[M3 Muscarnic Receptor Antagonist Mediates Cell Proliferation Apoptosis
 and Adhesion in Small Cell Lung Cancer]

Studies have shown that muscarinic receptors 3 (M3R) plays key roles in regulating tumorigenesis and tumor growth. The aim of this study is to investigate the expression of M3R in human small cell lung cancer (SCLC) cell line SBC3 and to explore the effect of M3R antagonist on cell proliferation, apoptosis and adhesion.

SBC3 cells were cultured in vitro. RT-PCR and Western blot were used to detect the expression of M3R in SBC-3. MTT assay and flow cytometry were used to determine the effects of M3R antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) on the proliferation and apoptosis of SBC-3 cells. Flow cytometry was used to detect the integrin expression in SBC3 and alteration of integrin expression after treating the cells with cholinergic receptor agonist acetylcholine iodide (acetylcholine iodide, Ach) and 4-DAMP. Fibronectin (Fn) coated 96-well plates were used to detect the effect of Ach, 4-DAMP and anti-integrin antibody on cell adhesion.

M3R was expressed in SBC3 cells. 4-DAMP significantly inhibited SBC3 cells proliferation in a dose-dependent manner. 4-DAMP promoted cell apoptosis at a concentration of 10-4 M of 4-DAMP compared with control. αvβ1 and α5β1 integrin were expressed in SBC3 cells. 10-4 M Ach stimulated cell adhesion toward Fn significantly (P<0.01). This effect was completely abrogated by 10-5 M 4-DAMP, 5 μg/mL anti-β1 integrin antibody or anti-αv and anti-α5 integrin antibodies (P<0.01) and partially abrogated by 5 μg/mL anti-αv or anti-α5 integrin antibody (P<0.05). But Ach and 4-DAMP did not alter Fn receptor (αvβ1 or α5β1 integrin) expression.

M3R is expressed in SBC3 cell. The M3R antagonist inhibits SBC3 cell proliferation, adhesion and enhances cell apoptosis. M3R antagonist inhibiting SBC3 cell adhesion is presumably modulated by functional alteration of β1 containing integrins (αvβ1 and α5β1), but not by any variation in their expression.
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