Image kindly provided by Dr. Magdalena Krol. Control tumor cells, tumor cells grown in macrophage-conditioned medium, tumor cells sorted from co-culture with macrophages, and macrophages from monocultures and sorted from co-culture with tumor cells were analyzed. Total protein concentrations in lysates were determined using a Bio-Rad protein assay. Proteins (50 mg) were resolved using SDS-PAGE and transferred onto PVDF membranes. The membranes were then blocked with 5% non-fat dry milk in TBS buffer containing 0.5% Tween 20. The membranes were then incubated overnight with the primary Rabbit Anti-DKK1 Polyclonal Antibody at 1:100 dilution. Subsequently, the membranes were washed three times in TBS containing 0.5% Tween 20 and incubated for 1 h at room temperature with secondary antibodies conjugated with the appropriate infrared (IR) fluorophore IRDyeH 800 CW or IRDyeH 680 RD at a dilution of 1:5000.