Recently, by using the PE system, we tried to introduce the R248Q mutation (CGG>CAG) of the TP53 gene, which is reported to be the most frequent relapse-specific TP53 gene mutation in BCP-ALL cases [30], into the 697 cell line, since it is not inducible by the existing BE systems. The gene discussed is TP53; the disease is acute lymphoblastic leukemia.