Photodynamic therapy: apoptosis, paraptosis and beyond

Synthesis and evaluation of 5,15-diaryltetrabenzoporphyrins as photosensitizers for photo-diagnosis and photodynamic activity of tumors

Photodynamic therapy (PDT) is a well-established treatment modality, typically conducted with single-wavelength irradiation, which may not always be optimal for varying tumor locations and sizes. To address this, photosensitizers with absorption wavelengths ranging from 550 to 760 nm are being explored. Herein, a series of 5,15-diaryltetrabenzoporphyrins (Ar2TBPs) were synthesized. All compounds displayed obvious absorption at 550-700 nm (especially at ∼668 nm), intense fluorescence, efficient generation of singlet oxygen and good photodynamic antitumor effects. Notably, compound I3 (5,15-bis[(4-carboxymethoxy)phenyl]tetrabenzoporphyrin) showed excellent cytotoxicity against Eca-109 cell line upon red light irradiation, with an IC50 value of 0.45 μM, and phototherapeutic index of 25.8. Flow cytometry revealed that I3 could induce distinct cell apoptosis. In vivo studies revealed that compound I3 selectively accumulated at tumor site and exhibited outstanding PDT effect with antitumor activity under single-time administration and light irradiation, and revealed more efficiency than the clinical photosensitizer Verteporfin. These findings underscore the considerable promise of I3 as a robust theranostic agent, offering capabilities in real-time fluorescence imaging and serving as a potent photosensitizer for personalized and precise photodynamic therapy of tumors.

Oxidative cell death in cancer: mechanisms and therapeutic opportunities

Reactive oxygen species (ROS) are highly reactive oxygen-containing molecules generated as natural byproducts during cellular processes, including metabolism. Under normal conditions, ROS play crucial roles in diverse cellular functions, including cell signaling and immune responses. However, a disturbance in the balance between ROS production and cellular antioxidant defenses can lead to an excessive ROS buildup, causing oxidative stress. This stress damages essential cellular components, including lipids, proteins, and DNA, potentially culminating in oxidative cell death. This form of cell death can take various forms, such as ferroptosis, apoptosis, necroptosis, pyroptosis, paraptosis, parthanatos, and oxeiptosis, each displaying distinct genetic, biochemical, and signaling characteristics. The investigation of oxidative cell death holds promise for the development of pharmacological agents that are used to prevent tumorigenesis or treat established cancer. Specifically, targeting key antioxidant proteins, such as SLC7A11, GCLC, GPX4, TXN, and TXNRD, represents an emerging approach for inducing oxidative cell death in cancer cells. This review provides a comprehensive summary of recent progress, opportunities, and challenges in targeting oxidative cell death for cancer therapy.

Theranostic dye entrapped in an optimized blended-polymer matrix for effective photodynamic inactivation of diseased cells

Despite the wide range of treatment options available for cancer therapy, including chemotherapy, radiation therapy, and surgical procedures, each of these treatments has a different side-effect profile and leaves the patient with no option but to choose. Due to their insensitivity and nonspecificity, conventional treatments damage normal cells together with cancer cells. In recent years, a significant amount of attention has been focused on photodynamic therapy (PDT) as a treatment for cancer and drug-resistant microbes. An activated photosensitizer is used as a part of the procedure along with oxygen molecules and a specific wavelength of light belonging to the visible or NIR spectral zone. A light-sensitive laser dye, rhodamine 6G (R6G), was used in the present study as a photosensitizer, taking a challenge to improve the aqueous solubility and ROS quantum yield using optimum concentration (160 mg/ml) of chitosan-alginate (Cs-Alg) blended polymeric nanoformulations. As evidenced by steady-state spectrophotometric and fluorometric measurements, ROS quantum yield increases three-fold over aqueous solution along with solubility gaining that was validated by PDT experiment using human epithelial carcinoma (KB) cell line. Phantom optical imaging was taken using the IVIS imaging system to establish the formulations as a fluorescence-based optical contrast agent, and zebrafish embryos were used to establish their safe in vivo use. The release profile of R6G was fitted using kinetic models, which followed the Non-Fickian kinetic profile. In conclusion, we recommend the formulations as a potential theranostic agent that will aid in PDT-based therapy in conjunction with optical imaging-based diagnosis.

The effect of autophagy on hemoporfin-mediated photodynamic therapy in human umbilical vein endothelial cells

SIGNIFICANCE

Hemoporfin-mediated photodynamic therapy (HMME-PDT) has been recognized as a safe and effective treatment for port wine stain (PWS). However, some patients show limited improvement even after multiple treatments. Herein, we aim to explore the effect of autophagy on HMME-PDT in human umbilical vein endothelial cells (HUVECs), so as to provide theoretical basis and treatment strategies to enhance clinical effectiveness.

METHODS

Establish the in vitro HMME-PDT system by HUVECs. Apoptosis and necrosis were identified by Annexin Ⅴ-FITC/PI flow cytometry, and autophagy flux was detected by monitoring RFP-GFP-LC3 under the fluorescence microscope. Hydroxychloroquine and rapamycin were employed in the mechanism study. Specifically, the certain genes and proteins were qualified by qPCR and Western Blot, respectively. The cytotoxicity was measured by CCK-8, VEGF-A secretion was determined by ELISA, and the tube formation of HUVECs was observed by angiogenesis assay.

RESULTS

In vitro experiments revealed that autophagy and apoptosis coexisted in HUVECs treated by HMME-PDT. Apoptosis was dominant in early stage, while autophagy gradually increased in the middle and late stage. AMPK, AKT and mTOR participated in the regulation of autophagy induced by HMME-PDT, in which AMPK was positive regulation, while AKT and mTOR were negative regulation. Hydroxychloroquine could not inhibit HMME-PDT-induced autophagy, but capable of blocking the fusion of autophagosomes with lysosome. Rapamycin might cooperate with HMME-PDT to enhance autophagy in HUVECs, leading to increased cytotoxicity, reduced VEGF-A secretion, and weakened angiogenesis ability.

CONCLUSIONS

Both autophagy and apoptosis contribute to HMME-PDT-induced HUVECs death. Pretreatment of HUVECs with rapamycin to induce autophagy might enhance the photodynamic killing effect of HMME-PDT on HUVECs. The combination of Rapamycin and HMME-PDT is expected to further improve the clinical efficacy.

Self-Amplified pH/ROS Dual-Responsive Co-Delivery Nano-System with Chemo-Photodynamic Combination Therapy in Hepatic Carcinoma Treatment

Background

Chemo-photodynamic combination therapy has demonstrated significant potential in the treatment of cancer. Triptolide (TPL), a naturally derived anticancer agent, when combined with the photosensitizer Chlorin e6 (Ce6), has shown to provide enhanced anti-tumor benefits. However, the development of stimuli-responsive nanovehicles for the co-delivery of TPL and Ce6 could further enhance the efficacy of this combination therapy.

Methods

In this study, we synthesized a pH/ROS dual-responsive mPEG-TK-PBAE copolymer, which contains a pH-sensitive PBAE moiety and a ROS-sensitive thioketal (TK) linkage. Through a self-assembly process, TPL and Ce6 were successfully co-loaded into mPEG-TK-PBAE nanoparticles, hereafter referred to as TPL/Ce6 NPs. We evaluated the pH- and ROS-sensitive drug release and particle size changes. Furthermore, we investigated both the in vitro suppression of cellular proliferation and induction of apoptosis in HepG2 cells, as well as the in vivo anti-tumor efficacy of TPL/Ce6 NPs in H22 xenograft nude mice.

Results

The mPEG-TK-PBAE copolymer was synthesized through a one-pot Michael-addition reaction and successfully co-encapsulated both TPL and Ce6 by self-assembly. Upon exposure to acid pH values and high ROS levels, the payloads in TPL/Ce6 NPs were rapidly released. Notably, the abundant ROS generated by the released Ce6 under laser irradiation further accelerated the degradation of the nanosystem, thereby amplifying the tumor microenvironment-responsive drug release and enhancing anticancer efficacy. Consequently, TPL/Ce6 NPs significantly increased PDT-induced oxidative stress and augmented TPL-induced apoptosis in HepG2 cells, leading to synergistic anticancer effects in vitro. Moreover, administering TPL/Ce6 NPs (containing 0.3 mg/kg of TPL and 4 mg/kg of Ce6) seven times, accompanied by 650 nm laser irradiation, efficiently inhibited tumor growth in H22 tumor-bearing mice, while exhibiting lower systemic toxicity.

Conclusion

Overall, we have developed a tumor microenvironment-responsive nanosystem for the co-delivery of TPL and Ce6, demonstrating amplified synergistic effects of chemo-photodynamic therapy (chemo-PDT) for hepatocellular carcinoma (HCC) treatment.

Indocyanine green based photodynamic therapy for keloids: Fundamental investigation and clinical improvement

BACKGROUND

Keloid, a prevalent pathological skin lesion, presents significant challenges in terms of treatment efficacy. Photodynamic therapy (PDT), an increasingly popular adjuvant treatment, has shown significant potential in the management of various disorders, including cancer. However, the therapeutic potential of indocyanine green-mediated photodynamic therapy (ICG-PDT) for keloids has not yet been demonstrated.

METHODS

In this study, we divided the experimental groups into control group, Photothermal Therapy group, Photodynamic Therapy group, and Combined Therapy group. The in vitro investigation aimed to optimize the clinical application of PDT for keloid treatment by elucidating its underlying mechanism. Subsequently, on this basis, we endeavored to manage a clinical case of keloid by employing surgical intervention in conjunction with modified ICG-PDT.

RESULTS

Our investigation revealed an unexpected outcome that ICG-PDT maximally inhibited the cellular activity and migration of keloid fibroblasts only when photodynamic mechanism took effect. Additionally, the induction of autophagy and apoptosis, as well as the inhibition of collagen synthesis, were particularly evident in this experimental group. Furthermore, the above therapeutic effect could be achieved at remarkably low drug concentrations. Building upon the aforementioned experimental findings, we successfully optimized the treatment modality for the latest case and obtained a more favorable treatment outcome.

CONCLUSIONS

This study investigated the mechanism of ICG-PDT treatment and optimized the in vivo treatment regimen, demonstrating the significant therapeutic potential of ICG-PDT treatment in clinical keloid treatment.

Stimuli-Responsive Polymer-Based Nanosystems for Cancer Theranostics

Stimuli-responsive polymers can respond to internal stimuli, such as reactive oxygen species (ROS), glutathione (GSH), and pH, biological stimuli, such as enzymes, and external stimuli, such as lasers and ultrasound, etc., by changing their hydrophobicity/hydrophilicity, degradability, ionizability, etc., and thus have been widely used in biomedical applications. Due to the characteristics of the tumor microenvironment (TME), stimuli-responsive polymers that cater specifically to the TME have been extensively used to prepare smart nanovehicles for the targeted delivery of therapeutic and diagnostic agents to tumor tissues. Compared to conventional drug delivery nanosystems, TME-responsive nanosystems have many advantages, such as high sensitivity, broad applicability among different tumors, functional versatility, and improved biosafety. In recent years, a great deal of research has been devoted to engineering efficient stimuli-responsive polymeric nanosystems, and significant improvement has been made to both cancer diagnosis and therapy. In this review, we summarize some recent research advances involving the use of stimuli-responsive polymer nanocarriers in drug delivery, tumor imaging, therapy, and theranostics. Various chemical stimuli will be described in the context of stimuli-responsive nanosystems. Accordingly, the functional chemical groups responsible for the responsiveness and the strategies to incorporate these groups into the polymer will be discussed in detail. With the research on this topic expending at a fast pace, some innovative concepts, such as sequential and cascade drug release, NIR-II imaging, and multifunctional formulations, have emerged as popular strategies for enhanced performance, which will also be included here with up-to-date illustrations. We hope that this review will offer valuable insights for the selection and optimization of stimuli-responsive polymers to help accelerate their future applications in cancer diagnosis and treatment.

Light dose effect of photodynamic therapy on growth inhibition and apoptosis induction in non-small cell lung cancer: A study in nude mouse model

BACKGROUND

Photodynamic therapy (PDT) is receiving increasing attention in treating non-small cell lung cancer (NSCLC) worldwide, but in clinical practice, the relationship between treatment effect and PDT light dose in NSCLC remains unclear. Therefore, we aimed to determine the optimal light dose for PDT by exploring molecular biomarkers and evaluating tumor growth data.

METHODS

We applied bioinformatics to identify promising genes and pathways in NSCLC and PDT. Then, the human lung adenocarcinoma cell line A549-bearing BALB/c nude mice were treated with hematoporphyrin derivative (HPD, 3 mg/kg) that is currently used widely for lung cancer treatment in the world even with photosensitization issues. After 48 h, tumor-bearing mice were irradiated superficially at doses of 100, 200, 300, 400, and 500 J/cm2. The tumor growth data and apoptotic molecules were assessed and calculated.

RESULTS

Bioinformatics results indicated that the apoptosis pathway was significantly enriched and caspase 3 was the most promising biomarker on prognosis in NSCLC-PDT. Compared to the untreated group, there was no difference in the relative tumor volume (RTV) of the 100 J/cm2 group, while the RTV of the other treatment groups (200-500 J/cm2) was significantly lower. In the 100 J/cm2 group, there were significant differences in the complete remission (CR, 0 %) and the percentage of tumor growth inhibition rate (TGI%) over 75 % (20 %) compared with the other treatment groups, especially the 300 and 400 J/cm2 groups (CR 70 %; TGI% 90 %). In the 300 and 400 J/cm2 groups, the expression of caspase 3, cleaved-caspase 3, PARP1, and Bax was increased significantly, while Bcl-2 expression was significantly lower.

CONCLUSIONS

Moderate doses of PDT (300 or 400 J/cm2) are more effective than low (100 or 200 J/cm2) or high doses (500 J/cm2) in the A549 tumor-bearing mice model. Since the A549 tumor is more akin to human tumors in pathological behavior, these experimental data may contribute to improving HPD-PDT illumination protocols for favorable clinical outcomes.

Unleashing novel horizons in advanced prostate cancer treatment: investigating the potential of prostate specific membrane antigen-targeted nanomedicine-based combination therapy

Prostate cancer (PCa) is a prevalent malignancy with increasing incidence in middle-aged and older men. Despite various treatment options, advanced metastatic PCa remains challenging with poor prognosis and limited effective therapies. Nanomedicine, with its targeted drug delivery capabilities, has emerged as a promising approach to enhance treatment efficacy and reduce adverse effects. Prostate-specific membrane antigen (PSMA) stands as one of the most distinctive and highly selective biomarkers for PCa, exhibiting robust expression in PCa cells. In this review, we explore the applications of PSMA-targeted nanomedicines in advanced PCa management. Our primary objective is to bridge the gap between cutting-edge nanomedicine research and clinical practice, making it accessible to the medical community. We discuss mainstream treatment strategies for advanced PCa, including chemotherapy, radiotherapy, and immunotherapy, in the context of PSMA-targeted nanomedicines. Additionally, we elucidate novel treatment concepts such as photodynamic and photothermal therapies, along with nano-theragnostics. We present the content in a clear and accessible manner, appealing to general physicians, including those with limited backgrounds in biochemistry and bioengineering. The review emphasizes the potential benefits of PSMA-targeted nanomedicines in enhancing treatment efficiency and improving patient outcomes. While the use of PSMA-targeted nano-drug delivery has demonstrated promising results, further investigation is required to comprehend the precise mechanisms of action, pharmacotoxicity, and long-term outcomes. By meticulous optimization of the combination of nanomedicines and PSMA ligands, a novel horizon of PSMA-targeted nanomedicine-based combination therapy could bring renewed hope for patients with advanced PCa.

Unleashing novel horizons in advanced prostate cancer treatment: investigating the potential of prostate specific membrane antigen-targeted nanomedicine-based combination therapy

Prostate cancer (PCa) is a prevalent malignancy with increasing incidence in middle-aged and older men. Despite various treatment options, advanced metastatic PCa remains challenging with poor prognosis and limited effective therapies. Nanomedicine, with its targeted drug delivery capabilities, has emerged as a promising approach to enhance treatment efficacy and reduce adverse effects. Prostate-specific membrane antigen (PSMA) stands as one of the most distinctive and highly selective biomarkers for PCa, exhibiting robust expression in PCa cells. In this review, we explore the applications of PSMA-targeted nanomedicines in advanced PCa management. Our primary objective is to bridge the gap between cutting-edge nanomedicine research and clinical practice, making it accessible to the medical community. We discuss mainstream treatment strategies for advanced PCa, including chemotherapy, radiotherapy, and immunotherapy, in the context of PSMA-targeted nanomedicines. Additionally, we elucidate novel treatment concepts such as photodynamic and photothermal therapies, along with nano-theragnostics. We present the content in a clear and accessible manner, appealing to general physicians, including those with limited backgrounds in biochemistry and bioengineering. The review emphasizes the potential benefits of PSMA-targeted nanomedicines in enhancing treatment efficiency and improving patient outcomes. While the use of PSMA-targeted nano-drug delivery has demonstrated promising results, further investigation is required to comprehend the precise mechanisms of action, pharmacotoxicity, and long-term outcomes. By meticulous optimization of the combination of nanomedicines and PSMA ligands, a novel horizon of PSMA-targeted nanomedicine-based combination therapy could bring renewed hope for patients with advanced PCa.

V. J, Pal S, Nair BG, Kar R, Mishra N. Paraptosis: a unique cell death mode for targeting cancer

Programmed cell death (PCD) is the universal process that maintains cellular homeostasis and regulates all living systems' development, health and disease. Out of all, apoptosis is one of the major PCDs that was found to play a crucial role in many disease conditions, including cancer. The cancer cells acquire the ability to escape apoptotic cell death, thereby increasing their resistance towards current therapies. This issue has led to the need to search for alternate forms of programmed cell death mechanisms. Paraptosis is an alternative cell death pathway characterized by vacuolation and damage to the endoplasmic reticulum and mitochondria. Many natural compounds and metallic complexes have been reported to induce paraptosis in cancer cell lines. Since the morphological and biochemical features of paraptosis are much different from apoptosis and other alternate PCDs, it is crucial to understand the different modulators governing it. In this review, we have highlighted the factors that trigger paraptosis and the role of specific modulators in mediating this alternative cell death pathway. Recent findings include the role of paraptosis in inducing anti-tumour T-cell immunity and other immunogenic responses against cancer. A significant role played by paraptosis in cancer has also scaled its importance in knowing its mechanism. The study of paraptosis in xenograft mice, zebrafish model, 3D cultures, and novel paraptosis-based prognostic model for low-grade glioma patients have led to the broad aspect and its potential involvement in the field of cancer therapy. The co-occurrence of different modes of cell death with photodynamic therapy and other combinatorial treatments in the tumour microenvironment are also summarized here. Finally, the growth, challenges, and future perspectives of paraptosis research in cancer are discussed in this review. Understanding this unique PCD pathway would help to develop potential therapy and combat chemo-resistance in various cancer.

Photodynamic and Photothermal Therapies: Synergy Opportunities for Nanomedicine

Tumoricidal photodynamic (PDT) and photothermal (PTT) therapies harness light to eliminate cancer cells with spatiotemporal precision by either generating reactive oxygen species or increasing temperature. Great strides have been made in understanding biological effects of PDT and PTT at the cellular, vascular and tumor microenvironmental levels, as well as translating both modalities in the clinic. Emerging evidence suggests that PDT and PTT may synergize due to their different mechanisms of action, and their nonoverlapping toxicity profiles make such combination potentially efficacious. Moreover, PDT/PTT combinations have gained momentum in recent years due to the development of multimodal nanoplatforms that simultaneously incorporate photodynamically- and photothermally active agents. In this review, we discuss how combining PDT and PTT can address the limitations of each modality alone and enhance treatment safety and efficacy. We provide an overview of recent literature featuring dual PDT/PTT nanoparticles and analyze the strengths and limitations of various nanoparticle design strategies. We also detail how treatment sequence and dose may affect cellular states, tumor pathophysiology and drug delivery, ultimately shaping the treatment response. Lastly, we analyze common experimental design pitfalls that complicate preclinical assessment of PDT/PTT combinations and propose rational guidelines to elucidate the mechanisms underlying PDT/PTT interactions.

Combination of Two Photosensitisers in Anticancer, Antimicrobial and Upconversion Photodynamic Therapy

Photodynamic therapy (PDT) is a special form of phototherapy in which oxygen is needed, in addition to light and a drug called a photosensitiser (PS), to create cytotoxic species that can destroy cancer cells and various pathogens. PDT is often used in combination with other antitumor and antimicrobial therapies to sensitise cells to other agents, minimise the risk of resistance and improve overall outcomes. Furthermore, the aim of combining two photosensitising agents in PDT is to overcome the shortcomings of the monotherapeutic approach and the limitations of individual agents, as well as to achieve synergistic or additive effects, which allows the administration of PSs in lower concentrations, consequently reducing dark toxicity and preventing skin photosensitivity. The most common strategies in anticancer PDT use two PSs to combine the targeting of different organelles and cell-death mechanisms and, in addition to cancer cells, simultaneously target tumour vasculature and induce immune responses. The use of PDT with upconversion nanoparticles is a promising approach to the treatment of deep tissues and the goal of using two PSs is to improve drug loading and singlet oxygen production. In antimicrobial PDT, two PSs are often combined to generate various reactive oxygen species through both Type I and Type II processes.

Photochemical defense as trait of fungi from Cortinarius subgenus Dermocybe

The photobiological activity of ten colorful species belonging to subgenus Dermocybe of the basidiomycete genus Cortinarius was investigated. Extracts of all species produced singlet oxygen and are thus photoactive. Pigment analysis was performed and showed similarities of the anthraquinone pigments across the species in dependency to their respective pigmentation types. Detailed content analysis of the pigments in the whole agaricoid fruiting body compared to the three different tissue types (pileus, stipe, and lamellae) revealed that the pigments emodin, dermocybin, and dermorubin, as well as their respective glycosides, are enhanced in the gills. In an independent experiment, the gills were shown to be the most photoactive tissues of the fruiting body. Photobiological experiments with invertebrates (i.e., glassworm Chaoborus crystallinus) proved a phototoxic effect of the methanolic extract of the red blood webcap (Cortinarius sanguineus var. aurantiovaginatus). This work adds further evidence to a common photobiological trait in Cortinarius subgenus Dermocybe and underpins the possibility of a photochemical defense mechanism in fungi.

An open-source LED array illumination system for automated multiwell plate cell culture photodynamic therapy experiments

Photodynamic therapy (PDT) research would benefit from an automated, low-cost, and easy-to-use cell culture light treatment setup capable of illuminating multiple well replicates within standard multiwell plate formats. We present an LED-array suitable for performing high-throughput cell culture PDT experiments. The setup features a water-cooling loop to keep the LED-array temperature nearly constant, thus stabilizing the output power and spectrum. The setup also features two custom-made actuator arms, in combination with a pulse-width-modulation (PWM) technique, to achieve programmable and automatic light exposures for PDT. The setup operates at ~ 690 nm (676-702 nm, spectral output full-width half-maximum) and the array module can be readily adapted to other LED wavelengths. This system provides an illumination field with adjustable irradiance up to 400 mW/cm² with relatively high spectral and power stability comparing with previously reported LED-based setups. The light doses provided by the LED array were validated with comparison to traditional laser PDT. This open-source illumination platform (including the detailed technical description, fabrication protocols, and parts list provided here) helps to make custom light sources more accessible and of practical use for photomedicine research.

Critical PDT theory II: Current concepts and indications

While photodynamic therapy (PDT) is effective for the eradication of select neoplasia and certain other pathologic conditions, it has yet to achieve wide acceptance in clinical medicine. A variety of factors contribute to this situation including relations with the pharmaceutical industry that have often been problematic. Some current studies relating to photodynamic effects are 'phenomenological', i.e., they describe phenomena that only reiterate what is already known. The net result has been a tendency of granting agencies to become disillusioned with support for PDT research. This report is intended to provide some thoughts on current research efforts that improve clinical relevance and those that do not.

Programmed cell death lives

Research on cell death mechanisms gets a lot of attention. This is understandable as it underlies biology in general, as well as the insight in pathological conditions and the development of opportunities for therapeutic intervention. Over the last years a steady rise in the number of scientific reports and in the impact of this literature on the different mechanisms of programmed cell death can be observed. A number of new concepts are highlighted.

Critical PDT Theory III: Events at the Molecular and Cellular Level

Photodynamic therapy (PDT) is capable of eradicating neoplastic cells that are accessible to sufficient light and oxygen. There is adequate information now available for assessing conditions where PDT might be the therapy of choice, but limited access to clinical facilities and impediments to regulatory approval of new agents have limited clinical usage. Early reports mainly involved clinical data with few thoughts towards finding death pathways. In 2022, there is a clear understanding of the determinants of successful tumor eradication. While PDT may be the optimal method for many clinical indications, support for this approach has lagged. This report provides a commentary on some elements of recent progress in PDT at the molecular and cellular levels, along with a discussion of some of the limitations in current research efforts.

Plasmon-Enhanced Photodynamic Therapy for Gastric Cancer by Integrating Targeted Gold Nanorods and Photosensitizer

Gold nanoparticles are widely used for biomedical purposes because of their unique optical, surface plasmon resonance properties, ease of surface functionalization, and high load capacity. Gold nanorods (AuNR), which are rod-shaped gold nanoparticles, have been used as an effective photodynamic treatment (PDT) carrier to boost singlet oxygen (SOG) generation through localized surface plasmon resonance (LSPR) effect and then improve PDT efficacy. However, the suitable spatial location should be established to enable photosensitizer to feel the LSPR enhancement. In this study, we utilized multifunctional PEG chain to adjust efficient distance to induce more photosensitizers to feel the enhanced LSPR effect of AuNR and used a novel gastric tumor angiogenesis marker to prevent the uncontrolled LSPR shift induced by the aggregation of AuNR, and then acquire plasmon-enhanced PDT. The synthesized nano-system of integrated photosensitizer and targeted AuNR could significantly enhance SOG generation and improve the apoptosis-inducing ability through activation of the mitochondria-mediated apoptotic pathway, and -shorten the induction time for apoptosis, thus acquire efficient plasmon-enhanced PDT. Comparing to the normal photosensitizer, half of the targeted photosensitizer produce same antitumor effect, which improves maximum tolerable dose. Generally, this novel targeted delivery system is a promising agent of plasmon-enhanced PDT for gastric cancer.

Forging Forward in Photodynamic Therapy

In 1978, a Cancer Research article by Dougherty and colleagues reported the first large-scale clinical trial of photodynamic therapy (PDT) for treatment of 113 cutaneous or subcutaneous lesions associated with ten different kinds of malignancies. In classic applications, PDT depends on excitation of a tissue-localized photosensitizer with wavelengths of visible light to damage malignant or otherwise diseased tissues. Thus, in this landmark article, photosensitizer (hematoporphyrin derivative) dose, drug-light interval, and fractionation scheme were evaluated for their therapeutic efficacy and normal tissue damage. From their observations came early evidence of the mechanisms of PDT's antitumor action, and in the decades since this work, our knowledge of these mechanisms has grown to build an understanding of the multifaceted nature of PDT. These facets are comprised of multiple cell death pathways, together with antivascular and immune stimulatory actions that constitute a PDT reaction. Mechanism-informed PDT protocols support the contribution of PDT to multimodality treatment approaches. Moreover, guided by an understanding of its mechanisms, PDT can be applied to clinical needs in fields beyond oncology. Undoubtedly, there still remains more to learn; new modes of cell death continue to be elucidated with relevance to PDT, and factors that drive PDT innate and adaptive immune responses are not yet fully understood. As research continues to forge a path forward for PDT in the clinic, direction is provided by anchoring new applications in mechanistically grounded protocol design, as was first exemplified in the landmark work conducted by Dougherty and colleagues. See related article by Dougherty and colleagues, Cancer Res 1978;38:2628-35.

Charged groups on pyropheophorbide-based photosensitizers dictate uptake by tumor cells and photodynamic therapy efficacy

This study investigated the impact of anionic and cationic substituents of the pyropheophorbide-based photosensitizers (PS) on uptake and retention by tumor epithelial cells and photodynamic therapy (PDT). A series of PSs were generated that bear carboxylic acid functionalities, alkyl amines with variable length of carbon units or as a quaternary ammonium salt introduced at position 17² of 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH). The nature of the functionalities in the macrocycle made a significant difference in overall lipophilicity (log D values at pH 7.4), and in binding to and retention by human and murine tumor cells. Depending on the presence of functional groups, the PSs showed a change in cellular uptake from diffusion to endocytosis and in the preference for subcellular localization to mitochondria/ER or lysosomes. Two and more carboxylic groups drastically reduced uptake by all cell types. In contrast, PSs with amine and quaternary amine salt showed higher cellular binding, uptake and in vitro PDT efficacy than HPPH. The enhanced cellular uptake of the cationic PSs was accompanied by a loss of tumor cell specificity and contributed to severe systemic toxicity in tumor-bearing mice intravenously injected with the PS and subjected to investigate their therapeutic potential.

A pH-sensitive supramolecular nanosystem with chlorin e6 and triptolide co-delivery for chemo-photodynamic combination therapy

The combination of Ce6, an acknowledged photosensitizer, and TPL, a natural anticancer agent, has been demonstrated as a useful strategy to reinforce the tumor growth suppression, as well as decrease the systemic side effects compared with their monotherapy. However, in view of the optimal chemo-photodynamic combination efficiency, there is still short of the feasible nanovehicle to steadily co-deliver Ce6 and TPL, and stimuli-responsively burst release drugs in tumor site. Herein, we described the synergistic antitumor performance of a pH-sensitive supramolecular nanosystem, mediated by the host–guest complexing between β-CD and acid pH-responsive amphiphilic co-polymer mPEG-PBAE-mPEG, showing the shell–core structural micelles with the tight β-CD layer coating. Both Ce6 and TPL were facilely co-loaded into the spherical supramolecular NPs (TPL+Ce6/NPs) by one-step nanoprecipitation method, with an ideal particle size (156.0 nm), acid pH-responsive drug release profile, and enhanced cellular internalization capacity. In view of the combination benefit of photodynamic therapy and chemotherapy, as well as co-encapsulation in the fabricated pH-sensitive supramolecular NPs, TPL+Ce6/NPs exhibited significant efficacy to suppress cellular proliferation, boost ROS level, lower MMP, and promote cellular apoptosis in vitro. Particularly, fluorescence imaging revealed that TPL+Ce6/NPs preferentially accumulated in the tumor tissue area, with higher intensity than that of free Ce6. As expected, upon 650-nm laser irradiation, TPL+Ce6/NPs exhibited a cascade of amplified synergistic chemo-photodynamic therapeutic benefits to suppress tumor progression in both hepatoma H22 tumor-bearing mice and B16 tumor-bearing mice. More importantly, lower systemic toxicity was found in the tumor-bearing mice treated with TPL+Ce6/NPs. Overall, the designed supramolecular TPL+Ce6/NPs provided a promising alternative approach for chemo-photodynamic therapy in tumor treatment.

Metal Nanoparticles for Photodynamic Therapy: A Potential Treatment for Breast Cancer

Breast cancer (BC) is the most common malignant tumor in women worldwide, which seriously threatens women’s physical and mental health. In recent years, photodynamic therapy (PDT) has shown significant advantages in cancer treatment. PDT involves activating photosensitizers with appropriate wavelengths of light, producing transient levels of reactive oxygen species (ROS). Compared with free photosensitizers, the use of nanoparticles in PDT shows great advantages in terms of solubility, early degradation, and biodistribution, as well as more effective intercellular penetration and targeted cancer cell uptake. Under the current circumstances, researchers have made promising efforts to develop nanocarrier photosensitizers. Reasonably designed photosensitizer (PS) nanoparticles can be achieved through non-covalent (self-aggregation, interfacial deposition, interfacial polymerization or core-shell embedding and physical adsorption) or covalent (chemical immobilization or coupling) processes and accumulate in certain tumors through passive and/or active targeting. These PS loading methods provide chemical and physical stability to the PS payload. Among nanoparticles, metal nanoparticles have the advantages of high stability, adjustable size, optical properties, and easy surface functionalization, making them more biocompatible in biological applications. In this review, we summarize the current development and application status of photodynamic therapy for breast cancer, especially the latest developments in the application of metal nanocarriers in breast cancer PDT, and highlight some of the recent synergistic therapies, hopefully providing an accessible overview of the current knowledge that may act as a basis for new ideas or systematic evaluations of already promising results.

Current Clinical and Pre-Clinical Imaging Approaches to Study the Cancer-Associated Immune System

In the light of the success and the expected growth of its arsenal, immuno-therapy may become the standard neoadjuvant procedure for many cancers in the near future. However, aspects such as the identity, organization and the activation status of the peri- and intra-tumoral immune cells would represent important elements to weigh in the decision for the appropriate treatment. While important progress in non-invasive imaging of immune cells has been made over the last decades, it falls yet short of entering the clinics, let alone becoming a standard procedure. Here, we provide an overview of the different intra-vital imaging approaches in the clinics and in pre-clinical settings and discuss their benefits and drawbacks for assessing the activity of the immune system, globally and on a cellular level. Stimulated by further research, the future is likely to see many technological advances both on signal detection and emission as well as image specificity and resolution to tackle current hurdles. We anticipate that the ability to precisely determine an immune stage of cancer will capture the attention of the oncologist and will create a change in paradigm for cancer therapy.

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.

Interrelationship among paraptosis, apoptosis and autophagy in lung cancer A549 cells induced by BEAP, an antitumor protein isolated from the edible porcini mushroom Boletus edulis

In today's world, cancer is still the leading cause of human death. Among them, the incidence and mortality of lung cancer remain high, and have become the focus of research in the world. BEAP, a protein with anti-lung cancer activity, was isolated and purified from the edible mushroom Boletus edulis. Previous studies have shown that BEAP can inhibit the proliferation of non-small cell lung cancer A549 cells by inducing apoptosis and cell cycle arrest in vitro and in vivo. However, there are many ways in which antitumor proteins from edible and medicinal mushroom play their roles. It is worth exploring whether there are other antitumor mechanisms of BEAP, which can provide reference value for the development of new drugs targeting non-small cell lung cancer and the repurposing of existing drugs.

Recent Advances in the Use of Iron-Gold Hybrid Nanoparticles for Biomedical Applications

Recently, there has been an increased interest in iron-gold-based hybrid nanostructures, due to their combined outstanding optical and magnetic properties resulting from the usage of two separate metals. The synthesis of these nanoparticles involves thermal decomposition and modification of their surfaces using a variety of different methods, which are discussed in this review. In addition, different forms such as core-shell, dumbbell, flower, octahedral, star, rod, and Janus-shaped hybrids are discussed, and their unique properties are highlighted. Studies on combining optical response in the near-infrared window and magnetic properties of iron-gold-based hybrid nanoparticles as multifunctional nanoprobes for drug delivery, magnetic-photothermal heating as well as contrast agents during magnetic and optical imaging and magnetically-assisted optical biosensing to detect traces of targeted analytes inside the body has been reviewed.

Paraptosis after ER Photodamage Initiated by m-tetra(hydroxyphenyl) Chlorin

Two cell lines, A549 (human-derived nonsmall-cell lung cancer) and 1c1c7 (mouse hepatoma), were photosensitized with m-THPC and irradiated under LD₉₀ conditions. After 4 h, a pattern of cytoplasmic vacuoles had formed consistent with the initiation of paraptosis. After irradiation, there was no detectable loss of the mitochondrial membrane potential indicating no significant photodamage to mitochondria. We did, however, observe localization of m-THPC in the endoplasmic reticulum (ER), as indicated by fluorescence microscopy. Subsequent ER perturbation is known to result in initiation of paraptosis, another pathway to cell death. While an apoptotic response to m-THPC has been reported, the ability to target ER and induce paraptosis could explain the efficacy of this agent which could therefore eradicate cell types with an impaired apoptotic response.

Death Pathways Associated with Photodynamic Therapy

This report describes studies involving ER vs. lysosomal targeting and is designed to assess the initiation of different death pathways as a function of subcellular targeting and PDT dose. Photodamage directed at mitochondria or lysosomes initiates apoptosis, a death pathway generally considered to be irreversible. Photodamage that involves the ER can lead to another death pathway termed paraptosis. This does not involve caspase activation, can eradicate cell types with impaired apoptosis; at high levels of irradiation, apoptosis and necrosis were observed. Autophagy has a cytoprotective function unless lysosomes are targeted; loss of lysosomal integrity can interfere with the autophagic recycling processes.

An update in clinical utilization of photodynamic therapy for lung cancer

Lung cancer is one of the leading causes of cancer-related death worldwide, with nearly 1.8 million-diagnosis and 1.59 million deaths. Surgery, radiotherapy, and chemotherapy in individual or combination are commonly used to treat lung cancers. Photodynamic therapy (PDT) is a highly selective method for the destruction of cancer cells by exerting cytotoxic activity on malignant cells. PDT has been the subject of numerous clinical studies and has proven to be an effective strategy for cancer therapy. Clinical studies revealed that PDT could prolong survival in patients with inoperable cancers and significantly improve quality of life. For inoperable lung cancer cases, PDT could be an effective therapy. Despite the clinical success reported, PDT is still currently underutilized to treat lung cancer and other tumors. PTD is still a new treatment approach for lung cancer mainly due to the lack of enough clinical research evaluating its' effectiveness and side effects. In this review, we discuss the current prospects and future potentials of PDT in lung cancer treatment.