Establishment of a murine breast tumor model by subcutaneous or orthotopic implantation

A number of murine models are used to mimic the pathology of breast cancer. Tissue inoculation and cell inoculation using orthotopic implantation (OS) and subcutaneous implantation (SQ) are commonly used to generate murine models to investigate cancer. However, limited information is available in regard to the variations of these methods. The present study compared growth, metastasis, survival and histopathology of tumors produced using OS and SQ to characterize features of the tumors produced by the two distinct methods. Additionally, the present study aimed at providing increased options for investigators when designing experiments. 4T1-luc2 cell suspension or 4T1-luc2 tissue suspension was inoculated using either OS or SQ into BALB/c mice. Tumor growth and metastasis were detected using an in vivo imaging system and calipers. Excised tumors and lung were assessed by tissue staining with hematoxylin and eosin, and the vessel marker cluster of differentiation 31. The results of the present study revealed that the cell suspension generated breast tumors of increased size, which was visualized and determined, following inoculation, using calipers at an earlier time point compared with tumors produced by tissue suspension. The increasing bioluminescent trend of OS tumors was more marked compared with that of SQ tumors. The volume of OS tumor was increased with decreased variation, compared with that of SQ tumors. In addition, the OS tumor exhibited increased microvessel density. Bioluminescent signals and histological results in regard to metastasis were consistent: OS implantation produced increased lung metastasis compared with that of SQ implantation, although they exhibited similar survival times. The results of the present study indicated that the inocula from distinct sources (tissue or cell) affected tumor growth. Furthermore, breast tumor progression and histopathological characteristics were distinct between OS and SQ, whereas OS exhibited increased malignant behavior. Understanding the characteristics of murine breast cancer models established by diverse methods may aid investigators to select appropriate animal models, according to the requirements of the study.