In line with these observations, our data also showed an enrichment of fetal markers in the squamous tumor component absent from epithelial cells from both AOM/DSS and APC tumors, including genes expressed in primitive gut (Trp63, Sox2, Pitx1), as well as metaplastic genes such as Tacstd2. We attempted to determine the origin of squamous lesions in AOM/DSS tumors using lineage tracing from Lrig1-expressing epithelial cells, since Lrig1 is not expressed in the anal epithelium (75). The gene discussed is PITX1; the disease is infectious otitis media.