CpG islands associated with MSX1 and OTX1 were methylated in the majority of lung squamous cell carcinomas, while the ones associated with RUNX1 were methylated in more than 80% of lung adenocarcinomas, being well known that hypermethylation of CpG islands is a signature of malignant progression (35). Here, MSX1 is linked to squamous cell lung carcinoma.