FVB-MMTV-PyMT Mouse

The Mouse Mammary Tumor Virus (MMTV) is a retrovirus transmitted through milk and belongs to the betaretrovirus class. This virus was discovered during the study of inbred mouse strains with a high incidence of mammary tumors and can cause breast cancer and lymphoma in mice. It is the most studied oncogenic virus, causing about 95% of mouse breast cancer. As an endogenously encoded β-retrovirus, MMTV is transmitted as an exogenous pathogen through milk, using breast milk to vertically transmit from the mother to the pups, integrating as a DNA provirus in the DNA of milk lymphocytes. During puberty, the virus enters the mammary gland with migrating lymphocytes and infects proliferating mammary epithelial cells. As a retrovirus, MMTV can insert its viral genome into the host genome ^[1-2]. The long terminal repeat sequence (LTR) of MMTV contains a glucocorticoid response element that acts as a promoter during transcription. Utilizing its viral tissue-specific promoter and enhancer functions, the related structure of this virus is also used to drive the specific expression of certain genes in tissues such as mouse mammary glands, for the construction of mammary tumor-like disease models or for conducting tissue-specific research related to the mammary glands ^[3-4].

The FVB-MMTV-PyMT mouse is a tumor research model, in which the cDNA sequence of the polyoma middle T antigen (PyVT/PyMT) from the polyoma virus is integrated into the mouse genome through transgenic technology. This is driven by the long terminal repeat sequence (LTR) of the mouse MMTV for its specific expression. The PyVT protein can be expressed in mammary epithelial cells, leading to widespread transformation of the mammary epithelium and rapid generation of multifocal breast cancer ^[5]. It has been reported that adenocarcinomas in MMTV-PyMT mice mainly occur in females, but can occasionally be observed in males. These adenocarcinomas are well differentiated, multifocal, and eventually involve the entire mammary fat pad ^[6]. Detection data show that female FVB-MMTV-PyMT mice can develop the disease as early as 8 weeks of age. The incidence rate is approximately 80% at 10 weeks of age, and lung metastasis occurs in the late stage. Compared with Cyagen's similar strains, MMTV-PyMT mice (C57BL/6JCya background, catalog number: C001212) and FVB;B6-MMTV-PyMT (F1) mice (catalog number: C001556), FVB-MMTV-PyMT mice with an FVB/NJCya background develop the disease earlier.