Lipocalin-2 (Lcn-2) as a potential target in triple negative breast carcinoma

Triple negative breast cancer (TNBC) is a type of refractory breast cancer and for decades has completely relied on chemotherapy as a treatment. Recent improvements are swiftly changing the treatment choice, whereby immunotherapy could be a viable treatment strategy. However, identification of relevant biomarkers and development of more active immunotherapy combination regimens are currently high priorities in the field. In this context, Lipocalin-2 (Lcn-2), a glycoprotein acting as a regulator of the alternative iron homeostasis pathway, could be a potential novel target. Lcn-2 was shown to deliver iron to rapidly proliferating cells and polarize tumor-associated macrophages (TAM) to a pro-tumoral phenotype in the tumor microenvironment (TME). Moreover, high Lcn-2 expression is recognized as an independent prognostic biomarker for reduced survival among patients with breast cancer, especially for those suffering from TNBC. Lcn-2 actively promotes breast cancer metastasis by inducing VEGF production, angiogenesis and epithelial-to-mesenchymal (EMT). In line with this, our data show that Lcn-2 is present in tumor single cell suspensions derived from E0771.LMB tumor bearing mice and that both host and E0771.LMB cells are an important source of Lcn-2. Moreover, absence of host Lcn-2 (using Lcn-2-/- mice) significantly reduces primary tumor growth. Interestingly, compared to WT mice, Lcn-2-/- mice showed a better anti-tumoral response as evidenced by the increased MHCIIhigh/MHCIIlow TAMs ratio and effector/naïve CD8+ T cell ratio. Yet, this effect may be limited since cancer cells can still produce Lcn-2. Hence, we have successfully generated a knocked-down Lcn-2 E0771 cell line using shRNA, which will improve delineating the role of stromal-derived versus cancer cell-derived Lcn-2 in tumor development. Furthermore, upon co-culturing of WT BMDMs with E0771 cells, iron homeostasis genes were reduced in BMDMs which was most pronounced when cancer cells do not express Lcn-2. Finally, aLcn-2 Nanobodies (Nbs) will be assessed, either as monotherapy or in combination with other therapeutic modalities.