CDKN2A mutations in Spanish cutaneous malignant melanoma families and patients with multiple melanomas and other neoplasia

The CDKN2A gene has been implicated in cutaneous malignant melanoma (CMM) in about 40% of families with linkage to chromosome 9p21, while a small proportion of families have mutations in the CDK4 gene. In order to estimate the importance of these genes in the predisposition to CMM in Spanish families and patients we have analysed, by SSCA, a total of 56 subjects belonging to 34 CMM families, and nine patients with multiple CMM and other neoplasia. We have detected germline CDKN2A mutations in six out of the 34 families (17%). A frameshift mutation (358delG) and four missense mutations (G59V, G101W (two cases), D84Y, and R87W) were identified. Five CMM patients from different families (14%) carried the A148T variant, which is known not to affect p16 activity. No mutations were detected in the patients with multiple CMM or other neoplasms. We have not found mutations either in exon 1 beta of the CDKN2A gene or in exon 2A of CDK4. Linkage analysis of the 9p21 region showed exclusion for one of the families for CMM and for four families for CMM/dysplastic naevi. This study indicates a small role for CDKN2A in Spanish CMM families and suggests that other genes are also responsible for CMM predisposition.

The Notch/Jagged pathway inhibits proliferation of human hematopoietic progenitors in vitro

The cell surface receptor Notch1 is expressed on CD34+ hematopoietic precursors, whereas one of its ligands, Jagged1, is expressed on bone marrow stromal cells. To examine the role of Notch signaling in early hematopoiesis, human CD34+ cells were cultured in the presence or absence of exogenous cytokines on feeder layers that either did or did not express Jagged1. In the absence of recombinant growth factors, Jagged1 decreased myeloid colony formation by CD34+ cells, as well as 3H-thymidine incorporation and entry into S phase. In the presence of a strong cytokine signal to proliferate and mature, (interleukin 3 [IL-3] and IL-6, stem cell factor [SCF], and G-CSF), Jagged1 did not significantly alter either the fold expansion or the types of colonies formed by CD34+ cells. However, in the presence of SCF alone, Jagged1 increased erythroid colony formation twofold. These results demonstrate that Notch can modulate a growth factor signal, and that in the absence of growth factor stimulation, the Jagged1-Notch pathway preserves CD34+ cells in an immature state.

Salmonella tel-el-kebir and terrapins

OBJECTIVES

An outbreak of Salmonella tel-el-kebir occurring over a 6-month period is described in this report. This is the first outbreak of S. tel-el-kebir in the reported literature.

METHODS

S. tel-el-kebir was isolated from human faecal samples using conventional laboratory methods.

RESULTS

Eight patients had S. tel-el-kebir isolated from faeces. All patients were owners of, or in close contact with, pet terrapins. The terrapins were purchased in the same pet shop, where they were imported from America. The epidemiological link with these pets was confirmed, as S. tel-el-kebir was isolated from cloacal swabs from the terrapins, and from terrapin water. Molecular biology studies using DNA amplification fingerprinting (DAF) gave identical fingerprint patterns for all human and terrapin isolates.

CONCLUSIONS

Salmonellosis associated with exotic pets is a re-emerging disease in the 1990s, and measures to reduce this are discussed.

Preservation of duplicate genes by complementary, degenerative mutations

The origin of organismal complexity is generally thought to be tightly coupled to the evolution of new gene functions arising subsequent to gene duplication. Under the classical model for the evolution of duplicate genes, one member of the duplicated pair usually degenerates within a few million years by accumulating deleterious mutations, while the other duplicate retains the original function. This model further predicts that on rare occasions, one duplicate may acquire a new adaptive function, resulting in the preservation of both members of the pair, one with the new function and the other retaining the old. However, empirical data suggest that a much greater proportion of gene duplicates is preserved than predicted by the classical model. Here we present a new conceptual framework for understanding the evolution of duplicate genes that may help explain this conundrum. Focusing on the regulatory complexity of eukaryotic genes, we show how complementary degenerative mutations in different regulatory elements of duplicated genes can facilitate the preservation of both duplicates, thereby increasing long-term opportunities for the evolution of new gene functions. The duplication-degeneration-complementation (DDC) model predicts that (1) degenerative mutations in regulatory elements can increase rather than reduce the probability of duplicate gene preservation and (2) the usual mechanism of duplicate gene preservation is the partitioning of ancestral functions rather than the evolution of new functions. We present several examples (including analysis of a new engrailed gene in zebrafish) that appear to be consistent with the DDC model, and we suggest several analytical and experimental approaches for determining whether the complementary loss of gene subfunctions or the acquisition of novel functions are likely to be the primary mechanisms for the preservation of gene duplicates. For a newly duplicated paralog, survival depends on the outcome of the race between entropic decay and chance acquisition of an advantageous regulatory mutation. Sidow 1996(p. 717) On one hand, it may fix an advantageous allele giving it a slightly different, and selectable, function from its original copy. This initial fixation provides substantial protection against future fixation of null mutations, allowing additional mutations to accumulate that refine functional differentiation. Alternatively, a duplicate locus can instead first fix a null allele, becoming a pseudogene. Walsh 1995 (p. 426) Duplicated genes persist only if mutations create new and essential protein functions, an event that is predicted to occur rarely. Nadeau and Sankoff 1997 (p. 1259) Thus overall, with complex metazoans, the major mechanism for retention of ancient gene duplicates would appear to have been the acquisition of novel expression sites for developmental genes, with its accompanying opportunity for new gene roles underlying the progressive extension of development itself. Cooke et al. 1997 (p. 362)

Trauma, mental representation, and the organization of memory for mother-referent material

Research on the effects of child maltreatment and exposure to community violence suggests that children who experience these types of traumatic events may be at risk for alterations and biases in attention and memory similar to those that have been observed in adults suffering from traumatic stress reactions. Along these lines, attachment theory posits that representational models of relationships also may act as moderators of similar cognitive biases by selectively guiding children's attention to and processing of interpersonal stimuli. Building upon the trauma and attachment literatures, the present investigation examined the links among trauma, representational models of caregivers, and children's memory for mother-relevant information using an incidental recall task in a sample of maltreated (n = 71) and nonmaltreated (n = 102) children between the ages of 8 and 13 years. Results were consistent with the hypothesis that experiences of trauma and representational models of caregivers are associated with differences in the way children process and retrieve information about positive and negative mother attribute words. In particular, experiences of trauma initially were associated with increased insecurity in children's representational models. Moreover, the interaction of traumatic experience and security of mental representation predicted children's recall for mother attribute words: victimized children with insecure models recalled the highest proportion of negative mother stimuli. Trauma and mental representation did not have a consistent effect on structurally encoded aspects of recall. Results were discussed in terms of the ways in which children who have experienced trauma process information about their worlds. The importance of assessing functioning in multiple developmental domains when studying memory also was discussed.

The rate of spontaneous mutation for life-history traits in Caenorhabditis elegans

Spontaneous mutations were accumulated in 100 replicate lines of Caenorhabditis elegans over a period of approximately 50 generations. Periodic assays of these lines and comparison to a frozen control suggest that the deleterious mutation rate for typical life-history characters in this species is at least 0.05 per diploid genome per generation, with the average mutational effect on the order of 14% or less in the homozygous state and the average mutational heritability approximately 0.0034. While the average mutation rate per character and the average mutational heritability for this species are somewhat lower than previous estimates for Drosophila, these differences can be reconciled to a large extent when the biological differences between these species are taken into consideration.

Genetic Simulation Library

SUMMARY

The Genetic Simulation Library (GSL) is a set of C++ programs and classes that can be used in individual-based simulation models of plant and animal populations. The classes in this library build representations of genes for a wide variety of different types of organisms, from asexually reproducing single-cell organisms to chromosome-structured sexually reproducing species.

AVAILABILITY

http://www.csi.uoregon.edu/projects/genetics/GSL . Free for non-commercial applications; others should contact the author.

Should doctors practise resuscitation skills on newly deceased patients? A survey of public opinion

Trainee doctors must acquire skills in resuscitation, but opportunities for learning on real patients are limited. One option is to practise these skills in newly deceased patients. We sought opinions from 400 multiethnic guests at an open-access dinner dance for members of a local community. The questionnaire could elicit the responses strongly agree, agree, unsure, disagree or strongly disagree. 332 (83%) guests responded. For non-invasive techniques, 32% of responders supported practice without consent, 74% with consent. Support diminished with increasing invasiveness of procedure. 91% of the sample were uncomfortable about the procedures, the commonest reason being 'respect for the body' (264/302). 86% of responders felt that practice should last for no more than 5 minutes. The most popular solutions were for people to carry a personal card giving consent (89%) and establishment of a central register of individuals consenting to be practised upon after death (79%).

Faecal progesterone metabolite analysis for non-invasive monitoring of reproductive function in the white rhinoceros (Ceratotherium simum)

The two subspecies of white rhinoceros, southern (Ceratotherium simum simum) and northern (Ceratotherium simum cottoni), breed poorly in captivity, and estimates of oestrous cycle length vary considerably (range, 25-90 days). To characterise reproductive patterns, faecal samples were collected 2-3 times/week for up to 56 months from non-pregnant animals (n=21) of both subspecies. Immununoreactive pregnanes containing a 20-oxo-group (20-oxo-P) were analysed in a group-specific enzyme immunoassay using an antibody against 5alpha-pregnane-3beta-ol-20-one 3HS:BSA. Reproductive patterns were highly variable among and within individual animals. However, rhinoceroses could be classified into four major categories on the basis of oestrous cycle length and luteal phase 20-oxo-P concentrations: (1) regular oestrous cycles of 10 weeks duration and > 800 ng/g (n=2 animals); (2) oestrous cycles between 4-10 weeks and 250-750 ng/g (n=6); (3) no apparent cycle regularity, but luteal activity indicated by 20-oxo-P concentrations of 100-200 ng/g (n=6); (4) no apparent luteal activity as indicated by 20-oxo-P of < 100 ng/g (n=7). In two attempts to induce ovarian activity, chlormadinone acetate was fed daily to one animal for 35 and 45 days, respectively. Each treatment was followed by a subsequent hCG injection which resulted in luteal phases of 17 and 18 days, respectively, beginning about 10 days after hCG. Concentration of faecal 20-oxo-P in one pregnant animal during the 4th and 5th month of gestation were markedly higher than those observed during the luteal phase of the cycle. In conclusion, two thirds of white rhinoceroses in this study had erratic or missing luteal activity, whereas variable cycles of 4-10 weeks in length were evident in six females, and regular oestrous cycles of 10 weeks in length were found in two animals.

Deleterious mutation accumulation in organelle genomes

It is well established on theoretical grounds that the accumulation of mildly deleterious mutations in nonrecombining genomes is a major extinction risk in obligately asexual populations. Sexual populations can also incur mutational deterioration in genomic regions that experience little or no recombination, i.e., autosomal regions near centromeres, Y chromosomes, and organelle genomes. Our results suggest, for a wide array of genes (transfer RNAs, ribosomal RNAs, and proteins) in a diverse collection of species (animals, plants, and fungi), an almost universal increase in the fixation probabilities of mildly deleterious mutations arising in mitochondrial and chloroplast genomes relative to those arising in the recombining nuclear genome. This enhanced width of the selective sieve in organelle genomes does not appear to be a consequence of relaxed selection, but can be explained by the decline in the efficiency of selection that results from the reduction of effective population size induced by uniparental inheritance. Because of the very low mutation rates of organelle genomes (on the order of 10(-4) per genome per year), the reduction in fitness resulting from mutation accumulation in such genomes is a very long-term process, not likely to imperil many species on time scales of less than a million years, but perhaps playing some role in phylogenetic lineage sorting on time scales of 10 to 100 million years.

Inferring the major genomic mode of dominance and overdominance

The mode of within-locus gene action in most genomic regions is termed as the major genomic mode, i.e., it is the within-locus allelic effects in most regions of the genome. Determining whether dominance or overdominance is the major genomic mode is important for two long-standing evolutionary genetics issues: 1. How is the genetic variation in most genomic regions maintained? 2. What is the major mechanism for heterosis? Many efforts have been made, but almost all of them suffer some explanational difficulties. Here we propose an alternative inference approach. It is based on the existent theoretical results on the correlation of the recombination rate and the level of neutral variation in different genomic regions. Positive and negative correlation suggest dominance and overdominance, respectively, as the major genomic mode. Zero correlations imply either few selected sites or about equal composition and distribution of dominant and overdominant regions in the genome, depending on the data distribution. This approach not only avoids all the problems associated with earlier approaches, but it is also particularly useful in organisms where controlled breeding is difficult. Well-corroborated data in Drosophila and recently emerging data in mice and humans all suggest dominance as the major genomic mode.

Evaluation of barriers to surgical compliance in the treatment of trichiasis

PURPOSE

Eyelid repair surgery can prevent the effects of trichiasis leading to visual loss. Cost, transportation difficulties, and familial responsibilities have been identified as major barriers to surgical compliance. We evaluated whether offering trichiasis surgery in the village was effective in increasing the rate of surgical acceptance and in decreasing perceived barriers to surgery.

METHODS

In 1989, 205 women with trichiasis were identified in Central Tanzania and were offered free surgery along with free transport. As of 1991, only 18% of these women had undergone the surgery. We followed-up these women 7 years later after village level surgery was introduced.

RESULTS

Since 1991, an additional 12% of the women had undergone eyelid surgery. 44% were conducted in the village. Surgical cases since 1991 reported shorter travel times to the place of surgery, similar post-surgical problems, and fewer days in the hospital. While providing benefits to the patient, increased village eye services did not increase the rate of surgical acceptance. The women who declined surgery did not know surgery in the village was available and the perceived cost and transportation difficulties continued to be barriers. 50% of the non-acceptors stated that there was nothing that would enable them to accept surgical intervention despite the fact that 3/4 of them reported eye symptoms that interfered with their daily activities.

CONCLUSIONS

The cost efficacy of village level eye services needs to be evaluated and the awareness of these services increased.

Actinomyces pyogenes septic arthritis in a diabetic farmer

We report a case of septic arthritis and osteomyelitis of the left ankle due to Actinomyces pyogenes in a diabetic farmer. Few confirmed human cases of A. pyogenes infection have been reported, partly because of inadequate identification of this bacterium. Bacteriological characteristics of the organism, which resembles Arcanobacterium haemolyticum, are described with a review of previous case reports.

An ecological-transactional analysis of children and contexts: the longitudinal interplay among child maltreatment, community violence, and children's symptomatology

Cicchetti and Lynch have conceptualized ecological contexts as consisting of nested levels with varying degrees of proximity to the individual. These levels of the environment interact and transact with each other over time in shaping individual development and adaptation. With a sample of maltreated (n = 188) and nonmaltreated (n = 134) children between the ages of 7 and 12 years, this investigation employed a 1-year longitudinal design to conduct an ecological-transactional analysis of the mutual relationships among community violence, child maltreatment, and children's functioning over time. Indicators of children's functioning were externalizing and internalizing behavior problems and self-rated traumatic stress reactions, depressive symptomatology, and self-esteem. Either full or partial support was obtained for the study's primary hypotheses. Rates of maltreatment, particularly physical abuse, were related to levels of child-reported violence in the community. In addition, child maltreatment and exposure to community violence were related to different aspects of children's functioning. Specific effects were observed for neglect and sexual abuse and for witnessing and being victimized by violence in the community. Finally, there was evidence that children and their contexts mutually influence each other over time. Results were discussed within the framework of an ecological-transactional model of development.

Retention of the CDKN2A locus and low frequency of point mutations in primary and metastatic cutaneous malignant melanoma

CDKN2A has been found mutated in melanoma families which show linkage to chromosome 9p21. In contrast, a low mutation rate has been found in melanomas, suggesting that CDKN2A might not be the first target for mutation in the development of this type of tumour. To elucidate the role of the CDKN2A gene and its alternative transcript p19ARF in the development of cutaneous malignant melanoma (CMM) we have analyzed 48 primary and metastasic CMM tumours for mutations and for loss of heterozygosity (LOH). Only one point mutation was detected (2%), while hemizygous deletions were identified in 20% of these tumours. Retention of the CDKN2A locus was found in 10 (47%) tumours with deletions at one or both sides of CDKN2A, suggesting that loss of this gene is not involved in CMM-tumour initiation and that another tumour-suppressor gene involved in melanoma is located at 9p21.

Aberrant regulation of transforming growth factor-alpha during the establishment of growth arrest and quiescence of growth factor independent cells

Autocrine transforming growth factor alpha (TGFalpha) is an important positive growth effector in malignant cells and plays a significant role in generating the growth factor-independent phenotype associated with malignant progression. However, the molecular mechanisms by which TGFalpha confers a growth advantage in progression is poorly understood. The highly tumorigenic cell line HCT116 up-regulates TGFalpha mRNA expression during growth arrest, whereas the poorly tumorigenic growth factor-dependent FET cell line down-regulates TGFalpha mRNA expression as it becomes quiescent. We have identified a 25-bp sequence at -201 to -225 within the TGFalpha promoter which mediates the differential regulation of TGFalpha expression during quiescence establishment in these two cell lines. This same sequence confers TGFalpha promoter responsiveness to exogenous growth factor or autocrine TGFalpha. The abberant upregulation of TGFalpha mRNA in quiescent HCT116 cells may allow them to return to the dividing state under more stringent conditions (nutrient replenishment alone) then quiescent FET cells (requires nutrients and growth factors). Antisense TGFalpha approaches showed that the dysregulated TGFalpha expression in quiescent HCT116 cells is a function of the strong TGFalpha autocrine loop (not inhibited by blocking antibodies) in these cells.

The anti-proliferative effect of suramin towards tamoxifen-sensitive and resistant human breast cancer cell lines in relation to expression of receptors for epidermal growth factor and insulin-like growth factor-I: growth stimulation in the presence of tamoxifen

BACKGROUND

A significant proportion of breast cancer patients receiving tamoxifen therapy relapse during treatment following acquisition of tamoxifen-resistant or oestrogen-independent phenotypes. The mechanism behind this rapid progression to oestrogen autonomy is at present unclear and further treatment modalities are limited. Suramin represents a novel potential second line therapy. The mechanism of the antineoplastic activity of suramin is not completely understood, although the drug binds to many growth factors including epidermal growth factor and insulin-like growth factors and can also dissociate growth factors from their receptors. In this study we have related suramin sensitivity to the expression of receptors for epidermal growth factor and insulin-like growth factor-I in a number of breast cancer cell lines including lines resistant to tamoxifen.

MATERIALS AND METHODS

The anti-proliferative effects of suramin were investigated in two oestrogen dependent breast cancer lines (ZR-75-1 and MCF-7), oestrogen independent (ZR-PR-LT) and tamoxifen resistant (ZR-75-9a1) variants of ZR-75-1 and a tamoxifen resistant (LY2) variant of MCF-7. Full dose response curves were constructed and IC50 values determined for each cell line. Sensitivity to suramin was correlated with the level of expression of receptors for epidermal growth factor (EGFR) and insulin-like growth factor-I (IGFR). On observing stimulation of cell proliferation by suramin in the tamoxifen resistant cell lines in the presence of tamoxifen we also investigated the possible role of suramin sequestration of transforming growth factor-beta in mediating this effect.

RESULTS

All cell lines exhibited a dose- and time-dependent response to suramin treatment. Tamoxifen resistant ZR-75-9a1 cells (day 6 IC50 85 micrograms ml-1) were more resistant to suramin than oestrogen independent ZR-PR-LT cells (day 6 IC50 45 micrograms ml-1), and the parent ZR-75-1 line (day 6 IC50 56 micrograms ml-1). Increased sensitivity to suramin was associated with increased expression of IGFR and decreased expression of EGFR. Tamoxifen resistant LY2 cells were significantly more sensitive to suramin (day 6 IC50 70 micrograms ml-1) than MCF-7 cells (day 6 IC50 350 micrograms ml-1). Both IGFR and EGFR expression by LY2 cells was lower than in the parent line. The antioestrogen-resistant ZR-75-9a1 and LY2 lines grown in the presence of 8 microM tamoxifen were growth stimulated by concentrations of the drug below 100 micrograms/ml. As growth stimulation observed in the presence of tamoxifen may have been due to suramin sequestration of tamoxifen induced TGF-beta 1 secretion we also investigated the response of the cells to this peptide in the presence and absence of suramin. All cell lines were growth inhibited by TGF-beta 1 except ZR-75-9a1 which was unresponsive. Responses to TGF-beta 1 were modified in the presence of 100 micrograms suramin ml-1 although TGF-beta 1 was unable to mimic the ability of tamoxifen to stimulate proliferation in the presence of suramin.

CONCLUSIONS

These results suggest that for ZR-75-1 cells and variants, increased sensitivity to suramin is associated with an increase in expression of IGFR and a decrease in EGFR numbers. However, tamoxifen resistant LY2 cells, in which both IGFR and EGFR expression is reduced were considerably more sensitive than parental MCF-7 cells suggesting that there is no clear relationship between EGFR and IGFR expression and suramin sensitivity. The unexpected stimulation of cell proliferation of the tamoxifen resistant variants by suramin in the presence of tamoxifen could not be explained by suramin sequestration of transforming growth factor-beta and the mechanism of this interaction remains unclear.

Synaptic and axonal remodeling of mossy fibers in the hilus and supragranular region of the dentate gyrus in kainate-treated rats

Seizures evoked by kainic acid and a variety of experimental methods induce sprouting of the mossy fiber pathway in the dentate gyrus. In this study, the morphological features and spatial distribution of sprouted mossy fiber axons in the dorsal dentate gyrus of kainate-treated rats were directly shown in granule cells filled in vitro with biocytin and in vivo with the anterograde lectin tracer Phaseolus vulgaris leucoagglutinin (PHAL). Sprouted axon collaterals of biocytin-filled granule cells projected from the hilus of the dentate gyrus into the supragranular layer in both transverse and longitudinal directions in kainate-treated rats but were not observed in normal rats. The sprouted axon collaterals projected into the supragranular region for 600-700 microm along the septotemporal axis. Collaterals from granule cells in the infrapyramidal blade crossed the hilus and sprouted into the supragranular layer of the suprapyramidal blade. Sprouted axon segments in the supragranular layer had more terminal boutons per unit length than the axon segments in the hilus of both normal and kainate-treated rats but did not form giant boutons, which are characteristic of mossy fiber axons in the hilus and CA3. Mossy fiber axons in the hilus of kainate-treated rats had more small terminal boutons, fewer giant boutons, and there was a trend toward greater axon length compared with mossy fibers in the hilus of normal rats. With the additional length of supragranular sprouted collaterals, there was an overall increase in the length of mossy fiber axons in kainate-treated rats. The synaptic and axonal remodeling of the mossy fiber pathway could alter the functional properties of hippocampal circuitry by altering synaptic connectivity in local circuits within the hilus of the dentate gyrus and by increasing the divergence of the mossy fiber terminal field along the septotemporal axis.

Regulation of transforming growth factor alpha expression in a growth factor-independent cell line

Aberrant transcriptional regulation of transforming growth factor alpha (TGF alpha) appears to be an important contributor to the malignant phenotype and the growth factor independence with which malignancy is frequently associated. However, little is known about the molecular mechanisms responsible for dysregulation of TGF alpha expression in the malignant phenotype. In this paper, we report on TGF alpha promoter regulation in the highly malignant growth factor-independent cell line HCT116. The HCT116 cell line expresses TGF alpha and the epidermal growth factor receptor (EGFR) but is not growth inhibited by antibodies to EGFR or TGF alpha. However, constitutive expression of TGF alpha antisense RNA in the HCT116 cell line resulted in the isolation of clones with markedly reduced TGF alpha mRNA and which were dependent on exogenous growth factors for proliferation. We hypothesized that if TGF alpha autocrine activation is the major stimulator of TGF alpha expression in this cell line, TGF alpha promoter activity should be reduced in the antisense TGF alpha clones in the absence of exogenous growth factor. This was the case. Moreover, transcriptional activation of the TGF alpha promoter was restored in an antisense-TGF alpha-mRNA-expressing clone which had reverted to a growth factor-independent phenotype. Using this model system, we were able to identify a 25-bp element within the TGF alpha promoter which conferred TGF alpha autoregulation to the TGF alpha promoter in the HCT116 cell line. In the TGF alpha-antisense-RNA-expressing clones, this element was activated by exogenous EGF. This 25-bp sequence contained no consensus sequences of known transcription factors so that the TGF alpha or EGF regulatory element within this 25-bp sequence represents a unique element. Further characterization of this 25-bp DNA sequence by deletion analysis revealed that regulation of TGF alpha promoter activity by this sequence is complex, as both repressors and activators bind in this region, but the overall expression of the activators is pivotal in determining the level of response to EGF or TGF alpha stimulation. The specific nuclear proteins binding to this region are also regulated in an autocrine-TGF alpha-dependent fashion and by exogenous EGF in EGF-deprived TGF alpha antisense clone 33. This regulation is identical to that seen in the growth factor-dependent cell line FET, which requires exogenous EGF for optimal growth. Moreover, the time response of the stimulation of trans-acting factor binding by EGF suggests that the effect is directly due to growth factor and not mediated by changes in growth state. We conclude that this element appears to represent the major positive regulator of TGF alpha expression in the growth factor-independent HCT116 cell line and may represent the major site of transcriptional dysregulation of TGF alpha promoter activity in the growth factor-independent phenotype.