CXCL1 and cancer: M1 macrophages co-cultured with cancer cell spheroids showed increased levels of CXCL1 (from M1 1 ng/mL to S + M1 3 ng/mL, p = 0.0377), CCL20 (from 5 to 50 pg/mL, p = 0.0096), and CX3CL1 (from 60 to 136 pg/mL, p = 0.0015, Figure S5a), which was likely due to the interaction of 4T1/GFP cancer cells with the M1 polarization factors IFNγ/Pam3SCK4 (Figure 5a,b).