Human β-defensin (hBD)-2, a cationic antimicrobial peptide primarily induced in epithelial cells in response to inflammatory stimuli, plays an important role in host defense. To elucidate the expression mechanism of hBD-2 in the lung, we investigated the modulation of hBD-2 transcription in pulmonary epithelial cells by mononuclear phagocytes stimulated with LPS. Coculture of A549 pulmonary epithelial cells with Mono-Mac-6 monocytic cells in the presence of Escherichia coli LPS markedly up-regulated hBD-2 promoter activity, whereas A549 alone did not respond to LPS to activate the hBD-2 promoter. Furthermore, IL-1β and TNF-α in the culture supernatants from LPS-stimulated monocytic cells activated the hBD-2 promoter in A549 cells. Of note, IL-1β was more potent than TNF-α in this effect. In addition, a mutation of the NF-κB site at −200 (pκB1 site) completely abolished this IL-1β- and TNF-α-induced hBD-2 promoter activation, whereas NF-κB inhibitors (MG-132 and helenalin) strongly suppressed it. Moreover, electrophoretic mobility shift assay suggested that NF-κB, consisting of p65-p50 heterodimer, could bind to the pκB1 site in cytokine-stimulated A549 cells. Interestingly, flow cytometric analysis revealed that A549 cells expressed CD14 but lacked Toll-like receptor 4, which may account for the hyporesponsiveness of A549 cells to LPS. Taken together, these results suggest that hBD-2 expression in pulmonary epithelial cells is modulated by NF-κB via the actions of IL-1β and TNF-α produced by LPS-stimulated mononuclear phagocytes.

Integrin-linked kinase (ILK) directly interacts with B integrins and phosphorylates Akt in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. In this study, we examined the functional role of ILK activation in leukemic and bone marrow stromal cells on their direct contact. Coculture of leukemic NB4 cells with bone marrow-derived stromal mesenchymal stem cells (MSC) resulted in robust activation of multiple signaling pathways, including ILK/Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), signal transducers and activators of transcription 3 (STAT3), and Notch1/Hes. Blockade of PI3K or ILK signaling with pharmacologic inhibitors LY294002 or QLT0267 specifically inhibited stroma-induced phosphorylation of Akt and glycogen synthase kinase 3B, suppressed STAT3 and ERK1/2 activation, and decreased Notch1 and Hes1 expression in leukemic cells. This resulted in induction of apoptosis in both leukemic cell lines and in primary acute myelogenous leukemia samples that was not abrogated by MSC coculture. In turn, leukemic cells growing in direct contact with bone marrow stromal elements induce activation of Akt, ERK1/2, and STAT3 signaling in MSC, accompanied by significant increase in Hes1 and Bcl-2 proteins, which were all suppressed by QLT0267 and LY294002. In summary, our results indicate reciprocal activation of ILK/Akt in both leukemic and bone marrow stromal cells. We propose that ILK/Akt is a proximal signaling pathway critical for survival of leukemic cells within the bone marrow microenvironment. Hence, disruption of these interactions by ILK inhibitors represents a potential novel therapeutic strategy to eradicate leukemia in the bone marrow microenvironment by simultaneous targeting of both leukemic cells and activated bone marrow stromal cells. [Cancer Res 2007;67(2):684-94]

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Peptide antibiotics possess the potent antimicrobial activities against invading microorganisms and contribute to the innate host defense. Antimicrobial human beta-defensins (hBDs) not only exhibit potent bactericidal activities against Gram-negative and Gram-positive bacteria but also function as immunomodulatory molecules by inducing cytokine and chemokine production and inflammatory and immune cell activation. Neutrophil is a critical effector cell in host defense against microbial infection, and its lifespan is regulated by various pathogen- and host-derived substances. Here, to further evaluate the role of hBDs in innate immunity, we investigated the action of hBD-1 to -4 on neutrophil apoptosis. Neutrophil apoptosis was assessed using human blood neutrophils based on the morphological changes. Of note, hBD-3 most potently suppressed neutrophil apoptosis among hBD-1 to -4, accompanied with the down-regulation of truncated Bid (a pro-apoptotic protein), up-regulation of Bcl-x(L) (an anti-apoptotic protein) and inhibition of mitochondrial membrane potential change and caspase 3 activity. Furthermore, we revealed that neutrophils expressed CC chemokine receptor (CCR) 6, and the action of hBD-3 was completely abrogated by a neutralizing anti-CCR6 mAb. Collectively, these observations suggest that hBDs, especially hBD-3, can not only kill bacteria but also modulate (suppress) neutrophil apoptosis via the action on CCR6. Suppression of neutrophil apoptosis results in the prolongation of their lifespan and may be advantageous for the host defense against bacterial invasion.

The multidrug resistance 1 (MDR1) gene product P-glycoprotein (P-gp) is frequently implicated in cross-resistance of tumors to chemotherapeutic drugs. In contrast, acute promyelocytic leukemia (APL) cells do not express MDR1 and are highly sensitive to anthracyclines. The combination of ATRA and the novel histone deacetylase inhibitor (HDACI) depsipeptide (FK228) induced P-gp expression and prevented growth inhibition and apoptosis in NB4 APL cells subsequently exposed to doxorubicin (DOX). ATRA/ FK228 treatment after exposure to DOX, however, enhanced apoptosis. Both agents, ATRA or FK228, induced MDR1 mRNA. This effect was significantly enhanced by ATRA/FK228 administered in combination, due in part to increased H4 and H3-Lys9 acetylation of the MDR1 promoter and recruitment of the nuclear transcription factor Y alpha (NFYA) transcription activator to the CCAAT box. Cotreatment with specific P-gp inhibitor PSC833 reversed cytoprotective effects of ATRA/FK228. G 1 cell-cycle arrest and p21 mRNA induction were also observed in response to ATRA/FK228, which may IntroductionAcute promyelocytic leukemia (APL) cells are highly sensitive to anthracyclines in part due to the lack of expression of the multidrug resistance 1 (MDR1) protein P-glycoprotein (P-gp). 1,2 In this study, we investigated the effects of ATRA and FK228, alone and in combination, on the cytotoxicity of doxorubicin (DOX). Pretreatment by ATRA combined with FK228 prevented DOX-induced apoptosis in NB4 APL cells. However, when DOX treatment preceded ATRA/FK228, DOXinduced cell death was enhanced.The MDR1 gene product P-gp functions as a transmembrane efflux pump for a variety of chemotherapeutic drugs, including anthracyclines, [3][4][5][6] and overexpression of the MDR1 gene is a negative prognostic factor in acute myelogenous leukemias (AMLs). 7 Numerous studies have reported the successful inhibition of P-gp function in vitro using cyclosporine A, PSC833, and other compounds. [8][9][10][11] MDR1 gene expression can also be silenced, however, by epigenetic mechanisms involving histone deacetylases (HDACs) and DNA methyltransferases. [12][13][14][15][16] For example, the nuclear transcription factor Y (NF-Y) heteromeric complex binds to the CCAAT core sequence in the promoters of a variety of eukaryotic genes, including human MDR1, 12,[16][17][18] and acts as a histone acetylation regulator and transcription activator. 12,19 APL cells, which do not express MDR1, are associated with the oncogenic transcription factor PML-RAR␣ that represses transcription of the genes encoding the RA receptor targets through histone deacetylation. The PML-RAR␣ chimeric protein, moreover, has been suspected to be the factor suppressing MDR1 through chromatin remodeling. 20 A number of HDAC inhibitors (HDACIs) are currently being tested in clinical trials against a variety of cancers. Recently, there has been strong interest in HDACIs as anti-APL agents because of their synergistic activity with ATRA. [21][22][23][24] In vivo data demonstrated that HDACIs can overcome ...