Research article
Isoliquiritigenin inhibits migration and invasion of prostate cancer cells: possible mediation by decreased JNK/AP-1 signaling

https://doi.org/10.1016/j.jnutbio.2008.06.005Get rights and content

Abstract

Isoliquiritigenin (ISL, 4,2′,4′-trihydroxychalcone), which is found in licorice, shallot and bean sprouts, is a potent antioxidant with anti-inflammatory and anti-carcinogenic effects. The purpose of this study was to investigate the effects of ISL treatment on the migration, invasion and adhesion characteristics of DU145 human prostate cancer cells. DU145 cells were cultured in the presence of 0–20 μmol/L ISL with or without 10 μg/L epidermal growth factor (EGF). ISL inhibited basal and EGF-induced cell migration, invasion and adhesion dose dependently. ISL decreased EGF-induced secretion of urokinase-type plasminogen activator (uPA), matrix metalloproteinase (MMP)-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), and vascular endothelial growth factor (VEGF), but increased TIMP-2 secretion in a concentration-dependent manner. In addition, ISL decreased the protein levels of integrin-α2, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), and mRNA levels of uPA, MMP-9, VEGF, ICAM and integrin-α2. Furthermore, basal and EGF-induced activator protein (AP)-1 binding activity and phosphorylation of Jun N-terminal kinase (JNK), c-Jun and Akt were decreased after ISL treatment. However, phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase was not altered. The JNK inhibitor SP600125 inhibited basal and EGF-induced secretion of uPA, VEGF, MMP-9 and TIMP-1, as well as AP-1 DNA binding activity and cell migration. These results provide evidence for the role of ISL as a potent antimetastatic agent, which can markedly inhibit the metastatic and invasive capacity of prostate cancer cells. The inhibition of JNK/AP-1 signaling may be one of the mechanisms by which ISL inhibits cancer cell invasion and migration.

Introduction

Chemoprevention of cancer has gained considerable attention recently, probably because it involves the use of dietary bioactive compounds either alone or in combination to reverse, suppress or prevent cancer progression [1]. Epidemiological studies followed by laboratory studies have shown that dietary agents are an important factor in reducing cancer risk [2], [3], [4]. Diets rich in naturally occurring polyphenolic flavonoids have been shown to be associated with a reduced incidence of various human cancers [2], [3], [4], [5].

Prostate cancer is the second leading cause of cancer-related deaths in men in the US [6], and the incidence of this disease is increasing in both developed and developing countries. Androgen deprivation therapy by either bilateral orchiectomy or treatment with gonadotrophin-releasing hormone agonist is the mainstay of therapy for advanced prostate cancer. However, androgen ablation therapy eventually fails, and prostate cancer progresses to a hormone-refractory state. Most patients with cancer die not because of the tumor in the original site, but because of the development of metastasis [7]. Therefore, it is important to inhibit the spread of tumor cells, thereby inhibiting the development of metastasis. Accordingly, the anti-metastastic effects of nontoxic dietary agents could be of special significance in the prevention, control and/or management of prostate cancer, especially that at an advanced and an androgen-independent stage of the disease. Many dietary bioactive components have shown promising anticancer activities with little or no toxicity to normal cells [8], [9], [10]. For that reason, investigations of how dietary bioactive components regulate adhesion, invasion and motility of cancer cells could play a significant role in the development of new agents with low toxicity to prevent and treat cancer.

Isoliquiritigenin (ISL, Fig. 1) is a flavonoid belonging to the chalcone family that is found in licorice, shallot and bean sprouts. ISL has been reported to inhibit 7,12-dimethylbenz[α]anthracene-initiated and 12-O-tetradecanoyl-phorbol-13-acetate-promoted skin papilloma formation [11], induction of aberrant crypt foci and colon carcinoma development in azoxymethane-treated ddY mice [12] and pulmonary metastasis of mouse renal cell carcinoma [13]. We and other investigators have reported that ISL inhibits cell growth and ErbB3 signaling, and induces apoptosis in prostate cancer cells [14], [15], [16]. However, the effects of ISL on metastasis of prostate cancer and the mechanisms underlying these effects have not been studied. The present study was performed to examine whether ISL inhibits adhesion, invasion and motility of prostate cancer cells. We demonstrated that ISL potently inhibits the metastastic potential of DU145 human prostate cancer cells, an effect which may be mediated through inhibition of Jun N-terminal kinase (JNK)/AP-1 signaling.

Section snippets

Materials

The following reagents were purchased from the indicated suppliers. ISL and SP600125, an inhibitor of JNK [17], Sigma (St. Louis, MO, USA); antibodies against Akt, JNK, extracellular signal-regulated kinase (ERK)1/2, p38 mitogen activated protein kinase (MAPK) and c-Jun, Cell Signaling (Beverly, MA, USA); antibodies against matrix metalloproteases (MMP)-9, integrin-α2, tissue inhibitor of metalloproteinase-1 (TIMP-1), TIMP-2, intercellular adhesion molecule (ICAM), vascular cell adhesion

EGF, and not IGF-I or heregulin-β, induces migration of DU145 cells

Since it has been reported that the androgen-independent human prostate cancer cell line DU145 and the androgen-sensitive prostate cancer cell line LNCaP are responsive to stimulation with EGF and IGF-I [22], we first examined whether IGF-I, heregulin-β or EGF stimulates cell migration and MMP secretion in DU145 cells. The Transwell migration assay revealed that EGF markedly increased DU145 cell migration, whereas neither IGF-I nor heregulin had any effect on cell migration (Fig. 2). Gelatin

Discussion

ISL has been reported to have anticarcinogenic effects in both in vivo and in vitro experimental models. Results from animal studies revealed that ISL inhibits chemically induced colonic tumorigenesis [12], skin papilloma formation [11] and lung metastasis of murine renal cell carcinoma cells [13]. In vitro studies showed that ISL has antiproliferation activity in skin [26], pulmonary [13], breast [27] and gastric [28] cancer cells. To date, only three studies have described the

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  • Cited by (0)

    This work was supported by Basic Research Program of the Korea Science and Engineering Foundation (R01-2004-000-10177-0) and a grant (code number: 20070301034039) from BioGreen 21 Program, Rural Development Administration, Republic of Korea.

    1

    The first two authors contributed equally to this work.

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