Abstract 435: Regulation of macropinocytosis-dependent cell survival in pancreatic cancer cells

Cancer cells utilize multiple scavenging mechanisms to support growth in nutrient-poor, hypoxic environments. Signaling pathways to accommodate these mechanisms may not be required for oncogenesis per se but are crucial for cancer cell survival. These processes, known as non-oncogene addiction, can be conferred by specific oncogenes that reprogram metabolism or by the tumor microenvironment. Understanding how these pathways are regulated can provide novel opportunities for therapeutic intervention.

Studies showed that KRAS-mutant cancer cells, including pancreatic ductal adenocarcinoma (PDAC), upregulate macropinocytosis, a caveolin- and clathrin-independent endocytic process, to import extracellular protein to support growth upon nutrient depletion. Similarly, high levels of macropinocytic uptake are observed in PDAC murine models and also in human PDAC specimens. This process serves as a scavenging mechanism for cancer cells to survive and proliferate in nutrient-deprived tumor microenvironments. Thus, uncovering the key players of this pathway and the mechanisms underlying their regulation will be important to find potential therapeutic targets.

Here, we used the Informer set of small molecules to screen regulators of survival in culture conditions supplemented with either glutamine or extracellular protein. The Informer set drug library consists of small molecules including FDA-approved drugs and clinical candidates that have high selectivity for their targets and regulate many cellular pathways. We find that survival of cells grown in conditions supplemented with glutamine or exogenous protein is differentially regulated by distinct drug subsets. This suggests that different pathways of nutrient uptake, processing, and utilization are used in cells depending on the nutrient source. Further examination to determine the mechanism of pathway inhibition and applicability may unravel potential uses for therapeutics.

Citation Format: Sung Eun Kim, Man-Tzu Wang, Frank McCormick. Regulation of macropinocytosis-dependent cell survival in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 435. doi:10.1158/1538-7445.AM2017-435

Abstract 1370: EGFR-mediated Spred1 phosphorylation inhibits NF1 to sustain constitutive Ras/MAPK signaling

Spred proteins negatively regulate Ras/MAPK signaling following growth factor stimulation. Inhibition of Ras primary occurs through Spreds ability to bind and localize NF1, a RasGAP and major tumor suppressor, to the plasma membrane. Spred1 and NF1 loss-of-function mutations occur across multiple cancer types including non-small cell lung carcinoma, glioblastoma, melanoma, stomach carcinoma, and uterine carcinosarcoma. Here we demonstrate that EGFR signaling disrupts Spred1-NF1 binding. Mass spectrometry was performed on cells overexpressing EGFRL858R to identify potential phosphorylation sites on Spred1 and NF1 that could disrupt Spred1-NF1 binding by steric hindrance. A serine phosphorylation site on Spred1 was identified in which a phosphomimetic and phosphodeficient mutant decreased or increased Spred1-NF1 binding, respectively. Phosphomimetic Spred1 is unable to suppress Ras-GTP following EGF stimulation. Therefore, phosphorylation of Spred1 at this site by a serine kinase downstream of EGFR may disrupt Spred1-NF1 binding. To identify the Spred1 kinase we are performing an in vitro kinase assay and an unbiased CRISPRa screen. Our findings provide one potential mechanism by which EGFR signaling disrupts negative feedback to sustain constitutive Ras signaling. Furthermore, this work may elucidate a novel therapeutic target for restoring NF1-mediated inhibition of Ras.

Citation Format: Evan Markegard, Ellen L. Mercado, Jillian M. Silva, Jacqueline Galeas, Marena I. Trinidad, Anatoly Urisman, Frank McCormick. EGFR-mediated Spred1 phosphorylation inhibits NF1 to sustain constitutive Ras/MAPK signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1370. doi:10.1158/1538-7445.AM2017-1370

Abstract 4589: Preclinical investigation of SGN-CD70A antibody-drug conjugate in T cell lymphomas

CD70 is a member of the tumor necrosis factor (TNF) superfamily and aberrantly expressed in several solid tumors and a variety of hematologic malignancies. The CD70 protein is expressed on highly activated lymphocytes (like in T and B cell lymphomas). Since normal lymphocytes do not express much CD70, it is suggested that anti-CD70 antibodies could be a potential treatment for CD70 positive lymphomas. SGN-CD70A is a novel antibody-drug conjugate that combines an anti-CD70 monoclonal antibody with a synthetic DNA cross-linking molecule, pyrrolobenzodiazepine (PBD) dimer. It is currently under phase I clinical trials for renal cell carcinoma, mantle-cell, diffuse large B-cell, and follicular lymphoma. The aim of this study is to investigate the anti-tumor activity of SGN-CD70A in T cell lymphomas. We first examined CD70 expression in 36 cases of mature T or NK cell lymphomas using immunohistochemical (IHC) staining of patient biopsy specimens. The IHC results were reviewed and scored by 2 independent pathologists. We further investigated CD70 expression in Sezary syndrome (SS), mycosis fungoides (MF), and T cell acute lymphoblastic leukemia (T-ALL) cell lines, along with patient-derived T cell lymphoma primary cells and healthy donors’ peripheral blood mononuclear cells (PBMC) by flow cytometry. We next evaluated the anti-tumor activity of SGN-CD70A in cutaneous T cell lymphoma (CTCL) cell lines and patient-derived T cell lymphoma primary cells. Cell lines or primary cells were treated with SGN-CD70A at various concentrations, after which growth inhibition and apoptosis were assessed by CellTiter-Glo Assay, flow cytometry or Caspase-Glo 3/7 Assay, respectively. CD70 negative T-ALL cell lines were treated in parallel as negative controls for CD70 positive CTCL cell lines. Additionally, h00d-1910, an isotype control of the anti-CD70 antibody conjugated to PBD, was used as the negative control for SGN-CD70A. CD70 expression was observed across all subtypes of T cell lymphomas and all CTCL cell lines. In contrast, CD70 is not expressed in PBMC from healthy subjects. We demonstrated that SGN-CD70A potently inhibited cell growth in CD70-positive CTCL lines, but had no significant activity in CD70-negative T-ALL lines. In addition, SGN-CD70A induced more apoptosis and cell death in CTCL cell lines compared with media and h00d-1910 treated controls. Furthermore, we showed that SGN-CD70A inhibited cell proliferation and induced higher caspase 3/7 activity in CD70-expressing patient-derived T cell lymphoma primary cells in a dose-dependent manner, while h00d-1910 treated in parallel had no significant effects. In summary, CD70 is expressed in both nodal and cutaneous T cell lymphomas but not in healthy donors. SGN-CD70A not only shows anti-tumor activity in CTCL cell lines expressing CD70, but also inhibits proliferation and induces apoptosis in patient-derived T cell lymphoma primary cells, indicating it is a promising treatment for T cell lymphomas.

Citation Format: Chen-Yen Yang, Linlin Wang, Laura Pincus, Frank McCormick, Ryan Gill, Wei Ai. Preclinical investigation of SGN-CD70A antibody-drug conjugate in T cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4589. doi:10.1158/1538-7445.AM2017-4589

Abstract 3182: Cytoskeletal modulation results in increased tumor survival and drug resistance through attenuation of p53 dependent apoptosis

One of the major challenges to eradicating cancer involves the evolution of drug resistant clones and persistence of residual disease that escapes our current limit of detection but may proliferate upon cessation of therapy. These microscopic foci of residual diseases often exhibit stem-cell like properties and are intrinsically more resistant to drug therapy. A better understanding of the mechanisms underlying the innate drug resistance of these cellular populations may lead to improved treatment strategies, resulting in more durable remissions and ultimately improved patient survival.

We utilize functional genomic platforms to identify mechanisms responsible for the persistence of drug tolerant cells. A genome wide shRNA enrichment screen was performed using the c-Met addicted cell line GTL-16 to identify genes whose knockdown conferred DTP survival. Inhibition of the RhoA-ROCK-myosin pathway promotes drug resistance in a variety of tumor models, including those treated with either targeted therapy or conventional chemotherapy. Furthermore, pharmacological validation using multiple small molecule inhibitors of ROCK1 phenocopied both myosin heavy chain (MYH9) and light chain (MYL12) shRNA knockdown. More recently, utilizing a combination of gene expression and biochemical approaches, we have identified attenuation of p53 induced apoptosis to be a key event in mediating survival of these drug tolerant persisters. Reactivation of p53 using nutlin results in increased cell death.

These findings demonstrate that modulation of cytoskeleton is an important, but underappreciated, mechanism of drug resistance across many tumor types. These downstream effectors may serve as novel therapeutic targets for intervention and also biomarkers to stratify patients and their response to treatment.

Citation Format: Victoria E. Wang, John Doench, David Root, Rene Bernards, Jeffrey Settleman, Frank McCormick. Cytoskeletal modulation results in increased tumor survival and drug resistance through attenuation of p53 dependent apoptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3182. doi:10.1158/1538-7445.AM2017-3182

RAS Proteins and Their Regulators in Human Disease

RAS proteins are binary switches, cycling between ON and OFF states during signal transduction. These switches are normally tightly controlled, but in RAS-related diseases, such as cancer, RASopathies, and many psychiatric disorders, mutations in the RAS genes or their regulators render RAS proteins persistently active. The structural basis of the switch and many of the pathways that RAS controls are well known, but the precise mechanisms by which RAS proteins function are less clear. All RAS biology occurs in membranes: a precise understanding of RAS' interaction with membranes is essential to understand RAS action and to intervene in RAS-driven diseases.

RAS Proteins and Their Regulators in Human Disease

RAS proteins are binary switches, cycling between ON and OFF states during signal transduction. These switches are normally tightly controlled, but in RAS-related diseases, such as cancer, RASopathies, and many psychiatric disorders, mutations in the RAS genes or their regulators render RAS proteins persistently active. The structural basis of the switch and many of the pathways that RAS controls are well known, but the precise mechanisms by which RAS proteins function are less clear. All RAS biology occurs in membranes: a precise understanding of RAS' interaction with membranes is essential to understand RAS action and to intervene in RAS-driven diseases.

Tumor RAS Gene Expression Levels Are Influenced by the Mutational Status of RAS Genes and Both Upstream and Downstream RAS Pathway Genes

The 3 human RAS genes play pivotal roles regulating proliferation, differentiation, and survival in normal cells and become mutated in 15% to 20% of all human tumors and amplified in many others. In this report, we examined data from The Cancer Genome Atlas to investigate the relationship between RAS gene mutational status and messenger RNA expression. We show that all 3 RAS genes exhibit increased expression when they are mutated in a context-dependent manner. In the case of KRAS, this increase is manifested by a larger proportional increase in KRAS4A than KRAS4B, although both increase significantly. In addition, the mutational status of RAS genes can be associated with expression changes in other RAS genes, with most of these cases showing decreased expression. The mutational status associations with expression are recapitulated in cancer cell lines. Increases in expression are mediated by both copy number variation and contextual differences, including mutational status of epidermal growth factor receptor (EGFR) and BRAF. These findings potentially reveal an adaptive response during tumor evolution that is dependent on the mutational status of proximal genes in the RAS pathway and cellular context. Cell contextual differences in these adaptations may influence therapeutic responsiveness and alternative resistance mechanisms.

ETS-targeted therapy: can it substitute for MEK inhibitors?

BACKGROUND

The RAS/MAPK pathway has been intensively studied in cancer. Constitutive activation of ERK1 and ERK2 is frequently found in cancer cells from a variety of tissues. In clinical practice and clinical trials, small molecules targeting receptor tyrosine kinases or components in the MAPK cascade are used for treatment. MEK1 and MEK2 are ideal targets because these enzymes are physiologically important and have narrow substrate specificities and distinctive structural characteristics. Despite success in pre-clinical testing, only two MEK inhibitors, trametinib and cobimetinib, have been approved, both for treatment of BRAF-mutant melanoma. Surprisingly, the efficacy of MEK inhibitors in other tumors has been disappointing. These facts suggest the need for a different approach. We here consider transcription factor ETS1 and ETS2 as alternate therapeutic targets because they are major MAPK downstream effectors.

MAIN TEXT

The lack of clinical efficacy of MEK inhibitors is attributed mostly to a subsequent loss of negative feedback regulation in the MAPK pathway. To overcome this obstacle, second-generation MEK inhibitors, so-called "feedback busters," have been developed. However, their efficacy is still unsatisfactory in the majority of cancers. To substitute ETS-targeted therapy, therapeutic strategies to modulate the transcription factor in cancer must be considered. Chemical targeting of ETS1 for proteolysis is a promising strategy; Src and USP9X inhibitors might achieve this by accelerating ETS1 protein turnover. Targeting the ETS1 interface might have great therapeutic value because ETS1 dimerizes itself or with other transcription factors to regulate target genes. In addition, transcriptional cofactors, including CBP/p300 and BRD4, represent intriguing targets for both ETS1 and ETS2.

CONCLUSIONS

ETS-targeted therapy appears to be promising. However, it may have a potential problem. It might inhibit autoregulatory negative feedback loops in the MAPK pathway, with consequent resistance to cell death by ERK1 and ERK2 activation. Further research is warranted to explore clinically applicable ways to inhibit ETS1 and ETS2.

Prospective Evaluation of Surgical Treatment of Humeral Avulsions of the Glenohumeral Ligament

BACKGROUND

Humeral avulsion of the glenohumeral ligament (HAGL) is an infrequent but significant contributor to shoulder dysfunction, instability, and functional loss.

PURPOSE

To prospectively identify patients with HAGL lesions and then conduct retrospective evaluation of the clinical history, examination findings, and surgical outcomes of these patients.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Over a 6-year period (2006-2011), patients with shoulder dysfunction and a HAGL lesion that was confirmed via magnetic resonance arthrogram (MRA) were prospectively evaluated with a minimum 2-year follow-up. Patient demographics, presentation, examination, and surgical findings were documented. Outcomes of return to activity as well as Western Ontario Shoulder Instability Index (WOSI) and Single Assessment Numeric Evaluation (SANE) scores were recorded at final follow-up. Anterior HAGL (aHAGL) lesions were repaired with a partial subscapularis tenotomy approach, while reverse (rHAGL) lesions were repaired arthroscopically.

RESULTS

Of 28 patients, 27 (96%) completed the study requirements at a mean of 36.2 months (range, 24-68 months). The sample contained 12 females (44%) and 15 males (56%), who had a mean age of 24.9 years (range, 18-34 years). The chief complaint reported was pain in 23 patients (85%), while only 4 (15%) patients complained primarily of recurrent instability symptoms. Fourteen patients (52%) had aHAGL lesions, 10 patients (37%) had rHAGL lesions, and 3 patients (11%) had combined aHAGL and rHAGL lesions. Ten patients (37%) had concomitant HAGL lesions and labral tears, whereas 17 patients (63%) had isolated HAGL lesion without labral tear. The 17 patients (63%) with aHAGL lesions or combined lesions underwent a partial subscapularis tenotomy approach, while the remaining 10 patients (37%) with rHAGL lesions underwent arthroscopic surgical repair. After surgery, WOSI outcomes improved from 54% to 88% and SANE outcomes improved from 50% to 91% ( P < .01 for both), with no reports in recurrence of instability symptoms at final follow-up.

CONCLUSION

This study demonstrated that patients with symptomatic HAGL lesions predominantly report shoulder pain and dysfunction, with few chief complaints of recurrent instability complaints. After surgery, patients showed predictable return to full activity, improvement in objective and patient-reported outcomes, and satisfaction with treatment outcome.

Family-focused practice within a recovery framework: practitioners' qualitative perspectives

Background

Family-focused practice (FFP) is an effective approach to supporting individuals with mental illness. ‘Recovery’ is also central to contemporary mental health care. However, there is a dearth of evidence about how the two concepts are related and subsequently implemented in practice. The aim of this study was to explore practitioners’ understandings and practices of FFP within a recovery framework.

Methods

Purposive/snowball sampling was used to recruit and conduct qualitative interviews with 11 mental health practitioners in rural Australia. Concurrent sampling and data collection were informed by thematic analysis and continued until data saturation was reached.

Results

Participants found it difficult to articulate their understandings of FFP within a recovery framework. Nonetheless they were able to describe practices that embodied family-focused recovery. Barriers to such practices included medical models of care, where there are often a shortage of skilled staff and high demands for care. Stigma (self and from others) and confidentiality were also identified as barriers to involving family members in recovery focused care.

Conclusions

Family-focused recovery care is a priority in many high-income countries. A family-focused recovery framework is needed to assist service planners, practitioners, family members and those with mental health needs and ensure such care is embedded within practice guidelines.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-017-2146-y) contains supplementary material, which is available to authorized users.

Abstract IA05: Regulation of Ras proteins and their effectors

Ras proteins regulate multiple phenotypes, including proliferation, contact inhibition, cell motility, metabolism, and genome integrity. This range of phenotypes may relate to the number of different effector pathways that Ras activates. The best validated of these is the Raf/MAPK pathway. Ras proteins can activate PI 3-kinase pathways directly, though this seems to vary between tissue types. Ras proteins bind and activate RalGDS, but this pathway is less well understood. In addition to these three major pathways, Ras proteins in their GTP state interact directly with several other potential effectors.

Analysis of the contributions that these pathways make towards cancer phenotypes using genetic approaches or RNA interference has been complicated by redundancies within each effector pathway. For example, there are three Raf isoforms, 3 PI 3-kinase isoforms, etc. This explains why screens for single genes that Ras depends on have not identified classical Ras effectors. Furthermore, each pathway may have several relevant phenotypes, such as effects on cell cycle progression, survival, and metabolic stress. Therefore, screens that depend on one phenotype, such as proliferation or survival, might miss other important functions. In addition to these technical complications, it is important to recognize differences in signaling between different tumor types. For example, in lung adenocarcinoma, the RTK/RAS/MAPK pathway can be activated by mutations in RTKs, activation of SOS, loss of NF1, mutation in KRAS, or activation of BRAF, with similar clinical outcomes. In pancreatic cancer, only mutation in KRAS appears capable of driving malignancy. In lung adenocarcinoma and pancreatic cancer, KRAS mutations are likely initiating events, in colorectal cancer they are definitely not, and exist in the context of un-regulated beta-catenin signaling.

To address these issues we analyzed the importance of each canonical effector pathway, plus 37 other potential effectors, in 100 cell lines derived from lung, pancreatic and GI tissues, measuring five different parameters on a single cell basis. We used combinations of highly potent and well characterized siRNAs that enabled us to knock down all the paralogs within an effector node at once. For example, we were able to knock down ARAF, BRAF and RAF1, together, in the “RAF node”. We took advantage of the variable nature of siRNA knockdown to generate dose-response curves for each node, measuring effects on five parameters on each cell.

This analysis revealed the expected dependence on tissue of origin, with pancreatic cells being more dependent on Ras signaling than lung adenocarcinoma. Unexpectedly, we found that most KRAS mutant tumor cell lines fell into two major classes: those that depend strongly on KRAS itself, and the Raf/MAPK pathway, and those that had lost dependence on KRAS, but were strongly dependent on RSK p90 S6 kinase. These cells were not dependent on PI 3-kinase genes themselves, but rather on PDK1, loss of LKB1 and other aspects of downstream PI 3-kinase signaling. We also identified a small number of cells that depended strongly on RalGDS. Each of these subsets had remarkably different properties, in terms of energy metabolism, EMT status, and cell-cell interaction. We conclude that oncogenic Ras proteins can indeed activate several downstream pathways, but in individual cell lines, one effector pathway predominates.

Citation Format: Tina Yuan, Frank McCormick. Regulation of Ras proteins and their effectors. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr IA05.

Abstract B11: Oncogenic KRAS regulates 4E-BP1, a repressor of cap-dependent translation, independently of growth factor activity

Oncogenic mutations in K-Ras often occur at high frequencies in human cancer resulting in the sustained activation of the ERK1/2 mitogen-activated protein kinase (MAPK) signaling pathway. However, the unique dependencies on upstream or downstream oncogenic signaling amongst the mutant K-Ras proteins remains elusive and often masked by the remaining wild-type allele, other Ras isoforms, or additional secondary genetic alterations. Thus, we employed an isogenic mouse embryonic fibroblast (MEFs) system devoid of H-, N-, and K-Ras alleles and reconstituted with a single Ras isoform to examine the dependencies of growth factors on K-Ras mediated control of translational regulation. Although oncogenic K-Ras G12D and G12V mutant MEF lines proliferated at twice the rate of K-Ras4b wild-type MEF cells, growth factor deprivation led to a cytostatic effect on the proliferation of all MEF lines. Analysis of signaling downstream of K-Ras revealed that phosphorylation of 4E-BP1, eIF4E, and ERK1/2 occurred in a growth factor-independent manner, which stood in contrast to the substantive effects of growth factor inhibition on AKT, p70S6K, and ribosomal protein S6 phosphorylation. Moreover, growth factor deprivation resulted in a marginal decrease of global protein synthesis with negligible effects on cap-dependent translation initiation in all K-Ras MEF cell lines. Taken together, these data suggest that oncogenic K-Ras signaling regulates 4E-BP1 phosphorylation independently of growth factor and mTORC1/2 effects.

Citation Format: Jillian M. Silva, Rachel K. Bagni, Davide Ruggero, Frank McCormick. Oncogenic KRAS regulates 4E-BP1, a repressor of cap-dependent translation, independently of growth factor activity. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr B11.

Abstract IA14: Targeting Ras

We are exploring multiple ways of targeting Ras proteins and Ras-driven cancers. We have identified compounds that covalently bind to cysteine-185 on K-Ras 4B, and to the G-domain of K-Ras 4A and 4B. We are also screening for compounds that bind directly to K-Ras using a new technique referred to as Second Harmonic Generation and are developing compounds that promote phosphorylation of K-Ras4B on serine-181. In addition, we are attempting to solve novel structures of oncogenic Ras proteins on their own, or complexed with effectors, regulators and chaperones, in an attempt to identify new targeting opportunities. For example, we have solved the structure of fully processed K-Ras 4B bound to PDE-delta. This co-structure suggests several new approaches to targeting K-Ras processing.

In addition to targeting K-Ras directly, we are validating downstream dependencies that are specific for K-Ras cancers, including the cytokine LIF, which is expressed at high levels in K-Ras transformed cells and plays a major role in stem-like properties of K-Ras cancers. Suppressing LIF expression using shRNA, CRISPR or monoclonal antibodies has profound effects on K-Ras tumor initiation and maintenance, and suggests new therapeutic opportunities. We are also analyzing signaling pathways that differ between Ras mutants and between Ras isoforms. These results, and their opportunities for intervention, will be discussed.

Citation Format: Frank McCormick. Targeting Ras. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr IA14.

Comparative proteomics of a model MCF10A-KRasG12V cell line reveals a distinct molecular signature of the KRasG12V cell surface

Oncogenic Ras mutants play a major role in the etiology of most aggressive and deadly carcinomas in humans. In spite of continuous efforts, effective pharmacological treatments targeting oncogenic Ras isoforms have not been developed. Cell-surface proteins represent top therapeutic targets primarily due to their accessibility and susceptibility to different modes of cancer therapy. To expand the treatment options of cancers driven by oncogenic Ras, new targets need to be identified and characterized at the surface of cancer cells expressing oncogenic Ras mutants. Here, we describe a mass spectrometry-based method for molecular profiling of the cell surface using KRasG12V transfected MCF10A (MCF10A-KRasG12V) as a model cell line of constitutively activated KRas and native MCF10A cells transduced with an empty vector (EV) as control. An extensive molecular map of the KRas surface was achieved by applying, in parallel, targeted hydrazide-based cell-surface capturing technology and global shotgun membrane proteomics to identify the proteins on the KRasG12V surface. This method allowed for integrated proteomic analysis that identified more than 500 cell-surface proteins found unique or upregulated on the surface of MCF10A-KRasG12V cells. Multistep bioinformatic processing was employed to elucidate and prioritize targets for cross-validation. Scanning electron microscopy and phenotypic cancer cell assays revealed changes at the cell surface consistent with malignant epithelial-to-mesenchymal transformation secondary to KRasG12V activation. Taken together, this dataset significantly expands the map of the KRasG12V surface and uncovers potential targets involved primarily in cell motility, cellular protrusion formation, and metastasis.

Structural basis of recognition of farnesylated and methylated KRAS4b by PDEδ

Farnesylation and carboxymethylation of KRAS4b (Kirsten rat sarcoma isoform 4b) are essential for its interaction with the plasma membrane where KRAS-mediated signaling events occur. Phosphodiesterase-δ (PDEδ) binds to KRAS4b and plays an important role in targeting it to cellular membranes. We solved structures of human farnesylated-methylated KRAS4b in complex with PDEδ in two different crystal forms. In these structures, the interaction is driven by the C-terminal amino acids together with the farnesylated and methylated C185 of KRAS4b that binds tightly in the central hydrophobic pocket present in PDEδ. In crystal form II, we see the full-length structure of farnesylated-methylated KRAS4b, including the hypervariable region. Crystal form I reveals structural details of farnesylated-methylated KRAS4b binding to PDEδ, and crystal form II suggests the potential binding mode of geranylgeranylated-methylated KRAS4b to PDEδ. We identified a 5-aa-long sequence motif (Lys-Ser-Lys-Thr-Lys) in KRAS4b that may enable PDEδ to bind both forms of prenylated KRAS4b. Structure and sequence analysis of various prenylated proteins that have been previously tested for binding to PDEδ provides a rationale for why some prenylated proteins, such as KRAS4a, RalA, RalB, and Rac1, do not bind to PDEδ. Comparison of all four available structures of PDEδ complexed with various prenylated proteins/peptides shows the presence of additional interactions due to a larger protein-protein interaction interface in KRAS4b-PDEδ complex. This interface might be exploited for designing an inhibitor with minimal off-target effects.

An orthopedist's guide to shoulder ultrasound: a systematic review of examination protocols

BACKGROUND

The utilization of musculoskeletal ultrasound has expanded within the setting of the orthopedic clinic as a cost-effective, point-of-care diagnostic tool for shoulder pathology. In experienced hands, ultrasound exhibits capabilities equivalent to that of magnetic resonance imaging in the diagnosis of many shoulder diseases including full-thickness and partial-thickness rotator cuff tears. Although similarly effective in identifying additional shoulder disease processes, major obstacles to its widespread use include user dependence and intrinsic limitation to extra-articular diagnosis.

OBJECTIVES

The purpose of this review is to present a step-by-step guide of how to perform a comprehensive shoulder examination and to discuss the appropriate use, economic benefit and implementation of ultrasound within the clinic.

METHODS

A systematic search (June 2016) of PubMed, Scopus, and EMBASE databases was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for literature presenting shoulder ultrasound examination protocols. Included studies were peer-reviewed articles or academic society endorsed protocols presenting comprehensive sonographic examinations of the adult shoulder. Papers with limited or single structure examination descriptions, non-English language, and publication dates before 1980 were excluded. Final papers meeting criteria were secondarily screened for publication after 2005 to reflect the current state of ultrasound imaging.

RESULTS AND CONCLUSIONS

The search yielded 1,725 unique articles with 17 studies meeting final selection criteria. Information from identified studies was summarized to formulate a 4-part shoulder examination protocol, including steps most pertinent to orthopedic in-office diagnoses. In agreement with previous studies, the inexperienced orthopedic surgeon can be quickly trained to expert level proficiency in shoulder ultrasound diagnosis. Using an established protocol, a comprehensive, yet effective shoulder ultrasound examination can be performed within ten minutes. Further, ultrasound provides opportunity to off-set costs through the engagement of revenue generating activity for the orthopedic practice.

Rating a Sports Medicine Surgeon's "Quality" in the Modern Era: an Analysis of Popular Physician Online Rating Websites

BACKGROUND

Consumer-driven healthcare and an increasing emphasis on quality metrics have encouraged patient engagement in the rating of healthcare. As such, online physician rating websites have become mainstream and may play a potential role in future healthcare policy.

QUESTIONS/PURPOSES

The purpose of this study was to evaluate online patient ratings for US sports medicine surgeons, determine predictors of positive ratings and analyze for inter-website scoring correlation.

METHODS

The American Orthopedic Society for Sports Medicine (AOSSM) member directory was sampled. Surgeon demographic and rating data were searched on three online physicians rating websites: HealthGrades.com (HG), RateMDs.com (RM) and Vitals.com (V). Written rating comments were categorized as relating to the following: surgeon competence, surgeon affability and process of care. Bivariate linear regression, Pearson correlation and multivariable analyses were used to determine factors associated with positive ratings.

RESULTS

Two hundred seventy-five sports medicine surgeons were included. Two hundred seventy-one (99%) had ratings on at least one of the three websites. Sports surgeons were rated highly across all three websites (mean >4.0/5); however, there was only a low to moderate degree of correlation among websites. On HG, female surgeons and surgeons in academia were more likely to receive higher overall ratings. Across all three websites, increased number of years in practice inversely correlated with ratings; this relationship neared significance for HG and was significant for RM. A surgeon's online presence or geographic location was not associated with higher ratings. In multivariable regression analysis for ratings on HG, female sex was the only significant predictor of higher ratings. Two thousand three hundred forty-one written comments were analyzed: perceived surgeon competence and communication influenced the direction of ratings for the top and bottom tier surgeons.

CONCLUSION

There was a low degree of correlation among online websites for surgeon ratings. Female surgeons and those with fewer years in practice appear to have higher ratings on these websites; comment content analysis suggests that high and low ratings are influenced by perceived surgeon competence and affability.

Abstract A06: Development of a drug discovery platform using clinically relevant patient-derived xenograft models for cutaneous T cell lymphomas

Introduction: Cutaneous T cell lymphomas (CTCL) represent a heterogeneous group of diseases. Mycosis fungoides (MF) and Sezary syndrome (SS) are the most common subtypes of CTCL. Discovery of new therapeutic targets in T cell lymphomas has been hampered by lack of appropriate discovery platforms. Few T cell lymphoma cell lines are available; and it is likely that they have departed significantly from the original disease through long-term in vitro cultivation.

Objectives: To develop patient-derived T cell lymphoma mouse xenograft models (PDX) that recapitulate the clinical presentation of human diseases and to establish a drug discovery platform using these PDX models.

Materials and Methods: To establish PDX models for MF and SS, we injected lymphocytes obtained from patients into an NSG mouse (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) either subcutaneously or intravenously. Next, we investigated whether tumor derived plasma cell-free DNA can serve as a surrogate for disease burden in PDX. We first established this method in xenografts bearing a subcutaneous tumor derived from a MF cell line. We measured tumor volume by manual caliper methods twice weekly and simultaneously, we collected plasma from these mice. We measured human-actin-specific cell-free DNA concentrations in the plasma by qPCR and examined whether they can correlate with the tumor volume measured by the caliber method. After validated this method in xenografts established with a MF cell line, we examined this method in PDX. To this end, we measured human-actin-specific cell-free DNA concentrations in PDX plasma at various time points post-inoculation and investigated whether they correlated with tumor progression in PDX.

Results: Three weeks after inoculation of patient-derived malignant lymphocytes, the MF PDX mouse developed clinical syndrome of MF with erythematous, scaly skin lesions and alopecia. Necropsy revealed lymphocyte infiltration in the skin, spleen, liver and lungs, resembling the disease distribution of MF in humans. The erythematous skin lesions showed atypical lymphocyte infiltration in the epidermis, a diagnostic hallmark for MF. Additionally, immunohistochemistry staining reveled malignant cells in the epidermis expressed CD3 and CD4 without co-expression of CD7, which is identical to those of the donor patient's. Furthermore, we analyzed T cell receptor (TCR) clonality by PCR and demonstrated a clonal T-cell population in both patient and mouse specimens with similar amplified peaks, consistent with successful xenograft.

Similarly, the PDX mouse for SS developed the clinical syndromes with skin rashes, alopecia and was found to have Sezary cells in the blood, a diagnostic hallmark for SS. Malignant cells isolated from the spleen of a SS PDX animal had the same immunophenotype and TCR clonality as that of the donor patients, indicating successful xenografts. Importantly, we were able to passage malignant cells from one generation of PDX to the next while maintaining the clinical presentation of the disease.

Finally, we were able to demonstrate that in cell-line derived xenograft mice bearing subcutaneous tumors, human-actin-specific cell-free DNA concentrations in the plasma correlated with tumor volume assessed by manual caliber measurements. Next, we extended these results to MF/SS PDX, and were able to correlate human-actin cell-free DNA concentrations with tumor progression in in these mice.

Conclusion: We established PDX models that recapitulate the clinic syndrome of MF and SS with characteristic skin, nodes and blood involvement by the malignant cells. Additionally, we demonstrated that tumor-specific cell-free DNA concentration can be used as a surrogate for tumor burden in PDX. Together, our results demonstrated that we can establish a drug discovery platform using clinically relevant PDX models for T cell lymphomas.

Citation Format: Wei Ai, Yen-Chen Yang Yang, Shervin Afghani, Huaxin Gao, Laura Pincus Pincus, Linlin Wang Wang, Taha Rakhshandhroo, Ronald Balassanian, James Rubenstein, Ryan Gill, Frank McCormick. Development of a drug discovery platform using clinically relevant patient-derived xenograft models for cutaneous T cell lymphomas. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A06.

Patient Satisfaction Reporting for the Treatment of Femoroacetabular Impingement

PURPOSE

The purpose of this study was to evaluate how patient satisfaction after surgical femoroacetabular impingement (FAI) treatment is measured and reported in the current evidence base.

METHODS

A review of the MEDLINE database was performed. Clinical outcome studies of FAI that reported a measure of patient satisfaction were included. Patient demographics, clinical outcome scores, and patient satisfaction measures were extracted. The NewCastle Ottawa Scale (NOS) was used to grade quality. Statistical analysis was primarily descriptive.

RESULTS

Twenty-six studies met inclusion criteria; the mean NOS score among included studies was 5.7. Most studies were level 3 or 4 (n = 25, 96.1%). A 0 to 10 numeric scale, described by some studies as a visual analog scale, was the most commonly used method to assess satisfaction (n = 21; 80.8%), and mean reported scores ranged from 6.8 to 9.2 out of 10. Four studies (15.4%) used an ordinal scale, and 1 study (3.8%) used willingness to undergo surgery again as the measure of satisfaction. None of the included studies assessed preoperative satisfaction or patient expectation. Pooled cohort analysis was limited by significant overlapping study populations. Predictors of patients' satisfaction identified in included studies were presence of arthritis and postoperative outcome scores.

CONCLUSIONS

Patient satisfaction was not uniformly assessed in the literature. Most studies used a 0- to 10-point satisfaction scale, but none distinguished between the process of care and the outcome of care. Although satisfaction scores were generally high, the quality of the methodologies in the studies that reported satisfaction was low, and the studies likely included overlapping patient populations. More work needs to be done to develop standardized ways for assessing patient satisfaction after arthroscopic hip surgery and other procedures in orthopaedic sports medicine.

LEVEL OF EVIDENCE

Level III, systematic review of Level III studies.

Abstract 3894: A xenograft mouse model coupled with in-depth cell surface proteome analysis facilitates further elucidation of K-Ras driven tumorigenesis in lung carcinoma

The purpose of this study was to develop a proteomic approach for analysis of cell surface proteins in tissue specimens and applied it on a K-Ras driven mouse model of metastatic lung carcinoma. Metastatic disease is the leading cause of lung cancer-related mortality in the United States. In spite of continuous efforts, effective treatments targeting oncogenic K-Ras in lung and other K-Ras driven malignancies are slow to develop. To expand the treatment options for lung cancer and facilitate better understanding of metastasis new targets need to be identified and characterized at the surface of cancer cells, preferably in their native tissue microenvironment. Towards this goal we developed a mass-spectrometry (MS)-based glyco-proteomic approach targeting specifically cell surface proteins in tissue specimens and applied it on a xenograft lung cancer mouse model. We used A549 cells expressing endogenous K-RasG12S to induce lung tumor xenografts in BALB/c mice via tail vein injection. A comparative surface glyco-proteomics of cultured A549 cells, dissected tumor tissue (TT), adjacent tumor (AT) tissue and normal mouse lung tissue (NT) obtained from saline-injected age-matched littermates yielded high enrichment (i.e., ≥80%) of surface proteins. It resulted in extensive catalogue/map of more than 400 glycoproteins identified on tumor cell surface. More than 50% of proteins identified on the surface of A549 cultured cells were unambiguously identified in mouse TT, featuring proteins and pathways implicated in metastasis, invadopodia formation and cancer cell migration. These markers also provide insight regarding species determination of tissue origin (i.e., human vs. mouse) differentiation of tumor parenchyma from stroma, and regulation of tumor immune response.

Citation Format: Xiaoying Ye, Gordon Whiteley, Dwight Nissley, Frank McCormick, Josip Blonder. A xenograft mouse model coupled with in-depth cell surface proteome analysis facilitates further elucidation of K-Ras driven tumorigenesis in lung carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3894.

Abstract 4373: Structural basis of recognition of farnesylated and methylated KRAS4b by PDEδ

KRAS is the most frequently mutated member of RAS superfamily in all human cancers. Post-translational farnesylation and methylation of KRAS at its C-terminal end plays an important role in its trafficking to proper subcellular compartments for cell signaling events. PDEδ acts as a chaperone for farnesylated members of the RAS superfamily and plays a key role in their trafficking from the place of biosynthesis or post-translational modification to a transport vesicle or plasma membrane. We solved the structures of wild-type full-length KRAS4b (farnesylated and methylated) in complex with PDEδ in two different crystal forms at 2 Ang resolution. Our structure showed that only the last six amino acids of hypervariable region (and not the G-domain) of KRAS4b interact with PDEδ. Farnesyl and methyl groups present on Cys185 bind tightly in the central hydrophobic pocket present in PDEδ. In crystal form II, we could see all amino acids present in the hypervariable region of KRAS4b, thus providing atomic details of hypervariable region of KRAS4b for the first time. Comparison of the two crystal forms suggests how PDEδ could bind to both farnesylated as well as geranylgeranylated KRAS4b. The structure provides the rationale for nucleotide-independent binding of KRAS4b to PDEδ and its interaction with other farnesylated but not palmitoylated members of RAS superfamily.

Citation Format: Sathiya Dharmaiah, Lakshman Bindu, Peter Frank, William Gillette, Dominic Esposito, Dwight Nissley, Frank McCormick, Andrew Stephen, Dhirendra Simanshu. Structural basis of recognition of farnesylated and methylated KRAS4b by PDEδ. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4373.

Abstract 388: Pathway-directed high throughput drug screen identifies PI3K inhibitors that synergistically potentiate anti-tumor activity of HDAC inhibitors in mycosis fungoides and Sézary syndrome

Introduction and Purposes: Mycosis fungoides and Sézary syndrome (MF/SS) represent a group of heterogeneous diseases. Recent studies demonstrated dysregulation of several signaling pathways in MF/SS, including PI3K/AKT, JAK/STAT, RAS and NFκB pathways. We performed a high throughput drug screen to determine the potential of novel agents targeting these pathways for the treatment of MF/SS.

Experimental Procedures: We compiled a library of 94 compounds targeting pathways known to be relevant in cancer biology. These included kinases involved in growth factor receptor signaling, HDACs, proteasome, DNA repair and regulators of apoptosis. The compounds were screened for anti-proliferative activity against four MF/SS cell lines in high throughput proliferation assays. Selected hits were further studied in xenograft models of MF/SS and in primary T cell lymphomas. Promising candidates from different classes were also tested in combination therapy assays using a matrix block method across dose gradients of each compound designed to detect synergistic activities.

Results: From the high throughput screen, we identified 14 compounds with anti-proliferative activity in MF/SS, including multiple inhibitors of the PI3K pathway. PI3K inhibitors emerged as preliminary hits in this screen and secondary validation assays confirmed the class effect of PI3K inhibitors. From this class, the PI3K inhibitor BKM120 was selected for in vivo studies. In a xenograft model of MF, BKM120 exhibited striking anti-tumor activity measured by a marked suppression of tumor growth and prolonged survival of tumor-bearing mice compared with vehicle control. In a search for even more effective combination therapies, we identified that BKM120 and the HDAC inhibitor class of compounds exhibit synergistic anti-proliferative effects in MF/SS tumor cells. Each of three HDAC inhibitors including LBH, Romidepsin and Vorinostat showed synergistic activity with BKM120, most evident at the GI50 concentrations of each drug, and apparent in both growth inhibition and apoptotic assays.

Conclusion: BKM120 is highly active in preclinical models of MF/SS. Furthermore, it synergistically potentiates the effect of HDAC inhibitors against MF/SS tumor cells. These are highly promising approaches for the treatment of MF/SS and warrant clinical investigation.

Citation Format: Chen-Yen Yang, Razan Faraj, Taha Rakhshandaroo, Shervin Afghani, Laura Pincus, Sourav Bandyopadhyay, Frank McCormick, Weiyun Ai. Pathway-directed high throughput drug screen identifies PI3K inhibitors that synergistically potentiate anti-tumor activity of HDAC inhibitors in mycosis fungoides and Sézary syndrome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 388.

Abstract 293: EGFR inhibition generates drug-tolerant persister cells by blocking AKT activity and thus inactivating Ets-1 function

In non-small-cell lung cancer (NSCLC)—the leading cause of cancer death worldwide—about 10-20% harbor mutations in epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK). Although treatment with EGFR tyrosine kinase inhibitors (TKIs) had shown promise, drug resistance has been the most important determinant limiting its success. Recent studies have identified the mechanisms of drug resistance to TKIs, but the origin of acquired resistant cells remains to be elucidated. We consider that they must arise from a small subset of surviving populations after EGFR inhibition. Thus, we have studied the mechanism by which the subset remains viable after EGFR inhibition, despite cell death in the vast majority. Our study demonstrates that EGFR inhibition in lung cancer cells generates a drug-tolerant subpopulation by blocking AKT activity and thus inactivating Ets-1 function. The remaining cells enter a dormant, non-dividing state because of the inhibited transactivation of Ets-1 target genes cyclins D1, D3, and E2. Moreover, Ets-1 inactivation inhibits transcription of dual specificity phosphatase 6 (DUSP6), a negative regulator specific for ERK1/2. As a result, ERK1/2 is activated, which combines with c-Src to renew activation of the Ras/MAPK pathway, causing increased cell survival by accelerating Bim protein turnover. Conversely, inhibition of elevated ERK1/2 by the addition of a MEK inhibitor enhances programmed cell death through rewiring apoptotic signaling. These observations may explain why a small subset of quiescent cells can tolerate TKIs, and might suggest that combined treatment of TKI and MEK inhibitor could overcome drug resistance in the population.

Citation Format: Janyaporn Phuchareon, David W. Eisele, Frank McCormick, Osamu Tetsu. EGFR inhibition generates drug-tolerant persister cells by blocking AKT activity and thus inactivating Ets-1 function. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 293.