Generation and characterization of a conditional and reporter mouse model for the atypical chemokine receptor 2

Purpose: Atypical chemokine receptor 2 is an atypical receptor that binds and degrade most CC infl ammatory chemokines. Today, there are no techniques to study ACKR2 expression in mice, due to the lack of a working antibody. Several studies indicate its expression in lymphatic endothelial cells and in trophoblast cells. The aim of this project is to generate a conditional and reporter mouse model to investigate the cell expression of the receptor, create an inducible and cell-specifi c knockout model to study ACKR2 regulation in cancer progression. Methods: We generated two different mouse models with a knock-out/knock-in strategy, in which the ACKR2 gene was replaced by a TdTomato/Luciferase reporter gene after Tamoxifen injection. Floxed mice has been crossed with inducible and ubiquitary Cre recombinase or with inducible Cre recombinase under Prox-1 promoter, marker of lymphatic endothelium cells. We characterized these mice by PCR, qPCR, in vivo imaging, FACS and confocal immunofl uorescence. Moreover, we evaluated the regulation of ACKR2 after subcutaneous injection of the melanoma cell line B16F10. Primary tumor and draining lymph nodes were analyses by immunofl uorescence and FACS. Results: We analyzed genomic and transcriptomics changes after gene recombination to demonstrate the properly working of the system. We found ACKR2 is expressed in skin, colon and lung by in vivo system, immunofl uorescence and FACS analysis. Finally, we found an increase of ACKR2 expression in lung measured by in vivo imaging in the melanoma model. Discussion: This study would to shed light on tumor control and cancer therapies, discovering how the control of chemokines concentration may have opposite functions according to the cell type examined. Conclusion: Taking advance of the ACKR2 reporter mouse, we studied the expression and regulation mechanism of the receptor in physiological and tumoral context strictly control the gene silencing during tumor progression.