lgk974 and Brain-Neoplasms

Wingless (Wnt) signaling is an important pathway in gliomagenesis and in the growth of stem-like glioma cells. Using immunohistochemistry to assess the translocation of β-catenin protein, we identified intranuclear staining suggesting Wnt pathway activation in 8 of 43 surgical samples (19%) from adult patients with glioblastoma and in 9 of 30 surgical samples (30%) from pediatric patients with glioblastoma. Wnt activity, evidenced by nuclear β-catenin in our cohort and high expression of its target AXIN2 (axis inhibitor protein 2) in published glioma datasets, was associated with shorter patient survival, although this was not statistically significant. We determined the effects of the porcupine inhibitor LGK974 on 3 glioblastoma cell lines with elevated AXIN2 and found that it reduced Wnt pathway activity by 50% or more, as assessed by T-cell factor luciferase reporters. Wnt inhibition led to suppression of growth, proliferation in cultures, and modest induction of cell death. LGK974 reduced NANOG messenger RNA levels and the fraction of cells expressing the stem cell marker CD133 in neurosphere cultures, induced glial differentiation, and suppressed clonogenicity. These data indicate that LGK974 is a promising new agent that can inhibit the canonical Wnt pathway in vitro, slow tumor growth, and deplete stem-like clonogenic cells, thereby providing further support for targeting Wnt in patients with glioblastoma.

Topics: Adult; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Child; Glioblastoma; Humans; Pyrazines; Pyridines; Tumor Stem Cell Assay; Wnt Signaling Pathway

The DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) is commonly overexpressed in cancers and is implicated in the development of chemoresistance. The use of drugs inhibiting MGMT has been hindered by their haematologic toxicity and inefficiency. As a different strategy to inhibit MGMT we investigated cellular regulators of MGMT expression in multiple cancers. Here we show a significant correlation between Wnt signalling and MGMT expression in cancers with different origin and confirm the findings by bioinformatic analysis and immunofluorescence. We demonstrate Wnt-dependent MGMT gene expression and cellular co-localization between active β-catenin and MGMT. Pharmacological or genetic inhibition of Wnt activity downregulates MGMT expression and restores chemosensitivity of DNA-alkylating drugs in mouse models. These findings have potential therapeutic implications for chemoresistant cancers, especially of brain tumours where the use of temozolomide is frequently used in treatment.

Topics: Animals; Antineoplastic Agents; Benzeneacetamides; beta Catenin; Brain Neoplasms; Camptothecin; Celecoxib; Cisplatin; Colorectal Neoplasms; Dacarbazine; DNA Modification Methylases; DNA Repair Enzymes; Doxorubicin; Drug Resistance, Neoplasm; Flow Cytometry; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Glioma; Glucose-6-Phosphate Isomerase; Heterocyclic Compounds, 3-Ring; Humans; Immunoblotting; Immunohistochemistry; Irinotecan; Medulloblastoma; Mice; Neoplasm Transplantation; Neoplasms; Neuroblastoma; Pyrans; Pyrazines; Pyridines; Real-Time Polymerase Chain Reaction; Sulfones; Temozolomide; Triazoles; Tumor Suppressor Proteins; Vincristine; Wnt Proteins; Wnt Signaling Pathway