TP53 and cancer: Alternatively, this specific variant may represent mosaicism resulting from somatic mutation in early embryonic cells.43,44 Genome doubling may also underlie development of oesophageal cancer following early TP53 inactivation.45 The status of the overrepresentation of the 12p region in the purified cancer stem cells GCNIS remains uncertain, but the observed balanced allele frequencies are in line with absence of 12p gain (Figs. 2a, c and Supplementary Fig. S8).