X-ray Activated Nanoplatforms for Deep Tissue Photodynamic Therapy

Photodynamic therapy (PDT), the use of light to excite photosensitive molecules whose electronic relaxation drives the production of highly cytotoxic reactive oxygen species (ROS), has proven an effective means of oncotherapy. However, its application has been severely constrained to superficial tissues and those readily accessed either endoscopically or laparoscopically, due to the intrinsic scattering and absorption of photons by intervening tissues. Recent advances in the design of nanoparticle-based X-ray scintillators and photosensitizers have enabled hybridization of these moieties into single nanocomposite particles. These nanoplatforms, when irradiated with diagnostic doses and energies of X-rays, produce large quantities of ROS and permit, for the first time, non-invasive deep tissue PDT of tumors with few of the therapeutic limitations or side effects of conventional PDT. In this review we examine the underlying principles and evolution of PDT: from its initial and still dominant use of light-activated, small molecule photosensitizers that passively accumulate in tumors, to its latest development of X-ray-activated, scintillator-photosensitizer hybrid nanoplatforms that actively target cancer biomarkers. Challenges and potential remedies for the clinical translation of these hybrid nanoplatforms and X-ray PDT are also presented.

Porphylipoprotein Accumulation and Porphylipoprotein Photodynamic Therapy Effects Involving Cancer Cell-Specific Cytotoxicity

In photodynamic therapy (PDT) for neoplasms, photosensitizers selectively accumulate in cancer tissue. Upon excitation with light of an optimal wavelength, the photosensitizer and surrounding molecules generate reactive oxygen species, resulting in cancer cell-specific cytotoxicity. Porphylipoprotein (PLP) has a porphyrin-based nanostructure. The porphyrin moiety of PLP is quenched because of its structure. When PLP is disrupted, the stacked porphyrins are separated into single molecules and act as photosensitizers. Unless PLP is disrupted, there is no photosensitive disorder in normal tissues. PLP can attenuate the photosensitive disorder compared with other photosensitizers and is ideal for use as a photosensitizer. However, the efficacy of PLP has not yet been evaluated. In this study, the mechanism of cancer cell-specific accumulation of PLP and its cytotoxic effect on cholangiocarcinoma cells were evaluated. The effects were investigated on normal and cancer-like mutant cells. The cytotoxicity effect of PLP PDT in cancer cells was significantly stronger than in normal cells. In addition, reactive oxygen species regulated intracellular PLP accumulation. The cytotoxic effects were also investigated using a cholangiocarcinoma cell line. The cytotoxicity of PLP PDT was significantly higher than that of laserphyrin-based PDT, a conventional type of PDT. PLP PDT could also inhibit tumor growth in vivo.

Nonsurgical Approaches to Treat Biliary Tract and Liver Tumors

Endoscopic and percutaneous therapies have been shown to prolong life and reduce morbidity for patients with unresectable advanced stages of primary hepatobiliary malignancies. This article reviews pertinent studies published within the last 5 years that involve locoregional techniques to manage hepatocellular carcinoma, perihilar and distal cholangiocarcinoma. A major emphasis is placed on photodynamic therapy, radiofrequency ablation, irreversible electroporation, and microwave ablation. Technical advances, combinational therapies, and postintervention outcomes are discussed. Despite widespread application, high-quality evidence does not show superiority of any particular locoregional technique for treating advanced hepatobiliary cancers.

SnxWO3 as a theranostic platform for realizing multi-imaging-guided photothermal/photodynamic combination therapy

Precise oncotherapy requires effective cancer treatments that are guided by clinical imaging techniques. One of the most representative cases is multi-imaging-guided phototherapy. This study presents a novel multifunctional theranostic agent of SnxWO3 tungsten bronze, which is an excellent light absorber in the near infrared (NIR) range. Theoretical calculations based on density functional theory confirm that the insertion of donor Sn atoms into orthorhombic WO3 gives rise to the broadband visible-NIR absorption. Accordingly, both the photothermal effect and reactive oxygen species (ROS) production could be realized under NIR light irradiation by SnxWO3 tungsten bronze nanocrystals, thereby triggering the potent in vivo photothermal and photodynamic synergistic therapy. Meanwhile, modified SnxWO3 tungsten bronze has the functions of photoacoustic imaging (PAI), X-ray computed tomography (CT) imaging and near-infrared fluorescence (NIRF) imaging for tumor detection as well. Finally, for investigating the antitumor mechanism of in vivo solid tumors, clinical imaging modalities of B-mode ultrasonography (US) and magnetic resonance imaging (MRI) are employed to monitor the tumor evolution process after the photo-treatment, verifying a typically liquefactive necrosis process. These results indicate that the SnxWO3 tungsten bronze nanostructure is a promising theranostic agent for imaging-guided cancer therapy.

Success of photodynamic therapy in palliating patients with nonresectable cholangiocarcinoma: A systematic review and meta-analysis

AIM

To perform a systematic review and meta-analysis on clinical outcomes of photodynamic therapy (PDT) in non-resectable cholangiocarcinoma.

METHODS

Included studies compared outcomes with photodynamic therapy and biliary stenting (PDT group) vs biliary stenting only (BS group) in palliation of non-resectable cholangiocarcinoma. Articles were searched in MEDLINE, PubMed, and EMBASE. Pooled proportions were calculated using fixed and random effects model. Heterogeneity among studies was assessed using the I2 statistic.

RESULTS

Ten studies (n = 402) that met inclusion criteria were included in this analysis. The P for χ2 heterogeneity for all the pooled accuracy estimates was > 0.10. Pooled odds ratio for successful biliary drainage (decrease in bilirubin level > 50% within 7days after stenting) in PDT vs BS group was 4.39 (95%CI: 2.35-8.19). Survival period in PDT and BS groups were 413.04 d (95%CI: 349.54-476.54) and 183.41 (95%CI: 136.81-230.02) respectively. The change in Karnofsky performance scores after intervention in PDT and BS groups were +6.99 (95%CI: 4.15-9.82) and -3.93 (95%CI: -8.63-0.77) respectively. Odds ratio for post-intervention cholangitis in PDT vs BS group was 0.57 (95%CI: 0.35-0.94). In PDT group, 10.51% (95%CI: 6.94-14.72) had photosensitivity reactions that were self-limiting. Subgroup analysis of prospective studies showed similar results, except the incidence of cholangitis was comparable in both groups.

CONCLUSION

In palliation of unresectable cholangiocarcinoma, PDT seems to be significantly superior to BS alone. PDT should be used as an adjunct to biliary stenting in these patients.

Oncologic Photodynamic Therapy: Basic Principles, Current Clinical Status and Future Directions

Photodynamic therapy (PDT) is a clinically approved cancer therapy, based on a photochemical reaction between a light activatable molecule or photosensitizer, light, and molecular oxygen. When these three harmless components are present together, reactive oxygen species are formed. These can directly damage cells and/or vasculature, and induce inflammatory and immune responses. PDT is a two-stage procedure, which starts with photosensitizer administration followed by a locally directed light exposure, with the aim of confined tumor destruction. Since its regulatory approval, over 30 years ago, PDT has been the subject of numerous studies and has proven to be an effective form of cancer therapy. This review provides an overview of the clinical trials conducted over the last 10 years, illustrating how PDT is applied in the clinic today. Furthermore, examples from ongoing clinical trials and the most recent preclinical studies are presented, to show the directions, in which PDT is headed, in the near and distant future. Despite the clinical success reported, PDT is still currently underutilized in the clinic. We also discuss the factors that hamper the exploration of this effective therapy and what should be changed to render it a more effective and more widely available option for patients.

Synthesis, characterization and biological evaluation of a novel biscarboxymethyl-modified tetraphenylchlorin compound for photodynamic therapy

Compound BCTC is an effective and a highly promising antitumor agent for photodynamic therapy.

Neoadjuvant Down-Sizing of Hilar Cholangiocarcinoma with Photodynamic Therapy--Long-Term Outcome of a Phase II Pilot Study

Hilar cholangiocarcinoma (CC) is non-resectable in the majority of patients often due to intrahepatic extension along bile duct branches/segments, and even after complete resection (R0) recurrence can be as high as 70%. Photodynamic therapy (PDT) is an established palliative local tumor ablative treatment for non-resectable hilar CC. We report the long-term outcome of curative resection (R0) performed after neoadjuvant PDT for downsizing of tumor margins in seven patients (median age 59 years) with initially non-resectable hilar CC. Photofrin(®) was injected intravenously 24-48 h before laser light irradiation of the tumor stenoses and the adjacent bile duct segments. Major resective surgery was done with curative intention six weeks after PDT. All seven patients had been curatively (R0) resected and there were no undue early or late complications for the neoadjuvant PDT and surgery. Six of seven patients died from tumor recurrence at a median of 3.2 years after resection, the five-year survival rate was 43%. These results are comparable with published data for patients resected R0 without pre-treatment, indicating that neoadjuvant PDT is feasible and could improve overall survival of patients considered non-curatively resectable because of initial tumor extension in bile duct branches/segments--however, this concept needs to be validated in a larger trial.

Temoporfin improves efficacy of photodynamic therapy in advanced biliary tract carcinoma: A multicenter prospective phase II study

Photodynamic therapy using porfimer (P-PDT) improves palliation and survival in nonresectable hilar bile duct cancer. Tumoricidal penetration depth of temoporfin-PDT (T-PDT) is twice that of P-PDT. In a single-arm phase II study we investigated the safety, efficacy, survival time, and adverse events of T-PDT compared with previous data on P-PDT. Twenty-nine patients (median 71 [range 47-88] years) with nonresectable hilar bile duct cancer were treated with T-PDT (median 1 [range 1-4] sessions) plus stenting and followed up every 3 months. The PDT was well tolerated. In patients with occluded segments at baseline (n=28) a reopening of a median of 3 (range 1-7) segments could be achieved: n=16 local response and n=11 stable local disease, one progressive disease. Cholestasis and performance significantly improved when impaired at baseline. Time to local tumor progression was a median of 6.5 (2.7-41.0) months. Overall survival time was a median of 15.4 (range 4.4-62.4) months. Patients died from tumor progression (55%), cholangitis (18%), pneumonia (7%), hemobilia (7%), esophagus variceal hemorrhage (3%), and vascular diseases (10%). Adverse events were cholangitis (n=4), liver abscess (n=2), cholecystitis (n=2), phototoxic skin (n=5), and injection site reactions (n=7). Compared to previous P-PDT, T-PDT shows prolonged time to local tumor progression (median 6.5 versus 4.3 months, P<0.01), fewer PDT treatments needed (median 1 versus 3, P<0.01), a higher 6-month survival rate (83% versus 70%, P<0.01), and a trend for longer overall median survival (15.4 versus 9.3 months, P=0.72) yet not significantly different. The risk of adverse events is not increased except for (avoidable) subcutaneous phototoxicity at the injection site.

CONCLUSION

Temoporfin-PDT can safely be delivered to hilar bile duct cancer patients and results in prolonged patency of hilar bile ducts, a trend for longer survival time, and similar palliation as with P-PDT.

Biliary Tumor Ablation with Photodynamic Therapy and Radiofrequency Ablation

Within the past two decades, major progress has been made in biliary endoscopy both with stenting and with ablative therapy. A primary goal in patients with malignant biliary lesions who are not candidates for surgery is to provide localized and efficient necrosis of the lesions. This article summarizes the current literature on biliary tumor ablation with photodynamic therapy and radiofrequency ablation. Prognosis, treatment technique, potential complications, treatment efficacy, and controversies are discussed.

Activated hedgehog pathway is a potential target for pharmacological intervention in biliary tract cancer

Hedgehog (Hh) signalling contributes to carcinogenesis and represents a valid druggable target in human cancers, possibly also in biliary tract cancer (BTC). We analysed the expression of Hh components in BTC using eight heterogeneously differentiated cell lines, xenograft tumours and a human tissue microarray. The dose-, time- and cell line-dependent effects of two Hh inhibitors (cyclopamine and Gant-61) were analysed in vitro for survival, apoptosis, cell cycle distribution and possible synergism with conventional chemotherapeutic agents. In human BTC samples, the sonic Hh ligand and the Gli1 transcription factor showed increased expression in tumours compared to normal adjacent tissue and were significantly associated with high tumour grade and positive lymph node status. In BTC cell lines, we could confirm the Hh component expression at varying extent within the employed cell lines in vitro and in vivo indicating non-canonical signalling. Both Hh inhibitors showed dose-dependent cytotoxicity above 5 µM with a stronger effect for Gant-61 inducing apoptosis whereas cyclopamine rather inhibited proliferation. Cytotoxicity was associated with low cytokeratin expression and higher mesenchymal marker expression such as vimentin. Additionally, drug combinations of Gant-61 with conventional chemotherapy (cisplatin) exerted synergistic effects. In conclusion, Hh pathway is significantly activated in human BTC tissue compared to normal adjacent tissue. The current data demonstrate for the first time an effective anticancer activity of especially Gant-61 in BTC and suggest second generation Hh pathway inhibitors as a potential novel treatment strategy in BTC.

Palliation: Hilar cholangiocarcinoma

Hilar cholangiocarcinomas are common tumors of the bile duct that are often unresectable at presentation. Palliation, therefore, remains the goal in the majority of these patients. Palliative treatment is particularly indicated in the presence of cholangitis and pruritus but is often also offered for high-grade jaundice and abdominal pain. Endoscopic drainage by placing stents at endoscopic retrograde cholangio-pancreatography (ERCP) is usually the preferred modality of palliation. However, for advanced disease, percutaneous stenting has been shown to be superior to endoscopic stenting. Endosonography-guided biliary drainage is emerging as an alternative technique, particularly when ERCP is not possible or fails. Metal stents are usually preferred over plastic stents, both for ERCP and for percutaneous biliary drainage. There is no consensus as to whether it is necessary to place multiple stents within advanced hilar blocks or whether unilateral stenting would suffice. However, recent data have suggested that, contrary to previous belief, it is useful to drain more than 50% of the liver volume for favorable long-term results. In the presence of cholangitis, it is beneficial to drain all of the obstructed biliary segments. Surgical bypass plays a limited role in palliation and is offered primarily as a segment III bypass if, during a laparotomy for resection, the tumor is found to be unresectable. Photodynamic therapy and, more recently, radiofrequency ablation have been used as adjuvant therapies to improve the results of biliary stenting. The exact technique to be used for palliation is guided by the extent of the biliary involvement (Bismuth class) and the availability of local expertise.

Phototriggerable liposomes: current research and future perspectives

The field of cancer nanomedicine is considered a promising area for improved delivery of bioactive molecules including drugs, pharmaceutical agents and nucleic acids. Among these, drug delivery technology has made discernible progress in recent years and the areas that warrant further focus and consideration towards technological developments have also been recognized. Development of viable methods for on-demand spatial and temporal release of entrapped drugs from the nanocarriers is an arena that is likely to enhance the clinical suitability of drug-loaded nanocarriers. One such approach, which utilizes light as the external stimulus to disrupt and/or destabilize drug-loaded nanoparticles, will be the discussion platform of this article. Although several phototriggerable nanocarriers are currently under development, I will limit this review to the phototriggerable liposomes that have demonstrated promise in the cell culture systems at least (but not the last). The topics covered in this review include (i) a brief summary of various phototriggerable nanocarriers; (ii) an overview of the application of liposomes to deliver payload of photosensitizers and associated technologies; (iii) the design considerations of photoactivable lipid molecules and the chemical considerations and mechanisms of phototriggering of liposomal lipids; (iv) limitations and future directions for in vivo, clinically viable triggered drug delivery approaches and potential novel photoactivation strategies will be discussed.