Current Medicinal Chemistry - Volume 20, Issue 33, 2013

Salinomycin, traditionally used as an anti-coccidial drug, has recently been shown to possess anti-cancer and anti-cancer stem cell (CSC) effects, as well as activities to overcome multi-drug resistance based on studies using human cancer cell lines, xenograft mice, and in case reports involving cancer patients in pilot clinical trials. Therefore, salinomycin may be considered as a promising novel anti-cancer agent despite its largely unknown mechanism of action. This review summarizes the pharmacologic effects of salinomycin and presents possible mechanisms by which salinomycin exerts its anti-tumorigenic activities. Recent advances and potential complications that might limit the utilization of salinomycin as an anti-cancer and anti-CSC agent are also presented and discussed.

In the past 50 years, thalidomide has undergone a remarkable metamorphosis from a notorious drug inducing birth defects into a highly effective therapy for treating leprosy and multiple myeloma. Today, most notably, thalidomide and its analogs have shown efficacy against a wide variety of diseases, including inflammation and cancer. The mechanism underlying its teratogenicity as well as its anticancer activities has been intensively studied. This review summarizes the biological effects and therapeutic uses of thalidomide and its analogs, and the underlying mechanisms of thalidomide’s action with a focus on its suppression of tumor growth.

Various epidemiological studies have demonstrated that vitamin D may play important roles in the pathogenesis and progression of cancer. Vitamin D is one of the most pivotal nutraceuticals whose active metabolite, calcitriol (1,25-dihydroxyvitamin D3), possesses anti-proliferative, pro-apoptotic, and pro-differentiating capabilities. Accumulating evidence indicates that the potential benefits of using vitamin D in cancer are not only anti-cancer cell proliferation which is linked with its anti-inflammatory effects, including the suppression of prostaglandin metabolism and inhibition of NF- κB signaling, but also suppressing tumor metastasis and angiogenesis. Here, we present a systematic summary of the effects of vitamin D in the chemoprevention and chemotherapy of cancer, especially anti-metastatic and anti-angiogenic actions.

Calcitriol (1, 25-dihydroxyvitamin D3) is the most biologically active metabolite derived from the secosteroid hormone vitamin D. Apart from its calcium homeostatic effects, epidemiological studies have shown that reduced serum calcitriol levels are associated with an increased risk of some types of cancer. Numerous recent epidemiological and experimental studies have reported that it elicits anti-proliferative, apoptotic and differentiation effects in several malignant cell types. The inhibition of calcitriol results in reduced effects of anticancer drugs. Results from a number of clinical trials revealed that sufficient dosing and exposure to calcitriol is critical for achieving antitumor effects during intermittent regimens. This review summarizes the role of calcitriol in anticancer therapy and the progress in understanding its mechanism.

Epidemiological and clinical studies have indicated that low vitamin D activity is not only associated with an increased cancer risk and a more aggressive tumor growth, but also connected with an aggravated liver damage caused by chronic inflammation. Meanwhile, increasing evidence has demonstrated that 1,25(OH)2D3 (the most biologically active metabolite of vitamin D) can inhibit inflammatory response in some chronic inflammatory associated cancer, which is considered to have the anti-tumor potency. However, the interaction between 1,25(OH)2D3 and inflammation during hepatocellular carcinoma (HCC) initiation and progression is not yet clear. Here, we report an anti-tumorigenesis effect of 1,25(OH)2D3 via decreasing inflammatory cytokine secretion in HCC and hypothesize the possible underlying mechanism. Firstly, we show that the enhanced tumor growth is associated with elevated inflammatory cytokine IL-6 and TNF-α in 1α(OH)ase gene-knockout mice. Secondly, 1,25(OH)2D3 can inhibit vitamin D receptor (VDR) shRNA interfered tumor cell growth through decreasing inflammatory cytokine secretion in vitro and in vivo. Finally, using p27kip1 gene knock-out mouse model, we demonstrate that the effect of 1,25(OH)2D3 in inhibiting immune cell related inflammatory cytokine secretion, exerts in a p27kip1 gene dependent way. Collectively, 1,25(OH)2D3 inhibits HCC development through up-regulating the expression of p27kip1 in immune cell and reducing inflammatory cytokine production.

Indometacin, an inhibitor of cyclooxygenase-2 (COX-2), has been shown to exert anticancer effects in a variety of cancers. However, the effect and mechanism of indometacin on high glucose (HG)-induced proliferation and invasion of pancreatic cancer (PC) cells remain unclear. Multiple lines of evidence suggest that a large portion of pancreatic cancer (PC) patients suffer from either diabetes or HG which contributing PC progression. In this study, we report that indometacin down-regulated HG-induced proliferation and invasion via up-regulating E-cadherin but not COX-2 in PC cells. Additionally, the E-cadherin transcriptional repressors, Snail and Slug, were also involved in the process. Furthermore, the proliferation and invasion of PC cells, incubated in HG medium and treated with indometacin were significantly increased when E-cadherin was knocked down (Si-E-cad). Moreover, the protein levels of MMP-2, MMP-9, and VEGF were increased in PC cells transfected with Si-E-cad. Finally, the activation of the PI3K/AKT/GSK-3β signaling pathway was demonstrated to be involved in indometacin reversing HG-induced cell proliferation and invasion in PC cells. In conclusion, these results suggest that indometacin plays a key role in down-regulating HG-induced proliferation and invasion in PC cells. Our findings indicate that indometacin could be used as a novel therapeutic strategy to treat PC patients who simultaneously suffer from diabetes or HG.

Inflammation has become a research hotspot in solid tumours and has been confirmed as a key factor in tumour development through the interactions of inflammatory mediators with gene expression, cell proliferation, and apoptosis. Pancreatic cancer (PC) is one of the most aggressive and deadliest forms of gastrointestinal cancer. A large case-control study found that aspirin, an anti-inflammatory drug, was associated with a decreased risk of PC. Moreover, aspirin has been shown to have inhibitory effects on PC in both in vitro and in vivo studies. However, the clinical data analysis has not been similarly promising. Results from genetic and pharmacological studies suggest that the anti-tumour effects of aspirin are mediated, at least in part, through the inhibition of COXs. Furtermore, other results suggest that the chemopreventive and therapeutic effects of aspirin are also mediated through COX-independent mechanisms. The COX-dependent and COX-independent mechanisms will be described in this review. In addition, we will discuss future research directions on the risks and benefits of the use of aspirin to treat PC and the potential cellular/molecular.

To explain a bimodal pattern of hazard of relapse among early stage breast cancer patients identified in multiple databases, we proposed that late relapses result from steady stochastic progressions from single dormant malignant cells to avascular micrometastases and then on to growing deposits. However in order to explain early relapses, we had to postulate that something happens at about the time of surgery to provoke sudden exits from dormant phases to active growth and then to detection. Most relapses in breast cancer are in the early category. Recent data from Forget et al. suggest an unexpected mechanism. They retrospectively studied results from 327 consecutive breast cancer patients comparing various perioperative analgesics and anesthetics in one Belgian hospital and one surgeon. Patients were treated with mastectomy and conventional adjuvant therapy. Relapse hazard updated Sept 2011 are presented. A common Non-Steroidal Anti-Inflammatory Drug (NSAID) analgesic used in surgery produced far superior disease-free survival in the first 5 years after surgery. The expected prominent early relapse events in months 9-18 are reduced 5-fold. If this observation holds up to further scrutiny, it could mean that the simple use of this safe, inexpensive and effective anti-inflammatory agent at surgery might eliminate early relapses. Transient systemic inflammation accompanying surgery could facilitate angiogenesis of dormant micrometastases, proliferation of dormant single cells, and seeding of circulating cancer stem cells (perhaps in part released from bone marrow) resulting in early relapse and could have been effectively blocked by the perioperative anti-inflammatory agent.

Ormeloxifene is a non-steroidal Selective Estrogen Receptor Modulator (SERM) that is used as an oral contraceptive. Recent studies have shown its potent anti-cancer activities in breast, head and neck, and chronic myeloid leukemia cells. Several in vivo and clinical studies have reported that ormeloxifene possesses an excellent therapeutic index and has been well-tolerated, without any haematological, biochemical or histopathological toxicity, even with chronic administration. A reasonably long period of time and an enormous financial commitment are required to develop a lead compound into a clinically approved anti-cancer drug. For these reasons and to circumvent these obstacles, ormeloxifene is a promising candidate on a fast track for the development or repurposing established drugs as anti-cancer agents for cancer treatment. The current review summarizes recent findings on ormeloxifene as an anti-cancer agent and future prospects of this clinically safe pharmacophore.

Resveratrol (trans-3,4’,5-trihydroxystilbene), a natural polyphenolic compound detected in grapes, berries, and peanuts, possesses a wide spectrum of pharmacological properties, including anti-tumor metastasis activities. However, the underlying mechanisms through which resveratrol inhibits the metastasis of pancreatic cancer are still not fully elucidated. As epithelial-to-mesenchymal transition (EMT) is a key player for metastasis in tumor, the aim of this study is to determine whether resveratrol affects EMT in pancreatic cancer cells and the related mechanism. The results showed that resveratrol not only inhibited cell proliferation, migration, and invasion in a dose-dependent manner, but also mediated the expression of EMT-related genes (E-cadherin, N-cadherin, vimentin, MMP-2, and MMP-9) which are important for cancer cellular motility, invasiveness and metastasis during tumorigenesis. In addition, the levels of phospho-Akt and phospho- NF-κB in BxPC-3 and Panc-1 cells were reduced by both resveratrol and LY294002 (a PI3-K inhibitor). Furthermore, transforming growth factor-β (TGF-β)-induced alterations in cell morphology that are characteristic of EMT as well as increased cell invasive ability could also be reversed by resveratrol. Taken together, these data indicate that resveratrol suppresses pancreatic cancer migration and invasion through the inhibition of the PI-3K/Akt/NF-κB signaling pathway. This study suggests that resveratrol may be a potential anticancer agent for pancreatic cancer.

To obtain information on anti-prostate cancer (CaP) activities of piceatannol, a metabolite biotransformed from resveratrol by cytochrome P450 CYP1B, CWR22Rv1 cells were incubated with increasing dose of piceatannol. Proliferation and apoptosis assays in exposed cells showed that piceatannol produced inhibition comparable to resveratrol. To determine whether quinone reductase 2 (NQO2) plays a role in the observed effects, in silico analysis was performed. Piceatannol interacted with NQO2 at the same site as resveratrol forming hydrogen bond with asparagine-161 (ASN161). NQO2 mediated anti-CaP effects of piceatannol were also tested and supported by the attenuation of anti-proliferative activity and reduction in extent of inhibition of NQO2 activity by piceatannol in NQO2-knockdown cells relative to NQO2- expressing cells, and by the copious expression of CYP1B in CWR22Rv1 cells. These results show that NQO2 is an intracellular target for piceatannol, suggesting that CaP prevention by resveratrol may be partially attributed to its conversion to piceatannol.