Timothy G. Murray, MD (Miami, FL),* Maria Elena Jockovich, PhD (Miami, FL), Yoland Pina, PhD (Miami, FL), Fernando Suarez, (Miami, FL), Sander Dubovy, MD (Miami, FL), Amy Schefler, MD (Miami, FL)

PURPOSE:

The purpose of this study is to evaluate blood vessel maturation in the murine transgenic model of retinoblastoma and to correlate with pediatric enucleated retinoblastoma tumors specimens to determine if vessel heterogeneity can be quantitated and vascular maturation documented. This study will establish the framework for vascular targeting treatment in pediatric retinoblastoma.

METHODS:

All experiments in this study were conducted in accordance with ARVO guidelines. Fifty-six murine transgenic retinoblastoma animals were evaluated for tumor vessel heterogeneity in retinal tumors at 4, 8, 12 and 16 weeks of age (n? 8 per group) and human retinoblastoma samples (n? 8) were assessed by immunofluorescence. Total blood vessels were detected by immunostaining with lectin from bandeira simplicifolia, novel vasculature with CD105 (endoglin) and pericyte-committed mature vessels with ? -smooth muscle actin. Vessel targeting efficacy was assessed by treating 12 week-old mice with a subconjunctival injection of the vessel targeting agent Combretastatin A4P (1mg/20 μl).

RESULTS:

Vessel heterogeneity is detected in large tumors harbored by LHBETATAG mice. Novel vasculature is detected early in tumor formation and the fraction of novel vessels to total vessels decreases in larger tumors at 16 weeks of age. Vessel maturation, as measured by pericyte-commitment, is detected in large tumors concomitant with a decrease in novel vasculature. Mature vessels are resistant to vessel targeting by Combretastatin A4P in these mice. Functional perfusion decreases in eyes undergoing vascular targeted therapy with Combratestatin A4P correlating with previous studies documenting vascular closure within 24 hours of a single subconjuctival injection. Both novel and pericyte commited, mature vessels, are detected in human retinoblastoma tumor samples.

CONCLUSION:

Retinoblastoma vascular heterogeneity is detected in retinal tumors of murine transgenic retinoblastoma animals. Mature vessels exhibit a limited response to vascular targeting using periocular Combratestatin A4p suggesting potential limitations in vascular targeting for advanced retinoblastoma. Pediatric retinoblastoma tumors exhibit both novel and mature, pericyte-committed tumor vessels.
* Financial interest disclosed