Anti-angiogenesis: new concept for therapy of solid tumors

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Pigment epithelium-derived factor: neurotrophic activity and identification as a member of the serine protease inhibitor gene family

Cultured pigment epithelial cells of the fetal human retina secrete a protein, pigment epithelium-derived factor (PEDF), that induces a neuronal phenotype in cultured human retinoblastoma cells. Morphological changes include the induction of an extensive neurite meshwork and the establishment of corona-like cellular aggregates surrounding a central lumen. The differentiated cells also show increases in the expression of neuron-specific enolase and the 200-kDa neurofilament subunit. Amino acid and DNA sequence data demonstrate that PEDF belongs to the serine protease inhibitor (serpin) family. The PEDF gene contains a typical signal-peptide sequence, initiator methionine codon, and polyadenylylation signal and matches the size of other members of the serpin superfamily (e.g., alpha 1-antitrypsin). It lacks homology, however, at the putative serpin reactive center. Thus, PEDF could exert a paracrine effect in the embryonic retina, influencing neuronal differentiation by a mechanism that does not involve classic inhibition of serine protease activity.

Posttranslational modification and microtubule stability

We have probed the relationship between tubulin posttranslational modification and microtubule stability, using a variation of the antibody-blocking technique. In human retinoblastoma cells we find that acetylated and detyrosinated microtubules represent congruent subsets of the cells' total microtubules. We also find that stable microtubules defined as those that had not undergone polymerization within 1 h after injection of biotin-tubulin were all posttranslationally modified; furthermore dynamic microtubules were all unmodified. We therefore conclude that in these cells the stable, acetylated, and detyrosinated microtubules represent the same subset of the cells' total network. Posttranslational modification, however, is not a prerequisite for microtubule stability and vice versa. Potorous tridactylis kidney cells have no detectable acetylated microtubules but do have a sizable subset of stable ones, and chick embryo fibroblast cells are extensively modified but have few stable microtubules. We conclude that different cell types can create specific microtubule subsets by modulating the relative rates of posttranslational modification and microtubule turnover.

Interaction of p107 with cyclin A independent of complex formation with viral oncoproteins

The p107 protein and the retinoblastoma protein (RB) both bind specifically to two viral oncoproteins, the SV40 T antigen (T) and adenoviral protein E1A (E1A). Like RB, p107 contains a segment (the pocket) that, alone, can bind specifically to T, E1A, and multiple cellular proteins. Cyclin A bound to the p107 pocket, but not the RB pocket. Although both pockets contain two, related collinear subsegments (A and B), the unique sequence in the p107 pocket that occupies the space between A and B is required for the interaction with cyclin A.

Cytotoxicity of 3-hydroxykynurenine in a neuronal hybrid cell line

The toxicity of 3-hydroxykynurenine (3HK), an endogenous tryptophan metabolite which is markedly elevated in rat CNS tissue as a result of neonatal vitamin B-6 deficiency, was investigated in a neuronally derived hybrid cell line (N18-RE-105). At concentrations in excess of 100 microM, 3HK was toxic to greater than 85% of cultured cells over the course of 24 h. The time course of 3HK toxicity was studied in cultures exposed to 500 microM 3HK. Cell lysis proceeded linearly to completion in 8-12 h, but the toxic effects of exposure for 2 h were irreversible. 3HK was the most potently toxic among several related kynurenine metabolites tested. The toxic effects of 3HK exposure were markedly attenuated or abolished in the presence of either catalase or glutathione, indicating, a role of oxidative stress in 3HK toxicity.

Inhibition of neovascularization by an extract derived from vitreous

An extract of the vitreous body, inhibited the growth of new blood vessels induced by tumors in the rabbit cornea. This extract was delivered by an inert, continuously releasing polymer. The average vessel growth rate in the region surrounding the polymer was 32% less in corneas containing the inhibitory substance than in control corneas.

Effect of docosahexaenoic acid on membrane fluidity and function in intact cultured Y-79 retinoblastoma cells

Considerable metabolic energy is expended in ensuring that membranes possess a characteristic fatty acid composition. The nature of the specific requirement of the retina for high levels of docosahexaenoic acid (DHA) is as yet undefined. Previous work has speculated that DHA is required to maintain the fluid nature and permeability necessary for optimal retinal function. Cultured Y-79 retinoblastoma cells were grown in serum-containing media with and without supplemental DHA. Resultant changes in membrane fluidity were assessed using fluorescent probes. No differences were observed in rotational probe mobility as assessed by fluorescence polarization despite a fourfold increase in cellular DHA content. Lateral probe mobility as assessed by pyrene eximer formation was significantly enhanced in DHA-supplemented cells. Both the DHA content and total fatty acid unsaturation index in retinoblastoma cells were directly correlated with membrane fluidity as reported by eximer formation (Pearson's rho = 0.96 and 0.92, respectively). DHA supplementation also resulted in a significant increase in cellular choline uptake. We speculate that the effect of DHA content on retinal function may be mediated by changes in membrane fluidity and associated enzyme and transport activities.

Cancer of the nasal cavity and ethmoid/sphenoid sinuses

During the period from October 1964 to September 1975, 32 patients were treated at the University of Florida for a variety of malignant tumors of the nasal cavity and ethmoid/sphenoid sinuses. All were treated with radical irradiation, 6091 to 7972 rad, in 6 to 9 weeks, cobalt-60. Pretreatment work-up revealed evidence of orbital invasion in 7 patients and involvement of the cranial contents, base of skull, or nasopharynx in an additional 15 patients. Local control was achieved in 95% of nasal cavity cases and 71% of ethmoid/sphenoid sinus cases at 2 years or more. The 5-year actuarial survival rate was 59%, and 5-year survival without evidence of disease was 50% (13/26). Patterns of extension in advanced lesions are clues to potential undetected extension in early cases which must be included in the treatment volume. Eye complications were minimal when it was possible to avoid treatment of the entire eye, but developed in all cases requiring treatment of the entire orbit. Acute and chronic complications involving the eye, ear, central nervous system, sinuses, and nose were reviewed and correlated with initial tumor extent, dose, and radiation treatment technique.