Identifying Invasion-Promoting Molecular Pathways In Retinoblastoma

Abstract

Purpose : Retinoblastoma is the most frequent malignant intraocular cancer in children. In advanced cases, dissemination in the CNS or metastasis to distant organs can lead to death. Our goal was to identify the molecular drivers and signaling pathways associated with tumor invasion and metastatic spread into the optic nerve and choroid in order to develop new prognostic markers and therapeutic targets.

Methods : RNA extracted from eleven snap frozen retinoblastoma specimens was analyzed by RNA-seq (low input, non-strand specific). Samples were divided between invasive (retrolaminar, n=4; intralaminar, n=1) and non-invasive (prelaminar, n=4, no optic nerve invasion, n=2). Four cases with optic nerve invasion and two without also showed focal (<3mm) choroidal invasion, but none had massive choroidal invasion.

Results : We found 267 genes whose expression was modified more than two-fold in invasive versus non-invasive retinoblastomas: 27 upregulated and 240 downregulated. In the invasive cohort, we observed about 28-fold induction of DLX6, a transcription factor known to enhance migration and invasion by upregulating Twist1, and 11-fold induction of the matrix metallo-proteinase MMP12, which promotes invasion by degrading the extracellular matrix. We also found 24-fold reduction in WIF1 (WNT Inhibitory Factor 1), a tumor suppressor epigenetically silenced in various cancers, 16-fold reduction in CLUSTERIN, associated with apoptosis, and 11-fold decrease in GLI3, an inhibitor of Sonic hedgehog signaling.

Conclusions : Our gene expression profile analysis showed that several genes and pathways were differentially expressed in invasive versus non-invasive retinoblastomas. In particular WNT, Sonic hedgehog, and MMP signaling might be responsible for driving CNS dissemination in retinoblastoma. Functional studies are in progress to confirm these data in retinoblastoma lines.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.