Imlunestrant Is an Oral, Brain-Penetrant Selective Estrogen Receptor Degrader with Potent Antitumor Activity in ESR1 Wild-Type and Mutant Breast Cancer.

Targeting of the estrogen receptor (ER) by antiestrogens is the standard of care for patients with ER+ HER2- advanced/metastatic breast cancer. Although antiestrogens that degrade ERα (fulvestrant) or block estrogen production (aromatase inhibitors) have improved patient outcomes, clinically important challenges remain related to drug administration, limited bioavailability, lack of brain exposure, and acquired resistance due to ESR1 mutations. These limitations indicate a need for more robust ER-targeted therapies.

Target actionability review to evaluate CDK4/6 as a therapeutic target in paediatric solid and brain tumours.

Background: Childhood cancer is still a leading cause of death around the world. To improve outcomes, there is an urgent need for tailored treatment. The systematic evaluation of existing preclinical data can provide an overview of what is known and identify gaps in the current knowledge.

Anti-VEGFR2 therapy delays growth of preclinical pediatric tumor models and enhances anti-tumor activity of chemotherapy.

Vascular endothelial growth factor receptor 2 (VEGFR2) is an attractive therapeutic target in solid malignancies due to its central role in tumor angiogenesis. Ramucirumab (Cyramza, LY3009806) is a human monoclonal antibody specific for VEGFR2 approved for several adult indications and currently in a phase 1 clinical trial for pediatric patients with solid tumors (NCT02564198). Here, we evaluated ramucirumab and the anti-murine VEGFR2 antibody DC101 with or without chemotherapy across a range of pediatric cancer models.

Aurora A-Selective Inhibitor LY3295668 Leads to Dominant Mitotic Arrest, Apoptosis in Cancer Cells, and Shows Potent Preclinical Antitumor Efficacy.

Although Aurora A, B, and C kinases share high sequence similarity, especially within the kinase domain, they function distinctly in cell-cycle progression. Aurora A depletion primarily leads to mitotic spindle formation defects and consequently prometaphase arrest, whereas Aurora B/C inactivation primarily induces polyploidy from cytokinesis failure. Aurora B/C inactivation phenotypes are also epistatic to those of Aurora A, such that the concomitant inactivation of Aurora A and B, or all Aurora isoforms by nonisoform-selective Aurora inhibitors, demonstrates the Aurora B/C-dominant cytokinesis failure and polyploidy phenotypes.

Broad Spectrum Activity of the Checkpoint Kinase 1 Inhibitor Prexasertib as a Single Agent or Chemopotentiator Across a Range of Preclinical Pediatric Tumor Models.

Purpose: Checkpoint kinase 1 (CHK1) inhibitors potentiate the DNA-damaging effects of cytotoxic therapies and/or promote elevated levels of replication stress, leading to tumor cell death. Prexasertib (LY2606368) is a CHK1 small-molecule inhibitor under clinical evaluation in multiple adult and pediatric cancers. In this study, prexasertib was tested in a large panel of preclinical models of pediatric solid malignancies alone or in combination with chemotherapy.

Aurora A Kinase Inhibition Is Synthetic Lethal with Loss of the Tumor Suppressor Gene.

Loss-of-function mutations in the retinoblastoma gene are common in several treatment-refractory cancers such as small-cell lung cancer and triple-negative breast cancer. To identify drugs synthetic lethal with mutation ( ), we tested 36 cell-cycle inhibitors using a cancer cell panel profiling approach optimized to discern cytotoxic from cytostatic effects. Inhibitors of the Aurora kinases AURKA and AURKB showed the strongest association in this assay.

Abemaciclib Is Active in Preclinical Models of Ewing Sarcoma via Multipronged Regulation of Cell Cycle, DNA Methylation, and Interferon Pathway Signaling.

Purpose: Ewing sarcoma (ES) is a rare and highly malignant cancer that occurs in the bone and surrounding tissue of children and adolescents. The fusion transcription factor that drives ES pathobiology was previously demonstrated to modulate cyclin D1 expression. In this study, we evaluated abemaciclib, a small-molecule CDK4 and CDK6 (CDK4 and 6) inhibitor currently under clinical investigation in pediatric solid tumors, in preclinical models of ES.

Genomic Aberrations that Activate D-type Cyclins Are Associated with Enhanced Sensitivity to the CDK4 and CDK6 Inhibitor Abemaciclib.

Most cancers preserve functional retinoblastoma (Rb) and may, therefore, respond to inhibition of D-cyclin-dependent Rb kinases, CDK4 and CDK6. To date, CDK4/6 inhibitors have shown promising clinical activity in breast cancer and lymphomas, but it is not clear which additional Rb-positive cancers might benefit from these agents. No systematic survey to compare relative sensitivities across tumor types and define molecular determinants of response has been described.

The Checkpoint Kinase 1 Inhibitor Prexasertib Induces Regression of Preclinical Models of Human Neuroblastoma.

Checkpoint kinase 1 (CHK1) is a key regulator of the DNA damage response and a mediator of replication stress through modulation of replication fork licensing and activation of S and G-M cell-cycle checkpoints. We evaluated prexasertib (LY2606368), a small-molecule CHK1 inhibitor currently in clinical testing, in multiple preclinical models of pediatric cancer. Following an initial assessment of prexasertib activity, this study focused on the preclinical models of neuroblastoma.

LY3009120, a panRAF inhibitor, has significant anti-tumor activity in BRAF and KRAS mutant preclinical models of colorectal cancer.

Activating mutations in the KRAS and BRAF genes, leading to hyperactivation of the RAS/RAF/MAPK oncogenic signaling cascade, are common in patients with colorectal cancer (CRC). While selective BRAF inhibitors are efficacious in BRAFmut melanoma, they have limited efficacy in BRAFmut CRC patients. In a RASmut background, selective BRAF inhibitors are contraindicated due to paradoxical activation of the MAPK pathway through potentiation of CRAF kinase activity.

Inhibition of CXCR4 by LY2624587, a Fully Humanized Anti-CXCR4 Antibody Induces Apoptosis of Hematologic Malignancies.

SDF-1 and CXCR4 are a chemokine and chemokine receptor pair playing critical roles in tumorigenesis. Overexpression of CXCR4 is a hallmark of many hematological malignancies including acute myeloid leukemia, chronic lymphocytic leukemia and non-Hodgkin's lymphoma, and generally correlates with a poor prognosis. In this study, we developed a humanized anti-CXCR4 monoclonal antibody, LY2624587 as a potent CXCR4 antagonist that was advanced into clinical study for cancer.

Discovery and characterization of LY2784544, a small-molecule tyrosine kinase inhibitor of JAK2V617F.

Owing to the prevalence of the JAK2V617F mutation in myeloproliferative neoplasms (MPNs), its constitutive activity, and ability to recapitulate the MPN phenotype in mouse models, JAK2V617F kinase is an attractive therapeutic target. We report the discovery and initial characterization of the orally bioavailable imidazopyridazine, LY2784544, a potent, selective and ATP-competitive inhibitor of janus kinase 2 (JAK2) tyrosine kinase. LY2784544 was discovered and characterized using a JAK2-inhibition screening assay in tandem with biochemical and cell-based assays.

A BMP7 variant inhibits the tumorigenic potential of glioblastoma stem-like cells.

Glioblastoma multiforme (GBM) is among the most aggressive tumor types and is essentially an incurable malignancy characterized by resistance to chemo-, radio-, and immunotherapy. GBM is maintained by a hierarchical cell organization that includes stem-like, precursor, and differentiated cells. Recurrence and maintenance of the tumor is attributed to a small population of undifferentiated tumor-initiating cells, defined as glioblastoma stem-like cells (GSLCs).

Knockdown of ubiquitin ligases in glioblastoma cancer stem cells leads to cell death and differentiation.

The cancer stem cell (CSC) hypothesis proposes that a subpopulation of CSCs is frequently responsible for chemotherapy resistance and metastasis and is now a point of attack for research into the next generation of therapeutics. Although many of these agents are directed at inducing CSC apoptosis (as well as the bulk tumor), some agents may also decrease cell "stemness" possibly through induction of differentiation. Ubiquitin ligases, critical to virtually all cellular signaling systems, alter the degradation or trafficking of most proteins in the cell, and indeed broad perturbation of this system, through inhibition of the proteosome, is a successful cancer treatment.

Tasisulam sodium, an antitumor agent that inhibits mitotic progression and induces vascular normalization.

LY573636-sodium (tasisulam) is a small molecule antitumor agent with a novel mechanism of action currently being investigated in a variety of human cancers. In vitro, tasisulam induced apoptosis via the intrinsic pathway, resulting in cytochrome c release and caspase-dependent cell death. Using high content cellular imaging and subpopulation analysis of a wide range of in vitro and in vivo cancer models, tasisulam increased the proportion of cells with 4N DNA content and phospho-histone H3 expression, leading to G(2)-M accumulation and subsequent apoptosis.

Therapeutic inhibition of MAP kinase interacting kinase blocks eukaryotic initiation factor 4E phosphorylation and suppresses outgrowth of experimental lung metastases.

Activation of the translation initiation factor 4E (eIF4E) promotes malignant transformation and metastasis. Signaling through the AKT-mTOR pathway activates eIF4E by phosphorylating the inhibitory 4E binding proteins (4E-BP). This liberates eIF4E and allows binding to eIF4G.

A robust high-content imaging approach for probing the mechanism of action and phenotypic outcomes of cell-cycle modulators.

High-content screening is increasingly used to elucidate changes in cellular biology arising from treatment with small molecules and biological probes. We describe a cell classifier for automated analysis of multiparametric data from immunofluorescence microscopy and characterize the phenotypes of 41 cell-cycle modulators, including several protein kinase inhibitors in preclinical and clinical development. This method produces a consistent assessment of treatment-induced phenotypes across experiments done by different biologists and highlights the prevalence of nonuniform and concentration-dependent cellular response to treatment.

Knockdown of cancer testis antigens modulates neural stem cell marker expression in glioblastoma tumor stem cells.

The cancer stem cell hypothesis posits that a subpopulation of cancer stem cells is frequently responsible for a tumor's progression and resistance to treatment. The differential cellular morphology and gene expression between cancer stem cells and the majority of the tumor is becoming a point of attack for research into the next generation of therapeutic agents that may work through an induction of differentiation rather than apoptosis. Advances in the field of high-content imaging (HCI), combined with modern shRNA technology and subpopulation analysis tools, have created an ideal screening system to detect these morphological changes in a subset of cells upon gene knockdown.

Phenotypic fingerprinting of small molecule cell cycle kinase inhibitors for drug discovery.

Phenotypic drug discovery, primarily abandoned in the 1980's in favor of targeted approaches to drug development, is once again demonstrating its value when used in conjunction with new technologies. Phenotypic discovery has been brought back to the fore mainly due to recent advances in the field of high content imaging (HCI). HCI elucidates cellular responses using a combination of immunofluorescent assays and computer analysis which increase both the sensitivity and throughput of phenotypic assays.

eIF4E activation is commonly elevated in advanced human prostate cancers and significantly related to reduced patient survival.

Elevated eukaryotic translation initiation factor 4E (eIF4E) function induces malignancy in experimental models by selectively enhancing translation of key malignancy-related mRNAs (c-myc and BCL-2). eIF4E activation may reflect increased eIF4E expression or phosphorylation of its inhibitory binding proteins (4E-BP). By immunohistochemical analyses of 148 tissues from 89 prostate cancer patients, we now show that both eIF4E expression and 4E-BP1 phosphorylation (p4E-BP1) are increased significantly, particularly in advanced prostate cancer versus benign prostatic hyperplasia tissues.

High-content imaging characterization of cell cycle therapeutics through in vitro and in vivo subpopulation analysis.

Although the cycling of eukaryotic cells has long been a primary focus for cancer therapeutics, recent advances in imaging and data analysis allow even further definition of cellular events as they occur in individual cells and cellular subpopulations in response to treatment. High-content imaging (HCI) has been an effective tool to elucidate cellular responses to a variety of agents; however, these data were most frequently observed as averages of the entire captured population, unnecessarily decreasing the resolution of each assay. Here, we dissect the eukaryotic cell cycle into individual cellular subpopulations using HCI in conjunction with unsupervised K-means clustering.

Therapeutic suppression of translation initiation factor eIF4E expression reduces tumor growth without toxicity.

Expression of eukaryotic translation initiation factor 4E (eIF4E) is commonly elevated in human and experimental cancers, promoting angiogenesis and tumor growth. Elevated eIF4E levels selectively increase translation of growth factors important in malignancy (e.g.

High-content imaging analysis of the knockdown effects of validated siRNAs and antisense oligonucleotides.

High-content imaging (HCI) provides researchers with a powerful tool for understanding cellular processes. Although phenotypic analysis generated through HCI is a potent technique to determine the overall cellular effects of a given treatment, it frequently produces complex data sets requiring extensive interpretation. The authors developed statistical analyses to decrease the time spent to determine the outcome of each HCI assay and to better understand complex phenotypic changes.

A 15-ketosterol is a liver X receptor ligand that suppresses sterol-responsive element binding protein-2 activity.

Hypercholesterolemia is a major risk factor for coronary artery disease. Oxysterols are known to inhibit cholesterol biosynthesis and have been explored as potential antihypercholesterolemic agents. The ability of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one (15-ketosterol) to lower non-HDL cholesterol has been demonstrated in rodent and primate models, but the mechanisms of action remain poorly understood.