Mono-L-aspartyl chlorin e6 (NPe6) and hematoporphyrin derivative (HpD) in photodynamic therapy administered to a human cholangiocarcinoma model

Smart glypican-3-targeting peptide-chlorin e6 conjugates for targeted photodynamic therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly aggressive and lethal malignancy with poor prognosis, necessitating the urgent development of effective treatments. Targeted photodynamic therapy (PDT) offers a promising way to selectively eradicate tumor cells without affecting normal cells. Inspired by promising features of peptide-drug conjugates (PDCs) in targeted cancer therapy, herein a novel glypican-3 (GPC3)-targeting PDC-PDT strategy was developed for the precise PDT treatment of HCC. The GPC3-targeting photosensitizer conjugates were developed by attaching GPC3-targeting peptides to chlorin e6. Conjugate 8b demonstrated the ability to penetrate HCC cells via GPC3-mediated entry process, exhibiting remarkable tumor-targeting capacity, superior antitumor efficacy, and minimal toxicity towards normal cells. Notably, conjugate 8b achieved complete tumor elimination upon light illumination in a HepG2 xenograft model without harm to normal tissues. Overall, this innovative GPC3-targeting conjugation strategy demonstrates considerable promise for clinical applications for the treatment of HCC.

Benefits and safety of photodynamic therapy in patients with hilar cholangiocarcinoma: A meta-analysis

BACKGROUND

Photodynamic therapy (PDT) is a therapy evaluated for the treatment of cancers resistant to standard oncological treatments. PDT might be beneficial for the palliation of hilar cholangiocarcinoma.

AIM

To evaluate the efficacy and safety of PDT for treating hilar cholangiocarcinoma.

METHODS

PubMed, Embase, the Cochrane Library, and Web of Science were searched for articles published up to May 2021. The patients were grouped as PDT+stent vs. stent alone. The outcomes were survival, quality of life, and adverse events (AEs). Data were summarized using hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals (CIs).

RESULTS

Six studies were included in this meta-analysis. There were 235 and 211 patients in the PDT+stent and stent groups, respectively. The 1-year survival rate of the PDT+stent group was 0.56, and that of the control group was 0.25. The 2-year survival rate of the PDT+stent group was 0.16, and that of the control group was 0.07. PDT significantly prolonged overall survival compared to the controls (P = 0.002). No differences were detected in the occurrence of cholangitis (P = 0.996) and all other AEs (early complications, stent malfunction, total AEs, acute pancreatitis, liver abscess, and biliary hemorrhage) between the two groups.

CONCLUSION

PDT in patients with hilar cholangiocarcinoma could improve survival without additional AEs. Large-scale randomized controlled trials are needed to confirm the findings.

Recent Advances in Photodynamic Imaging and Therapy in Hepatobiliary Malignancies: Clinical and Experimental Aspects

The therapeutic and diagnostic modalities of light are well known, and derivative photodynamic reactions with photosensitizers (PSs), specific wavelengths of light exposure and the existence of tissue oxygen have been developed since the 20th century. Photodynamic therapy (PDT) is an effective local treatment for cancer-specific laser ablation in malignancies of some organs, including the bile duct. Although curability for extrahepatic cholangiocarcinoma is expected with surgery alone, patients with unresectable or remnant biliary cancer need other effective palliative therapies, including PDT. The effectiveness of PDT for cholangiocarcinoma has been reported experimentally or clinically, but it is not the standard option now due to problems with accompanied photosensitivity, limited access routes of irradiation, tumor hypoxia, etc. Novel derivative treatments such as photoimmunotherapy have not been applied in the field hepatobiliary system. Photodynamic diagnosis (PDD) has been more widely applied in the clinical diagnoses of liver malignancies or liver vascularization. At present, 5-aminolevulinic acid (ALA) and indocyanine green (ICG) dyes are mainly used as PSs in PDD, and ICG has been applied for detecting liver malignancies or vascularization. However, no ideal tools for combining both PDD and PDT for solid tumors, including hepatobiliary malignancies, have been clinically developed. To proceed with experimental and clinical trials, it is necessary to clarify the effective photosensitive drugs that are feasible for photochemical diagnosis and local treatment.

Clinical Practice of Photodynamic Therapy Using Talaporfin Sodium for Esophageal Cancer

Photodynamic therapy (PDT) using a conventional photosensitizer was approved for esophageal cancer in the early 1990s; however, it was replaced by other conventional treatment modalities in clinical practice because of the high frequency of cutaneous phototoxicity and esophageal stricture after the procedure. The second-generation photosensitizer, talaporfin sodium, which features more rapid clearance from the body, was developed to reduce skin phototoxicity, and talaporfin sodium can be excited at longer-wavelength lights comparing with a conventional photosensitizer. Endoscopic PDT using talaporfin sodium was initially developed for the curative treatment of central-type early lung cancer in Japan, and was approved in the early 2000s. After preclinical experiments, PDT using talaporfin sodium was investigated for patients with local failure after chemoradiotherapy, which was the most serious unmet need in the practice of esophageal cancer. According to the favorable results of a multi-institutional clinical trial, PDT using talaporfin sodium was approved as an endoscopic salvage treatment for patients with local failure after chemoradiotherapy for esophageal cancer. While PDT using talaporfin sodium is gradually spreading in clinical practice, further evaluation at the point of clinical benefit is necessary to determine the importance of PDT in the treatment of esophageal cancer.

Plant-derived chlorophyll derivative loaded liposomes for tri-model imaging guided photodynamic therapy

Plant-derived chlorophyll derivatives with a porphyrin ring structure and intrinsic photosynthesis have been widely used in biomedicine for cancer theranostics. Owing to their poor water solubility, chlorophyll derivatives are very difficult to use in biomedical applications. In this work, pyropheophorbide acid (PPa) (liposome/PPa) nanoparticles, a liposome-encapsulated chlorophyll derivative, are designed for tri-model imaging guided photodynamic therapy (PDT) of cancer. The obtained liposome/PPa nanoparticles significantly enhance the water solubility of PPa, prolong blood circulation and optimize the bio-distribution in mice after intravenous injection. Utilizing their intrinsic fluorescence, high near-infrared (NIR) absorbance and extra radiolabeling, liposome/PPa nanoparticles could be used as excellent contrast agents for multimodal imaging including fluorescence (FL) imaging, photoacoustic (PA) imaging and SPECT/CT imaging. Under 690 nm laser irradiation at a low power density, liposome/PPa nanoparticles significantly inhibit tumor growth, further demonstrating the therapeutic efficiency of PDT using PPa. Therefore, our work developed liposome/PPa nanoparticles as multifunctional nanoagents for multimodal imaging guided PDT of cancer. This will further prompt the clinical applications of PPa in the future.

cRGD Peptide-Conjugated Pyropheophorbide-a Photosensitizers for Tumor Targeting in Photodynamic Therapy

Pyropheophorbide-a (Pyro) is a highly promising photosensitizer for tumor photodynamic therapy (PDT), although its very limited tumor-accumulation ability seriously restricts its clinical applications. A higher accumulation of photosensitizers is very important for the treatment of deeply seated and larger tumors. The conjugation of Pyro with tumor-homing peptide ligands could be a very useful strategy to optimize the physical properties of Pyro. Herein, we reported our studies on the conjugation of Pyro with a cyclic cRGDfK (cRGD) peptide, an integrin binding sequence, to develop highly tumor-specific photosensitizers for PDT application. To further reduce the nonspecific uptake and, thus, reduce the background distribution of the conjugates in normal tissues, we opted to add a highly hydrophilic polyethylene glycol (PEG) chain and an extra strongly hydrophilic carboxylic acid group as the linker to avoid the direct connection of the strongly hydrophobic Pyro macrocycle and cRGD ligand. We reported here the synthesis and characterization of these conjugates, and the influence of the hydrophilic modification on the biological function of the conjugates was carefully studied. The tumor-accumulation ability and photodynamic-induced cell-killing ability of these conjugates were evaluated through both in vitro cell-based experiment and in vivo distribution and tumor therapy experiments with tumor-bearing mice. Thus, the synthesized conjugate significantly improved the tumor enrichment and tumor selectivity of Pyro, as well as abolished the xenograft tumors in the murine model through a one-time PDT treatment.

Syntheses and PDT activity of new mono- and di-conjugated derivatives of chlorin e6

Syntheses of three new chlorin e6 conjugates for PDT of tumors are reported. One of the new compounds 17 is conjugated with lysine at the 131-position, but the others are mono-conjugated 14 or diconjugated 15 with the non-amino acid species ethanolamine. Cellular experiments with the three new compounds and previously synthesized non-amino acid 152-conjugates (7-10), 131-monoconjugates 14, 16, and a 131,152-diconjugate 12 are reported. In vitro cytotoxicity experiments show that the 131-conjugates are more toxic than the 152-conjugates, and the most toxic derivative (dark- and photo-toxicity) is the 131-ethylenediamine conjugate 11. The most useful PDT photosentitizers appear to be the ethanolamine derivatives, conjugated at the 152- and the 131,152-positions; these show high phototoxicity but relatively low dark toxicity compared with 11, and also the highest dark/photo cytotoxicity ratios.

Chlorin e6 131:152-Anhydride: A Key Intermediate in Conjugation Reactions of Chlorin e6

Since the patent for the photodynamic therapy agent Talaporfin (mono-L-aspartylchlorin e₆) was issued in 1987, confusion has existed regarding which of the three carboxylic acid groups in the chlorophyll degradation product, chlorin e₆ (1), is modified in standard amino acid type conjugations (using DCC or EDC and an organic base) with amino acids and other biomolecules. Here it is shown that the site of conjugation is the central 15²-carboxylic acid, such reactions proceeding in numerous examples via a 13¹,15²-anhydride for which a high resolution X-ray structure is reported. Conjugation with eight oxygen and nitrogen nucleophiles, in every case, afforded the 15²-conjugate, reinforcing the earlier conclusion that Talaporfin is the 15²-aspartyl conjugate of chlorin e₆ and suggesting that reports of 17³-conjugation of chlorin e₆ using stoichiometric peptide coupling procedures should be subjected to further scrutiny.

Role of photodynamic therapy and intraductal radiofrequency ablation in cholangiocarcinoma

Cholangiocarcinoma comprises 3% of all gastrointestinal malignancies. Prognosis is poor as the disease is locally advanced at the time of its presentation. Biliary endoprosthesis are widely used for biliary decompression, however, they only provides temporary relief. Photodynamic therapy and Radiofrequency ablation are two innovative approaches performed endoscopically to locally destruct the malignant tissue. This chapter focuses on their application and appropriate use along with their benefits and complications.

Photodynamic therapy in cholangiocarcinoma: an overview

Cholangiocarcinoma is a challenge to manage; mortality rate is nearly as high as the incidence. Unless curative resection is performed, these tumours are rapidly fatal because they respond poorly to current therapies. Symptoms occur late in cholangiocarcinoma and curative resection can be performed in less than half of the patients. In non-resectable disease, endoprostheses insertion can relieve jaundice and improve quality of life, provided that tumour extension does not lead to diffuse intrahepatic stenoses of ductal system. However, tumour growth cannot be influenced and therefore, prognosis remains dismal. Despite the fact, that radiotherapy and chemotherapy could reduce tumour volume and growth, no survival advantage has yet been shown. Photodynamic therapy has been evaluated as an new additional, palliative option. A randomised trial comparing photodynamic therapy plus endoprostheses insertion versus endoprostheses insertion alone, indicates a considerably benefit on survival time, cholestasis and quality of life in large, advanced cholangiocarcinoma. Furthermore, few specific side effects occurred. Since photodynamic therapy is the first approach leading to an improvement of prognosis, it should be offered to patients with non-resectable cholangiocarcinoma.

Current status of photodynamic therapy for bile duct cancer

The most common form in bile duct cancers is a highly desmoplastic cancer with a growth pattern characterized by periductal extension and infiltration. The prognosis of bile duct cancers, especially hilar cholangiocarcinoma, is limited by tumor spread along the biliary tree leading to refractory obstructive cholestasis, cholangitis, and liver failure. Although biliary endoprosthesis improves occlusion rates and reduces the number of therapeutic interventions, median survival time is not ameliorated. Photodynamic therapy (PDT) is a local photochemical tumor treatment that consists of a photosensitizing agent in combination with laser irradiation of a distinct wavelength. Tumor ablation with PDT combined with biliary stenting reduces cholestasis and significantly improves median survival time in selected patients with bile duct cancers.

Synergic effect of photodynamic therapy using talaporfin sodium with conventional anticancer chemotherapy for the treatment of bile duct carcinoma

BACKGROUND

Photodynamic therapy (PDT) is an effective laser treatment for locally treating advanced bile duct carcinoma (BDC). The study objective was to evaluate the synergic effect of PDT using a new photosensitizer, talaporfin sodium (Laserphyrin), in combination with conventional anticancer drug treatments.

METHODS

The range of the necrotic area, the percentage of apoptosis-positive cells, the vascular endothelial growth factor expression quantification, and the proliferating cell nuclear antigen-labeling index, as treatment effects, were examined in the BDC cell line (NOZ) in vitro and in vivo (4-wk-old male BALB/c mice).

RESULTS

Tumor viability was determined by an in vitro MTS assay. PDT with a single treatment of 5-fluorouracil, gemcitabine, oxaliplatin, and cis-diamminedichloroplatinum showed a significantly lower viability compared with the control or the PDT-alone group (P<0.05). Furthermore, administering PDT combined with two anticancer drugs showed a further decline in the tumor viability. A treatment of PDT combined with oxaliplatin and gemcitabine showed the least viability (P<0.05). Thus, this regimen was administered in the in vivo study. The tumor necrotic area, apoptosis positivity, and the vascular endothelial growth factor expression rate were higher in the PDT with anticancer drugs group compared with those of the other groups (P<0.05). The proliferating cell nuclear antigen-labeling index results in the PDT with the anticancer drugs group were significantly lower than those of the other groups (P<0.05).

CONCLUSIONS

A treatment of PDT combined with gemcitabine and oxaliplatin showed the best synergic effect for necrosis, apoptosis, and cytostatic alterations for the treatment of BDC.

Surface layer-preserving photodynamic therapy (SPPDT) in a subcutaneous mouse model of lung cancer

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) may be a less invasive treatment for lung cancer. Our newly developed surface layer-preserving PDT (SPPDT) technique enables us to irradiate deep tumor while preserving the overlying tissue. The aim of this basic study was to verify that the SPPDT technique might be applied to lung cancer.

STUDY DESIGN/MATERIALS AND METHODS

PDT with talaporfin sodium was performed using a pulsed laser with different pulse dose rates (PDRs, 2.5-20.0 mJ/cm(2) /pulse) in a mouse model of subcutaneous tumor. To mimic the tracheal wall structure and a thoracic tumor in the tracheobronchus, we also made a mouse model in which a piece of swine cartilage was placed between the dermis and the tumor, and PDT was carried out 2 weeks after implantation. In both experiments, the tissue samples were collected 48 hours after PDT and evaluated microscopically.

RESULTS

SPPDT using a high-PDR laser damaged the underlying tissue but left the superficial tissue intact in the mouse subcutaneous tumor model. In SPPDT, a higher PDR produced a thicker layer of intact superficial tissue than a lower PDR, while a lower PDR produced a deeper layer of damaged tissue than a higher PDR. SPPDT was also able to preserve the superficial tissue and to damage the tumor tissue beneath the cartilage implant.

CONCLUSION

SPPDT was able to damage tumor beneath the superficial normal tissue layer, which included tracheal cartilage in the mouse model. The thickness control of SPPDT was provided by controlling laser pulse intensity. SPPDT is a new technology, whose future potential is unknown. The initial clinical application of this technology could be endoscopic treatment (e.g., palliative therapy of thoracic malignancies via bronchoscopy).

Advantages of laserphyrin compared with photofrin in photodynamic therapy for bile duct carcinoma

BACKGROUND

The aim of this study was to compare the effects of laserphyrin-PDT (L-PDT) on biliary cancer with those of the conventional photosensitizer, photofrin-PDT (P-PDT).

METHODS

An animal tumor model was established by inoculation of NOZ cells in 4-week-old male BALB/c mice. The laser light wavelength was set at 630 nm for P-PDT and 660 nm for L-PDT, at a frequency of 10 Hz. Each group received a total energy flux of 60 J/cm(2). The proportion of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling)-positive cells, expression of VEGF (vascular endothelial growth factor) and the PCNA (proliferating cell nuclear antigen)-labeling index (LI) were assessed after PDT.

RESULTS

L-PDT had significantly more potent apoptotic effects at 48 and 72 h after light exposure compared with P-PDT (P < 0.001). The mean PCNA-LI was significantly lower in the L-PDT group than the P-PDT group and the index was significantly lower at several time points after PDT (6, 12, 24, 48 and 72 h after laser light exposure) in the L-PDT than P-PDT (P < 0.001 vs. control). The cell proliferative activity was significantly decreased at 12 and 24 h after P-PDT compared with the control (P < 0.001). VEGF expression was significantly higher at 3 h after L-PDT compared with the control (P < 0.05), whereas it was significantly higher at many time points after P-PDT (3, 6, 48 and 72 h; P < 0.05 vs. control).

CONCLUSIONS

L-PDT is a better approach for biliary cancer than the conventional P-PDT, based on its potent apoptotic and cytostatic effects.

Advances in photodynamic therapy for the treatment of hilar biliary tract cancer

The prognosis of patients with nonresectable hilar biliary tract cancer (hBTC) is poor. Responsiveness to chemotherapy or radiochemotherapy is moderate at best, and patients are at a high risk of dying early from complications of local tumor infiltration (e.g., cholestasis, septic cholangitis, empyema or liver failure) rather than systemic disease. Therefore, palliative local therapy for the prevention of tumor complications plays a central role and still yields the longest survival times. Photodynamic therapy (PDT) is a local-ablative, tumor tissue-specific treatment currently representing the standard of care for nonresectable hBTC. Throughout the literature, PDT plus biliary drainage achieves median survival times in the range of 9-21 months (average 14-16 months), compared with approximately 6 months for drainage only. This article summarizes the recent advances in preclinical and clinical experience of PDT for hBTC, including experimental in vitro and in vivo studies, clinical studies and an overview of the ongoing clinical trials.

The role of photodynamic therapy for hilar cholangiocarcinoma

The prognosis for hilar cholangiocarcinoma is limited by tumor spread along the biliary tree leading to refractory obstructive cholestasis, cholangitis, and liver failure. Palliation with biliary endoprostheses results in median survival times of 4-6 months for advanced bile duct cancer. Photodynamic therapy (PDT) is a local photochemical tumor treatment consisting of a photosensitizing agent combined with laser irradiation of a distinct wavelength. Tumor ablation with PDT combined with biliary stenting reduces cholestasis and significantly improves median survival time. However, the treatment is not widely available, and the photosensitizers used for PDT cause prolonged photosensitivity. Optimum control of tumor spread along the bile ducts and control of cholestasis and cholangitis will prolong survival in one to two thirds of patients, and renders them suitable for other antitumor therapies.

Photodynamic therapy for cholangiocarcinoma

Cholangiocarcinoma is the primary malignancy arising from the biliary epithelium, and it presents as jaundice, cholestasis, and cholangitis. Over 50 percent of patients present with advanced-stage disease, and the prognosis is poor with the survival measured in months even after biliary decompression. Palliative management has become the standard of care for unresectable disease, and this involves an endoscopic approach. Photodynamic therapy (PDT) involves the administration of a photosensitizer followed by local irradiation with laser therapy. The use of PDT for palliation of bile-duct tumors has produced promising results. Several studies conducted in Europe and the United States have shown that PDT produces a marked improvement in the symptoms of cholestasis, survival, and quality of life. This chapter summarizes the principle of PDT, the technique employed, and the published experience regarding PDT for cholangiocarcinoma.

The role of porphyrin chemistry in tumor imaging and photodynamic therapy

In recent years several review articles and books have been published on the use of porphyrin-based compounds in photodynamic therapy (PDT). This critical review is focused on (i) the basic concept of PDT, (ii) advantages of long-wavelength absorbing photosensitizers (PS), (iii) a brief discussion on recent advances in developing PDT agents, and (iv) the various synthetic strategies designed at the Roswell Park Cancer Institute, Buffalo, for developing highly effective long-wavelength PDT agents and their utility in constructing the conjugates with tumor-imaging and therapeutic potential (Theranostics). The clinical status of certain selected PDT agents is also summarized (205 references).

Novel photodynamic therapy against biliary tract carcinoma using mono-L: -aspartyl chlorine e6: basic evaluation for its feasibility and efficacy

BACKGROUND

Recently, a second-generation photosensory agent for photodynamic therapy (PDT), mono-L: -aspartyl chlorine e6 (NPe6), which degrades rapidly in vivo, has been developed. We evaluated its feasibility and efficacy for treatment in biliary tract carcinoma.

METHODS

A transmittance of semiconductor laser light (664 nm), sensitivity of a human biliary tract carcinoma cell line, and disorder to normal tissue including Glissonian constructs and adjacent hepatocytes were investigated.

RESULTS

The transmittance of the laser was 85-91% through yellow clear bile and that of the bile including 50 microg/ml NPe6 was 17-48%. The effective concentration of NPe6 which showed LD50 for a cell line was 12.5 microg/ml, and that of LD95 was 25 microg/ml. NPe6 in the supernatant reduced laser transmissiveness, but it had little influence on the antitumor effect in supernatant with or without NPe6. The NOZ cell-tumor volume was reduced significantly 14 days after irradiation in the PDT group (PDT 69.9 +/- 44.6 mm(3) vs control 296.3 +/- 239.9 mm(3) P < 0.05). No severe hepatic disorder including Glisson components was observed by the histological findings.

CONCLUSION

NPe6 PDT was effective in carcinomas even in the presence of bile, and causes no serious complication for the liver and Glisson structure. Therefore, NPe6 PDT will be a useful candidate as a new therapy for biliary tract carcinomas.

Unresectable cholangiocarcinoma: comparison of survival in biliary stenting alone versus stenting with photodynamic therapy

BACKGROUND & AIMS

Photodynamic therapy (PDT) for unresectable cholangiocarcinoma is associated with improvement in cholestasis, quality of life, and potentially survival. We compared survival in patients with unresectable cholangiocarcinoma undergoing endoscopic retrograde cholangiopancreatography (ERCP) with PDT and stent placement with a group undergoing ERCP with stent placement alone.

METHODS

Forty-eight patients were palliated for unresectable cholangiocarcinoma during a 5-year period. Nineteen were treated with PDT and stents; 29 patients treated with biliary stents alone served as a control group. Multivariate analysis was performed by using Model for End-Stage Liver Disease score, age, treatment by chemotherapy or radiation, and number of ERCP procedures and PDT sessions to detect predictors of survival.

RESULTS

Kaplan-Meier analysis demonstrated improved survival in the PDT group compared with the stent only group (16.2 vs 7.4 months, P<.004). Mortality in the PDT group at 3, 6, and 12 months was 0%, 16%, and 56%, respectively. The corresponding mortality in the stent group was 28%, 52%, and 82%, respectively. The difference between the 2 groups was significant at 3 months and 6 months but not at 12 months. Only the number of ERCP procedures and number of PDT sessions were significant on multivariate analysis. Adverse events specific to PDT included 3 patients with skin phototoxicity requiring topical therapy only.

CONCLUSIONS

ERCP with PDT seems to increase survival in patients with unresectable cholangiocarcinoma when compared with ERCP alone. It remains to be proved whether this effect is attributable to PDT or the number of ERCP sessions. A prospective randomized multicenter study is required to confirm these data.

Liver transplantation for hilar cholangiocarcinoma

Hilar cholangiocarcinoma was accepted as an indication for liver transplantation at the beginning of the transplantation era. Owing to disappointing long-term results for this indication, and in parallel, encouraging results in patients with benign disease, hilar cholangiocarcinoma has generally not been accepted as an indication for liver transplantation in recent years. To improve results, more aggressive approaches have been used: "abdominal organ cluster transplantation" and "extended bile duct resection", which lead to increased long-term survival rates. However, with improving results after conventional extrahepatic bile duct resection in combination with partial hepatectomy, extended procedures in combination with liver transplantation never became a real option in the treatment of hilar cholangiocarcinoma. However, new awareness of liver transplantation in the treatment of this cancer has been raised for patients with hilar cholangiocarcinoma in the context of underlying liver diseases such as primary sclerosing cholangitis, which preclude liver resection. Current results show increased survival figures, in particular in well-selected patients with early tumor stages. Further improvements in long-term survival may be reached with new adjuvant and neoadjuvant protocols. Patients with neoadjuvant radiochemotherapy show long-term results similar to those for liver transplantation for other indications. Also, photodynamic therapy and the use of new antiproliferative immunosuppressive agents may be an approach for further improvement of the long-term results. Currently, liver transplantation for the treatment of hilar cholangiocarcinoma should be restricted to centers with experience in the treatment of this cancer and should be taken into consideration in patients with contraindications to liver resection.

Mono-(l)-aspartylchlorin-e6?

Mono-(L)-aspartylchlorin-e6 (also known as Talaporfin, NPe6, MACE, and most recently LS-11) is a potent sensitizer for photodynamic therapy that is currently undergoing clinical trials. Using a combination of unambiguous partial synthesis from pheophytin-a and methyl pheophorbide-a, NMR spectroscopy, and single crystal X-ray diffraction, the structure of mono-(L)-aspartylchlorin-e6 is definitively shown to be the isomer in which the aspartyl residue is attached at the 15(2)-side chain position. This conclusion is contrary to earlier assumptions, but affirms the conclusions of a study based on NMR spectroscopy; a rationale for the unique formation of the 15(2)-aspartyl derivative is proposed.

Uptake and retention of the photosensitizer mono-l-asparthyl chlorine e6 in experimental malignant glioma

The objective of the study was to investigate the potential of mono-L-aspartyl chlorine e6 (NPe6), a water-soluble photosensitizer derived from chlorophyll, for use in photodynamic diagnosis (PDD) of malignant brain tumor. A C6 glioma cell line was transplanted in the SD rat brain to create a brain tumor model. Five days after transplantation, NPe6 was administrated via the tail vein at concentrations ranging from 1.25 to 10 mg/kg; then the skull was opened in the rat brain, the site of tumor transplant was irradiated with a diode laser beam at 664 nm, and the time-course intensity and distribution of emerging fluorescence were observed. Furthermore, the correlation between fluorescence distribution and histopathological findings was investigated in the removed brain. Fluorescence was observed in the site of brain tumor transplant from 5 min after injection, and stable fluorescence was recognized at the site until 4 h after administration. No differences were noted in fluorescence intensity at NPe6 doses of 2.5 mg/kg or more; therefore, it was possible to estimate the optimal dose range. Fluorescence distribution had a clear correlation with tumor cell density, and it was possible to capture the margin of tumor cell invasion with fluorescence. The photosensitizer NPe6 is capable of assessing tumor cell density in malignant glioma tissue in terms of differences in fluorescence intensity. The usefulness of PDD using 5-aminoleveulinic acid during surgery for malignant glioma has been recognized in recent years. The results of the present study suggested the potential of NPe6 as a promising photosensitizer for use in PDD for accurate grasp of the extent of removal during the course of malignant glioma surgery.

Technology insight: Photodynamic therapy for cholangiocarcinoma

Cholangiocarcinoma is, in most cases, rapidly fatal. Curative resection can only be offered to approximately 10% of patients. Even after seemingly curative resection, recurrence frequently occurs. Adjuvant chemotherapy and/or radiotherapy do not reduce the recurrence rate after resection. In the palliative setting, endoscopic or percutaneous biliary drainage is performed to relieve jaundice; however, poor results have been obtained in patients with tumors involving the intrahepatic bile ducts. Biliary drainage alleviates jaundice, but there is no evidence that it prolongs life. Palliative chemotherapy and/or radiotherapy have not been proven to prolong life and relieve jaundice. Photodynamic therapy (PDT) is a relatively new local, minimally invasive procedure that can be used to treat cholangiocarcinoma. PDT uses the physical properties of light-absorbing molecules, so-called photosensitizers, which accumulate within proliferating cells. Activation of the photosensitizer by a non-thermal laser leads to selective photochemical destruction of tumors. In a randomized trial of patients with nonresectable cholangiocarcinoma, PDT prolonged survival time, improved cholestasis and quality of life considerably, and had a favorable side-effect profile. A second randomized trial confirmed the beneficial effect of PDT. For the time being, PDT is recommended for patients with nonresectable disease. The role of PDT before and after surgical resection needs to be assessed.

In vitro behavior of Porfimer sodium and Talaporfin sodium with high intensity pulsed irradiation

We studied pulse energy density dependence of two distinctive clinical photosensitizers, Porfimer sodium and Talaporfin sodium, in terms of oxygen consumption, photodegradation in these photosensitizer solutions, and rat prostate cancer cell line photocytotoxicity. The transient transmittances during the pulsed irradiation to these photosensitizer solutions were measured with the pulse energy densities ranging from 0.31 to 31 mJ/cm2. We revealed that Talaporfin sodium was easier to produce absorption saturation than Porfimer sodium. The significant suppression of Talaporfin sodium mediated oxygen consumption, photodegradation, and photocytotoxicity which were observed with pulse energy densities increasing from 0.5 to 10 mJ/cm2. This result could be mainly attributed to absorption saturation. On the other hand, Porfimer sodium did not display significant absorption saturation with the pulse energy densities ranging from 0.31 to 31 mJ/cm2. The photodegradation mechanism for Porfimer sodium changed at high pulse energy density. This phenomenon might accelerate the photodegradation and cause the photocytotoxicity suppression.

Uses of photodynamic therapy in premalignant and malignant lesions of the gastrointestinal tract beyond the esophagus

Much has recently been written regarding the use of photodynamic therapy for the treatment of esophageal carcinoma and dysplastic Barrett's esophagus. This review, however, describes the clinical experience using photodynamic therapy with various photosensitizer agents for the treatment of diseases in other areas of the gut, especially the pancreaticobiliary tract where European studies have established the role of porfimer sodium photodynamic therapy in the management of patients with cholangiocarcinoma.

Pilot study to assess patient outcomes following endoscopic application of photodynamic therapy for advanced cholangiocarcinoma

BACKGROUND

Photodynamic therapy (PDT) has demonstrated promise in the palliative treatment of advanced cholangiocarcinoma. The aim of this pilot study was to assess the outcome in patients with non-resectable cholangiocarcinoma following endoscopic application of PDT directly into the biliary tract.

METHODS

In patients with advanced cholangiocarcinoma, endoscopic retrograde cholangiopancreatography (ERCP) was performed to define the proximal and distal extent of intraductal tumor. Sodium porfimer was administered intravenously to all patients. Forty-eight hours later, a commercially available cylindrical diffusing laser fiber (1-2.5 cm in length, OptiGuide) designed for esophageal use was advanced across the biliary strictures. Laser light was applied at a power of 400 mW/cm fiber for a total energy of 180 J/cm(2) using an argon-pumped tunable dye laser. Patients received endoscopic PDT every 3 months provided they maintained a favorable performance status. Plastic biliary stents were replaced immediately following light application and were maintained in all patients.

RESULTS

Using a preloaded catheter, adequate positioning of the laser fiber was achieved in all patients. Eight patients with advanced cholangiocarcinoma received a total of 19 PDT treatments, range 1-5 treatments/patient. All eight patients were followed until death; mean follow-up was 9.8 months. Median survival from the date of the first PDT treatment was 276 days, which compares favorably with published series that have reported median survival times between 45 and 127 days for patients with bismuth type III and IV tumors treated with stenting alone.

CONCLUSIONS

Endoscopic application of PDT demonstrates promise in prolonging survival in patients with advanced cholangiocarcinoma. Additional randomized clinical trials using commercially available fibers are needed to fully evaluate both the optimum frequency and treatment interval of endoscopic PDT in the management of advanced cholangiocarcinoma.

Spectrometric characteristics and tumor-affinity of a novel photosensitizer: mono-l-aspartyl aurochlorin e6 (Au-NPe6)

Photodiagnosis and photodynamic therapy with photosensitizers can be indicated only for tumors of the superficial type, because these approaches utilizing visible light are limited by said light penetrability. To overcome this disadvantage, we innovated a novel photosensitizer, mono-l-aspartyl aurochlorin e6 (Au-NPe6), by incorporating a gold atom in the center of tetrapyrrole ring of NPe6 with a coordination bond. The gold atom in Au-NPe6 plays a role as an X-ray interceptor to detect deeply sited tumors. In this study, the absorption spectrum of novel Au-NPe6 in the diagnosis of deeply sited tumors was investigated, and the results were compared with the parent photosensitizer NPe6. Furthermore, the tumor-affinity of Au-NPe6 was evaluated using atomic absorption spectrometry. Despite the fact that both photosensitizers display a difference in the absorption spectrum, waveform changes of either photosensitizer with human serum albumin established a saturation point at a molar ratio of 1:1. The results indicate that it is highly possible that Au-NPe6 bound with albumin at a molar ratio (1:1) similar to NPe6. The accumulation rate of gold in tumor tissues was always significantly (p<0.05) higher than that in normal muscle tissues during the observation terms. Moreover, absorption spectra of tumor-tissue homogenates obtained from tumor-bearing mice after Au-NPe6 administration revealed a common peak with a wavelength equivalent to that of albumin-bond Au-NPe. This result suggests that the gold atom and NPe6 probably remained bonded even when Au-NPe6 was incorporated in tumor tissues.

Effects of photodynamic therapy using a fractionated dosing of mono-l-aspartyl chlorin e6 in a murine tumor

One of the 'second generation' photosensitizing agents is N-acetyl chlorin e6 (NPe6). This product has a strong absorbance band at 665 nm, permitting treatment at a greater depth of tumor than earlier agents based on porphyrin structures. We examined the effects of fractionated drug administration on photodynamic efficacy. Prior studies had shown that it is the level of NPe6 in the circulation that predicts for photodynamic efficacy, indicating vascular shut-down to be the predominant mode of tumor control. Although pharmacokinetic studies revealed that >99% of NPe6 was lost from the circulation, it appears that a fractionated dosage protocol can promote photodamage to neoplastic tissue in vivo. This study also indicated the potential utility of an implantable micro array for tumor irradiation.

Novel bacteriochlorine for high tissue-penetration: photodynamic properties in human biliary tract cancer cells in vitro and in a mouse tumour model

Photodynamic therapy of bile duct cancer using hematoporphyrin derivative (HPD) and laser light of 630 nm wavelength is confined to a tumouricidal tissue penetration of 4 mm, which might be doubled with laser light between 700 and 800 nm. Therefore, we investigated the photosensitising properties of a novel bacteriochlorine, tetrakis-pyridyl-tetrahydroporphyrin tosylat (THP) with high absorption at 763 nm. Two biliary cancer cell lines (BDC, GBC) were incubated with HPD or THP to assess cellular uptake kinetics, dark cytotoxicity, and photodynamic cytotoxicity (laser light exposure 1-20 J/cm2). Tumours grown from BDC cells in subcutaneous tissue of severe combined immunodeficient mice were treated with laser light of 30 J/cm2 after injection of THP. The concentrations that killed 50% of cells in the dark were 680 microg/ml of HPD, but > 6400 microg/ml of THP in BDC cells, and 220 microg/ml of HPD, but 6400 microg/ml of THP in GBC cells. Both cell lines exhibited uptake and retention of THP and photodynamic cytotoxicity (up to 86% cells killed). THP induced tumour-selective phototoxicity in the cholangiocarcinoma model. The novel bacteriochlorine THP exhibits photosensitiser properties in biliary tract cancer cells in vitro and in vivo and could achieve deep tumouricidal tissue penetration due to photoactivation at 763 nm.

Photodynamic therapy in patients with non-resectable hilar cholangiocarcinoma: 5-year follow-up of a prospective phase II study

BACKGROUND

Median survival of patients with non-resectable hilar cholangiocarcinoma is 3 to 6 months, even after biliary drainage. Therefore, a single-arm phase II study was conducted (July 1996 to October 1998) to investigate the effect of local photodynamic therapy; a significant improvement in survival (74%) was noted at 6 months. The present study is an analysis of the long-term follow-up for patients enrolled in that phase II study.

METHODS

Five-year follow-up data for the 23 patients enrolled in the original prospective study were analyzed by using Kaplan-Meier log-rank analysis.

RESULTS

Median survival after treatment was 11.2 months for patients without distant metastases (M0) and 9.3 months for all patients (M0+M1). The 1-year, 2-year, 3-year, and 4-year survival rates were estimated to be 47%, 21%, 11% and 5%, respectively, for patients with stage M0 cholangiocarcinoma, and 39%, 17%, 9%, and 4%, respectively, for patients with stages M0 and M1. Of the patients who died, 73.9% (n=17) were because of tumor progression; 26.1% (n=6) died as a result of cholangitis (n=4), septic shock (n=1), or appendicitis/peritonitis (n=1). For all patients, except one with diffuse liver metastases, there was improvement in cholestasis, performance, and quality of life, which was maintained for an extended period.

CONCLUSIONS

This 5-year follow-up study confirms that photodynamic therapy is safe and effective for non-resectable hilar cholangiocarcinoma, although it does not prevent progression of the disease.

Photodynamic therapy in cholangiocarcinomas

Symptoms occur late in cholangiocarcinoma and therefore only about half of the patients at the time of diagnosis are candidates for curative surgery. In patients with advanced non-resectable cholangiocarcinoma palliative treatment options are limited. Until now, insertion of endoprostheses for the treatment of cholestasis has been the method of choice. However, tumour growth cannot be influenced and so that prognosis is dismal. Although radiotherapy and chemotherapy are frequently used, prospective, randomized trials showing an improvement in survival time are missing. Encouraging results from prospective, single-arm phase II trials and a randomized trial using photodynamic therapy (PDT) in non-resectable cholangiocarcinoma indicate considerable benefit on survival with a good quality of life. Furthermore, PDT is well tolerated, with only few specific side-effects. This is of great importance in patients with short life expectancy. PDT should therefore be offered to all patients with non-resectable cholangiocarcinoma. However, before initiating PDT or any other palliative measure, a proper staging and a surgical consultation is necessary to avoid missing a curative surgical option.

EUS-guided photodynamic therapy of the pancreas: a pilot study

BACKGROUND

Photodynamic therapy of pancreatic cancer by using percutaneously placed light catheters has been reported. The feasibility and safety of EUS-guided photodynamic therapy of the pancreas was studied in a porcine model.

METHODS

After injection of porfimer sodium, a 19-gauge needle was inserted into the pancreas, the liver, the spleen, and the kidney under EUS guidance. A small diameter quartz optical fiber was passed through the EUS needle and used to illuminate the tissue with laser light. The tissue response to photodynamic therapy was examined.

RESULTS

Localized tissue necrosis was achieved in all organs, without significant complication. There was no significant difference in inflammation induced by photodynamic therapy within the various organs.

CONCLUSIONS

EUS-guided photodynamic therapy is a safe and simple technique that can induce small areas of focal tissue ablation within the liver, the pancreas, the kidney, and the spleen, and potentially could be used to treat a variety of benign and malignant conditions.

Successful photodynamic therapy for nonresectable cholangiocarcinoma: a randomized prospective study

BACKGROUND & AIMS

In nonrandomized trials, photodynamic therapy (PDT) had a promising effect on nonresectable cholangiocarcinoma (NCC). This prospective, open-label, randomized, multicenter study with a group sequential design compared PDT in addition to stenting (group A) with stenting alone (group B) in patients with NCC.

METHODS

In patients with histologically confirmed cholangiocarcinoma, endoscopic or percutaneous double stenting was performed. Patients fulfilling inclusion criteria were randomized to group A (stenting and subsequent PDT) and group B (stenting alone). For PDT, Photofrin 2 mg/kg body wt was injected intravenously 2 days before intraluminal photoactivation (wavelength, 630 nm; light dose, 180 J/cm(2)). Further treatments were performed in cases of residual tumor in the bile duct. The primary outcome parameter was survival time. Secondary outcome parameters were cholestasis and quality of life.

RESULTS

PDT resulted in prolongation of survival (group A: n = 20, median 493 days; group B: n = 19, median 98 days; P < 0.0001). It also improved biliary drainage and quality of life.

CONCLUSIONS

PDT, given in addition to best supportive care, improves survival in patients with NCC. The study was terminated prematurely because PDT proved to be so superior to simple stenting treatment that further randomization was deemed unethical.

Neoadjuvant photodynamic therapy as a new approach to treating hilar cholangiocarcinoma: a phase II pilot study

BACKGROUND

Only 20-30% of patients with hilar cholangiocarcinomas (CC) are candidates for potentially curative resection. However, even after curative (R0) resection, these patients have a disease recurrence rate of up to 76%. The current prospective Phase II study investigated photodynamic therapy (PDT) as a neoadjuvant treatment for CC.

METHODS

Seven patients with advanced proximal bile duct carcinoma were evaluated. Patients were treated with PDT at the area of tumor infiltration and 2 cm beyond and underwent surgery after a median period of 6 weeks (range, 3-44 weeks).

RESULTS

One patient had a Bismuth-Corlette Type II tumor, two patients had Type IIIa, one patient had Type IIIb, and three patients had Type IV. Cholestasis parameters after PDT decreased significantly. No relevant adverse events from PDT occurred except for minor intraoperative phototoxicity in one patient. Three patients underwent right-sided liver resections, two patients underwent left-sided liver resections, and one patient received a combined hilar resection with partial pancreatoduodenectomy (PD) due to tumor extension into the distal bile duct. Liver transplantation and PD were performed in another patient. In all patients, R0 resection was achieved. Four patients developed minor surgical complications, even though the bilioenteric anastomoses were sewn to PDT-pretreated bile ducts. No viable tumor cells were found in the inner 4 mm layer of the surgical specimens. The PDT-pretreated epithelium of the tumor-free proximal resection margins exhibited only minimal inflammatory infiltration. Tumors recurred in 2 patients 6 and 19 months after surgery. The 1-year recurrence free survival rate was 83%.

CONCLUSIONS

Neoadjuvant PDT for hilar CC is a low-risk procedure with efficient selective destruction of the superficial 4 mm layer of bile duct tumor without complications exceeding series without neoadjuvant PDT. Neoadjuvant PDT should be evaluated prospectively to determine whether it reduces the rate of local disease recurrence after potentially curative resection.

Palliative treatment of unresectable bile duct cancer: which stent? which approach?

Nonsurgical options for the palliative treatment of unresectable bile duct cancer are discussed. Despite all of the available approaches, the disease remains uniformly fatal. The goal of managing unresectable bile duct cancer is to treat the symptoms that still contribute to significant morbidity and mortality. Further development of new treatment strategies and modalities is needed to improve the quality of life and survival of patients with this disease.

Cholangiocarcinoma: recent progress. Part 2: molecular pathology and treatment

Part 2 of this review discusses DNA damage in biliary epithelial cells in the development of cholangiocarcinoma, alterations in cell kinetics of biliary epithelial cells, biliary epithelial mitoinhibition, and apoptosis that includes the role of Bcl-2, transforming growth factor-beta, telomerase activities and deregulation of Ras and p53, cancer-associated antigens in cholangiocarcinoma, precancerous lesions, stroma formation and angiogenesis, cancer invasion, cell-cell and cell-matrix interactions, and the mechanism of evasion from immune surveillance. These discussions are followed briefly by treatments such as photodynamic therapy, and surgical approaches comparing resection and liver transplantation.

Endoscopic application of photodynamic therapy for cholangiocarcinoma

BACKGROUND

Previous studies indicate that photodynamic therapy provides effective relief from biliary obstruction in advanced cholangiocarcinoma. This report describes a method of applying photodynamic therapy in the biliary tract by using accessories available in the United States.

METHODS

Endoscopic retrograde cholangiography was performed to define the proximal and distal extent of intraductal tumor. Patients were injected with 2 mg/kg of sodium porfimer. Forty-eight hours later a commercially available cylindrical diffusing laser fiber was inserted into an 8F biliary catheter equipped with a 0.038 inch side-hole at its distal tip. After positioning of a 0.035 inch guidewire proximal to the biliary stricture, the preloaded catheter was advanced over the guidewire by using the monorail technique. Laser light was applied at a power of 400 mW/cm fiber for a total energy of 180 J/cm.(2)

RESULTS

Fourteen treatments were performed on 6 patients with tumors of Bismuth types IV (n = 2), III (n = 3), or II (n = 1). By using the preloaded biliary catheter, adequate positioning of the laser fiber was achieved in all patients. A fracture of the diffuser tip occurred during 1 of the treatments. Two patients developed acute cholangitis and 2 patients experienced skin phototoxicity.

CONCLUSIONS

Photodynamic therapy for cholangiocarcinoma is safe and technically feasible with a preloaded biliary catheter and a monorail technique for catheter positioning.

Photodynamic therapy in the biliary tract

Biliary tract cancers are rare malignancies usually characterized by slow growth and a low propensity for metastasis. Despite the relatively localized nature of these cancers, the only therapeutic measure with curative potential to date is surgical intervention. Because symptoms occur late, the diagnosis is rarely made at an early stage, and therefore only about half of the patients can have curative surgery. Patients with advanced disease face a dismal prognosis because palliative treatment options are limited. This review outlines recent advances in treatment of biliary cancer. Encouraging results from prospective, single-arm phase II trials of photodynamic therapy in nonresectable cholangiocarcinoma suggest considerable promise for this new palliative treatment modality. However, the apparent benefit of photodynamic therapy on survival, jaundice, and quality of life must be confirmed in a randomized multicenter trial.