Use of vaccinia virus vectors to study protein processing in human disease. Normal nerve growth factor processing and secretion in cultured fibroblasts from patients with familial dysautonomia

Neurotrophic factors in peripheral neuropathies: therapeutic implications

Neurotrophic factors are proteins which promote the survival of specific neuronal populations. Many have other physiological effects on neurons such as inducing morphological differentiation, enhancing nerve regeneration, stimulating neurotransmitter expression, and otherwise altering the physiological characteristics of neurons. These properties suggest that neurotrophic factors are highly promising as potential therapeutic agents for neurological disease. Neurotrophic factors will most likely be applied to the peripheral nervous system initially, since there are fewer problems for large proteins to gain access to peripheral neurons. Many of the most intensively studied factors are active in the peripheral nervous system. These include the neurotrophins (nerve growth factor, brain derived neurotrophic factor, neurotrophin-3, neurotrophin-4/5), the insulin like growth factors, ciliary neurotrophic factor, and glial cell derived neurotrophic factor and its related proteins. The biology of these factors and their receptors in the peripheral nervous system is reviewed here. We also review data suggesting that abnormal availability of some factors may contribute towards the pathogenesis of certain types of peripheral neuropathy. Finally, the pre-clinical data suggesting that individual factors might be effective in treating neuropathy is reviewed, along with data relating to possible side effects of neurotrophic factor therapy. Several factors have already entered clinical trials with variable success. The data from these trials is reviewed as well.

Balance of two secretion pathways of nerve growth factor in PC12 cells changes during the progression of their differentiation, with a decrease in constitutive secretion in more differentiated cells

Proteins are secreted from animal cells by either a constitutive or a regulated pathway. When cDNA of nerve growth factor (NGF) was introduced into PC12 cells, these cells produced and secreted active NGF, where NGF was secreted not only in constitutive but also in activity-dependent regulated way according to the results of pulse-chase and ELISA studies. The regulated secretion was caused by depolarization, cyclic AMP analogue, or beta-adrenergic agonist but not by glutamate or carbachol. Because these transfected cells differentiated into a morphology indistinguishable from that incubated with NGF protein, we next compared the secretion pathways of NGF from PC12 cells at different stages of the differentiation. NGF was secreted in both constitutive and regulated way at 2 and 7 days after the transfection of NGF-cDNA, but the constitutive secretion of NGF from the more differentiated cells of Day 7 was decreased and mature NGF tended to accumulate in the cells. These results indicate that the neurotrophin secretion mechanism is intimately regulated in the course of the differentiation of PC12 cells. Such a change in the protein secretion pathway might have an profound role in the development of neurons.

Abnormal enamel and pulp dimensions in familial dysautonomia

In familial dysautonomia (FD), a hereditary autonomic and sensory neuropathy, somatic growth is impaired. This study was conducted to explore the possibility that tooth dimensions are altered as a consequence of neural crest dysfunction known to be present in FD. Enamel, dentin, pulp, and tooth size measurements of mandibular primary and permanent molars from FD patients were compared with those of healthy controls. It was found that although tooth size in the FD patients was smaller than normal, the enamel was thicker on the occlusal table, while the pulp chamber was smaller and disproportional to tooth size. Our results suggest distorted tooth dimensions rather than a generalized growth arrest as observed in other hereditary syndromes, such as Down's or Crouzon.

Peripheral Neuropathies: Will Growth Factors Be Effective as Therapies?

Neurotrophic factors are proteins that promote the survival and differentiation of specific neuronal popula tions. With the successful cloning and large-scale production of many different neurotrophic factors, it has become practical to consider their application in the treatment of neurological disease. Several categories of neurotrophic factors hold particular promise for the treatment of peripheral neuropathy in the near future. Preclinical studies have demonstrated the potential utility of factors like nerve growth factor for the treatment of small-fiber peripheral neuropathy and, possibly, compressive sensory neuropathies. Brain-derived neu rotrophic factor, ciliary neurotrophic factor, and insulin-like growth factor-I are likely to be applied in the treatment of motor neuropathy. Neurotrophin-3 has particular promise for the treatment of large-fiber sensory neuropathy. Although, for the most part, neurotrophic factors do not appear to have major toxicity, they represent a new class of drugs and clinical trials must proceed with caution. Clinical trials of several of these growth factors are currently underway, and others are being planned. The Neuroscientist 1:176-182, 1995

A recombinant vaccinia virus expressing human carcinoembryonic antigen (CEA)

Carcinoembryonic antigen (CEA) is a 180-kDa glycoprotein expressed on most gastrointestinal carcinomas. A 2.4-kb cDNA clone, containing the complete coding sequence, was isolated from a human colon tumor cell library and inserted into a vaccinia virus genome. This newly developed construct was characterized by Southern blotting, DNA hybridization studies, and polymerase chain reaction analysis. The CEA gene was stably integrated into the vaccinia virus thymidine kinase gene. The recombinant was efficiently replicated upon serial passages in cell cultures and in animals. The recombinant virus expresses on the surface of infected cells a protein product recognized by a monoclonal antibody (COL-I) directed against CEA. Immunization of mice with the vaccinia construct elicited a humoral immune response against CEA. Pilot studies also showed that administration of the recombinant CEA vaccinia construct was able to greatly reduce the growth in mice of a syngeneic murine colon adenocarcinoma which had been transduced with the human CEA gene. The use of this new recombinant CEA vaccinia construct may thus provide an approach in the specific active immunotherapy of human GI cancer and other CEA expressing carcinoma types.