CDKN1A and cancer: While antisense constructs of Cyclin G1, antisense Cyclin D1, and enforced expression of p21, were each found to be effective as transgenes (payloads) in blocking cancer cell survival in vitro, Cyclin G1 was selected for clinical development in a series of truncation experiments, using both point mutations and deletion mutants, to discern a potent dominant-negative “blocking” construct of the Cyclin G1 pathway, which was determined to be essential for the survival and proliferation of cancer cells derived from each of the three germ layers.