PTGS2 and colorectal neoplasm: Transgenic cLys-Cox-2 x ApcMin/+ mouse colorectal tumours demonstrated an increase in Cox-2 immunoreactivity in the stromal cell compartment below the luminal tumour surface compared with non-transgenic ApcMin/+ mouse colorectal tumours (P = 0.02, Mann-Whitney U test; Fig. 2E–G).