RNA in situ hybridization and IHC analysis of colorectal cancer cases. Sections from sporadic/familial colorectal cancer and placenta (as positive control) were hybridised with Dig-labelled PSG9 RNA probes. Both PSG2 (b) and PSG9 (c) were expressed at a high level in placental tissue. Sense-probes were used as a negative control on placental tissue (a). In microscopic normal epithelial cells from FAP cases, PSG9 expression was detected at the top of crypt (d) (see discussion). PSG9 transcripts (shown as dark blue) were detected at very low levels in normal mucosa (e), adenomas (f), while high expression was detected in tumour cells from the same FAP case (g). In contrast to sporadic cases, PSG9 was detected in normal appearing mucosa in some FAP cases with APC germline mutations, suggesting that dose and level of APC have an impact on PSG9 levels in cells (e, i). A high level of PSG9 was detected in a sporadic case (k), while corresponding normal tissue was negative (i). Tumours and corresponding normal tissue were also examined for β-catenin stabilization by immunostaining (h, j, l). As expected, high levels of β-catenin were detected in all sporadic colorectal tumours (l), while the protein level was less intense in FAP cases (h) where PSG9 up-regulation could be measured (g).