Evaluation of cathepsin D immunostaining in colorectal adenocarcinoma

Cathepsin D (CD), an estrogen-regulated lysosomal protease, has been detected in a variety of tissues. CD expression has been correlated with the invasive potential of breast cancer, acting as an autocrine mitogen or as a protease that degrades the extracellular matrix. The role of CD expression in predicting prognosis or invasive potential in colorectal carcinomas is mostly unknown.

CD immunohistochemical expression was studied in 60 surgical specimens of colon adenocarcinomas. A three-step avidin biotinylated, horseradish immuno-peroxidase (ABC-HRP) staining technique was performed on 4 microm paraffin-embedded tissue sections with a polyclonal antibody to CD.

Carcinoma cells showed positive CD immunostaining in 41.6% of adenocarcinomas (50%, 43.7%, 37.5%, and 25% of Dukes' Stage A, B, C, and D, respectively). Nonneoplastic stromal cells demonstrated positive staining in 68.3% of the adenocarcinoma specimens (37.5%, 62.5%, 91.6%, and 75% of Stage A, B, C, and D, respectively). Patients with colorectal carcinomas exhibiting simultaneously negative and positive CD expression in malignant and stromal cells, respectively, had a worse 5-year overall survival (P < 0.05). The mean 5-year survival of the 16 patients overexpressing CD in nonneoplastic stromal cells (>15% of stromal cells positive for CD) was significantly worse in comparison with the rest of the adenocarcinomas (n = 44) (27.6 +/- 4.6 vs. 46 +/- 2.7 months, respectively, P < 0.01).

Expression of CD immunoreactivity by the stromal cells may be associated with a more invasive phenotype. Therefore, CD expression in tumor and stromal cells may serve as an important indicator of progression and guide postoperative treatment.