Role Of Calcium On The Proliferative Effect Of Substance P On Gastric Cancer Cells

【Background】Substance P is one of the major neurokinin receptors, it is ubiquitous in all kinds of tissues including nervous system. Besides acting as neurotransmitter and inflammatory mediator, SP could activate mitosis in many kinds of cells. Recently, many experiments demonstrated that SP could activate mitosis and promote proliferation in many cells including smooth muscle cells, epithelial cells and neurogenic cancer cells. Previous experiments demonstrated that much more SP immune-positive nerve fibers could be seen in Gastric cancer tissues than in normal Gastric cancer tissues. The distribution characteristic status of nerve fibers show that they are regenerate nerve fibers and induced by the Gastric cancer tissues. The result demonstrated that the peptidergic nerve fibers distributed in Gastric cancer tissues may promote gastric cancer cell proliferation directly. SP shows its physiological effect through binding with neurokinin receptor(NK). The binding of SP and neurokinin receptor could activate hydrolysis of lipositol, elevate intracellular calcium and cAMP concentration and activate MAPK, activate intracellular signal transduction and second messenger, and finally result in proliferation.【Objective】To investigate the expression of NK-1 receptor on MKN45 cells and the role of antagonist(NK-1 receptor antagonist, Nicardipine and neomycin) and substance P (SP) in the proliferative effect on gastric cancer cells, and explore its signal transduction mechanisms.【Methods】The fourth generation of cultured cells were used in the study, MKN45 cells were cultured in RPMI1640. At 48h postincubation, SP were added into the RPMI1640 in different concentration, respectively. MTT colorimetry was used to determine the proliferation of gastric cancer cell line. Additionally, we investigate whether the gastric cancer cell proliferative response to SP were modulated by preincubation for 1h with ASN-1377642(a specific antagonist of NK-1 receptor), neomycin(a PIP2 antagonist) and Nicardipine(a blocker of calcium channel) respectively. Laser confocal scanning microscope was used to investigate the concentration of calcium in this process.【Results】SP induced dose-dependent proliferative response of the cells, the effect of SP was blocked by ASN-1377642, neomycin and Nicardipine, the effect of neomycin and Nicardipine were not enhanced when the concentrations were increased. In Hanks solution, the concentration of calcium was significantly elevated by SP and greatly inhibited by ASN-1377642 and Nicardipine. In D-Hanks solution, the concentration of calcium also could be elevated by SP, but was lower than the concentration of calcium induced by SP in Hanks. 【Conclusions】1,NK-1 receptor is expressed on gastric cancer cell MKN45.2,SP could effectively promote proliferation of MKN45 through binding to its receptor NK-1.3,SP could elevate the concentration of intracellular calcium through bingding to its receptor NK-1.4,The elevation of intracellular calcium concentration includes the calcium influx and calcium release.5,The elevation of intracellular calcium concentration plays an important role in proliferation induced by SP.6,Nicardipine(a blocker of calcium channel) and neomycin(a PIP2 antagonist) could inhibit the proliferation effect.7,NK-1 receptor antagonist, calcium channel blocker and PIP2 antagonist have potential anticancer activity.