Allelic loss of a common microsatellite marker MYCL1: a useful prognostic factor of poor outcomes in colorectal cancer.

PURPOSE: Allelic loss involving chromosome arms 5q, 8p, 17p, and 18q is commonly detected in colorectal cancer (CRC). The short arm of chromosome 1 is also frequently affected in a whole range of cancer types, including CRC. Our aim in the present study was to determine whether allelic losses on 1p were likely to be of much value in predicting the prognosis of CRC cases. EXPERIMENTAL DESIGN: Genomic DNA was prepared from tumor and corresponding normal tissue specimens from 90 patients who had undergone curative resection for CRC. Loss of heterozygosity (LOH) on chromosome arms 1p, 2p, 5q, 7q, 8p, 17p, 17q, and 18q was examined using 14 microsatellite markers, and possible correlations between LOH and clinicopathological factors (including tumor recurrence and patient survival) were investigated. LOH at the MYCL1 microsatellite marker at 1p34 was detected in 12 of 74 (16.2%) patients who were informative for this marker. RESULTS: After controlling for tumor stage and gender and excluding findings for patients with remote metastasis, we found that patients who were positive for LOH at MYCL1 were 31 times more likely to experience recurrence than those who were negative for LOH at this locus (95% confidence intervals, 2.27- infinity; P = 0.04). There were indications of a similar tendency for LOH at the 14-3-3-sigma-TG microsatellite marker at 1p35, but we could find no evidence of a significant association between LOH at this site and tumor recurrence or patient survival. We were also unable to detect significant association between LOH at the various sites on 2p, 5q, 7q, 8p, 17p, 17q, and 18q and either tumor recurrence or patient survival. CONCLUSIONS: CRC patients whose tumors exhibited LOH at MYCL1 at chromosome 1p34 were likely to have a poor prognosis, suggesting that this marker may have clinical relevance.     

The clinical value of microsatellite instability and a loss in heterozygosity in sporadic breast cancers

We analyzed loss of heterozygosity (LOH) and microsatellite instability (MI) in 108 cases of sporadic breast cancers using 22 microsatellite markers on 12 chromosomes. LOH was frequently seen in 1p (13%), 6p (18%), 8p (11%), 11p (18%), 13q (21%), 16q (31%), 17p (44%) and 17q (29%). Individual patients were scored according to the degree of LOH at the above eight chromosomal markers. Patients with no LOH were scored as 1, patients with one to three LOH were scored as 2, and patients with four or more LOH were scored as 3. A high LOH score correlated with a high histological grade (p = 0.019) and a poor prognosis (p = 0.0035). Eleven (10.2%) of 108 patients with breast cancer showed MI, with 6 cases showing MI at a single locus and 5 at multiple loci. Of the 11 Mi-positive patients only one had lymph node involvement (p = 0.015), none had histological grade 3 disease, and Mi-positive patients tended to have a better prognosis than Mi-negative ones. These data suggest that MI may be an early event in mammary tumorigenesis, and that LOH occurs at a later stage. The LOH score may be a useful prognostic marker of operable breast cancer.     

Allelotype analysis of oesophageal adenocarcinoma: loss of heterozygosity occurs at multiple sites.

Deletions of tumour-suppressor genes can be detected by loss of heterozygosity (LOH) studies, which were performed on 23 cases of adenocarcinoma of the oesophagus, using 120 microsatellite primers covering all non-acrocentric autosomal chromosome arms. The chromosomal arms most frequently demonstrating LOH were 3p (64% of tumours), 5q (45%), 9p (52%), 11p (61%), 13q (50%), 17p (96%), 17q (55%) and 18q (70%). LOH on 3p, 9p, 13q, 17p and 18q occurred mainly within the loci of the VHL, CDKN2, Rb, TP53 and DCC tumour-suppressor genes respectively. LOH on 5q occurred at the sites of the MSH3 mismatch repair gene and the APC tumour-suppressor gene. 11p15.5 and 17q25-qter represented areas of greatest LOH on chromosomes 11p and 17q, and are putative sites of novel tumour-suppressor genes. LOH on 9p was significantly associated with LOH on 5q, and tumours demonstrating LOH at both the CDKN2 (9p21) and MSH3 (5q11-q12) genes had a significantly higher fractional allele loss than those retaining heterozygosity at these sites. Six of nine carcinomas displaying microsatellite alterations also demonstrated LOH at CDKN2, which may be associated with widespread genomic instability. Overall, there are nine sites of LOH associated with oesophageal adenocarcinoma.     

nm23-H1基因在喉癌中杂合性丢失和微卫星序列不稳定性分析及表达的研究

目的　探讨nm2 3 H1基因在喉鳞状细胞癌中杂合性丢失 (LOH)及表达情况。方法　选择nm2 3 H1基因内部及附近 5个微卫星多态标记 ,对 72例喉癌标本进行杂合性丢失和微卫星序列不稳定性检测 ,同时以RT PCR方法分析 38例配对喉鳞状细胞癌标本中nm2 3 H1基因表达情况。结果　LOH涉及至少 1个位点的频率高达 76 .39% ,5个位点均有LOH ,以D17S16 6 5处频率最高 ,达 38.10 %。 3个位点出现MI ,最高为 12 .70 %。nm2 3 H1基因杂合性丢失及微卫星不稳定与淋巴结转移、临床分期和肿瘤分化无显著相关性 (P >0 .0 5 ) ,但D17S16 6 5位点高LOH频率与低分化相关 (P <0 .0 5 )。癌、癌旁及转移淋巴结中nm2 3 H1表达不同 ,但差异无统计学意义 ,表达水平与淋巴结转移无关 (P >0 .0 5 )。结论　nm2 3 H1基因可能在喉鳞癌发生中起作用 ,杂合性丢失可能是影响基因功能的主要机制。     

Genetic alterrations of microsatellite markers at chromosome 17 in non-small cell lung cancer

Despite the high incidence and mortality, the exact molecular mechanism of the tumorigenesis and progression of lung cancer is still unclear. Alterations in oncogenes and onco-supressor genes have been described in lung cancer. Recent studies have started to define microsatellite instability (MI) and loss of heterozygosity (LOH) in genetic material of patients with lung cancer.[1] Microsatellite instability represents mutations of the short-tandem repeat sequences distributed within the geno…     

Characterization of sporadic colon cancer by patterns of genomic instability

Colorectal cancer (CRC) can progress through two pathways of genomic instability: chromosomal (CIN) and microsatellite instability (MSI). We hypothesized that these two pathways are not always independent and that some tumors therefore show a significant degree of overlap between these two mechanisms. We classified 209 high-risk stage II and stage III sporadic CRCs based on their MSI status, using a National Cancer Institute-recommended panel of microsatellite markers, and also identified MSI-associated mutations of CRC target genes such as TGFbetaRII. Evidence for CIN was gathered by identifying loss of heterozygosity (LOH) events on chromosomal arms 1p, 2p, 3p, 5q, 17p, and 18q, which are regions harboring mismatch-repair and tumor-suppressor genes that are significant in CRC development. Results of all molecular markers tested were correlated with clinicopathological variables of the cohort, including treatment outcome. Of the 209 cases, 65% cancers were microsatellite stable, 21% were MSI-low, and 14% were MSI-high (MSI-H). Overall, 51% of the tumors had at least one LOH event, with most frequent chromosomal losses observed on 18q (72.5%), followed by 5q (22%), 17p (21%), and 3p (14%). Interestingly, we observed a significant degree of overlap between MSI and CIN pathways. Of 107 cancers with LOH events, 7 (6.5%) were also MSI-H, and of 30 cancers that were MSI-H, 7 (23.3%) also had one or more LOH events. We also found that 37.8% of microsatellite-stable cancers had no LOH events identified, thus comprising a subgroup of tumors that were not representative of either of these two pathways of genomic instability. Our data suggest that molecular mechanisms of genomic instability are not necessarily independent and may not be fully defined by either the MSI or CIN pathways.     

Correlation of allelic losses and clinicopathological factors in 504 primary breast cancers

BACKGROUND: We have defined 18 chromosomal regions in which allelic losses were frequent among breast cancers. We examined whether specific allelic losses might correlate with any clinicopathological factors. METHODS: We tested DNA from matched normal and tumor tissues for loss of heterozygosity (LOH) at 18 microsatellite loci from a cohort of 504 patients who had undergone surgery for breast cancer. RESULTS: LOH at 3p14.3 correlated with a larger size of tumor (greater than 2 cm). LOH at 1p22, 3p25.1, 3p14.3, or 17q21.1 correlated with loss of estrogen receptors. LOH at as many as eleven regions correlated with loss of progesterone receptor, suggesting that these represent general phenomena associated with progression of cancer. Above all, allelic losses at 11q23-24, 13q12, 17p13.3, or 22q13 significantly correlated with lymph-node metastasis (11q23-24, p= 0.0042; 13q12, p=0.0207; 17p13.3, p=0.0478; 22q13, p=0.0162). CONCLUSION: These results suggest that some clinical characteristics of breast cancers are determined by loss of tumor suppressor genes present at specific chromosome regions. Especially, LOH at 11q23-24, 13q12, 17p13.3, and 22q13 is a significant predictor of lymph-node metastasis for patients who have undergone surgery for breast cancer, and may serve as a negative prognostic indicator.     

Detailed deletion mapping at chromosome 11q23 in colorectal carcinoma

Loss of heterozygosity (LOH) is frequent at the chromosomal region 11q22-q23 in several types of tumours of diverse cell origin. Previous investigations of LOH at this chromosomal region in colorectal carcinoma have been contradictory in their findings, and have only included between 1-4 loci. In order to define any regions of LOH on 11q23, we investigated 16 loci between D11S940 and D11S934 on the long arm of chromosome 11 using microsatellite analysis. Of 57 colorectal carcinomas specimens, 36 (63.2%) demonstrated LOH at one or more marker, with the highest frequencies of LOH at D11S1340 (41.0%), located between 105.13-111.97 Mb from the centromere, and D11S924 (37.1%) and D11S4107 (40.5%), both located approximately 113 Mb from the centromere. No statistically significant associations between LOH and age-of-presentation or Dukes' stage were found. LOH was observed in colorectal tumours of all Dukes' stages, including Dukes' stages A and B, suggesting that the inactivation of a tumour suppressor gene(s) on 11q23 occurs in the early stages of colorectal carcinoma. These results confirm the presence of putative tumour suppressor gene(s) at chromosome 11q23, involved in the carcinogenesis of colorectal carcinoma, and will facilitate future identification of candidate genes.     

Allelic loss of the PTEN region (10q23) in breast carcinomas of poor pathophenotype

Loss of heterozygosity (LOH) in loci of the 10q23 region that harbor the PTEN gene and mutations in the sequence of this gene have been found in several primary human tumors including breast carcinomas, suggesting that this gene could be implicated in their pathogenesis. We investigated allelic losses in microsatellites of the 10q23 region, and their correlations with nine pathologic parameters in 105 breast carcinomas. The LOH analysis was performcd by amplifying DNA by PCR, using five markers of the 10q23 region (D10S1687, D10S541, D10S2491, D10S583 and D10S571). LOH in at least one marker of the PTEN region was found in 29.5% of tumors. The statistical comparison between carcinomas with and without LOH in terms of the pathologic parameters showed significant differences in age (p=0.03), lymph node metastases (p=0.02), and higher histological grade (p=0.02); a trend toward significance was found for progesterone receptors (p=0.05). LOH in an individual marker and statistically significant relationships to tumor characteristics were observed at locus D10S541 for lymph node metastases (p=0.04), at D10S2491 (intragenic to the PTEN gene) for lymph node metastases (p=0.02), and at D10S583 for progesterone receptors (p=0.01) and for high grade (p=0.03). These results suggest the PTEN gene, or other genes of the 10q23 region, could be functionally related to breast cancer, probably influencing the development of histological features associated with poor prognosis.     

Genetic heterogeneity of surgically resected prostate carcinomas and their biopsy specimens is related to their histologic differentiation

BACKGROUND: In human prostate carcinogenesis, many genetic analyses including conventional loss of heterozygosity (LOH) studies and microsatellite LOH analyses using the polymerase chain reaction method have revealed frequent LOH events at specific regions on chromosomes 3p, 7q, 8p, 10q, 16q, 17q, and 18q. METHODS: Using the laser-captured microdissection method, the authors extracted genomic DNA from 23 cases of prostate carcinomas including 59 different lesions and 8 biopsy specimens. Using (32)P-labeled primers, the authors analyzed six microsatellite loci (D3S647, D3S1228, D7S522, D8S137, NEFL, and D10S190) at which frequent LOH events have been reported. RESULTS: Of 10 cases in which the authors found LOH at any of the loci, 8 cases showed a heterogeneous LOH pattern. In four cases, the authors also found replication error (RER) at some of the loci examined. There was no significant relation between histologic differentiation and frequency of LOH or RER events. The overall LOH rate was found to be significantly lower in foci at classification pT2 (1 of 28 foci, 3%) compared with those at classification pT3 (13 of 44 foci, 30%). In pT3 samples, LOH events in extraglandular foci (9 of 23 foci, 39%) tended to be more frequent compared with those in intraglandular foci (8 of 41 foci, 20%). The patterns of LOH events in biopsy specimens correlated well with those in foci from surgical material showing the same histologic characteristics. CONCLUSIONS: Prostate carcinoma is a genetically multicentric carcinoma, and the genetic heterogeneity is well correlated with histologic differentiation. The frequency of LOH events increased according to the degree of tumor progression.     

A statistical analysis of chromosome 11 and 17 loss of heterozygosity in epithelial ovarian cancer

Many regions of the genome exhibit loss of heterozygosity (LOH) in epithelial ovarian cancer (EOC) suggesting sites of recessive genetic elements such as tumor suppressor genes. We performed detailed LOH studies of chromosomes 17 and 11 using 24 microsatellite repeat markers in a population of 47 patients with EOC. Univariate statistical analysis revealed that significant co-losses of chromosomal loci occurred between 17p and 17q whole arms (p=0.0003), NME1 (17q21) with D11S922 (11p15.5) (p=0.0067) and D11S912 (11q24) with D11S935 (11p13) (p=0.0073). Statistical analysis of the relationship between LOH on particular chromosomal arms and clinicopathological factors revealed a significant association between serous histological subtype of ovarian adenocarcinoma and chromosome 17p (p=0.0052) and telomeric 17q (p=0.0007) LOH. An analysis of specific polymorphic chromosomal loci demonstrated that adverse survival was significantly associated with LOH at 11q24 (p=0.0067) and 17q21 (p=0.0076). There were nonsignificant trends suggesting a relationship between chromosome 17p LOH and poorly differentiated (p=0.025) and advanced FIGO stage (p=0.031) tumours. Considering these statistical associations, a preliminary multistep model for involvement of chromosomes 11 and 17 in ovarian neoplasia can be constructed.     

Loss of heterozygosity and microsatellite instability in hepatocellular carcinoma in Taiwan.

Elucidation of the basic genetic changes of human hepatocellular carcinoma is important for the understanding and treatment of this cancer. We used microsatellite polymorphism markers to study 30 cases of hepatocellular carcinoma (34 tumours) on all human chromosomes. DNA from 34 pairs of hepatocellular carcinomas and corresponding non-tumour parts was prepared. Loss of heterozygosity (LOH) and microsatellite instability on 23 chromosomes were investigated by 231 sets of microsatellite markers. More than 20% LOH was shown for loci on 16q (47.1%), 13q (32.4%), 17p (32.4%), 5q (26.5%), 11p (23.5%) and 9p (20.6%). The commonly affected regions were mapped to 16q12.1, 16q12.2, 16q24, 13q12.1-32, 17p13, 5q32, 5q34, 5q3, 11p15, 11q23-24 and 9p21. Hepatitis B virus carriers had a significantly higher frequency of LOH on chromosomes 5q, 11p and 16q. Furthermore, larger tumour size tended to have higher frequency of LOH at D16S409 locus (16q12.1). Microsatellte instability was only found in 12 of 231 markers and the frequency is very low. These data suggest that the chromosomes 16q, 13q, 17p, 5q, 11p and 9p might participate in hepatocarcinogenesis. However, microsatellite instability might play little role in the development of this cancer in Taiwan.     

Allelotype and replication error phenotype of small cell lung carcinoma

Allelotype and replication error (RER) phenotype analyses were performed to clarify the pathogenetic significance of inactivation of tumor suppressor genes and genomic instability in the genesis and progression of small cell lung carcinoma (SCLC). We examined 37 cases of SCLC for loss of heterozygosity (LOH) and microsatellite instability at 49 loci on all 39 nonacrocentric chromosomal arms. LOH was frequently (>70%) detected on chromosomes 3p (29/32, 90.6%), 5q (15/21, 71.4%), 13q (25/26, 96.2%), 17p (22/25, 88.0%), and 22q (24/33, 72.7%). Frequent LOH (>70%) on these loci was observed even among seven cases of stage I tumors. The incidence of LOH on all 39 nonacrocentric chromosomal arms was not significantly different between primary tumors and metastases. These results suggest that inactivation of multiple tumor suppressor genes accumulates relatively early during progression of SCLC and it may be responsible for clinically and biologically aggressive phenotype of SCLC. RER was observed in 6/37 (16.2%) of SCLC, however, RER at multiple loci was observed only in two cases. Therefore, it was indicated that genomic instability is uncommon, but might play a role in the genesis of a small subset of SCLC.      

Genetic pattern of prostate cancer progression

Genetic alterations in primary prostate cancer (CaP) have been extensively studied, yet little is known about the genetic mechanisms underlying progression of primary CaP to metastatic prostate cancer. As a result, it is not possible to distinguish clinically indolent localized disease from potentially life-threatening tumors with high metastatic potential. To address this question, we collected tissue from 34 autopsy-derived metastases, samples rarely analyzed in previous studies. These were compared to a separate set of 17 prostatectomy specimens containing 22 foci of CaP associated with 49 examples of high-grade prostatic intraepithelial neoplasia (PIN), a histological precursor of CaP. We compared the loss of heterozygosity (LOH) profiles of high-grade PIN, primary CaP and metastases by analyzing 33 microsatellite markers previously found to have high frequencies of LOH in primary CaP. These markers were on chromosomes 5q, 6q, 7q, 8p, 9p, 10q, 11p, 13q, 16q, 17, 18q and 21q. In addition, markers on chromosomes 4p, 11q, 14q and 20q with no reported LOH in primary CaP were analyzed to determine the frequency of background LOH. In PIN lesions, the rate of LOH was significant only at D5S806 (20%) and D16S422 (29%). In addition, different PIN lesions within the same prostate gland were genetically diverse, indicating divergent evolution of synchronous neoplastic precursor lesions. LOH frequency was progressively higher in primary CaP and metastatic lesions. In primary CaP, significant losses occurred at the 8p, 10q, 11p, 16q, 17p, 18q and 21q loci (range 17-43%). Distinct patterns of LOH frequencies were observed in primary CaP compared with metastases. Although some loci (D16S422, D17S960, D21S156) showed similar frequencies of LOH in primary CaP and metastatic CaP, most other loci showed up to 7-fold metastasis-related increases. The metastatic samples revealed previously unrecognized prostate cancer LOH at D5S806, D6S262, D9S157, D13S133 and D13S227. These significant stage-specific differences in LOH frequency specify genetic loci that may play key roles in CaP progression and could represent clinically useful biomarkers for CaP aggressiveness.     

Accumulation of genetic alterations in brain metastases of sporadic breast carcinomas is associated with reduced survival after metastasis.

Tumor progression is characterized by stepwise accumulation of genetic alterations. To identify alterations associated with breast cancer metastasis, an analysis of comparative loss of heterozygosity (LOH) was performed on 38 primary sporadic breast carcinomas and 16 distant metastases. Two loci at 5q21 and 18q21 were chosen because of their reported increased deletion frequency in metastatic tumors. LOH at 17q21, 13q12-13, 17p13.1 and 11q22-23 was analyzed to determine whether there is a specific involvement of these breast cancer-associated gene loci in the metastatic process. Our data show that distant metastases are characterized by markedly increased LOH frequency at all loci examined. In both gene locus groups, significantly more distant metastases are affected by combined LOH. Furthermore, a significantly reduced postmetastatic survival time has been observed in patients with brain metastases affected by synchronous allelic loss at the four breast cancer-associated gene loci. Our results suggest that cumulative LOH of breast cancer-related gene loci is associated with a more aggressive phenotype of metastatic breast tumors.     

Loss of BRCA2 correlates with reduced long-term survival of sporadic breast cancer patients

BACKGROUND: The present study was undertaken to analyze the prognostic value of loss of heterozygosity (LOH) at 13q12-13, 17q21 and 17p13, harboring BRCA2, BRCA1 and p53 to predict the clinical course of sporadic breast cancer patients. MATERIALS AND METHODS: LOH analysis was performed by PCR amplification of genomic DNA using nine microsatellite markers. Fifty-three sporadic breast cancer patients were followed clinically for a median of 55 months. Disease-free and overall survival was documented as the endpoint for statistical evaluation. RESULTS: Patients presenting with LOH in their tumor samples at at least one of the loci examined were found to have a reduced overall survival time compared to those retaining heterozygosity (61% versus 48%). Focusing on the three target regions, patients with LOH at the BRCA2 locus died earlier compared to patients retaining heterozygosity (69% versus 50%) and, in addition, BRCA2 LOH-positive patients showed a shorter metastasis-free interval (30 versus 37 months). In a multivariate analysis, LOH at the 13q12-13 locus was found to be a significant predictor for reduced long-term survival (risk ratio 2.33, 95% C.I., 1.0-5.3; p<0.05) and earlier metastases manifestation (risk ratio 2.32, 95% C.I., 1.0-5.3, p<0.05). CONCLUSION: Allelic loss at the BRCA2 locus may be of use as a negative predictor for metastases-free and overall survival.     

Clonal origin of lymph node metastases in bladder carcinoma

BACKGROUND: Evidence of genetic heterogeneity within urothelial carcinomas of the bladder has raised questions about the clonal origin of urothelial carcinoma and its metastases. High-grade urothelial carcinoma of the bladder frequently metastasizes to multiple regional lymph nodes in the pelvis. Whether or not these multiple lymph node metastases originate from the same tumor clone is uncertain. Molecular analysis of microsatellite alterations and X-chromosome inactivation status of distinct tumor cell populations from the same patient may further our understanding of the genetic basis of carcinoma progression and metastasis. METHODS: The authors examined 24 patients who underwent radical cystectomy for urothelial carcinoma. All patients had multiple (from two to four) lymph node metastases. Genomic DNA samples were prepared from formalin fixed, paraffin embedded tissue sections using laser-assisted microdissection. Loss of heterozygosity (LOH) assays for 3 microsatellite polymorphic markers on chromosome 9p21 (D9S171, region of putative tumor suppressor gene p16), 9q32 (D9S177, putative tumor suppressor gene involved in urothelial carcinoma tumorigenesis), and 17p13 (TP53, the p53 locus) were performed. In addition, X-chromosome inactivation analysis was performed in primary tumors and metastases from 10 female patients. RESULTS: In total, 79 tumors were analyzed. The overall frequency of allelic loss was 67% (16 of 24 tumors) in the primary urothelial carcinomas and 79% (19 of 24 tumors) in the metastatic carcinomas. The primary urothelial carcinoma showed LOH at the D9S171, D9S177, and TP53 loci in 39% (9 of 23 tumors), 30% (6 of 20 tumors), and 30% (7 of 23 tumors) of informative samples, respectively. LOH in > or = 1 lymph node metastases was seen at the D9S171, D9S177, and TP53 loci in 35% (8 of 23 tumors), 45% (9 of 20 tumors), and 48% (11 of 23 tumors) of informative samples, respectively. Eleven tumors demonstrated identical allelic loss patterns at all DNA loci both in the primary carcinoma and in all corresponding lymph node metastases. Three tumors showed allelic loss in the metastatic carcinoma but not in its matched primary carcinoma. Six tumors demonstrated a different LOH pattern in each of its lymph node metastases. Clonality analysis showed the same pattern of nonrandom X-chromosome inactivation both in the primary urothelial carcinoma and in all of the lymph node metastases in five of nine informative tumors studied. Four tumors showed a random pattern of X-chromosome inactivation in both the primary carcinoma and in the metastases. CONCLUSIONS: LOH and X-chromosome inactivation assays showed that multiple lymph node metastases and matched primary urothelial carcinomas of the bladder had the same clonal origin, suggesting that the capability for metastasis often arises in only a single clonal population in the primary tumor. The variable LOH patterns observed in some of the tumors likely reflect genetic divergence during the clonal evolution of urothelial carcinoma.     

Microsatellite alterations in squamous cell carcinoma of the head and neck - clustering of loss of heterozygosity in a distinct subset

Loss of heterozygosity (LOH) and microsatellite instability (MSI) have been recognized as important events in the carcinogenesis of many cancers, including squamous cell carcinoma of head and neck (SCCHN). However, microsatellite alterations have not been documented in SCCHN from Chinese patients. We investigated the frequency and clinical significance of LOH and MSI in 30 SCCHN from Hong Kong Chinese using polymerase chain reaction on 17 microsatellite markers on chromosomes 3p, 4q, 7q, 9p, 17p and 18q. LOH was present in nine tumours (30%) and MSI in four (13%). The incidence of LOH (7/13; 53.8%) in hypopharyngeal-laryngeal cancers was significantly higher than that (2/17; 11.8%) in the oral cancers (P=0.020). LOH was more often detected at the loci on chromosomes 7 and 9. Patients with tumours having LOH had slightly poorer outcome compared with those without, although the differences did not reach statistical significance. Our data show that the incidence of microsatellite alterations in SCCHN from Hong Kong Chinese is low. However, LOH may be one of the genetic mechanisms in the carcinogenesis of a subset of SCCHN (hypopharyngeal-laryngeal cancers).     

Microsatellite alterations on chromosome 9 in chewing tobacco-induced oral squamous cell carcinomas from India

Genomic instability as reflected by microsatellite alterations in specific target regions is an important characteristic of oral squamous cell carcinoma (OSCC). Microsatellite instability (MSI) and loss of heterozygosity (LOH) on chromosome 9 has been reported as an early event in oral cancers, primarily from patients in the USA and UK. Hence, we examined 77 primary oral cancer tissues and corresponding peripheral blood cell (PBC) DNA from Indian oral cancer patients for LOH and MSI, using a panel of 11 microsatellite markers spanning chromosome 9 on p and q arms. The patients were long-time (minimum 10 years) tobacco chewers. The matched DNA samples were amplified by polymerase chain reaction, resolved on a denaturing polyacrylamide gel and visualized by silver staining. An overall of 62% (48/77 cases) of the patients demonstrated microsatellite alterations including 27% MSI and 52% LOH, although at individual loci MSI was observed in 3-8% patients and LOH in the informative cases ranged from 4 to 41%. A majority of the alterations occurred on the p arm at 9p21-23, with 85% (41/48 cases) genetic alterations concentrated between markers D9S157 and D9S161. Multiple alterations were seen in 56% (27/48) of the affected cases with 17 patients showing microsatellite alterations in three to eight loci. Our data show the incidence of genetic alterations primarily in the chromosomal region 9p21-23, and may be indicative of involvement of p16 (CDKN2) tumor suppressor gene on chromosome 9p21, in a subset of chewing tobacco-induced oral cancers.     

Differential prognosis of replication error phenotype and loss of heterozygosity in sporadic colorectal cancer

Several distinct genetic alterations have been associated with colorectal tumorigenesis. This study investigated the frequency of microsatellite instability, also known as replication error (RER), and loss of heterozygosity (LOH) at six chromosome regions in sporadic colorectal cancer (CRC). Eighty-six tumour and paired normal mucosa samples were included in the study. A polymerase chain reaction (PCR)-based technique was performed to analyse six (CA)n dinucleotide repeats located near or within regions containing important genes implicated in the complex process of colorectal tumorigenesis (chromosomes 2p, 3p, 5q, 11p, 17p and 18q). Overall, LOH frequency was higher in RER-tumours (25/46, 54.3%) compared with RER+ tumours (9/40, 22.5) (P = 0.04). To investigate prognostic implications, survival analysis was performed for 66 patients. Compared with RER- tumours, patients with RER+ tumours at 2p, 3p, 5q, 11p or 18q were found to have an improved prognosis (overall survival, P = 0.02 and disease-free survival (DFS) P = 0.005) this variable being an independent prognostic factor by multivariate analysis (P = 0.001). Overall survival of patients whose tumours were LOH+ was significantly shorter compared with those without LOH (overall survival, P = 0.008 and DFS, P = 0.01). Thus, tumours displaying RER+ and LOH+ phenotype, as established by microsatellite analysis, show a differential prognosis. These data indicate that this may be a useful tool for the identification of patients at different risks affected by CRC.