Two articles in the American Journal of Pathology demonstrate the role of stromal caveolin-1 expression as a prognostic marker for breast cancer progression.

Caveolin-1, a protein that functions in endocytosis and signal transduction, plays a major role in breast cancer tumorigenesis. However, although calveolin-1 expression has been extensively studied in epithelial cells in breast cancer patients, the value of epithelial caveolin-1 as a prognostic marker has been limited.

Witkiewicz et al and Sloan et al therefore examined caveolin-1 expression in the stromal microenvironment of human breast cancer. Stromal expression of caveolin-1 correlated with reduced levels of metastasis, and caveolin-1 was not expressed in stroma of patients with poor clinical outcome. In addition, tumor onset in mice was accelerated in the absence of stromal caveolin-1. Caveolin-1 may therefore function as a tumor suppressor in the stromal microenvironment and serve as a new prognostic marker for breast cancer progression.

In a related commentary, Dr. Mina Bissell, who is not associated with these studies, suggests that "for now, the two studies presented in this issue of the AJP provide additional validation that the microenvironment is an important and potentially powerful source of clinical information to predict patient outcome, and demonstrate specifically that stromal Cav-1 may be a valuable clinical marker. Determining whether stromal Cav-1 functions to directly suppress tumor growth, and uncovering the factors which regulate its expression, may also reveal novel therapeutic avenues."

SOURCES:
American Journal of Pathology, June 2009
American Society for Investigative Pathology (http://www.asip.org)