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Signal transduction and activator of transcription 3(STAT3) signaling is constitutively activated in various tumors, and is involved in cell survival and proliferation during oncogenesis. There are few reports, however, on the role of STAT3 signaling in gastric cancer. The aim of the present study was to clarify the role of STAT3 signaling in apoptosis and cellular proliferation in gastric cancer. Here we reported that STAT3 was constitutively activated in various human gastric cancer cells and its inhibition by ectopic dominant-negative STAT3 or Janus kinase inhibitor, tyrphostin AG490, induced apoptosis. Furthermore, STAT3 inhibition markedly decreased survivin expression, and forced expression of survivin rescued AGS cells from apoptosis induced by STAT3 inhibition. Although some reports demonstrated that the PI3K/Akt pathway regulates survivin expression, inhibition of the PI3K/Akt pathway did not affect survivin expression in AGS and MKN1 cells. Finally, activated form of STAT3, Tyr-705 phospho-stat3, was found in the nucleus of cancer cells in 11 of 40 (27.5%) human gastric cancer specimens. These findings suggest that constitutively activated STAT3 signaling supports gastric cancer cell survival in association with survivin expression.

Gastrin stimulates the production of Reg protein in gastric ECL cells, which may be involved in the gastrin-induced gastric mucosal cell growth.

Since Dale and Laidlaw (1) first reported the contraction of smooth muscle by histamine, the pharmacological significance of this phenomenon has been extensively investigated. Three subtypes of histamine receptor (H1, H2, and H3) are known. The H1 receptor was identified by Ash and Schild (2) and H1 receptor antagonists have been used in the therapy of many allergic diseases, including urticaria, allergic rhinitis, pollenosis, and bronchial asthma. In peripheral tissues, the histamine H1 receptor mediates the contraction of smooth muscles, increase in capillary permeability due to contraction of terminal venules, and catecholamine release from adrenal medulla (3), as well as mediating neurotransmission in the central nervous system (4). Although signal transduction of the H1 receptor through Ca2l mobilization via an increase in the intracellular inositol 1,4,5-trisphosphate level has been extensively investigated (5,6), little is known about the molecular structure of the histamine H1 receptor. Recently, Isolation ofPoly(A)+ RNA. Total RNA was extracted by the acid guanidinium isothiocyanate/phenol/chloroform method (11). Poly(A)+ RNA was isolated by chromatography on oligo(dT)-cellulose (12).Expression Cloning of Histamine HI Receptor cDNA. Bovine adrenal medullary poly(A)+ RNA ('180 ug) was sizefractionated on a 5-25% (wt/vol) sucrose-density gradient.An aliquot (1 p1L) of each poly(A)+ RNA fraction (20,ul) was injected into Xenopus oocytes, and electrophysiological assay by measuring Ca2+-dependent inward Cl-currents was done as described (9). The fraction that showed the highest histamine-induced inward Cl-currents was used for oligo(dT)-primed cDNA synthesis. Double-stranded cDNAs of >2-kilobase (kb) pairs were size-selected by agarose gel electrophoresis followed by elution with Geneclean II (Bio 101, La Jolla, CA) and were ligated into AZAPII (Stratagene) at the EcoRI site. The library was divided and amplified in 65 pools of "'-20,000 independent clones each. In vitro transcription was done essentially according to the procedure ofJulius et al. (13). RNA transcripts (=5 ng) from each pool were individually injected into Xenopus oocytes. After incubation for 1-2 days, the oocytes were tested for inward Cl-currents induced by 100 ,uM histamine under a voltage clamp at -60 mV. The single positive pool of 20,000 clones was progressively subdivided into smaller pools of 8000, 4000, 400, and 15 clones until finally a single clone was obtained. cDNA encoding the histamine H1 receptor was sequenced by the M13 chain-termination method (14) using a DNA sequencer (model 370A, Applied Biosystems). The sequence homology search was done by using DNASIS (Hitachi Software Engineering, Yokohama, Japan).

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