Genetic changes in the transforming growth factor beta (TGF-beta) type II receptor gene in human gastric cancer cells: correlation with sensitivity to growth inhibition by TGF-beta

A Deletion in the Gene for Transforming Growth Factor β Type I Receptor Abolishes Growth Regulation by Transforming Growth Factor β in a Cutaneous T-Cell Lymphoma

Spontaneous regression of skin lesions is characteristic of lymphomatoid papulosis (LyP), a clonal cutaneous lymphoproliferative disorder. A minority of LyP patients progress to anaplastic large cell lymphoma (ALCL) in which skin lesions no longer regress and extracutaneous dissemination often occurs. In 1 such case, we developed a tumor cell line, JK cells, and show that these cells are resistant to the growth inhibitory effects of transforming growth factor β (TGF-β) due to the loss of cell surface expression of the TGF-β type I receptor (TβR-I). Reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing of JK cell TβR-I cDNA clones identified a deletion that spanned the last 178 bp of exon 1, including the initiating methionine. Hybridization of a radiolabeled fragment internal to the deletion was detected in the genomes of TGF-β–responsive cells, but not in JK cells, indicating that they contain no wild-type TβR-I gene. PCR primers that flanked the deleted TβR-I region amplified a single band from JK cell genomic DNA that lacked the last 178 bp of exon 1 and all of the ≈ 5 kb of intron 1. This JK cell-specific genomic TβR-I PCR product was distinct from products amplified from TGF-β–responsive cells and was also readily detected in tumor biopsies obtained before the establishment of the JK cell line. Our results identify the first inactivating mutation in TβR-I gene in a human lymphoma that renders it insensitive to growth inhibition by TGF-β.

The TGF-beta signaling inhibitor Smad7 enhances tumorigenicity in pancreatic cancer

Transforming growth factor-beta (TGF-beta) signaling is dependent on the heterodimerization of the type II TGF-beta receptor (TbetaRII) with the type I TGF-beta receptor (TbetaRI). Activated TbetaRI then mediates TGF-beta signals by inducing the phosphorylation of Smad2 and/or Smad3, which separately hetetorodimerize with Smad4 and translocate to the nucleus. Phosphorylation of Smad2/Smad3 by activated TbetaRI is inhibited by two newly discovered members of the Smad family, Smad6 and Smad7. We now report that Smad7 mRNA levels are increased in human pancreatic cancer by comparison with the normal pancreas, and that by in situ hybridization, Smad7 is over-expressed in the cancer cells within the tumor mass. Stable transfection of COLO-357 human pancreatic cancer cells with a full-length Smad7 construct leads to complete loss of the growth inhibitory response to TGF-beta1, without altering TGF-beta1-mediated induction of PAI-I. Furthermore, Smad7 transfected COLO-357 cells display enhanced anchorage-independent growth and accelerated growth in nude mice. These findings point to a previously unrecognized mechanism for selective suppression of TGF-beta-mediated growth inhibition in cancer cells that allows for continued activation of the PAI-I promoter by TGF-beta1, which may act to enhance the tumorigenicity of certain cancer cells.

Differential effects of transforming growth factor-beta(s) and glial cell line-derived neurotrophic factor on gene expression of presenilin-1 in human post-mitotic neurons and astrocytes

Mutations in the presenilin-1 gene are linked to the majority of early-onset familial Alzheimer's disease cases. We have previously shown that the expression of transforming growth factor-beta is altered in Alzheimer's patients, compared to controls. Here we examine presenilin- expression in human post-mitotic neurons (hNT cells), normal human astrocytes, and human brain tumor cell lines following treatment with three isoforms of transforming growth factor-beta, or glial cell line-derived neurotrophic factor, a member of the transforming growth factor-beta superfamily. As the NT2/D1 teratocarcinoma cell line is treated with retinoic acid to induce differentiation to hNT cells, presenilin-1 messenger RNA expression is dramatically increased. Furthermore, there is a 2-3-fold increase in presenilin-1 messenger RNA expression following treatment of hNT cells with growth factors and similar results are found by Western blotting and with immunohistochemical staining for presenilin-1 protein. However, treatment of normal human astrocytes with cytokines results in minimal changes in presenilin-1 messenger RNA and protein. Interestingly, the expression of presenilin-1 in human U87 MG astrocytoma and human SK-N-SH neuroblastoma cells is only increased when cells are treated with glial cell line-derived neurotrophic factor or transforming growth factor-beta3. These findings suggest that endogenous presenilin-1 gene expression in human neurons can be induced by growth factors present in normal and diseased brain tissue. Cytokines may play a major role in regulating expression of presenilin-1 which may affect its biological actions in physiological and pathological conditions.

Transforming growth factor-beta responsiveness in DPC4/SMAD4-null cancer cells

DPC4/SMAD4 is a candidate tumor suppressor gene with a strikingly high frequency of gene alterations in pancreatic cancer that suggests a discrete role for DPC4 in these tumors. DPC4 tumor-suppressive function has been implicated to mediate the transforming growth factor-beta (TGFbeta)-suppressive pathway; however, in a DPC4-null pancreatic cancer cell line, TGFbeta growth-inhibitory and transcriptional responses were found to be DPC4-independent. This was observed within native cells having a natural homozygous deletion and in clones engineered for stable expression of wild-type DPC4 integrated into the genome. This observation contrasted with the absolute DPC4 dependence of TGFbeta responses in a breast cancer cell line studied in parallel. This growth-inhibitory response to TGFbeta in DPC4-null cells relied on an intact ras effector pathway. These data further suggest a major categorization of TGFbeta responses into DPC4-dependent and -independent signaling pathways and specifically suggest that disruption of the TGFbeta-independent signal might be a basis of selection for the emergence of DPC4 alterations during tumorigenesis in the pancreas and other sites.

Does mutation of transforming growth factor-beta type II receptor gene play an important role in colorectal polyps?

Mutations in the transforming growth factor-beta type II receptor (RII) gene that remain uncorrected due to mutation and inactivation of mismatch repair genes play an important role in hereditary nonpolyposis colorectal cancer (HNPCC) and in a subset of sporadic colorectal cancers. Some colorectal cancers develop from colorectal polyps. To elucidate the role of the RII gene in the generation of colorectal polyps, we analyzed 137 colorectal polyps from 100 patients for RII mutations and microsatellite instability (MSI). MSI was detected in three of 36 polyps from 25 patients. For one of these three polyps, the mobilities of the PCR products between polyp and nonpolyp tissues was different for only one microsatellite marker, and for the other two polyps the mobilities were different for more than two markers. These two polyps were obtained from one patient with ascending colon carcinoma and suspected HNPCC based on his clinical profile and family history. An RII mutation was detected in only one of these two polyps. RII may play a minor role in sporadic colorectal polyps. RII gene analysis in colorectal polyps may be a useful screening measure for potential HNPCC patients.

Lack of responsiveness to TGF-beta1 in a thyroid carcinoma cell line with functional type I and type II TGF-beta receptors and Smad proteins, suggests a novel mechanism for TGF-beta insensitivity in carcinoma cells

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine. In the present study we have investigated the expression of TGF-beta receptors (TbetaR's) and SMAD proteins in non-neoplastic and neoplastic thyroid follicle cells. We found expression of all TbetaR's (type I, II and III) and SMAD proteins analysed (Smad2, Smad3, Smad4, Smad6 and Smad7). Five out of six human anaplastic thyroid carcinoma cell lines were growth inhibited by addition of TGF-beta1, and therefore considered to be TGF-responsive. One cell line however, HTh 7, did not respond to TGF-beta1 with growth inhibition, induction of the extracellular matrix protein fibronectin or immediate early genes junB, Smad6 and Smad7 mRNA. Analysis of the TGF-beta intracellular signalling pathway in HTh 7 cells showed that receptors were capable of signalling, e.g. Smad2 phosphorylation and SMAD nuclear translocation. In summary, our data shows abundant expression of TGF-beta signalling components in thyroid follicle cells, and the escape from TGF-beta sensitivity in one anaplastic thyroid carcinoma despite an apparently functional TGF-beta/SMAD-signalling pathway, indicating a novel mechanism for TGF-beta insensitivity.

Transforming growth factor-beta type II receptor confers tumor suppressor activity in murine renal carcinoma (Renca) cells

OBJECTIVES

To demonstrate that the introduction of the transforming growth factor-beta (TGF-beta) type II receptor (TbetaR-II) decreases tumorigenicity in an aggressive murine renal carcinoma line, Renca. These cells do not express TbetaR-II. Because the presence of TbetaR-II in benign epithelial cells is ubiquitous, the ability to restore tumor suppressor activity in the Renca cell line with its introduction would elucidate the role of TbetaR-II as a tumor suppressor gene.

METHODS

Renca cells were stably transfected with a retrovirus-mediated TbetaR-II expression vector. In vitro sensitivity to growth inhibitory effect of TGF-beta was assessed by the 3H-thymidine incorporation assay. For in vivo testing, xenograft tumors were produced by subcutaneous injection of tumor cells into immunodeficient nude mice. The tumorigenicity of these TbetaR-II transfected cells was tested. Wild-type Renca cells and cells transfected with the control vector were also tested for comparison.

RESULTS

Expression of TbetaR-II mRNA was evident in Renca cells after transfection with the TbetaR-II construct. In vitro sensitivity to the growth inhibitory effect of TGF-beta was restored. This effect of TGF-beta was reversible with a neutralizing antibody specific for the extracellular domain of TbetaR-II. Xenografts grown from TbetaR-II transfected cells were significantly smaller, weighed less, and developed tumors later than those developed from wild-type Renca cells and those transfected with the control vector.

CONCLUSIONS

We conclude that TbetaR-II is a central mediator of tumorigenicity in Renca cells. As with other tumor suppressor genes, the loss of TbetaR-II expression allows for the development of an aggressive phenotype.

Mechanistic aspects of green tea as a cancer preventive: effect of components on human stomach cancer cell lines

It is now well accepted that (-)-epigallocatechin gallate (EGCG) inhibits carcinogenesis in the digestive tract in rodents. To understand the mechanisms of anticarcinogenesis, we first studied growth inhibition by EGCG in human stomach cancer cell lines established at Seoul National University (SNU cell lines). Inhibition by EGCG of [3H]thymidine incorporation into eight SNU cell lines was examined, in relation to transforming growth factor-beta (TGF-beta) responsiveness. Various tea polyphenols derived from green tea and black tea induced growth inhibition and apoptosis of human stomach cancer cell line KATO III, and inhibition of tumor necrosis factor-alpha (TNF-alpha) release from the cells, in the order of (-)-epicatechin gallate (ECG), EGCG, (-)-epigallocatechin (EGC), teaflavins (TF) and (-)-epicatechin (EC). In addition, we demonstrated that EGCG inhibited TNF-alpha gene expression in KATO III cells, as well as okadaic acid-induced AP-1 and NF-kappa B activation. The inhibitory potencies of EGCG for AP-1 and NF-kappa B binding to DNA were different between KATO III cells and mouse fibroblast cell line BALB/3T3. Thus, EGCG and other tea polyphenols may interact with various transcription factors, in addition to AP-1 and NF-kappa B, in nuclei of various cells, resulting in inhibition of TNF-alpha gene expression and TNF-alpha release.

Dual roles of peptic ulcer in the carcinogenesis or extension of early gastric cancer

BACKGROUND

Early gastric cancer (EGC) often coexists with peptic ulcer. In this study we investigated the roles of peptic ulcer in the carcinogenesis and extension of gastric cancer.

METHODS

The clinicopathological characteristics of EGC and peptic ulcer and their relationship, as well as that of the background intestinal metaplasia, were compared among the following three groups: patients with peptic ulcer only inside the EGC (Contained group, 53 patients); patients with peptic ulcer only outside the EGC (Separate group, 26 patients); and patients of EGC with no peptic ulcer (Absent group, 43 patients).

RESULTS

In the Separate group, a male preponderance was observed (P = .006), and all EGCs developed in the middle or lower third of the stomach (P = .06). Most of the EGCs were an intestinal type of cancer with severe background intestinal metaplasia. Topographically, 88% of the peptic ulcers in the Separate group developed proximal to the EGC. On the other hand, in the Contained group, most EGCs developed in the middle third of the stomach with an intestinal/diffuse type ratio of 1:1. Peptic ulcers inside the EGC were significantly more shallow than those that developed outside the EGC (P = 0.008). Although the incidences of submucosal cancer were nearly the same among the three groups, the maximum cancer diameter tended to be increased in the Contained group compared to that in the Absent group, and the incidence of lymph node involvement tended to be higher in the Contained group (8%) as compared with the other two groups (4%-5%).

CONCLUSIONS

These results suggest that peptic ulcer outside the EGC contributes to the development of the intestinal type of EGC, with the background of more severe intestinal metaplasia during the peptic ulcer healing processes, whereas peptic ulcer inside the EGC develops secondary to EGC and favors cancer extension and metastasis. Peptic ulcer associated with EGC can be considered to exert different biological roles in the carcinogenesis or extension of ECG according to the location of the peptic ulcer.

Gene mutation of transforming growth factor beta1 type II receptor in hepatocellular carcinoma

Alteration of transforming growth factor beta1 (TGF-beta1) type II receptor (RII) appears to cause unresponsiveness to TGF-beta1 in tumorigenic cells. Defect in the mononucleotide repeat sequence, i.e., poly A region of TGF-beta1RII gene has been reported to be related to replication error-positive cancer cells. We examined if there is any TGF-beta1RII mutation in a coding microsatellite in hepatocellular carcinoma (HCC). Genomic DNAs were extracted from formalin-fixed, paraffin-embedded liver tissues obtained at surgery or autopsy in 3 normal individuals and 96 patients with hepatitis C virus-induced chronic liver disease; 3 with chronic hepatitis, 20 with liver cirrhosis and 73 with HCC. The DNA was PCR-amplified at 2 segments of TGF-beta1RII: poly A region which includes the (A)10 microsatellite sequence, and poly GT region. PCR products were directly sequenced. DNA from normal and patients with chronic liver disease contained the 10 wild-type adenines but 3 cases with liver cirrhosis in whom there were only 9 adenines within poly A tract. This microdeletion of one A resulted in a frameshift and truncated a predicted length of amino acids. In HCC lesions, the same deletion was noted in 4 cases (25%) of well-differentiated type, 10 (40%) of moderately differentiated type, 18 (53%) of poorly differentiated type. None of the lesions had mutations within the GT region. Our findings indicate that one adenine deletion of poly A microsatellite tract within TGF-beta1RII is frequently detected in patients with HCC, and the mutation may cause the abrogation of the function of TGF-beta1RII gene.

Establishment and characterization of human laryngeal squamous cell carcinoma cell lines

OBJECTIVES

Six human laryngeal squamous cell carcinoma cell lines (SNU-46, -585, -899, -1066, -1076, -1214) established from Korean patients are reported.

STUDY DESIGN

In vitro culture of six squamous cell carcinoma cell lines derived from primary tumors of the larynx. Description of the cell line phenotypes and determination of molecular characteristics.

METHODS

Six laryngeal squamous cell carcinoma cell lines were cultured. The cell phenotypes, including the histopathology of the primary tumors and in vitro growth characteristics, were determined. Molecular characterization was also performed, including DNA fingerprinting analysis and abnormalities of p15, p16, p53, and TGF-betaRII genes by polymerase chain reaction-based single strand conformation polymorphism and sequencing analysis.

RESULTS

All cell lines grew as adherent cells; five lines grew as monolayers and one other line grew as stratifying colonies. All lines showed 1) high viability (75%-92%) with various doubling times (36-96 h); 2) absence of Mycoplasma and other bacteria; and 3) genetic heterogeneity by DNA profile analysis. p53 Mutations were found in three lines and p16 mutations were observed in five cell lines. TGF-betaRII mutations were found in two lines: one line had frameshift mutation and another line had a missense mutation at the kinase domain.

CONCLUSIONS

These newly established and characterized laryngeal squamous cell carcinoma cell lines will be useful for investigating the biologic characteristics of laryngeal cancer.

Rapid induction of p21WAF1 but delayed down-regulation of Cdc25A in the TGF-beta-induced cell cycle arrest of gastric carcinoma cells

Transforming growth factor-beta (TGF-beta) is a multifunctional polypeptide that inhibits cellular proliferation in most epithelial cells. cdk4 and several cyclin-dependent kinase (cdk) inhibitors (p15INK4B, p21WAF1/Cip1 and p27Kip1) have been implicated in the TGF-beta-induced cell cycle arrest. More recently, down-regulation of Cdc25A, a cdk activator, was additionally suggested as a mechanism underlying growth inhibition by TGF-beta. The existence of diverse cellular mediators of TGF-beta, however, raises the question of whether their involvement might occur in a redundant manner or coordinately in a certain cell type. Using two TGF-beta-sensitive gastric carcinoma cell lines (SNU-16 and -620), we addressed the contributory roles of several cdk inhibitors, and of cdk4 and Cdc25A, in TGF-beta-induced cell cycle arrest by comparing their temporal expression pattern in response to TGF-beta. Among the cdk inhibitors examined, p21 mRNA was most rapidly (in less than 1 h) and prominently induced by TGF-beta. In contrast, p15 mRNA was more slowly induced than p21 in SNU-620 cells, and not expressed in SNU-16 cells harbouring homozygous deletion of p15. Western blotting results confirmed the rapid increase of p21, while opposite patterns of p27 expression were observed in the two cell lines. The down-regulation of Cdc25A mRNA occurred, but was more delayed than that of p15 or p21. Until G1 arrest was established, changes in the protein levels of both Cdc25A and cdk4 were marginal. Co-immunoprecipitation with anti-cdk4 antibody showed that induced p21 associates with cdk4 and that its kinase activity is reduced by TGF-beta, which kinetically correlates closely with G1 arrest following TGF-beta treatment of both cell lines. These results suggest that in certain human epithelial cells, p21 may play an early role in TGF-beta-induced cell cycle arrest, and its cooperation with other cdk inhibitors is different depending on cell type. Delayed down-regulation of Cdc25A and cdk4 may contribute to cell adaptation to the quiescent state in the two gastric carcinoma cell lines studied.

Truncation of the TGF-beta type II receptor gene results in insensitivity to TGF-beta in human gastric cancer cells

The transforming growth factor-beta (TGF-beta receptor system has been implicated in the development of resistance to the growth-inhibitory effects of TGF-beta. It has been reported that resistance to TGF-beta correlates with inactivation of the TGF-beta type II receptor (RII). In the present report, we examine the genetic changes in the TGF-beta RII gene of human gastric cancer cell lines, SNU-5 and SNU-668, which we had previously reported to express truncated TGF-beta RII transcripts. By independent PCR and Southern hybridization analysis of genomic DNA, we found that the genomic sequence of TGF-beta RII is truncated after exon 2 in SNU-5 and after exon 3 in SNU-668. This was confirmed by sequencing the TGF-beta RII cDNA cloned from a SNU-5 cDNA library. Predicted TGF-beta RII protein of SNU-5 cells based on sequencing data contains only a part of extracellular domain of TGF-beta RII. We demonstrate that cotransfection of 3TP-Lux and wild type TGF-beta RII restores the TGF-beta responsiveness in SNU-5 cells, suggesting that genetic changes in the TGF-beta RII gene of SNU-5 cells are responsible for the loss of sensitivity to TGF-beta. This is the first report demonstrating that truncation of the TGF-beta RII gene is an alternative mechanism to inactivate the TGF-beta signal transduction pathways.

Smad3-Smad4 and AP-1 complexes synergize in transcriptional activation of the c-Jun promoter by transforming growth factor beta

Transcriptional regulation by transforming growth factor beta (TGF-beta) is a complex process which is likely to involve cross talk between different DNA responsive elements and transcription factors to achieve maximal promoter activation and specificity. Here, we describe a concurrent requirement for two discrete responsive elements in the regulation of the c-Jun promoter, one a binding site for a Smad3-Smad4 complex and the other an AP-1 binding site. The two elements are located 120 bp apart in the proximal c-Jun promoter, and each was able to independently bind its corresponding transcription factor complex. The effects of independently mutating each of these elements were nonadditive; disruption of either sequence resulted in complete or severe reductions in TGF-beta responsiveness. This simultaneous requirement for two distinct and independent DNA binding elements suggests that Smad and AP-1 complexes function synergistically to mediate TGF-beta-induced transcriptional activation of the c-Jun promoter.

Early castration-induced upregulation of transforming growth factor beta1 and its receptors is associated with tumor cell apoptosis and a major decline in serum prostate-specific antigen in prostate cancer patients

BACKGROUND

The mechanism behind castration-induced apoptosis in prostate cells is unknown, but data from other species suggest that transforming growth factor beta1 (TGF-beta1) may be involved.

METHODS

By using quantitative RT-PCR and immunohistochemistry, expression of TGF-beta1 and its receptors type I and II (RI and RII) was studied in normal and tumor areas of core biopsies taken before and 2-11 days after castration therapy. The TGF-beta responses were related to changes in apoptotic index and to changes in serum prostate-specific antigen (PSA).

RESULTS

In normal prostate tissue, apoptosis was generally increased by castration, and apoptosis was accompanied by an increase in TGF-beta1 and RII mRNA levels (P < 0.05). In tumors, apoptosis was seen only in 44% of the cases and in these, but not in the others, TGF-beta1, RI, and RII mRNA levels were increased (P < 0.05). In the patients showing a prognostically favorable PSA response (nadir PSA <5 ng/ml), but not in the others, RI and RII mRNA levels were significantly upregulated (P < 0.05).

CONCLUSIONS

Short-term upregulation of TGF-beta1 and its receptors is associated with apoptosis in human prostate and prostate cancer, and possibly with a favorable clinical outcome after castration therapy.

Inactivation of the transforming growth factor beta type II receptor in human small cell lung cancer cell lines

Transforming growth factor beta (TGF-beta) exerts a growth inhibitory effect on many cell types through binding to two types of receptors, the type I and II receptors. Resistance to TGF-beta due to lack of type II receptor (RII) has been described in some cancer types including small cell lung cancer (SCLC). The purpose of this study was to examine the cause of absent RII expression in SCLC cell lines. Northern blot analysis showed that RII RNA expression was very weak in 16 of 21 cell lines. To investigate if the absence of RII transcript was due to mutations, we screened the poly-A tract for mutations, but no mutations were detected. Additional screening for mutations of the RII gene revealed a GG to TT base substitution in one cell line, which did not express RII. This mutation generates a stop codon resulting in predicted synthesis of a truncated RII of 219 amino acids. The nature of the mutation, which has not previously been observed in RII, has been linked to exposure to benzo[a]-pyrene, a component of cigarette smoke. Since RII has been mapped to chromosome 3p22 and nearby loci are often hypermethylated in SCLC, it was examined whether the lack of RII expression was due to hypermethylation. Southern blot analysis of the RII promoter did not show altered methylation patterns. The restriction endonuclease pattern of the RII gene was altered in two SCLC cell lines when digested with Smal. However, treatment with 5-aza-2'-deoxycytidine did not induce expression of RII mRNA. Our results indicate that in SCLC lack of RII mRNA is not commonly due to mutations and inactivation of RII transcription was not due to hypermethylation of the RII promoter or gene. Thus, these data show that in most cases of the SCLC cell lines, the RII gene and promoter is intact in spite of absent RII expression. However, the nature of the mutation found could suggest that it was caused by cigarette smoking.

Smad6 suppresses TGF-beta-induced growth inhibition in COLO-357 pancreatic cancer cells and is overexpressed in pancreatic cancer

Transforming growth factor (TGF)-beta signaling is initiated by heterodimerization of TGF-beta receptor type I (TbetaRI) and type II (TbetaRII). Subsequently, the signal is transduced via Smad proteins, which upon phosphorylation and heterodimerization translocate to the nucleus and regulate gene transcription. Smad6 functions as an intracellular antagonist of TGF-beta signaling. In the present study we demonstrate that Smad6 is overexpressed in vivo in human pancreatic cancer cells. We also show that stable transfection of a full-length Smad6 construct into COLO-357 pancreatic cancer cells abrogates TGF-beta1 induced growth inhibition, and leads to enhanced anchorage-independent growth. Thus, enhanced expression of the TGF-beta signaling inhibitor Smad6 in pancreatic cancer may present a novel mechanism of TGF-beta resistance, which might have the potential to enhance the transformed phenotype of human cancer cells.

Frequent aberration of the transforming growth factor-beta receptor II gene in cell lines but no apparent mutation in pre-invasive and invasive carcinomas of the uterine cervix

The type II transforming growth factor-beta (TGF-beta) receptor (RII) gene located at 3p22 plays an important role in regulating growth and differentiation of epithelium, including that of the uterine cervix. Loss-of-function mutations of RII have frequently been found in gastrointestinal cancers, with a replication-error (RER) phenotype characterized by the presence of microsatellite instability (MI). In this study, genomic PCR, SSCP and DNA sequencing were conducted to investigate the coding sequences of the RII gene in cell lines (n = 5) and tissues (n = 15) of squamous carcinomas of the uterine cervix. Intragenic deletions were noted in 2 of 5 cervical-cancer cell lines (ME180 and HeLa cells). However, no mutation, other than DNA polymorphisms, was found in 15 cervical cancers with either alleleic loss at 3p22 (n = 11) or MI (n = 4). Further analysis of squamous intraepithelial lesions (SIL) with (n = 12) or without (n = 4) MI for the (A)10 change, a prototypic mutation found in over 90% of RER-positive colon cancers, also showed no aberration. Our study concludes that the RII gene is frequently disrupted in cervical-cancer cell lines, but is rarely mutated in CC and SIL tissues, including those showing MI or alleleic loss at 3p22. The underlined mechanism of genomic instability in CC and SIL may thus differ from that of colorectal cancer. The allelic loss at 3p22-24 in CC does not involve the coding sequence of the RII gene. The non-coding sequence of RII or an unidentified gene may be responsible for it.

Development of TGF-beta resistance during malignant progression

Transforming growth factor-beta (TGF-beta) is the prototypical multifunctional cytokine, participating in the regulation of vital cellular activities such as proliferation and differentiation as well as a number of basic physiological functions. The effects of TGF-beta are critically dependent on the expression and distribution of a family of TGF-beta receptors, the TGF-beta types I, II, and III. It is now known that a wide variety of human pathology can be caused by aberrant expression and function of these receptors. The coding sequence of the type II receptor (RII) appears to render it uniquely susceptible to DNA replication errors in the course of normal cell division. By virtue of its key role in the regulation of cell proliferation, TGF-beta RII should be considered as a tumor suppressor gene. High levels of mutation in the TGF-beta RII gene have been observed in a wide range of primarily epithelial malignancies, including colon and gastric cancer. It appears likely that mutation of the TGF-beta RII gene may be a very critical step in the pathway of carcinogenesis.

Desensitization of melanoma cells to autocrine TGF-beta isoforms

Previous studies have suggested that transforming growth factor-beta 1 (TGF-beta1) acts as an autocrine growth inhibitor on normal human melanocytes, while melanoma cells may not respond to this stimulus. The role of other TGF-beta isoforms such as TGF-beta2 and TGF-beta3 remained less well characterized. In the present study, the mRNA and protein levels of all three isoforms of TGF-beta were analyzed in a panel of human melanoma cell lines and in cultures of normal human melanocytes in vitro. Northern analysis showed that the degree of TGF-beta1, -beta2, -beta3 mRNA expression varied considerably in melanoma cells, whereas TGF-beta expression was very low in melanocytes. In melanoma cells, secreted amounts of TGF-beta1 and TGF-beta3 were found increased in comparison to normal melanocytes: 615 pg/ml vs. 118 pg/ml and 193 pg/ml vs. 30 pg/ml (mean values). In addition, low levels of TGF-beta2 were detected (mean value: 28 pg/ml). Although TGF-beta secretion increased, the proliferation of melanoma cells was found to be only moderately inhibited by TGF-beta isoforms, in contrast to its strong antiproliferative effect on normal human melanocytes: - 15%, -11%, and -18% vs. -52%, -46%, and -50% average inhibition at 0.5 ng/ml TGF-beta1, -beta2, and -beta3, respectively. The different efficacy of TGF-beta on melanocyte and melanoma cells was highly significant (P<0.0001); in addition, TGF-beta-dependent growth inhibition of melanoma cells from primary tumors vs. cells from metastases showed a trend for further decreased response for the metastatic populations (P< or = 0.075). Measurements of DNA synthesis revealed even more pronounced differences between melanocytes (-86%, -78%, and -80% inhibition, respectively, for TGF-beta1, -beta2, and -beta3) and melanoma cells (no inhibition). Our data show loss of responsiveness of melanoma cells to the growth-inhibitory function of TGF-beta isoforms but not of melanocytes. Although melanoma cells are not growth-inhibited by all three TGF-beta isoforms, they secrete significantly higher levels of TGF-beta, as compared to melanocytes. The reduced response indicates their escape from TGF-beta surveillance with ongoing tumor progression.

Overexpression of transforming growth factor beta-type II receptor reduces tumorigenicity and metastastic potential of K-ras-transformed thyroid cells

Expression of type II receptor of transforming growth factor beta (TbetaRII) is necessary for this factor to inhibit the growth of thyroid epithelial cells. In rat thyroid transformed cells, the resistance to transforming growth factor beta (TGFbeta) is associated with a decreased expression of TbetaRII mRNA and protein. Reduced TbetaRII expression has also been found in human thyroid differentiated and undifferentiated carcinomas. To investigate the role of TbetaRII in modulating the tumorigenic potential of k-ras-transformed thyroid cells, we transfected these cells with an expression vector carrying the human TbetaRII gene, regulated by an inducible promoter. Isolated clones, overexpressing TbetaRII, showed a reduction in the anchorage-dependent and -independent cell growth, compared with control k-ras-transformed cells. When transplanted in athymic nude mice, the transfected clones presented a decrease in tumorigenicity with respect to the highly malignant parental cells. Moreover, the diminished tumorigenic ability of the clones studied was accompanied by a statistically significant reduction in spontaneous and lung artificial metastases. Taken together, our data demonstrate that TbetaRII acts as a potent tumor suppressor gene when overexpressed in malignant thyroid cells.

Analyses of microsatellite instability and the transforming growth factor-beta receptor type II gene mutation in sporadic breast cancer and their correlation with clinicopathological features

To determine the incidence of microsatellite instability (MSI) and its relationship with both clinicopathologic parameters and patient survival, 101 cases of breast cancer were investigated. In addition, transforming growth factor-beta (TGF-beta) receptor type II (RII) gene mutation was also examined to clarify the relation to MSI in breast cancer development. MSI and RII gene mutation were screened by single strand conformation polymorphism (SSCP). The mutations of the RII gene were confirmed by a direct sequence. An association between the MSI status and the clinicopathological features was examined to assess the potential of the MSI status as a prognostic indicator in sporadic breast cancer cases. MSI was detected in 12 of 101 (11.9%) breast cancer cases. The positive MSI breast cancer cases showed relatively more advanced disease than negative MSI cases, and also exhibited relatively poorer prognoses. No RII gene mutations were observed in any of the breast cancer cases. Our data suggest that the MSI status may thus be a useful indicator for the prognosis of sporadic breast cancer cases. However, the breast seems to be an infrequent target organ for cancer development through RII gene mutations. As a result, tumor progression through this pathway appears to be related to organ specificity. For positive MSI breast cancers, other target genes therefore still need to be identified.

Transfection of the type I TGF-beta receptor restores TGF-beta responsiveness in pancreatic cancer

Transforming growth factor-beta (TGF-beta) signaling is initiated following heterodimerization of the type II TGF-beta receptor (TbetaRII) with the type I TGF-beta receptor (TbetaRI). Both receptors are required for TGF-beta responsiveness. In the present study, we characterized the actions of TGF-beta1 in T3M4 human pancreatic cancer cells, which express low levels of TbetaRI and high levels of TbetaRII. Cells were transiently transfected with p3TP-Lux, a TGF-beta-responsive luciferase reporter gene construct. TGF-beta1 was without effect in parental T3M4 cells, but caused a time- and dose-dependent increase in luciferase activity in T3M4 cells co-transfected with a TbetaRI cDNA expression vector. Co-transfection of TbetaRI with a truncated Smad4 cDNA that is known to block TGF-beta-dependent signaling, abrogated the TbetaRI-induced increase in luciferase activity. Sequencing of the TbetaRI and the Smad4 genes in T3M4 cells did not reveal any mutations. These findings indicate that one mechanism for TGF-beta resistance in pancreatic cancer is due to a quantitative decrease in TbetaRI expression.

Transforming growth factor beta1 is associated with angiogenesis, metastasis, and poor clinical outcome in prostate cancer

BACKGROUND

Prostate tumors express high levels of transforming growth factor-beta1 (TGF-beta1) and seem to acquire resistance to its antiproliferative effects with tumor progression. Moreover, TGF-beta1 could be involved in tumor-promoting processes such as angiogenesis, cell migration, and immunosuppression.

METHODS

Immunoreactivity for TGF-beta1 and its receptors type I and type II (TGFbeta-RI and TGFbeta-RII), tumor vascular count, and cell proliferation were studied in 73 cases of prostate cancer, diagnosed between 1975-1983 and followed with surveillance.

RESULTS

Patients with tumor overproduction of TGF-beta1 had shorter median cancer-specific survival than patients with normal TGF-beta1 immunoreactivity (5.0 vs. 10 years, P = 0.006). Furthermore, increased TGF-beta1 staining was associated with tumor grade, high vascular counts, and metastasis (P = 0.02, 0.02, and 0.01, respectively). Patients with loss of tumor TGFbeta-RII expression in combination with TGF-beta1 overproduction showed particularly short survival (2.6 vs. 10 years, P = 0.0000), when compared to patients with normal immunoreactivity.

CONCLUSIONS

Overproduction of TGF-beta1 and loss of TGFbeta-RII expression are associated with poor clinical outcome in prostate cancer, and TGF-beta1 may promote tumor progression by stimulating angiogenesis and metastasis.

Changes in TGF-beta receptors of rat hepatocytes during primary culture and liver regeneration: increased expression of TGF-beta receptors associated with increased sensitivity to TGF-beta-mediated growth inhibition

To clarify the role of transforming growth factor-beta (TGF-beta) and its receptors in hepatocyte growth, we studied the expression of TGF-beta1 and its receptors and the sensitivity to growth inhibition by TGF-beta1 protein in rat hepatocytes derived from resting and regenerating livers. In hepatocytes derived from resting livers, mRNAs for TGF-beta type II receptor (TbetaR-II), insulin-like growth factor-II/mannose 6-phosphate receptor (IGF-II/M-6-PR), and TGF-beta1 increased with time in primary culture. The cell surface TGF-beta receptor proteins (TbetaR-I, II, and III), examined by the receptor affinity-labeling assay using 125I-TGF-beta1, also increased, especially after 48 hr of culture. Hepatocytes were more sensitive to inhibition of DNA synthesis, when the TGF-beta1 protein was added at later times in culture, corresponding to the presence of increased TGF-beta receptors. In hepatocytes from regenerating livers after a partial hepatectomy (PH), an increase of TbetaR-I, TbetaR-II, TbetaR-III, IGF-II/M-6-PR, and TGF-beta1 mRNAs was found, compared with hepatocytes from resting livers. Similarly, using TGF-beta receptor affinity-labeling assay, hepatocytes from PH livers were found to have an increase in TbetaR-I, II, and III proteins, with a peak at 4 days post-PH, compared with hepatocytes from resting livers. When TGF-beta1 protein was added for a short period (6 or 24 hr) after cell attachment to hepatocyte cultures, it inhibited DNA synthesis more effectively in hepatocytes from regenerating compared with resting livers. Our results show that hepatocyte TGF-beta receptors and sensitivity to growth inhibition by TGF-beta1 protein change together and are modulated during liver regeneration, as well as during the conditions of primary culture.

Altered regulation of Src tyrosine kinase by transforming growth factor beta1 in a human hepatoma cell line

Transforming growth factor betas (TGF-betas) are the potent growth inhibitors for various cell types. Certain transformed cells, however, show poor response to TGF-beta-induced growth inhibition, which contributes to their uncontrolled proliferation. Recently, we have reported that TGF-beta1 induces degradation of activated Src tyrosine kinase in rat fibroblasts. To elucidate the alteration in TGF-beta signaling pathway in tumor cells that cannot respond to the cytokine, we compared the effects of TGF-beta1 on Src kinase in two human hepatoma cell lines, TGF-beta1-insensitive Mahlavu cells and TGF-beta1-sensitive HepG2 cells. TGF-beta1 decreased Src kinase activity in HepG2 cells, but increased cellular Src levels and Src kinase activity in Mahlavu cells. Co-incubation of Mahlavu cells with TGF-beta1 and 12-O-tetradecanoyl phorbol 13-acetate (TPA) decreased Src protein levels and Src kinase activity, inducing TGF-beta1 sensitivity. TGF-beta1 induced tyrosine dephosphorylation of Ras guanosine triphosphatase-activating protein (Ras-GAP) and Ras inactivation in HepG2 cells, but induced Ras-GAP phosphorylation and Ras activation in Mahlavu cells. The Src kinase inhibitor abolished the increase of Src kinase activity in TGF-beta1-treated Mahlavu cells, and induced TGF-beta1 sensitivity. These findings suggest that regulation of Src kinase by TGF-beta1 is altered in Mahlavu cells. The altered regulation of Src may contribute to TGF-beta1 insensitivity in this cell line, at least in part through activation of Ras.

TGF-beta activity and expression of its receptors in B-cell chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in Western countries and results from the accumulation of B-lymphocytes which are functionally abnormal and predominantly non-cycling in vivo. Consequently, it is important to understand why B-CLL cells accumulate in GO phase. Since TGF-beta is an important negative regulator of the immune system, a loss of responsiveness to this factor might provide a selective advantage to B-CLL cells. Here we review data on the role of TGF-beta in B-CLL. We show that the B-CLL cell response to TGF-beta signals is abnormal in vitro (inhibition of proliferation and induction of apoptosis). This lack of response of B-CLL cells to TGF-beta inhibition appears to be accompanied by a decrease or a loss of TGF-beta receptor expression.

Cell-cycle-dependent expression of transforming growth factor beta type I receptor correlates with differential proliferative effects of TGFbeta1 in articular chondrocytes

We previously found that transforming growth factor beta type 1 (TGFbeta1) had bifunctional effects on articular chondrocytes in culture depending on the proliferative state of the cells. Here, TGFbeta1 responses and the expression of TGFbeta receptors I and II were investigated as a function of growth state in rabbit articular chondrocytes (RAC) and Mv1Lu cells, a cell line which is growth inhibited by TGFbeta1. In contrast to these latter cells, in which DNA synthesis was decreased by TGFbeta1 independently of the cell cycle phases, exponentially growing RAC responded with a stimulation of DNA synthesis while confluent or quiescent cells were growth inhibited. Using synchronized RAC cultures, we showed that inhibitory responses were associated with the G0/G1 phase, whereas proliferative effects were S-phase dependent. Type I receptor mRNA level was severalfold greater in quiescent and slowly proliferating than in exponentially growing cells. In contrast, the expression of type II mRNA did not change. 125I-TGFbeta1 binding to RI in G0/G1-arrested cells was greater than in S-phase, suggesting a correlation with the growth-inhibitory effect of TGFbeta1. Transfection of an RI expression vector in exponentially growing RAC, which normally are growth stimulated by TGFbeta1, induced an inhibitory response, supporting the idea that this effect was due to increased RI expression. These results indicate that the ratio of type I to type II levels is cell cycle dependent and could lead to either negative or positive proliferative responses. In contrast, no influence on the TGFbeta1-induced stimulation of matrix gene transcriptional activity was seen, confirming that TGFbeta cell growth and matrix effects are controlled by separate pathways.

Transcriptional activation of the type II transforming growth factor-beta receptor gene upon differentiation of embryonal carcinoma cells

Previously, it has been shown that differentiation of embryonal carcinoma (EC) cells turns on the expression of functional transforming growth factor type-beta receptors. Here, we show that the type II receptor (TbetaR-II) gene is activated at the transcriptional level when EC cells differentiate. We show that the differentiated cells, but not the parental EC cells, express transcripts for TbetaR-II. In addition, the expression of TbetaR-II promoter/reporter gene constructs are elevated dramatically when EC cells differentiate and we identify at least two positive and two negative regulatory regions in the 5' flanking region of the TbetaR-II gene. Moreover, we identify a cAMP response element/activating transcription factor site that acts as a positive cis-regulatory element in the TbetaR-II promoter, and we demonstrate that the transcription factor ATF-1 binds to this site and strongly stimulates the expression of the TbetaR-II promoter/reporter gene constructs when ATF-1 is overexpressed in EC-derived differentiated cells. Equally important, we identify a negative regulatory element in a 53-base pair region that had previously been shown to inhibit strongly the expression of TbetaR-II promoter/reporter gene constructs. Specifically, we demonstrate that this region, which contains an inverted CCAAT box motif, binds the transcription factor complex NF-Y (also referred to as CBF) in vitro. Furthermore, expression of a dominant-negative NF-YA mutant protein, which prevents DNA binding by NF-Y, enhances TbetaR-II promoter expression. Together, these studies suggest that the transcription factors ATF-1 and NF-Y play important roles in the regulation of the TbetaR-II gene.

Genetic integrity of transforming growth factor beta (TGF-beta) receptors in cervical carcinoma cell lines: loss of growth sensitivity but conserved transcriptional response to TGF-beta

Transforming growth factor beta (TGF-beta) exerts an inhibitory effect on the growth of most epithelial cell types, and the loss of responsiveness to this growth inhibition has been implicated in the development of a variety of human cancers. The genetic alteration of TGF-beta receptors is known to play a critical role in this escape from growth regulation. We asked whether there is a correlation between TGF-beta sensitivity and the genetic status of TGF-beta type I and type II receptors (RI and RII, respectively) in human cervical carcinoma cell lines. Among 8 cell lines examined, 3 (ME-180, C-33A and HeLaS3) showed resistance to TGF-beta and 3 (SiHa, CaSki and HeLa229) showed minimal response to the growth inhibitory effect of TGF-beta; the other cell lines (HeLa and HT-3) were sensitive. Northern blot analysis revealed that the RII mRNA was not expressed in 2 TGF-beta-resistant cell lines (ME-180 and C-33A) but was expressed in the other cell lines. Southern blot analysis of RI and RII revealed a homozygous deletion of the entire TGF-beta RII gene in the cell line ME-180. We then asked whether the other TGF-beta-resistant or refractory cell lines had microsatellite instability and/or poly-adenine tract mutations of RII. We also checked for point mutations in the individual exons of the entire RII using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP). Although C-33A exhibited poly-adenine microsatellite instability, its RII gene showed no signs of mutation. The molecular integrity of the TGF-beta, receptors in all cell lines, except ME-180 and C-33A, could be confirmed by examining the distinct transcriptional induction of plasminogen activator inhibitor-1 (PAI-1), p21(WAF1/CIP1) and, in some cases, the accompanying downregulation of c-myc in response to TGF-beta. Our observations, taken together, indicate that inactivation of the RII contributes to the resistance to TGF-beta of some cervical carcinoma cell lines. Loss of or attenuated sensitivity to TGF-beta growth inhibition in other cells may be attributed to the disruption of distal components in the TGF-beta signal pathway, but not to the receptor system.

Expression of transforming growth factor-beta receptor type II and tumorigenicity in human breast adenocarcinoma MCF-7 cells

To analyze transforming growth factor-beta (TGF-beta) response during MCF-7 cell progression, early passage (MCF-7E, < 200 passage) and late passage (MCF-7L, > 500 passage) cells were compared. MCF-7E cells showed an IC50 of approximately 10 ng/ml of TGF-beta1, whereas MCF-7L cells were insensitive. MCF-7E cells contained approximately threefold higher levels of TGF-beta receptor type II (TbetaRII) mRNA than MCF-7L, but their TbetaRI levels were similar. MCF-7E parental cells showed higher TbetaRII promoter activity than MCF-7L cells, which could be attributed to changes in Sp1 nuclear protein levels. Receptor cross-linking studies indicated that the cell surface receptor levels parallel mRNA levels in both cell lines. Limiting dilution clones of MCF-7E cells were established to determine the heterogeneity of TbetaRII expression in this cell line, and they showed varying degrees of TbetaRII expression. Fibronectin was induced at higher levels in cells expressing higher TbetaRII levels. All three TGF-beta isoforms were detected in limiting dilution clones and parental cells, but TGF-beta1 was more abundant relative to TGF-beta2 or 3, and no correlation between TGF-beta isoform profile with TGF-beta sensitivity was found. MCF-7L cells were tumorigenic and formed xenografts rapidly and progressively, whereas MCF-7E parental and limiting dilution clonal cells showed transient tumor formation followed by regression. These results indicate that decreased TbetaRII transcription in breast cancer cells leads to a loss of TbetaRII expression, resulting in cellular resistance to TGF-beta which contributes to escape from negative growth regulation and tumor progression.

SV40 Tag transformation of the normal invasive trophoblast results in a premalignant phenotype. I. Mechanisms responsible for hyperinvasiveness and resistance to anti-invasive action of TGFbeta

Invasion of the uterus by first trimester human placental extravillous trophoblast (EVT) cells depends on mechanisms shared by malignant cells. However, unlike tumor invasion, trophoblast invasion of the uterus is stringently controlled in situ by local molecules such as transforming growth factor (TGF)beta. Since EVT cells possess active invasion-associated genes but are nontumorigenic, our objective was to induce premalignant and then malignant phenotype into a normal EVT cell line in order to identify the molecular basis of tumor progression. Simian virus 40 large T antigen (SV40 Tag) was introduced into a normal human first trimester invasive EVT cell line, HTR8, established in our laboratory. Since the HTR8 line has a limited in vitro lifespan of 12-15 passages, SV40 Tag-transformed cells were selected on the basis of extended lifespan. A long-lived line, RSVT-2, was produced and an immortalized subclone, RSVT2/C, was further derived under a forced crisis regimen. We examined transformation-induced alterations in proliferative and invasive abilities, responses to the invasion and proliferation-regulating growth factor TGFbeta and changes in gene expression for invasion-associated enzymes or enzyme inhibitors. RSVT-2 and RSVT2/C cell lines were hyperproliferative and hyperinvasive when compared with the parental HTR8 cell line. They were also variably resistant to the anti-proliferative and anti-invasive signals from TGFbeta. Since both cell lines remained non-tumorigenic in nude mice, these properties indicate that they attained a premalignant phenotype. Both cell lines showed reduced expression of tissue inhibitor of metalloproteases (TIMP)-1, while TIMP-2 and plasminogen activator inhibitor (PAI)-I expression was was also reduced in RSVT2/C cells, thus contributing to their hyperinvasiveness. Their resistance to the anti-invasive action of TGFbeta was explained by the failure of TGFbeta to upregulate TIMPs and PAI-I, in contrast to the TGFbeta-induced upregulation noted in parental HTR8 cells.

Transforming growth factor-beta expression in mouse lung carcinogenesis

Transforming growth factor-beta (TGF-beta) is a multifunctional growth modulator that inhibits the proliferation of many epithelial cells while stimulating the proliferation of most fibroblasts. To examine the role of TGF-beta in mouse lung chemically induced tumorigenesis, expression of the TGF-beta 1, -beta 2, and -beta 3 proteins was examined in A/J mice treated with the carcinogen urethane to induce lung adenomas using immunohistochemical staining analysis. Immunostaining for the TGF-beta ligands was detected in the epithelium of the bronchioles of untreated A/J mice with immunostaining being more intense for TGF-beta 1 than for TGF-beta 2 and TGF-beta 3; immunostaining for each TGF-beta ligand was also detected in the bronchiolar epithelium of urethane-treated A/J mice at levels similar to untreated mice. Immunostaining for the TGF-beta ligands was also detected in adenomas by 2 months; staining for TGF-beta 1, -beta 2, and -beta 3 in adenomas was detected at levels comparable with bronchioles. Following treatment with urethane for 8 months, immunostaining for TGF-beta s 1, 2, and 3 in bronchioles persisted at levels comparable to that in normal bronchioles and also persisted in adenomas, with staining for the TGF-beta ligands being very prominent on the edge of the tumor. Expression of TGF-beta 1 mRNA was examined in urethane-treated mouse lung tissue using Northern blot hybridization; here, expression of TGF-beta 1 mRNA increased 2-fold in 3-month urethane-treated lung tissue and an additional 2.5-fold by 8 months following urethane administration. Expression of TGF-beta 1 mRNA was also examined in nontumorigenic and tumorigenic mouse lung cells; in these cells, expression of TGF-beta 1 mRNA was higher in the tumorigenic cells than in the nontumorigenic cell line. These data show that there is an increase in expression of TGF-beta 1 during tumorigenesis and suggest that TGF-beta may play an important role in mouse lung carcinogenesis induced by urethane.

Induction of transforming growth factor-beta receptor type II expression in estrogen receptor-positive breast cancer cells through SP1 activation by 5-aza-2'-deoxycytidine

Previous studies suggest that estrogen receptor-positive (ER+) breast cancer cells acquire resistance to transforming growth factor-beta (TGF-beta) because of reduced expression levels of TGF-beta receptor type II (RII). We now report that treatment of ER+ breast cancer cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-2'-dC) leads to accumulation of RII transcript and protein in three different cell lines. RII induction restored TGF-beta response in MCF-7L breast cancer cells as indicated by the enhanced activity of a TGF-beta responsive promoter-reporter construct (p3TP-Lux). A transiently transfected RII promoter-reporter element (RII-chloramphenicol acetyltransferase) showed an increase in activity in the 5-aza-2'-dC-treated MCF-7L cells compared with untreated cells, suggesting the activation of a transactivator of RII transcription. Using electrophoretic mobility shift assays, the enhanced binding of proteins from 5-aza-2'-dC-treated MCF-7L nuclear extracts to radiolabeled Sp1 oligonucleotides was demonstrated. An RII promoter-chloramphenicol acetyltransferase construct containing a mutation in the Sp1 site was not expressed in the 5-aza-2'-dC-treated MCF-7L cells, further demonstrating that induction of Sp1 activity by 5-aza-2'-dC in the MCF-7L cells was critical to RII expression. Northern analysis indicated that 5-aza-2'-dC treatment did not affect the Sp1 transcript levels. Western blot analysis revealed an increase of Sp1 protein in the 5-aza-2'-dC-treated MCF-7L cells, but there was no change in the c-Jun levels. Studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5-aza-2'-dC-treated MCF-7L extracts compared with untreated control extracts. These results indicate that the transcriptional repression of RII in the ER+ breast cancer cells is caused by suboptimal activity of Sp1, whereas treatment with 5-aza-2'-dC stabilizes the protein thus increasing steady-state Sp1 levels and thereby leads to enhanced RII transcription and subsequent restoration of TGF-beta sensitivity.

Novel mutations in the polyadenine tract of the transforming growth factor beta type II receptor gene are found in a subpopulation of human pancreatic adenocarcinomas

In this study, we determined the incidence of microsatellite instability (MIN) in pancreatic adenocarcinoma and determined whether MIN might target, for mutations, the simple nucleotide repeats of the transforming growth factor beta type II receptor (TGFBR2) gene. Forty-eight surgically resected pancreatic tumor tissue samples and two normal pancreas tissue samples were analyzed in this study. Microsatellite analysis was performed for six loci in 14 of the 48 tumor specimens for which we had matching normal genomic DNA. Only four of the 14 tumors (29%) were MIN-positive as determined by the presence of microsatellite variations in more than one locus. Interestingly, eight of the 14 specimens (57%) showed microsatellite variations or loss of heterozygosity at D18S34, suggesting that this locus may be a critical region of genetic instability in pancreatic tumorigenesis. Of the 48 tumors, only two (4%) showed mutations in the polyA region, one of the MIN-targeted sites of the TGFBR2 gene. DNA sequence analysis of these two specimens showed the presence of a two-base deletion in one tumor specimen and the other tumor specimen showed a base substitution in the polyA tract at codon 128 of the TGFBR2 gene. The fact that these mutations occurred in the polyA tract of some pancreatic tumors suggests that a subpopulation of these tumors may be susceptible to MIN-targeted mutations. The incidence of these mutations are low and similar to that reported for nonhereditary, sporadic colon cancers.

Expression of transforming growth factor beta receptors in normal human colon and sporadic adenocarcinomas

BACKGROUND & AIMS

An absence or a presence of mutated transforming growth factor (TGF)-beta receptors is a possible hypothesis explaining the resistance of cancer cells to the growth-inhibitory effect of TGF-beta. Mutations involving microsatellite-like regions of the type II TGF-beta receptor have been described in subgroups of colorectal cancers. The aim of this study was to investigate the expression and distribution of TGF-beta receptors in sporadic colorectal cancers and normal tissues.

METHODS

Thirty-three sporadic colorectal cancers and 20 normal colonic tissues were explored by immunohistochemistry for the expression of type I and type II TGF-beta receptors. Eighteen tumor and 20 normal samples were used for radioactive thermocycling and sequencing of the two microsatellite-like regions of the type II receptor.

RESULTS

Both receptors were overexpressed in tumors compared with normal samples. There was a relationship between the abundance of type II receptor expression and the degree of differentiation of the tumors but not the Dukes' staging or the localization of the neoplasias. No mutation was observed in the microsatellite-like regions of receptor II in any of the samples.

CONCLUSIONS

Sporadic colorectal cancers do not show an absence or a presence of mutated TGF-beta receptors that could explain a resistance to TGF-beta-mediated growth inhibition. The pathways to tumorigenesis of sporadic colorectal cancers may be different from those of some hereditary ones.

Rapid assessment of replication error phenotype in gastric cancer

Forty gastric tumors were investigated for microsatellite instability at the D2S119 and L-myc loci. These tumors and 143 other gastrointestinal cancers were previously analyzed for instability at several different microsatellites. By evaluating previous and present results, repeated sequences were selected that frequently underwent replication errors (RERs). To coamplify these sequences, the following multiplex polymerase chain reactions (PCRs) were performed: 1) D2S119/L-myc/D18S59; 2) D2S119/L-myc/D3S1076; and 3) D2S177/L-myc/BAT-RII. Therefore, the 40 gastric tumors in the present survey were rescreened using multiplex PCRs. Each multiplex allowed detection of nearly all RER+ tumors (80% for multiplex 3 and 87% for multiplexes 1 and 2) that had been previously identified by amplifying 9 different loci with independent reactions. Moreover, for multiplexes 1 and 2, the size differences between normal and RER alleles were sufficient to be detected by electrophoresis on conventional polyacrylamide gels after DNA staining with ethidium bromide. This approach allows a rapid and easy assessment of RER phenotype in gastric tumors.

Autocrine secretion of TGF-beta 1 and TGF-beta 2 by pre-adipocytes and adipocytes: a potent negative regulator of adipocyte differentiation and proliferation of mammary carcinoma cells

We have developed an in vitro system to examine the influence of adipocytes, a major mammary stromal cell type, on the growth of a murine mammary carcinoma, SP1. Previously, we have shown that 3T3-L1 adipocytes release a mitogenic factor, hepatocyte growth factor, which strongly stimulates proliferation of SP1 cells. We now show that 3T3-L1 pre-adipocytes secrete active inhibitory molecules which inhibit DNA synthesis in SP1 cells. In addition, latent inhibitory activity is present in conditioned media (CM) from both pre-adipocytes and adipocytes, and is activated following acid treatment. CM also inhibited DNA synthesis in Mv1Lu wild type epithelial cells, but not DR27 mutant epithelial cells which lack TGF-beta type II receptor. Inhibitory activity of CMs was partially abrogated by neutralizing anti-TGF-beta1 and anti-TGF-beta2 antibodies, and was removed following ultrafiltration through membranes of 10,000 Mr but not 30,000 Mr pore size. These results show that the inhibitory effect on DNA synthesis is mediated by TGF-beta1-like and TGF-beta2-like molecules. In addition, acid-treated CM as well as purified TGF-beta inhibited differentiation of pre-adipocytes. Untreated pre-adipocyte CM, but not mature adipocyte CM, spontaneously inhibited adipocyte differentiation. Together, these findings indicate that pre-adipocytes spontaneously activate their own secreted TGF-beta, whereas mature adipocytes do not, and suggest that activation of TGF-beta has a potent negative regulatory effect on adipocyte differentiation and tumor growth. Thus, TGF-beta may be an important modulator of tumor growth and adipocyte differentiation via both paracrine and autocrine mechanisms. These findings emphasize the importance of adipocyte-tumor interactions in the regulation of tumor microenvironment.

A novel missense mutation and frameshift mutations in the type II receptor of transforming growth factor-beta gene in sporadic colon cancer with microsatellite instability

Microsatellite instability of DNA samples of 79 sporadic colon cancer patients were analyzed. These samples were also screened to search mutations in the repeat sequences in the gene for the type II receptor of transforming growth factor-beta (TGF-beta RII) using polymerase chain reaction (PCR), electrophoresis with urea gel, and PCR-single strand conformation polymorphism (PCR-SSCP) method. The incidence of microsatellite instability, defined as severe replication error phenotype (RER) with microsatellite alterations in more than three loci, was 6%. Deletion and insertion of an A residue in the (A)10 region, which cause frameshift mutation, were found in four samples and their incidence in the samples with microsatellite instability was 80%. A novel nucleotide substitution of T for G at 1918, which causes missense mutation of arginine to leucine at codon 528, was found in a sample with microsatellite instability. The mutation at 1918 was in highly conservative amino acid residue.

Regulation of transforming growth factor-beta type II receptor expression in human breast cancer MCF-7 cells by vitamin D3 and its analogues

In view of the tumor suppressor role of the transforming growth factor-beta (TGFbeta) type II receptor (RII), the identification and characterization of agents that can induce the expression of this receptor are of potential importance to the development of chemoprevention approaches as well as treatment of cancer. To date, the identification of exogenous agents that control RII expression has been rare. We demonstrated that proliferation of MCF-7 early passage cells (MCF-7 E), which express RII and are sensitive to TGFbeta growth inhibition activity, was significantly inhibited by vitamin D3 and its analogue EB1089. In contrast, proliferation of MCF-7 late passage cells (MCF-7 L), which have lost cell surface RII and are resistant to TGFbeta, was not affected by these two compounds. TGFbeta-neutralizing antibody was able to block the inhibitory effect on MCF-7 E cells by these compounds, indicating that treatment induced autocrine-negative TGFbeta activity. An RNase protection assay showed approximately a 3-fold induction of the RII mRNA, while a receptor cross-linking assay revealed a 3-4-fold induction of the RII protein. In contrast, there was no change in either RII mRNA or protein in the MCF-7 L cells.

Localization of transforming growth factor-beta1 and type II receptor in developing normal human prostate and carcinoma tissues

Transforming growth factor-beta1 (TGF-beta1) is implicated in prostate development, and elevated expression of TGF-beta1 has been correlated with prostate carcinogenesis. In this study, cell type specificity of TGF-beta1 and TGF-beta receptor Type II (RcII) protein expression was determined by immunocytochemistry in human normal prostate and compared to prostate carcinoma tissues. Heterogeneous localization patterns of LAP-TGF-beta1 (TGF-beta1 precursor) and RcII were observed in both epithelial and mesenchymal cells in fetal prostate, with LAP-TGF-beta1 localizing to more basal epithelial cells. Homogeneity of LAP-TGF-beta1 staining was increased in neonatal, prepubertal, and adult prostate, with elevated immunoreactivity noted in epithelial acini relative to stromal tissue for both LAP-TGF-beta1 and RcII proteins. In stromal tissues, RcII cell localization exhibited staining patterns nearly identical to smooth muscle alpha-actin. In prostate carcinoma, LAP-TGF-beta1 localized to carcinoma cells with an increased staining heterogeneity relative to normal prostate. In contrast to normal epithelial cells, carcinoma epithelial cells exhibited low to nondetectable RcII staining. Stromal cell staining patterns for LAP-TGF-beta1 and RcII in carcinoma, however, were identical to those of normal prostate stromal cells. These studies implicate both epithelial and stromal cells as sites of TGF-beta1 synthesis and RcII localization in the developing and adult normal human prostate. In addition, these data indicate a loss of epithelial expression of RcII concurrent with altered LAP-TGF-beta1 expression in human prostate carcinoma cells.

Proapoptotic gene BAX is frequently mutated in hereditary nonpolyposis colorectal cancers but not in adenomas

BACKGROUND & AIMS

The p53 and BAX genes have been linked to apoptosis. p53 was not frequently found to be mutated in colorectal carcinomas with a microsatellite mutator phenotype, but frame-shift mutations in a tract of eight guanines within BAX were frequently found in these carcinomas. To understand the roles of these genes in hereditary nonpolyposis colorectal cancer (HNPCC) tumorigenesis, we examined whether BAX mutations occur in adenoma and carcinoma specimens from patients with HNPCC and also determined the frequencies of p53 mutations.

METHODS

Thirteen colorectal adenomas and 24 adenocarcinomas from patients with HNPCC showing a microsatellite instability phenotype were screened by polymerase chain reaction followed by denaturing polyacrylamide gel electrophoresis and direct sequencing.

RESULTS

Two of the 13 adenomas (15.4%) and 13 of the 24 adenocarcinomas (54.2%) showed mutation patterns and were confirmed to have frame-shift mutations at the BAX repeat site by direct sequencing. For p53, only 1 of the 24 adenocarcinomas (4.2%) showed a missense mutation.

CONCLUSIONS

In HNPCC colorectal carcinomas, BAX was significantly (P = 0.024) more mutated than in adenomas. p53 was not frequently found to be mutated in these carcinomas. These data suggest that mutations in BAX, rather than mutations in p53, may contribute to the adenoma-carcinoma transition in HNPCC tumorigenesis.