BREAST CANCER MODEL DEVELOPED THROUGH ORTHOTOPIC EHRLICH CELL INJECTION FOR INVESTIGATION OF MECHANISMS IN MALIGNANCY AND METASTASIS

Nicoli Serquiz de Azevedo, Patricia Kajikawa, Gabriel Y. Ikejiri, Gislaine A. F. Carvasan, Natalie Rios Almeida, Tamara P. de Oliveira, Renato Z. Torresan, César C. dos Santos

Institution: UNB. University Center of Brasília UNICEUB

Objectives: We aimed to establish an optimal orthotopic cancer model for breast cancer in immunocompetent Swiss female mice, describing the detailed microanatomy of the breast, as well as the sentinel lymph node (SLN) and lymphatic mapping, evaluating histopathological changes and characterizing the tumor by computer microtomography and interleukins expression. Methodology: The distribution of the ductal network model was observed employing staining techniques. To obtain the tumor growth curve, Ehrlich ascitic tumor cell suspension (1 × 106) was inoculated in 10 experimental groups, according to fresh or frozen viable tumor cells and the time of the tumor analysis, at 1, 2, 7, 14 and 21 days after the orthotopic inoculation. Samples from the tumors, the contralateral mammary gland and several organs were used to evaluate the tumor progression and metastasis. Trypan Blue was used to access the lymphatic mapping and reveal the SLNs and nodal network 7 and 14 days after tumor cell implantation, and cytokines were evaluated only at the 14th day. Results: The inoculation of fresh Ehrlich tumor cells led to a detectable tumor as early as 24 hours later and after 7 days mammary, muscular, dermal vascular and lymphatic invasions were observed and also micrometastases in mammary adipose tissue, SLN and contralateral lymph nodes. From the inoculation site the tumor invaded the host mammary gland structures, the dermis and endomysium of skeletal muscle tissue. Th1 cytokine levels (IL-1β and IL-17) were significantly higher than anti-inflammatory Th2 (IL-4) after inoculation of fresh tumor cells. Differently, frozen tumor cells induced tumor development only 14 days after the inoculation, while presenting expression of distinct interleukins. Conclusion: Besides demonstrating that orthotopic transplantation provides the critical microenvironment involved in the development of cancer and metastasis, this study provided anatomical support for the understanding the lymphatic process of the spread of cancer cells.

Keywords: immunocompetent animal cancer model; Ehrlich tumor; orthotopic animal cancer model; sentinel lymph node; lymphatic mapping”