STK11 and neoplasm: Despite reduced levels of Lkb1 mRNA and protein in various tissues from Lkb1XTR/XTR mice as compared to Lkb1 wild-type mice, Lkb1XTR/XTR mice developed normally, were born at the expected Mendelian ratio, and did not develop gastrointestinal polyps as would be expected if the Lkb1XTR allele greatly compromised LKB1 tumor suppressor activity (Supplementary Fig. 2a–d)39.