conjugates (ADCs) or photosensitizers with a near-infrared (NIR) absorption peak. Finally, the prospects for the development of PDTs are presented, taking into account advances in nanotechnology and biomedical engineering. The references include both older and newer works. In many cases, when writing about a given group of first- or second-generation photosensitizers, older publications are used because the properties of the compounds described therein have not changed over the years. Moreover, older articles provide information that serves as an introduction to a given group of drugs.

Stereotactic Photodynamic Therapy of Recurrent Malignant Gliomas

The aim of the study is to assess the effectiveness and safety of stereotactic photodynamic therapy (sPDT) with 5-aminolevulinic acid (5-ALA) in patients with recurrent malignant supratentorial gliomas in functionally relevant brain areas.

Materials and Methods

In a retrospective single-center study the results of sPDT with 5-ALA in 10 patients (6 of 10 were male), aged 30 to 62 years (median: 51.5 years; 95% CI: 38-59 years) with recurrent malignant brain gliomas after standard therapy who underwent surgery during the period of 2020-2023 were analyzed. sPDT was conducted during 15 min using 5-ALA at a dosage of 20 mg/kg, a diode laser with a wavelength of 635 nm and power of 1 W, and the LFT-02-BIOSPEC unit (BIOSPEC, Russia). Three patients got repeated sPDT after 3, 7, and 15 months due to a relapse. The number of target points and the optimal position for intervention paths were determined according to the data of preoperative stereotactic MRI of the brain with contrast intensification using the CRW Precision stereotactic navigation system (Integra, USA) and intraoperative registration of the area with the highest intensity of protoporphyrin IX fluorescence along the path (according to fluorescence biospectroscopy).

Results

Glioblastoma (grade IV, WHO) was diagnosed in 7 patients, anaplastic astrocytoma (grade III, WHO) - in 3 persons. Genetic studies were performed for 9 patients, 7 of them had tumors without the IDH1 gene mutation. None of the patients had a combined 1p/19q deletion. The median volume of the contrast-enhancing part of the recurrent tumor was 7.95 cm3 (95% CI: 3.3-13.6 cm3). The median time to relapse after sPDT in patients with anaplastic astrocytomas and glioblastomas was 14.5 and 6.5 months, respectively. The median survival time after sPDT in patients with glioblastomas was 15.8 months (95% CI: 0.5-20.1 months), and in patients with anaplastic astrocytomas - 46.3 months (95%, CI not specified). In the early postoperative period, two patients had motor aphasia and hemiparesis, which further regressed.

Conclusion

The results of a small group of patients allow to consider sPDT with 5-ALA as a promising technique to treat patients with recurrent high-grade gliomas in functionally relevant brain areas and require further prospective assessment.

New Avenues and Major Achievements in Phytocompounds Research for Glioblastoma Therapy

Phytocompounds have been evaluated for their anti-glioblastoma actions for decades, with promising results from preclinical studies but only limited translation into clinics. Indeed, by targeting multiple signaling pathways deregulated in cancer, they often show high efficacy in the in vitro studies, but their poor bioavailability, low tumor accumulation, and rapid clearance compromise their efficacy in vivo. Here, we present the new avenues in phytocompound research for the improvement of glioblastoma therapy, including the ways to enhance the response to temozolomide using phytochemicals, the current focus on phytocompound-based immunotherapy, or the use of phytocompounds as photosensitizers in photodynamic therapy. Moreover, we present new, intensively evaluated approaches, such as chemical modifications of phytochemicals or encapsulation into numerous types of nanoformulations, to improve their bioavailability and delivery to the brain. Finally, we present the clinical trials evaluating the role of phytocompounds or phytocompound-derived drugs in glioblastoma therapy and the less studied phytocompounds or plant extracts that have only recently been found to possess promising anti-glioblastoma properties. Overall, recent advancements in phytocompound research are encouraging; however, only with more 3D glioblastoma models, in vivo studies, and clinical trials it is possible to upgrade the role of phytocompounds in glioblastoma treatment to a satisfactory level.

Enhancing photodynamic therapy efficacy through silica nanoparticle-mediated delivery of temoporfin for targeted in vitro breast cancer treatment

Photodynamic therapy (PDT), an approach to cancer treatment, relies fundamentally on two key elements: a light source and a photosensitizing agent. A primary challenge in PDT is the efficient delivery of photosensitizers to the target tissue, hindered by the body's reticuloendothelial system (RES). Silica nanoparticles (SiNPs), known for their unique properties, emerge as ideal carriers in this context. In this study, SiNPs are utilized to encapsulate Temoporfin, a photosensitizer, aiming to enhance its delivery and reduce toxicity, particularly for treating MCF-7 cancer cells in vitro. The synthesized SiNPs were meticulously characterized by their size and shape using Transmission Electron Microscopy (TEM). The study also involved evaluating the cytotoxicity of both encapsulated and naked Temoporfin across various concentrations. The objective was to determine the ideal concentration and exposure duration using red laser light (intensity approximately 110 mW/cm2) to effectively eradicate MCF-7 cells. The findings revealed that Temoporfin, when encapsulated in SiNPs, demonstrated significantly greater effectiveness compared to its naked form, with notable improvements in concentration efficiency (50 %) and exposure time efficiency (76.6 %). This research not only confirms the superior effectiveness of encapsulated Temoporfin in eliminating cancer cells but also highlights the potential of SiNPs as an efficient drug delivery system in photodynamic therapy. This sets the groundwork for more advanced strategies in cancer treatment.

Water-soluble red fluorescent protein dimers for hypoxic two-photon photodynamic therapy

In this study, two water-soluble red fluorescent protein (RFP) dimers, FP2R' and FP2R'', were synthesized by linking two phenothiazine-based RFP chromophore analogues through alkyl chains or alkoxy chains for hypoxic two-photon photodynamic therapy. RFP dimers are heavy-atom-free two-photon photosensitizers in which the intersystem crossing process is boosted by S and N heteroatoms. In terms of the aqueous solubility, the saturation concentration of FP2R'' was 3.5 mM, the emission wavelength was 677 nm, the singlet oxygen yield was 18%, and the two-photon absorption coefficient (β) was 2.1 × 10-11 cm W-1. Further, the RFP dimer FP2R'' showed excellent biocompatibility, negligible dark toxicity, and could produce 1O2 and O2˙- simultaneously. Under 460 nm illumination, the photosensitizer FP2R'' showed high phototoxicity with an IC50 value of 4.08 μM in an hypoxia environment, indicating that the photosensitizer FP2R'' has an excellent anti-hypoxia ability. In addition, the photosensitizer FP2R'' demonstrated a precise localization ability to lysosomes and its Pearson's colocalization coefficient was 0.94, which could guide the aggregation of photosensitizers in the lysosomes of tumor cells to effectively improve its photodynamic therapy (PDT) effect. In particular, when exposed to 800 nm two-photon excitation, FP2R'' effectively produced 1O2 and O2˙- in zebrafish and exhibited a bright two-photon fluorescence imaging capability. At the same time, the efficacy of two-photon photodynamic therapy mediated by the photosensitizer FP2R'' was verified in the tumor zebrafish model, and the growth of tumor cells in zebrafish was significantly inhibited under a two-photon laser irradiation. The water-soluble two-photon photosensitizer FP2R'' that was reasonably constructed in this study can be used as a high-efficiency hypoxic two-photon photosensitizer to inhibit deep tumor tissues.

Photodynamic Therapy and Immunological View in Gastrointestinal Tumors

Gastrointestinal cancers are a specific group of oncological diseases in which the location and nature of growth are of key importance for clinical symptoms and prognosis. At the same time, as research shows, they pose a serious threat to a patient's life, especially at an advanced stage of development. The type of therapy used depends on the anatomical location of the cancer, its type, and the degree of progression. One of the modern forms of therapy used to treat gastrointestinal cancers is PDT, which has been approved for the treatment of esophageal cancer in the United States. Despite the increasingly rapid clinical use of this treatment method, the exact immunological mechanisms it induces in cancer cells has not yet been fully elucidated. This article presents a review of the current understanding of the mode of action of photodynamic therapy on cells of various gastrointestinal cancers with an emphasis on colorectal cancer. The types of cell death induced by PDT include apoptosis, necrosis, and pyroptosis. Anticancer effects are also a result of the destruction of tumor vasculature and activation of the immune system. Many reports exist that concern the mechanism of apoptosis induction, of which the mitochondrial pathway is most often emphasized. Photodynamic therapy may also have a beneficial effect on such aspects of cancer as the ability to develop metastases or contribute to reducing resistance to known pharmacological agents.