Frequency Of LOH Research Articles

Refined deletion mapping of loss of heterozygosity on 22q13 in sporadic colorectal carcinoma

To screen the candidate TSGs on 22q13 involved in sporadic colorectal cancer. The DNA samples of 83 cases with colorectal carcinoma and normal tissues were analyzed using eight fluorescent labeled polymorphic microsatellite markers by PCR. PCR products were electrophoresed on an ABI 377 DNA sequencer. Genescan 3.7 and Genotype 3.7 software was used for LOH scanning and analysis. Comparison between LOH frequency and clinicopathological factors were performed by chia2 test. The prevalence of LOH was 35.58%, and the average hereditary distance was 1.9 cM. The highest frequency of LOH (D22S1160 locus) and the lowest (D22S1170 locus) were 64.71% and 20%, respectively. Two obvious LOH regions were detected: One between D22S1171 locus and D22S274 locus (about 2.7 cM); another between D22S1160 and D22S1149 locus (about 1.8 cM). Furthermore,significant differences were observed between the frequency of LOH on D22S1171 locus and tumors location (P=0.020), the frequency of LOH on D22S114 locus and liver metastasis (P=0.008), the frequency of LOH on D22S1160 locus and lymph node metastasis (P=0.016). No significant differences were found between LOH on other loci and those factors above. Gene function screening revealed that ARHGAP8 and PPARA gene were involved in carcinogenesis. Two obvious high frequency LOH regions are detected by refined deletion mapping. One locates between D22S1171 locus and D22S274 locus (about 2.7 cM); another locates between D22S1160 and D22S1149 locus (about 1.8cM), ARHGAP8 and PPARA gene may be TSGs which contribute to carcinogenesis and progression of sporadic CRC on 22q13 region.

Analysis of the candidate tumor suppressor Ris-1 in primary human breast carcinomas

Frequent chromosome 3 losses have been described in several tumors types, which strongly suggest the presence of one or several tumor suppressor genes. Recently, a novel candidate tumor suppressor gene termed Ris-1 (for Ras-induced senescence 1) has been identified at chromosomal position 3p21.3. Ris-1 has been proposed to participate in anti-tumor responses that resemble cellular senescence and that are elicited by oncogenes such as Ras. To analyze the role of Ris-1 as a putative tumor suppressor gene in human breast cancer, we have performed a real-time quantitative analysis of its mRNA expression in 60 patients. Moreover, we carried out a first approach to evaluate the most common inactivation mechanism that can affect expression levels of tumor suppressor genes (mutation, promoter hypermethylation and allelic losses). Furthermore, a correlation study between expression as well as inactivating mechanisms of Ris-1 and several clinico-pathological parameters of the tumors was designed, with the objective of appraising the prognostic value of Ris-1 status. Decreased expression of Ris-1 was observed in 23% of the cases and overexpressed Ris-1 was detected in 15% of the primary breast tumors. Our data showed high frequency of LOH (30%) at one of the markers used. Nevertheless, a polymorphism related with the expression levels was described. Statistically significant correlations were found between decreased Ris-1 expression and negative progesterone receptors, as well as between overexpressing Ris-1 tumors and high histological grade. Despite all these data, we conclude that the suggested role of Ris-1 as tumor suppressor gene is not evident, at least in breast cancer. Future and larger series studies in different tumor types are necessary to clarify Ris-1 function in human cancer.

212 POSTER The potential role of oval cell presence in experimental liver fibrosis

Ionizing radiation is a well-known carcinogen, but its potency may be influenced by other environmental carcinogens, which is of practical importance in the assessment of risk. Data are scarce, however, on the combined effect of radiation with other environmental carcinogens and the underlying mechanisms involved. We studied the mode and mechanism of the carcinogenic effect of radiation in combination with N-ethyl-N-nitrosourea (ENU) using doses approximately equal to the corresponding thresholds. B6C3F1 mice exposed to fractionated X-irradiation (Kaplan's method) followed by ENU developed T-cell lymphomas in a dose-dependent manner. Radiation doses above an apparent threshold acted synergistically with ENU to promote lymphoma development, whereas radiation doses below that threshold antagonized lymphoma development. Ikaros, which regulates the commitment and differentiation of lymphoid lineage cells, is a critical tumor suppressor gene frequently altered in both human and mouse lymphomas and shows distinct mutation spectra between X-ray- and ENU-induced lymphomas. In the synergistically induced lymphomas, we observed a low frequency of LOH and an inordinate increase of Ikaros base substitutions characteristic of ENU-indcued point mutations, G:C to A:T at non-CpG, A:T to G:C, G:C to T:A and A:T to T:A. This suggests that radiation doses above an apparent threshold activate the ENU mutagenic pathway. This is the first report on the carcinogenic mechanism elicited by combined exposure to carcinogens below and above threshold doses based on the mutation spectrum of the causative gene. These findings constitute a basis for assessing human cancer risk following exposure to multiple carcinogens.

Chromosome 1q loss of heterozygosity frequently occurs in sporadic insulinomas and is associated with tumor malignancy

The pathogenesis of sporadic insulinomas is not clear, and there are no reliable genetic determinants that are useful to distinguish malignant and benign forms of this tumor. It was reported that 1q LOH might contribute to pathogenesis in gastrinomas and was correlated with tumor progression. However, little data are available on 1q LOH in sporadic insulinomas. In our study, we determine whether 1q LOH occurs in sporadic insulinomas and is associated with tumor malignancy by performing 1q allelotyping with 17 markers in 40 tumors and pair normal DNA. Thirty-five (88%) insulinomas had 1q LOH. Of the 35 insulinomas with 1q LOH, 14 (40%) had 1q21.3-23.2 LOH over a 7.5 cM region (SRO-1), whereas LOH in 21 tumors (60%) occurred at 1q31.3 over an 11.4 cM area (SRO-2). Of 24 tumors without MEN1 LOH, 20 had either SRO-1 or SRO-2 LOH (83%), whereas in 16 tumors with MEN1 LOH, 9 were shown to have LOH at either SRO-1 or SRO-2 (56%) (p = 0.065). This result suggests that LOH at 2 SRO might be MEN1 gene independent and may contribute to the pathogenesis in a subset of insulinomas without MEN1 gene LOH. The presence of 1q21.3-23.2 LOH is significantly associated with malignancy of insulinomas (p = 0.014). The high frequency of LOH at 1q 21.3-23.2 and 1q31.3 suggests these 2 areas may harbor putative tumor suppressor genes that may play an important role in the tumorigenesis of a subset of insulinomas. LOH at 1q21.3-23.2, which was associated with tumor malignancy, could be one of the genetic markers for identifying malignancy in sporadic insulinomas.

Population-Based Studies on Incidence, Survival Rates, and Genetic Alterations in Astrocytic and Oligodendroglial Gliomas

Published data on prognostic and predictive factors in patients with gliomas are largely based on clinical trials and hospital-based studies. This review summarizes data on incidence rates, survival, and genetic alterations from population-based studies of astrocytic and oligodendrogliomas that were carried out in the Canton of Zurich, Switzerland (approximately 1.16 million inhabitants). A total of 987 cases were diagnosed between 1980 and 1994 and patients were followed up at least until 1999. While survival rates for pilocytic astrocytomas were excellent (96% at 10 years), the prognosis of diffusely infiltrating gliomas was poorer, with median survival times (MST) of 5.6 years for low-grade astrocytoma WHO grade II, 1.6 years for anaplastic astrocytoma grade III, and 0.4 years for glioblastoma. For oligodendrogliomas the MSTwas 11.6 years for grade II and 3.5 years for grade III. TP53 mutations were most frequent in gemistocytic astrocytomas (88%), followed by fibrillary astrocytomas (53%) and oligoastrocytomas (44%), but infrequent (13%) in oligodendrogliomas. LOH 1p/19q typically occurred in tumors without TP53 mutations and were most frequent in oligodendrogliomas (69%), followed by oligoastrocytomas (45%), but were rare in fibrillary astrocytomas (7%) and absent in gemistocytic astrocytomas. Glioblastomas were most frequent (3.55 cases per 100,000 persons per year) adjusted to the European Standard Population, amounting to 69% of total incident cases. Observed survival rates were 42.4% at 6 months, 17.7% at one year, and 3.3% at 2 years. For all age groups, survival was inversely correlated with age, ranging from an MST of 8.8 months (<50 years) to 1.6 months (>80 years). In glioblastomas, LOH 10q was the most frequent genetic alteration (69%), followed by EGFR amplification (34%), TP53 mutations (31%), p16INK4a deletion (31%), and PTEN mutations (24%). LOH 10q occurred in association with any of the other genetic alterations, and was the only alteration associated with shorter survival of glioblastoma patients. Primary (de novo) glioblastomas prevailed (95%), while secondary glioblastomas that progressed from low-grade or anaplastic gliomas were rare (5%). Secondary glioblastomas were characterized by frequent LOH 10q (63%) and TP53 mutations (65%). Of the TP53 mutations in secondary glioblastomas, 57% were in hot-spot codons 248 and 273, while in primary glioblastomas, mutations were more evenly distributed. G:C-->A:T mutations at CpG sites were more frequent in secondary than primary glioblastomas, suggesting that the acquisition of TP53 mutations in these glioblastoma subtypes may occur through different mechanisms.

Analysis of somatic molecular changes, clinicopathological features, family history, and germline mutations in colorectal cancer families: evidence for efficient diagnosis of HNPCC and for the existence of distinct groups of non-HNPCC families

Objective: To analyse somatic molecular changes, clinicopathological features, family history, and germline mutations in families with colorectal cancer (CRC). Methods: Molecular changes (K-ras and β-catenin mutations, chromosome 18q allele loss...

Functional investigation of tumor suppressive role of chromosome 9 in esophageal squamous cell carcinoma

9571 Background: Esophageal carcinoma (EC) is a very deadly disease, but its molecular basis for tumorigenesis is still largely unknown. The microcell chromosome transfer technique is useful to functionally validate the presence of tumor suppressor genes (TSGs). Early studies indicate there might be important TSGs for EC on chromosome 9. Our study found the LOH frequency of chromosome 9 was very high and three commonly deleted regions were observed at 9p23–22, 9q13–22.3, and 9q34, which suggest the probable locations of TSGs on chromosome 9 involved in esophageal tumorigenesis. Methods: Transfer of chromosome 9 into the highly tumorigenic EC cell line, SLMT-1S1, was accomplished by the method of microcell-mediated chromosome transfer (MMCT). Hybrid cells and their corresponding tumor segregants were studied for the ability to form tumors in a nude mouse model and 33 microsatellite markers were used to detect critical regions associated with their tumor suppression. Results: Comparison of the tumor suppres...

Functional investigation of tumor suppressive role of chromosome 9 in esophageal squamous cell carcinoma

9571 Background: Esophageal carcinoma (EC) is a very deadly disease, but its molecular basis for tumorigenesis is still largely unknown. The microcell chromosome transfer technique is useful to functionally validate the presence of tumor suppressor genes (TSGs). Early studies indicate there might be important TSGs for EC on chromosome 9. Our study found the LOH frequency of chromosome 9 was very high and three commonly deleted regions were observed at 9p23–22, 9q13–22.3, and 9q34, which suggest the probable locations of TSGs on chromosome 9 involved in esophageal tumorigenesis. Methods: Transfer of chromosome 9 into the highly tumorigenic EC cell line, SLMT-1S1, was accomplished by the method of microcell-mediated chromosome transfer (MMCT). Hybrid cells and their corresponding tumor segregants were studied for the ability to form tumors in a nude mouse model and 33 microsatellite markers were used to detect critical regions associated with their tumor suppression. Results: Comparison of the tumor suppressive hybrid cell lines and their paired tumor segregants, showed some critical regions were non-randomly eliminated, including the 9q22.1 and 9q22.3 regions. Conclusions: These results indicate several chromosome 9q regions may contain important TSGs for EC. These functional complementation experiments are expected to map the putative TSGs of EC. No significant financial relationships to disclose.

The role of chromosome 18 abnormalities in the progression of pancreatic adenocarcinoma.

To date, the events that mediate tumor progression in pancreatic cancer are still poorly understood. Cytogenetic, allelotype, and somatic cell hybrid studies in human pancreatic adenocarcinoma have suggested that chromosome 18 may carry tumor suppressor genes (TSGs), including SMAD4. We previously identified that LOH of 18q at the SMAD4 locus, along with LOHs on 17p and 12q, positively associated with poor prognoses of pancreatic cancer patients. However, restoration of the SMAD4 gene did not suppress in vitro proliferation of pancreatic cancer cells that harbored homozygous deletion of this gene. An intraductal papillary mucinous neoplasm (IPMN ) is thought to be one of the premalignant lesions of the pancreas that progresses to carcinoma. Although there were frequent LOH (7/14, 50%) at the SMAD4 locus in IPMN samples, SMAD4 protein was observed immunohistochemically in tumor cells, and no mutations of the SMAD4 gene were observed, suggesting that it is the existence of a TSG in 18q, other than SMAD4, that suppresses cell growth. To functionally assess the activity of chromosome 18 in pancreatic cancer, we transferred a normal copy of the chromosome into pancreatic ductal carcinoma cells with and without completely inactivated SMAD4. In this study, in vitro growth of the hybrid cells was significantly suppressed compared with the parental cells, regardless of the initial SMAD4 status. To estimate the metastatic ability of the hybrids, we used a lung colonization model. At the end of the experiment, there was significant suppression of the number of surface metastases developing in mice injected with hybrids in comparison with those injected with parental cells. To identify and characterize genes that are involved in the progression of pancreatic cancer, we used micro-array expression analysis employing a 20k oligo-array system. It was revealed that there was increased expression of 4 genes relating to apoptosis in the 18 chromosome hybrids cells compared with the parental cells. We are now analyzing the function of these genes.

Allelotype of ampulla of Vater cancer: highly frequent involvement of chromosome 11.

To determine the genetic differences/similarities in ampulla of Vater cancers (AVC) with respect to other pancreatic tumor types. We analyzed eight cases of primary AVC by genome-wide allelotyping on DNA obtained from frozen tissue. A total of 372 microsatellite loci were used for each case, for a total of 2,976 microsatellites analyzed. Of the 2,159 informative markers, 400 were allelic losses and 1,759 markers were retained for an average fractional allelic loss of 0.19. Seven cases showed LOH on at least two markers on chromosomal arm 11p, while six cases showed allelic losses on 11q. The high frequency of LOH on chromosome 11 was also confirmed by analysis of an additional 17 paraffin-embedded AVC. Frequent LOH (50% or greater) was also found on chromosome arms 5q, 6q, 9p, 13, 16p, 17p, and 18p. It can be inferred that the targets of inactivation on chromosomes 5q, 9p, and 17p appear to be APC, p16, and p53, respectively, while the critical target(s) of inactivation at the other frequently lost loci remain to be characterized. The resulting allelotype reveals that distinctive chromosomal alterations are present in these neoplasms, indicating that it is a tumor entity distinct from pancreatic adenocarcinoma.

Lymphatic metastasis and nm23H1 genetic instability in Chinese colon cancer patients.

To investigate the pathogenic mechanism of colon cancer at the molecular level and to elucidate the relationship between intercellular adhesion molecule-1 (ICAM-1) and nm23H(1) genes and Chinese patients with colon cancer. DNA was extracted from paraffin-embedded materials. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) was used to analyze MSI and LOH. Expression of ICAM-1 was detected by Envision immuno-histochemistry. Experimental results were analyzed with Leica-Qwin computer imaging techniques and SPSS software of statistics. ICAM-1 expression of lymphatic endothelium was negative in normal colon and positive in colon cancer respectively. The number of lymphatics positive for ICAM-1 was gradually increased with degree of cancer invasion (P<0.01). In the group with metastasis of colon cancer, the number of lymphatics positive for ICAM-1 in lymph nodes was more than that in the group with no metastasis (P<0.01). The frequency of MSI, LOH and nm23H(1) protein was 26.67%, 20.00% and 53.33% in colon cancer, respectively. In TNM staging, MSI (43.75%) and nm23H(1) protein (81.25%) in stages I+II were detected more easily than the corresponding indexes (MSI: 7.14%, P<0.05 and nm23H(1): 21.43%, P<0.01) in stages III+IV. By comparison, the frequency of LOH (35.71%) in stages III+IV was more than that of LOH (6.25%, P<0.05) in stages I+II. LOH exhibited a rising trend along with the Duke's staging. nm23H(1) protein in the group of tubular adenocarcinoma (60.00%) was higher expressed than that in the group of mucoid adenocarcinoma (20.00%) (P<0.01), and exhibited a rising trend with the differentiation degrees of tubular adenocarcinoma. nm23H(1) protein in MSI positive group was higher expressed (75%) than that in MSI negative group (45.45%, P<0.05). The expression of ICAM-1 in lymphatic vessels is beneficial to the judgement of the invasion and metastasis ability of colon cancer and the anti-tumor immunity function, and shows an important clinical significance in predicting lymphatic metastasis of colon cancer. MSI and LOH may separately control the development of sporadic colon cancer with different pathways. LOH mostly arises in the late period of sporadic colon cancer and endows a high aggressive and poor prognostic phenotype. By compassion, MSI may be an early period molecule marker for sporadic colon cancer, enhanced expression of nm23H(1) protein can effectively inhibit colon cancer metastasis and improve prognosis of sporadic colon cancer patients.

Genome-wide search for loss of heterozygosity in Chinese patients with sporadic colorectal cancer.

In an attempt to integrally investigate the loss of tumor suppressor genes and search for putative suppressor loci associated with tumor occurrence and progression, we conducted a genome-wide loss of hetero zygosity (LOH) study of 83 tumor samples obtained from Chinese patients with sporadic colorectal cancer. We employed 400 fluorescence-labeled microsatellite marker primers to amplify the corresponding loci of the genomic DNA and then electrophoresed the polymerase chain reaction products and analyzed the fluorescent signals. The LOH frequencies were high (>35%) but were not associated with the tumor stage and progression in 20 loci, including the regions where TP53, E-cadherin, deleted in colorectal carcinoma (DCC), phosphatase and tensin homolog deleted on chromosome 10 (PTEN), mothers against decapentaplegic, Drosophila, homolog of 2 (MADH2) and mothers against decapentaplegic, Drosophila, homolog of 4 (MADH4) reside. Loss of other loci, including two narrow regions on chromosome 2, was found to relate to the tumor stage, suggesting that this genomic instability may contribute to tumor progression.

Loss of heterozygosity and its correlation with expression profiles in subclasses of invasive breast cancers.

Gene expression array profiles identify subclasses of breast cancers with different clinical outcomes and different molecular features. The present study attempted to correlate genomic alterations (loss of heterozygosity; LOH) with subclasses of breast cancers having distinct gene expression signatures. Hierarchical clustering of expression array data from 89 invasive breast cancers identified four major expression subclasses. Thirty-four of these cases representative of the four subclasses were microdissected and allelotyped using genome-wide single nucleotide polymorphism detection arrays (Affymetrix, Inc.). LOH was determined by comparing tumor and normal single nucleotide polymorphism allelotypes. A newly developed statistical tool was used to determine the chromosomal regions of frequent LOH. We found that breast cancers were highly heterogeneous, with the proportion of LOH ranging widely from 0.3% to >60% of heterozygous markers. The most common sites of LOH were on 17p, 17q, 16q, 11q, and 14q, sites reported in previous LOH studies. Signature LOH events were discovered in certain expression subclasses. Unique regions of LOH on 5q and 4p marked a subclass of breast cancers with "basal-like" expression profiles, distinct from other subclasses. LOH on 1p and 16q occurred preferentially in a subclass of estrogen receptor-positive breast cancers. Finding unique LOH patterns in different groups of breast cancer, in part defined by expression signatures, adds confidence to newer schemes of molecular classification. Furthermore, exclusive association between biological subclasses and restricted LOH events provides rationale to search for targeted genes.

Granular cell astrocytomas show a high frequency of allelic loss but are not a genetically defined subset.

Granular cell astrocytomas (GCA) are an uncommon morphologic variant of infiltrative glioma that contains a prominent population of atypical granular cells. As a rule, they are biologically aggressive compared to similar tumors without granular features. We sought to determine whether GCAs possess distinct genotypic alterations that might reflect their unique morphology or clinical behavior. Eleven GCAs occurring in 7 men and 4 women ranging in age from 46 to 75 years were investigated for genetic alterations of known significance in glial tumorigenesis, including LOH at 1p, 9p, 10q, 17p, and 19q, point mutations of TP53, deletions of p16(CDKN2A) and p14ARF, as well as EGFR amplifications. Tumors included had an infiltrative growth pattern and consisted of large, round cells packed with eosinophilic, PAS-positive granules that varied in quantity, ranging from 30 to 100% of tumor cells. Three tumors were of WHO grade II, one was grade III, and 7 were grade IV lesions. Overall, the tumors showed higher frequencies of LOH at 1p, 9p, 10q, 17p, and 19q than typical infiltrating astrocytomas of similar grades. Losses on 9p and 10q occurred in nearly all cases, including low grade lesions. TP53 mutations were identified in 2 grade IV GCAs, while combined p14ARF and p16(CDKN2A) homozygous deletions were noted in only one grade IV lesion. None showed EGFR amplification. We found no genetic alterations specific for GCA. Instead, it appears that granular cell change occurs across genetic subsets. The high frequency of allelic loss, especially on 9p and 10q, may confer aggressive growth potential and be related to their rapid clinical progression.

Genetic analysis of benign ovarian tumors.

Ovarian cancer represents a major cause of cancer death among women and yet remarkably little is known about its etiology. The paradigm established by the colorectal carcinogenesis model would suggest that ovarian cancers are likely to arise through malignant transformation of benign ovarian tumors. However, molecular genetic data that could answer this important question is lacking. In our study, we analyzed 80 benign ovarian tumors for TP53 and K-ras mutations and for LOH on chromosomes 6, 7, 9, 11 and 17 using 56 microsatellite markers. Twenty-five percent (5/20) of non-epithelial tumors and 73% (44/60) of epithelial tumors exhibited LOH on at least 1 chromosome arm. A particularly high frequency of LOH was detected among the epithelial tumors on chromosome arms 6q (17%), 7p (17%), 7q (27%) and 11p (18%), which are also regions of frequent LOH among ovarian carcinomas. No K-ras mutations were detected in any tumor but somatic TP53 mutations were detected in 2/34 (6%) serous and 1/26 (4%) mucinous epithelial tumors. In contrast to most previous studies our data is derived from a relatively large number of microdissected tumors and is likely to represent a more accurate picture of the frequency of alterations in these tumors. We conclude that LOH is common in benign ovarian tumors, suggesting that inactivation of tumor suppressor genes are pivotal in their development. The high frequency of alterations is consistent with their being precursors to malignant disease but does not unequivocally prove this continuum. It does however provide a framework for future analysis of the molecular genetic etiology of ovarian tumorigenesis.

Frequent hypermethylation of promoter region of RASSF1A in tumor tissues and voided urine of urinary bladder cancer patients

High frequency loss of 3p21.3 region where RASSF1A located was demonstrated in several tumors. We aimed to investigate the methylation status of RASSF1A and the frequency of LOH in 3p21.3 region in bladder cancer. Three bladder cancer cell lines, 40 cases of bladder TCC and 14 cases of paired voided urine samples were subjected to methylation analysis. By methylation specific PCR, complete methylation of promoter region of RASSF1A gene were detected in cell lines T24 and UMUC3. Demethylation treatment re-expressed RASSF1A in these 2 cell lines. Methylation of RASSF1A was also detected in 47.5% (19/40) of the TCC cases but not in 6 carcinoma in situ (CIS) or 6 normal urothelium samples. For LOH study, loss of 3p21.3 region was detected in 57.9% (11/19) of our cases. Interestingly, methylation of RASSF1A was found in 72.7% (8/11) of the cases with LOH but only in 12.5% (1/8) of the cases without LOH. Methylation of RASSF1A was detected in 50% (7/14) of voided urine samples, but not in normal control. It showed a higher sensitivity than conventional urine cytology in detecting cancer cells, especially for low grade cases. In conclusion, our results demonstrated a high frequency of RASSF1A methylation with frequent LOH in 3p21.3 region in bladder cancer. It suggested that it may be a potential tumor suppressor gene in this chromosomal region and can be silenced by promoter hypermethylation. Detection of aberrant gene methylation in routine voided urine was feasible and may provide a non-invasive and sensitive approach for cancer detection.

Microsatellite analysis of chromosome 3p region in sporadic renal cell carcinomas.

The etiology and progression of renal carcinomas (RCC) is still poorly understood. RCC have been classified into several pathological entities. The most frequent type, clear cell carcinoma, accounts for about 80% of sporadic RCC and shows several chromosome abnormalities documented both by conventional cytogenetics, loss of eterozygosity (LOH) and replication error (RER) studies. In 10 clear cell type sporadic RCC we evaluated LOH and RER using a set of 10 microsatellite markers covering the chromosome 3p region, which has been suggested for interstitial deletions. Electrophoresis was performed by automated sequencer ABI Prism 377 and data were analyzed with Genescan and Genotyper 2.5 softwares. We revealed allelic loss in 48,7% of informative microsatellites and a single case of RER. We found the highest LOH frequency in 3p25-26 region where maps Von Hippel-Lindau (VHL) oncosuppressor gene. In addition, DNA hypermethylation, an alternative mechanism of VHL gene silencing, was evaluated by methylation-specific PCR. However hypermethylation status was not detected in any of our tumor samples.

Genetic alterations in adenoma-carcinoma sequencing of intraductal papillary-mucinous neoplasm of the pancreas

We investigated the adenoma-carcinoma sequence in intraductal papillary-mucinous neoplasm from the aspect of genetic changes. The formalin-fixed paraffin-embedded tumors and surrounding normal pancreatic tissues from patients with 16 intraductal papillary-mucinous adenoma of the pancreas (IPMA) and 10 intraductal papillary-mucinous carcinoma of the pancreas (IPMC) were provided for DNA extraction after microdissection. SSCP-DNA sequencing analysis demonstrated K-ras mutations at codon 12 in 75% of IPMA and 70% of IPMC, while those at codon 13 were observed neither in IPMA nor IPMC. There were no characteristic K-ras mutation types in IPMA and IPMC and no significant differences in incidence of K-ras mutations between the two categories. The frequencies of p53 mutations analyzed by SSCP-DNA sequencing were not high in IPMA (18.8%) and IPMC (30%), showing no significant difference between them. LOHs of APC in IPMA and IPMC were infrequent (6.3 and 20%, respectively) and showed no significant difference in incidence between the two categories. The LOH frequencies of DCC in IPMA and IPMC were 31.3 and 40%, respectively, and were not statistically different from each other. Taken together, genetic changes such as K-ras, p53, APC and DCC mutations may not be associated with adenoma-carcinoma sequence in intraductal papillary-mucinous neoplasm of pancreas.

Carcinogenesis modifier loci in rat tongue are subject to frequent loss of heterozygosity.

Rats of the DA strain are highly susceptible to 4NQO-induced TCs, whereas WF rats are barely susceptible. In (DA x WF)F2 rats, 5 QTL, Tscc1-5, are responsible for most of the phenotypic variations, though they do not account for all of the phenotypic differences between WF and DA rats. Analysis of 40 tongue tumors >5 mm in diameter from (DA x WF)F1 rats for LOH at the Tscc loci revealed a high frequency of LOH in chromosomal regions where the Tscc2, -3 and -4 loci map. In most cases of LOH, the allele of the barely susceptible WF strain was lost, suggesting that these loci in the WF strain encode tumor-suppressor genes. Analysis of the same tumors for somatic mutations in oncogenes indicated frequent alteration of Ha-ras, which maps in the Tscc3 region, but rare mutation of the p15(INK4B) and p16(INK4A) genes or the p53 and Msh2 genes. Frequent LOH was also found on rat chromosomes 5 (RNO5) and 6 (RNO6). Tumors of large size accumulated LOH at multiple loci, suggesting the involvement of Tscc loci in tumor progression.

Review of collecting duct carcinoma with focus on clinical and pathobiological aspects.

In recent years, the concept of collecting duct carcinoma (CDC) has been established. CDCs constitute about 0.4 to 2% of RCCs. Macroscopically, CDCs occur in the renal medulla. On the cut surface, they are generally firm, white or grey and poorly circumscribed. Histologically, CDCs are characterized by various cytological and histological appearances. Furthermore, desmoplastic stromal reaction around the tumor and atypical hyperplastic changes or carcinoma in situ in the adjacent medullary collecting duct are frequently observed. Histological distinction from papillary RCCs is most important, because both tumors share some structural and histochemical features, and it seems that some investigators have confused diagnostic criteria for CDCs. On the other hand, the concept of medullary carcinoma, which preferentially occurs in a black race and shows histological features similar to those of CDC, has also recently been established. Although there have been few studies on chromosomal abnormalities of CDCs and consistent abnormalities have not been identified, a recent study using microsatellite analysis has shown a high frequency (60%) of LOH in 1q32.1-32.2. Further studies are needed to elucidate the genetic characteristics of CDCs and to determine the relationship or difference between CDCs and medullary carcinomas.