Photodynamic therapy of human lung cancer xenografts in mice

Photodynamic Therapy in Combination with Doxorubicin Is Superior to Monotherapy for the Treatment of Lung Cancer

We have previously shown that a radioactive (123I)-analog of methyl 3-(1'-(iodobexyloxy) ethyl-3-devinylpyropheophorbide-a (PET-ONCO), derived from chlorophyll-a can be used for positron emission tomography (PET) imaging of a variety of tumors, including those where 18F-FDG shows limitations. In this study, the photodynamic therapy (PDT) efficacy of the corresponding non-radioactive photosensitizer (PS) was investigated in a variety of tumor types (NSCLC, SCC, adenocarcinoma) derived from lung cancer patients in mice tumor models. The in vitro and in vivo efficacy was also investigated in combination with doxorubicin, and a significantly enhanced long-term tumor response was observed. The toxicity and toxicokinetic profile of the iodinated PS was also evaluated in male and female Sprague-Dawley rats and Beagle dog at variable doses (single intravenous injections) to assess reversibility or latency of any effects over a 28-day dose free period. The no-observed-adverse-effect (NOAEL) of the PS was considered to be 6.5 mg/kg for male and female rats, and for dogs, 3.45 mg/kg, the highest dose levels evaluated, respectively. The corresponding plasma Cmax and AYClast for male and female rats were 214,000 and 229,000 ng/mL and 3,680,000 and 3,810,000 h * ng/mL, respectively. For male and female dogs, the corresponding plasma Cmax and AYClast were 76,000 and 92,400 ng/mL and 976,000 and 1,200,000 h * ng/mL, respectively.

Subcutaneous Xenograft Models for Studying PDT In Vivo

The most facile, reproducible, and robust in vivo models for evaluating the anticancer efficacy of photodynamic therapy (PDT) are subcutaneous xenograft models of human tumors. The accessibility and practicality of light irradiation protocols for treating subcutaneous xenograft models also increase their value as relatively rapid tools to expedite the testing of novel photosensitizers, respective formulations, and treatment regimens for PDT. This chapter summarizes the methods used in the literature to prepare various types of subcutaneous xenograft models of human cancers and syngeneic models to explore the role of PDT in immuno-oncology. This chapter also summarizes the PDT treatment protocols tested on the subcutaneous models, and the procedures used to evaluate the efficacy at the molecular, macromolecular, and host organism levels.

Synthesis of N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines and their photodynamic properties in the human skin melanoma cell line G361

A small series of N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines was synthesized from easily accessible 1-phenyl-1H-pyrazol-3-ol via 7-iodo-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine and 7-iodo-4-methyl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine intermediates and their subsequent use in palladium catalyzed Buchwald-Hartwig cross-coupling reaction with various anilines. Majority of the compounds were not significantly cytotoxic to melanoma G361 cells in the dark up to 10 µM concentration, but their activity could be increased by irradiation with visible blue light (414 nm). The most active compound 10 possessed EC₅₀ values of 3.5, 1.6 and 0.9 µM in cells irradiated with 1, 5 and 10 J/cm², respectively. The treatment caused generation of reactive oxygen species in cells and extensive DNA damage, documented by the comet assay and by detection of phosphorylated histone H2A.X, followed by apoptotic cell death. Our results suggest that N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines could serve as a potential source of photosensitizing compounds with anticancer activities.

Measurement of Cyanine Dye Photobleaching in Photosensitizer Cyanine Dye Conjugates Could Help in Optimizing Light Dosimetry for Improved Photodynamic Therapy of Cancer

Photodynamic therapy (PDT) of cancer is dependent on three primary components: photosensitizer (PS), light and oxygen. Because these components are interdependent and vary during the dynamic process of PDT, assessing PDT efficacy may not be trivial. Therefore, it has become necessary to develop pre-treatment planning, on-line monitoring and dosimetry strategies during PDT, which become more critical for two or more chromophore systems, for example, PS-CD (Photosensitizer-Cyanine dye) conjugates developed in our laboratory for fluorescence-imaging and PDT of cancer. In this study, we observed a significant impact of variable light dosimetry; (i) high light fluence and fluence rate (light dose: 135 J/cm², fluence rate: 75 mW/cm²) and (ii) low light fluence and fluence rate (128 J/cm² and 14 mW/cm² and 128 J/cm² and 7 mW/cm²) in photobleaching of the individual chromophores of PS-CD conjugates and their long-term tumor response. The fluorescence at the near-infrared (NIR) region of the PS-NIR fluorophore conjugate was assessed intermittently via fluorescence imaging. The loss of fluorescence, photobleaching, caused by singlet oxygen from the PS was mapped continuously during PDT. The tumor responses (BALB/c mice bearing Colon26 tumors) were assessed after PDT by measuring tumor sizes daily. Our results showed distinctive photobleaching kinetics rates between the PS and CD. Interestingly, compared to higher light fluence, the tumors exposed at low light fluence showed reduced photobleaching and enhanced long-term PDT efficacy. The presence of NIR fluorophore in PS-CD conjugates provides an opportunity of fluorescence imaging and monitoring the photobleaching rate of the CD moiety for large and deeply seated tumors and assessing PDT tumor response in real-time.

Structural and Epimeric Isomers of HPPH [3-Devinyl 3-{1-(1-hexyloxy) ethyl}pyropheophorbide-a]: Effects on Uptake and Photodynamic Therapy of Cancer

The tetrapyrrole structure of porphyrins used as photosentizing agents is thought to determine uptake and retention by malignant epithelial cancer cells. To assess the contribution of the oxidized state of individual rings to these cellular processes, bacteriochlorophyll a was converted into the ring "D" reduced 3-devinyl-3-[1-(1-hexyloxy)ethyl]pyropheophorbide-a (HPPH) and the corresponding ring "B" reduced isomer (iso-HPPH). The carboxylic acid analogs of both ring "B" and ring "D" reduced isomers showed several-fold higher accumulation into the mitochondria and endoplasmic reticulum by primary culture of human lung and head and neck cancer cells than the corresponding methyl ester analogs that localize primarily to granular vesicles and to a lesser extent to mitochondria. However, long-term cellular retention of these compounds exhibited an inverse relationship with tumor cells generally retaining better the methyl-ester derivatives. In vivo distribution and tumor uptake was evaluated in the isogenic model of BALB/c mice bearing Colon26 tumors using the respective ¹⁴C-labeled analogs. Both carboxylic acid derivatives demonstrated similar intracellular localization and long-term tumor cure with no significant skin phototoxicity. PDT-mediated tumor action involved vascular damage, which was confirmed by a reduction in blood flow and immunohistochemical assessment of damage to the vascular endothelium. The HPPH stereoisomers (epimers) showed identical uptake (in vitro & in vivo), intracellular retention and photoreaction.

Novel nanoparticulate systems for lung cancer therapy: an updated review

Lung cancer is the leading cause of cancer-related deaths in the world. Conventional therapy for lung cancer is associated with lack of specificity and access to the normal cells resulting in cytotoxicity, reduced cellular uptake, drug resistance and rapid drug clearance from the body. The emergence of nanotechnology has revolutionized the treatment of lung cancer. The focus of nanotechnology is to target tumor cells with improved bioavailability and reduced toxicity. In the recent years, nanoparticulate systems have extensively been exploited in order to overcome the obstacles in treatment of lung cancer. Nanoparticulate systems have shown much potential for lung cancer therapy by gaining selective access to the tumor cells due to surface modifiability and smaller size. In this review, various novel nanoparticles (NPs) based formulations have been discussed in the treatment of lung cancer. Nanotechnology is expected to grow fast in future, and it will provide new avenues for the improved treatment of lung cancer. This review article also highlights the characteristics, recent advances in the designing of NPs and therapeutic outcomes.

High Aspect Ratio Nanotubes Formed by Tobacco Mosaic Virus for Delivery of Photodynamic Agents Targeting Melanoma

Melanoma is a highly aggressive cancer that is unresponsive to many traditional therapies. Recently, photodynamic therapy has shown promise in its treatment as an adjuvant therapy. However, conventional photosensitizers are limited by poor solubility and limited accumulation within target tissue. Here, we report the delivery of a porphyrin-based photosensitizer encapsulated within a plant viral nanoparticle. Specifically, we make use of the hollow, high aspect ratio nanotubes formed by the nucleoprotein components of tobacco mosaic virus (TMV) to encapsulate the drug for delivery and targeting of cancer cells. The cationic photosensitizer was successfully and stably loaded into the interior channel of TMV via electrostatic interactions. Cell uptake and efficacy were evaluated using a model of melanoma. The resulting TMV-photosensitizer exhibited improved cell uptake and efficacy when compared to free photosensitizer, making it a promising platform for improved therapy of melanoma.