Isolation and identification of DNA fragments frequently deleted from tumor cell lines of human esophageal cancer

OBJECTIVE: To clone tumor suppressor genes associated with human esophageal cancer (EC). METHODS: DNA fragments deleted from cell lines of esophageal cancer EC8712 and EC8733 were isolated by using modified genomic substractive hybridization. Twenty EC tissues paired with adjacent normal mucosa were analysed by Southern blot and PCR with these fragments as probes. RESULTS: Seven DNA fragments deleted from EC cell lines obtained were named as 12H1, 12H2, 33H3, 33H4, 12B1, 33B2 and 33B3. Sequencing revealed their size of 512bp, 428bp, 509bp, 355bp, 680bp (partially sequencing), 519bp and 425bp, respectively. 12H1 and 33H3 showed high homology (98%) to a new repeated sequence in human genome. 33H4 displayed 87% nucleotide identity with human alphoid-like repetitive sequence located on chromosome 17. 12B1 was homologous (90%) to LINE 1 transoposon containing two open reading frames. 12H2, 33B2 and 33B3 were novel sequences. These DNA fragments were deleted in 20%-60% of EC tissues and in 10%-20% of adjacent mucosa. CONCLUSIONS: Loss of 33H4 may be accompanied by deletion of an adjacent gene. 12B1 as transposon may suppress the tumorigenesis by activating suppressor genes or/and by inactivating oncogenes. 12H1/33H3, 12H2, 33B2 and 33B3 may be candidates of tumor suppressor genes associated with the development and the progression of esophageal cancer.     

Amplification of DNA sequences from chromosome 19q13.1 in human pancreatic cell lines

Conventional cytogenetics and comparative genomic hybridization (CGH) were utilized to identify recurrent chromosomal imbalances in 12 pancreatic adenocarcinoma cell lines. Multiple deletions and gains were observed in all cell lines. Losses affecting chromosomes or chromosome arms 9p, 13, 18q, 8p, 4, and 10p and gains involving chromosome arms or bands 19q13.1, 20q, 5p, 7p, 11q, 3q25-qter, 8q24, and 10q were commonly observed. Interestingly, 19 distinct sites of high-level amplification were found by CGH. Recurrent sites involved 19q13.1 (6 cases), 5p (3 cases), and 12p and 16p (2 cases). Amplification of KRAS2 was demonstrated in 2 cell lines and that of ERBB2 in another. To define the occurrence of chromosome 19 amplification further, two-dimensional analysis of NotI genomic restriction digests and fluorescence in situ hybridization using probes from band 19q13.1 were utilized. High-level amplification of overlapping sets of chromosome 19 NotI fragments was exhibited in 3 cell lines of which 2 showed amplification of both OZF and AKT2 genes and 1 that of AKT2 alone. In these 3 cell lines, amplification of chromosome 19 sequences was associated with the presence of a homogeneously staining region. Our results provide evidence of heterogeneity in the extent of chromosome 19 amplification and suggest the existence of yet unknown amplified genes that may play a role in pancreatic carcinogenesis.     

c-myc copy number gains in bladder cancer detected by fluorescence in situ hybridization

Amplification and overexpression of c-myc have been suggested as prognostic markers in human cancer. To assess the role of c-myc gene copy number alterations in bladder cancer, 87 bladder tumors were examined for c-myc aberrations by fluorescence in situ hybridization. Dual labeling hybridization with a repetitive pericentromeric probe specific for chromosome 8 and a probe for the c-myc locus (at 8q24) was performed to analyze c-myc copy number in relation to chromosome 8 copy number on a cell by cell basis. A clear-cut c-myc amplification (up to 40 to 150 copies per cell) was found in 3 tumors. There was a low level c-myc copy number increase in 32 of the remaining 84 tumors. There was no association of low level c-myc copy number increase with c-myc protein overexpression. This suggests that a c-myc gene copy number gain as detected by fluorescence in situ hybridization does not necessarily reflect a disturbed c-myc gene function but may indicate a structural chromosome 8 abnormality including gain of distal 8q. The strong association of low level c-myc (8q) gains with tumor grade (P < 0.0001), stage (P < 0.0001), chromosome polysomy (P < 0.0001), p53 protein expression (P = 0.0019), p53 deletion (P = 0.0403), and tumor cell proliferation (Ki67 labeling index; P = 0.0021) is consistent with a role of chromosome 8 alterations in bladder cancer progression.     

Comparative genomic analysis of tumors: detection of DNA losses and amplification

We demonstrate the use of representational difference analysis for cloning probes that detect DNA loss and amplification in tumors. Using DNA isolated from human tumor cell lines to drive hybridization against matched normal DNA, we were able to identify six genomic regions that are homozygously deleted in cultured cancer cells. When this method was applied in the reverse way, using normal DNA to drive hybridization against tumor cell DNA, we readily isolated probes detecting amplification. Representational difference analysis was also performed on DNAs derived from tumor biopsies, and we thereby discovered a probe detecting very frequent homozygous loss in colon cancer cell lines and located on chromosome 3p.     

Localization of a second NM23 gene, NME2, to chromosome 17q21-q22

NM23 is a candidate tumor suppressor protein and has recently been identified as an NDP kinase. The expression of NM23 is inversely related to the metastatic potential of tumor cells. Two NM23 genes, NME1 and NME2, that code for the A and B chains of the kinase, respectively, have been cloned. To determine the human chromosomal location of the NME2 gene, we have analyzed DNA from rodent-human cell lines and hybrid cell lines containing portions of chromosome 17 by a combination of PCR amplification and Southern hybridization. The NME2 gene was mapped to the chromosome region 17q21-q22, the same region in which the NME1 gene has been localized. This region is linked to the early onset breast/ovarian locus (BRCA1) and allelic deletions of NME1 have been associated with metastatic potential of colorectal carcinomas.     

Cyclin D1/PRAD1 as a central target in oncogenesis

Understanding the genetic elements controlling the process of tumor metastasis to distant organ sites such as the liver may be the key to improving survivorship from colon cancer. By using standard cytogenetic techniques in combination with comparative genomic hybridization, multiple genetic imbalances within three human colon cancer cell lines previously selected for differences in liver-metastatic behavior were identified. The entire genome of one poorly metastatic cell line (KM12C) was compared directly with that of two highly metastatic cell lines (KM12SM, KM12L4A) derived from it. A number of chromosomal gains (8q, 12q15, 20q11.2) and losses (5p13, 6p21.3, 18) were common to all three cell lines and are likely related to early tumor development rather than to the selection process used to generate cell lines of increased metastatic potential. Chromosomal imbalances detected only in the highly metastatic cell lines were also observed. KM12SM showed losses of portions of 2p22, 2q24.3--> 2q32.2, 4p15.3--> cen, 4q24 without the 13q and 15q22.3 gains noted for KM12C. Both gains (1p31.3--> 1p21, 2q22--> 2q33, 3cen--> 3q26.2, 5q14--> 5q23, 6cen--> 6q23) and losses (16p, 17p, 17q 19p, 19q 22q) were observed for KM12L4A but not for the other two cell lines. Identification of these alterations provides valuable insight into the process of experimental liver metastasis and is a first step towards mapping genes linked to the terminal phases of human colon cancer progression.     

Comparative genomic hybridization and loss of heterozygosity analyses identify a common region of deletion at 15q11.1-15 in human malignant mesothelioma

Comparative genomic hybridization analysis was performed to identify chromosomal imbalances in 24 human malignant mesothelioma (MM) cell lines derived from untreated primary tumors. Chromosomal losses accounted for the majority of genomic imbalances. The most frequent underrepresented segments were 22q (58%) and 15q1.1-21 (54%); other recurrent sites of chromosomal loss included 1p12-22 (42%), 13q12-14 (42%), 14q24-qter (42%), 6q25-qter (38%), and 9p21 (38%). The most commonly overrepresented segment was 5p (54%). DNA sequence amplification at 3p12-13 was observed in two cases. Whereas some of the regions of copy number decreases (i.e., segments in 1p, 6q, 9p, and 22q) have previously been shown to be common sites of karyotypic and allelic loss in MM, our comparative genomic hybridization analyses identified a new recurrent site of chromosomal loss within 15q in this malignancy. To more precisely map the region of 15q deletion, loss of heterozygosity analyses were performed with a panel of polymorphic microsatellite markers distributed along 15q, which defined a minimal region of chromosomal loss at 15q11.1-15. The identification of frequent losses of a discrete segment in 15q suggests that this region harbors a putative tumor suppressor gene whose loss/inactivation may contribute to the pathogenesis of many MMs.     

Genomic organization and mutation analysis of Hel-N1 in lung cancers with chromosome 9p21 deletions

Allelic loss of chromosome 9p21 is common in small cell lung cancer (SCLC), but inactivation of the tumor suppressor gene CDKN2a is rare, implying the existence of another target gene at 9p21. A recent deletion mapping study of chromosome 9p has also identified a site of deletion in non-small cell lung cancer (NSCLC) centered around D9S126. The Hel-N1 (human elav-like neuronal protein 1) gene encodes a neural-specific RNA binding protein that is expressed in SCLC. We have mapped this potentially important gene in lung tumorigenesis to within 100 kb of the D9S126 marker at chromosome band 9p21 by using homozygously deleted tumor cell lines and fluorescence in situ hybridization to normal metaphase spreads. Hel-N1 is, therefore, a candidate target suppressor gene in both SCLC and NSCLC. We have determined the genomic organization and intron/exon boundaries of Hel-N1 and have screened the entire coding region for mutations by sequencing 14 primary SCLCs and cell lines and 21 primary NSCLCs preselected for localized 9p21 deletion or monosomy of chromosome 9. A homozygous deletion including Hel-N1 and CDKN2a was found in a SCLC cell line, and a single-base polymorphism in exon 2 of Hel-N1 was observed in eight tumors. No somatic mutations of Hel-N1 were found in this panel of lung tumors. Hel-N1 does not appear to be a primary inactivation target of 9p21 deletion in lung cancer.     

Molecular analysis of childhood primitive neuroectodermal tumors defines markers associated with poor outcome

PURPOSE: The diagnostic and prognostic significance of well-defined molecular markers was investigated in childhood primitive neuroectodermal tumors (PNET). MATERIALS AND METHODS: Using microsatellite analysis, Southern blot analysis, and fluorescence in situ hybridization (FISH), 30 primary tumors and six CSF metastasis specimens were analyzed for loss of heterozygosity (LOH) of chromosomes 1q31, 6q, 9q22, 10q, 11, 16q22, and 17p13.1 and/or high-level amplification of the c-myc gene. Experimental data were compared with clinical stage and outcome. RESULTS: LOH of chromosome 17p13.1 was found most frequently (14 of 30 tumors, six of six CSF metastasis specimens); LOH of chromosomes 10q, 16q22, 11, 6, 9q22, and 1q31 was observed in 20.6%, 20%, 14.3%, 12%, 10%, and 0%, respectively. Eight of 32 tumors and CSF specimens showed amplification of c-myc. All tumors with amplification of c-myc were resistant to therapy and had a fatal outcome (mean survival time, 9.3 months). Tumors that displayed LOH of chromosome 17p were associated with metastatic disease. The prognosis of these tumors was worse only when associated with amplification of c-myc. Three of three patients with LOH of 9q22 relapsed. CONCLUSION: In our study, amplification of c-myc was a poor-prognosis marker in PNET. LOH of chromosome 17p was associated with metastatic disease. Molecular analysis of primary tumors using these markers may be useful for stratification of children with PNET in future prospective studies. The other aberrations investigated were not of significant prognostic value, but may provide an entry point for future large-scale molecular studies.     

A longitudinal study of markers of bone turnover in Graves'' disease and their value in predicting bone mineral density

Alterations of chromosome 8, including deletions of 8p, occur frequently in many tumors. In this study, fluorescence in situ hybridization was used to study the relationship between 8p deletions, 8q gains, and phenotype in bladder cancer. Cells from 87 tumors were examined by dual-labeling fluorescence in situ hybridization with a centromere 8 probe (pJM12) and P1 probes for 8p22, 8p12, 8q12, and 8q24. Both 8p22 deletions and 8q24 gains were strongly associated with tumor phenotype. There was a marked difference in 8p22 deletions between noninvasive (pTa) tumors (3/33) and minimally invasive (pT1) tumors (8/19; P = 0.005) whereas there was no significant difference between pT1 and muscle-invasive (pT2-4) tumors (19/35; P = 0.3926). Six tumors with 8p22 deletion were examined at 8p12. Three of these tumors showed no 8p12 deletion, narrowing down the site of a putative tumor suppressor gene distal to 8p12. In one other case, there was a marked increase in 8p12 copy number (> 40 per cell; amplification), suggesting the presence of an oncogene involved in bladder cancer at 8p12. The marked difference in 8p22 deletions between noninvasive (pTa) and minimally invasive (pT1) tumors is consistent with a role of a putative tumor suppressor gene on 8p for development of invasive tumor phenotype.     

Frequent inactivation of PTEN in prostate cancer cell lines and xenografts

Loss of chromosome 10q is a frequently observed genetic defect in prostate cancer. Recently, the PTEN/MMAC1 tumor suppressor gene was identified and mapped to chromosome 10q23.3. We studied PTEN structure and expression in 4 in vitro cell lines and 11 in vivo xenografts derived from six primary and nine metastatic human prostate cancers. DNA samples were allelotyped for eight polymorphic markers within and surrounding the PTEN gene. Additionally, the nine PTEN exons were tested for deletions. In five samples (PC3, PC133, PCEW, PC295, and PC324), homozygous deletions of the PTEN gene or parts of the gene were detected. PC295 contained a small homozygous deletion encompassing PTEN exon 5. In two DNAs (PC82 and PC346), nonsense mutations were found, and in two (LNCaP and PC374), frame-shift mutations were found. Missense mutations were not detected. PTEN mRNA expression was clearly observed in all cell lines and xenografts without large homozygous deletions, showing that PTEN down-regulation is not an important mechanism of PTEN inactivation. The high frequency (60%) of PTEN mutations and deletions indicates a significant role of this tumor suppressor gene in the pathogenesis of prostate cancer.     

Anaerobic regulation of the Escherichia coli dmsABC operon requires the molybdate-responsive regulator ModE

The 9804 gene, which encodes a human Ly-6 protein most similar to mouse differentiation Ag TSA-1/Sca-2, has also been called RIG-E. Like mouse TSA-1, it has a broad tissue distribution with varied expression levels in normal human tissues and tumor cell lines. Like some members of the murine Ly-6 family, the 9804 gene is responsive to IFNs, particularly IFN-alpha. Overlapping genomic fragments spanning the 9804 gene (5543 bp) have been isolated and characterized. The gene organization is analogous to that of known mouse Ly-6 genes. The first exon, 2296 bp upstream from exon II, is entirely untranslated. The three coding exons (II, III, and IV) are separated by short introns of 321 and 131 bp, respectively. Primers were developed for specific amplification of 9804 gene fragments. Screening of human-hamster somatic cell hybrids and yeast artificial chromosomes (YACs) indicated that the gene is distal to c-Myc, located in the q arm of human chromosome 8. No positives were detected from the Centre d'Etude du Polymorphisme Humain mega-YAC A or B panels, nor from bacterial artificial chromosome libraries; two positive cosmids (c101F1 and c157F6) were isolated from a human chromosome 8 cosmid library (LA08NC01). Fluorescence in situ hybridization of metaphase spreads of chromosome 8, containing hybrid cell line 706-B6 clone 17 (CL-17) with cosmid c101F1, placed the 9804 gene close to the telomere at 8q24.3. This mapping is significant, since the region shares a homology with a portion of mouse chromosome 15, which extends into band E where Ly-6 genes reside. Moreover, the gene encoding E48, the homologue of mouse Ly-6 molecule ThB, has also been mapped to 8q24.     

Transforming growth factor-beta receptors on human endometrial cells: identification of the type I, II, and III receptors and glycosyl-phosphatidylinositol anchored TGF-beta binding proteins

BACKGROUND: Mutation of the p53 tumor suppressor gene is the most commonly found genetic alteration in human cancer. The E6 gene product of human papillomavirus (HPV) 16 and 18 can inactivate the p53 protein by promoting its degradation. Because most HPV-positive cervical carcinoma cell lines contain wild-type p53 whereas HPV-negative cell lines have point mutations in the p53 gene, a major role in the development of HPV-negative cervical cancer has been attributed to p53. Recent studies, however, have observed no consistent presence of p53 mutation in HPV-negative primary cervical carcinomas. The MDM2 oncogene, which forms an autoregulatory loop with the wild-type p53 protein, has been found amplified in a high percentage of human sarcomas, thus abolishing the antiproliferative function of p53. METHODS: Forty-three primary cervical carcinomas and 10 autopsy-derived distant metastases from one patient were examined for p53 mutation and MDM2 amplification. These tumors had been selected from 238 cervical cancers that had been HPV-typed by Southern blot hybridization and polymerase chain reaction as a representative sample for their HPV status and their clinicopathologic characteristics. Seventeen of the cases had a remarkably good or poor clinical outcome. Human papillomavirus DNA sequences had been detected in 30 of these 43 primary tumors and 13 were negative for HPV by both methods. p53 mutation in the highly conserved exons 5-8 was studied by single-strand conformation polymorphism analysis and direct sequencing. MDM2 amplification was analyzed by Southern blot hybridization. RESULTS: Only two missense point mutations and one nucleotide sequence polymorphism were detected: a TAC-->TGC transition in codon 234 in exon 7, resulting in a Tyr-->Lys substitution, a CGT-->TGT transition in codon 273 in exon 8, resulting in an Arg-->Cys substitution and a polymorphism (CGA-->CGG) in codon 213 in exon 6. Both tumors revealing the point mutations were HPV-negative carcinomas. Amplification of the MDM2 gene was observed in 1 of the 53 specimens tested. CONCLUSIONS: In contrast to data derived from cultured cervical carcinoma cell lines and primary sarcomas, these results indicate that p53 mutation and amplification of the MDM2 oncogene are rare even in HPV-negative primary cervical carcinomas. However, to the authors; knowledge, this is the first observation of MDM2 amplification in humans outside sarcomas and neuroepithelial tumors.     

Genetic alterations and molecular mechanisms underlying colorectal tumorigenesis

Tumor cells are cells that have acquired damage to genes that directly regulate their cell cycles. In the multistep process leading to colorectal carcinoma, the adenoma-carcinoma sequence is characterized by progressive accumulation of genetic abnormalities (K-ras oncogene mutation, allelic deletion on chromosome 5q, 18q, 17p). In a hereditary non-polyposis syndrome (Lynch syndrome II) and in about a quarter of the cases of sporadic colorectal cancer there is a DNA micro-instability which contributes to the acquisition of mutations that cause loss of tumor-suppressor function. The p53 tumor-suppressor gene is the most frequently mutant gene in human cancer. In colorectal cancer cells missense p53 mutations and allelic deletion on chromosomal locus 17p13.1 are found with very high frequency. One of biological roles of p53 gene is to ensure that, in response to genotoxic damage, cells arrest in G1 and attempt to repair their DNA before it is replicated. In addition, p53 is required for apoptosis in response to severe DNA damage, included the damage induced by chemotherapeutics drugs and ionizing radiation. The loss of p53 function results in genomic instability and has been implicated in the evolution of normal cells into cancer cells.     

Cyclin DI amplification is not associated with reduced overall survival in primary breast cancer but may predict early relapse in patients with features of good prognosis

Amplification of chromosome 11q13 is frequently observed in human malignancies, including breast cancers. A candidate oncogene at this locus is the CCND1 gene, which encodes the cell cycle regulatory protein cyclin D1. Because published data on the relationship between 11q13 amplification and prognosis in breast cancer have been controversial, we investigated the clinical significance of CCND1 amplification and its association with established clinicopathological features of prognosis in 1014 primary breast cancer patients. Amplification of the CCND1 gene and the INT-2/FGF-3 gene, which also maps to 11q13, was 10% and 17%, respectively. There were no associations between CCND1 or INT-2 amplification and patient age, tumor size, tumor grade, axillary lymph node status, HER/neu amplification, MIB-1 monoclonal antibody to Ki67 antigen count, or p53 expression. CCND1 amplification was predominantly observed in hormone receptor-positive tumors; at a copy number >/=3, CCND1 amplification was significantly correlated with both estrogen receptor (ER; P = 0.036) and progesterone receptor (P = 0.012) positivity. After a median follow-up period of 66 months, CCND1 or INT-2 amplification was not associated with significant increases in relapse or death from breast cancer. However, in the node-negative and ER-positive subgroups, there was a trend for an increased relapse rate in patients with INT-2 or CCND1 amplification. Thus, in this study, assessment of CCND1 or INT-2 amplification at 11q13 by slot-blot hybridization was of little use in determining phenotype or disease outcome in the whole group of patients but had a potential role in identifying a subset of poor-prognosis patients within the node-negative or ER-positive, good-prognosis groups. Because the prevalence of CCND1 amplification is much lower than the reported prevalence of cyclin D1 overexpression, additional studies are required to determine the true prognostic significance of altered cyclin D1 expression in breast cancer.     

Numerical chromosome alterations in colorectal carcinomas detected by fluorescence in situ hybridization. Relationship to 17p and 18q allelic losses

This study concerns DNA ploidy, numerical changes of chromosomes 7, 8, 10, 17 and 18, and allelic losses at chromosomes 17p13.3 (flanking the p53 gene) and 18q21 (location of the DCC gene) in 31 freshly resected colorectal tumours. Cytological smears were used to determine DNA ploidy by image analysis, and chromosome numbers by fluorescence in situ hybridization (FISH) using chromosome-specific pericentromeric alpha-satellite DNA probes. Allelic losses were assessed by Southern blotting and by the polymerase chain reaction loss of heterozygosity method. Approximately 50% of the tumours were aneuploid. There was heterogeneity with respect to chromosome numbers, but gains and losses of chromosomes, or both, were detected in all carcinomas examined, including 10 that were nonaneuploid by image analysis. Trisomy 7 was found in 74% of the tumours, and monosomy of chromosome 18 in 32%. Allelic loss at chromosome 17p13.3 was evident in 13 of 26 informative cases, and only one case exhibited monosomy 17. In comparison monosomy 18 was found in 10 cases; 7 of them corresponded to approximately half of the cases with allelic loss within the DCC gene, and the other three were noninformative. These findings indicate that the loss of one chromosome 18 is an important mechanism producing allelic deletion of the DCC gene in colorectal carcinomas. Our data also suggest that monosomy 18 is a useful indicator for studying colorectal cancer progression on a cell by cell basis.     

Amplification of the genes BCHE and SLC2A2 in 40% of squamous cell carcinoma of the lung

Gene amplification is a common genetic change in human cancer cells. Previously, we provided the first evidence for gene amplification at chromosome band 3q26 in squamous cell lung carcinoma. In this study, the following analyses were performed: (a) we evaluated biopsies and paraffin-embedded tissues of 16 additional squamous cell lung carcinomas for gene amplification using reverse chromosome painting. Of the 16 tumors, 3 tumors showed an amplification of the entire long arm of chromosome 3, and 3 tumors showed various amplifications on 3q, all of which involved chromosome band 3q26; (b) we tested eight genes encompassing region 3q25-qter in two different tumors to identify amplified genes on chromosome 3q. The genes SI, BCHE, and SLC2A2 were amplified in both tumors; and (c) we analyzed 15 additional paraffin-embedded tissues to determine the amplification frequency of these genes. Of the 15 squamous cell lung carcinomas, 6 showed amplification for at least 1 of the genes, with BCHE and SLC2A2 as the genes most frequently amplified. Together, our reverse chromosome painting data and our PCR analysis indicate gene amplification at 3q26 in 40% of all squamous cell lung carcinomas with BCHE and SLC2A2 as possible target genes of the amplification unit in squamous cell lung carcinoma.     

Fluorescence in situ hybridization analyses of hematologic malignancies reveal frequent cytogenetically unrecognized 12p rearrangements

Thirty-two hematologic malignancies--nine with cytogenetically identified 12p abnormalities and 23 with whole or partial losses of chromosome 12--were selected for fluorescence in situ hybridization (FISH) investigations of 12p. These analyses revealed structural 12p changes, such as translocations, deletions, insertions, inversions and amplification, in 20 cases. ETV6 rearrangements were detected in three acute leukemias. One acute undifferentiated leukemia had t(4;12)(q12;p13) as the sole anomaly. The second case, an acute myeloid leukemia (AML), displayed complex abnormalities involving, among others, chromosomes 9 and 12. The third case, also an AML, had an insertion of the distal part of ETV6 into chromosome arm 11q and into multiple ring chromosomes, which also contained chromosome 11 material, resulting in an amplification of a possible fusion gene. The fusion partners in these cases remain to be identified. Thirty-one additional breakpoints on 12p could be characterized in detail. The majority of these breaks were shown to result in interchromosomal rearrangements, possibly indicating the location of hitherto unrecognized genes of importance in the pathogenesis of hematologic malignancies. The FISH analyses disclosed terminal or interstitial 12p deletions in 18 cases. Seven myeloid malignancies showed deletions restricted to a region, including ETV6 and CDKN1B, which has been reported to be frequently lost in leukemias. In four cases, the deletions involved both these genes, whereas two AML displayed loss of CDKN1B but not ETV6, supporting previously reported findings indicating a region of deletion not including this gene. However, one myelodysplastic syndrome lacked one copy of ETV6 but not CDKN1B. Hence, we suggest a minimal region of deletion on 12p located between the ETV6 and CDKN1B genes.