Biomedical subjects

C D Woodworth

Publications and source records attributed to C D Woodworth.

At least 19 recordsLinked to original sources

PubMed2005

Visualization of cytoskeletal elements by the atomic force microscope.

We describe a novel application of atomic force microscopy (AFM) to directly visualize cytoskeletal fibers in human foreskin epithelial cells. The nonionic detergent Triton X-100 in a low concentration was used to remove the membrane, soluble proteins, and organelles from the cell. The remaining cytoskeleton can then be directly visualized in either liquid or air-dried ambient conditions. These two types of scanning provide complimentary information. Scanning in liquid visualizes the surface filaments of the cytoskeleton, whereas scanning in air shows both the surface filaments and the total "volume" of the cytoskeletal fibers. The smallest fibers observed were ca. 50 nm in diameter. The lateral resolution of this technique was ca.20 nm, which can be increased to a single nanometer level by choosing sharper AFM tips. Because the AFM is a true 3D technique, we are able to quantify the observed cytoskeleton by its density and volume. The types of fibers can be identified by their size, similar to electron microscopy.

Cells, Cultured↗

PubMed2001

Papillomavirus type 16 oncogenes downregulate expression of interferon-responsive genes and upregulate proliferation-associated and NF-kappaB-responsive genes in cervical keratinocytes.

Infection with high-risk human papillomaviruses (HPV) is a major risk factor for development of cervical cancer. Expression of the HPV E6 and E7 oncoproteins increases in differentiating keratinocytes, resulting in inactivation of the p53 and retinoblastoma proteins, two important transcriptional regulators. We used cDNA microarrays to examine global alterations in gene expression in differentiating cervical keratinocytes after infection with retroviruses encoding HPV type 16 (HPV-16) E6 and E7. Expression of 80 cellular genes (approximately 4% of the genes on the array) was altered reproducibly by E6 and/or E7. Cluster analysis classified these genes into three functional groups: (i) interferon (IFN)-responsive genes, (ii) genes stimulated by NF-kappaB, and (iii) genes regulated in cell cycle progression and DNA synthesis. HPV-16 E6 or a dominant negative p53 protein downregulated multiple IFN-responsive genes. E6 decreased expression of IFN-alpha and -beta, downregulated nuclear STAT-1 protein, and decreased binding of STAT-1 to the IFN-stimulated response element. E7 alone was less effective; however, coexpression of E6 and E7 downregulated IFN-responsive genes more efficiently than E6. The HPV-16 E6 protein also stimulated expression of multiple genes known to be inducible by NF-kappaB and AP-1. E6 enhanced expression of functional components of the NF-kappaB signal pathway, including p50, NIK, and TRAF-interacting protein, and increased binding to NF-kappaB and AP-1 DNA consensus binding sites. Secretion of interleukin-8, RANTES, macrophage inflammatory protein 1alpha, and 10-kappaDa IFN-gamma-inducible protein were increased in differentiating keratinocytes by E6. Thus, high-level expression of the HPV-16 E6 protein in differentiating keratinocytes directly alters expression of genes that influence host resistance to infection and immune function.

Cell Cycle↗

PubMed2001

Microarrays: spotlight on gene function and pharmacogenomics.

The introduction of microarray technology has dramatically changed the way that researchers address many biomedical questions. DNA microarrays can measure expression of thousands of genes simultaneously, providing extensive information on gene interaction and function. Microarray technology is a powerful tool for identifying novel molecular drug targets and for elucidating mechanisms of drug action. Furthermore, microarrays can monitor the global profile of gene expression in response to specific pharmacologic agents, providing information on drug efficacy and toxicity. Over the last several years, dramatic advancements have occurred in array technology. In this review we describe basic aspects of microarray instrumentation and experimentation. Each of the major array formats including oligonucleotides arrays, spotted arrays, and macroarrays are examined, and advantages and options for using each format are presented. Important factors in the design and analysis of microarray experiments are also discussed. Most importantly, we explore recent developments in microarray technology that are relevant to pharmacogenomics and the discovery of gene function.

Animals↗

PubMed2000

Targeted disruption of the epidermal growth factor receptor inhibits development of papillomas and carcinomas from human papillomavirus-immortalized keratinocytes.

The epidermal growth factor receptor (EGF-R) is frequently overexpressed in human papillomavirus (HPV)-associated dysplasias and carcinomas, implying that it is important for the progression of keratinocytes to malignancy. We used mice with a targeted disruption of the EGF-R gene to directly examine its role in cell immortalization and tumor development. Epidermal keratinocytes were cultured from EGF-R knockout, heterozygous, and wild-type mice, infected with retroviruses encoding HPV-16 E6 and E7 oncogenes, and grafted to nude mice. E6/E7 induced immortalization of EGF-R wild-type cells 5-fold more efficiently than null cells. Immortal EGF-R null cells grew more slowly, achieved a lower saturation density, and were more sensitive to apoptosis than the immortalized wild-type or heterozygous cells. Analyses using cDNA expression arrays showed that EGF-R null cells expressed increased levels of RNAs encoding p21waf and insulin-like growth factor-binding protein-2. EGF-R-positive immortal keratinocytes formed papillomas in 17% (15 of 90) of skin grafts, and seven grafts progressed to squamous carcinoma after 6-12 months. EGF-R null keratinocytes did not form papillomas, but 1 of 96 grafts progressed to a squamous carcinoma after 1 year. However, treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate induced tumors in 18 and 35% of grafts containing EGF-R null or EGF-R-positive cells, respectively. Transduction with an activated v-Ha-ras gene, which signals downstream of the EGF-R, induced rapidly growing carcinomas in all grafts regardless of EGF-R genotype. These results directly show that the EGF-R is important, but not essential, for immortalization by HPV and for progression of immortal cells to papillomas and carcinomas.

Animals↗

PubMed2000

Human papillomavirus type 16 E6 and E7 proteins inhibit differentiation-dependent expression of transforming growth factor-beta2 in cervical keratinocytes.

Infection with high-risk human papillomaviruses (HPVs) represents a major risk factor for the development of cervical cancer. The HPV-16 E6 and E7 proteins are highly expressed in differentiating keratinocytes, where they inactivate the p53 and retinoblastoma (pRb) proteins, two important transcriptional regulators. We have used cDNA expression arrays to identify global alterations in gene expression induced by E6 and E7 in differentiating cultures of human cervical keratinocytes. We show that E6 and E7 decrease expression of TGF-beta2 mRNA and alter expression of multiple TGF-beta-responsive genes involved in cell cycle regulation, apoptosis, and tissue remodeling. E6 and E7 inhibited expression of TGF-beta2 RNA 7-fold (relative effectiveness, E6/ E7 > E6 > E7 > control) and decreased secretion of biologically active TGF-beta2 by 70-80% (reduced from 70 to 10 pg/10(6) cells/24 h). Downregulation occurred through p53- and pRb-dependent pathways. In contrast, E6 and E7 did not alter expression of TGF-beta1 and TGF-beta3. Down-regulation of TGF-beta2 was biologically relevant because the addition of recombinant cytokine (10-200 pg/ml) to E6/E7-expressing cells restored expression of TGF-P-responsive genes, inhibited growth of keratinocytes, and decreased immortalization by E6 and E7. These results suggest that TGF-32- and TGF-3-responsive genes are important targets for the HPV-16 E6 and E7 oncoproteins in differentiating cervical keratinocytes.

Blotting, Northern↗

PubMed2000

Tumor necrosis factor-alpha promotes human papillomavirus (HPV) E6/E7 RNA expression and cyclin-dependent kinase activity in HPV-immortalized keratinocytes by a ras-dependent pathway.

Tumor necrosis factor-alpha (TNF-alpha) inhibits growth of normal cervical keratinocytes but stimulates proliferation of human papillomavirus (HPV)-immortalized and cervical carcinoma-derived cell lines when mitogens such as epidermal growth factor (EGF) or serum are depleted. Current work identifies the mechanism of growth stimulation. TNF-alpha promoted cell cycle progression by increasing expression of HPV-16 E6/E7 RNAs and enhancing activity of cyclin-dependent kinase (cdk)2 and cdc2 after 3 d. Increased kinase activity was mediated by upregulation of cyclins A and B and decreases in cdk inhibitors p21(waf) and p27(kip). TNF-alpha stimulated these changes in part by increasing transcription and stabilization of RNA for amphiregulin, an EGF receptor ligand, and amphiregulin directly increased HPV-16 E6/E7 and cyclin A RNAs. To define which components of the EGF receptor signaling pathway were important, HPV-immortalized cells were transfected with activated or dominant negative mutants of Ha-ras, raf, or MAPKK. Expression of activated Ha-ras maintained HPV-16 and cyclin gene expression and promoted rapid growth in the absence of EGF. Furthermore, ras activation was necessary for TNF-alpha mitogenesis as transfection with a dominant negative ras mutant (Asn-17) strongly inhibited growth. Thus, activation of ras promotes expression of HPV-16 E6/E7 RNAs, induces cyclins A and B, and mediates growth stimulation of immortal keratinocytes by TNF-alpha. These studies define a pathway by which ras mutations, which occur in a subset of cervical cancers, may contribute to pathogenesis. Mol. Carcinog. 27:97-109, 2000. Published by Wiley-Liss, Inc.

Cell Cycle↗

PubMed1999

Inhibitory effect of Bcl-2 on p53-mediated transactivation following genotoxic stress.

In the cellular response to genotoxic stress, cell cycle checkpoint and apoptosis are considered to be two of the major biological events in maintaining genomic stability. The tumor suppressor p53 has been shown to play critical roles in these stress-induced cellular responses at least in part through the activation of its down-stream genes, such as p21CIP1/WAF1, GADD45 and BAX. In addition, p53 has been found to down-regulate the expression of BCL-2, which is able to block apoptosis induced by both p53-dependent and independent signaling events. In this report, we have found that increased expression of Bcl-2 protein in the human Burkitt's lymphoma WMN cell line suppressed apoptosis induced by different DNA-damaging agents. The induction of p53-regulated genes including GADD45, p21CIP1/WAF1 and BAX by genotoxic stress was substantially reduced in cells expressing high levels of Bcl-2 protein. Furthermore, Bcl-2 protein was shown to specifically suppress the p53-mediated transactivation of p21CIP1/WAF1 and PG13-CAT, which is a typical p53-binding-site reporter construct. Similarly, the inhibitory effect of Bcl-2 protein was seen in a GADD45 promoter reporter construct after treatment with methylmethane sulfonate or UV-radiation. These results indicate that in addition to its apoptosis-suppressing activity, Bcl-2 protein is able to inhibit transactivation of p53-regulated genes, which function in multiple important cellular responses to genotoxic stress, including the control of cell cycle checkpoints, cell growth suppression and DNA repair.

Apoptosis↗

PubMed1998

Human papillomavirus type 16 E7 protein sensitizes cervical keratinocytes to apoptosis and release of interleukin-1alpha.

Interleukin-1alpha (IL-1alpha) is a multifunctional cytokine that promotes inflammation, tissue remodeling and epithelial hyperplasia. Keratinocytes produce and sequester large amounts of biologically active IL-1alpha which can be released after injury or infection. We show that high level expression of human papillomavirus (HPV) type 16 E6 and E7 oncoproteins enhanced release of IL-1alpha from cultures of normal cervical keratinocytes (relative effectiveness E7 > E6/E7 >> E6 > control). The amount of IL-1alpha released was directly related to the ability of E7 or E6/E7 to stimulate apoptosis. E7 proteins that bound the retinoblastoma protein (Rb) strongly (HPV-16 and -18) induced more IL-1alpha release than those that bound poorly (HPV-6 and an HPV-16 E7 24gly mutant). Furthermore, overexpression of the E2F-1 transcription factor, a downstream target of Rb, induced extensive apoptosis and IL-1alpha release. Apoptosis and IL-1alpha release in response to growth factor removal occurred in part through a p53-independent pathway as coexpression of E6 and downregulation of p53 did not prevent either response. Immunohistochemical analyses showed that IL-1alpha was expressed by keratinocytes in normal cervical epithelia, low and high grade dysplasias, and cervical carcinomas. However, HPV-16 E6/E7 RNA expression and apoptosis increased in parallel in proliferating keratinocytes in severe dysplasias and carcinomas suggesting that IL-1alpha release is associated with progression to high grade disease. Thus, high level expression of the HPV-16 E7 protein sensitizes keratinocytes to apoptosis which results in release of IL-1alpha.

Apoptosis↗

PubMed1998

Relationship of stable integration of herpes simplex virus-2 Bg/II N subfragment Xho2 to malignant transformation of human papillomavirus-immortalized cervical keratinocytes.

Transfection of the right end Xho2 subfragment of Bg/II N of herpes simplex virus-2 (HSV-2) into human genital keratinocytes immortalized by human papillomavirus (HPV) type 16 or 18 resulted in invasive and noninvasive indolent cystic squamous carcinomas when cells were injected into immunocompromised mice. Retention and expression of the right end portion of the Bg/II N fragment correlated with malignancy, as the corresponding HSV-2 sequences were integrated and transcribed in the tumorigenic cell lines. HPV-immortalized cells alone were not tumorigenic. In contrast, previous results have shown that using the entire Bg/II N region can malignantly transform HPV-immortalized cells, although HSV2 DNA was not retained. Together, these observations localize the transforming activity of Bg/II N to Xho2 and suggest that the remaining sequences have an inhibitory effect on stable integration. The Xho2 sequence is 2480 bp long and contains an open reading frame (ORF) extending from nucleotides 559 to 1797. The ORF encodes a putative protein of 412-aa with a m.w. of 42-43 kDa and is highly homologous to UL43 of HSV-I. The correlation of tumorigenicity with stable integration and expression of Xho2 DNA in HPV-immortalized cells indicates that HSV-2 should be investigated further for a possible role in cervical cancer.

Amino Acid Sequence↗

PubMed1997

Expression of 4alpha-carbinolamine dehydratase in human epidermal keratinocytes.

4alpha-Carbinolamine dehydratase is a bifunctional protein involved in the regeneration of tetrahydrobiopterin during the hydroxylation of the aromatic amino acids. It is also a dimerization cofactor of HNF1 and therefore is believed to function as part of the hepatic gene transcription system. In view of the recent discoveries that the distribution and developmental pattern of the dehydratase do not correlate strictly with those of the aromatic amino acid hydroxylases and HNF1, the hypothesis that the dehydratase may have other unknown functions has been put forward. In the present paper, we demonstrate unambiguously that human epidermal keratinocytes express detectable levels of this protein as indicated by enzyme assay, immunoprecipitation, Western blot, and RT-PCR. Its complete coding sequence has been cloned and was found to be identical with the human liver counterpart. The possible function of the dehydratase in skin is discussed.

Blotting, Western↗

PubMed1997

Early ultraviolet B-induced G1 arrest and suppression of the malignant phenotype by wild-type p53 in human squamous cell carcinoma cells.

Wild-type p53 (wt-p53) negatively controls cell cycle progression after cellular stress mediating either a temporary growth arrest or apoptosis, depending on the cell type and nature of the cellular stress. The aberrant proliferation which is characteristic of tumor cells may be suppressed by exogenous wt-p53 and appears to depend strongly on the level of reexpression. We performed retroviral-mediated gene transfer of wt-p53 into a human squamous cell carcinoma cell line from the head and neck region (A253 cell line) lacking endogenous p53. This allowed us to study the effect of wt-p53 on the malignant phenotype and on the response to the DNA damaging agent ultraviolet B (UVB). Restoration of wt-p53 in malignant keratinocytes suppressed tumorigenicity in nude mice although p53-reconstituted cells eventually formed small tumors with long latency. Cells derived from these tumors showed reduced expression of wt-p53. Exogenous wt-p53 increased baseline mRNA expression of the small proline rich proteins 1 and 2, consistent with a prodifferentiating effect. After exposure to a biological UVB dose, only p53-positive A253 cells underwent an early and transient G1 arrest. Both p53-positive and -negative A253 cells displayed a late G2 delay/arrest. We conclude that reexpression of wt-p53 in squamous cell carcinoma A253 cells decreases their malignant phenotype and reestablishes a G1 checkpoint after UVB.

Animals↗

PubMed1997

Altered expression of Erg and Ets-2 transcription factors is associated with genetic changes at 21q22.2-22.3 in immortal and cervical carcinoma cell lines.

Human Papillomavirus (HPV) type 16 is the most frequently detected HPV in cervical cancer. Although epidemiologic and experimental evidence indicates a prominent role for HPV infection in the development of this disease, other factors are also involved. Altered expression of the ets family transcription factors erg and ets-2 was found associated with the development of cervical carcinoma. Overexpression also occurred in a HPV-16-immortalized cervical cell line, CX16-2, which has HPV integrated at a translocation breakpoint t(19;21) involving 21q22.2-22.3, where these genes have been mapped. Six of 10 cervical carcinoma cell lines overexpressed ets-2 RNA suggesting an association of overexpression with cervical cell neoplasia. A clonally related pair of cervical carcinoma cell lines, C-4I and C-4II, showed differential expression of erg and ets-2. C-4I overexpressed ets-2 RNA compared to normal cervical cells and C-4II. C-4II expressed a 5.3 kb erg transcript not seen in C-4I, ectocervical cells or other cervical carcinoma cell lines examined. Pulsed field gel electrophoresis was used to analyse changes in DNA fragments related to structural changes and to construct a physical map encompassing erg and ets-2. Alterations in erg and ets-2 RNA expression in each of three different cell lines examined were associated with translocations. Association between altered expression of erg and ets-2 and altered regional structural suggests that these genes are important targets in cervical carcinogenesis.

Blotting, Northern↗

PubMed1996

Overexpression of the insulin-like growth factor-1 receptor and autocrine stimulation in human cervical cancer cells.

We characterized mechanisms of growth control involving insulin-like growth factor-1 (IGF-1), IGF-2, and IGF-1 receptor (IGF-1R) by investigating their expression in human cervical cancer cell lines, primary cervical tumor cell cultures, and normal ectocervical epithelial cells maintained in short-term culture. By reverse transcription followed by PCR, IGF-1 mRNA was not detected in any of the cell lines, whereas IGF-2 mRNA transcripts were detected in all of them. Using the RNase protection assay, low levels of IGF-2 mRNA were also detected in all of the cervical cancer cell lines, primary cervical tumor cell cultures, and normal ectocervical cultures tested, but no IGF-1 transcripts were detected. Scatchard analysis revealed 3- and 5-fold increases in IGF-1R expression by the primary cervical cancer cell cultures and cervical cancer cell lines, respectively, compared with the normal ectocervical cells. In proliferation assays, epidermal growth factor (EGF) consistently enhanced cervical cancer cell growth, but an antisense oligonucleotide to IGF-2 uniformly inhibited the EGF-induced mitogenic effect. These studies suggest that autocrine production of IGF-2 and overexpression of the IGF-1R are important components controlling the proliferation of cervical carcinoma cells, and that autocrine IGF-2 production in cervical cancer cells may participate in the mitogenic signaling of EGF.

Base Sequence↗

PubMed1996

Immortalization of human adult prostatic adenocarcinoma cells by human papilloma virus HPV16 and -18 DNA.

Primary prostate epithelial and prostate adenocarcinoma cells cultured in serum-free medium grew for up to 10 passages before senescence. Cells from prostate adenocarcinoma of a 55-year-old patient without lymph node involvement were transfected with plasmids containing recombinant human papilloma virus HPV16 or HPV18 DNA and the selectable neomycin-resistance gene. After G-418 selection, cells underwent crisis, and surviving cells infected with retroviruses encoding the HPV18 E6/E7 genes (HPV-PAC1), transfected with a head-to-tail dimer of the complete HPV16 genome (HPV-PAC2), or transfected with HPV18 E6/E7 early genes (HPV-PAC3) were established. HPV-PAC1 and HPV-PAC2 cultures appeared morphologically similar to primary cultures even after 40 passages. However, HPV-PAC2 cultures had a clonal morphology. All lines were positive for cytokeratin 18, had acquired vimentin expression, and contained either HPV16 or HPV18 sequences integrated into host DNA. None was tumorigenic in nude mice or formed colonies in soft agar. These cells did not secrete prostate specific antigen nor respond to androgen although tamoxifen inhibited the growth of the cells. Immunohistochemistry showed no evidence of p53 overexpression. Further characterization of these cell lines and examination of their response to chemotherapeutic agents may provide relevant information for the study of hormone-independent PC.

Adenocarcinoma↗

PubMed1996

Papillomaviruses and potential copathogens.

An in vitro multistage genital epithelial cell model for cervical cancer that parallels the in vivo neoplastic process has been developed using recombinant human papillomavirus (HPV) DNA and genital cells. HPV-16-immortalized genital cells are responsive to the genotoxic action of known chemical carcinogens (polycyclic hydrocarbons, alkylating agents or cigarette smoke condensate), but are not converted to malignancy. Ras oncogene and human herpes virus-2 did convert HPV immortalized cells to malignancy, whereas human herpes virus-6 infection only increased HPV expression. Human immunodeficiency virus did not infect genital cells.

Carcinogens↗

PubMed1996

Characterization of an immortalized cell line from a patient with epidermolytic hyperkeratosis.

The most frequent mutation that causes the autosomal dominant skin disease epidermolytic hyperkeratosis (EHK) is an arginine to histidine substitution at position 10 in the 1A segment of the rod domain of keratin 10. As an initial step toward developing a strategy for treating EHK, a cell line, EH18-1, was established after keratinocytes derived from an EHK patient with this mutation were immortalized by a recombinant retrovirus encoding the E6 and E7 genes of human papillomavirus type 18. EH18-1 cells synthesize considerable amounts of keratin 10 mRNA and protein when maintained in either submerged cultures or in organotypic cultures. When grown in organotypic culture, EH18-1 cells form multiple layers and express keratin 10 and filaggrin predominantly in the upper layers. Thus, the EH18-1 cell line exhibits several morphological and biochemical markers of terminal epidermal differentiation. A semiquantitative reverse transcriptase polymerase chain reaction assay for keratin 10 mRNA was developed to distinguish between expression of the normal and the mutant alleles. The EH18-1 keratinocyte cell line will be useful in developing protocols for gene therapy of EHK that may be monitored by reverse transcriptase polymerase chain reaction of either allele.

Alleles↗

PubMed1996

Expression and action of parathyroid hormone-related peptide in human cervical epithelial cells.

Parathyroid hormone-related peptide (PTHRP) expression and activity were analyzed in normal human ectocervical keratinocytes (HCX) and keratinocytes immortalized by transfection with human papillomavirus (HPV) types 16 and 18 DNAs. In normal cells, trans-retinoic acid (RA) and 2.0 mM Ca2+ significantly stimulated PTHRP mRNA expression and secretion and led to a significant reduction in the rate of proliferation. In contrast, the basal level of PTHRP production decreased sharply in confluent HCX, and induction by Ca2+ or exogenous growth factors was reduced or lost. After stable transfection with HPV16 and HPV18 DNAs, we observed a sharp decrease of PTHRP production in high-passage poorly differentiated HCX. Finally, addition of exogenous PTHRP-(1-141) inhibited proliferation of both normal cells and low-passage well-differentiated HPV16 immortalized cells. High-passage poorly differentiated cells were refractory to PTHRP. These results demonstrate that PTHRP production varies greatly with the degree of cell proliferation and differentiation and suggest that this peptide acts as an autocrine negative growth regulator for cervical keratinocytes.

Calcium↗

PubMed1996

Transforming growth factor beta 1 supports autonomous growth of human papillomavirus-immortalized cervical keratinocytes under conditions promoting squamous differentiation.

Transforming growth factor beta (TGF-beta) inhibits proliferation of keratinocytes cultured from normal anogenital epithelia; however, human papillomavirus (HPV)-immortalized cell lines often exhibit increased resistance. Present results demonstrate that TGF-beta 1 (1-10 pM) stimulates growth of multiple HPV-immortalized cell lines when cultures are maintained under conditions promoting squamous differentiation (MCDB153-LB medium with 1.0 mM calcium and without epidermal growth factor and bovine pituitary extract). Growth stimulation by TGF-beta 1 was not due to altered expression of type I or II receptors, but was increased after extended passage of cells in culture. Differentiation of immortal keratinocytes resulted in induction of RNAs encoding two markers of squamous differentiation, involucrin and keratin 1, and decreased expression of RNAs for the epidermal growth factor (EGF) receptor and two ligands, amphiregulin and TGF-alpha. Growth stimulation by TGF-beta 1 occurred indirectly via establishment of an autocrine loop. TGF-beta 1 increased expression of RNAs encoding the EGF-R and amphiregulin, and also increased numbers of cell-surface EGF-Rs without altering their affinity. In contrast, TGF-beta 1 inhibited autonomous growth and transcription of amphiregulin RNA in normal keratinocytes. Growth stimulation by TGF-beta 1 could be blocked by a monoclonal antibody that competes for binding to the EGF-R or by a mixture of monoclonal antibodies that neutralize amphiregulin activity, confirming the importance of this autocrine pathway. Thus, partial abrogation of the growth inhibitory response to TGF-beta 1 sensitizes HPV-immortalized keratinocytes to a growth stimulatory signal mediated by an EGF-R-dependent pathway involving autocrine stimulation by amphiregulin.

Animals↗