A. Linn Murphree

Prediction of familial predisposition to retinoblastoma.

Retinoblastoma is a childhood cancer, predisposition to which is inherited as an autosomal dominant trait. We used restriction-fragment-length and isozymic alleles of loci on chromosome 13 in five families predisposed to retinoblastoma, to provide identification before illness of persons likely to have tumors. The likelihood of disease was predicted in two cases, and freedom from disease in three. The calculated predictive accuracy was greater than 94 percent in cases with informative loci flanking the retinoblastoma (RB1) locus, and our prediction has been fulfilled in each such instance. A case that was informative at several loci indicated the occurrence of meiotic recombination, and accurate prediction was based on data obtained with DNA markers and isozymic forms of esterase D. The calculated predictive accuracy in another case, which was informative only for loci distal to the retinoblastoma locus, was about 70 percent. This patient was expected to acquire the disease but had not done so at the age of one year, illustrating the need for more markers that are also more informative and genetically closer to the retinoblastoma locus. These studies provide the basis for prenatal and postnatal prediction of susceptibility to inherited cancer using arbitrary recombinant DNA markers. Such predictions should make genetic counseling for familial retinoblastoma more accurate and lead to earlier tumor detection and more effective therapy.

Retinoblastoma: One World, One Vision

Retinoblastoma is curable when diagnosed early and treated appropriately; however, the prognosis is dismal when the basic elements of diagnosis and treatment are lacking. In developing countries, poor education, lower socioeconomic conditions, and inefficient health care systems result in delayed diagnosis and suboptimal care. Furthermore, the complexity of multidisciplinary care required is seldom possible. Whereas ocular salvage is a priority in the Western world, death from retinoblastoma is still a major problem in developing countries. To bring the 2 ends of this spectrum together and provide a forum for discussion, the “One World, One Vision” symposium was organized, at which clinicians and researchers from various cultural, geographic, and socioeconomic backgrounds converged to discuss their experiences. Strategies for early diagnosis in developing countries were discussed. Elements of the development of retinoblastoma centers in developing countries were discussed, and examples of successful programs were highlighted. An important component in this process is twinning between centers in developing countries and mentor institutions in high-income countries. Global initiatives by nongovernmental organizations such as the International Network for Cancer Treatment and Research, Orbis International, and the International Agency for Prevention of Blindness were presented. Treatment of retinoblastoma in developing countries remains a challenge; however, it is possible to coordinate efforts at multiple levels, including public administrations and nonprofit organizations, to improve the diagnosis and treatment of retinoblastoma and to improve the outcome for these children.

Nonrandom chromosomal changes in untreated retinoblastomas

The karyotypic patterns of 15 retinoblastomas were examined. Five tumors were found to have two distinct stem lines and, therefore, the chromosomal patterns of 20 tumor cell lines are reported. Three nonrandom chromosomal changes, namely, a loss of a chromosome #13, the presence of an i(6p), or a trisomy of 1q were observed. The potential importance of these chromosomal changes in tumor development is discussed, particularly the loss of a chromosome #13 or the gain of an i(6p). At least one of the three chromosomal changes was found in 75% of the tumor lines analyzed.

The gene responsible for the development of retinoblastoma and osteosarcoma.

The gene responsible for the formation of both retinoblastoma and osteosarcoma recently has been isolated. This represents the first human recessive cancer gene ever cloned. Structural deletions within one or both retinoblastoma gene alleles were commonly noted in the retinoblastomas and an osteosarcoma. Whether or not changes were observed at the DNA level there was either no expression or an abnormal expression of the gene in the tumor. The fact that we could detect changes in the fibroblasts of some patients with the hereditary form of retinoblastoma also indicates that the gene can be used for diagnostic purposes.

Approaches to treatment for extraocular retinoblastoma: Children's Hospital Los Angeles experience.

Extraocular retinoblastoma is associated with a very poor outcome. At Childrens Hospital Los Angeles, 10 of 207 patients with retinoblastoma had extraocular disease. Four patients with no histopathologic risk factors developed extraocular disease. All patients with direct extension into the central nervous system or with distant metastatic disease died. One of three patients with trilateral retinoblastoma and one patient with regional recurrence are alive after autologous bone marrow transplant. Patients with extraocular retinoblastoma who achieve remission may benefit from consolidation of their therapy with autologous bone marrow transplant.

Long-term outcomes of Group D eyes in bilateral retinoblastoma patients treated with chemoreduction and low-dose IMRT salvage.

To evaluate outcomes of Group D eyes of bilateral retinoblastoma patients treated with primary chemoreduction and external beam radiation as salvage.

THE EVOLUTION OF PHOTODYNAMIC THERAPY TECHNIQUES IN THE TREATMENT OF INTRAOCULAR TUMORS

Abstract The techniques of photodynamic therapy (PDT) and the indications for its use in the treatment of intraocular tumors have evolved during the years in which it has been assessed in patients at our institution. It is now clear that transcorneal PDT delivered at a subthermal dose‐rate to the surface of a pigmented lesion such as choroidal melanoma has little effect. In the absence of pigment, however, as in the case of retinoblastoma or amelanotic melanoma of the iris or choroid, the tumor kill attributed to PDT alone is significant. Data from animal tumor models in our institution and from patient studies elsewhere suggest that the addition of heat with the light delivery will predictably improve the outcome of the treatment of pigmented lesions. Ocular PDT delivered in conjunction with heat will be useful clinically as an adjunct to scleral plaque therapy by reducing the height of a lesion and concurrently the dose of radiation necessary at the base of the tumor for sterilization. Since the clinical tumoricidal effect of PDT is now known to be due at least in part to vascular damage, trans‐scleral application of light to the base of melanomas and occlusion of its blood supply holds significant promise of efficacy with continued improvement of the light delivery system. Finally, a transpupillary approach to occlusion of the choroidal vascular supply to a melanoma by surrounding the tumor with photodynamic lesions may provide the best approach for ocular PDT as a primary therapy.

Microbial Keratitis in Children

Forty-seven eyes with microbial keratitis occurring in 44 children under 16 years of age were studied. Under the age of three, 92% of the infections involved Pseudomonas aeruginosa and/or various streptococcal species; later in childhood the typical adult pattern of infection was more common. Overwhelming systemic infections, malignant disease with orbital involvement and congenital ocular adnexal disease were important predisposing factors in the infant years; trauma and acquired external eye disease became increasingly important in mid-childhood. Surgery was necessary in 28% of the eyes. Frequent tearing and lack of patient cooperation preclude reliance on topical antibiotic therapy alone. Despite the difficulties, the mainstay of management involves daily biomicroscopic evaluation and regular subconjunctival antibiotic injections. The logistical problems of achieving these aims are discussed.

Transformation and mutagenic potential of porphyrin photodynamic therapy in mammalian cells.

The transformation and mutagenic potential of porphyrin photodynamic therapy has been examined in mammalian cells. The mutagenic frequency in Chinese hamster cells at the Na+/K+ ATPase locus was measured by resistance to ouabain following treatment with either photodynamic therapy (PDT) or UV irradiation. The C3H 10T 1/2 mouse embryo cell system was used to document the transformation frequency following PDT, UV irradiation, gamma irradiation or exposure to 3-methylcholanthrene (MCA). Treatments with UV irradiation were effective in producing mutants resistant to ouabain, and treatments with UV irradiation, gamma irradiation and MCA generated transformants at frequencies comparable to those which are reported in the literature. However, PDT treatment conditions (which produced a full range of cytotoxicity) did not induce any mutagenic or transformation activity above background levels.

Non-fastidious, melanoma-specific CD8+ cytotoxic T lymphocytes from choroidal melanoma patients

To characterize the anti-melanoma reactivity of CD8+ cytotoxic T lymphocytes (CTL) from choroidal melanoma patients, CTL clones were isolated from the peripheral blood of three patients after mixed lymphocyte/tumor cell culture (MLTC). Clones were derived from lymphocytes stimulated by allogeneic (OCM-1, A24, A28) or autologous (OCM-3, Al, A30) melanoma cells. Their reactivity against a panel of HLA-typed melanoma and nonmelanoma cells was assessed, to determine whether a single CTL clone could recognize and lyse a variety of allogeneic melanoma cell lines. While proportionately more clones derived from autologous MLTC were melanoma-specific than allogeneic MLTC (42% versus 14%), melanoma-specific CTL were recovered from both. Notably, a novel melanoma specificity was identified. These CTL clones were termed non-fastidious because they were capable of lysing melanoma cells with which they had no HLA class I alleles in common. Nonetheless, lysis was mediated by the HLA class I molecule. Since lysis was specific for melanoma cells, these CTL appeared to recognize a shared melanoma peptide(s). Because of their prevalence, we propose that non-fastidious CTL are integral to human anti-melanoma T cell immunity. This reinforces clinical findings that allogeneic melanomas can substitute for autologous tumors in active specific immunotherapy. By circumventing the need for autologous melanoma, it is possible to treat patients after removal of the primary choroidal melanoma in an attempt to prevent metastasis.