AUTHOR=Wu BinXi , Lejeune Amandine , Affolter Verena K. , Iamone Giulia , Riondato Fulvio , Kol Amir TITLE=Development of a flow cytometric panel to assess prognostic biomarkers in fine needle aspirates of canine cutaneous or subcutaneous mast cell tumors JOURNAL=Frontiers in Veterinary Science VOLUME=10 YEAR=2023 URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1279881 DOI=10.3389/fvets.2023.1279881 ISSN=2297-1769 ABSTRACT=

Mast cell tumor (MCT) is a common skin cancer in dogs that has a wide range of clinical behaviors. The purpose of this study was to develop a novel multicolor flow cytometry (FC) panel that will enable the quantification of candidate prognostic markers (Ki-67 and pKIT) in fine needle aspirate (FNA) samples prior to surgical removal of the tumors. FNA of canine MCTs and the NI-1 cell line were utilized to develop a FC panel that includes a viability dye (FVS620, BD Biosciences; 7-AAD, Invitrogen) and the following primary conjugated antibodies: CD117-PE (ACK45, BD Biosciences), pKIT-A647 (polyclonal bs-3242R, BIOSS) and Ki-67-FITC (20Raj1, eBioscience; MIB-1, DAKO). A total of nine FNA samples of canine MCTs were collected, seven out which produced sufficient cells for FC analysis. The Ki-67 antibody clone 20Raj1 produced a positive signal when applied to blood leukocytes but failed to provide robust labeling of neoplastic mast cells. The Ki-67 antibody clone MIB-1 delivered a superior staining quality in both the NI-1 cells and primary MCT cells. CD117-PE signal was adequate post fixation and permeabilization and in the combination of 7-AAD. pKIT produced non-specific staining and was not suitable for this multicolor FC panel. In conclusion, FNA samples of canine MCTs can often yield adequate cell numbers for FC analysis, and a multicolor FC panel was developed that can detect Ki-67 in canine mast cells. This would permit further studies into the potential use of this panel for canine cutaneous and subcutaneous MCT prognostication purposes.