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Blood, 26 February 2009, Vol. 113, No. 9, pp. 2003-2013.
Prepublished online as a Blood First Edition Paper on October 24, 2008; DOI 10.1182/blood-2008-04-151944.
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LYMPHOID NEOPLASIA
Modification of the cysteine residues in I B kinase and NF- B (p65) by xanthohumol leads to suppression of NF- B–regulated gene products and potentiation of apoptosis in leukemia cells
Kuzhuvelil B. Harikumar1,
Ajaikumar B. Kunnumakkara1,
Kwang S. Ahn1,
Preetha Anand1,
Sunil Krishnan2,
Sushovan Guha3, and
Bharat B. Aggarwal1
1 Cytokine Research Laboratory, Department of Experimental Therapeutics,
2 Department of Radiation Oncology, and
3 Department of Gastroenterology, Hepatology and Nutrition, University of Texas M. D. Anderson Cancer Center, Houston
Xanthohumol (XN), a prenylated chalcone isolated from hop plant, exhibits anti-inflammatory, antiproliferative, and antiangiogenic properties through an undefined mechanism. Whether examined by intracellular esterase activity, phosphatidylserine externalization, DNA strand breaks, or caspase activation, we found that XN potentiated tumor necrosis factor–induced apoptosis in leukemia and myeloma cells. This enhancement of apoptosis correlated with down-regulation of nuclear factor- B (NF- B) survivin, bcl-xL, XIAP, cIAP1, cIAP2, cylin D1, and c-myc. XN down-regulated both constitutive and inducible NF- B activation, inhibition of phosphorylation and degradation of I B , suppression of p65 nuclear translocation, and NF- B–dependent reporter gene transcription. XN directly inhibited tumor necrosis factor-induced I B kinase (IKK) activation and a reducing agent abolished this inhibition, indicating the role of cysteine residue. XN had no effect on the IKK activity when cysteine residue 179 of IKK was mutated to alanine. XN also directly inhibited binding of p65 to DNA, a reducing agent reversed this effect, and mutation of cysteine residue 38 to serine of p65 abolished this effect. Thus, our results show that modification of cysteine residues of IKK and p65 by XN leads to inhibition of the NF- B activation pathway, suppression of antiapoptotic gene products, and potentiation of apoptosis in leukemia cells.

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S. LUST, B. VANHOECKE, M. VAN GELE, J. BOELENS, H. VAN MELCKEBEKE, M. KAILEH, W. VANDEN BERGHE, G. HAEGEMAN, J. PHILIPPE, M. BRACKE, et al.
Xanthohumol Activates the Proapoptotic Arm of the Unfolded Protein Response in Chronic Lymphocytic Leukemia
Anticancer Res,
October 1, 2009;
29(10):
3797 - 3805.
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