The
serine proteinase inhibitor maspin is a
tumor-suppressor protein that stimulates apoptosis and inhibits motility, invasion and
cancer metastasis. Mutant
maspin galvanises partial loss of
tumor-suppressor function, reducing susceptibility to apoptosis and facilitating malignant progression. Mutant
maspin has been reported in many
tumor types. We recently analyzed
maspin expression in 128 colorectal lesions: 39 hyperplastic
polyps (HPs), 29 sessile serrated
adenoma/
polyps (SSA/Ps), three traditional serrated
adenomas (TSAs), 20 conventional colorectal
adenomas (CCRAs), 5
carcinomas evolving from CCRA, 12 active
inflammatory bowel disease (IBD), 2
ulcerative colitis (UC) in remission, 4 solitary
ulcers (rectum) and 12 normal colorectal mucosa. The topographic distribution of
maspin in the cytoplasm was classified into i) extensive, ii) focal, or iii) negative. The intensity of
maspin expression in the cytoplasm was classified into i) unquestionable or ii) negative. Cases with faint (questionable)
maspin expression were also recorded as negative. Extensive
maspin expression was recorded in 95% (39/41) of the HPs, in 100% (29/29) of the SSA/Ps (including one
carcinoma arising in a SSA/P), in 66% (2/3) of the TSAs, but only in 10% (2/20) of the CCRAs. None of the specimens with
carcinoma arising in CCRA, with UC in remission or with solitary
ulcer exhibited extensive
maspin expression. Importantly,
maspin was not expressed in the normal mucosa (including that adjacent to HP, SSA/P,
TSA and CCRA). It is submitted that extensive
maspin expression might be a manifestation of mutant
maspin in lesions central to the serrated pathway of colorectal
carcinogenesis.