Focal Adhesion Kinase Overexpression in Endometrial Neoplasia

Abstract

Focal adhesion kinase (FAK) is a protein tyrosine kinase that is a critical mediator of signaling events between cells and their extracellular matrix. Elevations in FAK mRNA and protein overexpression have been linked to tumor cell capacity for invasion and metastasis. FAK expression has been shown to be elevated in a variety of solid tumors. The purpose of this study was to evaluate for FAK upregulation in endometrial neoplasia. Tissue microarray blocks were made from formalin-fixed, paraffin-embedded archival tissue, including 115 carcinoma (100 endometrioid, 10 serous, and 5 clear cell), 28 hyperplasia, and 38 normal specimens using 1-mm punches. The tissue was immunostained with monoclonal antibody for FAK and p53. Immunoreactivity was scored by intensity (0-4+ scale) and percent positive staining. FAK overexpression was categorized as 4+ cytoplasmic intensity in more than 90% of neoplastic cells. Positive p53 was categorized at least 2+ nuclear intensity in more than 10% of neoplastic cells. Higher rates of FAK upregulation were identified in endometrial hyperplasia (P = 0.025) and carcinoma (P < 0.001) versus normal endometrium. FAK overexpression in carcinoma correlated with higher FIGO grade (P = 0.025) and p53 overexpression (P < 0.001). FAK was consistently overexpressed in high-grade tumors regardless of subtype, including 8 of 10 serous tumors, 4 of 5 clear cell tumors, and 16 of 23 grade 3 endometrioid tumors. In conclusion, upregulation of FAK is seen in both endometrial hyperplasia and carcinoma, implying that FAK may play an important role in endometrial carcinogenesis. FAK overexpression in endometrial carcinoma correlates with higher FIGO grade and p53 overexpression.