Expression of multidrug-resistance associated proteins in human retinoblastoma treated by primary enucleation

AIM: To reveal the expression of multidrug-resistance associated proteins: glutathione-S-transferase pi (GST pi), P-glycoprotein (P-gp) and vault protein lung resistance protein (LRP) in retinoblastoma (RB) without any conservative treatment before primary enucleation and to correlate this expression with histopathological tumor features. METHODS: A total of 42 specimens of RB undergone primary enucleation were selected for the research. Sections from the formalin-fixed, paraffin-embedded specimens were stained with HE and immunohistochemistry to detect the expression of GST pi, P-gp and LRP. RESULTS: GST pi was expressed in 39/42 (92.86%) RBs and in 9/9 (100%) well-differentiated RBs. P-gp/GSTp was found in 30 (71.42%) of 42 RBs. Totally 9 (21.43%) tumors were well differentiated and 33 (78.57%) were poorly differentiated. Totally 15 (35.71%) eyes had optic nerve (ON) tumor invasion, 36 (85.71%) had choroidal tumor invasion, and 14 (33.33%) had simultaneous choroidal and ON invasion. There was no statistically significant relationship between P-gp, GST pi, LRP positivity and the degree of ocular layer tumor invasion and ON tumor invasion (P>0.05). CONCLUSION: RB intrinsically expresses GST pi, P-gp and LRP. GST pi expression is positive in 100% well-differentiation ones, so in which way it is correlated with differentiation. But the other two proteins expressions are not related to tumor differentiation and to the degree of tumor invasion. GST pi may be a new target of chemotherapy in RB.