Chronic inflammation is one of the predisposing factors for neoplastic transformation. Targeting inflammation through suppression of the pro-inflammatory pathway by dietary phytochemicals provides an important strategy for cancer prevention. Maslinic acid is a novel natural triterpenoid known to inhibit proliferation and induce apoptosis in some tumor cell lines. Although maslinic acid has cytotoxic and pro-apoptotic effects on cancer cells, the underlying mechanisms of its effects on the inflammatory pathway have yet to be elucidated. It has been reported that abnormal expression of pro-inflammatory enzyme cyclooxygenase-2 (COX-2) causes promotion of cellular proliferation, suppression of apoptosis, enhancement of angiogenesis and invasiveness. In the present study, the suppressive effect of maslinic acid on COX-2 expression and the binding activity of upstream transcription factors NF- κB and AP-1, which are known to regulate COX-2 transcriptional activation, were assessed using Raji cells. The anti-inflammatory action of maslinic acid was benchmarked against oleanolic acid and other standard drugs. Western blot analysis and electrophoretic mobility shift assay (EMSA) were employed to analyze COX-2 expression as well as NF- κB and AP-1 binding activity. Our results showed that maslinic acid suppresses COX-2 expression in a concentration-dependent manner. Likewise, the constitutive nuclear NF- κB (p65) activity as well as phorbol 12-myristate 13-acetate (PMA)- and sodium N-butyrate (SnB)-induced AP-1 binding activity in Raji cells were significantly reduced following treatment with maslinic acid. Since maslinic acid suppresses COX-2 expression in Raji cells at concentrations that also lowered the NF- κB (p65) and AP-1 binding activity, it is possible that the suppression of COX-2 by this natural triterpenoid might be achieved, at least in part, via the NF- κB and AP-1 signaling pathways.

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Protein Kinase C (PKC) is widely documented to be involved in the regulation of cancer cell growth, proliferation, survival, inflammation and apoptosis. This study evaluates the capability of 2-Methoxy-1,4-Naphthoquinone (MNQ) in regulating PMA-induced PKC expression in human Burkitt's lymphoma cell line (Raji cells). MNQ exhibited stronger anti-tumour-promoting activity than genistein based on the inhibitory assay of Epstein-Barr virus (EBV) activation. The IC50 values attained were 2.92 and 7.40 μM, respectively. The suppressive effects of MNQ on PKC expression was determined by using the PepTag® non-radioactive detection of PKC assay. The IC50 values achieved for staurosporine and rottlerin (standard control), and MNQ were 0.01, 6.38, and 13.13 μM, respectively. These preliminary results indicate that MNQ specifically suppressed the expression of PKC βI, δ, and ζ in a concentration-dependent manner in Raji cells.