Absence of fibroblast growth factor 2 does not prevent tumor formation originating from the RPE

Abstract

We have analysed the importance of fibroblast growth factor 2 (FGF2) in tumor development. In a transgenic mouse model (Tyrp1-Tag) tumors form in the retinal pigment epithelium (RPE), invade surrounding tissues, and metastasize to lymph node and spleen. To address whether RPE tumor formation is dependent on FGF2, we generated FGF2-deficient mice. Such mice appeared healthy and exhibited no impairment of growth or development. Tyrp1-Tag transgenic mice, which are lacking FGF2 (FGF2-/-) developed RPE tumors that metastasize to spleen and lymph nodes. Tumor growth and survival rate are identical to Tyrp1-Tag transgenic littermates expressing FGF2. Cell lines were isolated from RPE tumors of wild-type and FGF2-deficient mice. They grow in culture, are pigmented and form vascularized tumors, when injected subcutaneously into nude mice of either FGF2-/- or FGF2+/+ genetic background. Kinetics of tumor growth was identical and independent of presence of FGF2. Together, these results demonstrate that FGF2 is not essential for tumor formation of the RPE thus suggesting that tumor growth in general may not be dependent on FGF2.