Investigating the Role of Atypical Chemokine Receptor 3 in Cancer Development

Atypical Chemokine Receptor 3 (ACKR3) is a seven-transmembrane spanning receptor with pleiotropic functions in development, homeostasis and pathophysiology. The spatiotemporal expression of ACKR3 is tightly regulated, a fact that highlights its importance in several biological processes. ACKR3, similar to the other atypical chemokine receptors, does not signal through G proteins. ACKR3 exerts its functions by a) recruiting the β arrestins and b) scavenging its ligands thus shaping their concentration in the extracellular milieu. ACKR3 expression is often dysregulated in pathophysiological conditions, including cancer. There is a growing body of evidence that implicates ACKR3 in certain types of human cancers. In the present study, we interrogated publicly available databases of cancer patients in order to assess ACKR3 expression in different types of human cancers. These analyses revealed that ACKR3 is upregulated in several types of human cancers, including lung cancer. To this end, we investigated the role of ACKR3 in cancer progression with a particular focus on lung cancer. In order to overcome the lack of specific ACKR3 antibodies, we used a GFP fluorescent reporter mouse to assess ACKR3 expression in the different stromal cell populations in the lung. Our approach revealed that ACKR3 is expressed in the fibroblasts, blood and lymphatic endothelial cells in the resting lung. Furthermore, in this study, we tried to address the discrepancies in the literature about ACKR3 expression that is a result of the nonspecific nature of commercially available antibodies. More specifically, we tested commercially available flow cytometry anti-ACKR3 antibodies in the GFP/ACKR3 reporter mouse. Our approach revealed that both of the ACKR3 antibodies that were tested were inefficient in staining but also nonspecific in all the cell populations that were tested. Subsequently, we employed the CRISPR/Cas9 genome editing technologies to generate ACKR3 null cancer cell lines that we used subsequently in vivo in different mouse models. Our study identified ACKR3 as a positive regulator in lung cancer progression. Furthermore, ACKR3 was also identified as a crucial player at the early steps of metastasis and colonisation of metastatic circulating tumour cells in the lung. Collectively our data suggest that ACKR3 is a promising candidate for drug targeting in certain types of human lung cancer.