Purpose:
To compare the expression of multidrug resistance proteins in retinoblastoma tumors among eyes treated with primary enucleation and eyes treated with primary systemic chemotherapy and/or external beam radiation (EBRT).
Methods:
A tissue microarray was constructed with the pathology specimens from 31 enucleated eyes Using standard immunohistochemical techniques, the tissue microarrays were studied for the expression of 4 ABC transporters: multidrug resistance–1/ P–glycoprotein (MDR1/P–gp), breast cancer resistance protein (BCRP/ABCG2), multidrug resistant protein 1 (MRP1/ABCC1), multidrug resistant protein 2 (MRP2/ABCC2), and multidrug resistant protein 4 (MRP4/ABCC4).
Results:
Of the 31 eyes studied, 20 were primarily enucleated, 4 had been treated with chemotherapy alone, one had been treated with EBRT alone, and 5 had been treated with both chemotherapy and EBRT. Results are summarized for each cohort in the table.
Conclusions:
Our preliminary data shows a variable expression of the multidrug resistant proteins in retinoblastoma tumors, which does not appear to be affected by treatment prior to enucleation. This would suggest that neither chemotherapy nor EBRT select for ABC–mediated resistance that might eventually lead to treatment failure. Results of an ongoing review of an additional cohort of retinoblastoma tumors enucleated after treatment failure will confirm whether treatment–related differences in ABC transporter expression exist. A covariate analysis to assess patient variables that might relate to expression of these transport proteins is being performed.
Keywords: retinoblastoma • oncology • immunohistochemistry