Analysis of WT and Casp11−/− colons at the 6 week tumour development stage revealed significantly increased IEC proliferation in Casp11−/− colons compared with treatment matched WT colons, as assessed by staining and histological evaluation of the proliferation markers PCNA (Fig. 5c, d) and Ki67 (Fig. 5e, f). Here, PCNA is linked to neoplasm.