Global expression analysis of ECL cells in Mastomys natalensis gastric mucosa identifies alterations in the AP-1 pathway induced by gastrin-mediated transformation.

Enterochromaffin-like (ECL) cell hyperplasia and then irreversible neoplasia can be generated in the African rodent Mastomys natalensis using the H2 receptor blocker, loxtidine, for 8-16 wk. We used a GeneChip approach complemented by standard technologies to identify gene expression alterations in the gastric mucosa during gastrin-mediated ECL cell transformation. Gastric mucosa (mucosal scrapping) and ECL cell-enriched fractions were obtained from untreated Mastomys (controls) and from animals treated with loxtidine for 8 wk (hyperplasia). Tumor ECL cells were obtained by hand-dissection of gastric ECL cell nodules from animals treated with loxtidine for >16 wk and from a spontaneously developed ECL cell tumor. RNA was isolated, examined on rat U34A GeneChips, and comparison analysis was performed to identify altered gene expression. Alterations in gene expressions were examined further by immunohistochemistry, quantitative RT-PCR (Q-RT-PCR), sequencing and Western blot. GeneSpring analysis demonstrated alterations in few genes (<20) in hyperplastic and tumor mucosa. The histamine H1 receptor was consistently increased in proliferating mucosa. This gene change was confirmed by Q-RT-PCR. Other genes showing alterations included neural-(chromogranin A and somatostatin), cell-cycle-, and AP-1-associated genes. Immunostaining confirmed alterations in neural markers. Cluster analysis of ECL cell-enriched samples demonstrated that c-fos and junD were differently regulated. Q-RT-PCR and Western blot in prospectively collected gastric mucosal samples confirmed the differential expression of Fos and Jun. The negative regulators of AP-1, JunD, and Menin were decreased in tumor mucosa. A missense of unknown function was noted in the menin gene. Hypergastrinemia in an animal model of gastric carcinoids differentially altered the histamine type 1 receptor and gene expression and protein composition of AP-1. These results suggest that expression of this receptor and an altered composition of AP-1 with a loss of inhibition play a role in ECL cell transformation.

Molecular strategies and 111in-labelled somatostatin analogues in defining the management of neuroendocrine tumour disease: a new paradigm for surgical management.

This manuscript provides a gene-chip examination of gastric ECL cell proliferation in an animal model of neuroendocrine tumour disease. Data that were used to identify molecular targets were then utilised to develop novel therapeutic strategies as appropriate adjuncts to surgery in human disease. Alterations in growth-mediated cell signaling (the AP-1 pathway) and in the cell cycle were identified in ECL cell tumours in the animal model and confirmed in human tumour tissue. The growth-inhibitory somatostatin receptor subtype 2 was identified as a potential clinical target. An investigation of patients with neuroendocrine tumours treated using SSTR2 targeted radiotherapy [111In]pentetreotide producing encouraging preliminary results. Fifty-six per cent of patients with evaluable hormone markers demonstrated stable levels or a significant decrease in one or more measured markers. This data demonstrate that gene pathways recognised to be altered in an animal model of a human disease can be used to identify therapeutic agents. This approach was successfully used to discover novel strategies that can be both effective and appropriate adjuncts to surgery for patients with neuroendocrine tumour disease.