Direct and indirect photodynamic therapy effects on the cellular and molecular components of the tumor microenvironment

Glucocorticoid receptor mediated sensitization of colon cancer to photodynamic therapy induced cell death

Photodynamic therapy (PDT) is a clinically approved, non-invasive alternate cancer therapy. A synthetic glucocorticoid (GC), dexamethasone (Dex) has previously been demonstrated to sensitize cancer cells to chemotherapy. However, to the best of our knowledge, the sensitization effect of GCs on PDT has not yet been investigated. We hypothesized that glucocorticoid receptor (GR) targeting can selectively make cancer cells more sensitive to PDT treatment, as PDT induces hypoxia wherein GR-activity gets enhanced. In addition, Dex was reported to act against the PDT-induced cell survival pathways like HIF-1α, NRF2, NF-κB, STAT3 etc. Thus, both the treatments can complement each other and may result in increasing the effectiveness of combination therapy. Hence, in this study, we developed liposomal formulations of our previously reported PDT agent P-Nap, either alone (D1P-Nap) or in combination with Dex (D1XP-Nap) to elucidate the sensitization effect. Interestingly, our RT-PCR results in hypoxic conditions showed down-regulation of HIF-1α and over expression of GR-activated genes for glucose-6-phosphatase (G6Pase) and PEPCK enzymes, indicating prominent GR-transactivation. We also observed higher phototoxicity in CT26.WT cells treated with D1XP-Nap PDT under hypoxic conditions as compared to normoxic conditions. These effects were reversed when cells were pre-treated with RU486, a competitive inhibitor of GCs. Moreover, our in vivo findings of subcutaneous tumor model of Balb/C mice for colon cancer revealed a significant decrease in tumor volume as well as considerable enhancement in the survivability of PDT treated tumor-bearing mice when Dex was present in the formulation. A high Bax/Bcl-xL ratio, high p53 expression, enhanced E-cadherin expression and down-regulation of pro-tumorigenic transcription factors NF-κB and c-Myc were found in tumor lysates from mice treated with D1XP-Nap under PDT, indicating GR-mediated sensitization of the tumor to PDT-induced cell death and enhancement of life-span for tumor bearing mice.

Review of three-dimensional spheroid culture models of gynecological cancers for photodynamic therapy research

Photodynamic therapy (PDT) is a specific cancer treatment with minimal side effects. However, it remains challenging to apply PDT clinically, partially due to the difficulty of translating research findings to clinical settings as the conventional 2D cell models used for in vitro research are accepted as less physiologically relevant to a solid tumour. 3D spheroids offer a better model for testing PDT mechanisms and efficacy, particularly on photosensitizer uptake, cellular and subcellular distribution and interaction with cellular oxygen consumption. 3D spheroids are usually generated by scaffold-free and scaffold-based methods and are accepted as physiologically relevant models for PDT anticancer research. Scaffold-free methods offer researchers advantages including high efficiency, reproducible, and controlled microenvironment. While the scaffold-based methods offer an extracellular matrix-like 3D scaffold with the necessary architecture and chemical mediators to support the spheroid formation, the natural scaffold used may limit its usage because of low reproducibility due to patch-to-patch variation. Many studies show that the 3D spheroids do offer advantages to gynceologcial cancer PDT investigation. This article will provide a review of the applications of 3D spheroid culture models for the PDT research of gynaecological cancers.

A Multiple Stimuli-Responsive NanoCRISPR Overcomes Tumor Redox Heterogeneity to Augment Photodynamic Therapy

Redox heterogeneity of tumor cells has become one of the key factors leading to the failure of conventional photodynamic therapy (PDT). Exploration of a distinctive therapeutic strategy addressing heterogeneous predicaments is an appealing yet highly challenging task. Herein, a multiple stimuli-responsive nanoCRISPR (Must-nano) with spatial arrangement peculiarities in nanostructure and intracellular delivery is fabricated to overcome redox heterogeneity at both genetic and phenotypic levels for tumor-specific activatable PDT. Must-nano consists of a redox-sensitive core loading CRISPR/Cas9 targeting hypoxia-inducible factors-1α (HIF-1α) and a rationally designed multiple-responsive shell anchored by chlorin e6 (Ce6). Benefiting from the perfect coordination of structure and function, Must-nano avoids enzyme/photodegradation of the CRISPR/Cas9 system and exerts prolonged circulation, precise tumor recognition, and cascade-responsive performances to surmount tumor extra/intracellular barriers. After internalization into tumor cells, Must-nano could undergo hyaluronidase-triggered self-disassembly with charge reversal and rapid endosomal escape, followed by site-specific release and spatially asynchronous delivery of Ce6 and CRISPR/Cas9 under stimulations of redox signals, which not only improves tumor vulnerability to oxidative stress by complete HIF-1α disruption but also destroys the intrinsic antioxidant mechanism through glutathione depletion, thereby homogenizing redox-heterogeneous cells into oxidative stress-sensitive cell subsets. Under laser irradiation, Must-nano eventually exhibits optimal potency to amplify oxidative damage, effectively inhibiting the growth and hypoxia survival of redox-heterogeneous tumor in vitro and in vivo. Overall, our redox homogenization tactic significantly maximizes PDT efficacy and offers a promising strategy to overcome tumor redox heterogeneity in the development of antitumor therapies.

Metronomic Photodynamic Therapy with Conjugated Polymer Nanoparticles in Glioblastoma Tumor Microenvironment

Alternative therapies such as photodynamic therapy (PDT) that combine light, oxygen and photosensitizers (PSs) have been proposed for glioblastoma (GBM) management to overcome conventional treatment issues. An important disadvantage of PDT using a high light irradiance (fluence rate) (cPDT) is the abrupt oxygen consumption that leads to resistance to the treatment. PDT metronomic regimens (mPDT) involving administering light at a low irradiation intensity over a relatively long period of time could be an alternative to circumvent the limitations of conventional PDT protocols. The main objective of the present work was to compare the effectiveness of PDT with an advanced PS based on conjugated polymer nanoparticles (CPN) developed by our group in two irradiation modalities: cPDT and mPDT. The in vitro evaluation was carried out based on cell viability, the impact on the macrophage population of the tumor microenvironment in co-culture conditions and the modulation of HIF-1α as an indirect indicator of oxygen consumption. mPDT regimens with CPNs resulted in more effective cell death, a lower activation of molecular pathways of therapeutic resistance and macrophage polarization towards an antitumoral phenotype. Additionally, mPDT was tested in a GBM heterotopic mouse model, confirming its good performance with promising tumor growth inhibition and apoptotic cell death induction.

Decontamination of lithium disilicate ceramics using various photosensitizers, herbal and chemical disinfectants, and the effect of surface conditioners on bond strength values

AIM

To assess and compare the antimicrobial efficacy of disinfectants on lithium disilicate ceramic (LDC) used in dental applications and shear bond strength (SBS) of LDC after using different conditioners hydrofluoric acid (HF), self-etching ceramic primers (SECP) and Neodymium-doped yttrium orthovanadate (Nd: YVO4).

MATERIALS AND METHODS

One hundred and twenty LDC discs were fabricated by auto-polymerizing acrylic resin using the lost wax technique. S. aureus, S. mutans, and C. albican were inoculated on thirty discs (n=30 each). Each group was further divided into three subgroups based on different disinfecting agents used (n=30) Group 1: Garlic extract, Group 2: Rose Bengal (RB) activated by PDT, and Group 3: Sodium hypochlorite (NaOCl). An assessment of the survival rate of microorganisms was performed. The remaining thirty samples were surface treated using three different LDC surface conditioners (n=10) Group 1: HF + Silane (S), group 2: SECP, and Group 3: Nd: YVO4 laser+S. SBS and failure mode analysis were performed using a universal testing machine and stereomicroscope at 40x magnification, The statistical analysis was conducted using one-way ANOVA and Post Hoc Tukey test.

RESULTS

Garlic extract, RB, and 2% NaOCl sample displayed comparable outcomes of antimicrobial potency against C. albicans, S aureus, and S. mutans (p>0.05). Furthermore, SBS analysis showed HF+S, SECP, and Nd: YVO4+S exhibited comparable outcomes of bond strength (p>0.05).

CONCLUSION

Garlic extract and Rose bengal activated by PDT can be contemplated as alternatives to the chemical agent NaOCl used for LDC disinfection. Similarly, SECP and Nd: YVO4 possess the potential to be used for the surface conditioning of LDC to improve the bond integrity with resin cement.

Increasing cancer permeability by photodynamic priming: from microenvironment to mechanotransduction signaling

The dense cancer microenvironment is a significant barrier that limits the penetration of anticancer agents, thereby restraining the efficacy of molecular and nanoscale cancer therapeutics. Developing new strategies to enhance the permeability of cancer tissues is of major interest to overcome treatment resistance. Nonetheless, early strategies based on small molecule inhibitors or matrix-degrading enzymes have led to disappointing clinical outcomes by causing increased chemotherapy toxicity and promoting disease progression. In recent years, photodynamic therapy (PDT) has emerged as a novel approach to increase the permeability of cancer tissues. By producing excessive amounts of reactive oxygen species selectively in the cancer microenvironment, PDT increases the accumulation, penetration depth, and efficacy of chemotherapeutics. Importantly, the increased cancer permeability has not been associated to increased metastasis formation. In this review, we provide novel insights into the mechanisms by which this effect, called photodynamic priming, can increase cancer permeability without promoting cell migration and dissemination. This review demonstrates that PDT oxidizes and degrades extracellular matrix proteins, reduces the capacity of cancer cells to adhere to the altered matrix, and interferes with mechanotransduction pathways that promote cancer cell migration and differentiation. Significant knowledge gaps are identified regarding the involvement of critical signaling pathways, and to which extent these events are influenced by the complicated PDT dosimetry. Addressing these knowledge gaps will be vital to further develop PDT as an adjuvant approach to improve cancer permeability, demonstrate the safety and efficacy of this priming approach, and render more cancer patients eligible to receive life-extending treatments.

Overview of Nanoparticle-Based Approaches for the Combination of Photodynamic Therapy (PDT) and Chemotherapy at the Preclinical Stage

Simple Summary

The present review represents the outstanding and promising recent literature reports (2017–2022) on nanoparticle-based formulations developed for anticancer therapy with photodynamic therapy (PDT), photosensitizers, and chemotherapeutics. Besides brief descriptions of chemotherapeutics’ classification and of PDT mechanisms and limitations, several examples of nanosystems endowed with different responsiveness (e.g., acidic pH and reactive oxygen species) and peculiarity (e.g., tumor oxygenation capacity, active tumor targeting, and biomimetic features) are described, and for each drug combination, in vitro and in vivo results on preclinical cancer models are reported.

Abstract

The widespread diffusion of photodynamic therapy (PDT) as a clinical treatment for solid tumors is mainly limited by the patient’s adverse reaction (skin photosensivity), insufficient light penetration in deeply seated neoplastic lesions, unfavorable photosensitizers (PSs) biodistribution, and photokilling efficiency due to PS aggregation in biological environments. Despite this, recent preclinical studies reported on successful combinatorial regimes of PSs with chemotherapeutics obtained through the drugs encapsulation in multifunctional nanometric delivery systems. The aim of the present review deals with the punctual description of several nanosystems designed not only with the objective of co-transporting a PS and a chemodrug for combination therapy, but also with the goal of improving the therapeutic efficacy by facing the main critical issues of both therapies (side effects, scarce tumor oxygenation and light penetration, premature drug clearance, unspecific biodistribution, etc.). Therefore, particular attention is paid to the description of bio-responsive drugs and nanoparticles (NPs), targeted nanosystems, biomimetic approaches, and upconverting NPs, including analyzing the therapeutic efficacy of the proposed photo-chemotherapeutic regimens in in vitro and in vivo cancer models.

NIR-Triggered Generation of Reactive Oxygen Species and Photodynamic Therapy Based on Mesoporous Silica-Coated LiYF4 Upconverting Nanoparticles

To date, the increase in reactive oxygen species (ROS) production for effectual photodynamic therapy (PDT) treatment still remains challenging. In this study, a facile and effective approach is utilized to coat mesoporous silica (mSiO₂) shell on the ligand-free upconversion nanoparticles (UCNPs) based on the LiYF₄ host material. Two kinds of mesoporous silica-coated UCNPs (UCNP@mSiO₂) that display green emission (doped with Ho³⁺) and red emission (doped with Er³⁺), respectively, were successfully synthesized and well characterized. Three photosensitizers (PSs), merocyanine 540 (MC 540), rose bengal (RB), and chlorin e6 (Ce6), with the function of absorption of green or red emission, were selected and loaded into the mSiO₂ shell of both UCNP@mSiO₂ nanomaterials. A comprehensive study for the three UCNP@mSiO₂/PS donor/acceptor pairs was performed to investigate the efficacy of fluorescence resonance energy transfer (FRET), ROS generation, and in vitro PDT using a MCF-7 cell line. ROS generation detection showed that as compared to the oleate-capped and ligand-free UCNP/PS pairs, the UCNP@mSiO₂/PS nanocarrier system demonstrated more pronounced ROS generation due to the UCNP@mSiO₂ nanoparticles in close vicinity to PS molecules and a higher loading capacity of the photosensitizer. As a result, the three LiYF₄ UCNP@mSiO₂/PS nanoplatforms displayed more prominent therapeutic efficacies in PDT by using in vitro cytotoxicity tests.

Targeting Microenvironment of Melanoma and Head and Neck Cancers in Photodynamic Therapy

Background:

Photodynamic therapy (PDT), in comparison to other skin cancers, is still far less effective for melanoma, due to the strong absorbance and the role of melanin in cytoprotection. The tumour microenvironment (TME) has a significant role in tumour progression, and the hypoxic TME is one of the main reasons for melanoma progression to metastasis and its resistance to PDT. Hypoxia is also a feature of solid tumours in the head and neck region that indicates negative prognosis.

Objective:

The aim of this study was to individuate and describe systematically the main strategies in targeting the TME, especially hypoxia, in PDT against melanoma and head and neck cancers (HNC), and assess the current success in their application.

Methods:

PubMed was used for searching, in MEDLINE and other databases, for the most recent publications on PDT against melanoma and HNC in combination with the TME targeting and hypoxia.

Results:

In PDT for melanoma and HNC, it is very important to control hypoxia levels, and amongst the different approaches, oxygen self-supply systems are often applied. Vascular targeting is promising, but to improve it, optimal drug-light interval, and formulation to increase the accumulation of the photosensitiser in the tumour vasculature, have to be established. On the other side, the use of angiogenesis inhibitors, such as those interfering with VEGF signalling, is somewhat less successful than expected and needs to be further investigated.

Conclusion:

The combination of PDT with immunotherapy by using multifunctional nanoparticles continues to develop and seems to be the most promising for achieving a complete and lasting antitumour effect.

Molecular Effectors of Photodynamic Therapy-Mediated Resistance to Cancer Cells

Photodynamic therapy (PDT) is currently enjoying considerable attention as the subject of experimental research to treat resistant cancers. The preferential accumulation of a non-toxic photosensitizer (PS) in different cellular organelles that causes oxidative damage by combining light and molecular oxygen leads to selective cell killing. However, one major setback, common among other treatment approaches, is tumor relapse and the development of resistance causing treatment failure. PDT-mediated resistance could result from increased drug efflux and decreased localization of PS, reduced light exposure, increased DNA damage repair, and altered expression of survival genes. This review highlights the essential insights of PDT reports in which PDT resistance was observed and which identified some of the molecular effectors that facilitate the development of PDT resistance. We also discuss different perceptions of PDT and how its current limitations can be overturned to design improved cancer resistant treatments.

Photodynamic Therapy: A Compendium of Latest Reviews

Photodynamic therapy (PDT) is a promising therapy against cancer. Even though it has been investigated for more than 100 years, scientific publications have grown exponentially in the last two decades. For this reason, we present a brief compendium of reviews of the last two decades classified under different topics, namely, overviews, reviews about specific cancers, and meta-analyses of photosensitisers, PDT mechanisms, dosimetry, and light sources. The key issues and main conclusions are summarized, including ways and means to improve therapy and outcomes. Due to the broad scope of this work and it being the first time that a compendium of the latest reviews has been performed for PDT, it may be of interest to a wide audience.

Nanoconjugates to enhance PDT-mediated cancer immunotherapy by targeting the indoleamine-2,3-dioxygenase pathway

BACKGROUND

Photodynamic therapy (PDT) may elicit antitumor immune response in addition to killing cancer cells. However, PDT as a monotherapy often fails to induce a strong immunity. Immune checkpoint inhibitors, which selectively block regulatory axes, may be used in combination with PDT to improve treatment outcomes. Indoleamine 2,3-dioxygenase (IDO) is an immunoregulatory enzyme and an important meditator of tumor immune escape. Combination therapy with PDT and IDO-targeted immune checkpoint blockage is promising but has been seldom been explored.

METHODS

Herein we report a composite nanoparticle that allows for simultaneous delivery of photosensitizer and IDO inhibitor. Briefly, we separately load ZnF16Pc, a photosensitizer, and NLG919, an indoleamine 2,3-dioxygenase (IDO) inhibitor, into ferritin and poly(lactide-co-glycolic)-block-poly(ethylene glycol) (PEG-PLGA) nanoparticles; we then conjugate these two compartments to form a composite nanoparticle referred to as PPF NPs. We tested combination treatment with PPF NPs first in vitro and then in vivo in B16F10-tumor bearing C57/BL6 mice.

RESULTS

Our results showed that PPF NPs can efficiently encapsulate both ZnF16Pc and NLG919. In vivo studies found that the combination treatment led to significantly improved tumor suppression and animal survival. Moreover, the treatment increased tumor infiltration of CD8+ T cells, while reducing frequencies of MDSCs and Tregs. 30% of the animals showed complete tumor eradication, and they successfully rejected a second tumor inoculation. Overall, our studies introduce a unique composite nanoplatform that allows for co-delivery of photosensitizer and IDO inhibitor with minimal inter-species interference, which is ideal for combination therapy.

Understanding the glioblastoma tumor biology to optimize photodynamic therapy: From molecular to cellular events

Photodynamic therapy (PDT) has recently gained attention as an alternative treatment of malignant gliomas. Glioblastoma (GBM) is the most prevalent within tumors of the central nervous system (CNS). Conventional treatments for this CNS tumor include surgery, radiation, and chemotherapy. Surgery is still being considered as the treatment of choice. Even so, the poor prognosis and/or recurrence of the disease after applying any of these treatments highlight the urgency of exploring new therapies and/or improving existing ones to achieve the definitive eradication of tumor masses and remaining cells. PDT is a therapeutic modality that involves the destruction of tumor cells by reactive oxygen species induced by light, which were previously treated with a photosensitizing agent. However, in recent years, its experimental application has expanded to other effects that could improve overall performance against GBM. In the current review, we revisit the main advances of PDT for GBM management and also, the recent mechanistic insights about cellular and molecular aspects related to tumoral resistance to PDT of GBM.

Heparin modified photosensitizer-loaded liposomes for tumor treatment and alleviating metastasis in phototherapy

Phototherapy holds promise in cancer treatment for its prominent antitumor efficacy and low systematic toxicity compared with traditional chemotherapy. However, the higher risk of tumor metastasis caused by the severe hypoxic state during phototherapy is a threat in practical use. Here, in order to tackle this challenge, we developed a delivery system via loading the photosensitizer indocyanine green (ICG) into the low molecular weight heparin (LMWH) modified liposomes (LMWH-ICG-Lip) to realize the synergistic effects between photosensitizer and drug vehicle, achieving better phototherapeutic efficacy and meanwhile alleviating the potential risk of tumor metastasis caused by phototherapy. In this system, besides elongating the photosensitizers' circulation time and enhancing their accumulating efficacy to tumor tissues, LMWH itself also exhibited anti-metastasis efficacy via inhibiting adhesion of platelets to tumor cells and decreasing migration and invasion capability of tumor cells. In vivo efficacy evaluation was conducted on orthotopic 4T1 breast cancer model, and the system of LMWH-ICG-Lip could alleviate metastasis potential of residual tumor cells after irradiation, and elicit optimistic antitumor and anti-metastasis efficacy for phototherapy.

The Potential of Lonidamine in Combination with Chemotherapy and Physical Therapy in Cancer Treatment

Simple Summary

The unique characteristics of tumor energy metabolism (highly dependent on aerobic glycolysis, namely, the Warburg effect) make it an interesting and attractive target for drug discovery. Radio- and chemoresistance are closely associated with the Warburg effect. Lonidamine (LND), as a glycolytic inhibitor, although having low anticancer activity when used alone, exhibits selectivity to various tumors, and its adverse effects do not overlap when combined with other chemotherapeutic drugs. Therefore, LND may be very promising as a sensitizer of tumors to chemotherapeutic agents and physical therapies. This review summarizes the advance of LND in combination with chemotherapy and physical therapy over the past several decades, as well as the promising LND derivative adjudin (ADD). The underlying sensitizing mechanisms were also analyzed and discussed, which may contribute to an improved therapeutic effect in future clinical cancer treatment.

Abstract

Lonidamine (LND) has the ability to resist spermatogenesis and was first used as an anti-spermatogenic agent. Later, it was found that LND has a degree of anticancer activity. Currently, LND is known to target energy metabolism, mainly involving the inhibition of monocarboxylate transporter (MCT), mitochondrial pyruvate carrier (MPC), respiratory chain complex I/II, mitochondrial permeability transition (PT) pore, and hexokinase II (HK-II). However, phase II clinical studies showed that LND alone had a weak therapeutic effect, and the effect was short and reversible. Interestingly, LND does not have the common side effects of traditional chemotherapeutic drugs, such as alopecia and myelosuppression. In addition, LND has selective activity toward various tumors, and its toxic and side effects do not overlap when combined with other chemotherapeutic drugs. Therefore, LND is commonly used as a chemosensitizer to enhance the antitumor effects of chemotherapeutic drugs based on its disruption of energy metabolism relating to chemo- or radioresistance. In this review, we summarized the combination treatments of LND with several typical chemotherapeutic drugs and several common physical therapies, such as radiotherapy (RT), hyperthermia (HT), and photodynamic therapy (PDT), and discussed the underlying mechanisms of action. Meanwhile, the development of novel formulations of LND in recent years and the research progress of LND derivative adjudin (ADD) as an anticancer drug were also discussed.

Elucidation of the Intersystem Crossing Mechanism in a Helical BODIPY for Low-Dose Photodynamic Therapy

Intersystem crossing (ISC) of triplet photosensitizers is a vital process for fundamental photochemistry and photodynamic therapy (PDT). Herein, we report the co-existence of efficient ISC and long triplet excited lifetime in a heavy atom-free bodipy helicene molecule. Via theoretical computation and time-resolved EPR spectroscopy, we confirmed that the ISC of the bodipy results from its twisted molecular structure and reduced symmetry. The twisted bodipy shows intense long wavelength absorption (ϵ=1.76×105  m-1  cm-1 at 630 nm), satisfactory triplet quantum yield (ΦT =52 %), and long-lived triplet state (τT =492 μs), leading to unprecedented performance as a triplet photosensitizer for PDT. Moreover, nanoparticles constructed with such helical bodipy show efficient PDT-mediated antitumor immunity amplification with an ultra-low dose (0.25 μg kg-1 ), which is several hundred times lower than that of the existing PDT reagents.

Trojan horse monocyte-mediated delivery of conjugated polymer nanoparticles for improved photodynamic therapy of glioblastoma

Aim: To assess monocyte-based delivery of conjugated polymer nanoparticles (CPNs) for improved photodynamic therapy (PDT) in glioblastoma (GBM). Materials & methods: Human monocyte cells (THP-1) and murine monocytes isolated from bone marrow (mBMDMs) were employed as stealth CPN carriers to penetrate into GBM spheroids and an orthotopic model of the tumor. The success of PDT, using this cell-mediated targeting strategy, was determined by its effect on the spheroids. Results: CPNs did not affect monocyte viability in the absence of light and did not show nonspecific release after cell loading. Activated monocytes incorporated CPNs in a higher proportion than monocytes in their naive state, without a loss of cellular functionality. In vitro PDT efficacy using cell-mediated delivery was superior to that using non vehiculized CPNs. Conclusion: CPN-loaded monocytes could efficiently deliver CPNs into GBM spheroids and the orthotopic model. Improved PDT in spheroids was confirmed using this delivery strategy.

Natural photosensitizers in photodynamic therapy: In vitro activity against monolayers and spheroids of human colorectal adenocarcinoma SW480 cells

Photodynamic Therapy (PDT), is a treatment option for cancer.It involves the photochemical interaction of light, photosensitizer (PS) and molecular oxygen to produce radical species as well as singlet oxygen which induce cell death. Anthraquinones (AQs) have been extensively studied with respect to their UV/Vis absorption characteristics and their photosensitizing properties in photodynamic reactions. We study the photoactivity of different natural AQs (Parietin, Soranjidiol and Rubiadin) in treating monolayers and multicellular tumor spheroids (MCTSs). Rubiadin and soranjidiol were isolated and purified from the stem and leaves of Heterophyllae pustulata, and PTN was from the liquen Teloschistes flavicans by using repeated combination of several chromatographic techniques. Monolayer and spheroids of human colorectal adenocarcinoma SW480 cells were incubated with different concentrations of the AQs and then irradiated at room temperature. 24 h post-PDT cell viability, nuclear morphology and type of cell death were analyzed. We observed that Soranjidiol and Rubiadin showed no significant difference in the photosensitizing ability on monoculture of colon cancer cells (LD₈₀ at 50 μM and 10 J/cm², for both AQs). Nevertheless, for Parietin (PTN) LD₈₀ was achieved at (20 μM using the same light dose (10 J/cm²). The death mechanism induced post-PDT was necrosis by use of Soranjidol and Rubiadin and apoptosis by use of PTN. Furthermore, in MCTSs of 300 and 900 μm, the treatment PTN- PDT produces the greatest cytotoxic effect. The three AQs analyzed could be promising chemotherapeutic candidates as anticancer PDT agents.

Recapitulation of Hypoxic Tumor-stroma Microenvironment to Study Photodynamic Therapy Implications

Tumor microenvironment (TME) is a dynamic ecosystem where fibroblasts are recruited in order to provide a niche to support growth and, in some extent, to promote therapeutic resistance. However, the role of fibroblasts in stimulating or impairing photodynamic therapy (PDT) outcome has not yet been fully addressed. PDT is based on interactions between light, oxygen and photosensitizer, leading to phototoxic reactions that culminate in cell death. In this study, we demonstrated the consequences of a hypoxic stromal phenotype on tumor mass for exploring PDT response. We mimicked TME complexity implementing colon cancer cells and fibroblasts 3D cultures called spheroids. Using hypoxia reporting lines, we verified that homotypic spheroids exhibited a size-dependent transcriptional HIF-1 activity. When cocultured, fibroblasts were localized in the hypoxic core. In homotypic stromal spheroids, the distribution of the endogenous photosensitizer PpIX was homogeneous while decreased in hypoxic areas of tumor 3D cultures. When monocultured, fibroblasts were more efficient to produce PpIX from its prodrug Me-ALA. Interestingly, the cross talk between cancer cells and fibroblasts attenuated PpIX accumulation and conferred tumor PDT resistance when compared to homotypic 3D cultures. Overall, our data suggest that stroma and tumor act in an integrated, reciprocal fashion which could ultimately influence on therapeutic response.

Dendritic Cells and Immunogenic Cancer Cell Death: A Combination for Improving Antitumor Immunity

The safety and feasibility of dendritic cell (DC)-based immunotherapies in cancer management have been well documented after more than twenty-five years of experimentation, and, by now, undeniably accepted. On the other hand, it is equally evident that DC-based vaccination as monotherapy did not achieve the clinical benefits that were predicted in a number of promising preclinical studies. The current availability of several immune modulatory and targeting approaches opens the way to many potential therapeutic combinations. In particular, the evidence that the immune-related effects that are elicited by immunogenic cell death (ICD)-inducing therapies are strictly associated with DC engagement and activation strongly support the combination of ICD-inducing and DC-based immunotherapies. In this review, we examine the data in recent studies employing tumor cells, killed through ICD induction, in the formulation of anticancer DC-based vaccines. In addition, we discuss the opportunity to combine pharmacologic or physical therapeutic approaches that can promote ICD in vivo with in situ DC vaccination.

Chlorophyll treatment combined with photostimulation increases glycolysis and decreases oxidative stress in the liver of type 1 diabetic rats

Photodynamic therapy (PDT) promotes cell death, and it has been successfully employed as a treatment resource for neuropathic complications of diabetes mellitus (T1DM) and hepatocellular carcinoma. The liver is the major organ involved in the regulation of energy homeostasis, and in pathological conditions such as T1DM, changes in liver metabolic pathways result in hyperglycemia, which is associated with multiple organic dysfunctions. In this context, it has been suggested that chlorophyll-a and its derivatives have anti-diabetic actions, such as reducing hyperglycemia, hyperinsulinemia, and hypertriglyceridemia, but these effects have not yet been proven. Thus, the biological action of PDT with chlorophyll-a on hepatic parameters related to energy metabolism and oxidative stress in T1DM Wistar rats was investigated. Evaluation of the acute effects of this pigment was performed by incubation of isolated hepatocytes with chlorophyll-a and the chronic effects were evaluated by oral treatment with chlorophyll-based extract, with post-analysis of the intact liver by in situ perfusion. In both experimental protocols, chlorophyll-a decreased hepatic glucose release and glycogenolysis rate and stimulated the glycolytic pathway in DM/PDT. In addition, there was a reduction in hepatic oxidative stress, noticeable by decreased lipoperoxidation, reactive oxygen species, and carbonylated proteins in livers of chlorophyll-treated T1DM rats. These are indicators of the potential capacity of chlorophyll-a in improving the status of the diabetic liver.

Photodynamic Modulation of Type 1 Interferon Pathway on Melanoma Cells Promotes Dendritic Cell Activation

The immune response against cancer generated by type-I-interferons (IFN-1) has recently been described. Exogenous and endogenous IFN-α/β have an important role in immune surveillance and control of tumor development. In addition, IFN-1s have recently emerged as novel DAMPs for the consecutive events connecting innate and adaptive immunity, and they also have been postulated as an essential requirement for induction of immunogenic cell death (ICD). In this context, photodynamic therapy (PDT) has been previously linked to the ICD. PDT consists in the administration of a photosensitizer (PS) and its activation by irradiation of the affected area with visible light producing excitation of the PS. This leads to the local generation of harmful reactive oxygen species (ROS) with limited or no systemic defects. In the current work, Me-ALA inducing PpIX (endogenous PS) was administrated to B16-OVA melanoma cells. PpIX preferentially localized in the endoplasmic reticulum (ER). Subsequent PpIX activation with visible light significantly induced oxidative ER-stress mediated-apoptotic cell death. Under these conditions, the present study was the first to report the in vitro upregulation of IFN-1 expression in response to photodynamic treatment in melanoma. This IFN-α/β transcripts upregulation was concurrent with IRF-3 phosphorylation at levels that efficiently activated STAT1 and increased ligand receptor (cGAS) and ISG (CXCL10, MX1, ISG15) expression. The IFN-1 pathway has been identified as a critical molecular pathway for the antitumor host immune response, more specifically for the dendritic cells (DCs) functions. In this sense, PDT-treated melanoma cells induced IFN-1-dependent phenotypic maturation of monocyte-derived dendritic cells (DCs) by enhancing co-stimulatory signals (CD80, MHC-II) and tumor-directed chemotaxis. Collectively, our findings showed a new effect of PDT-treated cancer cells by modulating the IFN-1 pathway and its impact on the activation of DCs, emphasizing the potential relevance of PDT in adoptive immunotherapy protocols.

Enhancement of Photodynamic Cancer Therapy by Physical and Chemical Factors

The viable use of photodynamic therapy (PDT) in cancer therapy has never been fully realized because of its undesirable effects on healthy tissues. Herein we summarize some physicochemical factors that can make PDT a more viable and effective option to provide future oncological patients with better-quality treatment options. These physicochemical factors include light sources, photosensitizer (PS) carriers, microwaves, electric fields, magnetic fields, and ultrasound. This Review is meant to provide current information pertaining to PDT use, including a discussion of in vitro and in vivo studies. Emphasis is placed on the physicochemical factors and their potential benefits in overcoming the difficulty in transitioning PDT into the medical field. Many advanced techniques, such as employing X-rays as a light source, using nanoparticle-loaded stem cells and bacteriophage bio-nanowires as a photosensitizer carrier, as well as integration with immunotherapy, are among the future directions.

Characterisation of resistance mechanisms developed by basal cell carcinoma cells in response to repeated cycles of Photodynamic Therapy

Photodynamic Therapy (PDT) with methyl-aminolevulinate acid (MAL-PDT) is being used for the treatment of Basal cell carcinoma (BCC), but recurrences have been reported. In this work, we have evaluated resistance mechanisms to MAL-PDT developed by three BCC cell lines (ASZ, BSZ and CSZ), derived from mice on a ptch+/- background and with or without p53 expression, subjected to 10 cycles of PDT (10thG). The resistant populations showed mesenchymal-like structure and diminished proliferative capacity and size compared to the parental (P) cells. The resistance was dependent on the production of the endogenous photosensitiser protoporphyrin IX in the CSZ cell line and on its cellular localisation in ASZ and BSZ cells. Moreover, resistant cells expressing the p53 gene presented lower proliferation rate and increased expression levels of N-cadherin and Gsk3β (a component of the Wnt/β-catenin pathway) than P cells. In contrast, 10thG cells lacking the p53 gene showed lower levels of expression of Gsk3β in the cytoplasm and of E-cadherin and β-catenin in the membrane. In addition, resistant cells presented higher tumorigenic ability in immunosuppressed mice. Altogether, these results shed light on resistance mechanisms of BCC to PDT and may help to improve the use of this therapeutic approach.

Combination of photodynamic therapy (PDT) and anti-tumor immunity in cancer therapy

Photodynamic therapy (PDT) is performed using a photosensitizer and light of specific wavelength in the presence of oxygen to generate singlet oxygen and reactive oxygen species(ROS) in the cancer cells. The accumulated photosensitizers in target sites induce ROS generation upon light activation, then the generated cytotoxic reactive oxygen species lead to tumor cell death via apoptosis or necrosis, and damages the target sites which results tumor destruction. As a consequence, the PDT-mediated cell death is associated with anti-tumor immune response. In this paper, the effects of PDT and immune response on tumors are reviewed. Activation of an immune response regarding the innate and adaptive immune response, interaction with immune cells and tumor cells that associated with antitumor efficacy of PDT are also discussed.

Biomedical Platform Development of a Chlorophyll-Based Extract for Topic Photodynamic Therapy: Mechanical and Spectroscopic Properties

Photodynamic therapy (PDT) is a therapeutic modality that has shown effectiveness in the inactivation of cancer cell lines and microorganisms. Treatment consists of activating the photosensitizer (PS) upon light irradiation of adequate wavelength. After reaching the excited state, the PS can handle the intersystem conversion through energy transfer to the molecular oxygen, generating reactive oxygen species. This especially applies to singlet oxygen (¹O₂), which is responsible for the selective destruction of the sick tissue. Photosensitizing compounds (chlorophylls and derivatives) existing in the spinach extract have applicability for PDT. This study aimed to develop and characterize the thermoresponsive bioadhesive system composed of Pluronic F127 20.0%- and Carbopol 934P 0.2% (w/w) (FC)-containing chlorophyll-based extract 0.5% (w/w) (FC-Chl). Mechanical and rheological properties, in vitro release, sol-gel transition temperature, and ex vivo permeability of the spinach extract PS components (through pig ear skin) were investigated. Furthermore, photodynamic activity of the system was accessed through uric acid and time-solved measurements. The sol-gel transition temperature obtained for the FC-Chl system was 28.8 ± 0.3 °C. Rheological and texture properties of the platform were suitable for use as a dermatological system, exhibiting easy application and good characteristics of retention in the place of administration. In vitro release studies showed the presence of two distinct mechanisms that reasonably obey the zero-order and first-order kinetics models. PS components presented skin permeability and reached a permeation depth of 830 μm (between the epidermis and dermis). The photodynamic evaluation of the FC-Chl system was effective in the degradation of uric acid. The quantum yield (Φ_Δ¹O₂) and life time (τ¹O₂) of singlet oxygen showed similar values for the spinach extract and the isolated chlorophyll a species in ethanol. These results allowed for the classification of the FC-Chl platform as potentially useful for the delivery of the chlorophyll-based extract in the topic PDT, suggesting that it is worthy for in vivo evaluation.

A fluorescent nanoprobe for real-time monitoring of intracellular singlet oxygen during photodynamic therapy

Sensing of intracellular singlet oxygen (¹O₂) is required in order to optimize photodynamic therapy (PDT). An optical nanoprobe is reported here for the optical determination of intracellular ¹O₂. The probe consists of a porous particle core doped with the commercial ¹O₂ probe 1,3-diphenylisobenzofuran (DPBF) and a layer of poly-L-lysine. The nanoparticle probes have a particle size of ~80 nm in diameter, exhibit good biocompatibility, improved photostability and high sensitivity for ¹O₂ in both absorbance (peak at 420 nm) and fluorescence (with excitation/emission peaks at 405/458 nm). Nanoprobes doped with 20% of DPBF are best suited even though they suffer from concentration quenching of fluorescence. In comparison with the commercial fluorescent ¹O₂ probe SOSG, 20%-doped DPBF-NPs (aged) shows higher sensitivity for ¹O₂ generated at an early stage. The best nanoprobes were used to real-time monitor the PDT-triggered generation of ¹O₂ inside live cells, and the generation rate is found to depend on the supply of intracellular oxygen. Graphical abstract A fluorescent nanoprobe featured with refined selectivity and improved sensitivity towards ¹O₂ was prepared from the absorption-based probe DBPF and used to real-time monitoring of the generation of intracellular ¹O₂ produced during PDT.

The photodynamic therapy activity of 3-(1-hydroxylethyl)-3-devinyl-131-(dicyanomethylene) pyropheophorbide-a methyl ester (HDCPPa) against HeLa cell in vitro

Photodynamic therapy (PDT) has been a potential therapeutic method for the treatment of various cancers, with photosensitizer being the key component in photodynamic therapy. In this paper, we prepared a photosensitizer 3-(1-hydroxylethyl)-3-devinyl-131-(dicyanomethylene) pyropheophorbide-a methyl ester (HDCPPa), based on chlorophyll pyropheophorbide-a according to the previous report, and systematically investigated the fluorescence emission spectrum and ultraviolet absorption spectrum HDCPPa has long absorption in the near-infrared spectral region (around 695 nm). The excitation wavelength and the emission wavelength were 415 nm and 699 nm respectively in dichloromethane, 1O2 quantum yield was 63.5%. HDCPPa also had high stability in PBS solution, DMEM cell culture medium and normal saline (NS) in vitro. After irradiation by the light of 675 nm (10 J.cm[Formula: see text]) for 70 min the degradation rate of HDCPPa was 12.5%, which indicated that the target compound showed high stability under light. The in vitrophotodynamic therapy activities against HeLa cells were also studied, which showed that HDCPPa had extremely low dark toxicity but great phototoxicity, and the cell viability is lower than 10% under the light irradiation of 675 nm (10 J.cm[Formula: see text]). Moreover, HDCPPa can quickly enter the cell after being incubated with HeLa cells in less than 30 min. We also evaluated the mechanism of the photochemical reaction, which had proved that Type II is primarily responsible for the cell death. Therefore HDCPPa could serve as a very promising photosensitizer for photodynamic therapy.

Strategies for optimizing the delivery to tumors of macrocyclic photosensitizers used in photodynamic therapy (PDT)

This review briefly summaries the principles and mechanisms of action of photodynamic therapy (PDT) as concerns its application in the oncological field, highlighting its drawbacks and some of the strategies that have been or are being explored to overcome them. The major aim is to increase the efficiency and selectivity of the photosensitizer (PS) uptake in the cancer cells for optimizing the PDT effects on tumors while sparing normal cells. Some attempts to achieve this are based on the conjugation of the PS to biomolecules (small ligands, peptides) functioning as carriers with the ability to efficiently penetrate cells and/or specifically recognize and bind proteins/receptors overexpressed on the surface of cancer cells. Alternatively, the PS can be entrapped in nanocarriers derived from various types of materials that can target the tumor by exploiting the enhanced permeability and retention (EPR) effects. The use of nanocarriers is particularly attractive because it allows the simultaneous delivery of more than one drug with the possibility of combining PDT with other therapeutic modalities.

Brazilian Green Propolis Extract Synergizes with Protoporphyrin IX-mediated Photodynamic Therapy via Enhancement of Intracellular Accumulation of Protoporphyrin IX and Attenuation of NF-κB and COX-2

Brazilian green propolis (BGP) is noted for its impressive antitumor effects and has been used as a folk medicine in various cultures for many years. It has been demonstrated that BGP could enhance the cytotoxic effect of cytostatic drugs on tumor cells. Photodynamic therapy (PDT) is a therapeutic approach used against malignant cells. To assess the synergistic effect of BGP extract on protoporphyrin IX (PpIX)-mediated photocytotoxicity, MTT assays were performed using A431 and HeLa cells. TUNEL assay and Annexin V-FITC/PI staining were performed to confirm the induction of apoptosis. Western blotting analysis was performed to examine the pro-apoptotic proteins, anti-apoptotic proteins and inflammation related proteins in A431 cells. Intracellular accumulation of PpIX was examined by flow cytometry. The synergistic effect of BGP extract in PpIX-PDT was also evaluated with a xenograft model. Our findings reveal that BGP extract increased PpIX-mediated photocytotoxicity in A431 and HeLa cells. PpIX-PDT with BGP extract treatment resulted in a decrease in Bcl-xL and an increase in NOXA, Bax and caspase-3 cleavage. The protein expression levels of p-IKKα/β, NF-κB and COX-2 were upregulated by PpIX-PDT but significantly attenuated when in combination with BGP extract. BGP extract was also found to significantly enhance the intracellular accumulation of PpIX in A431 cells. BGP extract increased PpIX-mediated photocytotoxicity in a xenograft model as well. Our findings provide evidence for a synergistic effect of BGP extract in PpIX-PDT both in vitro and in vivo.

Cationic dendritic starch as a vehicle for photodynamic therapy and siRNA co-delivery

Cationic enzymatically synthesized glycogen (cESG) is a naturally-derived, nano-scale carbohydrate dendrite that has shown promise as a cellular delivery vehicle owing to its flexibility in chemical modifications, biocompatibility and relative low cost. In the present work, cESG was modified and evaluated as a vehicle for tetraphenylporphinesulfonate (TPPS) in order to improve cellular delivery of this photosensitizer and investigate the feasibility of co-delivery with short interfering ribonucleic acid (siRNA). TPPS was electrostatically condensed with cESG, resulting in a sub-50nm particle with a positive zeta potential of approximately 5mV. When tested in normal ovarian surface epithelial and ovarian clear cell carcinoma cell culture models, encapsulation of TPPS in cESG significantly improved cell death in response to light treatment compared to free drug alone. Dosages as low as 0.16μM TPPS resulted in cellular death upon illumination with a 4.8J/cm² light dosage, decreasing viability by 96%. cESG-TPPS was then further evaluated as a co-delivery system with siRNA for potential combination therapy, by charge-based condensation of an siRNA directed at reducing expression of manganese superoxide dismutase (Sod2) as a proof of principle target. Simultaneous delivery of TPPS and siRNA was achieved, reducing Sod2 protein expression to 48%, while maintaining the photodynamic properties of TPPS under light exposure and maintaining low dark toxicity. This study demonstrates the versatility of cESG as a platform for dual delivery of small molecules and oligonucleotides, and the potential for further development of this system in combination therapy applications.

Photodynamic Therapy Mediated by Nontoxic Core-Shell Nanoparticles Synergizes with Immune Checkpoint Blockade To Elicit Antitumor Immunity and Antimetastatic Effect on Breast Cancer

An effective, nontoxic, tumor-specific immunotherapy is the ultimate goal in the battle against cancer, especially the metastatic disease. Checkpoint blockade-based immunotherapies have been shown to be extraordinarily effective but benefit only the minority of patients whose tumors have been pre-infiltrated by T cells. Here, we show that Zn-pyrophosphate (ZnP) nanoparticles loaded with the photosensitizer pyrolipid (ZnP@pyro) can kill tumor cells upon irradiation with light directly by inducing apoptosis and/or necrosis and indirectly by disrupting tumor vasculature and increasing tumor immunogenicity. Furthermore, immunogenic ZnP@pyro photodynamic therapy (PDT) treatment sensitizes tumors to checkpoint inhibition mediated by a PD-L1 antibody, not only eradicating the primary 4T1 breast tumor but also significantly preventing metastasis to the lung. The abscopal effects on both 4T1 and TUBO bilateral syngeneic mouse models further demonstrate that ZnP@pyro PDT treatment combined with anti-PD-L1 results in the eradication of light-irradiated primary tumors and the complete inhibition of untreated distant tumors by generating a systemic tumor-specific cytotoxic T cell response. These findings indicate that nanoparticle-mediated PDT can potentiate the systemic efficacy of checkpoint blockade immunotherapies by activating the innate and adaptive immune systems in tumor microenvironment.

Raman microspectroscopy of Hematoporphyrins. Imaging of the noncancerous and the cancerous human breast tissues with photosensitizers

Raman microspectroscopy combined with fluorescence were used to study the distribution of Hematoporphyrin (Hp) in noncancerous and cancerous breast tissues. The results demonstrate the ability of Raman spectroscopy to distinguish between noncancerous and cancerous human breast tissue and to identify differences in the distribution and photodegradation of Hematoporphyrin, which is a photosensitizer in photodynamic therapy (PDT), photodynamic diagnosis (PDD) and photoimmunotherapy (PIT) of cancer. Presented results show that Hematoporphyrin level in the noncancerous breast tissue is lower compared to the cancerous one. We have proved also that the Raman intensity of lipids and proteins doesn't change dramatically after laser light irradiation, which indicates that the PDT treatment destroys preferably cancer cells, in which the photosensitizer is accumulated. The specific subcellular localization of photosensitizer for breast tissues samples soaked with Hematoporphyrin was not observed.

Ratiometric Biosensor for Aggregation-Induced Emission-Guided Precise Photodynamic Therapy

Photodynamic therapy faces the barrier of choosing the appropriate irradiation region and time. In this paper, a matrix metalloproteinase-2 (MMP-2) responsive ratiometric biosensor was designed and synthesized for aggregation-induced emission (AIE)-guided precise photodynamic therapy. It was found that the biosensor presented the MMP-2 responsive AIE behavior. Most importantly, it could accurately differentiate the tumor cells from the healthy cells by the fluorescence ratio between freed tetraphenylethylene and protoporphyrin IX (PpIX, internal reference). In vivo study demonstrated that the biosensor could preferentially accumulate in the tumor tissue with a relative long blood retention time. Note that the intrinsic fluorescence of PpIX and MMP-2-triggered AIE fluorescence provided a real-time feedback which guided precise photodynamic therapy in vivo efficiently. This strategy demonstrated here opens a window in the precise medicine, especially for phototherapy.

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S₀) to an excited singlet state (S₁-Sn), followed by intersystem crossing to an excited triplet state (T₁). The energy transferred from T₁ to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (¹O₂, H₂O₂, O₂*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

Oncologic photodynamic diagnosis and therapy: confocal Raman/fluorescence imaging of metal phthalocyanines in human breast cancer tissue in vitro

Raman microspectroscopy and confocal Raman imaging combined with confocal fluorescence were used to study the distribution and aggregation of aluminum tetrasulfonated phthalocyanine (AlPcS4) in noncancerous and cancerous breast tissues. The results demonstrate the ability of Raman spectroscopy to distinguish between noncancerous and cancerous human breast tissue and to identify differences in the distribution and aggregation of aluminum phthalocyanine, which is a potential photosensitizer in photodynamic therapy (PDT), photodynamic diagnosis (PDD) and photoimmunotherapy (PIT) of cancer. We have observed that the distribution of aluminum tetrasulfonated phthalocyanine confined in cancerous tissue is markedly different from that in noncancerous tissue. We have concluded that Raman imaging can be treated as a new and powerful technique useful in cancer photodynamic therapy, increasing our understanding of the mechanisms and efficiency of photosensitizers by better monitoring localization in cancer cells as well as the clinical assessment of the therapeutic effects of PDT and PIT.

Polymeric nanocarrier systems for photodynamic therapy

Photodynamic therapy (PDT) is an emerging treatment modality that involves the combined action of photosensitizers (PSs) and light for treatment of solid tumor and other diseases. Although this therapeutic method has been considered as an alternative to classical cancer treatments, clinical PDT requires further advances in selectivity and therapeutic efficacy to overcome numerous shortages related to conventional PDT. In this regard, great efforts have been devoted to the development of polymeric nanocarrier-encapsulated PSs for targeted PDT, aiming at improvement of water solubility and tumor-specificity of hydrophobic PSs. Here, we discuss the general concepts and considerations of polymeric nanocarriers for efficient delivery of PSs. In recent, the amphiphilic PS-polymer conjugate-based self-quenchable nanoparticles and PS-polymer-conjugate/quencher nanocomplexes have emerged as an attractive delivery platform for efficient and reliable PDT. They can incorporate and deliver the PS in a photodynamically inactive state but demonstrate cytotoxic effects by tumor environment-sensitive activation mechanisms, so that the photodynamic cancer treatment can achieve maximum target specificity. Here, we report the recent achievements on the development of activatable PS formulations based on PS-polymer conjugates.

Evaluation of photodynamic therapy in adhesion protein expression

Photodynamic therapy (PDT) is a treatment modality that has clinical applications in both non-neoplastic and neoplastic diseases. PDT involves a light-sensitive compound (photosensitizer), light and molecular oxygen. This procedure may lead to several different cellular responses, including cell death. Alterations in the attachment of cancer cells to the substratum and to each other are important consequences of photodynamic treatment. PDT may lead to changes in the expression of cellular adhesion structure and cytoskeleton integrity, which are key factors in decreasing tumor metastatic potential. HEp-2 cells were photosensitized with aluminum phthalocyanine tetrasulfonate and zinc phthalocyanine, and the proteins β1-integrin and focal adhesion kinase (FAK) were assayed using fluorescence microscopy. The verification of expression changes in the genes for FAK and β1 integrin were performed by reverse transcription-polymerase chain reaction (RT-PCR). The results revealed that HEp-2 cells do not express β-integrin or FAK 12 h following PDT. It was concluded that the PDT reduces the adhesive ability of HEp-2 cells, inhibiting their metastatic potential. The present study aimed to analyze the changes in the expression and organization of cellular adhesion elements and the subsequent metastatic potential of HEp-2 cells following PDT treatment.

Cytotoxic efficacy of photodynamic therapy in osteosarcoma cells in vitro

In recent years, there has been the difficulty in finding more effective therapies against cancer with less systemic side effects. Therefore Photodynamic Therapy is a novel approach for a more tumor selective treatment. Photodynamic Therapy (PDT) that makes use of a nontoxic photosensitizer (PS), which, upon activation with light of a specific wavelength in the presence of oxygen, generates oxygen radicals that elicit a cytotoxic response(1). Despite its approval almost twenty years ago by the FDA, PDT is nowadays only used to treat a limited number of cancer types (skin, bladder) and nononcological diseases (psoriasis, actinic keratosis)(2). The major advantage of the use of PDT is the ability to perform a local treatment, which prevents systemic side effects. Moreover, it allows the treatment of tumors at delicate sites (e.g. around nerves or blood vessels). Here, an intraoperative application of PDT is considered in osteosarcoma (OS), a tumor of the bone, to target primary tumor satellites left behind in tumor surrounding tissue after surgical tumor resection. The treatment aims at decreasing the number of recurrences and at reducing the risk for (postoperative) metastasis. In the present study, we present in vitro PDT procedures to establish the optimal PDT settings for effective treatment of widely used OS cell lines that are used to reproduce the human disease in well established intratibial OS mouse models. The uptake of the PS mTHPC was examined with a spectrophotometer and phototoxicity was provoked with laser light excitation of mTHPC at 652 nm to induce cell death assessed with a WST-1 assay and by the counting of surviving cells. The established techniques enable us to define the optimal PDT settings for future studies in animal models. They are an easy and quick tool for the evaluation of the efficacy of PDT in vitro before an application in vivo.

Autophagy Modulation in Disease Therapy: Where Do We Stand?

Since it was first described more than 50 years ago autophagy has been examined in many contexts, from cell survival to pathogen sequestration and removal. In more recent years our understanding of autophagy has developed sufficiently to allow effective targeted therapeutics to be developed against various diseases. The field of autophagy research is expanding rapidly, demonstrated by increases in both numbers of investigators in the field and the breadth of topics being addressed. Some diseases, such as the many cancers, have come to the fore in autophagy therapeutics research as a better understanding of their underlying mechanisms has surfaced. Numerous treatments are being developed and explored, from creative applications of the classic autophagy modulators chloroquine and rapamycin, to repurposing drugs approved for other treatments, such as astemizole, which is currently in use as an antimalarial and chronic rhinitis treatment. The landscape of autophagy modulation in disease therapy is rapidly changing and this review hopes to provide a cross-section of the current state of the field.

Targeting tumour energy metabolism potentiates the cytotoxicity of 5-aminolevulinic acid photodynamic therapy

Background:

Cancerous cells usually exhibit increased aerobic glycolysis, compared with normal tissue (the Warburg effect), making this pathway an attractive therapeutic target.

Methods:

Cell viability, cell number, clonogenic assay, reactive oxygen (ROS), ATP, and apoptosis were assayed in MCF-7 tumour cells and corresponding primary human mammary epithelial cells (HMEC).

Results:

Combining the glycolysis inhibitors 2-deoxyglucose (2DG; 180 mM) or lonidamine (300 μM) with 10 J cm⁻² 5-aminolevulinic acid (ALA) photodynamic therapy (PDT) increases MCF-7 cytotoxicity (by 3.5-fold to 70% death after 24 h, and by 10-fold in 9-day clonogenic assays). However, glycolysis inhibition only slightly increases HMEC PDT cytotoxicity (between two-fold and three-fold to a maximum of 9% death after 24 h). The potentiation of PDT cytotoxicity only occurred if the glycolysis inhibitors were added after ALA incubation, as they inhibited intracellular accumulation of photosensitiser if coincubated with ALA.

Conclusion:

As 2DG and lonidamine are already used as cancer chemotherapeutic agents, our results are directly translatable to combination therapies with existing topical PDT.