The higher expression of NET1 in OE33 OAC cells compared with the other two OAC cell lines may be a reflection of the poor level of differentiation these cells represent, and it has been shown elsewhere that NET1 is seen at high levels in the later metastatic stages of other cancers [17, 20]. In a recent study (Lahiff et al 2013, under review British Journal of Cancer; Lahiff, et al. Gut 2012; 61: (Suppl 2) A255 (abstract); and Lahiff et al. Gastroenterology

2012; Erlotinib 142:5 (Suppl 1) S-531 (abstract)].) we have analysed the levels of NET1 mRNA in OAC tumor tissue. We showed that type I (Siewert classification) oesophago-gastric junction (OGJ) adenocarcinomas expressed significantly higher levels of NET1, with lowest expression in type III and intermediate levels in type II (p = 0.01). In patients with gastric and OGJ type III tumours, NET1 positive patients were more likely have advanced stage cancer (p = 0.03), had a higher number of transmural cancers (p = 0.006)

and had a significantly higher median number of positive lymph nodes (p = 0.03). In this subgroup, NET1 was associated with worse median overall (23 versus 15 months, p = 0.02) and disease free (36% versus 11%, p = 0.02) survival. In the current study, we investigated the role of NET1 in OAC by modulating its expression and investigating the effect on cell function. LPA stimulates invasion and migration in OE33 cells. We have previously shown that LPA, a phospholipid

which acts through G protein check details coupled receptors and is known to activate RhoA, promotes gastric cancer cell invasion via NET1 [4]. In this current study we have shown that not only does LPA drive NET1 expression in OAC but that the functional effects of LPA stimulation in these cells are NET1 dependent. Although not explored in the current study, our ongoing efforts will define whether LPA drives RhoA activation in OAC cells as it does in gastric cancer cells. The mechanism by which LPA induces transcription for of NET1 in OAC cells remains to be elucidated. We also previously reported LPA to drive the expression of NET1 mRNA in gastric cancer cells [4]. Likewise, we previous showed [16] that stimulation of gastric cancer cells with LPA resulted in the differential expression of over 2000 genes. Further work will elucidate the mechanism via which LPA induces NET1 mRNA transcription in OAC cells. The results of the functional in vitro experiments presented here are broadly consistent across proliferation, migration and trans-membrane invasion assays. NET1 knockdown significantly reduced OE33 cancer cell proliferation, migration and invasion. LPA, a recognised mitogen, had no effect on proliferation in these OAC cells. However, when we examine the effect of LPA on scramble siRNA control cells compared with its effect after NET1 knockdown there was significant differences in proliferation, migration and invasion.