Purpose: The aim of this study was to evaluate the changes in tumor burden and hypoxia in the LH(BETA)T(AG) retinal tumors after treatment with a focal, single-modality, and combination therapy using periocular carboplatin and 2-deoxy-d-glucose (2-DG).
Methods: Seventeen-week-old LH(BETA)T(AG) transgenic mice (n = 25) were treated with periocular injections of varying doses of 2-DG (62.5, 125, 250, 500 mg/kg) to obtain a dose response. Same-aged mice (n = 30) received periocular injections of saline, carboplatin, and 2-DG. Mice were divided into six groups: saline; carboplatin (31.25 μg/20 μL, subtherapeutic dose); 2-DG (250 mg/kg); 2-DG (500 mg/kg); carboplatin (31.25 μg/20 μL) and 2-DG (250 mg/kg); and carboplatin (31.25 μg/20 μL) and 2-DG (500 mg/kg). Injections were administered twice weekly for three consecutive weeks. Eyes were enucleated at 20 weeks of age, snap frozen, and analyzed for hypoxic regions and tumor volume.
Results: The difference in percentage of hypoxia after treatment with 500 mg/kg 2-DG was statistically significant from the other dose groups (P < 0.015). The difference in tumor burden was statistically significant from the 250 mg/kg dose (P < 0.015) and 500 mg/kg dose (P < 0.001). Highly significant differences were found between the treatment types for tumor burden, percentage of hypoxia, and pimonidazole intensity (P < 0.001). Tumor burden decreased significantly after all forms of treatment (P < 0.001); however, tumor burden became significantly more reduced after treatment with combination therapy of carboplatin and 2-DG than with either treatment alone (P < 0.001). The percentage of hypoxia and pimonidazole intensity decreased after treatment with 2-DG alone and in combination with carboplatin (P < 0.001) in all treatment groups using 2-DG regardless of the 2-DG dose used. There was no percentage reduction of hypoxia after treatment with carboplatin alone (P = 0.25).
Conclusions: This study demonstrates the efficacy of focal, periocular 2-DG as an adjunct to carboplatin chemotherapy to decrease both intratumoral hypoxia and tumor burden. Hypoxia is increasingly present in advanced disease of LH(BETA)T(AG) retinal tumors. The use of glycolytic inhibitors as a therapeutic strategy has the potential to enhance current retinoblastoma treatments.