Establishment of Patient-derived Xenografts of Retinoblastoma & Choroidal Melanoma on the Avian Chorioallantoic Membrane

Background: To develop a viable in vivo chorioallantoic membrane (CAM) model to study the growth and invasion of patient-derived Retinoblastoma (RB) and Choroidal Melanoma (CM) xenografts (PDXs). The study utilizes primary tumor samples instead of cancer cell lines which provides a more authentic representation of tumors due to conserved morphology and heterogeneity. Methods: : Fertilized chicken eggs were procured, windowed, and their CAM layers were dropped. On embryonic development day (EDD) 10, freshly cut patient-derived CM and RB tumors were implanted on the CAM layer and the set-up was incubated for 7 days. The tumor-embedded CAM layer was harvested on EDD-17 and the extracted tumor samples were subjected to Hematoxylin and Eosin staining and Immunohistochemical analysis to evaluate the extent of tumor invasion. Results: : Significant changes in the vascularity around the RB and CM PDXs were observed indicating an angiogenic environment. The cross-sectional histological view of the tumor implant site revealed the invasion of both the tumor types into CAM. Invasion of CM to CAM mesoderm was visualized in the form of pigmented nodules and of RB was indicated by synaptophysin and Ki-67 positivity in IHC. Conclusion: The CAM xenograft model was successfully able to support the growth of CM and RB PDXs and their invasion in CAM, thus presenting as a feasible alternative to mammalian models for studying tumorigenicity and invasiveness of ocular tumors. Moreover, this model can further be utilized to develop personalized medicine by inoculating patient-specific tumors for pre-clinical drug screening.