Clinical Implications of Immune Checkpoints and the RANK/RANK-L Signaling Pathway in High-Grade Canine Mast Cell Tumors.

Mast cell tumors (MCTs) are the most common malignant cutaneous tumors in dogs, and they present extremely variable biological behavior. The interaction between RANK, RANK-L, and immune checkpoints is frequently detected in the tumor microenvironment, and, together, they participate in every stage of cancer development. Thus, the aim of this study was to characterize the molecular profiles of PD-L1, CTLA-4, RANK/RANK-L signaling pathway, and IFN-γ in primary tumors and lymph node metastases. Formalin-fixed, paraffin-embedded slides of MCTs and metastatic lymph nodes of ten dogs were submitted to immunohistochemical investigations. The results demonstrated that the tumor microenvironment of the high-grade mast cell tumors showed moderate or intense immunolabeling of all proteins, and the lymph node metastases also showed moderate or intense immunolabeling of checkpoint proteins. In addition, MCTs larger than 3 cm were associated with intensified PD-L1 (p = 0.03) in metastatic lymph nodes and RANK-L (p = 0.049) immunoreactivity in the tumor. Furthermore, dogs with a survival time of less than 6 months showed higher PD-L1 immunoreactivity (p = 0.042). In conclusion, high-grade MCT is associated with an immunosuppressive microenvironment that exhibits elevated RANK/RANK-L signaling and enhanced immune checkpoint immunoreactivity, potentially facilitating intratumorally immune escape. These biomarkers show promise as clinical indicators of disease progression and might response to immunotherapy in dogs with high-grade MCTs, thus emphasizing their importance for guiding treatment decisions and improving outcomes.

Topical and intradermal delivery of PpIX precursors for photodynamic therapy with intense pulsed light on porcine skin model.

In order to purposely decrease the time of the photodynamic therapy (PDT) sessions, this study evaluated the effects of PDT using topical and intradermal delivery of two protoporphyrin (PpIX) precursors with intense pulsed light (IPL) as irradiation source. This study was performed on porcine skin model, using an IPL commercial device (Intense Pulse Light, HKS801). IPL effect on different administration methods of two PpIX precursors (ALA and MAL) was investigated: a topical cream application and an intradermal application using a needle-free, high-pressure injection system. Fluorescence investigation showed that PpIX distribution by needle-free injection was more homogeneous than that by cream, suggesting that a shorter drug-light interval in PDT protocols is possible. The damage induced by IPL-PDT assessed by histological analysis mostly shows modifications in collagens fibers and inflammation signals, both expected for PDT. This study suggested an alternative protocol for the PDT treatment, possibility half of the incubation time and with just 3 min of irradiation, making the IPL-PDT, even more, promising for the clinical treatment.

Radical Cystectomy and Cutaneous Ureterostomy in 4 Dogs with Trigonal Transitional Cell Carcinoma: Description of Technique and Case Series.

OBJECTIVE: To describe radical cystectomy followed by cutaneous ureterostomy as a treatment of invasive bladder neoplasia in dogs. STUDY DESIGN: Retrospective study. ANIMALS: Client-owned dogs with transitional cell carcinoma of the bladder trigone (n=4). METHODS: Perioperative complications and long-term outcomes of dogs that underwent cutaneous ureterostomy following radical cystectomy and lymphadenectomy for transitional cell carcinoma of the urinary bladder trigone were reviewed. Both ureters were transected and anastomosed to the ventral abdominal skin. Polyvinyl chloride catheters were placed in the ureteral stomas and maintained for 5 days. After catheter removal, dogs were managed with an absorbent diaper over the stomas. Long-term outcome and survival were documented by follow-up visits or phone contact. RESULTS: Median age at the time of surgery was 10.3 years (range, 8-12). Average procedural time was ∼4.7 hours (range, 3.8-6.1). Minor complications occurred in all dogs, including bleeding and edema of the ureterostomy site during the first 2-3 days after surgery. One dog developed urine scald that resolved with improved stoma care and hygiene. Median survival time after surgery was 278.6 days (range, 47-498). Distant metastases were documented in 2 dogs at 47 days (bone) and 369 days (lung) after surgery. CONCLUSION: Radical cystectomy with cutaneous ureterostomy is a viable salvage procedure for urinary diversion after cystectomy in dogs with invasive bladder neoplasia. Postoperative management and quality of life were considered acceptable by most owners. Future studies are warranted to evaluate survival time in a larger number of animals.

Assessment of ALA-induced PpIX production in porcine skin pretreated with microneedles.

Photodynamic therapy (PDT) is used for skin treatments of premalignant and cancer lesions and recognized as a non-invasive technique that combines tissue photosensitization and subsequent exposure to light to induce cell death. However, it is limited to the treatment of superficial lesions, mainly due to the low cream penetration. Therefore, the improvement of transdermal distribution of aminolevulinic acid (ALA) is needed. In this study, the kinetics and homogeneity of production of ALA-induced PpIX after the skin pre-treatment with microneedles rollers of 0.5, 1.0 and 1.5 mm length were investigated. An improvement in homogeneity and production of PpIX was shown in a porcine model. Widefield fluorescence imaging three hours after the topical application of ALA-cream in the combined treatment with microeedles rollers.