CCNK and esophageal squamous cell carcinoma: For instance, ecDNA in a sample consisted of cancer gene MYC, CCND1, and MMPs. Interestingly, ecDNA-driven genes might have preferential partners, as ecDNA of CCND1 is more likely to connect with MMPs. In addition to well-established cancer genes involved in ESCC, there were two ecDNA-amplified regions located at chromosome chr13:113-114 Mb consisting of gene CUL4A and chr14:100 Mb consisting of gene CCNK (Fig. 8c).