In 2017, Ren M et al. enrolled in 123 LC cases and 130 healthy controls to investigate the relationship between LC and the methylation levels of RASSF1A and SHOX2. They found that the methylation-positive rates of RASSF1A and SHOX2 were higher in LC group (50.4% and 64.2%) compared to the control group (3.8% and 7.7%). This evidence concerns the gene SHOX2 and laryngotracheoesophageal cleft.