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

Colorectal cancer stem cells (Co-CSCs) are a small subpopulation of tumor cells which have been proposed to be tumor-initiating cells in colorectal cancer (CRC) and to be implicated in resistance to standard chemotherapy. Chemoresistance is a common problem in the clinic. However, the interrelation between Co-CSCs and chemoresistant cells has yet to be elucidated. The present study investigated the Co-CSC phenotype in colonospheres and chemoresistant CRC cell lines and aimed to identify targets for therapy. Colonospheres and chemoresistant CRC cells were found to be enriched with the CSC markers CD133 and CD44, and exhibited similar phenotypes. Furthermore, it was found that Notch signaling may simultaneously regulate Co-CSCs and chemoresistant cells and may represent a novel strategy for targeting this pathway in CRC.

Topics: AC133 Antigen; Amyloid Precursor Protein Secretases; Animals; Antigens, CD; Antineoplastic Agents; Cell Proliferation; Colorectal Neoplasms; Dipeptides; Drug Resistance, Neoplasm; Fluorouracil; Gene Expression Regulation, Neoplastic; Glycoproteins; HCT116 Cells; Humans; Hyaluronan Receptors; Injections, Intraperitoneal; Male; Mice; Mice, Nude; Neoplastic Stem Cells; Organoplatinum Compounds; Oxaliplatin; Peptides; Phenotype; Receptors, Notch; Signal Transduction; Spheroids, Cellular; Xenograft Model Antitumor Assays

The Wnt and Notch1 signaling pathways play major roles in intestinal development and tumorigenesis. Sub-cellular localization of β-catenin has been implicated in colorectal carcinogenesis. However, the β-catenin and Notch intracellular domain (NICD) interaction has to be addressed. Immunohistochemistries of β-catenin, NICD, and dual immunofluorescence of β-catenin and NICD were analyzed in colorectal tissues and HT29 cell line. Moreover, real-time PCR analysis of CyclinD1, Hes1 and MUC2 was done in HT29 cells upon N-[N-(3, 5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) treatment. Dual staining emphasized the strong interaction of β-catenin and NICD in adenoma and adenocarcinoma than in normal tissues. Hes1 transcript levels were decreased 1.5- and 7.1-fold in 12.5 and 25 µM DAPT-treated HT29 cells. CyclinD1 transcript levels decreased 1.2- and 1.6-fold, and MUC2 transcript level increased 4.3- and 7.5-fold in 12.5 and 25 µM DAPT-treated HT29 cells. The results of this study showed that the sub-cellular localization of β-catenin converges with NICD inducing proliferation through the activation of CyclinD1 and Hes1. Moreover, the inhibition of Notch1 signaling by DAPT leads to the arrest of cell proliferation and induces apoptosis leading to the upregulation of MUC2, a secretory cell lineage marker.

Topics: Adenocarcinoma; Adenoma; Basic Helix-Loop-Helix Transcription Factors; beta Catenin; Cell Proliferation; Colonic Neoplasms; Colorectal Neoplasms; Cyclin D1; Dipeptides; Dose-Response Relationship, Drug; Gene Expression Regulation, Neoplastic; Homeodomain Proteins; HT29 Cells; Humans; Mucin-2; Protein Structure, Tertiary; Receptor, Notch1; Reference Values; Signal Transduction; Transcription Factor HES-1

Notch1 signaling plays a key role in normal developmental processes and in cancer. The association between Notch activation and development of cancer has been well documented. Notch activation and outcome of the disease depend upon the crosstalk with other regulatory pathways including Nuclear Factor kappa B (NFκB) pathway. In this study, we have investigated the interaction of Notch intracellular domain (NICD) with NFκBp65 in colorectal cancer which resulted in the upregulation of Bcl-xL resulting in the inhibition of apoptosis. Mesenchymal marker Slug expression and down regulation of E-cadherin, an epithelial phenotypic marker were demonstrated in colon cancer tissues. The study was also illustrated by using the gamma secretase inhibitor, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) in HT29 cells. Immunohistochemistry (NICD, NFκBp65, and Slug) and double immunofluorescence analysis (NICD, NFκBp65) revealed that NICD and NFκBp65 were highly expressed in HT29 cells and in tumor tissue compared to normal tissue. Slug and Bcl-xL protein expressions were significantly reduced in DAPT treated HT 29 cells. Immunoprecipitation and dual staining emphasized the strong interaction of NICD with NFκBp65 in adenocarcinoma than in normal tissue. It appeared that Notch1 and NFκB could independently contribute to tumor progression. However, their interaction and synergism might be the determinants that would affect the outcome of the disease and therapeutic interventions.

Topics: Adenocarcinoma; bcl-X Protein; Cadherins; Colorectal Neoplasms; Dipeptides; Epithelial-Mesenchymal Transition; HT29 Cells; Humans; Protein Structure, Tertiary; Receptor, Notch1; Reference Values; Signal Transduction; Snail Family Transcription Factors; Transcription Factor RelA; Transcription Factors

Notch signaling may be mechanistically involved the colorectal carcinogenesis. Blocking of Notch signaling by gamma-secretase inhibitor may constitute a novel molecular therapy for cancer. In the present study, we blocked the Notch signaling by DAPT (N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, a gamma-secretase inhibitor) and investigated the effects on the proliferative and invasive potential of human colorectal cancer LS174T cells, a goblet cell-like colorectal cancer cell line which produces high-levels of MUC2 continuously. DAPT inhibited the proliferation and invasion of LS174T cells. Blocking of Notch signaling by DAPT could down-regulate its downstream target gene Hes1, while enhancing the expression of Math1 and MUC2 in LS174T cells. In conclusion, we demonstrated that blocking of Notch signaling by DAPT could inhibit the proliferation and invasion of human colorectal cancer LS174T cells and suggested that gamma-secretase inhibitors may provide a targeted therapy for MUC2-positive colorectal tumors.

Topics: Amyloid Precursor Protein Secretases; Antineoplastic Agents; Blotting, Western; Cell Line, Tumor; Cell Movement; Cell Proliferation; Colorectal Neoplasms; Dipeptides; Enzyme Inhibitors; Humans; Mucin-2; 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