n-(n-(3-5-difluorophenacetyl)alanyl)phenylglycine-tert-butyl-ester and Cell-Transformation--Neoplastic

Aldehyde dehydrogenase 1 (ALDH1) is a cancer stem-like cell (CSC) marker in human cancers; however, the specific ALDH1-regulated function and its underlying signalling pathways have not been fully demonstrated. Here, we investigated the ALDH1-regulated function and its underlying signalling and tested whether all-trans retinoic acid (ATRA) can suppress ALDH1-regulated tumour behaviour in ovarian cancer cells. By modulating ALDH1 expression using flow cytometry enrichment and exogenous overexpression or knockdown, we showed that the ALDH1 activity is positively correlated with stemness in ovarian cancer cells according to measures such as sphere formation and CSC marker expression as well as tumourigenesis in a mouse xenograft model. The findings indicate that the ALDH1 directly regulates the functions of ovarian cancer cells. We also showed that ALDH1 can regulate the expression of FoxM1 and Notch 1, which are involved in the downstream signalling of ALDH1-mediated biofunctions. Inhibition of FoxM1 by Thiostrepton and of Notch1 by DAPT downregulated the sphere formation ability of cells. ATRA reduced ALDH1 expression, suppressed tumour formation and inhibited sphere formation, cell migration and invasion in ALDH1-abundant ovarian cancer cells. We conclude that ATRA downregulates ALDH1/FoxM1/Notch1 signalling and suppresses tumour formation in ovarian cancer cells.

Topics: Aldehyde Dehydrogenase 1 Family; Animals; Antineoplastic Agents; Cell Movement; Cell Transformation, Neoplastic; Dipeptides; Down-Regulation; Female; Forkhead Box Protein M1; Forkhead Transcription Factors; Humans; Isoenzymes; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Invasiveness; Neoplasm Transplantation; Neoplastic Stem Cells; Ovarian Neoplasms; Receptor, Notch1; Retinal Dehydrogenase; RNA Interference; RNA, Small Interfering; Spheroids, Cellular; Thiostrepton; Transplantation, Heterologous; Tretinoin; Tumor Cells, Cultured

Although transplanted pluripotent stem cell-derived neurons can contribute to functional recovery in animal models of Parkinson's disease, the risk of tumor formation hinders clinical applications of this approach. Removing undifferentiated cells from the donor population is critical to reduce tumorigenesis. Moreover, immature neural progenitors in transplants can proliferate unpredictably, resulting in neural overgrowth and long-term risks of compressing the surrounding host tissue. Because Notch signaling plays a role in maintaining the multipotency and proliferative capacity of neural progenitors, we used γ-secretase inhibitors (GSIs) to dampen Notch signaling in human-induced pluripotent stem cell-derived neural progenitors before transplantation and examined the effects on the growth of proliferative grafts. We observed a marked reduction in the percentage of dividing cells and increased neuronal maturation in GSI-treated samples in vitro. Next, grafts were transplanted into the striata of nonobese diabetic/severe combined immune deficiency mice. Histological analyses performed 8 weeks after the operation showed that grafts pretreated with GSIs--N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester or compound E--were significantly smaller than control samples. Immunohistologic analyses revealed that briefly treating the donor population with GSIs not only reduced the graft volume, but also altered the composition of the graft; control grafts showed neural overgrowth with numerous PAX6+ and Ki67+ neural rosettes, whereas GSI-treated samples developed into mature neuronal grafts containing primarily Tubβ3+ cells. These results suggest that pretreating potentially proliferative progenitors with GSIs may improve the safety of cell replacement therapies using pluripotent stem cells.

Topics: Amyloid Precursor Protein Secretases; Animals; Benzodiazepinones; Cell Differentiation; Cell Line; Cell Proliferation; Cell Transformation, Neoplastic; Dipeptides; Dopaminergic Neurons; Humans; Induced Pluripotent Stem Cells; Mice; Mice, Inbred NOD; Mice, SCID; Neural Stem Cells

Ectopic Myc expression plays a key role in human tumorigenesis, and Myc dose-dependent tumorigenesis has been well established in transgenic mice, but the Myc target genes that are dependent on Myc levels have not been well characterized. In this regard, we used the human P493-6 B cells, which have a preneoplastic state dependent on the Epstein-Barr viral EBNA2 protein and a neoplastic state with ectopic inducible Myc, to identify putative ectopic Myc target genes. Among the ectopic targets, JAG2 that encodes a Notch receptor ligand Jagged2, was directly induced by Myc. Inhibition of Notch signaling through RNAi targeting JAG2 or the gamma-secretase Notch inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-(S)-phenylglycine t-butyl ester (DAPT) preferentially inhibited the neoplastic state in vitro. Furthermore, P493-6 tumorigenesis was inhibited by DAPT in vivo. Ectopic expression of JAG2 did not enhance aerobic cell proliferation, but increased proliferation of hypoxic cells in vitro and significantly increased in vivo tumorigenesis. Furthermore, the expression of Jagged2 in P493-6 tumors often overlapped with regions of hypoxia. These observations suggest that Notch signaling downstream of Myc enables cells to adapt in the tumor hypoxic microenvironment.

Topics: Animals; B-Lymphocytes; Cell Hypoxia; Cell Proliferation; Cell Transformation, Neoplastic; Dipeptides; Gene Expression Profiling; Gene Expression Regulation, Leukemic; Humans; Intercellular Signaling Peptides and Proteins; Jagged-2 Protein; Lymphoma, B-Cell; Membrane Proteins; Mice; Models, Biological; Proto-Oncogene Proteins c-myc; Receptors, Notch; RNA Interference; Transcriptional Activation