CHARACTERIZATION OF EO771-TUMOR AS IN VIVO MODEL TO STUDY BREAST CANCER CELL? IMMUNE SYSTEM INTERACTIONS

PAULA AGUIRRE; MARCOS PALAVECINO; LILIAN CASTILLO; ROBERTO MEISS; SANTIAGO RODRIGUEZ.- SEGUÍ; OMAR COSO; EVA WERTHEIMER; EDITH KORDON; MARINA SIMIAN; ANDREA ERRASTI; ALBANA GATTELLI; MANUEL DE LA MATA; ANTONIO CARRERA-SILVA; JUAN PABLO FEDEDA

VIRTUAL

Congreso; REUNION CONJUNTA SAIB-SAMIGE 2020; 2020

SAIB-SAMIGE

Mouse model systems have been key in understanding novel mechanisms underpinning breast cancer development anddelivering new therapies. Among them, the EO771 triple negative-like cell line is emerging as a new spontaneous model tostudy breast cancer in the C57BL/6 mice background. Here, we confirm the hormone-dependency, and we characterize thechanges in the immune and inflammatory compartments associated to the progression states of EO771 tumor growth usingflow cytometry. Tumor-associated macrophages (TAMs) are relevant cells of the tumor microenvironment, and in the clinicM2 subtypes associated with the promotion of tumor progression. By interrogating the myeloid compartment present in theEO771-tumor model, we found that tumor progression associates with increased M2 macrophage polarization. Interestingly,we observed a decrease in MHCII+ Antigen Presenting Cells (APCs) in advanced tumors, which is consistent with tumormediated immunosuppression by antigen presentation inhibition. Furthermore, by investigating the tumor infiltratinglymphocytes (TILs) landscape, we observed a marked increase in the CD4+/CD8+ratio during the tumor progression,mimicking the high CD4+/CD8+ratios associated with poor prognosis in triple negative breast cancer (TNBC) patients.Moreover, CD4+ PD1high TILs population is increase in later stages, which is consistent with CD4+ TIL exhaustion duringtumor progression. In summary, we found that EO771-tumor progression elicits key features of the clinically observed immunesystem response in TNBC, making it an ideal model to study TNBC tumor-immune system interactions