PC-cell derived growth factor (PCDGF/GP88): A novel circulating biomarker in breast cancer (BC) patients

551 Background: The identification of a measurable biomarker that is also a therapeutic target of malignant transformation or malignant progression of breast carcinoma (BC) is needed. PCDGF/GP88, an 88 kDa glycoprotein autocrine growth factor is expressed in human BC tumors in a positive correlation with their tumorigenicity. In estrogen receptor positive (ER+) cells, PCDGF/GP88 expression is low and is stimulated by estradiol whereas in ER negative cells, it is constitutively overexpressed. In ER+ cells, PCDGF/GP88 mediates estrogen mitogenic activity and its overexpression renders cells estrogen-independent and tamoxifen-resistant. Inhibition of PCDGF/GP88 expression by antisense transfection leads to inhibition of breast tumor incidence and growth in nude mice. PCDGF/GP88 is expressed in 80% of human invasive ductal carcinomas and correlates with expression of markers of poor prognosis whereas normal tissues and benign breast lesions are negative. Methods: A blood sampling study was conducted to determ...