Systemic miRNA-7 delivery inhibits tumor angiogenesis and growth in murine xenograft glioblastoma.

Tumor-angiogenesis is the multi-factorial process of sprouting of endothelial cells (EC) into micro-vessels to provide tumor cells with nutrients and oxygen. To explore miRNAs as therapeutic angiogenesis-inhibitors, we performed a functional screen to identify miRNAs that are able to decrease EC viability. We identified miRNA-7 (miR-7) as a potent negative regulator of angiogenesis. Introduction of miR-7 in EC resulted in strongly reduced cell viability, tube formation, sprouting and migration. Application of miR-7 in the chick chorioallantoic membrane assay led to a profound reduction of vascularization, similar to anti-angiogenic drug sunitinib. Local administration of miR-7 in an in vivo murine neuroblastoma tumor model significantly inhibited angiogenesis and tumor growth. Finally, systemic administration of miR-7 using a novel integrin-targeted biodegradable polymeric nanoparticles that targets both EC and tumor cells, strongly reduced angiogenesis and tumor proliferation in mice with human glioblastoma xenografts. Transcriptome analysis of miR-7 transfected EC in combination with in silico target prediction resulted in the identification of OGT as novel target gene of miR-7. Our study provides a comprehensive validation of miR-7 as novel anti-angiogenic therapeutic miRNA that can be systemically delivered to both EC and tumor cells and offers promise for miR-7 as novel anti-tumor therapeutic.

Correction: A Functional Screen Identifies Specific MicroRNAs Capable of Inhibiting Human Melanoma Cell Viability.

[This corrects the article DOI: 10.1371/journal.pone.0043569.].

A functional screen identifies specific microRNAs capable of inhibiting human melanoma cell viability.

Malignant melanoma is an aggressive form of skin cancer with poor prognosis. Despite improvements in awareness and prevention of this disease, its incidence is rapidly increasing. MicroRNAs (miRNAs) are a class of small RNA molecules that regulate cellular processes by repressing messenger RNAs (mRNAs) with partially complementary target sites. Several miRNAs have already been shown to attenuate cancer phenotypes, by limiting proliferation, invasiveness, tumor angiogenesis, and stemness. Here, we employed a genome-scale lentiviral human miRNA expression library to systematically survey which miRNAs are able to decrease A375 melanoma cell viability. We highlight the strongest inhibitors of melanoma cell proliferation, including the miR-15/16, miR-141/200a and miR-96/182 families of miRNAs and miR-203. Ectopic expression of these miRNAs resulted in long-term inhibition of melanoma cell expansion, both in vitro and in vivo. We show specifically miR-16, miR-497, miR-96 and miR-182 are efficient effectors when introduced as synthetic miRNAs in several melanoma cell lines. Our study provides a comprehensive interrogation of miRNAs that interfere with melanoma cell proliferation and viability, and offers a selection of miRNAs that are especially promising candidates for application in melanoma therapy.

Characterization of a large panel of patient-derived tumor xenografts representing the clinical heterogeneity of human colorectal cancer.

PURPOSE: Patient-derived xenograft models are considered to represent the heterogeneity of human cancers and advanced preclinical models. Our consortium joins efforts to extensively develop and characterize a new collection of patient-derived colorectal cancer (CRC) models. EXPERIMENTAL DESIGN: From the 85 unsupervised surgical colorectal samples collection, 54 tumors were successfully xenografted in immunodeficient mice and rats, representing 35 primary tumors, 5 peritoneal carcinoses and 14 metastases. Histologic and molecular characterization of patient tumors, first and late passages on mice includes the sequence of key genes involved in CRC (i.e., APC, KRAS, TP53), aCGH, and transcriptomic analysis. RESULTS: This comprehensive characterization shows that our collection recapitulates the clinical situation about the histopathology and molecular diversity of CRC. Moreover, patient tumors and corresponding models are clustering together allowing comparison studies between clinical and preclinical data. Hence, we conducted pharmacologic monotherapy studies with standard of care for CRC (5-fluorouracil, oxaliplatin, irinotecan, and cetuximab). Through this extensive in vivo analysis, we have shown the loss of human stroma cells after engraftment, observed a metastatic phenotype in some models, and finally compared the molecular profile with the drug sensitivity of each tumor model. Through an experimental cetuximab phase II trial, we confirmed the key role of KRAS mutation in cetuximab resistance. CONCLUSIONS: This new collection could bring benefit to evaluate novel targeted therapeutic strategies and to better understand the basis for sensitivity or resistance of tumors from individual patients.

Identification of a GαGßγ, AKT and PKCα signalome associated with invasive growth in two genetic models of human breast cancer cell epithelial-to-mesenchymal transition.

The epithelial-to-mesenchymal transition (EMT) confers an aggressive subtype associated with chemotherapy resistance in epithelial cancers. However, the mechanisms underlying the EMT and its associated signaling dysfunctions are still poorly understood. In two genetic models of MCF-7 breast cancer cells induced to EMT by WISP-2 silencing and Snail transformation, we investigated the status of several signaling elements downstream of G-protein receptors (GPR) and their functional roles in the invasive growth potential. We report that the E-cadherin repressors Slug, Zeb1/2 and Twist are overexpressed in these EMT cells characterized by a triple negative phenotype (loss of estrogen ERα and progesterone PRA/PRB receptors, no HER2 amplification), combined with loss of the alternative GPR30 estrogen receptor and induction of the invasive growth in collagen type I gels. Ectopic Snail expression suppressed WISP-2 transcripts and down-regulated WISP-2 gene promoter expression in transfected cells. Accordingly, WISP-2 transcripts and Wisp-2 protein were depleted in these two convergent models of BC cell EMT. The EMT caused dominance of several proinvasive pathways downstream of GPR, including GαGßγ subunits, PKCα, AKT and c-Jun induction, constitutive activation of the actin-remodeling GTPase Rac1, coupled with growth responses (more cells at S and G2/M phases of the cell cycle), in line with inhibition of the p27kip1/cyclin-dependent kinase CDK3 cascade. RNA interference or selective inhibitors targeting GαGßγ subunits (BIM-46187, gallein), PKCα (Gö6976, MT477, sh-RNAs) and PI3K-AKT (wortmannin) alleviated the invasive phenotype. In contrast, MCF-7 cells in EMT showed signaling independence to inhibitors of HER family tyrosine kinases and the mitogen- and stress-activated protein kinases. Our study suggests that the signaling protagonists GαGßγ, PKCα and PI3K-AKT are promising candidates as predictive molecular biomarkers and therapeutic targets in the management of clinical BC in EMT.

A model of primary culture of colorectal cancer and liver metastasis to predict chemosensitivity.

BACKGROUND: Prediction of chemosensitivity is a major goal of modern oncology. The aim of this study was to establish a simple and effective model of primary culture of colorectal cancer fragments and to test whether it allows prediction of chemosensitivity. METHODS: Colorectal cancer fragments (primary tumors or liver metastases) of 94 consecutive and previously untreated patients were obtained, prepared, and cultured in polyHEMA. For each fragment cultured, a proliferative index (PI) was calculated after immunostaining at d 0 and after 7 d in culture with media alone or supplemented for 24h with the topoisomerase I inhibitor metabolite SN-38. The correlation between in vitro response (decrease in PI after exposure to the drug) and in vivo response (RECIST criteria) was studied in a subset of patients who had measurable metastases and were treated with a topoisomerase I inhibitor. RESULTS: PolyHEMA allowed three-dimensional culture of tumor fragments up to 7 d without fibroblastic invasion and with a slight but significant decrease of PI (59% at d 0 versus 51% after 7 d in culture, P < 0.001). In vitro drug efficacy was tested in 67 fragments, the mean PI after culture with SN-38 dropped to 22% (P < 0.001). In a subset of 12 patients, there was no statistically significant correlation between in vitro and in vivo response (P = 0.13). CONCLUSION: Primary culture in polyHEMA was easy to perform successfully in 71% of cases. On this model, the antiproliferative effect of SN-38 could be measured and results correlated to clinical data.

Autocrine induction of invasive and metastatic phenotypes by the MIF-CXCR4 axis in drug-resistant human colon cancer cells.

Metastasis and drug resistance are major problems in cancer chemotherapy. The purpose of this work was to analyze the molecular mechanisms underlying the invasive potential of drug-resistant colon carcinoma cells. Cellular models included the parental HT-29 cell line and its drug-resistant derivatives selected after chronic treatment with either 5-fluorouracil, methotrexate, doxorubicin, or oxaliplatin. Drug-resistant invasive cells were compared with noninvasive cells using cDNA microarray, quantitative reverse transcription-PCR, flow cytometry, immunoblots, and ELISA. Functional and cellular signaling analyses were undertaken using pharmacologic inhibitors, function-blocking antibodies, and silencing by retrovirus-mediated RNA interference. 5-Fluorouracil- and methotrexate-resistant HT-29 cells expressing an invasive phenotype in collagen type I and a metastatic behavior in immunodeficient mice exhibited high expression of the chemokine receptor CXCR4. Macrophage migration-inhibitory factor (MIF) was identified as the critical autocrine CXCR4 ligand promoting invasion in drug-resistant colon carcinoma HT-29 cells. Silencing of CXCR4 and impairing the MIF-CXCR4 signaling pathways by ISO-1, pAb FL-115, AMD-3100, monoclonal antibody 12G5, and BIM-46187 abolished this aggressive phenotype. Induction of CXCR4 was associated with the upregulation of two genes encoding transcription factors previously shown to control CXCR4 expression (HIF-2alpha and ASCL2) and maintenance of intestinal stem cells (ASCL2). Enhanced CXCR4 expression was detected in liver metastases resected from patients with colon cancer treated by the standard FOLFOX regimen. Combination therapies targeting the CXCR4-MIF axis could potentially counteract the emergence of the invasive metastatic behavior in clonal derivatives of drug-resistant colon cancer cells.

Evidence of heterogeneity within colorectal liver metastases for allelic losses, mRNA level expression and in vitro response to chemotherapeutic agents.

A goal of oncology is to predict chemosensitivity of tumors. This approach assumes that in a patient all tumor deposits are homogeneous. We have tested the heterogeneity between several samples of the same liver metastasis (LM; intrametastatic heterogeneity) or between multiple LM (intermetastatic heterogeneity) from colorectal cancer in a single patient. In 16 untreated patients, several fragments of LM and nontumorous liver were collected. Heterogeneity to anticancer drug treatment was assessed in vitro on primary tissue cultures on poly-HEMA-coated surface with or without the topoisomerase-I inhibitor metabolite SN-38. Heterogeneity of response to SN-38 was observed in 55% of cases from one fragment to another in the same LM and in 64% of cases from one LM to another in the same patient. Allelic losses were characterized on 5q, 8p, 17p, 18q, 22q using 29 microsatellites markers. Seven patients (58%) had a perfect homogeneity for allelic losses in their LM whereas 3 (21%) had intrametastatic and 2 (18%) had intermetastatic heterogeneity. The analysis of gene expression was carried out by real time RT-PCR quantification using specific probes for TS, TOPO1, ERCC1, and CES2. Level expression of genes tested appeared heterogeneous with average variations of 57(+ or - 23)%, 52(+ or - 18)%, 53(+ or - 18)%, 56(+ or - 16)% for TS, TOPO1, ERCC1, and CES2 respectively for intermetastatic variability and 47(+ or - 26)%, 36(+ or - 14)%, 38(+ or - 19)%, and 56(+ or - 29)%, respectively for intrametastatic variability. Our results demonstrate intermetastatic and intrametastatic heterogeneity suggesting that pretherapeutic analysis of a single tumor biopsy is likely to lead to a misinterpretation of sensitivity to anticancer treatment.

3D imaging of the response to CDC25 inhibition in multicellular spheroids.

Multicellular tumor spheroids closely mimic the 3D organization of avascular microregions within tumors and thereby represent a valuable model for the evaluation of anticancer drugs. In this study, we performed a 3D analysis of the response to the CDC25 phosphatase inhibitor IRC-083864 in HCT116 spheroids. Continuous exposure to IRC-083864 strongly inhibits the growth of spheroids and is shown to correlate with a decrease in Ki-67 positive cells. The cytotoxicity induced by IRC-083864 was examined by two-photon laser microscopy imaging and 3D reconstruction. Visualization in 3D allowed us to demonstrate that IRC-083864 treatment results in the inhibition of mitosis and induces cell death specifically localized in the outer proliferative cell layers of the spheroid structure. These results emphasize the importance of 3D models and of in toto analysis for the evaluation of anticancer drugs cytotoxicity.

Inhibition of heterotrimeric G protein signaling by a small molecule acting on Galpha subunit.

The simultaneous activation of many distinct G protein-coupled receptors (GPCRs) and heterotrimeric G proteins play a major role in various pathological conditions. Pan-inhibition of GPCR signaling by small molecules thus represents a novel strategy to treat various diseases. To better understand such therapeutic approach, we have characterized the biomolecular target of BIM-46187, a small molecule pan-inhibitor of GPCR signaling. Combining bioluminescence and fluorescence resonance energy transfer techniques in living cells as well as in reconstituted receptor-G protein complexes, we observed that, by direct binding to the Galpha subunit, BIM-46187 prevents the conformational changes of the receptor-G protein complex associated with GPCR activation. Such a binding prevents the proper interaction of receptors with the G protein heterotrimer and inhibits the agonist-promoted GDP/GTP exchange. These observations bring further evidence that inhibiting G protein activation through direct binding to the Galpha subunit is feasible and should constitute a new strategy for therapeutic intervention.

Upregulation of the CDC25A phosphatase down-stream of the NPM/ALK oncogene participates to anaplastic large cell lymphoma enhanced proliferation.

Here, we demonstrate that the expression of the dual specificity phosphatase CDC25A, a key regulator of cell cycle progression, is deregulated in Ba/F3 cells expressing the oncogenic protein NPM/ALK and in human cell lines derived from NPM/ALK-positive anaplastic large cell lymphomas (ALCL). Both transcriptional and post-translational mechanisms account for the constitutive expression of the protein, and the PI3K/Akt pathway is essential for this process. Importantly, pharmacological inhibition of CDC25 dramatically inhibits the proliferation of NPM/ALK-expressing cells, while moderately affecting the proliferation of control Ba/F3 cells. RNA interference-mediated downregulation of CDC25A confirmed that NPM/ALK-expressing cells are highly dependent on this protein for their proliferation. Moreover, similar PI3K/AKt-mediated constitutive expression of CDC25A takes place down-stream of other hematological oncogenes, including BCR/ABL in Chronic Myeloid Leukemia and FLT3-ITD in Acute Myeloid Leukemia. Altogether, our data point to the functional link between hematopoietic oncogenic tyrosine kinases and the G(1) cell cycle regulator CDC25A, and we propose that this protein may be a potential therapeutic target in ALCL and other hematological malignancies.

IRC-083864, a novel bis quinone inhibitor of CDC25 phosphatases active against human cancer cells.

CDC25 phosphatases are key actors in cyclin-dependent kinases activation whose role is essential at various stages of the cell cycle. CDC25 expression is upregulated in a number of human cancers. CDC25 phosphatases are therefore thought to represent promising novel targets in cancer therapy. Here, we report the identification and the characterization of IRC-083864, an original bis-quinone moiety that is a potent and selective inhibitor of CDC25 phosphatases in the low nanomolar range. IRC-083864 inhibits cell proliferation of a number of cell lines, regardless of their resistance to other drugs. It irreversibly inhibits cell proliferation and cell cycle progression and prevents entry into mitosis. In addition, it inhibits the growth of HCT-116 tumor spheroids with induction of p21 and apoptosis. Finally, IRC-083864 reduced tumor growth in mice with established human prostatic and pancreatic tumor xenografts. This study describes a novel compound, which merits further study as a potential anticancer agent.

IRC-083927 is a new tubulin binder that inhibits growth of human tumor cells resistant to standard tubulin-binding agents.

Tubulin is a validated target for antitumor drugs. However, the effectiveness of these microtubule-interacting agents is limited by the fact that they are substrates for drug efflux pumps (P-glycoprotein) and/or by the acquisition of point mutations in tubulin residues important for drug-tubulin binding. To bypass these resistance systems, we have identified and characterized a novel synthetic imidazole derivative IRC-083927, which inhibits the tubulin polymerization by a binding to the colchicine site. IRC-083927 inhibits in vitro cell growth of human cancer cell lines in the low nanomolar range. More interesting, it remains highly active against cell lines resistant to microtubule-interacting agents (taxanes, Vinca alkaloids, or epothilones). Such resistances are due to the presence of efflux pumps (NCI-H69/LX4 resistant to navelbine and paclitaxel) and/or the presence of mutations on beta-tubulin and on alpha-tubulin and beta-tubulin (A549.EpoB40/A549.EpoB480 resistant to epothilone B or paclitaxel). IRC-083927 displayed cell cycle arrest in G(2)-M phase in tumor cells, including in the drug-resistant cells. In addition, IRC-083927 inhibited endothelial cell proliferation in vitro and vessel formation in the low nanomolar range supporting an antiangiogenic behavior. Finally, chronic oral treatment with IRC-083927 (5 mg/kg) inhibits the growth of two human tumor xenografts in nude mice (C33-A, human cervical cancer and MDA-MB-231, human hormone-independent breast cancer). Together, the antitumor effects induced by IRC-083927 on tumor models resistant to tubulin agents support further investigations to fully evaluate its potential for the treatment of advanced cancers, particularly those resistant to current clinically available drugs.

Molecular signature and therapeutic perspective of the epithelial-to-mesenchymal transitions in epithelial cancers.

The mechanisms involved in the epithelial to mesenchymal transition (EMT) are integrated in concert with master developmental and oncogenic pathways regulating in tumor growth, angiogenesis, metastasis, as well as the reprogrammation of specific gene repertoires ascribed to both epithelial and mesenchymal cells. Consequently, it is not unexpected that EMT has profound impacts on the neoplastic progression, patient survival, as well as the resistance of cancers to therapeutics (taxol, vincristine, oxaliplatin, EGF-R targeted therapy and radiotherapy), independent of the "classical" resistance mechanisms linked to genotoxic drugs. New therapeutic combinations using genotoxic agents and/or EMT signaling inhibitors are therefore expected to circumvent the chemotherapeutic resistance of cancers characterized by transient or sustained EMT signatures. Thus, targeting critical orchestrators at the convergence of several EMT pathways, such as the transcription pathways NF-kappaB, AKT/mTOR axis, MAPK, beta-catenin, PKC and the AP-1/SMAD factors provide a realistic strategy to control EMT and the progression of human epithelial cancers. Several inhibitors targeting these signaling platforms are already tested in preclinical and clinical oncology. In addition, upstream EMT signaling pathways induced by receptor and nonreceptor tyrosine kinases (e.g. EGF-R, IGF-R, VEGF-R, integrins/FAK, Src) and G-protein-coupled receptors (GPCR) constitute practical options under preclinical research, clinical trials or are currently used in the clinic for cancer treatment: e.g. small molecule inhibitors (Iressa: targeting selectively the EGF-R; CP-751,871, AMG479, NVP-AEW541, BMS-536924, PQIP, AG1024: IGF-R; AZD2171, ZD6474: VEGF-R; AZD0530, BMS-354825, SKI606: Src; BIM-46174: GPCR; rapamycin, CCI-779, RAD-001: mTOR) and humanized function blocking antibodies (Herceptin: ErbB2; Avastin: VEGF-A; Erbitux: EGF-R; Abegrin: alphavbeta3 integrins). We can assume that silencing RNA and adenovirus-based gene transfer of therapeutic miR and dominant interferring expression vectors targeting EMT pathways and signaling elements will bring additional ways for the treatment of epithelial cancers. Identification of the factors that initiate, modulate and effectuate EMT signatures and their underlying upstream oncogenic pathways should provide the basis of more efficient strategies to fight cancer progression as well as genetic and epigenetic forms of drug resistance. This goal can be accomplished using global screening of human clinical tumors by EMT-associated cDNA, proteome, miRome, and tissue arrays.

The novel inhibitor of the heterotrimeric G-protein complex, BIM-46187, elicits anti-hyperalgesic properties and synergizes with morphine.

BIM-46187 (7-[2-amino-1-oxo-3-thio-propyl]-8-cyclohexylmethyl-2-phenyl-5,6,7,8-tetrahydro-imidazo-[1,2a]-pyrazine dimer, hydrochloride) is an inhibitor of the heterotrimeric G-protein complex signalling. Since many mediators of pain act through G-protein coupled receptors, the anti-hyperalgesic effects of BIM-46187 were assessed on experimental models of pain. In addition since opioids are widely used in pain management and act through specific G-protein-coupled receptors, the effects of BIM-46187 on the analgesic properties of morphine have also been investigated. BIM-46187 elicited a dose dependent analgesic effect in the models of carrageenan-induced hyperalgesia (0.1-1 mg/kg; i.v.) and chronic constriction injury (0.3-3 mg/kg; i.v.) in rats. BIM-46187, however, up to 10 mg/kg did not modify the paw oedema induced by carrageenan excluding an anti-inflammatory effect. In addition, at these doses, the compound was not sedative as shown by the lack of effect on the motor performance in the rotarod test. The combination of BIM-46187 and morphine (ratio 1/1) resulted in an unexpected synergistic effect in the model of carrageenan-induced hyperalgesia and in the chronic constriction injury model in rats when evaluated by isobolographic analysis. This synergy allowed a reduction of at least 20 fold in the dose of each compound. Conversely, the drug combination did not increase the side effects of morphine as assessed in the rotarod test. In conclusion, BIM-46187 elicits a potent anti-hyperalgesic effect and strongly synergizes with morphine. This work highlights the role of heterotrimeric G-protein complexes in pain and supports further investigations of the use of BIM-46187 alone, or in combination with low doses of morphine, in the management of pain.

Synthesis and bioevaluation of 22-hydroxyacuminatine analogs.

A series of 22-hydroxyacuminatine analogs was prepared by using different Friedländer condensations. Several of the new compounds were tested for antiproliferative activity on cancer cell lines and for topoisomerase I inhibitory activity.

STX140 is efficacious in vitro and in vivo in taxane-resistant breast carcinoma cells.

PURPOSE: The aim of these studies was to characterize the action of STX140 in a P-glycoprotein-overexpressing tumor cell line both in vitro and in vivo. In addition, its efficacy was determined against xenografts derived from patients who failed docetaxel therapy. EXPERIMENTAL DESIGN: The effects of STX140, Taxol, and 2-methoxyestradiol (2-MeOE2) on cell proliferation, cell cycle, and apoptosis were assessed in vitro in drug-resistant cells (MCF-7(DOX)) and the parental cell line (MCF-7(WT)). Mice bearing an MCF-7(DOX) tumor on one flank and an MCF-7(WT) tumor on the other flank were used to assess the in vivo efficacy. Furthermore, the responses to STX140 of three xenografts, derived from drug-resistant patients, were assessed. RESULTS: In this study, STX140 caused cell cycle arrest, cyclin B1 induction, and subsequent apoptosis of both MCF-7(DOX) and MCF-7(WT) cells. Taxol and 2-MeOE2 were only active in the MCF-7(WT) parental cell line. Although both STX140 and Taxol inhibited the growth of xenografts derived from MCF-7(WT) cells, only STX140 inhibited the growth of tumors derived from MCF-7(DOX) cells. 2-MeOE2 was ineffective at the dose tested against both tumor types. Two out of the three newly derived docetaxel-resistant xenografts, including a metastatic triple-negative tumor, responded to STX140 but not to docetaxel treatment. CONCLUSIONS: STX140 shows excellent efficacy in both MCF-7(WT) and MCF-7(DOX) breast cancer xenograft models, in contrast to Taxol and 2-MeOE2. The clinical potential of STX140 was further highlighted by the efficacy seen in xenografts recently derived from patients who had failed on taxane therapy.

What's new on CDC25 phosphatase inhibitors.

The CDC25 phosphatases are key regulators of cell cycle progression and play a central role in the checkpoint response to DNA damage. Their inhibition may therefore represent a promising therapeutic approach in oncology, and small molecule design strategies are currently leading to the identification of various classes of CDC25 inhibitors. Most structures developed so far are quinonoid-based compounds, but also phosphate surrogates or electrophilic entities. Considering the characteristics of the highly conserved active sites of the enzymes, many mechanisms of action have been proposed for these inhibitors. Quinonoid compounds may oxidize the catalytic site cysteine, but can also be considered as Michaël acceptors capable of reacting with the activated thiolate or other electrophilic entities. Phosphate surrogates are thought to interfere with the arginine residue, leading to reversible enzyme inhibition. But some inhibitors can combine in the same molecule several of these mechanisms, thus by fitting into the active site of the enzyme through one part of the molecule and bringing the reactive moiety in close proximity to the catalytic cysteine. This review summarizes novel classes of inhibitors that show specificity for the CDC25s over other phosphatases, cause cell proliferation inhibition and cell cycle arrest in vitro but also, for several of them, inhibition of xenografted tumoral cell growth in vivo. These promising results confirm the interest of the inhibition of CDC25 phosphatases as an anticancer therapeutic strategy.

Pharmacologic inhibition of CDC25 phosphatases impairs interphase microtubule dynamics and mitotic spindle assembly.

The CDC25 cell cycle regulators are promising targets for new pharmacologic approaches in cancer therapy. Inhibitory compounds such as BN82685 have proven to be effective in specifically targeting CDC25 in cultured cells and in inhibiting tumor cell growth. Here, we report that BN82685 impairs microtubule dynamic instability and alters microtubule organization and assembly at the centrosome in interphase cells. Treatment of mitotic cells with BN82685 delays mitotic spindle assembly, chromosome capture, and metaphase plate formation. Furthermore, we show that combining low concentrations of both BN82685 and paclitaxel inhibits the proliferation of HT29 human colon cancer cells. Our results show a role for CDC25 phosphatases in regulating microtubule dynamics throughout the cell cycle and suggest that combinations of CDC25 inhibitors with microtubule-targeting agents may be of therapeutic value.