Troglitazone activates p21Cip/WAF1 through the ERK pathway in HCT15 human colorectal cancer cells
Introduction
Troglitazone (TRO) is a member of the family of thiazolidinediones (TZDs), which are orally active drugs that improve insulin sensitivity in both animals and humans with insulin resistance [1], [2]. TRO binds to and activates peroxisome proliferator-activated receptor γ (PPARγ), a member of the ligand-activated nuclear receptor family [3], [4]. Activated PPARγ regulates transcription of target genes, which are mainly involved in fatty acid and lipid metabolism of fat cells, and are associated with the differentiation of fat cells [5]. However, recent studies found that TRO also inhibits growth of human breast and prostate cancers, myeloid leukemia, and vascular smooth muscle cells [6], [7], [8], [9]. A role of TRO in the growth regulation of colorectal cancer cells was also identified and related to the activation of the PPARγ [10]. However, a no-regulatory mechanism of cell growth by TRO independent of PPARγ has been identified. A recent study also found that TRO induced cyclin-dependent kinase inhibitor p21Cip/WAF1, and this resulted in the suppression of the growth of a myeloid leukemia cell line [8]. However, the p21Cip/WAF1 induction by TRO has not been reported in solid tumors, and the mechanism of p21Cip/WAF1 induction has not been determined. The p21Cip/WAF1 induction is closely related to the growth arrest of many different cell types, including colorectal cancer cells [11], [12], and this is dependent on the activation of either p53 tumor suppressor [13] or the extracellular signal regulated kinase (ERK) pathway [14], [15], [16]. In addition, high aberrant ERK activities were observed in normal colonic epithelial cells, as compared with the paired tumors, and this might be involved in growth regulation [17]. Therefore, the ERK pathway is likely to be involved in the growth arrest, as well as the proliferation of cells [14], [15], [16].
In this study, we found that TRO induces p21Cip/WAF1 cell cycle regulator in HCT15 human colorectal cancer cells, and further identified a mechanism for the induction and nuclear localization of p21Cip/WAF1 by TRO. The p21Cip/WAF1 activation is related to the anti-proliferation of colorectal cancer cells, and this provides an alternative mechanism for the growth regulation of HCT15 colorectal cancer cells by TRO, which is independent of PPARγ.
Section snippets
Materials
HCT15 (CCL-225) and HT29 (HTB-38) human colorectal cell lines were obtained from the American Type Culture Collection (ATCC, Rockville, MD, USA). Dulbecco's modified Eagle's medium (DMEM), McCoy's 5A medium, fetal bovine serum (FBS), antibiotics and Lipofectamin plus reagent were purchased from Life Technologies, Inc. (Grand Island, NY, USA). Phospho-ERK and phospho-MEK antibodies were obtained from New England Biolabs Inc. (Beverly, MA, USA), and ERK antibody from Stratagene (La Jolla, CA,
TRO transiently increases ERK activity and subsequently induces p21Cip/WAF1 cell cycle regulator
The ERK pathway, which is also often called the MAPK pathway, is an important signaling route in cell proliferation, and aberrant activation of the MAPK pathway by genetic alterations of the signaling components often results in the development of cancers [20], [21], [22]. However, recent studies have also shown that the activation of the MAPK pathway plays a role in the growth arrest of the cells, and that this is related to the activation of the cell cycle regulator, p21Cip/WAF1 [14], [15],
Discussion
The p21Cip/WAF1 is a cell cycle regulator, which is involved in the anti-proliferation of cells by inhibiting cell cycle progression at the G1 to S phase; moreover, the induction of p21Cip/WAF1 is a good indicator of growth arrest in colorectal cancer cells [11], [12]. In the present study, we identified a mechanism for the activation (induction and nuclear localization) of p21Cip/WAF1 by TRO in HCT15 cells, and related this to cell growth. Transient activation of the ERK pathway appeared to be
Acknowledgements
We would like to thank Drs G. Johnson and J.H. Kim for providing kinase inactive MEK and dominant inhibitory Raf-1 kinase construct, respectively. This work was supported by the following grants to K.-Y.C.: the 1999 Korean National Cancer Control Program, Ministry of Health and Welfare, Korea; grant 1999-1-212-001-5 from the basic research program, and Research Center for Biomedical Resources of the Korean Science and Engineering Foundation. J.-A.K., K.-S.P. and H.-I.K. are recipients of a
References (26)
- et al.
An antidiabetic thiazolidinedione is a high affinity ligand for peroxisome proliferator-activated receptor gamma (PPAR gamma)
J. Biol. Chem.
(1995) - et al.
Adipogenesis and obesity: rounding out the big picture
Cell
(1996) - et al.
Troglitazone suppresses cell growth of myeloid leukemia cell lines by induction of p21WAF1/CIP1 cyclin-dependent kinase inhibitor
Biochem. Biophys. Res. Commun.
(1999) - et al.
The effects of thiazolidinediones on vascular smooth muscle cell activation by angiotensin II
Biochem. Biophys. Res. Commun.
(2000) - et al.
Butyrate activates the WAF1/Cip1 gene promoter through Sp1 sites in a p53-negative human colon cancer cell line
J. Biol. Chem.
(1997) - et al.
WAF1, a potential mediator of p53 tumor suppression
Cell
(1993) - et al.
Lessons from hereditary colorectal cancer
Cell
(1996) - et al.
The MEK pathway is required for stimulation of p21Waf1/CIP1 by transforming growth factor-β
J. Biol. Chem.
(1999) - et al.
PD98059 is a specific inhibitor of the activation of mitogen-activated protein kinase kinase in vitro and in vivo
J. Biol. Chem.
(1995) - et al.
MEK inhibitors: the chemistry and biological activity of U0126, its analogs, and cyclization products
Bioorg. Med. Chem. Lett.
(1998)
Improvement in glucose tolerance and insulin resistance in obese subjects treated with troglitazone
N. Engl. J. Med.
Thiazolidinediones in the treatment of insulin resistance and type II diabetes
Diabetes
The structure–activity relationship between peroxisome proliferator-activated receptor gamma agonism and the antihyperglycemic activity of thiazolidinediones
J. Med. Chem.
Cited by (28)
Targeting PPAR ligands as possible approaches for metabolic reprogramming of T cells in cancer immunotherapy
2020, Immunology LettersCitation Excerpt :While some studies have reported the benefits of PPAR-γ agonists on T cells metabolic reprogramming leading to the function preservation of effector T cells in the inhibitory milieu of the tumor microenvironment, there are also studies indicating that PPAR-γ agonists may cause cell growth arrest and apoptosis in immune cells and tumor cells. Due to the metabolic reprogramming within cells following treatment with PPAR-γ agonists, it is believed that they may result in cell growth arrest and cell death in a broad spectrum of cells particularly tumor cells [69–71]. It has been demonstrated that activation of PPAR-γ pathway in T cells may induce apoptosis/cell death and act as a potent anti-inflammatory signal [72].
Thiazolidinediones inhibit REG Iα gene transcription in gastrointestinal cancer cells
2009, Biochemical and Biophysical Research CommunicationsCitation Excerpt :Taken together, it is quite possible that the inhibitory effects of TZDs on REG Iα gene transcription in gastrointestinal cancer cells depend on their endogenous PPARγ protein expression levels. TZDs, especially troglitazone, are reported to inhibit cell growth through a PPARγ-independent pathway in some cancer cells [13,16]. In order to examine the involvement of PPARγ in the inhibition of REG Iα gene transcription by TZDs, we studied the effects of a non-TZD PPARγ agonist GW1929 [20] and a specific PPARγ-antagonist GW9662 [21].
Receptor-independent actions of PPAR thiazolidinedione agonists: Is mitochondrial function the key?
2005, Biochemical PharmacologyTroglitazone inhibits cyclin D1 expression and cell cycling independently of PPARγ in normal mouse skin keratinocytes
2004, Journal of Investigative DermatologyCitation Excerpt :Cdk inhibitor p21 is known to be involved in PPARγ-induced adipose differentiation. Interestingly, p21 expression is also upregulated by troglitazone in several tumor cells (Koga et al, 2001;Kim et al, 2002). p21 causes G1 arrest through inhibiting phosphorylation of Rb by cdks and inhibiting G1-S transition.
Troglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) ligand, selectively induces the early growth response-1 gene independently of PPARγ: A novel mechanism for its anti-tumorigenic activity
2003, Journal of Biological ChemistryCitation Excerpt :This result is consistent with Western analysis for Egr-1 expression as shown in Fig. 7 Cand indicates that TGZ-induced Egr-1 transactivity is dependent on the ERK pathway. Although the anti-tumorigenic activities of PPARγ ligands are well established in human cancer, controversy exists in the literature with regard to the relative contributions of nuclear receptor-dependent (13, 41, 42) and -independent mechanisms (43-45). In this report, we demonstrate that troglitazone, a PPARγ agonist, induces human colorectal cancer cells to undergo apoptosis and inhibits their growth on soft agar.
Possible protective effects of thiazolidinediones antidiabetic drugs in colorectal cancer
2019, Critical Reviews in Oncogenesis