Abstract 2057: Delivering on the Vision of Bench to Bedside: A Rare Disease Funding Community Collaboration to Develop Effective Therapies for Neurofibromatosis Type 1 Tumors

The time from identifying a drug target to a new drug approval is often measured in decades and can take even longer for therapies to treat rare diseases. In fact, 95% of rare diseases do not have a specific therapy approved at all. Coordinated efforts to augment the drug development pipeline along with long-term and comprehensive support that enable scientific breakthroughs for rare diseases is possible, but it requires integration across multiple stakeholders. With the recently announced granted acceptance from the FDA to file status of the AstraZeneca and MSD (Merck) application for the MEK inhibitor selumetinib to treat plexiform neurofibromas in children, a major milestone towards the first-ever approved treatment for people with Neurofibromatosis Type 1 (NF1) associated tumors is closer than ever. This study analyzes the coordinated funding efforts of four federal and philanthropic organizations to advance drug development for NF1 associated tumors and discusses how these organizations collaborated and evolved practices to optimize funding and research support. This model could be replicated for other rare diseases if funders are able to take an active, coordinated approach to identify gaps, tools, and infrastructures most needed for that specific disease area.

Citation Format: Salvatore La Rosa, Annette C. Bakker, Vidya Browder, Jaishri O. Blakeley, Sharad K. Verma, Ling M. Wong, Jill Morris, Naba Bora. Delivering on the Vision of Bench to Bedside: A Rare Disease Funding Community Collaboration to Develop Effective Therapies for Neurofibromatosis Type 1 Tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2057.

Funding community collaboration to develop effective therapies for neurofibromatosis type 1 tumors

The time from identifying a drug target to a new drug approval is often measured in decades and can take even longer for therapies to treat rare diseases. In fact, 95% of rare diseases do not have a specific therapy approved at all. Coordinated efforts to augment the drug development pipeline along with long-term and comprehensive support that enable scientific breakthroughs for rare diseases are possible, but it requires integration across multiple stakeholders. This article analyzes the coordinated funding efforts of four federal and philanthropic organizations to advance drug development for neurofibromatosis type 1-associated tumors and discusses how these organizations have been collaborating and evolved practices to optimize funding and research support.

Expression of B7 molecules in the eye during experimental autoimmune anterior uveitis (EAAU)

PURPOSE

We have reported that CTLA4-Fc, a fusion protein that binds B7, prevents the induction of EAAU and reduces the severity of disease in Lewis rats. Since B7.1 and B7.2 have distinctive roles in other autoimmune diseases, we investigated their roles in the development of EAAU.

METHODS

Lewis rats were immunized with melanin associated antigen (MAA). Eyes were collected at different stages of EAAU and the expression of B7 on iris and ciliary body (ICB) cell suspensions determined by flow cytometry analysis. The incidence of EAAU after treatment with anti B7, and the requirement of B7.1 and B7.2 for proliferation and cytokine production of lymphoid cells to MAA were also studied.

RESULTS

B7.2 is up-regulated in resident ICB cells or bone-marrow derived cells which have infiltrated the ICB by day 10 and remains elevated during the acute phase of disease. B7.1 is expressed later during the acute phase. Both B7.1 and B7.2 are down-regulated during remission, with low levels of B7.2 and no detectable B7.1. The incidence of EAAU was reduced by anti-B7.2 treatment and completely inhibited by a combination of both B7.1 and B7.2 antibodies. Neither anti-B7.1 nor anti-B7.2 alone affected proliferation or cytokine production. However, administration of both anti-B7.1 and B7.2 completely inhibited proliferation as well as IL-2 and TNF-alpha production.

CONCLUSIONS

B7.1 and B7.2 are expressed in the eye at different times during EAAU. Both B7 molecules are required for the induction of EAAU, although they probably have different roles.

Fibroblast growth factor-2 decreases hyperoxia-induced photoreceptor cell death in mice

Fibroblast growth factor-2 (FGF2) has neurotrophic effects in vitro and in vivo. It has been demonstrated to decrease photoreceptor cell death in rats exposed to constant light and in rats with an inherited defect in retinal pigmented epithelium (RPE) phagocytosis, but the effects of intravitreous injections of FGF2 in mice are equivocal. In this study, we used transgenic mice with increased expression of FGF2 in photoreceptors (rhodopsin promoter/FGF2 transgenics) to investigate the effects of sustained increased expression of FGF2 in mice with various types of photoreceptor degeneration, including rd mice that are homozygous for mutated phosphodiesterase beta subunit, Q344ter mice that undergo photoreceptor degeneration because of expression of mutated rhodopsin, and mice exposed to 75% oxygen for 1 or 2 weeks. At P21, the outer nuclear layer was markedly reduced in rd mice or Q344ter mice regardless of whether they inherited the rhodopsin promoter/FGF2 transgene. However, after 2 weeks of exposure to 75% oxygen, outer nuclear layer thickness was significantly reduced in littermate control mice compared to FGF2 transgenic mice (P = 0.0001). These data indicate that increased expression of FGF2 in photoreceptors protects them from hyperoxia-induced damage, but does not decrease cell death related to expression of mutated proteins involved in the phototransduction pathway. This suggests that FGF2 protects photoreceptors from oxidative damage, which may play a role in complex genetic diseases such as age-related macular degeneration.

Evidence of decreased adhesion between the neural retina and retinal pigmented epithelium of the Mitfvit (vitiligo) mutant mouse

In order for the retina to function properly, photoreceptor cell outer segments must be in contact with the adjacent retinal pigmented epithelium (RPE). A mouse model homozygous for the vitiligo mutation of the microphthalmia (Mitf) gene manifests disruption of the outer segment/RPE interdigitation and demonstrates progressive loss of the photoreceptor cells. The mouse nevertheless has near normal levels of rhodopsin for many weeks and it is not known whether there is an in vivo loss of adhesion or whether the disruption is visible following tissue processing for histology. To assess this, a mechanical separation experiment was performed in which neural retinas were peeled free from the RPE and examined for the amount of pigment adherent to them. The peeling experiment indicated that control neural retinas retained significant amounts of adherent pigment at all ages examined. Neural retinas of mutant mice at age 2 weeks demonstrated adherent pigment, but older animals retained minimal pigment. Scanning electron microscopy indicated that the RPE cells of control mice were markedly damaged upon peeling and displayed different planes of cleavage, whereas those of mutants showed minimal cellular damage upon peeling, suggestive of decreased adhesion. A recombination experiment revealed that the mutant RPE/eyecup could reappose mutant and control retinas under in vitro conditions, suggesting that RPE fluid transport abilities were intact. The data provide the first direct experimental evidence that the Mitfvit mutant mouse has a naturally occurring retinal detachment and hence support its value as a model for studies of retina/RPE adhesion.

Transient overexpression of the Microphthalmia gene in the eyes of Microphthalmia vitiligo mutant mice

The murine microphthalmia gene (Mitf) encodes a basic helix-loop-helix transcription factor thought to regulate transcription of genes encoding proteins of the pigmentation pathway. It may promote pigment cell survival and development. The protein encoded by Mitf appears to be critical for eye development, because mutant alleles demonstrate varying degrees of ocular malformation. One of the mildest of these is the Mitf vitiligo (Mitfvit) mutant allele, which exhibits uneven pigmentation of the retinal pigment epithelium (RPE) and slow, progressive photoreceptor cell loss, eventually leading to blindness. In the present study, the expression of Mitf during early eye development in the Mitfvit mutant was compared with that of pigmented wild type mice. Mitf expression quantified by reverse transcriptase-polymerase chain reaction amplification demonstrated a transient elevation of Mitf between embryonic day 10.5 (E10.5) and E13.5 in the Mitfvit mutant compared with wild type mice. In situ hybridization analysis confirmed this elevation and localized Mitf expression to the neuroepithelium during onset of optic vesicle formation (E9.0-E9.5) and, subsequently, to the RPE during optic cup formation (E10-E11.5) in both mutant and wild type eyes. This is the first report of transient elevation of Mitf in any of the Mitf mutants, and the elevation may be relevant to altered levels of pigmentation proteins as well as to the RPE abnormalities observed in the Mitfvit mutant.

Photoreceptor cells in the vitiligo mouse die by apoptosis. TRPM-2/clusterin expression is increased in the neural retina and in the retinal pigment epithelium

PURPOSE

To determine the mechanism of photoreceptor cell death in the vitiligo mouse, a model of retinal degeneration in which the genetic defect is not retina specific but is instead caused by single point mutation in the microphthalmia (mi) gene that codes for a basic helix-loop-helix DNA transcription factor.

METHODS

Detection of apoptotic cells was performed in fixed retinal tissue using the TUNEL assay in animals 1, 2, 4, 6, 8, 16, 32, 40, and 52 weeks. Electron microscopic analysis was used to confirm the morphologic hallmarks of apoptosis, and Southern blot analysis was used to detect internucleosomal DNA fragmentation. Additionally, the expression of a gene associated with apoptosis, TRPM-2/clusterin, was examined.

RESULTS

At ages beyond the time of normal retinal programmed cell death, vitiligo retinas had significantly more TUNEL-positive photoreceptor cells and more photoreceptor cells with condensed chromatin than controls. DNA internucleosomal fragmentation ladders were present in vitiligo retinas even as late as 15 weeks, a time well beyond developmental apoptosis in controls. TRPM-2/clusterin mRNA levels in vitiligo neural retinas were similar to controls initially but were two times greater than controls by 12 weeks. Surprisingly, TRPM-2/clusterin mRNA levels were elevated in the retinal pigment epithelium in the mutant; the expression at one week was two times greater than normals and remained elevated for many months, even though retinal pigment epithelial cells showed no morphologic evidence of apoptosis.

CONCLUSIONS

The morphologic and biochemical data suggest that photoreceptor cells die by apoptosis in vitiligo mice. The increased retinal TRPM-2/clusterin mRNA levels may be a direct response to these events. The increased expression of this gene in the retinal pigment epithelium, however, may reflect its role in tissue regression and membrane remodeling. Mechanisms by which the mi gene defect might result in the vitiligo retinopathy are proposed.

The use of C0t-1 probe DNA for the detection of low levels of DNA fragmentation

In many apoptotic systems the final demise of the DNA results in the generation of multinucleosomal-sized DNA fragments, which appear as a DNA ladder after agarose electrophoresis. Extensive DNA fragmentation can be detected by ethidium bromide staining. Visualization of low levels of DNA fragmentation, however, requires both a more sensitive detection system, as well as a method of DNA extraction, that limits the extent of high molecular weight DNA shearing. We have found that the use of C0t-1 repetitive DNA as a probe for Southern analysis of DNA ladders is a sensitive method to detect low levels of DNA fragmentation. We have applied this methodology in the detection of DNA fragmentation in the normal developing C57BL/6 mouse retina at stages in which there is known DNA fragmentation, as well as in human Y-79 retinoblastoma cells grown in culture. We have found that in many instances in which there is no detectable DNA ladder with ethidium bromide staining a very definitive DNA ladder can be visualized via Southern blot analysis with a C0t-1 DNA probe.