PI3Kα Translocation Mediates Nuclear PtdIns(3,4,5)P3 Effector Signaling in Colorectal Cancer.

The canonical view of PI3Kα signaling describes phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3) generation and activation of downstream effectors at the plasma membrane or at microtubule-bound endosomes. Here, we show that colorectal cancer (CRC) cell lines exhibit a diverse plasma membrane-nuclear distribution of PI3Kα, controlling corresponding levels of subcellular PtdIns(3,4,5)P3 pools. PI3Kα nuclear translocation was mediated by the importin ß-dependent nuclear import pathway. By PtdIns(3,4,5)P3 affinity capture mass spectrometry done in the presence of SDS on CRC cell lines with PI3Kα nuclear localization, we identified 867 potential nuclear PtdIns(3,4,5)P3 effector proteins. Nuclear PtdIns(3,4,5)P3 interactome proteins were characterized by noncanonical PtdIns(3,4,5)P3-binding domains and showed overrepresentation for nuclear membrane, nucleolus, and nuclear speckles. The nuclear PtdIns(3,4,5)P3 interactome was enriched for proteins related to RNA metabolism, with splicing reporter assays and SC-35 foci staining suggesting a role of epidermal growth factor-stimulated nuclear PI3Kα signaling in modulating pre-mRNA splicing. In patient tumors, nuclear p110α staining was associated with lower T stage and mucinous histology. These results indicate that PI3Kα translocation mediates nuclear PtdIns(3,4,5)P3 effector signaling in human CRC, modulating signaling responses.

Characteristics and outcomes of participants in colorectal cancer biomarker trials versus a real-world cohort.

BACKGROUND: The restrictive eligibility criteria of therapy-focused cancer clinical trials can limit the external validity of the results. The characteristics and survival outcomes of patients enrolled in stand-alone biomarker studies have yet to be explored. We examined the characteristics of patients enrolled in a series of biomarker studies in stage II and III colorectal cancer (CRC) and of the broader patient population from which the study cohorts were recruited. MATERIAL AND METHODS: We examined three distinct trial scenarios: a retrospective cohort study (RCS) where archival tissue samples were analyzed, a prospective observational study (POS) where blood samples were collected but patients received standard treatment and a randomized clinical trial (RCT) where biomarker analysis could inform clinical care. Clinical data for each study time period were extracted from a prospective registry. RESULTS: For all CRC patients (n = 4033) in this study, the median age was 70 years and 54% were ECOG 0. For patients in the RCS (n = 450), POS (n = 284) and RCT (n = 230), the median age was 72, 65 and 64 years, with 45%, 74% and 79% being ECOG 0. For the POS and RCT, 33% and 36% of all patients with the relevant disease stage were enrolled over the study recruitment period. Survival outcomes were similar for patients in the RCS and POS. RCT outcome data are not available. CONCLUSION: As for therapy-based trials, enrollment in prospective biomarker studies may be selective, despite relatively broad eligibility criteria. Characteristics and recruitment were similar for POS and RCT patients, indicating study complexity may not necessarily limit patient recruitment. For the prospective biomarker study cohorts examined, the selective recruitment did not significantly impact survival outcomes, suggesting potential for high external validity.

Imbalance of the renin-angiotensin system may contribute to inflammation and fibrosis in IBD: a novel therapeutic target?

OBJECTIVE: We evaluated the influence of the renin-angiotensin system (RAS) on intestinal inflammation and fibrosis. DESIGN: Cultured human colonic myofibroblast proliferation and collagen secretion were assessed following treatment with angiotensin (Ang) II and Ang (1-7), their receptor antagonists candesartan and A779, and the ACE inhibitor captopril. Circulating and intestinal RAS components were evaluated in patients with and without IBD. Disease outcomes in patients with IBD treated with ACE inhibitors and angiotensin receptor blockers (ARBs) were assessed in retrospective studies. RESULTS: Human colonic myofibroblast proliferation was reduced by Ang (1-7) in a dose-dependent manner (p<0.05). Ang II marginally but not significantly increased proliferation, an effect reversed by candesartan (p<0.001). Colonic myofibroblast collagen secretion was reduced by Ang (1-7) (p<0.05) and captopril (p<0.001), and was increased by Ang II (p<0.001). Patients with IBD had higher circulating renin (mean 25.4 vs 18.6 mIU/L, p=0.026) and ACE2:ACE ratio (mean 0.92 vs 0.69, p=0.015) than controls without IBD. RAS gene transcripts and peptides were identified in healthy and diseased bowels. Colonic mucosal Masson's trichrome staining correlated with Ang II (r=0.346, p=0.010) and inversely with ACE2 activity (r=-0.373, p=0.006). Patients with IBD who required surgery (1/37 vs 12/75, p=0.034) and hospitalisation (0/34 vs 8/68, p=0.049) over 2 years were less often treated with ACE inhibitors and ARBs than patients not requiring surgery or hospitalisation. CONCLUSIONS: The RAS mediates fibrosis in human cell cultures, is expressed in the intestine and perturbed in intestinal inflammation, and agents targeting this system are associated with improved disease outcomes.

Immunohistochemical evaluation of the prognostic and predictive power of epidermal growth factor receptor ligand levels in patients with metastatic colorectal cancer.

For patients with metastatic colorectal cancer (mCRC), epidermal growth factor receptor (EGFR) inhibitors are limited to patients with RAS wild-type tumours. Not all patients will benefit from treatment and better predictive biomarkers are needed. Here we investigated the prognostic and predictive impact of the EGFR ligands amphiregulin (AREG) and epiregulin (EREG). Expression levels were assessed by immunohistochemistry on 99 KRAS wild-type tumours. AREG and EREG positivity was seen in 49% and 50% of cases, respectively. No difference in expression was observed by primary tumour side. There was no significant difference in OS by AREG or EREG expression. In the subset of patients who received an EGFR inhibitor, EREG positivity was associated with longer OS (median 34.0 vs. 27.0 months, p = 0.033), driven by a difference in patients with a left-sided primary (HR 0.37, p = 0.015). Our study supports further investigation into EREG as a predictive biomarker in mCRC.

Epidermal growth factor receptor ligands: targets for optimizing treatment of metastatic colorectal cancer.

The discovery of epidermal growth factor (EGF) and its receptor (EGFR) revealed the connection between EGF-like ligands, signaling from the EGFR family members and cancer. Over the next fifty years, analysis of EGFR expression and mutation led to the use of monoclonal antibodies to target EGFR in the treatment of metastatic colorectal cancer (mCRC) and this treatment has improved outcomes for patients. The use of the RAS oncogene mutational status has helped to refine patient selection for EGFR antibody therapy, but an effective molecular predictor of likely responders is lacking. This review analyzes the potential utility of measuring the expression, levels and activation of EGF-like ligands and associated processes as prognostic or predictive markers for the identification of patient risk and more effective mCRC therapies.

Epidermal growth factor receptor: Structure-function informing the design of anticancer therapeutics.

Research on the epidermal growth factor (EGF) family and the family of receptors (EGFR) has progressed rapidly in recent times. New crystal structures of the ectodomains with different ligands, the activation of the kinase domain through oligomerisation and the use of fluorescence techniques have revealed profound conformational changes on ligand binding. The control of cell signaling from the EGFR-family is complex, with heterodimerisation, ligand affinity and signaling cross-talk influencing cellular outcomes. Analysis of tissue homeostasis indicates that the control of pro-ligand processing is likely to be as important as receptor activation events. Several members of the EGFR-family are overexpressed and/or mutated in cancer cells. The perturbation of EGFR-family signaling drives the malignant phenotype of many cancers and both inhibitors and antagonists of signaling from these receptors have already produced therapeutic benefits for patients. The design of affibodies, antibodies, small molecule inhibitors and even immunotherapeutic drugs targeting the EGFR-family has yielded promising new approaches to improving outcomes for cancer patients. In this review, we describe recent discoveries which have increased our understanding of the structure and dynamics of signaling from the EGFR-family, the roles of ligand processing and receptor cross-talk. We discuss the relevance of these studies to the development of strategies for designing more effective targeted treatments for cancer patients.

Colorectal Cancer Cell Line Proteomes Are Representative of Primary Tumors and Predict Drug Sensitivity.

BACKGROUND AND AIMS: Proteomics holds promise for individualizing cancer treatment. We analyzed to what extent the proteomic landscape of human colorectal cancer (CRC) is maintained in established CRC cell lines and the utility of proteomics for predicting therapeutic responses. METHODS: Proteomic and transcriptomic analyses were performed on 44 CRC cell lines, compared against primary CRCs (n=95) and normal tissues (n=60), and integrated with genomic and drug sensitivity data. RESULTS: Cell lines mirrored the proteomic aberrations of primary tumors, in particular for intrinsic programs. Tumor relationships of protein expression with DNA copy number aberrations and signatures of post-transcriptional regulation were recapitulated in cell lines. The 5 proteomic subtypes previously identified in tumors were represented among cell lines. Nonetheless, systematic differences between cell line and tumor proteomes were apparent, attributable to stroma, extrinsic signaling, and growth conditions. Contribution of tumor stroma obscured signatures of DNA mismatch repair identified in cell lines with a hypermutation phenotype. Global proteomic data showed improved utility for predicting both known drug-target relationships and overall drug sensitivity as compared with genomic or transcriptomic measurements. Inhibition of targetable proteins associated with drug responses further identified corresponding synergistic or antagonistic drug combinations. Our data provide evidence for CRC proteomic subtype-specific drug responses. CONCLUSIONS: Proteomes of established CRC cell line are representative of primary tumors. Proteomic data tend to exhibit improved prediction of drug sensitivity as compared with genomic and transcriptomic profiles. Our integrative proteogenomic analysis highlights the potential of proteome profiling to inform personalized cancer medicine.

TGF-ß and IL-6 family signalling crosstalk: an integrated model.

Mathematical models for TGF-ß and IL-6 signalling have been linked, providing a platform for analyzing the crosstalk between the systems. An integrated IL-6:TGF-ß model was developed via a reduced set of reaction equations which incorporate both feedback loops and appropriate time-delays for transcription and translation processes. The model simulates stable, robust and realistic responses to both ligands. Pulsatile (multiple pulses) inputs for both TGF-ß and IL-6 have been simulated to investigate the effects of each ligand on the sensitivity, equilibrium and dynamic responses of the integrated signalling system. In our simulations the crosstalk between constant IL-6 and TGF-ß signalling via SMAD7 does not appear to be sufficient to render the cells resistant to TGF-ß inhibition. However, the simulations predict that pulsatile IL-6 stimulation would increase SMAD7 levels substantially and consequentially, lead to resistance to TGF-ß. The model also allows the prediction of the integrated signalling pathway responses to the mutation of key components, e.g. Gp130 F/F.

Discrete Element Framework for Modelling Extracellular Matrix, Deformable Cells and Subcellular Components.

This paper presents a framework for modelling biological tissues based on discrete particles. Cell components (e.g. cell membranes, cell cytoskeleton, cell nucleus) and extracellular matrix (e.g. collagen) are represented using collections of particles. Simple particle to particle interaction laws are used to simulate and control complex physical interaction types (e.g. cell-cell adhesion via cadherins, integrin basement membrane attachment, cytoskeletal mechanical properties). Particles may be given the capacity to change their properties and behaviours in response to changes in the cellular microenvironment (e.g., in response to cell-cell signalling or mechanical loadings). Each particle is in effect an 'agent', meaning that the agent can sense local environmental information and respond according to pre-determined or stochastic events. The behaviour of the proposed framework is exemplified through several biological problems of ongoing interest. These examples illustrate how the modelling framework allows enormous flexibility for representing the mechanical behaviour of different tissues, and we argue this is a more intuitive approach than perhaps offered by traditional continuum methods. Because of this flexibility, we believe the discrete modelling framework provides an avenue for biologists and bioengineers to explore the behaviour of tissue systems in a computational laboratory.

Notch ligand delta-like1: X-ray crystal structure and binding affinity.

The Notch pathway is a fundamental signalling system in most multicellular animals. We have determined the X-ray crystal structure of the extracellular domain of the Notch ligand delta-like ligand-1 (Dll-1). The structure incorporates the N-terminal C2 domain, receptor-binding DSL domain and the first six (of eight) EGF (epidermal growth factor)-like repeats, which form a highly extended conformation, confirmed by analytical ultracentrifugation. Comparison of our structure with a fragment of Jagged1 ligand allows us to dissect the similarities and differences between the ligand families. Differences in the C2 domains of Dll-1 and Jagged1 suggest their lipid-binding properties are likely to differ. A conserved hydrophobic patch on the surface of both Dll-1 and Jagged1 provides a likely receptor-interaction site that is common to both ligands. We also explore the binding affinity of Dll-1 for a fragment of Notch1 using different techniques. Apparent binding affinities vary when different techniques are used, explaining discrepancies in the literature. Using analytical ultracentrifugation, we perform for the first time binding analyses where both receptor and ligand are in solution, which confirms a Kd of 10 µM for this interaction.

FunRich: An open access standalone functional enrichment and interaction network analysis tool.

As high-throughput techniques including proteomics become more accessible to individual laboratories, there is an urgent need for a user-friendly bioinformatics analysis system. Here, we describe FunRich, an open access, standalone functional enrichment and network analysis tool. FunRich is designed to be used by biologists with minimal or no support from computational and database experts. Using FunRich, users can perform functional enrichment analysis on background databases that are integrated from heterogeneous genomic and proteomic resources (>1.5 million annotations). Besides default human specific FunRich database, users can download data from the UniProt database, which currently supports 20 different taxonomies against which enrichment analysis can be performed. Moreover, the users can build their own custom databases and perform the enrichment analysis irrespective of organism. In addition to proteomics datasets, the custom database allows for the tool to be used for genomics, lipidomics and metabolomics datasets. Thus, FunRich allows for complete database customization and thereby permits for the tool to be exploited as a skeleton for enrichment analysis irrespective of the data type or organism used. FunRich (http://www.funrich.org) is user-friendly and provides graphical representation (Venn, pie charts, bar graphs, column, heatmap and doughnuts) of the data with customizable font, scale and color (publication quality).

Wild-type APC predicts poor prognosis in microsatellite-stable proximal colon cancer.

BACKGROUND: APC mutations (APC-mt) occur in ∼70% of colorectal cancers (CRCs), but their relationship to prognosis is unclear. METHODS: APC prognostic value was evaluated in 746 stage I-IV CRC patients, stratifying for tumour location and microsatellite instability (MSI). Microarrays were used to identify a gene signature that could classify APC mutation status, and classifier ability to predict prognosis was examined in an independent cohort. RESULTS: Wild-type APC microsatellite stable (APC-wt/MSS) tumours from the proximal colon showed poorer overall and recurrence-free survival (OS, RFS) than APC-mt/MSS proximal, APC-wt/MSS distal and APC-mt/MSS distal tumours (OS HR⩾1.79, P⩽0.015; RFS HR⩾1.88, P⩽0.026). APC was a stronger prognostic indicator than BRAF, KRAS, PIK3CA, TP53, CpG island methylator phenotype or chromosomal instability status (P⩽0.036). Microarray analysis similarly revealed poorer survival in MSS proximal cancers with an APC-wt-like signature (P=0.019). APC status did not affect outcomes in MSI tumours. In a validation on 206 patients with proximal colon cancer, APC-wt-like signature MSS cases showed poorer survival than APC-mt-like signature MSS or MSI cases (OS HR⩾2.50, P⩽0.010; RFS HR⩾2.14, P⩽0.025). Poor prognosis APC-wt/MSS proximal tumours exhibited features of the sessile serrated neoplasia pathway (P⩽0.016). CONCLUSIONS: APC-wt status is a marker of poor prognosis in MSS proximal colon cancer.

Recruitment of the adaptor protein Grb2 to EGFR tetramers.

Adaptor protein Grb2 binds phosphotyrosines in the epidermal growth factor (EGF) receptor (EGFR) and thereby links receptor activation to intracellular signaling cascades. Here, we investigated how recruitment of Grb2 to EGFR is affected by the spatial organization and quaternary state of activated EGFR. We used the techniques of image correlation spectroscopy (ICS) and lifetime-detected Förster resonance energy transfer (also known as FLIM-based FRET or FLIM-FRET) to measure ligand-induced receptor clustering and Grb2 binding to activated EGFR in BaF/3 cells. BaF/3 cells were stably transfected with fluorescently labeled forms of Grb2 (Grb2-mRFP) and EGFR (EGFR-eGFP). Following stimulation of the cells with EGF, we detected nanometer-scale association of Grb2-mRFP with EGFR-eGFP clusters, which contained, on average, 4 ± 1 copies of EGFR-eGFP per cluster. In contrast, the pool of EGFR-eGFP without Grb2-mRFP had an average cluster size of 1 ± 0.3 EGFR molecules per punctum. In the absence of EGF, there was no association between EGFR-eGFP and Grb2-mRFP. To interpret these data, we extended our recently developed model for EGFR activation, which considers EGFR oligomerization up to tetramers, to include recruitment of Grb2 to phosphorylated EGFR. The extended model, with adjustment of one new parameter (the ratio of the Grb2 and EGFR copy numbers), is consistent with a cluster size distribution where 2% of EGFR monomers, 5% of EGFR dimers, <1% of EGFR trimers, and 94% of EGFR tetramers are associated with Grb2. Together, our experimental and modeling results further implicate tetrameric EGFR as the key signaling unit and call into question the widely held view that dimeric EGFR is the predominant signaling unit.

EGF receptor family: twisting targets for improved cancer therapies.

The epidermal growth factor receptor (EGFR) undergoes a conformational change in response to ligand binding. The ligand-induced changes in cell surface aggregation and mobility have a profound effect on the function of all the family members. Ligand also activates the EGFR intracellular kinase, stimulating proliferation and cell survival. The EGFR family are often activated, overexpressed or mutated in cancer cells and therapeutic drugs (including antibodies) can slow the progress of some cancers. This article provides a brief, annotated summary of the presentations and discussion which occurred at the Epidermal Growth Factor Receptor - Future Directions Conference held in Jerusalem in November 2013.

Colonic myofibroblast cell line stimulates colonoid formation.

A stable and efficient system for the culture of murine colon epithelial cells or crypts is required to facilitate studies of the dynamics and factors affecting colon stem cell niche and crypt formation. Survival of colonic epithelial cells or crypts in vitro was not established until recently, when it was found that exogenous Wnt3A and R-spondin could promote cell survival and formation of spheroids (colonospheres) or some advanced organoids with well-developed crypts (colonoids). However, after 6-8 days in these culture conditions, only small numbers of colonospheres form organoids with crypt-like structures (colonoids). This study describes the use of a myofibroblast cell line and a coculture system that increases the efficiency of colonoid formation from isolated crypts. The enhanced coculture system has significantly improved colonoid-forming efficiency compared with results from previous systems. Crypt formation can be detected as early as day 2. The coculture system will facilitate the characterization of the colon stem cell niche and the changes that occur as a result of perturbations or mutations in colon stem or epithelial cells, such as those that favor precancerous adenoma or cancer.

Epidermal growth factor potentiates EGFR(Y992/1173)-mediated therapeutic response of triple negative breast cancer cells to cold atmospheric plasma-activated medium.

Cold atmospheric plasma (CAP) holds promise as a cancer-specific treatment that selectively kills various types of malignant cells. We used CAP-activated media (PAM) to utilize a range of the generated short- and long-lived reactive species. Specific antibodies, small molecule inhibitors and CRISPR/Cas9 gene-editing approaches showed an essential role for receptor tyrosine kinases, especially epidermal growth factor (EGF) receptor, in mediating triple negative breast cancer (TNBC) cell responses to PAM. EGF also dramatically enhanced the sensitivity and specificity of PAM against TNBC cells. Site-specific phospho-EGFR analysis, signal transduction inhibitors and reconstitution of EGFR-depleted cells with EGFR-mutants confirmed the role of phospho-tyrosines 992/1173 and phospholipase C gamma signaling in up-regulating levels of reactive oxygen species above the apoptotic threshold. EGF-triggered EGFR activation enhanced the sensitivity and selectivity of PAM effects on TNBC cells. The proposed approach based on the synergy of CAP and EGFR-targeted therapy may provide new opportunities to improve the clinical management of TNBC.

Identification of a Wnt-induced protein complex by affinity proteomics using an antibody that recognizes a sub-population of ß-catenin.

ß-catenin is a signaling protein with diverse functions in cell adhesion and Wnt signaling. Although ß-catenin has been shown to participate in many protein-protein interactions, it is not clear which combinations of ß-catenin-interacting proteins form discrete complexes. We have generated a novel antibody, termed 4B3, which recognizes only a small subset of total cellular ß-catenin. Affinity proteomics using 4B3, in combination with subcellular fractionation, has allowed us to define a discrete trimeric complex of ß-catenin, α-catenin and the tumor suppressor APC, which forms in the cytoplasm in response to Wnt signaling. Depletion of the limiting component of this complex, APC, implicates the complex in mediating Wnt-induced changes in cell-cell adhesion. APC is also essential for N-terminal phosphorylation of ß-catenin within this complex. Each component of ß-catenin/APC/α-catenin complex co-exists in other protein complexes, thus use of a selective antibody for affinity proteomics has allowed us to go beyond the generation of a list of potential ß-catenin-interacting proteins, and define when and where a specific complex forms.

Chain-specific antibodies for laminin-511.

Mouse monoclonal antibodies (mAbs) that bind to specific chains of laminin-511 (LM-511) have been developed. Antibody 2F12 binds to the LMα5 chain, 3G10 binds to the LMß1 chain and 3C12 binds to the LMγ1 chain. These antibodies can be used to purify LM-511, to detect LM-511 in cell extracts or to detect the location of LM-511 in tissue by immunohistochemistry. In combination, the antibodies recognize all three chains of LM-511 and combinations of the antibodies can be used to quantitate levels of LM-511 in physiological fluids. One of the antibodies (3G10) is a potent inhibitor of the activity of LM-511 in cell adhesion, spreading and proliferation assays.

S100 family proteins are linked to organoid morphology and EMT in pancreatic cancer.

Epithelial-mesenchymal transition (EMT) is a continuum that includes epithelial, partial EMT, and mesenchymal states, each of which is associated with cancer progression, invasive capabilities, and ultimately, metastasis. We used a lineage-traced sporadic model of pancreatic cancer to generate a murine organoid biobank from primary and secondary tumors, including sublines that underwent partial EMT and complete EMT. Using an unbiased proteomics approach, we found that organoid morphology predicts the EMT state, and the solid organoids are associated with a partial EMT signature. We also observed that exogenous TGFß1 induces solid organoid morphology that is associated with changes in the S100 family, complete EMT, and the formation of high-grade tumors. S100A4 may be a useful biomarker for predicting EMT state, disease progression, and outcome in patients with pancreatic cancer.