t-0070907 and Breast-Neoplasms

Overexpression of the adverse prognostic marker ERBB2 occurs in 30% of breast cancers and is associated with aggressive disease and poor outcomes. Our recent findings have shown that NR1D1 and the peroxisome proliferator-activated receptor-γ (PPARγ)-binding protein (PBP) act through a common pathway in upregulating several genes in the de novo fatty acid synthesis network, which is highly active in ERBB2-positive breast cancer cells. NR1D1 and PBP are functionally related to PPARγ, a well-established positive regulator of adipogenesis and lipid storage. Here, we report that inhibition of the PPARγ pathway reduces the aldehyde dehydrogenase (ALDH)-positive population in ERBB2-positive breast cancer cells. Results from in vitro tumorsphere formation assays demonstrate that the PPARγ antagonists GW9662 and T0070907 decrease tumorsphere formation in ERBB2-positive cells, but not other breast cells. We show that the mechanism by which GW9662 treatment causes a reduction in ALDH-positive population cells is partially due to ROS, as it can be rescued by treatment with N-acetyl-cysteine. Furthermore, global gene expression analyses show that GW9662 treatment suppresses the expression of several lipogenic genes, including ACLY, MIG12, FASN and NR1D1, and the stem-cell related genes KLF4 and ALDH in BT474 cells. Antagonist treatment also decreases the level of acetylation in histone 3 and histone 4 in BT474 cells, compared with MCF7 cells. In vivo, GW9662 pre-treatment inhibits the tumor-seeding ability of BT474 cells. Together, these results show that the PPARγ pathway is critical for the cancer stem cell properties of ERBB2-positive breast cancer cells.

Topics: Acetylcysteine; Aldehyde Dehydrogenase; Anilides; Animals; Benzamides; Breast Neoplasms; Cell Line, Tumor; Female; Humans; Kruppel-Like Factor 4; MCF-7 Cells; Mediator Complex Subunit 1; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Transplantation; Neoplastic Stem Cells; Nuclear Receptor Subfamily 1, Group D, Member 1; PPAR gamma; Pyridines; Reactive Oxygen Species; Receptor, ErbB-2

Peroxisome proliferator-activated receptor gamma (PPARγ) is overexpressed in many types of cancer, including breast cancer, and it is regulated by ligand binding and post-translational modifications. It was previously demonstrated that endogenous transactivation promotes an aggressive phenotype of malignant breast cells. This study examines whether selective antagonism of PPARγ with T0070907 is a potential strategy for breast cancer therapy.. PPARγ activation was inhibited using both pharmacological and molecular approaches and proliferation, apoptosis, migration and invasion were measured in MDA-MB-231 and MCF-7 breast cancer cells.. T0070907 treatment inhibited proliferation, invasion and migration but did not significantly affect apoptosis. Molecular inhibition using a dominant negative (Δ462) receptor yielded similar results. T007 also mediated a dose-dependent decrease in phosphorylation of PPARγ, and its ability to bind to DNA, and may directly affect mitogen-activated protein kinase signaling.. These data indicate that inhibiting endogenous PPARγ signaling may be a promising new approach to breast cancer therapy.

Topics: Apoptosis; Benzamides; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; DNA, Neoplasm; Female; Focal Adhesion Protein-Tyrosine Kinases; Gene Expression Regulation, Neoplastic; Genes, Dominant; Humans; Mitogen-Activated Protein Kinases; Mutation; Neoplasm Invasiveness; Phenotype; Phosphorylation; PPAR gamma; Protein Binding; Pyridines; Response Elements; Signal Transduction; Transcription, Genetic