n-(n-(3-5-difluorophenacetyl)alanyl)phenylglycine-tert-butyl-ester and Carcinoma

The cancer stem cell (CSC) is responsible for the initiation, proliferation and radiation resistance. Side population (SP) cells are a rare subset of cells enriched with CSCs. The targeting of key signaling pathways that are active in CSCs is a therapeutic approach to treating cancer. Notch signaling is important for the self-renewal and maintenance of stem cells. Our previous studies demonstrated that downregulation of Notch signaling could enhance radiosensitivity of nasopharyngeal carcinoma (NPC) cells. In this study, we found that Notch signaling was highly activated in SP cells compared with that of non-SP (NSP) cells of NPC. Therefore, Notch inhibition could reduce the proportion of SP cells. As SP cells decreased, proliferation, anti-apoptosis and tumorigenesis were also decreased. This study shows that Notch inhibition may be a promising clinical approach in CSC-targeting therapy for NPC.

Topics: Animals; Carcinoma; Cell Growth Processes; Cell Line, Tumor; Dipeptides; Female; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Neoplastic Stem Cells; Receptors, Notch; Side-Population Cells; Signal Transduction

Currently, the main approach to nasopharyngeal carcinoma (NPC) treatment is radiotherapy (RT), but for many NPC patients, RT is not effective. Increasing RT sensitivity of NPC cells would provide a significant treatment advance for NPC patients. While γ-secretase inhibitors (GSIs) have gained recent attention as novel anticancer drugs, the mechanism of action of GSIs as radiosensitizers is not well understood. In the present study, radiation-induced anti-proliferative effects of the one GSI (N-[(3,5-difluorophenyl)acetyl]-L-alanyl-2-phenyl]glycine-1,1-dimethylethyl ester, DAPT), on CNE2 cells were investigated with the MTT assay; in vitro radiosensitization effects were evaluated by the apoptosis assay and the cell colony formation assay. The activation status of the Notch signaling pathway in DAPT- or dimethyl sulfoxide-treated CNE2 cells was also examined. Notch signaling in NPC cells was found to be down-regulated by DAPT; therefore, DAPT could significantly inhibit CNE2 growth and improve NPC radiosensitization, thus, enhancing RT-induced anti-proliferative effects and apoptosis. Taken together, our data show that Notch signaling down-regulation by GSIs could enhance radiosensitivity of NPC cells, suggesting clinical applications for GSIs as radiosensitizers for NPC therapy.

Topics: Amyloid Precursor Protein Secretases; Carcinoma; Cell Line, Tumor; Combined Modality Therapy; Dipeptides; Down-Regulation; Humans; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Radiation Tolerance; Receptors, Notch; Signal Transduction

The development of effective drug delivery systems capable of transporting small interfering RNA (siRNA) has been elusive. We have previously reported that colorectal cancer tumor xenograft growth was arrested following treatment with liposomal preparation of siDCAMKL-1. In this report, we have utilized Nanoparticle (NP) technology to deliver DCAMKL-1 specific siRNA to knockdown potential key cancer regulators. In this study, mRNA/miRNA were analyzed using real-time RT-PCR and protein by western blot/immunohistochemistry. siDCAMKL-1 was encapsulated in Poly(lactide-co-glycolide)-based NPs (NP-siDCAMKL-1); Tumor xenografts were generated in nude mice, treated with NP-siDCAMKL-1 and DAPT (γ-secretase inhibitor) alone and in combination. To measure let-7a and miR-144 expression in vitro, HCT116 cells were transfected with plasmids encoding the firefly luciferase gene with let-7a and miR-144 miRNA binding sites in the 3'UTR.. Administration of NP-siDCAMKL-1 into HCT116 xenografts resulted in tumor growth arrest, downregulation of proto-oncogene c-Myc and Notch-1 via let-7a and miR-144 miRNA-dependent mechanisms, respectively. A corresponding reduction in let-7a and miR-144 specific luciferase activity was observed in vitro. Moreover, an upregulation of EMT inhibitor miR-200a and downregulation of the EMT-associated transcription factors ZEB1, ZEB2, Snail and Slug were observed in vivo. Lastly, DAPT-mediated inhibition of Notch-1 resulted in HCT116 tumor growth arrest and down regulation of Notch-1 via a miR-144 dependent mechanism.. These findings demonstrate that nanoparticle-based delivery of siRNAs directed at critical targets such as DCAMKL-1 may provide a novel approach to treat cancer through the regulation of endogenous miRNAs.

Topics: Animals; Carcinoma; Colorectal Neoplasms; Dipeptides; Doublecortin-Like Kinases; Down-Regulation; Gene Expression Regulation, Neoplastic; HCT116 Cells; Humans; Intracellular Signaling Peptides and Proteins; Mice; Mice, Nude; MicroRNAs; Nanoparticles; Protein Serine-Threonine Kinases; Proto-Oncogene Mas; Proto-Oncogene Proteins c-myc; Receptor, Notch1; Transcription Factors; Up-Regulation; Xenograft Model Antitumor Assays

To investigate the effect of DAPT (gamma-secretase inhibitor) on the growth of human tongue carcinoma cells and to determine the molecular mechanism to enable the potential application of DAPT to the treatment of tongue carcinoma.. Human tongue carcinoma Tca8113 cells were cultured with DAPT. Cell growth was determined using Indigotic Reduction method. The cell cycle and apoptosis were analyzed by flow cytometry. Real-time PCR and Immuno-Fluorescence (IF) were employed to determine the intracellular expression levels.. DAPT inhibited the growth of human tongue carcinoma Tca8113 cells by inducing G0-G1 cell cycle arrest and apoptosis. The mRNA levels of Hairy/Enhancer of Split-1 (Hes-1), a target of Notch activation, were reduced by DAPT in a dose-dependent manner. Coincident with this observation, DAPT induced a dose-dependent promotion of constitutive Caspase-3 in Tca8113 cells.. DAPT may have a therapeutic value for human tongue carcinoma. Moreover, the effects of DAPT in tumor inhibition may arise partly via the modulation of Notch-1 and Caspase-3.

Topics: Amyloid Precursor Protein Secretases; Antineoplastic Agents; Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Carcinoma; Caspase 3; Cell Line, Tumor; Cell Membrane; Cell Nucleus; Cyclin D1; Dipeptides; Dose-Response Relationship, Drug; G1 Phase; Homeodomain Proteins; Humans; Receptor, Notch1; Repressor Proteins; Resting Phase, Cell Cycle; Tongue Neoplasms; Transcription Factor HES-1