Targeting the Platelet-Derived Growth Factor-beta Stimulatory Circuitry to Control Retinoblastoma Seeds

Modelling the complex nature of the tumor microenvironment: 3D tumor spheroids as an evolving tool

Cancer remains a serious burden in society and while the pace in the development of novel and more effective therapeutics is increasing, testing platforms that faithfully mimic the tumor microenvironment are lacking. With a clear shift from animal models to more complex in vitro 3D systems, spheroids emerge as strong options in this regard. Years of development have allowed spheroid-based models to better reproduce the biomechanical cues that are observed in the tumor-associated extracellular matrix (ECM) and cellular interactions that occur in both a cell-cell and cell-ECM manner. Here, we summarize some of the key cellular interactions that drive tumor development, progression and invasion, and how successfully are these interactions recapitulated in 3D spheroid models currently in use in the field. We finish by speculating on future advancements in the field and on how these can shape the relevance of spherical 3D models for tumor modelling.

The predictive capacity of in vitro preclinical models to evaluate drugs for the treatment of retinoblastoma

Retinoblastoma is a rare childhood cancer of the eye. Of the small number of drugs are used to treat retinoblastoma, all have been repurposed from drugs developed for other conditions. In order to find drugs or drug combinations better suited to the improved treatment of retinoblastoma, reliable predictive models are required, which facilitate the challenging transition from in vitro studies to clinical trials. In this review, the research performed to date on the development of 2D and 3D in vitro models for retinoblastoma is presented. Most of this research was undertaken with a view to better biological understanding of retinoblastoma, and we discuss the potential for these models to be applied to drug screening. Future research directions for streamlined drug discovery are considered and evaluated, and many promising avenues identified.

The roles of mouse double minute 2 (MDM2) oncoprotein in ocular diseases: A review

Mouse double minute 2 (MDM2), an E3 ubiquitin ligase and the primary negative regulator of the tumor suppressor p53, cooperates with its structural homolog MDM4/MDMX to control intracellular p53 level. In turn, overexpression of p53 upregulates and forms an autoregulatory feedback loop with MDM2. The MDM2-p53 axis plays a pivotal role in modulating cell cycle control and apoptosis. MDM2 itself is regulated by the PI3K-AKT and RB-E2F-ARF pathways. While amplification of the MDM2 gene or overexpression of MDM2 (due to MDM2 SNP T309G, for instance) is associated with various malignancies, numerous studies have shown that MDM2/p53 alterations may also play a part in the pathogenetic process of certain ocular disorders (Fig. 1). These include cancers (retinoblastoma, uveal melanoma), fibrocellular proliferative diseases (proliferative vitreoretinopathy, pterygium), neovascular diseases, degenerative diseases (cataract, primary open-angle glaucoma, age-related macular degeneration) and infectious/inflammatory diseases (trachoma, uveitis). In addition, MDM2 is implicated in retinogenesis and regeneration after optic nerve injury. Anti-MDM2 therapy has shown potential as a novel approach to treating these diseases. Despite major safety concerns, there are high expectations for the clinical value of reformative MDM2 inhibitors. This review summarizes important findings about the role of MDM2 in ocular pathologies and provides an overview of recent advances in treating these diseases with anti-MDM2 therapies.

Survival and ocular preservation in a long-term cohort of Japanese patients with retinoblastoma

Background

Retinoblastoma is an ocular tumor in infants with cancer predisposition. Treatment of the rare tumor needs to be optimized for ocular preserved survival without second primary malignancy (SPM).

Methods

We studied the outcomes of all patients with retinoblastoma at a tertiary center in 1984–2016, when preservation method changed from radiotherapy (1984–2001) to systemic chemotherapy (2002–2016).

Results

One-hundred sixteen infants developed unilateral- (n = 77), bilateral- (n = 38), or trilateral-onset (n = 1) tumor. Ten (8.6%) had a positive family history, despite a few studies on RB1 gene. Contralateral disease occurred in one unilateral-onset case. One-hundred eight of 155 eyes (70%) were enucleated. Nine binocular survivors were from 5 bilateral- and 4 unilateral-onset cases. Two survivors received bilateral enucleation. Six deaths occurred; brain involvement (including 3 trilateral diseases) in 4 bilateral-onset, systemic invasion in a unilateral-onset, and SPM (osteosarcoma) in a bilateral-onset case(s). Two others survived SPM of osteosarcoma or lymphoma. The 10-year overall survival (OS: 98.5% vs. 91.3%, p = 0.068) and binocular survivors (13.2% vs. 5.2%, p = 0.154) between bilateral- and unilateral-onsets did not differ statistically. The 10-year OS and cancer (retinoblastoma/SPM)-free survival (CFS) rates of all patients were 94.9 and 88.5%, respectively. The proportion of preserved eyes did not differ between radiotherapy and chemotherapy eras. The CFS rate of bilateral-onset cases in systemic chemotherapy era was higher than that in radiotherapy era (p = 0.042). The CFS rates of bilateral-onset patients with neoadjuvant chemotherapy (upfront systemic therapy for preservation) was higher than those without it (p = 0.030).

Conclusions

Systemic chemotherapy and local therapy raised OS and binocular survival rates of bilateral-onset patients similarly to those of unilateral-onset patients. All but one death was associated with a probable germline defect of the RB1 gene. Neoadjuvant stratified chemotherapy may support the long-term binocular life with minimized risk of SPM.

The Role of Intraarterial Chemotherapy in the Management of Retinoblastoma

Introduction. Retinoblastoma is the most common primary intraocular neoplasm in children. With the advances in medicine, the armamentarium of available treatment modalities has grown. Intraarterial chemotherapy is a relatively new treatment method with promising outcomes. The purpose of this literature review is to evaluate its role in the management of retinoblastoma.

Preclinical studies reveal MLN4924 is a promising new retinoblastoma therapy

RB1 loss (RB1 null ) or MYCN amplification (MYCN amp ) in fetal human retina causes retinoblastoma. SKP2 loss kills RB1 null cells, but small molecule SKP2 inhibitors remain unexplored therapeutically. Whether SKP2 is synthetic lethal in MYCN amp retinoblastoma is unclear. SKP2 is the substrate recognition component of two Cullin-RING Ligase complexes (CRL1SKP2/SCFSKP2, and CRL4SKP2), a family of multiprotein E3 ubiquitin ligases. NEDD8 activating enzyme (NAE) is required for Cullin neddylation and thus CRL activation. Here, we show that the NAE inhibitor, Pevonedistat (MLN4924), potently inhibits RB1 null and MYCN amp tumors. Intravitreal MLN4924 suppressed multiple human xenografts with EC80s from 20 ng to 3.5 μg. Maximum tolerated dose (MTD) was 10-30 μg, highlighting a favorable therapeutic window. Inhibition of Cullin neddylation was similar in all cases, but cellular effects ranged from G1 arrest with apoptosis to G2/M arrest with endoreplication. However, even in less sensitive lines (EC50 ≈ 1 μM), prolonged exposure was lethal or induced persistent cytostasis. Mechanistically, depleting any single Cullin did not fully recapitulate drug phenotypes, but sensitivity to SKP2 loss correlated with that of drug. Thus, intravitreal MLN4924 is a promising new retinoblastoma therapy, mimicking the cancer-specific lethality of eliminating SKP2 complexes.