Regional and temporal differences in gene expression of LH(BETA)T(AG) retinoblastoma tumors

Identification of pathogenic genes of pterygium based on the Gene Expression Omnibus database

AIM

To identify the pathogenic genes in pterygium.

METHODS

We obtained mRNA expression profiles from the Gene Expression Omnibus database (GEO) to identify differentially expressed genes (DEGs) between pterygium tissues and normal conjunctiva tissues. The Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway analysis, protein-protein interaction (PPI) network and transcription factors (TFs)-target gene regulatory network was performed to understand the function of DEGs. The expression of selected DEGs were validated by the quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

A total of 557 DEGs were identified between pterygium and normal individual. In PPI network, several genes were with high degrees such as FN1, KPNB1, DDB1, NF2 and BUB3. SSH1, PRSS23, LRP5L, MEOX1, RBM14, ABCA1, JOSD1, KRT6A and UPK1B were the most downstream genes regulated by TFs. qRT-PCR results showed that FN1, PRSS23, ABCA1, KRT6A, ECT2 and SPARC were significantly up-regulated in pterygium and MEOX1 and MMP3 were also up-regulated with no significance, which was consistent with the our integrated analysis.

CONCLUSION

The deregulated genes might be involved in the pathology of pterygium and could be used as treatment targets for pterygium.

Evidence of Tumour Microenvironment and Stromal Cellular Components in Retinoblastoma

BACKGROUND

The tumour microenvironment (TME) consisting of tumour cells and multiple stromal cell types regulate tumour growth, invasion and metastasis. While the concept of TME and presence of stromal cellular components is widely established in cancers, its significance in the paediatric intraocular malignancy, retinoblastoma (RB), remains unknown.

METHODS

The study qualitatively identified the presence of multiple stromal cellular subtypes in RB TME by immunohistochemistry.

RESULTS

Results of the study identified the presence of stromal cell types such as endothelial cells, tumour-associated macrophages, fibroblasts, cancer-associated fibroblasts, retinal astrocytes and glia in RB TME. The extent of stromal marker positivity, however, did not correlate with histopathological features of RB.

CONCLUSIONS

The findings of the study convincingly suggest the presence of a stromal component in RB tumours. The interactions between stromal cells and tumour cells might be of profound importance in RB progression.

Targeting Notch signaling as a novel therapy for retinoblastoma

Retinoblastoma is the most common intraocular malignancy of childhood. Notch plays a key role in retinal cells from which retinoblastomas arise, and we therefore studied the role of Notch signaling in promoting retinoblastoma proliferation. Moderate or strong nuclear expression of Hes1 was found in 10 of 11 human retinoblastoma samples analyzed immunohistochemically, supporting a role for Notch in retinoblastoma growth. Notch pathway components were present in WERI Rb1 and Y79 retinoblastoma lines, with Jag2 and DLL4 more highly expressed than other ligands, and Notch1 and Notch2 more abundant than Notch3. The cleaved/active form of Notch1 was detectable in both lines. Inhibition of the pathway, achieved using a γ-secretase inhibitor (GSI) or by downregulating Jag2, DLL4 or CBF1 using short hairpin RNA, potently reduced growth, proliferation and clonogenicity in both lines. Upregulation of CXCR4 and CXCR7 and downregulation of PI3KC2β were identified by microarray upon Jag2 suppression. The functional importance of PI3KC2β was confirmed using shRNA. Synergy was found by combining GSI with Melphalan at their IC₅₀. These findings indicate that Notch pathway is active in WERI Rb1 and Y79, and in most human retinoblastoma samples, and suggest that Notch antagonists may represent a new approach to more effectively treat retinoblastoma.

Genetic causes of hypomagnesemia, a clinical overview

Magnesium is essential to the proper functioning of numerous cellular processes. Magnesium ion (Mg2+) deficits, as reflected in hypomagnesemia, can cause neuromuscular irritability, seizures and cardiac arrhythmias. With normal Mg2+ intake, homeostasis is maintained primarily through the regulated reabsorption of Mg2+ by the thick ascending limb of Henle's loop and distal convoluted tubule of the kidney. Inadequate reabsorption results in renal Mg2+ wasting, as evidenced by an inappropriately high fractional Mg2+ excretion. Familial renal Mg2+ wasting is suggestive of a genetic cause, and subsequent studies in these hypomagnesemic families have revealed over a dozen genes directly or indirectly involved in Mg2+ transport. Those can be classified into four groups: hypercalciuric hypomagnesemias (encompassing mutations in CLDN16, CLDN19, CASR, CLCNKB), Gitelman-like hypomagnesemias (CLCNKB, SLC12A3, BSND, KCNJ10, FYXD2, HNF1B, PCBD1), mitochondrial hypomagnesemias (SARS2, MT-TI, Kearns-Sayre syndrome) and other hypomagnesemias (TRPM6, CNMM2, EGF, EGFR, KCNA1, FAM111A). Although identification of these genes has not yet changed treatment, which remains Mg2+ supplementation, it has contributed enormously to our understanding of Mg2+ transport and renal function. In this review, we discuss general mechanisms and symptoms of genetic causes of hypomagnesemia as well as the specific molecular mechanisms and clinical phenotypes associated with each syndrome.

Optical coherence tomography enables imaging of tumor initiation in the TAg-RB mouse model of retinoblastoma

PURPOSE

Retinoblastoma is the most common primary intraocular malignancy in children. Although significant advances in treatment have decreased mortality in recent years, morbidity continues to be associated with these therapies, and therefore, there is a pressing need for new therapeutic options. Transgenic mouse models are popular for testing new therapeutics as well as studying the pathophysiology of retinoblastoma. The T-antigen retinoblastoma (TAg-RB) model has close molecular and histological resemblance to human retinoblastoma tumors; these mice inactivate pRB by retinal-specific expression of the Simian Virus 40 T-antigens. Here, we evaluated whether optical coherence tomography (OCT) imaging could be used to document tumor growth in the TAg-RB model from the earliest stages of tumor development.

METHODS

The Micron III rodent imaging system was used to obtain fundus photographs and OCT images of both eyes of TAg-RB mice weekly from 2 to 12 weeks of age and at 16 and 20 weeks of age to document tumor development. Tumor morphology was confirmed with histological analysis.

RESULTS

Before being visible on funduscopy, hyperreflective masses arising in the inner nuclear layer were evident at 2 weeks of age with OCT imaging. After most of these hyperreflective cell clusters disappeared around 4 weeks of age, the first tumors became visible on OCT and funduscopy by 6 weeks. The masses grew into discrete, discoid tumors, preferentially in the periphery, that developed more irregular morphology over time, eventually merging and displacing the inner retinal layers into the vitreous.

CONCLUSIONS

OCT is a non-invasive imaging modality for tracking early TAg-RB tumor growth in vivo. Using OCT, we characterized TAg-positive cells as early as 2 weeks, corresponding to the earliest stages at which tumors are histologically evident, and well before they are evident with funduscopy. Tracking tumor growth from its earliest stages will allow better analysis of the efficacy of novel therapeutics and genetic factors tested in this powerful mouse model.

Intravitreal and subconjunctival melphalan for retinoblastoma in transgenic mice

Purpose. To measure the chemotherapeutic effects of focal melphalan (intravitreal and subconjunctival) on tumor burden, hypoxia, and vasculature in LHBETATAG murine retinoblastoma model. Methods. LHBETATAG transgenic mice were treated with a single 1 mcg intravitreal injection of melphalan, 100 mcg subconjunctival injection, or semiweekly 10 mcg subconjunctival injections for 3 weeks. At 1 or 3 weeks, eyes were enucleated, serially sectioned, and processed with haematoxylin and eosin (H&E) for tumor burden measurements and probed with immunofluorescence to analyze tumor hypoxia and vasculature. Results. Focal melphalan significantly reduced retinal tumor size (P < 0.02) when given intravitreally or subconjunctivally. Eyes treated with a one-time intravitreal injection of 1 mcg melphalan had significantly smaller tumors at both 1 week (P = 0.017) and at 3 weeks after injection (P = 0.005). Intratumoral hypoxia showed a significant decline in hypoxia at 1 week following intravitreal injection and after maximum dosage of subconjunctival melphalan. Total vasculature was not significantly affected following intravitreal administration. Conclusion. Focal delivery of melphalan via intravitreal or subconjunctival injection has a significant effect on reducing tumor burden, hypoxia, and vasculature, in the treatment of murine retinoblastoma tumors.

Retinoblastoma treatment: impact of the glycolytic inhibitor 2-deoxy-d-glucose on molecular genomics expression in LH(BETA)T(AG) retinal tumors

PURPOSE

The purpose of this study was to evaluate the effect of 2-deoxy-D-glucose (2-DG) on the spatial distribution of the genetic expression of key elements involved in angiogenesis, hypoxia, cellular metabolism, and apoptosis in LH(BETA)T(AG) retinal tumors.

METHODS

The right eye of each LH(BETA)T(AG) transgenic mouse (n = 24) was treated with either two or six subconjunctival injections of 2-DG (500 mg/kg) or saline control at 16 weeks of age. A gene expression array analysis was performed on five different intratumoral regions (apex, center, base, anterior-lateral, and posterior-lateral) using Affymetrix GeneChip Mouse Gene 1.0 ST arrays. To test for treatment effects of each probe within each region, a two-way analysis of variance was used.

RESULTS

Significant differences between treatment groups (ie, 0, 2, and 6 injections) were found as well as differences among the five retinal tumor regions evaluated (P < 0.01). More than 100 genes were observed to be dysregulated by ≥2-fold difference in expression between the three treatment groups, and their dysregulation varied across the five regions assayed. Several genes involved in pathways important for tumor cell growth (ie, angiogenesis, hypoxia, cellular metabolism, and apoptosis) were identified.

CONCLUSIONS

2-DG was found to significantly alter the gene expression in LH(BETA)T(AG) retinal tumor cells according to their location within the tumor as well as the treatment schedule. 2-DG's effects on genetic expression found here correlate with previous reported results on varied processes involved in its in vitro and in vivo activity in inhibiting tumor cell growth.

The TAg-RB murine retinoblastoma cell of origin has immunohistochemical features of differentiated Muller glia with progenitor properties

PURPOSE

Human retinoblastoma arises from an undefined developing retinal cell after inactivation of RB1. This is emulated in a murine retinoblastoma model by inactivation of pRB by retinal-specific expression of simian virus 40 large T-antigen (TAg-RB). Some mutational events after RB1 loss in humans are recapitulated at the expression level in TAg-RB, supporting preclinical evidence that this model is useful for comparative studies between mouse and human. Here, the characteristics of the TAg-RB cell of origin are defined.

METHODS

TAg-RB mice were killed at ages from embryonic day (E)18 to postnatal day (P)35. Tumors were analyzed by immunostaining, DNA copy number PCR, or real-time quantitative RT-PCR for TAg protein, retinal cell type markers, and retinoblastoma-relevant genes.

RESULTS

TAg expression began at P8 in a row of inner nuclear layer cells that increased in number through P21 to P28, when clusters reminiscent of small tumors emerged from cells that escaped a wave of apoptosis. Early TAg-expressing cells coexpressed the developmental marker Chx10 and glial markers CRALBP, clusterin, and carbonic anhydrase II (Car2), but not TuJ1, an early neuronal marker. Emerging tumors retained expression of only Chx10 and carbonic anhydrase II. As with human retinoblastoma, TAg-RB tumors showed decreased Cdh11 DNA copy number and gain of Kif14 and Mycn. It was confirmed that TAg-RB tumors lose expression of tumor suppressor cadherin-11 and overexpress oncogenes Kif14, Dek, and E2f3.

CONCLUSIONS

TAg-RB tumors displayed molecular similarity to human retinoblastoma and origin in a cell with features of differentiated Müller glia with progenitor properties.