# Establishment and Partial Characterization of Canine Mammary Tumor Cell Lines

## TL;DR

Researchers created and tested canine mammary tumor cell lines to better understand and treat breast cancer in both dogs and humans.

## Contribution

The establishment and partial characterization of new canine mammary tumor cell lines for breast cancer research.

## Key findings

- Seven cell lines were derived from primary tumors and three from metastatic sites in dogs.
- Doxorubicin showed the highest growth-inhibitory effect among tested drugs in canine mammary tumor cell lines.
- Five cell lines exhibited tumorigenic capacity in vitro and were positive for vimentin but negative for hormonal receptors.

## Abstract

Mammary tumors are the most frequent neoplasia in female dogs. Canine mammary cell lines represent a model of study for women breast cancer research that could benefit both species. The aim of our study was to establish and partially characterize canine mammary tumor cell lines. Ten cell cultures were generated from tumor tissue obtained from canines with mammary tumors. Seven cell lines were generated from primary mammary tumors and three cell lines from metastatic sites. Immunocytochemistry (ICC) analysis revealed a negative expression of hormonal receptors (estrogen receptor [ER] and progesterone receptor [PR]) in five cell lines and positive in one cell line, whereas six cell lines were human epidermal growth factor receptor 2 (HER2)-negative and positive for vimentin. Several cell lines showed tumorigenicity capacity in vitro. The susceptibility of five cell lines to different drugs was evaluated with the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, where doxorubicin (DOX) showed the highest growth-inhibitory effect (DOX > Paclitaxel > Colchicine > 5-Fluorouracil [5-FU] > Carboplatin). The cell lines generated represent a model of study for breast cancer that can be used for developing and testing new treatments to improve the survival of canine and human patients.

Mammary tumors are the most common neoplasms diagnosed in female dogs and have been considered excellent models for studying human breast cancer. Establishing cell lines from primary cultures of canine mammary tumors provides an in vitro model to better understand the disease and develop new treatments. This study aimed to establish and characterize canine mammary tumor cell lines. Ten cell cultures were generated from tumor tissue obtained from affected dogs, including seven from primary mammary tumors and three from metastatic sites. Characterization included molecular marker expression (ER, PR, HER2, cytokeratin 5/6 (CK5/6), vimentin, and the marker of cell proliferation Ki67) and in vitro tumorigenic capacity assessment. Additionally, the susceptibility of five cell lines to DOX, 5-FU, paclitaxel, colchicine, and carboplatin was evaluated using the MTT assay. ICC analysis revealed negative expression of hormonal receptors (ER and PR) in five cell lines, while only one cell line was positive for both. Six cell lines were HER2-negative and positive for vimentin. Five cell lines exhibited in vitro tumorigenic capacity, forming colonies in soft agar. DOX showed the highest growth-inhibitory effect (DOX > Paclitaxel > Colchicine > 5-FU > Carboplatin). Two cell lines had a minimal concentration for 50% inhibition in vitro (IC50) < 0.63 µM and 4.37 ± 0.40 µM for DOX, while one was sensitive to colchicine and paclitaxel (IC50 0.19 µM and 0.04 µM, respectively). All tested cell lines were resistant to carboplatin and 5-FU. These cell lines provide a valuable model for studying breast cancer in humans and dogs and evaluating new potential therapeutic strategies.