European Journal of Pharmaceutical Sciences 25 (2005) 57–65 Vanillin suppresses in vitro invasion and in vivo metastasis of mouse breast cancer cells Kriengsak Lirdprapamongkol a, c , Hiroaki Sakurai a, b , Noritaka Kawasaki a , Min-Kyung Choo a , Yurika Saitoh a , Yasushi Aozuka a , Pattama Singhirunnusorn a , Somsak Ruchirawat d , Jisnuson Svasti c, e , Ikuo Saiki a, b, ∗ a Division of Pathogenic Biochemistry, Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan b The 21th Century COE Program, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan c Laboratory of Biochemistry, Chulabhorn Research Institute, Bangkok 10210, Thailand d Laboratory of Natural Products, Chulabhorn Research Institute, Bangkok 10210, Thailand e Department of Biochemistry, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand Received 10 June 2004; received in revised form 22 December 2004; accepted 24 January 2005 Available online 7 March 2005 Abstract Vanillin, a food flavoring agent, has been reported to show anti-mutagenic activity and to inhibit chemical carcinogenesis. In this study, we examined the effect of vanillin on the growth and metastasis of 4T1 mammary adenocarcinoma cells in BALB/c mice. Mice orally administered with vanillin showed significantly reduced numbers of lung metastasized colonies compared to controls. In vitro studies revealed that vanillin, at concentrations that were not cytotoxic, inhibited invasion and migration of cancer cells and inhibited enzymatic activity of MMP-9 secreted by the cancer cells. Vanillin also showed growth inhibitory effect towards cancer cells in vitro. However, vanillic acid, a major metabolic product of vanillin in human and rat, was not active in these in vitro activity assays. Our findings suggest that vanillin has anti-metastatic potential by decreasing invasiveness of cancer cells. Since vanillin is generally regarded as safe, it may be of value in the development of anti-metastatic drugs for cancer treatment. © 2005 Elsevier B.V. All rights reserved. Keywords: Anti-metastatic; Migration; Matrix metalloproteinase; Breast cancer 1. Introduction Metastasis, the spread of cancer in the body, is a major cause of death in cancer patients. The metastatic process is a multi-step phenomenon, by which cells in the primary tumor invade surrounding tissue, penetrate into blood and lymphatic vessels, so that they can travel to distant sites via the circu- latory system, and extravasate into the organ parenchyma, proliferating to form metastatic colonies at secondary sites. Cancer invasion takes place when the cancer cells respond and migrate towards gradients of stimuli such as growth fac- ∗ Corresponding author. Tel.: +81 76 434 7620; fax: +81 76 434 5058. E-mail address: byosei@ms.toyama-mpu.ac.jp (I. Saiki). tors, and also requires proteolysis of basement membrane (BM) and extracellular matrix (ECM) proteins to create a path for migration. Matrix metalloproteinases (MMPs) are a group of enzymes responsible for the proteolysis of BM and ECM proteins, and the expression level of MMPs appears to correlate with the invasiveness of cancer cells (Woodhouse et al., 1997). Current chemotherapeutic treatments generally aim to use cytotoxic agents to kill proliferated cancer cells, but such treatment can also affect rapidly growing normal cells. More- over, regrowth of tumors often occurs after treatment, and repeated cycles of treatment and regrowth can lead to a lethal outcome. A new approach in cancer treatment is cytostatic therapy, which aims to stabilize a non-pathologic state of the 0928-0987/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ejps.2005.01.015