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ABSTRACTIntroductionAnimal models play a crucial role in breast cancer research, in particular mice and rats, who develop mammary tumors that closely resemble their human counterparts. These models allow the study of mechanisms behind breast carcinogenesis, as well as the efficacy and safety of new, and potentially more effective and advantageous therapeutic approaches. Understanding the advantages and disadvantages of each model is crucial to select the most appropriate one for the research purpose.Area coveredThis review provides a concise overview of the animal models available for breast cancer research, discussing the advantages and disadvantages of each one for searching new and more effective approaches to treatments for this type of cancer.Expert opinionRodent models provide valuable information on the genetic alterations of the disease, the tumor microenvironment, and allow the evaluation of the efficacy of chemotherapeutic agents. However, invivomodels have limitations, and one of them is the fact that they do not fully mimic human diseases. Choosing the most suitable model for the study purpose is crucial for the development of new therapeutic agents that provide better care for breast cancer patients.

This work aimed to understand how lifelong exercise training promotes the remodelling of the immune system and prostate signalome in a rat model of PCa. Fifty-five male Wistar rats were divided into four groups: control sedentary, control exercised, induced PCa sedentary and induced PCa exercised. Exercised animals were trained in a treadmill for 53 weeks. Pca induction consisted on the sequential administration of flutamide, N-methyl-N-nitrosourea and testosterone propionate implants. Serum concentrations of C-reactive protein (CRP) and tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) were not different among groups. Peripheral levels of γδ T cells were higher in Pca exercised group than in the PCa sedentary group (p< 0.05). Exercise training also induced Oestrogen Receptor (ESR1) upregulation and Mitogen-activated Protein Kinase 13 (MAPK13) downregulation, changed the content of the phosphorylated (at Ser-104) form of this receptor (coded by the gene ESR1) and seemed to increase Erα phosphorylation and activity in exercised PCa rats when compared with sedentary PCa rats. Our data highlight the exercise-induced remodelling of peripheral lymphocyte subpopulations and lymphocyte infiltration in prostate tissue. Moreover, exercise training promotes the remodelling prostate signalome in this rat model of prostate carcinogenesis.

This study aimed to evaluate the impact of long‐term exercise training on the vascularization of rat mammary tumors. Female rats were divided into 4 groups: N‐methyl‐N‐nitrosourea (MNU) treated sedentary, MNU treated exercised, control sedentary, and control exercised. Tumor development was induced in the MNU groups by MNU administration. Exercised groups were trained for 35 weeks. Tumor vascularization was evaluated by pulsed Doppler and contrast‐enhanced ultrasonography. The pulsatility and resistive indices were slightly higher in the MNU sedentary group (P> .05). Mammary tumors mainly had centripetal and heterogeneous enhancement of the contrast, clear margins, and the presence of penetrating vessels. The MNU exercised group had a lower arrival time and time to peak and higher peak intensity, wash‐in, and wash‐out (P> .05). The area under the curve was similar between groups (P> .05). The contrast‐enhanced ultrasonographic study did not detect differences in mammary tumor vascularization between MNU sedentary and MNU exercised groups previously detected by power Doppler imaging, B‐flow imaging, and immunohistochemistry.