The inhibition of autophagy potentiates anti-angiogenic effects of sulforaphane by inducing apoptosis.

BACKGROUND: Sulforaphane (SUL), a kind of isothiocyanate, has recently been focused due to its strong pro-apoptotic effect on cancer cells as well as tumor vascular endothelial cells (ECs). And recently, we demonstrated the induction of autophagy by colon cancer cells as a protective mechanism against SUL. In the present study, we aimed to investigate the possible role of autophagy induction by ECs as a defense mechanism against SUL. METHODS: Human umbilical vein endothelial cells (HUVECs) were used as the in vitro model of angiogenic ECs. The induction of autophagy was evaluated by the detection of acidic vesicular organelles (AVOs) by flow-cytometry, after the staining with acridine orange, as well as the detection of light chain 3(LC3) by Western blot. Finally, the functional implication of autophagy inhibition and SUL treatment in ECs was investigated by their ability to form vascular-like structures on Matrigel. RESULTS: Treatment of HUVECs with relatively low concentrations of SUL for 16 h resulted in the evident formation of AVOs and the recruitment of LC3 to autophagosomes, the pathognomonic features of autophagy. Co-treatment of cells with the specific autophagy inhibitor (3-methyladenine) potentiated the proapoptotic effect of SUL. And inhibition of autophagy potentiated the inhibitory effect of SUL on the ability of ECs to form capillary-like structures. CONCLUSION: Similar to cancer cells, ECs induced autophagy in response to the pro-apoptotic agent, SUL, and the inhibition of autophagy potentiated the pro-apoptotic effect. These findings open premises for the use of autophagy inhibitors in combination with anti-angiogenic agents.

Isoprenoid geranylgeranylacetone inhibits human colon cancer cells through induction of apoptosis and cell cycle arrest.

Geranylgeranylacetone (GGA), an isoprenoid compound, is a widely used antiulcer drug developed in Japan. GGA is structurally similar to plaunotol and geranylgeraniol, another isoprenoid reported to exert strong anticancer effects. In an earlier study, GGA was shown to inhibit ovarian cancer invasion by attenuating not only Rho activation, but also Ras-MAPK activation. In this study, we aimed to test whether GGA could have a therapeutic effect on colon cancer cells. As a result, we found that GGA induced a dose-dependent decrease in the proliferative activity through induction of cell apoptosis and cell cycle arrest in the G1 phase. The induction of apoptosis was mediated by the activation of both caspase-8 and caspase-9 pathways. The induction of G1 arrest was mediated by the increase of p21 and p27, and also the decrease of phosphorylated retinoblastoma protein levels. This study showed the potential anticancer activity of GGA. As this drug is already available in Japan for clinical use as an antiulcer/antigastritis agent, clinical trials will be designed to confirm its potential usefulness for cancer patients.

Chloroquine potentiates the anti-cancer effect of 5-fluorouracil on colon cancer cells.

BACKGROUND: Chloroquine (CQ), the worldwide used anti-malarial drug, has recently being focused as a potential anti-cancer agent as well as a chemosensitizer when used in combination with anti-cancer drugs. It has been shown to inhibit cell growth and/or to induce cell death in various types of cancer. 5-Fluorouracil (5-FU) is the chemotherapeutic agent of first choice in colorectal cancer, but in most cases, resistance to 5-FU develops through various mechanisms. Here, we focused on the combination of CQ as a mechanism to potentiate the inhibitory effect of 5-FU on human colon cancer cells. METHODS: HT-29 cells were treated with CQ and/or 5-FU, and their proliferative ability, apoptosis and autophagy induction effects, and the affection of the cell cycle were evaluated. The proliferative ability of HT-29 was analyzed by the MTS assay. Apoptosis was quantified by flow-cytometry after double-staining of the cells with AnnexinV/PI. The cell cycle was evaluated by flow-cytometry after staining of cells with PI. Autophagy was quantified by flow-cytometry and Western blot analysis. Finally, to evaluate the fate of the cells treated with CQ and/or 5-FU, the colony formation assay was performed. RESULTS: 5-FU inhibited the proliferative activity of HT-29 cells, which was mostly dependent on the arrest of the cells to the G0/G1-phase but also partially on apoptosis induction, and the effect was potentiated by CQ pre-treatment. The potentiation of the inhibitory effect of 5-FU by CQ was dependent on the increase of p21Cip1 and p27Kip1 and the decrease of CDK2. Since CQ is reported to inhibit autophagy, the catabolic process necessary for cell survival under conditions of cell starvation or stress, which is induced by cancer cells as a protective mechanism against chemotherapeutic agents, we also analyzed the induction of autophagy in HT-29. HT-29 induced autophagy in response to 5-FU, and CQ inhibited this induction, a possible mechanism of the potentiation of the anti-cancer effect of 5-FU. CONCLUSION: Our findings suggest that the combination therapy with CQ should be a novel therapeutic modality to improve efficacy of 5-FU-based chemotherapy, possibly by inhibiting autophagy-dependent resistance to chemotherapy.

Inhibition of autophagy potentiates sulforaphane-induced apoptosis in human colon cancer cells.

BACKGROUND: Sulforaphane (SUL), an isothiocyanate naturally present in widely consumed vegetables, particularly broccoli, has recently attracted attention due to its inhibitory effects on tumor cell growth by inducing apoptosis. We investigated the ability of SUL to induce autophagy in human colon cancer cells and whether inhibition of autophagy could potentiate the proapoptotic effect of SUL. METHODS: The proliferation of cells treated with SUL was assessed by MTS assay and colony-forming assay. Apoptosis and caspases activity were investigated by flow cytometry. The formation of acidic vesicular organelles (AVOs) was detected in acridine-orange-stained cells by flow cytometry. Western blotting was used for the detection of light chain 3 (LC3). Localizations of LC3 and cytochrome c were analyzed by immunocytochemistry. RESULTS: The proapoptotic effect was observed by treatment of cells with relatively high concentrations of SUL for long periods of time. After 16 h of treatment, evident formation of AVOs and recruitment of LC3 to autophagosomes, features of autophagy, were observed. Treatment of cells with a specific autophagy inhibitor (3-methyladenine) potentiated the proapoptotic effect of SUL, which was dependent on the activation of caspases and the release of cytochrome c to the cytosol. CONCLUSION: The present results demonstrate induction of autophagy in colon cancer cells as a protective reaction against the proapoptotic effect of SUL, and consequently, the potentiation of the proapoptotic effect by autophagy inhibition. These findings provide a premise for use of autophagy inhibitors in combination with chemotherapeutic agents for treatment of colorectal cancer.

Antiangiogenic effect of a selective 5-HT4 receptor agonist.

BACKGROUND: Serotonin (5-hydroxytryptamine, 5-HT) is reported to regulate cell growth in a wide variety of cell types in different carcinomas. 5-HT exerts complex actions on blood vessels, dependent on its interactions with a multiplicity of 5-HT receptors. In the present study, we aimed to investigate the potential antiangiogenic effect of mosapride citrate, a selective 5-HT4 receptor agonist, known to have prokinetic properties on the gastrointestinal tract. For this purpose, cultured human umbilical vein endothelial cells (HUVECs) were used as an in vitro model. MATERIAL AND METHODS: The effect of mosapride citrate on the proliferative activity of HUVECs was assessed by the MTS assay. Then, the apoptosis and the cell cycle detection assays were performed. The effect of mosapride citrate on the ability of HUVECs to adhere and migrate on extracellular matrix proteins (ECMs), as well as their ability to form vascular-like structures on Matrigel was investigated. RESULTS: Mosapride citrate inhibited the proliferative activity of HUVECs, dependent on cell cycle arrest, and not on apoptosis. A dose-dependent increase in the percentage of cells in the G0/G1 phase of the cell cycle in mosapride-treated HUVECs was observed. Mosapride citrate also significantly inhibited the ability of HUVECs to migrate, but not to adhere on ECMs. Additionally, mosapride citrate dose-dependently inhibited the tube-like formation ability of HUVECs on matrigel, an important event in the process of angiogenesis. CONCLUSION: The present results demonstrate the antiangiogenic activity of mosapride citrate in vitro and the possibility of its application as a new anti-cancer agent is suggested.

Id1/Id3 knockdown inhibits metastatic potential of pancreatic cancer.

BACKGROUND: The Id (inhibitor of DNA binding/differentiation) proteins belong to the helix-loop-helix transcriptional regulatory factors, and play important roles in tumor development. Previously, we and others have shown that targeting Id in tumor cells could have important clinical implications. In the present study, we aimed to evaluate the effects of Id inhibition in human pancreatic cancer cells. MATERIALS AND METHODS: Id1 and Id3 were stably double-knockdown in human pancreatic cancer cell line MIA-Paca2 by means of RNA interference. Expression of Id and integrins were analyzed by flow-cytometry. Cell proliferation was evaluated by MTS assay. Migration was measured by wound closure assay. Adhesion assay was performed to evaluate binding capacity for different extracellular matrix proteins. Finally, in vivo properties of tumor cells were observed in a mouse model of peritoneal metastasis. RESULTS: Id1/Id3 double-knockdown resulted in decreased ability of pancreatic cancer cells to proliferate and migrate. In addition, Id1/Id3 double-knockdown caused decreased expression of integrins alpha3, alpha6, and beta1, and consequently reduced adhesion of tumor cells to laminin. Finally, peritoneal metastases of Id1/Id3 double-knockdown tumor cells were significantly reduced. CONCLUSIONS: We concluded that the Id proteins play a pivotal role in the development of peritoneal metastasis of pancreatic cancer, and consequently, their targeting would be a novel strategy for the prevention and treatment of pancreatic cancer.

Sulforaphane stimulates activation of proapoptotic protein bax leading to apoptosis of endothelial progenitor cells.

Sulforaphane (SUL) is an isothiocyanate naturally present in widely consumed vegetables, particularly in broccoli. SUL has recently been focused as a result of its inhibitory effects on tumor cell growth in vitro and in vivo. We used endothelial progenitor cells (EPCs) as an in vitro model to investigate the effect of SUL on the various steps of vasculogenesis and angiogenesis. Peripheral blood mononuclear cells from blood of normal human volunteers were plated on fibronectin-coated 100 mm dishes and incubated for 7 days. The viability of EPCs, treated with SUL at different doses, was assessed by MTS assay. Cell apoptosis was analyzed by flow cytometry. To determine the relative contributions of caspase-8 and caspase-9 pathways to SUL-induced apoptosis, the effect of caspase inhibitors was determined. The expression of apoptosis-related proteins (Bax, Bcl-2) was investigated by Western blot test. Finally, the effect of SUL on the ability of EPCs to form vascular-like structures on Matrigel was investigated. We clearly demonstrated that SUL induced the dose-dependent inhibition of EPCs' viability by induction of apoptosis. All caspases (caspase-3, -8, and -9) were activated during apoptosis induction by SUL, but the effect of caspase-9 was more prominent than that of caspase-8. Also, the expression of Bax was upregulated by SUL treatment. In addition to apoptosis induction, SUL dose-dependently inhibited the tube-like formation by EPCs on Matrigel. The present results demonstrate the antivasculogenic/antiangiogenic activity of SUL in vitro and open premise for the use of SUL as a multipotent anticancer agent that targets both cancer cells and the angiogenic endothelium.

Anti-angiogenic property of zoledronic acid by inhibition of endothelial progenitor cell differentiation.

BACKGROUND: Zoledronic acid (ZOL) is clinically available for the treatment of skeletal complications. In preclinical studies, strong anti-cancer activities against breast cancer, prostate cancer, and leukemia were reported. It also inhibited the proliferation of cultured human endothelial cells, suggestive of an anti-angiogenic activity. Since ZOL has the tendency to accumulate in bone, we investigated the effect of ZOL on endothelial progenitor cells (EPCs), which originate from the bone marrow, and play important roles in angiogenesis. MATERIALS AND METHODS: Human peripheral blood mononuclear cells were cultured for 7 d to differentiate into EPCs. Cells were treated without/with ZOL or with geranylgeraniol (GGOH). Their endothelial phenotype was confirmed by the expression of CD144 and vascular endothelial growth factor receptor 2 and the tube-like formation ability on Matrigel (Becton Dickinson, Bedford, MA). Annexin V/propidium iodide staining was used to analyze apoptosis. RESULTS: ZOL treatment, even at low doses, from d 2 to 7 of culture resulted in impaired EPC differentiation and could be restored by co-treatment with GGOH. On the other hand, treatment of putative EPCs with ZOL at concentrations higher than 10 mum resulted in induction of apoptosis. CONCLUSION: ZOL dose-dependently inhibited the differentiation of EPCs, the effect being observed even at low drug levels. At high concentrations, ZOL also induced the apoptotic death of putative EPCs. Since GGOH restored the inhibitory effect of ZOL on EPCs differentiation, the effect of ZOL appears to be dependent on the inhibition of prenylation of small-G-proteins. From these findings, we conclude that ZOL could be a potential anticancer agent by inhibiting angiogenesis.

Plaunotol and geranylgeraniol induce caspase-mediated apoptosis in colon cancer.

BACKGROUND: Plaunotol, a kind of isoprenoid extracted from a Thai medical plant, plau-noi, is structurally similar to geranylgeraniol (GGOH), another isoprenoid reported to exert strong anticancer effects. Recently, we have reported on its inhibitory effects on tumor angiogenesis and direct effects on gastric cancer cells. Here, we aimed to test whether plaunotol could have some therapeutic effect on colon cancer. MATERIALS AND METHODS: Human colon cancer cell line DLD1 was used. Tumor cells were cultured in the presence of plaunotol or GGOH, and their proliferation was measured by MTS assay. Apoptosis was evaluated by Annexin V and propidium iodide double-staining or terminal-deoxynucleotidyl assay. The activation of caspase-3, -8, and -9 was analyzed by flow cytometry and Western blot analysis for PRRP cleavage. RESULTS: Plaunotol and GGOH strongly inhibited the proliferative activity of DLD1, dependent on induction of apoptosis. The induction of apoptosis by either plaunotol or GGOH was dependent on the activation of both caspase-8 and caspase-9 pathways. CONCLUSIONS: Plaunotol would be a potential anticancer agent against colon cancer, and since it is already available in Japan and Thailand for clinical use as an anti-ulcer/antigastritis agent, clinical trials will be designed to confirm the present findings.

Apoptosis induction by p38 MAPK inhibitor in human colon cancer cells.

BACKGROUND/AIMS: The p38 mitogen-activated protein kinases (p38 MAPKs) function in a wide variety of signaling pathways. However, the role of p38s is cell type- and stimulus-dependent. The present study aimed to evaluate the effects of p38 MAPK inhibitor on human colon cancer cells. METHODOLOGY: The effect of p38 MAPK inhibitor, FR167653, on DLD-1 and SW480 was investigated related to cell proliferation, apoptosis induction and caspase activity. Additionally, the effect of FR167653 on colon cancer cell migration, MMPs production and ability to adhere to extracellular matrix was investigated. RESULTS: Inhibitor of p38 MAPK dose-dependently suppressed the proliferative activity of both cell lines, and increased the induction of cell apoptosis. The caspase-3, 8, and 9 activities were accompanied in the pathway. Neither cell migration, MMPs production, nor the ability to adhere extracellular matrix were affected by FR167653. CONCLUSIONS: Inhibitor of p38 MAPK suppressed the proliferation of colon cancer cells by induction of cell apoptosis through the caspase activation. The present results suggest the pro-oncogenic role ofp38 in colon cancer, and its inhibition would be a novel strategy for the prevention and treatment of colon cancer.

Pilot study of anti-angiogenic vaccine using fixed whole endothelium in patients with progressive malignancy after failure of conventional therapy.

Vaccines targeting tumour angiogenesis were recently shown to inhibit tumour growth in animal models. However, there is still a lack of information about the clinical utility of anti-angiogenic vaccination. Therefore, here, we aimed to test the clinical effects of a vaccine using glutaraldehyde-fixed human umbilical vein endothelial cells (HUVECs). Six patients with recurrent malignant brain tumours and three patients with metastatic colorectal cancer received intradermal injections of 5x10(7) HUVECs/dose (in total 230 vaccinations). ELISA and flow cytometry revealed immunoglobulin response against HUVECs' membrane antigens. ELISPOT and chromium-release cytotoxicity assay revealed a specific cellular immune response against HUVECs, which were lysed in an effectors:targets ratio-dependent manner. Gadolinium-contrasted MRI showed partial or complete tumour responses in three malignant brain tumour patients. Except for a DTH-like skin reaction at the injection site, no adverse effect of vaccination could be observed. Our results suggest that the endothelial vaccine can overcome peripheral tolerance of self-angiogenic antigens in clinical settings, and therefore should be useful for adjuvant immunotherapy of cancer.

Plaunotol induces apoptosis of gastric cancer cells.

Although some isoprenoids, such as taxans and geranylgeraniol (GGOH), have been reported to have strong anticancer activities, the effect of plaunotol, the isoprenoid extracted from the leaves of Plau-noi, on cancer has not yet been evaluated. Here, we aimed to investigate the effect of plaunotol on gastric cancer cell lines. Three gastric cancer cell lines, namely MKN-45, MKN-74 and AZ-521 were used. Plaunotol was tested at 10, 20, 30 and 40 micromol/L. Plaunotol dose-dependently inhibited the growth of all gastric cancer cells, dependent on the induction of apoptosis. Caspases-8, -9 and -3, were found to be activated in the apoptotic cells. The expression of Bax protein was increased, but Bcl-2 and Bcl-xL protein expressions were not significantly affected. Plaunotol should be a promising new antitumor agent, and since it is already available for clinical use in Japan, its anticancer properties should be confirmed in clinical trials.

Sulforaphane induces inhibition of human umbilical vein endothelial cells proliferation by apoptosis.

Sulforaphane (SUL), one of the isothiocyanates (ITCs), has recently been focused due to its inhibitory effects on tumor cell growth in vitro and in vivo, which is dependent on the direct effect on cancer cells. In the present study, we aimed to investigate the potential anti-angiogenic effect of SUL and its mechanism of action. Using the human umbilical vein endothelial cells (HUVECs) as a model of angiogenesis, we investigated the effect of SUL on the various steps of angiogenesis, including the proliferation of endothelial cells, tubular formation, and matrix metalloproteinase (MMP) production. Sulforaphane induced a dose-dependent decrease in the proliferative activity of endothelial cells, which was dependent on cell apoptosis. Also SUL inhibited tube formation on matrigel, but did not affect MMP production. The present results demonstrate the anti-angiogenic activity of SUL and its potential use as an anti-cancer drug is suggested.

Effects of down-regulating the Id genes in human colorectal cancer cells on early steps of haematogenous metastasis.

Id genes (inhibitor of DNA binding/differentiation) play important roles in tumour growth. We have previously described crucial roles of Id gene over-expression in endothelial cells for tumour angiogenesis. Here, we have evaluated direct effects of Id gene down-regulation on tumour cells, namely on cell proliferation, motility, and adhesion to lung microvasculature during haematogenous metastasis. For this purpose, Id genes were stably down-regulated by RNA interference in human colorectal cancer cells. These cells showed delayed proliferation, inhibited motility and decreased expression of integrin alpha6 and consequently reduced adhesion to lung microvasculature in mice. Static adhesion assays and laminar flow assays revealed decreased laminin binding capacity of these cells, and blocking experiments confirmed that it could be attributed to decreased expression of integrin alpha6. The present results indicate important roles of Id genes in tumour cells during early steps of haematogenous metastasis and suggest dual effects from their therapeutic inhibition.

Early-outgrowth of endothelial progenitor cells can function as antigen-presenting cells.

Endothelial progenitor cells (EPCs) have been recently found to exist circulating in peripheral blood of adults, and home to sites of neovascularization in peripheral tissues. They can also be differentiated from peripheral blood mononuclear cells (PBMNCs). In tumor tissues, EPCs are found in highly vascularized lesions. Few reports exist in the literature concerning the characteristics of EPCs, especially related to their surface antigen expressions, except for endothelial markers. Here, we aimed to investigate the surface expression of differentiation markers, and the functional activities of early-outgrowth of EPCs (EO-EPCs), especially focusing on their antigen-presenting ability. EO-EPCs were generated from PBMNCs, by culture in the presence of angiogenic factors. These EO-EPCs had the morphological and functional features of endothelial cells and, additionally, they shared antigen-presenting ability. They induced the proliferation of allogeneic lymphocytes in a mixed-lymphocyte reaction, and could generate cytotoxic lymphocytes, with the ability to lyze tumor cells in an antigen-specific manner. The antigen-presenting ability of EO-EPCs, however, was weaker than that of monocyte-derived dendritic cells, but stronger than peripheral blood monocytes. Since EO-EPCs play an important role in the development of tumor angiogenesis, targeting EPCs would be an effective anti-angiogenic strategy. Alternatively, due to their antigen-presenting ability, EO-EPCs can be used as the effectors of anti-tumor immunotherapy. Since they share endothelial antigens, the activation of a cellular immunity against angiogenic vessels can be expected. In conclusion, EO-EPCs should be an interesting alternative for the development of new therapeutic strategies to combat cancer, either as the effectors or as the targets of cancer immunotherapy.

Targeting Id1 and Id3 inhibits peritoneal metastasis of gastric cancer.

Inhibitor of DNA binding (Id) proteins are essential for cell differentiation, proliferation, migration, invasion and angiogenesis. Recently, they have been shown to correlate with less differentiated phenotypes, high malignant potential and poor clinical outcome in various kinds of tumors. In an attempt to develop new strategies for the treatment of peritoneal metastasis of gastric cancer, we prepared an Id1, 3 double-knockdown gastric cancer cell line, MKN45, by RNA interference and investigated its effects on the development of metastatic nodules in the peritoneal cavity. Both cell proliferation and migration capabilities were decreased in Id1, 3 double-knockdown cells, as was their ability to bind to laminin, which could be explained by the decreased expression of integrin alpha6. These are important steps in the metastatic process. In a mouse model, the number of peritoneal metastatic nodules formed by Id1, 3 double-knockdown cells was reduced compared to mock-transfected control cells, as was the size of individual tumors. In this study, we clearly demonstrated that Id1, 3 double-knockdown significantly impaired the ability of gastric cancer cells to form peritoneal metastasis. Id should be considered an ideal target for the treatment and prevention of gastric cancer, and RNA interference is an attractive and promising strategy to achieve it.

Anti-angiogenic properties of plaunotol.

We have investigated a potential anti-angiogenic effect of plaunotol, an extract from the leaves of Plau-noi, in an angiogenesis model consisting of human umbilical vein endothelial cells (HUVECs). Plaunotol inhibited the proliferative activity of HUVECs in a dose-dependent manner. In addition, it caused a remarkable decrease of the ability of HUVECs to adhere and spread on gelatin and vitronectin, but not fibronectin. Tube-like formation in Matrigel was also inhibited in a dose-dependent way. These results strongly suggest the specific inhibition of integrin alphavbeta3 to be the main event of plaunotol-induced suppression of angiogenesis. The alphavbeta3 antagonists are known to be potent inhibitors of tumor angiogenesis and plaunotol, by causing the functional inhibition of alphavbeta3, should be considered a promising new anti-angiogenic drug.

Selective inhibition of cyclooxygenase-2 inhibits colon cancer cell adhesion to extracellular matrix by decreased expression of beta1 integrin.

High level expression of cyclooxygenase (COX)-2 is reported in 80-90% of colorectal adenocarcinomas. In the recent years, selective inhibitors of COX-2 have been developed, and are shown to effectively protect against cancer development and progression. Colon cancer cells, as well as the epithelial cells in general, are dependent on appropriate interactions with the extracellular matrix (ECM) proteins to achieve a number of important functions, such as proliferation, differentiation, invasion and survival. These interactions are mediated via a family of cell-surface receptors called integrins, which interact with cytoskeletal proteins on the cytoplasmic side of the plasma membrane and thereby provide a link between the ECM and the cytoskeleton. In the present study, a high-COX-2 (high level COX-2 expression) colon cancer cell line, HT-29, and a low-COX-2 (low level COX-2 expression), DLD-1, were used to investigate the anticolon cancer effect of the selective COX-2 inhibitor, JTE-522. Moreover, to clarify its mechanisms of action, we focused especially on the ability to adhere to and to migrate on ECM. We could clearly demonstrate that, in addition to the decrease of the proliferative activity, JTE-522 caused a dose-dependent decrease in both the ability of colon cancer cells to adhere to and to migrate on ECM. These effects were, at least in part, dependent on the down-regulation of beta1-integrin expression, which was evident in HT-29, the high-COX-2 colon cancer cells, but not the low-COX-2, DLD-1. In addition, prostaglandin E2 almost completely reversed the effect of JTE-522, strongly suggesting the involvement of a COX-2-dependent pathway. In conclusion, for the first time, we could demonstrate the down-regulation of beta1 integrin caused by COX-2 inhibition, with consequent impairment of the ability of cancer cells to adhere to and to migrate on ECM, which are crucial steps for cancer metastases to develop.

Epigallocatechin gallate induces apoptosis of monocytes.

BACKGROUND: Monocytes are the main effector cells of the immune system, and the regulation of their survival and apoptosis is essential for monocyte-involved immune responses. Green tea polyphenol catechin has been reported to have antiallergic and anti-inflammatory activities, but its effect on monocytes has not yet been explored. OBJECTIVE: To elucidate the mechanisms of the anti-inflammatory effect of catechin, we studied the effect of catechin, especially epigallocatechin gallate (EGCG), on the apoptosis of monocytes. METHODS: Isolated peripheral blood monocytes were incubated without or with catechin, and apoptosis was evaluated by annexin V and propidium iodide double-staining or terminal deoxynucleotidyl assay. The activation of caspases 3, 8, and 9 was also evaluated by flow cytometry. The influence of GM-CSF or LPS, the known monocyte survival factors, on the EGCG-induced apoptosis of monocytes was investigated. RESULTS: Among the 4 catechin derivatives tested, EGCG and epicatechin gallate induced apoptosis of monocytes. Caspases 3, 8, and 9, which play a central role in the apoptotic cascade, were dose-dependently activated by EGCG treatment. The EGCG-induced apoptosis of monocytes was not affected by GM-CSF or LPS. CONCLUSION: Catechin, especially EGCG, by promoting monocytic apoptosis, may be a new promising anti-inflammatory agent, and should be tested in clinical trials.