In vitro chemosensitivity of canine mast cell tumors grades II and III to all-trans-retinoic acid (ATRA)

Clinical Utility of Patient-Derived Cell-Based In Vitro Drug Sensitivity Testing for Optimizing Adjuvant Therapy in Dogs with Solid Tumors: A Retrospective Study (2019-2023)

Inter-individual variations in drug responses are major concerns in cancer treatment in human and veterinary oncology. Consequently, preclinical models have been proposed to predict drug responses and determine optimal individualized therapy. We aimed to evaluate the clinical utility of in vitro drug sensitivity testing using a patient-derived cell culture model to select appropriate adjuvant therapies for dogs with solid tumors. We screened medical records of 126 dogs with suspected tumors, including 33 dogs with solid tumors (guided group, 16; empirical group, 17). Anticancer drugs used for adjuvant therapy were determined based on in vitro drug sensitivity testing (guided group) or histopathological examination (empirical group) results. Time to tumor progression (TTP) was compared between groups. The guided group had significantly longer TTP than the empirical group (949 vs. 109 days). Median TTPs were significantly longer in the guided group than in the empirical group for dogs with incomplete surgical margin (949 vs. 109 days), dogs with mitotic count < 20 per 10 high power fields (949 vs. 105 days), dogs with no evidence of metastatic disease at initial diagnosis (455 vs. 196 days), and dogs receiving tyrosine kinase inhibitors (949 vs. 109 days). Our study suggests that in vitro drug sensitivity testing may be a useful tool for optimizing adjuvant therapy in dogs with solid tumors.

Characterisation and Sensitivity of a Canine Mast Cell Tumour Line to Oncolytic Viruses

Canine mast cell tumours (MCTs) are one of the most common skin cancers of dogs. Surgical removal is the primary treatment, but recurrence and metastasis can occur even with low-grade tumours. As a result, new treatment strategies are being sought. We tested the potential of several oncolytic viruses (OVs) to infect and kill a cell line isolated from a canine MCT. Employing a resazurin-based metabolic assay and flow cytometry technology, we used recombinant vesicular stomatitis virus (rVSV-Δm51), avian orthoavulavirus-1 (AOaV-1), and Orf viruses in our assessment. Our study aimed to evaluate the potential of oncolytic virotherapy in treating canine cancers. We found that MCT-1 cells showed different sensitivities to the OVs, with rVSV-Δm51 showing the most promising results in vitro. These findings suggest that further investigation into using OVs for treating canine MCTs is needed, although clinical efficacy is yet to be determined.

Intercellular interactions between mast cells and stromal fibroblasts obtained from canine cutaneous mast cell tumours

Mast cell tumours (MCTs) are the most frequent malignant skin neoplasm in dogs. Due to the difficulty in purifying large numbers of canine neoplastic mast cells, relatively little is known about their properties. A reproducible in vitro model is needed to increase the understanding about the phenotype and functional properties of neoplastic mast cells. In the present study, we describe the establishment of primary cocultures of neoplastic mast cells from canine cutaneous MCTs and cancer-associated fibroblasts. We confirmed the inability of canine neoplastic mast cells to remain viable for long periods in vitro without the addition of growth factors or in vivo passages in mice. Using a transwell system, we observed that mast cell viability was significantly higher when there is cell-to-cell contact in comparison to non-physical contact conditions and that mast cell viability was significantly higher in high-grade than in low-grade derived primary cultures. Moreover, the use of conditioned medium from co-cultured cells led to a significantly higher tumoral mast cell viability when in monoculture. Signalling mechanisms involved in these interactions might be attractive therapeutic targets to block canine MCT progression and deserve more in-depth investigations.

In vitro inhibitory effect of trichostatin A on canine grade 3 mast cell tumor

Mast cell tumor (MCT) is one of the most prevalent neoplasms that affect skin and soft tissue in dogs. Because mast cell tumors present a great variety of clinical appearance and behavior, their treatment becomes a challenge. Trichostatin A (TSA), an antifungal antibiotic, has shown inhibitory effects on the proliferation and induction of apoptosis in various types of cancer cells. In order to evaluate the potential of trichostatin A as a therapeutic drug, cells of grade 3 MCT were cultured and treated with concentrations of 1 nM to 400 nM of TSA. MTT assay and trypan blue exclusion assays were performed to estimate cell growth and cell viability, and cell cycle analysis was evaluated. TSA treatment showed a reduction in numbers of viable cells and an increase of cell death by apoptosis. The cell cycle analysis showed an increase of hypodiploid cells and a reduction of G0/G1 and G2/M -phases. According to these results, trichostatin A may be an interesting potential chemotherapeutic agent for the treatment of canine MCT.