Ganoderiol F, a ganoderma triterpene, induces senescence in hepatoma HepG2 cells Ue-Min Chang a , Chyi-Hann Li c , Liang-In Lin a,b , Cheng-Po Huang a , Lou-Sing Kan c, ⁎ , Shwu-Bin Lin a,b, ⁎ a Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, Taiwan ROC b Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University, Taiwan ROC c Institute of Chemistry, Academia Sinica, Taipei, Taiwan ROC Received 17 October 2005; accepted 13 March 2006 Abstract Ganoderiol F (GolF), a tetracyclic triterpene, was isolated from Ganoderma amboinense and found to induce senescence of cancer cell lines. GolF induced growth arrest of cancer cell lines HepG2, Huh7 and K562, but exerted much less effect in hepatoma Hep3B cells and normal lung fibroblast MRC5 cells, and no effect on peripheral blood mononuclear cells. GolF treatment of the cancer cells, with the exception of Hep3B, resulted in prompt inhibition of DNA synthesis and arrest of cell progression cycle in G1 phase. Short-term exposure of HepG2 cells to GolF temporarily arrested progression of the cell cycle; cell growth was recovered if the drug was withdrawn from the medium after a 24-h exposure. After 18 days of continuous treatment of HepG2 cells with 30 μM GolF, over 50% of cells were found to be enlarged and flattened, and were β- galactosidase positive phenotypes of senescent cells. GolF was found to inhibit activity of topoisomerases in vitro, which may contribute to the inhibition of cellular DNA synthesis. Activation of the mitogen-activated protein kinase EKR and up-regulation of cyclin-dependent kinase inhibitor p16 were found in early stages of GolF treatment and were presumed to cause cell-cycle arrest and trigger premature senescence of HepG2 cells. The growth-arrest and senescence induction capability on cancer cells suggest anticancer potential of GolF. © 2006 Elsevier Inc. All rights reserved. Keywords: Ganoderiol F; Ganoderma triterpene; Cell senescence; G1 cell-cycle arrest; p16; pERK Introduction In long-lived multi-cellular organisms, senescence of normal cells is a mechanism contributing to oppose neoplastic transformation (Lloyd, 2002). Senescent cells are arrested in the G1 phase of the cell cycle, typically appear enlarged and flattened in shape, with increased cytoplasmic granularity and they express senescence associated β-galactosidase (SA-β-gal) (Dimri et al., 1995). It has been shown that cell senescence as the result of cells responding to cellular stress, e.g. shortening of telomeres, DNA damage or mitogenic signals, is controlled by tumor suppressor proteins such as retinoblastoma protein (pRb) or p53, and constitutes a potent anticancer mechanism (Itahana et al., 2004; Shay and Roninson, 2004). Cancer cells might be induced to undergo senescence through expression of tumor suppressor genes or inhibition of oncogenes (Campisi, 2005; Mathon and Lloyd, 2001; Goodwin et al., 2000). It has been shown that some anticancer agents may induce long-term growth arrest and consequently senescence of cancer cells. Activation of the senescence program in cancer cells seems to be an alternative therapeutic strategy other than induction of apoptosis (Chang et al., 1999; Roninson et al., 2001). Fruit bodies of ganoderma fungi have been used in traditional Chinese medicine for a long time and are believed to have anti-cancer and immunomodulatory activities. The medicinal mushroom is also taken in tonics and remedies for ailments such as cough, asthma, insomnia, indigestion, bronchitis, hepatitis and hypertension (Yan et al., 1999). The Life Sciences 79 (2006) 1129 – 1139 www.elsevier.com/locate/lifescie ⁎ Corresponding authors. Lou-sing Kan is to contacted at Institute of Chemistry, Academia Sinica, Taipei, Taiwan R.O.C. Fax: +886 2 27884184. Shwu-Bin Lin, 1 Chang-Te Street, 10016 Taipei, Taiwan, ROC. Fax: +886 2 23711574. E-mail addresses: lskan@chem.sinica.edu.tw (L.-S. Kan), sblin@ntumc.org (S.-B. Lin). 0024-3205/$ - see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2006.03.027