The gene expression sequence of radiated mucosa in an animal mucositis model.

Oral mucositis is a common, dose-limiting, acute toxicity of radiation therapy administered for the treatment of cancers of the head and neck. Accumulating data would suggest that the pathogenesis of mucositis is complex and involves the sequential interaction of all cell types of the oral mucosa, as well as a number of cytokines and elements of the oral environment. While a number of studies have reported on gene expression of particular cell types in response to radiation, the overall response of irradiated mucosa has only been evaluated in a limited way. The present study was undertaken to evaluate the expression of a target group of genes using RNA quantification assays and, more broadly, to assess patterns of mucosal gene expression using DNA microarray hybridization. Our results demonstrate the sequential upregulation of a series of genes that, when taken collectively, suggest an intricate functional interaction.

Transforming growth factor-B3 protects murine small intestinal crypt stem cells and animal survival after irradiation, possibly by reducing stem-cell cycling.

Damage to the normal replacing tissues of the body, specifically the gastro-intestinal tract, limits the treatment and hence, cure rate of cancer patients. Here, we investigate the possibility that the sensitivity of the gastro-intestinal tract can be manipulated by transforming growth factor beta3 (TGF-beta3), making it more resistant to radiation in a murine model. The effects of TGF-beta3 were assessed using the crypt microcolony assay, a test of crypt stem-cell functional competence, in animal survival studies examining diarrhoea severity, labelling index and crypt size. Prior treatment with TGF-beta3 can result in a 3- to 4-fold increase (protection factor, PF) in surviving crypts, whilst longer exposure can raise the PF to almost 12. Protection of intestinal clonogenic stem cells results in marked protection of survival with a corresponding reduction in the duration and level of diarrhoea and ultimate restoration of normal histology in surviving mice. Inhibition of proliferation can be demonstrated when sufficient TGF-beta3 exposure is studied. Crypt size is also reduced. In conclusion, TGF-beta3 protects small intestinal clonogenic stem cells from radiation damage, reducing diarrhoea and animal mortality. The mode of action is believed to be specific inhibition of stem-cell proliferation.

Oral mucosal permeability and stability of transforming growth factor beta-3 in vitro.

PURPOSE: To investigate the permeability and localization of topically applied 125I-TGF-beta3 in porcine floor-of-mouth mucosa as a function of concentration and exposure. METHODS: The 125I-TGF-beta3 diluted in three different vehicles was applied to the tissue samples mounted in perfusion cells maintained at 37 degrees C. Flux and Kp values were calculated from the perfusate collected over a 24 hour period. The quantity of 125I-TGF-beta3 present in the tissue was determined by horizontal sectioning and subsequent counting. The stability of 125I-TGF-beta3 in saliva and in the tissue was analyzed by SDS polyacrylamide gradient gel electrophoresis. RESULTS: 125I-TGF-beta3 was relatively stable in saliva and in the epithelium; approximately 50% of the total counts in the deeper epithelium were resident in the 25kDa TGF-beta3 homodimer. A steady-state flux was reached approximately 6 hours post application and Kp value was 4.0+/-0.6 x 10(-6) (mean +/- sem). Penetration of 125I-TGF-beta3 to the basal cell layer was concentration dependent but reached nanomolar concentrations even after extensive surface rinsing, representing over one-thousand fold the IC50 for epithelial cell cycle arrest. CONCLUSIONS: The data suggest that topical application of TGF-beta3 to the oral mucosa in an appropriate vehicle can provide effective therapeutic delivery to the tissue.

Identification of Id2 as a globin regulatory protein by representational difference analysis of K562 cells induced to express gamma-globin with a fungal compound.

A fungus-derived compound (OSI-2040) which induces fetal globin expression in the absence of erythroid cell differentiation was identified in a high-throughput drug discovery program. We utilized this compound to isolate gamma-globin regulatory genes that are differentially expressed in OSI-2040-induced and uninduced cells in the human erythroleukemia cell line K562. Representational difference analysis (RDA) of cDNA revealed several genes that were significantly up- or down-regulated in OSI-2040-induced cells. One gene whose expression was markedly enhanced was the gene for the helix-loop-helix (HLH) transcription factor Id2. Southern analysis of RDA amplicons demonstrated progressive enrichment of Id2 with each successive subtraction of uninduced cDNA from induced cDNA. Northern analysis of OSI-2040-induced K562 cells confirmed that Id2 expression was directly up-regulated coordinately with gamma-globin. Analysis of other inducers of fetal globin demonstrated up-regulation of Id2 with sodium butyrate but not with hemin. Retrovirus-mediated overexpression of Id2 in K562 cells reproduced the enhancement of endogenous globin expression observed with OSI-2040 induction. Functional assays demonstrated that an E-box element in hypersensitivity site 2 is required for Id2-dependent enhancement of gamma-promoter activity. Protein binding studies suggest that alterations in E-box site occupancy by basic HLH proteins may influence this activity, thus expanding the potential role of these factors in globin gene regulation.

Transforming growth factor-beta3 protection of epithelial cells from cycle-selective chemotherapy in vitro.

The transforming growth factor-beta (TGF-beta) family of regulatory growth factors can reversibly arrest cell division in the G1 phase of the cell cycle. Previously, TGF-beta3 was shown to protect epithelial cells and hematopoietic cells from cytotoxic damage in vitro and in vivo, and to reduce the severity and duration of oral mucositis induced by 5-fluorouracil (5-FU) in vivo. In the present study, we tested whether TGF-beta3 can protect epithelial cells from a range of chemotherapy drugs with differing mechanisms of action, using the CCL64 cell line as a model system. We report that preincubation of cells with TGF-beta3 for 24 hr resulted in enhanced clonogenicity following exposure to vinblastine, vincristine, etoposide, taxol, ara-C, methotrexate, or 5-FU. Protection was measured in colony-forming assays, which demonstrated that the protected cells could re-enter the cell cycle and undergo multiple rounds of cell division. At high cytotoxic drug concentrations, absolute colony counts were increased for the cultures prearrested by TGF-beta3, as compared with the proliferating control cultures. The effects of TGF-beta3 were reduced for cisplatin and doxorubicin, drugs that are toxic to cells throughout the cell cycle. Thus, TGF-beta3 can effectively reduce the cytotoxicity of anticancer drugs that act predominantly in S or M phase of the cell cycle.

Transforming growth factor-beta 3 mediated modulation of cell cycling and attenuation of 5-fluorouracil induced oral mucositis.

Mucositis is a common, dose-limiting complication in patients receiving cancer chemotherapy, which derives from damage to the epithelial cell layer. We have shown that transforming growth factor-beta 3 (TGF-beta 3) negatively regulates epithelial cell proliferation and reduces the incidence of oral mucositis. Here, we report the findings of a large study examining the effects of TGF-beta 3 administration in a hamster model on oral epithelial cell cycling in vivo, on oral mucositis, on weight retention and on survival. Topical application of TGF-beta 3 to the buccal mucosa significantly reduced basal cell proliferation, as measured by proliferating cell nuclear antigen (PCNA) immunohistochemistry and DNA ploidy. Administration of topical TGF-beta 3 prior to chemotherapy with 5-fluorouracil (5-FU) significantly reduced the severity of mucositis with respect to time, reduced chemotherapy-associated weight loss and increased survival.

Pretreatment with transforming growth factor beta-3 protects small intestinal stem cells against radiation damage in vivo.

The gastrointestinal tract, with its rapid cell replacement, is sensitive to cytotoxic damage and can be a site of dose-limiting toxicity in cancer therapy. Here, we have investigated the use of one growth modulator to manipulate the cell cycle status of gastrointestinal stem cells before cytotoxic exposure to minimize damage to this normal tissue. Transforming growth factor beta-3 (TGF-beta3), a known inhibitor of cell cycle progression through G1, was used to alter intestinal crypt stem cell sensitivity before 12-16 Gy of gamma irradiation, which was used as a model cytotoxic agent. Using a crypt microcolony assay as a measure of functional competence of gastrointestinal stem cells, it was shown that the administration of TGF-beta3 over a 24-h period before irradiation increased the number of surviving crypts by four- to six-fold. To test whether changes in crypt survival are reflected in the well-being of the animal, survival time analyses were performed. After 14.5 Gy of radiation, only 35% of the animals survived within a period of about 12 days, while prior treatment with TGF-beta3 provided significant protection against this early gastrointestinal animal death, with 95% of the treated animals surviving for greater than 30 days.

Umbilical cord transforming growth factor-beta 3: isolation, comparison with recombinant TGF-beta 3 and cellular localization.

The transforming growth factor beta (TGF-beta) family of growth modulators play critical roles in tissue development and maintenance. Recent data suggest that individual TGF-beta isoforms (TGF-beta 1, -beta 2 and -beta 3) have overlapping yet distinct biological actions and target cell specificities, both in developing and adult tissues. The TGF-beta 3 isoform was purified to homogeneity from both natural and recombinant sources and characterized by laser desorption mass spectrometry, by protein sequencing, by amino acid analysis and by biological activity. TGF-beta 3 was the major TGF-beta isoform in umbilical cord (230 ng/g), and was physically and biologically indistinguishable from recombinant TGF-beta 3 and from the tumor growth inhibitory (TGI) protein found in umbilical cord. Immunohistochemistry using antipeptide TGF-beta 3 specific antibody showed TGF-beta 3 localization in perivascular smooth muscle.

Physical and biological characterization of a growth-inhibitory activity purified from the neuroepithelioma cell line A673.

Epithelial- and haematopoietic-cell growth-inhibitory activities have been identified in the conditioned medium of the human peripheral neuroepithelioma cell line A673. An A673-cell-derived growth-inhibitory activity was previously fractionated into two distinct components which inhibited the proliferation of human carcinoma and leukaemia cells in culture. One inhibitory activity was shown to comprise interleukin-1 alpha (IL-1 alpha). Here, we have purified to homogeneity a distinct activity which inhibited the growth of the epithelial cells in vitro. Using a combination of protein-sequence analysis and mass spectrometry, we demonstrated that biological activity can be assigned to a dimeric protein with a molecular mass of 25,576 (+/- 4) Da and an N-terminal sequence identical with that of transforming growth factor-beta 1 (TGF-beta 1). Further characterization of the growth inhibitor with TGF-beta-isoform-specific antibodies showed that > 90% of the bioactivity consists of TGF-beta 1 and not TGF-beta 2 or TGF-beta 3. Although A673 cells were growth-inhibited by exogenous TGF-beta 1, we showed that TGF-beta 1 in A673-cell-conditioned media was present in the latent, biologically inactive, form which did not act as an autocrine growth modulator of A673 cells in vitro.

Gene expression as a target for new drug discovery.

Over the last 7 years we have carried out a major research effort focused on gene transcription as a novel approach to drug discovery. The goal is to identify small molecular weight compounds that modulate the expression of a target gene in a specific manner, thereby either increasing or decreasing the concentration of the corresponding protein product. Transcriptional modulation not only provides a potential means to replace recombinant proteins as drugs, but also provides a novel approach to manipulate key gene targets in many therapeutic areas. This article describes some of the features and advantages of transcription-based pharmaceuticals and illustrates how this approach can be applied to drug discovery with a program we are pursuing to identify new treatments for sickle cell disease and beta-thalassemia.

Prevention of chemotherapy-induced ulcerative mucositis by transforming growth factor beta 3.

Mucositis is a common, dose-limiting complication in patients receiving cancer chemotherapy, which appears to be a consequence of the rate of epithelial proliferation. The beta transforming growth factors have been shown to be negative regulators of epithelial cell proliferation. Here we show that transforming growth factor beta 3 administration reduced proliferation of oral epithelium in vitro and in vivo. Topical application of transforming growth factor beta 3 to the oral mucosa of the Syrian golden hamster prior to chemotherapy significantly reduced the incidence, severity, and duration of oral mucositis, reduced chemotherapy-associated weight loss, and increased survival.

TGF-beta 3 protects normal human hematopoietic progenitor cells treated with 4-hydroperoxycyclophosphamide in vitro.

In this study we have investigated the ability of transforming growth factor-beta 3 (TGF-beta 3, 1000 pM) to protect hematopoietic bone marrow (BM) progenitor cells from the cytotoxic activity of 4-hydroperoxycyclophosphamide (4-HC, 100 microM) in vitro. Hematopoietic progenitors were purified by negative depletion of accessory and maturing cells or enriched by positive (CD 34+ cells) selection. For comparison the same treatment was tested on three different lymphoid cell lines CEM, SK-DHL-2, and LY-16. The experimental protocol was designed to mimic ex vivo purging conditions. Therefore, tumor cells and enriched hematopoietic precursors were mixed with irradiated BM cells. Our results demonstrated that preincubation of enriched progenitor cells with TGF-beta 3 for up to 72 h followed by 4-HC treatment resulted in an increased survival of colonies derived from granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) colony-forming cells, whereas a substantially lower number of colonies was observed in the control group. Similar results were observed when BM cells were first treated with 4-HC followed by TGF-beta 3 incubation for 24 or 48 h. In contrast, TGF-beta 3 provided no protection to the 4-HC cytotoxicity toward the lymphoma and leukemia cell lines. Three to four log of tumor cell killing was induced by 4-HC in the presence or absence of preincubation with TGF-beta 3. These data suggest that TGF-beta 3 is able to protect normal BM progenitors from the cytotoxic activity of an alkylating agent (4-HC) in vitro, whereas it does not offer any protection to lymphoma cell lines. These findings will have important implications for developing better purging conditions for autologous GM transplantation.

The effects of transforming growth factor beta 3 on the growth of highly enriched hematopoietic progenitor cells derived from normal human bone marrow and peripheral blood.

The effects of transforming growth factor beta 3 (TGF-beta 3) on growth in semisolid cultures of enriched hematopoietic progenitors derived from normal human marrow and blood were evaluated. Conditioned media from the Mo-T cell line (MoCM) were the source of colony-stimulating factors used to optimally stimulate primitive progenitors. To assess whether a proportion of granulocyte/monocyte (GM) progenitors were prevented from cycling, all sizes of GM aggregates were evaluated from 3 to 20 days. The activity of TGF-beta 3 on the growth of erythroid burst-forming units (BFU-E) and granulocyte-macrophage colony-forming units (CFU-GM) was similar to that observed for TGF-beta 1. TGF-beta 3 (10, 100, and 1,000 pmol/liter), added initially or 72 h after initiation of culture, did not significantly affect the total number of marrow GM aggregates at 3, 7, 14, and 20 days, but TGF-beta 3 (1,000 pmol/liter), added initially, reduced the total number of blood GM aggregates. This suggests that some blood GM progenitors might be blocked from cycling but that the great majority of marrow GM progenitors are not blocked. Whether TGF-beta 3 (10, 100, and 1,000 pmol/liter) was added initially or after 72 h of stimulation by MoCM, there was a dose-dependent reduction of marrow and blood GM colony size even when the total number of colonies was unaffected. TGF-beta 3 (10, 100, and 1,000 pmol/liter), added initially or at 72 h, reduced in a dose-dependent manner the size of marrow and blood-derived BFU-E. TGF-beta 3 (1,000 pmol/liter) was more likely to reduce the total number of marrow and blood BFU-E, and this increased sensitivity of the erythroid lineage may prevent the development of this population in colonies derived from multipotential colony-forming unit-granulocyte/erythroid/monocyte (CFU-GEM). The results suggest that the main effect of TGF-beta 3 and TGF-beta 1 is to slow the rate of proliferation of hematopoietic progenitors rather than to prevent them from beginning proliferation. This results in a reduction in colony size which prevents the identification of primitive versus mature progenitor on the basis of standard criteria of colony size.

Contributory effects of de novo transcription and premature transcript termination in the regulation of human epidermal growth factor receptor proto-oncogene RNA synthesis.

Overexpression of the epidermal growth factor (EGF) receptor (c-erbB) proto-oncogene is a frequent occurrence in human carcinoma and appears to accompany autocrine or paracrine transforming growth factor-alpha expression, which in model systems can result in activation of EGF receptor tyrosine kinase activity and phenotypic transformation. Here we have investigated the transcriptional regulation of the EGF receptor gene, by run-on transcription in isolated nuclei derived from epithelioid tumor lines. The level of transcription was measured at various points on the 100-kilobase pair EGF receptor gene locus, on either sense or antisense DNA strands. We find the level of sense strand transcription along exon 1 is 8-fold higher than transcription in exons 2-26. Primary EGF receptor transcripts appear to pause or terminate prematurely between exons 1 and 2. Termination was mapped to a sequenced region approximately 2 kilobase pairs 3' of exon 1, proximal to a previously reported DNase I hypersensitive site and an enhancer-like activity. Transcription in the CpG-rich region surrounding exon 1 is bidirectional, with antisense transcripts initiating in intron 1 and extending through the coding first exon. Activation of protein kinase C results in a 5-fold induction of EGF receptor transcription, accompanied by a slow release in the block RNA elongation between exon 2 and exon 26, showing that EGF receptor RNA synthesis may be altered by changes in de novo transcription and by a block to RNA elongation.

Regulation of epidermal growth factor receptor expression and activation: a brief review.

The epidermal growth factor receptor, a transmembrane protein tyrosine kinase, plays a crucial role in cellular signalling both in embryonic development and in adult tissues. By phosphorylation of substrate proteins on tyrosine, signals may be transmitted which result in gene expression, ion flux and mitogenesis to name but a few of the pleiotropic effects of receptor activation. The epidermal growth factor receptor is relatively well studied amongst an increasing family of tyrosine kinases and makes a good model system for studying structure-function relationships involved in signal transduction. Here, the structure-function relationships for cellular transformation by the EGF receptor proto-oncogene are reviewed as well as data pertaining to its overexpression in human tumors.

Analysis of mammalian fibroblast transformation by normal and mutated human EGF receptors.

Activation of the EGF receptor (c-erbB) tyrosine kinase has been implicated in tumorigenesis, either by overexpression of the normal receptor in the presence of EGF, or through expression of a truncated receptor lacking the EGF binding domain as in the viral oncogene v-erbB. Here, normal and truncated human EGF receptors expressed in Rat1 fibroblasts were analysed for receptor tyrosine kinase activity and several transformation parameters in comparison with polyoma middle T and EJ-ras. Expression of a truncated EGF receptor lacking the extracellular ligand binding domain induced transformation of immortalized rodent fibroblasts and appears to activate the intrinsic tyrosine kinase. The transformed phenotype becomes enhanced by further truncation of the C-terminal domain containing the tyrosine autophosphorylation sites P1 and P2. Over expression of EGF receptors with an intact extracellular region in transfected Rat1 cells shows EGF dependent transformation, which is reduced by C-terminal truncation. Transformation is dependent on the cellular receptor concentration and can be selected as a stable phenotype. We conclude that expression of receptors with a truncated EGF-binding domain alone is sufficient to transform mammalian fibroblasts, in contrast to chick fibroblasts transformed by v-erbB where additional deletion of C-terminal receptor sequences appears to be an absolute requirement.

Loss of three major auto phosphorylation sites in the EGF receptor does not block the mitogenic action of EGF.

The EGF receptor cDNA has been transfected into receptor-negative Chinese hamster ovary (CHO) cells. A mutant cell line (CHO 11) was isolated that expresses a receptor of lower molecular weight than the EGF receptor from A431 cells (150,000 daltons compared to 170,000 daltons) and which appeared as a doublet on SDS-PAGE. By digestion of the receptor with endoglycosidase F it was shown that an altered pattern of glycosylation could not account for the smaller size of the protein, although it could explain the appearance of the CHO 11 receptor as a doublet protein. A deletion was located to the transfected cDNA and shown to involve the removal of coding sequences for the most C-terminal 20,000 daltons of the EGF receptor, which contains the three major autophosphorylation sites. Despite the loss of these sites the EGF receptor from CHO 11 cells binds EGF, demonstrates protein tyrosine kinase activity in response to EGF, and transduces a mitogenic signal. The CHO 11 receptor protein is still autophosphorylated on alternative tyrosine residues. We conclude that phosphorylation of the three tyrosines (P1, P2, and P3) in the C-terminal domain of the receptor is not required for signal transduction by the EGF receptor in these cells.

Cosmid library construction.

To study the organization and regulation of eucaryotic genes from cloned DNA, vectors capable of maintaining large inserts have been constructed, largely from bacteriophage λ, where nonessential intergenic regions were identified. It had been noted that only λ DNA 37-52 kb in length (or 78-102% of the wild-type length) were efficiently packaged and passaged in vivo. Thus vectors from which the intergenic region had been removed could be positively selected for by the insertion of target DNA, thus restoring a packagable DNA length and producing viable phage.

Primed synthesis and direct sequencing in the isolation of cDNA clones using short oligonucleotides.

With the development of improved techniques for the construction of cDNA libraries representing rare messenger species has come increased demand for screening techniques to isolate specific cDNAs. A variety of techniques has been developed: 1. The use of exact and degenerate oligonucleotides complementary to RNAs coding for established protein sequence. 2. Bacterial expression of cDNA and immunological detection of the protein products. 3. Selection by hybrid-arrest or hybrid-select translation. 4. Differential hybridization using cDNAs obtained under different physiological conditions. 5. Bacterial expression of cDNA and selection by biological assay. 6. Transfer of cDNA libraries in eukaryotic expression vectors into mammalian cell lines and subsequent biological selection. 7. Expression of cloned cDNAs and mRNA in SP6 vectors with subsequent microinjection of RNA and biological selection of decreasing pools.