Case Report: Proteomic analysis of cerebrospinal fluid in a retinoblastoma patient

Abstract

This study focuses on the proteomic analysis of cerebrospinal fluid (CSF) in a patient with stage III retinoblastoma (RB) with the aim to identify molecular changes associated with central nervous system (CNS) relapse. The child received systemic chemotherapy and intrathecal topotecan as CNS prophylaxis, along with enucleation of the left eye. After two chemotherapy cycles, CNS relapse occurred, evidenced by positive CSF findings and magnetic resonance imaging (MRI) showing leptomeningeal involvement at the anterior skull base. The child's condition deteriorated, and two months later, he died due to progressive CNS disease. The aim of the study was to analyze serial CSF samples collected at different stages of treatment, as well as a control sample, to identify differences in CSF protein expression profiles during CNS RB relapse. Using mass spectrometry, a total of 1,029 proteins were identified across all CSF samples, samples were analyzed in duplicate ensuring technical replication. An unsupervised heatmap revealed 46 differentially expressed proteins. Over-regulated proteins in CSF-RB samples were primarily involved in inflammation, extracellular matrix remodeling, epithelial mesenchymal transition initiation, migration, invasion, and cellular metabolism (PON1, RNPEP, MCAM, NEGR1, NID1, SERPINA1, FAT2, RELN, NEGR1, and SEZ6). These processes are key drivers of cancer progression and metastasis. Proteomic analysis could be valuable in identifying proteins modulated in CSF during disease progression in RB patients, offering potential for new prognostic biomarkers.

Keywords: case report; cerebrospinal fluid (CSF); liquid biopsy; proteomic analysis; retinoblastoma.

Figure 1

MRI of the patient throughout the entire treatment, along with the corresponding sample time points. (A–C) axial DIXON T1 post-CM: the timeline of optic nerve involvement. (A) presence of pathological tissue localized in the left retro bulbar site. This tissue takes the contrast medium (MDC) which localizes in the left retro bulbar region, is characterized by irregular profiles and extends to partially involve the extrinsic muscles, making their distal portion difficult to identify. The retro bulbar segment of the optic nerve is also partially affected, showing pathological enhancement. Additionally, there is pathological enhancement of the periorbital soft tissues. (B) Extensive involvement of the left optic nerve is evident following enucleation (C) Further progression of optic nerve involvement is observed, with irregular profiles of optic nerve. (a–c) axial T1w pst-CM: timeline of meningeal involvement. (a) no meningeal enhancement, (b) no meningeal enhancement, (c) intense meningeal enhancement.

Figure 2

(A) Venn diagram showing a total of 1029 proteins detected in all CSF samples (CSF-CTRL, CSF-RB1, CSF-RB2, CSf-RB3), 500 proteins were in common in all samples. 733, 713, 809 and 789 proteins were found in CSF-CTRL, CSF-RB1, CSF-RB2 and CSF-RB3 respectively; 131, 18, 27 and 31 were exclusively present in CSF-CTRL, CSF-RB1, CSF-RB2 and CSF-RB3 respectively (B) Unsupervised hierarchical-clustered heatmap of proteins identified by significance B test. Heatmap showing the distinctive proteomic signature of the CSF-CTRL vs CSF-RB1, CSF-RB2, CSF-RB3. A red-blue scale corresponds to high and low protein amount, respectively. C-D) Graphical representation of biological processes gene enrichment obtained by FunRich software for low expressed (C) and high expressed (D) protein in CSF-RB (CSF-RB1; CSF-RB2; CSF- RB3) vs CSF-CTRL.