The EGF/TGFalpha response element within the TGFalpha promoter consists of a multi-complex regulatory element

Potential for functional redundancy in EGF and TGFalpha signaling in desmoid cells: a cDNA microarray analysis

Genes that replace or duplicate the function of other genes are considered functionally redundant. In this cDNA microarray study, using an Agilent microarray platform and GeneSifter analysis software, we evaluated (1) the degree of downstream transcriptional redundancy and (2) the level of genetic uniqueness apparent in desmoid tumor cells stimulated in vitro for 3 h or for 24 h with 100 ng/ml of exogenous recombinant human EGF (rhEGF) or with recombinant human transforming growth factor alpha (rhTGFalpha). Our intent was to identify genes costimulated, or genes unique to, desmoid cells stimulated in vitro with rhEGF and rhTGFalpha. This experimental approach demonstrated a 55% transcriptional redundancy in the number of desmoid genes significantly upregulated or downregulated following 3 h of stimulation with rhEGF or with rhTGFalpha, and a 65% transcriptional redundancy following 24 h of growth factor stimulation. Approximately 150 genes costimulated by rhEGF and rhTGFalpha were identified. This study suggests that EGF and TGFalpha retain some level of functional redundancy, possibly resulting from their divergence from a common ancestral gene.

Signal peptide of eosinophil cationic protein upregulates transforming growth factor-alpha expression in human cells

Eosinophil cationic protein (ECP) is a major component of eosinophil granule protein that is used as a clinical bio-marker for asthma and allergic inflammatory diseases. Previously, it has been reported that the signal peptide of human ECP (ECPsp) inhibits the cell growth of Escherichia coli (E. coli) and Pichia pastoris (P. pastoris), but not mammalian A431 cells. The inhibitory effect is due to the lack of human signal peptide peptidase (hSPP), a protease located on the endoplasmic reticulum (ER) membrane, in the lower organisms. In this study, we show that the epidermal growth factor receptor (EGFR) is upregulated by the exogenous ECPsp-eGFP as a result of the increased expression of the transforming growth factor-alpha (TGF-alpha) at both transcriptional and translational levels in A431 and HL-60 clone 15 cell lines. Furthermore, the N-terminus of ECPsp fragment generated by the cleavage of hSPP (ECPspM1-G17) gives rise to over threefold increase of TGF-alpha protein expression, whereas another ECPsp fragment (ECPspL18-A27) and the hSPP-resistant ECPsp (ECPspG17L) do not show similar effect. Our results indicate that the ECPspM1-G17 plays a crucial role in the upregulation of TGF-alpha, suggesting that the ECPsp not only directs the secretion of mature ECP, but also involves in the autocrine system.

A critical role for enhanced TGF-α and EGFR expression in the initiation of parathyroid hyperplasia in experimental kidney disease

The parathyroid hyperplasia secondary to kidney disease is associated with enhanced expression of the growth promoter transforming growth factor-α (TGF-α). TGF-α stimulates growth through activation of its receptor, the epidermal growth factor receptor (EGFR), normally expressed in the parathyroid glands. Because enhanced coexpression of TGF-α and EGFR causes aggressive cellular growth, these studies utilized highly specific inhibitors of EGFR tyrosine kinase, a step mandatory for TGF-α-induced EGFR activation, to assess the contribution of growth signals from enhanced expression of TGF-α exclusively or both TGF-α and EGFR to the rapid parathyroid growth induced by kidney disease and exacerbated by high-phosphorus (P) and low-calcium (Ca) diets in rats. The enhancement in parathyroid gland weight and proliferating activity (proliferating cell nuclear antigen/Ki67) induced by kidney disease and aggravated by either high P or low Ca intake, within the first week after 5/6 nephrectomy, in rats, coincided with simultaneous increases (2- to 3-fold) in TGF-α and EGFR content. Conversely, prevention of the increases in both TGF-α and EGFR paralleled the efficacy of either P restriction or high-Ca intake in ameliorating uremia-induced parathyroid hyperplasia. More importantly, suppression of TGF-α/EGFR signaling, through prophylactic administration of potent and highly selective inhibitors of ligand-induced EGFR activation, completely prevented both high-P- and low-Ca-induced parathyroid hyperplasia as well as TGF-α self-upregulation. Thus enhanced parathyroid TGF-α/EGFR expression, self-upregulation, and growth signals occur early in kidney disease, are aggravated by low-Ca and high-P intake, and constitute the main pathogenic mechanism of the severity of parathyroid hyperplasia.

Smad3 Knockout Mice Exhibit a Resistance to Skin Chemical Carcinogenesis

It has been shown that Smad3 exerts both tumor-suppressive and -promoting roles. To evaluate the role of Smad3 in skin carcinogenesis in vivo, we applied a chemical skin carcinogenesis protocol to Smad3 knockout mice (Smad3(-/-) and Smad3(+/-)) and wild-type littermates (Smad3(+/+)). Smad3(-/-) mice exhibited reduced papilloma formation in comparison with Smad3(+/+) mice and did not develop any squamous cell carcinomas. Further analysis revealed that Smad3 knockout mice were resistant to 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal hyperproliferation. Concurrently, increased apoptosis was observed in TPA-treated Smad3(-/-) skin and papillomas when compared with those of wild-type mice. Expression levels of activator protein-1 family members (c-jun, junB, junD, and c-fos) and transforming growth factor (TGF)-alpha were significantly lower in TPA-treated Smad3(-/-) skin, cultured keratinocytes, and papillomas, as compared with Smad3(+/+) controls. Smad3(-/-) papillomas also exhibited reduced leukocyte infiltration, particularly a reduction of tumor-associated macrophage infiltration, in comparison with Smad3(+/+) papillomas. All of these molecular and cellular alterations also occurred to a lesser extent in Smad3(+/-) mice as compared with Smad3(+/+) mice, suggesting a Smad3 gene dosage effect. Given that TGF-beta1 is a well-documented TPA-responsive gene and also has a potent chemotactic effect on macrophages, our study suggests that Smad3 may be required for TPA-mediated tumor promotion through inducing TGF-beta1-responsive genes, which are required for tumor promotion, and through mediating TGF-beta1-induced macrophage infiltration.

1,25-Dihydroxyvitamin D downregulation of TGFalpha/EGFR expression and growth signaling: a mechanism for the antiproliferative actions of the sterol in parathyroid hyperplasia of renal failure

Elevated serum levels of parathyroid hormone (PTH) contribute to the increased morbidity and mortality in renal failure patients. Parathyroid gland hyperplasia is a major cause of high serum PTH. The present studies used the rat model of renal failure to address the mechanisms underlying uremia-induced parathyroid hyperplasia and the antiproliferative properties of vitamin D therapy (1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) or its less calcemic analogs). Enhanced TGFalpha/EGFR co-expression is the major mitogenic signal in uremic parathyroid glands. At early stages of renal failure, vitamin D therapy efficiently counteracts uremia- and high phosphorus-induced hyperplasia by inhibiting the increases in parathyroid-TGFalpha/EGFR co-expression. In established hyperparathyroidism, characterized by highly enhanced-TGFalpha/EGFR co-expression, vitamin D therapy arrests growth by suppressing EGFR-growth signals from the plasma membrane and nuclear EGFR actions as a transactivator of the cyclin D1 gene, an important contributor to parathyroid hyperplasia in humans. In advanced renal failure, reduced-parathyroid vitamin D receptor levels limits the antiproliferative efficacy of vitamin D therapy. However, non-antiproliferative doses of 1,25-dihydroxyvitamin D enhance the anti-EGFR actions of EGFR-tyrosine kinase inhibitors (TKI). In fact, combined 1,25-dihydroxyvitamin D/TKI therapy inhibits parathyroid hyperplasia more efficiently than phosphorus restriction, the most powerful promoter of parathyroid growth arrest available at present.

Pseudocarcinomatous change in lymphomatoid papulosis and primary cutaneous CD30+ lymphoma: a clinicopathologic and immunohistochemical study of 6 patients

We report 6 cases of pseudoepitheliomatous hyperplasia (PEH) mimicking squamous cell carcinoma in association with an atypical CD30+ dermal infiltrate. Three patients had lymphomatoid papulosis type A, and 3 patients had cutaneous CD30+ lymphoma. All 6 cases showed histologic evidence of PEH with keratinocyte atypia. In 4 cases there was significant atypia to prompt a diagnosis of squamous cell carcinoma. Three of these received treatment with wide local excision and 2 had been engrafted. Immunohistochemical staining for epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) showed similar expression in lesional and perilesional skin. Epidermal growth factor receptor (EGFR) expression by the proliferating epithelium was similar to that of the suprabasal adjacent normal epidermis. There was no aberrant expression of EGF, TGF-alpha, and EGFR by atypical lymphocytes. These cases demonstrate that PEH associated with CD30+ lymphoproliferative disease may closely resemble squamous cell carcinoma, thereby leading to inappropriate diagnosis and treatment.