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Tumor Suppressor Role of INPP4B in Chemoresistant Retinoblastoma

ABSTRACT: Chemotherapy of retinoblastoma (RB), a malignant ocular childhood disease, is often limited by the development of resistances against commonly used drugs. We identified inositol polyphosphate 4-phosphatase type II (INPP4B) as a differentially regulated gene in etoposide resistant RB cell lines, potentially involved in the development of RB resistances. INPP4B is controversially discussed as a tumor suppressor and an oncogenic driver in various cancers, but its role in retinoblastoma in general and chemoresistant RB in particular is yet unknown. In the study presented, we investigated the expression of INPP4B in RB cell lines and patients and analyzed the effect of INPP4B overexpression on etoposide resistant RB cell growth in vitro and in vivo. INPP4B mRNA levels were significantly downregulated in RB cells lines compared to the healthy human retina, with even lower expression levels in etoposide resistant compared to the sensitive cell lines. Besides, a significant increase in INPP4B expression was observed in chemotherapy treated RB tumor patient samples compared to untreated tumors. INPP4B overexpression in etoposide resistant RB cells resulted in a significant reduction in cell viability with reduced growth, proliferation, anchorage-independent growth, and in ovo tumor formation. Caspase-3/7 mediated apoptosis was concomitantly increased, suggesting a tumor suppressive role of INPP4B in chemoresistant RB cells. No changes in AKT signalling were discernible, but p-SGK3 levels increased following INPP4B overexpression, indicating a potential regulation of SGK3 signalling in etoposide-resistant RB cells. RNAseq analysis of INPP4B overexpressing, etoposide resistant RB cell lines revealed differentially regulated genes involved in cancer progression, mirroring observed in vitro and in vivo effects of INPP4B overexpression and strengthening INPP4B`s importance for cell growth control and tumorigenicity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE226408 | GEO | 2023/03/15

REPOSITORIES: GEO

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Project description:Chemotherapy resistance is one of the reasons for the loss of the eye in retinoblastoma (RB) pa-tients. RB chemotherapy resistance has been investigated in different cell culture models like WERI RB1. Furthermore, chemotherapy resistant RB subclones like the etoposide resistant WERI ETOR cell line have been established to improve understanding of chemotherapy resistance in RB. Ob-jective of this study was to characterize the cell line models of an etoposide sensitive WERI RB1 and its etoposide resistant subclone WERI ETOR by proteomics analysis. Subsequently, quantitative proteomic data served for correlation analysis with known drug perturbation profiles. . WERI RB1 and WERI ETOR were cultured and prepared for quantitative mass spectrometry. Comparative proteomic profiling was performed with electrospray ionization tandem mass spectrometry in data-independent acquisition mode (SWATH). The raw SWATH files were processed using neural networks in library free mode along with machine learning algorithms. Pathway enrichment was performed using the REACTOME pathway resource and correlated to the Molecular Signature Database (MSigDB) hallmark gene set collections for functional annotation. Also, a drug connec-tivity analysis using the L1000 database was used to correlate the mechanism-of-action (MOA) for different anticancer reagents to WERI RB1 / WERI ETOR signatures. A total 4,756 proteins were identified across all samples which revealed a distinct clustering between groups. Of these pro-teins, 64 proteins were significantly altered (q < 0.05 & log2FC |>2|, 22% higher in WERI ETOR). Pathway analysis showed an enriched metabolic pathway for retinoid metabolism and transport pathway in WERI ETOR and for sphingolipid de novo biosynthesis in WERI RB1. In addition, this study showed similar protein signatures of topoisomerase inhibitors and WERI ETOR as well as of ATPase inhibitors, acetylcholine receptor antagonists and VEGFR inhibitors and WERI RB1. In this study, WERI RB1 and WERI ETOR were characterized as a cell line model for chemotherapy re-sistance in RB by using data-independent mass spectrometry. The global proteome revealed the activation of sphingolipid de novo biosynthesis in WERI RB1 and potential treatment options for etoposide resistant RB.

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Tumor Suppressor Role of INPP4B in Chemoresistant Retinoblastoma

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