Genetic alterations in gastric cancers from British patients

Systematic Review and Meta-analysis of TP53, HER2/ERBB2, KRAS, APC, and PIK3CA Genes Expression Pattern in Gastric Cancer

Background: With a global prevalence of about 10%, gastric cancer is among the most prevalent cancers. Currently, there has been an ongoing trend toward investigating genetic disruptions in different cancers because they can be used as a target-specific therapy. We aimed to systemically review some gene expression patterns in gastric cancer. Methods: The current systematic review was designed and executed in 2020. Scopus, PubMed, Cochrane Library, Google Scholar, web of knowledge, and Science Direct were searched for relevant studies. A manual search of articles (hand searching), reference exploring, checking for grey literature, and seeking expert opinion were also done. Results: In this review, 65 studies were included, and the expression pattern of HER2/ ERBB2, ER1/Erb1/EGFR, PIK3CA, APC, KRAS, ARID1A, TP53, FGFR2 and MET was investigated. TP53, APC, KRAS, and PIK3CA mutation cumulative frequency were 24.8 (I²=95.05, Q value=525.53, df=26, P<0.001), 7.2 (I²=89.79, Q value=48.99, df=5, P<0.001), 7.8 (I²=93.60, Q value=140.71, df=9, P=0.001) and 8.6 (I²=80.78, Q value=525.53, df=9, P<0.001) percent, respectively. Overexpression was investigated for HER1/ Erb1/EGFR, PIK3CA, APC, KRAS, ARID1A, TP53, CCND1, FGFR2, MET and MYC. The frequency of TP53 and HER2/ERBB2 were 43.1 (I²=84.06, Q value=58.09, df=9, P<0.001) and 20.8 (I²=93.61, Q value=234.89, df=15, P<0.001) percent, respectively. Conclusion: More research is encouraged to investigate the genes for which we could not perform a meta-analysis.

Polymorphism of DNA repair genes in breast cancer

Aim

The aim of the study was to determine the relationship between single nucleotide polymorphisms (SNPs) of DNA repair genes and modulation of the risk of breast cancer. The following SNPs were analysed: XRCC1-Arg399Gln (rs25487), hMSH2-Gly322Asp (rs4987188), XRCC2-Arg188His (rs3218536), XPD- Lys751Gln (rs13181), RAD51--4719A/T (rs2619679) and RAD51--4601A/G (rs5030789).

Material and Methods

The study included n = 600 patients: 300 with breast cancer and 300 healthy controls. The HRM (High-Resolution Melter) technique was applied for polymorphism analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each genotype and allele.

Results

Statistically significant correlations were identified between four single nucleotide polymorphisms and the breast cancer risk: XRCC1-Arg399Gln, hMSH2-Gly322Asp, XPD- Lys751Gln and RAD51--4719A/T. Allele XRCC1-Gln (OR 6.37; 95% CI 4.86-8.35, p < .0001), hMSH2-Asp (OR 4.41; 95% CI 3.43-5.67, p < .0001), XPD -Gln (OR 2.56; 95% CI 2.02-3.25, p < .0001) and RAD51-T genes (OR 1.44; 95% CI 1.15-1.80, p = 0.002) strongly correlated with breast carcinoma. No relationship was observed between the studied polymorphisms and the cancer progression grade according to Scarf-Bloom-Richardson classification.

Conclusions

The results implies that polymorphisms of DNA repair genes may be associated with breast cancer occurrence.

Role of peptidylarginine deiminase type 4 in gastric cancer

Peptidylarginine deiminase type 4 (PADI4) post-translationally converts peptidylarginine to citrulline, appearing to be overexpressed in numerous carcinomas. The current study aimed to investigate the expression of PADI4 in gastric cancer tissues and its effect on the biological activities of SGC-7901 and AGS tumor cell lines. The expression of PADI4 was determined in gastric cancer and normal gastric mucosa tissues using western blot analysis and reverse transcription-quantitative polymerase chain reaction. Gastric cancer cell lines were divided into the following groups: Mock group (subjected to transfection reagent); negative group [subjected to small interfering RNA (siRNA) transfection]; PADI4 siRNA group (subjected to PADI4 siRNA transfection); 5-fluorouracil (5-Fu) group (subjected to 5-Fu); and 5-Fu + siRNA transfection group (subjected to 5-Fu and PADI4 siRNA transfection). The effects of silencing PADI4 with the above measures on the proliferation and invasion of SGC-7901 and AGS cells were determined by MTT and Transwell chamber assays. In addition, propidium iodide staining was performed to detect the effects of PADI4 on the cell cycle. A significant increase in the expression of PADI4 mRNA in gastric cancer tissue compared with normal mucosa tissue was identified (P<0.05). The proliferation and invasion of SGC-7901 and AGS cells were significantly decreased in the PADI4 siRNA group. Furthermore, flow cytometry DNA analysis revealed that silencing PADI4 resulted in significant S phase arrest and marked decrease of cells in the G2/M phase. PADI4 siRNA coupled with 5-Fu significantly enhanced its inhibitory effect on the proliferation of gastric cancer cells. In conclusion, PADI4 demonstrated high expression in gastric cancer and served an important role in the biological activities of gastric cancer cells involving cell proliferation, invasion and cell cycle. As a result, PADI4 may be a valid cancer susceptibility gene and potential target for cancer therapy.

Gly322Asp and Asn127Ser single nucleotide polymorphisms (SNPs) of hMSH2 mismatch repair gene and the risk of triple-negative breast cancer in Polish women

Triple-negative breast cancer (TNBC) is characterised by worse clinical outcome and poor prognosis. The alterations in the oncogenes and tumor suppressor genes as well as microsatellite instability (MSI) have been associated with breast cancer development. It is knowledge that the most common mechanism inducing MSI in many cancer is genomic rearrangements found in the hMSH2 (human MutS homolog 2) gene. In this report we genotyped two polymorphisms of hMSH2 DNA repair gene in 70 TNBC patients and 70 age-matched cancer-free women using RFLP–PCR. The following polymorphisms were studied: an A/G transition at 127 positions producing an Asn/Ser substitution at codon 127 (the Asn127Ser polymorphism, rs17217772) and a G/A transition at 1032 position resulting in a Gly/Asp change at codon 322 (the Gly322Asp polymorphism, rs4987188). We found an association between the hMSH2 Asp/Asp and Gly/Asp genotypes and TNBC occurence. Variant Asp allele of hMSH2 decreased cancer risk [odds ratio (OR) 0.11; 95 % confidence interval (CI) 0.05–0.21]. The risk of TNBC in the carriers of the Gly322Gly–Asn127Ser combined genotype was increased (OR 3.71; 95 % CI 1.36–10.10). However the risk of TNBC was not alter by polymorphism Asn127Ser of the hMSH2 gene. The Gly322Asp polymorphism of the hMSH2 gene may be linked with TNBC occurrence in Polish women.

Role of p53 in the progression of gastric cancer

Intestinal metaplasia (IM) is a premalignant lesion associated with gastric cancer (GC) but is poorly described in terms of molecular changes. Here, we explored the role of TP53, a commonly mutated gene in GC, to determine if p53 protein expression and/or the presence of somatic mutations in TP53 can be used as a predictive marker for patients at risk of progressing to GC from IM. Immunohistochemistry and high resolution melting were used to determine p53 protein expression and TP53 mutation status respectively in normal gastric mucosa, IM without concurrent GC (IM-GC), IM with concurrent GC (IM+GC) and GC. This comparative study revealed an incremental increase in p53 expression levels with progression of disease from normal mucosa, via an IM intermediate to GC. TP53 mutations however, were not detected in IM but occurred frequently in GC. Further, we identified increased protein expression of Mdm2/x, both powerful regulators of p53, in 100% of the IM+GC cohort with these samples also exhibiting high levels of wild-type p53 protein. Our data suggests that TP53 mutations occur late in gastric carcinogenesis contributing to the final transition to cancer. We also demonstrated involvement of Mdmx in GC.

The significance of NTR1 expression and its correlation with β-catenin and EGFR in gastric cancer

BACKGROUND

Several reports indicate the high-affinity receptor of NT (neurotensin), NTR1 (neurotensin receptor 1), in numerous detrimental functions linked to neoplastic progression of several cancer types. Recently, it has also been shown that NTR1 gene is a target of the Wnt/APC oncogenic pathways connected with the β-catenin/Tcf transcriptional complex and NT can stimulate cancer proliferation in an EGFR-dependent mechanism. In this study, we explored NTR1, β-catenin and EGFR expression in gastric cancer. The possible associations of NTR1 expression with clinicopathological factors, prognosis, β-catenin and EGFR were analyzed.

METHODS

NTR1, β-catenin and EGFR expression in gastric cancer tissues and the adjacent normal tissues of 210 cases was detected by Immunohistochemistry. The possible associations of NTR1 expression with clinicopathological data, prognosis, β-catenin and EGFR were analyzed.

RESULTS

1. NTR1 expression in tumor tissues was significantly higher than that in adjacent normal tissues (P <0 .01). 2. Its expression was positively correlated with pathological grade, T stage, N stage and TNM stage and was not correlated with sex, age, tumor size and Lauren's classification. 3. A co-expression of NTR1 and nuclear β-catenin was in 53 (25.2 %) of cases and NTR1 expression was positively correlated with β-catenin nuclear translocation. NTR1 expression was not correlated with EGFR expression, but at a critical value (P = 0.05). 4. By log-rank test, higher expression of NTR1, higher pathological grade, diffusion Lauren's classification and advanced TNM stage showed worse prognosis (P <0 .05). Age, sex, tumor size, β-catenin and EGFR had no prognostic significance. Multivariate Cox analysis showed that NTR1 expression and TNM clinical stage (P <0 .05) were the independent prognostic factors for patients with GC.

CONCLUSION

By immunohistochemistry, we found that a high expression of NTR1 in GC specimens, which showed a bad prognosis, besides, NTR1 expression was related to invasion and migration of GC. These findings provide new and important information on the progression of GC. This study indicated that NTR1 may play an important role in tumor progression of GC and have its potential to be a predictive biomarker or a therapeutic molecular target in GC. The interaction between NTR1 and β-catenin may participate in the development of GC. However, the relationship between NTR1 and EGFR needs to be further investigated.

Aberrant expression of the autocrine motility factor receptor correlates with poor prognosis and promotes metastasis in gastric carcinoma

AMFR, autocrine motility factor receptor, also called gp78, is a cell surface cytokine receptor which has a dual role as an E3 ubiquitin ligase in endoplasmic reticulum-associated degradation. AMFR expression is associated with tumor malignancy. We here investigated the clinical significance of AMFR and its role in metastasis and prognosis in gastric cancer. Expression of AMFR, E-cadherin and N-cadherin in cancer tissues and matched adjacent normal tissues from 122 gastric cancer (GC) patients undergoing surgical resection was assessed by immunohistochemistry. Levels of these molecules in 17 cases selected randomly were also analysed by Western blotting. AMFR expression was significantly increased in gastric cancer tissues, and associated with invasion depth and lymph node metastasis. Kaplan-Meier analysis showed AMFR expression correlated with poor overall survival and an increased risk of recurrence in the GC cases. Cox regression analysis suggested AMFR to be an independent predictor for overall and recurrence-free survival. E-cadherin expression was decreased in gastric cancer tissues; conversely, N-cadherin was increased. Expression of AMFR negatively correlated with E-cadherin expression, whereas N-cadherin expression showed a significant positive correlation with AMFR expression. AMFR might be involved in the regulation of epithelial-mesenchymal transition, with aberrant expression correlating with a poor prognosis and promoting invasion and metastasis in GCs.

Altered expression of Krüppel-like factor 4 and β-catenin in human gastric cancer

The effects of the interaction between KLF4 and β-catenin may be significant in human carcinogenesis and tumor development. This study aimed to determine whether the expression of KLF4 and β-catenin in gastric cancer tissues is associated with clinicopathological characteristics. Western blot analysis and immunohistochemistry were performed to detect KLF4 and β-catenin expression in tumor and corresponding non-cancerous tissues from 49 patients. The data revealed that KLF4 expression was significantly reduced in gastric cancer tissues compared with normal tissues. By contrast, the expression of the β-catenin protein was significantly increased in all tumor tissues, but was not expressed in distant normal mucosae. The altered expression of the KLF4 and β-catenin proteins was associated with advanced tumor stage and gastric cancer. In addition, the expression of the KLF4 and β-catenin proteins was inversely associated in moderately differentiated human gastric cancers. This study showed that β-catenin expression is significantly increased and KLF4 protein expression is markedly decreased in gastric cancer tissues, thus showing that the expression of KLF4 is inversely correlated with that of β-catenin in gastric cancer. The altered expression of the two proteins is associated with advanced tumor stage in gastric cancer.

Genetic mutations of p53 and k-ras in gastric carcinoma patients from Hunan, China

This case-control study investigated the mutations in p53 and k-ras genes of 123 gastric carcinoma patients and 129 normal individuals from Hunan, China. By isolating genomic DNA from peripheral blood and employing polymerase chain reaction-single strand conformation polymorphism and DNA sequencing, the mutations of p53 exons-5, 6, 7, and 8 and k-ras were detected. The overall mutation frequency of p53 was 29.3%, and mutation was found in all four exons studied. The point mutations were predominant and among them, G:C→A:T was the highest (41.7%), followed by A:T→G:C (25%), G:C→C:G (11.1%), G:C→T:A (8.3%), and A:T→T:A (2.8%). The frameshift mutation was 11.1%. Mutations were detected in codons-131, 132, 133, 135, 149, 151, 162, 167, 173, 174, and 175 of exon 5, codons-193, 197, 213, and 215 of exon 6, codons-245, 246, 248, 249, and 270 of exon 7, and codons-271, 272, 273, and 282 of exon 8 of p53. The overall frequency of mutation in k-ras was 9.8%, mostly in codon-12 (91.7%) and in codon-13 (8.3%). There was no significant relationship between p53 and k-ras gene mutation in gastric carcinoma patients. Also, the relationships between p53 mutation and age, sex, smoking or drinking, and tumor metastasis were not significant. However, the patients with high/high-middle differentiated gastric carcinoma had a higher association with of p53 mutations. This study identified some novel p53 mutations in gastric cancer and showed mutation pattern and frequency of p53 and k-ras in the population of the central southern region of China.

Expression of the PUMA gene in gastric cancer tissue and cell lines

AIM: To investigate the expression of four mRNA isoforms of the p53 up-regulated modulator of apoptosis (PUMA) gene in gastric cancer tissue and cell lines.

METHODS: The open reading frames of four mRNA isoforms of the PUMA gene were analyzed by bioinformatics method. The expression of these four mRNA isoforms in gastric cancer tissue, normal tissue and two gastric cancer cell lines were detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: PUMA-α and -β were positively expressed in normal tissue, but hardly detected in cancer tissue (t = 9.492 and 15.875, respectively; both P < 0.05). PUMA-γ and -δ were expressed both in cancer tissue and normal tissue, and their expression levels were significantly higher in tumor-adjacent tissue than in cancer tissue (t = 4.823 and 4.056, respectively; both P < 0.05). The expression of the four PUMA isoforms was detected in the two gastric cancer cell lines. The expression level of PUMA-β was significantly higher in low-differentiated BGC-823 cells than in moderately differentiated SGC-7901 cells (t = 8.710, P < 0.05).

CONCLUSION: The expression of PUMA isoforms is down-regulated in gastric cancer tissue and may be negatively correlated with the pathogenesis of gastric cancer. The expression of PUMA-β may be involved in gastric cancer cell differentiation.

DNA copy number changes in gastric adenocarcinomas: high resolution-comparative genomic hybridization study in Turkey

BACKGROUND AND AIMS

Multiple genetic alterations are responsible for development and progression of gastric cancer which is one of the leading causes of cancer-related deaths worldwide. The aim of this study was to identify the genomic imbalances of gains and/or losses in gastric adenocarcinomas from Turkish patients and to investigate their association with development and progression of this type of cancer.

METHODS

Forty three patients with gastric adenocarcinoma were enrolled in this study and genomic imbalances were analyzed by high-resolution-comparative genomic hybridization (HR-CGH).

RESULTS

In 36/43 cases (84%) of gastric adenocarcinomas, genomic imbalances have involved all chromosomes in various combinations. The mean number of gains was 3.95+/-4.19 and the most common gains observed were 7q (35%), 8q (35%), 7p (28%), 1q (26%), 13q (26%), and 20q (21%). The calculated mean number of losses was 3.65+/-3.55 and the most common losses were found on arms 18q (26%), 5q (21%), and 14q (21%). High-level amplifications involved chromosomes 1, 7, 8, 9, 13, and 16. No significant differences in chromosomal imbalances were observed in different tumor stages, tumor grades, and Helicobacter pylori infection status groups. The most striking result in this study was the involvement of the 13q gains with increased lymph node metastasis (p=0.046). Late-stage tumors displayed a somewhat significantly higher number of losses than early-stage tumors (p=0.053).

CONCLUSIONS

A series of gains, losses and amplifications concerned with gastric adenocarcinoma identified in this study are presented in detail. In particular, 13q21-q32 was prominent because it has been linked to increased lymph node metastasis.

Cytogenetic and molecular aspects of gastric cancer: clinical implications

Gastric cancer is of major importance world-wide being the second most common cause of cancer-related death in the world. According to Lauren's histological classification gastric cancer is divided in two groups, the better differentiated intestinal carcinomas and the poorly differentiated diffuse-type cancers. The genetic changes underlying the initiation and progression of gastric cancer are not well defined. Gastric carcinogenesis is a multistep process involving a number of genetic and epigenetic factors. Although it has been proposed that different genetic pathways exist for differentiated and undifferentiated carcinomas, the two histological subtypes of gastric cancer share some common genetic alterations. Currently, tumor histology and pathologic stage are the major prognostic variables used in the clinical practice for gastric cancer patients. However, it is known that tumors with similar morphology may differ in biological aggressiveness, prognosis and response to treatment. Molecular genetic analysis of gastric cancer revealed a number of associations of certain genetic changes with pathological features, tumor biological behavior and prognosis of gastric cancer patients, suggesting that these genetic abnormalities might play an important role in gastric tumorigenesis. Increasing evidence suggests that the molecular genetic changes could be helpful in the clinical setting, contributing to prognosis and management of patients. Regarding epigenetic events in gastric tumorigenesis, a number of methylating markers have been proposed for risk assessment, prognostic evaluation and as therapeutic targets. However, further research is required in order to systematically investigate the genetic changes in gastric cancer estimating also their usefulness in the clinical practice. A good understanding of the genetic changes underlying gastric carcinogenesis may provide new perspectives for prognosis and screening of high risk individuals. Some of the genetic alterations could definitely improve tumor classification and management of gastric cancer patients. Also, based on molecular data identified in gastric cancer novel therapeutics might help to improve the treatment of this disease.

Genetic changes in Slovenian patients with gastric adenocarcinoma evaluated in terms of microsatellite DNA

OBJECTIVES

Adenocarcinoma of the stomach is a relatively frequent malignant disease in Slovenia. We investigated the frequency of microsatellite instability (MSI) and loss of heterozygosity (LOH) in gastric carcinomas from the Slovenian population to determine their prognostic significance.

METHODS

We evaluated MSI of mismatch repair associated loci and LOH on loci associated with following tumour suppressors: APC, nm23, Rb and p53. Results of the multiplex-PCR amplifications were correlated with clinicopathological factors for 73 patients.

RESULTS

LOH was found in 52% of informative samples (20.5% LOH-H; 31.5% LOH-L). We found correlation of MSI with low-frequency LOH (LOH-L) in 11% of cases and with high-frequency LOH (LOH-H) tumours in 4% of cases. LOH-H and high-frequency MSI (MSI-H) were not associated. LOH was found in APC 36%, p53 33%, Rb 24% and nm23 33% of informative samples, whereas MSI was found in 30% of samples (12% MSI-H; 18% MSI-L). LOH-H status was associated with ulceration (P=0.029). LOH-N status was associated with diagnosis at higher TNM status (0.074) and infiltrative growth (P=0.006). Interestingly, in 6% of samples we found MSI on LOH loci as well. MSI-H was associated with higher age at diagnosis (r=0.24; P=0.04), antral location (r=0.252; P=0.04), intestinal type (P=0.044), expansive growth (P=0.001), tubular type (0.014), better differentiation (P=0.01), less nodal involvement (0.006) and better survival (P=0.022). The poorest prognosis was found in patients with both low-frequency MSI (MSI-L) and low-frequency LOH (LOH-L) tumours.

CONCLUSION

The experimental design presented in the study may be of potential value for clinicians: at least five relevant markers for both MSI and LOH analysis may be needed to evaluate a gastric cancer (GC) patient's clinical status.

p75 neurotrophin receptor suppresses the proliferation of human gastric cancer cells

Identifying an effective therapeutic target is pivotal in the treatment of gastric cancer. In this study, we investigated the expression of p75 neurotrophin receptor (p75NTR) in gastric cancer and the impact of its alteration on tumor growth. p75NTR expression was absent or significantly decreased in 212 cases of gastric cancers compared with the normal gastric mucosa (P < .05). Moreover, p75NTR expression was also lost or significantly decreased in various human gastric cancer cell lines. p75NTR inhibited in vitro growth activities and caused dramatic attenuation of tumor growth in animal models by induction of cell cycle arrest. Upregulation of p75NTR led to downregulation of cyclin A, cyclin D1, cyclin E, cyclin-dependent kinase 2, p-Rb, and PCNA, but to upregulation of Rb and p27 expressions. Conversely, downregulating p75NTR with specific siRNA yielded inverse results. The rescue of tumor cells from cell cycle progression by a death domain-deleted dominant-negative antagonist of p75NTR (Deltap75NTR) showed that the death domain transduced antiproliferative activity in a ligand-independent manner and further demonstrated the inhibitive effect of p75NTR on growth in gastric cancer. Therefore, we provided evidence that p75NTR was a potential tumor suppressor and may be used as a therapeutic target for gastric cancer.

RUNX3 inhibits the expression of vascular endothelial growth factor and reduces the angiogenesis, growth, and metastasis of human gastric cancer

PURPOSE

Recent studies indicated that RUNX3 exhibits potent antitumor activity. However, the underlying molecular mechanisms of this activity remain unclear. In the present study, we used a gastric cancer model to determine the effect of RUNX3 expression on tumor angiogenesis.

EXPERIMENTAL DESIGN

The effects of increased RUNX3 expression on vascular endothelial growth factor (VEGF) expression in and angiogenic potential of human gastric cancer cells were determined in vitro and in animal models. RUNX3 and VEGF expression was determined in 120 human gastric cancer specimens and their relationship was analyzed.

RESULTS

RUNX3 gene transfer suppressed VEGF expression in human gastric cancer cells. Down-regulation of VEGF expression correlated with a significantly impaired angiogenic potential of human gastric cancer cells. Furthermore, RUNX3 restoration inhibited tumor growth and metastasis in animal models, which was consistent with inhibition of angiogenesis as determined by evaluating VEGF expression and tumor microvessel formation. In gastric cancer specimens, loss or decrease in RUNX3 expression inversely associated with increased VEGF expression and elevated microvessel formation.

CONCLUSIONS

Our clinical and experimental data provide a novel molecular mechanism for the antitumor activity of RUNX3 and may help design effective therapy targeting RUNX3 pathway to control gastric cancer growth and metastasis.

Polymorphisms of the DNA mismatch repair gene HMSH2 in breast cancer occurence and progression

The response of the cell to DNA damage and its ability to maintain genomic stability by DNA repair are crucial in preventing cancer initiation and progression. Therefore, polymorphism of DNA repair genes may affect the process of carcinogenesis. The importance of genetic variability of the components of mismatch repair (MMR) genes is well documented in colorectal cancer, but little is known about its role in breast cancer. hMSH2 is one of the crucial proteins of MMR. We performed a case-control study to test the association between two polymorphisms in the hMSH2 gene: an A --> G transition at 127 position producing an Asn --> Ser substitution at codon 127 (the Asn127Ser polymorphism) and a G --> A transition at 1032 position resulting in a Gly --> Asp change at codon 322 (the Gly322Asp polymorphism) and breast cancer risk and cancer progression. Genotypes were determined in DNA from peripheral blood lymphocytes of 150 breast cancer patients and 150 age-matched women (controls) by restriction fragment length polymorphism and allele-specific PCR. We did not observe any correlation between studied polymorphisms and breast cancer progression evaluated by node-metastasis, tumor size and Bloom-Richardson grading. A strong association between breast cancer occurrence and the Gly/Gly phenotype of the Gly322Asp polymorphism (odds ratio 8.39; 95% confidence interval 1.44-48.8) was found. Therefore, MMR may play a role in the breast carcinogenesis and the Gly322Asp polymorphism of the hMSH2 gene may be considered as a potential marker in breast cancer.

Emerging role of KLF4 in human gastrointestinal cancer

Recent analyses revealed that Krüppel-like factors (KLFs) play important roles in both normal development and carcinogenesis. Of the 16 known KLFs, KLF4 has been shown to be involved in the regulation of proliferation, differentiation and tumorigenesis of gastrointestinal tract epithelium. Clinical, experimental and mechanistic findings indicate that KLF4 is a bona fide tumor suppressor for both gastric and colorectal cancers. In this review, we summarize how this growing area of research has formed and the challenging new frontiers for better understanding of the oncogenic potential of the KLFs.

Loss of RUNX3 expression significantly affects the clinical outcome of gastric cancer patients and its restoration causes drastic suppression of tumor growth and metastasis

Identification of precise prognostic marker and effective therapeutic target is pivotal in the treatment of gastric cancer. In the present study, we determined the level of RUNX3 expression in gastric cancer cells and gastric cancer specimens and the impact of its alteration on cancer biology and clinical outcome. There was a loss or substantial decrease of RUNX3 protein expression in 86 cases of gastric tumors as compared with that in normal gastric mucosa (P < 0.0001), which was significantly associated with inferior survival duration (P = 0.0005). In a Cox proportional hazards model, RUNX3 expression independently predicted better survival (P = 0.036). Moreover, various human gastric cancer cell lines also exhibited loss or drastic decrease of RUNX3 expression. Enforced restoration of RUNX3 expression led to down-regulation of cyclin D1 but to up-regulation of p27, caspase 3, 7, and 8 expression, cell cycle arrest, and apoptosis in vitro, and dramatic attenuation of tumor growth and abrogation of metastasis in animal models. Therefore, we offered both clinical and mechanistic evidence that RUNX3 was an independent prognostic factor and a potential therapeutic target for gastric cancer.

Drastic down-regulation of Krüppel-like factor 4 expression is critical in human gastric cancer development and progression

Krüppel-like factor 4 (KLF4) is highly expressed in epithelial tissues such as the gut and skin. However, the role of KLF4 in human gastric cancer development and progression is unknown. Here we show that KLF4 protein expression was decreased or lost in primary tumors and, in particular, lymph node metastases when compared with that in normal gastric mucosa. Moreover, loss of KLF4 expression in the primary tumors was significantly associated with poor survival, and also an independent prognostic marker in a multivariate analysis. Consistently, most human gastric cancer cell lines exhibited loss of or a substantial decrease in KLF4 expression at both RNA and protein levels. Enforced restoration of KLF4 expression resulted in marked cell growth inhibition in vitro and significantly attenuated tumor growth and total abrogation of metastasis in an orthotopic animal model of gastric cancer. Mechanism studies indicated that promoter hypermethylation and hemizygous deletion contributed to the down-regulation of KLF4 expression and the induction of apoptosis contributed to the antitumor activity of KLF4. Collectively, our data provide first clinical and casual evidence and potential mechanism that the alteration of KLF4 expression plays a critical role in gastric cancer development and progression.

Novel regions of chromosomal amplification at 6p21, 5p13, and 12q14 in gastric cancer identified by array comparative genomic hybridization

Gastric cancer (GC) frequently displays changes in DNA copy number, but few studies have precisely correlated specific genetic alterations with changes in gene expression. We undertook both array comparative genomic hybridization (aCGH) and expression analyses of 20 primary GCs using a cDNA microarray with more than 9,300 genes. Diverse clinical and histopathologic tumor subtypes, including signet-ring tumors and tumors at the gastroesophageal junction, were analyzed. All tumors showed changes in gene copy number, with the majority showing multiple changes. Regions of gain and loss were generally consistent with previous cytogenetic reports; however, the use of aCGH greatly increased the resolution of measured genomic change. By comparing gene expression and high-resolution measurement of gene copy number directly, we were able to identify several regions of high-level gain associated with substantially increased gene expression that have not been defined previously in GC. Novel candidate oncogenes included dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 2 (DYRK2) and protein tyrosine kinase 7 (PTK7).

Mutations in the hMLH1 gene in Slovenian patients with gastric carcinoma

Alterations of multiple oncogenes and tumor suppressor genes, together with genetic instability, are responsible for carcinogenesis in gastric cancer. The microsatellite mutator phenotype is the cause of many somatic frameshift and point mutations in non-coding repetitive sequences and in coding regions associated with cell proliferation and apoptosis. Genetic mutations in hMLH1 and transcriptional silencing of its promoter by hypermethylation lead to the inactivation of the mismatch repair system. In our study, we screened for mutations the hMLH1 gene in patients expressing the microsatellite instability genotype by using single-strand conformational polymorphism analysis and direct sequencing. Seven changes were identified; of these, three (A92P, E433Q, and K618A) were germline mutations and the other four (IVS5 453 + 79 A > G, I219V, 1039 - 7 del (T)(n), and IVS15 1668 - 19 A > G) germline polymorphisms. A92P and E433Q are novel, previously unidentified mutations. In addition, we found a rather complex distribution of mutations and polymorphisms in individual patients and in two cases also a methylated hMLH1 promoter.

TP53 in gastric cancer: mutations in the l3 loop and LSH motif DNA-binding domains of TP53 predict poor outcome

The aim of this study was to clarify whether specific p53 mutations may have biological relevance in terms of disease relapse or death in gastric carcinomas (GC). Resected specimens from a consecutive series of 62 patients with GC undergoing potentially curative surgery were prospectively studied. The mutational status of exons 5-8 of the p53 gene was investigated in 62 cases using the PCR-SSCP and sequencing. Presence of microsatellite instability (MSI) was evaluated in 56 cases by analyzing loci highly sensitive of MSI. Twenty mutations of p53 were detected in 17 of the 62 cases analyzed (27%). Ten mutations (50%) occurred in highly conserved domains. According to the p53 specific functional domains: 4/20 mutations (20%) were in the L3 loop and 3/20 (15%) in LSH motif. Eight of the 56 GC resulted MSI-H, 5 (9%) MSI-L, and 43 (77%) MSI stable (MSS). None of the 8 (14%) MSI-H GC showed p53 mutations. p53 mutations were associated with intestinal histotype. Moreover, specific mutations in functional domain (L3 and LSH), together with advanced TNM stage, node involvement, depth of invasion, diffuse histotype, proved to be significantly related to quicker relapse and to shorter overall survival. Specific mutations in p53 functional domains, rather than any mutations in this gene, may be biologically more significant in terms of patients outcome, indicating that these mutations might have biological relevance to identify subgroups of patients at higher risk of relapse or death who might benefit from a more aggressive therapeutic approach.

Alterations of APC, c-met, and p53 genes in tumor tissue and serum of patients with gastric cancers

BACKGROUND

Gastric cancer is one of the most significant causes of cancer-related death worldwide. A genetic model consisting of sequential accumulations of alterations in specific genes for gastric cancer has been proposed.

MATERIALS AND METHODS

The significance of adenomatous polyposis coli (APC) and p53 gene mutations in cancer tissues and their paired serum of 34 gastric cancer patients was investigated using polymerase chain reaction single-strand conformation polymorphism analysis (PCR-SSCP), followed by direct sequencing. c-met mRNA expression was evaluated by reverse-transcription PCR (RT-PCR). Additionally, analyses were carried out to detect the serum carcinoembryonic antigen (CEA) levels, and their correlation to these three molecular markers. Finally, serum molecular markers and their correlation to the presence of postoperative recurrence/metastasis were analyzed.

RESULTS

Of all, 32.4% of patients presented mutations in APC and p53, respectively, and 58.8% presented the overexpression in c-met, overall, at least one of these genetic alterations in 79.4% of tumor tissues. Comparison of three molecular markers showed that the individual detection rate in the serum of patients with tumors harboring the same abnormalities was 18.2, 70.0, and 36.4% for APC, c-met, and p53 genes, respectively. In general, 59.3% of serum from cancerous tissues with gene alterations was demonstrated as positive, whereas all healthy volunteers' sera remained negative. Regarding gene alterations in tumor tissues, c-met overexpression was significantly related to the tumor size (P = 0.017), depth of tumor invasion (P = 0.007), lymph-node metastasis (P < 0.001), and TNM stage (P = 0.001). In the serum, c-met overexpression was closely associated with lymph-node metastasis (P = 0.008) and TNM stage (P = 0.016). The overall positive tumor gene detection rate in the serum was prominently correlated to the serum CEA levels (P = 0.038). In addition, a significantly higher postoperative metastasis/recurrence rate in patients harboring gene mutations with serum molecular markers than those without serum molecular markers was also demonstrated (P = 0.014).

CONCLUSIONS

Our findings suggest that serum molecular markers can be detected in a substantial proportion of gastric cancer patients, and these may offer an auxiliary approach in the noninvasive detection and prognosis of gastric cancer.

No germline mutations in the histone acetyltransferase gene EP300 in BRCA1 and BRCA2 negative families with breast cancer and gastric, pancreatic, or colorectal cancer

Introduction

Mutations in BRCA1, BRCA2, ATM, TP53, CHK2 and PTEN account for many, but not all, multiple-case breast and ovarian cancer families. The histone acetyltransferase gene EP300 may function as a tumour suppressor gene because it is sometimes somatically mutated in breast, colorectal, gastric and pancreatic cancers, and is located on a region of chromosome 22 that frequently undergoes loss of heterozygosity in many cancer types. We hypothesized that germline mutations in EP300 may account for some breast cancer families that include cases of gastric, pancreatic and/or colorectal cancer.

Methods

We screened the entire coding region of EP300 for mutations in the youngest affected members of 23 non-BRCA1/BRCA2 breast cancer families with at least one confirmed case of gastric, pancreatic and/or colorectal cancer. These families were ascertained in Australia through the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer.

Results

Denaturing HPLC analysis identified a heterozygous alteration at codon 211, specifically a GGC to AGC (glycine to serine) alteration, in two individuals. This conservative amino acid change was not within any known functional domains of EP300. The frequency of the Ser211 variant did not differ significanlty between a series of 352 breast cancer patients (4.0%) and 254 control individuals (2.8%; P = 0.5).

Conclusion

The present study does not support a major role for EP300 mutations in breast and ovarian cancer families with a history of gastric, pancreatic and/or colorectal cancer.

Detection of p53 mutations in precancerous gastric tissue

Intestinal-type gastric cancer is preceded by gastritis and intestinal metaplasia. There is uncertainty regarding the stage at which genetic alterations in the p53 gene occur. Reactive oxygen species (ROS) may participate in the production of mutations and the inactivation of p53 is due to infection by the bacterium Helicobacter pylori. We have investigated whether alterations of the p53 gene can be detected in gastritis and intestinal metaplasia using the restriction site mutation assay. We also assessed the potential contribution of ROS to p53 inactivation using electron spin resonance spectroscopy (ESR) and correlated with the presence of H. pylori. In all, 35% of the gastritis samples and 45% of the intestinal metaplasia samples were found to contain mutations in exons 5–8 of the p53 gene. Electron spin resonance spectroscopy analysis showed a significant increase in free radical levels in gastritis samples compared with normal, intestinal metaplasia and cancer samples, suggesting that free radicals present in gastritis may contribute to p53 mutations. There was no significant difference in free radical levels between the H. pylori-positive and -negative groups. However, a small subpopulation of the H. pylori-negative patients had much higher levels of free radicals. This suggests a more prominent role for other factors in ROS production.

cDNA suppression subtraction library for screening down-regulated genes in gastric carcinoma

AIM: To establish cDNA suppression subtraction library with a high subtraction efficiency by counterpart normal gastric mucosa mixture mRNA subtracting gastric cancer cells mixture mRNA for screening down-regulated genes in gastric carcinoma.

METHODS: RNA of gastric cancer tissues and counterpart normal gastric mucosa were respectively isolated in five patients with gastric cancer, and their mRNA was purified. cDNA suppression subtraction library was established by counterpart normal gastric mucosa mixture mRNA (tester) subtracting gastric cancer tissues mixture mRNA (driver) of five patients with gastric carcinoma. The library plasmids were transformed into competent bacteria DH5a after ligation of the library cDNA fragments with T vectors. Library plasmids were extracted after picking colonies and shaking bacteria overnight. Its subtraction efficiency was confirmed by PCR and reverse hybridization of a nylon filter onto which the colonies of bacteria were transfered with probes of reverse transcription products cDNA of gastric cancer tissues mRNA and counterpart normal gastric mucosa mRNA labeled with α-³²P dCTP.

RESULTS: mRNA purified from total RNA of gastric cancer tissues and counterpart normal gastric mucosa in five patients with gastric carcinoma revealed a good quality. cDNA suppression subtraction library constructed for screening down-regulated genes in gastric carcinoma represented a high subtraction efficiency. 86% of differential expression in down-regulated genes between counterpart normal gastric mucosa and gastric carcinoma was confirmed.

CONCLUSION: cDNA suppression subtraction library with a high subtraction efficiency for screening down-regulated genes in gastric carcinoma is successfully established.

Prospective cohort study of comprehensive prevention to gastric cancer

AIM: To evaluate the preliminary effects of comprehensive prevention of gastric cancer in Zhuanghe County epidemiologically.

METHODS: Stratified sampling and cluster sampling were applied to define the intervention group and the control group. The prospective cohort study was used for evaluating the effect of preventing gastric cancer. The relative risk (RR) and attributable risk percent (AR%) of intervention on gastric cancer death were calculated. Potential years of life lost (PLYY) of the disease was analyzed, and the RR and AR% of PYLL were calculated. Survival analysis was applied among the screened patients.

RESULTS: In the first 4 years after intervening, the relative risk (RR) of intervention on death was 0.5059 (95%CI: 0.3462-0.7392, P < 0.05) with significance statistically. AR% of the intervention on death was 49.41%. The RR of intervention on cumulative PYLL was 0.6778 (95%CI: 0.5604-0.8198, P < 0.05) with statistic significance. AR% of the intervention on cumulative PYLL was 30.32%. The four-year survival rate of the screened patients was 0.6751 (95%CI: 0.5298-0.9047).

CONCLUSION: The initiative intervention results showed that the intervention approach used in the trial was effective, it reduced mortality and increased survival rate, and alleviated the adverse effect of gastric cancer on the health and life of screened population.

TP53 and gastric carcinoma: a review

In this article, we survey the major p53 (TP53) alterations identified in gastric carcinomas and their precursors. These include p53 expression, mutations, and loss of heterozygosity (LOH). Not only are the various abnormalities summarized, but in addition there is a survey of the literature with respect to the impact of these changes on patient prognosis and treatment response. The majority of published studies involve the immunohistochemical detection of the protein. These use different antibodies, different detection techniques, and different methods of interpretation. Therefore not surprisingly, the results of many of the studies are contradictory with one another. Overall, however, it appears that p53 alterations occur early in the development of gastric carcinoma, being present even in the nonneoplastic mucosa and they increase in frequency as one progresses along the pathway of gastric carcinoma development. p53 immunoreactivity is seen in 17%-90.7% of invasive gastric carcinomas. p53 alterations occur much more commonly in proximal lesions than in distal ones, suggesting that the molecular events leading to the development of gastric carcinoma may be very different in proximal vs. distal tumors. p53 mutations occur in 0%-77% of gastric carcinomas. The mutations are distributed widely across the gene from exons 4-11 with hot spots of mutation at codons 175, 248, 273, 282, 245, and 213. G:C>A:T transitions at CpG sites are the commonest type of mutation. At least 60% of carcinomas with mutations also exhibit p53 LOH.

Mutation analysis of APC gene in gastric cancer with microsatellite instability

AIM: To evaluate the role of APC mutation in gastric carcinogenesis and to correlate APC mutation with microsatellite instability (MSI) in gastric carcinomas.

METHODS: APC mutation was measured with multiplex PCR, denaturing gradient gel electrophoresis and DNA sequencing; and MSI was analyzed by PCR-based methods.

RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for APC mutation at exon 15 and MSI. APC mutaions were detected in 15 (22.1%) gastric cancers. Frequence of APC mutation (33.3%) in intestinal type of gastric cancer was significantly higher than that in diffuse type (13.1%, P < 0.05). On the contrary, no association was observed between APC mutation and tumor size, differentiation, depth of invasion, metastasis or clinical stages. Using five microsatellite markers, MSI in at least one locus was detected in 17 of 68 (25%) of the tumors analyzed. APC mutations were all detected in MSI-L (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51), but no mutation was found in MSI-H (≥ 2 loci, n = 8).

CONCLUSION: APC mutation is involved in carcinogenesis of intestinal type of gastric cancer and is independent of MSI phenotype but related to the LOH pathway in gastric cancer.

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 LOH at 5 loci on the long arm of chromosome 22 in sporadic colorectal cancer to identify additional loci involved in colorectal tumorigenesis.

METHODS: Five polymorphic microsatellite markers were analyzed in 83 cases of colorectal and normal DNA by PCR. 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. Comparison between LOH frequency and clinicopathological data were performed by χ² test. P < 0.05 was considered as statistically significant.

RESULTS: The average LOH frequency on chromosome 22q was 28.38%. The region between markers D22S280 and 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).8 cases showed LOH at all informative loci, suggesting that one chromosome 22q had been completely lost. On D22S274 locus, LOH frequency of rectal cancer was 50% (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 rectum 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 different 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 22q12.2-12.3 and/or 22q13.32-13.33.