mrk-003 and Breast-Neoplasms

Breast cancer is one of the most common types of carcinoma in humans. The aim of the present study was to identify the role of Notch 1 in the proliferation and invasion of human breast cancer cells. Firstly, the levels of Notch 1 were determined by western blot analysis in breast cancer cell lines, and the results revealed that the expression levels of Notch 1 were markedly higher in MDA‑MB‑231 and MCF‑7 cells, and lower in MCF‑10A cells, compared with human mammary epithelial cells. An MTT assay was used to determine the viability of breast cancer cells. The optical density (OD)490 values were significantly decreased in Notch 1 short hairpin (sh)RNA‑transfected MCF‑7 and MDA‑MB‑231 cells, compared with the OD490 values in the negative control shRNA‑transfected cells. The MCF‑7 cells and MDA‑MB‑231 cells were also treated with increasing concentrations of MRK003, a Notch 1 inhibitor, for 24, 48 and 72 h, respectively. The inhibition rate was gradually increased in the MRK003‑treated cells in a time‑ and dose‑dependent manner. The invasive ability of the cells was determined using a Transwell migration assay. The migration ability was significantly decreased in the Notch 1‑transfected MCF‑7 cells and MDA‑MB‑231 cells. The molecular mechanism was examined, and the knockdown of Notch 1 significantly decreased the expression levels of β‑catenin, matrix metalloproteinase (MMP)‑2 and MMP‑9, and was also correlated with the downregulation of β‑catenin in the nucleus. In conclusion, Notch 1 was key in the progression of breast cancer, and knocking down the expression of Notch 1 significantly suppressed the proliferation and invasion of breast cancer cells. This provides novel clues for cancer therapy in human breast cancer.

Topics: beta Catenin; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cyclic S-Oxides; Female; Gene Expression; Gene Expression Regulation; Gene Knockdown Techniques; Humans; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; MCF-7 Cells; Receptor, Notch1; RNA Interference; RNA, Small Interfering; Signal Transduction; Thiadiazoles

We reported that Notch-1, a potent breast oncogene, is activated in response to trastuzumab and contributes to trastuzumab resistance in vitro. We sought to determine the preclinical benefit of combining a Notch inhibitor (γ-secretase inhibitor (GSI)) and trastuzumab in both trastuzumab-sensitive and trastuzumab-resistant, ErbB-2-positive, BT474 breast tumours in vivo. We also studied if the combination therapy of lapatinib plus GSI can induce tumour regression of ErbB-2-positive breast cancer.. We generated orthotopic breast tumour xenografts from trastuzumab- or lapatinib-sensitive and trastuzumab-resistant BT474 cells. We investigated the antitumour activities of two distinct GSIs, LY 411 575 and MRK-003, in vivo.. Our findings showed that combining trastuzumab plus a GSI completely prevented (MRK-003 GSI) or significantly reduced (LY 411 575 GSI) breast tumour recurrence post-trastuzumab treatment in sensitive tumours. Moreover, combining lapatinib plus MRK-003 GSI showed significant reduction of tumour growth. Furthermore, a GSI partially reversed trastuzumab resistance in resistant tumours.. Our data suggest that a combined inhibition of Notch and ErbB-2 signalling pathways could decrease recurrence rates for ErbB-2-positive breast tumours and may be beneficial in the treatment of recurrent trastuzumab-resistant disease.

Topics: Amyloid Precursor Protein Secretases; Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Breast Neoplasms; Cell Line, Tumor; Cyclic S-Oxides; Drug Resistance, Neoplasm; Female; Gene Targeting; Genes, erbB; Genes, erbB-2; Humans; Lapatinib; Mice; Mice, Nude; Neoplasm Transplantation; Quinazolines; Receptor, ErbB-2; Receptors, Notch; Recurrence; Signal Transduction; Thiadiazoles; Trastuzumab

ERBB2/neu and Notch signaling are known to be deregulated in many human cancers. However, pathway cross-talk and dependencies are not well understood. In this study, we use an ERBB2-transgenic mouse model of breast cancer (neuT) to show that Notch signaling plays a critical role in tumor maintenance. Inhibition of the Notch pathway with a gamma-secretase inhibitor (GSI) decreased both the Notch and the mammalian target of rapamycin/AKT pathways. Antitumor activity resulting from GSI treatment was associated with decreased cell proliferation as measured by Ki67 and decreased expression of glucose transporter Glut1. Positron emission tomography (PET) imaging showed that the functional consequences of decreased Glut1 translated to reduced glucose uptake and correlated with antitumor effects as measured by micro-computed tomography imaging. The decrease of Glut1 in neuT tumors was also observed in several human breast cancer cell lines following GSI treatment. We provide evidence that approximately 27% of ERBB2-positive human breast cancer specimens display high expression of HES1, phospho-S6RP, and GLUT1. Together, these results suggest that pathways downstream of Notch signaling are, at least in part, responsible for promoting tumor growth in neuT and also active in both neuT and a subset of human breast cancers. These findings suggest that GSI may provide therapeutic benefit to a subset of ERBB2-positive breast cancers and that [(18)F]FDG-PET imaging may be useful in monitoring clinical response.

Topics: Amyloid Precursor Protein Secretases; Animals; Breast Neoplasms; Cyclic S-Oxides; Down-Regulation; Female; Fluorodeoxyglucose F18; Glucose; Glucose Transporter Type 1; Humans; Intracellular Signaling Peptides and Proteins; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; Mice, Transgenic; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinases; Protein Serine-Threonine Kinases; Receptor, ErbB-2; Receptors, Notch; Signal Transduction; Thiadiazoles; TOR Serine-Threonine Kinases

Cancer stem cells (CSCs) are believed to be responsible for breast cancer formation and recurrence; therefore, therapeutic strategies targeting CSCs must be developed. One approach may be targeting signaling pathways, like Notch, that are involved in stem cell self-renewal and survival.. Breast cancer stem-like cells derived from cell lines and patient samples were examined for Notch expression and activation. The effect of Notch inhibition on sphere formation, proliferation, and colony formation was determined.. Breast cancer stem-like cells consistently expressed elevated Notch activation compared with bulk tumor cells. Blockade of Notch signaling using pharmacologic and genomic approaches prevented sphere formation, proliferation, and/or colony formation in soft agar. Interestingly, a gamma-secretase inhibitor, MRK003, induced apoptosis in these cells.. Our findings support a crucial role for Notch signaling in maintenance of breast cancer stem-like cells, and suggest Notch inhibition may have clinical benefits in targeting CSCs.

Topics: Amyloid Precursor Protein Secretases; Breast Neoplasms; Cell Line, Tumor; Cyclic S-Oxides; Female; Humans; Neoplastic Stem Cells; Receptor, ErbB-2; Receptors, Notch; Signal Transduction; Spheroids, Cellular; Thiadiazoles