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1.  HDAC6 and SIRT2 regulate the acetylation state and oncogenic activity of mutant K-RAS 
Molecular cancer research : MCR  2013;11(9):1072-1077.
Activating point mutations in K-RAS are extremely common in cancers of the lung, colon, and pancreas and are highly predictive of poor therapeutic response. One potential strategy for overcoming the deleterious effects of mutant K-RAS is to alter its post-translational modification. While therapies targeting farnesylation have been explored, and ultimately failed, the therapeutic potential of targeting other modifications remains to be seen. We recently demonstrated that acetylation of lysine 104 attenuates K-RAS transforming activity by interfering with GEF-induced nucleotide exchange. Here, we have identified HDAC6 and SIRT2 as deacetylases that regulate the acetylation state of K-RAS in cancer cells. By extension, inhibition of either of these enzymes dramatically affects the growth properties of cancer cell lines expressing mutationally activated K-RAS. These results suggest that therapeutic targeting of HDAC6 and/or SIRT2 may represent a new way to treat cancers expressing mutant forms of K-RAS.
PMCID: PMC3778089  PMID: 23723075
2.  The Cinnamon-derived Dietary Factor Cinnamic Aldehyde Activates the Nrf2-dependent Antioxidant Response in Human Epithelial Colon Cells 
Molecules (Basel, Switzerland)  2010;15(5):3338-3355.
Colorectal cancer (CRC) is a major cause of tumor-related morbidity and mortality worldwide. Recent research suggests that pharmacological intervention using dietary factors that activate the redox sensitive Nrf2/Keap1-ARE signaling pathway may represent a promising strategy for chemoprevention of human cancer including CRC. In our search for dietary Nrf2 activators with potential chemopreventive activity targeting CRC, we have focused our studies on trans-cinnamic aldehyde (cinnamaldeyde, CA), the key flavor compound in cinnamon essential oil. Here we demonstrate that CA and an ethanolic extract (CE) prepared from Cinnamomum cassia bark, standardized for CA content by GC-MS analysis, display equipotent activity as inducers of Nrf2 transcriptional activity. In human colon cancer cells (HCT116, HT29) and non-immortalized primary fetal colon cells (FHC), CA- and CE-treatment upregulated cellular protein levels of Nrf2 and established Nrf2 targets involved in the antioxidant response including heme oxygenase 1 (HO-1) and γ-glutamylcysteine synthetase (γ-GCS, catalytic subunit). CA- and CE-pretreatment strongly upregulated cellular glutathione levels and protected HCT116 cells against hydrogen peroxide-induced genotoxicity and arsenic-induced oxidative insult. Taken together our data demonstrate that the cinnamon-derived food factor CA is a potent activator of the Nrf2-orchestrated antioxidant response in cultured human epithelial colon cells. CA may therefore represent an underappreciated chemopreventive dietary factor targeting colorectal carcinogenesis.
PMCID: PMC3101712  PMID: 20657484
colon cancer; Nrf2-activator; cinnamic aldehyde; antioxidant response
3.  GLO1 Overexpression in Human Malignant Melanoma 
Melanoma research  2010;20(2):85-96.
Glyoxalase I [lactoylglutathione lyase (EC encoded by GLO1] is a ubiquitous cellular defense enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis. Accumulative evidence suggests an important role of GLO1 expression in protection against methylglyoxal-dependent protein adduction and cellular damage associated with diabetes, cancer, and chronological aging. Based on the hypothesis that GLO1 upregulation may play a functional role in glycolytic adaptations of cancer cells, we examined GLO1 expression status in human melanoma tissue. Quantitative RT-PCR analysis of a cDNA tissue array containing 40 human melanoma tissues (stages III and IV) and 13 healthy controls revealed pronounced upregulation of GLO1 expression at the mRNA level. Immunohistochemical analysis of a melanoma tissue microarray confirmed upregulation of glyoxalase 1 protein levels in malignant melanoma tissue versus healthy human skin. Consistent with an essential role of GLO1 in melanoma cell defense against methylglyoxal cytotoxicity, siRNA interference targeting GLO1-expression (siGLO1) sensitized A375 and G361 human metastatic melanoma cells towards the antiproliferative, apoptogenic, and oxidative stress-inducing activity of exogenous methylglyoxal. Protein adduction by methylglyoxal was increased in siGLO1-transfected cells as revealed by immunodetection using a monoclonal antibody directed against the major methylglyoxal-derived epitope argpyrimidine that detected a single band of methylglyoxal-adducted protein in human LOX, G361, and A375 total cell lysates. Using 2D-proteomics followed by mass spectrometry the methylglyoxal-adducted protein was identified as heat shock protein 27 (Hsp27; HSPB1). Taken together, our data suggest a function of GLO1 in the regulation of detoxification and target-adduction by the glycolytic byproduct methylglyoxal in malignant melanoma.
PMCID: PMC2891514  PMID: 20093988
Malignant melanoma; glyoxalase 1; methylglyoxal; heat shock protein 27; protein adduction
4.  Antimelanoma Activity of the Redox Dye DCPIP (2,6-Dichlorophenolindophenol) is Antagonized by NQO1 
Biochemical pharmacology  2009;78(4):344-354.
Altered redox homeostasis involved in the control of cancer cell survival and proliferative signaling represents a chemical vulnerability that can be targeted by prooxidant redox intervention. Here, we demonstrate that the redox dye 2,6-dichlorophenolindophenol (DCPIP) may serve as a prooxidant chemotherapeutic targeting human melanoma cells in vitro and in vivo. DCPIP-apoptogenicity observed in the human melanoma cell lines A375 and G361 was inversely correlated with NAD(P)H:quinone oxidoreductase (NQO1) expression levels. In A375 cells displaying low NQO1 activity, DCPIP induced apoptosis with procaspase-3 and PARP cleavage, whereas G361 cells expressing high levels of enzymatically active NQO1 were resistant to DCPIP-cytotoxicity. Genetic (siRNA) or pharmacological (dicoumarol) antagonism of NQO1 strongly sensitized G361 cells to DCPIP apoptogenic activity. DCPIP-cytotoxicity was associated with the induction of oxidative stress and rapid depletion of glutathione in A375 and NQO1-modulated G361 cells. Expression array analysis revealed a DCPIP-induced stress response in A375 cells with massive up-regulation of genes encoding Hsp70B’ (HSPA6), Hsp70 (HSPA1A), heme oxygenase-1 (HMOX1), and early growth response protein 1 (EGR1) further confirmed by immunodetection. Systemic administration of DCPIP displayed significant antimelanoma activity in the A375 murine xenograft model. These findings suggest feasibility of targeting tumors that display low NQO1 enzymatic activity using DCPIP.
PMCID: PMC2742658  PMID: 19394313
melanoma; oxidative stress; NQO1; 2,6-dichlorophenolindophenol; Hsp70B’; xenograft
5.  The Cinnamon-derived Michael Acceptor Cinnamic Aldehyde Impairs Melanoma Cell Proliferation, Invasiveness, and Tumor Growth 
Free radical biology & medicine  2008;46(2):220-231.
Redox dysregulation in cancer cells represents a chemical vulnerability that can be targeted by prooxidant redox intervention. Dietary constituents that contain an electrophilic Michael acceptor pharmacophore may therefore display promising chemopreventive and chemotherapeutic anti-cancer activity. Here, we demonstrate that the cinnamon-derived dietary Michael acceptor trans-cinnamic aldehyde (CA) impairs melanoma cell proliferation and tumor growth. Feasibility of therapeutic intervention using high doses of CA (120 mg/kg, p.o., q.d., 10 days) was demonstrated in a human A375 melanoma SCID-mouse xenograft model. Low micromolar concentrations (IC50 < 10 μM) of CA, but not closely related CA-derivatives devoid of Michael acceptor activity, suppressed proliferation of human metastatic melanoma cell lines (A375, G361, LOX) with G1 cell cycle arrest, elevated intracellular ROS, and impaired invasiveness. Expression array analysis revealed that CA induced an oxidative stress response in A375 cells, up-regulating heme oxygenase-1 (HMOX1), sulfiredoxin 1 homolog (SRXN1), thioredoxin reductase 1 (TXNRD1), and other genes including the cell cycle regulator and stress-responsive tumor suppressor gene cyclin-dependent kinase inhibitor 1A (CDKN1A), a key mediator of G1 phase arrest. CA, but not Michael-inactive derivatives, inhibited NFκB transcriptional activity and TNFα-induced IL-8 production in A375 cells. These findings support a previously unrecognized role of CA as a dietary Michael acceptor with potential anticancer activity.
PMCID: PMC2650023  PMID: 19000754
melanoma; oxidative stress; Michael acceptor; cinnamic aldehyde; NFκB; p21 (CDKN1A); xenograft

Results 1-5 (5)