Expression of pro‐apoptotic Bax and anti‐apoptotic Bcl‐2 proteins in human retinoblastoma

Abstract Background Regulation of apoptosis is a complex process that involves a number of genes, including Bcl ‐2, Bcl ‐x, Bax and other Bcl ‐2 family members. The aim of the present study is to assess the expression of Bcl ‐ 2 and Bax in retinoblastoma, and correlate them with clinical and histopathological parameters. Methods The expression of Bcl ‐2 and Bax proteins were examined using immunohistochemistry, Western blotting and reverse transcriptase‐polymerase chain reaction in a series of 60 prospective cases of primary retinoblastoma tissues. Results Immunohistochemistry showed expression of Bcl ‐2 in 40/60 (66.6%), whereas Bax expression was found only in 18/60 (30%) cases, and these correlated with mRNA expression. The Western blotting results also correlated well with the immunohistochemical expression of Bcl ‐2 (25 kDa) and Bax (21 kDa) proteins. Bcl ‐2 was expressed in 96% (24/25) of invasive tumours and in 45.7% (16/35) of non‐invasive tumours. Expression of Bcl ‐2 significantly correlated with tumour invasiveness ( P = 0.0274) and poor differentiation ( P = 0.0163), whereas loss of Bax correlated with massive choroidal invasion and Pathological Tumor‐Node‐Metastasis ( pTNM ) ( P = 0.0341). However, no correlation was found between Bax and Bcl ‐2 expression. Conclusions Our findings suggest that these apoptotic regulatory proteins may serve as poor prognostic markers and can be used as a therapeutic target for the treatment of invasive retinoblastoma. Further functional studies are required to explore the role of Bax and Bcl ‐2 in retinoblastoma.