Early-onset Gastric Cancer Research Articles

Low frequency of HER2 amplification and overexpression in early onset gastric cancer

BackgroundThe recent ToGA trial results indicated that trastuzumab is a new, effective, and well-tolerated treatment for HER2-positive gastric cancer (GC). Although GC mainly affects older patients, fewer than 10% of GC patients are considered early-onset (EOGC) (presenting at the age of 45 years or younger). These EOGC show different clinicopathological and molecular profiles compared to late onset GC suggesting that they represent a separate entity within gastric carcinogenesis. In light of potential trastuzumab benefit, subpopulations of GC such as EOGC (versus late onset) should be evaluated for their frequency of amplification and overexpression using currently available techniques.MethodsTissue microarray (TMA) blocks of 108 early onset GC and 91 late onset GC were stained by immunohistochemistry (IHC, Hercep test, DAKO) and chromogenic in situ hybridization (CISH, SPoT-Light, Invitrogen).ResultsOverall, we found only 5% HER2 high level amplification and 3% HER2 3+ overexpression (6/199). In addition, 8 patients (4%) showed a low level CISH amplification and 9 patients (4.5%) showed a 2+ IHC score. IHC and CISH showed 92% concordance and CISH showed less heterogeneity than IHC. In 2/199 cases (1%), IHC showed clinically relevant heterogeneity between TMA cores, but all cases with focal IHC 3+ expression were uniformly CISH high level amplified. Early onset GCs showed a significantly lower frequency of HER2 amplification (2%) and overexpression (0%) than late onset GCs (8% and 7% respectively) (p = 0.085 and p = 0.008 respectively). Proximal GC had more HER2 amplification (9% versus 3%) and overexpression (7% versus 2%) than distal tumours although this difference was not significant (p = 0.181 and p = 0.182 respectively). HER2 CISH showed more high level amplification in the intestinal type (7%, 16% if low-level included) compared to the mixed (5%, 5% if low-level included) and diffuse type (3%, 4% if low-level included) GCs (p = 0.029). A similar association was seen for HER2 IHC and histologic type (p = 0.008). Logistic regression indicated a significant association between HER2 expression and age, which remained significant when adjusted for both location and histological type.ConclusionsEven focal HER2 overexpression in GC points to uniform HER2 amplification by CISH. We show for the first time that early onset GC has a lower frequency of HER2 amplification and overexpression than late onset GC, and confirm that intestinal type GC shows the highest rate of HER2 amplification and overexpression.

Early-onset gastric cancer: A distinct clinical entity with a different prognosis?

22 Background: This study aimed to evaluate the early onset gastric cancer (EOGC), considered as gastric cancer in a patient younger than 45 years, as a distinct entity with a different prognosis. Methods: This study is related to 1,256 patients admitted with gastric or gastroesophageal junction carcinoma in our department between January 1988 and December 2008. There were 10.59% (133 cases) of EOGC in our series. The following clinical, pathological and staging parameters were studied: age, gender, tumor location, ressecability, type of resection surgery, type of resection, type of lymphadenectomy (Siewert and Japanese classifications), number of lymph nodes studied, tumor dimensions, macroscopic form, histological classification (Lauren and Ming), venous invasion, lymphatic permeation, perineural invasion, depth wall invasion (T), lymph node metastases (N) – TNM and Japanese classification and lymph node ratio – distance metastases (M) and stage. Results: Significant differences were observed in the type of resection surgery (p<0.001) and type of lymphadenectomy (p=0.008), with more radical surgery performed in EOGC patients. Some tumor characteristics also showed significant differences: tumor dimensions (p=0.004), with EOGC usually smaller; diffuse type according to Lauren's classification (p<0.001); infiltrative type according to Ming's classification (p=0.001); less venous invasion (p=0.005); less lymphatic permeation (p=0.029). There were no significant differences in the staging parameters. There were significant differences in the survival rate (p<0.001), with 5-year survival rate of 44% in patients with EOGC compared with 31% in older patients. Cox-regression analysis revealed that age was an independent prognostic factor (HR 2,166, 1,133-4,139 CI 95%, p = 0.019), as well as depth wall invasion (T) and lymph node ratio. Conclusions: In this study, EOGC revealed to be a distinct clinical entity that presented differences in various clinico-pathological parameters. Despite EOGC presented more aggressive pathological characteristics, there was a better survival in this group, probably because the physical status of younger patients which allowed a more aggressive treatment. No significant financial relationships to disclose.

Histopathology of familial and early-onset gastric cancer

Early-onset gastric cancer (EOGC) is defined as gastric cancer presenting at the age of 45 or younger. Approximately 10% of gastric cancer patients fall into the EOGC category. Furthermore, 10% of young gastric cancer patients have a positive family history, some of which are accounted for by inherited gastric cancer predisposition syndromes. Although the underlying genetic events are not always known, it can involve CDH1 germline mutations, encoding an aberrant form of E-cadherin, resulting in Hereditary diffuse gastric cancer (HDGC) and this occurs in 25–40% of tested families. Management options for asymptomatic mutation carriers are fraught, since endoscopic surveillance can miss cancer foci and prophylactic gastrectomy has profound clinical sequelae. This review serves to bring us up-to-date with the latest findings in EOGC and HDGC including implications for the clinician, geneticist and pathologist.

Polymorphisms in prostate stem cell antigen gene rs2294008 increase gastric cancer risk in Chinese

A recent genome-wide study identified a strong association between polymorphisms in the prostate stem cell antigen (PSCA) gene and the risk of diffuse-type of gastric cancer in Japanese and Korean population. In this case-control study, we aimed to investigate the possible association between PSCA rs2294008 C/T with clinicopathological features and the prognosis of gastric cancer in a Southern Chinese population. Genotypes of 460 gastric cancer patients and 549 controls were determined by PCR-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing. We found that individuals with at least one copy of the rs2294008T allele (CT or TT genotype) had an increased risk for gastric cancer compared with CC genotype (OR = 1.42, 95% CI = 1.10-1.82, P = 0.006). Further stratification analyses indicated that the effect of PSCA rs2294008T carriers was noteworthy in intestinal type (OR = 1.55, 95% CI = 1.18-2.04, P = 0.002), poorly differentiated (OR = 1.59, 95% CI = 1.19-2.13, P = 0.002), noncardia (OR = 1.55, 95% CI = 1.17-2.04, P = 0.002) subtypes of gastric cancer. Cox proportional hazards analyses demonstrated that TT genotype (HR = 2.12, 95% CI = 1.22-3.69, P = 0.008) as well as TNM staging were prognostic factors of gastric cancer patients. In conclusion, The T allele of PSCA rs2294008 is associated with increased risk of gastric cancer, especially intestinal type, poorly differentiated, early onset, and noncardia gastric cancer in Chinese population. TNM staging and TT genotype might be involved in the prognosis of gastric cancer patients.

E-cadherin genetic screening and clinico-pathologic characteristics of early onset gastric cancer

Aim CDH1 germline alterations occur in about 40% of hereditary diffuse gastric cancer (HDGC) families. CDH1 germline mutations are also documented in few early onset diffuse gastric cancer patients (EODGC) without family history, but the real frequency in this setting in unknown. In these patients, the advanced stage at the time of diagnosis remains a clinical burden due to the poor long term survival. Methods The entire coding region and exon flanking sequences of the CDH1 gene was analysed by direct sequencing in 21 EODGC patients aged ⩽50 years. The potential deleterious nature for a new CDH1 missense variant was assessed by cell–cell aggregation and invasion assays. Somatic CDH1 mutation, loss of heterozigosity (LOH) and promoter hypermethylation was explored in the tumour from one CDH1 germline mutation carrier. Results Two novel CDH1 germline variants were identified in 21 EODGC cases, c.670C>T and –63C>A. Functional analysis of the c.670C>T missense variant classified this mutation as non-pathogenic. The analysis of CDH1 somatic second hits failed to demonstrate E-cadherin structural and epigenetic alterations in the tumour sample. Conclusion Data from the present work and a systematic review of the literature revealed that CDH1 germline mutations occurred in 7.2% of EOGC patients invariably with diffuse of mixed histology. From these, proved CDH1 mutation pathogenicity has been assigned only to 2.3% of the cases who were recurrently diagnosed before 35 years old. Germline CDH1 mutation remain the only germline genetic defect described in this type of patients and CDH1 mutation screening should be recommended for patients with these characteristics.

788 Investigation of the differentially expressed C-FABP & FABP-pm in human prostate tissues and cell lines: histopathological and molecular biology study

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset (≤50 yrs) gastric cancer. We identified 211 cases of early onset gastric cancer in Central-East Ontario from 1989 to 1993, with archival material available for 139 cases. Testing included a six-mononucleotide marker panel and a three-MMR immunohistochemical panel. Overall, 30% (41 of 139) of GC were MSI+, with allelic shifts at one to eight markers. An unexpected discordance between the BAT-25, BAT-26, and BAT-40 markers was observed in the MSI+ cases. Six cases showing multiple loci instability (≥3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P = 0.04) and Lauren histotype (P = 0.006) and tumor grade (P = 0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.

Early-onset gastric cancer: Learning lessons from the young

There is by no means a clear-cut pattern of mutations contributing to gastric cancers, and gastric cancer research can be hampered by the diversity of factors that can induce gastric cancer, such as Helicobacter pylori infection, diet, ageing and other environmental factors. Tumours are unquestionably riddled with genetic changes yet we are faced with an unsolvable puzzle with respect to a temporal relationship. It is postulated that inherited genetic factors may be more important in early-onset gastric cancer (EOGC) than in gastric cancers found in older patients as they have less exposure to environmental carcinogens. EOGC, therefore, could provide a key to unravelling the genetic changes in gastric carcinogenesis. Gastric cancers occurring in young patients provide an ideal background on which to try and uncover the initiating stages of gastric carcinogenesis. This review summarizes the literature regarding EOGC and also presents evidence that these cancers have a unique molecular-genetic phenotype, distinct from conventional gastric cancer.

Allele-specific CDH1 downregulation and hereditary diffuse gastric cancer

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer susceptibility syndrome characterized by early-onset diffuse gastric cancer (DGC) and lobular breast cancer. E-cadherin (CDH1) heterozygous germline mutations and deletions are found in 40% of families. Independent of CDH1 alterations, most HDGC tumours display mislocalized or absent E-cadherin immunoexpression, therefore undetected defects at the CDH1 locus may still be involved. We aimed at determining whether CDH1 mutation-negative probands display germline CDH1 allele-specific expression (ASE) imbalance, using a single-nucleotide primer extension-based procedure and tried to uncover the underlying molecular defect. CDH1 ASE analysis was performed using three intragenic SNPs in RNA extracted from the blood of 21 cancer-free individuals and 22 HDGC probands (5 CDH1 mutation carriers and 17 CDH1 negative). Germline promoter methylation, deletions and haplotype-related susceptibility at the CDH1 locus were analysed. Both CDH1 alleles from cancer-free individuals displayed equivalent expression levels, whereas monoallelic CDH1 expression or high allelic expression imbalance (AI) was present in 80% of CDH1 mutant and 70.6% (n = 12) of CDH1-negative HDGC probands. Germline deletions and promoter hypermethylation were found in 25% of probands displaying high CDH1 AI. No particular haplotype was found to be associated with CDH1 high AI. Germline CDH1 AI is highly frequent among CDH1 mutation-negative probands but was not seen in cancer-free individuals. This implicates the CDH1 locus in the majority of mutation-negative HDGC families.

Absence of germline mono-allelic promoter hypermethylation of the CDH1 gene in gastric cancer patients

BackgroundGermline mono-allelic promoter hypermethylation of the MLH1 or MSH2 gene in families with hereditary nonpolyposis colorectal cancer has recently been reported. The purpose of this study was to evaluate if germline promoter hypermethylation of the tumor suppressor gene CDH1 (E-cadherin) might cause predisposition to gastric cancer.MethodsWe prepared two groups of samples, a group of blood samples from 22 patients with familial gastric cancer or early-onset gastric cancer selected from among 39 patients, and a group of non-cancerous gastric tissue samples from 18 patients with sporadic gastric cancer showing loss of CDH1 expression selected from among 159 patients. We then investigated the allele-specific methylation status of the CDH1 promoter by bisulfite sequencing of multiple clones.ResultsAlthough there was a difference between the methylation level of the two alleles in some samples, there was no mono-allelic promoter hypermethylation in any of the samples.ConclusionThese results suggest that germline mono-allelic hypermethylation of the CDH1 promoter is not a major predisposing factor for gastric cancer.

Early Onset Gastric Cancer No Longer Presents as an Advanced Disease with Ominous Prognosis

Background: This study aimed to characterize the clinicopathological features and prognosis of early onset gastric carcinomas (EOGCs) in a sample of young Portuguese adults. Material and Methods: A subset of 415 patients submitted to gastric resection was divided into 2 groups: A – patients aged 45 years or less (n = 108), and B – patients older than 45 years (n = 307). The groups were compared for several clinicopathological features and the survival of the patients was analyzed by uni- and multivariate analysis. Results: The surgical resection rate was higher in young patients, in whom tumors more frequently displayed an ulcerative shape (p < 0.001) and diffuse/isolated cell-type histology (p < 0.001). In the elderly, the rate of vascular invasion was significantly higher (p = 0.002). Overall, the survival of young patients was higher than in the elderly (p < 0.001). Survival curves were higher in young patients, except for pT4 and pM1 cases. In the multivariate survival analysis, age (p < 0.001), depth of tumor invasion (p < 0.001), nodal status (p < 0.001), vascular invasion (p = 0.011) and distant metastases (p = 0.007) emerged as independent prognostic factors for gastric carcinoma. Conclusion: Young gastric cancer patients no longer present with more advanced disease than the elderly and, overall, survival is better in young patients.

Cyclooxygenase-2 Mediated Regulation of E-Cadherin Occurs in Conventional But Not Early-Onset Gastric Cancer Cell Lines

Background: COX-2 and E-cadherin, involved in invasion and metastasis, are molecules critical for gastric carcinogenesis. A relationship between them is documented in non-small cell lung and prostate cancer. We present novel evidence of a relationship between COX-2 and E-cadherin expression in gastric cancer.Methods: Using qPCR and Western blots analysis on celecoxib and PGE2 treated and untreated gastric cancer cell lines derived from tumours of the intestinal type (MKN45, MKN28, AGS3, MKN7) and immunohistochemistry of 178 gastric cancers on tissue microarrays (TMA), we examined the COX-2/E-cadherin relationship.Results: Down-regulation of COX-2 by celecoxib led to up-regulation of E-cadherin mRNA and protein levels in conventional gastric cancer cell lines, whereas expression was down regulated in the early-onset gastric cancer (EOGC) cell line. Immunohistochemistry on TMAs of 178 gastric cancers showed no correlation between COX-2 and E-cadherin expression in the conventional or early gastric cancer groups.Conclusions: The results suggest that COX-2 has an impact on transcriptional regulation of E-cadherin in gastric cancer and our findings further highlight the intriguing nature of EOGCs which appear to have a molecular phenotype distinct from conventional gastric cancer. In addition, our findings also suggest that reduction of COX-2 using nonsteroidal anti-inflammatory drugs in gastric cancer chemoprevention may only be relevant for older patients.

Cyclooxygenase-2 mediated regulation of E-cadherin occurs in conventional but not early-onset gastric cancer cell lines.

Background: COX-2 and E-cadherin, involved in invasion and metastasis, are molecules critical for gastric carcinogenesis. A relationship between them is documented in non-small cell lung and prostate cancer. We present novel evidence of a relationship between COX-2 and E-cadherin expression in gastric cancer. Methods: Using qPCR and Western blots analysis on celecoxib and PGE2 treated and untreated gastric cancer cell lines derived from tumours of the intestinal type (MKN45, MKN28, AGS3, MKN7) and immunohistochemistry of 178 gastric cancers on tissue microarrays (TMA), we examined the COX-2/E-cadherin relationship. Results: Down-regulation of COX-2 by celecoxib led to up-regulation of E-cadherin mRNA and protein levels in conventional gastric cancer cell lines, whereas expression was down regulated in the early-onset gastric cancer (EOGC) cell line. Immunohistochemistry on TMAs of 178 gastric cancers showed no correlation between COX-2 and E-cadherin expression in the conventional or early gastric cancer groups. Conclusions: The results suggest that COX-2 has an impact on transcriptional regulation of E-cadherin in gastric cancer and our findings further highlight the intriguing nature of EOGCs which appear to have a molecular phenotype distinct from conventional gastric cancer. In addition, our findings also suggest that reduction of COX-2 using nonsteroidal anti-inflammatory drugs in gastric cancer chemoprevention may only be relevant for older patients.

IL-1B −31T&gt;C promoter polymorphism is associated with gastric stump cancer but not with early onset or conventional gastric cancers

It has been reported that interleukin-1beta (IL-1B) genes play a crucial role in the genetic predisposition to gastric cancer although there is no information about their role in different subtypes of gastric cancer. We performed single nucleotide polymorphism analysis of IL-1B in 241 gastric cancers including early onset gastric cancers (EOGC), conventional gastric cancers, and gastric stump cancers (GSCs) as well as 100 control patients, using real-time polymerase chain reaction and sequence analysis. The C allele was present in 60% of EOGCs, 59% of conventional gastric cancers, and 90% of GSCs, compared to 62% in the control group. Interestingly, there was no difference between early onset and conventional gastric cancer with respect to the IL-1B -31T>C polymorphism distribution. A statistically significant difference in the presence of the C allele compared to the control group was found in patients with gastric stump cancer (p = 0.008) with the T allele conferring protection against gastric stump cancer. In summary, we have shown that the IL-1B -31C allele promoter polymorphism is significantly associated with gastric stump cancer compared to the control group. Although several molecular differences have been identified between conventional gastric cancer and early onset gastric cancer, the IL-1B -31 allele distribution is similar between these two groups.

The COX-2 promoter polymorphism –765 G>C is associated with early-onset, conventional and stump gastric cancers

COX-2 overexpression is known to be an important mechanism in gastric carcinogenesis. Previously we have found that early-onset gastric cancer has a unique COX-2 low-expressing phenotype that differs significantly from that of the frequent overexpression seen in conventional gastric cancers. To investigate whether the COX-2 –765 G>C promoter polymorphism (known to lead to a reduction of COX-2 promoter activity in the colon) may explain this difference in expression, we carried out single-nucleotide polymorphism (SNP) analysis of 241 gastric cancers, including early-onset gastric cancer, conventional gastric cancers and gastric stump cancers, as well as in 100 control patients, using real-time PCR and sequence analysis, and correlated these findings with COX-2 expression using immunohistochemistry. We found that the C allele was present in 30% of early-onset gastric cancers, 24% of conventional gastric cancer, 23% of stump cancers, in contrast to 41% in the control group. There was a statistically significant difference in the presence of the C allele in patients with gastric cancer compared with the control group (P=0.007), with the C allele being associated with protection against gastric cancer. However, there was no significant difference between the early-onset, conventional and stump gastric cancer groups. Interestingly, there was no correlation between the presence of the C allele and a difference in COX-2 expression. In summary, we show that the COX-2 –765 G allele promoter polymorphism is significantly associated with gastric cancer when compared with the normal control group, but does not appear to be related directly to COX-2 expression pattern in gastric cancer. Although early-onset gastric cancers appear to have a unique COX-2 expression pattern when compared with conventional gastric cancer, the exact mechanism by which this occurs is yet to be elucidated.

Cyclin E low molecular weight isoforms occur commonly in early-onset gastric cancer and independently predict survival

Background:Post-translational cleavage of full-length cyclin E from the N-terminus can produce low molecular weight (LMW) isoforms of cyclin E containing the C-terminus only.Aim:To assess their presence in early-onset gastric cancer...

Initial findings from the Memorial Sloan-Kettering Early Onset and Familial Gastric Cancer Registry (EOFGCR)

4619 Background: Hereditary Diffuse Gastric Cancer(HDGC) is an autosomal dominant cancer susceptibility syndrome defined as having 2 or more diffuse GC(one of which diagnosed before the age of 50) or 3 or more diffuse GC in 1st or 2nd degree relatives. A germline mutation in E-Cadherin(CDH1) is found in 20–30% of HDGC families. HDGC is responsible for 30% of all hereditable GC. The genetic cause for the remaining 70% of hereditable GC is unknown. We created a registry for early onset and familial gastric cancer to capture epidemiologic and family history data matched with DNA and tissue to characterize various phenotypic and risk factor profiles and their associations with HDGC and other non-HDGC hereditable GC. Methods: Patients with a family history(patients with one first degree relative or 2 second degree relatives with GC) or who developed GC at an early age(age &lt; 50) were eligible for registry participation. Participants complete a GC risk factor questionnaire, family history, provide blood and tissue for repository, and meet with a genetics counselor to consider germline CDH1 mutation testing. Results: 57 patients have enrolled since January 2006: 36 patients with early onset, 21 with familial GC. Eleven patients have a family history meeting HDGC criteria, two with known CDH1 mutations. Three of the 11 HDGC families are from Ecuador. GC risk factor questionnaires are available from 46 patients(81%), see table . Although no novel CDH1 mutations were found in 13 fully sequenced patients, 4 patients(31%) were found to have uncommon genotypes, including two with early onset of disease diagnosis (ages 22 and 34) with multiple variants in CDH1. Conclusions: HDGC patients tend to have more high risk features including smoking history, use of salt, and H. pylori infection. We have identified a cluster of patients with HDGC of Ecuadorian descent. Genetic variation in CDH1 suggests that novel haplotypes may be associated early onset GC risk.(Supported by the DeGregorio Family Foundation) [Table: see text] No significant financial relationships to disclose.

Early Onset Gastric Cancer: On the Road to Unraveling Gastric Carcinogenesis

Gastric cancer is thought to result from a combination of environmental factors and the accumulation of specific genetic alterations due to increasing genetic instability, and consequently affects mainly older patients. Less than 10% of patients present with the disease before 45 years of age (early onset gastric carcinoma) and these patients are believed to develop gastric carcinomas with a molecular genetic profile differing from that of sporadic carcinomas occurring at a later age. In young patients, the role of genetics is presumably greater than in older patients, with less of an impact from environmental carcinogens. As a result, hereditary gastric cancers and early onset gastric cancers can provide vital information about molecular genetic pathways in sporadic cancers and may aid in the unraveling of gastric carcinogenesis. This review focuses on the molecular genetics of gastric cancer and also focuses on early onset gastric cancers as well as familial gastric cancers such as hereditary diffuse gastric cancer. An overview of the various pathways of importance in gastric cancer, as discovered through in-vitro, primary cancer and mouse model studies, is presented and the clinical importance of CDH1 mutations is discussed.

Early-onset gastric cancers have a different molecular expression profile than conventional gastric cancers

Many studies examine the molecular genetics of gastric cancer, but few look at young patients in particular and there is no comparison of molecular expression between early-onset gastric cancer (≤45 years old) and conventional gastric cancers. Expression of cycloxygenase-2 (COX-2) is elevated in gastric adenocarcinomas compared to non-neoplastic mucosa, and in light of studies showing reduced risk of gastric cancer in nonsteroidal anti-inflammatory drug users, we have chosen to investigate the expression of COX-2 and related molecules in 113 early-onset gastric cancers and compare it with 91 conventional gastric cancers, using tissue microarrays. These markers include molecules known to be important in conventional gastric carcinogenesis, such as E-Cadherin, p53, COX-2, Trefoil Factor-1 (TFF1), β-catenin, p16 and c-myc; as well as molecules not yet described as being important in gastric cancer, such as the transcription factor c-jun, the COX-2 mRNA stabilizer HuR, and C/EBP-β, a transcription factor for COX-2. All markers showed a statistically significant difference between early-onset gastric cancers and conventional gastric cancers, using a χ2 test. In particular, early-onset gastric cancers displayed a COX-2 Low, TFF1-expressing phenotype, whereas COX-2 overexpression and loss of TFF1 was found in conventional cancers, and this difference between early-onset gastric cancers and conventional cancers remained statistically significant when adjusted for location and histology (P<0.0001 and P=0.002 respectively). We found that COX-2 overexpression correlates significantly with loss of TFF1 (P=0.001), overexpression of C/EBP-β (P<0.001) and cytoplasmic HuR (P=0.016). COX-2 was significantly associated with p53 positivity (P=0.003). Abnormalities in E-Cadherin correlated significantly with diffuse phenotype, whereas high expression of COX-2, loss of TFF1 and overexpression of C/EBP-β correlated with the intestinal phenotype. Our results provide further evidence that early-onset gastric cancer exhibits a distinctive expression profile that may have practical implications.

Tumor Microsatellite Instability in Early Onset Gastric Cancer

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset (<or=50 yrs) gastric cancer. We identified 211 cases of early onset gastric cancer in Central-East Ontario from 1989 to 1993, with archival material available for 139 cases. Testing included a six-mononucleotide marker panel and a three-MMR immunohistochemical panel. Overall, 30% (41 of 139) of GC were MSI+, with allelic shifts at one to eight markers. An unexpected discordance between the BAT-25, BAT-26, and BAT-40 markers was observed in the MSI+ cases. Six cases showing multiple loci instability (>or=3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P=0.04) and Lauren histotype (P=0.006) and tumor grade (P=0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.

Characterization of a Recurrent Germ Line Mutation of the E-Cadherin Gene: Implications for Genetic Testing and Clinical Management

To identify germ line CDH1 mutations in hereditary diffuse gastric cancer (HDGC) families and develop guidelines for management of at risk individuals. We ascertained 31 HDGC previously unreported families, including 10 isolated early-onset diffuse gastric cancer (DGC) cases. Screening for CDH1 germ line mutations was done by denaturing high-performance liquid chromatography and automated DNA sequencing. We identified eight inactivating and one missense CDH1 germ line mutation. The missense mutation conferred in vitro loss of protein function. Two families had the previously described 1003C>T nonsense mutation. Haplotype analysis revealed this to be a recurrent and not a founder mutation. Thirty-six percent (5 of 14) of the families with a documented DGC diagnosed before the age of 50 and other cases of gastric cancer carried CDH1 germ line mutations. Two of 10 isolated cases of DGC in individuals ages <35 years harbored CDH1 germ line mutations. One mutation positive family was ascertained through a family history of lobular breast cancer (LBC) and another through an individual with both DGC and LBC. Occult DGC was identified in five of six prophylactic gastrectomies done on asymptomatic, endoscopically negative 1003C>T mutation carriers. In addition to families with a strong history of early-onset DGC, CDH1 mutation screening should be offered to isolated cases of DGC in individuals ages <35 years and for families with multiple cases of LBC, with any history of DGC or unspecified GI malignancies. Prophylactic gastrectomy is potentially a lifesaving procedure and clinical breast screening is recommended for asymptomatic mutation carriers.