The serotonin 5-HT2A receptor antagonist ritanserin induces apoptosis in human colorectal cancer and acts in synergy with curcumin

Ramin Ataee1, Talal Oufkir2, Amin Ataee3, Cathy Vaillancourt2. 1Mazandaran University of Medical Sciences, Pharmaceutical research center, 47157-73449, Iran, 2INRS, Centre Institut Armand Frappier, H7V 1B7, Canada, 3Babol University of Medical Sciences, Department of Pharmacology, 47148-85795, Iran

Curcumin exhibits both cancer-preventive activity and growth inhibitory effects on several neoplastic cells including human colon cancer. Serotonin and its receptors have also been implicated in tumour biology. Especially, the 5-HT2A receptor agonists act as a mitogenic receptor in different cancer cell types including breast, prostate and choriocarcinoma. Moreover, some serotonin receptor antagonists exhibit an anti-mitogenic effect in cancer cells, such as colorectal cells.

Aim: This study investigated the effect ritanserin, a selective serotonin 5-HT2A receptor antagonist, alone and in combination with curcumin on colorectal cancer cell lines.

Methods: For immunohistochemistry analysis (IHC) paraffin blocks from patients with colorectal cancer or normal marginal tissue samples were obtained from the department of pathology of Reza and Yahyanejad hospitals (Babol, Iran). Biopsies were limited to grade II and III of colon or rectum adenocarcinoma. Colorectal cancer cell lines (HT29, SW480 and SW742) were then growth in RPMI supplemented with 10% FBS. Cells treated for 48 h or 24 h with drugs and cell viability or apoptosis was determined by MTT or TUNEL assay respectively. For MTT assay, immunohistochemistry and TUNEL experiments, data analysis was performed by Student t-test analysis.

Results: IHC analysis shows the expression of the serotonin 5-HT2A receptor in colorectal tissues with higher expression in tumour than in normal colorectal tissues. Ritanserin, in a dose-dependent manner (0, 3.125, 6.25, 12.5, 25, 50 and 100 µM), reduces cell viability and increases apoptosis in HT29, SW480 and SW742 colorectal cancer cell lines as analyzed by MTT and TUNEL assay, respectively. Moreover, combined with curcumin (25 µM), ritanserin (25 µM) synergistically increased the number of hypodiploid cells and DNA fragmentation (58.0 ± 2.6 %) and decreased cell viability (48.0 ± 3.4 %) in HT29 colorectal cancer cell line.

Conclusion: This study demonstrates that curcumin and ritanserin have a synergic anti-mitogenic and apoptotic effect on colorectal cancer cell lines. These results suggest a potential use of serotonin 5-HT2A receptor antagonist in co-treatment with curcumin in colon cancer therapy.

This work was financially supported by Institute Pasteur of Iran and by a Natural Sciences and Engineering Research Council of Canada –discovery grant.