Deletion Of Tumor Suppressor Gene Research Articles

Biologic Markers to Predict Recurrence in Oral Squamous Cell Carcinoma

Statement of the Problem: Background: Despite advances in multimodality therapy of oral squamous cell carcinoma (OSCC), there continues to be poor overall patient survival. Although, early stage tumors have been traditionally associated with the most favorable outcome, there continues to be a subset of patients with small tumors that are easily extirpated that continue to have local or regional failure with high mortality rates. Several tumor sites such as breast and colon malignancies have been shown to have molecular markers that can be identified at the time of tumor extirpation that lead to the modification of postoperative treatment with targeted therapies with improved patient outcomes. Purpose: The purpose of this study was to identify patients diagnosed with T1 OSCC and treated at the Mayo Clinic from 1986 to the present. Tissue specimens for all patients were subjected to assessment with immunohistochemical stains in an attempt to identify markers which may be predictive of patients progressing to early recurrences and mortality from these early stage tumors. Materials and Methods: The records of patients treated for T1 intraoral squamous cell carcinoma treated at Mayo Clinic (Rochester, MN) were identified from the tumor registry from 1986 to the present. All patients with T1 OSCC were included. Patient demographic and tumor characteristics will be collected. Tissue specimens will be analyzed with immunohistochemistry techniques by a single pathologist to identify tumors with p53 tumor suppressor gene, CD34 and microsatellite instability in an attempt to correlate tumor characteristics to recurrence rates and patient survival. Method of Data Analysis: Data will be statistically analyzed in an attempt to identify predictors of loco-regional control and disease-free survival. Descriptive statistics will be calculated for each variable and survival calculated using the Kaplan-Meier and logistical regression methods. Results: One hundred and seventy-five patients met inclusion criteria, this included 129 males (53%) and 117 females (47%) with an average age of 61.6 years (Range 21.2-91.8 with a SD / 13.6). Average tumor size was 1.4 cm (SD) in length. Site distribution is 46% tongue, 15% gingival, 56 17% floor of the mouth, 8% palate, and 11% buccal mucosa. Histologic grade distribution is 15% grade 1, 46% grade 2, 36% grade 3, 3% grade 4, and 3% did not have histologic grade recorded. Treatment included 97% of patients undergoing surgical resection alone, 4 (1%) radiotherapy and 2% had alternative or no treatment. All patients presented were treated without neck dissection. Mean follow-up was 58.5 months (range 0.0-197.0 months) (SD /49.36). Local and regional recurrences were observed in 8.5% and 16% of patients respectively. Conclusion: The presence of P53 tumor suppressor gene deletions led to increased rates of early recurrence and death, while the presence of microsatellite instability from the tumor specimens did not correlate with poor patient survival.

Whole Genome Amplification of Plasma-Circulating DNA Enables Expanded Screening for Allelic Imbalance in Plasma

Apoptotic and necrotic tumor cells release DNA into plasma, providing an accessible tumor biomarker. Tumor-released plasma-circulating DNA can be screened for tumor-specific genetic changes, including mutation, methylation, or allelic imbalance. However, technical problems relating to the quantity and quality of DNA collected from plasma hinder downstream genetic screening and reduce biomarker detection sensitivity. Here, we present a new methodology, blunt-end ligation-mediated whole genome amplification (BL-WGA), that efficiently amplifies small apoptotic fragments (<200 bp) as well as intermediate and large necrotic fragments (>5 kb) and enables reliable high-throughput analysis of plasma-circulating DNA. In a single-tube reaction, purified double-stranded DNA was blunted with T4 DNA polymerase, self-ligated or cross-ligated with T4 DNA ligase and amplified via random primer-initiated multiple displacement amplification. Using plasma DNA from breast cancer patients and normal controls, we demonstrate that BL-WGA amplified the plasma-circulating genome by approximately 1000-fold. Of 25 informative polymorphic sites screened via polymerase chain reaction-denaturating high-performance liquid chromatography, 24 (95%) were correctly determined by BL-WGA to be allelic retention or imbalance compared to 44% by multiple displacement amplification. By enabling target magnification and application of high-throughput genome analysis, BL-WGA improves sensitivity for detection of circulating tumor-specific biomarkers from bodily fluids or for recovery of nucleic acids from suboptimally stored specimens.

Deletion of Tumor Suppressor Genes (TSGS) in Patients with Myelodysplastic Syndrome (MDS).

Background: The deletion of genomic sites harboring TSGs is known to be a powerful prognostic indicator in various chronic hematologic malignancies. However, the clinical significance of TSGs loss in MDS has not been thoroughly investigated.Aims: To summarize our experience on the incidence and essential clinical correlates of TSGs deletions in MDS, providing preliminary results from the study of 27 patients.Methods: The study included 17 men and 10 women (median age 74; range 38–84 years) with a documented diagnosis of MDS. The distribution of FAB subtypes was RA in 13, RARS in 3, RAEB in 6, RAEB-T in 4 and CMML in 1 case. According to the IPSS stratification, 5 patients were characterized as “low-risk”, 16 as “intermediate-risk” (11 as INT-1 and 5 as INT-2) and 6 as “high-risk” patients. The diagnostic bone marrow smears were studied with fluorescence in-situ hybridization (FISH) for deletions of chromosome regions 9p21 (p16/p14 and p15 genes), 9q34, 12p13 (TEL gene), 13q14 (RB1 gene D13S319 locus) and 17p13 (p53 gene).Results: A deletion in at least one of the chromosome regions or loci studied was detected in 10 patients (37%). In 6 of them, more than one region locus was lost, making up a total of 20 deletions. The commonest finding was loss of the 17p13 region (5 cases; two of them homozygous), followed by 9p21 loss (5 cases; one of them homozygous). Overall, the presence of TSGs deletions was associated with complex karyotype, high IPSS score and risk of death (regardless of leukemic progression). Interestingly, deletion in at least one of the TSGs studied was found in 5 of the 17 patients presenting with normal karyotype. In 3 of these patients, the MDS progressed to acute leukemia. Two of the 5 patients died at one and six months from diagnosis of the MDS, without leukemic conversion.Summary/Conclusions: Deletions of TSGs are not uncommon in MDS. Interestingly, we have found that certain TSGs, such as the p16/p14 and p15 genes at 9p21, the loss of which is mostly involved in the initiation or progression of lymploid neoplasms, are also frequently deleted in MDS. Overall, TSGs deletion in this small group of patients is apparently associated with other adverse biological and clinical features and poor outcome. Therefore, these preliminary observations justify the expansion of the study in a larger patient cohort, in order to clarify if the loss of certain TSGs is an independent prognostic factor in MDS and, thus, may be of help in the initial diagnostic approach and risk stratification of the patients.

Loss of Heterozygosity Identified in Acute Myeloid Leukemia with Normal Karyotype Using SNP Microarrays.

Loss of heterozygosity (LOH) is detectable in many forms of cancer including leukemia and contributes to tumorigenesis through the deletion of tumor suppressor genes. It derives from the loss of one of the two alleles at a given locus caused by deletion or uniparental disomy (UPD). In this study we describe the genome wide analysis of LOH in purified leukemic blasts from acute myeloid leukemia (AML) samples with normal karyotype using a novel technique based on single nucleotide polymorphisms (SNP). In total we selected 50 peripheral blood samples of de novo AML patients with normal karyotype at the time of diagnosis. Patients were treated according to the AML-96 multi-center protocol of the DSIL. Pure leukemic cells and tumor free material (T cells) from each patient were obtained using FACS-Vantage cell-sorting (BD Sciences, Germany). DNA was isolated from sorted cells. Genome wide SNP analysis was carried out according to the standard GeneChip Mapping Assay protocol (Affymetrix, USA) with pre-amplified DNA (Repli-g™ Kit; Molecular Staging Inc. USA) using the Human Mapping 10K Arrays XbaI 131 (Affymetrix). Individual regions of potential LOH identified by the Affymetrix® GeneChip® Chromosome Copy Number Analysis tool were confirmed by microsatellite analysis of short tandem repeat (STR) markers using the matched non-manipulated original DNA samples. Genome wide analysis of SNP in pre amplified DNA of FACS sorted cells from AML samples with normal karyotype detected long stretches of hemizygosity, indicative of LOH in 8/49 evaluable patients (16%). In 6 of these cases STR-analysis of T cells representing the corresponding tumor free material confirmed the regions of partial UPD. UPD affected four different chromosomes (chromosome 2p and 11q, in each case twice; chromosome 8q, and 13q) and covered between 11.5 and 88 Mb. To our surprise in the healthy material of the remaining two cases no heterozygote loci were identified at the affected chromosomal regions (chromosome 3 14.5 Mb; chromosome 20 29.3 Mb) and consequently identified as unusual long stretches of homozygosity present in both the malignant and the healthy cells. These cases might reflect genotypes with high susceptibility to malignant mutations. No differences were observed for any clinical factors, including age, WBC-counts, sex and FAB-subtype. Also, several of the mutations frequently identified in patients with normal karyotype (FLT3-ITD, MLL-PTD, NPM1) had a comparable prevalence in patients with and without UPD. Interestingly, although 5/6 patients with UPD achieved complete remission after induction chemotherapy, 4/5 (80%) relapsed within the first 6 months. In contrast the rate of relapse in patients without UPD was only 54% (15/28). The only patient positive for UPD and alive in remission received an allogeneic stem cell transplantation. In conclusion, the combination of whole genome amplification method and SNP array technology allows the identification and mapping of LOH in AML patients with normal karyotype. Our data also point to the necessity to analyze tumor free material to confirm the somatic origin of the alteration. Although small numbers of patients were investigated, our data might indicate that patients with UPD have a high rate of treatment failure. This should be further investigated in larger cohorts of patients.

Chromosomal Deletions and Amplifications in Multiple Myeloma Detected by 500K Single Nucleotide Polymorphism Array Analysis.

Genetic aberrations, such as deletions and amplifications are among the major pathogenetic mechanisms underlying malignant transformation and progression. Analysis of chromosomal aberrations is particularly important as amplifications of oncogenes and deletions of tumor suppressor genes are major steps in the “multi-hit” process of tumorigenesis. Genome-wide molecular analyses, such as loss of heterozygosity (LOH) profiling and comparative genomic hybridization (CGH) have significantly enhanced our ability to detect chromosomal aberrations in cancer cells and assess their role in tumorigenesis. The recent introduction of high-density oligonucleotide arrays capable of measuring up to 500K single nucleotide polymorphisms (SNP) loci is able to analyze small areas of gains or losses. Here we describe the use of high-density array representing upto 500K SNPs to not only characterize SNPs but also evaluate genome-wide areas of gains and losses in myeloma. We purified CD138+ myeloma cells from 5 patients and also obtained their peripheral blood mononuclear cells. Purified genomic DNA from these cells was digested with Sty and Nsp restriction enzymes, PCR amplified and hybridized to 500K SNP array. Results from DNA obtained from CD138+ myeloma cells were compared with DNA from normal peripheral blood mononuclear cells from the same patient using the dChip software for LOH and copy number analysis. Areas of deletions and amplifications were identified and correlated with gene expression profile obtained from CD138+ myeloma cells of the same patient. The preliminary analysis identified various areas of amplifications and deletions. The significant areas of structural gains or losses included Chromosome 1, 6, 8, 11, 12, 13, 14, 15, 22, X among others and ranged in size from 1 Mb to the loss of entire chromosome (13q−). In this small sample we have identified recurrent LOH shared by 2 or more samples including 1p21, 6q, 12p13 and 13q. The derived CGH results correlated with known cytogenetic abnormalities in the patients, with identification of additional areas of abnormality not detected by conventional cytogenetics or FISH. These structural changes also corresponded with the results from gene expression profiling of MM cells from same patients, thus validating the technique and its application. A large series of patient samples are now under investigation using 500K SNP chip to define regions of homozygous deletions as well as amplification. In conclusion, these results demonstrate that SNP array analysis provides a powerful new tool for the analysis of allelic imbalance in myeloma. Furthermore, this technique can identify novel candidate loci to study in pathogenesis of myeloma and advance identification of potential therapeutic targets for this fetal disease.

Promoter methylation and loss of coding exons of the fragile histidine triad (FHIT) gene in intrahepatic cholangiocarcinomas

About 10-30% of primary liver cancers represent intrahepatic cholangiocarcinomas (IHCC). Since chromosomal losses of 3p are detectable in about 40% of cholangiocarcinomas our study aimed at the identification of mechanisms leading to functional deletion of tumor suppressor genes in this region. Our efforts focussed on genomic losses and epigenetic inactivation of two tumor suppressor genes, the fragile histidine triad (FHIT) and the ras association domain family 1 (RASSF1A) genes, both located on the short arm of chromosome 3. Methylation-specific PCR (MSP) and combined bisulfite-dependent restriction analysis (COBRA) were applied to detect epigenetic silencing of gene promoters. Genomic duplex PCR was used to identify exon losses of the FHIT gene. Nineteen paraffin-embedded samples of intrahepatic cholangiocarcinomas were studied. Here we report for the first time that in addition to frequent losses of the exons 5 and 6, hypermethylation of the FHIT promoter occured in a significant portion of IHCC. Methylation specific PCR (MSP) detected epigenetic inactivation of the FHIT/FRA3B locus in 8 of 19 (42%) cases. Combined bisulfite restriction analysis (COBRA) revealed that high levels of methylated FHIT promoter sequences were present in 6 of the 8 methylation positive samples. In agreement with previous reports MSP identified hypermethylation of the RASSF1A gene in 13 of 19 (68%) IHCC specimens examined. Epigenetic silencing of the FHIT tumor suppressor gene is a novel inactivation mechanism to be considered in the development of intrahepatic cholangiocarcinomas. However, a statistically significant inverse correlation between K-Ras activation and RASSF1A inactivation was not found.

Detection of Her2/neu, c-MYC and ZNF217 gene amplification during breast cancer progression using fluorescence in situ hybridization

The deletion of tumor suppressor genes and amplification of activating oncogenes appear to be critical events in tumorigenesis. We carried out fluorescence in situ hybridization (FISH) analysis of the breast cancer cell line MCF7 and clinically obtained cancer tissue sections on the basis of which we suggest a breast cancer development model. We selected 28 genes for FISH probes from breast cancer patients. Of the 28 genes studied, 14 were shown to be consistently amplified in the breast cancer cell line MCF7. We selected three genes from clinical tumor samples on the basis of results from MCF7 analysis. The amplification of Her2/neu or ZNF217 is closely associated with the stages of breast cancer. The frequency of amplification of Her2/neu increased notably in patients at stages later than IIB based on TNM staging, whereas the amplification of ZNF217 correlated with T2N1M0 at stage IIB and later stages. c-MYC amplification was not related to the stage. Her2/neu, ZNF217 and c-MYC were found to have a significantly increased copy number in breast cancer cells. In breast cancer progression, c-MYC amplification is an early event, while ZNF217 and Her2/neu amplification may play a role in the later stage of tumor development.

Microsatellite Analysis of Early Stage (la-Ilb) Uterine Cervical Squamous Carcinoma

Cervical cancer is the most common gynecologic malignancy of the developing world. The oncogenic role of human papilloma virus (HPV) is well known. Attention is now focusing on the complicit genetic changes, which allow progression of these tumors. Regarding these changes, deletion of tumor suppressor genes (loss of heterozygosity [LOH]) is the preferred pathway of progression with only a subset manifesting microsatellite instability (MSI). Implicated loci include 3p14.1-22. Several studies suggest that the mutator phenotype in cervical cancer may correlate with higher grade tumors, more advanced disease stage, and poor outcome. Unlike colorectal cancer, in which an inverse relationship has been demonstrated between microsatellite instability and loss of heterozygosity, cervical cancers expressing MSI have been found to coexpress LOH at other loci. In this study we analyzed 8-microsatellite loci including p53, DCC, APC, the MMR gene hMLH1 and 2 regions of interest on chromosome 3 in a high-risk population group in which HPV infection is endemic.

Detection of gene amplification and deletion in high-grade gliomas using a genome DNA microarray (GenoSensor Array 300).

Glioblastoma is a rapidly growing tumor that accounts for more than 50% of all primary gliomas. Amplification of oncogenes and deletion of tumor suppressor genes frequently affects tumor progression. Thus, the goal of this study was to conduct a comprehensive analysis of gene aberrations of individual glioblastomas. A genome DNA microarray (GenoSensor Array 300), spotted with 287 target genes, was used to analyze resected tissue from 11 different high-grade gliomas. The average number of gene aberrations was 9.0 per case (WHO grade III) and 13.3 per case (WHO grade IV). EGFR was the most frequent amplified gene in this series (4 of 11 cases), and high-level amplification was also detected for EGFR, SAS/CDK4, and AKT1. A high frequency of deleted genes was observed in 6 of 11 cases (54.5%), including FGFR2, MTAP, and DMBT1. The detected gene aberrations were matched to the classical primary glioblastoma pathway in five of nine cases. We conclude that the GenoSensor Array 300 genomic DNA microarray is a useful method for the comprehensive identification of amplified and deleted genes in glioblastoma.

Genetic alterations in cancer as a result of breakage at fragile sites

The organization and replication of DNA render fragile sites (FSs) prone to breakage, recombination as well as becoming preferential targets for mutagens–carcinogens and integration of oncogenic viruses. For many years, attempts to link FSs and cancer generated mostly circumstantial evidence. The discoveries that chromosome translocations, amplification of proto-oncogenes, deletion of tumor suppressor genes, and integration of oncogenic viruses all result from the specific breakage of genomic DNA at FSs, however, have provided compelling support for such a link, further suggesting a causative role for FSs in cancer.

Deletion of tumor suppressor genes in Chinese non-small cell lung cancer

In the present study, we used 22 microsatellite markers flanking to or within 13 known or candidate tumor suppressor genes (TSGs) to detect loss of heterozygosity (LOH) in these chromosomal regions among 41 cases of non-small cell lung cancer, including 28 squamous cell carcinoma (SCC) and 13 adenocarcinoma (ADC). The studied TSGs comprised FHIT, VHL, APC, PRLTS, p16, IFNA, PTEN, p57, ATM, p53, BRCA1, DPC4 and DCC. Our data demonstrated frequent allelic losses of FHIT, p53, IFNA, VHL and p16 in both SCC and ADC. PTEN and ATM showed the least frequency of LOH, while no deletion of BRCA1 was detected in all tumor samples. LOH analysis of PRLTS was extended to 26 cases of ADC, which demonstrated significantly higher frequency of LOH than SCC. Our data indicated a possible correlation between specific TSG(s) and either histological type of lung cancer, and more attention should be paid to the PRLTS gene, which might play an important role in the development of ADC.

Molecular characterization of head and neck tumors by analysis of telomerase activity and a panel of microsatellite markers

Head and neck cancer is a frequent malignancy with a complex, and up to now not clear etiology. The reactivation of telomerase activity and losses or gains of specific chromosomal regions, which point to deletions of tumor suppressor genes or amplification of oncogenes are supposed to be the molecular processes during the development and progression of head and neck cancer. Therefore, we analyzed telomerase activity and microsatellite markers using a genome wide panel of 28 microsatellite markers in 38 head and neck squamous-cell carcinomas (HNSCC). Our microsatellite marker set included distinct chromosomal areas that all likely harbor genes contributing to the carcinogenesis of HNSCC. DNA or protein lysates were obtained from primary tumors and compared to peripheral lymphocytes or corresponding normal tissue. At least one genomic alteration [loss of heterozygosity (LOH), or microsatellite instability (MSI)] was found in 31 of the 38 cases (82%). Most frequently we detected an LOH in the chromosomal region 9p12-21 where at least the tumor suppressor genes (TSG) p16INK4A, p14ARF and p15INKB are localized. The comparison between grade two and grade three tumors showed a highly changed frequency of LOH in the chromosomal region 7q31, where a putative TSG is predicted. Telomerase activity was present in 31/37 (83.8%) tumor samples independent of the histopathological staging and grading of the tumors. These molecular characterizations of HNSCC may be a further hint for the involvement of additional, so far unknown, TSGs in the tumor progression and will elucidate the regulation of telomerase.

Frequent Deletions of Tumor Suppressor Genes in Pure Pancreatic Juice from Patients with Tumoral or Nontumoral Pancreatic Diseases

Background/Aims: K-ras codon 12 mutation is the most frequent genetic alteration in pancreatic cancer. Sensitivity and specificity of K-ras are not high enough to detect all pancreatic cancers, especially at early stage. This study investigated whether detection of p16 and/or DPC4 deletions along with K-ras mutation in DNA samples could improve the definition of patients at risk of pancreatic cancer. Methods: K-ras mutations were investigated by sequencing. p16 and DPC4 homozygous deletions were studied using comparative multiplex polymerase chain reaction of DNA in pancreatic juice sampled during endoscopic retrograde pancreatography in 57 patients with either pancreatic cancer (group I, 18 patients), chronic pancreatitis (group II, 20 patients), or nontumoral pancreatobiliary disease (group III, 19 patients). Results: The frequencies of Ki-ras mutations were 61% in group I, 10% in group II, and 10.5% in group III. The frequencies of p16 exon 2 and DPC4 deletions were, respectively, 28 and 36% in group I, 50 and 58% in group II, and 24 and 36% in group III. Conclusions: The combination of p16 and DPC4 deletions with K-ras mutation does not improve the diagnosis of pancreatic cancer based on K-ras mutation alone. These data suggest that tumor suppressor gene inactivation can occur with a high frequency during nonmalignant pancreatic diseases.

Comparative Genomic Hybridization (CGH)—Detection of Unbalanced Genetic Aberrations Using Conventional and Micro‐Array Techniques

This unit presents comparative genomic hybridization (CGH), a genome-wide screening technique for genetic aberrations in tumor samples. Specific emphasis is placed on recent applications to the analysis of murine model systems for human cancer. CGH is an invaluable tool for identifying the characteristic genetic rearrangements in these models. The authors discuss an exciting new method currently being developed, array CGH, which results in a tremendous increase in resolution. Oncogene amplifications and deletions of tumor-suppressor genes are detected on a single-gene level. Detailed protocols are supplied for CGH analysis of both human and mouse chromosomes.

Comparisons of Tumor Suppressor p53, p21, and p16 Gene Therapy Effects on Glioblastoma Tumorigenicity in Situ

The mutation and/or deletion of tumor suppressor genes have been postulated to play a major role in the genesis and the progression of gliomas. In this study, the functional expression and efficacy in tumor suppression of 3 tumor suppressor genes (p53, p21, and p16) were tested and compared in a rat GBM cell line (RT-2) after retrovirus mediated gene delivery in vitro and in vivo. Significant reductions in tumor cell growth rate were found in p16 and p21 infected cells (60 ± 12% vs 66 ± 15%) compared to p53 (35 ± 9%). In vitro colony formation assay also showed significant reductions after p16 and p21 gene delivery (98 ± 5% vs 91 ± 10%) compared to p53 (50 ± 18%). In addition, the tumor suppression efficacy were investigated and compared in vivo. Retroviral mediated p16 and p21 gene deliveries in glioblastomas resulted in more than 90% reductions in tumor growth (92 ± 26% vs 90 ± 22%) compared to p53 (62 ± 18%). Tumor suppressor gene insertions in situ further prolonged animal survival. Overall p16 and p21 genes showed more powerful tumor suppressor effects than p53. The results were not surprising, as p16 and p21 are more downstream in the cell cycle regulatory pathway compared to p53. Moreover, the mechanism involved in each of their suppressor effects is different. This study demonstrates the feasibility of using tumor suppressor genes in regulating the growth of glioma in vitro and in situ.

Germline sequence variant S836S in the RET proto-oncogene is associated with low level predisposition to sporadic medullary thyroid carcinoma in the Spanish population.

The molecular basis of sporadic medullary thyroid carcinoma (MTC) remains elusive. While germline gain-of-function mutations in the RET proto-oncogene cause hereditary MTC, somatic activating RET mutations and loss of heterozygosity of markers in various chromosomal regions representing deletions of tumour suppressor genes, have been described in a variable number of sporadic MTC. A previous report suggested that the presence of a germline variant at RET codon 836 (S836S) was associated with the development of sporadic MTC and, furthermore, that the presence of S836S was highly correlated with somatic RET M918T mutation in the MTC. Thus, we sought to determine if the S836S variant would be associated with sporadic MTC from a completely different population base, that of Andalucia. This is a case-control study to determine whether the presence of RET germline S836S is correlated with sporadic MTC in Andalucia. Thirty-two patients with sporadic MTC from the Andalucia region of Spain, serviced by our University Hospital, were ascertained throughout the period 1995-99. Sporadic MTC was defined as a lack of personal or family history suggestive of multiple endocrine neoplasia type 2 (MEN 2) and lack of germline RET mutations which define any MEN 2 subtype. A region and race matched cohort of 250 controls was also obtained. The frequency of the S836S allele was determined in cases and controls and compared using the standard chi-squared statistic and Fisher's exact test. The polymorphic allele frequency at codon 836 in the control population (18/500 chromosomes, 3.6%) differed significantly from the MTC case cohort, 9.3% of case chromosomes (six of 64 alleles, Fisher's exact test, two-tailed, P = 0.043). Germline RET S836S variant is associated with a two- to three-fold risk of sporadic MTC in the Spanish population, in accordance with a previous study based on German cases. Our observations suggest that this phenomenon might be universal and not limited to Germany.

Hamartomatous polyposis syndromes: molecular genetics, neoplastic risk, and surveillance recommendations.

Hamartomatous polyposis syndromes are characterized by an overgrowth of cells or tissues native to the area in which they normally occur. Juvenile polyposis syndrome (JPS) results from germ-line mutations in the SMAD-4 gene (18q21.1) that encodes for an enzyme involved in transforming growth factor beta(TGF-beta) signal transduction. The increased neoplastic risk may result from SMAD-4 mutations in the stromal component, which stimulate epithelial dysplasia and progression to invasive malignancy. Peutz-Jeghers syndrome (PJS) is associated with germ-line mutations in the LKB1 gene (19p13.3) that encodes a multifunctional serine-threonine kinase. These mutations occur in the epithelial component, suggesting a direct tumor suppressor effect. Patients are at an increased risk of intestinal and extraintestinal malignancies, including breast, pancreatic, ovarian, testicular, and cervical cancer. Cowden's disease is associated with germ-line mutations in the PTEN gene (10q22-23) and an increased risk of breast and thyroid malignancies. Ruvalcaba-Myhre-Smith syndrome is less common; controversy suggests that it may represent a variant of Cowden's disease. Genetic alterations underlying hamartomatous polyposis syndromes are diverse. Carcinogenesis may result from either germ-line mutations in the stroma (JPS) or as a direct result of functional deletion of tumor suppressor genes (PJS). Diagnosis depends on clinical presentation and patterns of inheritance within families. Suggested surveillance guidelines for the proband and first-degree relatives are outlined.

Incidence and prognostic significance of deletions of tumor suppressor genes and aneuploidies in multiple myeloma: an interphase FISH study

Incidence and prognostic significance of deletions of tumor suppressor genes and aneuploidies in multiple myeloma: an interphase FISH study

Analysis of the P53, RB/D13S25, and P16 Tumor Suppressor Genes in Marginal Zone B-cell Lymphoma : An Interphase Fluorescence In Situ Hybridization Study

The genetic mechanisms underlying the genesis, disease progression, and high-grade transformation of marginal zone B-cell lymphoma (MZBCL) are poorly understood. We analyzed 33 cases of histologically and immunophenotypically well-characterized MZBCL (12 extranodal, 11 nodal, and 10 splenic MZBCL; 27 at primary diagnosis and six during the course of disease) by dual-color interphase fluorescence in situ hybridization (FISH) for deletions of tumor suppressor genes. We investigated loci known to play a role in the genesis or disease progression of other subtypes of lymphoid malignancies, namely the P53 gene (17p13), the retinoblastoma gene (RB, 13q14), the D13S25 locus (13q14), and the P16 INK4A gene (9p21). Heterozygous deletions of P53 were detected in three out of the 33 cases, including two splenic and one extranodal MZBCL. One of these patients was analyzed at primary diagnosis and two during the course of disease. Heterozygous deletions of the RB gene (nodal MZBCL) and D13S25 (splenic MZBCL) were found in one case each. P16 deletions were not detected in any of our cases. We conclude that deletions of the analyzed tumor suppressor genes are relatively rare in MZBCL, which contrasts with the findings in some other subtypes of NHL.

Mutation of the RB1 Gene Caused Unilateral Retinoblastoma in Early Age

Fluorescence in situ hybridization (FISH) was applied for the detection of the retinoblastoma tumor-suppressor gene deletion on retinoblastoma tumor cells obtained from the unilateral tumor of a 3-month-old boy. Both retinoblastoma tumor cells and peripheral lymphocytes of the patient showed one hybridization signal per cell at the retinoblastoma-1 locus, indicating that one copy of the gene was deleted. Peripheral blood lymphocytes obtained from the patient's parents had two copies per cell for the gene. Retinoblastoma nuclear phosphoprotein expression could not be detected in the tumor tissue. No copy number alterations were detected with ten different centromeric DNA probes in the tumor cells. The deletion at the RB1 locus detected by FISH suggested that this gene alteration was heritable. The parental peripheral blood lymphocytes did not show the loss of the gene; thus the first deletion may have taken place in either of the parental germ cells. The second somatic mutation of the RB1 gene was probably under the detection limit of FISH. The second allelic alterations were detected by using the polymerase chain reaction for all exons of the retinoblastoma gene.