Identification of a new target region on the long arm of chromosome 7 in gastric carcinoma by loss of heterozygosity

AIM: To define the common deleted region on the long arm of haman chromosome 7q linked to primary gastric carcinomas in Chinese by loss of heterozygosity (LOH) and its clinical significance. METHODS: Nine microsatellite markers distributed over chromosome 7q with an average marker density of 10cM were used to examine 70 primary gastric carcinomas for LOH by PCR amplification. The PCR products were separated by electrophoresis on polyacrylamide gel. Genescan and Genotyper softwares were used to analyze LOH. RESULTS: LOH with at least one marker on 7q occurred in 34.3% (12/50) of the tumors. Among them, LOH at D7S486 and D7S798 was higher in 24.0% (24/70) and 19.2% (5/26), respectively. By statistical analysis we also observed an obvious genotype-phenotype correlation on 7q (P<0.05). The frequency of LOH at D7S486 in patients with lymph node metastasis was significantly higher than that in those without lymph node metastasis (P=0.015). CONCLUSION: The high incidence of LOH at D7S486 and its correlation with poorer prognosis suggest that there might be putative tumor suppressor genes in this region involved in the tumorigenesis and progression of gastric carcinoma.     

Allelotyping for loss of heterozygosity on chromosome 18 in gastric cancer

AIM: To investigate the association between loss of heterozygosity (LOH) on chromosome 18 and sporadic gastric cancer. METHODS: Multiplex PCR was used to screen 14 highly polymorphic microsatellite markers on chromosome 18 in 45 cases of primary gastric cancer. PCR products were separated on polyacrylamide gels and the electrophoresis maps were analyzed with Genescan and Genotyper. RESULTS: The LOH frequencies in gastric cancer at all 14 markers ranged from 10% to 58%. Eleven markers were found with over 20% LOH frequencies, in which 9 markers located in 18q, and 2 markers in 18p. Two overlapping deleted regions were identified: R1 between D18S61-D18S1161 at 18q22 (9cM) with 24% LOH frequency; R2 between D18S462-D18S70 at 18q22-23(6cM) with 32% LOH frequency. CONCLUSION: LOH of chromosome 18 (18q and 18p) may be involved in gastric tumorigenesis. Two overlapping deleted fragments suggested that there might be unidentified tumor suppressor genes in those two regions.     

Loss of heterozygosity and microsatellite instabilities of fragile histidine triad gene in gastric carcinoma

AIM: To detect the loss of heterozygosity (LOH) and microsatellite instabilities (MSI) of fragile histidine triad (FHIT) gene in gastric carcinoma and to study their association with the clinical pathological characteristics of gastric carcinoma. METHODS: LOH and MSI of FHIT gene were detected at four microsaterllite loci D3SI3H, D3S4I03, D3SI48I and D3S1234 using PCR in matched normal and cancerous tissues from 50 patients with primary gastric cancer. RESULTS: The average frequency of LOH and MSI of FHIT gene in gastric cancer was 32.4% and 26.4% respectively. LOH and MSI of FHIT gene in gastric cancer had no association with histological, Borrmann, and Lauren's classification. LOH of FHIT gene in gastric cancer was related to invasive depth. The frequency of FHIT LOH in gastric cancer with serosa-penetration was obviously higher than that in gastric cancer without serosa-penetration (73.5% vs 37.5%, P < 0.05). MSI of FHIT gene in gastric cancer was associated with the lymph node metastasis. The frequency of MSI in gastric cancer without lymph node metastasis was significantly higher than that in gastric cancer with lymph node metastasis (66.7% vs 34.3%, P < 0.05). CONCLUSION: LOH of FHIT gene is correlated with invasive depth of gastric carcinoma. MSI of FHIT gene is correlated with lymph node metastases. LOH and MSI of FHIT gene play an important role in carcinogenesis of gastric cancer.     

Detailed deletion mapping of loss of heterozygosity on 22q13 in sporadic colorectal cancer

AIM: Both development and progression of malignancies occur as a multistep process, requiring the activation of oncogenes and the inactivation of several tumor suppressor genes. The loss of heterozygosity (LOH) of tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer (CRC). In this study, we analyzed the LOH of seven loci on chromosome 22q13 in an effort to identify candidate tumor suppressor genes involved in colorectal carcinogenesis. METHODS: Matched tumor and normal tissue DNA were analyzed by PCR using fluorescence-labeled polymorphic microsatellite markers in 83 CRC patients. PCR products were eletrophoresed and LOH was determined by calculating the peak height acquired through computer software. Comparisons between LOH frequency and clinicopathological features were performed by x2 test. P<0.05 was considered as statistical significance. RESULTS: The average LOH frequency of chromosome 22q13 was 28.38%. The highest LOH frequency was 64.71% on D22S1160 locus, and the lowest was 21.43% on D22S1141 locus. We detected two obvious minimal deletion regions: one between markers D22S1171 and D22S274, the other flanked by markers D22S1160 and D22S1149, each about 2.7 and 1.8 cm, respectively. None had lost in all informative loci. LOH frequency on D22S1171 is 50% on distal colon, which was higher than that on proximal one (P= 0.020); on D22S114 locus, none LOH event occurred in patients with liver metastasis, whilst 46.94% occurred in patients without liver metastasis (P= 0.008); on D22S1160 locus, LOH frequency in lymph nodes metastasis patients was 83.33%, which was much higher than 43.75% without lymph nodes metastasis ones (P= 0.016). There was no statistical significance between clinicopathological features and other loci. CONCLUSION: This study provides evidence of two minimal deletion regions, which may harbor putative tumor suppressor genes related to progression and metastasis in sporadic colorectal carcinoma on chromosome 22q13.     

浸润性乳腺癌及乳腺增生细胞3p、9p上5个微卫星位点的杂合性缺失观察

目的探讨乳腺浸润性导管癌及乳腺增生细胞中染色体3p、9p上5个微卫星位点（MS）杂合性缺失（LOH）模式。方法显微分离技术分离病变细胞,PCR．微卫星技术分析18例乳腺单纯性导管增生（UDH组）、15例不典型导管增生（ADH组）和35例乳腺浸润性导管癌（IDC组）细胞的3p、9p上D3S1447、D3S1612、D3S1597、D9S171及D9S1748位点的LOH模式。结果UDH组中仅1例D3S1447位点发生LOH（10％）,ADH组5个位点均发生一定频率的LOH（10％-22％）,IDC组5个位点均发生高频LOH（19％～48％）。至少1个位点发生LOH者,UDH组为6％、ADH组为33％、IDC组为71％,三组相比,P〈0．05;2个或以上位点发生LOH者,UDH组为0、ADH组为13％、IDC组为40％,UDH组、ADH组与IDC组相比,P均〈0．05。IDC组中D3S1612发生高频LOH者在有淋巴结转移组为63％,无淋巴结转移组为19％,两组相比,P〈0．05。结论UDH组的D3S1447位点发生的LOH和ADH组的5个位点发生的LOH有作为癌变风险预测分子标记的可能性,分析多个MS的LOH模式对于乳腺癌的早期预测和早期诊断有一定参考价值,D3S1612位点的LOH可能是IDC发生淋巴结转移的重要分子机制。     

Genetic instability of BRCA1 gene at locus D17S855 is related to clinicopathological behaviors of gastric cancer from Chinese population

AIM: To investigate genetic instability of gene BRCAl at locus D17S855, and their relationship with clinicopatho-logical characteristics of gastric cancer in Chinese population. METHODS: Microsatellite instability (MSI) and loss of heterozygosity (LOH) of gene BRCAl at locus D17S855 were compared between 37 samples of gastric cancer and corresponding non-cancerous gastric tissue. RESULTS: MSI at locus D17S855 was positive in 7 of 37 samples of gastric cancer (18.95%). MSI had a close relationship with TNM staging but no relation with lymph node metastasis, histological type or tumor differentiation. MSI positive frequency in TNM I II (31.58%, 6/19) was much higher than that in TNM III IV (5.56%, 1/18), (P < 0.05). LOH positive rate was 18.92% (7/37). LOH had no relationship to histological type, tumor differentiation or lymph node metastasis, but LOH positive rate in TNM III IV was 33.33% (6/18), much higher than that in TNM I II ( 5.26%, 1/19), (P < 0.05). BRCAl protein was expressed in 14 of 37 samples of gastric cancer. The positive rates of BRCAl protein in TNM I II and TNM III IV were 57.89% and 16.67%, respectively, {P < 0.05). The positive rate of BRCAl protein was 77.78% in high differentiation samples, 30.77% in middle differentiation and 12.50% in lower differentiation samples, (P < 0.05). CONCLUSION: MSI of BRCAl gene could be used as a molecular marker in early phases of sporadic gastric cancer in Chinese population. LOH occurs at later period of gastric cancer, therefore, it could be used as prognostic factor.     

Tumor suppress genes screening analysis on 4q in sporadic colorectal carcinoma

AIM： To search candidate tumor suppressor genes （TSGs） on chromosome 4q through detecting high loss of heterozygosity （LOH） regions in sporadic colorectal carcinoma in Chinese patients. METHODS： Thirteen fluorescent labeled polymorphic microsatellite markers were analyzed in 83 cases of colorectal carcinoma and matched normal tissue DNA by polymerase chain reaction （PCR）. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genescan 3.7 and Genotype 3.7 software were used for LOH scanning and analysis. Comparison between LOH frequency and clinicopathological factors were performed by χ^2 test.
RESULTS： Data were collected on all informative loci. The average LOH frequency on 4q was 28.56%, The D4S2915 locus showed highest LOH frequency （36.17%）. Two obvious deletion regions were detected： one between D4S3000 and D4S2915 locus （4q12-21.1）, another flanked by D4S407 and D4S2939 locus （4q25-31.1）. None case showed complete deletion of 4q, most cases displayed interstitial deletion pattern solely. Furthermore, compared with clinicopathological features, a significant relationship was observed between LOH frequencies on D4S3018 locus. In tumors larger than 5 cm in diameter, LOH frequency was significantly higher than tumors that were less than 5 cm （56% vs 13.79%, P = 0.01）. On D4S1534 locus, LOH was significantly associated with liver metastasis （80% vs 17.25%, P = 0.012）. No relationship was detected on other locus compared with clinicopathologial features.
CONCLUSION： By high resolution deletion mapping, two high frequency regions of LOH （4q12-21.1 and 4q25-31.1） were detected, which may contribute to locate TSGs on chromosome 4q involved in carcinogenesis and progression of sporadic colorectal carcinoma.     

Loss of heterozygosity on hromosome 1 in sporadic colorectal carcinoma

AIM: Loss of heterozygosity (LOH) on tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer. When it occurs at a tumor suppressor gene locus with abnormal allele, neoplastic transformation happens. In this study, we analyzed the LOH at 21 loci on chromosome 1 in sporadic colorectal cancer to identify additional loci involved in colorectal tumorigenesis. METHODS: Twenty-one polymorphic micro-satellite DNA markers were analyzed with PCR both in 83 cases of colorectal cancer and in normal tissues. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for LOH scanning and analysis. χ² test was used to compare LOH frequency with clinicopathological data. P < 0.05 was considered as statistically significant. RESULTS: The average LOH frequency of chromosome 1, short arm and long arm was 19.83%, 18.00% and 21.66%, respectively. The 2 highest LOH loci with a frequency of 36.54% and 32.50% were identified on D1S468 (1p36.33-p36.31) and D1S413 (1q31.3), respectively. On D1S2726 locus, LOH frequency of rectal cancer was 28.57% (6/21), which was higher than that of colon cancer (0.00%, 0/33) (P = 0.002), suggesting that the mechanism of carcinogenisis was different in both groups. CONCLUSION: Putative tumor suppressor genes on chromosome 1 may relate to sporadic colorectal carcinomas. Tumor-suppressor-genes might locate on 1p36.33-36.31 and/or 1q31.3.     

Loss of heterozygosity on chromosome 1 in sporadic colorectal carcinoma

AIM: Loss of heterozygosity (LOH) on tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer. When it occurs at a tumor suppressor gene locus with abnormal allele, neoplastic transformation happens. In this study, we analyzed the LOH at 21 loci on chromosome 1 in sporadic colorectal cancer to identify additional loci involved in colorectal tumorigenesis. METHODS: Twenty-one polymorphic micro-satellite DNA markers were analyzed with PCR both in 83 cases of colorectal cancer and in normal tissues. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for LOH scanning and analysis. chi2 test was used to compare LOH frequency with clinicopathological data. P<0.05 was considered as statistically significant. RESULTS: The average LOH frequency of chromosome 1, short arm and long arm was 19.83%, 18.00% and 21.66%, respectively. The 2 highest LOH loci with a frequency of 36.54% and 32.50% were identified on D1S468 (1p36.33-p36.31) and D1S413 (1q31.3), respectively. On D1S2726 locus, LOH frequency of rectal cancer was 28.57% (6/21), which was higher than that of colon cancer (0.00%, 0/33) (P=0.002), suggesting that the mechanism of carcinogenesis was different in both groups. CONCLUSION: Putative tumor suppressor genes on chromosome 1 may relate to sporadic colorectal carcinomas. Tumor-suppressor-genes might locate on 1p36.33-36.31 and/or 1q31.3.     

Genome-wide analyses on loss of heterozygosity in hepatocellular carcinoma in Southern China

BACKGROUND/AIMS: To conduct a genome-wide analysis of loss of heterozygosity (LOH) and its clinical significance in hepatocellular carcinoma (HCC) in Southern China where high incidence of HCC was documented. METHODS: LOH of 382 microsatellite loci on all autosomes were detected with polymerase chain reaction-based microsatellite polymorphism analyses in 104 HCC tumor tissues. RESULTS: High frequency of LOH (>55.7%) was observed on chromosome 1p, 1q, 2q, 3p, 4q, 6q, 8p, 9p, 13q, 16q, and 17p. LOH rates on loci D4S2964 (4q21.21), D8S277 (8p23.1-pter) and D17S938 (17p13.1-p13.3) were significantly higher in cases with positive HBsAg than in those with negative HBsAg. Similarly, LOH on loci D1S214 (lp36.3), D1S2797 (1p34) and D3S3681 (3p11.2-p14.2) were more frequently detected in tumors with intrahepatic metastasis than in those without. CONCLUSIONS: Status of LOH in HCC in Southern China is similar to that reported previously in other countries and areas. However, we firstly identified high-frequency LOH on chromosome 3p in HCC. Furthermore, HBV infection, as well as tumor intrahepatic metastasis, may be correlated with allelic losses on certain chromosome regions.     

Loss of heterozygosity on long arm of chromosome 22 in sporadic colorectal carcinoma

AIM：The loss of heterozygosity(LOH)on tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer.In this study,we analyzed the LOHat5loci on the 1ong arm of chromosome22in sporadic colorectal cancer to identify additional loci involved in colorectal tumorigenesis.METHODS:Five poly morphic microsatellite markers were analyzed in 83cases of colorectal and normal DNAby PCR.PCRproducts were eletrophoresed on an ABI377DNA sequencer;Genescan3.1and Genotype2.1software were used for LOH scanning and analysis.Comparison between LOH frequency and clinicopathological data were performed by X^2test.P&lt;0.05was considered as statistically significant.RESULTS:The average LOHfrequency on chromosome 22q was 28.38%.The region between markers D22S280and D22S274(22q12.2-q13.33)exhibited relatively high LOH frequency.The two highest LOH loci with frequencies of 35.09%and 34.04%was identified on D22S280(22q12.2-12.3)and D22S274(22q13.32-13.33).8cases showed LOH at allinformative loci,suggesting that one chromosome 22q had been completely lost.On D22S274locus.LOH frequency of rectal cancer was50%(9/18),which was higher than that of proximal colon cancer(12%,2/17)(P=0.018).The frequency of distal colon cancer was 42%(5/12).also higher than that of proximal colon cancer.But there was no statistical significance.Putting both the tumors in distal colon and rectm together into consideration.the frequency,47%(14/30),was higher than that of proximal colon cancer(P=0.015),suggesting the mechanism of carcinogenisis was diffenent in both groups.CONCLUSIONS:This study provided evidence for the involvement of putative tumor suppressor genes related to the sporadic colorectal carcinoma on chromosome 22q.The tumor-suppressor-gene(s)might locate on the 22q12.2-12.3and/or 22q13.32-13.33.     

Three distinct regions of allelic deletion on chromosome 17 involved in sporadic gastric cancer

BACKGROUND/AIMS: Based on the authors' data collected by comparative genomic hybridization (CGH), loss at multiple loci on whole chromosome 17 is believed to be associated with sporadic gastric cancer (GC). METHODOLOGY: In this study, previous results were extended by analyzing further loss of heterozygosity (LOH) at 15 loci along chromosome 17 in 45 sporadic GC patients using fluorescent microsatellite markers and an ABI 377 sequencer/genotyper. RESULTS: Allelic losses at all 15 markers were observed in most GC patients with the range of 11-61% LOH frequencies. Thirty-three of 45 GC patients (73%) showed LOH at least at one site, 22 at two or more sites. Ten markers were found with over 20% LOH frequencies (5 markers at 17p and 5 markers at 17q), suggesting that frequent allelic losses occur at multiple loci on chromosome 17 in GC. Three distinct regions of deletions were identified: R1 between D17S831-D17S921 at 17p12-13.3 (30cM), R2 between D17S1868-D17S787 at 17q21. 3-22 (11cM) and R3 between D17S785-D17S928 at 17q25.3 (23cM), respectively. CONCLUSIONS: The observations in this study of the three distinct deleted regions on chromosome 17 may provide some novel abnormalities of potential significance in gastric cancers, suggesting the involvement of TSGs residing in those regions in the genesis of the disease.     

Refined mapping of loss of heterozygosity on 1q31.1-32.1 in sporadic colorectal carcinoma

AIM： To explore precise deleted regions and screen the candidate tumor suppressor genes related to sporadic colorectal carcinoma. METHODS： Six markers on 1q31.1-32.1 were chosen. These polymorphic microsatellite markers in 83 colorectal cancer patients tumor and normal DNA were analyzed via PCR. PCR products were electrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for Loss of heterozygosity （LOH） scanning and analysis. Comparison between LOH frequency and clinicopathological factors was performed by χ2 test. RESULTS： 1q31.1-32.1 exhibited higher LOH frequency in colorectal carcinoma. The average LOH frequency of 1q31.1-32.1 was 23.0%, with the highest frequency of 36.7% （18/49） at D1S2622, and the lowest of 16.4% （11/67） at D1S412, respectively. A minimal region of frequent deletion was located within a 2 cM genomic segment at D1S413-D1S2622 （1q31.3-32.1）. There was no significant association between LOH of each marker on 1q31.1-32.1 and the clinicopathological data （patient sex, age, tumor size, growth pattern or Dukes stage）, which indicated that on 1q31.1-32.1, LOH was a common phenomenon in all kinds of sporadic colorectal carcinoma. CONCLUSION： Through our refined deletion mapping,the critical and precise deleted region was located within 2 cM chromosomal segment encompassing 2 loci （D1S413, D1S2622）. No significant association was found between LOH and clinicopathologic features in 1q31.1-32.1.     

Loss of heterozygosity at adenomatous polyposis coli,mutation in colorectal cancer and deleted in colorectal cancer genetic loci in colorectal cancers

AIM: To evaluate the role and analyze the loss of heterozygosity (LOH) of adenomatous polyposis coli (APC), mutation in colorectal cancer (MCC) and deleted in colorectal cancer (DCC) genes in the development and progression of colorectal cancers. METHODS: LOH at APC, MCC and DCC genes was examined in 41 surgically resected specimens of colorectal carcinomas by polymerase chain reaction and restriction fragment length polymorphism analysis technique. RESULTS: LOH of APC and MCC were observed in 7 of 25 (28.0%) and 8 of 22 (36.4%) of informative cases, respectively. When considered as one locus, the LOH frequency for APC/MCC was 14 of 36 (38.9%). LOH at DCC gene locus was detected in 21 of 38 (55.3%) of informative cases. No correlation was found between the LOH at APC or MCC gene and tumor histological types, size, invasion, lymph node metastasis and Dukes’ stages (P > 0.05). However, LOH rates at DCC locus in the group with lymph-node metastasis (80.0%) and in Dukes’ stages III and IV (71.4%) were significantly higher than those without lymph node metastasis (39.1%) and in Dukes’ stages I and II (35.3%) (P < 0.05). CONCLUSION: LOH at APC and/or MCC may occur more frequently in the early stages and plays a role in the initiation of colorectal cancer while LOH at DCC is frequent at late event and associated with the progression and metastasis of colorectal cancer.     

肝癌患者血浆循环DNA杂合性缺失的检测及其临床意义

目的检测HCC患者血浆循环DNA杂合性缺失（LOH），并探讨将其作为有关临床预测标记的可能性。方法选择位于染色体8p上3个具有高度多态性的微卫星标记D8S277、D8S298和D8S1771，对62份HCC患者血浆循环DNA进行LOH检测，并进一步探讨LOH与患者HBsAg表达、是否肝硬化、血清AFP水平、肿瘤大小及细胞分化程度和有无肝内转移等临床病理特征之间的关系。结果在62份HCC患者血浆循环DNA标本中，36份（58．1％）在1个或多个位点发生LOH，D8S277、D8S298和D8S1771位点杂合度分别为74．2％（46／62）、75．8％（47／62）和69．4％（43／62），LOH频率分别为32．6％（15／46）、44．7％（21／47）和46．5％（20／43）。D8S298位点有肝内转移患者血浆循环DNA标本的LOH频率（62．5％）明显高于无肝内转移者（26．1％），差异有统计学意义（P〈0．05）；其他临床病理特征与3个位点上的LOH频率无明显相关。结论血浆循环DNA中D8S298位点LOH有可能成为HCC术后转移复发及预后的一个潜在的预测标记。     

Prophylactic lymph node dissection for early gastric cancer invading submucosa

BACKGROUND/AIMS: Prophylactic lymph node dissection for gastric cancer patients was considered to prolong survival time and D2 lymph node dissection was a standard treatment for early gastric cancer invading submucosa without lymph node metastasis. We investigated the possibility of minimizing the extent of prophylactic lymph node dissection for early gastric cancer invading submucosa if there was no evidence of lymph node metastasis. METHODOLOGY: We analyzed data on 404 patients with early gastric cancer invading the submucosa who underwent gastrectomy from 1979 to 1998 in the National Kyushu Medical Center, Fukuoka, Japan. The postoperative survival rate of patients with standard D2 dissection was compared with cases of those with limited D2 dissection which was defined as confined as D2 dissection dissections No.7 (lymph nodes were those along the left gastric artery), No.8 (lymph nodes along the anterosuperior common hepatic artery) and No.9 (lymph nodes along the celiac artery). RESULTS: Of the 404 patients, 52 and 17 had lymph node metastasis in group 1 and group 2 nodes, respectively. Of 17 patients with lymph node metastasis in group 2, 14 (82.4%) had metastasis confined to No.7, 8 and 9 of group 2 nodes. The 5-year survival rate of patients with submucosal cancer without lymph node metastasis was 94.4% after limited D2 dissection and 97.3% after standard D2 dissection, respectively. CONCLUSIONS: The appropriate prophylactic lymph node dissection for early gastric cancer invading the submucosa without lymph node metastasis was considered to be minimized to limited D2 dissection.     

Clinico-pathological significance of cell-type-specific loss of heterozygosity on chromosome 7q21: analysis of 318 microdissected thyroid lesions

A careful pathological examination often reveals the presence of different lesions at various stages of tumor progression and invasion, even in those thyroid glands presenting with solitary nodules. Each thyroid lesion is composed of many different cell types, reflecting the marked heterogeneity of normal thyroid tissue. Among the different chromosome regions altered in thyroid tumors, 7q21 appears to be specifically involved in malignant tumors, especially of the follicular type. This study was conducted to analyze the loss of heterozygosity (LOH) pattern at 7q21 in pure populations of cells from each single lesion harbored in surgically removed thyroid glands, and to evaluate its clinical significance. One hundred and forty-two thyroid glands were examined, all showing, as a common trait, a goitrous appearance associated with one single lesion in 114 cases and with more than one in the remaining 28 cases. A total number of 318 lesions was analyzed, consisting of 142 goiters (TG), 48 hyperplasias (TH), 80 adenomas (TA) and 48 carcinomas (TC). Five different types of cells were isolated by laser capture microdissection from each lesion. DNA was analyzed by PCR and polyacrylamide gel electrophoresis in search of LOH affecting five microsatellite markers, D7S660, D7S630, D7S492, D7S657, and D7S689. We detected LOH at 7q21 not only in thyroid malignant tumors but also in benign lesions. Allelic loss occurred exclusively in dark nucleus and eosinophilic cytoplasm cells, commonly observed in the follicular type of lesions. In these types of lesions allelic loss frequency increases along with neoplastic transformation (9% in TG, 41% in TH, 68% in TA and 100% in TC), and is directly correlated with thyroid gland volume as well as with the presence of multiple lesions. The highest LOH rate was observed for D7S492, indicating that the recurrent region of deletion was localized at the corresponding genetic locus at 7q21.2, in the same position where the common fragile site FRA7E was previously mapped. LOH at this locus represents an early event in the development of follicular TC and is associated with intense growth of thyroid glands.     

The correlation of genetic instability of PINX1 gene to clinico-pathological features of gastric cancer in the Chinese population

Purpose  This project explored the influence of loss of heterozygosity (LOH) and microsatellite instability (MSI) of locus D8S277 to PINX1 expression of gastric cancer in Chinese people. Methods  LOH and MSI of locus D8S277 in 90 paraffin-embedded gastric carcinoma specimens were detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). Envision immunohistochemistry was used to assess the expression of PINX1. Results  The frequency of LOH was higher in cases with lymph node metastasis than those without (18.57 vs. 0.00%, P < 0.01), and was higher in the specimens that were at TNM stage III + IV than those at stage I + II (21.43 vs. 2.94%, P < 0.01). In terms of the frequency of MSI, it was lower in cases with lymph node metastasis than those without (10.00 vs. 30.00%,P < 0.05). The positive rate of PINX1 protein was higher in samples without lymph node metastasis than those with lymph node metastasis (80.00 vs. 50.00%, P < 0.01); and was higher in the cases at TNM stage I + II than those at stage III + IV; and was lower in the cases between 40 and 60 years old than those above 60 years old (43.75 vs. 65.52%, P < 0.05). Conclusion  LOH and MSI of PINX1 may play major role in tumor development and regulate it through different pathways. Because LOH plays a major role in negative expression of PINX1, it can be regarded as a sign of gastric cancer development and MSI may affect the prognosis and tumor turnover.