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Loss of photoreceptorness and gain of genomic alterations in retinoblastoma reveal tumor progression.

ABSTRACT: Retinoblastoma is a pediatric eye cancer associated with RB1 loss or MYCN amplification (RB1 (+/+) MYCN(A) ). There are controversies concerning the existence of molecular subtypes within RB1(-/-) retinoblastoma. To test whether these molecular subtypes exist, we performed molecular profiling.Genome-wide mRNA expression profiling was performed on 76 primary human retinoblastomas. Expression profiling was complemented by genome-wide DNA profiling and clinical, histopathological, and ex vivo drug sensitivity data.RNA and DNA profiling identified major variability between retinoblastomas. While gene expression differences between RB1 (+/+) MYCN(A) and RB1(-/-) tumors seemed more dichotomous, differences within the RB1(-/-) tumors were gradual. Tumors with high expression of a photoreceptor gene signature were highly differentiated, smaller in volume and diagnosed at younger age compared with tumors with low photoreceptor signature expression. Tumors with lower photoreceptor expression showed increased expression of genes involved in M-phase and mRNA and ribosome synthesis and increased frequencies of somatic copy number alterations.Molecular, clinical and histopathological differences between RB1(-/-) tumors are best explained by tumor progression, reflected by a gradual loss of differentiation and photoreceptor expression signature. Since copy number alterations were more frequent in tumors with less photoreceptorness, genomic alterations might be drivers of tumor progression.Retinoblastoma is an ocular childhood cancer commonly caused by mutations in the RB1 gene. In order to determine optimal treatment, tumor subtyping is considered critically important. However, except for very rare retinoblastomas without an RB1 mutation, there are controversies as to whether subtypes of retinoblastoma do exist. Our study shows that retinoblastomas are highly diverse but rather than reflecting distinct tumor types with a different etiology, our data suggests that this diversity is a result of tumor progression driven by cumulative genetic alterations. Therefore, retinoblastomas should not be categorized in distinct subtypes, but be described according to their stage of progression.

SUBMITTER: Kooi IE

PROVIDER: S-EPMC4534696 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Loss of photoreceptorness and gain of genomic alterations in retinoblastoma reveal tumor progression.

Kooi Irsan E IE Mol Berber M BM Moll Annette C AC van der Valk Paul P de Jong Marcus C MC de Graaf Pim P van Mil Saskia E SE Schouten-van Meeteren Antoinette Y N AY Meijers-Heijboer Hanne H Kaspers Gertjan L GL Te Riele Hein H Cloos Jacqueline J Dorsman Josephine C JC

EBioMedicine 20150708 7

<h4>Background</h4>Retinoblastoma is a pediatric eye cancer associated with RB1 loss or MYCN amplification (RB1 (+/+) MYCN(A) ). There are controversies concerning the existence of molecular subtypes within RB1(-/-) retinoblastoma. To test whether these molecular subtypes exist, we performed molecular profiling.<h4>Methods</h4>Genome-wide mRNA expression profiling was performed on 76 primary human retinoblastomas. Expression profiling was complemented by genome-wide DNA profiling and clinical, h ...[more]

PMID: 26288838

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Project description:ImportanceComprehensive understanding of the genomic and gene-expression differences between retinoblastoma tumors from patients with bilateral disease may help to characterize risk and optimize treatment according to individual tumor characteristics.ObjectiveTo compare the genomic features between each eye and a specimen from an orbital relapse in patients with bilateral retinoblastoma.Design, setting, and participantsIn this case, 2 patients with retinoblastoma underwent upfront bilateral enucleation. Tumor samples were subjected to genomic and gene-expression analysis. Primary cell cultures were established from both of the tumors of 1 patient and were used for gene-expression studies.Main outcomes and measuresWhole-exome sequencing was performed on an Illumina platform for fresh tumor samples and DNA arrays (CytoScan or OncoScan) were used for paraffin-embedded samples and cell lines. Gene-expression analysis was performed using Agilent microarrays. Germinal and somatic alterations, copy number alterations, and differential gene expression were assessed.ResultsAfter initial bilateral enucleation, patient 1 showed massive choroidal and laminar optic nerve infiltration, while patient 2 showed choroidal and laminar optic nerve invasion. Patient 1 developed left-eye orbital recurrence and bone marrow metastasis less than 1 year after enucleation. Both ocular tumors showed gains on 1q and 6p but presented other distinct genomic alterations, including an additional gain in 2p harboring the N-myc proto-oncogene (MYCN) in the left tumor and orbital recurrence. Similar copy number alterations between the orbital recurrence and the left eye supported the origin of the relapse, with an additional 11q loss only detected in the orbital relapse. Specimens from patient 2 showed common copy number gains and losses, but further evolution rendered a 2p gain spanning MYCN in the left tumor. For this patient, microarray expression analysis showed differential expression of the MYCN and the forkhead box protein G1 (FOXG1) gene pathways between the left and right tumors.Conclusions and relevanceDifferential genomic and gene expression features were observed between tumors in 2 patients with bilateral disease, confirming intereye heterogeneity that might be considered if targeted therapies are used in such patients. Chromosomal alteration profile supported the origin of the orbital recurrence from the homolateral eye in 1 patient. Loss in chromosome 11q may have been associated with extraocular relapse in this patient.

Dataset Information

Loss of photoreceptorness and gain of genomic alterations in retinoblastoma reveal tumor progression.

Publications

Loss of photoreceptorness and gain of genomic alterations in retinoblastoma reveal tumor progression.

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