Vet World   Vol.18   November-2025  Article - 2 

Establishment and characterization of canine mammary tumors 622: A novel luminal B CMT cell line exhibiting partial epithelial–mesenchymal transition and intermediate drug sensitivity

Background and Aim: Canine mammary tumors (CMTs) serve as valuable comparative models for human breast cancer (HBC) owing to their shared biological and molecular features. However, well-defined cell lines representing the luminal B subtype remain limited. This study aimed to establish and characterize a novel CMT cell line, designated CMT-622, to expand available in vitro models for luminal B breast cancer research.

Materials and Methods: Primary tumor tissue was collected from an 11-year-old female dog diagnosed with high-grade mammary carcinoma (T3N1M0). Tumor cells were isolated using enzymatic digestion and differential adhesion. Morphological, cytogenetic, and immunophenotypic characteristics were assessed using hematoxylin-eosin staining, immu­nohistochemistry, and immunofluorescence. Growth kinetics, clonogenicity, and chromosomal analyses were performed, and tumorigenicity was evaluated through xenograft assays in nude mice. Drug sensitivity and apoptosis were compared with two existing CMT lines (CMT-1211 and CMT-n7) using the cell counting kit-8 (CCK)-8 assay and flow cytometry.

Results: CMT-622 cells maintained stable proliferation beyond 40 passages with a doubling time of 46.23 h and >15% clon­ing efficiency. Karyotyping revealed hyperdiploidy (80–110 chromosomes; modal = 87). Immunohistochemistry and immu­nofluorescence confirmed estrogen receptor (+), progesterone receptor (–), and human epidermal growth factor receptor 2 (weak +) expression, consistent with a luminal B phenotype. Co-expression of cytokeratin-18 and vimentin indicated a par­tial epithelial–mesenchymal transition (EMT) state. In nude mice, CMT-622 exhibited moderate tumorigenicity and pulmo­nary metastasis. The line showed intermediate osthole sensitivity (half-maximal inhibitory concentration = 50.48 μM) and an apoptosis rate of 21%, between CMT-1211 and CMT-n7, indicating balanced proliferative and drug-responsive behavior.

Conclusion: CMT-622 represents a newly established luminal B CMT cell line with stable growth, EMT plasticity, and mod­erate drug sensitivity, reflecting clinically relevant tumor aggressiveness. Its molecular and phenotypic consistency across in vitro and in vivo models underscores its reliability for translational oncology applications. CMT-622 provides a robust pre­clinical platform for exploring tumorigenesis, metastasis, and therapeutic responses in both veterinary and HBC contexts, bridging comparative and translational cancer research.

Keywords: canine mammary tumor, cell line establishment, epithelial–mesenchymal transition, luminal B subtype, osthole sensitivity, xenograft model.

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How to cite this article: Peng Q, Ma S, Lu Z, Shi J, Zheng Q, and Zhang T (2025) Establishment and characterization of canine mammary tumors 622: A novel luminal B CMT cell line exhibiting partial epithelial–mesenchymal transition and intermediate drug sensitivity, Veterinary World, 18(11): 3306-3321.

Received: 23-07-2025   Accepted: 14-10-2025   Published online: 06-11-2025

Corresponding author: Tao Zhang    E-mail: zt951122@163.com

DOI: 10.14202/vetworld.2025.3306-3321

Copyright: Peng, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.