Nicotine-induced human breast cancer cell proliferation attenuated by garcinol through down-regulation of the nicotinic receptor and cyclin D3 proteins

Abstract

Previous studies have demonstrated that the persistent exposure of human bronchial epithelial cells to nicotine (Nic) through nicotinic acetylcholine receptors increases cyclin D1 promoter activity and protein expression. The main purpose of this study is to elucidate the carcinogenic role of cyclin D3, which is involved in breast tumorigenesis when induced by Nic. Real-time PCR analysis revealed that cyclin D3 is highly expressed at the mRNA level in surgically dissected breast tumor tissue, compared to the surrounding normal tissue (tumor/normal fold ratio = 17.93, n = 74). To test whether Nic/nicotinic acetylcholine receptor (nAChR) binding could affect cyclin D3 expression in human breast cancer cells, the transformed cell line MCF-10A-Nic (DOX) was generated from normal breast epithelial cells (MCF-10A) with inducible α9-nAChR gene expression, using the adenovirus tetracycline-regulated Tet-off system. Tet-regulated overexpression of α9-nAChR in MCF-10A-Nic (DOX) xenografted BALB/c-nu/nu mice resulted in a significant induction of cyclin D3. In contrast, cyclin D3 expression was down-regulated in α9-nAChR knock-down (siRNA) MDA-MB-231-xenografted tumors in NOD.CB17-PRKDC(SCID)/J(NOD-SCID) mice. Furthermore, we found that Nic-induced human breast cancer (MDA-MB-231) cell proliferation was inhibited by 1 μM of garcinol (Gar), isolated from the edible fruit Garcinia indica, through down-regulation of α9-nAChR and cyclin D3 expression. These results suggest that α9-nAChR-mediated cyclin D3 overexpression is important for nicotine-induced transformation of normal human breast epithelial cells. The homeostatic regulation of cyclin D3 has the potential to be a molecular target for antitumor chemotherapeutic or chemopreventive purposes in clinical breast cancer patients.

Garcinol, a Polyisoprenylated Benzophenone Modulates Multiple Proinflammatory Signaling Cascades Leading to the Suppression of Growth and Survival of Head and Neck Carcinoma

“…We further noticed that garcinol suppressed the expression of several STAT3-and NF-kB-regulated genes, including proliferative (cyclin D1), antiapoptotic (Bcl-2, Bcl-xL, survivin, and Mcl-1), and angiogenic gene product (VEGF). The inhibition of cyclin D1 expression may account for its ability to inhibit proliferation in various tumor cell lines (48,49). Activation of STAT3 signaling also induces survivin gene expression and confers resistance to apoptosis in human breast cancer cells (50).…”

Cigarette Smoking and Breast Cancer: a Case-control Study in Serbia

“…The findings that former smokers were at increased risk for breast cancer is in line with results from some other investigations showing that breast cancer risk is higher in former that in current smokers (Manjer et al, 2000;Manjer et al, 2004;Saquib et al, 2013). Tobacco smoke contains chemicals, which are carcinogenic to humans and can cause mammary tumors in animals (Chen et al, 2011). At the same time smoking can reduce breast cancer risk through its antiestrogenic effect (Band et al, 2002).…”

Nicotinic Acetylcholine Receptor-Based Blockade: Applications of Molecular Targets for Cancer Therapy

“…1) (4). These signaling pathways are closely correlated to the formation of several cancers; in particular, a7-nAChR is associated with lung (5), bladder (6), and colon cancers (7), and a9-nAChR is associated with breast cancer (8)(9)(10) (Fig. 1).…”

“…The established a9-nAChR overexpressing cells (Tet-Off group) were transplanted into nude mice, resulting in increased tumor growth volume (2.33-fold) when compared with the control (Tet-On) group. Moreover, specific inhibition of a9-nAChR expression using RNA-interference (siRNA) or compounds derived from plants was previously found to concomitantly inhibit cancer cell growth, soft-agar colony formation, and tumor growth in SCID mice (8,10,93). Nicotine-induced breast cancer cell proliferation can be inhibited by garcinol (1 mM) derived from the edible fruit Garcinia indica through down-regulation of a9-nAChR and cyclin D3 expression (94).…”