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Resting membrane potential (RMP) and intracellular Ca2+ concentration [(Ca2+)i] are involved in tumorigenesis and metastasis. The present study investigated whether functional cardiac Na+ channels are expressed in human melanoma cells (WM 266-4) and its nonmalignant human melanocytes (HMC), as well as whether they participate in RMP maintenance and Ca2+ homeostasis. Confocal microscopy and western blot analysis were used to detect Na+ channels. The patch-clamp technique was employed to record Na+ currents and action potentials. Cytoplasmic Ca2+ was measured by loading Fluo-4. Cardiac (Nav1.5) Na+ channels were expressed in HMCs and WM 266-4 cells. Tetrodotoxin (TTX) dose-dependently blocked Na+ currents in WM 266-4 while HMCs had no Na+ currents. Ultraviolet light induced similar action potentials in HMCs and WM 266-4 cells, which were abolished by transient receptor potential A1 channel-specific blocker, HC-030031. Compared with HMCs, RMP was substantially depolarized in WM 266-4. TTX hyperpolarized RMP in WM 266-4 cells at a concentration of 30 µM, which facilitated Ca2+ influx. Compared with HMCs, (Ca2+)i was significantly higher in WM 266-4 cells and was elevated by 30 µM TTX. Collectively, Cardiac Na+ channels depolarize RMP and inhibit Ca2+ uptake in melanoma cells possibly contributing to tumorigenesis and metastasis. Na+ channel agonists may be developed to treat melanoma such as WM 266-4.

Doxorubicin has been used clinically to treat various types of cancer, and yet the molecular mode of actions of doxorubicin remains to be fully unraveled. In this study, we investigated the effect of doxorubicin on cultured ovarian cancer cells (CaOV3). MTT assay data showed that doxorubicin inhibits cell proliferation in a time- and dose-dependent manner. Phagokinetic cell motility assay data indicated that doxorubicin inhibits both basal level and EGF-induced cell migration in CaOV3 cells. Confocal microscopic data revealed that doxorubicin induces reorganization of cytoskeletal proteins including actin, tubulin and vimentin. Doxorubicin induces phosphorylation of p53 at Ser15 and 20, acetylation of p53 and ATM activation. Doxorubicin also induces phosphorylation of histone H2AX at Ser139. Interestingly, doxorubicin also inhibits mTOR activity, measured by phosphorylation of S6 ribosomal protein. Pretreatment of CaOV3 cells with antioxidant N-acetylcysteine (NAC), but not pyrrolidine dithiocarbamate (PDTC) potentiates doxorubicin-induced phosphorylation of p53 and ATM. Collectively, we conclude that doxorubicin induces ATM/p53 activation leading to reorganization of cytoskeletal networks, inhibition of mTOR activity, and inhibition of cell proliferation and migration. Our data also suggest that removal of oxidants by antioxidants such as NAC may enhance the efficacy of doxorubicin in vivo.

Solar ultraviolet (UV) irradiation is one of the most significant extrinsic factors contributing to skin photoaging. One major characteristic of photoaging induced by UV is water loss of the skin. Water movement across the plasma membrane can occur via two pathways: by diffusion through the lipid bilayer and by membrane-inserted water channels (aquaporins). In this study we demonstrate that UV induces aquaporin-3 (AQP3) downregulation in cultured keratinocytes (HaCaT cells). PD98059 and U0126, MEK/ERK inhibitors, inhibit UV-induced AQP3 loss. Trans-Zeatin (tZ), which alone induces AQP3 expression, attenuates UV-induced loss of AQP3. We found that tZ inhibits UV-induced MEK/ERK activation; the latter serves as the key signal pathway mediating UV-induced AQP3 loss. Using specific AQP3 siRNA knockdown, we found AQP3 is involved in wound healing in human skin keratinocytes. Loss-of-AQP3-mediated delayed wound healing in UV-radiated skin keratinocytes is attenuated by tZ pretreatment. tZ pretreatment also attenuates UV-induced decreased water permeability in HaCaT cells. We concluded that UV radiation downregulates AQP3 in HaCaT cells. MEK/ERK activation is involved in this process. tZ treatment attenuates UV-induced AQP3 loss, in vitro wound healing delay and water permeability decrease. This work provides a new explanation for the anti-photoaging potential of tZ.

Our previous study has shown that VIT1 gene in Chinese vitiligo patients is de facto the FBXO11 gene, and the silencing of that gene has an impact on the ultrastructure of melanocytes. In this study, we further identified the role of the FBXO11 gene in melanocytes and the relationship between dilated endoplasmic reticulum (ER) and tyrosinase by inhibition and overexpression of FBXO11 gene. Cell proliferation, apoptosis, cycle and migration of melanocytes were examined when the FBXO11 gene was silenced or overexpressed. The results showed that FBXO11 gene promoted cell proliferation and suppressed cell apoptosis, and yet had little effect on cell migration. Obvious swelling of ER was found in the cells transfected with siRNA of FBXO11 gene. Interestingly, protein level of tyrosinase was extraordinarily high following inhibition of FBXO11 gene. Further examination revealed that tyrosinase and calreticulin were co-localized in ER of transfected cells following siRNA of FBXO11 gene, suggesting that tyrosinase could not be exported from ER effectively. Collectively, our results support the notion that FBXO 11 plays an important role in regulating proliferation and apoptosis of melanocytes, and functional export of tyrosinase from ER in vitiligo melanocytes.

The CD3 molecule is a critical component of both humoral and cellular immune responses, and yet while the structure and molecular assembly of other key mediators such as CD4 and CD8 have been reported, individual CD3 subunits have not been well characterized. Our understanding of the manner in which they interact remains limited, and the question of how many subunits are required for a functional CD3 molecular complex is yet to be addressed. It has been suggested that CD3 epsilon pairs with CD3 gamma or with CD3 delta, forming CD3 epsilon gamma and CD3 epsilon delta heterodimers that associate with alpha/beta T cell receptors (TCRs) and CD3 zeta 2 dimers. In this study we investigated whether interactions between each CD3 epsilon subunit play a role in the formation of the CD3 molecular complex. Our results revealed that the human CD3 epsilon subunit forms a homodimer structure, which is a crucial piece of information for the elucidation of cellular signaling following TCR receptor ligation, and provide insight into our understanding of the molecular assembly of the CD3 molecular complex.

Ultraviolet (UV) radiation is one of the important cataract risk factors. The migration of human lens epithelial cells (HLECs) plays a crucial role in the remodeling of lens capsule and cataract formation. The purpose of the present study was to investigate the molecular mechanisms of UV-induced lens cell migration. We found that UVB radiation induces cell migration in cultured human lens epithelial cells. Further, we observed that UVB radiation induces NADPH oxidase activity and ROS generation which are inhibited by NADPH oxidase inhibitor diphenylene iodonium or DPI and antioxidant epigallocatechin gallate (EGCG). In addition, DPI and EGCG also block UVB irradiation-induced MMP-2, and -9 activity and expression and nuclear translocation of NF-kappaB. Collectively, our data suggest that NADPH oxidase may be a major source for the UVB-induced ROS generation, and it plays an essential role in the activation of NF-kappaB, which is involved in the activities of MMP-2 and MMP-9 and cell migration induced by UVB in HELCs. Understanding the cell signaling pathways may constitute potential therapeutic targets in for UVB-induced cataract.

Ultraviolet (UV) irradiation induces the expression of matrix metalloproteinases (MMPs), disturbing the metabolism of extracellular matrix (ECM), and causes the characteristic changes of photoaging in skin. Inhibition of induction of MMPs is suggested to alleviate photoaging induced by UV irradiation. Zeatin, purified from Zea mays, is a member of the cytokinin group of plant growth factors, the activity of which is attributed to its more stable trans form. In this study, we investigated the effect of trans-Zeatin on UVB-induced matrix metalloproteinase-1 (MMP-1) expression in cultured human skin fibroblasts (HSFs) and studied the mechanisms of its actions. We found that pretreatment with trans-Zeatin significantly inhibits UVB-induced MMP-1 expression and c-Jun activation in a dose-dependent manner. We also observed that trans-Zeatin inhibits UVB-induced phosphorylation of ERK, JNK and p38 MAP kinases (MAPKs) dose-dependently. As expected, PD98059, an ERK inhibitor, SP600125, a JNK inhibitor and SB203580, a p38 MAPK inhibitor effectively inhibit UVB-induced phosphorylation of ERK, JNK and p38 MAPKs, respectively. Moreover, the inhibitory mechanism of trans-Zeatin was further demonstrated in MMP-1 secretion using MAPK-specific inhibitors. PD98059, SP600125 and SB203580 suppressed UVB-induced MMP-1 secretion, which is consistent with the above results. Collectively, our results suggest that trans-Zeatin inhibits UVB-induced MMP-1 expression, which may be mediated by inhibition of ERK, JNK and p38 MAPKs signaling pathways in HSFs. Trans-Zeatin is a potential agent for the management of skin photoaging.

Vitiligo is an acquired and progressive disorder manifested by the selective destruction of melanocytes in the skin. An extremely high level of hydrogen peroxide (H2O2) in plasma as well as in lesional skin has been reported in vitiligo patients. High H2O2 level has been suggested to be responsible for the disappearance of melanocytes in vitiligo. JNK and p38 MAPK are strongly induced by oxidative stress and related to neuron loss in neurodegenerative disorders. Minocycline, an antibiotic possessing antioxidant activity, is capable of attenuating oxidative stress-induced neurotoxicity. To investigate whether minocycline rescues melanocytes from H2O2-induced apoptosis, cultured mouse melanocytes (B10BR) were treated with H2O2 in the presence or absence of minocycline. Our data showed that H2O2 decreases cell viability in a concentration-dependent manner which is attenuated by minocycline. Also, H2O2 treatment activates JNK and p38 MAPK, and executive caspase 3 in B10BR cells. Minocycline significantly inhibits H2O2-induced activation of JNK, p38 MAPK and caspase 3. Collectively, we concluded that minocycline protects melanocytes against H2O2-induced apoptosis in vitro. Its protective effect is associated with the inhibition of JNK and p38 MAPK. Our findings suggest that minocycline, a clinically well-tolerated, safe antibiotic, may be used to prevent melanocyte loss in the early stage of vitiligo.

Chronic exposure to solar ultraviolet radiation (UV) induces photoaging, and ultimately photocarcinogenesis. Senescent human skin fibroblasts (HSFs) in UVB stress-induced premature senescence (UVB-SIPS) share a similar extracellular matrix (ECM) phenotype with other types of senescent fibroblast. ECM from senescent fibroblasts induced by a variety of stresses has been shown to promote preneoplastic and neoplastic epithelial cell growth, a potential mechanism in carcinogenesis. We undertook this study to explore whether the extracellular matrices from UVB-induced senescent fibroblasts have any effect on the proliferation of HaCaT cells. The results showed that ECM secreted from HSFs in UVB-SIPS has 13.15 and 29.27% more stimulatory effect on proliferation than ECM secreted from presenescent HSFs and non-ECM, respectively. ECM from fibroblasts in UVB-SIPS activates FAK, ERK, and AKT in HaCaT cells. ERK and PI3K/AKT inhibitors inhibit ECM-induced ERK, AKT activation and cell proliferation. Cytochalasin D, a destructive agent of the cytoskeleton, inhibits ECM-induced FAK activation and cell proliferation in HaCaT cells. Collectively, we conclude that ECM secreted from HSFs in UVB-SIPS promotes cell proliferation via ERK and PI3K/AKT pathways and modulation of FAK and cytoskeletal proteins in HaCaT cells. Pharmacological manipulation of those signaling components may lead to the prevention and treatment of skin cancer induced by chronic solar exposure.

Chronic exposure to solar UV irradiation leads to photoaging, immunosuppression, and ultimately carcinogenesis. Cellular senescence is thought to play an important role in tumor suppression and apoptosis resistance. However, the relationships among stress-induced premature senescence (SIPS), tumorigenesis and apoptosis induced by UVB remain unknown. We developed a model of UVB-induced premature senescence in human skin fibroblasts (HSFs). After five repeated subcytotoxic UVB exposures at a dose of 10 mJ/cm2, the following biomarkers of senescence were markedly present: senescence-associated beta-galactosidase (SA beta-gal) activity, growth arrest, and the overexpression of senescence-associated genes. Firstly, there was an increase in the proportion of cells positive for SA beta-gal activity. Secondly, there was a loss of replicative potential as assessed by MTT assay. FACS analysis showed that UVB-stressed HSFs were blocked mostly in the G1 phase of the cell cycle, and replicative senescence, and protein expression of p53, p21(WAF-1) and p16(INK-4a) increased significantly. Thirdly, the mRNA levels of three senescence-associated genes, fibronectin, osteonectin and SM22, also increased. A real time PCR array to investigate the mRNA expression of p53-related genes involved in growth arrest, apoptosis and tumorigenesis indicated that p53, p21, p19, Hdm2, and Bax were up-regulated, and bcl, HIF-1alpha and VEGF were down-regulated. Collectively, our data suggest that UVB-induced SIPS plays an important role in p53-related apoptosis resistance and tumor suppression activity.

Ovarian cancer remains the leading cause of fatality among all gynecologic cancers, although promising therapies are in the making. It has been speculated that metastasis is critical for ovarian cancer, and yet the molecular mechanisms of metastasis in ovarian cancer are poorly understood. Growth factors have been proven to play important roles in cell migration associated with metastasis, and inhibition of growth factor receptors and their distinct cell signaling pathways has been intensively studied, and yet the uncovered interaction or crosstalk among various growth factor receptors complicates this otherwise promising approach. We investigated the crosstalk between EGFR and TrkB, both of which have been known to be important in cell survival and migration in response to EGF and BDNF. Our results showed that both EGF and BDNF induced cell migration and cell proliferation in cultured human ovarian cancer cells (Caov3 cell line). EGF and BDNF transactivated TrkB and EGFR respectively, and activated downstream cell survival components such as Akt. EGFR and TrkB kinase inhibitors inhibited EGF- and BDNF-induced TrkB and EGFR activation and Akt phosphorylation, and cell proliferation and migration. Using EGFR knockout cells, we further demonstrated that EGFR is required for EGF-induced cell migration. Collectively, our data indicate that EGFR and TrkB crosstalk each other in response to EGF and BDNF, leading to cell survival pathway activation in ovarian cancer cells. Our data suggest that a combination of inhibitors of both receptors with cell survival pathway inhibitors would provide a better outcome in the clinical treatment of ovarian cancer.

EGFR is involved in the UV signal transduction pathway leading to skin cancer. UV radiation, mediated by EGFR, induces activation of PI3 kinase and AKT with a result of activation of a number of transcription factors. Transcription factor HIF-1alpha correlates with tumorigenicity and angiogenesis. Transcription factors DEC1 and DEC2 also play pivotal roles in multiple signaling pathways impacting various biological processes including development, cell differentiation, cell death, and oncogenesis. We investigated whether UV radiation and associated hypoxia induce expression of HIF-1alpha and its target genes such as VEGF and the signaling pathway mediating such responses. We found that UV radiation induced HIF-1alpha and VEGF protein expression in a dose- and time-dependent manner in cultured human keratinocytes. UV radiation also induced VEGF mRNA expression in a dose-dependent manner with maximum effect at 4 h post treatment, but did not affect HIF-1alpha mRNA expression. We also observed that UV radiation induced activation of EGFR in a time- and dose-dependent manner which was inhibited by EGFR inhibitor PD153035. In egfr (-/-) MEF cells, UV radiation did not induce HIF-1alpha and VEGF expression, in contrast, in egfr (+/+) MEF cells, UV radiation strongly induced HIF-1alpha and VEGF expression. EGFR kinase inhibitor, PD153035, inhibited UV-induced HIF-1alpha and VEGF protein expression in a dose-dependent manner. Further, we found that PI3K inhibitors, LY294002 and Wortmannin, inhibited HIF-1alpha and VEGF expression induced by UV radiation. In DEC1 (-/-) HaCat cells, UV radiation did not induce HIF-1alpha and VEGF expression, in contrast, in DEC1 (+/+) HaCat cells, UV radiation strongly enhanced HIF-1alpha and VEGF protein expression. We conclude that UV radiation induces HIF-1alpha and VEGF expression via the EGFR/PI3K/DEC1 signaling pathway.

Trichostatin A (TSA), a hydroxamate-type inhibitor of mammalian histone deacetylases, is emerging as one of a potentially new class of anticancer agents. TSA is known to act by promoting the acetylation of histones, leading to uncoiling of chromatin and activation of a variety of genes implicated in the regulation of cell survival, proliferation, differentiation, and apoptosis. In addition, there is an increasing appreciation of the fact that TSA may act through mechanisms other than induction of histone acetylation. Accumulated experimental data indicate that TSA activates phosphatidyl inositol-3-kinase (PI3K)/AKT signaling. Using human ovarian cancer cell line Caov3 cells, we observed that TSA induced cell death in a time- and dose-dependent manner and also inhibited cell migration. TSA transiently activated EGFR tyrosine phosphorylation and AKT activation in a time- and dose-dependent manner, which had been inhibited by EGFR inhibitor PD153035 and PI3 kinase inhibitor LY294002. We also observed that TSA transiently induced survivin expression that had been inhibited by PD153035 and LY294002, suggesting that TSA-induced survivin expression is mediated by EGFR/PI3 kinase pathway. Combination of EGFR inhibitor 153035 or PI3 kinase inhibitor LY294002 with TSA enhanced TSA-induced cell death and TSA reduction of cell migration. Collectively, our data demonstrate that TSA transiently activated EGFR/PI3K/AKT cell survival pathway, leading to expression of survivin. Inhibition of this pathway enhanced TSA-induced cell death and inhibited cell migration. Our data suggest that combination of EGFR/PI3K/AKT cell survival pathway inhibitors with TSA be a better approach to ovarian cancer treatment.

Environmentally mediated systemic involvement of autoimmunity, allergy and carcinogenesis are very common by clinical and epidemiological investigation. However, there is an unknown relationship between environment and environmentally mediated systemic involvement of autoimmunity, allergy and carcinogenesis. This unknown molecular communication or response conducts the primary injury sites of the skin, and surface mucosa in the respiratory, alimentary, or reproductive tracts, to the secondary sites or even the whole body under some physiological and pathological conditions. Also, this unknown molecular communication or response involves a variety of molecular events, detectable in systemic differentiation, overexpression, hyperplasia, carcinogenesis, allergies or autoimmunity. The family members of proteins and their relatives are almost ubiquitous, and distribution is tightly regulated at all three administrative levels to form an interacting multiprotein complex. The key question is whether there is unknown communication or response among the family members and, if there is, is it associated with some social property of the proteins in the open body system?

Solar UV light comprises UVB wavelengths (290-320 nm) and UVA wavelengths (320-400 nm). UVB radiation reaches the epidermis and, to a lesser extent, the upper part of the dermis, while UVA radiation penetrates more deeply into human skin. Existing studies have demonstrated that UV-irradiated epidermal keratinocytes release cytokines that indirectly promote MMP-1 production in dermal fibroblasts. In this study, we first investigated the effect of IL-1 on MAPK activity, c-Jun and c-Fos mRNA expression, and MMP-1 and MMP-2 production in UVA-irradiated human dermal fibroblasts. The results showed that UVA irradiation dose-dependently increased MMP-1 but not MMP-2 production in human skin fibroblasts. IL-1alpha and IL-1beta promoted MMP-1 but not MMP-2 production in UVA-irradiated fibroblasts. Both IL-1alpha and IL-1beta activated MAP kinase, significantly elevating c-Jun and c-Fos mRNA expression. We then investigated the indirect effect of UVB-irradiated keratinocyte culture medium on MMP-1 production in UVA-irradiated primary cultured human dermal fibroblasts and the effect of IL-1Ra. The results showed that cell culture medium from UVB-irradiated keratinocytes increased MMP-1 production in UVA-irradiated fibroblasts, and IL-1Ra dose-dependently inhibited MMP-1 production. IL-1Ra dose-dependently inhibited c-Jun mRNA expression of fibroblasts with no significant effect on c-Fos mRNA expression. These results demonstrate that UVB-irradiated keratinocytes promoted MMP-1 production in UVA-irradiated fibroblasts in a paracrine manner while IL-1Ra reduced MMP-1 production through inhibiting c-Jun mRNA expression. Collectively, our data suggest that IL-1 plays an important role in the dermal collagen degradation associated with UV-induced premature aging of the skin and IL-1Ra may be applied for the prevention and treatment of photoaging.

Ultraviolet (UV) radiation from the sun is widely considered as a major cause of human skin photoaging and skin cancer. UV radiation-induced proinflammatory cytokines mediated by NF-kappaB reportedly play important roles in photoaging and cancer. NF-kappaB and cytokines have been thus perceived as molecular targets for pharmacological intervention. With an increasing amount of knowledge of the actions of green tea extracts at cellular and molecular levels, the beneficial effect of drinking green tea has become well recognized if not completely accepted. The components in green tea have even been added to skin-care products unregulated, while the molecular mechanisms of the actions of those components on human skin are being unraveled. Using cultured human keratinocytes, we investigated the effects of (-)-epigallocatechin-3-gallate (EGCG), a major polyphenolic constituent in green tea, on UV-induced activation of transcription factor NF-kappaB and proinflammatory pathway by measuring nuclear translocation of NF-kappaB and IL-6 secretion in vitro. Immunohistochemical and Western blot analysis and ELISA indicated that both nuclear p65 and secreted IL-6 were significantly (p

p38 has been shown to be involved in TGF-beta-induced gene expression, but the upstream of the signaling pathway leading to the activation of p38 is left undefined. We investigated the pathway in cultured human keratinocytes (HaCat cells). Western blot analysis revealed that TGF-beta induced the activation of p38 within 1 h post TGF-beta treatment. H2O2 also strongly induced p38 activation in a time dependent manner. We also observed that TGF-beta-induced p38 activation was inhibited by PDTC, pyrrolidinedithiocarbamate, a known antioxidant, and DPI, diphenylene iodonium chloride, one of the known NADPH oxidase inhibitors. In contrast, TGF-beta-induced Smad2 phosphorylation was not affected. To test whether reactive oxygen species (ROS) is involved in TGF-beta-induced p38 activation, we examined the generation of ROS and activation of NADPH oxidase. FACS analysis showed that TGF-beta induced generation of ROS in time-dependent manner. DPI, an inhibitor of NADPH oxidase, inhibited TGF-beta-induced ROS production. Lucigenin-based NADPH oxidase assay indicated that TGF-beta-induced NADPH oxidase activity started as early as 5 min following treatment and peaked at about 15 min with induction of about 2-folds. The activity remained elevated up to 1 h. Immunofluorescence microscopy study showed that Rac1, one of the subunits of NADPH oxidase, translocated from cytoplasm to the membrane within 5 min. Pretreatment with DPI dramatically reduced TGF-beta-induced NADPH oxidase activity. Collectively, our data suggest that TGF-beta-induced p38 activation is mediated by Rac1-regulated generation of reactive oxygen species in cultured human keratinocytes.

Ultraviolet (UV) irradiation causes human skin aging and skin cancer through the activation of matrix metalloproteinases (MMPs) which are responsible for the degradation of collagen and tumor progression in human skin. The molecular mechanisms of UV-induced MMPs are yet to be defined. Our previous studies and others suggest that i) the transient activation of cell surface receptors and subsequent activation of MAP kinase cascade contributes to the transcriptional up-regulation of MMPs; and ii) UV-induced expression of pro-inflammatory cytokines such as IL-1 beta and TNF-alpha may also account for the expression of MMPs. However, signaling pathway through which cytokines induce MMP expression remains to be unraveled. In this study, we investigated the pathway that leads to the IL-1 beta-induced up-regulation of MMP-1 in human keratinocytes. IL-1 beta activated epidermal growth factor (EGF) receptor in cultured human keratinocytes in a time- and dose-dependent manner. IL-1 beta-induced EGF receptor tyrosine phosphorylation started at 5 min and peaked at 10 min and remained elevated up to 40 min post IL-1 beta treatment. EGF receptor kinase inhibitor PD153035 and AG1478 inhibited IL-1 beta-induced EGF receptor tyrosine phosphorylation. To test the effect of EGF receptor transactivation on downstream components, we examined the ERK activation by IL-1 beta. We found that IL-1 beta-induced ERK phosphorylation, PD153035 and MEK inhibitor PD98059 blocked IL-1 beta-induced ERK activity. Furthermore, both inhibitors also dramatically reduced IL-1 beta-induced expression of c-jun and c-fos mRNA which are required for up-regulation of MMPs. EGF receptor kinase inhibitor PD153035 and AG1478 and MEK inhibitor PD98059 also blocked IL-1 beta induction of MMP-1 in cultured human keratinocytes. Collectively, our data indicate that IL-1 beta-induced expression of MMP-1 is mediated by transactivation of EGF receptor and through ERK pathway in human keratinocytes.

AMP-activated protein kinase (AMPK), an evolutionarily conserved serine/threonine protein kinase, serves as an energy sensor in all eukaryotic cells. Recent findings suggest that AMPK activation strongly suppresses cell proliferation and induces cell apoptosis in a variety of cancer cells. Our study demonstrated that chemopreventive agent curcumin strongly activates AMPK in a p38-dependent manner in CaOV3 ovarian cancer cells. Pretreatment of cells with compound C (AMPK inhibitor) and SB203580 (p38 inhibitor) attenuates curcumin-induced cell death. We also observed that curcumin induces p53 phosphorylation (Ser 15) and both compound C and SB203580 pretreatment inhibit p53 phosphorylation. Collectively, our data suggest that AMPK is a new molecular target of curcumin and AMPK activation partially contributes to the cytotoxic effect of curcumin in ovarian cancer cells.