The Expression of Focal Adhesion Kinase (FAK) in Retinoblastoma

Abstract

Purpose: : Focal Adhesion Kinase (FAK) is a non-receptor protein tyrosine kinase that controls a number of cell signaling pathways including proliferation, cell viability and survival. It has been demonstrated that inhibition of FAK impairs growth in different types of cancer, including cutaneous melanoma, breast, lung and ovary carcinomas, and neural tumors such as neuroblastoma. The aim of this study is to evaluate the expression of FAK in Retinoblastoma (RB).

Methods: : Twenty formalin-fixed, paraffin-embedded cases of RB were analyzed. Immunohistochemistry for FAK (Anti-FAK [pY³⁹⁷]) was performed using a fully automated system. The expression was classified according to the intensity and percentage of positive tumor cells (0 - 3). The scores were summed and a final score was given to each case. The final score was classified as weak (≤3), moderate (4-5) or strong (6). The final immunohistochemical score was correlated to histopathological prognostic factors such as optic nerve, anterior chamber and choroidal invasion, tumor differentiation, and vitreous seeding.

Results: : The median age was 27.5 months. There were 11 females. Nine tumors were in the OD and 11 in the OS. Three cases were well-differentiated, 6 were moderate and 11 were poorly differentiated. All cases were positive for FAK in the nucleus and in the cytoplasm, except 2 that were positive only in the cytoplasm. Three (15%) cases presented weak expression, while 12 (60%) moderate and 5 (25%) presented strong expression. There was no significant correlation between FAK expression and histopathological prognostic factors.

Conclusions: : To the best of our knowledge, this is the first study showing the expression of FAK in Retinoblastoma. Retinoblastoma should be included in the group of tumors that express FAK. This result supports a potential role of FAK signaling in RB. FAK may represent a potential target for future therapies with low-toxicity drugs in RB patients.

Keywords: retinoblastoma • immunohistochemistry • pathology: human