Immunohistochemical expression of CD117 and vascular endothelial growth factor in retinoblastoma: possible targets of new therapies

CD117 (C-kit) is thought to play an important role in tumourigenesis. There are limited data in the literature concerning C-kit expression in retinoblastoma. To date, no immunohistochemical studies have been performed to assess the possible association of C-kit with vascular endothelial growth factor (VEGF) in retinoblastoma. This study was designed to investigate C-kit and VEGF immunoexpression in retinoblastoma, their relationship with prognostic parameters as well as the correlation between them. A prospective immunohistochemical study was conducted on 56 retinoblastoma cases. Patients who had received preoperative chemotherapy were excluded. Positive C-kit and VEGF immunoreactivity was observed in 48.2% and 76.8% of retinoblastoma cases respectively. No C-kit immunostaining was seen in the adjacent uninvolved retina. However, VEGF expression was detected within its vasculature. Retinoblastomas with combined pattern of tumour growth revealed a highly significant positive C-kit expression (P = 0.002) compared to cases with endophytic or exophytic growths. Also, positive C-kit expression was statistically higher in cases with optic nerve invasion (P = 0.001) and choroidal invasion (P ≤ 0.01) compared to negative cases. A highly significant positive VEGF expression was detected in cases with optic nerve invasion (P = 0.013) compared to negative cases. Moreover, a highly significant positive correlation was detected between C-kit and VEGF expression (P = 0.006). C-kit is a feature of more aggressive retinoblastomas, with increased expression in tumours spreading beyond the retina. Moreover, VEGF is vastly expressed in retinoblastoma and is associated with optic nerve invasion. Both C-kit and VEGF may represent potential therapeutic targets for retinoblastomas.