Genomic structure of human mismatch repair gene, hMLH1, and its mutation analysis in patients with hereditary non-polyposis colorectal cancer (HNPCC)

Mutation of hMLH1, a gene involved in DNA mismatch repair, is responsible for some families carrying the hereditary non-polypotic colorectal cancer (HNPCC) syndrome. To establish a basis for presymptomatic diagnosis of HNPCC patients who carry germline mutations in this gene, we determined the exon-intron organization of hMLH1. The results indicated that hMLH1 consists of 19 coding exons spanning approximately 100 kb, and that exons 1-7 contain a region that is highly conserved in the MLH1 and PMS1 genes of yeast. We used PCR-SSCP analysis and DNA sequencing to examine the entire coding region of the MLH1 gene in DNAs of 34 unrelated cancer patients who belong to HNPCC pedigrees. Germline mutations were detectable in eight (24%) of these patients; four of them were missense mutations, one had occurred in an intron where it would affect splicing, and the remaining three were frameshift mutations resulting in truncation of the gene product downstream of the mutation site.

Adult Hirschsprung's disease. Results of the Duhamel's procedure

Eleven patients with adult Hirschsprung's disease were treated at Seoul National University Hospital (SNUH, 8 cases) and Chosun University Hospital (CUH, 3 cases) between 1985 and 1992. Of the 11 patients, seven were male. The age of the patients ranged from 11 to 30 years, and all presented with chronic constipation and recurrent faecal impactions that required periodic enemas and laxatives. The Duhamel's operation, as a single or staged procedure, was performed in all patients. Levels of aganglionosis in 9 patients were confined to the rectosigmoid colon (82%). There were three major post-operative complications. Two patients developed fistula-in-ano at the anastomotic site, and one patient developed ileus. However, these complications resolved with conservative management. The longterm results were excellent except for one patient who developed impotence. The mean frequency of bowel movements was usually once or twice a day without the aid of other treatments. Our results indicate that Duhamel's operation is a highly acceptable procedure in the management of adult Hirschsprung's disease.

Molecular dissection of Fc gamma receptor-mediated phagocytosis

Using an experimental model in COS-1 cells, we have examined the structural requirements for phagocytosis of IgG-sensitized cells by Fc gamma receptors. We have established that isoforms of each of the 3 classes of the Fc gamma receptors, Fc gamma RI, Fc gamma RII and Fc gamma RIII, are able to transmit a phagocytic signal in the absence of the other receptor class. Fc gamma I and Rc gamma RIIIA require a gamma-subunit for this signaling event, but Fc gamma RIIA does not. Fc gamma RIIA and the gamma-subunit associated with Fc gamma RI and Fc gamma RIIIA contain 2 copies of a conserved tyrosine-containing cytoplasmic sequence, YXXL. This sequence is important for phagocytosis and is phosphorylated on tyrosine after receptor ligation. The Fc gamma receptors Fc gamma RIIB1 and Fc gamma RIIB2 which contain only 1 copy of the YXXL cytoplasmic sequence do not include the phagocytosis of IgG-coated cells. Thus, the Fc gamma receptor isoforms differ in their ability to transmit a phagocytic signal. Structure/function studies also indicate that the Fc gamma receptors which induce phagocytosis differ in their requirements for phagocytic signaling.

CpG island promoter region methylation patterns of the inactive-X-chromosome hypoxanthine phosphoribosyltransferase (Hprt) gene

Inactive-X-chromosome genes in mammalian females have methylated CpG islands. We have questioned whether there are variable levels of cytosine methylation at different CpG sites within the island that might indicate the presence of primary sites of methylation which may be critical for the maintenance of gene repression and candidate sites for the initiation of inactivation. To address these questions, we have analyzed the methylation patterns of 32 CpG sites of the X-linked hypoxanthine phosphoribosyltransferase (Hprt) gene on the active and inactive X chromosomes of mouse tissues and cell lines, using genomic sequencing of bisulfite-treated genomic DNA. Cytosine is deaminated by bisulfite, but methylcytosine is not affected. Cell lines that were heterozygous for the Hprt deletion mutation (Hprtb-m3) and a functional Hprt allele were selected with 6-thioguanine. The resulting cell populations uniformly carry the intact Hprt allele on the inactive X chromosome. The methylation of these CpG sites was determined either by the direct sequence analysis of bisulfite-treated and amplified DNA or by the sequence analysis of clones derived from the amplified DNA. No CpG methylation was detected on the active Hprt genes from either males or the active X chromosome of females. On average, 22 CpGs were methylated in the other 50% of female DNA, and the level of methylation at individual sites varied from 42 to 100%. Analysis of the inactive Hprt gene in two cell lines showed that averages of 14 and 18 CpGs were methylated and that the frequency of methylation at 32 individual sites ranged from 3 to 100%. The highest frequency of methylation in cell lines coincided with the sequences flanking transcription initiation sites. These results suggest that methylation patterns are heterogeneous within a tissue and even in clonal cell populations and that specific subsets of CpG sites sustain high methylation frequencies which may be critical for the maintenance of X-chromosome inactivation. The bisulfite method identified which CpG sites were methylated on the inactive X chromosome, and it provided a quantitative estimate of the frequency of methylation of these sites in genomic DNA.

Os acromiale associated with rotator cuff impingement: MR imaging of the shoulder

PURPOSE

To evaluate the magnetic resonance (MR) imaging findings of os acromiale in rotator cuff disease.

MATERIALS AND METHODS

Retrospective analysis was performed of 10 shoulder MR studies of 10 patients older than 25 years with os acromiale. The authors subdivided these patients into three types on the basis of seven possible configurations.

RESULTS

Eight of the 10 patients with os acromiale showed failure of fusion between the mesoacromion and meta-acromion (type A), one between the preacromion and mesoacromion (type B), and one between the meta-acromion and basiacromion (type C). Osteophytic lipping was seen at the margins of the acromial gap in nine cases. The os acromiale could be detected on the oblique sagittal image, oblique coronal image, or both, and in each case, there was a lesion in the supraspinatus tendon: tendinitis in four patients and tendon tear in six.

CONCLUSION

Os acromiale can be an important cause of rotator cuff impingement and can be detected with routine MR imaging of the shoulder.

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

We have found several genetic changes in the TGF-beta-type II receptor gene in human gastric cancer cell lines resistant to the growth inhibitory effect of TGF-beta. Southern blot analysis showed deletion of the type II receptor gene in two of eight cell lines and amplification in another two lines. The single cell line we studied that is sensitive to growth inhibition by TGF-beta showed no structural abnormalities of the type II receptor gene. Some of the gastric cancer cells resistant to the growth inhibitory effect of TGF-beta express either truncated or no detectable TGF-beta type II receptor mRNAs, whereas the one that retains responsiveness to the growth inhibitory effect of TGF-beta expresses a full-size type II receptor mRNA. Immunoprecipitation followed by Western blot analysis showed parallel changes in TGF-beta type II receptor expression. Our results suggest that one of the possible mechanisms of escape from autocrine or paracrine growth control by TGF-beta during carcinogenesis could involve genetic changes in the TGF-beta type II receptor gene itself or altered expression of its mRNA.

Presymptomatic diagnosis of familial adenomatous polyposis coli

Familial adenomatous polyposis (FAP), an autosomal dominant inherited disease, confers a high risk of colon cancer, and recently the gene responsible for FAP, termed adenomatous polyposis coli (APC) gene, was identified and fully characterized.

PURPOSE

For the presymptomatic diagnosis of FAP, we have performed linkage studies using two polymorphic systems close to or at the APC locus; cytosine-adenine dinucleotide repeat length polymorphism and restriction endonuclease RsaI site polymorphism.

METHODS AND RESULTS

Based on the two polymorphic systems, we have determined the haplotype at the APC locus in 23 individuals of two Korean families with FAP. From these haplotypes of individuals, we could make the diagnosis, whether affected or unaffected, in 74 percent of 31 at-risk persons. To decrease the chance of misdiagnosis caused by recombinant events, the use of haplotypes was better than using one polymorphic system. In addition to polymorphic analysis, we have also searched germline mutations of the APC gene in eight individuals (26 percent of all 31 at risk persons) of another two FAP families which could not be diagnosed definitely by linkage analysis. A 5 base-pairs deletion at codon 1309 was detected in one of the families, and a 5 base-pairs deletion at codon 1185 was also identified in another family by using a ribonuclease protection assay followed by DNA sequencing. From these results, we could diagnose FAP with 100 percent accuracy.

CONCLUSION

Linkage studies by the RsaI site polymorphism and cytosine-adenine repeat length polymorphism as well as the polymerase chain reaction-based sequencing method provide accurate and efficient tools for presymptomatic diagnosis of FAP in their families.

Synthesis and antitumor activity of a series of [2-substituted-4,5-bis(aminomethyl)-1,3-dioxolane]platinum(II) complexes

The synthesis, physical properties, antitumor activity, structure-activity relationships, and nephrotoxicity of a series of [2-substituted-4,5-bis(aminomethyl)-1,3-dioxolane]platinum(II) complexes are described. The 42 platinum(II) complexes having a seven-membered ring structure in this series have been prepared and characterized by 1H NMR, 13C NMR, IR, FAB-MS, and elemental analysis. All members of the series were designed to have a 1,3-dioxolane ring moiety in their carrier ligands to increase water solubility. The solubility of platinum complexes was related to the nature of leaving ligands and 2-substituents in the 4,5-bis(aminomethyl)-1,3-dioxolane carrier ligands. In general, compounds having two different R1 and R2 substituents in the 4,5-bis(aminomethyl)-1,3-dioxolane moiety were more water-soluble than those having the same substituents. Most members of this series showed the excellent antitumor activity against murine L1210 leukemia cells transplanted in mice and were superior to cisplatin and carboplatin. The (4R,5R)-stereoisomer 1a-h exhibited the higher antitumor activity than the corresponding (4S,5S)-stereoisomer 2a-h in the (1,1-cyclobutanedicarboxylato)platinum(II) complexes. The (glycolato)-platinum(II) complexes were highly cytotoxic toward four human stomach cancer cell lines, SNU-1, SNU-5, SNU-16, and NCI-N87, and among them, complexes 3d-g were even more cytotoxic than cisplatin. The (malonato)platinum(II) complex 1m and the (glycolato)platinum(II) complexes 3d-g were selected for further studies based on the greater in vivo and in vitro antitumor activity and desirable physical properties. The complexes 3e-g were almost equally cytotoxic to cisplatin toward human stomach cancer cell lines, KATO-III and MKN-45, and a human non-small cell lung cancer cell line, PC14. In contrast with cisplatin and carboplatin, five complexes selected significantly increased in life span in mice transplanted with cisplatin-resistant L1210 cells. Nephrotoxicity studies in ICR mice indicated that serum BUN and creatinine levels were not elevated when five complexes were given at a dose equal to 1.5 times the optimal dose determined in the in vivo L1210 screening system.

MDR1 gene expression: its effect on drug resistance to doxorubicin in human hepatocellular carcinoma cell lines

BACKGROUND

Hepatic tumors are resistant to many chemotherapeutic agents. Although elevated MDR1 (also known as PGY1) gene expression has been shown in such tumors, no direct association has been established between the gene expression and multidrug resistance.

PURPOSE

To evaluate the role of the MDR1 gene in the drug resistance of hepatoma, we tested nine human hepatoma cell lines for their expression of the MDR1 gene.

METHODS

We measured the MDR1 messenger RNA (mRNA) expression by RNA slot-blot analysis and by immunocytochemical staining with a P-glycoprotein-specific monoclonal antibody, MRK16. The in vitro chemosensitivity of these cell lines to fluorouracil, doxorubicin, mitomycin C, cisplatin, and etoposide (VP-16) was determined using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) colorimetric assay. For doxorubicin cytotoxicity, we also tested the potentiating effect of several multidrug resistance-reversing agents.

RESULTS

Slot-blot analysis and immunocytochemistry showed that two cell lines expressed high levels of MDR1 mRNA, one expressed an intermediate level, and all others were low expressors. The MTT assay results showed that all cell lines tested were generally resistant to chemotherapeutic agents. The assay area under the curve (AUC) was within a clinically achievable range only for VP-16 in one of nine cell lines. When the IC50 values were compared among the cell lines, the results revealed a close association with the MDR1 gene expression only for doxorubicin resistance. Verapamil and quinidine lowered the IC50 values of doxorubicin for MDR1-positive cell lines. The lowered assay AUC levels for both reversing agents, however, were still higher than the clinically achievable range.

CONCLUSION

These results indicate that the MDR1 gene probably has a role in doxorubicin resistance in hepatocellular carcinoma and that the resistance can be overcome by some multidrug resistance-reversing agents.

IMPLICATIONS

Some widely used anticancer agents might be ineffective for treating hepatocellular carcinoma in clinical situations even when combined with reversing agents.

Overexpression of phospholipase C-gamma 1 in familial adenomatous polyposis

Phosphoinositide-specific phospholipase C (PLC) isozymes occupy a central role in the signal transduction system by regulating various cellular processes including proliferation and differentiation. In the present study, we examined the contents of PLCs in colorectal adenomas, carcinomas, and normal mucosa obtained from 4 familial adenomatous polyposis patients to find out whether this enzyme plays any role in the pathogenesis of adenomas and/or carcinomas in familial adenomatous polyposis. Radioimmunoassay and immunoblot analysis revealed that in contrast to little difference in PLC-beta 1 and PLC-delta 1 content, a considerably higher level of PLC-gamma 1 was detected in 3 of 4 cases for adenoma and in all cases for carcinoma as compared to normal mucosa. The level of PLC-gamma 1 expression increased from normal mucosa to adenoma, and finally to carcinoma progressively. Immunohistochemical findings also confirmed this observation. Likewise, activity of PLC-gamma 1 was considerably higher in adenomas and carcinomas than in normal mucosa. These results suggest that PLC-gamma 1-mediated signal transduction may play a significant role in the progression of colorectal tumors in patients with familial adenomatous polyposis.

Elevated content of phospholipase C-gamma 1 in colorectal cancer tissues

BACKGROUND

Phospholipase C isozymes (PLC) play a role in ligand-mediated signal transduction for cellular activity, such as proliferation and differentiation. However, the biologic significance of their molecules in carcinogenesis or tumor progression is yet to be determined.

METHODS

Using PLC isozyme-specific antibodies, the relative content of PLC in human colorectal carcinomas and in normal colonic mucosa was examined.

RESULTS

Immunoreactive analysis revealed considerably higher levels of PLC-gamma 1 protein in 15 of 17 colorectal carcinomas and little difference in PLC-beta 1 or PLC-gamma 1 content compared with normal colorectal tissues. By radioimmunoassay and Western blotting, PLC-gamma 1 showed three-fold to fourfold more expression in carcinomas than that in normal tissues.

CONCLUSION

Although factors that might influence the level of PLC-gamma 1 expression in colorectal carcinomas still remain obscure, the fact that most colorectal carcinomas display elevated levels of PLC-gamma 1 expression implies that PLC-gamma 1 may play an important role in proliferation of colorectal carcinoma cells.

Genetic instability in pancreatic cancer and poorly differentiated type of gastric cancer

To examine genetic instability during carcinogenesis, we screened 171 carcinomas of the breast, liver, proximal colon, stomach, pancreas, uterine cervix, and ovary for replication error at four microsatellite marker loci on chromosome 2, 3, and 17. A significantly high incidence of genetic instability was observed in pancreatic (6 of 9 tumors) and gastric cancers (22 of 57 cases). In other types of carcinoma, the incidence of replication error-positive cases was relatively low (3-16%). Among gastric carcinomas, significantly more replication error-positive cases were observed in the poorly differentiated types (16 of 25 cases) than in well differentiated types (3 of 18) (P = 0.0023 by Fisher's exact test). Our results suggested that genetic instability is likely to play an important role in development of pancreatic and gastric cancers, particularly poorly differentiated adenocarcinomas.

Conserved cytoplasmic tyrosine residues of the gamma subunit are required for a phagocytic signal mediated by Fc gamma RIIIA

Fc receptors for immunoglobulins are found on many cells and are important in host defense. We transfected Fc gamma RIIIA, present on macrophages and natural killer (NK) cells, into COS-1 cells to study its role in phagocytosis and calcium mobilization in the absence of other Fc gamma receptors. Human Fc gamma RIIIA-alpha (CD16) was cotransfected with its associated chains, either Fc gamma RIIIA gamma or zeta. Both gamma and zeta were observed to induce a phagocytic signal, but gamma was at least sixfold more effective than zeta. Conservative substitution by phenylalanine of either one of the two cytoplasmic tyrosine residues in the gamma chain resulted in markedly diminished phagocytosis and calcium mobilization. Tyrphostin 23, an inhibitor of tyrosine kinases, reversibly inhibited phagocytosis. Further, in vitro kinase assays with the wild type and mutant gamma chains demonstrated that the wild type gamma chain, but not the mutant gamma chains, is phosphorylated. These results suggest that the cytoplasmic tyrosine residues and tyrosine phosphorylation are required for Fc gamma RIIIA to mediate two signal transduction events: phagocytosis and calcium mobilization.

In the absence of other Fc receptors, Fc gamma RIIIA transmits a phagocytic signal that requires the cytoplasmic domain of its gamma subunit

The transmembrane isoform of Fc gamma RIII, Fc gamma RIIIA, is found on NK cells, cultured monocytes, and tissue macrophages in association with a dimer of an accessory subunit, either gamma or zeta. Functions of individual Fc receptors have been difficult to analyze due to coexpression of the receptors on hematopoietic cells and permanent cell lines expressing Fc receptors. cDNAs for the alpha and gamma subunits of Fc gamma RIIIA were cotransfected into COS-1 cells, which lack endogenous Fc receptors, to evaluate receptor-mediated phagocytosis and changes in [Ca2+]i. Transfectants both bound and phagocytosed IgG-sensitized erythrocytes and, following activation of Fc gamma RIIIA, increased [Ca2+]i. The gamma subunit was essential both for the surface expression of the receptor and for transduction of the phagocytic signal. Truncation of the gamma subunit cytoplasmic domain (amino acids 65-80) eliminated phagocytic function. Phorbol ester inhibited phagocytosis in a concentration-dependent manner, but did not affect IgG-sensitized erythrocytes binding, suggesting that a protein kinase C-dependent pathway inhibits phagocytosis. The data indicate that a tyrosine containing cytoplasmic domain within the gamma subunit is required for phagocytosis by Fc gamma RIIIA.

Expression of carcinoembryonic antigen and related genes in lung and gastrointestinal cancers

Carcinoembryonic antigen (CEA), a tumor marker for lung cancers of small cell (SCLC) and non-small cell (NSCLC) types, belongs in a multigene family which includes non-specific cross-reacting antigen (NCA) and biliary glycoprotein 1 (BGP). We used specific cDNA probes and a CEA immunoassay to determine the pattern of expression in normal and malignant lung and gastrointestinal (GI) tissues. Normal lung contained high amounts of NCA and a low concentration of CEA. All 3 genes were expressed discordantly in lung tumors and cell lines. In contrast, all three genes were expressed in most G1 tumor cell lines. In both lung and colorectal cell lines expression of NCA RNA was relatively high, while BGP RNA was relatively low, and the median concentrations of CEA were greater than in corresponding non-malignant tissues. While CEA protein concentrations in lung cell lines were similar to those present in G1 cell lines, the ratio of NCA:CEA RNA was significantly higher in lung cancer lines than in colorectal lines. Thus, NCA constitutes most of the "CEA-like" immunoreactivity previously described in lung cancers. There was excellent concordance between expression of CEA RNA and CEA protein, as well as between concentrations of CEA protein in cell line pellets and supernatant fluids. Of interest, significantly higher rates of CEA expression were present in lung cancers expressing neuroendocrine (NE) markers. The association between CEA expression and NE cell properties is intriguing and may prove to be of clinical interest.

Risk of gastric cancer among Korean familial adenomatous polyposis patients. Report of three cases

Gastric cancer has been recognized as an extracolonic manifestation in patients with familial adenomatous polyposis (FAP). In Korea, gastric cancer is the most common malignant neoplasm. In a recent survey, we collected data from 72 Korean patients with FAP. Among them, three (4.2 percent) were found to have associated gastric cancer. This incidence of gastric cancer in our series is much higher than the previous reports from Japan and other countries. The expected cumulative incidence of gastric cancer among these 72 patients was 0.44, which gives the standardized incidence ratio of 6.9 (95 percent CI, 1.4-20.1). This difference in incidence of gastric cancer was statistically significant (P less than 0.05), which implies that patients with FAP are at significantly higher risk of developing gastric cancer compared with the general population in Korea. These findings confirm an increased risk of gastric cancer in FAP patients, even in a region where gastric cancer is highly prevalent.

Large-scale molecular mapping of human c-myb locus: c-myb proto-oncogene is not involved in 6q- abnormalities of lymphoid tumors

Chromosomal abnormalities in the 6q region have been observed frequently in several T-cell and myeloid leukemias. Interestingly, this region was found to contain three cellular oncogenes, c-myb, c-fyn and c-ros. Several of the tumors that exhibit 6q- abnormalities have also been found to express high levels of c-myb and, in some cases, amplification of the c-myb gene, leading to the suggestion that this gene could lie in proximity to the deletions observed in these tumors. To determine if c-myb gene activation is associated with 6q- abnormalities, we developed a megabase map of the human c-myb locus using pulsed-field gel electrophoresis. We then examined the occurrence of abnormalities near the c-myb gene in several hematopoietic tumor cell lines containing well-characterized 6q- abnormalities. Our results show that no rearrangements or deletions occur within a region of 1.0 Mbp of the c-myb locus in these cell lines. However, several of the cell lines exhibited differential and partial methylation patterns which seem to be prevalent amongst different cell lines.

Effects of buthionine sulfoximine treatment on cellular glutathione levels and cytotoxicities of cisplatin, carboplatin and radiation in human stomach and ovarian cancer cell lines

Chemotherapy failure remains a significant medical problem in the treatment of neoplastic disease and is thought to be due to many different factors including membrane transport, p-glycoprotein in multidrug resistance, glutathione and its related enzymes, topoisomerase II and DNA repair. Glutathione is a major constituent of non-protein thiol and participates in detoxification of chemotherapy and radiation. Thus, glutathione concentration is correlated with sensitivity to alkylating agents and radiation, and increased in resistant cell lines. Buthionine sulfoximine (BSO) is an inhibitor of glutathione biosynthesis and may increase cytotoxicities of alkylating agents, including melphalan and cisplatin, and radiation in sensitive and resistant cell lines. We studied effects on cellular glutathione levels and cytotoxicities of cisplatin, carboplatin and radiation by BSO treatment in human stomach cancer cell line (SNU-1) and ovarian cancer cell line (OVCAR-3). The results were as follow: 1) After BSO treatment of 1 mM and 2 mM for 2 days, the intracellular thiol concentration was depleted to 75.7% and 76.2% in SNU-1, and 74.1% and 63.0% in OVCAR-3, respectively. 2) The intracellular thiol concentration in SNU-1 was depleted to 33.4% after BSO 2 mM for only 2 hours incubation and 71.5% after small amount of BSO (0.02 mM) for 2 days. 3) The recovery of intracellular thiol concentration required more than 3 days after BSO removal. 4) BSO inhibited partially the growth of SNU-1 and OVCAR-3. 5) The cytotoxicities of cisplatin and carboplatin were markedly enhanced both in SNU-1 and OVCAR-3 by BSO treatment. 6) The cytotoxicities of radiation was increased in OVCAR-3 and SNU-1 by BSO treatment. Therefore, it is concluded that BSO can deplete effectively the intracellular thiol concentration and enhance the cytotoxicities of cisplatin, carboplatin and radiation.

Chromogranin-a expression in gastric and colon cancer tissues

We studied the expression of chromogranin A (CgA) in human gastric (n = 17) and colorectal (n = 18) adenocarcinomas by nucleic acid hybridization and immunohistochemical analyses using a specific monoclonal antibody (MAb) to human chromogranin A (CgA). Some corresponding adjacent non-malignant mucosal tissues were also examined.

RESULTS

(1) Northern blotting: of 3 normal gastric mucosas examined, 2 (67%) had an easily detected signal for expression of CgA. Only one of 14 gastric carcinomas (7%) and one of 18 colorectal carcinomas (6%) had easily detected RNA signals. (2) Immunohistochemical staining: all non-malignant samples of gastric and colonic mucosa contained CgA-positive neuroendocrine (NE) cells. Two of 17 (12%) gastric adenocarcinomas, and 3 of 18 (17%) of colorectal adenocarcinomas contained CgA-positive tumor cells. Interestingly, the positive cases detected by immunohistochemistry included both cases detected by Northern blotting. Of the 5 cases detected by immunohistochemistry, 2 gastric cancers and 1 rectal carcinoma contained many diffusely scattered positive cells, occurring singly or in small clusters, while 2 colorectal carcinomas contained only occasional single CgA-positive tumor cells. In one of the positive gastric cases, a well-differentiated adenocarcinoma arising in a tubular adenoma, both the adenomatous and the carcinomatous elements contained positively staining cells. Our specific assays for CgA indicate that (1) a NE cell component, either diffusely scattered or occasional, occurs in about 15% of gastric and colorectal tumors; (2) there is no correlation between the presence of NE cells and degree of tumor differentiation; and (3) because only a minority of the tumor cells in positive cases stain for CgA, immunohistochemistry is a more sensitive method than Northern blotting.

Autonomous proliferation of colon cancer cells that coexpress transforming growth factor alpha and its receptor. Variable effects of receptor-blocking antibody

Four human colon adenocarcinoma cell lines, SNU-C1, SNU-C4, SNU-C5, and NCI-H716, that are capable of proliferating autonomously in serum-free medium containing no added peptide growth factors were identified. All four cell lines show epidermal growth factor (EGF) receptors (EGFRs), express transforming growth factor alpha (TGF-alpha) messenger RNA, and release anti-TGF-alpha-immunoreactive molecules. The blocking anti-EGFR monoclonal antibody (mAb) 225 blocks autonomous proliferation of SNU-C1 and SNU-C4 cells. In both of these cell lines, the inhibitory effect of mAb 225 is reversible by the addition of EGF, TGF-alpha, or conditioned medium from any of the four cell lines. In contrast, autonomous proliferation of SNU-C5 and NCI-H716 cells is not inhibited by mAb 225 and is not affected by exogenous EGF, TGF-alpha, or conditioned medium. Together, these data confirm the previous finding that anti-EGFR antibodies can inhibit the proliferation of some carcinoma cell lines that coexpress TGF-alpha and EGFR. However, here it is shown that the mechanisms of autonomous proliferation of colon carcinoma cell lines are heterogeneous and not always sensitive to antibody disruption of TGF-alpha/EGFR autocrine interactions.

Pattern of growth factor, proto-oncogene and carcinoembryonic antigen gene expression in human colorectal carcinoma cell lines

The aim of the present study was to examine whether the expression of growth factor genes, proto-oncogenes and carcinoembryonic antigen (CEA) gene in human colorectal cancer cell lines was related to their clinicobiological behavior. A significant variability among cell lines was detected for both insulin-like growth factor II and transforming growth factor beta gene message. Detectable levels of c-myc, Her-2, c-myb, K-ras and EGF receptor mRNA were found in most cell lines, whereas only 1/11 and 2/11 cell lines were positive for N-myc and c-sis message, respectively. N-myc expression was limited to a cell line originated from a tumor with neuroendocrine features, while high levels of K-ras message were found only in a cell line derived from a radioresistant tumor. CEA mRNA levels correlated well with the concentration of antigen in each cell line. On the basis of these results, our findings demonstrated that human colorectal cancer cell lines show heterogeneous expression of growth factor and CEA genes and proto-oncogenes; however, with the exception of K-ras, N-myc and CEA, other correlations between gene expression and the clinicobiological characteristics of these cell lines could not be demonstrated.

Occurrence of p53 gene abnormalities in gastric carcinoma tumors and cell lines

We explored the state of the p53 gene in gastric cancer. Using one or more methods, we examined 15 specimens from primary carcinomas (14 tumors, one cell line), five cell lines derived from metastases, and seven paired samples of nonmalignant gastric mucosa. Sequence analyses of complementary DNA containing the entire p53 gene open reading frame demonstrated abnormalities in one of five samples from primary tumors and in all five samples from metastases. The single cell line derived from a primary carcinoma had no abnormality of the gene. The six abnormalities included four point mutations, one base-pair deletion resulting in a frame shift, and a 24 base-pair deletion caused by an intronic point mutation (as determined by sequence analysis of genomic DNA). Four of the six mutations mapped to regions highly conserved among species or involved in simian virus 40 T-antigen binding. Restriction fragment length polymorphism studies confirmed that chromosome 17p allelic deletions occur only in a minority of primary tumors, but that they may occur more frequently in metastases. Northern blotting and ribonuclease protection assays detected only a fraction of the p53 gene abnormalities detected by sequencing. Our findings indicate that mutations of the p53 gene are relatively rare in primary gastric tumors but appear to be relatively frequent in cell lines derived from metastatic lesions. Our results may help in understanding the molecular events associated with progression and metastasis in gastric carcinoma.