Recurrent 1;17 translocations in human neuroblastoma reveal nonhomologous mitotic recombination during the S/G2 phase as a novel mechanism for loss of heterozygosity.

Neuroblastomas often show loss of heterozygosity of the chromosomal region 1p36 (LOH 1p), probably reflecting loss of a tumor-suppressor gene. Here we describe three neuroblastoma tumors and two cell lines in which LOH 1p results from an unbalanced translocation between the p arm of chromosome 1 and the q arm of chromosome 17. Southern blot and cytogenetic analyses show that in all cases the chromosome 17 homologue from which the 1;17 translocation was derived is still present and intact. This suggests a model in which a translocation between the short arm of chromosome 1 and the long arm of chromosome 17 takes place in the S/G2 phase of the cell cycle and results in LOH 1p. Nonhomologous mitotic recombination in the S/G2 phase is a novel mechanism of LOH.     

Comparative genomic hybridization study of nasal-type NK/T-cell lymphoma

BACKGROUND: Nasal-type NK/T-cell lymphoma is a rare type of non-Hodgkin's lymphoma. The genetic changes associated with pathogenesis have not been well defined. This study investigates the nonrandom genetic alteration of nasal-type NK/T-cell lymphoma. METHODS: Nine cases were studied. Comparative genomic hybridization (CGH) was carried out using fresh tumor tissues of seven nasal-type NK/T-cell lymphomas. To complement the data by CGH, loss of heterozygosity (LOH) of chromosomes 6q, 1p, and 17p using polymorphic markers and p53 gene mutation by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) were analyzed. RESULTS: The DNA copy number changes of seven nasal-type NK/T-cell lymphomas were gains on chromosomes 2q(5), 13q(4), 10q(3), 21q(2), 3q(2), 5q(2), and 17q(2), and losses involving chromosomes 1p(4), 17p(4), 12q(3), 13q(2), and 6q(1). One of six cases informative for at least two markers for chromosome 6q showed LOH at D6S300, D6S1639, D6S261, D6S407, and D6S292. Two cases showing loss of 1p and 17q by CGH revealed LOH at D1S214, D1S503, and D17S559. P53 mutation was detected in exon 8 in one of nine cases. CONCLUSIONS: Frequent DNA losses at 1p, 17p, and 12q and gains at 2q, 13q, and 10q suggested that these regions could be targets for further molecular genetic analysis to investigate tumor suppressor genes or oncogenes associated with tumorigenesis of NK/T-cell lymphoma. Infrequent alteration of 6q contrary to previous studies raises doubt about an implication of 6q loss in the pathogenesis of early-stage NK/T-cell lymphoma. Further studies on more defined cases are required to verify their association.     

Loss of heterozygosity at chromosome 6 as a marker of early genetic alterations in cervical intraepithelial neoplasias and microinvasive carcinomas

Oncogenic human papillomaviruses (mostly HPV types 16 and 18) are the major cause of cervical intraepithelial neoplasia (CIN), which progresses into cervical cancer (CC). To reveal early genetic alterations of chromosome 6 that are important for CC progression, we analyzed the loss of heterozygosity (LOH) in DNAs from 45 CIN cases, 47 microcarcinomas, and 19 invasive squamous cell carcinomas stage IB. LOH analysis of DNA samples prepared with microdissection from all CIN foci, as well as from CC lesions and synchronous CIN, permitted investigation of CIN and CC heterogeneity. Out of all CC stage I cases, 79% showed LOH with six microsatellite markers at chromosome 6. LOH with the microsatellite markers D6S276 (6p22) and TNFa (6p21.3) was found in 50% of the CC cases. LOH frequency in CIN lesions synchronous with CC was higher then in CIN cases without cancer; the statistical significance (P = 0.004) was shown for D6S291 (6p21.2). The finding suggests that the high frequency of LOH in CIN lesions is a marker of unfavorable prognosis for CIN. Progression from microcarcinoma to invasive CC of stage IB was associated with a higher LOH frequency at D6S344 (6p25) and TNFa (6p21.3). Early genetic alterations were found in CIN with microsatellites D6S273 and TNFa located at 6p21.3. Moreover, LOH frequency at D6S273 remained the same in both CIN and CC cases. Based on HPV typing, LOH analysis, and X-chromosome inactivation, the polyclonality of CC lesions, as well as CIN, was observed in a few patients.     

Loss of heterozygosity on chromosomes 1, 2, 8, 9 and 17 in cerebral atherosclerotic plaques

OBJECTIVE: Atherosclerosis is a fibroproliferative disease which has been attributed to several factors including genetic and molecular alterations. Initial studies have shown genetic alterations at the microsatellite level in the DNA of atherosclerotic plaques. Extending our initial findings, we performed a microsatellite analysis on cerebral atherosclerotic plaques. METHODS: Twenty-seven cerebral atherosclerotic plaques were assessed for loss of heterozygosity (LOH) and microsatellite instability (MI) using 25 microsatellite markers located on chromosomes 2, 8, 9 and 17. DNA was extracted from the vessels as well as the respective blood from each patient and subjected to polymerase chain reaction. RESULTS: Our analyses revealed that specific loci on chromosomes 2, 8, 9 and 17 exhibited a significant incidence of LOH. Forty-six percent of the specimens showed loss of heterozygosity at 2p13-p21, 48% exhibited LOH at 8p12-q11.2, while allelic imbalance was detected in 47% of the cases. The LOH incidence was 39%, 31% and 27% at 17q21, 9q31-34 and 17p13, respectively. Genetic alterations were detected at a higher rate as compared to the corresponding alterations observed in plaques from other vessels. DISCUSSION: This is the first microsatellite analysis using atherosclerotic plaques obtained from cerebral vessels. Our results indicate an elevated mutational rate on specific chromosomal loci, suggesting a potential implication of these regions in atherogenesis.     

应用双色FISH技术检测肝癌中HER—2的定量扩增及其临床意义

为探讨原发性肝细胞癌(HCC)中原癌基因HER-2的扩增激活情况及其与临床病理特征和预后的关系,应用双色荧光原位杂交(dualFISH)技术检测42例原发性肝癌间期细胞核中HER-2的扩增和17号染色体的数目及其比值,并用统计学分析HER-2的扩增与临床病理特征及预后的相关性.结果在42例肝癌中有9例HER-2扩增(amplification),占21.4%,其中高拷贝扩增(HC)有4例(9.5%),低拷贝扩增(LC)有5例(11.9%),HER-2的扩增与性别、年龄、AFP水平、HBV感染、术后复发及临床分期无关(P＞0.05),而与术后2年生存期相关(P=0.046)且HER-2扩增病人的肿瘤有比无扩增病人的肿瘤增大的倾向(P=0.085);同时,在42例肝癌中有3l例为HER-2拷贝数增加(gain),占73.8%,其中9例(21.4%)为扩增所致,22例(52.4%)为17号染色体多倍体或异倍体(polysomy17/aneusomy17)所致,HER-2拷贝数增加与性别、临床分期、肿瘤大小、术后复发及术后2年生存期无关(P＞0.05),但与年龄、AFP水平和HBV感染有关(P＜0.05).以上结果提示原发性肝癌中存在较低频的HER-2癌基因扩增激活及较高频的17号染色体异倍体/多倍体;HER-2癌基因的扩增激活可能与部分肝癌的发生发展有关,是肝癌术后生存期短的有价值独立预后因子.     

Comparison of multiplex ligation dependent probe amplification to immunohistochemistry for assessing HER-2/neu amplification in invasive breast cancer

The HER-2/neu transmembrane tyrosine kinase receptor is both a prognostic marker and a therapeutic target for breast cancer. Accurate determination of HER-2/neu status is a prerequisite for selecting breast tumors for HER-2/neu immunotherapy or for taxan based chemotherapy. Unfortunately, there is no consensus concerning how this determination should be reached. We compared assessment of HER-2/neu status using Multiplex ligation-dependent probe amplification (MLPA) and immunohistochemistry (IHC). The patient group comprised 60 Indonesian breast cancers patients. IHC was performed on paraffin sections using the CB11 antibody from Novocastra. Results were scored according to the Hercept test. For MLPA, DNA was extracted from frozen samples, PCR amplified with a probe set containing three hemi-primer sets for the HER-2 locus and another nine control probes spread over chromosome 17 and other chromosomes, and analyzed on a gene scanner. A ratio above two for at least two HER-2 locus probes compared to the control probes was regarded as amplification. IHC for HER-2/neu was negative in 36 cases, and 24 cases (40%) showed expression. Seven, eight and nine of the latter cases were 1+, 2+ and 3+ positive, respectively. Forty-seven cases showed no amplification by MLPA, and 13 cases (22%) were amplified. Comparison of IHC and MPLA showed that none of the 36 IHC-negative or seven IHC 1+ cases was amplified. Five of the eight (63%) 2+ cases were amplified, and eight of nine (89%) of the IHC 3+ tumors showed gene amplification by MLPA assay. For HER-2/neu, there is a good correlation between gene amplification detected by MLPA and overexpression by IHC in invasive breast cancer. It appears that MLPA can detect the HER-2 amplified cases in the IHC 2+ class. Because MLPA is quick and inexpensive, it is an attractive method for detecting HER-2/neu amplification in daily laboratory practice.     

Genomic instability on hMSH2, hMLH1, CD48 and IRF4 loci in pulmonary sarcoidosis

Pulmonary sarcoidosis shares certain features with immune disease and neoplasia, and microsatellite DNA alterations are detectable in sputum specimens of pulmonary sarcoidosis patients. The biological basis and significance of these findings remain obscure, while information regarding the genetic basis of the disease is limited. Using multiplex PCR-based microsatellite analysis, we investigated 40 markers located on 1p, 1q, 2p, 2q, 3p, 5q, 6p, 7p, 9p, 11q, 14q and 17p in 38 sputum specimens of pulmonary sarcoidosis patients. Loss of heterozygosity (LOH) was found in 13 of 38 (34.2%) patients in at least one locus. These alterations occurred in the subset of markers located in or close to DNA mismatch repair (MMR) genes, hMSH2 (2p22.3-p16.1) and hMLH1 (3p2l.32-p21.1), as well as in CD48 (1q21-q23) and IRF4 (6p23-p25), genes associated with lymphocyte activation. Microsatellite instability (MIN) was observed in five cases (13.2%) in at least one locus. Our data suggest that genomic instability in pulmonary sarcoidosis could be due to MMR defects, while alterations of lymphocyte-specific agents could account for granuloma formation.     

Comparison of multiplex ligation dependent probe amplification to immunohistochemistry for assessing HER-2/neu amplification in invasive breast cancer.

The HER-2/neu transmembrane tyrosine kinase receptor is both a prognostic marker and a therapeutic target for breast cancer. Accurate determination of HER-2/neu status is a prerequisite for selecting breast tumors for HER-2/neu immunotherapy or for taxan based chemotherapy. Unfortunately, there is no consensus concerning how this determination should be reached. We compared assessment of HER-2/neu status using Multiplex ligation-dependent probe amplification (MLPA) and immunohistochemistry (IHC). The patient group comprised 60 Indonesian breast cancers patients. IHC was performed on paraffin sections using the CB11 antibody from Novocastra. Results were scored according to the Hercept test. For MLPA, DNA was extracted from frozen samples, PCR amplified with a probe set containing three hemi-primer sets for the HER-2 locus and another nine control probes spread over chromosome 17 and other chromosomes, and analyzed on a gene scanner. A ratio above two for at least two HER-2 locus probes compared to the control probes was regarded as amplification. IHC for HER-2/neu was negative in 36 cases, and 24 cases (40%) showed expression. Seven, eight and nine of the latter cases were 1+, 2+ and 3+ positive, respectively. Forty-seven cases showed no amplification by MLPA, and 13 cases (22%) were amplified. Comparison of IHC and MPLA showed that none of the 36 IHC-negative or seven IHC 1+ cases was amplified. Five of the eight (63%) 2+ cases were amplified, and eight of nine (89%) of the IHC 3+ tumors showed gene amplification by MLPA assay. For HER-2/neu, there is a good correlation between gene amplification detected by MLPA and overexpression by IHC in invasive breast cancer. It appears that MLPA can detect the HER-2 amplified cases in the IHC 2+ class. Because MLPA is quick and inexpensive, it is an attractive method for detecting HER-2/neu amplification in daily laboratory practice.     

Further characterization of loss of heterozygosity enhanced by p53 abrogation in human lymphoblastoid TK6 cells: disappearance of endpoint hotspots

Loss of heterozygosity (LOH) is the predominant mechanism of spontaneous mutagenesis at the heterozygous thymindine kinase locus (tk) in TK6 cells. LOH events detected in spontaneous TK(-) mutants (110 clones from p53 wild-type cells TK6-20C and 117 clones from p53-abrogated cells TK6-E6) were analyzed using 13 microsatellite markers spanning the whole of chromosome 17. Our analysis indicated an approximately 60-fold higher frequency of terminal deletions in p53-abrogated cells TK6-E6 compared to p53 wild-type cells TK6-20C whereas frequencies of point mutations (non-LOH events), interstitial deletions, and crossing over events were found to increase only less than twofold by such p53 abrogation. We then made use of an additional 17 microsatellite markers which provided an average map-interval of 1.6Mb to map various LOH endpoints on the 45Mb portion of chromosome 17q corresponding to the maximum length of LOH tracts (i.e. from the distal marker D17S932 to the terminal end). There appeared to be four prominent peaks (I-IV) in the distribution of LOH endpoints/Mb of Tk6-20C cells that were not evident in p53-abrogated cells TK6-E6, where they appeared to be rather broadly distributed along the 15-20Mb length (D17S1807 to D17S1607) surrounding two of the peaks that we detected in TK6-20C cells (peaks II and III). We suggest that the chromosomal instability that is so evident in TK6-E6 cells may be due to DNA double-strand break repair occurring through non homologous end-joining rather than allelic recombination.     

A Common Region of Deletion on Chromosome 17q in Both Sporadic and Familial Epithelial Ovarian Tumors Distal to BRCA1

Linkage analysis in familial breast and ovarian cancer and studies of allelic deletion in sporadic ovarian tumors have identified a region on chromosome 17q containing a candidate tumor-suppressor gene (referred to as BRCA1) of likely importance in ovarian carcinogenesis. We have examined normal and tumor DNA samples from 32 patients with sporadic and 8 patients with familial forms of the disease, for loss of heterozygosity (LOH) at 21 loci on chromosome 17 (7 on 17p and 14 on 17q). LOH on 17p was 55% (22/40) for informative 17pl3.1 and 17pl3.3 markers. When six polymorphic markers flanking the familial breast/ovarian cancer susceptibility locus on 17ql2-q21 were used, LOH was 58% (23/40), with one tumor showing telomeric retention. Evaluation of a set of markers positioned telomeric to BRCA1 resulted in the highest degree of LOH, 73% (29/40), indicating that a candidate locus involved in ovarian cancer may reside distal to BRCA1. Five of the tumors demonstrating allelic loss for 17q markers were from individuals with a strong family history of breast and ovarian cancer. More important, two of these tumors (unique patient number [UPN] 57 and UPN 79) retained heterozygosity for all informative markers spanning the BRCA1 locus but showed LOH at loci distal to but not including the anonymous markers CMM86 (D17S74) and 42D6 (D17S588), respectively. Deletion mapping of seven cases (two familial and five sporadic) showing limited LOH on 17q revealed a common region of deletion, distal to GH and proximal to D17S4, that spans −25 cM. These results suggest that a potential tumor-suppressor gene involved in both sporadic and familial ovarian cancer may reside on the distal portion of chromosome 17q and is distinct from the BRCA1 gene.     

Further characterization of loss of heterozygosity enhanced by p53 abrogation in human lymphoblastoid TK6 cells: disappearance of endpoint hotspots

Loss of heterozygosity (LOH) is the predominant mechanism of spontaneous mutagenesis at the heterozygous thymindine kinase locus (tk) in TK6 cells. LOH events detected in spontaneous TK⁻ mutants (110 clones from p53 wild-type cells TK6-20C and 117 clones from p53-abrogated cells TK6-E6) were analyzed using 13 microsatellite markers spanning the whole of chromosome 17. Our analysis indicated an approximately 60-fold higher frequency of terminal deletions in p53-abrogated cells TK6-E6 compared to p53 wild-type cells TK6-20C whereas frequencies of point mutations (non-LOH events), interstitial deletions, and crossing over events were found to increase only less than twofold by such p53 abrogation. We then made use of an additional 17 microsatellite markers which provided an average map-interval of 1.6 Mb to map various LOH endpoints on the 45 Mb portion of chromosome 17q corresponding to the maximum length of LOH tracts (i.e. from the distal marker D17S932 to the terminal end). There appeared to be four prominent peaks (I–IV) in the distribution of LOH endpoints/Mb of Tk6-20C cells that were not evident in p53-abrogated cells TK6-E6, where they appeared to be rather broadly distributed along the 15–20 Mb length (D17S1807 to D17S1607) surrounding two of the peaks that we detected in TK6-20C cells (peaks II and III). We suggest that the chromosomal instability that is so evident in TK6-E6 cells may be due to DNA double-strand break repair occurring through non homologous end-joining rather than allelic recombination.     

The role of STAT transcription factors in apoptosis regulation of hypothalamic neurons in aging in HER-2/neu transgenic mice and wild-type FVB/N mice

For the firsts time, the involvement of the STAT pathway in the regulation of neuronal apoptosis in physiological aging and in old mice overexpressing the HER-2/neu oncogene was studied. We showed that suppression of STAT3, STAT5, and STAT6 and overexpression of the proapoptotic factor STAT1, which provides p53-mediated apoptosis, are the causes for increasing the number of apoptotic neurons in physiological aging. HER-2 tyrosine kinase receptor overexpression promotes neuronal survival through activation of STAT-signaling pathway with simultaneous suppression of the proapoptotic factor STAT1.     

At least four different chromosomal regions are involved in loss of heterozygosity in human breast carcinoma

Three chromosome regions, i.e., 11p15, 13q, and 17p, were previously reported by three independent groups to be specifically reduced to hemizygosity in human primary breast cancer. We examined the DNA of 64 mammary tumors for loss of heterozygosity (LOH) with 28 polymorphic DNA markers dispersed on 10 arms of 8 different chromosomes. Complete or near-complete absence of LOH was observed on 5 arms (5 chromosomes). LOH at all three previously invoked regions was confirmed, and the highest frequency was found on 17p (67% of heterozygous patients). Allele loss of a marker from chromosome 3 (region p14-p21) was found in 7 of 15 informative cases. Concurrent LOH at 2 to 4 loci was noted in 20 of the 43 tumors showing LOH. Allele losses did not correlate with any of the six clinico-histopathological variables investigated, but in a group of patients in which we were unable to demonstrate LOH, the absence of distant metastases was statistically significant (P less than 0.05). These results suggest that some of the observed allele losses reflect random events, possibly as a result of genetic instability, but are not without biological significance for the progression of particular subclasses of breast tumors.     

Loss of heterozygosity and K-ras gene mutations in gastric cancer

In order to identify relevant genetic lesions in gastric carcinoma, we searched for tumor suppressor gene inactivation and K-ras gene mutations by analyzing tumor and control DNAs from 34 patients. These were from an epidemiologically defined area of Italy characterized by one of the world's highest incidences of stomach cancer. Allele losses were investigated by the Southern blotting procedure at 16 polymorphic loci on 11 different chromosomes. Our data demonstrate that chromosomal regions 5q, 11p, 17p and 18q are frequently deleted, and that 7q and 13q chromosome arms are also involved, although at a lower frequency. Loss of heterozygosity (LOH) at region 11p was not found during other surveys carried out on patients of different geographic origins. No specific combination of allelic losses could be recognized in the samples analyzed, the only exception being that tumors with 17p allelic loss also showed LOH on the 18q region. When matching frequent LOH events and the stage of progression of the tumors, we observed a trend of association between advanced stages and allelic losses on 17p and 18q chromosome arms. The analysis of K-ras, carried out by the polymerase chain reaction and denaturing gradient gel electrophoresis, demonstrated transforming mutations in only 3 out of 32 cases. Colorectal tumorigenesis proceeds by the accumulation of genetic alterations, including K-ras mutations and inactivation of tumor suppressor genes on the 5q, 17p and 18q regions. Our data indicate that, although gastric and colorectal neoplasias share common genetic alterations, they probably progress through different pathways.     

17p13 (p53 locus), 5q21 (APC locus) and 9p21 (p16 locus) allelic deletions are frequently found in oral exfoliative cytology cells from smoker patients with non-small-cell lung cancer

Molecular cytogenetic and LOH analyses of non-small cell lung cancer (NSCLC) have shown frequent allelic deletions in a variety of chromosomes where tumour suppressor genes are located. Allelic loss at 9p21 (p16 locus), 17p13 (p53) and 5q21(APC) has been frequently described in NSCLC and has also been described in premalignant epithelial lesions of the bronchus and normal bronchial cells. These findings suggest that a tissue field of somatic genetic alterations precedes the histopathological phenotypic changes of carcinoma. Similar changes have been described in oral and laryngeal epithelial tumours associated with smoke exposure. We previously reported frequent LOH at 5q21, 9p21 and TP53 in tumor cells and peritumoral normal bronchial cells from surgically resected NSCLC. We now analyze 96 cases of normal oral exfoliative cytology in which normal epithelial cells were obtained: 43 cases from smoker patients with NSCLC diagnosis, 33 smoker patients with no evidence of malignancy and 20 non-smoker patients with no evidence of tumour. All groups had a similar age and sex distribution. PCR amplification was performed utilising the specific markers D5S346, D9S157 and TP53. In normal oral mucosae cells from patients with NSCLC, we found that 21% of the informative cases showed LOH at any of the three analyzed loci distributed as follows: 14.3% of the informative cases showed LOH at 5q21, 7.7% at 9p21 and 22.2% at TP53. Within the smoker risk group only one case (4% of the informative cases) showed LOH at TP53, while no LOH was found at 5q21 or 9p21. No LOH was found in non-smokers. In conclusion, our results show that a significant number of patients with NSCLC have LOH at TP53, 5q21 and 9p21 in normal oral mucosae, while LOH at these loci is unusual in similar cells obtained from patients with no evidence of malignancy. Our study demonstrates that LOH studies can detect smoker patients with a mutated genotype in normal epithelial cells. Further prospective studies may confirm whether LOH studies can detect patients with a higher risk of NSCLC.     

Genomic profiling maps loss of heterozygosity and defines the timing and stage dependence of epigenetic and genetic events in Wilms' tumors

To understand genetic and epigenetic pathways in Wilms' tumors, we carried out a genome scan for loss of heterozygosity (LOH) using Affymetrix 10K single nucleotide polymorphism (SNP) chips and supplemented the data with karyotype information. To score loss of imprinting (LOI) of the IGF2 gene, we assessed DNA methylation of the H19 5' differentially methylated region (DMR). Few chromosomal regions other than band 11p13 (WT1) were lost in Wilms' tumors from Denys-Drash and Wilms' tumor-aniridia syndromes, whereas sporadic Wilms' tumors showed LOH of several regions, most frequently 11p15 but also 1p, 4q, 7p, 11q, 14q, 16q, and 17p. LOI was common in the sporadic Wilms' tumors but absent in the syndromic cases. The SNP chips identified novel centers of LOH in the sporadic tumors, including a 2.4-Mb minimal region on chromosome 4q24-q25. Losses of chromosomes 1p, 14q, 16q, and 17p were more common in tumors presenting at an advanced stage; 11p15 LOH was seen at all stages, whereas LOI was associated with early-stage presentation. Wilms' tumors with LOI often completely lacked LOH in the genome-wide analysis, and in some tumors with concomitant 16q LOH and LOI, the loss of chromosome 16q was mosaic, whereas the H19 DMR methylation was complete. These findings confirm molecular differences between sporadic and syndromic Wilms' tumors, define regions of recurrent LOH, and indicate that gain of methylation at the H19 DMR is an early event in Wilms' tumorigenesis that is independent of chromosomal losses. The data further suggest a biological difference between sporadic Wilms' tumors with and without LOI.     

Homozygous deletions and point mutations of the Rit1/Bcl11b gene in gamma-ray induced mouse thymic lymphomas

Allelic loss (LOH) mapping and sequence analysis were conducted for gamma-ray induced mouse thymic lymphomas and a novel tumor suppressor gene, Rit1/Bcl11b, on chromosome 12 was isolated. Bi-allelic changes were found in 17 of the 66 p53-proficient lymphomas with Rit1 LOH but in only 2 of the 54 p53-deficient lymphomas. This suggests an association between the presence of functional p53 and inactivation of the Rit1 gene in the lymphoma development. Introduction of Rit1 into HeLa cells lacking Rit1 expression suppressed cell growth. These results indicate that loss-of-function mutations of Rit1 contribute to mouse lymphomagenesis and possibly to human cancer development.     

Microsatellite Alterations and Protein Expression of 5 Major Tumor Suppressor Genes in Gastric Adenocarcinomas

PURPOSE: In gastric adenocarcinoma (GC), the major tumor suppressor genes (TSGs) such as p16, PTEN, Rb, E-cadherin, and p53, may play important roles in various regulatory pathways and in tumor suppression. This study evaluated the loss of heterozygosity (LOH) of microsatellite and protein expression of 5 TSGs and the results were examined for their correlation with clinicopathological factors. METHODS: LOH analysis was carried out using polymerase chain reactions with 15 polymorphic microsatellite markers of 5 chromosomes containing TSGs in 100 surgically resected tumors. Protein expression was evaluated by immunohistochemistry (IHC). RESULTS: LOH was detected in 83% of GCs. LOH of 9p21, 10q23, 13q14, 16q22, and 17p13 were detected in 26%, 31%, 24%, 22%, and 35% of cases, respectively. Protein expression of p16, PTEN, Rb, E-cadherin, and p53 were found to be 31%, 39%, 28%, 32%, and 46% of cases. Advanced GCs showed significantly higher rates of 17p13 LOH and p53 expression. 9p21 LOH and E-cadherin IHC were correlated with higher tumor grade. Lymph node metastasis was correlated with the LOH of 9p21, 16q22, and 17p13 and IHC of the Rb and p53. A higher stage was correlated with 10q23 and 17p13 in LOH and p53 for IHC. CONCLUSION: These results suggest that LOH and protein expression of various TSGs are important in carcinogenesis and tumor invasion. Additionally, LOH and IHC may be useful clinical indicators for determining the prognosis of patients with GCs. In particular, the 17p13 LOH and p53 for IHC can be applied as simple evaluations in the clinic.