mrk-003 and Adenocarcinoma

Uterine serous carcinoma (USC) represents an aggressive subtype of endometrial cancer. We sought to understand Notch pathway activity in USC and determine if pathway inhibition has anti-tumor activity.. Patient USC tissue blocks were obtained and used to correlate clinical outcomes with Notch1 expression. Three established USC cell lines were treated with gamma-secretase inhibitor (GSI) in vitro. Mice harboring cell line derived or patient derived USC xenografts (PDXs) were treated with vehicle, GSI, paclitaxel and carboplatin (P/C), or combination GSI and P/C. Levels of cleaved Notch1 protein and Hes1 mRNA were determined in GSI treated samples. Statistical analysis was performed using the Wilcoxon rank sum and Kaplan-Meier methods.. High nuclear Notch1 protein expression was observed in 58% of USC samples with no correlation with overall survival. GSI induced dose-dependent reductions in cell number and decreased levels of cleaved Notch1 protein and Hes1 mRNA in vitro. Treatment of mice with GSI led to decreased Hes1 mRNA expression in USC xenografts. In addition, GSI impeded tumor growth of cell line xenografts as well as UT1 USC PDXs. When GSI and P/C were combined, synergistic anti-tumor activity was observed in UT1 xenografts.. Notch1 is expressed in a large subset of USC. GSI-mediated Notch pathway inhibition led to both reduced cell numbers in vitro and decreased tumor growth of USC some xenograft models. When combined with conventional chemotherapy, GSI augmented anti-tumor activity in one USC PDX line suggesting that targeting of the Notch signaling pathway is a potential therapeutic strategy for future investigation.

Topics: Adenocarcinoma; Aged; Amyloid Precursor Protein Secretases; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Line, Tumor; Cyclic S-Oxides; Female; Homeodomain Proteins; Humans; Mice; Receptor, Notch1; RNA, Messenger; Signal Transduction; Thiadiazoles; Transcription Factor HES-1; Tumor Cells, Cultured; Uterine Neoplasms; Xenograft Model Antitumor Assays

The cancer stem cell theory postulates that tumors contain a subset of cells with stem cell properties of self-renewal, differentiation, and tumor initiation. The purpose of this study is to determine the role of Notch activity in identifying lung cancer stem cells.. We investigated the role of Notch activity in lung adenocarcinoma using a Notch GFP reporter construct and a γ-secretase inhibitor (GSI), which inhibits Notch pathway activity.. Transduction of lung cancer cells with Notch GFP reporter construct identified a subset of cells with high Notch activity (GFP-bright). GFP-bright cells had the ability to form more tumor spheres in serum-free media and were able to generate both GFP-bright and GFP-dim (lower Notch activity) cell populations. GFP-bright cells were resistant to chemotherapy and were tumorigenic in serial xenotransplantation assays. Tumor xenografts of mice treated with GSI had decreased expression of downstream effectors of Notch pathway and failed to regenerate tumors upon reimplantation in NOD/SCID mice. Using multivariate analysis, we detected a statistically significant correlation between poor clinical outcome and Notch activity (reflected in increased Notch ligand expression or decreased expression of the negative modulators), in a group of 443 patients with lung adenocarcinoma. This correlation was further confirmed in an independent group of 89 patients with adenocarcinoma in which Hes-1 overexpression correlated with poor overall survival.. Notch activity can identify lung cancer stem cell-like population and its inhibition may be an appropriate target for treating lung adenocarcinoma.

Topics: Adenocarcinoma; Animals; Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Cell Cycle; Cell Line, Tumor; Cyclic S-Oxides; Flow Cytometry; Gene Expression Regulation, Neoplastic; Green Fluorescent Proteins; Homeodomain Proteins; Humans; Immunohistochemistry; Kaplan-Meier Estimate; Lung Neoplasms; Mice; Mice, Inbred NOD; Mice, Nude; Mice, SCID; Multivariate Analysis; Neoplastic Stem Cells; Protein Isoforms; Receptors, Notch; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Thiadiazoles; Transcription Factor HES-1; Xenograft Model Antitumor Assays

The Notch signaling pathway plays a significant role in differentiation, proliferation, apoptosis, and stem cell processes. It is essential for maintenance of the normal colon crypt and has been implicated in colorectal cancer oncogenesis. Downregulation of the Notch pathway through gamma-secretase inhibitors (GSIs) has been shown to induce apoptosis and enhance response to chemotherapy in a variety of malignancies. In this study, we analyzed the effect of MRK-003 (Merck), a potent inhibitor of gamma-secretase, on oxaliplatin-induced apoptosis in colon cancer. Unexpectedly, gamma-secretase inhibition reduced oxaliplatin-induced apoptosis while GSI treatment alone was shown to have no effect on growth or apoptosis. We determined that the underlying mechanism of action involved an increase in protein levels of the anti-apoptotic Bcl-2 family members Mcl-1 and/or Bcl-xL which resulted in reduced Bax and Bak activation. Blocking of Mcl-1 and/or Bcl-xL through siRNA or the small molecule inhibitor obatoclax restored the apoptotic potential of cells treated with both oxaliplatin and MRK-003. Moreover, obatoclax synergized with MRK-003 alone to induce apoptosis. Our findings warrant caution when treating colon cancer with the combination of GSIs and chemotherapy, whereas other drug combinations, such as GSIs plus obatoclax, should be explored.

Topics: Adenocarcinoma; Amyloid Precursor Protein Secretases; Antineoplastic Agents; Apoptosis; bcl-X Protein; Cell Line, Tumor; Colonic Neoplasms; Cyclic S-Oxides; Drug Synergism; Humans; Indoles; Myeloid Cell Leukemia Sequence 1 Protein; Organoplatinum Compounds; Oxaliplatin; Pyrroles; RNA, Small Interfering; Signal Transduction; Thiadiazoles