Hypericin and photodynamic therapy decreases human pancreatic cancer in vitro and in vivo

Photodynamic therapy for pancreatic and biliary tract carcinoma

The prognosis of patients with pancreatic and biliary tract cancer treated with conventional therapies such as stent insertion or chemotherapy is often poor, and new approaches are urgently needed. Surgery is the only curative treatment but is appropriate in less than 20% of cases, and even then it is associated with a 5-yr survival of less than 30% in selected series. Photodynamic therapy represents a novel treatment for pancreaticobiliary malignancy. It is a way of producing localized tissue necrosis with light, most conveniently from a low-power, red laser, after prior administration of a photosensitizing agent, thereby initiating a non-thermal cytotoxic effect and tissue necrosis. This review outlines the mechanisms of action of photodynamic therapy including direct cell death, vascular injury, and immune system activation, and summarizes the results of preclinical and clinical studies of photodynamic therapy for pancreaticobiliary malignancy.

Lens α-Crystallin and Hypericin: A Photophysical Mechanism Explains Observed Lens Damage†¶

Determining whether alpha-crystallin (the major lens protein) affects the photophysics of hypericin, a photosensitizing agent found in various plants, such as St. John's Wort, is important. Hypericin shows promise in cancer and human immunodeficiency virus therapy but may harm individuals taking St. John's Wort extracts (for mild to moderate depression). Hypericin causes hypericism, which is characterized by cellular damage in light-exposed areas. Ocular tissues are at risk for photosensitized damage; thus, we investigated the effects on hypericin photophysics by alpha-crystallin. We measured the transient absorption spectra and the 1270 nm luminescence of singlet (1Deltag) oxygen produced from hypericin in the presence of alpha-crystallin. alpha-Crystallin complexes hypericin, extending the lifetime of its triplet excited state; the Stern-Volmer slope is negative, but not linear, after a saturation curve. Damage to the lens protein by hypericin is known to occur via singlet oxygen, which oxidizes methionine, tryptophan and histidine residues. Binding to alpha-crystallin does not inhibit singlet oxygen formation by hypericin. alpha-Crystallin reacts with singlet oxygen with a rate constant of 1.3 x 10(8) M(-1) s(-1). Thus, we anticipate that hypericin will be an effective photosensitizer in the lens.

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Infrared laser activation of indocyanine green inhibits growth in human pancreatic cancer

INTRODUCTION

Indocyanine green (ICG) is a clinically-approved, water-soluble dye that generates reactive singlet oxygen when activated by infrared light. Infrared light offers the advantage of deeper tissue penetration making ICG photodynamic therapy (PDT) ideal for treatment of intra-abdominal cancers such as pancreatic adenocarcinoma.

AIMS

To determine the cytotoxicity of ICG PDT in human pancreatic cancer.

METHODOLOGY

MIA PaCa-2, PANC-1, and BxPC-3 pancreatic cancer cells were incubated for 1 hour with 0 to 50 microg/mL ICG, serially washed to remove unbound dye, and then briefly exposed to infrared light from a diode laser at 0.45 W. MTT cell viability assays were performed at 72 hours post-treatment.

RESULTS

Toxicity to ICG or infrared laser alone was not observed in any of the cell lines. Cell viability assays showed an ICG dose-dependent ablation when combined with laser exposure (+L). In all 3 cancer cell lines, significant growth inhibition was seen at 10 microg/mL ICG + L with nearly total ablation at 20 microg/mL ICG + L (P < 0.01).

CONCLUSION

ICG PDT induces consistent and dramatic pancreatic cancer cell death. Since neither ICG nor laser alone caused toxicity, combination therapy may offer effective control of tumor growth with minimal side effects in patients with unresectable primary or metastatic pancreatic cancer.

Hyperforin a constituent of St John's wort (Hypericum perforatum L.) extract induces apoptosis by triggering activation of caspases and with hypericin synergistically exerts cytotoxicity towards human malignant cell lines

Hyperforin (HP) is an abundant component of St John's wort with antibiotic and antidepressive activity. We report here the ability of HP and that of polyphenolic procyanidin B2 (PB-2) to inhibit the growth of leukemia K562 and U937 cells, brain glioblastoma cells LN229 and normal human astrocytes. HP inhibited the growth of cells in vitro with GI(50) values between 14.9 and 19.9 microM. The growth inhibitory effect of PB-2 was more pronounced in leukemia cell lines K562 and U937, the GI(50) concentrations being about 12.5 microM established after 48 h incubation differed significantly (P<0.05) from those of LN229 and normal human astrocytes (103.1 and 96.7 microM), respectively. Further, HP and hypericin (HY) (a naphthodianthrone from St John's wort) acted synergistically in their inhibitory effect on leukemic (K562, U937) cell growth. Cell death occurred after 24 h treatment with HP and PB-2 by apoptosis. A dose-dependent loss of membrane phospholipid asymmetry associated with apoptosis was induced in all cell lines as evidenced by the externalization of phosphatidylserine (PS) and morphological changes in cell size and granulosity by scatter characteristics. In leukemia U937 cells, HP increased the activity of caspase-9 and caspase-3 and in K562 cells caspase-8 and caspase-3. In addition, the broad spectrum caspase inhibitor z-VAD-fmk inhibited both the appearance of PS exposure and the activation of caspases, illustrating the functional relevance of caspase activation during HP-induced apoptosis. Cytocidal effects of HP and its cooperation with HY on tumor growth inhibition in a synergistic manner make the St John's wort an interesting option in cancer warranting further in vitro and in vivo investigation.

[Methyl-D3]2hypericin as internal standard for quantification in human plasma

The multistep synthesis and negative ion-ESI fragmentation pattern of [methyl-D(3)](2)hypericin (1-D(6)) is described. The application of 1-d(6) as internal standard for the quantification of hypericin (1) in the ng mL(-1) range in human plasma by isotope-dilution LC-MS is demonstrated. The hypericin-containing plasma samples are spiked with 1-D(6), deproteinized and extracted with ethyl acetate. The extracts are injected into a HPLC-ESI-ion-trap system and the mass-separated negative ions from 1 and 1-D(6) are analysed. From their intensities linear standard curves over the concentration range from 1 to 10 ng mL(-1) are obtained. Accuracy, precision and recovery are discussed.

Potentiation of Photodynamic Therapy with Hypericin by Mitomycin C in the Radiation-induced Fibrosarcoma–1 Mouse Tumor Model¶

Hypericin, a polycyclic quinone obtained from plants of the genus Hypericum, has been shown to be a promising photosensitizer. We investigated the combination of hypericin-photodynamic therapy (PDT) and a bioreductive drug mitomycin C (MMC) in the present study. The radiation-induced fibrosarcoma-1 tumors were exposed to laser light (120 J/cm2 at 595 nm) 24 h after an intravenous injection of hypericin (1 mg/kg). Hypericin-PDT alone significantly decreased tumor perfusion and oxygen tension as demonstrated by India ink staining technique and OxyLite pO2 measurement, respectively. The in vivo-in vitro cell-survival assay revealed about 60% direct tumor cell killing immediately after PDT. No significant delayed tumor cell death was observed after PDT, which suggests that vascular damage does not contribute significantly to the overall tumor cell death. Injection of a 2.5 mg/kg dose of MMC 20 min before light application significantly decreased tumor cell survival and delayed tumor growth compared with PDT or MMC alone. No greater skin reaction was observed after the combination of MMC and PDT than after PDT alone. Our study demonstrates that combining hypericin-PDT with MMC can be effective in enhancing tumor response with little side effect.

Antivascular tumor eradication by hypericin-mediated photodynamic therapy

Photodynamic therapy (PDT) with hypericin has been shown to inhibit tumor growth in different tumor models, and tumor vascular damage was suggested to be mainly responsible for the antitumoral effect. Here, we demonstrate tumor vascular damage and its consequence on local tumor control after hypericin-mediated PDT by using both short and long drug-light intervals. Radiation-induced fibrosarcoma-1 tumors were exposed to laser light at either 0.5 or 6 h after a 5 mg/kg dose of hypericin. Tumor perfusion was monitored by fluorescein dye-exclusion assay and by Hoechst 33342 staining of functional blood vessels. Significant reduction in tumor perfusion was found immediately after both PDT treatments. A complete arrest of vascular perfusion was detected by 15 h after the 0.5 h-interval PDT, whereas well-perfused areas could still be found at this time in tumors after the 6 h-interval PDT. A histological study confirmed that primary vascular damage was involved in both PDT treatments. Tumor cells appeared intact shortly after light treatment, degenerated at later hours and became extensively pycnotic at 24 h after the 0.5 h-interval PDT. PDT under this condition led to complete tumor cure. In contrast, significant numbers of viable tumor cells, especially at the tumor periphery, were found histologically at 24 h after the 6 h-interval PDT. No tumor cure was obtained when PDT was performed at this time. Our results strongly suggest that targeting the tumor vasculature by applying short drug-light interval PDT with hypericin might be a promising way to eradicate solid tumors.

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%.

The correlation between hydrophilicity of hypericins and helianthrone: internalization mechanisms, subcellular distribution and photodynamic action in colon carcinoma cells

The internalization mechanism and subcellular distribution of hypericin (Hyp), hypericin tetrasulfonic acid (HypS4) and 1,3,4,6-tetrahydroxyhelianthrone (Hel) were studied in murine colon carcinoma CT26 cells, in protein-free medium or in the presence of serum proteins. The correlation between the extent of uptake of the sensitizers by cells that were incubated in the presence of different serum components, and the internalization mechanisms, was studied. The results indicate that sensitizer internalization may be a result of three mechanisms: partitioning, pinocytosis and endocytosis, and as a direct consequence is targeted to specific subcellular sites. While Hyp and Hel, the two lipophilic sensitizers, were localized in the endoplasmic reticulum after protein-free internalization, the hydrophilic HypS4 was localized in the cytoplasmic membrane and in lysosomes. An endolysosomal internalization route was revealed for Hyp and Hel under serum-enriched conditions showing lysosomal localization, as for HypS4. The lysosomal accumulation of Hyp-serum and specifically Hyp-LDL points to an endocytotic mechanism which is supported by its higher uptake parameter in an LDL-enriched medium, compared to the medium with 10% serum. The different uptake parameters of Hyp to cells, with or without serum, reflect the different mechanisms. Smaller differences in the uptake parameter for HypS4 reflect the distinction between partitioning and endocytosis, which, in this case, are both targeted to the lysosomes. The same uptake parameter of Hel to cells incubated in media with or without serum indicates the absence of the endocytotic mechanism. The interrelationship between subcellular targeting and photodynamic treatment was shown for the three sensitizers Hyp was found to be the most efficient sensitizer for PDT under our illumination protocol and it was dependent on internalization and localization sites.

Photodynamic therapy with hypericin induces vascular damage and apoptosis in the RIF-1 mouse tumor model

Hypericin, a polycyclic quinone obtained from plants of the genus Hypericum, has been proven to be a potent photosensitizer. The mechanism of tumor eradication and mode of cell death induced by in vivo photodynamic therapy (PDT) with hypericin were investigated in the present study using 2 therapeutic protocols. RIF-1 tumors were exposed to laser light at either 0.5 hr or 6 hr after hypericin administration (5 mg/kg, i.v.). A significant reduction in tumor perfusion, as determined by the retention of fluorescein in the tumor tissue, was detected immediately after both PDT treatments. Further decrease in tumor perfusion was observed in the hours after treatment. The re-establishment of tumor perfusion, however, occurred 24 hr after 6 hr-interval PDT, but not after 0.5 hr-interval PDT. The kinetics of tumor cell survival estimated by the in vivo/in vitro clonogenic assay revealed no or limited cell death when tumors were explanted immediately after irradiation, whereas a delayed but progressive cell death was detected when tumors remained in situ after both PDT treatments. The detection of nucleosomal DNA fragmentation by agarose gel electrophoresis or TUNEL assay and the assessment of cell morphology by light microscopy indicated that apoptosis was the most prominent tumor response to hypericin-mediated PDT. Furthermore, immunohistochemical analysis of the tumor tissue showed an increased expression of both Fas and Fas ligand after irradiation, suggesting that this cell death pathway might contribute to the overall PDT-induced apoptotic response. In conclusion, our results demonstrate that apoptosis, likely occurring as a result of vascular damage, is responsible for the tumor eradication by PDT with hypericin in this tumor model.

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.

Vascular endothelial growth factor is increased in ascites from metastatic pancreatic cancer

INTRODUCTION

Vascular endothelial growth factor (VEGF) is an angiogenic factor that increases vascular permeability. VEGF stimulates capillary formation and has mitogenic effects on vascular endothelial cells. The development of malignant ascites causes significant morbidity. We hypothesized that increased levels of VEGF play a role in the development of malignant ascites in patients with pancreatic cancer.

METHODS

Athymic mice underwent orthotopic implantation of human pancreatic ductal adenocarcinoma tumors (250,000 cells) into the body of the pancreas. Tumors were allowed to grow for 12 weeks, at which time ascites develops in 50% of mice. Paracentesis was performed on mice with noticeable ascites. Saline lavage was performed in mice with equivalent pancreatic tumor masses without ascites and served as control. Both ascites and tumor masses were harvested for VEGF protein quantitation by ELISA.

RESULTS

VEGF protein levels were elevated in malignant ascites by 15-fold compared to control mice with equivalent tumors (N = 6, P < 0.001, t test). VEGF levels were slightly higher in the primary tumor masses harvested from mice without ascites. Mice with ascites also had metastatic nodules throughout the abdominal cavity.

CONCLUSIONS

We are reporting for the first time that VEGF levels are increased in the ascites of nude mice with orthotopically transplanted human pancreatic cancers. VEGF increases vascular permeability and allows for extrapancreatic seeding of tumors. Irrespective of primary tumor size, intraperitoneal VEGF levels are increased when ascites and extrapancreatic nodules are present, while a paradoxical decrease is observed in VEGF levels of primary tumors.

St John's wort (Hypericum perforatum L.): a review of its chemistry, pharmacology and clinical properties

The chemical composition of St. John's wort has been well-studied. Documented pharmacological activities, including antidepressant, antiviral, and antibacterial effects, provide supporting evidence for several of the traditional uses stated for St John's wort. Many pharmacological activities appear to be attributable to hypericin and to the flavonoid constituents; hypericin is also reported to be responsible for the photosensitive reactions that have been documented for St. John's wort. With regard to the antidepressant effects of St John's wort, hyperforin, rather than hypericin as originally thought, has emerged as one of the major constituents responsible for antidepressant activity. Further research is required to determine which other constituents contribute to the antidepressant effect. Evidence from randomised controlled trials has confirmed the efficacy of St John's wort extracts over placebo in the treatment of mild-to-moderately severe depression. Other randomised controlled studies have provided some evidence that St John's wort extracts are as effective as some standard antidepressants in mild-to-moderate depression. There is still a need for further trials to assess the efficacy of St John's wort extracts, compared with that of standard antidepressants, particularly newer antidepressant agents, such as the selective serotonin reuptake inhibitors (recent comparative studies with fluoxetine and sertraline have been conducted). Also, there is a need for further studies in well-defined groups of patients, in different types of depression, and conducted over longer periods in order to determine long-term safety. St John's wort does appear to have a more favourable short-term safety profile than do standard antidepressants, a factor that is likely to be important in patients continuing to take medication. Concerns have been raised over interactions between St John's wort and certain prescribed medicines (including warfarin, ciclosporin, theophylline, digoxin, HIV protease inhibitors, anticonvulsants, selective serotonin reuptake inhibitors, triptans, oral contraceptives); advice is that patients taking these medicines should stop taking St John's wort, generally after seeking professional advice as dose adjustment of conventional treatment may be necessary.

Photodynamic therapy of murine fibrosarcoma with topical and systemic administration of hypericin

The in vivo antitumour activity of the natural photosensitizer hypericin was evaluated. C3H/DiSn mice inoculated with fibrosarcoma G5:1:13 cells were intraperitoneally or intratumourally injected with hypericin (5 mg/kg) and 2 hours later the mice were locally irradiated with laser light (488 nm, 150 mW/cm2, 180 J/cm2) when the tumour reached volume of 40-80 mm3 (approximately 17 days after inoculation). Tumours treated with hypericin alone as well as those irradiated with laser light alone have similar growth rates and none of these tumours regressed spontaneously. The mean tumour volume in hypericin-PDT treated groups was significantly lower in comparison to that found in the control group 3-5 weeks after the therapy. A higher proportion of animals with tumour volume less than 5-fold of the initial volume has been observed in both hypericin-PDT treated groups. Complete response to PDT has been observed for 44.4% of the animals with intraperitoneally administered hypericin and for 33.3% of the animals with intratumourally administered hypericin. Complete remission occurred in treated lesions with 3 mm or less in height. Hypericin-PDT significantly increased survival. However, no statistically significant difference in survival rate of animals has been found between the intratumoural and the intraperitoneal schedule of administration of hypericin.