LEPR and colorectal carcinoma: Previous studies on gene and smoking interactions in CRC have been based on candidate genes such as CYP1A1 [32], CYP1A2 [32], GPX1 [33], GSTM1 [32, 34–38], GSTT1 [35–38], LEPR [39], MAD1L1 [40], mEH3 [41], mEH4 [41], NAT1 [36], NAT2 [32, 42, 43], NQO1 [44], OGG1 [33], PTEN [45], SMAD7 [46], and TGFBR1 [46].