Background

Recurrence of retinoblastoma (RB) following chemoreduction is common and is often managed with local (intra-arterial/intravitreal) chemotherapy. However, some tumors are resistant to even local administration of maximum feasible drug dosages, or effective tumor control and globe preservation may be achieved at the cost of vision loss due to drug-induced retinal toxicity. The aim of this study was to identify drugs with improved antitumor activity and more favorable retinal toxicity profiles via screening of potentially repurposable FDA-approved drugs in patient-derived tumor organoids.

Methods

Genomic profiling of five RB organoids and the corresponding parental tissues was performed. RB organoids were screened with 133 FDA-approved drugs, and candidate drugs were selected based on cytotoxicity and potency. RNA sequencing was conducted to generate a drug signature from RB organoids, and the effects of drugs on cell cycle progression and proliferative tumor cone restriction were examined. Drug toxicity was assessed with human embryonic stem cell-derived normal retinal organoids. The efficacy/toxicity profiles of candidate drugs were compared with those of drugs in clinical use.

Results

RB organoids maintained the genomic features of the parental tumors. Sunitinib was identified as highly cytotoxic against both classical RB1-deficient and novel MYCN-amplified RB organoids and inhibited proliferation while inducing differentiation in RB. Sunitinib was a more effective suppressor of proliferative tumor cones in RB organoids and had lower toxicity in normal retinal organoids than either melphalan or topotecan.

Conclusion

The efficacy and retinal toxicity profiles of sunitinib suggest that it could potentially be repurposed for local chemotherapy of RB.

MYCN proto-oncogene, bHLH transcription factor (MYCN) amplification is associated with aggressive retinoblastoma (RB) and neuroblastoma (NB) cancer recurrence that is resistant to chemotherapies. Therefore, there is an urgent need to identify new therapeutic tools. This study aimed to evaluate the potential repurposing of ceftriaxone for the treatment of MYCN-amplified RB and NB, based on the clinical observations that the drug was serendipitously found to decrease the volume of the MYCN-driven RB subtype. Using patient-derived tumor organoids and tumor cell lines, we demonstrated that ceftriaxone is a potent and selective growth inhibitor targeting MYCN-driven RB and NB cells. Profiling of drug-induced transcriptomic changes, cell-cycle progression, and apoptotic death indicated cell-cycle arrest and death of drug-treated MYCN-amplified tumor cells. Drug target identification, using an affinity-based proteomic and molecular docking approach, and functional studies of the target proteins revealed that ceftriaxone targeted DEAD-box helicase 3 X-linked (DDX3X), thereby inhibiting translation in MYCN-amplified tumors but not in MYCN-nonamplified cells. The data suggest the feasibility of repurposing ceftriaxone as an anticancer drug and provide insights into the mechanism of drug action, highlighting DDX3X as a potential target for treating MYCN-driven tumors.