Correlation between the status of the p53 gene and survival in patients with stage I non-small cell lung carcinoma

The association of p53 abnormalities with the prognosis of patients with non-small cell lung carcinoma (NSCLC) has been extensively investigated to date, however, this association is still controversial. Therefore, we investigated the prognostic significance of p53 mutations through exons 2 to 11 and p53 protein expression in 103 cases of stage I NSCLC. p53 mutations were detected in 49 of 103 (48%) tumors. Two separate mutations were detected in four tumors giving a total of 53 unique mutations in 49 tumors. Ten (19%) of mutations occurred outside exons 5-8. Positive immunohistochemical staining of p53 protein was detected in 41 of 103 (40%) tumors. The concordance rate between mutations and protein overexpression was only 69%. p53 mutations, but not expression, were significantly associated with a shortened survival of patients (P<0.001). Furthermore, we investigated the correlation between the types of p53 mutations and prognosis. p53 missense mutations rather than null mutations were associated with poor prognosis (P < 0.001 in missense mutations and P=0.243 in null mutations). These results indicated that p53 mutations, in particular missense mutations, rather than p53 expression could be a useful molecular marker for the prognosis of patients with surgically resected stage I NSCLC.

The p16 (CDKN2A) gene is involved in the growth of neuroblastoma cells and its expression is associated with prognosis of neuroblastoma patients

We previously reported that loss of heterozygosity (LOH) on chromosome 9p21 correlates with poor prognosis of neuroblastoma and the p16 gene is not expressed in approximately two thirds of neuroblastoma cell lines. Here we demonstrated that p16 expression was induced by 5-aza-2-deoxycytidine treatment in cell lines with 5' CpG island methylation but not in cell lines without methylation. Furthermore, the cell cycle of neuroblastoma cell lines significantly delayed with accumulation of cells in G1 phase by transfection of a wild-type p16 expression vector. These results indicate that p16 is inactivated in part by DNA methylation and its expression is involved in the growth of neuroblastoma cells in vitro. To assess the biological and clinical significance of p16 expression in primary tumors, we undertook immunohistochemical analysis in 74 paraffin sections of neuroblastomas. p16 protein was undetectable in 45 of 74 cases (61%) and lack of p16 expression significantly correlated with poor prognosis of patients and advanced stage of the disease. There was no correlation between loss of p16 expression and N-myc amplification in these tumors. These results indicate that inactivation of the p16 gene is involved in the progression of neuroblastoma independently of N-myc amplification.

Clinicopathological significance of Fhit protein expression in stage I non-small cell lung carcinoma

Abnormalities in structure and expression of the FHIT gene have been detected in a considerable fraction of primary lung tumors. Previous reports indicated that FHIT gene alterations can be simply detected by immunohistochemical methods. Therefore, we investigated the association of Fhit expression with clinicopathological features and allelic imbalance (AI) at the FHIT locus in 105 stage I non-small cell lung cancers (NSCLC) by the immunohistological method and PCR analysis. Thirty-six of 105 (34%) tumors showed marked reduction of Fhit immunoreactivity. Fhit expression was markedly reduced in most squamous cell carcinomas (24 of 28, 86%), whereas such a reduction was detected only in a small subset of adenocarcinomas (7 of 67, 10%; P < 0.001). A marked reduction of Fhit protein expression was observed more frequently in patients with a smoking history (32 of 80, 40%) than in patients without a smoking history (4 of 25, 16%; P = 0.013). These results indicate that FHIT gene alterations preferentially occur in squamous cell carcinomas and in smokers. Furthermore, a reduction of Fhit protein expression in tumor cells was associated with a poorer survival of patients with stage I NSCLC, irrespective of histological subtypes of tumors (P = 0.005; log-rank test). Fhit expression was reduced preferentially in tumors with AI at the FHIT locus; however, AI at the FHIT locus did not correlate with patients' survival (P = 0.262; log-rank test). These results suggested that Fhit protein expression could be a useful molecular marker for the prognosis of patients with surgically resected stage I NSCLC.

Sp1-mediated transcription of the Werner helicase gene is modulated by Rb and p53

The regulation of Werner's syndrome gene (WRN) expression was studied by characterizing the cis-regulatory elements in the promoter region and the trans-activating factors that bind to them. First, we defined the transcription initiation sites and the sequence of the 5' upstream region (2.8 kb) of WRN that contains a number of cis-regulatory elements, including 7 Sp1, 9 retinoblastoma control element (RCE), and 14 AP2 motifs. A region consisting of nucleotides -67 to +160 was identified as the principal promoter of WRN by reporter gene assays in HeLa cells, using a series of WRN promoter-luciferase reporter (WRN-Luc) plasmids that contained the 5'-truncated or mutated WRN upstream regions. In particular, two Sp1 elements proximal to the transcription initiation site are indispensable for WRN promoter activity and bind specifically to Sp1 proteins. The RCE enhances WRN promoter activity. Coexpression of the WRN-Luc plasmids with various dosages of plasmids expressing Rb or p53 in Saos2 cells lacking active Rb and p53 proteins showed that the introduced Rb upregulates WRN promoter activity a maximum of 2. 5-fold, while p53 downregulates it a maximum of 7-fold, both dose dependently. Consistently, the overexpressed Rb and p53 proteins also affected the endogenous WRN mRNA levels in Saos2 cells, resulting in an increase with Rb and a decrease with p53. These findings suggest that WRN expression, like that of other housekeeping genes, is directed mainly by the Sp1 transcriptional control system but is also further modulated by transcription factors, including Rb and p53, that are implicated in the cell cycle, cell senescence, and genomic instability.

Evidence for a putative telomerase repressor gene in the 3p14.2-p21.1 region

Telomeres, which are the repeated sequences located on both ends of chromosomes in eukaryotes, are known to shorten with each cell division, and their eventual loss is thought to result in cellular senescence. Unlike normal somatic cells, most tumor cells show activation of telomerase, a ribonucleoprotein enzyme that stably maintains telomere length by addition of the sequences of TTAGGG repeats to telomeres. The KC12 cell line derived from a renal cell carcinoma in a patient with von Hippel-Lindau disease showed telomerase activity and loss of heterozygosity on the short arm of chromosome 3. Introduction of a normal human chromosome 3 into KC12 cells by microcell fusion induced cellular senescence, accompanied by suppression of telomerase activity and shortening of telomere length. Microcell hybrids that escaped from cellular senescence maintained telomere length and telomerase activity similar to those of the parental KC12 cells. We previously showed a similar suppression of telomerase activity by introduction of chromosome 3 into another renal cell carcinoma cell line, RCC23. The putative telomerase repressor gene was mapped to chromosome region 3p14.2-p21.1 by deletion mapping of KC12 + chromosome 3 revertants that escaped from cellular senescence and by transfer of subchromosomal fragments of chromosome 3 into RCC23 cells.

[Early saturated form of slow phase eye velocity in optokinetic nystagmus in dizzy patients]

The peculiar form of the optokinetic nystagmus (OKN) in the electro-oculogram (EOG) was studied in 26 dizzy patients. The slow phase velocity is saturated below 60 degrees (53.7 +/- 6.5) and keeps steady state level in response to higher stimulus velocities, while the peak velocity rises up to 94.6 +/- 16.5 degrees in healthy subjects. In contrast, the frequency of slow phase nystagmus (200.3 +/- 22.6) ranges within normal limits (218.0 +/- 23.4). These characteristics were significant in the student t-test. In Cohen and Raphan's model, slow phase of OKN is supposed to be composed of two components: one is the direct pathway which is responsible for a initial rapid rise. Another is the indirect pathway which contains the velocity storage integrator and is responsible for a slower rise to a steady state level. According to Waespe et al (1983), the initial rapid rise was severely attenuated and the peak velocity of OKN declined to the preoperated saturation level of OKAN after flocculectomy in monkeys. These findings were remarkably coincident with the present study. Additionally, in 5 cases, neuroradiological studies revealed small lesions in the cerebellum. Thus, it is concluded such form of OKN is suggested to be the small lesion in the cerebellum, especially flocculus.

Molecular karyotype (amplotype) of metastatic colorectal cancer by unbiased arbitrarily primed PCR DNA fingerprinting

Genomic instability characterizes the aneuploid cancer cell. Losses of genetic material are critical in cancer by exposing recessive mutations in tumor suppressor genes. Gains of genetic material also may lead to overexpression of genes contributing to tumor progression either in the presence or absence of mutation. However, the detection of moderate gains (such as tri-tetraploidy) has been a challenge in cancer research. Unbiased DNA fingerprinting by the arbitrarily primed PCR allows the detection of moderate gains (in addition to losses) of DNA sequences of known chromosomal localization. We have generated in this manner a molecular karyotype of metastatic colon cancer. This amplotype shows that sequences from several chromosomes undergo both losses (1, 4, 9, 14, and 18) and gains (6, 7, 12, and 20) in over half of the tumors. Moreover, gains of sequences from chromosomes 8 and 13 occurred in most tumors, indicating the existence in these chromosomes of positive regulators of cell growth or survival that are under strong positive selection during tumor progression. We conclude that overrepresentation of these chromosomal regions is a critical step for metastatic colorectal cancer. Comparative amplotype analysis from primary and metastatic tumors suggest the existence in chromosome 4 of gene(s) whose loss is specifically selected in cells that reach the metastatic stage.

A novel tumor suppressor locus on chromosome 18q involved in the development of human lung cancer

The high incidence of loss of heterozygosity (LOH) on chromosome 18q in advanced non-small cell lung carcinomas indicates the presence of tumor suppressor gene(s) on this chromosome arm, which plays an important role in the acquisition of malignant phenotypes in lung cancers. In the present study, we examined 62 lung cancer specimens and 54 lung cancer cell lines for allelic imbalance at 11 microsatellite loci to define common regions of 18q deletions. Allelic imbalance of 18q was detected in 24 (55.8%) non-small cell lung carcinoma specimens and in 6 (31.6%) small cell lung carcinoma specimens, whereas a similar frequency of LOH was statistically inferred to occur in cell lines by analyzing marker homozygosity as an indirect measure of LOH. Five specimens and 11 cell lines showed partial or interstitial deletions of chromosome 18q, and 2 of them had homozygous deletions at the 18q21.1 region. A commonly deleted region was assigned between the D18S46 and y953G12R loci. The size of this region is less than 1 Mb, and the coding exons of three candidate tumor suppressor genes, Smad2, Smad4, and DCC, were mapped outside the region. This result suggests that the common region harbors a novel tumor suppressor gene involved in the progression of lung cancer.

Infrequent mutations of the hOGG1 gene, that is involved in the excision of 8-hydroxyguanine in damaged DNA, in human gastric cancer

DNA glycosylase, encoded by the hOGG1 gene, repairs 8-hydroxyguanine (oh8Gua), which is an oxidatively damaged mutagenic base. To clarify whether the DNA repair activity of hOGG1 protein is involved in gastric carcinogenesis, we examined 9 gastric cancer cell lines and 35 primary gastric cancers for mutations and genetic polymorphisms of the hOGG1 gene by polymerase chain reaction-single strand conformation polymorphism analysis. A G-to-A transition was detected in a gastric cancer cell line, MKN1. This nucleotide change caused the conversion of the amino acid from Arg to His at codon 154, which is located in a domain highly conserved among human, mouse, and yeast OGG1 proteins. No mutation was detected in primary gastric cancers. We compared the distribution of the polymorphic alleles associated with enzymatic activity (hOGG1-Ser326 vs. hOGG1-Cys326) between 35 gastric cancer patients and 42 healthy individuals. Although the frequency of the Cys326 allele, associated with low enzymatic activity, in gastric cancer patients was a little higher than that in healthy individuals, the difference did not reach statistical significance. These results suggest that low hOGG1 activity due to mutations and genetic polymorphisms is involved in the development of only a small subset of gastric cancers.

Association of CDKN2A(p16)/CDKN2B(p15) alterations and homozygous chromosome arm 9p deletions in human lung carcinoma

To elucidate the possibility of the existence of multiple tumor suppressor genes on chromosome arm 9p, we performed genetic and epigenetic analyses of the CDKN2A/p16/MTS1 and CDKN2B/p15/MTS2 genes as well as homozygous deletion mapping of 9p in human lung carcinoma. To avoid overlooking genetic alterations due to contamination of noncancerous cells, we examined 32 non-small cell lung carcinoma (NSCLC) and 16 cell small cell lung carcinoma (SCLC) cell lines. (CDKN2A was mutated or homozygously deleted in 20 (63%) of 32 NSCLC cell lines, and methylation of the CpG island in the CDKN2A gene was detected in six of the 12 cell lines carrying the wild-type CDKN2A gene. Although homozygous deletions of the CDKN2B gene were also detected in NSCLC cell lines with CDKN2A deletions, mutation and methylation in the CDKN2B gene were infrequent. Thus, it was indicated that the CDKN2A gene rather than the CDKN2B gene plays a critical role as a tumor suppressor gene in NSCLC. Homozygous deletions on 9p were detected in 14 (44%) NSCLC cell lines. It is of note that two common regions of homozygous deletions were mapped proximal to the CDKN2A and CDKN2B loci, suggesting that tumor suppressor genes other than CDKN2A are present on 9p. In contrast to NSCLC, homozygous deletions on 9p as well as CDKN2A and CDKN2B alterations were infrequent in SCLC. Therefore, the pathogenetic significance of 9p alterations is likely to differ between SCLC and NSCLC.

Genetic polymorphisms and alternative splicing of the hOGG1 gene, that is involved in the repair of 8-hydroxyguanine in damaged DNA

The hOGG1 gene encodes a DNA glycosylase that excises 8-hydroxyguanine (oh8Gua) from damaged DNA. Structural analyses of the hOGG1 gene and its transcripts were performed in normal and lung cancer cells. Due to a genetic polymorphism at codon 326, hOGG1-Ser326 and hOGG1-Cys326 proteins were produced in human cells. Activity in the repair of oh8Gua was greater in hOGG1-Ser326 protein than in hOGG1-Cys326 protein in the complementation assay of an E. coli mutant defective in the repair of oh8Gua. Two isoforms of hOGG1 transcripts produced by alternative splicing encoded distinct hOGG1 proteins: one with and the other without a putative nuclear localization signal. Loss of heterozygosity at the hOGG1 locus was frequently (15/ 23, 62.2%) detected in lung cancer cells, and a cell line NCI-H526 had a mutation leading to the formation of the transcripts encoding a truncated hOGG1 protein. However, the oh8Gua levels in nuclear DNA were similar among lung cancer cells and leukocytes irrespective of the type of hOGG1 proteins expressed. These results suggest that the oh8Gua levels are maintained at a steady level, even though multiple hOGG1 proteins are produced due to genetic polymorphisms, mutations and alternative splicing of the hOGG1 gene.

Inactivation of the PTEN/MMAC1/TEP1 gene in human lung cancers

The PTEN/MMAC1/TEP1 gene has been isolated as a tumor suppressor gene that is altered in several types of human tumors including brain, breast, and prostate cancers. In the present study, we report PTEN/MMAC1/TEP1 alterations in human lung cancers. Intragenic homozygous deletions were detected in 6 (40%) of 15 small cell lung carcinoma (SCLC) cell lines and in 2 (8%) of 25 non-small cell lung carcinoma (NSCLC) cell lines. A nonsense mutation and a missense mutation were detected in 2 (8%) NSCLC cell lines. An intragenic homozygous deletion, a 1-bp frameshift mutation, and a nonsense somatic mutation were also detected in three (6%) of 47 surgical specimens. All the lung tumors with PTEN/MMAC1/TEP1 mutations were homozygous for the mutant alleles. These findings suggest that PTEN/MMAC1/TEP1 plays a role as a tumor suppressor gene in the genesis and/or progression of human lung cancer.

Status of deleted in colorectal cancer gene expression correlates with neuroblastoma metastasis

Neuroblastoma is an embryonal tumor of neural crest origin noted for its heterogeneity at the clinical, histologic, and molecular levels. The deleted in colorectal cancer (DCC) protein is an adhesion family molecule of unequivocal importance in neural development that has also been implicated in several malignancies, including neuroblastoma, through its apparent loss of function. Immunohistochemical assessment of the DCC protein was performed on a group of 49 neuroblastoma specimens and examined in relation to important clinical, histologic, and molecular parameters. DCC expression was significantly associated with neuroblastoma dissemination as primary tumors from Stage 1 to 3 patients (15/20, 75%) more frequently exhibited the DCC protein than those from Stage 4 patients (5/13, 38%; p = 0.0415). Primary tumors were more frequently DCC-positive (20/33, 61%) as compared with metastatic deposits (3/16, 19%; p = 0.0063), and a single case of a paired primary and metastatic deposit demonstrated the apparent loss of DCC gene expression with tumor progression. The remaining five paired specimens were DCC-negative in both the primary tumor and metastatic deposit. No significant association was appreciated between DCC expression and patient age, the Shimada histologic classification, or N-Myc amplification. These results provide evidence that DCC expression may be lost in the course of metastatic spread in a subset of neuroblastomas. Moreover, DCC function is implicated in neuroblastoma dissemination in a manner independent of N-Myc.

Orthotopic growth and metastasis of human non-small cell lung carcinoma cell injected into the pleural cavity of nude mice

We have constructed a metastatic model of human non-small cell lung cancer (NSCLC) by injection of NSCLC cell lines directly into the left pleural cavity of BALB/c nude mice. All of seven NSCLC cell lines, which are tumorigenic after subcutaneous injection, were successfully transplanted in the pleural cavity, while only three of the seven cell lines produced lung metastatic colonies after intravenous injection. Tumors grew extensively in the pleural cavity and infiltrated into the lung parenchyma directly. Furthermore, tumors metastasized to the mediastinum and contralateral pleural cavity through lymphatic routes. Since this model is easy to perform and the result is reproducible, it would be useful for studies on the biological behavior and treatment of human NSCLC in vivo.

Mutation analysis of the Smad2 gene in human colon cancers using genomic DNA and intron primers

In mammals, one of the Mad homologues, Smad2, was reported to be a mediator of TGF-beta signaling, and was found mutated in some cases of colon and lung cancers. To extend the analysis of this gene, we previously investigated the genomic organization of the human Smad2 gene and defined the structure of 12 exons and flanking introns. In this study, we designed 11 sets of intron-based primers to examine the entire coding region of the Smad2 gene. By the PCR-SSCP method using these primers, we screened genomic DNA sequences of colorectal cancers for mutations of the Smad2 gene. Though there was no mutation within all exons of the Smad2 gene, two of 60 sporadic colorectal cancers displayed deletions in the polypyrimidine tract preceding exon 4. Deletions of this region were also detected in colon cancer cell lines, and were clustered within cells exhibiting microsatellite instability. Deletions in the polypyrimidine tract had various effects on pre-mRNA splicing, but had no effect on the splicing of the Smad2 gene in these cases. However, our data support the idea that the polypyrimidine tract in the splicing acceptor site is a target of mutations in mismatch repair-deficient tumors.

Germline mutations of the PTEN/MMAC1 gene in Japanese patients with Cowden disease

Cowden disease (CD) is an autosomal dominant disorder which confers a high susceptibility to diverse benign and malignant tumors. The PTEN/MMAC1 gene was identified as being responsible for CD, since its germline mutations have been identified in affected individuals in the United States and Europe. We identified three novel germline PTEN mutations, a 2-bp deletion, a 1-bp insertion and a missense mutation, in three of five Japanese patients with CD. The missense mutation resided outside of the region encoding a putative phosphatase domain of the predicted PTEN protein, where previously reported missense mutations in CD patients have been clustered. The present result suggests that a wide range of germline PTEN mutations may play a role in the pathogenesis of CD.

Computerized tomography angiography of ruptured cerebral aneurysms: factors affecting time to maximum contrast concentration

OBJECT

This study was conducted to assess the diagnostic value of three-dimensional computerized tomography (3-D CT) angiography in demonstrating cerebral aneurysms in 42 consecutive patients presenting with acute subarachnoid hemorrhage (SAH).

METHODS

To obtain the volume data for selective visualization of the cerebral arteries without enhancement of the venous system, the time delay was established between the injection of contrast medium and the start of scanning by using two different methods. The circulation time was calculated with Schad's formula in the first 13 cases, but the results were not satisfactory. In the 29 subsequent cases the time delay was established using a single-level dynamic CT prescan. The dynamic prescan demonstrated the statistical differences in peak time with regard to patient age, SAH grade, and the postresuscitation state after cardiopulmonary arrest. The 3-D CT angiograms were generated from the volume data by using a voxel transmission method. Computerized tomography angiography obtained after optimally adjusted time delay demonstrated the contour of the cerebral arteries in 97% of cases, and aneurysms were detected in 93%. Enhancement of the cavernous sinus and major cortical veins was avoided. Even in patients who suffered cardiopulmonary arrest, images of the major arteries were clearly demonstrated after resuscitation.

CONCLUSIONS

In an emergency situation, CT angiography with a dynamic prescan may be an alternative to magnetic resonance angiography or digital subtraction angiography in the diagnosis of ruptured aneurysms. This modality would also be useful for the precise assessment of small aneurysms, blebs, and aneurysms adjacent to the cavernous sinus.

Homozygous deletion and frequent allelic loss of the 21q11.1-q21.1 region including the ANA gene in human lung carcinoma

The frequent occurrence of 21q deletions in human non-small cell lung carcinoma (NSCLC) indicates the presence of a tumor suppressor gene on this chromosome arm. Since the ANA (Abundant in Neuroepithelium Area) gene, a member of an antiproliferative gene family, was mapped to 21q11.2-q21.1, we searched for genetic alterations of the ANA gene in human lung cancers. The gene was homozygously deleted in a human NSCLC cell line, Ma17. The gene was mapped in the 0.33 Mb Not1 fragment at 21q21.1 of the Not1 restriction map for 21q. Loss of heterozygosity (LOH) at this locus was detected in 24/47 (51.1%) of NSCLC, and the frequency of LOH in brain metastases was significantly higher than that in stage I-II primary tumors (P = 0.018). These results suggested that the homozygously deleted region harbors a novel tumor suppressor gene involved in NSCLC progression. Since mutation of the ANA gene was not detected in other lung cancer cell lines and fresh lung tumors with LOH at this locus, it is unlikely that the ANA gene is a target gene inactivated by two mutational events in this chromosomal region. Physical mapping of the homozygously deleted region showed that the deletion had occurred interstitially at 21q11.1-q21.1 and the size of the deletion was estimated as being more than 3 Mb. Our mapping results will facilitate further efforts to identify a tumor suppressor gene on 21q.

Identification and characterization of families with aggregation of lung cancer

BACKGROUND

To clarify genetic factors involved in the susceptibility to lung cancer, it is essential to identify families with lung cancer clustering and to characterize the mode of clustering. Since somatic mutations of the p53, RB and p16 genes occur frequently in lung cancer and the replication error phenotype is seen in a subset of lung cancer, it is possible that germ-line mutations of the p53, RB, p16 and mismatch repair genes influence the susceptibility to lung cancer.

METHODS

In this work, cases with familial clustering of lung cancer were selected from 1068 families with primary lung cancer cases in analogy with the criteria for hereditary non-polyposis colorectal cancer (HNPCC). Cases with Li-Fraumeni syndrome, familial retinoblastoma, familial melanoma and HNPCC were also searched among these 1068 families.

RESULTS

There were only four families (0.4%) in which more than three relatives were affected by lung cancer. Two successive generations were affected in 36 families (3.4%). Patients with lung cancer before the age of 50 were present in 165 families (15.5%). However, no family conformed to all three criteria. There was only one family with Li-Fraumeni syndrome and no family with familial retinoblastoma, familial melanoma and HNPCC.

CONCLUSION

Familial aggregation of lung cancer is rare and germ-line mutations of the p53, RB, p16 and mismatch repair genes may not contribute greatly to susceptibility to lung cancer.

Identification of CpG islands hypermethylated in human lung cancer by the arbitrarily primed-PCR method

DNA hypermethylation is believed to be involved in human carcinogenesis, since it suppresses the transcription of defined genes and is associated with chromosomal instability. In this study, we identified CpG islands that are hypermethylated in human lung cancer by a modified arbitrarily primed-polymerase chain reaction method using genomic DNAs digested with a methylation-sensitive restriction enzyme, HpaII, as templates. When we analyzed genomic DNAs from normal lung tissues and non-small cell lung carcinoma cell lines using three arbitrary primers, three DNA fragments were amplified from lung cancer DNAs but not from normal lung DNAs. Restriction mapping and Southern blot analysis revealed that all of these bands were amplified from CpG islands that were hypermethylated in the lung cancer cell lines. These islands were mapped to chromosomes 4q34, 10q26 and 17p13.1-p13.2, respectively, and these chromosomal regions were also hypermethylated in a subset of primary lung tumors in vivo. Thus, diverse chromosomal regions are hypermethylated in lung cancer cells. The results also indicate that this method is simple and effective for screening of CpG islands that are hypermethylated in cancer cells.

Expression of the Elm1 gene, a novel gene of the CCN (connective tissue growth factor, Cyr61/Cef10, and neuroblastoma overexpressed gene) family, suppresses In vivo tumor growth and metastasis of K-1735 murine melanoma cells

We previously isolated a partial cDNA fragment of a novel gene, Elm1 (expressed in low-metastatic cells), that is expressed in low-metastatic but not in high-metastatic K-1735 mouse melanoma cells. Here we determined the full-length cDNA structure of Elm1 and investigated the effect of Elm1 expression on growth and metastatic potential of K-1735 cells. The Elm1 gene encodes a predicted protein of 367 amino acids showing approximately 40% amino acid identity with the CCN (connective tissue growth factor [CTGF], Cyr61/Cef10, neuroblastoma overexpressed gene [Nov]) family proteins, which consist of secreted cysteine-rich proteins with growth regulatory functions. Elm1 is also a cysteine-rich protein and contains a signal peptide and four domains conserved in the CCN family proteins. Elm1 was highly conserved, expressed ubiquitously in diverse organs, and mapped to mouse chromosome 15. High-metastatic K-1735 M-2 cells, which did not express Elm1, were transfected with an Elm1 expression vector, and several stable clones with Elm1 expression were established. The in vivo growth rates of cells expressing a high level of Elm1 were remarkably slower than those of cells expressing a low level of Elm1. Metastatic potential of transfectants was reduced in proportion to the level of Elm1 expression. Thus, Elm1 is a novel gene of CCN family that can suppress the in vivo growth and metastatic potential of K-1735 mouse melanoma cells.

Phenotypic alterations of small cell lung carcinoma induced by different levels of wild-type p53 expression

p53 induces both growth arrest and apoptosis in cancer cells. To clarify whether the level of p53 expression determines the response of small cell lung carcinoma (SCLC) cells, we assessed the effect of various p53 levels on a p53-null SCLC cell line, N417, using a tetracycline (Tc)-regulated inducible p53 expression system. Apoptosis was induced in SCLC cells with high p53 expression. Although low levels of p53 induced G1 arrest accompanied by p21 expression, cells with G1 arrest seemed to undergo apoptosis after further cultivation. Expression of exogenous p21 induced G1 arrest but not apoptosis in SCLC cells, suggesting that p53-mediated G1 arrest was induced through p21 expression. Moreover, high level of p53 expression down-regulated Bcl-2 expression in SCLC cells, while Bax was consistently expressed irrespective to the level of p53 expression. These results suggest that p53-mediated apoptosis and G1 arrest depend on level of p53 expression in SCLC cells and that the relative dominancy of Bax to Bcl-2 is involved in the induction of apoptosis by high level of p53 expression.

RER phenotype and its associated mutations in familial gastric cancer

To clarify the genetic background of gastric cancer, we collected 28 familial gastric cancers (FGCs) with reference to the Amsterdam criteria in hereditary non-polyposis colorectal cancer (HNPCC) and investigated the frequency of replication error (RER) at six microsatellite loci and frameshift mutations in its related genes in these tumors. RER was detected in seven (25%) of the 28 gastric cancers. Five (18%) cases showed RER at more than two loci. The apparent increased incidence of RER in FGC was not detected compared with that reported in sporadic gastric cancers previously. Among four cases with RER at more than three loci, frameshift mutations in the (A)8 track of the hMSH3 gene were detected in all the four cases and mutations in the (A)10 track of the transforming growth factor-beta type II receptor (TGF-beta RII) gene were detected in the three of them. Histologically, three of the four cases were of the intestinal type, and the other one was the diffuse type. No mutation was detected in the (C)8 and (GT)3 tracks of the hMSH6 and TGF-beta RII genes respectively. These results indicate that the acquisition of the RER phenotype equally influences the gastric carcinogenesis of both sporadic and familial cases, and that the majority of FGC is pathogenetically distinct from HNPCC.