DH-I-180-3–Mediated Photodynamic Therapy: Biodistribution and Tumor Vascular Damage

Dendritic Cell-Based Immunotherapy for Solid Tumors

As a treatment for solid tumors, dendritic cell (DC)-based immunotherapy has not been as effective as expected. Here, we review the reasons underlying the limitations of DC-based immunotherapy for solid tumors and ask what can be done to improve immune cell-based cancer therapies. Several reports show that, rather than a lack of immune induction, the limited efficacy of DC-based immunotherapy in cases of renal cell carcinoma (RCC) likely results from inhibition of immune responses by tumor-secreted TGF-β and an increase in the number of regulatory T (Treg) cells in and around the solid tumor. Indeed, unlike DC therapy for solid tumors, cytotoxic T lymphocyte (CTL) responses induced by DC therapy inhibit tumor recurrence after surgery; CTL responses also limit tumor metastasis induced by additional tumor-challenge in RCC tumor-bearing mice. Here, we discuss the mechanisms underlying the poor efficacy of DC-based therapy for solid tumors and stress the need for new and improved DC immunotherapies and/or combination therapies with killer cells to treat resistant solid tumors.

Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles

In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one of the most perspective compound in this series—pyropheophorbide-a 17-diethylene glycol ester (Compound 21) was performed. This new compound is characterized by lower dark cytotoxicity and higher photoinduced cytotoxicity than previously described in a similar compound (DH-I-180-3) and clinically used Photolon^TM. Using fluorescent microscopy, it was shown that Compound 21 quickly penetrates the cells. Analysis of caspase-3 activity indicated an apoptosis induction 40 min after exposure to red light (λ = 660 nm). The induction of DNA damages and apoptosis was shown using Comet assay. The results of expression analysis of the stress-response genes indicate an activation of the genes which control the cell cycle and detoxification of the free radicals after an exposure of HeLa cells to Compound 21 and to red light. High photodynamic activity of this compound and the ability to oxidize biomolecules was demonstrated on nuclear-free mice erythrocytes. In addition, it was shown that Compound 21 is effectively activated with low energy 700 nm light, which can penetrate deep into the tissue. Thus, Compound 21 is a prospective substance for development of the new drugs for photodynamic therapy of cancer.

Photodynamic therapy-mediated DC immunotherapy is highly effective for the inhibition of established solid tumors

Dendritic cell (DC)-mediated immunotherapy has not been as effective as expected for most solid tumors. This study demonstrates immune responses against solid tumors mediated by DCs charged with photodynamic therapy (PDT)-induced tumor lysates, which contain the heat shock protein (HSP) 70. PDT tumor lysate-pulsed DC (PDT-DC) inhibited the growth of mammary EMT6 tumors to a greater extent than freeze/thawed tumor lysate-pulsed DC (FT-DC) or PDT tumor lysates. PDT-DC also showed significant anti-tumor effects against fully-established (i.e., late-stage) solid tumors. Taken together, these results suggest that PDT-DC vaccination is more effective than conventional DC therapy for the treatment of cancers.

Complete blood vessel occlusion in the chick chorioallantoic membrane using two-photon excitation photodynamic therapy: implications for treatment of wet age-related macular degeneration

Complete blood vessel occlusion is required for the treatment of age-related macular degeneration (AMD). AMD is the leading cause of blindness in developed countries and current treatment regimes have potential to cause collateral damage, or do not remove pre-existing unwanted vasculature. It has been proposed that two-photon excitation (TPE) photodynamic therapy (PDT) can be applied to cause local blood vessel occlusion without damaging surrounding retinal tissues. The in ovo chicken chorioallantoic membrane (CAM) is used as the model for vascularization in the wet form of AMD; novel techniques for the utilization of the CAM are reported. Complete occlusion of CAM vessels approximately 15 microm in diameter is achieved using the clinically approved photosensitizer Verteporfin (Visudyne, QLT, Incorporated, Vancouver, British Columbia, Canada) and TPE activation. The average and peak irradiances used for treatment are 3.3x10(6) Wcm(2) and 3.7x10(11) Wcm(2), respectively. A total fluence of 1.1x10(8) Jcm(2) is the dosage required for successful occlusion, and it is expected that for optimal conditions it will be much less. These results are the first proof-of-principle evidence in the literature that indicate TPE-PDT can be used to occlude small blood vessels. Further investigation will help determine the utility of TPE-PDT for treating wet AMD, perhaps through targeting feeder vessels.