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Bin Zhong

Publications and source records attributed to Bin Zhong.

7 recordsLinked to original sources
PubMed2005

Stat3 activity in melanoma cells affects migration of immune effector cells and nitric oxide-mediated antitumor effects.

Infiltration of immune effector cells in tumors is critical for antitumor immune responses. However, what regulates immune cell infiltration of tumors remains to be identified. Stat3 is constitutively activated with high frequency in diverse cancers, promoting tumor cell growth and survival. Blocking Stat3 signaling in tumors in vivo results in tumor growth inhibition that involves killing of nontransfected tumor cells and infiltration of immune effector cells, suggesting that Stat3 activity in tumor cells might affect immune cell recruitment. However, dying tumor cells can also attract immune cells. In this study, we show in isogenic murine melanomas that natural Stat3 activity is associated with tumor growth and reduction of T cell infiltration. Blocking Stat3 signaling in the melanoma cells containing high Stat3 activity results in expression of multiple chemoattractants, leading to increased migration of lymphocytes, NK cells, neutrophils, and macrophages. In addition, blocking Stat3 triggers tumor cells to produce soluble factors capable of activating macrophage production of NO in vitro and in vivo. TNF-alpha and IFN-beta, which are secreted by Stat3-inhibited tumor cells, are able to activate macrophage NO production, whereas neutralizing TNF-alpha in the tumor supernatant from Stat3-blocked tumor cells abrogates nitrite production. Moreover, interrupting Stat3 signaling in tumor cells leads to macrophage-mediated, nitrite-dependent cytostatic activity against nontransduced tumor cells. These results suggest that tumor Stat3 activity affects recruitment of diverse immune effectors and it can be manipulated to activate the effector phase of innate immune responses.

Animals↗
PubMed2004

[Preliminary study on in vitro tendon engineering using tenocytes and polyglycolic acids].

OBJECTIVE: To find out the feasibility of tendon engineering in vitro using expanded tenocytes and polyglycolic acids (PGA). METHODS: Tenocytes were isolated using tissue explant method and expanded in vitro. Tenocytes (20 x 10(6)) at the second passage were collected and then seeded onto PGA unwoven fibers to form a cell-scaffold construct in a shape of tendon. The constructs were cultured in DMEM with 20% FBS for 1 week. The cell-scaffold constructs were then cultured under constant tension generated by a U-shaped spring (n = 5), which served as experimental group, or cultured without tension (n = 4), which served as control group 1. PGA fibers alone were cultured (n = 3), which served as control group 2. Small fragments at the end of the constructs were harvested at 2, 4 and 6 weeks respectively for histological and immunohistochemistry (IHC) analysis. Six-week samples were also evaluated by transmission electron microscope (TEM) and mechanical test. RESULTS: No obvious difference was observed among the three groups at 2 weeks grossly and histologically as the constructs remained to be mainly undegraded PGA fibers. By 4 weeks, a neo-tendon was formed in the experimental group and control group 1 grossly, and histology and IHC revealed the formation of collagen fibers. In contrast, PGA fibers alone in control group 2 were mostly degraded. At 6 weeks, tendons of control group 1 were much thicker [(2.55 +/- 0.18) mm in diameter] than those of experimental group [(1.44 +/- 0.13) mm in diameter]. Periodical striae were observed in collagen fibers of experimental group and control group 1 by TEM. However, histology of tendons in experimental group revealed longitudinally aliened collagen fibers, which resembled the structure of normal tendon more closely than that of control group 1 tendons. Furthermore, the maximum tensile stress (N/mm(2)) of experimental group (1.107 +/- 0.327) was greater than that of control group 1 (0.294 +/- 0.138) (P < 0.05). CONCLUSION: It is possible to use an engineering to construct tendon tissue in vitro. Periodical strain generated by bioreactor may be the optimal mechanical stimulation, which is currently under investigation.

Animals↗
PubMed2003

Human neutrophils utilize a Rac/Cdc42-dependent MAPK pathway to direct intracellular granule mobilization toward ingested microbial pathogens.

Elevated levels of mitogen-activated protein kinase/extracellular regulatory kinase (MAPK/ERK) activity are frequently found in some cancer cells. In efforts to reduce tumor growth, attempts have been made to develop cancer therapeutic agents targeting the MAPK. Here, by use of biologic, biochemical, and gene manipulation methods in human polymorphonuclear neutrophils (PMNs), we have identified a key pathway important in normal cell function involving MAPK/ERK in PMNs for growth inhibition of Candida albicans. Contact with C albicans triggered MAPK/ERK activation in PMNs within 5 minutes, and blocking of MAPK/ERK activation, either by the pharmacologic reagent PD098059 or by dominant-negative MAPK kinase (MEK) expression via vaccinia viral delivery, suppressed antimicrobial activity. Rac and Cdc42, but not Ras or Rho, were responsible for this MAPK/ERK activation. Expression of dominant-negative Rac (N17Rac) or Cdc42 (N17Cdc42) eliminated not only C albicans- mediated ERK phosphorylation but also phagocytosis and granule migration toward the ingested microbes, whereas dominant-negative Ras (N17Ras) and Rho (N19Rho) did not. PAK1 (p21-activated kinase 1) activation is induced by C albicans, suggesting that PAK1 may also be involved in the Rac1 activation of MAPK/ERK. We conclude from these data that Rac/Cdc42-dependent activation of MAPK/ERK is a critical event in the immediate phagocytic response of PMNs to microbial challenge. Therefore, use of MAPK pharmacologic inhibitors for the treatment of cancer may result in the interruption of normal neutrophil function. A balance between therapeutic outcome and undesirable side effects must be attained to achieve successful and safe anticancer therapy.

Candida albicans↗
PubMed2002

Regulation of Akt-dependent cell survival by Syk and Rac.

Interleukin-2 (IL-2) prevents cell apoptosis and promotes survival, but the involved mechanisms have not been completely defined. Although phosphatidylinositide 3-kinase (PI 3-kinase) has been implicated in IL-2-mediated survival mechanisms, none of the 3 chains of the IL-2 receptor (IL-2R) expresses a binding site for PI 3-kinase. However, IL-2Rbeta does express a Syk-binding motif. By using an IL-2-dependent natural killer (NK) cell line, followed by validation of the results in fresh human NK cells, we identified Syk as a critical effector essential for IL-2-mediated prosurvival signaling in NK cells. Down-regulation of Syk by piceatannol treatment impaired NK cellular viability and induced prominent apoptosis as effectively as suppression of PI 3-kinase function by LY294002. Expression of kinase-deficient Syk or pretreatment with piceatannol markedly suppressed IL-2-stimulated activation of PI 3-kinase and Akt, demonstrating that Syk is upstream of PI 3-kinase and Akt. However, constitutively active PI 3-kinase reversed this loss of Akt function caused by kinase-deficient Syk or piceatannol. Thus, Syk appears to regulate PI 3-kinase, which controls Akt activity during IL-2 stimulation. More important, we observed Rac1 activation by IL-2 and found that it mediated PI 3-kinase activation of Akt. This conclusion came from experiments in which dominant-negative Rac1 significantly decreased IL-2-induced Akt activation, whereas constitutively active Rac1 reelevated Akt activity not only in Syk-impaired but also in PI 3-kinase-impaired NK cells. These results constitute the first report of a Syk --> PI3K --> Rac1 --> Akt signal cascade controlled by IL-2 that mediates NK cell survival.

Blood Cells↗
PubMed2002

Syk regulation of phosphoinositide 3-kinase-dependent NK cell function.

Emerging evidence suggests that NK-activatory receptors use KARAP/DAP12, CD3zeta, and FcepsilonRIgamma adaptors that contain immunoreceptor tyrosine-based activatory motifs to mediate NK direct lysis of tumor cells via Syk tyrosine kinase. NK cells may also use DAP10 to drive natural cytotoxicity through phosphoinositide 3-kinase (PI3K). In contrast to our recently identified PI3K pathway controlling NK cytotoxicity, the signaling mechanism by which Syk associates with downstream effectors to drive NK lytic function has not been clearly defined. In NK92 cells, which express DAP12 but little DAP10/NKG2D, we now show that Syk acts upstream of PI3K, subsequently leading to the specific signaling of the PI3K-->Rac1-->PAK1-->mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase-->ERK cascade that we earlier described. Tumor cell ligation stimulated DAP12 tyrosine phosphorylation and its association with Syk in NK92 cells; Syk tyrosine phosphorylation and activation were also observed. Inhibition of Syk function by kinase-deficient Syk or piceatannol blocked target cell-induced PI3K, Rac1, PAK1, mitogen-activated protein/ERK kinase, and ERK activation, perforin movement, as well as NK cytotoxicity, indicating that Syk is upstream of all these signaling events. Confirming that Syk does not act downstream of PI3K, constitutively active PI3K reactivated all the downstream effectors as well as NK cytotoxicity suppressed in Syk-impaired NK cells. Our results are the first report documenting the instrumental role of Syk in control of PI3K-dependent natural cytotoxicity.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Functional role of phosphatidylinositol 3-kinase in direct tumor lysis by human natural killer cells.

Cytotoxicity is a key function of natural killer (NK) and T cells; yet the molecular mechanism is unclear. We have biological, biochemical and molecular evidence to demonstrate that phosphatidyl-inositol (PI) 3-kinase is critical for direct NK lysis of tumor cells, via control of intracellular granule movement. Tumor cell engagement rapidly activated PI 3-kinase in NK cells within 5 min, as demonstrated by p85 subunit tyrosine phosphorylation and its ability to generate phosphatidylinositol 3-phosphate, PI(3)P, from PI. Wortmannin and LY294002 effectively inhibited NK cells to lyse 51Cr-labeled tumor cells at the same doses that blocked PI-phosphorylating function in tumor-activated NK cells. Immunostaining demonstrated that tumor engagement for only 5 min mobilized perforin and granzyme B from NK cells unidirectionally towards the target, and prior treatment of NK cells with either PI 3-kinase inhibitor effectively stopped this intracellular polarization. Lastly, ectopic expression of dominant-negative p85 or p110 mutant markedly suppressed NK lytic capacity. These results taken together demonstrate that PI 3-kinase may control NK lytic function via granule polarization towards the contacted target cell.

Androstadienes↗