Racial differences in breast cancer survival: the effect of residual disease

BACKGROUND

A survival difference has been seen in numerous studies between African-American (AA) and Caucasian (C) women with breast cancer. The purpose of this study was to elucidate the differences in patient characteristics and outcomes between AA and C women with breast cancer in our population.

METHODS

We performed a retrospective analysis of 1345 women with newly diagnosed breast cancer who were entered into our tumor registry from October 1980 to December 1998.

RESULTS

The association between race and stage at presentation was significant, as was the difference in the overall median survival between C and AA women. The data revealed no significant differences in survival between C and AA women presenting with Stage I or II disease. However, the differences between the median survival times for AA and C women presenting with Stage III and IV disease were both highly significant. A significantly lower percentage of AA women became "disease free" after initial therapy as compared with C women (P < 0.001). Interestingly, when data were stratified by stage, only in Stage III and IV were there significant differences between the races for becoming disease free.

CONCLUSIONS

AA women tend to present at a later stage and have poorer survival from later-stage disease as compared with C women. The poorer survival appears to be related to the decreased ability to achieve disease-free status in AA women with advanced disease. The underlying causes of this difference in treatment outcome need further evaluation.

A POU domain transcription factor-dependent program regulates axon pathfinding in the vertebrate visual system

Axon pathfinding relies on the ability of the growth cone to detect and interpret guidance cues and to modulate cytoskeletal changes in response to these signals. We report that the murine POU domain transcription factor Brn-3.2 regulates pathfinding in retinal ganglion cell (RGC) axons at multiple points along their pathways and the establishment of topographic order in the superior colliculus. Using representational difference analysis, we identified Brn-3.2 gene targets likely to act on axon guidance at the levels of transcription, cell-cell interaction, and signal transduction, including the actin-binding LIM domain protein abLIM. We present evidence that abLIM plays a crucial role in RGC axon pathfinding, sharing functional similarity with its C. elegans homolog, UNC-115. Our findings provide insights into a Brn-3.2-directed hierarchical program linking signaling events to cytoskeletal changes required for axon pathfinding.

Nicotinic acetylcholine receptor gene expression in developing chick autonomic ganglia

The developmental expression patterns of ten genes encoding nicotinic acetylcholine receptor subunits were analyzed using Northern blots and in situ hybridization in chick peripheral ganglia of neural crest, placodal and dual embryonic origin. The superior cervical and ciliary ganglia were investigated in detail because they accumulated relatively abundant transcripts of the alpha3, beta4, alpha5 and alpha7 genes. In the superior cervical ganglion, these four mRNA species had similar developmental time-courses. They appeared at embryonic day 8 (E8), increased steadily until E16 and maintained a rather high plateau level until E18. In the ciliary ganglion, alpha7 transcripts were already abundant at E6, increased until E10, and considerably decreased thereafter. High-resolution in situ hybridization showed that alpha7 transcripts were present in all cell types of the E6 ciliary ganglion, whereas they were restricted to large neuronal somas at E16. Transfections with a reporter gene under the control of the alpha7 promoter demonstrated that a sharp developmental divide occurred at E11-12, after which stage the promoter was activatable in neurons exclusively.

Effects of a hair cell transcription factor, Brn-3.1, gene deletion on homozygous and heterozygous mouse cochleas in adulthood and aging

The transcription factor Brn-3.1, is expressed in the inner ear hair cells throughout life and is necessary for the development of these cells. Mutant mice in which the Brn-3.1 encoding region has been deleted have no identifiable hair cells, greatly reduced numbers of spiral ganglion cells and are deaf. A mutation in the human homologue of this gene has been shown to be related to adult onset, sensorineural hearing loss (Vahava et al., 1998). The question whether haploinsufficiency in the mutant Brn-3.1 mouse with a mixed C57BL6/129Sv genetic background could affect the adult or aged cochlea was tested, therefore, by measuring the auditory brainstem responses and examining the cochlea's histologically at 2, 18 and 24 months of age. The heterozygotes had a comparable hearing to the wild-type animals and similar patterns of cochlear degeneration. Both groups showed an about 30 dB hearing loss beginning at 18 months of age, outer hair cell degeneration and loss of spiral ganglion neurons in the basal turn. There appeared to be no effect of Brn-3.1 haploinsufficiency on the mouse cochlea, implying that one intact copy of the gene is sufficient to maintain a normal cochlea.

POU domain factors in neural development

Transcription factors serve critical roles in the progressive development of general body plan, organ commitment, and finally, specific cell types. Comparison of the biological roles of a series of individual members within a family permits some generalizations to be made regarding the developmental events that are likely to be regulated by a particular class of transcription factors. Here, we evidence that the developmental functions of the family of transcription factors characterized by the POU DNA binding motif exerts roles in mammalian development. The POU domain family of transcription factors was defined following the observation that the products of three mammalian genes, Pit-1, Oct-1, and Oct-2, and the protein encoded by the C. elegans gene unc-86, shared a region of homology, known as the POU domain. The POU domain is a bipartite DNA binding domain, consisting of two highly conserved regions, tethered by a variable linker. The approximately 75 amino acid N-terminal region was called the POU-specific domain and the C-terminal 60 amino acid region, the POU-homeodomain. High-affinity site-specific DNA binding by POU domain transcription factors requires both the POU-specific and the POU-homeodomain. Resolution of the crystal structures of Oct-1 and Pit-1 POU domains bound to DNA as a monomer and homodimer, respectively, confirmed several of the in vitro findings regarding interactions of this bipartite DNA binding domain with DNA and has provided important information regarding the flexibility and versatility of POU domain proteins. Overall the crystal structure of a monomer of the Oct-1 POU domain bound to the octamer element was similar to that predicted by the NMR solution structures of the POU-specific domain and the POU-homeodomain in isolation, with the POU-specific domain consists of four alpha helices, with the second and third helices forming a structure similar to the helix-turn-helix motif of the lambda and 434 repressors; several of the DNA base contacts are also conserved. A homodimer of the Pit-1 POU domain was crystallized bound to a Pit-1 dimer DNA element that is closely related to a site in the proximal promoter of the prolactin gene. The structure of the Pit-1 POU domain on DNA is very similar to that of Oct-1, and the Pit-1 POU-homeodomain/DNA structure is strikingly similar to that of other homeodomains, including the Oct-1 POU-homeodomain. The DNA contacts made by the Pit-1 POU-specific domain are also similar to those of Oct-1 and conserved with many made by the prokaryotic repressors. In the Oct-1 crystal, the POU-specific domain recognizes a GCAT half-site, while the corresponding sequence recognized by the Pit-1 POU-specific domain, GTAT, is on the opposing strand. As a result, the orientation of the Pit-1 POU-specific domain relative to the POU-homeodomain is flipped, as compared to the Oct-1 crystal structure, indicating the remarkable flexibility of the POU-specific domain in adapting to variations in sequence within the site. Also in contrast to the Oct-1 monomer structure is the observation that the POU-specific and POU-homeodomain of each Pit-1 molecule make major groove contacts on the same face of the DNA, consistent with the constraints imposed by its 15 amino acid linker. As a result, the Pit-1 POU domain homodimer essentially surrounds its DNA binding site. In the Pit-1 POU domain homodimer the dimerization interface is formed between the C-terminal end of helix 3 of the POU-homeodomain of one Pit-1 molecule and the N-terminus of helix 1 and the loop between helices 3 and 4 of the POU-specific domain of the other Pit-1 molecule. In contrast to other homeodomain crystal structures, the C-terminus of helix 3 in the Pit-1 POU-homeo-domain has an extended structure. (ABSTRACT TRUNCATED)

The neuronal alpha6 subunit forms functional heteromeric acetylcholine receptors in human transfected cells

We examine some of the biological and physiological properties of the avian alpha6 neuronal nicotinic acetylcholine receptor (nAChR) subunit. We show here that, beginning at embryonic day 5, alpha6 mRNA is abundantly expressed in the developing chick neuroretina, where it coexists with other nicotinic receptor subunit mRNAs such as alpha3, beta2 and beta4. In contrast, alpha6 mRNA is absent from the optic tectum and from the peripheral ganglia. Despite numerous efforts, the alpha6 subunit has long failed the critical test of functional reconstitution. Here we use patch-clamp techniques and confocal laser microscopy to measure ACh-activated currents and nicotine-elicited Ca2+ transients in human BOSC 23 cells transfected with chick alpha6 in combination with other chick nAChR neuronal subunits. Heterologously expressed alpha6 and beta4 subunits form functional heteromeric nAChRs, which are permeable to Ca2+ ions and blocked by the nicotinic antagonist methyllycaconitine (10 microM). Likewise, ACh elicits measurable currents in cells transfected with alpha6 and beta2. Hill analysis of the dose-response curves in cells transfected with alpha3, beta4 and alpha6 cDNAs, suggests the assembly of functional alpha3beta4alpha6 receptor, with an apparent affinity for ACh threefold lower than alpha3beta4. Our results indicate that alpha6-containing nAChRs assemble in heterologous expression systems and are probably present in retinal cells.

Requirement for Brn-3.0 in differentiation and survival of sensory and motor neurons

Specific families of transcription factors mediate events in the sequential maturation of distinct neuronal phenotypes. Members of one such family, the class IV POU domain transcription factor Brn-3.0, and two highly related factors Brn-3.1 and Brn-3.2, are differentially expressed in the developing and mature mammalian nervous system. The expression pattern of Brn-3.0 suggested that it has an important role in the development of sensory ganglia, as well as red nucleus, inferior olive, and nucleus ambiguus. Analysis of mice null for the Brn-3.0 locus shows that Brn-3.0 is required for the survival of subpopulations of proprioceptive, mechanoreceptive and nociceptive sensory neurons, where deletion of the gene affects neurotrophin and neurotrophin-receptor gene expression. Deletion of Brn-3.0 also alters either differentiation, migration or survival of specific central neuronal populations.

Role of transcription factors Brn-3.1 and Brn-3.2 in auditory and visual system development

The neurally expressed genes Brn-3.1 and Brn-3.2 (refs 1-6) are mammalian orthologues of the Caenorhabditis elegans unc-86 gene that constitute, with Brn-3.0 (refs 1-3,8,9), the class IV POU-domain transcription factors. Brn-3.1 and Brn-3.2 provide a means of exploring the potentially distinct biological functions of expanded gene families in neural development. The highly related members of the Brn-3 family have similar DNA-binding preferences and overlapping expression patterns in the sensory nervous system, midbrain and hindbrain, suggesting functional redundancy. Here we report that Brn-3.1 and Brn-3.2 critically modulate the terminal differentiation of distinct sensorineural cells in which they exhibit selective spatial and temporal expression patterns. Deletion of the Brn-3.2 gene causes the loss of most retinal ganglion cells, defining distinct ganglion cell populations. Mutation of Brn-3.1 results in complete deafness, owing to a failure of hair cells to appear in the inner ear, with subsequent loss of cochlear and vestibular ganglia.

Characterization of the nicotinic acetylcholine receptor beta 3 gene. Its regulation within the avian nervous system is effected by a promoter 143 base pairs in length

Genomic and cDNA clones encoding the chicken neuronal nicotinic acetylcholine receptor beta 3 subunit were isolated and sequenced. The beta 3 gene consists of six protein-encoding exons and the deduced protein has the structural features found in all other members of the neuronal nicotinic acetylcholine receptor subunit family. Although they are undetectable in most brain compartments, beta 3 mRNAs are relatively abundant in the developing retina and in the trigeminal ganglion. In situ hybridization and immunohistochemical analysis demonstrated that in retina, beta 3 transcripts and protein are confined to subpopulations of cells in the inner nuclear and ganglion cell layers. Beta 3 is expressed in the proximal and distal regions of the developing trigeminal ganglion, i.e. in both placode- and neural crest-derived neurons. Transient transfection assays in cells freshly dissociated from selected regions of the central nervous system at different developmental stages allowed the identification of genetic elements involved in the neuronal-selective expression of the beta 3 gene. A promoter fragment 143 base pairs in length and containing TATA, CAAT, and other consensus sequences is sufficient to restrict reporter gene expression to a subpopulation of retinal neurons. This promoter is totally inactive upon transfection into neuronal and non-neuronal cells from other regions of the central nervous system.

A monoclonal antibody distinguishes anterior horn cells of human embryonic spinal cord during a transient period of development

Monoclonal antibodies were prepared by using the anterior horn region of human embryonic spinal cord as immunogen. To increase the specificity of the immune response towards the anterior horn cells, mice were first injected with antigens from the posterior horn and then immunosuppressed with cyclophosphamide; subsequently antigens from the anterior horn were injected. One of the monoclonal antibodies recognizes a small population of anterior horn cells of human embryonic spinal cord during a transient period of development (9-10th embryonic week); these cells are probably motoneurons according to their location in the spinal cord, their positive staining for acetylcholinesterase and their large nuclei. The staining pattern has a special axial distribution as it is limited to the cervical and thoracic regions of the spinal cord. The antibody is species-specific and shows a high degree of tissue specificity. Since this antibody distinguishes a small group of anterior horn cells in the spinal cord during a specific developmental stage, it opens stimulating perspectives for further investigation on the nature of the antigen and its putative role during the development of the human embryonic spinal cord.

Alpha 5, alpha 3, and non-alpha 3. Three clustered avian genes encoding neuronal nicotinic acetylcholine receptor-related subunits

In vertebrates, neuronal nicotinic acetylcholine receptors (nAChRs) assemble in an unknown stoichiometry from two homologous subunits, an alpha and a non-alpha. How large is the repertoire of these subunits and how many subtypes of functionally different nAChRs can they constitute? We found in the avian genome a cluster of three closely linked genes spanning 28 kilobase pairs and encoding three proteins, n alpha 3, alpha 3, and alpha 5, that have the features expected of neuronal nAChR subunits. Gene n alpha 3 lies 5' of alpha 3 (whose role in cholinoception has already been established) and is transcribed from the same DNA strand, whereas alpha 5 lies 3' of alpha 3 and is transcribed from the opposite DNA strand. The structure of the n alpha 3 and alpha 5 genes consists of six exons with precisely conserved splice sites and is identical to the structure of the previously characterized avian neuronal receptor subunit genes alpha 2, alpha 3, alpha 4, and n alpha 1. alpha 3, n alpha 3, and alpha 5 transcripts are rare in the central nervous system, but alpha 3 and n alpha 3 are readily detectable in embryonic superior cervical and ciliary ganglia. In order to assay function, the gene encoding n alpha 3 and the cDNAs encoding alpha 3, alpha 4, alpha 5, and n alpha 1 were subcloned into an expression vector, and the constructs were injected into Xenopus oocyte nuclei, either singly or in pairwise combinations of one alpha and one non-alpha. One to five days later, ACh sensitivity of the injected oocytes was examined in voltage clamp. The n alpha 3 gene and n alpha 1 cDNA elicited assembly of nAChRs when coinjected with alpha 3 or alpha 4 cDNA and the electrophysiological properties of the four pairwise combinations were significantly different. alpha 5, however, did not direct the assembly of functional nAChRs when injected alone or in combination with n alpha 1 or n alpha 3.

Interferon induces astrocyte maturation causing an increase in cholinergic properties of cultured human spinal cord cells

It has been well established that interferon-gamma (IFN-gamma) can modify the immune status of cells in the central nervous system (CNS) by inducing major histocompatibility antigens. Furthermore, it has been shown that endogenous IFN can be produced in the brain following viral infection and a form of IFN-alpha/beta can be produced by astrocytes in culture. Here we show that IFN can induce astrocyte maturation and alter neurotransmitter properties in cultured CNS neurons at a given developmental stage. IFN causes a dose-dependent increase in choline acetyltransferase activity and glial fibrillary acidic protein (GFAP) immunoreactivity in cultures of human embryonic spinal cord neurons. The GABAergic activity and the Thy1 immunoreactivity remain unchanged. IFN-gamma does not act directly on the neurons but via the nonneuronal cells, probably the astrocytes, which in turn stimulate the cholinergic traits. These studies could be important for demonstrating an action of the immune system on glial cell maturation and on the neurotransmitter phenotype expression in CNS neurons.

Characterization of dissociated monolayer cultures of human spinal cord

Embryonic human spinal cord cells have been grown in dissociated monolayer cultures for 1 to 7 weeks. Using cell type specific markers, it was possible to show that the cultures contain neurons, astrocytes and fibroblasts. Electrical membrane properties were studied with patch electrodes using the whole cell recording technique. Neurons had short duration action potentials that could be blocked by tetrodotoxin. The membrane currents in these neurons were studied in voltage clamp experiments. Three types of voltage-dependent currents were observed: a sodium current; a potassium current made up of two components, IA and IK; and a calcium current. Both cholinergic and GABAergic neurons are present in the cultures. There is more choline acetyltransferase activity in cultures prepared from the anterior as compared to the posterior part of the spinal cord, suggesting that the cultures contain motoneurons. This tissue culture preparation was developed for the study of amyotrophic lateral sclerosis; we have been unable to detect the presence of any toxic agent from the serum of these patients on the cultured cells. Experiments are in progress to purify the motoneurons using Percoll gradients.

Partial purification of lymphoblasts after in vitro immunization increases the yield in Ig-producing hybridomas

Using in vitro immunization with a human plasma protein (apolipoprotein-A1) as antigen, we have shown that it is possible to prepare more monoclonal antibodies using a ten-fold lower concentration of antigen compared to in vivo immunization procedures (Weech et al., 1985). In addition, we can increase the number of Ig-producing hybridomas after in vitro immunization by a simple one-step separation of the lymphoblasts on a Percoll gradient before the fusion procedure. In order to apply this procedure to in vivo immunization techniques, it is necessary to expand the B-blast/plasma cell population by culturing the spleen cells for 4-6 days before fusion. Only antibodies of the IgM class were produced with the in vitro technique. However, by combining in vivo priming with in vitro immunization, it is possible to produce specific antibodies to both IgG and IgM classes.