Transcriptional regulation by the gamma5 subunit of a heterotrimeric G protein during adipogenesis

The adipocyte enhancer-binding protein (AEBP1) is a novel transcriptional repressor with carboxypeptidase activity. A two-hybrid screen was conducted to identify components of AEBP1 that might be important in regulating its activity. The gamma5 subunit of a heterotrimeric G protein was shown to bind specifically to AEBP1 and to attenuate its transcriptional repression activity. Adipogenic stimulation selectively decreased the Ggamma5 level and enhanced the transcriptional repression activity of AEBP1 during mitotic clonal expansion at the onset of adipogenesis. Thus, the actions of Ggamma5 and AEBP1 are directly linked, which could provide the basis for the regulation of transcription at the onset of differentiation. This report shows that a signal-transducing molecule is involved, by direct protein-protein interaction, in the regulation of transcription during adipogenesis.

Prognostic factors in 2230 Korean colorectal cancer patients: analysis of consecutively operated cases

To define the prognostic factors in Korean colorectal cancer patients, univariate and multivariate analysis were performed on data from 2230 consecutive patients who underwent resection for colorectal cancer at the Seoul National University Hospital. The prognostic variables used for the analysis included patient's age, gender, bowel obstruction, bleeding, symptom duration, preoperative leukocyte count, preoperative serum carcinoembryonic antigen (CEA) level, Dukes' stage, tumor location, tumor size, depth of bowel wall invasion, number of lymph node metastases, histologic differentiation, and gross morphology of tumor. The overall 5-year survival rate was 62%. In the univariate analysis, all the factors except sex, symptom duration, and tumor size were associated with prognosis. Among the factors significant in the univariate analysis, Dukes' stage (p < 0.001), number of lymph node metastasis (p < 0.001), CEA level (p < 0.001), tumor location (p = 0.003), gross morphology of tumor (p = 0.017), and depth of bowel wall invasion (p = 0.031) were significant in the multivariate analysis. Several differences in prognostic factors between colon cancer and rectal cancer were observed. In the multivariate analysis, gross tumor morphology was significant only for colon cancer, and histologic differentiation was significant only for rectal cancer. Lymph node metastasis was an independent prognostic variable for both colon and rectal cancer, but its significance was more prominent for rectal cancer. Although Dukes' stage is the most reliable prognostic predictor, this study shows that other factors (preoperative CEA level, gross morphology of tumor, location of tumor, nodal status) also provide important information for the outcome of the patient.

Establishment and characterization of 12 human colorectal-carcinoma cell lines

In this article, we describe the characteristics of 12 human colorectal-carcinoma cell lines established from 6 primary tumors and 6 metastatic sites of 11 Korean colorectal-carcinoma patients, including the morphology in vivo and in vitro and mutations of K-ras2, p15, p16, p53, APC, beta-catenin, hMLH1 and hMSH2 genes in vitro. No lines were contaminated with Mycoplasma or bacteria. All lines were proven to be unique by DNA-fingerprinting analysis. All lines expressed the surface carcino-embryonic antigen and secreted it into the supernatant fluid. The morphological correlation between the original tumors and cultured cells suggested that the original tumors showing mucinous adenocarcinoma correlated with floating aggregates in culture, and degree of desmoplasia in the original tumor correlated with attached growth in culture. Five of the cell lines showed mutations in the K-ras2 gene, and 6 of the cell lines showed mutations in the p53 gene. The p15 gene was deleted in 2 cell lines, and the p16 gene was hypermethylated in 3 cell lines. The mutation of mismatch-repair genes (hMLH1 and hMSH2) was found in 4 lines, the APC gene and beta-catenin gene were mutated in 9 and 2 lines respectively. These well-characterized colorectal-cancer cell lines should serve as useful tools for investigating the biological characteristics of colorectal cancer.

Establishment and characterization of 12 human colorectal-carcinoma cell lines

In this article, we describe the characteristics of 12 human colorectal-carcinoma cell lines established from 6 primary tumors and 6 metastatic sites of 11 Korean colorectal-carcinoma patients, including the morphology in vivo and in vitro and mutations of K-ras2, p15, p16, p53, APC, beta-catenin, hMLH1 and hMSH2 genes in vitro. No lines were contaminated with Mycoplasma or bacteria. All lines were proven to be unique by DNA-fingerprinting analysis. All lines expressed the surface carcino-embryonic antigen and secreted it into the supernatant fluid. The morphological correlation between the original tumors and cultured cells suggested that the original tumors showing mucinous adenocarcinoma correlated with floating aggregates in culture, and degree of desmoplasia in the original tumor correlated with attached growth in culture. Five of the cell lines showed mutations in the K-ras2 gene, and 6 of the cell lines showed mutations in the p53 gene. The p15 gene was deleted in 2 cell lines, and the p16 gene was hypermethylated in 3 cell lines. The mutation of mismatch-repair genes (hMLH1 and hMSH2) was found in 4 lines, the APC gene and beta-catenin gene were mutated in 9 and 2 lines respectively. These well-characterized colorectal-cancer cell lines should serve as useful tools for investigating the biological characteristics of colorectal cancer.

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.

Suspected hereditary nonpolyposis colorectal cancer: International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer (ICG-HNPCC) criteria and results of genetic diagnosis

PURPOSE

The aim of this study was to determine the frequency of mutations in the mismatch repair genes in families suspected of having hereditary nonpolyposis colorectal cancer.

METHODS

We devised two criteria for families suspected of having hereditary nonpolyposis colorectal cancer (Criteria I and II). Criteria I consist of at least two first-degree relatives affected with colorectal cancer with at least one of the following: development of multiple colorectal tumors including adenomatous polyp, at least one colorectal cancer case diagnosed before the age of 50, and occurrence of a hereditary nonpolyposis colorectal cancer extracolonic cancer (endometrium, urinary tract, small intestine, stomach, hepatobiliary system, or ovary) in family members. Criteria II consist of one colorectal cancer patient with at least one of the following: early age of onset (<40 years); endometrial, urinary tract, or small intestine cancer in the index patient or a sibling (one aged <50 years); and two siblings with other integral hereditary nonpolyposis colorectal cancer extracolonic cancers (one aged <50 years). A questionnaire was mailed to members of the International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer to determine the mutation detection rate in mismatch repair genes from the families fulfilling these criteria. For comparison the mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria in each institution was also obtained.

RESULTS

Data were obtained from eight different institutions (in 7 different countries). In a total of 123 patients from 123 families (67 families fulfilling Criteria I and 56 families fulfilling Criteria II), genetic testing for germline mismatch repair gene variants was performed. Germline mutations of the hMLH1 or hMSH2 genes were identified in 24 families (20 percent). Of these, the mutation detection rate for families fulfilling Criteria I was 28 percent (19/67). The mutation detection rate for families fulfilling Criteria II was 9 percent (5/56). In these eight institutions, the overall mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria was 50 percent (77/154).

CONCLUSION

The Criteria I for suspected hereditary nonpolyposis colorectal cancer have the advantages that they can be applied to nuclear families and they can include extracolonic cancers. The results of this study suggest that families fulfilling Criteria I should be offered genetic testing. The relatively low mutation detection rate in those families fulfilling Criteria II suggests that, using current techniques, genetic testing in these families is not practical.

Germline mutations of E-cadherin gene in Korean familial gastric cancer patients

Gastric cancer is the most common cancer in Korea. Germline mutations of the E-cadherin gene have recently been identified in familial gastric cancer patients. We screened five Korean familial gastric cancer patients to investigate germline mutations of the E-cadherin gene. These patients fulfilled the following criteria: presence of at least two gastric cancer patients within first-degree relatives and one patient diagnosed before the age of 50 years. Abnormal band patterns were found in exons 6 and 10 in two familial gastric cancer patients by polymerase chain reaction-single strand conformation polymorphism analysis (probands from the SNU-G2 and SNU-G1001 families, respectively). DNA sequencing analysis of the E-cadherin gene of these two patients revealed missense mutations in each exon. The SNU-G2 proband harbored a missense mutation from aspartic acid (GAT) to glycine (GGT) at codon 244 in exon 6 of the E-cadherin gene, and the SNU-G1001 proband had a missense mutation from valine (GTG) to alanine (GCG) at codon 487 in exon 10. The SNU-G2 proband was diagnosed with gastric cancer at the age of 38; three brothers and two sisters had died of gastric cancer under the age of 50, and their mother had died of gastric cancer at the age of 63. The SNU-G1001 proband was diagnosed with gastric cancer at the age of 42 and one brother had died of gastric cancer at the age of 49. In summary, we found germline mutations of the E-cadherin gene in two of five Korean familial gastric cancer patients screened.

Structural requirements of Syk kinase for Fcgamma receptor-mediated phagocytosis

The tyrosine kinase Syk plays a critical role in the phagocytic pathway mediated by Fcgamma receptors (FcgammaR). In transfected COS1 cells co-expression of Syk enhances FcgammaR mediated phagocytosis. The other member of the Syk kinase family, the highly homologous tyrosine kinase Zap70, also plays a role in signaling by immunoglobulin gene family receptors, but does not increase the phagocytic efficiency of FcgammaRs. The homologous tandem SH2 and kinase domains of Syk and Zap70 are separated by a nonhomologous region referred to as the unique domain. Zap70's inability to enhance phagocytosis was not due to unique domain tyrosine 292, previously implicated in negative regulation of Zap70 function. We determined the regions of Syk important for its interaction with the phagocytic pathway. An intact kinase domain was required for Syk's effect on phagocytosis. Furthermore, the Syk variant SykB, lacking 23 amino acids in the unique region, signaled for phagocytosis as efficiently as did Syk. We then constructed exchange chimeras between Syk and Zap70 and determined the contributions of the SH2, unique and kinase domains to phagocytic signaling. Our data suggest that the Syk kinase domain, which has high intrinsic kinase activity, is important for facilitating phagocytic signaling by FcgammaRI and FcgammaRIIIA.

Experience of 1446 rectal cancer patients in Korea and analysis of prognostic factors

In order to investigate the changing pattern of rectal cancers in Korea and to identify prognostic factors, we investigated the case histories of 1446 rectal cancer patients who had received surgical treatment. During the study period there were trends toward a decrease in the ratio of rectal cancer to colon cancer, earlier detection (more Dukes' stages A and B and fewer C), a decrease in the number of abdominoperineal resections, and an increase in the number of sphincter-preserving operations. Univariate analysis of prognostic factors showed that gender, obstruction symptoms, preoperative serum carcinoembryonic antigen (CEA) level, tumor size, depth of bowel wall invasion, lymph node metastases (presence and number), tumor differentiation, operative method, and date of operation were significant, but age, symptom duration, and tumor location were not. The use of sphincter-saving operations did not adversely affect the clinical outcome. Multivariate analysis showed lymph node metastasis factor to be the most significant factor (P < 0.001); the depth of bowel wall invasion, differentiation, CEA level, and date of operation were also significant (0.001 < P < 0.05). This study shows that although anatomical extent of disease (depth of invasion and lymph node metastasis) is the most reliable prognostic predictor in rectal cancer, other factors such as preoperative CEA level and tumor differentiation also provide important information on the outcome and use of an anal-preserving operation does not adversely affect the patient survival.

Germline mutations of the APC gene in Korean familial adenomatous polyposis patients

We extensively analyzed genomic DNA and messenger RNA (mRNA) from 62 unrelated Korean patients with familial adenomatous polyposis (FAP) for identification of germline adenomatous polyposis coli (APC) gene mutations. We adopted both single-strand conformation polymorphism (SSCP) analysis and a method of analysis involving the reverse transcription-polymerase chain reaction (RT-PCR) followed by a protein truncation test (PTT). DNA sequencing confirmed all alterations represented by aberrant bands. Germline mutations were identified in 38 patients (61%). Nineteen of the detected mutations were presumed to be novel, thus emphasizing the heterogeneity of the mutational spectrum in Korean FAP patients. In the initial 48 patients, SSCP analysis was followed by PTT for those patients for whom no detectable mutations were found by SSCP. Using this combined approach, we identified germline APC gene mutations in 29 of the 48 FAP patients (60%), including 6 patients in whom SSCP analysis failed to distinguish the mutant allele. In the 14 later patients, we identified truncating mutations in 9 patients (64%) using PTT only. Our results confirm that the mutation detection rate with PTT was superior to that with SSCP, and suggest that PTT would be a more practical screening method to detect germline mutations of the APC gene in FAP patients.

Transcript titers of ecdysteroid receptor components vary between tissues and stages during Drosophila development

In Drosophila, the ecdysteroids trigger the key regulatory cascades controlling the coordinated changes in the developmental pathway of molting and metamorphosis. Ecdysone action is mediated by a heterodimer consisting of the three ecdysone receptor (EcR) isoforms and the ultraspiracle proteins (USP). Heterodimers of these proteins bind to the ecdysone response element and ecdysone to modulate gene transcription. In this study, we developed a competitive reverse transcription polymerase chain reaction (RT-PCR) method to quantify the transcripts of functional ecdysone receptor components in individual tissues and for the whole body. The relatively small amount of variation in usp transcripts of the different tissues indicates that this gene does not perform a spatially restricted function in the late third instar wandering larvae while EcR isoforms were expressed in a more tissue-restricted pattern in the same stage. EcR-B1 was expressed at higher levels in larval tissues that are fated for histolysis, whereas EcR-A predominates in the imaginal discs. This result supports the hypothesis that a particular metamorphic response requires particular EcR isoforms. The transcript levels of the functional ecdysone receptor components fluctuate dramatically during development, suggesting that the regulations of the transcriptional and posttranscriptional levels of these genes play some role in ecdysteroid response during Drosophila development.

Germline mutations in a polycytosine repeat of the hMSH6 gene in Korean hereditary nonpolyposis colorectal cancer

Somatic mutations within a mononucleotide repeat sequence present in the hMSH6 and hMSH3 coding regions have been frequently observed in various human cancer tissues and cell lines showing genomic instability. However, relatively few germline mutations of the repeat sequence have been identified. Two germline mutations in the hMSH6 region have been reported in hereditary nonpolyposis colorectal cancer (HNPCC); however, no germline mutations in the hMSH3 gene have been reported yet. To investigate genetic alterations within an 8 bp polycytosine repeat of the hMSH6 gene and an 8-bp polyadenine repeat of the hMSH3 gene, we amplified the mononucleotide repeat sequences of 35 HNPCC patients, 44 patients suspected of having HNPCC who did not fulfill the criteria of the International Collaborative Group on HNPCC, and 45 patients with sporadic early-onset colorectal cancer who developed colorectal cancer before the age of 40 years without any family history of colorectal cancer. Genetic alteration of the repeat sequence of the hMSH3 gene was not observed, whereas germline frame-shift mutations (one C insertion) in the hMSH6 gene were found in two of the 44 suspected HNPCC patient in whom germline mutations of hMSH2 or hMLH1 had not been detected. An identical frameshift mutation was also observed in another affected member of a suspected HNPCC family. These results suggest that the mutation of hMSH6 is responsible for tumorigenesis in minor groups of suspected HNPCC patients.

Peutz-Jeghers syndrome: a new understanding

Peutz-Jeghers syndrome is an autosomal dominant inherited disorder characterized by hamartomatous polyps in the small bowel and mucocutaneous pigmentation. Patients with Peutz-Jeghers syndrome often present as surgical emergencies with complications of the polyps, such as intussusception, bowel obstruction and bleeding. Furthermore, repeated operations may be needed in some patients, which may result in short bowel syndrome. Although early reports did not demonstrate a predisposition to cancer in patients with this syndrome, more recent studies have described an increased risk for both gastrointestinal and extra-gastrointestinal cancers. Women with the Peutz-Jeghers syndrome have the extremely high risk for breast and gynecologic cancer. Recently, Peutz-Jeghers syndrome susceptibility gene, encoding the serine threonine kinase STK11 (also called LKB1), was identified in families with Peutz-Jeghers syndrome. The identifications of germline mutations in families with Peutz-Jeghers syndrome could be a turning point in the management of Peutz-Jeghers syndrome.

Differentiation of a colon cancer cell line on a reconstituted basement membrane in vitro

Basement membrane, a thin extracellular matrix, functions as a tissue stabilizer that promotes tissue integrity and differentiated phenotype. We studied a human colon cancer cell line, SNU 61, to evaluate its ability to differentiate on basement membrane. Cells were cultured on plastic, reconstituted basement membrane (Matrigel) or polyhydroxyethyl methacrylate (poly HEMA) for 72 h and evaluated by light and electron microscopy. On Matrigel, the cells showed gland formation with highly polarized cells containing basal nuclei and well developed brush border microvilli on the luminal surface. Apoptosis was noted mainly at the luminal side. On electron microscopic examination, numerous long microvilli, abundant cytoplasmic organelles and intercellular junctions were noted in the Matrigel-cultured cells. Intermediate cytoskeletons were scattered in the cytoplasm and existed on the axes of microvilli. Junctional complexes and desmosomes were frequently formed along intercellular spaces. The cells cultured on poly HEMA, on the other hand, were poorly differentiated and contained a few glandular structures with small lumens. Brush border microvilli, characteristic of enterocytic differentiation, were few in number and were developed on the basal surface. Intermediate filaments and microtubules were fewer than in the Matrigel-cultured cells. Carcinoembryonic antigen was expressed on the luminal surface of the Matrigel-cultured cells and in the cytoplasm of the poly HEMA cultured cells. CD44 stained the basolateral surface in the Matrigel-cultured cells, but the basal side was not stained in the poly HEMA cultured cells. These results are consistent with the different localization of microvilli in the Matrigel and in the poly HEMA cultured cells. Our observations suggest that human colon cancer cells on basement membrane can undergo glandular differentiation and that extracellular matrix is an important factor in morphogenesis.

Synthesis and pharmacokinetic profile of 3-methoxymethyl cephalosporin prodrugs

Preparation and biological activity of prodrug-type 3-methoxymethyl cephalosporins were described. From the mixtures, R- and S-prodrugs were separated and their absolute configurations were determined, and also their bioavailability was investigated.

Antitumor activity of 7-[2-(N-isopropylamino)ethyl]-(20S)-camptothecin, CKD602, as a potent DNA topoisomerase I inhibitor

We developed a novel water-soluble camptothecin analogue, CKD602, and evaluated the inhibition of topoisomerase I and the antitumor activities against mammalian tumor cells and human tumor xenografts. CKD602 was a nanomolar inhibitor of the topoisomerase I enzyme in the cleavable complex assay. CKD602 was found to be 3 times and slightly more potent than topotecan and camptothecin as inhibitors of topoisomerase, respectively. In tumor cell cytotoxicity, CKD602 was more potent than topotecan in 14 out of 26 human cancer cell lines tested, while it was comparable to camptothecin. CKD602 was tested for the in vivo antitumor activity against the human tumor xenograft models. CKD602 was able to induce regression of established HT-29, WIDR and CX-1 colon tumors, LX-1 lung tumor, MX-1 breast tumor and SKOV-3 ovarian tumor as much as 80, 94, 76, 67, 87% and 88%, respectively, with comparable body weight changes to those of topotecan. Also the therapeutic margin (R/Emax: maximum tolerance dose/ED58) of CKD602 was significantly higher than that of topotecan by 4 times. Efficacy was determined at the maximal tolerated dose levels using schedule dependent i.p. administration in mice bearing L1210 leukemia. On a Q4dx4 (every 4 day for 4 doses) schedule, the maximum tolerated dose (MTD) was 25 mg/kg per administration, which caused great weight loss and lethality in < 5% tumor bearing mouse. This schedule brought significant increase in life span (ILS), 212%, with 33% of long-term survivals. The ex vivo antitumor activity of CKD602 was compared with that of topotecan and the mean antitumor index (ATI) values recorded for CKD602 were significantly higher than that noted for topotecan. From these results, CKD602 warrants further clinical investigations as a potent inhibitor of topoisomerase I.

Absence or decreased levels of the hMLH1 protein in human gastric carcinoma cell lines: implication of hMLH1 in alkylation tolerance

Defective hMLH1 function has been increasingly associated with acquired cellular resistance to DNA alkylation damage in human colorectal and endometrial cancer cells. To investigate the relationship between the DNA alkylation tolerance and the hMLH1 status in human gastric carcinoma cells, we determined the cellular response to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the mutational changes, and the expression of hMLH1 in 11 human gastric carcinoma cell lines. Of 11 cell lines, 4 (SNU-5, -16, -620, and -719) were sensitive, whereas 7 (SNU-1, -216, -484, -520, -601, -638, and -668) were resistant to the cytotoxic effect of MNNG. As determined by Western analysis, it was evident that all the MNNG-resistant cell lines except one (SNU-601) produced very low or undetectable levels of hMLH1 protein compared to the MNNG-sensitive cell lines. A homozygous non-sense mutation that resulted in truncated protein was found in one MNNG-resistant cell line (SNU-1). Therefore, to determine whether the sensitivity of cells to MNNG can be restored by exogenous expression of hMLH1 protein, wild-type hMLH1 cDNA was introduced into the MNNG-resistant cells (SNU-1). The cytotoxicity test showed that expression of exogenous wild-type hMLH1 protein caused an increase in sensitivity to the cytotoxic effect of MNNG. This restoration was confirmed by an increase in the cell population containing less than the G1 amount of DNA (cell death) in the wild-type hMLH1-transfected cells, as determined by flow cytometry analysis. Together our results suggest that (1) the absence or decreased level of wild-type hMLH1 protein may be a frequent event in the human gastric carcinoma cell lines, (2) such alterations in the hMLH1 protein are closely associated with the MNNG tolerance in the human gastric carcinoma cell lines, and (3) the hMLH1 protein participates not only in the repair of DNA mismatches but also in the mechanism of escape from the cytotoxic effects of DNA alkylation damage.

Germline mutations of hMLH1 and hMSH2 genes in patients with suspected hereditary nonpolyposis colorectal cancer and sporadic early-onset colorectal cancer

PURPOSE

The present study was designed to determine the frequency of germline mutations in the hMLH1 and hMSH2 genes in 31 families suspected of having hereditary nonpolyposis colorectal cancer who do not fulfill the criteria of the International Collaborative Group on Hereditary Nonpolyposis Colorectal Cancer but in whom a genetic basis for colon cancer is strongly suspected and 45 patients with sporadic early-onset colorectal cancer who developed colorectal cancer before the age of 40 years without any family history of colorectal cancer.

METHODS

Genomic DNAs were prepared from peripheral blood samples of patients who were tested. All coding exons and exon-intron borders of these two genes were screened, first with the polymerase chain reaction-single-strand conformation polymorphism method, followed by sequencing of the DNA fragments displaying an abnormal single-strand conformation polymorphism pattern.

RESULTS

In 31 families with suspected hereditary nonpolyposis colorectal cancer, we found six different germline mutations in seven unrelated families, including one missense mutation and three frame-shift mutations in the hMLH1 gene and one missense mutation and one frame-shift mutation in the hMSH2 gene. Totally, frequency of mutation was 23 percent, 16 percent and 7 percent in the hMLH1 and hMSH2, respectively. Only one missense mutation of the hMSH2 gene was identified in 45 patients (2 percent) with sporadic early-onset colorectal cancer. The mutation detection rate in families with suspected hereditary nonpolyposis colorectal cancer was significantly higher than that of patients with sporadic early-onset colorectal cancer (P < 0.05).

CONCLUSION

Our definition of suspected hereditary nonpolyposis colorectal cancer is useful in the diagnosis of hereditary nonpolyposis colorectal cancer and for identifying those families who need genetic presymptomatic diagnosis. Our results indicate that it may be important to perform DNA testing in families suspected of having hereditary nonpolyposis colorectal cancer. On the other hand, we only detected a low mutation rate (2 percent) in 45 patients with sporadic early-onset colorectal cancer.

Genetic identification and management of hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is a syndrome involving a predisposition to cancers of the colon, endometrium and several other extra-colonic sites, accounting for approximately 1-5% of all colorectal cancer cases. It is not easily recognized because of a lack of distinctive clinical markers, making diagnosis and management of this disease problematic. To provide a basis for uniformity in diagnosis of HNPCC, the Amsterdam criteria were proposed and are currently in use. More recently, the discovery of four human mismatch repair genes (hMSH2, hMLH1, hPMS1 and hPMS2) has provided novel insight into the genetic basis of this disease, and raised the possibility of genetic diagnosis for management of HNPCC patients and their family members. This report summarizes the clinicopathologic aspects of HNPCC, reviews the recent genetic findings and surveillance strategies, and suggests a novel designation of certain patients as suspected HNPCC.

Inhibition of Fcgamma receptor-mediated phagocytosis by a nonphagocytic Fcgamma receptor

There are three major classes of human Fcgamma receptors (FcgammaRI, FcgammaRII, and FcgammaRIII) and various isoforms of each class are capable of mediating phagocytosis. FcgammaRIIA is an unusual Fcgamma receptor in that it transmits a phagocytic signal in the absence of an additional receptor subunit. The cytoplasmic domain of FcgammaRIIA contains a conserved motif containing two copies of the sequence YXXL. The tyrosines (Y) within the motif are phosphorylated after receptor crosslinking and the integrity of these conserved sequences is required for efficient phagocytosis. The FcgammaRIIB receptors, FcgammaRIIB1 and FcgammaRIIB2, contain one copy of the cytoplasmic YXXL sequence and do not transmit a phagocytic signal. In B cells, FcgammaRIIB negatively regulates B-cell activation by the B-cell antigen receptor. Human macrophages express both FcgammaRIIA and FcgammaRIIB and while FcgammaRIIA mediates phagocytosis, the function of FcgammaRIIB in these cells is unknown. Using the epithelial/fibroblast-like cell line COS-1 as a model to examine the molecular events that regulate the phagocytosis of IgG-coated cells (EA), we investigated the effect of FcgammaRIIB on FcgammaRIIA signaling. FcgammaRIIB inhibited phagocytosis mediated both by FcgammaRIIA and by a chimeric FcgammaRIIA receptor containing the extracellular domain of FcgammaRI and the transmembrane and cytoplasmic domains of FcgammaRIIA. This inhibition occurred at an early signaling stage because tyrosine phosphorylation of the FcgammaRIIA cytoplasmic domain was inhibited after concurrent stimulation of these receptors with EA. FcgammaRIIB mutations showed the importance of the FcgammaRIIB YXXL for inhibition of FcgammaRIIA-mediated phagocytosis. Deletion of the FcgammaRIIB YXXL or conservative replacement of the YXXL tyrosine substantially reduced the inhibitory signal. FcgammaRIIB had a lesser inhibitory effect on phagocytosis by the Fcgamma receptor FcgammaRIIIA, which requires a gamma subunit to mediate a phagocytic signal. These results show that FcgammaRIIB negatively regulates phagocytic signaling by FcgammaRIIA and suggests that FcgammaRIIB plays a role in modulating FcgammaRIIA function in vivo.

Growth suppression mediated by transfection of wild-type hMLH1 in human cancer cells expressing endogenous truncated hMLH1 protein

Many genes that are frequently mutated in human cancer are known to be involved in the control of normal cellular proliferation. One of the genes involved in DNA mismatch repair is hMLH1, defective mutations of which are found in some familial and various sporadic cancers. Although the DNA mismatch repair activity of hMLH1 has been identified, other biological functions of hMLH1 have not been well investigated. To investigate the effect of wild-type hMLH1 in cellular proliferation, wild-type hMLH1 cDNA was introduced into human colorectal carcinoma cell line HCT116 and human gastric carcinoma cell line SNU-1, each containing a homozygous non-sense mutation at codon 252 and 226 in hMLH1, repectively. The hMLH1-transfected stable clones showed mRNA and protein expression of transfected hMLH1. Three in vitro cell growth experiments demonstrated that compared with parental and vector-transfected control counterparts, both hMLH1-transfected HCT116 and SNU-1 clones displayed: i) decreased cellular proliferation; ii) a significant decrease in the rate of DNA synthesis and iii) a dramatic reduction of anchorage-independence and the size of colonies in semisolid medium. In addition to DNA repair activity, these results suggest that hMLH1 may play a role in the negative regulation of HCT116 and SNU-1 cell growth.

Effect of suramin on differentiation of human stomach cancer cell lines

This study was designed to demonstrate that differentiation of stomach cancer cells can be modified by microenvironmental change and to look for a method inducing or promoting tumor cell differentiation. To evaluate the biomorphological characterization of tumor cell differentiation in suramin-containing in vitro culture of human stomach cancer cell lines, inverted phase-contrast microscopic examination, analysis of growth curves and BrdU-positive S-phase fraction, immunocytochemical study, radioimmunoassay for CEA, transmission electron microscopic examination, DNA flow cytometry, and heterotransplantation in SCID mice were performed. Suramin inhibited tumor cell growth. Development of intracytoplasmic lumina and intercellular lumina was noted in suramin-containing culture with formation of numerous microvilli and frequent desmosomes. The amount of CEA released by a cell was increased in suramin-containing culture. Suramin inhibited heterotransplantation, and a transplant from suramin-containing culture revealed a much higher degree of differentiation than that from suramin-absent culture. Suramin induced no change in DNA ploidy pattern. Elimination of suramin from the culture medium did not reverse the tumor cell differentiation. Each stomach cancer cell line showed a different degree of responsiveness to suramin. In conclusion, this study shows that suramin inhibits growth of SNU-5 and SNU-16 cells and that suramin induces differentiation of SNU-16 cells.

Establishment and characterization of cell lines derived from uterine malignant mixed Müllerian tumor

OBJECTIVE

We report the establishment and characterization of three new cell lines derived from uterine malignant mixed müllerian tumor (MMMT).

METHODS

Three uterine MMMT cell lines from primary tumors of Korean patients were cultured and the involved cell morphology, growth properties, DNA profiles, immunohistochemical properties, tumor-associated antigen secretion, and genetic alterations of related oncogenes and tumor suppressor genes were studied as well.

RESULTS

Three MMMT cell lines were successfully established including one homologous tumor SNU-539 and two heterologous tumors SNU-685 and SNU-1077. All lines showed substrate adherence and high viability and were proven by DNA fingerprinting analysis to be unique. Contamination by mycoplasma and bacteria was excluded. SNU-539 and SNU-1077 cells stained positively for both epithelial and mesenchymal antigens, while SNU-685 cells only stained positively for mesenchymal antigens. The level of secretion of tumor-associated antigens, CA125 and CEA, was shown to be undetectable in all three lines. One missense mutation from AAC to GAC at codon 239 of exon 7 in the p53 gene was identified in SNU-539.

CONCLUSIONS

These newly established and characterized permanent uterine MMMT cell lines might be regarded as valuable resources for a multitude of in vitro investigations, which should be used for clarifying the obscure histogenetic origin and understanding the biological behavior of this aggressive tumor.

Characteristics of human gastric carcinoma cell lines with induced multidrug resistance

In contrast to intrinsic drug resistance, induced multidrug resistance in gastric cancer cells has not been well studied. Therefore, two doxorubicin-resistant cell lines, (SNU-1DOX, SNU-16DOX), were derived in vitro from gastric carcinoma cell lines (SNU-1, SNU-16) respectively, and their characteristics were investigated. These resistances were not associated with overexpression of mdrl, multidrug resistance associated protein 1 (MRP1), pi or liver class of glutathione S transferase (GST pi, GSTL), heat shock protein 70 (HSP70), p53 or transglutaminase C (TGC). Levels of p21WAF1 RNA and topoisomerase II protein were decreased in the SNU-16DOX, but not in SNU-1DOX. However, the subsequent enzyme activity of topoisomerase II in SNU-16DOX was not decreased, but rather increased in SNU-16DOX. Furthermore, both resistant cell lines showed lower uptake and higher efflux of doxorubicin and induced cross-resistance to etoposide and vincristine in addition to doxorubicin, indicating a multi-drug resistance phenotype. In summary, we report two gastric carcinoma cell lines exhibiting induced multidrug resistance phenotype and suggest that mdrl, MRP1, GST, TGC, HSP70 and p53 do not play important roles in induced drug resistance in these cell lines. The role of changes in topoisomerase II activity and/or protein is still inconclusive, and p21WAF1 is associated with induced multidrug resistance in the SNU-16DOX gastric carcinoma cell line.