On the other hand, BIRC2 and YAP1, two genes present in a narrow amplicon in oral squamous cell carcinomas [27], esophageal squamous cell carcinoma [28], and lung [29], pancreatic [30], and hepatocellular carcinomas, have recently been shown to collaboratively promote tumor formation in mice [31], indicating that the extent of some tumor amplicons may be determined by selection for multiple neighboring collaborating oncogenes. This evidence concerns the gene YAP1 and esophageal squamous cell carcinoma.