In Vitro and In Vivo Antipsoriatic Efficacy of Protected and Unprotected Sugar-Zinc Phthalocyanine Conjugates.

Psoriasis, a chronic immune-mediated skin disorder affecting over 125 million people globally, is characterized by abnormal keratinocyte proliferation and immune cell infiltration. Photodynamic therapy (PDT) remains underutilized in the treatment of psoriasis despite its potential as a promising and effective therapeutic approach. This study aimed to explore the efficacy of zinc phthalocyanine (ZnPc) and its sugar conjugates as potential antipsoriatic agents. We successfully synthesized protected and unprotected sugar-conjugated zinc phthalocyanines and evaluated their potential against cytokine-stimulated HaCaT keratinocytes, as well as an established IMQ psoriasis-like in vivo model. Tetrasubstituted protected glucose-ZnPc (Glu-4-ZnPc-P) demonstrated superior phototoxicity (IC50 = 2.55 µM) compared to unprotected glucose conjugate (IC50 = 22.7 µM), protected galactose-ZnPc (IC50 = 7.13 µM), and free ZnPc in cytokine-stimulated HaCaT cells (IC50 = 5.84 µM). Cellular uptake analysis revealed that IL-17A, a cytokine that plays a central role in the pathogenesis of psoriasis, enhanced unprotected Glu-4-ZnPc uptake by 56.3%, while GLUT1 inhibitor BAY-876 reduced its accumulation by 23.8%. Intracellular ROS generation following Glu-4-ZnPc-P-PDT was significantly increased after stimulation with IL-17A, correlating with in vitro photocytotoxicity. In vivo PDT using Glu-4-ZnPc-P exhibited significant improvement in Psoriasis Area and Severity Index (PASI), inhibiting splenomegaly and restoring normal skin morphology. This study highlights sugar-conjugated zinc phthalocyanines as potential candidates for targeted PDT in psoriasis, providing a basis for further clinical investigations.

NRF2 interacts with distal enhancer and inhibits nitric oxide synthase 2 expression in KRAS-driven pancreatic cancer cells.

Nitric oxide is a pleiotropic free radical produced by three nitric oxide synthases (NOS1-3), of which inducible NOS2 is involved in tumor initiation and progression. In this study, RNA-seq, ChIP-seq and qRT-PCR experiments combined with bioinformatic analyses showed that NRF2 is a repressor of NOS2 gene by maintaining a distal enhancer located 22 kb downstream of TSS in an inactive state. Deletion of NRF2 leads to activation of the enhancer, which exerts a pioneering function before it is fully activated. Specifically, NRF2 controls the expression of NOS2 in response to intracellular oxidative stress and extracellular oxygen pressure. We found that abrogation of NOS2 expression by siRNAs partially reduced the ability of WT Panc-1 cells to form 3D spheroids, but strongly reduced the formation of 3D spheroids by NRF2-depleted Panc-1 cells. Mechanistically, this effect correlates with the finding that NOS2 and nitric oxide stimulate epithelial-to-mesenchymal transition in NRF2-depleted Panc-1 and MIA PaCa-2 cells. We also found that knockdown of NOS2 leads to blockade of 3D matrigel invasion of NRF2-depleted PDAC cells, demonstrating that a short-circuit in the reciprocal regulation of NOS2 and NRF2 attenuates the malignancy of PDAC cells. In summary, we show for the first time that: (i) NRF2 is a suppressor of NOS2 in pancreatic cancer cells; (ii) NRF2 binds to and inactivates an enhancer located 22 kb downstream of TSS of the NOS2 gene; (iii) activation of NOS2 requires suppression of NRF2; (iv) NOS2 is required for NRF2-depleted Panc-1 cells to maintain their malignancy and invasiveness.

Suppression of the KRAS-NRF2 axis shifts arginine into the phosphocreatine energy system in pancreatic cancer cells.

In pancreatic ductal adenocarcinomas (PDAC), the KRASG12D-NRF2 axis controls cellular functions such as redox homeostasis and metabolism. Disruption of this axis through suppression of NRF2 leads to profound reprogramming of metabolism. Unbiased transcriptome and metabolome analyses showed that PDAC cells with disrupted KRASG12D-NRF2 signaling (NRF2-/- cells) shift from aerobic glycolysis to metabolic pathways fed by amino acids. Metabolome, RNA-seq and qRT-PCR analyses revealed a blockade of the urea cycle, making NRF2-/- cells dependent on exogenous arginine for survival. Arginine is channeled into anabolic pathways, including the synthesis of phosphocreatine, which generates an energy buffer essential for cell growth. A similar switch was observed in tumor clones that had survived FOLFIRINOX therapy or blockade of KRAS signaling. Inhibition of the creatine pathway with cyclocreatine reduced both ATP and invasion rate in 3D spheroids from NRF2-deficient PDAC cells. Our study provides basis for the rational development of combination therapies for pancreatic cancer.

Potent Virucidal Activity In Vitro of Photodynamic Therapy with Hypericum Extract as Photosensitizer and White Light against Human Coronavirus HCoV-229E.

The emergent human coronavirus SARS-CoV-2 and its high infectivity rate has highlighted the strong need for new virucidal treatments. In this sense, the use of photodynamic therapy (PDT) with white light, to take advantage of the sunlight, is a potent strategy for decreasing the virulence and pathogenicity of the virus. Here, we report the virucidal effect of PDT based on Hypericum extract (HE) in combination with white light, which exhibits an inhibitory activity of the human coronavirus HCoV-229E on hepatocarcinoma Huh-7 cells. Moreover, despite continuous exposure to white light, HE has long durability, being able to maintain the prevention of viral infection. Given its potent in vitro virucidal capacity, we propose HE in combination with white light as a promising candidate to fight against SARS-CoV-2 as a virucidal compound.

Bystander effect in photosensitized prostate cancer cells with a different grade of malignancy: The role of nitric oxide.

Photodynamic therapy (PDT) is a therapeutic modality based on the simultaneous action of three elements: photosensitizer, light and oxygen. This triad generates singlet oxygen and reactive oxygen species that can reduce the mass of a tumor. PDT is also able to stimulate iNOS, the enzyme that generates nitric oxide (NO). The role of NO in PDT-treated cancer cells has been investigated in several studies. They showed that low iNOS/NO levels stimulate signaling pathways that promote tumor survival, while high iNOS/NO levels arrest tumor growth. There is increasing evidence that ROS/RNS control both proliferation and migration of cells in the vicinity of PDT-treated tumor cells (so-called bystander cells). In this work, we addressed the question of how NO, which is generated by weak PDT, affects bystander cells. We used a conditioned medium: medium of PDT-treated tumor cells containing the stressors produced by the cells was added to untreated cells mimicking the neighboring bystander cells to investigate whether the conditioned medium affects cell proliferation. We found that low-level NO in prostate cancer cells affects the bystander tumor cells in a manner that depends on their malignancy grade.

Photosensitization of pancreatic cancer cells by cationic alkyl-porphyrins in free form or engrafted into POPC liposomes: The relationship between delivery mode and mechanism of cell death.

Cationic porphyrins bearing an alkyl side chain of 14 (2b) or 18 (2d) carbons dramatically inhibit proliferation of pancreatic cancer cells following treatment with light. We have compared two different ways of delivering porphyrin 2d: either in free form or engrafted into palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes (L-2d). Cell cytometry shows that while free 2d is taken up by pancreatic cancer cells by active (endocytosis) and passive (membrane fusion) transports, L-2d is internalized solely by endocytosis. Confocal microscopy showed that free 2d co-localizes with the cell membrane and lysosomes, whereas L-2d partly co-localizes with lysosomes and ER. It is found that free 2d inhibits the KRAS-Nrf2-GPX4 axis and strongly triggers lipid peroxidation, resulting in cell death by ferroptosis. By contrast, L-2d does not affect the KRAS-Nrf2-GPX4 axis and activates cell death mainly through apoptosis. Overall, our study demonstrates for the first time that cationic alkyl porphyrins, which have a IC50 ~ 23 nM, activate a dual mechanism of cell death, ferroptosis and apoptosis, where the predominant form depends on the delivery mode.

HSA-Binding Prodrugs-Based Nanoparticles Endowed with Chemo and Photo-Toxicity against Breast Cancer.

Exploiting the tumor environment features (EPR effect, elevated glutathione, reactive oxygen species levels) might allow attaining a selective and responsive carrier capable of improving the therapeutic outcome. To this purpose, the in situ covalent binding of drugs and nanoparticles to circulating human serum albumin (HSA) might represent a pioneering approach to achieve an effective strategy. This study describes the synthesis, in vitro and in vivo evaluation of bioresponsive HSA-binding nanoparticles (MAL-PTX2S@Pba), co-delivering two different paclitaxel (PTX) prodrugs and the photosensitizer pheophorbide a (Pba), for the combined photo- and chemo-treatment of breast cancer. Stable and reproducible MAL-PTX2S@Pba nanoparticles with an average diameter of 82 nm and a PTX/Pba molar ratio of 2.5 were obtained by nanoprecipitation. The in vitro 2D combination experiments revealed that MAL-PTX2S@Pba treatment induces a strong inhibition of cell viability of MDA-MB-231, MCF7 and 4T1 cell lines, whereas 3D experiments displayed different trends: while MAL-PTX2S@Pba effectiveness was confirmed against MDA-MB-231 spheroids, the 4T1 model exhibited marked resistance. Lastly, despite using a low PTX-PDT regimen (e.g., 8.16 mg/Kg PTX and 2.34 mg/Kg Pba), our formulation showed to foster primary tumor reduction and curb lung metastases growth in 4T1 tumor-bearing mice, thus setting the basis for further preclinical validations.

Kinetics and mechanism of formation of nickel(II)porphyrin and its interaction with DNA in aqueous medium.

Kinetics between 5,10,15,20-tetrakis(N-methylpyridium-4-yl)porphyrin and Ni2+ species were investigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO3). Speciation of Ni2+ was done in I = 0.10 M (NaNO3) for knowing distribution of Ni2+ species with solution pH. Experimental data were compared with speciation diagram constructed from the values of hydrolysis constants of Ni2+ ion. Speciation data showed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH2)6-n(OH)n]2-n species with solution pH. According to speciation of Ni2+ and pH dependent rate constants, rate expression can be written as: d[Ni(TMPyP)4+]/dt = (k 1[Ni2+ (aq)] + k 2[Ni(OH)+ (aq)] + k 3[Ni(OH)2 o (aq)] + k 4[Ni(OH)3 - (aq)])[H2TMPyP4+], where k 1, k 2, k 3 and k 4 were found to be k 1 = (0.62 ± 0.22) × 10-2; k 2 = (3.60 ± 0.40) × 10-2; k 3 = (2.09 ± 0.52) × 10-2, k 4 = (0.53 ± 0.04) × 10-2 M-1s-1 at 25 ±1 °C, respectively. Formation of hydrogen bonding between [Ni(H2O)5(OH)]+ and [H2TMPyP]4+ causes enhanced reactivity. Rate of formation of [Ni(II)TMPyP]4+ complex was to be 3.99 × 10-2 M-1s-1 in I = 0.10 M, NaNO3 (25 ± 1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP]4+ and [H2(TMPyP)]4+ interact with DNA via outside binding with self-stacking and intercalation, respectively. SYNOPSIS. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12039-021-01945-y.

Is haem the real target of COVID-19?

Although a vaccination campaign has been launched in many countries, the COVID-19 pandemic is not under control. The main concern is the emergence of new variants of SARS-CoV-2; therefore, it is important to find approaches to prevent or reduce the virulence and pathogenicity of the virus. Currently, the mechanism of action of SARS-CoV-2 is not fully understood. Considering the clinical effects that occur during the disease, attacking the human respiratory and hematopoietic systems, and the changes in biochemical parameters (including decreases in haemoglobin [Hb] levels and increases in serum ferritin), it is clear that iron metabolism is involved. SARS-CoV-2 induces haemolysis and interacts with Hb molecules via ACE2, CD147, CD26, and other receptors located on erythrocytes and/or blood cell precursors that produce dysfunctional Hb. A molecular docking study has reported a potential link between the virus and the beta chain of haemoglobin and attack on haem. Considering that haem is involved in miRNA processing by binding to the DGCR8-DROSHA complex, we hypothesised that the virus may check this mechanism and thwart the antiviral response.

Role of nitric oxide in the response to photooxidative stress in prostate cancer cells.

A continuous state of oxidative stress during inflammation contributes to the development of 25% of human cancers. Epithelial and inflammatory cells release reactive oxygen species (ROS) and reactive nitrogen species (RNS) that can damage DNA. ROS/RNS have biological implications in both chemoresistance and tumor recurrence. As several clinically employed anticancer drugs can generate ROS/RNS, we have addressed herein how inducible nitric oxide synthase and nitric oxide (iNOS/•NO) affect the molecular pathways implicated in the tumor response to oxidative stress. To mimic the oxidative stress associated with chemotherapy, we used a photosensitizer (pheophorbide a) that can generate ROS/RNS in a controlled manner. We investigated how iNOS/•NO modulates the tumor response to oxidative stress by involving the NF-κB and Nrf2 molecular pathways. We found that low levels of iNOS induce the development of a more aggressive tumor population, leading to survival, recurrence and resistance. By contrast, high levels of iNOS/•NO sensitize tumor cells to oxidative treatment, causing cell growth arrest. Our analysis showed that NF-κB and Nrf2, which are activated in response to oxidative stress, communicate with each other through RKIP. For this critical role, RKIP could be an interesting target for anticancer drugs. Our study provides insight into the complex signaling response of cancer cells to oxidative treatments as well as new possibilities for the rational design of new therapeutic strategies.

The ROS-KRAS-Nrf2 axis in the control of the redox homeostasis and the intersection with survival-apoptosis pathways: Implications for photodynamic therapy.

In highly proliferating cancer cells oncogenic mutations reprogram the metabolism and increase the production of reactive oxygen species (ROS). Cancer cells prevent ROS accumulation by upregulating antioxidant systems. Here we show that an increase of oxidative stress (ROS and singlet oxygen), generated by photoactivated TMPyP4, results in the upregulation of KRAS and Nrf2, the major regulator of the redox homeostasis. In agreement with a previous observation, the ectopic expression of KRAS G12D or G12 V is found to stimulate Nrf2. This suggests that ROS, KRAS and Nrf2 establish a molecular axis controlling the redox homeostasis in cancer cells. We found that this axis also modulates the function of the NF-kB/Snail/RKIP circuitry, regulating the survival and apoptosis pathways. Our data show that low ROS levels, obtained when Nrf2 is activated by KRAS, results in the upregulation of prosurvival Snail and simultaneous downregulation of proapoptotic RKIP: an expression pattern favouring cell proliferation. By contrast, high ROS levels, obtained when Nrf2 is inhibited by a small molecule (luteolin), favour apoptosis by upregulating proapoptotic RKIP and downregulating prosurvival Snail. The results of this study are useful to design efficient photodynamic therapy (PDT) against cancer. We hypothesize that cancer cells can be sensitized to PDT when the photosensitizer is used in the presence of an inhibitor of Nrf2 (adjuvant). To test this hypothesis, we used luteolin (3',4',5,7-tetrahydroflavone) as Nrf2 inhibitor, since it reduces the expression of Nrf2 and increases intracellular ROS. By means of colony formation and viability assays we found that when Nrf2 is inhibited, PDT shows an increase of efficiency up to 45%.

Effect of methylene blue photodynamic therapy on human neutrophil functional responses.

Photodynamic therapy (PDT) has become an emerging novel therapeutic approach for treating localized microbial infections, particularly those sustained by multidrug-resistant strains. Given the irreplaceable role played by professional phagocytes in limiting infections, such as polymorphonuclear neutrophils, any newly designed antimicrobial therapeutic approach must not interfere with their function. The present investigation presents a detailed analysis of the effect of PDT on the viability and several functional responses of human polymorphonuclear neutrophils loaded with methylene blue (MB), one of the more commonly used photosensitizers in antimicrobial PDT. Taking advantage of the use of a specifically-designed optical LED array for illuminating MB-loaded human polymorphonuclear neutrophils, a number of cell functions have been assayed under miniaturized, strictly controlled and reproducible experimental conditions. The major findings of this study are the following: (1) MB-PDT increases human neutrophils adhesion and does not modify myeloperoxidase release; (2) MB-PDT markedly enhances reactive oxygen species generation that is independent of superoxide-forming phagocytic oxidase and very likely ascribable to LED-dependent excitation of accumulated methylene blue; (3) MB-PDT almost abolishes human neutrophils candidacidal activity by hindering the engulfing machinery. This in vitro study may represent a valuable reference point for future research on PDT applications for treating localized microbial infections.

Folate-Decorated Amphiphilic Cyclodextrins as Cell-Targeted Nanophototherapeutics.

Nowadays, active targeting of nanotherapeutics is a challenging issue. Here, we propose a rational design of a ternary nanoassembly (SAP) composed of nonionic amphiphilic ß-cyclodextrins (amphiphilic CD) incorporating pheophorbide (Pheo) as a phototherapeutic and an adamantanyl-folic acid conjugate (Ada-FA) to target tumor cells overexpressing α-folate receptor (FR-α(+)). Dynamic light scattering and ζ-potential pointed out the presence of nanoassemblies bearing a negative surface charge (ζ = -51 mV). Morphology of SAP was investigated by atomic force microscopy and microphotoluminescence, indicating the presence of highly emissive near-spherical assemblies of about 280 nm in size. Complementary spectroscopic techniques such as ROESY-NMR, UV/vis and steady-state fluorescence revealed that the folic acid protrudes out of amphiphilic CD rims, prone for recognition with FR-α. Pheo was strongly loaded in the nanoassembly mostly in monomeric form, thus generating singlet oxygen (1O2) and consequentely showing phototherapeutic action. SAP remained stable until 2 weeks in aqueous solutions. Stability studies in biologically relevant media pointed out the ability of SAP to interact with serum proteins by means of the oligoethylenglycole fringe, without destabilization. Release experiments demonstrated the sustained release of Pheo from SAP in environments mimiking physiological conditions (∼20% within 1 week), plausibly suggesting low Pheo leaking and high integrity of the assembly within 24 h, time spent on average to reach the target sites. Cellular uptake of SAP was confirmed by confocal microscopy, pointing out that SAP was internalized into the tumoral cells expressing FR-α more efficiently than SP. SAP showed improved phototoxicity in human breast MCF-7 cancer cells FR-α(+) (IC50 = 270 nM) with respect to human prostate carcinoma PC3 cells (IC50 = 700 nM) that express a low level of that receptor (FR-α(-)). Finally, an improved phototoxicity in FR-α(+) MCF-7 cells (IC50 = 270 nM) was assessed after treatment with SAP vs SP (IC50 = 600 nM) which was designed without Ada-FA as a targeting unit.

Critical role of hnRNP A1 in activating KRAS transcription in pancreatic cancer cells: A molecular mechanism involving G4 DNA.

KRAS is one of the most mutated genes in human cancer. Its crucial role in the tumourigenesis of pancreatic ductal adenocarcinoma (PDAC) has been widely demonstrated. As this deadly cancer does not sufficiently respond to conventional chemotherapies, it is important to increase our knowledge of pancreatic cancer biology, in particular how oncogenic KRAS is regulated. The promoter of KRAS contains a GA-element composed of runs of guanines that fold into a G4 structure. This unusual DNA conformation is recognized by several nuclear proteins, including MAZ and hnRNP A1. Recent data have revealed that KRAS is interconnected to ILK and hnRNP A1 in a circuitry that enables pancreatic cancer cells to maintain an aggressive phenotype. The present review illustrates recent advances on how KRAS is regulated in pancreatic cancer cells, focusing on the formation of G4 structures in the KRAS promoter and their interaction with hnRNP A1. The newly discovered KRAS-ILK-hnRNP A1 regulatory loop is discussed, emphasizing its potential as a therapeutic target for PDAC-specific molecules. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

A photodynamic bifunctional conjugate for prostate cancer: an in vitro mechanistic study.

Photodynamic therapy (PDT) has drawn considerable attention for its efficacy against certain types of cancers. It shows however limits in the case of deep cancers, favoring tumor recurrence under suboptimal conditions. More insight into the molecular mechanisms of PDT-induced cytotoxicity and cytoprotection is essential to extend and strengthen this therapeutic modality. As PDT induces iNOS/NO in both tumor and microenvironment, we examined the role of nitric oxide (NO) in cytotoxicity and cytoprotection. Our findings show that NO mediates its cellular effects by acting on the NF-κB/YY1/RKIP loop, which controls cell growth and apoptosis. The cytoprotective effect of PDT-induced NO is observed at low NO levels, which activate the pro-survival/anti-apoptotic NF-κB and YY1, while inhibiting the anti-survival/pro-apoptotic and metastasis suppressor RKIP. In contrast, high PDT-induced NO levels inhibit NF-κB and YY1 and induce RKIP, resulting in significant anti-tumor activity. These findings reveal a critical role played by NO in PDT and suggest that the use of bifunctional PDT agents composed of a photosensitizer and a NO-donor could enhance the photo-treatment effect. A successful application of NO in anticancer therapy requires control of its concentration in the target tissue. To address this issue we propose as PDT agent, a bimolecular conjugate called DR2, composed of a photosensitizer (Pheophorbide a) and a non-steroidal anti-androgen molecule capable of releasing NO under the exclusive control of light. The mechanism of action of DR2 in prostate cancer cells is reported and discussed.

Photosensitizers binding to nucleic acids as anticancer agents.

Cationic porphyrins (Prs) and phthalocyanines (Pcs) are strong photosensitizers that have drawn much attention for their potential in photodynamic therapy. These compounds have the interesting property of binding to nucleic acids, in particular G-rich quadruplex-forming sequences in DNA and RNA. In this review, we highlight their potential as anticancer drugs.

Highlights of the Fifth International Workshop on Nitric Oxide and Cancer.

Nitric oxide (NO) is an endogenous molecule that performs key physiological signaling functions. The overall biological effect exerted by NO strongly depends on its concentration. Indeed, at a low concentration NO acts as a signal transducer affecting many physiological processes, such as blood flow regulation, iron homeostasis, and neurotransmission, while at a high concentration it preferentially exerts cytotoxic effects. Gaining knowledge about the molecular pathways involved in the NO-tumor response represents a great scientific and clinical challenge for developing novel anticancer strategies based on either endogenous or exogenous NO regulation and induction. This review summarizes the most recent advances in the pathological and therapeutic roles of NO in cancer achieved by prominent experts in the field. In particular, the following topics are reviewed: the role of inducible nitric oxide synthase (iNOS) in chronic inflammation and tumorigenesis; the connection between NOS and IL-10 and their function in immunity at the tumor site; the role of NO in photodynamic therapy; and the role of S-nitrosylation in cancer. Finally, an overview of NO-mediated therapies for cancer treatment is provided, including iNOS inhibitors, NO-releasing compounds, and molecular conjugates and nanoparticles that induce NO formation upon irradiation with light.

Dual roles of nitric oxide in the regulation of tumor cell response and resistance to photodynamic therapy.

Photodynamic therapy (PDT) against cancer has gained attention due to the successful outcome in some cancers, particularly those on the skin. However, there have been limitations to PDT applications in deep cancers and, occasionally, PDT treatment resulted in tumor recurrence. A better understanding of the underlying molecular mechanisms of PDT-induced cytotoxicity and cytoprotection should facilitate the development of better approaches to inhibit the cytoprotective effects and also augment PDT-mediated cytotoxicity. PDT treatment results in the induction of iNOS/NO in both the tumor and the microenvironment. The role of NO in cytotoxicity and cytoprotection was examined. The findings revealed that NO mediates its effects by interfering with a dysregulated pro-survival/anti-apoptotic NF-κB/Snail/YY1/RKIP loop which is often expressed in cancer cells. The cytoprotective effect of PDT-induced NO was the result of low levels of NO that activates the pro-survival/anti-apoptotic NF-κB, Snail, and YY1 and inhibits the anti-survival/pro-apoptotic and metastasis suppressor RKIP. In contrast, PDT-induced high levels of NO result in the inhibition of NF-kB, Snail, and YY1 and the induction of RKIP, all of which result in significant anti-tumor cytotoxicity. The direct role of PDT-induced NO effects was corroborated by the use of the NO inhibitor, l-NAME, which reversed the PDT-mediated cytotoxic and cytoprotective effects. In addition, the combination of the NO donor, DETANONOate, and PDT potentiated the PDT-mediated cytotoxic effects. These findings revealed a new mechanism of PDT-induced NO effects and suggested the potential therapeutic application of the combination of NO donors/iNOS inducers and PDT in the treatment of various cancers. In addition, the study suggested that the combination of PDT with subtoxic cytotoxic drugs will result in significant synergy since NO has been shown to be a significant chemo-immunosensitizing agent to apoptosis.

Androgen Receptor Targeted Conjugate for Bimodal Photodynamic Therapy of Prostate Cancer in Vitro.

Prostate cancer (PC) represents the most common type of cancer among males and is the second leading cause of cancer death in men in Western society. Current options for PC therapy remain unsatisfactory, since they often produce uncomfortable long-term side effects, such as impotence (70%) and incontinence (5-20%) even in the first stages of the disease. Light-triggered therapies, such as photodynamic therapy, have the potential to provide important advances in the treatment of localized and partially metastasized prostate cancer. We have designed a novel molecular conjugate (DR2) constituted of a photosensitizer (pheophorbide a, Pba), connected to a nonsteroidal anti-androgen molecule through a small pegylated linker. This study aims at investigating whether DR2 represents a valuable approach for PC treatment based on light-induced production of single oxygen and nitric oxide (NO) in vitro. Besides being able to efficiently bind the androgen receptor (AR), the 2-trifluoromethylnitrobenzene ring on the DR2 backbone is able to release cytotoxic NO under the exclusive control of light, thus augmenting the general photodynamic effect. Although DR2 is similarly internalized in cells expressing different levels of androgen receptor, the AR ligand prevents its efflux through the ABCG2-pump. In vitro phototoxicity experiments demonstrated the ability of DR2 to kill cancer cells more efficiently than Pba, while no dark toxicity was observed. Overall, the presented approach is very promising for further development of AR-photosensitizer conjugates in the multimodal photodynamic treatment of prostate cancer.