Comparison of the effect of two methods of intraductal injection of the nipple catheter and modified up-the-teat intraductal injection in construction of tree shrew breast cancer model

Background: Topical administration through the mammary duct is an important way to study breast cancer treatment. However, there is a lack of suitable primate animal model of breast cancer for studying topical administration treatment through the mammary duct. Methods: 12 female healthy tree shrews at the age of 6 months were selected and randomly divided into experimental group (n=6) and control group (n=6). The experimental and control groups were respectively treated using protecting the intraductal injection of the nipple catheter (PIINC) method and modified up-the-teat intraductal injection (MUTII) method to establish the tree shrew breast cancer model. The degree of drug dispersion in mammary duct system, morphological changes of nipples after injection, efficiency and time of tumor formation were compared between the two groups. Results: The drug injected by PIINC method can successfully enter the mammary gland along the ductal-alveolar tree just like by MUTII method. However, edema, bleeding and injury of nipples and surrounding tissues were not observed after the PIINC injection but can be observed after MUTII injection. More importantly, intraductal injection by PIINC not only can successfully construct the tree shrew breast cancer model but also can be repeated in the same nipple after the model construction which could not be realized by MUTII. There was no significant difference in the efficiency and time of tumor formation between the two methods (P<0.05). Conclusions: PIINC is a more suitable method than MUTII to construct the tree shrew breast cancer model for studying topical administration treatment through the mammary duct.