The oncogenic relevance of the other four hub genes – including the heat shock protein HSP90AA1 [30–32], the lymphoid-enhancer binding factor LEF1 [21, 33–35], the DNA mismatch repair gene MLH1 [36–38], and the tumor suppressor RNA-binding motif protein RBM5 [39–41] - have been reviewed elsewhere [30–32, 36–41], further supporting this network as a molecular link between air pollution exposure and lung cancer risk. Here, MLH1 is linked to lung cancer.