Cellular photodestruction induced by hypericin in AY-27 rat bladder carcinoma cells

Fluorescence-Guided Laparoscopy after Oral Hypericin Administration for Staging of Locally Advanced Gastric Cancer-A Pilot Study

(1) Background: Laparoscopic staging is essential in gastric cancer (GC) to rule out peritoneal metastasis (PM). Hypericin, a plant-derived fluorescent compound, has been suggested to improve laparoscopic visualization of PM from GC. This prospective, single-arm, open-label clinical trial aimed to assess the feasibility and safety of oral hypericin administration as well as the suitability of fluorescence-guided laparoscopy (FGL) for improving the sensitivity and specificity of staging in GC patients (EudraCT-Number: 2015-005277-21; clinicaltrials.gov identifier: NCT-02840331). (2) Methods: GC patients received Laif® 900, an approved hypericin-containing phytopharmaceutical, once orally two to four hours before white light and ultraviolet light laparoscopy. The peritoneal cancer index was evaluated, biopsies taken and hypericin concentrations in serum and peritoneal tissue were determined by mass spectrometry. (3) Results: Between 2017 and 2021, out of 63 patients screened for eligibility, 50 patients were enrolled and treated per protocol. The study intervention was shown to be feasible and safe in all patients. Standard laparoscopy revealed suspicious lesions in 27 patients (54%), among whom 16 (59%) were diagnosed with PM. FGL identified suspicious areas in 25 patients (50%), among whom PM was confirmed in 13 cases (52%). Although hypericin concentrations in serum reached up to 5.64 ng/mL, no hypericin was detectable in peritoneal tissue biopsies. (4) Conclusions: FGL in patients with GC was shown to be feasible but futile in this study. Sufficient levels of hypericin should be ensured in target tissue prior to reassessing FGL with hypericin.

Metal-based nanoparticles in cancer therapy: Exploring photodynamic therapy and its interplay with regulated cell death pathways

Photodynamic therapy (PDT) represents a non-invasive treatment strategy currently utilized in the clinical management of selected cancers and infections. This technique is predicated on the administration of a photosensitizer (PS) and subsequent irradiation with light of specific wavelengths, thereby generating reactive oxygen species (ROS) within targeted cells. The cellular effects of PDT are dependent on both the localization of the PS and the severity of ROS challenge, potentially leading to the stimulation of various cell death modalities. For many years, the concept of regulated cell death (RCD) triggered by photodynamic reactions predominantly encompassed apoptosis, necrosis, and autophagy. However, in recent decades, further explorations have unveiled additional cell death modalities, such as necroptosis, ferroptosis, cuproptosis, pyroptosis, parthanatos, and immunogenic cell death (ICD), which helps to achieve tumor cell elimination. Recently, nanoparticles (NPs) have demonstrated substantial advantages over traditional PSs and become important components of PDT, due to their improved physicochemical properties, such as enhanced solubility and superior specificity for targeted cells. This review aims to summarize recent advancements in the applications of different metal-based NPs as PSs or delivery systems for optimized PDT in cancer treatment. Furthermore, it mechanistically highlights the contribution of RCD pathways during PDT with metal NPs and how these forms of cell death can improve specific PDT regimens in cancer therapy.

Hypericin as a promising natural bioactive naphthodianthrone: A review of its pharmacology, pharmacokinetics, toxicity, and safety

Hypericin can be derived from St. John's wort, which is widely spread around the world. As a natural product, it has been put into clinical practice such as wound healing and depression for a long time. In this article, we review the pharmacology, pharmacokinetics, and safety of hypericin, aiming to introduce the research advances and provide a full evaluation of it. Turns out hypericin, as a natural photosensitizer, exhibits an excellent capacity for anticancer, neuroprotection, and elimination of microorganisms, especially when activated by light, potent anticancer and antimicrobial effects are obtained after photodynamic therapy. The mechanisms of its therapeutic effects involve the induction of cell death, inhibition of cell cycle progression, inhibition of the reuptake of amines, and inhibition of virus replication. The pharmacokinetics properties indicate that hypericin has poor water solubility and bioavailability. The distribution and excretion are fast, and it is metabolized in bile. The toxicity of hypericin is rarely reported and the conventional use of it rarely causes adverse effects except for photosensitization. Therefore, we may conclude that hypericin can be used safely and effectively against a variety of diseases. We hope to provide researchers with detailed guidance and enlighten the development of it.

Hypericin-mediated photodynamic therapy for the treatment of cancer: a review

OBJECTIVES

Hypericin is a polycyclic aromatic naphthodianthrone that occurs naturally. It is also an active ingredient in some species of the genus Hypericum. Emerging evidence suggests that hypericin has attracted great attention as a potential anticancer drug and exhibits remarkable antiproliferative effect upon irradiation on various tumour cells. This paper aims to summarise the anticancer effect and molecular mechanisms modulated by hypericin-medicated photodynamic therapy and its potential role in the cancer treatment.

KEY FINDINGS

Hypericin-medicated photodynamic therapy could inhibit the proliferation of various tumour cells including bladder, colon, breast, cervical, glioma, leukaemia, hepatic, melanoma, lymphoma and lung cancers. The effect is primarily mediated by p38 mitogen-activated protein kinase (MAPK), JNK, PI3K, CCAAT-enhancer-binding protein homologous protein (CHOP)/TRIB3/Akt/mTOR, TRAIL/TRAIL-receptor, c-Met and Ephrin-Eph, the mitochondria and extrinsic signalling pathways. Furthermore, hypericin-medicated photodynamic therapy in conjunction with chemotherapeutic agents or targeted therapies is more effective in inhibiting the growth of tumour cells.

SUMMARY

During the past few decades, the anticancer properties of photoactivated hypericin have been extensively investigated. Hypericin-medicated photodynamic therapy can modulate a variety of proteins and genes and exhibit a great potential to be used as a therapeutic agent for various types of cancer.

Antibody-Based Immunotherapy: Alternative Approaches for the Treatment of Metastatic Melanoma

Melanoma is the least common form of skin cancer and is associated with the highest mortality. Where melanoma is mostly unresponsive to conventional therapies (e.g., chemotherapy), BRAF inhibitor treatment has shown improved therapeutic outcomes. Photodynamic therapy (PDT) relies on a light-activated compound to produce death-inducing amounts of reactive oxygen species (ROS). Their capacity to selectively accumulate in tumor cells has been confirmed in melanoma treatment with some encouraging results. However, this treatment approach has not reached clinical fruition for melanoma due to major limitations associated with the development of resistance and subsequent side effects. These adverse effects might be bypassed by immunotherapy in the form of antibody–drug conjugates (ADCs) relying on the ability of monoclonal antibodies (mAbs) to target specific tumor-associated antigens (TAAs) and to be used as carriers to specifically deliver cytotoxic warheads into corresponding tumor cells. Of late, the continued refinement of ADC therapeutic efficacy has given rise to photoimmunotherapy (PIT) (a light-sensitive compound conjugated to mAbs), which by virtue of requiring light activation only exerts its toxic effect on light-irradiated cells. As such, this review aims to highlight the potential clinical benefits of various armed antibody-based immunotherapies, including PDT, as alternative approaches for the treatment of metastatic melanoma.

Selective photodynamic effects on cervical cancer cells provided by P123 Pluronic®-based nanoparticles modulating hypericin delivery

At present, cervical cancer is the fourth leading cause of cancer among women worldwide with no effective treatment options. In this study we aimed to evaluate the efficacy of hypericin (HYP) encapsulated on Pluronic® P123 (HYP/P123) photodynamic therapy (PDT) in a comprehensive panel of human cervical cancer-derived cell lines, including HeLa (HPV 18-positive), SiHa (HPV 16-positive), CaSki (HPV 16 and 18-positive), and C33A (HPV-negative), compared to a nontumorigenic human epithelial cell line (HaCaT). Were investigated: (i) cell cytotoxicity and phototoxicity, cellular uptake and subcellular distribution; (ii) cell death pathway and cellular oxidative stress; (iii) migration and invasion. Our results showed that HYP/P123 micelles had effective and selective time- and dose-dependent phototoxic effects on cervical cancer cells but not in HaCaT. Moreover, HYP/P123 micelles accumulated in endoplasmic reticulum, mitochondria and lysosomes, resulting in photodynamic cell death mainly by necrosis. HYP/P123 induced cellular oxidative stress mainly via type II mechanism of PDT and inhibited cancer cell migration and invasion mainly via MMP-2 inhibition. Taken together, our results indicate a potentially useful role of HYP/P123 micelles as a platform for HYP delivery to more specifically and effectively treat cervical cancers through PDT, suggesting they are worthy for in vivo preclinical evaluations.

Selective Photodynamic Effects on Breast Cancer Cells Provided by p123 Pluronic®- Based Nanoparticles Modulating Hypericin Delivery

BACKGROUND

Breast cancer is the most relevant type of cancer and the second cause of cancer- related deaths among women in general. Currently, there is no effective treatment for breast cancer although advances in its initial diagnosis and treatment are available. Therefore, the value of novel anti-tumor therapeutic modalities remains an immediate unmet need in clinical practice. Following our previous work regarding the properties of the Pluronics with different photosensitizers (PS) for photodynamic therapy (PDT), in this study we aimed to evaluate the efficacy of supersaturated hypericin (HYP) encapsulated on Pluronic® P123 (HYP/P123) against breast cancer cells (MCF-7) and non-tumorigenic breast cells (MCF-10A).

METHODS

Cell internalization and subcellular distribution of HYP/P123 was confirmed by fluorescence microscopy. The phototoxicity and citototoxicity of HYP/P123 was assessed by trypan blue exclusion assay in the presence and absence of light. Long-term cytotoxicity was performed by clonogenic assay. Cell migration was determined by the wound-healing assay. Apoptosis and necrosis assays were performed by annexin VFITC/ propidium Iodide (PI) by fluorescence microscopy.

RESULTS

Our results showed that HYP/P123 micelles had high stability and high rates of binding to cells, which resulted in the selective internalization in MCF-7, indicating their potential to permeate the membrane of these cells. Moreover, HYP/P123 micelles accumulated in mitochondria and endoplasmic reticulum organelles, resulting in the photodynamic cell death by necrosis. Additionally, HYP/P123 micelles showed effective and selective time- and dose dependent phototoxic effects on MCF-7 cells but little damage to MCF-10A cells. HYP/P123 micelles inhibited the generation of cellular colonies, indicating a possible capability to prevent the recurrence of breast cancer. We also demonstrated that HYP/P123 micelles inhibit the migration of tumor cells, possibly by decreasing their ability to form metastases.

CONCLUSION

Taken together, the results presented here indicate a potentially useful role of HYP/P123 micelles as a platform for HYP delivery to more specifically and effectively treat human breast cancers through photodynamic therapy, suggesting they are worthy for in vivo preclinical evaluations.

Biphasic dose-response of antioxidants in hypericin-induced photohemolysis

In the present paper the photodynamic effect of hypericin on superoxide dismutase activity and the possibility of reduction of hypericin phototoxicity by antioxidants were studied. It was shown an almost twice decrease in superoxide dismutase activity of red blood cells under the photosensitization by hypericin. The influence of antioxidants (ascorbic acid and quercetin) on hypericin photodynamic action has revealed that these antioxidants suppress or stimulate photohemolysis caused by hypericin. The photosensitization reaction realized by hypericin could be shifted from type II to type I or vice versa by manipulating the antioxidant concentration. Strengthening of photohemolysis by antioxidants in some concentrations indicates the switching of alternative mechanisms of hypericin photodynamic action and its complicated manner. Thus the selection of antioxidant concentrations is of extreme importance for changing the efficacy of photodynamic therapy with hypericin.

Photodynamic therapy using topically applied hypericin: comparative effect with methyl-aminolevulinic acid on UV induced skin tumours

Photodynamic therapy (PDT) is a treatment option particularly well-suited for superficial (pre)malignant skin lesions due to the skin's accessibility to light. In the present study, the efficacy of topical hypericin-PDT was evaluated using a mouse model for actinic keratosis. For comparison, similar experiments were conducted with methyl-aminolevulinic acid (Me-ALA). Small skin tumours (1-2 mm) were induced in hairless mice by chronic UV irradiation. After topical application of hypericin (0.1% in gelcream for 24 h) or Me-ALA (Metvix® for 4 h), the lesional/non-lesional skin surface fluorescence ratio was determined and fluorescence microscopy was used to study the skin penetration of the photosensitizers. The antitumour activity of topical PDT (20 mW cm(-2), 40 J cm(-2)) was evaluated by measurement of the lesional diameters. Moreover, biopsies were taken at various time points after PDT for histological evaluation of the therapy. Our results demonstrate that after topical application of hypericin and Me-ALA, tumour selectivity is limited in mouse skin. The microscopic distribution of hypericin fluorescence showed an accumulation in the stratum corneum and low fluorescence levels in the rest of the lesions, whereas the distribution of PpIX in the skin was more homogenous. Topical hypericin-PDT was found to be less efficient (44% total lesional clearance) as compared to Me-ALA-PDT (80% total lesional clearance). Full lesional necrosis was observed in responsive lesions, and the atypical cells of actinic keratosis were replaced by normal keratinocytes 3 weeks later, both after hypericin-PDT and Me-ALA-PDT.

Light-independent metabolomics of endophytic Thielavia subthermophila provides insight into microbial hypericin biosynthesis

The possible microbial mechanism of hypericin (1) and emodin (2) biosynthesis was studied in axenic submerged culture conditions in the endophytic fungus Thielavia subthermophila, isolated from Hypericum perforatum. The growth and secondary metabolite production of the endophyte remained independent of the illumination conditions. This production remained unaltered on spiking the medium with 3 or 5 mM 2, although the biomass accumulation was reduced. Neither emodin anthrone (3) nor protohypericin (4) could be detected at any stage of fermentation, irrespective of either spiking or illumination conditions. The endophytic metabolites exhibited photodynamic cytotoxicity against the human acute monocytic leukemia cell line (THP-1), at 92.7 vs 4.9%, and 91.1 vs 1.0% viability by resazurin and ATPlite assays, in light and in the dark, respectively. In trying to ascertain the presence/expression of the candidate hyp-1 gene in the endophyte, it was revealed that the hyp-1 gene was absent in T. subthermophila, indicating that the biosynthetic pathway in the endophytic fungus might be different and/or governed by a different molecular mechanism than the host plant or host cell suspension cultures. We have discussed the biosynthetic principles and evolutionary implications relating to endophytic T. subthermophila based on the results obtained.

Role of p38 MAPKs in hypericin photodynamic therapy-induced apoptosis of nasopharyngeal carcinoma cells

The present study aims to determine the role of mitogen-activated protein kinases (MAPKs) in hypericin-mediated photodynamic therapy (HY-PDT)-induced apoptosis of the HK-1 nasopharyngeal carcinoma (NPC) cells. HY-PDT was found to induce proteolytic cleavage of procaspase-9 and -3 in HK-1 cells. Apoptotic nuclei were observed at 6 h after PDT whereas B-cell leukemia/lymphoma-2-associated-X-protein (Bax) translocation and formation of Bax channel is responsible for the cell death. Increase in phosphorylation of p38 MAPKs and c-Jun N-terminal kinase 1/2 (JNK1/2) was detected at 15-30 min after HY-PDT. The appearance of phosphorylated form of p38 MAPKs and JNK1/2 was inhibited by the singlet oxygen scavenger l-histidine. HY-PDT-induced cell death was enhanced by the chemical inhibitors for p38 MAPKs (SB202190 and SB203580), but not by the JNKs inhibitor SP600125. Knockdown of the p38alpha and p38beta MAPK isoforms by small interfering RNA (siRNA) are more effective than the p38delta in enhancing PDT-induced cell death. Augmentation of apoptosis by p38alpha or p38beta knockdown is also correlated with the increased proteolytic cleavage of procaspase-9 after HY-PDT treatment. Our results suggested that HY-PDT activated p38 MAPKs through the production of singlet oxygen. Inhibition of p38 MAPKs with chemical inhibitors or siRNA enhances HY-PDT-induced apoptosis of the HK-1 NPC cells.

An endophytic fungus from Hypericum perforatum that produces hypericin

For the first time, an endophytic fungus has been isolated from the stems of the medicinal herb Hypericum perforatum (St. John's Wort). The fungus produced the napthodianthrone derivative hypericin ( 1) in rich mycological medium (potato dextrose broth) under shake flask and bench scale fermentation conditions. Emodin ( 2) was also produced simultaneously by the fungus under the same culture conditions. We propose 2 as the main precursor in the microbial metabolic pathway to 1. The fungus was identified by morphology and authenticated by 28S (LSU) rDNA sequencing. Compounds 1 and 2 were identified by LC-HRMS, LC-MS/MS, and LC-HRMS/MS and confirmed by comparison with authentic standards. In bioassays with a panel of laboratory standard pathogenic control strains, including fungi and bacteria, both fungal 1 and 2 possessed antimicrobial activity comparable to authentic standards. This endophytic fungus has significant scientific and industrial potential to meet the pharmaceutical demands for 1 in a cost-effective, easily accessible, and reproducible way.

Necrosis predominates in the cell death of human colon adenocarcinoma HT-29 cells treated under variable conditions of photodynamic therapy with hypericin

Photodynamic therapy (PDT) represents a new rapidly-developing anticancer approach based on administration of a non- or weakly-toxic photosensitizer and its activation with light of appropriate wavelength. Hypericin, one of the promising photosensitizers, is known to induce apoptosis with high efficiency in various cell line models. However, here we report the prevalence of necrosis accompanied by suppression of caspase-3 activation in colon adenocarcinoma HT-29 cells exposed to an extensive range of PDT doses evoked by variations in two variables -- hypericin concentration and light dose. Necrosis was the principal mode of cell death despite different PDT doses and the absence of anti-apoptotic Bcl-2 expression, even if the same condition induced caspase-3 activity at similar toxicity in HeLa cells. Introduction of Bcl-2 into HT-29 cells invoked caspase-3 activation, changed the Bcl-X(L) expression pattern, increased the apoptosis ratio with no effect on overall toxicity, and supported arrest in the G(2)/M-phase of cell cycle. Since it is known that Bcl-2 suppression in HT-29 is reversible and linked to the over-expression of mutated p53 and also considering our data, we suggest that the mutation in p53 and events linked to this feature may play a role in cell death signalling in HT-29 colon cancer cells.

Evidence for intracellular aggregation of hypericin and the impact on its photocytotoxicity in PAM 212 murine keratinocytes

We have assessed photoinduced toxicity of hypericin in PAM 212 murine keratinocytes and the relationship between concentration, incubation time and light fluence to evaluate the effect of intracellular aggregation at high concentrations. Confocal microscopy was used to establish the subcellular localization of hypericin at 5 and 50 microM and incubation times of 1 and 3 h. From fluorescence uptake time course studies, intracellular hypericin was demonstrated to exist predominantly in the monomeric form for up to 26 h incubation at 5 microM. However, there was a pronounced aggregation effect at 50 microM, with intracellular hypericin fluorescence levels initially showing an increase followed by a decrease with incubation time. This effect was subsequently shown to exert an effect on the phototoxicity of hypericin. On irradiation, the photocytotoxicity for 1 and 7 h incubation with 50 microM hypericin was comparable, whereas using 5 microM the photocytotoxicity showed good correlation with the intracellular fluorescence measurements at 1 and 7 h incubation.

Hypericum perforatum L. extract – Novel photosensitizer against human bladder cancer cells

The polar methanolic fraction (PMF) of the Hypericum perforatum L. extract has recently been developed and tested as a novel, natural photosensitizer for use in the photodynamic therapy (PDT), and photodynamic diagnosis (PDD). PMF has been tested on HL-60 leukemic cells and cord blood hemopoietic progenitors. In the present study, the efficacy of PMF as a phototoxic agent against urinary bladder carcinoma has been studied using the T24 (high grade metastatic cancer), and RT4 (primary low grade papillary transitional cell carcinoma) human bladder cancer cells. Following cell culture incubation, PMF was excited using 630 nm laser light. The photosensitizer exhibited significant photocytotoxicity in both cell lines at a concentration of 60microg/ml, with 4-8 J/cm(2) light dose, resulting in cell destruction from 80% to 86%. At the concentration of 20microg/ml PMF was not active in either cell line. These results were compared with the results obtained in the same cell lines, under the same conditions with a clinically approved photosensitizer, Photofrin. Photofrin was used in the maximum clinically tolerable dose of 4microg/ml, and it was also excited with 630 nm laser light. In the T24 cell Photofrin exhibited slightly less photocytotocixity, compared with PMF, resulting in 77% cell death with 8J/cm(2) light dose. However, against the RT4 cells Photofrin resulted in minimal cell death (9%) with even 8J/cm(2) light dose. Finally, the type of cell death induced by PMF photoactivation was studied using flow cytometry and DNA laddering. Cell death by PMF photodynamic action in these two bladder cell lines is caused predominently by apoptosis. The reported significant photocytotoxicity, selective localization, natural abundance, easy, and inexpensive preparation, underscore that the PMF extract hold the promise of being a novel, effective PDT photosensitizer.

Hypericin-photodynamic therapy (PDT) using an alternative treatment regime suitable for multi-fraction PDT

Photodynamic therapy (PDT) outcome depends on the conditions under which it is carried out. Maintaining the tumour tissue oxygen level is important for PDT efficacy and using a low fluence rate can improve outcome. In this work we studied the response of human nasopharyngeal carcinoma tumours in murine models to hypericin-PDT carried out under low fluence and fluence rate. A drug-light interval (DLI) of 1h or 6h was used for 1h-PDT and 6h-PDT, respectively. Evan's blue test was used to assess necrosis and TUNEL staining for apoptosis. Nuclear microscopy was used to quantify elemental concentrations in tumours. Serum vascular endothelial growth factor (VEGF) levels were also determined. TUNEL results showed that 6h-PDT induced significantly more apoptosis compared to 1h-PDT (p<0.01). This was supported by nuclear microscopy showing an increase in calcium and a decrease in zinc levels (both known triggers of apoptosis) in 6h-PDT tumours compared to non-PDT tumours (p<0.05). These results further imply a zinc-mediated pathway in hypericin-PDT induced apoptosis. 6h-PDT also resulted in a significant increase in copper concentrations compared to non-PDT tumours (p<0.05). Serum VEGF levels measured after 6h-PDT were lower than those obtained after 1h-PDT. Overall tumour response to hypericin-PDT under low fluence and fluence rate and using a 6h DLI showed increased apoptosis and lower serum VEGF levels. This treatment regime is suitable for the alternative approach of multi-fraction PDT in which the tumour can be exposed to multiple PDT fractions for complete tumour response. This alternative approach might yield improved outcome.

Photosensitizers and antioxidants: a way to new drugs?

Photodynamic therapy (PDT) is a relatively new modality of treatment of diseases involving uncontrolled cell proliferation. It is based on the production of reactive species upon illumination of a photosensitizer in the presence of oxygen. Antioxidants are primarily reducing agents prone to scavenge reactive species in one way or another. Their presence in photodynamic reactions usually reduces the efficacy of PDT. Some antioxidants like ascorbic acid, alpha-tocopherol or butyl-4-hydroxyanisole, however, when added to cells at adequate concentrations may enhance the photodamaging activity of PDT. The presence of transition metals and precise timing of antioxidant administration may also be important factors in increasing the efficacy of PDT. Antioxidant carrier sensitizers have been designed, synthesised and tested for their antibacterial PDT activity. The promising results raise the question whether the introduction of antioxidant moieties into sensitizer molecules would lead to the synthesis of highly effective new drugs.

Intracellular signaling mechanisms in photodynamic therapy

In photodynamic therapy (PDT) a sensitizer, light and oxygen are used to induce death of tumor cells and in the treatment of certain noncancerous conditions. Cell death in PDT may occur by apoptosis or by necrosis, depending on the sensitizer, on the PDT dose and on the cell genotype. Some sensitizers that have been used in PDT are accumulated in the mitochondria, and this may explain their efficiency in inducing apoptotic cell death, both in vitro and in vivo. In this review we will focus on the events that characterize apoptotic death in PDT and on the intracellular signaling events that are set in motion in photosensitized cells. Activation of phospholipases, changes in ceramide metabolism, a rise in the cytosolic free Ca2+ concentration, stimulation of nitric oxide synthase (NOS), changes in protein phosphorylation and alterations in the activity of transcription factors and on gene expression have all been observed in PDT-treated cells. Although many of these metabolic reactions contribute to the demise process, some of them may antagonize cell death. Understanding the signaling mechanisms in PDT may provide means to modulate the PDT effects at the molecular level and potentiate its antitumor effectiveness.

Whole bladder wall photodynamic therapy of transitional cell carcinoma rat bladder tumors using intravesically administered hypericin

Whole-bladder wall photodynamic therapy (PDT) is a promising treatment for carcinoma in situ (CIS) and diffuse premalignant changes of the bladder. After the results of our clinical studies showing that intravesical hypericin selectively accumulates in superficial bladder tumors, we investigated the hypericin-PDT efficacy in an AY-27 orthotopic transitional cell carcinoma rat bladder tumor model. After the instillation of hypericin (30 microM, 2 hr) in the bladder, tumors were irradiated (25-50 mW/cm 6-48 J/cm(2)) using 595 nm laser light. Data demonstrate that light doses of 12-48 J/cm(2) resulted in selective PDT-induced urothelial tumor damage without damaging detrusor musculature. Histological assessment of bladder sections 2 days after PDT showed tumor destruction, with tumor cells shrinking and detaching from the bladder wall. There were tumor regrowth 1-3 weeks after treatment. The in vivo/in vitro clonogenic assay results revealed up to 98% of tumor cell kill by hypericin PDT. In conclusion, hypericin PDT can be used to safely induce a selective urothelial tumor damage without damaging detrusor musculature, when optimum hypericin concentration and light fluences are used. A small percentage (2-5%) of tumor cells that survive the photodynamic treatment resulting in tumor regrowth after a prolonged period of time is likely due to oxygen depletion during light irradiation.

Fluorescence detection of bladder cancer: a review

An effective therapeutic outcome in the treatment of bladder cancer is largely defined by its early detection. In this context, big expectations have been placed on the fluorescence-guided diagnosis of bladder cancer. This paper reviews the applications of endo- and exogenous fluorescence for early diagnosis of in situ carcinoma of the bladder. Despite certain advantages of autofluorescence, exogenous fluorescence, based on the intravesical instillation of fluorophores with the following visible light excitation, has been shown to be more effective in terms of sensitivity and specificity for detecting carcinoma in situ. The equipment consists of a slightly modified light source in order to choose between white (conventional endoscopy) or blue light (fluorescence endoscopy) excitation, and specific lenses, in order to enhance maximally the contrast between normal (blue) autofluorescence and red fluorescence from malignancies. Among exogenous fluorophores, a particular emphasis will be put on the 5-aminolevulinic acid (ALA), its ester derivative (h-ALA) and hypericin. These dyes demonstrated an excellent sensitivity above 90% and specificity ranging from 70% to 90%.

Phosphorylation of Bcl-2 in G2/M phase-arrested cells following photodynamic therapy with hypericin involves a CDK1-mediated signal and delays the onset of apoptosis

The role of Bcl-2 in photodynamic therapy (PDT) is controversial, and some photosensitizers have been shown to induce Bcl-2 degradation with loss of its protective function. Hypericin is a naturally occurring photosensitizer with promising properties for the PDT of cancer. Here we show that, in HeLa cells, photoactivated hypericin does not cause Bcl-2 degradation but induces Bcl-2 phosphorylation in a dose- and time-dependent manner. Bcl-2 phosphorylation is induced by sublethal PDT doses; increasing the photodynamic stress promptly leads to apoptosis, during which Bcl-2 is neither phosphorylated nor degraded. Bcl-2 phosphorylation involves mitochondrial Bcl-2 and correlates with the kinetics of a G(2)/M cell cycle arrest, preceding apoptosis. The co-localization of hypericin with alpha-tubulin and the aberrant mitotic spindles observed following sublethal PDT doses suggest that photodamage to the microtubule network provokes the G(2)/M phase arrest. PDT-induced Bcl-2 phosphorylation is not altered by either the overexpression or inhibition of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun NH(2)-terminal protein kinase 1 (JNK1) nor by inhibiting the extracellular signal-regulated kinases (ERKs) or protein kinase C. By contrast, Bcl-2 phosphorylation is selectively suppressed by the cyclin-dependent protein kinase (CDK)-inhibitor roscovitine, completely blocked by the protein synthesis inhibitor cycloheximide and enhanced by the overexpression of CDK1, suggesting a role for this pathway. However, in an in vitro kinase assay, active CDK1/cyclin B1 complex failed to phosphorylate immunoprecipitated Bcl-2, suggesting that this protein kinase may not directly modify Bcl-2. Mutation of serine-70 to alanine in Bcl-2 abolishes PDT-induced phosphorylation and restores the caspase-3 activation to the same levels of the vector-transfected cells, indicating that Bcl-2 phosphorylation may be a signal to delay apoptosis in G(2)/M phase-arrested cells.

Wavelength-dependent properties of photodynamic therapy using hypericin in vitro and in an animal model

Wavelength effects in photodynamic therapy (PDT) with hypericin (HY) were examined in a C26 colon carcinoma model both in vitro and in vivo. Irradiation of HY-sensitized cells in vitro with either 550 or 590 nm caused the loss of cell viability in a drug- and light-dose-dependent manner. The calculated ratio of HY-based PDT (HY-PDT) efficiencies at these two wavelengths was found to correlate with the numerical ratio of absorbed photons at each wavelength. In vivo irradiation of C26-derived tumors, 6 h after intraperitoneal administration of HY (5 mg/kg), caused extensive vascular damage and tumor necrosis. The depth of tumor necrosis (d) was more pronounced at 590 than at 550 nm and increased when the light dose was raised from 60 to 120 J/cm2. The maximal depths of tumor necrosis (at 120 J/cm2) were 7.5+/-1.5 mm at 550 nm and 9.9+/-0.8 mm at 590 nm. Both values are rather high in view of the limited penetration of green-yellow light into the tissue. Moreover, the depth ratio, d590/d550 = 1.3 (P < 0.001), is smaller than expected considering the 2.2-fold lower HY absorbance and the 1.7-fold lower tissue penetration of radiation at 550 than at 590 nm. This finding indicates that in vivo the depth at which HY-PDT elicits tumor necrosis is not only determined by photophysical considerations (light penetration, number of absorbed photons) but is also influenced significantly by other mechanisms such as vascular effects. Therefore, despite the relatively short-wavelength peaks of absorption, our observations suggest that HY is an effective photodynamic agent that can be useful in the treatment of tumors with depths in the range of 1 cm.

Hypericin in cancer treatment: more light on the way

Photodynamic therapy (PDT) has been described as a promising new modality for the treatment of cancer. PDT involves the combination of a photosensitizing agent (photosensitizer), which is preferentially taken up and retained by tumor cells, and visible light of a wavelength matching the absorption spectrum of the drug. Each of these factors is harmless by itself, but when combined they ultimately produce, in the presence of oxygen, cytotoxic products that cause irreversible cellular damage and tumor destruction. Hypericin, a powerful naturally occurring photosensitizer, is found in Hypericum perforatum plants, commonly known as St. John's wort. In recent years increased interest in hypericin as a potential clinical anticancer agent has arisen since several studies established its powerful in vivo and in vitro antineoplastic activity upon irradiation. Investigations of the molecular mechanisms underlying hypericin photocytotoxicity in cancer cells have revealed that this photosensitizer can induce both apoptosis and necrosis in a concentration and light dose-dependent fashion. Moreover, PDT with hypericin results in the activation of multiple pathways that can either promote or counteract the cell death program. This review focuses on the more recent advances in the use of hypericin as a photodynamic agent and discusses the current knowledge on the signaling pathways underlying its photocytotoxic action.