Atypical chemokine receptor CCRL2 shapes tumor spheroid 2 structure and immune signaling in melanoma

C-C motif chemokine receptor-like 2 (CCRL2) is an atypical chemokine receptor (ACKR) 15 that binds chemerin with high affinity but lacks classical G protein-coupled signaling. In-16 stead, it functions as a non-signaling presenter of chemerin to CMKLR1-expressing cells, 17 modulating antitumor immunity. CCRL2 is highly expressed in the tumor microenviron-18 ment and various human cancers, and its expression has been linked to delayed tumor 19 growth in mouse models, primarily through the chemerin/CMKLR1 axis. While CCRL2's 20 role in immune surveillance is well established, its tumor cell-intrinsic functions remain 21 less clear. Here, we investigated the impact of CCRL2 overexpression and knockout on 22 tumor cell behavior in vitro. Although CCRL2 did not affect proliferation, migration, or 23 clonogenicity in B16F0 melanoma and LLC carcinoma cells, it significantly influenced 24 spheroid morphology in B16F0 cells. Transcriptomic analysis revealed that CCRL2 modu-25 lates innate immune signaling pathways, including TLR4 and IFN-?/STAT1, with context-26 dependent downstream effects. These findings suggest that CCRL2 shapes tumor archi-27 tecture by rewiring inflammatory signaling networks in a cell-intrinsic manner. Further 28 studies in other cancer types and cell models are needed to determine whether CCRL2's 29 regulatory role is broadly conserved and to explore its potential as a therapeutic target in 30 solid tumors. Overall design: RNAseq on Control B16 melanoma, B16-CCRL2 overexpression and B16-CCRL2 knockout spheroids collected at day