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Cancer-associated fibroblasts (CAFs), as the activated fibroblasts in tumor stroma, are important modifiers of tumor progression. However, the mechanisms underlying stromal fibroblast activation and their promotion of tumor growth remain largely unknown in gastric cancer. Here, we show that normal fibroblasts (NFs) from non-cancerous regions of gastric cancer exhibit the traits of CAFs when grown together with gastric cancer cells in vivo. Activation of NFs can be induced by co-culture with gastric cancer cells, while deprivation of hepatocyte growth factor (HGF) using a neutralizing antibody inhibits the activation of NFs. Moreover, we identify HGF as an important factor from CAFs that acts in a paracrine manner to promote tumorigenesis in vitro and in vivo. Taken together, these results suggest that HGF may play a pivotal role in the regulatory circuit between gastric cancer cells and stromal fibroblasts, and neutralization of HGF inhibits both activation and tumor-promoting properties of CAFs.

Emerging evidence has indicated microRNAs are involved in tumor development and progression, acting as tumor suppressors or oncogenes. Here we report that miR-409-3p was significantly downregulated in gastric cancer (GC) cell lines and tissues. Overexpression of miR-409-3p in SGC-7901 gastric cancer cells dramatically suppressed cell proliferation and induced cell apoptosis both in vitro and in vivo. Furthermore, we demonstrate that the transcriptional regulator PHF10 was a target of miR-409-3p. Taken together, these findings suggest that miR-409-3p may function as a novel tumor suppressor in GC and its anti-oncogenic activity may involve the direct targeting and inhibition of PHF10.

MicroRNAs have emerged as important gene regulators and are recognised as key players in carcinogenesis. In the present study, we show that miR-126 was significantly down-regulated in gastric cancer tissues compared with matched normal tissues and was associated with clinicopathological features, including tumour size, lymph node metastasis, local invasion and tumour-node-metastasis (TNM) stage. Ectopic expression of miR-126 in SGC-7901 gastric cancer cells potently inhibited cell growth by inducing cell cycle arrest in G0/G1 phase, migration and invasion in vitro as well as tumorigenicity and metastasis in vivo. Mechanistically, we identified the adaptor protein Crk as a target of miR-126. Taken together, our results suggest that miR-126 may function as a tumour suppressor in gastric cancer, with Crk as a direct target.