While a retrospective study of associations identified in patients cannot determine causation, we were able to show that systemic LRRK2 KO increased tumor initiation and size in carcinogen-driven early lung cancer in mice, providing orthologous evidence that LRRK2 reduction is not merely a passenger aberration but a link between environmental insult and potential AT2 cell transformation. This evidence concerns the gene LRRK2 and lung cancer.