Clinical pharmacokinetics of anti-angiogenic photodynamic therapy with benzoporphyrin derivative monoacid ring-A in dogs having naturally occurring neoplasms

Hippo signaling pathway in companion animal diseases, an under investigated signaling cascade

The Hippo pathway is a highly conserved kinase cascade in mammals with the proteins YAP and TAZ as its most important downstream effectors that shuttle between cytoplasma and nucleus. It has a crucial role in processes such as embryogenesis, organ size control, homeostasis and tissue regeneration, where mechanosensing and/or cell-cell interactions are involved. As the pathway is associated with many essential functions in the body, its dysregulation is related to many diseases. In contrast to human pathology, a PubMed-search on Hippo, YAP/TAZ and companion animals (horse, equine, dog, canine, cat, feline) retrieved few publications. Because of its high level of functional conservation, it is anticipated that also in veterinary sciences aberrant Hippo YAP/TAZ signaling would be implicated in animal pathologies. Publications on Hippo YAP/TAZ in companion animals are mainly in cats and dogs and related to oncology. Here, we emphasize the important role of YAP/TAZ in liver diseases. First the liver has a remarkable regeneration capacity and a strict size control and the liver has a moderate liver cell renewal (homeostasis). The last years numerous papers show the importance of YAP/TAZ in hepatocellular carcinoma (HCC), hepatocyte differentiation and bile duct epithelial (BEC) cell survival. YAP/TAZ signaling is involved in activation of hepatic stellate cells crucial in fibrogenesis. The availability of drugs (e.g. verteporfin) targeting the YAP/TAZ pathway are described as is their potential usage in veterinary medicine. The aim of this overview is to stimulate researchers' and clinicians' interest in the potential role of Hippo YAP/TAZ signaling in veterinary medicine.

Cellular localization of Visudyne as a function of time after local injection in an in vivo model of squamous cell carcinoma: an investigation into tumor cell death

OBJECTIVE

To evaluate the effects of time on cellular localization of Visudyne after local injection.

ANIMALS

Twenty athymic nude mice.

PROCEDURES

A squamous cell carcinoma (SCC) cell line (A-431) was injected into right and left dorsolumbar subcutaneous tissue of each mouse, representing treatment (T) and control (C) tumors. In experiment 1 (Exp 1; n = 10) and 2 (Exp 2; n = 10), the T tumors received a local injection of Visudyne (0.1 mg/cm(3)), and C tumors received an equal dose of 5% dextrose in water (D5W). Mice were randomly subdivided into two groups (A and B; n = 5 per group). Mice in Exp 1A and B were sacrificed 1 and 30 min after local injection, respectively. Experiment 1A and B tumors were evaluated by fluorescence microscopy to determine drug localization. Experiment 2A and B tumors were exposed to LED illumination 1 and 30 min after injection, respectively, and evaluated by transmission electron microscopy (TEM) to determine ultrastructural tumor cell damage.

RESULTS

Fluorescence was detected within the cytoplasm of T tumors in both Exp 1A and B. Significance was detected in fluorescence intensity between T1 min vs. T30 min (P = 0.03) and between T1 min and C1 min tumors (P = 0.01), respectively. Tumors in Exp 2A and B demonstrated evidence of apoptotic cell death.

CONCLUSIONS

Fluorescence microscopy demonstrated higher Visudyne concentration within SCC cytoplasm of 1 min compared with 30-min tumors. Transmission electron microscopy results revealed that tumors treated by photodynamic therapy (PDT) within 30 min of local injection undergo cellular apoptosis.

Antiangiogenic photodynamic therapy with targeted liposomes

Antiangiogenic photodynamic therapy (PDT) is a promising modality for cancer treatment, since it causes efficient cutoff of oxygen and nutrients to the tumor cells and thus indirectly eradicates the tumor cells. For the improvement of therapeutic efficacy of antiangiogenic PDT by using a photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA) in a liposomal formulation, we endowed the liposomes with an active-targeting probe, Ala-Pro-Arg-Pro-Gly (APRPG), a peptide specific for angiogenic endothelial cells. APRPG-PEG-modified liposomal BPD-MA (APRPG-PEG-LipBPD-MA) accumulated in tumor tissues to a similar extent as PEG-LipBPD-MA at 3-h postinjection. In contrast, APRPG-PEG-LipBPD-MA strongly suppressed tumor growth by PDT treatment, but PEG-LipBPD-MA did not. This finding suggests that antiangiogenic PDT with targeted liposomes is an efficient modality for tumor treatment, whereas PEG-modified nontargeted liposomes are not suitable as a carrier of photosensitizers. The reason for the observed ineffectiveness of PEG-LipBPD-MA is as follows: In the case of PDT, the amount of photosensitizer bound to or taken up into the target cells during the time interval between injection of the agent and laser irradiation is critical, rather than the total amount of photosensitizer in tumor tissue. Therefore, active-targeting technology is quite useful for antiangiogenic PDT.

Efficacy of antivascular photodynamic therapy using benzoporphyrin derivative monoacid ring A (BPD-MA) in 14 dogs with oral and nasal tumors

Antivascular photodynamic therapy (PDT) suppresses tumor growth and prolonged the survival in solid tumor-bearing mice. The purpose of this study was to assess the efficacy of antivascular PDT using BPD-MA for treatment of oral and nasal tumors in 14 dogs. At 15 min after initiating intravenous infusion of 0.5 mg/kg benzoporphyrin derivative monoacid ring A, tumors were irradiated with laser light at 690 nm emitted by a diode laser. The 1-year survival rate of 7 dogs with oral tumors was 71%. The 1-year survival rate of 7 dogs with nasal tumors was 57%. Imaging of each tumor was performed by using angiographic computed tomography before and after each antivascular PDT. Contrast-enhanced tumors were observed before antivascular PDT, but these tumors were not enhanced with contrast medium following antivascular PDT. Antivascular PDT is suggested to be a promising method for dogs with oral and nasal tumors that cannot be effectively treated with current antitumor therapies.