Summary Background Analyses of microRNA expression profiles have shown that many microRNAs are expressed aberrantly and correlate with tumorigenesis, progression, and prognosis of various haematological and solid tumours. We aimed to assess the relation between microRNA expression and progression and prognosis of gastric cancer. Methods 353 gastric samples from two independent subsets of patients from Japan were analysed by microRNA microarray. MicroRNA expression patterns were compared between non-tumour mucosa and cancer samples, graded by diffuse and intestinal histological types and by progression-related factors (eg, depth of invasion, metastasis, and stage). Disease outcome was calculated by multivariable regression analysis to establish whether microRNAs are independent prognostic factors. Findings In 160 paired samples of non-tumour mucosa and cancer, 22 microRNAs were upregulated and 13 were downregulated in gastric cancer; 292 (83%) samples were distinguished correctly by this signature. The two histological subtypes of gastric cancer showed different microRNA signatures: eight microRNAs were upregulated in diffuse-type and four in intestinal-type cancer. In the progression-related signature, miR-125b, miR-199a, and miR-100 were the most important microRNAs involved. Low expression of let-7g (hazard ratio 2·6 [95% CI 1·3–4·9]) and miR-433 (2·1 [1·1–3·9]) and high expression of miR-214 (2·4 [1·2–4·5]) were associated with unfavourable outcome in overall survival independent of clinical covariates, including depth of invasion, lymph-node metastasis, and stage. Interpretation MicroRNAs are expressed differentially in gastric cancers, and histological subtypes are characterised by specific microRNA signatures. Unique microRNAs are associated with progression and prognosis of gastric cancer. Funding National Cancer Institute.

Wnt-5a is a representative ligand that activates a B-cateninindependent pathway in the Wnt signaling. Although abnormal activation of B-catenin-dependent pathway is often observed in human cancer, the relationship between Bcatenin-independent pathway and tumorigenesis is not clear. We sought to clarify how Wnt-5a is involved in aggressiveness of gastric cancer. Abnormal expression of Wnt-5a was observed in 71 of 237 gastric cancer cases by means of immunohistochemistry. The positivity of Wnt-5a expression was correlated with advanced stages and poor prognosis of gastric cancer. Wnt-5a had the abilities to stimulate cell migration and invasion in gastric cancer cells. Wnt-5a activated focal adhesion kinase and small GTP-binding protein Rac, both of which are known to play a role in cell migration. Cell migration, membrane ruffling, and turnover of paxillin were suppressed in Wnt-5a knockdown cells. Furthermore, anti-Wnt-5a antibody suppressed gastric cancer cell migration. These results suggest that Wnt-5a stimulates cell migration by regulating focal adhesion complexes and that Wnt-5a is not only a prognostic factor but also a good therapeutic target for gastric cancer.

Gastric cancer is classified into intestinal and diffuse types, the latter including a highly malignant form, linitis plastica. A two-stage genome-wide association study (stage 1: 85,576 SNPs on 188 cases and 752 references; stage 2: 2,753 SNPs on 749 cases and 750 controls) in Japan identified a significant association between an intronic SNP (rs2976392) in PSCA (prostate stem cell antigen) and diffuse-type gastric cancer (allele-specific odds ratio (OR) = 1.62, 95% CI = 1.38-1.89, P = 1.11 x 10(-9)). The association was far less significant in intestinal-type gastric cancer. We found that PSCA is expressed in differentiating gastric epithelial cells, has a cell-proliferation inhibition activity in vitro and is frequently silenced in gastric cancer. Substitution of the C allele with the risk allele T at a SNP in the first exon (rs2294008, which has r(2) = 0.995, D' = 0.999 with rs2976392) reduces transcriptional activity of an upstream fragment of the gene. The same risk allele was also significantly associated with diffuse-type gastric cancer in 457 cases and 390 controls in Korea (allele-specific OR = 1.90, 95% CI = 1.56-2.33, P = 8.01 x 10(-11)). The polymorphism of the PSCA gene, which is possibly involved in regulating gastric epithelial-cell proliferation, influences susceptibility to diffuse-type gastric cancer.

Hypoxia-inducible factor-1 (HIF-1) is a pivotal factor that regulates cellular responses to hypoxia and is presumably linked to regulation of angiogenesis and tumor growth. We assessed the difference in transcription activity of two HIF-1alpha polymorphic variants (P582S and A588T), along with molecular epidemiological study among head and neck squamous cell carcinoma (HNSCC) patients. Both HIF-1alpha variants revealed significantly higher transcription activity than wild-type (WT) did, under normoxic and hypoxic conditions (P < 0.02). Furthermore, tumors from HNSCC patients with heterozygous alleles having P582S or A588T had significantly increased numbers of microvessels compared with those with homozygous WT (P = 0.02). In addition, all patients with tumors of T1 (below 2 cm diameter) were WT, while 14 of 47 patients with tumors of > or =T2 were heterozygous. The elevated transactivation capacity of variant forms of HIF-1alpha implies a role of HIF-1alpha polymorphisms in generating individually different tumor progression.

The receptor for advanced glycation end-products (RAGE) is a newly recognized factor regulating cancer cell invasion and metastasis. This study investigated the expression of RAGE in gastric carcinomas and its association with invasion and metastasis. Of eight gastric cancer cell lines examined, seven constitutively expressed RAGE messenger ribonucleic acid (mRNA), MKN45 being the exception. RAGE protein expression of MKN28 cells treated with RAGE antisense S-oligodeoxynucleotide was nine times less than that of sense S-oligodeoxynucleotide-treated cells. Growth of cells under RAGE antisense S-oligodeoxynucleotide treatment was not different from that seen under sense S-oligodeoxynucleotide treatment in MKN28 (a cell line producing high levels of RAGE) and MKN45 (a non-RAGE-expressing cell line). RAGE antisense S-oligodeoxynucleotide treatment suppressed the invasive activity of RAGE-positive MKN28 cells, as estimated by in vitro invasion assay. The number of MKN28 cells invading the type IV collagen-coated membrane under RAGE antisense S-oligodeoxynucleotide treatment was significantly lower than under RAGE sense S-oligodeoxynucleotide treatment (p<0.0001). In contrast, antisense and sense S-oligodeoxynucleotide-treated RAGE-negative MKN45 cells showed no difference. A wound-healing assay showed that no RAGE antisense S-oligodeoxynucleotide-treated MKN28 cells migrated into the scraped area, whereas sense S-oligodeoxynucleotide-treated cells showed many budding nests in the scraped area. Immunohistochemistry of gastric carcinoma tissue showed that 62 (65%) of the 96 cases examined were RAGE-positive and that poorly differentiated adenocarcinomas preferentially expressed RAGE protein (38/42, 90%) (p<0.0001). Strong RAGE immunoreactivity was also correlated with depth of invasion and lymph node metastasis (p<0.0001). RAGE-positive cancer cells tended to be distributed at the invasive front of primary tumours and were detected in all metastatic foci in lymph nodes. In contrast, a major RAGE ligand, amphoterin, was expressed in 82 (85%) of the 96 cases, regardless of histological type and disease progression. RAGE expression appears to be closely associated with invasion and metastasis in gastric cancer.