Project description:Retinoblastoma (RB) is a cancer that forms in the developing retina of babies and toddlers. The goal of therapy is to cure the tumor, save the eye and maximize vision. However, it is difficult to predict which eyes are likely to respond to therapy. Predictive molecular biomarkers are needed to guide prognosis and optimize treatment decisions. Direct tumor biopsy is not an option for this cancer; however, the aqueous humor (AH) is an alternate source of tumor-derived cell-free DNA (cfDNA). Here we show that DNA methylation profiling of the AH is a valid method to identify the methylation status of RB tumors. We identify 294 genes directly regulated by methylation that are implicated in p53 tumor suppressor (RB1, p53, p21, and p16) and oncogenic (E2F) pathways. Finally, we use AH to characterize molecular subtypes that can potentially be used to predict the likelihood of treatment success for retinoblastoma patients.
Project description:Aqueous humor (AH) liquid biopsy has been established as a surrogate tumor biopsy for retinoblastoma (RB). Previous AH studies have focused on highly recurrent RB somatic copy number alterations (SCNAs) including gain of 1q, 2p, 6p, and loss of 13q and 16q. In this retrospective study, we provide a comprehensive, whole-genome analysis of RB SCNAs and evaluate associated clinical features for 68 eyes of 64 RB patients from whom AH was obtained between December 2014 and October 2020. Shallow whole-genome sequencing of AH cell-free DNA was performed to assess for SCNAs. The prevalence of specific non-highly recurrent SCNAs, such as 20q gain and 8p loss, differed between primarily and secondarily enucleated eyes. Increases in chromosomal instability predict more advanced seeding morphology (p = 0.015); later age of diagnosis (p < 0.0001); greater odds of an endophytic tumor growth pattern (without retinal detachment; p = 0.047); tumor heights >10 mm (p = 0.09); and containing 6p gain, a biomarker of poor ocular prognosis (p = 0.004). The AH liquid biopsy platform is a high-yield method of whole-genome RB SCNA analysis, and SCNAs are associated with numerous clinical findings in RB eyes. Prospective analyses are encouraged to further elucidate the clinical relevance of specific SCNAs in RB.
Project description:Germline alterations in the RB1 tumor suppressor gene predispose patients to develop retinoblastoma (RB) in both eyes. While similar treatment is given for each eye, there is often a variable therapeutic response between the eyes. Herein, we use the aqueous humor (AH) liquid biopsy to evaluate the cell-free tumor DNA (ctDNA) from each eye in a patient with bilateral RB. Despite the same predisposing germline RB1 mutation, AH analysis identified a different somatic RB1 mutation as well as separate and distinct chromosomal alterations in each eye. The longitudinal alterations in tumor fraction (TFx) corresponded to therapeutic responses in each eye. This case demonstrates that bilateral RB tumors develop separate genomic alterations, which may play a role in tumorigenesis and prognosis for eye salvage. Identifying these inter-eye differences without the need for enucleated tumor tissue may help direct active management of RB, with particular usefulness in bilateral cases.
Project description:There is significant potential clinical utility for the application of a liquid biopsy platform for retinoblastoma, given that direct tumor biopsy is prohibited in these patients. The aqueous humor (AH) forms in a separate compartment from the tumor but is enclosed within the same ocular space. Thus, it is an enriched source of eye-specific tumoral genomic information that can be used as a liquid biopsy or surrogate to tumor biopsy for this disease. This manuscript details a methodology for safely extracting the AH from retinoblastoma eyes via clear corneal paracentesis. Additionally, the steps for genomic analysis, including cell-free DNA isolation and purification, next-generation sequencing, somatic copy number alteration (SCNA) analysis, RB1 single nucleotide variant (SNV) mutation identification, and tumor fraction estimation are presented. The pre-analytical, analytical, and early clinical validity of the AH liquid biopsy platform have been evaluated; however, it is not without limitations. These are largely a consequence of the quantity of cell-free DNA that is required for certain steps of the assay. Compared to other blood-based liquid biopsy platforms currently under investigation for retinoblastoma, an AH-based platform is limited by the volume of biofluid (and thus the quantity of DNA) that can be extracted from the eye; the benefit is that AH is eye-specific. The platform discussed here is unique in that it detects circulating tumor DNA in the AH via two mechanisms (SCNAs and RB1 SNVs), yielding a higher sensitivity for identifying tumoral genomic information. The AH liquid biopsy has the potential for direct clinical application to precision oncology for retinoblastoma patients, with particular importance for patients with bilateral disease as the AH is specific to the tumors in each eye. There is ongoing research with applications of this platform to patients with other ocular tumors as well.
Project description:ImportanceRetinoblastoma (Rb) is one of the first tumors to have a known genetic etiology. However, because biopsy of this tumor is contraindicated, it has not been possible to define the effects of secondary genetic changes on the disease course.ObjectiveTo investigate whether the aqueous humor (AH) of Rb eyes has sufficient tumor-derived DNA to perform genetic analysis of the tumor, including DNA copy number alterations.Design, setting, and participantsThis investigation was a case series study at a tertiary care hospital (Children's Hospital Los Angeles) with a large Rb treatment center. Cell-free DNA (cfDNA) was isolated from 6 AH samples from 3 children with Rb, including 2 after primary enucleation and 1 undergoing multiple intravitreous injections of melphalan for vitreous seeding. Samples were taken between December 2014 and September 2015.Main outcomes and measuresMeasurable levels of nucleic acids in the AH and identification of tumor-derived DNA copy number variation in the AH. The AH was analyzed for DNA, RNA, and micro-RNA using Qubit high-sensitivity kits. Cell-free DNA was isolated from the AH, and sequencing library protocols were optimized. Shallow whole-genome sequencing was performed on an Illumina platform, followed by genome-wide chromosomal copy number variation profiling to assess the presence of tumor DNA fractions in the AH cfDNA of the 3 patients. One child's cfDNA from the AH and tumor DNA were subjected to Sanger sequencing to isolate the RB1 mutation.ResultsSix AH samples were obtained from 3 Rb eyes in 3 children (2 male and 1 female; diagnosed at ages 7, 20, and 28 months). A corroborative pattern between the chromosomal copy number variation profiles of the AH cfDNA and tumor-derived DNA from the enucleated samples was identified. In addition, a nonsense RB1 mutation (Lys→STOP) from 1 child was also identified from the AH samples obtained during intravitreous injection of melphalan, which matched the tumor sample postsecondary enucleation. Sanger sequencing of the AH cfDNA and tumor DNA with polymerase chain reaction primers targeting RB1 gene c.1075A demonstrated this same RB1 mutation.Conclusions and relevanceIn this study evaluating nucleic acids in the AH from Rb eyes undergoing salvage therapy with intravitreous injection of melphalan, the results suggest that the AH can serve as a surrogate tumor biopsy when Rb tumor tissue is not available. This novel method will allow for analyses of tumor-derived DNA in Rb eyes undergoing salvage therapy that have not been enucleated.
Project description:Because direct tumor biopsy is prohibited for retinoblastoma (RB), eye-specific molecular biomarkers are not used in clinical practice for RB. Recently, we demonstrated that the aqueous humor (AH) is a rich liquid biopsy source of cell-free tumor DNA. Herein, we detail clinically-relevant molecular biomarkers from the first year of prospective validation data. Seven eyes from 6 RB patients who had AH sampled at diagnosis and throughout therapy with ≥12 months of follow-up were included. Cell-free DNA (cfDNA) from each sample was isolated and sequenced to assess genome-wide somatic copy number alterations (SCNAs), followed by targeted resequencing for pathogenic variants using a RB1 and MYCN custom hybridization panel. Tumoral genomic information was detected in 100% of diagnostic AH samples. Of the seven diagnostic AH samples, 5/7 were positive for RB SCNAs. Mutational analysis identified RB1 variants in 5/7 AH samples, including the 2 samples in which no SCNAs were detected. Two eyes failed therapy and required enucleation; both had poor prognostic biomarkers (chromosome 6p gain or MYCN amplification) present in the AH at the time of diagnosis. In the context of previously established pre-analytical, analytical, and clinical validity, this provides evidence for larger, prospective studies to further establish the clinical utility of the AH liquid biopsy and its applications to precision oncology for RB.