Faculty Bibliography

Exposure of male rats to estrogens during the neonatal period retards prostate branching morphogenesis, blocks epithelial differentiation, and predisposes the adult prostate to hyperplasia and dysplasia. The mechanism of neonatal estrogenization is not well understood. The present study evaluated transforming growth factor-beta (TGFbeta) in the neonatally estrogenized ventral prostate to determine whether this paracrine/autocrine factor may in part mediate the effects ofestrogen on the developing prostate gland. Immunocytochemistry using antibodies against active TGFbeta1 and its latency-associated peptide localized this molecule to the periductal smooth muscle cells in the developing prostate. Although neonatal estrogenization increased the accumulation of total and active TGFbeta1 in the smooth muscle layer as early as day 6 of life, it was physically separated from the epithelial ducts by a proliferating layer of fibroblasts surrounding the basement membrane. RT-PCR demonstrated that alterations in TGFbeta1 levels were not due to alterations in TGFbeta1 transcription. TGFbeta2 and TGFbeta3 were primarily immunolocalized to differentiating epithelial cells in developing prostates, and this was markedly dampened between days 10-30 after neonatal estrogen exposure. Immunocytochemistry for TGFbeta signaling components revealed that neonatal estrogenization transiently reduced TGFbeta type I receptor levels in the prostate epithelium, but not in stroma, between days 6-15, whereas there was no effect on TGFbeta type II receptor. Levels of the intracellular signal Smad2 (52 kDa) were detected in epithelial cells but were not altered after estrogenization. To analyze the functional status of the TGFbeta signaling pathway, immunocytochemistry was performed for p21(cip-1/waf-1), a cyclin-dependent kinase inhibitor that is inducible by TGFbeta1 in the prostate. Transient nuclear localization of p21(cip-1/waf-1) was normally observed in epithelial cells between days 6-15 and was associated with entry of cells into a terminal differentiation pathway. Neonatal estrogenization prevented this transient expression of p21(cip-1/waf-1). The present findings demonstrate that the TGFbeta signaling system is perturbed at several levels in the estrogenized prostate, which may in part account for the epithelial cell differentiation blockade as well as the proliferation of periductal fibroblasts in this model.

Fibronectin (Fn) binds to fibrin in clots by covalent and non-covalent interactions. The N- and C-termini of Fn each contain one non-covalent fibrin-binding site, which are composed of type 1 (F1) structural repeats. We have previously localized the N-terminal site to the fourth and fifth F1 repeats (4F1.5F1). In the current studies, using proteolytic and recombinant proteins representing both the N- and C-terminal fibrin-binding regions, we localized and characterized the C-terminal fibrin-binding site, compared the relative fibrin-binding activities of both sites and determined the contribution of each site to the fibrin-binding activity of intact Fn. By fibrin-affinity chromatography, a protein composed of the 10F1 repeat through to the C-terminus of Fn (10F1-COOH), expressed in COS-1 cells, and 10F1-12F1, produced in Saccharomyces cerevisiae, displayed fibrin-binding activity. However, since 10F1 and 10F1.11F1 were not active, the presence of 12F1 is required for fibrin binding. A proteolytic fragment of 14.4 kDa, beginning 14 residues N-terminal to 10F1, was isolated from the fibrin-affinity matrix. Radio-iodinated 14.4 kDa fibrin-binding peptide/protein (FBP) demonstrated a dose-dependent and saturable binding to fibrin-coated wells that was both competitively inhibited and reversed by unlabelled 14.4 kDa FBP. Comparison of the fibrin-binding affinities of proteolytic FBPs from the N-terminus (25.9 kDa FBP), the C-terminus (14.4 kDa) and intact Fn by ELISA yielded estimated Kd values of 216, 18 and 2.1 nM, respectively. The higher fibrin-binding affinity of the N-terminus was substantiated by the ability of both a recombinant 4F1.5F1 and a monoclonal antibody (mAb) to this site to maximally inhibit biotinylated Fn binding to fibrin by 80%, and by blocking the 90% inhibitory activity of a polyclonal anti-Fn, by absorption with the 25.9 kDa FBP. We propose that whereas the N-terminal site appears to contribute to most of the binding activity of native Fn to fibrin, the specific binding of the C-terminal site may strengthen this interaction

BACKGROUND: Transforming growth factor betas (TGF-betas) are multifunctional polypeptides that have been suggested to influence tumor growth. They mediate their functions via specific cell surface receptors (type I ALK5 and type II TGF-beta receptors). The aim of this study was to analyze the roles of the three TGF-betas and their signaling receptors in human hepatocellular carcinoma (HCC). METHODS: HCC tissue samples were obtained from 18 patients undergoing partial liver resection. Normal liver tissues from 7 females and 3 males served as controls. The tissues for histological analysis were fixed in Bouin's solution and paraffin embedded. For RNA analysis, freshly obtained tissue samples were snap frozen in liquid nitrogen and stored at -80 degrees C until used. Northern blot analysis was used in normal liver and HCC to examine the expression of TGF-beta1, -beta2, -beta3 and their receptors: type I ALK5 (TbetaR-I ALK5), type II (TbetaR-II), and type III (TbetaR-III). Immunohistochemistry was performed to localize the corresponding proteins. RESULTS: All three TGF-betas demonstrated a marked mRNA overexpression in HCC in comparison with normal controls, whereas the levels of all three TGF-beta receptors showed no significant changes. Intense TGF-beta1, TGF-beta2, and TGF-beta3 immunostaining was found in hepatocellular carcinoma cells and in the perineoplastic stroma with immunohistochemistry, whereas no or mild immunostaining was present in the normal liver. For TbetaR-I ALK5 and TbetaR-II, the immunostaining in both HCC and normal liver was mild to moderate, with a slightly higher intensity in the normal tissues. CONCLUSION: The upregulation of TGF-betas in HCC suggests an important role for these isoforms in hepatic carcinogenesis and tumor progression. Moreover, the localization of the immunoreactivity in both malignant hepatocytes and stromal cells suggests that TGF-betas act via autocrine and paracrine pathways in this neoplasm

BACKGROUND: Human immunodeficiency virus-associated nephropathy (HIVAN) is a renal disease of unknown pathogenesis. Recent evidence suggests that the fibrogenic cytokine transforming growth factor-beta (TGF-beta) might be involved. We hypothesized that overproduction of TGF-beta in the kidney might be involved in the pathogenesis of HIVAN. METHODS: The mRNA and protein expression of TGF-beta isoforms, TGF-beta 1, TGF-beta 2, and TGF beta 3, deposition of matrix proteins induced by TGF-beta, and levels of HIV Tat protein were studied in HIVAN. Controls included normal and diseased kidneys from HIV-positive and -negative patients. The ability of Tat to induce production of TGF-beta and matrix proteins was also studied in human mesangial cells. RESULTS: Normal kidneys, thin basement membrane nephropathy, and minimal change disease were negative for the three TGF-beta isoforms and Tat. In HIVAN, levels of TGF-beta isoforms and Tat were significantly increased, along with the expression of TGF-beta mRNA and deposition of matrix proteins stimulated by TGF-beta. Increased levels of TGF-beta isoforms, but not Tat, were also found in other glomerular diseases characterized by matrix accumulation. HIV infection, in the absence of HIVAN, was not associated with an increase in TGF-beta or Tat expression. Tat stimulated the expression and production of TGF-beta 1 and matrix proteins by human mesangial cells. CONCLUSIONS: Our findings suggest that overproduction of TGF-beta is involved in the pathogenesis of HIVAN

Uncontrolled cellular proliferation is a hallmark of cancer. Thus, a relevant and important question is how cancer cells have escaped from normal growth regulatory mechanisms to become malignant and, further, what events favor progression and metastasis. Growth regulatory proteins of the transforming growth factor-beta family (TGF-beta) are one of the few classes of endogenous inhibitors of cell growth. Contrary to the first notion that these proteins may be downregulated in cancer cells to promote their growth, generally it has been otherwise found that there is a marked increase in the expression of TGF-beta mRNA and protein in human cancers (in vivo), including those of the pancreas, colon, stomach, lung, endometrium, prostate, breast, brain, and bone. Furthermore, in many of these cancers high expression correlates with more advanced stages of malignancy and decreased survival. The increased expression of TGF-beta is usually accompanied by a loss in the growth inhibitory response to TGF-beta. For example, certain tumor cells in culture (i.e., colon carcinoma and glioblastoma multiforme) demonstrate a progressive loss of the growth inhibitory response to TGF-beta that varies directly with the malignant stage of the original tumor, and the most aggressive forms actually switch to being autocrine and/or paracrine growth stimulated by TGF-beta. The study of the molecular events associated with the escape of tumor cells from growth regulation by TGF-beta has provided insight into mechanisms underlying carcinogenesis. The mechanisms for upregulation of TGF-beta are unknown. However, once malignant cells lose their growth inhibitory response to TGF-beta and produce massive amounts of these proteins, the increased expression of TGF-beta provides a selective advantage for tumor cell survival as TGF-betas are also angiogenic and have potent immunosuppressive effects, including specifically inhibiting tumoricidal natural and lymphocyte-activated killer cells. In light of the significant role for TGF-betas in regulating cell growth, it is not surprising that in more recent years studies have shown that specific genetic alterations involved in the signaling pathway for TGF-beta-mediated growth inhibition have occurred in many human cancers. Specific defects in TGF-beta receptors, TGF-beta-related-signal transduction/gene activation, and TGF-beta-regulated cell cycle proteins, have all been implicated in the oncogenesis of many human cancers. In this context, components of the TGF-beta growth response pathway are considered to be tumor suppressor genes, as absence (or malfunction) of one or more receptors or signaling proteins would have the potential to cause loss of growth regulation. More recently, the posttranslational reduction of levels of the cyclin-dependent kinase inhibitor (CKI), p27kip1, which mediates TGF-beta growth inhibition, provides an additional means for cancer cells to escape negative growth regulation by TGF-beta. This review provides background information on TGF-beta and updates the status of our knowledge of the role for TGF-beta in specific human malignancies. Understanding the molecular events involved in TGF-beta function in normal cells and its lack of function in tumor cells should identify novel therapeutic targets in human cancers

Members of the Transforming Growth Factor-beta (TGF-beta) family are one of the few endogenous inhibitors of cell growth. As uncontrolled cellular proliferation is a hallmark of cancer, an important question to address is how cancer cells escape normal growth regulatory mechanisms to become malignant. In this context, components of the TGF-beta growth response pathway are considered to be tumor suppressor genes, as absence of one or more of TGF-beta receptor and signaling proteins cause loss of cell growth regulation through an inability to regulate proteins that directly block cells in G1 phase of the cell cycle. Endometrial carcinoma (ECA) provides an excellent paradigm to study the changes that accompany loss of TGF-beta-mediated growth, control as a function of neoplastic development, since it is generally preceded by complex hyperplasia. Type 1 ECA is characterized as an estrogen-induced cancer, which responds well to progestin therapy. Since it has become increasingly evident that steroids can regulate growth through growth factors, ECA is also an ideal model for investigating the role for gonadal steroids in the loss of TGF-beta growth regulation in the etiopathogenesis of ECA. Thus, hormonal carcinogenesis adds another level of complexity in studying loss of growth regulation in human cancers. The purpose of this review is to 1) provide the most current background information on how TGF-beta functions including its activation, receptors, signal transduction mechanisms, and control of the cell cycle. 2) present recent information that shows how malignant cells subvert the growth inhibitory effects of TGF-beta by incurring defects in every aspect of the pathway that mediates the TGF-beta growth inhibitory response, and 3) describe the putative role for TGF-beta in the oncogenesis of ECA, provided primarily by the results from our laboratory. Understanding the molecular events involved in TGF-beta function in normal cells and its lack of function in tumor cells should identify novel therapeutic targets in human cancers

BACKGROUND: Transforming growth factor betas (TGF-betas) are a group of homologous polypeptides that exert pleiotropic effects on various cell types and stimulate the formation of extracellular matrix and fibrosis. To evaluate whether TGF-beta isoforms (TGF-beta1, TGF-beta2 and TGF-beta3) and their receptors (types I-III) are also of importance in the pathophysiology of liver cirrhosis, we analysed their concomitant expression and localization in human liver cirrhosis. PATIENTS: Cirrhotic liver tissue samples were obtained from 17 patients (four women, 13 men) with a median age of 41 years (range 22-67). Normal liver tissues from ten patients (seven women, three men) with a median age of 55 years (range 45-75) served as controls. METHODS: The tissues were fixed in Bouin's solution and paraffin-embedded for histological analysis. For RNA analysis, freshly obtained tissue samples were snap-frozen in liquid nitrogen and stored at -80 degrees C until analysed. Northern blot analysis was used to examine the expression of TGF-beta1, beta2 and beta3 and their receptors, type I (TbetaR-I), type II (TbetaR-II) and type III (TbetaR-III). Immunohistochemistry was performed to determine the localization of the corresponding proteins in the normal and the cirrhotic liver. RESULTS: Northern blot analysis revealed enhanced expression (P < 0.05) of TGF-beta1 (twofold increase), TGF-beta2 (threefold increase) and TGF-beta3 (8.5-fold increase) and of TbetaR-II (threefold increase) mRNA in liver cirrhosis in comparison with normal controls. In contrast, TbetaR-I (ALK-5) and TbetaR-III mRNA expression showed no significant changes. No TGF-beta isoform immunoreactivity was present in hepatocytes in either normal livers or in liver cirrhosis. However, in liver cirrhosis, intense TGF-beta1 immunoreactivity was present in bile duct and ductular epithelial cells (including ductular proliferations) and in inflammatory cells. In a few sinusoidal lining cells, faint TGF-beta1 and moderate TGF-beta2 immunoreactivity was present. TGF-beta3 immunostaining was present in bile duct and ductular epithelial cells, in inflammatory cells and in fibroblast-like spindle cells in liver cirrhosis. For TbetaR-I and TbetaR-II, the immunoreactivity was localized in hepatocytes and biliary cells in normal and cirrhotic liver tissues, with higher intensity for TbetaR-II in the cirrhotic liver. CONCLUSION: Enhanced expression of all three TGF-bea isoforms and of TbetaR-II in liver cirrhosis suggests their involvement in this fibrotic disorder. The higher immunoreactivity of the three TGF-beta isoforms in the bile duct epithelial cells in cirrhotic tissues suggests a possible role of these cells in the pathogenesis of liver cirrhosis

Although transforming growth factor (TGF)-beta1 is a potent growth inhibitor of normal epithelial cells including colonocytes, TGF-beta1 has also been implicated as an enhancer of colon cancer metastasis. Decreasing TGF-beta1 protein levels in the metastatic U9 colon cancer cell line by antisense methodology decreased both U9 cell metastasis to the liver and s.c. tumor formation in a nude mouse system, and the tumors that did arise had regained TGF-beta1 expression (F. Huang et al, Cell Growth Differ., 6: 1635-1642, 1995). In addition, in a clinical immunohistochemistry study, colon cancers with elevated TGF-beta1 protein levels were found to be 18 times more likely to recur as distant metastases than colon cancers expressing low TGF-beta1 levels, after resection of the primary tumor (E. Friedman et al, Cancer Epidemiol. Biomark. Prev., 4:549-554, 1995). Because both studies implicated TGF-beta1 in colon cancer metastasis, we wished to know whether a selection bias for TGF-beta1 was maintained in metastatic cells or was only a property of the primary site tumors that were likely to metastasize. TGF-beta1 levels were measured using two different antibodies in paired primary site cancers and their metastases by immunohistochemistry and, in selected cases, by Western blot analysis. In 16 of 21 cases (76%) with antibody G and 23 of 31 cases (74%) with antibody P, higher expression of TGF-beta1 was found in colon cancer cells invading local lymph nodes compared with primary site colon cancer cells, or (2 and 6 cases, respectively) high TGF-beta1 expression in the primary site cancer was maintained in invasive cells. Analysis by Western blotting using both antibodies also demonstrated that higher levels of TGF-beta1 protein were found in metastases compared with the primary site tumor or normal tissue. Additional cases of paired primary site colon cancer, local lymph node metastases, and cancer cells metastasizing to distant sites were examined. In six of eight such cases (75%), TGF-beta1 levels were increased in both invasive cell populations compared with the primary site cancer (five cases), or high levels in the primary site cancer were maintained in the metastatic cells (one case). These data suggest that TGF-beta1 plays a role in promoting colon cancer metastasis throughout the metastatic process in roughly 75% of cases. TGF-beta1 may increase metastasis by paracrine mechanisms, such as suppression of local immune response or increased angiogenesis, as was seen with the U9 cell line. In those cancers with nonmutated TGF-beta receptors and nonmutated smad proteins like U9 cells, TGF-beta1 could also act in an autocrine manner to increase invasion by increasing cell motility (Hsu et al., Cell Growth Differ., 5: 267-275, 1994)

The accumulation of proteoglycans (PGs) in atherosclerosis contributes to disease progression and stenosis and may partly depend on local regulation by growth factors such as platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-beta. In this study, the distribution of the major extracellular PGs is compared with that of PDGF and TGF-beta isoforms in developing lesions of atherosclerosis from hypercholesterolemic nonhuman primates. Strong immunostaining for decorin, biglycan, versican, and hyaluronan is observed in both intermediate and advanced lesions. Perlecan staining is weak in intermediate lesions but strong in advanced lesions in areas bordering the plaque core. Immunostaining for PDGF-B and TGF-beta1 is particularly prominent in macrophages in intermediate and advanced lesions. In contrast, TGF-beta2 and TGF-beta3 and PDGF-A are present in both macrophages and smooth muscle cells. Overall, PG deposits parallel areas of intense growth factor immunostaining, with trends in relative localization that suggest interrelationships among certain PGs and growth factors. Notably, decorin and TGF-beta1 are distributed similarly, predominantly in the macrophage-rich core, whereas biglycan is prominent in the smooth muscle cell matrix adjoining TGF-beta1-positive macrophages. Versican and hyaluronan are enriched in the extracellular matrix adjacent to both PDGF- and TGF-beta1-positive cells. These data demonstrate that PG accumulation varies with lesion severity, structural characteristics, and the proximity of PDGF and TGF-beta

OBJECTIVES: To determine which mechanisms are involved in pancreatic remodeling, repair, and fibrosis after acute necrotizing pancreatitis (NP) in humans. SUMMARY BACKGROUND DATA: Transforming growth factor betas (TGF-betas) are multifunctional polypeptides that have been implicated in the regulation and formation of extracellular matrix and fibrosis. They exert their functions by binding to specific receptors. In this study, we analyze the expression of TGF-beta1, TGF-beta2, and TGF-beta3 and their receptors type I (Tbeta-RI [ALK5]), type II (Tbeta-RII), and type III (Tbeta-RIII) in NP. PATIENTS: Pancreatic tissue samples were obtained from 6 female and 8 male patients with a median age of 65 years (range, 37 to 77 years) undergoing surgery for NP. The median Ranson score of the patients was 6 (range, 2 to 9). The operation was performed a median 5.5 days (range, 4 to 17 days) after the onset of acute pancreatitis. Pancreatic tissue obtained from 12 previously healthy organ donors (6 male, 6 female; median age of 43 years) served as controls. METHODS: The expression of TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), Tbeta-RII, Tbeta-RIII, and collagen type I mRNA was analyzed by Northern blot analysis. In addition, immunohistochemical analysis using polyclonal antibodies was performed to detect TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), and Tbeta-RII. RESULTS: Northern blot analysis showed an increase in TGF-betas and their receptors in NP tissue samples compared with samples from normal controls. The increase was 3.5-fold for TGF-beta1 (p < 0.05), 2.7-fold for TGF-beta2 (p < 0.05), 3.5-fold for TGF-beta3 (p < 0.05), 10-fold for Tbeta-RI (ALK5) (p < 0.05), 5.7-fold for Tbeta-RII (p < 0.05), and 1.4-fold for Tbeta-RIII (not significant). Collagen type I mRNA was also markedly increased in NP samples and correlated with the level of TGF-betas. Immunohistochemical analysis demonstrated intense TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), and Tbeta-RII immunoreactivity in the remaining acinar and ductal cells in most NP samples; in the normal control pancreas, there was weak to moderate immunoreactivity for these factors only in some acinar cells and a few ductal cells. CONCLUSION: The marked increase in expression of TGF-betas and their signaling receptors Tbeta-RI (ALK5) and Tbeta-RII suggests a role for TGF-betas in the repair process after the onset of NP in humans and raises the possibility that TGF-betas might be involved in tissue remodeling and the fibrotic reaction that occurs in the pancreas after necrosis