技术资料

Tandem pleckstrin homology domain proteins (TAPPs) are recruited to the plasma membrane via binding to phosphoinositides produced by phosphoinositide 3-kinases (PI3Ks). Whereas PI3Ks are critical for B-cell activation,the functions of TAPP proteins in B cells are unknown. We have identified 40 potential interaction partners of TAPP2 in B cells,including proteins involved in cytoskeletal rearrangement,signal transduction and endocytic trafficking. The association of TAPP2 with the cytoskeletal proteins utrophin and syntrophin was confirmed by Western blotting. We found that TAPP2,syntrophin,and utrophin are coexpressed in normal human B cells and B-chronic lymphocytic leukemia (B-CLL) cells. TAPP2 and syntrophin expression in B-CLL was variable from patient to patient,with significantly higher expression in the more aggressive disease subset identified by zeta-chain-associated protein kinase of 70 kDa (ZAP70) expression and unmutated immunoglobulin heavy chain (IgH) genes. We examined whether TAPP can regulate cell adhesion,a known function of utrophin/syntrophin in other cell types. Expression of membrane-targeted TAPP2 enhanced B-cell adhesion to fibronectin and laminin,whereas PH domain-mutant TAPP2 inhibited adhesion. siRNA knockdown of TAPP2 or utrophin,or treatment with PI3K inhibitors,significantly inhibited adhesion. These findings identify TAPP2 as a novel link between PI3K signaling and the cytoskeleton with potential relevance for leukemia progression. View Publication

PURPOSE: There are no effective therapies for patients with poorly differentiated papillary thyroid cancer (PTC) or anaplastic thyroid cancer (ATC),and metastasis to the bone represents a significantly worse prognosis. Src family kinases (SFKs) are overexpressed and activated in numerous tumor types and have emerged as a promising therapeutic target,especially in relation to metastasis. We recently showed that Src is overexpressed and activated in thyroid cancer. We therefore tested whether inhibition of Src with dasatinib (BMS-354825) blocks thyroid cancer growth and metastasis. EXPERIMENTAL DESIGN: The effects of dasatinib on thyroid cancer growth,signaling,cell cycle,and apoptosis were evaluated in vitro. The therapeutic efficacy of dasatinib was further tested in vivo using an orthotopic and a novel experimental metastasis model. Expression and activation of SFKs in thyroid cancer cells was characterized,and selectivity of dasatinib was determined using an Src gatekeeper mutant. RESULTS: Dasatinib treatment inhibited Src signaling,decreased growth,and induced cell-cycle arrest and apoptosis in a subset of thyroid cancer cells. Immunoblotting showed that c-Src and Lyn are expressed in thyroid cancer cells and that c-Src is the predominant SFK activated. Treatment with dasatinib blocked PTC tumor growth in an orthotopic model by more than 90% (P = 0.0014). Adjuvant and posttreatment approaches with dasatinib significantly inhibited metastasis (P = 0.016 and P = 0.004,respectively). CONCLUSION: These data provide the first evidence that Src is a central mediator of thyroid cancer growth and metastasis,indicating that Src inhibitors may have a higher therapeutic efficacy in thyroid cancer,as both antitumor and antimetastatic agents. View Publication

The development of strategies to eradicate primary human acute myelogenous leukemia (AML) cells is a major challenge to the leukemia research field. In particular,primitive leukemia cells,often termed leukemia stem cells,are typically refractory to many forms of therapy. To investigate improved strategies for targeting of human AML cells we compared the molecular mechanisms regulating oxidative state in primitive (CD34(+)) leukemic versus normal specimens. Our data indicate that CD34(+) AML cells have elevated expression of multiple glutathione pathway regulatory proteins,presumably as a mechanism to compensate for increased oxidative stress in leukemic cells. Consistent with this observation,CD34(+) AML cells have lower levels of reduced glutathione and increased levels of oxidized glutathione compared with normal CD34(+) cells. These findings led us to hypothesize that AML cells will be hypersensitive to inhibition of glutathione metabolism. To test this premise,we identified compounds such as parthenolide (PTL) or piperlongumine that induce almost complete glutathione depletion and severe cell death in CD34(+) AML cells. Importantly,these compounds only induce limited and transient glutathione depletion as well as significantly less toxicity in normal CD34(+) cells. We further determined that PTL perturbs glutathione homeostasis by a multifactorial mechanism,which includes inhibiting key glutathione metabolic enzymes (GCLC and GPX1),as well as direct depletion of glutathione. These findings demonstrate that primitive leukemia cells are uniquely sensitive to agents that target aberrant glutathione metabolism,an intrinsic property of primary human AML cells. View Publication

Aldehyde dehydrogenase-1A1 (ALDH1A1) expression characterizes a subpopulation of cells with tumor-initiating or cancer stem cell properties in several malignancies. Our goal was to characterize the phenotype of ALDH1A1-positive ovarian cancer cells and examine the biological effects of ALDH1A1 gene silencing. In our analysis of multiple ovarian cancer cell lines,we found that ALDH1A1 expression and activity was significantly higher in taxane- and platinum-resistant cell lines. In patient samples,72.9% of ovarian cancers had ALDH1A1 expression in which the percentage of ALDH1A1-positive cells correlated negatively with progression-free survival (6.05 vs. 13.81 months; P textless 0.035). Subpopulations of A2780cp20 cells with ALDH1A1 activity were isolated for orthotopic tumor-initiating studies,where tumorigenicity was approximately 50-fold higher with ALDH1A1-positive cells. Interestingly,tumors derived from ALDH1A1-positive cells gave rise to both ALDH1A1-positive and ALDH1A1-negative populations,but ALDH1A1-negative cells could not generate ALDH1A1-positive cells. In an in vivo orthotopic mouse model of ovarian cancer,ALDH1A1 silencing using nanoliposomal siRNA sensitized both taxane- and platinum-resistant cell lines to chemotherapy,significantly reducing tumor growth in mice compared with chemotherapy alone (a 74%-90% reduction; P textless 0.015). These data show that the ALDH1A1 subpopulation is associated with chemoresistance and outcome in ovarian cancer patients,and targeting ALDH1A1 sensitizes resistant cells to chemotherapy. ALDH1A1-positive cells have enhanced,but not absolute,tumorigenicity but do have differentiation capacity lacking in ALDH1A1-negative cells. This enzyme may be important for identification and targeting of chemoresistant cell populations in ovarian cancer. View Publication

PURPOSE: The Aurora kinase family plays pivotal roles in mitotic integrity and cell cycle. We sought to determine the effects of inhibiting Aurora kinase on ovarian cancer growth in an orthotopic mouse model using a small molecule pan-Aurora kinase inhibitor,MK-0457. EXPERIMENTAL DESIGN: We examined cell cycle regulatory effects and ascertained the therapeutic efficacy of Aurora kinase inhibition both alone and combined with docetaxel using both in vitro and in vivo ovarian cancer models. RESULTS: In vitro cytotoxicity assays with HeyA8 and SKOV3ip1 cells revealed textgreater10-fold greater docetaxel cytotoxicity in combination with MK-0457. After in vivo dose kinetics were determined using phospho-histone H3 status,therapy experiments with the chemosensitive HeyA8 and SKOV3ip1 as well as the chemoresistant HeyA8-MDR and A2780-CP20 models showed that Aurora kinase inhibition alone significantly reduced tumor burden compared with controls (P valuestextless0.01). Combination treatment with docetaxel resulted in significantly improved reduction in tumor growth beyond that afforded by docetaxel alone (P textlessor= 0.03). Proliferating cell nuclear antigen immunohistochemistry revealed that MK-0457 alone and in combination with docetaxel significantly reduced cellular proliferation (P valuestextless0.001). Compared with controls,treatment with MK-0457 alone and in combination with docetaxel also significantly increased tumor cell apoptosis by approximately 3-fold (Ptextless0.01). Remarkably,compared with docetaxel monotherapy,MK-0457 combined with docetaxel resulted in significantly increased tumor cell apoptosis. CONCLUSIONS: Aurora kinase inhibition significantly reduces tumor burden and cell proliferation and increases tumor cell apoptosis in this preclinical orthotopic model of ovarian cancer. The role of Aurora kinase inhibition in ovarian cancer merits further investigation in clinical trials. View Publication

There is increasing evidence that many cancers,including breast cancer,contain populations of cells that display stem-cell properties. These breast cancer stem cells,by virtue of their relative resistance to radiation and cytotoxic chemotherapy,may contribute to treatment resistance and relapse. The elucidation of pathways that regulate these cells has led to the identification of potential therapeutic targets. A number of agents capable of targeting breast cancer stem cells in preclinical models are currently entering clinical trials. Assessment of the efficacy of the agents will require development of innovative clinical trial designs with appropriate biologic and clinical end points. The effective targeting of breast cancer stem cells has the potential to significantly improve outcome for women with both early-stage and advanced breast cancer. View Publication

The cancer stem cell hypothesis asserts that malignancies arise in tissue stem and/or progenitor cells through the dysregulation or acquisition of self-renewal. In order to determine whether the dietary polyphenols,curcumin,and piperine are able to modulate the self-renewal of normal and malignant breast stem cells,we examined the effects of these compounds on mammosphere formation,expression of the breast stem cell marker aldehyde dehydrogenase (ALDH),and Wnt signaling. Mammosphere formation assays were performed after curcumin,piperine,and control treatment in unsorted normal breast epithelial cells and normal stem and early progenitor cells,selected by ALDH positivity. Wnt signaling was examined using a Topflash assay. Both curcumin and piperine inhibited mammosphere formation,serial passaging,and percent of ALDH+ cells by 50% at 5 microM and completely at 10 microM concentration in normal and malignant breast cells. There was no effect on cellular differentiation. Wnt signaling was inhibited by both curcumin and piperine by 50% at 5 microM and completely at 10 microM. Curcumin and piperine separately,and in combination,inhibit breast stem cell self-renewal but do not cause toxicity to differentiated cells. These compounds could be potential cancer preventive agents. Mammosphere formation assays may be a quantifiable biomarker to assess cancer preventive agent efficacy and Wnt signaling assessment can be a mechanistic biomarker for use in human clinical trials. View Publication

Acute myeloid leukemia (AML) cells are characterized by a constitutive and abnormal activation of the nuclear factor-kappaB (NF-kappaB) transcription factor. This study,conducted in vitro on 18 patients,shows that targeting the IKB kinase 2 (IKK2) kinase with the specific pharmacologic inhibitor AS602868 to block NF-kappaB activation led to apoptosis of human primary AML cells. Moreover,AS602868 potentiated the apoptotic response induced by the current chemotherapeutic drugs doxorubicin,cytarabine,or etoposide (VP16). AS602868-induced cell death was associated with rupture of the mitochondrial transmembrane potential and activation of cellular caspases. NF-kappaB inhibition did not affect normal CD34+ hematopoietic precursors,suggesting that it could represent a new adjuvant strategy for AML treatment. View Publication

Summary The cytokine TWEAK and its cognate receptor Fn14 are members of the TNF/TNFR superfamily and are upregulated in tumors. We found that Fn14,when expressed in tumors,causes cachexia and that antibodies against Fn14 dramatically extended lifespan by inhibiting tumor-induced weight loss although having only moderate inhibitory effects on tumor growth. Anti-Fn14 antibodies prevented tumor-induced inflammation and loss of fat and muscle mass. Fn14 signaling in the tumor,rather than host,is responsible for inducing this cachexia because tumors in Fn14- and TWEAK-deficient hosts developed cachexia that was comparable to that of wild-type mice. These results extend the role of Fn14 in wound repair and muscle development to involvement in the etiology of cachexia and indicate that Fn14 antibodies may be a promising approach to treat cachexia,thereby extending lifespan and improving quality of life for cancer patients. View Publication

Aberrant expression and/or activity of members of the Src family of nonreceptor protein tyrosine kinases (SFK) are commonly observed in progressive stages of human tumors. In prostate cancer,two SFKs (Src and Lyn) have been specifically implicated in tumor growth and progression. However,there are no data in preclinical models demonstrating potential efficacy of Src inhibitors against prostate cancer growth and/or metastasis. In this study,we used the small molecule SFK/Abl kinase inhibitor dasatinib,currently in clinical trials for solid tumors,to examine in vitro and in vivo effects of inhibiting SFKs in prostate tumor cells. In vitro,dasatinib inhibits both Src and Lyn activity,resulting in decreased cellular proliferation,migration,and invasion. In orthotopic nude mouse models,dasatinib treatment effectively inhibits expression of activated SFKs,resulting in inhibition of both tumor growth and development of lymph node metastases in both androgen-sensitive and androgen-resistant tumors. In primary tumors,SFK inhibition leads to decreased cellular proliferation (determined by immunohistochemistry for proliferating cell nuclear antigen). In vitro,small interfering RNA (siRNA)-mediated inhibition of Lyn affects cellular proliferation; siRNA inhibition of Src affects primarily cellular migration. Therefore,we conclude that SFKs are promising therapeutic targets for treatment of human prostate cancer and that Src and Lyn activities affect different cellular functions required for prostate tumor growth and progression. View Publication