To uncover the role of CXCL13 in BaP-induced lung cancer, Cxcl13 knockout mice (Cyster et al., 2000) were treated with 100 mg/kg BaP twice a week for 8 weeks (Figure 4—figure supplement 1A,B), and the tumor burden of the mice was evaluated. The gene discussed is CXCL13; the disease is lung cancer.