TP53 and neoplasm: In addition, two knock-in conditional Trp53R172H (corresponding to human TP53R175H) and Trp53R270H (corresponding to human TP53R273H) alleles (referred to as Trp53LSL-mut), in which a loxP flanked STOP cassette was inserted into the first intron to block mutant Trp53 expression, have been utilized to study different types of cancers including breast cancer7–9.