Stromal Caveolin-1 Expression in Breast Carcinoma. Correlation with Early Tumor Recurrence and Clinical Outcome

Caveolin- (cav-1) has been linked to tumor progression and clinical outcome in breast cancer, but its role as a prognostic marker is still unclear. We evaluated stromal and tumor caveolin-1 expression in 91 breast carcinomas, and assessed the association between their expression and clinicopathologic variables as well as patient outcome and early tumor recurrence. Absence of stromal caveolin-1 expression was detected in 18.7% of cases, while 25.3% of cases revealed tumor epithelial caveolin-1 expression. Combined stromal and tumor caveolin-1 immunopositivity was seen in 24.2% of cases. Absence of stromal cav-1 associated with larger tumor size, higher grade, higher nodal stage, higher number of positive nodes, higher TNM stage, positive HER2 status, higher recurrence rate, and shorter mean progression free survival (PFS). Stromal cav-1 status was a significant predictor of PFS in ER+, PR +, and HER2 + tumors. In tamoxifen-treated patients, absence of stromal Cav-1 was a significant predictor of poor clinical outcome, suggestive of tamoxifen resistance. Conversely, tumor epithelial and combined caveolin-1 expression, didnot associate with patient outcome. In multivariate analysis, only TNM stage independently associated with survival. Loss of stromal caveolin-1 is a novel breast cancer biomarker that can predict early tumor recurrence, short PFS, and tamoxifen- resistance. Thus, its use as a predictive biomarker, especially in lower grade, lower stage, ER+, PR+, HER2+, and tamoxifen treated patients may allow for early interventions with more aggressive therapies. Thus, stromal marker expression and epithelial-stromal cross talk may be critical for tumor progression and metastasis.