Pre-clinical studies of Notch signaling inhibitor RO4929097 in inflammatory breast cancer cells

• Published in: Breast cancer research and treatment Vol. 134; no. 2; pp. 495 - 510
• Main Authors: Debeb, Bisrat G., Cohen, Evan N., Boley, Kimberly, Freiter, Erik M., Li, Li, Robertson, Fredika M., Reuben, James M., Cristofanilli, Massimo, Buchholz, Thomas A., Woodward, Wendy A.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.07.2012; Springer; Springer Nature B.V
• Subjects: Aldehyde Dehydrogenase - metabolism; Amyloid Precursor Protein Secretases - antagonists & inhibitors; Antigens, CD - metabolism; Antineoplastic Agents - pharmacology; Benzazepines - pharmacology; Biological and medical sciences; Breast cancer; Cancer; Cancer research; Cancer therapies; Cell Line, Tumor - drug effects; Cell Line, Tumor - radiation effects; Cell Movement; Cell Proliferation - drug effects; Cell Proliferation - radiation effects; Cell Survival - drug effects; Clinical trials; Drug Screening Assays, Antitumor; Female; Gene Expression - drug effects; Gynecology. Andrology. Obstetrics; Humans; Inflammation Mediators - metabolism; Inflammatory Breast Neoplasms - drug therapy; Inhibitor drugs; Interleukin-6 - metabolism; Interleukin-6 - secretion; Interleukin-8 - metabolism; Interleukin-8 - secretion; Leukocytes, Mononuclear - drug effects; Lymphocyte Activation - drug effects; Mammary gland diseases; Medical sciences; Medicine; Medicine & Public Health; Neoplastic Stem Cells - drug effects; Neoplastic Stem Cells - radiation effects; Nuclear radiation; Oncology; Oncology, Experimental; Preclinical Study; Radiation; Radiation-Sensitizing Agents - pharmacology; Receptors, Antigen, T-Cell - metabolism; Receptors, Notch - antagonists & inhibitors; Receptors, Notch - metabolism; Signal Transduction - drug effects; Spheroids, Cellular; Stem cells; T cells; Tumors; Inflammatory breast cancer; R04929097; Cancer stem cells; Notch; Radiation; Notch receptor; Breast disease; Stem cell; Preclinical trial; Breast cancer; Inflammation; Malignant tumor; Cell signaling; Mammary gland diseases; Signal transduction; Inhibitor; Inflammatory cell; Tumor cell; Cancer
• ISSN: 0167-6806; 1573-7217
• DOI: 10.1007/s10549-012-2075-8

Basal breast cancer, common among patients presenting with inflammatory breast cancer (IBC), has been shown to be resistant to radiation and enriched in cancer stem cells. The Notch pathway plays an important role in self-renewal of breast cancer stem cells and contributes to inflammatory signaling which promotes the breast cancer stem cell phenotype. Herein, we inhibited Notch signaling using a gamma secretase inhibitor, RO4929097, in an in vitro model that enriches for cancer initiating cells (3D clonogenic assay) and conventional 2D clonogenic assay to compare the effect on radiosensitization of the SUM149 and SUM190 IBC cell lines. RO4929097 downregulated the Notch target genes Hes1, Hey1, and HeyL , and showed a significant reduction in anchorage independent growth in SUM190 and SUM149. However, the putative self-renewal assay mammosphere formation efficiency was increased with the drug. To assess radiosensitization of putative cancer stem cells, cells were exposed to increasing doses of radiation with or without 1 μM RO4929097 in their standard (2D) and self-renewal enriching (3D) culture conditions. In the conventional 2D clonogenic assay, RO4929097 significantly sensitized SUM190 cells to ionizing radiation and has a modest radiosensitization effect in SUM149 cells. In the 3D clonogenic assays, however, a radioprotective effect was seen in both SUM149 and SUM190 cells at higher doses. Both cell lines express IL-6 and IL-8 cytokines known to mediate the efficacy of Notch inhibition and to promote self-renewal of stem cells. We further showed that RO429097 inhibits normal T-cell synthesis of some inflammatory cytokines, including TNF-α, a potential mediator of IL-6 and IL-8 production in the microenvironment. These data suggest that additional targeting agents may be required to selectively target IBC stem cells through Notch inhibition, and that evaluation of microenvironmental influences may shed further light on the potential effects of this inhibitor.