Evaluation of the potential of cancer chemopreventive activity mediated by inhibition of 12-O-tetradecanoyl phorbol 13-acetate-induced ornithine decarboxylase activity

Regulation of Polyamine Metabolism by Curcumin for Cancer Prevention and Therapy

Curcumin (diferuloylmethane), the natural polyphenol responsible for the characteristic yellow pigment of the spice turmeric (Curcuma longa), is traditionally known for its antioxidant, anti-inflammatory, and anticarcinogenic properties. Capable of affecting the initiation, promotion, and progression of carcinogenesis through multiple mechanisms, curcumin has potential utility for both chemoprevention and chemotherapy. In human cancer cell lines, curcumin has been shown to decrease ornithine decarboxylase (ODC) activity, a rate-limiting enzyme in polyamine biosynthesis that is frequently upregulated in cancer and other rapidly proliferating tissues. Numerous studies have demonstrated that pretreatment with curcumin can abrogate carcinogen-induced ODC activity and tumor development in rodent tumorigenesis models targeting various organs. This review summarizes the results of curcumin exposure with regard to the modulation of polyamine metabolism and discusses the potential utility of this natural compound in conjunction with the exploitation of dysregulated polyamine metabolism in chemopreventive and chemotherapeutic settings.

Ornithine decarboxylase: a promising and exploratory candidate target for natural products in cancer chemoprevention

Ornithine decarboxylase (ODC), the first enzyme in the polyamine biosynthesis, plays an important role in tumor progression, cell proliferation and differentiation. In recent years, ODC has been the subject of intense study among researchers, as a target for anti-cancer therapy and specific inhibitory agents, have the potential to suppress carcinogenesis and find applications in clinical therapy. In particular, it is suggested that ODC is a promising candidate target for natural products in cancer chemoprevention. Future exploration of ornithine decarboxylase inhibitors present in nature may offer great hope for finding new cancer chemopreventive agents.

Nordihydroguaiaretic acid increases endothelial nitric oxide synthase expression via the transcription factor AP-1

It has been previously reported that the antioxidant compound nordihydroguaiaretic acid (NDGA) increases endothelial nitric oxide synthase (eNOS) expression in cultured bovine aortic endothelial cells. However, the exact mechanism for this effect was unresolved. Thus, the purpose of this study was to further elucidate the effect of NDGA on eNOS protein expression and enzymatic activity in fetal pulmonary arterial endothelial cells (FPAECs), and to identify the transcription factors involved in this regulation. Following overnight exposure to 0-32 microM NDGA, we observed a 2- to 2.5-fold increase in eNOS protein expression in FPAECs, with a similar increase observed in eNOS activity. For eNOS gene promoter analysis, we initially used two promoter-reporter constructs: a 1.6 kb promoter fragment and an 840 bp construct, both of which include an AP-1-specific binding site. NDGA exposure induced a significant increase in eNOS promoter activity in both constructs. However, the NDGA-mediated increase was abolished when we used either a truncated promoter construct lacking the AP-1 element or a construct in which the AP-1 binding site was mutated. AP-1 binding efficiency was also determined by electrophoretic mobility shift assay, where we observed an increase in AP-1 binding in FPAECs treated with NDGA while the binding of AP-1 was found to be decreased when a mutated AP-1 consensus sequence was used. Further, supershift analyses indicated that the AP-1 complex consisted of c-Jun and FosB. We therefore conclude that NDGA antioxidant activity regulates eNOS expression via AP-1 and that antioxidant therapy could potentially be used to increase eNOS expression in diseases, such as persistent pulmonary hypertension of the newborn, where eNOS expression and activity are known to be reduced.

Biological properties of curcumin-cellular and molecular mechanisms of action

Curcuminoids, a group of phenolic compounds isolated from the roots of Curcuma longa (Zingiberaceae), exhibit a variety of beneficial effects on health and on events that help in preventing certain diseases. A vast majority of these studies were carried out with curcumin (diferuloyl methane), which is a major curcuminoid. The most detailed studies using curcumin include anti-inflammatory, antioxidant, anticarcinogenic, antiviral, and antiinfectious activities. In addition, the wound healing and detoxifying properties of curcumin have also received considerable attention. As a result of extensive research on the therapeutic properties of curcumin, some understanding on the cellular, molecular, and biochemical mechanism of action of curcumin is emerging. These findings are summarized in this review.