Purpose: Retinoblastoma (RB) is a life-threatening malignancy that arises from the retina and is activated upon homozygous inactivation of the tumor suppressor RB1. Gene therapy targeting RB1 is an effective strategy to treat RB. However, it is difficult to target the RB1 gene by site-specific repair, with up to 3366 gene mutation sites identified in RB1. Thus, it is necessary to construct a promising and efficacious gene therapeutic strategy for patients with RB.
Methods: To recover the function of the RB1 protein, we constructed a recombinant adeno-associated virus 2 (rAAV2) expressing RB1 that can restore RB1 function and significantly inhibit RB progression. To confirm the clinical feasibility of rAAV2-RB1, the RB1 protein was validated in vitro and in vivo after transfection. To further evaluate the clinical efficacy, RB patient-derived xenograft models were established and applied. The biosafety of rAAV2-RB1 was also validated in immunocompetent mice.
Results: rAAV2-RB1 was a rAAV2 expressing the RB1 protein, which was validated in vitro and in vivo. In vitro, rAAV2-RB1 was effectively expressed in patient-derived RB cells. In mice, intravitreal administration of rAAV2-RB1 in a population-based patient-derived xenograft trial induced limited tumor growth. Moreover, after transfection of rAAV2-RB1 in immunocompetent mice, rAAV2-RB1 did not replicate and was expressed in other important organs, except retinas, inducing minor local side effects.
Conclusions: Our study suggested a promising efficacy gene therapeutic strategy, which might provide a chemotherapy-independent treatment option for RB.