Muscarinic acetylcholine receptor M3 in proliferation and perineural invasion of cholangiocarcinoma cells.

Background: Cholangiocarcinoma, a type of malignant tumor, originates from epithelial cells of the bile duct. Perineural invasion is common path for cholangiocarcinoma metastasis, and it is highly correlated with postoperative recurrence and poor prognosis. It has been reported that muscarinic acetylcholine receptor M3 (mAChR M3) is widely expressed in digestive tract cancer, and may play an important role in the proliferation, differentiation, transformation and carcinogenesis of tumors. This study was to explore the effect of mAChR M3 on the growth of cholangiocarcinoma cells in vitro and provide a new approach to the pathogenesis and treatment of cholangiocarcinoma.

Methods: Streptavidin-biotin complex immunohistochemistry was carried out to assess the expression of mAChR M3 in surgical specimens of cholangiocarcinomas (40 cases) and normal bile duct tissues (9), as well as to investigate nerve infiltration. The cholangiocarcinoma cells were treated with different concentrations of selective M-receptor agonist pilocarpine and M-receptor blocker atropine sulfate to induce changes in cell proliferation. The experimental data were analyzed by the Chi-square test.

Results: The strongly-positive expression rate of mAChR M3 was much higher in poorly-differentiated (69%, 9/13) than in well- and moderately-differentiated cholangiocarcinomas (30%, 8/27) (X2=5.631, P<0.05). The strongly-positive mAChR M3 expression rate in hilar cholangiocarcinoma (50%, 14/28) was higher than that in cholangiocarcinomas from the middle and lower common bile duct (25%, 3/12) (X2=2.148, P<0.05). Cholangiocarcinomas with distant metastasis had a strongly-positive expression rate (75%, 9/12), which was much higher than those without distant metastasis (29%, 8/28) (X2=7.410, P<0.01). The absorbance value in the pilocarpine+atropine group was significantly higher than the corresponding value in the pilocarpine group.

Conclusions: The expression of mAChR M3 is influenced by the extent of differentiation, distant metastasis and the site of cholangiocarcinoma. It also plays a key role in the proliferation and metastasis of cholangiocarcinoma.