Search

The spice-derived phenolic, malabaricone B (mal B) showed selective toxicity to human lung cancer (A549), malignant melanoma (A375) and T cell leukemia (Jurkat) cell lines, without showing toxicity to human normal intestinal (INT407), human kidney (HEK293) and lung fibroblast (WI-38) cells. Among the chosen cancer cell lines, mal B showed maximum cytotoxicity to the A549 cells (IC50 = 8.1 ± 1.0 μM), which was significantly better than that of curcumin (IC50 = 26.7 ± 3.1 μM). Further morphological studies by phase contrast microscopy and a clonogenic assay of the A549 cells revealed that mal B treatment increased the number of shrinking cells and also abolished the clonal proliferation of the cells. Mal B induced apoptotic cell death was confirmed by DNA laddering and quantified by cytoplasmic oligonucleosome formation and annexin V/PI assays. The mal B-induced apoptosis was mediated by an increase in the intracellular reactive oxygen species (ROS), because the cell-permeable antioxidants, N-acetylcysteine (NAC) and PEG-SOD, strongly inhibited its cytotoxicity to the A549 cells. Mal B increased the BAX level while simultaneously decreasing the BCL-2 and BCL-XL levels in the A549 cells, triggering the mitochondrial apoptotic pathway as revealed from the release of cytochrome c, and the activation of caspase-9 and caspase-3. Pre-treatment of cells with caspase-9, caspase-3 and pan-caspase inhibitors made them more resistant to mal B treatment. This effect of mal B was strongly associated with the concomitant decrease in anti-apoptotic (IAP1, IAP2 and survivin), angiogenic (growth factors) and cancer invasiveness (matrix metalloproteinase-9, COX-2) modulating proteins. Mal B induced cytotoxicity was unaffected by the shRNA-mediated depletion of p53 in A549 cells. Most importantly, mal B sensitized a wide range of human carcinoma cells regardless of their p53 status. Finally, mal B (100 mg kg-1) also inhibited lung tumor (xenograft) growth in SCID mice.

Background: Given that lung cancer is the second leading cause of cancer-related deaths with low survival rates, the project was aimed to formulate an efficient drug with minimum side effects, and rationalize its action mechanistically., Methods: Mitochondria deficient cells, shRNA-mediated BCL2 and ATM depleted cells and pharmacological inhibition of DNA-damage response proteins were employed to explore the signaling mechanism governed between nucleus and mitochondria in response to mal C., Results: Mal C decreased cell viability in three lung carcinoma cells, associated with DNA damage, p38-MAPK activation, imbalance in BAX/BCL2 expression, mitochondrial dysfunction and cytochrome-c release. Mitochondria depletion and p38-MAPK inhibition made A549 cells extremely resistant, but BCL2 knock-down partially sensitized the cells to mal C treatment. The mal C-induced apoptosis in A549 cells was initiated by DNA single strand breaks that led to double strand breaks (DSBs). DSB generation paralleled the induction of ATM- and ATR-mediated CHK1 phosphorylation. ATM silencing and ATR inhibition partially attenuated the mal C-induced p38-MAPK activation, CHK1 phosphorylation and apoptosis, which were completely suppressed by CHK1 inhibition., Conclusions: Mal C activates the ATM-CHK1-p38 MAPK cascade to cause mitochondrial cell death in lung carcinoma cells., General Significance: Given that mal C has appreciable natural abundance and is non-toxic to mice, further in vivo evaluation would help in establishing its anti-cancer property., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The spice-derived phenolic, malabaricone C (mal C), has recently been shown to accelerate healing of the indomethacin-induced gastric ulceration in mice. In this study, we explored its anti-inflammatory activity and investigated the underlying mechanism of the action. Mal C suppressed the microvascular permeability and the levels of tumor necrosis factor-α, interleukin-1β, and nitric oxide in the lipopolysaccharide (LPS)-administered mice. At a dose of 10 mg/kg, it showed anti-inflammatory activity comparable to that of omeprazole (5 mg/kg) and dexamethasone (50 mg/kg). It also reduced the expression and activities of inducible nitric oxide synthase, cyclooxygenase-2, as well as the pro- vs anti-inflammatory cytokine ratio in the LPS-treated RAW macrophages. Mal C was found to inhibit LPS-induced NF-kB activation in RAW 264.7 cells by blocking the MyD88-dependent pathway. Mal C suppressed NF-κB activation and iNOS promoter activity, which correlated with its inhibitory effect on IκB phosphorylation and degradation, and NF-κB nuclear translocation, in the LPS-stimulated macrophages. It also inhibited LPS-induced phosphorylation of p38 and JNK, which are also upstream activators of NF-κB, without affecting Akt phosphorylation. Mal C also effectively blocked the PKR-mediated activation of NF-κB. These findings indicate that mal C exerts an anti-inflammatory effect through NF-κB-responsive inflammatory gene expressions by inhibiting the p38 and JNK-dependent canonical NF-κB pathway as well as the PKR pathway, and is a potential therapeutic agent against acute inflammation., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The nuclease activities of the malabaricones have been studied so as to establish a structure-activity correlation and deduce the mechanistic pathway of the process. The inactivity of malabaricone A and malabaricone D revealed that the resorcinol moiety, present in the malabaricones did not contribute to the nuclease activity. Amongst the test compounds, malabaricone C (mal C) containing a B-ring catechol moiety showed significantly better Cu(II)-dependent nuclease activity than the partially methylated catechol derivative, mal B and curcumin. Mal C was found to bind efficiently with Cu(II) and DNA to facilitate the DNA nicking via a site-specifically generated Cu(I)-peroxo complex. Consistent with its Cu(II)-dependent nuclease property, mal C showed better cytotoxicity (IC(50)=5.26±1.20 μM) than curcumin (IC(50)=24.46±3.32 μM) against the MCF-7 human breast cancer cell line. The mal C-induced killing of the MCF-7 cells followed an apoptotic pathway involving oxidative damage to the cellular DNA., (Copyright © 2010 Elsevier Ltd. All rights reserved.)