DHTKD1 and neoplasm: Most importantly, as the CR2 region of E1A is thoroughly lost in JH293-C21-C14-C28 cells, the produced RCA will be the CR2 region deleted and can only propagate in Rb-deficient tumor cells even if homologous recombination occurs between the AdVs and the JH293-C21-C14-C28 cell genome.