Anthraquinone emodin inhibits human cancer cell invasiveness by antagonizing P2X7 receptors

• Published in: Carcinogenesis (New York) 2013-07, Vol.34 (7), p.1487-1496
• Main Authors: Jelassi, Bilel, Anchelin, Monique, Chamouton, Julie, Cayuela, María Luisa, Clarysse, Lucie, Li, Junying, Goré, Jacques, Jiang, Lin-Hua, Roger, Sébastien
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Calcium - metabolism; Calcium Signaling; Cell Shape - drug effects; Cell Survival - drug effects; Emodin - pharmacology; Extracellular Matrix - metabolism; Female; HEK293 Cells; Humans; Inhibitory Concentration 50; Models, Animal; Neoplasm Invasiveness - pathology; Neoplasm Invasiveness - prevention & control; Neoplasm Metastasis - drug therapy; Neoplasm Metastasis - pathology; Purinergic P2X Receptor Antagonists - pharmacology; Receptors, Purinergic P2X7 - metabolism; Rheum - chemistry; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Transfection; Zebrafish - embryology; Zebrafish - metabolism
• ISSN: 0143-3334; 1460-2180
• DOI: 10.1093/carcin/bgt099

The adenosine 5'-triphosphate (ATP)-gated Ca(2+)-permeable channel P2X7 receptor (P2X7R) is strongly upregulated in many tumors and cancer cells, and has an important role in cancer cell invasion associated with metastases. Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is an anthraquinone derivative originally isolated from Rheum officinale Baill known for decades to possess anticancer properties. In this study, we examined the effects of emodin on P2X7R-dependent Ca(2+) signaling, extracellular matrix degradation, and in vitro and in vivo cancer cell invasiveness using highly aggressive human cancer cells. Inclusion of emodin at doses ≤10 µM in cell culture had no or very mild effect on the cell viability. ATP elicited increases in intracellular Ca(2+) concentration were reduced by 35 and 60% by 1 and 10 µM emodin, respectively. Emodin specifically inhibited P2X7R-mediated currents with an IC50 of 3 µM and did not inhibit the currents mediated by the other human P2X receptors heterologously expressed in human embryonic kidney (HEK293T) cells. ATP-induced increase in gelatinolytic activity, in cancer cell invasiveness in vitro and in cell morphology changes were prevented by 1 µM emodin. Furthermore, such ATP-evoked effects and inhibition by emodin were almost completely ablated in cancer cells transfected with P2X7R-specific small interfering RNA (siRNA) but not with scrambled siRNA. Finally, the in vivo invasiveness of the P2X7R-positive MDA-MB-435s breast cancer cells, assessed using a zebrafish model of micrometastases, was suppressed by 40 and 50% by 1 and 10 µM emodin. Taken together, these results provide consistent evidence to indicate that emodin inhibits human cancer cell invasiveness by specifically antagonizing the P2X7R.