AM-18002, a derivative of natural anmindenol A, enhances radiosensitivity in mouse breast cancer cells.

Natural anmindenol A isolated from the marine-derived bacteria Streptomyces sp. caused potent inhibition of inducible nitric oxide synthase without any significant cytotoxicity. This compound consists of a structurally unique 3,10-dialkylbenzofulvene skeleton. We previously synthesized and screened the novel derivatives of anmindenol A and identified AM-18002, an anmindenol A derivative, as a promising anticancer agent. The combination of AM-18002 and ionizing radiation (IR) improved anticancer effects, which were exerted by promoting apoptosis and inhibiting the proliferation of FM3A mouse breast cancer cells. AM-18002 increased the production of reactive oxygen species (ROS) and was more effective in inducing DNA damage. AM-18002 treatment was found to inhibit the expansion of myeloid-derived suppressor cells (MDSC), cancer cell migration and invasion, and STAT3 phosphorylation. The AM-18002 and IR combination synergistically induced cancer cell death, and AM-18002 acted as a potent anticancer agent by increasing ROS generation and blocking MDSC-mediated STAT3 activation in breast cancer cells.

Breast cancer malignancy is governed by regulation of the macroH2A2/TM4SF1 axis, the AKT/NF-κB pathway, and elevated MMP13 expression.

The histone variant, macroH2A (mH2A) influences gene expression through epigenetic regulation. Tumor suppressive function of mH2A isoforms has been reported in various cancer types, but few studies have investigated the functional role of mH2A2 in breast cancer pathophysiology. This study aimed to determine the significance of mH2A2 in breast cancer development and progression by exploring its downstream regulatory mechanisms. Knockdown of mH2A2 facilitated the migration and invasion of breast cancer cells, whereas its overexpression exhibited the opposite effect. In vivo experiments revealed that augmenting mH2A2 expression reduced tumor growth and lung metastasis. Microarray analysis showed that TM4SF1 emerged as a likely target linked to mH2A2 owing to its significant suppression in breast cancer cell lines where mH2A2 was overexpressed among the genes that exhibited over twofold upregulation upon mH2A2 knockdown. Suppressing TM4SF1 reduced the migration, invasion, tumor growth, and metastasis of breast cancer cells in vitro and in vivo. TM4SF1 depletion reversed the increased aggressiveness triggered by mH2A2 knockdown, suggesting a close interplay between mH2A2 and TM4SF1. Our findings also highlight the role of the mH2A2/TM4SF1 axis in activating the AKT/NF-κB pathway. Consequently, activated NF-κB signaling leads to increased expression and secretion of MMP13, a potent promoter of metastasis. In summary, we propose that the orchestrated regulation of the mH2A2/TM4SF1 axis in conjunction with the AKT/NF-κB pathway and the subsequent elevation in MMP13 expression constitute pivotal factors governing the malignancy of breast cancer.

Downregulation of complement factor H attenuates the stemness of MDA­MB­231 breast cancer cells via modulation of the ERK and p38 signaling pathways.

The complement system is a powerful innate immune system deployed in the immediate response to pathogens and cancer cells. Complement factor H (CFH), one of the regulators involved in the complement cascade, can interrupt the death of target cells. Certain types of cancer, such as breast cancer, can adopt an aggressive phenotype, such as breast cancer stem cells (BCSCs), through enhancement of the defense system against complement attack by amplifying various complement regulators. However, little is known about the association between CFH and BCSCs. In the present study, the roles of CFH in the CSC characteristics and radioresistance of MDA-MB-231 human breast cancer cells were investigated. CFH knockdown in MDA-MB-231 cells decreased the viability of the cells upon complement cascade activation. Notably, CFH knockdown also decreased cell survival and suppressed mammosphere formation, cell migration and cell invasion by attenuating radioresistance. Additionally, CFH knockdown further enhanced irradiation-induced apoptosis through G2/M cell cycle arrest. It was also discovered that CFH knockdown attenuated the aggressive phenotypes of cancer cells by regulating CSC-associated gene expression. Finally, by microarray analysis, it was found that the expression of erythrocyte membrane protein band 4.1-like 3 (EPB41L3) was markedly increased following CFH knockdown. EPB41L3 inhibited ERK and activated the p38 MAPK signaling pathway. Taken together, these results indicated that CFH knockdown attenuated CSC properties and radioresistance in human breast cancer cells via controlling MAPK signaling and through upregulation of the tumor suppressor, EPB41L3.

G9a Knockdown Suppresses Cancer Aggressiveness by Facilitating Smad Protein Phosphorylation through Increasing BMP5 Expression in Luminal A Type Breast Cancer.

Epigenetic abnormalities affect tumor progression, as well as gene expression and function. Among the diverse epigenetic modulators, the histone methyltransferase G9a has been focused on due to its role in accelerating tumorigenesis and metastasis. Although epigenetic dysregulation is closely related to tumor progression, reports regarding the relationship between G9a and its possible downstream factors regulating breast tumor growth are scarce. Therefore, we aimed to verify the role of G9a and its presumable downstream regulators during malignant progression of breast cancer. G9a-depleted MCF7 and T47D breast cancer cells exhibited suppressed motility, including migration and invasion, and an improved response to ionizing radiation. To identify the possible key factors underlying these effects, microarray analysis was performed, and a TGF-ß superfamily member, BMP5, was selected as a prominent target gene. It was found that BMP5 expression was markedly increased by G9a knockdown. Moreover, reduction in the migration/invasion ability of MCF7 and T47D breast cancer cells was induced by BMP5. Interestingly, a G9a-depletion-mediated increase in BMP5 expression induced the phosphorylation of Smad proteins, which are the intracellular signaling mediators of BMP5. Accordingly, we concluded that the observed antitumor effects may be based on the G9a-depletion-mediated increase in BMP5 expression and the consequent facilitation of Smad protein phosphorylation.

Inhibitory effect of ginsenoside Rg3 on cancer stemness and mesenchymal transition in breast cancer via regulation of myeloid-derived suppressor cells.

Ginsenoside Rg3 (Rg3) has been studied in several cancer models and is suggested to act through various pharmacological effects. We investigated the anticancer properties of Rg3 through myeloid-derived suppressor cell (MDSC) modulation in FM3A mouse mammary carcinoma cells. The effects of Rg3 on MDSCs and consequent changes in cancer stem-like cells (CSCs) and epithelial-mesenchymal transition (EMT) were evaluated by diverse methods. MDSCs promoted cancer by enhancing breast cancer stemness and promoting EMT. Rg3 at a dose without obvious cytotoxicity downregulated MDSCs and repressed MDSC-induced cancer stemness and EMT. Mechanistic investigations suggested that these inhibitory effects of Rg3 on MDSCs and corresponding cancer progression depend upon suppression of the STAT3-dependent pathway, tumor-derived cytokines, and the NOTCH signaling pathway. In a mouse model, MDSCs accelerated tumor progression, and Rg3 delayed tumor growth, which is consistent with the results of in vitro experiments. These results indicated that Rg3 could effectively inhibit the progression of breast cancer. The anticancer effect of Rg3 might be partially due to its downregulation of MDSCs and consequent repression of cancer stemness and EMT in breast cancer. Hence, we suggest the regulation of MDSCs through Rg3 treatment as an effective therapeutic strategy for breast cancer patients.

Downregulation of UHRF1 increases tumor malignancy by activating the CXCR4/AKT-JNK/IL-6/Snail signaling axis in hepatocellular carcinoma cells.

UHRF1 (ubiquitin-like, with PHD and RING finger domains 1) plays a crucial role in DNA methylation, chromatin remodeling and gene expression and is aberrantly upregulated in various types of human cancers. However, the precise role of UHRF1 in cancer remains controversial. In this study, we observed that hypoxia-induced downregulation of UHRF1 contributes to the induction of the epithelial-mesenchymal transition (EMT) in hepatocellular carcinoma cells. By negatively modulating UHRF1 expression, we further showed that UHRF1 deficiency in itself is sufficient to increase the migratory and invasive properties of cells via inducing EMT, increasing the tumorigenic capacity of cells and leading to the expansion of cancer stem-like cells. Epigenetic changes caused by UHRF1 deficiency triggered the upregulation of CXCR4, thereby activating AKT and JNK to increase the expression and secretion of IL-6. In addition, IL-6 readily activated the JAK/STAT3/Snail signaling axis, which subsequently contributed to UHRF1 deficiency-induced EMT. Our results collectively demonstrate that UHRF1 deficiency may play a pivotal role in the malignant alteration of cancer cells.

Accumulation of low-dose BIX01294 promotes metastatic potential of U251 glioblastoma cells.

BIX01294 (Bix) is known to be a euchromatic histone-lysine N-methyltransferase 2 inhibitor and treatment with Bix suppresses cancer cell survival and proliferation. In the present study, it was observed that sequential treatment with low-dose Bix notably increases glioblastoma cell migration and metastasis. It was demonstrated that U251 cells sequentially treated with low-dose Bix exhibited induced characteristic changes in critical epithelial-mesenchymal transition (EMT) markers, including E-cadherin, N-cadherin, ß-catenin and zinc finger protein SNAI2. Notably, sequential treatment with Bix also increased the expression of cancer stem cell-associated markers, including sex determining region Y-box 2, octamer-binding transcription factor 4 and cluster of differentiation 133. Neurosphere formation was significantly enhanced in cells sequentially treated with Bix, compared with control cells (control: P=0.011; single treatment of Bix, P=0.045). The results of the present study suggest that accumulation of low-dose Bix enhanced the migration and metastatic potential of glioblastoma cells by regulating EMT-associated gene expression, which may be the cause of the altered properties of glioblastoma stem cells.

Estradiol, TGF-ß1 and hypoxia promote breast cancer stemness and EMT-mediated breast cancer migration.

Breast cancer is one of the most common cancer types among women, acting as a distinct cause of mortality, and has a high incidence of recurrence. External stimuli, including 17ß-estradiol (E2), transforming growth factor (TGF)-ß1 and hypoxia, may be important in breast cancer growth and metastasis. However, the effects of these stimuli on breast cancer stem cell (CSC) regulation have not been fully investigated. In the present study, the proportion of cluster of differentiation (CD)44+/CD24-/low cells increased following treatment with E2, TGF-ß1 and hypoxia in MCF-7 cells. The expression of CSC markers, including SOX2, KLF4 and ABCG2, was upregulated continually by E2, TGF-ß1 and hypoxia. In addition, the expression levels of epithelial-mesenchymal transition-associated factors increased following treatment with E2, TGF-ß1 and hypoxia. Therefore, the migration ability of E2-, TGF-ß1- and hypoxia-treated MCF-7 cells was enhanced compared with control cells. In addition, the enhancement of apoptosis by 5-flurouracil or radiation was abolished following treatment with E2, TGF-ß1 and hypoxia. These results indicate that E2, TGF-ß1 and hypoxia are important for regulating breast CSCs, and that the modulation of the microenvironment in tumors may improve the efficiency of breast cancer therapy.

Downregulation of UHRF1 promotes EMT via inducing CXCR4 in human cancer cells.

Activation of epithelial-mesenchymal transition (EMT) is important for malignant tumor progression exhibiting migratory and invasive properties. UHRF1 (ubiquitin-like, with PHD and RING finger domains 1), as an epigenetic regulator, plays a crucial role in DNA CpG methylation, chromatin remodeling and gene expression. Many studies demonstrated that UHRF1 is aberrantly expressed in various types of human cancer. However, the precise role of UHRF1 in human cancers remains highly controversial. In the present study, we found that downregulation of UHRF1 enhances the migratory and invasive properties of human cancer cells by inducing EMT, and that the CXCR4 signaling pathway is strictly necessary for UHRF1 deficiency-mediated induction of EMT. Downregulation of UHRF1 induced the expression of the EMT-regulating transcription factors, Zeb1, Slug and Snail and then led to decreased protein level of E-cadherin, and increased protein level of N-cadherin and vimentin, including increased migratory and invasive properties of human cancer cells. In addition, siRNA targeting of Zeb1 or Snail effectively attenuated UHRF1 deficiency-induced EMT, but siRNA targeting of Slug did not, indicating that Zeb1 and Snail play key roles in this event. Moreover, downregulation of UHRF1 induced the expression of CXCR4 in HepG2 cells. siRNA targeting of CXCR4 greatly suppressed the UHRF1 deficiency-induced EMT, as evidenced by a reversal of expression patterns of Snail and Zeb1, and by reduced migratory and invasive properties of HepG2 cells. In conclusion, our results demonstrate that downregulation of UHRF1 contributes to the induction of EMT in human cancer cells via the activation of CXCR4 signaling pathway. Our observation also suggests that UHRF1 may play a pivotal role in suppressing the malignant alteration of cancer cells.

Naphthazarin enhances ionizing radiation-induced cell cycle arrest and apoptosis in human breast cancer cells.

Naphthazarin (Naph, DHNQ, 5,8-dihydroxy-l,4-naphthoquinone) is one of the naturally available 1,4-naphthoquinone derivatives that are well-known for their anti-inflammatory, antioxidant, antibacterial and antitumor cytotoxic effects in cancer cells. Herein, we investigated whether Naph has effects on cell cycle arrest and apoptosis in MCF-7 human breast cancer cells exposed to ionizing radiation (IR). Naph reduced the MCF-7 cell viability in a dose-dependent manner. We also found that Naph and/or IR increased the p53-dependent p21 (CIP/WAF1) promoter activity. Noteworthy, our ChIP assay results showed that Naph and IR combined treatment activated the p21 promoter via inhibition of binding of multi-domain proteins, DNMT1, UHRF1 and HDAC1. Apoptosis and cell cycle analyses demonstrated that Naph and IR combined treatment induced cell cycle arrest and apoptosis in MCF-7 cells. Herein, we showed that Naph treatment enhances IR-induced cell cycle arrest and death in MCF-7 human breast cancer cells through the p53-dependent p21 activation mechanism. These results suggest that Naph might sensitize breast cancer cells to radiotherapy by enhancing the p53-p21 mechanism activity.

Epigenetically regulated MIR941 and MIR1247 target gastric cancer cell growth and migration.

Altered expression of microRNA (miRNA) can significantly contribute to cancer development and recent studies have shown that a number of miRNAs may be regulated by DNA methylation. Through a candidate gene approach, we identified MIR941 and MIR1247 to be transcriptionally silenced by DNA hypermethylation in several gastric cancer cell lines. We confirmed that these miRNAs are also densely methylated in primary gastric cancers but not in normal gastric tissues. In addition, we demonstrated that ectopic expression of these two miRNAs in AGS gastric cancer cells resulted in suppression of growth and migration. Furthermore, we tested genes predicted to be the targets of MIR941 and MIR1247 and identified 7 and 6 genes, whose expressions were significantly downregulated by transfection of MIR941 and MIR1247 mimics, respectively, in gastric cancer cell lines. Some of these genes are known to promote proliferation and invasion, phenotypes we observed upon ectopic expression of the two miRNAs. Thus, we examined these candidates more closely and found that downregulation of mRNA corresponded to a decrease in protein levels (observed by western blot). Our study provides unequivocal evidence that MIR941 and MIR1247 are transcriptionally regulated by DNA methylation in gastric cancer and that they have tumor suppressor properties through their inhibition of key cancer promoting genes in this context.

The combination of sorafenib and radiation preferentially inhibits breast cancer stem cells by suppressing HIF-1α expression.

The importance of anticancer stem cell research for breast cancer lies in the possibility of providing new approaches for an improved understanding of anticancer activity and cancer treatment. In this study, we demonstrated that the preclinical therapeutic efficacy of combining the multikinase inhibitor sorafenib with radiation was more effective in hypoxia-exposed breast cancer stem cells. We assessed cell viability and Annexin V to evaluate the combined effect of sorafenib and radiation following exposure to hypoxia. Our results showed that the synergistic cytotoxicity increased tumor cell apoptosis significantly and reduced cell proliferation in MDA-MB-231 and MCF-7 cells under hypoxic conditions compared to sorafenib or radiation alone in vitro. Additionally, the combined treatment induced G2/M cell cycle arrest. Notably, the combination of sorafenib and radiation eliminated CD44+CD24-/low cells preferentially, which highly expressed hypoxia-inducible factor (HIF)-1α and effectively inhibited primary and secondary mammosphere formation in MDA-MB-231 cells. A combined effect on MDA-MB­231 cells in response to hypoxia was shown by inhibiting angiogenesis and metastasis by suppression of HIF-1α and matrix metalloproteinase-2 (MMP-2). Collectively, these results indicate that the efficacy of sorafenib combined with radiation for treating human breast cancer cells is synergistic and suggest a new therapeutic approach to prevent breast cancer progression by eliminating breast cancer stem cells.

Phospholipase C activator m-3M3FBS protects against morbidity and mortality associated with sepsis.

Although phospholipase C (PLC) is a crucial enzyme required for effective signal transduction and leukocyte activation, the role of PLC in polymicrobial sepsis remains unclear. In this study, we show that the direct PLC activator m-3M3FBS treatment significantly attenuates vital organ inflammation, widespread immune cell apoptosis, and mortality in a mouse sepsis model induced by lethal cecal ligation and puncture challenge. Mechanistically, m-3M3FBS-dependent protection was largely abolished by pretreatment of mice with the PLC-selective inhibitor U-73122, thus confirming PLC agonism by m-3M3FBS in vivo. PLC activation enhanced the bactericidal activity and hydrogen peroxide production of mouse neutrophils, and it also enhanced the production of IFN-γ and IL-12 while inhibiting proseptic TNF-α and IL-1ß production in cecal ligation and puncture mice. In a second model of sepsis, PLC activation also inhibited the production of TNF-α and IL-1ß following systemic LPS challenge. In conclusion, we show that agonizing the central signal transducing enzyme PLC by m-3M3FBS can reverse the progression of toxic shock by triggering multiple protective downstream signaling pathways to maintain organ function, leukocyte survival, and to enhance microbial killing.

A WKYMVm-containing combination elicits potent anti-tumor activity in heterotopic cancer animal model.

The development of efficient anti-cancer therapy has been a topic of intense interest for several decades. Combined administration of certain molecules and immune cells has been shown to be an effective form of anti-cancer therapy. Here, we examined the effects of administering an immune stimulating peptide (WKYMVm), 5-fluoro-uracil (5-FU), and mature dendritic cells (mDCs) against heterotopic cancer animal model. Administration of the triple combination strongly reduced tumor volume in CT-26-inoculated heterotopic cancer animal model. The induced anti-tumor activity was well correlated with FAS expression, caspase-3 activation, and cancer cell apoptosis. The triple combination treatment caused recruitment of CD8 T lymphocytes and natural killer (NK) cells into the tumor. The production of two cytokines, IFN-γ and IL-12, were strongly stimulated by administration of the triple combination. Depletion of CD8 T lymphocytes or NK cells by administration of anti-CD8 or anti-asialoGM1 antibody inhibited the anti-tumor activity and cytokine production of the triple combination. The triple combination strongly inhibited metastasis of colon cancer cells in a heterotopic cancer animal model as well as in a metastatic cancer animal model, and enhanced the survival rate of the mice model. Adoptive transfer of CD8 T lymphocytes and NK cells further increased the survival rate. Taken together, we suggest that the use of triple combination therapy of WKYMVm, 5-FU, and mDCs may have implications in solid tumor and metastasis treatment.

Identification of novel peptides that stimulate human neutrophils.

Neutrophils play a key role in innate immunity, and the identification of new stimuli that stimulate neutrophil activity is a very important issue. In this study, we identified three novel peptides by screening a synthetic hexapeptide combinatorial library. The identified peptides GMMWAI, MMHWAM, and MMHWFM caused an increase in intracellular Ca2+ in a concentration-dependent manner via phospholipase C activity in human neutrophils. The three peptides acted specifically on neutrophils and monocytes and not on other non-leukocytic cells. As a physiological characteristic of the peptides, we observed that the three peptides induced chemotactic migration of neutrophils as well as stimulated superoxide anion production. Studying receptor specificity, we observed that two of the peptides (GMMWAI and MMHWFM) acted on formyl peptide receptor (FPR)1 while the other peptide (MMHWAM) acted on FPR2. Since the three novel peptides were specific agonists for FPR1 or FPR2, they might be useful tools to study FPR1- or FPR2-mediated immune response and signaling.

Activation of CXCR2 by extracellular matrix degradation product acetylated Pro-Gly-Pro has therapeutic effects against sepsis.

RATIONALE: Acetylated Pro-Gly-Pro (Ac-PGP) is an endogenous degradation product of extracellular collagen that binds to leukocyte-expressed chemoattractant receptor CXCR2. Although certain agents that block CXCR2-mediated signaling protect against experimental sepsis, the roles of Ac-PGP and CXCR2 in sepsis are unclear. OBJECTIVES: To investigate the role of Ac-PGP and its receptor, CXCR2, in murine models of cecal ligation and puncture (CLP)-induced polymicrobial sepsis and organ injury. METHODS: The impact of in vivo Ac-PGP treatment on animal survival after induction of experimental sepsis was assessed. Vital organ inflammation and immune cell apoptosis were evaluated by histology, and the modulation of proinflammatory cytokine production and bactericidal activity by Ac-PGP in mouse and human blood leukocytes was measured. MEASUREMENTS AND MAIN RESULTS: The activation of CXCR2 by tripeptide agonist Ac-PGP dramatically improved survival in three experimental sepsis models. Ac-PGP elicited bactericidal activity via the generation of hydrogen peroxide, inhibited lung inflammation, and reduced immune cell apoptosis. Fluorescein isothiocyanate-labeled PGP bound directly to CXCR2, and the protective effect of Ac-PGP in sepsis was abolished in CXCR2-deficient mice. Ac-PGP treatment enhanced the production of type 1 cytokines (IFN-γ and IL-12) but inhibited the production of proinflammatory cytokines (tumor necrosis factor [TNF]-α, IL-1ß, and IL-6) in vivo. In vitro, Ac-PGP directly increased IFN-γ production and decreased the LPS-stimulated production of TNF-α by mouse splenocytes and human leukocytes. Furthermore, direct treatment of LPS-stimulated splenocytes with IFN-γ resulted in diminished secretion of TNF-α and IL-6. CONCLUSIONS: CXCR2 and Ac-PGP are thus novel target and starting molecules, respectively, for the development of therapeutic agents against sepsis.

Sphingosylphosphorylcholine stimulates CCL2 production from human umbilical vein endothelial cells.

Sphingosylphosphorylcholine (SPC) is a component of high-density lipoprotein particles. We investigated the functional role of SPC in HUVECs. SPC stimulation induced production of the CCL2 chemokine in a PTX-sensitive G-protein-dependent manner. SPC treatment caused the activation of NF-κB and AP-1, which are essential for SPC-induced CCL2 production, and induced the activation of three MAPKs, ERK, p38 MAPK, and JNK. Inhibition of p38 MAPK or JNK by specific inhibitors caused a dramatic decrease in SPC-induced CCL2 production. The Jak/STAT3 pathway was also activated upon SPC stimulation of HUVECs. Pretreatment with a Jak inhibitor blocked not only SPC-induced p38 MAPK and JNK activation, but also NF-κB and AP-1 activation. Our results suggest that SPC stimulates HUVECs, resulting in Jak/STAT3-, NF-κB-, and AP-1-mediated CCL2 production. We also observed that SPC stimulated expression of the adhesion molecule ICAM-1 in HUVECs. Our results suggest that SPC may contribute to atherosclerosis; therefore, SPC and its unidentified target receptor offer a starting point for the development of a treatment for atherosclerosis.

Activation of human monocytes by a formyl peptide receptor 2-derived pepducin.

We synthesized and investigated the effect of formyl peptide receptor 2 (FPR2)-derived pepducins in human monocytes. The FPR2-based cell-penetrating lipopeptide, "pepducin" (F2pal-16), stimulated intracellular calcium increase in human monocytes via pertussis toxin (PTX)-sensitive G-protein and phospholipase C (PLC) activity. From a functional aspect, we showed that F2pal-16 stimulated monocyte chemotaxis. F2pal-16 also stimulated the generation of superoxide anion in human monocytes. Moreover, F2pal-16 dramatically increased the production of several kinds of pro-inflammatory cytokines (CXCL8, CCL2, IL-1ß and TNF-α) in human monocytes via NF-κB activation. Since FPR2 plays an important role in immune responses, F2pal-16 can serve as a useful reagent for the study of FPR2-mediated immune modulation.

A pertussis toxin sensitive G-protein-independent pathway is involved in serum amyloid A-induced formyl peptide receptor 2-mediated CCL2 production.

Serum amyloid A (SAA) induced CCL2 production via a pertussis toxin (PTX)-insensitive pathway in human umbilical vein endothelial cells (HUVECs). SAA induced the activation of three MAPKs (ERK, p38 MAPK, and JNK), which were completely inhibited by knock-down of formyl peptide receptor 2 (FPR2). Inhibition of p38 MAPK and JNK by their specific inhibitors (SB203580 and SP600125), or inhibition by a dominant negative mutant of p38 MAPK dramatically decreased SAA-induced CCL2 production. Inactivation of G((i)) protein(s) by PTX inhibited the activation of SAA-induced ERK, but not p38 MAPK or JNK. The results indicate that SAA stimulates FPR2-mediated activation of p38 MAPK and JNK, which are independent of a PTX-sensitive G-protein and are essential for SAA-induced CCL2 production.

Functional expression of formyl peptide receptor family in human NK cells.

We determined the expression of the formyl peptide receptor (FPR) family and the functional roles of the FPR family in NK cells. All tested human NK cells express two members of the FPR family (FPR1 and FPR2). The expression of FPR3 was noted to occur in a donor-specific manner. The stimulation of NK cells with FPR family-selective agonists (fMLF (N-formyl-Met-Leu-Phe), MMK-1, F2L, and WKYMVm (Trp-Lys-Tyr-Met-Val-d-Met)) elicited cytolytic activity in resting NK cells, but not in IL-2-activated NK cells; the cytolytic activity was not inhibited by pertussis toxin. The FPR family agonists also stimulated chemotactic migration of IL-2-activated NK cells, but not resting NK cells; the chemotactic migration was completely inhibited by pertussis toxin. WKYMVm stimulates ERK, p38 MAPK, and JNK activities in both resting and IL-2-activated NK cells. WKYMVm-induced chemotactic migration was partially inhibited by PD98059 (2'-amino-3'-methoxyflavone); however, the inhibition of JNK by its selective inhibitor (SP600125, anthra[1,9-cd]pyrazol-6(2H)-one) dramatically inhibited the WKYMVm-induced cytolytic activity. Furthermore, WKYMVm-induced chemotactic migration and cytolytic activity were partly inhibited by FPR family-selective antagonists (cyclosporin H and WRWWWW). Taken together, our findings indicate that human NK cells express functional members of the FPR family, and in turn the activation of the three members of the FPR receptor family elicit cytolytic activity in NK cells, thus suggesting that the receptors are potentially important therapeutic targets for the modulation of NK cell-mediated immune responses.