ABSTRACT
Oncogenic mutations in the serine/threonine kinase B-RAF (also known as BRAF) are found in 50-70% of malignant melanomas. Pre-clinical studies have demonstrated that the B-RAF(V600E) mutation predicts a dependency on the mitogen-activated protein kinase (MAPK) signalling cascade in melanoma-an observation that has been validated by the success of RAF and MEK inhibitors in clinical trials. However, clinical responses to targeted anticancer therapeutics are frequently confounded by de novo or acquired resistance. Identification of resistance mechanisms in a manner that elucidates alternative 'druggable' targets may inform effective long-term treatment strategies. Here we expressed â¼600 kinase and kinase-related open reading frames (ORFs) in parallel to interrogate resistance to a selective RAF kinase inhibitor. We identified MAP3K8 (the gene encoding COT/Tpl2) as a MAPK pathway agonist that drives resistance to RAF inhibition in B-RAF(V600E) cell lines. COT activates ERK primarily through MEK-dependent mechanisms that do not require RAF signalling. Moreover, COT expression is associated with de novo resistance in B-RAF(V600E) cultured cell lines and acquired resistance in melanoma cells and tissue obtained from relapsing patients following treatment with MEK or RAF inhibitors. We further identify combinatorial MAPK pathway inhibition or targeting of COT kinase activity as possible therapeutic strategies for reducing MAPK pathway activation in this setting. Together, these results provide new insights into resistance mechanisms involving the MAPK pathway and articulate an integrative approach through which high-throughput functional screens may inform the development of novel therapeutic strategies.
Subject(s)
Drug Resistance, Neoplasm , MAP Kinase Kinase Kinases/metabolism , MAP Kinase Signaling System , Mitogen-Activated Protein Kinases/metabolism , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Proto-Oncogene Proteins/metabolism , Allosteric Regulation , Cell Line, Tumor , Clinical Trials as Topic , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Enzyme Activation/drug effects , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Gene Library , Humans , Indoles/pharmacology , Indoles/therapeutic use , MAP Kinase Kinase Kinases/genetics , Melanoma/drug therapy , Melanoma/enzymology , Melanoma/genetics , Melanoma/metabolism , Mitogen-Activated Protein Kinase Kinases/antagonists & inhibitors , Mitogen-Activated Protein Kinase Kinases/metabolism , Open Reading Frames/genetics , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins B-raf/chemistry , Proto-Oncogene Proteins B-raf/genetics , Proto-Oncogene Proteins B-raf/metabolism , Proto-Oncogene Proteins c-raf/genetics , Proto-Oncogene Proteins c-raf/metabolism , Sulfonamides/pharmacology , Sulfonamides/therapeutic use , VemurafenibABSTRACT
The human gastrointestinal tract is populated by a vast and diverse community of microbes. This gut microbiota participates in host metabolism, protects from invading microbes, and facilitates immune system development and function. In this review, we consider the contributions of intestinal microbes to the pathogenesis of infectious diseases. Key concepts of colonization resistance, host-commensal microbe interaction in immunity, antibiotics and gut bacterial communities, viral-gut bacterial interactions, and evolving methods for studying commensal microbes are explored.
ABSTRACT
BACKGROUND: Aberrant beta-catenin signaling plays a key role in several cancer types, notably colon, liver and breast cancer. However approaches to modulate beta-catenin activity for therapeutic purposes have proven elusive to date. METHODOLOGY: To uncover genetic dependencies in breast cancer cells that harbor active beta-catenin signaling, we performed RNAi-based loss-of-function screens in breast cancer cell lines in which we had characterized beta-catenin activity. Here we identify CSNK1E, the gene encoding casein kinase 1 epsilon (CK1epsilon) as required specifically for the proliferation of breast cancer cells with activated beta-catenin and confirm its role as a positive regulator of beta-catenin-driven transcription. Furthermore, we demonstrate that breast cancer cells that harbor activated beta-catenin activity exhibit enhanced sensitivity to pharmacological blockade of Wnt/beta-catenin signaling. We also find that expression of CK1epsilon is able to promote oncogenic transformation of human cells in a beta-catenin-dependent manner. CONCLUSIONS/SIGNIFICANCE: These studies identify CK1epsilon as a critical contributor to activated beta-catenin signaling in cancer and suggest it may provide a potential therapeutic target for cancers that harbor active beta-catenin. More generally, these observations delineate an approach that can be used to identify druggable synthetic lethal interactions with signaling pathways that are frequently activated in cancer but are difficult to target with the currently available small molecule inhibitors.
Subject(s)
Casein Kinase 1 epsilon/metabolism , Signal Transduction , beta Catenin/metabolism , Animals , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Casein Kinase 1 epsilon/antagonists & inhibitors , Casein Kinase 1 epsilon/genetics , Cell Line , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Transformation, Neoplastic/drug effects , Dose-Response Relationship, Drug , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Humans , Immunoblotting , Indoles/pharmacology , Mice , NIH 3T3 Cells , Oligonucleotide Array Sequence Analysis , Phloroglucinol/analogs & derivatives , Phloroglucinol/pharmacology , RNA Interference , beta Catenin/geneticsABSTRACT
Lineage-survival oncogenes are activated by somatic DNA alterations in cancers arising from the cell lineages in which these genes play a role in normal development. Here we show that a peak of genomic amplification on chromosome 3q26.33 found in squamous cell carcinomas (SCCs) of the lung and esophagus contains the transcription factor gene SOX2, which is mutated in hereditary human esophageal malformations, is necessary for normal esophageal squamous development, promotes differentiation and proliferation of basal tracheal cells and cooperates in induction of pluripotent stem cells. SOX2 expression is required for proliferation and anchorage-independent growth of lung and esophageal cell lines, as shown by RNA interference experiments. Furthermore, ectopic expression of SOX2 here cooperated with FOXE1 or FGFR2 to transform immortalized tracheobronchial epithelial cells. SOX2-driven tumors show expression of markers of both squamous differentiation and pluripotency. These characteristics identify SOX2 as a lineage-survival oncogene in lung and esophageal SCC.