Mus tales: a hands-on view

Histone Deacetylase Inhibitors and Microtubule Inhibitors Induce Apoptosis in Feline Luminal Mammary Carcinoma Cells

Simple Summary

Feline mammary tumors (FMT) are very common in cats, associated with very aggressive behavior and a short life expectancy. Surgery is the most used treatment but tumor recurrence is common. Currently, available therapies are insufficient, therefore, new molecular targets are needed to develop more efficient therapeutics. Histone deacetylases inhibitors (HDACis) have been developed to target tumor cells, by disrupting gene expression and leading to cell death. Microtubules inhibitors (MTIs) have also been a focus of research, to target polymerization of microtubules, and consequently disturbing the cytoskeleton and leading to cell cycle arrest and apoptosis. However, there are few studies on the use of HDACis and MTIs in cats. In this study, we addressed if these two drug classes could be used as new therapeutic options in FMTs. All HDACis and MTIs exhibited suitable and dose-dependent antitumor effects in FMT cell lines. Immunoblot analysis confirmed that the mode of action of HDACis is conserved in feline mammary tumor cell lines. Finally, flow cytometry showed that exposure with HDACis and MTIs lead to the induction of cellular apoptosis. In summary, HDACis and MTIs possess antitumor properties suggesting further studies on their use in the treatment of feline mammary tumors.

Abstract

Feline mammary carcinoma (FMC) is the third most common type of neoplasia in cats, sharing similar epidemiological features with human breast cancer. In humans, histone deacetylases (HDACs) play an important role in the regulation of gene expression, with HDAC inhibitors (HDACis) disrupting gene expression and leading to cell death. In parallel, microtubules inhibitors (MTIs) interfere with the polymerization of microtubules, leading to cell cycle arrest and apoptosis. Although HDACis and MTIs are used in human cancer patients, in cats, data is scarce. In this study, we evaluated the antitumor properties of six HDACis (CI-994, panobinostat, SAHA, SBHA, scriptaid, and trichostatin A) and four MTIs (colchicine, nocodazole, paclitaxel, and vinblastine) using three FMC cell lines (CAT-MT, FMCp, and FMCm), and compared with the human breast cancer cell line (SK-BR-3). HDACis and MTIs exhibited dose-dependent antitumor effects in FMC cell lines, and for all inhibitors, the IC50 values were determined, with one feline cell line showing reduced susceptibility (FMCm). Immunoblot analysis confirmed an increase in the acetylation status of core histone protein HDAC3 and flow cytometry showed that HDACis and MTIs lead to cellular apoptosis. Overall, our study uncovers HDACis and MTIs as promising anti-cancer agents to treat FMCs.

A Comparative Study on the In Vitro Effects of the DNA Methyltransferase Inhibitor 5-Azacytidine (5-AzaC) in Breast/Mammary Cancer of Different Mammalian Species

Murine models are indispensible for the study of human breast cancer, but they have limitations: tumors arising spontaneously in humans must be induced in mice, and long-term follow up is limited by the short life span of rodents. In contrast, dogs and cats develop mammary tumors spontaneously and are relatively long-lived. This study examines the effects of the DNA methyltransferase (DNMT) inhibitor 5-Azacytidine (5-AzaC) on normal and tumoral mammary cell lines derived from dogs, cats and humans, as proof of concept that small companion animals are useful models of human breast cancer. Our findings show that treatment with 5-AzaC reduces in vitro tumorigenicity in all three species based on growth and invasion assays, mitochondrial activity and susceptibility to apoptosis. Interestingly, we found that the effects of 5-AzaC on gene expression varied not only between the different species but also between different tumoral cell lines within the same species, and confirmed the correlation between loss of methylation in a specific gene promotor region and increased expression of the associated gene using bisulfite sequencing. In addition, treatment with a high dose of 5-AzaC was toxic to tumoral, but not healthy, mammary cell lines from all species, indicating this drug has therapeutic potential. Importantly, we confirmed these results in primary malignant cells isolated from canine and feline adenocarcinomas. The similarities observed between the three species suggest dogs and cats can be useful models for the study of human breast cancer and the pre-clinical evaluation of novel therapeutics.

Mammary stem cell research in veterinary science: an update

The mammary gland is an organ with a remarkable regenerative capacity that can undergo multiple cycles of proliferation, lactation, and involution. Growing evidence suggests that these changes are driven by the coordinated division and differentiation of mammary stem cell populations (MaSC). Whereas information regarding MaSC and their role in comparative mammary gland physiology is readily available in human and mice, such information remains scarce in most veterinary mammal species such as cows, horses, sheep, goats, pigs, and dogs. We believe that a better knowledge on the MaSC in these species will not only help to gain more insights into mammary gland (patho) physiology in veterinary medicine, but will also be of value for human medicine. Therefore, this review summarizes the current knowledge on stem cell isolation and characterization in different mammals of veterinary importance.

Stem/progenitor cells in non-lactating versus lactating equine mammary gland

The mammary gland is a highly regenerative organ that can undergo multiple cycles of proliferation, lactation, and involution. Based on the facts that (i) mammary stem/progenitor cells (MaSC) are proposed to be the driving forces behind mammary growth and function and (ii) variation exists between mammalian species with regard to physiological and pathological functioning of this organ, we believe that studying MaSC from different mammals is of great comparative interest. Over the years, important data has been gathered on MaSC of men and mice, although knowledge on MaSC in other mammals remains limited. Therefore, the aim of this work was to isolate and characterize MaSC from the mammary gland of horses. Hereby, our salient findings were that the isolated equine cells met the 2 in vitro hallmark properties of stem cells, namely the ability to self-renew and to differentiate into multiple cell lineages. Moreover, the cells were immunophenotyped using markers for CD29, CD44, CD49f, and Ki67. Finally, we propose the mammosphere assay as a valuable in vitro assay to study MaSC during different physiological phases since it was observed that equine lactating mammary gland contains significantly more mammosphere-initiating cells than the inactive, nonlactating gland (a reflection of MaSC self-renewal) and, moreover, that these spheres were significantly larger in size upon initial cultivation (a reflection of progenitor cell proliferation). Taken together, this study not only extends the current knowledge of mammary gland biology, but also benefits the comparative approach to study and compare MaSC in different mammalian species.