Updates on the Molecular Pathology of Selected Ocular and Ocular Adnexal Tumors: Potential Targets for Future Therapy

Role of MYCN in retinoblastoma: A review of current literature

Chromosomal abnormalities that involve the MYCN gene are rare; however, it is one of the most commonly mutated genes in retinoblastoma (RB) after the RB1 gene. MYCN is amplified in approximately 1-9 % of all RB tumors. It plays a role in RB oncogenesis via many mechanisms, including synergism with RB1 deletion, positive feedback with MDM2, upregulation of cell cycle regulating genes, upregulation of miRNA, and upregulation of glucose metabolism. MYCN amplifications are not mutually exclusive and can occur even in the presence of RB1 gene mutations. Clinically, RB1+/+MYCNA tumors present as sporadic, unilateral, advanced tumors in very young children and tend to follow an aggressive course. Magnetic resonance imaging features include peripheral tumor location, placoid configuration, retinal folding, tumor-associated hemorrhage, and anterior chamber enhancement. Genetic testing for MYCNA is especially recommended in patients with unilateral RB where genetic blood testing and tumor tissue show a lack of RB1 mutation. MYCN-targeted therapies are evolving and hold promise for the future.

Integrative genomic analysis reveals cancer-associated mutations in patients with ophthalmic tumors

OBJECTIVE

Apart from the role of the retinoblastoma gene, the genomic events associated with poor outcomes in patients with ophthalmic tumors are poorly understood.

METHODS

We retrospectively analyzed 48 patients with six types of ophthalmic tumors. We searched for high-frequency mutated genes and susceptibility genes in these patients using combined exome and transcriptome analysis.

RESULTS

We identified four clearly causative genes (TP53, PTCH1, SMO, BAP1). Susceptibility gene analysis identified hotspot genes, including RUNX1, APC, IDH2, and BRCA2, and high-frequency gene analysis identified several genes, including TP53, TTN, and MUC16. Transcriptome analysis identified 5868 differentially expressed genes, of which TOP2A and ZWINT were upregulated in all samples, while CFD, ELANE, HBA1, and HBB were downregulated. Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that the phosphoinositide 3-kinase (PI3K)-Akt and Transcriptional misregulation in cancer signaling pathways may be involved in ophthalmic tumorigenesis.

CONCLUSIONS

TP53 is clearly involved in ophthalmic tumorigenesis, especially in basal cell carcinoma, and the PI3K-Akt signaling pathway may be an essential pathway involved in ophthalmic tumorigenesis. RUNX1, SMO, TOP2A, and ZWINT are also highly likely to be involved in ophthalmic tumorigenesis, but further functional experiments are needed to verify the mechanisms of these genes in regulating tumorigenesis.

NGS Analysis Confirms Common TP53 and RB1 Mutations, and Suggests MYC Amplification in Ocular Adnexal Sebaceous Carcinomas

Ocular adnexal (OA) sebaceous carcinomas generally demonstrate more aggressive clinical and histopathological phenotypes than extraocular cases, but the molecular drivers implicated in their oncogenesis remain poorly defined. A retrospective review of surgical and ocular pathology archives identified eleven primary resection specimens of OA sebaceous carcinomas with adequate tissue for molecular analysis; two extraocular cases were also examined. Next-generation sequencing was used to evaluate mutations and copy number changes in a large panel of cancer-associated genes. Fluorescence in situ hybridization (FISH) confirmed MYC copy number gain in select cases, and immunohistochemistry to evaluate MYC protein expression. The commonest mutations occurred in TP53 (10/13) and RB1 (7/13). Additional mutations in clinically actionable genes, or mutations with a frequency of at least 25%, included the NF1 (3/12), PMS2 (4/12), ROS1 (3/12), KMT2C (4/12), MNX1 (6/12), NOTCH1 (4/12), PCLO (3/12), and PTPRT (3/12) loci. Low level copy number gain suggestive of amplification of the MYC locus was seen in two cases, and confirmed using FISH. MYC protein expression, as assessed by immunohistochemistry, was present in almost all sebaceous carcinoma cases. Our findings support the concept that alterations in TP53 and RB1 are the commonest alterations in sebaceous carcinoma, and suggest that MYC may contribute to the oncogenesis of these tumors.