Another study found that hotspot mutations c.1624G>A[p.E542K] and c.1633G>A [p.E545K] on PIK3CA were significantly enriched in ESCCs with Signatures 2 and 13, suggesting that APOBEC activity is a driver of PIK3CA mutagenesis in ESCC [25]. This evidence concerns the gene PIK3CA and esophageal squamous cell carcinoma.