Establishment and characterisation of six human biliary tract cancer cell lines

Human cell lines established from biliary tract cancers are rare, and only five have been reported previously. We report the characterisation of six new six biliary tract cancer cell lines (designated SNU-245, SNU-308, SNU-478, SNU-869, SNU-1079 and SNU-1196) established from primary tumour samples of Korean patients. The cell lines were isolated from two extrahepatic bile duct cancers (one adenocarcinoma of common bile duct, one hilar bile duct cancer), two adenocarcinomas of ampulla of Vater, one intrahepatic bile duct cancer (cholangiocarcinoma), and one adenocarcinoma of the gall bladder. The cell phenotypes, including the histopathology of the primary tumours and in vitro growth characteristics, were determined. We also performed molecular characterisation, including DNA fingerprinting analysis and abnormalities of K-ras, p15, p16, p53, hMLH1, hMSH2, DPC4, beta-catenin, E-cadherin, hOGG1, STK11, and TGF-betaRII genes by PCR-SSCP and sequencing analysis. In addition, we compared the genetic alterations in tumour cell lines and their corresponding tumour tissues. All lines grew as adherent cells. Population doubling times varied from 48-72 h. The culture success rate was 20% (six out of 30 attempts). All cell lines showed (i) relatively high viability; (ii) absence of mycoplasma or bacteria contamination; and (iii) genetic heterogeneity by DNA fingerprinting analysis. Among the lines, three lines had p53 mutations; and homozygous deletions in both p16 and p15 genes were found three and three lines, respectively; one line had a heterozygous missense mutation in hMLH1; E-cadherin gene was hypermethylated in two lines. Since the establishment of biliary tract cancer cell lines has been rarely reported in the literature, these newly established and well characterised biliary tract cancer cell lines would be very useful for studying the biology of biliary tract cancers, particularly those related to hypermethylation of E-cadherin gene in biliary tract cancer.

Carcinogen-induced pancreatic lesions in the mouse: effect of Smad4 and Apc genotypes

Mutations in the tumour suppressor genes SMAD4 (DPC4, deleted in pancreatic cancer locus 4) and adenomatous polyposis coli (APC) have been implicated in the development of pancreatic cancer in humans. Treatment of wild-type, Smad4(+/-), Apc(Min/+) or Apc(Min/+)Smad4(+/-) mice with N-Nitroso-N-Methyl Urea (NMU) results in abnormal foci in pancreatic acinar cells characterized by increased levels of beta-catenin. Previously such foci have been shown to be the precursors of pancreatic neoplasia. Interestingly, only NMU-treated Apc(Min/+)Smad4(+/-) mice exhibit a significant increase in abnormal pancreas, which was found to be due to increased number of abnormal foci rather than increased focus size. A range of foci sizes were analysed, but only smaller abnormal foci were characterized by morphological nuclear atypia. These studies suggest functional co-operation between TGF-beta and Wnt signalling pathways in the suppression of pancreatic tumorigenesis in the mouse.

Evaluation of candidate genes MAP2K4, MADH4, ACVR1B, and BRCA2 in familial pancreatic cancer: deleterious BRCA2 mutations in 17%

It is estimated that familial aggregation and genetic susceptibility play a role in as many as 10% of pancreatic ductal adenocarcinomas. To investigate the role of germ-line mutations in the etiology of pancreatic cancer, we have analyzed samples from patients with pancreatic cancer enrolled in the NFPTR for mutations in four tumor suppressor candidate genes: (a) MAP2K4; (b) MADH4; (c) ACVR1B; and (d) BRCA2 by direct sequencing of constitutional DNA. These genes are mutated in clinically sporadic pancreatic cancer, but germ-line mutations are either not reported or anecdotal in familial pancreatic cancer. Pancreatic cancer patient samples were selected from kindreds in which three or more family members were affected with pancreatic cancer, at least two of which were first-degree relatives. No mutations were identified in mitogen-activated protein kinase kinase 4 (0 of 22), MADH4 (0 of 22), or ACVR1B (0 of 29), making it unlikely that germ-line mutations in these genes account for a significant number of inherited pancreatic cancers. BRCA2 gene sequencing identified five mutations (5 of 29, 17.2%) that are believed to be deleterious and one point mutation (M192T) unreported previously. Three patients harbored the common 6174delT frameshift mutation, one had the splice site mutation IVS 16-2A > G, and one had the splice site mutation IVS 15-1G > A. Two of the five BRCA2 mutation carriers reported a family history of breast cancer, and none reported a family history of ovarian cancer. These findings confirm the increased risk of pancreatic cancer in individuals with BRCA2 mutations and identify germ-line BRCA2 mutations as the most common inherited genetic alteration yet identified in familial pancreatic cancer.

Frequent loss of SMAD4/DPC4 protein in colorectal cancers

BACKGROUND AND AIMS

Loss of DNA sequences from chromosome 18q21 is a major genetic change in colorectal tumorigenesis. Multiple genes have been identified in this area. One of these, DPC4 (deleted in pancreatic cancer 4, also known as SMAD4), is mutated in a minor subset of colorectal carcinomas as well as in germlines of humans predisposed to colon tumours.

PATIENTS AND METHODS

The involvement of SMAD4 in sporadic colorectal neoplasia was evaluated by immunohistochemistry in 53 unselected cases and 27 cases displaying microsatellite instability.

RESULTS

SMAD4 expression was absent in 20 of 53 (38%) unselected colorectal carcinomas, and reduced in another 15 (28%) cases. However, 26 of 27 cancers displaying microsatellite instability and TGF-betaIIR mutations were positive for SMAD4 immunostaining.

CONCLUSIONS

Loss of SMAD4 expression may play a more prominent role in colon cancer than anticipated based on genetic evidence, but not in mutator phenotype tumours.

Ampulla of vater cancers: T-stage and histological subtype but not Dpc4 expression predict prognosis

Loss of immunohistochemical expression of Dpc4 occurs in about 50% of pancreatic ductal cancers and its loss correlates with DPC4/Smad4 gene inactivation. Dpc4 expression was also lost in 6 of 16 (37%) ampulla of Vater cancers (AVCs) previously analyzed. Furthermore, chromosomal losses involving 18q, where DPC4 is located, have been observed in 34% of AVCs and are associated with decreased survival. To evaluate the possibility that expression of Dpc4 may be correlated with survival, we analyzed 89 AVCs for inactivation of DPC4 by immunohistochemical staining. Thirty-seven cases showed no expression of Dpc4 (41%). Multivariate survival analysis was performed including age, sex, tumor size, histological subtype (intestinal or pancreatobiliary), grade of differentiation, T-stage, lymph-node metastases and Dpc4 status. T-stage and histological subtype were selected as independent prognostic factors, while Dpc4 immunostaining was not significantly associated with any clinicopathological variable, including histological subtype. Although Dpc4 expression is of no clinical relevance, its involvement in AVC gives additional weight to the hypothesis that, among all pancreatic exocrine and endocrine tumors, only AVC and common ductal adenocarcinomas have similar molecular fingerprints. Moreover, comparison of the frequencies of allelic loss on chromosomal arm 18q and the loss of Dpc4 expression (34% and 41%, respectively) is highly suggestive that DPC4 is the major target of these losses.

Juvenile polyposis: massive gastric polyposis is more common in MADH4 mutation carriers than in BMPR1A mutation carriers

Juvenile polyposis syndrome (JPS) is an autosomal dominant predisposition to multiple juvenile polyps in the gastrointestinal tract. Germline mutations in the MADH4 or BMPR1A genes have been found to be causative of the disease in a subset of JPS patients. So far, no genotype-phenotype correlation has been reported. We examined 29 patients with the clinical diagnosis of JPS for germline mutations in the MADH4 or BMPR1A genes and identified MADH4 mutations in seven (24%) and BMPR1A mutations in five patients (17%). A remarkable prevalence of massive gastric polyposis was observed in patients with MADH4 mutations when compared with patients with BMPR1A mutations or without identified mutations. This is the first genotype-phenotype correlation observed in JPS.

Epstein-Barr virus BZLF1 gene is activated by transforming growth factor-beta through cooperativity of Smads and c-Jun/c-Fos proteins

Induction of Epstein-Barr virus (EBV) production in an EBV-positive cell is achieved by expression of the gene BZLF1 that switches the latent state into a lytic state. The expression of the BZLF1 gene is initiated from the promoter Zp, which is normally suppressed in EBV-transformed B cells. The BZLF1 gene can be induced for expression by activating agents, such as transforming growth factor-beta (TGF-beta) and 12-O-tetradecanoylphorbol-13-acetate. The 12-O-tetradecanoylphorbol-13-acetate-responsive element located in the Zp is the AP-1 motif. The TGF-beta-responsive element, however, has not been determined. We demonstrated that the Smad4-binding element site, GTCTG, from -233 to -229, was located in the regulatory region of the Zp relative to the BZLF1 transcription initiation site and was physically associated with Smad4. This association was important for the TGF-beta induction of Zp. We also showed from the results of co-transfection experiments and electrophoretic mobility shift assays that both the AP-1 motif and Smad4-binding element site appeared to be required for the TGF-beta-induced activation of Zp. This effect was mediated through the cooperation of Smad3/Smad4 and c-Jun/c-Fos that formed a complex. TGF-beta treatment of Rael cells induced production of infectious EBV particles that was capable of infecting EBV-negative CA46 cells and transforming normal cord blood B cells, in vitro. Those data support a mechanism that TGF-beta induces the latent EBV in cells to enter the viral lytic cycle through regulation of key viral proteins by TGF-beta signal transducers. Those findings also suggest a role of TGF-beta in EBV-associated diseases.

A novel Xenopus Smad-interacting forkhead transcription factor (XFast-3) cooperates with XFast-1 in regulating gastrulation movements

In early Xenopus embryos, the prototypical XFast-1/Smad2/Smad4 complex ARF1 is induced at the Mix.2 ARE by activin overexpression. We have characterised ARF2, a related, but much more abundant, complex formed during gastrulation in response to endogenous TGFβ family members and we have identified a novel Fast family member, XFast-3, as its transcription factor component. Endogenous ARF2 efficiently competes out ARF1 at early gastrulation, due to the ability of XFast-3 to interact with activated Smads with much higher affinity than XFast-1. We demonstrate that ARF1 and ARF2 are activated by distinct TGFβ family members. Using morpholino antisense oligonucleotides to deplete levels of the constituent transcription factors XFast-1 and XFast-3 specifically, we demonstrate an important role for ARF1 and ARF2 in early Xenopus embryos in controlling the convergent extension movements of gastrulation.

Suppression of the tumorigenic phenotype by chromosome 18 transfer into pancreatic cancer cell lines

A number of lines of evidence have suggested that the long arm of chromosome 18 apart from SMAD4 may carry a tumor-suppressor gene(s) that plays a role in the early stage of pancreatic ductal carcinogenesis. Thus, adenovirus-mediated introduction of SMAD4 does not suppress in vitro growth in cells with completely inactivated SMAD4, and frequent loss of 18q at the SMAD4 locus is observed in pancreatic cancers but no abnormalities of the normal SMAD4 homolog have been detected. In this study, we introduced a normal copy of chromosome 18 into some pancreatic ductal carcinoma cells with and without a complete inactivation of SMAD4. Both anchorage-dependent and -independent proliferation as well as invasiveness were significantly suppressed in the hybrid clones compared with that of their parental cells. Moreover, significant suppression of tumorigenesis was observed after inoculation in nude mice, irrespective of the SMAD4 status. Our present study provides the first functional evidence of the existence of an additional tumor-suppressor gene(s), other than SMAD4 and DCC, that is responsible for the pathogenesis in the early stage of pancreatic ductal carcinogenesis.

Smad10 is required for formation of the frog nervous system

Before the nervous system establishes its complex array of cell types and connections, multipotent cells are instructed to adopt a neural fate and an anterior-posterior pattern is established. In this report, we show that Smad10, a member of the Smad family of intracellular transducers of TGFbeta signaling, is required for formation of the nervous system. In addition, two types of molecules proposed as key to neural induction and patterning, bone morphogenetic protein (BMP) antagonists and fibroblast growth factor (FGF), require Smad10 for these activities. These data suggest that Smad10 may be a central mediator of the development of the frog nervous system.

Smad4 and transforming growth factor beta1 expression in patients with squamous cell carcinoma of the esophagus

PURPOSE

The members of the Smad family play key rolesin regulating gene expression in the transforming growth factor (TGF)-beta1 signaling pathways. Activation of Smads causes their translocation from the cytoplasm to the nucleus, where they function as transcription factors. The present study analyzed the expression and clinicopathological significance of Smad4 and TGF-beta1 in squamous cell carcinoma of the esophagus.

EXPERIMENTAL DESIGN

Immunohistochemistry was used to investigate the expression of Smad4 and TGF-beta1 proteins in 258 patients with squamous cell carcinoma of the esophagus. The relationship between expression of these proteins and clinicopathological factors was analyzed, and the usefulness of Smad4 in disease prognosis was evaluated in relation to TGF-beta1 expression.

RESULTS

Smad4 expression was preserved in 32.2% of tumors, and TGF-beta1 expression was identified in 42.6% of tumors. Patients with preserved expression of Smad4 had a higher rate of early-stage carcinoma (P < 0.01) and fewer lymph node metastases (P < 0.01) than those with reduced Smad4 expression. The expression of TGF-beta1 was not associated with any of the clinicopathological factors. Postoperative survival analysis indicated that patients with a tumor in which Smad4 expression was reduced had worse clinical outcomes than those with preserved expression (P = 0.01). In patients with TGF-beta1-negative tumors, the survival rate was significantly higher in patients with a preserved level of Smad4 expression than in those with reduced Smad4 expression (P = 0.02). However, according to multivariate analysis, Smad4 expression could not be used as an independent prognostic factor.

CONCLUSIONS

Although Smad4 expression could not be used as a prognostic factor, its expression reflected tumor progression such as tumor depth and lymph node metastasis.

Aberrant p16(INK4A) and DPC4/Smad4 expression in intraductal papillary mucinous tumours of the pancreas is associated with invasive ductal adenocarcinoma

BACKGROUND AND AIMS

Intraductal papillary mucinous tumours (IPMT) of the pancreas constitute a unique pathological entity with an overall incidence of associated invasive malignancy of 20%. The malignant potential of an individual IPMT cannot be accurately predicted. Preoperative estimation of the risk of associated invasive malignancy with IPMT would be of significant clinical benefit. As aberrations in cell cycle regulatory genes are associated with the progression of precursor pancreatic ductal lesions to invasive adenocarcinoma, we examined expression of key cell cycle regulatory genes in the cyclin D1/retinoblastoma pathway and the transforming growth factor beta/Smad4 signalling pathway in a cohort of patients with surgically resected IPMT.

METHODS

Sections of formalin fixed paraffin embedded pancreatic tissue from a cohort of 18 patients with IPMT were examined using immunohistochemistry for protein expression of cell cycle regulatory genes p16(INK4A), p21(CIP1), p27(KIP1), cyclin D1, pRb, and p53, as well as the cell signalling molecule Smad4. A comparison of expression levels was made between adenoma/borderline IPMT (10 patients) and intraductal papillary mucinous carcinoma (IPMC) (eight patients, four of whom harboured invasive carcinoma). Statistical analysis was performed using the chi(2) and Fisher's exact tests.

RESULTS

Aberrant expression of the proteins examined increased in frequency from adenoma/borderline IPMT to IPMC. Specifically, there was a significantly greater incidence of loss of p16(INK4A) expression in IPMC: 8/8 lesions (100%) compared with 1/10 (10%) adenoma/borderline IPMT (p<0.001). Similarly, loss of Smad4 expression was associated with IPMC: 3/8 (38%) versus adenoma/borderline IPMT 0/10 (p<0.03). Loss of Smad4 expression within the IPMT was the best marker for the presence of invasive carcinoma (p<0.001).

CONCLUSIONS

These data indicate that loss of p16(INK4A) and Smad4 expression occur more frequently in IPMC alone, or with associated invasive carcinoma, compared with adenoma/borderline IPMT. Aberrant protein expression of these cell cycle regulatory genes in IPMT and pancreatic intraepithelial neoplasia in the current model of pancreatic cancer progression suggest similarities in their development and may also represent the subsequent risk of invasive carcinoma.

[Genetics of pancreatic cancer: recent advances in molecular diagnosis]

Pancreatic cancer is an important cause of death from cancer throughout the world. Until recently, pancreatic cancer was a poorly understood disease. Research in the past decade has shown conclusively, however, that pancreatic cancer is primarily genetic in nature. Inactivation with a variety of tumor-suppressor genes such as p53, p16, and DPC4, and genome-maintenance genes such as BRCA2, coupled with the activation of oncogenes such as K-ras, are a few of the mutations that trigger the growth of cancerous cells. The genetic profile of pancreatic cancer has reshaped the nomenclature describing histological progression in pancreatic ductal tumorigenesis. K-ras mutations frequently occur early, whereas changes in the expression and genetic integrity of the p16 gene appear in intermediate lesions, and the inactivation of the p53 and DPC4 genes and activation of telomerase occur late in the neoplastic progression. Although the majority of pancreatic cancers occur sporadically, a minority has been shown to aggregate in families and has aided our understanding of pancreatic tumorigenesis. An improved understanding of the genetics of pancreatic cancer should lead to the development of gene-based screening tests and novel rational therapies.

Common deletion of SMAD4 in juvenile polyposis is a mutational hotspot

Juvenile polyposis (JP) is an autosomal dominant syndrome in which affected patients develop upper- and/or lower-gastrointestinal (GI) polyps. A subset of families with JP have germline mutations in the SMAD4 (MADH4) gene and are at increased risk of GI cancers. To date, six families with JP have been described as having the same SMAD4 deletion (1244-1247delAGAC). The objective of the present study is to determine whether this deletion is a common ancestral mutation or a mutational hotspot. DNA from members of four families with JP, from Iowa, Mississippi, Texas, and Finland, that had this 4-bp deletion was used to genotype 15 simple tandem repeat polymorphism (STRP) markers flanking the SMAD4 gene, including 2 new STRPs within 6.3 and 70.9 kb of the deletion. Haplotypes cosegregating with JP in each family were constructed, and the distances of the closest markers were determined from the draft sequence of the human genome. No common haplotype was observed in these four families with JP. A 14-bp region containing the deletion had four direct repeats and one inverted repeat. Because no common ancestor was suggested by haplotype analysis and the sequence flanking the deletion contains repeats frequently associated with microdeletions, this common SMAD4 deletion in JP most likely represents a mutational hotspot.

Interaction between the transforming growth factor-beta type II receptor/Smad pathway and beta-catenin during transforming growth factor-beta1-mediated adherens junction disassembly

The aim of the current study was to examine the influence of transforming growth factor (TGF)-beta 1 on proximal tubular epithelial cell-cell interaction, with particular emphasis on the regulation of adherens junction complex formation. Stimulation of the proximal tubular cell line HK-2 cells by TGF-beta 1 led to loss of cell-cell contact and disassembly of both adherens and tight junctional complexes. Adherens junction disassembly was associated with reduction of both Triton-soluble and Triton-insoluble E-cadherin, and an increase in detergent-soluble beta-catenin. Under these conditions, immunoprecipitation and Western analysis demonstrated decreased association of beta-catenin, both with E-cadherin, alpha-catenin, and the cell cytoskeleton. Confocal microscopy after immunostaining, showed decreased intensity of peripheral E-cadherin staining, and redistribution of beta-catenin expression to a perinuclear location. Tight junction disassembly was manifest by a reduction in the expression of Triton-soluble occludin and ZO-1 by Western analysis and their disassociation manifested by immunostaining and confocal microscopy. Loss of cell-cell contact and disassembly of adherens junctions were seen after addition of TGF-beta 1 to the basolateral aspect of the cells. Immunoprecipitation experiments demonstrated co-localization of E-cadherin, beta-catenin, and TGF-beta 1 RII in unstimulated cells. After TGF-beta 1 stimulation, the TGF-beta 1 RII no longer associated with either E-cadherin or beta-catenin. Dissociation of the adherens junction protein from the TGF-beta 1 receptor was associated with increased beta-catenin tyrosine phosphorylation and decreased threonine phosphorylation. Furthermore after receptor ligand binding, beta-catenin became associated with the TGF-beta 1-signaling molecules Smad3 and Smad4.

Resistance to TGF-beta1-mediated growth inhibition correlates with sustained Smad2 phosphorylation in primary murine splenocytes

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional cytokine that regulates cell growth and differentiation in many types of cells. TGF-beta1 is especially known to exert a variety of regulatory functions in the immune system, such as T cell differentiation and T cell function. Signal transduction of TGF-beta1 is mediated by phosphorylation of R-Smads upon receptor activation. Hetero-oligomers of R- and Co-Smads translocate into the nucleus and regulate transcription of specific target genes. Here we describe the effect of long-term exposure to TGF-beta1 on the effector function of differentially stimulated primary murine splenocytes and purified primary murine CD8(+) cytotoxic T cells. Long-term exposure to TGF-beta1 results in non-responsiveness to TGF-beta1-induced Smad2 phosphorylation. This is seen either by no phosphorylation or sustained phosphorylation of Smad2. Furthermore, we observed a strong correlation between sustained Smad2 phosphorylation and resistance to TGF-beta1-mediated growth inhibition. In contrast, splenocyte cultures strongly growth inhibited by TGF-beta1 showed no Smad2 phosphorylation. Lytic activity of these cultures, however, was found to be suppressed regardless of proliferation properties and Smad2 phosphorylation pattern. These findings may contribute to understanding the mechanisms of how TGF-beta1 suppresses immune responses and promotes tumor progression.

K-ras, p53, and DPC4 (MAD4) alterations in fine-needle aspirates of the pancreas: a molecular panel correlates with and supplements cytologic diagnosis

Between January 1997 and February 2000, 101 fine-needle pancreatic aspirates were obtained. After a cytologic diagnosis was made, possible molecular alterations were determined on the 94 aspirates with adequate tissue using a molecular panel (K-ras, p53, and DPC4 [MAD4] genes). The 94 aspirates were categorized as follows: diagnostic of adenocarcinoma, 48 (51%); atypical (suggestive of but not diagnostic of adenocarcinoma), 19 (20%); negative for adenocarcinoma, 25 (2 7%); diagnostic of a neoplasm other than adenocarcinoma, 2 (2%). Clinical follow-up revealed that 3 patients (12%) with negative cytologic diagnoses and 12 patients (63%) with atypical cytologic diagnoses had adenocarcinoma. Of 63 with a final diagnosis of adenocarcinoma, 42 (67%) had an alteration in at least 1 of the genes analyzed. In contrast, only 2 (6%) of 31 patients without adenocarcinoma had an alteration in 1 gene on the panel. Overall, the molecular analyses supported the diagnosis of adenocarcinoma in 6 (32%) of 19 aspirates originally diagnosed as atypical by cytology alone. A molecular panel that includes the K-ras, p53, and DPC4 (MAD4) genes correlates with and can supplement traditional cytologic diagnosis of pancreatic fine-needle aspirates.

Allelotype analysis of the PTEN, Smad4 and DCC genes in biliary tract cancer

Aberrations of the PTEN, Smad4 and DCC genes have not been determined in biliary tract cancers. We performed allelotype analysis to screen for alterations of these genes. We looked for the presence of allelic imbalance (AI) at the PTEN and Smad4 genes in extrahepatic bile duct (EHBD) and ampullary cancers using polymorphic microsatellite markers. These tumors were also examined for AI at the DCC gene using polymerase chain reaction amplification of variable numbers of tandem repeats. AI at the PTEN, Smad4 and DCC genes was observed in 5.3%, 8.3% and 20.7%, respectively, of EHBD tumor cases. AI at the PTEN, Smad4 and DCC genes was detected in 13.3%, 50% and 8.3%, respectively, of ampullary cancer cases. Our results suggest that (a) alteration of the Smad4 gene is a major factor in the development of ampullary cancer and (b) PTEN, Smad4 and DCC genes are altered infrequently in EHBD cancers.

[Alterations of DPC4/SMAD4/MADH4 gene detected in paraffin-embedded tissues of human pancreatic carcinomas]

OBJECTIVE

To demonstrate the alterations of DPC4/SMAD4/MADH4 gene in paraffin-embedded tissues of pancreatic carcinomas.

METHODS

Forty-six cases of resected specimens containing carcinomatous tissue and normal pancreatic tissue were analysed for possible DPC4 gene mutations by polymerase chain reaction (PCR)and single-strand conformation polymorphism (SSCP). The DNA sequencing technique was applied to determine the patterns of gene mutation in the PCR-SSCP positive cases. Fifty-six cases of pancreatic carcinoma along with the specimens corresponding normal pancreatic tissues were studied by in situ hybridization (ISH) and immunohistochemistry (IHC) techniques for gene expression in mRNA and protein level.

RESULTS

The homozygous deletion rate of exon 1, 2, 3, 4, 8, 11 of DPC4 gene in pancreatic carcinoma was 28.26%, while the mutation rate of DPC4 gene was 21.74%. In these tumors, there were 3 cases of nonsense mutation, 5 cases of missense mutation, 1 case of deletion and missense mutation, 1 case of insertion mutation. Positive rates of SMAD4 in carcinomatous tissues detected by the ISH and IHC were 53.57% and 58.93% respectively, whereas they were 91.07% and 89.29% in the matched normal tissue respectively. There were significant difference between cancer and normal tissue (P < 0.05). Thrity-two cases were positive of DPC4/SMAD4 with all methods mentioned above, the coincident rate was 87.50% (28/32). The coincidence between gene detection and ISH of SMAD4 was 87.50%, and it was 96.88% between gene detection and IHC of SMAD4. Of all 56 cases, the coincidence of the positive rates of SMAD4 detected by ISH and IHC was 91.07%. No significant difference among the positive rates of DPC4/SMAD4 as detected by the three different techniques (P > 0.05).

CONCLUSIONS

The main mechanisms of inactivation of DPC4 gene in pancreatic carcinoma are homozygous deletion and mutation. The product of DPC4 expression is significantly decreased in cancer group compared with the normal tissues. As a tumor suppressor gene, DPC4 alteration is an important molecular event in pancreatic carcinoma, and probably plays a crucial role in cancer development and progression.

Deficient R-smad/smad4 complex formation in fibroblasts growth-stimulated by TGF-beta 1

Although most cell types are inhibited by TGF-beta 1 some mesenchymal cells are growth-stimulated by TGF-beta 1. Here, using two cell models, in which the normal untransformed cells (WI38 human embryo and NIH3T3 mouse fibroblasts) are stimulated to proliferate by TGF-beta 1 and their SV40 Large T-transformed counterparts are inhibited, we show that the two former cells are deficient in smad2-smad4 and smad3-smad4 complex formation, whereas these complexes are present in the two latter cells. In addition, endogenous smad4 levels in total cell extracts are lower in WI38 and NIH3T3 fibroblasts than in their Large T-expressing counterparts. In WI38 fibroblasts smad4 is, at best, inefficiently translocated to the nucleus. TGF-beta 1-mediated growth-stimulation of these normal fibroblasts does not appear to involve the presently known smads, but this situation is reversed in the Large T-transformed cells inhibited by TGF-beta 1.

The mucin profile of noninvasive and invasive mucinous cystic neoplasms of the pancreas

Recently, it was shown that ductal adenocarcinomas and intraductal papillary-mucinous neoplasms of the pancreas differ in their expression of the mucin markers MUC1 and MUC2 while both tumors express MUC5AC. It is not known whether mucinous cystic neoplasms of the pancreas have their own mucin profile. To clarify this issue, 22 mucinous cystic neoplasms were examined immunohistologically for their expression of MUC1, MUC2, MUC5AC, and MUC6 and also for the protein products of the tumor suppressor genes p53 and DPC4 and the mismatch repair genes. Noninvasive mucinous cystic neoplasms, regardless of the degree of cellular atypia, were all positive for MUC5AC and negative for MUC1, with the exception of the cyst-lining epithelium of a single case with eosinophilic cytology (case no. 16). Only in cases with an invasive component was MUC1 expression observed. MUC2 expression was restricted to goblet cells scattered within the epithelium of the mucinous cystic neoplasms and was often accompanied by endocrine cells, a further indication of intestinal differentiation. DPC4 expression was maintained in all tumors, except for three invasive carcinomas. p53 nuclear reactivity was found in one borderline tumor and four invasive mucinous cystic carcinomas. The results suggest that the epithelium of noninvasive mucinous cystic neoplasms does not differ in its expression of MUC5AC from ductal adenocarcinomas, intraductal papillary-mucinous neoplasms, and metaplastic pancreatic duct epithelium. The fact that noninvasive mucinous cystic neoplasms lack MUC1 expression (except for an eosinophilic variant) but express it when they become invasive might be used as a marker indicating the step of progression from noninvasiveness to invasiveness.

Transforming growth factor beta 1 induces proliferation in colon carcinoma cells by Ras-dependent, smad-independent down-regulation of p21cip1

Transforming growth factor beta1 (TGFbeta1) can act as a tumor suppressor or a tumor promoter depending on the characteristics of the malignant cell. We recently demonstrated that colon carcinoma cells transfected with oncogenic cellular K-rasV12, but not oncogenic cellular H-rasV12, switched from TGFbeta1-insensitive to TGFbeta1-growth-stimulated and also became more invasive (Yan, Z., Deng, X., and Friedman, E. (2001) J. Biol. Chem. 276, 1555-1563). We now demonstrate that TGFbeta1 growth stimulation of colon carcinoma cells is Ras-dependent and smad-independent. In U9 colon carcinoma cells, which are responsive to TGFbeta1 by growth stimulation, a truncating mutation at Gln-311 was found in the smad4 gene. Very little smad4 protein was detected in these cells. Loss of smad4 protein was confirmed by functional studies. In U9 cells co-transfected wild-type smad4, but not mutant smad4, mediated response of the 3TP-lux and pSBE promoter reporter constructs to TGFbeta1. Proliferation initiated by TGFbeta1 in U9 cells required Ras-mediated down-regulation of p21cip1 protein. Less p21cip1 was associated with cdk2 small middle dotcyclin complexes in TGFbeta1-treated U9 cells, and the cdk2 complexes had increased kinase activity. Elevation of p21cip1 levels diminished proliferative response to TGFbeta1. U9 cells expressing DN-N17ras neither proliferated in response to TGFbeta1 nor down-regulated the cdk inhibitor p21cip1, and TGFbeta1 activation of 3TP-lux in U9 cells was inhibited by DN-N17ras in a dose-dependent manner. TGFbeta1 also decreased p21cip1 levels and stimulated proliferation in SW480 cells, which express mutant K-Ras but no smad4 protein. TGFbeta1 did not activate or inhibit the p21cip1 promoter construct in U9 cells even in the presence of co-transfected smad4, or alter p21cip1 mRNA levels. Thus the decrease in p21cip1 levels was mediated by a TGFbeta-initiated Ras-dependent, but smad-independent post-transcriptional mechanism.

Transforming growth factor-beta-induced mobilization of actin cytoskeleton requires signaling by small GTPases Cdc42 and RhoA

Transforming growth factor-beta (TGF-beta) is a potent regulator of cell growth and differentiation in many cell types. The Smad signaling pathway constitutes a main signal transduction route downstream of TGF-beta receptors. We studied TGF-beta-induced rearrangements of the actin filament system and found that TGF-beta 1 treatment of PC-3U human prostate carcinoma cells resulted in a rapid formation of lamellipodia. Interestingly, this response was shown to be independent of the Smad signaling pathway; instead, it required the activity of the Rho GTPases Cdc42 and RhoA, because ectopic expression of dominant negative mutant Cdc42 and RhoA abrogated the response. Long-term stimulation with TGF-beta 1 resulted in an assembly of stress fibers; this response required both signaling via Cdc42 and RhoA, and Smad proteins. A known downstream effector of Cdc42 is p38(MAPK); treatment of the cells with the p38(MAPK) inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(pyridyl)1H-imidazole (SB203580), as well as ectopic expression of a kinase-inactive p38(MAPK), abrogated the TGF-beta-induced actin reorganization. Moreover, treatment of cells with the inhibitors of the RhoA target-protein Rho-associated coiled-coil kinase (+)-R-trans-4-(aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide (Y-27632) and 1-5(-isoquinolinesulfonyl)homopiperazine (HA-1077), as well as ectopic expression of kinase-inactive Rho coiled-coil kinase-1, abrogated the TGF-beta 1-induced formation of stress fibers. Collectively, these data indicate that TGF-beta-induced membrane ruffles occur via Rho GTPase-dependent pathways, whereas long-term effects require cooperation between Smad and Rho GTPase signaling pathways.