PTEN expression in colorectal adenomas: relationship to morphology and cell heterogeneity

Colorectal adenomas are the most frequent benign colorectal tumors. These tumors are characterized by dysplasia, low and high grade, the latter having the potential to evolve to adenocarcinoma. The aim of this study was to study the expression patterns of PTEN protein in a series of colorectal adenomas and the relationships to cell proliferation and CD133, marker of stem phenotype.

Colorectal adenomas were studied for the immunohistochemical expression of PTEN on tissue microarrays. PTEN expression was analysed with regard to morphological features and with regard to the Ki67 and CD133-positive cell compartments by using the Kendall rank-correlation test.

PTEN was expressed in 92% adenomas, either in a cytoplasmic or nuclear pattern. Cytoplasmic PTEN was correlated to cytoplasmic CD133 (p = 0.02, tau 0.191) while nuclear PTEN to decreased adenoma size and to tubular architecture (p = 0.01, τ-0.184 and p = 0.01, τ-0.183). Nuclear PTEN was also correlated to low grade intraepithelial neoplasia, while global PTEN (nuclear or cytoplasmic) was correlated to the presence of a decreased Ki67-positive component but with marginal significance (p = 0.06, τ-0.144 and p = 0.07, τ-0.213).

The results of this study suggest a role for PTEN in colorectal adenoma morphogenesis and cell protein heterogeneity, being correlated to decreased size, tubular architecture and a high CD133-positive component.