Deguelin inhibits the growth of colon cancer cells through the induction of apoptosis and cell cycle arrest
Introduction
During the past 20 years, the identification of novel cancer preventive agents has received considerable attention 1, 2, 3. The mechanism of action of a chemopreventive agent is often related to the stage of carcinogenesis at which it is active [4]. For example, antioxidants are often anti-initiators, whereas inhibitors of ornithine decarboxylase (ODC), agents that obstruct cell differentiation or induce programmed cell death, are generally anti-promoters. Chemotherapeutic agents, on the other hand, are used for established tumours that are aggressively progressing. The major difference between chemopreventive and chemotherapeutic agents is that chemopreventive agents are generally non-toxic, whereas chemotherapeutic agents are highly cytotoxic with narrow therapeutic ranges. Thus, there appears to be an ill-defined discrimination between the chemopreventive and chemotherapeutic effects of a compound, especially if the compound is active during the later stages of carcinogenesis. Under these circumstances, chemopreventive agents acting during the progression stage of carcinogenesis can be considered as potential chemotherapeutic agents. Since chemopreventive agents, by definition, must be non-toxic, these agents may serve as safer alternatives. Accordingly, a variety of chemopreventive agents have been considered as potential adjuvant chemotherapeutic agents [5]. These include retinoids, cyclooxygenase (COX) inhibitors, ODC inhibitors, flavonoids, triterpenes, and others [6].
Deguelin, a rotenoid, was identified as a potential chemopreventive agent from Mundulea sericea within the Leguminosae family (Fig. 1). This was accomplished during the process of activity-guided fractionation in an effort to identify novel chemopreventive agents [7]. Deguelin is a potent inhibitor of ODC activity with an IC50 of 0.7 ng/ml in cultured mouse 308 cells, and has been shown to inhibit phorbol-12-myristate 13-acetate (TPA)-induced ODC activity in mouse skin epidermis [8]. Typically, rotenoids are toxic piscicidal agents, however, deguelin is tolerated by mammals at concentrations of up to 4 mg/kg body weight without inducing toxic effects when administered intragastrically to rats [9]. Unlike rotenone, deguelin does not inhibit microtubule assembly or tubulin polymerisation [10]. Due to the activity mediated by deguelin in in vitro models, it has been evaluated as a potential chemopreventive agent. For example, deguelin inhibited the development of carcinogen-induced precancerous lesions in mouse mammary gland organ cultures (MMOC), and suppressed the development of skin papillomas in a two-stage mouse skin carcinogenesis model [11]. In addition, deguelin inhibited tumour multiplicity in a rat mammary carcinogenesis model [11]. Although studies have provided suggestive evidence for the chemoprotective and therapeutic roles of deguelin in different cell types, the mechanism of action by which this rotenoid functions has not been described.
Each year, approximately 140,000 new cases of colorectal cancer are diagnosed in the United States, making it the third leading cause of cancer deaths [12]. Cytotoxic chemotherapy has been used to treat patients with advanced colorectal cancer with limited success, often at the expense of severe side-effects. Therefore, identification of novel chemotherapeutic agents for colon cancer with fewer side-effects is warranted.
Section snippets
Reagents and chemicals
Roswell Park Memorial Institute (RPMI) 1640 was purchased from Life Technologies, Inc. (Rockville, MD). Monoclonal antibodies against proliferating cell nuclear antigen (PCNA; clone PC10), E2F-1 (clone KH129), cyclin E (clone HE12) were purchased from NeoMarkers (Fremont, CA). Mouse monoclonal anti-p27 antibody (clone 57) was obtained from Transduction Laboratories (Lexington, KY). Goat polyclonal anti-actin antibody (clone I-19) was purchased from Santa Cruz Biotechnology (Santa Cruz, CA);
Growth inhibition in HT-29 cells
Effects of various concentrations of deguelin (10 nM–10 μM) were examined in HT-29 colon cancer cells. Deguelin mediated growth inhibition in a dose-dependent manner (Fig. 2), with 70% inhibition at a concentration of 1 μM and an IC50 of 4.32 × 10−8 M. The maximum anti-proliferative response of deguelin was observed after 5 days of treatment. Anti-proliferative effects were also evident in the colon cancer cell lines SW-620 and SW-480 with an IC50 of 4.62 × 10−7 M and 4.59 × 10−8 M,
Discussion
Current evidence suggests that cancer progression may involve the loss of cell cycle checkpoint controls that regulate passage through the cell-cycle. These checkpoints monitor the integrity of the DNA and ensure that genes are expressed in a coordinated manner [17]. By complementing existing cell cycle machinery with extrinsic cell cycle regulators, it may be possible to block the initiation or progression of cancer. Many cancer chemopreventive agents, including naturally occurring and
Acknowledgements
This work was supported in part by programme project P01 CA48112.
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2021, Ecotoxicology and Environmental SafetyCitation Excerpt :The remaining review papers that more generally looked at the association between occupational or environmental exposure to pesticides and CRC risk found that farmers, crop and animal production, and agricultural populations showed mostly significant inverse associations with colon cancer, rectal cancer, or CRC risk (Acquavella et al., 1998; Alexander et al., 2012; Blair and Freeman, 2009; Blair et al., 1985a; Oddone et al., 2014). There have also been some research studies that suggest some pesticides, such as Metarhizium anisopliae (Dornetshuber-Fleiss et al., 2013), deguelin (Murillo et al., 2003, 2002), oryzalin (Powis et al., 1997), benzimidazole carbamates (Wales et al., 2015), rotenone (Yoshitani et al., 2001), and thujone (Zhou et al., 2016) are anti-carcinogenic. Additionally, studies have shown a lower incidence of CRC in farmers compared to the general population (Garabrant et al., 1984).
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2021, European Journal of CancerDeguelin targets multiple oncogenic signaling pathways to combat human malignancies
2021, Pharmacological ResearchCitation Excerpt :Hypophosphorylated Rb binds to the E2 transcription factor 1 (E2F1) and blocks the E2F1 release, thus leading to cell cycle arrest in the G1-S phase. Murillo et al. [34] and Liu et al. [35]showed that deguelin decreased cyclin D1/pRb ratio and subsequent G1-S phase arrest in lymphoma and triple-negative breast cancer cells. In a study using oesophageal squamous cell carcinoma cells, Yu et al. [36] demonstrated the promising role of deguelin in inhibiting Aurora B kinase, which is known to be essential to promote mitotic cell division.
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2019, Chemical Data CollectionsCitation Excerpt :Deguelin (Fig. 1) is a nature rotenoid separated from the African plant Mundulea sericea (Leguminosae) [1] and widely used as a natural cancer chemopreventive agent [2] for its potent apoptotic and antiangiogenic activities against many transformed cells and cancer cells in vitro [3,4]. Many researches have shown that deguelin could reduce the formation of the preneoplastic lesions [5], prevent tobacco carcinogen-induced lung carcinogenesis by impeding Akt activation [6], and inhibit the growth of colon cancer cells [7]. Heat shock proteins (HSPs) are a small group of proteins in cell generating under the exposure to environmental insults [8].