Immunoreactive Transforming Growth Factor β-1, Its Receptor,bcl-2 Protein,and p53 Protein in Colorectal Adenomas

Abstract: Immunoreactive transforming growth factor-β1 (TGF-β1), its receptor (TGFR), bcl-2 protein, and p53 protein were stained in 47 samples of normal colonic mucosa and 33 samples of colorectal adenoma, with the aim of exploring an alternate, novel pathway of colorectal tumorigenesis. There was no difference in the percentage of cells positive for TGF-β1 immunoreactivity between normal mucosae and adenomas. TGFR immunoreactivity was detected in a significantly higher percentage of normal mucosae than of adenomas (p ±0.05). Bcl-2 protein and p53 protein immunoreactivities were detected in a significantly higher percentage of adenomas than of normal mucosae (p ±0.01). Expression of these immunoreactive proteins did not correlate with any of the clinicopathological features of adenomas, except for a significant negative correlation between TGFR expression and large tumor size (p±0.05) and a positive correlation between p53 protein expression and the grade of dysplasia (p±0.05). These findings indicate that (1) TGF-β1 plays little role in the tumorigenesis of colorectal adenomas, (2) TGFR is lost in most adenomas during tumorigenesis, (3) bcl-2 protein plays an important role in transformation of normal mucosa into adenoma, and (4) p53 protein is involved in the very early phase of malignant transformation from adenoma to carcinoma.