The OGG1 gene encodes a repair enzyme for oxidatively damaged DNA and is involved in human carcinogenesis

8-Hydroxyguanine (oh8G) is a major base lesion produced by reactive oxygen species. oh8G in DNA causes G:C to T:A transversions and, thus, could be responsible for mutations that lead to carcinogenesis. A human DNA glycosylase/AP lyase encoded by the OGG1 gene has an activity to remove directly oh8G from DNA, and suppresses the mutagenic effect of oh8G. OGG1 protein has a helix-hairpin-helix-GPD motif as a domain for both DNA binding and catalysis, a nuclear localization signal, and a mitochondria targeting signal. Among multiple OGG1 isoforms, OGG1-type la is expressed predominantly in human cells and repairs chromosomal DNA in the nucleus. Inactivation of the OGG1 gene in yeast and mice leads to elevated spontaneous mutation frequency in the cells. The human OGG1 gene maps to chromosome 3p26.2, and allelic deletions of this region occur frequently in a variety of human cancers. Moreover, the OGG1 gene is somatically mutated in some cancer cells and is highly polymorphic among human populations. Repair activities of some mutated and polymorphic OGG1 proteins are lower than those of wild-type OGG1-type la-Ser326 protein and, thus, could be involved in human carcinogenesis.

Enhancement of OGG1 protein AP lyase activity by increase of APEX protein

8-Hydroxyguanine (oh(8)G) is a major form of oxidative DNA damage produced by reactive oxygen species (ROS). The human OGG1 gene encodes a DNA glycosylase that excises oh(8)G from double-stranded DNA. In this study, we investigated a mode of interaction between OGG1 and APEX proteins in the repair of oh(8)G under oxidative stresses. DNA cleavage assay using oh(8)G-containing oligonucleotides showed that the phosphodiester bond on the 3'-side of oh(8)G was cleaved by the AP lyase activity of GST-OGG1 protein and the phosphodiester bond on the 5'-side of oh(8)G was cleaved by the DNA 3'-repair diesterase activity of APEX protein. Gel mobility shift assay showed that the complex of GST-OGG1 protein and oh(8)G-containing oligonucleotides mostly changed into the complex of APEX protein and oligonucleotides by addition of APEX protein into the reaction mixture. We next analyzed alterations in the amount of 8-hydroxydeoxyguanosine (oh(8)dG) in DNA and the levels of OGG1 and APEX expression in HeLa S3 cells treated with 2mM hypochlorous acid, a kind of ROS. An approximately four-fold increase in the amount of oh(8)G was detected by the HPLC-ECD method. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analyses indicated that the level of APEX expression increased approximately four-fold, whereas the level of OGG1 expression was unchanged. However, in the DNA cleavage assay, the AP lyase activity of GST-OGG1 protein was significantly increased in the presence of a molar excess of APEX protein. These results indicate that, under severe oxidative stresses, OGG1 mRNA is not induced and the amount of OGG1 protein is not remarkably increased, but the activity of OGG1 protein is enhanced by the increase of APEX protein in the cells.

Germline p53 mutation in a patient with multiple primary cancers

We report a case of multiple primary cancers having a germline missense mutation of the p53 gene. The patient was a Japanese female and had a history of five different types of cancers. PCR/direct sequencing analysis revealed the presence of a nucleotide substitution, AGC (Ser) to AGG (Arg), at codon 106 of the p53 gene in DNA from non-cancerous breast tissue. This is the first case of germline p53 mutation at codon 106, and could contribute to establishing correlations between the types and locations of germline p53 mutations and their phenotypical consequences.

Alterations in expression of E2F-1 and E2F-responsive genes by RB, p53 and p21(Sdi1/WAF1/Cip1) expression

RB, p53 and p21(Sdi1/WAF1/Cip1) interact in the induction of G1 arrest. We established osteosarcoma cell lines in which a tetracycline-regulatable promoter controls the induction of RB, p53 and p21. By using these cell lines, we investigated whether RB, p53 or p21 regulates, in the same manner or differently, expression and function of E2F-1 and its responsive genes. E2F-1 gene products and transcripts of the E2F-responsive genes decreased in response to RB. Similar changes occurred to p53 and p21 when RB is present. However, in the absence of RB, some of the E2F-responsive genes decreased in response to p53 but not to p21. Thus, RB is a critical component for regulating the E2F-responsive genes, while p53 alone affects only a subset of these genes.

Volume supplementation with iso-sodium solution prevents hypernatremia after head injury

OBJECTIVE

To evaluate our developed volume supplement protocol in preventing hypernatremia after head injury.

METHODS

Iso-sodium solution was infused to keep the 8-hour water balance positive in 20 head-injured patients with hypotonic urine.

RESULTS

Serum sodium concentrations moved to within a normal range in 6 patients and were temporarily increased in 12 patients. Seven of the 12 showed a negative cumulative water balance and slightly low creatinine clearance. Mean arterial pressure in the other five patients was lower after supplementation and was positively related to sodium excretion. Hypernatremia could not be prevented in the other two patients and they did not survive. Creatinine clearance was below 40 mL/min/m2 in these two patients before supplementation.

CONCLUSION

Our protocol worked effectively in patients in whom renal function was preserved. Decreased creatinine clearance because of preexisting dehydration and lower arterial pressure disturbed increase in urinary sodium excretion and temporarily aggravated the hypernatremia.

Somatic mutations and single nucleotide polymorphisms of base excision repair genes involved in the repair of 8-hydroxyguanine in damaged DNA

To elucidate the involvement of 8-hydroxyguanine (oh(8)G) repair genes in human lung carcinogenesis, 47 lung cancer cell lines and 55 primary lung cancers were examined for somatic mutations and genetic polymorphisms in all coding exons of the MYH and APEX genes, and exon 8 of the OGG1 gene by polymerase chain reaction-single strand conformation polymorphism analysis. In the MYH gene, one missense mutation was detected in a cell line, NCI-H157, whereas no mutations were detected in primary cancers. There were no mutations in the APEX and OGG1 genes in the cell lines or primary cancers. Ten single nucleotide polymorphisms (SNPs) were identified, and seven of them were accompanied by amino acid substitutions. Differences in the oh(8)G repair activities of MYH, APEX and OGG1 proteins due to somatic mutations and SNPs can be involved in human carcinogenesis.

Genetic alterations and expression of the protein phosphatase 1 genes in human cancers

Recent studies have revealed that genetic alterations of the protein phosphatase genes, including PTEN, PPP2R1A, PPP2R1B and PPP1R3, are involved in human carcinogenesis. In the present study, we examined the genetic and expression status of nine protein phosphatase 1 (PP1) genes in 55 human cancer cell lines, consisting of 10 small cell lung cancers, 22 non-small cell lung cancers, 11 colorectal cancers, 7 gastric cancers and 5 ovarian cancers. The PP1 genes examined were three catalytic subunit genes, PPP1CA, PPP1CB and PPP1CC, and six regulatory subunit genes, PPP1R1A, PPP1R2, PPP1R5, PPP1R6, PPP1R7 and PPP1R8. Three catalytic subunit genes and three regulatory subunit genes, PPP1R2, PPP1R7 and PPP1R8, were ubiquitously expressed in the 55 cell lines, while PPP1R1A, PPP1R5, and PPP1R6 were differentially expressed. Possible missense mutations of the PPP1R5, PPP1R7 and PPP1R8 genes were detected in one (2%), two (4%) and one (2%) cell line, respectively. A rare, non-synonymous polymorphism was also identified in the PPP1R5 gene. Four of the 55 cell lines carried genetic alterations of several protein phosphatase genes, including PTEN, PPP1R3, PPP1R7 and PPP1R8. Ubiquitous expression as well as a lack of genetic diversity of catalytic subunit genes suggested the essential role of these genes for the growth of cancer cells. In contrast, differential expression, somatic mutations and/or genetic polymorphisms of several regulatory subunit genes indicate the involvement of these genes in multistep carcinogenesis.

Constitutive activation of the Wnt signaling pathway by CTNNB1 (beta-catenin) mutations in a subset of human lung adenocarcinoma

Constitutive activation of the Wnt signaling pathway as a result of genetic alterations of APC, AXIN1, and CTNNB1 has been found in various human cancers, including those of the colon, liver, endometrium, ovary, prostate, and stomach. To investigate the pathogenetic significance of constitutive activation of the Wnt signaling pathway in human lung carcinogenesis, CTNNB1 alterations in exon 3, a region known to represent a mutation hot spot, were screened in 46 lung cancer cell lines and 47 primary lung cancers. Missense mutations causing substitutions of Ser/Thr residues critical for regulation by GSK-3beta were detected in one (2%) of the cell lines, A427, and two (4%) of the surgical specimens. The three lung cancers with CTNNB1 mutations were adenocarcinomas. To explore the prevalence of constitutive activation of the Wnt signaling pathway in human lung cancer, we assessed 15 lung cancer cell lines representing major histological subtypes of lung cancers for constitutive Tcf transcriptional activity (CTTA). CTTA was observed only in the A427 adenocarcinoma cell line, but not in the remaining 14 cell lines. The data indicate that constitutive activation of the Wnt signaling pathway caused by CTNNB1 mutation is involved in the development and/or progression of a subset of lung carcinoma, preferentially in adenocarcinoma.

Absence of p51 alteration in human ovarian cancer

The p51 gene encodes a protein with significant homology to p53, thus, it is a candidate tumor suppressor gene. To investigate the involvement of the p51 gene in human ovarian carcinogenesis, p51 gene alterations were examined in primary ovarian cancers and ovarian cancer cell lines. Mutation analysis of the p51 gene was performed in 40 primary ovarian cancers and 6 ovarian cancer cell lines using the PCR-SSCP and direct sequencing methods. Expression of p51 mRNA was examined in 9 primary ovarian cancers and 5 ovarian cancer cell lines by Northern blot and RT-PCR analyses. No mutations of the p51 gene causing amino acid substitutions or frameshifts were detected in either primary tumors or cancer cell lines by PCR-SSCP analysis of the entire coding region, although several genetic polymorphisms were detected in three samples. Allelic imbalance was detected in 3 of 19 (16%) primary ovarian cancers. No p51 gene expression was detected in 9 primary ovarian cancers and the corresponding normal ovarian tissues by Northern blot and by RT-PCR analyses. One of 5 ovarian cancer cell lines showed p51 gene expression by Northern blot analysis (20%). These results indicated that p51 gene expression was silent in normal ovarian tissues and primary ovarian cancers, and that mutation of the p51 gene does not play a major role in the development of ovarian cancer.

Physical and transcriptional map of a 311-kb segment of chromosome 18q21, a candidate lung tumor suppressor locus

Here, we report the complete genomic sequence and the characterization of the 311-kb region of 18q21, a candidate tumor suppressor locus containing a region of homozygous deletion in a lung cancer cell line, Ma29. This region contained two known genes, SMAD4 and ME2 (mitochondrial malate oxydoreductase), and two novel genes, D29 (deleted in Ma29 HGMW-approved symbol ELAC1), encoding an evolutionarily conserved protein, and B29 (beside the Ma29 deletion HGMW-approved symbol C18orf3), with no significant homology to any known genes. The deleted DNA segment in Ma29, which was estimated to be 195 kb in size, included all the coding exons of ME2 and D29, but not the coding exons of SMAD4 and B29. The deleted region also included exon 0, a 5'-noncoding exon, of SMAD4, and the expression of SMAD4 was greatly reduced in Ma29 cells. Mutations of SMAD4 and D29 were detected in 1 of 45 lung cancer cell lines examined, while those of ME2 and B29 were not detected, indicating that these four genes are not major targets for 18q21 deletions. The physical and transcriptional map constructed in this study will provide basic information for the identification of a tumor suppressor gene(s) at 18q21 involved in lung carcinogenesis.

Adenine excisional repair function of MYH protein on the adenine:8-hydroxyguanine base pair in double-stranded DNA

Adenine paired with 8-hydroxyguanine (oh(8)G), a major component of oxidative DNA damage, is excised by MYH base excision repair protein in human cells. Since repair activity of MYH protein on an A:G mismatch has also been reported, we compared the repair activity of His(6)-tagged MYH proteins, expressed in Spodoptera frugiperda Sf21 cells, on A:oh(8)G and A:G mismatches by DNA cleavage assay and gel mobility shift assay. We also compared the repair ability of type 1 mitochondrial protein with type 2 nuclear protein, as well as of polymorphic type 1-Q(324) and 2-Q(310) proteins with type 1-H(324) and 2-H(310) proteins by DNA cleavage assay and complementation assay of an Escherichia coli mutM mutY strain. In a reaction buffer with a low salt (0-50 mM) concentration, adenine DNA glycosylase activity of type 2 protein was detected on both A:oh(8)G and A:G substrates. However, in a reaction buffer with a 150 mM salt concentration, similar to physiological conditions, the glycosylase activity on A:G, but not on A:oh(8)G, was extremely reduced and the binding activity of type 2 protein for A:G, but not for A:oh(8)G, was proportionally reduced. The glycosylase activity on A:oh(8)G and the ability to suppress spontaneous mutagenesis were greater for type 2 than type 1 enzyme. There was apparently no difference in the repair activities between the two types of polymorphic MYH proteins. These results indicate that human MYH protein specifically catalyzes the glycosylase reaction on A:oh(8)G under physiological salt concentrations.

Identification of a 428-kb homozygously deleted region disrupting the SEZ6L gene at 22q12.1 in a lung cancer cell line

Frequent allelic losses on chromosome 22q in small cell lung carcinomas (SCLCs) and advanced non-small cell lung carcinomas indicate the presence of tumor suppressor gene(s) on this chromosome arm. We detected a homozygous deletion at 22q12.1 in a SCLC cell line, Lu24. Cloning of the breakpoints of the Lu24 deletion revealed that the deletion was interstitial and 428, 131 bp in size. The deleted region contained the SEZ6L (Seizure 6-like) gene, whose structure had been partially determined by the chromosome 22 sequencing project. We determined the full length cDNA sequence for the SEZ6L gene based on the genomic sequence for the SEZ6L locus using the GENSCAN program and the RT - PCR method. The deduced SEZ6L protein was a transmembrane protein of 1024 amino acids with multiple domains involved in protein - protein interaction and signal transduction. SEZ6L expression was detected in a variety of human tissues, including lung, while its expression was detected in 14 (30%) of 46 lung cancer cell lines examined. Missense mutations were detected in three (7%) of the 46 cell lines, and a 1 bp deletion in the polypyrimidine tract preceding exon 4 was detected in one (2%) of 46 primary lung cancers. Therefore, it is possible that genetic and/or epigenetic SEZ6L alterations are involved in the development and/or progression in a subset of lung cancer, although functional analysis of the SEZ6L gene as well as molecular analysis of other genes in the homozygously deleted region is necessary to understand the pathogenetic significance of 22q deletions in human lung carcinogenesis.

[Clinical data obtained through coagulation testing suggests that hypothermia exerts influence on a patient's blood coagulation reaction]

It often takes longer to achieve hemostasis when performing an operation on a patient in cerebral hypothermia therapy than in a normal patient, despite the lack of abnormal clinical blood coagulation findings, and this study was conducted to investigate the cause of delays in coagulation in patients with hypothermia. In this study, 93 samples of plasma were collected at our center from 10 patients(7 men and 3 women; mean age, 33.7) who were in cerebral hypothermia therapy with a urinary bladder temperature maintained at 32-34 degrees C. Each sample was divided into two, and PT(prothrombin time) and APTT(activated partial thromboplastin time) were measured at the normal analysis temperature of 37 degrees C in one sample, and at the hypothermia temperature of 32-34 degrees C in the other sample. The results showed that PT and APTT tended to shorter at 37 degrees C, than those measured at 32-34 degrees C. Thus, we suggest that it is necessary to regulate the temperature of patients with accidental hypothermia or in whom hypothermia therapy is performed.

A novel gene, MEL1, mapped to 1p36.3 is highly homologous to the MDS1/EVI1 gene and is transcriptionally activated in t(1;3)(p36;q21)-positive leukemia cells

The reciprocal translocation t(1;3)(p36;q21) occurs in a subset of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), which is frequently characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and poor prognosis. Previously, the breakpoint cluster region (BCR) at 3q21 was identified within a 60-kilobase (kb) region centromeric to the BCR of 3q21q26 syndrome and that at 1p36.3 within a 90-kb region. In this study, genes were searched near the breakpoints at 1p36.3, and a novel gene was isolated that encoded a zinc finger protein with a PR domain, which is highly homologous to the MDS1/EVI1 gene. The novel gene, designated as MEL1 (MDS1/EVI1-like gene 1), with 1257 amino acid residues is 64% similar in nucleotide and 63% similar in amino acid sequences to MDS1/EVI1 with the same domain structure. The MEL1 gene is expressed in leukemia cells with t(1;3) but not in other cell lines or bone marrow, spleen, and fetal liver, suggesting that MEL1 is specifically in the t(1;3)(p36;q21)-positive MDS/AML. On the basis of the positional relationship between the EVI1 and MEL1 genes in each translocation, it was suggested that both genes are transcriptionally activated by the translocation of the 3q21 region with the Ribophorin I gene. Because of the transcriptional activation of the EVI1 family genes in both t(1;3)(p36;q21)-positive MDS/AML and 3q21q26 syndrome, it is suggested that they share a common molecular mechanism for the leukemogenic transformation of the cells.

Alterations of the PPP1R3 gene in hematological malignancies

PPP1R3 (protein phosphatase 1, regulatory subunit 3) is a candidate tumor suppressor gene at chromosome 7q31, since nonsense and missense mutations of the PPP1R3 gene have been detected in a variety of human cancers. Loss of chromosome 7q is a recurrent abnormality in hematological malignancies, especially of myeloid lineage, and a common region of 7q deletions has been mapped to 7q31. Thus, it has been suggested that 7q31 harbors a tumor suppressor gene whose functional loss contributes to leukemogenesis. To evaluate the possible involvement of the PPP1R3 gene in the development of hematological malignancies, we examined 72 leukemia and lymphoma cell lines for alterations of the PPP1R3 gene by PCR-SSCP and direct sequence analyses. Mutations were detected in 1 (2.8%) of 36 myeloid cell lines, 4 (20.0%) of 20 B-lineage lymphoid cell lines and none of 16 T-lineage lymphoid cell lines. All the mutations were heterozygous, and they consisted of two missense mutations and three silent mutations. The PPP1R3 gene was expressed in cell lines of various cell lineages. These results indicate that PPP1R3 is not a major target of 7q deletions in myeloid leukemia, however, alterations of the PPP1R3 gene may contribute to the development of a subset of hematological malignancies.

Population-based mapping of pulmonary adenoma susceptibility 1 locus

Pulmonary adenoma susceptibility 1 (Pas1), the major locus affecting inherited predisposition to lung tumor development in mice, maps near the Kras2 gene. We previously reported a significant association between a KRAS2/RsaI polymorphism and the risk and prognosis of lung adenocarcinoma (ADCA) in the Italian population. In the present case-control study, we examined 269 lung ADCA patients, 121 squamous cell lung carcinoma patients, and 632 healthy individuals (general population controls) in the Japanese population with genetic markers spanning approximately 1200 kb in the KRAS2 region. Allele-specific oligonucleotide hybridization revealed the same KRAS2/RsaI polymorphism associated with risk and prognosis as in Italian lung ADCA patients; the polymorphism was significantly associated with clinical stage (P < 0.001) and survival rate (log rank = 0.0014), confirming the mapping of PAS1 and pointing to the role of this locus in human lung cancer.

Extensive subdural empyema treated with drainage and barbiturate therapy under intracranial pressure monitoring: case report

In subdural empyema (SDE), if the mass effect and vasogenic edema are not controlled, the brain can be fatally damaged. Massive SDE over the skull base often requires repeated surgical drainage for removal of accumulated pus. Intracranial pressure (ICP) management until obliteration of the empyema is important to the improvement of clinical outcome. An 18-year-old man was admitted to our center in a nearly comatose state and with a mild fever. CT scan showed massive SDE extending to the skull base and parafalx. ICP was measured with a pressure transducer through an intraventricle tube. Repeated surgical drainage was performed while ICP was controlled with barbiturate therapy. He was discharged with no neurological deficits. In patients with an extensive SDE over the cerebral hemisphere, ICP control with barbiturate therapy may enhance the therapeutic effect of surgical drainage.

Spontaneous disappearance and reappearance of a ruptured cerebral aneurysm: one case found in a group of 33 consecutive patients with subarachnoid hemorrhage who underwent repeat angiography

The spontaneous disappearance and reappearance of a ruptured cerebral aneurysm is generally assumed to be a rare phenomenon although the actual incidence is unknown. Among 39 consecutive cases of acute subarachnoid hemorrhage (SAH), 33 were studied by three-dimensional computed tomographic angiography (CTA) within 6 h after the onset of SAH, followed by digital subtraction angiography (DSA) within 24 h after the ictus. Of those patients, one, a 58-year-old woman, had a saccular aneurysm at the distal anterior cerebral artery; the aneurysm was clearly demonstrated by CTA 2.5 h after the SAH onset, but was not shown by a subsequent DSA performed 8.5 h after the ictus. A follow-up DSA detected the neck of aneurysm on day 11, and the whole aneurysm was visualized on day 19. The observations in this particular case suggest that the spontaneous disappearance of a ruptured cerebral aneurysm may occur during the ultra-early stage of SAH and that reappearance may follow during the next few weeks. The patient did not suffer complications such as vasospasm or systemic hypotension nor was she treated with antifibrinolytic agents. The aneurysmal shape and the surrounding clot are considered as putative factors possibly related to the intermittent appearance of the aneurysm.

Absence of germline CHK2 mutations in familial gastric cancer

Recently, the CHK2 gene was identified as being a candidate gene responsible for Li-Fraumeni syndrome (LFS). Gastric cancer is often clustered in families with LFS, so it is possible that germline CHK2 mutation is also present in familial gastric cancer (FGC). We therefore defined the genomic structure of the CHK2 gene, designed intronic primers, and searched for germline CHK2 mutations in 25 FGC cases by polymerase chain reaction-single strand conformational polymorphism analysis of the entire coding region. In all of the 25 cases, at least two siblings had histories of gastric cancer. There were no FGC cases that showed germline CHK2 mutations. Thus, it was indicated that germline CHK2 mutations do not contribute to the familial clustering of gastric cancer.

Differential expression of the LAMB3 and LAMC2 genes between small cell and non-small cell lung carcinomas

To identify genes differentially expressed between small cell lung carcinoma (SCLC) cells and non-SCLC cells, mRNA differential display was applied to 3 SCLC cell lines and 6 non-SCLC cell lines. The LAMB3 gene was identified as being expressed only in non-SCLC cells and not in SCLC cells. The LAMB3 gene encodes the laminin beta3 chain, which is a unique component of laminin-5. Laminin-5 is a heterotrimer protein consisting of the alpha3, beta3, and gamma2 chains, and another unique component of laminin-5 is the gamma2 chain encoded by the LAMC2 gene. RT-PCR analysis of the LAMB3 and LAMC2 genes in 45 lung cancer cell lines revealed that both the LAMB3 and LAMC2 genes were co-expressed in 21 of 32 non-SCLC cell lines (66%) but only in one of 13 SCLC cell lines (8%). Coexpression of the LAMB3 and LAMC2 genes was also observed in all 4 cases of primary non-SCLC cells examined but not in the corresponding non-cancerous lung cells. Since alpha6beta4 integrin, the specific laminin-5 binding receptor, is known to be expressed only in non-SCLC cells and not in SCLC cells, it was indicated that laminin-5 is a critical microenvironmental factor for the growth of non-SCLC cells but not of SCLC cells. The differences in the expression of integrins and laminins would be critical factors to distinguish SCLC and non-SCLC cells, and such differences might be associated with the unique biological properties of SCLC cells, including metastatic potential and drug sensitivity.

Ovarian cancer: loss of heterozygosity frequently occurs in the ATM gene, but structural alterations do not occur in this gene

Ataxia-telangiectasia is a multisystem recessive disease characterized clinically by cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency, sensitivity to radiomimetic agents and an increased predisposition to cancer. This pleiotropic disorder is caused by mutations in the ATM gene, which is located at the human chromosomal region 11q23. Loss of heterozygosity (LOH) at 11q22-q23 is a frequent event in ovarian cancer, suggesting the presence of a tumor suppressor gene in this region. We have found that LOH in the ATM gene occurred in 44% of informative cases in a series of 22 primary ovarian tumors. LOH of this region occurred at the same frequency during the advanced stages (III-IV; 3/9, 33%) as in the early stages (I-II; 4/13, 31%) of ovarian cancer. To investigate the role of ATM in ovarian cancer, we used a PCR-based single-strand conformation polymorphism assay for mutation detection of the entire coding sequence of the ATM gene (65 exons) in 22 ovarian tumors. No somatic alterations of the ATM gene were found in these ovarian cancer samples including those with LOH present in the ATM gene. Our study has identified a region (11q23) which probably contains a frequently altered tumor suppressor gene in ovarian cancer, and this gene does not appear to involve the coding sequences of the ATM gene.