In one study, Ji et al. combined Lkb1 inactivation with Kras activation and found that mice with the Kras Lkb1−/− phenotype developed metastases to intraparenchymal lung lymph nodes (equivalent to stage 2 human lung cancer) at a rate of 50-60%; however, fewer than 4% of mice developed distal metastases outside of the thoracic cavity [42]. This evidence concerns the gene KRAS and lung cancer.