Prognostic significance of platelet immunorelated GPIb expression in breast cancer

PURPOSE Prior reports have indicated that adhesive glycoprotein receptors expressed by tumor cells enhance their invasive and metastatic properties. We have recently isolated and characterized a platelet immunorelated GPIb receptor expressed by cultured breast tumor cell lines that participates in initial adhesive events in the metastatic process. Whether expression of this receptor predicts tumor behavior or clinical prognosis remains unknown. PATIENTS AND METHODS Forty sequential breast tissue specimens were examined for GPIb alpha, GPIb/IX, and alpha(IIb)beta(3) (GPIIb/IIIa) expression by immunohistochemical staining. Of 35 assessable breast specimens, 20 were invasive ductal carcinomas or lobular invasive carcinomas, six were ductal carcinomas in situ (DCIS), and the remaining nine consisted of nonmalignant pathologies. RESULTS The expression of an immunorelated GPIb alpha and GPIb/IX complex by invasive mammary carcinoma specimens was highly significant (P < 0.0001). However there was no correlation between alpha(IIb)beta(3) expression and invasive breast cancer. A GPIb alpha or GPIb/IX staining score of less than or equal to 2.0 and > 2.0 correlated highly with the diagnosis DCIS and invasive carcinoma, respectively (P < 0.0039). Invasive breast carcinoma specimens demonstrated a 120% (P < 0.001) and 140% (P < 0.027) increase in GPIb alpha and GPIb/IX staining score in comparison with DCIS specimens. Expression of GPIb alpha and GPIb/IX correlated significantly with a tumor stage of greater than or equal to III (P < 0.008), a tumor size of > 3 cm (P < 0.012), involved axillary nodes (P < 0.004), and estrogen receptor negativity (P < 0.008). Finally, a significant correlation was observed between this receptor's expression and the presence of nodal and/or visceral metastases (P < 0.0035). DISCUSSION These results demonstrate a significant correlation between GPIb expression and breast malignancy. The expression of the GPIb receptor appears to represent an unfavorable prognostic factor and a biomarker predictive of aggressive disease.