Precise Quantification of Behavioral Individuality From 80 Million Decisions Across 183,000 Flies

Individual animals behave differently from each other. This variability is a component of personality and arises even when genetics and environment are held constant. Discovering the biological mechanisms underlying behavioral variability depends on efficiently measuring individual behavioral bias, a requirement that is facilitated by automated, high-throughput experiments. We compiled a large data set of individual locomotor behavior measures, acquired from over 183,000 fruit flies walking in Y-shaped mazes. With this data set we first conducted a "computational ethology natural history" study to quantify the distribution of individual behavioral biases with unprecedented precision and examine correlations between behavioral measures with high power. We discovered a slight, but highly significant, left-bias in spontaneous locomotor decision-making. We then used the data to evaluate standing hypotheses about biological mechanisms affecting behavioral variability, specifically: the neuromodulator serotonin and its precursor transporter, heterogametic sex, and temperature. We found a variety of significant effects associated with each of these mechanisms that were behavior-dependent. This indicates that the relationship between biological mechanisms and behavioral variability may be highly context dependent. Going forward, automation of behavioral experiments will likely be essential in teasing out the complex causality of individuality.

Settlement Constellations and the Dynamics of Fields Formed Around Social and Environmental Issues

Firms are increasingly responding to social and environmental issues in highly complex and heterogeneous organizational fields that transcend national boundaries. Yet, we still have a limited understanding of how these fields are structured and the implications of structural variation on how issues are addressed over time. We advance theory in this area by arguing that issue fields are characterized by varying settlement constellations that structure these fields. We develop a typology of three settlement constellations—unified, fragmented, and bifurcated—and describe their impact on field structure and the challenges they raise for addressing field-defining issues. We then theorize the evolution of fields with different settlement constellations and explain how and why constellations are sustained over time as well as when they may change. Our paper helps advance theory on organizational fields, private regulation, and firm responses to social and environmental issues. More broadly, our paper highlights the unique position of organizational and institutional scholars to examine complex social and environmental issues, or “grand challenges.”

Medication Errors at a Tertiary Hospital Intensive Care Unit

Background

The intensive care unit (ICU) generates more medication prescriptions per patient day than any other unit in the hospital. The dynamics of the ICU environment, coupled with the complexity of patient pathology, increases the risk of medication errors. This study aimed to evaluate the incidence and spectrum of medication errors in an adult general ICU in Johannesburg, South Africa.

Methods

A retrospective chart review was conducted at a 19-bed ICU in a tertiary-level hospital in Johannesburg. Data were independently collected by two of the study investigators. The doctors’ prescription and the nurses’ administration section of patient bedside charts were scrutinized for drug prescription and administration errors.

Results

Of the 656 patient days studied, 3237 drugs (5.6 drugs per patient day) were prescribed. There were a total of 359 medication errors, comprising 237 (66.0%) prescription and 122 (34.0%) administration errors. The total error rate per 1000 patient days was 621.1, while the total error rate per 1000 drug prescriptions was 110.9. The most common errors were incorrect dose prescribed (n=69, 19.2%), incorrect dosing interval prescribed (n=48, 13.4%), incorrect dose administered (n=42, 11.7%) and failure to administer the prescribed drug (n=38, 10.6%).

Conclusion

The overall occurrence of medication errors is high but is in keeping with general international trends. Targeted interventions should be implemented to minimize the frequency of medication errors in the ICU and consequent risk to patients.

Inside the Velvet Glove: Sustaining Private Regulatory Institutions Through Hollowing and Fortifying

The forces that threaten to break apart private regulatory institutions are well known, but the forces that sustain them are not. Through a longitudinal inductive study of the Towards Sustainable Mining (TSM) program in the Canadian mining industry, we demonstrate how private regulatory institutions are sustained by strategically manipulating different aspects of an institution’s stringency. Our findings show how shifts in external conditions decreased benefits of participation for firms, triggering institutional destabilization. We demonstrate how the interdependent mechanisms of hollowing—actions that ratchet down aspects of stringency associated with high compliance costs—and fortifying—actions that ratchet up aspects of stringency associated with low compliance costs—worked together to stabilize the institution by rebalancing the competing pressures that underpin it. However, these same mechanisms can hinder the ability of these institutions to substantively address the targeted issues, even as they become more stringent in some areas. Our study advances research on private regulation by showing how different aspects of stringency can be simultaneously ratcheted up and ratcheted down to sustain private regulatory institutions. Further, in positioning institutional stability as an ongoing negotiation, we elucidate the key custodial role of governing organizations like trade associations in institutional maintenance.

Abstract 41: Tumor resistance to CDK4/6 inhibitors and degraders determined by the expression state of CDK6

CDK4 and CDK6 kinases are master regulators of cell cycle progression, and they have thus been attractive targets for cancer therapy. CDK4/6 inhibitors (CDK4/6i) showed significant clinical effectiveness in ER+ breast cancers, and three CDK4/6i are now FDA-approved for this indication. However, in several tumor types, CDK4/6i have only been modestly effective, but the underlying mechanism(s) accounting for the discrepancy have remained elusive. To identify the basis of resistance to CDK4/6i, we employed a variety of biochemical, genetic and proteomic approaches, we developed a potent and selective CDK4/6-directed degrader (PROTAC) to investigate in-cell binding of compounds and validated our findings in large tumor and clinical-based data. Our studies revealed that tumor response to CDK4/6i is critically determined by the expression of CDK6. Tumors with low CDK6 expression (CDK6-low) depend on CDK4, and are uniformly sensitive to CDK4/6i. CDK6-low tumors include both entire cancer types (e.g. Ewing Sarcomas, MCL), as well as subgroups of large tumor types, such as portion of non-small cell lung adenocarcinomas (NSCLC). We further validated this finding in NSCLC patients previously treated with CDK4/6i in a clinical trial. In contrast, tumors that express both CDK4 and CDK6 universally depend on CDK6, which is expressed as either CDK4/6i-sensitive CDK6 (CDK6-S) or CDK4/6-resistant CDK6 (CDK6-R) in different cells. Using a CDK4/6-directed PROTAC, we further found that CDK4/6i binds strongly CDK6-S but weakly CDK6-R, indicating different conformations adopted by CDK6 in the two states. An unbiased proteomic analysis identified binding of components of the HSP90/CDC37 complex associated with the state of CDK6: in tumors in which CDK6 is expressed as a thermo-unstable, strong HSP90/CDC37-client, CDK4/6i (and consequently CDK4/6 PROTACs) bind and potently inhibit CDK6 and downstream Rb/E2F signaling. In contrast, tumors resistant to CDK4/6i express CDK6 as a thermostable, weak HSP90/CDC37-client that binds weakly to CDK4/6i. Our data uncover the expression state of CDK6 and its dependence on the HSP90/CDC37 complex as a critical determinant of tumor response to CDK4/6i. We further identify low CDK6 expression as a molecular predictor of tumor sensitivity to current CDK4/6i, indicating a potential biomarker for selection of patients that are more likely to benefit from these drugs. Finally, our findings underline the need for novel inhibitors targeting the thermostable CDK6-R to be used for the treatment of the large number of patients with of Rb-proficient solid tumors that are resistant to current clinical CDK4/6i. Thus, this unexpected dualism in the dependence of CDK6 kinase on HSP90 explains resistance of a large portion of tumors to current CDK4/6i, and provides a roadmap for developing more effective CDK4/6-directed pharmacologic strategies for cancer therapy.

Citation Format: Xuewei Wu, Xiaobao Yang, Yan Xiong, Ruitong Li, Takahiro Ito, Tamer Ahmed, Zoi Karoulia, Christos Adamopoulos, Hong Wang, Li Wang, Ling Xie, Beatrix Ueberheide, Stuart Aaronson, Xian Chen, William Sellers, Sean Buchanan, Jian Jin, Poulikos I. Poulikakos. Tumor resistance to CDK4/6 inhibitors and degraders determined by the expression state of CDK6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 41.

Is the History of Erectile Dysfunction a Reliable Risk Factor for New Onset Acute Myocardial Infarction? A Systematic Review and Meta-Analysis

Acute myocardial infarction (AMI) occurs as a manifestation of coronary atherosclerotic disease. The occurrence of erectile dysfunction (ED) following AMI is well documented and this association and pathophysiology is often interrelated. Few studies have objectively assessed the diagnostic value of ED as a risk factor for AMI, in general. In this review, we aimed to better outline the diagnostic predictability of ED as a precursor for 'first/new onset' AMI. This review was performed using selective search terms, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. The Cochrane, Embase, PubMed, Scopus and Web of Science databases were searched (September 2018). Selected studies were further assessed for relevance and quality (Critical Appraisal Skills Program tool-Oxford). Four studies [573 participants; mean 143 (SD ± 76.3604) and median 141 participants] were eligible for analysis. Meta-analysis of the studies resulted in a pooled sensitivity of 51.36% (95% CI: 47.37-55.33%). For the single study which reported true negative and false positive cases, a specificity of 76.53% (95% CI: 68.57-83.00%) was calculated. The results of this systematic review and meta-analysis suggest that a history of ED should be used as a risk factor for new onset AMI.

Geospatial epidemiology of Staphylococcus aureus in a tropical setting: an enabling digital surveillance platform

Delivery of information to clinicians on evolving antimicrobial susceptibility needs to be accurate for the local needs, up-to-date and readily available at point of care. In northern Australia, bacterial infection rates are high but resistance to first- and second-line antibiotics is poorly described and currently-available datasets exclude primary healthcare data. We aimed to develop an online geospatial and interactive platform for aggregating, analysing and disseminating data on regional bacterial pathogen susceptibility. We report the epidemiology of Staphylococcus aureus as an example of the power of digital platforms to tackle the growing spread of antimicrobial resistance in a high-burden, geographically-sparse region and beyond. We developed an online geospatial platform called HOTspots that visualises antimicrobial susceptibility patterns and temporal trends. Data on clinically-important bacteria and their antibiotic susceptibility profiles were sought from retrospectively identified clinical specimens submitted to three participating pathology providers (96 unique tertiary and primary healthcare centres, n = 1,006,238 tests) between January 2008 and December 2017. Here we present data on S. aureus only. Data were available on specimen type, date and location of collection. Regions from the Australian Bureau of Statistics were used to provide spatial localisation. The online platform provides an engaging visual representation of spatial heterogeneity, demonstrating striking geographical variation in S. aureus susceptibility across northern Australia. Methicillin resistance rates vary from 46% in the west to 26% in the east. Plots generated by the platform show temporal trends in proportions of S. aureus resistant to methicillin and other antimicrobials across the three jurisdictions of northern Australia. A quarter of all, and up to 35% of methicillin-resistant S. aureus (MRSA) blood isolates in parts of the northern Australia were resistant to inducible-clindamycin. Clindamycin resistance rates in MRSA are worryingly high in regions of northern Australia and are a local impediment to empirical use of this agent for community MRSA. Visualising routinely collected laboratory data with digital platforms, allows clinicians, public health physicians and guideline developers to monitor and respond to antimicrobial resistance in a timely manner. Deployment of this platform into clinical practice supports national and global efforts to innovate traditional disease surveillance systems with the use of digital technology and to provide practical solutions to reducing the threat of antimicrobial resistance.

Abstract PD2-09: The genomic landscape of intrinsic and acquired resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in patients with hormone receptor-positive (HR+)/HER2- metastatic breast cancer (MBC)

Background: The CDK4/6 inhibitors have emerged as standard first- or second-line regimens in combination with an antiestrogen for patients with HR+/HER2- MBC. While these agents convey significant clinical benefit in many patients, intrinsic resistance can occur and, in patients who respond, acquired resistance is unfortunately inevitable. Despite their widespread use, we have limited insight into the molecular mechanisms governing response and resistance to these agents.

Methods: Whole exome sequencing (WES) was performed on metastatic tumor biopsies from 58 patients (pts) with HR+/HER2- MBC who received a CDK4/6 inhibitor with or without an antiestrogen at the Dana-Farber Cancer Institute, including 7 pts with pre/post-exposure biopsy pairs. Among these biopsies, 69.5% were characterized as resistant (intrinsic or acquired) and 30.5% were characterized as sensitive. To validate putative resistance mediators identified in patient samples, HR+/HER2- breast cancer cells were modified via CRISPR knockout or lentiviral overexpression. Sensitivity of these cells to antiestrogens and CDK4/6i was interrogated via cell-titer-glo assay. In parallel, HR+/HER2- breast cancer cells were cultured to resistance in the presence of an escalating dose of CDK4/6i. Derivative cell lines were subjected to western blotting in an effort to interrogate the putative resistance mediators identified in pts. Novel dependencies were identified in these derivative cell lines via treatment with targeted therapeutic agents in vitro.

Results: WES of tumors with CDK4/6i exposure revealed candidate mechanisms of resistance including biallelic RB1 disruption (n=4, 10%) and activating events in AKT1 (n=5, 12.5%), RAS (n=4, 10%), aurora kinase A (AURKA, n=11, 27.5%), and cyclin E2 (CCNE2, n=6, 15%). Convergent evolution toward biallelic RB1 disruption was identified in a single patient with one pre- and two post-exposure biopsies, while acquisition of AKT1 mutation and amplification was identified in two separate instances. Knockout of RB1 and overexpression of AKT1, KRAS G12D, AURKA, and CCNE2 provoked CDK4/6i and antiestrogen resistance in vitro. Breast cancer cells cultured to resistance in CDK4/6i demonstrated concordant acquisition of RB1 downregulation, RAS/ERK activation, AURKA overexpression, and CCNE2 overexpression. Derivative resistant cell lines with RB1 loss or AURKA gain demonstrated enhanced sensitivity to a novel AURKA inhibitor (LY3295668), while cells with RAS activation were highly sensitive to ERK inhibition (via LY3214996). CCNE2-overexpressing cells were highly sensitive to prexasertib, a CHEK1 inhibitor.

Conclusions: The genomic landscape of resistance to CDK4/6i is heterogeneous with multiple potential mediators that play well-established roles in cell division and oncogenic signal transduction. We present novel mechanisms of clinical resistance including activation of AKT1 and RAS family oncogenes as well as amplification of AURKA and CCNE2. These drivers were able to provoke resistance to CDK4/6i in vitro. Finally, in each case, a novel dependency was identified which is readily translatable into the clinic. These results underscore the potential of next-generation sequencing as a critical tool to enable identification of resistance mediators, while also suggesting that the presence of specific genomic alterations may define new therapeutic opportunities in CDK4/6i-resistant HR+ MBC.

Citation Format: Seth A. Wander, Ofir Cohen, Xueqian Gong, Gabriela N. Johnson, Jorge Buendia-Buendia, Maxwell Lloyd, Dewey Kim, Flora Luo, Pingping Mao, Karla Helvie, Kailey Kowalski, Utthara Nayar, Stephen Parsons, Ricardo Martinez, Lacey Litchfield, Xiang Ye, Chun Ping Yu, Valerie Jansen, Levi A. Garraway, Eric P. Winer, Sara M. Tolaney, Nancy U. Lin, Sean Buchanan, Nikhil Wagle. The genomic landscape of intrinsic and acquired resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in patients with hormone receptor-positive (HR+)/HER2- metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD2-09.

Corralling Organizational Institutionalism

In this essay, I respond to Alvesson, Hallett, and Spicer’s recent piece focusing on the problems stemming from organizational institutionalism’s unprecedented growth and proliferation. I focus my attention specifically on the current definitional problems in the literature and offer some suggestions for how scholars in the area might address these issues in the future.

A pan-cancer transcriptome analysis identifies replication fork and innate immunity genes as modifiers of response to the CHK1 inhibitor prexasertib

The combined influence of oncogenic drivers, genomic instability, and/or DNA damage repair deficiencies increases replication stress in cancer. Cells with high replication stress rely on the upregulation of checkpoints like those governed by CHK1 for survival. Previous studies of the CHK1 inhibitor prexasertib demonstrated activity across multiple cancer types. Therefore, we sought to (1) identify markers of prexasertib sensitivity and (2) define the molecular mechanism(s) of intrinsic and acquired resistance using preclinical models representing multiple tumor types. Our findings indicate that while cyclin E dysregulation is a driving mechanism of prexasertib response, biomarkers associated with this aberration lack sufficient predictive power to render them clinically actionable for patient selection. Transcriptome analysis of a pan-cancer cell line panel and in vivo models revealed an association between expression of E2F target genes and prexasertib sensitivity and identified innate immunity genes associated with prexasertib resistance. Functional RNAi studies supported a causal role of replication fork components as modulators of prexasertib response. Mechanisms that protect cells from oncogene-induced replication stress may safeguard tumors from such stress induced by a CHK1 inhibitor, resulting in acquired drug resistance. Furthermore, resistance to prexasertib may be shaped by innate immunity.

[Pharmacological Effects of CDK4 & 6 Selective Inhibitor Abemaciclib in Hormone Receptor-Positive Breast Cancer]

Abemaciclib, a selective cyclin dependent kinases 4 and 6(CDK4 & 6)inhibitor, is under development for the treatment of hormone receptor(HR)-positive, HER2-negative breast cancer. CDK4 & 6 inhibitors attenuate Rb phosphorylation resulting in a G1 arrest and tumor growth inhibition. Abemaciclib potently inhibits both CDK4 and CDK6, with 14-fold higher potency for CDK4-cyclin D1 complexes than CDK6-cyclin D3 in enzymatic assays. Low frequency of severe neutropenia requiring drug holiday in clinical trials of abemaciclib in breast cancer patients enables continuous daily dosing. Abemaciclib's preclinical difference in selectivity for CDK4 vs CDK6 could help explain its safety profile and ability to be dosed on a continuous schedule. Continuous inhibition of CDK4 & 6 by abemaciclib results in irreversible growth inhibition through induction of senescence and apoptosis in breast cancer cell lines. Abemaciclib shows its growth inhibitory effect particularly in estrogen receptor(ER)- positive breast cancer, and sensitivity to abemaciclib is associated with high ER levels and Rb positivity. In animals bearing ERpositive breast cancer, significant tumor growth inhibition was shown by single-agent and combination with anti-estrogen agents. Abemaciclib penetrates the blood-brain barrier and showed antitumor activity in glioma models. As described above, there are some characteristics demonstrate differences of abemaciclib and other CDK4 & 6 inhibitors. In clinical studies, abemaciclib has demonstrated efficacy and generally tolerable safety profile in HR-positive, HER2-negative breast cancer patients.

Abstract LB-083: Combination of an ERK1/2 inhibitor (LY3214996) with pan-RAF inhibitor enhances anti-tumor activity in KRAS mutant colorectal cancer (CRC) and non-small cell lung cancer (NSCLC)

Cancer patients with KRAS mutations have poor prognosis and represent an unmet medical need. Mutant KRAS driven MAPK activation is present in ~ 40% and ~ 30% of CRC and NSCLC patients, respectively. ERK1/2, a key downstream effector of KRAS mutations, is involved in the critical signaling network to drives cell proliferation, survival, metastasis and drug resistance. LY3214996, an ERK1/2 inhibitor which is in Phase I clinical trial (NCT02857270), has potent anti-tumor activities in KRAS mutant tumor cells in vitro and in vivo. However, some KRAS mutant cancer cells were less sensitive to LY3214996 single agent, suggesting that combination therapy is needed to maximize the benefit from ERK1/2 inhibition. The combined inhibition of RAS/RAF/MEK/ERK pathway components (such as the inhibition of both BRAF and MEK) has shown the promising anti-cancer activity in melanoma. Based on interaction between activated RAS with RAF which is responsible for cancer progression and resistance in KRAS mutant cancers, we hypothesized that inhibiting both ERK and RAF may augment efficacy of the single agents and delay the resistance. Therefore in this study we have investigated the combination effect of LY3214996 with a pan-RAF inhibitor LY3009120 in KRAS mutant CRC and NSCLC in vitro and in vivo. The combination of LY3214996 and LY3009120 showed synergistic or additive inhibition of cell proliferation in all KRAS mutant CRC (n=8) and NSCLC (n=8) cell lines tested. The LY3214996 and LY3009120 combination significantly decreased the phosphorylation levels of ERK, Rb, S6 and H3, and induced more complete cell death in NCI-H2122 (G-12C), A549 (G-12S), NCI-H441 (G-12V), HCT-116 (G-13D) and in LY3009120-resistant HCT-116 cells compared with either single agent. Subsequent combination efficacy was evaluated in the HCT-116 xenograft model. LY3214996 alone, LY3009120 alone and the combination of LY3214996 and LY3009120 resulted in 52%, 68% and 94% tumor growth inhibition, respectively; and the combination significantly augmented the efficacy (p <0.001). Furthermore the combination efficacy of LY3214996 with a different pan-RAF inhibitor (LSN3074753, a surrogate and an analogue of LY3009120) was also assessed in the H441 NSCLC orthotopic model, and the combination increased the inhibition of both primary tumor growth and spontaneous metastasis (including lymph node metastasis and chest wall metastasis) when compared with the respective single agent activity. Overall, the combined inhibition of ERK1/2 and RAF was tolerated and enhanced antitumor efficacy in KRAS mutant CRC and NSCLC preclinical models. These data support the feasibility of combining ERK inhibitor LY3214996 with a pan-RAF inhibitor as a promising strategy for the treatment of KRAS mutant CRC and NSCLC.

Citation Format: Wenjuan Wu, Shripad Bhagwat, Lisa Kindler, William McMillen, Sajan Joseph, Sean Buchanan, Christoph Reinhard, Ramon V. Tiu, Sheng-Bin Peng. Combination of an ERK1/2 inhibitor (LY3214996) with pan-RAF inhibitor enhances anti-tumor activity in KRAS mutant colorectal cancer (CRC) and non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-083.

Abstract 2535: Enhanced gene expression of replication fork and other E2F targets genes is associated with sensitivity and, paradoxically, also with acquired drug resistance, to the Chk1 inhibitor prexasertib

Many cancers are under replicative stress (RS) arising from the combined influence of oncogenic drivers (i.e. Cyclin E, E2F, Myc), genomic instability and/or deficiencies in DNA Damage Repair (DDR). Tumors survive RS by upregulating checkpoints such as those driven by the ATR/CHK1 pathway. Dependence of tumors under high RS on the Chk1 pathway is currently being explored in the clinic with the Chk1 kinase inhibitor prexasertib. Preclinical and clinical studies have demonstrated evidence of efficacy in various cancers supporting the notion that this drug has the potential to improve the standard of care for patients with these malignancies. Two pivotal steps to ultimately fulfill the promise of a novel therapeutic in the clinic are, 1) to enable a patient selection strategy via predictive biomarkers of drug response or de novo resistance; 2) to gain insight into mechanisms underlying the development of acquired resistance, a common phenomenon of cancer therapeutics that contributes to non-durable response. Two experimental objectives to address these challenges for prexasertib were set, 1) to profile a large pan-cancer tumor cell line panel for prexasertib response and explore the association between drug response and baseline molecular profile via transcriptomic profiling, (2) to establish an in vitro tumor line with acquired resistance to prexasertib and characterize it via transcriptomic and targeted proteomic profiling to probe the mechanism of acquired resistance to prexasertib. Key observations from this study: A) pathways corresponding to E2F targets, G2M checkpoint and the Spindle Assembly Checkpoint (SAC), with a distinct enrichment for replication fork genes emerged across three different studies, (a) across a pan-cancer tumor line panel associated with prexasertib sensitivity, (b) associated with resistance in a tumor cell line with acquired resistance to prexasertib and (c) as top hits in an unbiased functional shRNA screen aimed at identifying genes that upon knockdown sensitize the resistant tumor cell line to prexasertib. B)knockdown of specific replication fork components in the drug-resistant tumor line was associated with marked sensitization to prexasertib and concomitant evidence of RS and DNA damage.To explain these paradoxical observations, we postulate that tumors may upregulate the expression of E2F target/G2M/SAC genes to resist oncogene-induced RS and that they may rely on similar genes to survive prexasertib-induced RS. Based on this data, transcriptomic profiling may prove of utility in the identification of patient tailoring biomarkers for prexasertib and as tool to unravel mechanisms of acquired resistance.

Citation Format: Wayne D. Blosser, Jack A. Dempsey, Ann M. McNulty, Wenjuan Wu, Philip J. Ebert, Jason C. Ting, Yue W. Webster, Trent R. Stewart, Xueqian Gong, Farhana F. Merzoug, Sean Buchanan, Ricardo Martinez. Enhanced gene expression of replication fork and other E2F targets genes is associated with sensitivity and, paradoxically, also with acquired drug resistance, to the Chk1 inhibitor prexasertib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2535.

The 'John Thomas' sign and pelvic fractures-Fact or humorous myth?: A systematic review and meta-analysis

OBJECTIVES

An incidental and sometimes humorous finding on an Antero-Posterior (AP) pelvis X-ray view is that of the John Thomas Sign (JTS), which is defined as positive, when the penile shadow points towards the side of a hip or pelvic fracture in male patients. Despite previous research reports and studies performed on the JTS sign, uncertainty with regards to its clinical relevance still remains. The objective of this review was to assess the clinical validity and accuracy of this sign by performing a systematic review and meta-analysis.

METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search was performed (May 2017), using the following databases: BMJ best practice, Cochrane Database of Systematic Reviews, EMBASE, PubMed and Scopus. Studies comparing the predictability of the JTS were critically appraised. The summary effect (and 95% CI) was estimated using a random effect model and the Restricted Maximum Likelihood Method. The pooled sensitivity as well as the summary effect log odds ratio was determined. Selected studies were further ranked for quality and relevance using the Critical Appraisal Skills Program (CASP) (Oxford 2013) tool.

RESULTS

In total, nine articles were isolated and assessed. A total of 1942 participants were included. The mean sample size amongst these included studies was 243 participants with a median of 198 participants. Since the necessary data needed for the Meta-analysis was only present in the 6/9 studies assessed, these 6 were analyzed further. The JTS was positive in 1089 out of 1439 patients with a pooled sensitivity of 75.7% (95%CI, 73.4%-77.9%). There was a large variation in the sensitivity and specificity amongst studies, accounting for a non-significant summary Odds Ratio effect of -0.03.

CONCLUSIONS

Based on this review, there is insufficient statistical evidence to support the reliability of the JTS to predict the laterality in the case of a hip fracture on the standard AP pelvis x-ray.

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 EWS/ETS 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.

EXPERIMENTAL DESIGN

Using Western blot, high-content imaging, flow cytometry, ELISA, RNA sequencing, and CpG methylation assays, we characterized the in vitro response of ES cell lines to abemaciclib. We then evaluated abemaciclib in vivo in cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models of ES as either a monotherapy or in combination with chemotherapy.

RESULTS

Abemaciclib induced quiescence in ES cell lines via a G₁ cell-cycle block, characterized by decreased proliferation and reduction of Ki-67 and FOXM1 expression and retinoblastoma protein (RB) phosphorylation. In addition, abemaciclib reduced DNMT1 expression and promoted an inflammatory immune response as measured by cytokine secretion, antigen presentation, and interferon pathway upregulation. Single-agent abemaciclib reduced ES tumor volume in preclinical mouse models and, when given in combination with doxorubicin or temozolomide plus irinotecan, durable disease control was observed.

CONCLUSIONS

Collectively, our data demonstrate that the antitumor effects of abemaciclib in preclinical ES models are multifaceted and include cell-cycle inhibition, DNA demethylation, and immunogenic changes.

Abstract 336: Anti-tumor activity of the Chk1 inhibitor prexasertib (LY2606368) as a single agent in triple negative breast cancer models

Triple-negative breast cancer (TNBC), the most aggressive subtype of breast cancer, is diagnosed in approximately 15% of all breast cancer patients and characterized by high level of genomic instability, defects in DNA damage response (DDR) and increased replication stress (RS). Currently the treatment options for TNBC are limited, and new approaches are needed. Checkpoint kinase 1 (Chk1) is a key kinase that regulates the cell cycle, DDR and RS through the modulation of cell cycle checkpoints and replication fork licensing; and has emerged as an attractive target for anti-cancer therapy. Prexasertib (LY2606368), an ATP-competitive inhibitor of Chk1 has demonstrated single agent activity in vitro and in vivo. Prexasertib is being evaluated in an ongoing TNBC Phase 2 trial sponsored by NCI; and preliminary results suggest modest single-agent activity in sporadic TNBC patients (https://academic.oup.com/annonc/article/27/suppl_6/231PD/2798970). To understand the biology and mechanisms underlying prexasertib's activity and/or identify the potential biomarkers that may predict response or identify novel combinations that could improve prexasertib's efficacy, we evaluated the anti-tumor activity of prexasertib as a single agent in TNBC cancer cell lines in vitro and in vivo, including xenograft, orthotopic and patient-derived xenograft (PDX) tumor models. Prexasertib inhibited cell proliferation in 12 TNBC cell lines with IC50 values ranging from 0.32 nM to 117.3 nM; and demonstrated inhibition of Chk1 auto-phosphorylation and activation of γH2AX, RPA32 and DNAPKc in TNBC cell lines including HCC1187, HCC1806, MX-1 and MDA-MB-231. Treatment with prexasertib inhibited tumor growth by 83.8%, 85.5% and 94.2% in HCC1187, MX-1 and HCC1806 xenograft models, respectively. Prexasertib also inhibited primary tumor growth by 74.4% and lung metastasis by 97.48% in a MDA-MB-231 mammary fat pad orthotopic model. The anti-tumor effect of prexasertib was further assessed in 40 TNBC PDX models. Prexasertib treatment resulted in 10% (4/40) of models achieving complete tumor regression, 40% (16/40) achieving partial tumor regression/stasis and 50% (20/40) not deriving benefit. Potential biomarkers of prexasertib were investigated. TNBC cells with higher phosphorylation levels of DNAPKc and RPA32 demonstrated higher sensitivity to prexasertib treatment. TNBC PDX tumors with higher RNA message levels of CyclinE1, Cyclin D1 and c-Myc showed better prexasertib response. Together these findings will inform subsets of TNBC and/or individual patient characteristics that should be considered for future clinical assessments and development of potential combination therapy strategies.

Citation Format: Wenjuan Wu, Constance King, Gregory Donoho, Philip Iversen, Andrew Capen, Mark Castanares, Jennifer Stephens, Yan Ding, Susan Pratt, Ricardo Martinez, Sean Buchanan, Christoph Reinhard, Richard Beckmann, Aimee Lin. Anti-tumor activity of the Chk1 inhibitor prexasertib (LY2606368) as a single agent in triple negative breast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 336.

Abstract LB-185: Combination of an ERK1/2 inhibitor (LY3214996) with VEGFR-2 inhibitor enhances anti-tumor activity in KRAS mutant non-small cell lung cancer

Lung cancer is a leading cause of cancer death worldwide. ERK1/2, a key downstream effector of RAS mutations, is involved in the signaling network which drives cell proliferation, survival, metastasis and cancer resistance to drug treatment. KRAS mutation driven MAPK activation is present in ~ 30% of lung cancer patients. Non-small cell lung cancer (NSCLC) patients with KRAS mutation have poor prognosis and represents an unmet medical need. LY3214996, an ERK1/2 inhibitor which is in a phase I clinical trial, has anti-tumor activities in RAS mutant tumor cells in vitro and in vivo (http://cancerres.aacrjournals.org/content/77/13_Supplement/4973). Ramucirumab, a fully-human monoclonal antibody to human VEGFR-2 was approved as an anti-angiogenic treatment for several cancer indications including second-line NSCLC. Combination strategies in cancer including targeting both tumor cells and the surrounding stroma including endothelial cells have been shown to be effective in various tumor subtypes. In this study, the combination effect of LY3214996 with VEGFR-2 inhibitor DC101 (a monoclonal antibody specific for murine VEGFR-2 and a surrogate for ramucirumab) were evaluated in KRAS mutant NSCLC models, including NCI-H2122 (G-12C), A549 (G-12S) and NCI-H441 (G-12V). LY3214996 treatment alone resulted in 41%, 91% and 101% tumor growth inhibition in H2122, A549 and H441 xenograft tumors, respectively. DC101 treatment alone resulted in 64%, 75% and 102% tumor growth inhibition in H2122, A549 and H441, respectively. The combination of LY3214996 with DC101 led to better tumor growth inhibition 83%, 115% (i.e. 15% regression) and 146% (i.e. 46% regression) for H2122, A549 and H441, respectively when compared with single agent treatment. The molecular mechanism was further investigated in H2122 tumor xenograft tumors in terms of MAPK signaling, MAPK gene signatures, tumor vascularization, cell proliferation and apoptosis. LY3214996 together with DC101 led to greater reduction in tumor blood vessels density compared to DC101 alone. Similarly, the analysis of multiple cell cycle markers (including pRb, pH3 and Ki67) indicated that the combination treatment resulted in greater inhibited of cell proliferation compared to single agent. Moreover, the combination effect of LY3214996 with ramucirumab was also investigated via tumor cell driven cord formation assays in vitro; and the data indicated that the combination enhanced the inhibition of cord formation when compared to single agent. Overall, combined inhibition of ERK1/2 and VEGFR-2 enhanced both anti-angiogenesis and antitumor effects. Taken together, these data support further clinical development of the combination of an ERK1/2 inhibitor, LY3214996 with ramucirumab in the treatment of KRAS mutant NSCLC.

Citation Format: Wenjuan Wu, Shripad V. Bhagwat, Bonita D. Jones, Michelle L. Swearingen, Beverly L. Falcon, William T. McMillen, Sajan Joseph, Sean Buchanan, Sheng-Bin Peng, Christoph Reinhard, Ramon V. Tiu. Combination of an ERK1/2 inhibitor (LY3214996) with VEGFR-2 inhibitor enhances anti-tumor activity in KRAS mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-185.

Abstract 1852: Combination of the CDK4/6 inhibitor abemaciclib with xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, results in synergistic antineoplastic effects in human breast cancer cell lines

Background: The proliferative and pro-survival signals driven by the insulin-like growth factor (IGF) ligands, IGF-1 and IGF-2, are transmitted through their binding to the IGF-1 receptor (IGF-1R). In addition, IGF-2 promotes proliferation through activation of the insulin receptor variant A (IR-A) that is expressed during embryonic development as well as in many cancers. IGF survival signaling has been implicated in driving resistance to cancer therapies with diverse mechanisms of action, due to cross-talk between cellular signaling networks. Recent studies[1][2] suggest that the combination of IGF-1R signaling inhibitors with CDK4/6 inhibitors can result in enhanced anti-tumor activity. The aim of this study was to explore the potential of the IGF-1/-2 ligand blocking antibody, xentuzumab (BI 836845[3]), to enhance the anti-tumor activity of the CDK4/6 inhibitor abemaciclib, alone or in combination with fulvestrant, in human breast cancer (BC) cell lines.

Methods: The anti-proliferative activity of the xentuzumab/abemaciclib combination was evaluated using CellTiter-Glo and propidium iodide staining in a panel of 51 and 20 BC cell lines, respectively. Detailed studies of abemaciclib (+/- fulvestrant), xentuzumab and combinations thereof were performed in MCF7 cells. Cell cycle analysis was done by FACS and BrdU ELISA, cellular signaling was assessed by Western blotting, proliferation was evaluated by Incucyte, CellTiter-Glo and alamarBlue assay. Apoptosis was measured by detection of cleaved PARP and caspase 3.

Results:

Among a panel of BC cell lines, enhanced anti-proliferative activity of xentuzumab+abemaciclib vs. abemaciclib alone was observed specifically in hormone receptor positive (HR+) cell lines. Combined treatment resulted in more pronounced cell cycle arrest in MCF7 cells, associated with synergistic blockade of IGF survival signaling and suppression of cell cycle genes downstream of CDK4/6. The triple combination with fulvestrant more effectively inhibited tumor cell proliferation than the doublet abemaciclib+fulvestrant, and led to induction of apoptosis.

Conclusion: The study results show that addition of the IGF-1/-2 neutralizing antibody xentuzumab to abemaciclib, in the absence or presence of fulvestrant, leads to improved anti-proliferative activity and, in the triple combination, results in cellular death in MCF7 HR+ breast cancer cells. A phase Ib trial evaluating the abemaciclib+xentuzumab combination, including triplets with endocrine therapy in HR+BC patients, is currently ongoing.

References:

[1] Miller ML et al. (2013). Sci Signal 6;ra85

[2] Heilmann AM et al. (2014). Cancer Res 74:3947-58

[3] Friedbichler K et al. (2014). Mol Cancer Ther 13(2):399-409

Citation Format: Ulrike Weyer-Czernilofsky, Rosa Baumgartinger, Susanne Schmittner, Xueqian Gong, Sean Buchanan, Richard P. Beckmann, Carlos Marugan, Raquel Torres, Karsten Boehnke, Maria Jose Lallena, Flavio Solca, Norbert Kraut, Thomas Bogenrieder. Combination of the CDK4/6 inhibitor abemaciclib with xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, results in synergistic antineoplastic effects in human breast cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1852.

The ultrasonographic "whirlpool sign" in testicular torsion: valuable tool or waste of valuable time? A systematic review and meta-analysis

PURPOSE

A positive whirlpool sign (WS) is defined as the presence of a spiral-like pattern when the spermatic cord is assessed during ultrasonography (US), using standard, high-resolution ultrasonography (HRUS) and/or color Doppler sonography (CDS), in the presence of testicular torsion. The objective of this review was to assess the validity and accuracy of this sign by performing a comprehensive systematic literature review and meta-analysis.

METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, a comprehensive literature search was performed (August, 2017), using the following databases: BMJ Best Practice, Cochrane Library, Embase, PubMed, Scopus, and Web of Science. Selected studies were further assessed for relevance and quality using the Oxford 2010 Critical Appraisal Skills Program (CASP).

RESULTS

Of the studies assessed, a total of 723 participants were included, with a mean of 72.3 (SD 71.9) participants. Of the participants, 226 (31.3%) were diagnosed with testicular torsion (TT). Meta-analysis of the studies that provided sufficient data resulted in a pooled sensitivity and specificity of the WS of 0.73 (95% CI, 0.65-0.79) and 0.99 (95% CI, 0.92-0.99), respectively. Removal of all neonates increased the pooled sensitivity to 0.92 (95% CI, 0.70-0.98) while the pooled specificity remained almost unchanged at 0.99 (95% CI, 0.95-1.00). The estimated summary effect of all studies with sufficient data was 4.34 (95% CI, 1.01-7.67; n = 394; p = 0.001). A large degree of heterogeneity was suggested by an I² statistic of 88.27% (95% CI, 68.60-98.68%). Removal of neonatal subjects increased the estimated summary effect to 5.32 (95% CI, 1.59-9.05; n = 375; p = 0.001).

CONCLUSION

The WS, when correctly diagnosed, may be viewed as a very definitive sign for TT in the pediatric and adult populations. However, its role in neonates is limited.

Abstract B108: Antitumor efficacy of EGFR antibody necitumumab and dual PI3K/mTOR inhibitor (LY3023414) in preclinical tumor models

Necitumumab (Nmab) in combination with chemotherapy has demonstrated overall survival benefit in patients with advanced or metastatic squamous non-small cell lung cancer (SqNSCLC). The PI3K/ mTOR pathway shows aberrant activity in multiple tumor types and is implicated in the development of intrinsic and acquired resistance to anti-EGFR therapy. LY3023414, a potent dual PI3K/mTOR inhibitor, is currently undergoing clinical evaluation. The objective of this study was to evaluate the combination effects of Nmab and LY3023414 in multiple tumor models. Nmab and/or LY3023414 were evaluated using Cancer Cell Sensitivity Profiling (CCSP) using a panel of ~500 genetically and histologically diverse human tumor cell lines. The combination treatment showed greater inhibition of tumor cell growth as compared to single-agent treatments in a large fraction of the cell lines tested. The combination effect was further assessed in 21 patient-derived xenograft (PDX) models across multiple tumor types with and without genetic alterations in the PI3K pathway. Compared to both monotherapies, the combination treatment demonstrated greater efficacy in 16 of 21 models, and reached statistical significance in 6 models. Nmab -/+ LY3023414 was also evaluated in a panel of 40 SqNSCLC PDX models using a single-mouse trial format. Combination therapy exhibited significant benefit over either monotherapy as exemplified by disease control (61% for combination vs 17.5% and 34.3% for Nmab and LY3023414, respectively) and overall response rate (22% for combination vs 10% and 5.7% for Nmab and LY3023414, respectively). Median time to tumor doubling or event-free survival (mEFS) was also in favor of the combination therapy (mEFS = 38.9 days for combination vs 14.2 and 32.4 days for Nmab and LY3023414, respectively). To gain mechanistic insights into the combinatorial effect observed, we employed a high-content gene/protein expression assay (nCounter Vantage 3D RNA:Protein Solid Tumor Signaling Pathways Panel) in a SqNSCLC PDX model harboring PIK3CA mutation that was highly sensitive to the combination therapy. nCounter Vantage 3D analysis confirmed inhibition of the PI3K/mTOR pathway in LY3023414-treated tumors. A more robust effect on signaling events downstream of mTOR was observed in the combination group. Furthermore, pathway analysis of the gene expression data suggested alterations in cell cycle/apoptosis, DNA repair, Notch, TGFb, and Wnt signaling in the combination group. Collectively, these data indicate that the Nmab/LY3023414 combination provides a benefit over both monotherapies. A more profound blockade of the PI3K/ mTOR pathway accompanied by inhibition of tumor cell cycle, survival, and DNA repair mechanisms may underlie this effect.

Citation Format: Maxine A. Melchior, Xuemei Guo, Gregory P. Donoho, Philip W. Iversen, Thompson N. Doman, Manisha Brahmachary, Xueqian Gong, Gerald E. Hall, Jason R. Manro, Yung-mae M. Yao, Sean Buchanan, Tod Smeal, Michael D. Kalos, Ruslan D. Novosiadly. Antitumor efficacy of EGFR antibody necitumumab and dual PI3K/mTOR inhibitor (LY3023414) in preclinical tumor models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B108.

Categorizing Competence: Consumer debt and the reproduction of gender-based status differences

We examine how gender inequalities are reproduced through categorization processes in mainstream discourse. Drawing from an analysis of six years of US media coverage of credit card borrowers throughout the recent financial crisis, we show how categorization processes facilitate gender-based status differences by categorizing male and female credit card borrowers based on competence. We find that three dimensions of competence—savviness, responsibility, and agency—are constructed through two discursive mechanisms: accounts and vocabularies. Additionally, we highlight how vocabularies work to amplify stereotype-consistent accounts, yet undermine stereotype-inconsistent accounts. We contribute to research on institutional maintenance by highlighting the role of categorization processes in the reproduction of institutionalized relations of inequality. Further, we contribute to research on gender inequality by offering an in-depth examination of the micro-processes involved in the social construction of gender-based status differences. In this way, we shed new light on the cultural means through which gender inequalities are reproduced.

Discovery of a Highly Selective NAMPT Inhibitor That Demonstrates Robust Efficacy and Improved Retinal Toxicity with Nicotinic Acid Coadministration

NAMPT, an enzyme essential for NAD⁺ biosynthesis, has been extensively studied as an anticancer target for developing potential novel therapeutics. Several NAMPT inhibitors have been discovered, some of which have been subjected to clinical investigations. Yet, the on-target hematological and retinal toxicities have hampered their clinical development. In this study, we report the discovery of a unique NAMPT inhibitor, LSN3154567. This molecule is highly selective and has a potent and broad spectrum of anticancer activity. Its inhibitory activity can be rescued with nicotinic acid (NA) against the cell lines proficient, but not those deficient in NAPRT1, essential for converting NA to NAD⁺ LSN3154567 also exhibits robust efficacy in multiple tumor models deficient in NAPRT1. Importantly, this molecule when coadministered with NA does not cause observable retinal and hematological toxicities in the rodents, yet still retains robust efficacy. Thus, LSN3154567 has the potential to be further developed clinically into a novel cancer therapeutic. Mol Cancer Ther; 16(12); 2677-88. ©2017 AACR.

Abstract LB-318: Characterization of the mechanism of action of abemaciclib in NSCLC cell lines harboring KRAS mutation

Lung cancer is the most common tumor cancer worldwide and approximately 15-25% of the patients with lung adenocarcinoma have KRAS driven tumors. These malignancies involve, in the majority of cases, a constitutive activation of KRAS signaling pathway (1,2) and are associated with poor prognosis in patients with advanced disease (metastatic setting).

Currently there is no specific therapy to target KRAS driven tumors approved by FDA (3), then finding alternative targeted therapies is a need to cover for this disease.

Pharmacological inhibition of CDK4 was been suggested as a beneficial therapy to treat NSCLC patients carrying K-RAS oncogenes; and researchers base the potential efficacy of this approach on a synthetic lethal interaction between K-ras and CDK4 in in this type of tumors (4). Hence, CDK4/6 inhibitors appear as promising therapy to treat this type of tumors.

Abemaciclib is a cell cycle inhibitor with selective activity against CDK4 and CDK6 and is being evaluated in advanced clinical trials for its potential to reduce NSCLC cancer growth. Here we describe studies towards the in-vitro mechanism of action of abemaciclib to reduce tumor cells growth in NSCLC cell lines harboring mutations in KRAS. Overall, abemaciclib reduces NSCLC cell growth as indicated by a reduction of cell number and proliferation biomarker Ki67 upon treatment. This tumor growth inhibition is mediated by arrest of cell cycle in G1 phase as a direct consequence of Rb phosphorylation blockade. In this study we are further reporting a phenotypic characterization of sensitive cell lines monitoring cell proliferation, senescence, and apoptosis markers using flow cytometry and high content imaging approaches as well as metabolic profiling.

. Bibliography

(1)

Schubbert S, Shannon K and Bollang G (2007) Nature Rev. Cancer 7(4) 295-308.

(2)

Ihle NT et al (2012) J Natl Cancer Inst. 104(3): 228-239.

(3)

Roberts PJ et al (2010) J Clin Oncol. 28(31):4769-77

(4)

Puyol M et al (2010) Cancer Cell 1(13): 63-73.

Citation Format: Raquel Torres-Guzmán, Carmen Baquero, Carlos Marugan, Cecilia Mur, Severine I. Gharbi, Sandra Gomez, Joaquín Amat, Karsten Boehnke, Philip W. Iversen, Alfonso deDios, Xueqian Gong, Sean Buchanan, Richard P. Beckman, Maria José J. Lallena. Characterization of the mechanism of action of abemaciclib in NSCLC cell lines harboring KRAS mutation [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 LB-318. doi:10.1158/1538-7445.AM2017-LB-318

Abstract 317: Combination of a novel ERK1/2 inhibitor (LY3214996) with CDK4 and CDK6 inhibitor (abemaciclib) enhances antitumor efficacy in KRAS mutant non-small cell lung cancer (NSCLC)

ERK1/2, a key downstream effector of RAS mutations, is involved in the signaling network which drives cell proliferation, survival, metastasis and cancer resistance to drug treatment (including MEK and BRAF inhibitors). Lung cancer is a leading cause of cancer death worldwide. KRAS mutation present in up to 30% of NSCLC patients is associated with a poor prognosis and represents an unmet medical need. In KRAS mutant NSCLC, enhanced ERK activation cooperates with dysregulation of the cell cycle checkpoint (e.g., cyclin D, CDK4 and CDK6 complex), and contributes to tumor progression; thus, the simultaneous inhibition of ERK and the CDK4/6 pathway is hypothesized to augment tumor growth inhibition. LY3214996, a novel and highly selective small molecule inhibitor of ERK1 and ERK2, is currently in phase I clinical trial and has been shown to inhibit cell proliferation in RAS or BRAF mutant tumor cells in vitro and xenograft tumor growth in vivo. Abemaciclib, a CDK4 and CDK6-selective inhibitor is currently in phase III studies for ER positive breast cancer and KRAS mutant NSCLC. In this study we explore the potential efficacy of combined inhibition of ERK1/2 and CDK4 and CDK6 in KRAS mutant NSCLC. The combination of LY3214996 and abemaciclib synergistically inhibited cell proliferation in 85% of KRAS mutant cells in an unbiased NSCLC panel. Combination treatment with LY3214996 and abemaciclib significantly decreased levels of phospho- p90RSK, phospho-Rb, phospho-S6 and Ki67; and synergistically inhibited cell proliferation and survival in KRAS mutant NSCLC cell lines including NCI-H2122 (G-12C), A549 (G-12S) and NCI-H441 (G-12V). Subsequent in vivo studies showed that the combination treatment with LY3214996 and abemaciclib was well tolerated and led to more robust tumor growth inhibition or regression in all KRAS mutant NSCLC xenograft models (H2122, A549 and H441) compared with either single agent treatment (p≤0.002). Furthermore, in xenograft tumors the combination of LY3214996 and abemaciclib resulted in more significant reduction of phospho-p90RSK, phospho-Rb, phospho-S6 and Ki67 in H2122 tumors compared with either single agent. Overall, the combined inhibition of ERK1/2 and CDK4 and CDK6 was tolerated and enhanced antitumor efficacy in several KRAS mutant NSCLC preclinical models. These data support the feasibility of combining ERK inhibitor LY3214996 with CDK4 and CDK6 inhibitor abemaciclib as a promising strategy for the treatment of KRAS mutant NSCLC patients, and provides the rationale for the combination study in the on-going phase I LY3214996 clinic trial (NCT02857270).

Citation Format: Wenjuan Wu, Shripad V. Bhagwat, Constance King, Susan Pratt, Xueqian Gong, Julie Stewart, Bonita Jones, Robert Flack, Richard Beckman, Beverly Falcon, Jason Manro, William T. McMillen, Ramon V. Tiu, Sheng-Bin Peng, Christoph Reinhard, Sajan Joseph, Sean Buchanan. Combination of a novel ERK1/2 inhibitor (LY3214996) with CDK4 and CDK6 inhibitor (abemaciclib) enhances antitumor efficacy in KRAS mutant non-small cell lung cancer (NSCLC) [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 317. doi:10.1158/1538-7445.AM2017-317

Preclinical characterization of abemaciclib in hormone receptor positive breast cancer

Abemaciclib is an ATP-competitive, reversible kinase inhibitor selective for CDK4 and CDK6 that has shown antitumor activity as a single agent in hormone receptor positive (HR+) metastatic breast cancer in clinical trials. Here, we examined the mechanistic effects of abemaciclib treatment using in vitro and in vivo breast cancer models. Treatment of estrogen receptor positive (ER+) breast cancer cells with abemaciclib alone led to a decrease in phosphorylation of Rb, arrest at G1, and a decrease in cell proliferation. Moreover, abemaciclib exposure led to durable inhibition of pRb, TopoIIα expression and DNA synthesis, which were maintained after drug removal. Treatment of ER+ breast cancer cells also led to a senescence response as indicated by accumulation of β-galactosidase, formation of senescence-associated heterochromatin foci, and a decrease in FOXM1 positive cells. Continuous exposure to abemaciclib altered breast cancer cell metabolism and induced apoptosis. In a xenograft model of ER+ breast cancer, abemaciclib monotherapy caused regression of tumor growth. Overall these data indicate that abemaciclib is a CDK4 and CDK6 inhibitor that, as a single agent, blocks breast cancer cell progression, and upon longer treatment can lead to sustained antitumor effects through the induction of senescence, apoptosis, and alteration of cellular metabolism.

Abstract A12: The CDK4/CDK6 inhibitor abemaciclib inhibits transcriptional targets which facilitate growth in ER+ breast cancer cells

Abemaciclib (LY2835219) is an ATP-competitive inhibitor of cyclin dependent kinases 4 and 6 (CDK4/6), which is currently undergoing clinical evaluation as a single-agent treatment and in combination with the anti-hormonal therapy (SERD) fulvestrant in estrogen receptor positive (ER+) breast cancer (BrCa). Breast cancer cell line (15 lines) sensitivity to treatment with abemaciclib was assessed using multiple approaches including EdU incorporation, phosphorylation of retinoblastoma protein at serine 807/811 (pRb_s807/811) and RNA transcriptional profiling. We identified molecular features including ER-positivity (ER+), and luminal histology, as key to greater sensitivity while loss of Rb was associated with lower sensitivity. Changes in the Modaplex based RNA transcriptional array profiles of 29 cell cycle related target genes across a panel of 15 human breast cancer cell lines further characterized sensitivity to abemaciclib and highlighted potential targets of response. A sub-group of targets including MKi67, E2F1, MCM7, FOXM1, RRM2 and TOPIIα were significantly inhibited in highly sensitive cell lines previously characterized with EC50 < 50nM (EdU, pRb_serine 807/811). Additionally, we looked at abemaciclib induced transcriptional changes in vivo treating nude mice bearing human, ER+ breast cancer (ER+/HER2-) tumor xenografts and found that the inhibition of expression of this same group of transcriptional targets plus CCNE1 and CDKN2C correlated with the concentration-dependent inhibition of CDK4/CDK6. Abemaciclib washout studies following longer-term exposure in T47-D (ER+/HER2-) demonstrated durable cell cycle inhibition resulting in significant inhibition of pRb_s807/811 even after the removal (washout) of abemaciclib while longer exposure also resulted in inhibition of estrogen receptor-α (ERα) expression in a panel of ER+ breast cancer cell lines that were evaluated over a 8 day time course.

Using taqman low density RNA array (TLDA) cards designed with known ERα driven transcriptional targets, we investigated the impact of abemaciclib single agent and in combination with fulvestrant on changes in RNA expression in four day treated breast cancer cells (ER+/HER2-). Single agent abemaciclib appeared to inhibit a subset of ERα driven targets including TFF1, GREB1, ESR1, E2F1, CDC45, FOXM1 and IGFBP4 (inhibition >%50). Interestingly, comparing single agent (% inhibition) abemaciclib to fulvestrant monotherapy in MCF-7 cells, we found that abemaciclib inhibited CDC45, E2F1, ESR1 and FOXM1 to a greater extent than that observed for these same targets following monotherapy with fulvestrant. Combining abemaciclib with fulvestrant identified an additional sub-group of ERα driven targets whereby the combination provided greater inhibition than that observed with any of the single agent treatments (IGFBP4, E2F1, FOXM1 and CDC45). Additionally, the combination treatment as compared to single-agent treatments also induced greater inhibition of various cell cycle regulatory genes including MCM7, CDKN2C, TOP2a, RRM2, and MKi67.

Citation Format: Ann M. McNulty, Teresa Burke, Jack A. Dempsey, Christophe C. Marchal, Andrew E. Schade, Hadrian P. Szpurka, Michele S. Dowless, Jennifer Stephens, Jennifer Stephens, Denise Edmondson, Keith Stayrook, William C. Caldwell, Sean Buchanan, Farhana F. Merzoug, Richard P. Beckmann. The CDK4/CDK6 inhibitor abemaciclib inhibits transcriptional targets which facilitate growth in ER+ breast cancer cells. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A12.

Abstract 930: Combined inhibition of pan-RAF and VEGFR-2 mediates antitumor activity in KRAS mutant non-small cell lung cancer (NSCLC) through enhanced inhibition of tumor angiogenesis and growth

Lung cancer is the leading cause of cancer death worldwide. MAPK activation via KRAS mutation is present in up to 30% of lung cancer patients. NSCLC patients with KRAS mutation is associated with poor prognosis and represents an unmet medical need. LY3009120, a pan-RAF and RAF dimer inhibitor which is in phase I clinical trial, was previously demonstrated to have anti-tumor activities in BRAF or RAS mutant tumor cells in vitro and in vivo. Ramucirumab, a fully-human antagonist monoclonal antibody to human VEGFR-2 was recently approved as an anti-angiogenic treatment for several cancer indications including second-line NSCLC. Combination strategies in cancer including targeting both tumor cells and the surrounding stroma cells have been shown to be effective in various disease subtypes. In this study, the combination effect of LSN3074753 (a surrogate and an analogue of LY3009120) with VEGFR-2 inhibitor DC101 (a monoclonal antibody specific for murine VEGFR-2 and a surrogate for ramucirumab) were evaluated in KRAS mutant NSCLC models, including NCI-H2122 (G-12C), A549 (G-12S) and NCI-H441 (G-12V). LSN3074753 treatment alone resulted in 66.9% and 82.4% tumor growth inhibition in H2122 and A549 xenograft tumors, respectively; and 41.4% tumor regression in H441 xenograft tumors. DC101 treatment alone resulted in 64.5%, 75% and 102.2% tumor growth inhibition in H2122, A549 and H441, respectively. The combination of LSN3074753 and DC101 led to more significant tumor growth inhibition (87.2% of tumor growth inhibition for H2122, p<0.001) or tumor regression (16.3% and 51.5% tumor regression for A549 and H441, respectively, p<0.001) when compared to single agent treatment. The molecular mechanism was further investigated in H2122 and H441 tumor xenografts in terms of MAPK signaling and its gene signatures, tumor vascularization, cell proliferation and apoptosis. Treatment with LSN3074753 or DC101 alone reduced the tumor vessels and pericytes, but the combination treatment showed better effects. Similarly, the analysis of multiple cell cycle markers indicated that the combination treatment inhibited cell proliferation more than the single agent alone. Moreover, the combination effect of LSN3074753 with ramucirumab was also investigated in vitro, including endothelial cell sprouting, cord formation and tumor cell driven cord formation assays to further understand the molecular mechanisms underlying the combination benefit on different tumor compartments including tumor and stroma cells. Overall, combined inhibition of pan-RAF and VEGFR-2 enhanced both antiangiogenesis and antitumor effects, and the data support that combining a panRAF inhibitor with ramucirumab represents a promising strategy for the treatment of KRAS mutant NSCLC.

Citation Format: Wenjuan Wu, Julie Stewart, Constance King, Bonita Jones, Robert Flack, Susan Pratt, Randi Berryman, Michelle Swearingen, Diane Bodenmiller, Xi Lin, Mark Uhlik, Beverly Falcon, Anthony Fischl, Jason Manro, Ramon Tiu, Sudhakar Chintharlapalli, Bronislaw Pytowski, Shripad V. Bhagwat, Sean Buchanan, Sheng-Bin Peng. Combined inhibition of pan-RAF and VEGFR-2 mediates antitumor activity in KRAS mutant non-small cell lung cancer (NSCLC) through enhanced inhibition of tumor angiogenesis and growth. [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 930.

Abstract 2829: Preclinical analysis and characterization of abemaciclib using three-dimensional patient-derived colorectal cancer organoid cultures

Proper patient-tailoring strategy and the validation of novel therapeutic targets remain enormous challenges during drug discovery processes. Patient-derived three-dimensional organoid cell culture models possess great potential to associate compound sensitivity and disease complexity in order to provide a key missing link between compound screening and clinical trials. Abemaciclib is a reversible, ATP competitive, selective inhibitor of the kinase activity of both CDK4 and CDK6 and is currently undergoing advanced clinical testing.

In this study, we established and characterized three-dimensional organoid cultures from primary colorectal cancer patients and validated their use as drug sensitivity models. We aimed to explore the antitumor activity of abemaciclib in colon cancer organoid cultures by assessing markers for cell viability, proliferation, cell cycle, senescence and apoptosis. Single cell suspension of patient-derived samples were precultured for four days to allow for complete morphogenesis of three-dimensional organoid structures. Subsequently, the cultures were treated for at least two population doubling times and analyzed by luminescent cell viability, immunohistochemistry and flow cytometry assays.

Our data suggest that abemaciclib treatment decreased the cell viability of patient-derived colorectal cancer organoid cultures characterized by G1 cell cycle arrest and reduced Ki-67-positive cells. Furthermore, treated cultures showed elevated levels of reactive oxygen species and increased markers for early and late apoptosis. In summary, complex organoid models have the potential to further evaluate the antitumor activity of abemaciclib in various tumor types by enabling mechanistic studies in a patient-specific preclinical setting.

Citation Format: Karsten Boehnke, Bruna Calsina, Joaquín Amat, Ana Hermoso, Raquel Torres, Christoph Reinhard, Juan A. Velasco, Philip W. Iversen, Alfonso De Dios, Sean Buchanan, Richard P. Beckmann, Dirk Schumacher, Christian RA Regenbrecht, Marie-Laure Yaspo, Hans Lehrach, María José Lallena. Preclinical analysis and characterization of abemaciclib using three-dimensional patient-derived colorectal cancer organoid cultures. [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 2829.

Abstract 282: Pan-RAF inhibitor LY3009120 sensitizes RAS or BRAF mutant cancer to CDK4 and 6 inhibition by abemaciclib via superior inhibition of phospho-RB and suppression of cyclin D1

KRAS, NRAS and BRAF mutations are among the most important oncogenic drivers in many major cancer types, including melanoma, lung, colorectal, and pancreatic cancer. There is currently no effective therapy for the treatment of RAS mutant cancers. LY3009120, a pan-RAF and RAF dimer inhibitor currently in phase I clinical trial, has been shown to inhibit cell proliferation of RAS- or BRAF-mutant tumor cells in vitro and xenograft tumor growth in vivo. An unbiased screen for compounds that synergize with LY3009120 in RAS/BRAF mutant cancers identified inhibitors of CDK4 among the top hits. In this study, we found that combined inhibition of RAF and CDK4 and 6 by LY3009120 and abemaciclib cooperatively reduced viability of tumor cells with KRAS, NRAS or BRAF mutation in vitro. In animal models, the LY3009120 and abemaciclib combination exhibited synergistic regression of tumor growth in multiple xenograft models with KRAS, NRAS, or BRAF mutation. Molecular mechanistic analysis revealed that pan-RAF inhibitor treatment suppressed the cyclin D1 upregulation which was mediated through CDK4 and CDK6 inhibition by abemaciclib, and the combination treatment cooperatively demonstrated more complete inhibition of RB phosphorylation. These results were further verified by CDK4 and CDK6 siRNA knockdown and another CDK4 and CDK6 selective inhibitor palbociclib. Importantly, the more complete phospho-RB inhibition and cyclin D1 suppression by LY3009120 and abemaciclib combinational treatment led to more significant cell cycle G0/G1 arrest and apoptosis of tumor cells. These preclinical findings suggest that the combinational inhibition of RAF and CDK4 and CDK6 signaling by LY3009120 and abemaciclib is synergistic and should be further studied compared to single agents in the treatment of cancer in patients with KRAS, NRAS or BRAF mutations.

Citation Format: Shih-Hsun Chen, Youyan Zhang, Robert D. Van Horn, Tinggui Yin, Lysiane Huber, Teresa F. Burke, Xueqian Gong, Wenjuan Wu, Shripad Bhagwat, Sean Buchanan, Richard P. Beckmann, Ramon V. Tiu, Sheng-Bin Peng. Pan-RAF inhibitor LY3009120 sensitizes RAS or BRAF mutant cancer to CDK4 and 6 inhibition by abemaciclib via superior inhibition of phospho-RB and suppression of cyclin D1. [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 282.

Oncogenic BRAF Deletions That Function as Homodimers and Are Sensitive to Inhibition by RAF Dimer Inhibitor LY3009120

We have identified previously undiscovered BRAF in-frame deletions near the αC-helix region of the kinase domain in pancreatic, lung, ovarian, and thyroid cancers. These deletions are mutually exclusive with KRAS mutations and occur in 4.21% of KRAS wild-type pancreatic cancer. siRNA knockdown in cells harboring BRAF deletions showed that the MAPK activity and cell growth are BRAF dependent. Structurally, the BRAF deletions are predicted to shorten the β3/αC-helix loop and hinder its flexibility by locking the helix in the active αC-helix-in conformation that favors dimer formation. Expression of L485-P490-deleted BRAF is able to transform NIH/3T3 cells in a BRAF dimer-dependent manner. BRAF homodimer is confirmed to be the dominant RAF dimer by proximity ligation assays in BRAF deletion cells, which are resistant to the BRAF inhibitor vemurafenib and sensitive to LY3009120, a RAF dimer inhibitor. In tumor models with BRAF deletions, LY3009120 has shown tumor growth regression, whereas vemurafenib is inactive.

SIGNIFICANCE

This study discovered oncogenic BRAF deletions with a distinct activation mechanism dependent on the BRAF dimer formation in tumor cells. LY3009120 is active against these cells and represents a potential treatment option for patients with cancer with these BRAF deletions, or other atypical BRAF mutations where BRAF functions as a dimer.

Oncogenic BRAF Deletions That Function as Homodimers and Are Sensitive to Inhibition by RAF Dimer Inhibitor LY3009120

We have identified previously undiscovered BRAF in-frame deletions near the αC-helix region of the kinase domain in pancreatic, lung, ovarian, and thyroid cancers. These deletions are mutually exclusive with KRAS mutations and occur in 4.21% of KRAS wild-type pancreatic cancer. siRNA knockdown in cells harboring BRAF deletions showed that the MAPK activity and cell growth are BRAF dependent. Structurally, the BRAF deletions are predicted to shorten the β3/αC-helix loop and hinder its flexibility by locking the helix in the active αC-helix-in conformation that favors dimer formation. Expression of L485-P490-deleted BRAF is able to transform NIH/3T3 cells in a BRAF dimer-dependent manner. BRAF homodimer is confirmed to be the dominant RAF dimer by proximity ligation assays in BRAF deletion cells, which are resistant to the BRAF inhibitor vemurafenib and sensitive to LY3009120, a RAF dimer inhibitor. In tumor models with BRAF deletions, LY3009120 has shown tumor growth regression, whereas vemurafenib is inactive.

SIGNIFICANCE

This study discovered oncogenic BRAF deletions with a distinct activation mechanism dependent on the BRAF dimer formation in tumor cells. LY3009120 is active against these cells and represents a potential treatment option for patients with cancer with these BRAF deletions, or other atypical BRAF mutations where BRAF functions as a dimer.

Abstract A24: Beta-klotho expression is associated with the antitumor activity of pan-FGFR inhibitor in human malignancies with FGF19 amplification

Fibroblast growth factor receptor 4 (FGFR4) is an attractive target in Oncology. A gene encoding fibroblast growth factor 19 (FGF19), the main ligand of FGFR4, is frequently amplified (A) and/or overexpressed (OE) in human malignancies according to The Cancer Genome Atlas (TCGA) (breast cancer 12.8% A, 0.6% OE; head and neck cancer 20.5% A, 7.1% OE; squamous cell carcinoma of the lung 11.6% A, 11.8% OE; hepatocellular carcinoma (HCC) 4.2% A, 21.1% OE; colorectal carcinoma 0% A, 15.4% OE; pancreatic carcinoma 0% A, 32.1% OE; endometrial carcinoma 0.8% A, 17.7% OE; bladder carcinoma 8.5% A, 1.9% OE). The objective of this study was to identify the hallmarks of FGFR4 pathway dependence in human tumors. LY2874455, a selective SMI with a potent activity against FGFR1, 2, 3 and 4, was tested in vitro using Cancer Cell Line Sensitivity Panel that included 539 histologically and genetically diverse tumor cell lines representing human malignancies. Cell lines that were most sensitive to LY2874455 were enriched for genetic FGFR pathway aberrations including FGF19 amplification. We therefore hypothesized that FGF19 amplification and/or overexpression might be molecular predictors of antitumor efficacy of LY2874455. We further tested LY2874455 in a panel of 14 HCC, 4 colorectal, 4 esophageal, 2 breast, 2 pancreatic and 1 head and neck carcinoma cell lines with FGF19 amplification and/or expression using a cell viability assay. Among all cell lines tested, LY2874455 activity was restricted to HCC cell lines with concurrent FGF19 amplification and expression (IC50 = 0.001-72 nM). It is known that endocrine effects of FGF19 require beta-klotho (KLB), a co-receptor whose expression is restricted to very few cell types including hepatocytes. We thus speculated that KLB expression could underlie FGFR4 pathway dependence in a subset of HCC with FGF19 amplification and/or overexpression. To corroborate this hypothesis, we employed doxycycline-inducible shRNA-mediated KLB knockdown in FGF19-amplified HCC cell lines, and demonstrated that ablated KLB expression decreased sensitivity to LY2874455 in JHH-7 (IC50 shift from 3.9 to 198 nM) and Hep3B (IC50 shift from 0.6 to 18 nM). Furthermore, in Hep3B cells, KLB knockdown was associated with a disrupted downstream signaling as exemplified by abrogated early growth response 1 (EGR1) and FBJ murine osteosarcoma viral oncogene homolog (FOS) expression upon FGF19 stimulation. These results suggest that FGF19 amplification or overexpression per se do not confer tumor cell sensitivity to FGFR blockade. Instead, FGFR4 inhibition seems to be most efficacious in FGF19-amplified tumor cells with concomitant FGF19, FGFR4 and KLB expression. This study established a mechanistic link between KLB expression and FGFR SMI efficacy in the setting of FGF19 amplification and/or overexpression and revealed a molecular profile of HCC patients that may benefit from FGFR inhibitors.

Citation Format: Amelie Forest, Sandra Nakasone, Ying Wang, Xuemei Guo, Timothy R. Mack, Genshi Zhao, Yong G. Yue, Xueqian Gong, Trent Stewart, Sean Buchanan, Christoph Reinhard, Ruslan Novosiadly. Beta-klotho expression is associated with the antitumor activity of pan-FGFR inhibitor in human malignancies with FGF19 amplification. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A24.

Inhibition of RAF Isoforms and Active Dimers by LY3009120 Leads to Anti-tumor Activities in RAS or BRAF Mutant Cancers

LY3009120 is a pan-RAF and RAF dimer inhibitor that inhibits all RAF isoforms and occupies both protomers in RAF dimers. Biochemical and cellular analyses revealed that LY3009120 inhibits ARAF, BRAF, and CRAF isoforms with similar affinity, while vemurafenib or dabrafenib have little or modest CRAF activity compared to their BRAF activities. LY3009120 induces BRAF-CRAF dimerization but inhibits the phosphorylation of downstream MEK and ERK, suggesting that it effectively inhibits the kinase activity of BRAF-CRAF heterodimers. Further analyses demonstrated that LY3009120 also inhibits various forms of RAF dimers including BRAF or CRAF homodimers. Due to these unique properties, LY3009120 demonstrates minimal paradoxical activation, inhibits MEK1/2 phosphorylation, and exhibits anti-tumor activities across multiple models carrying KRAS, NRAS, or BRAF mutation.

Abstract 2142: Novel oncogenic BRaf deletions functioning as BRaf homodimer and sensitive to inhibition by LY3009120, a pan Raf and Raf dimer inhibitor

BRAF mutations, particularly the somatic hot spot BRAF V600E mutation, were discovered as major oncogenic mutations in many cancer types. It was shown that BRAF V600E is a potent oncogene that activates the MAPK pathway and functions as a BRaf monomer. BRaf selective inhibitors, vemurafenib and dabrafenib, which are effective in inhibiting the kinase activity of BRaf monomer, have demonstrated robust anti-tumor activities in BRAF mutant xenograft models and significant clinical benefit among BRAF mutant melanoma patients. In this study, we have identified and characterized novel BRaf aberrant variants, which have in-frame deletions within or adjacent to the L485-P490 region in patient samples and/or cell lines of lung, pancreatic, and ovarian cancers. Tumor cells with these endogenous BRaf deletions are resistant to BRaf monomer inhibitor vemurafenib based on inhibition of phospho-MEK and phospho-ERK, cell proliferation, and cell cycle progression. However, these cells are sensitive to LY3009120, a pan Raf and Raf dimer inhibitor. Further analysis using siRNA showed that the MEK-ERK activity in these cells is mainly dependent on BRaf, not CRaf or ARaf. Ectopical expression of the L485-P490 deleted BRaf in mouse NIH3T3 cells is able to transform the cells and form colonies comparable to BRaf V600E mutation in three-dimensional soft agar growth. More importantly, the Raf dimer disrupting mutation BRafR509H abolished the transforming activity of the L485-P490 deleted BRaf, suggesting that this BRaf deletion functions as a dimer. Further, ectopical expression of the L485-P490 deleted BRaf promotes primarily BRaf homodimerization as revealed by proximity ligation assays (PLA). It was also confirmed by PLA that BRaf homodimer is the dominant form of Raf dimers in tumor cells harboring these BRaf deletions. In lung and pancreatic tumor xenograft models developed with tumor cells with these BRaf deletions, LY3009120 treatment demonstrated significant tumor growth inhibition and regression, whereas vemurafenib treatment showed no in vivo activity. Overall, we have identified novel oncogenic BRaf deletions that function as BRaf homodimer and are sensitive to pan Raf and Raf dimer inhibitor LY3009120.

Citation Format: Shih-Hsun Chen, Sean Buchanan, Youyan Zhang, Robert Van Horn, Tinggui Yin, Vipin Yadav, Swee Seong Wong, Lysiane Huber, James Henry, Ilaria Conti, James J. Starling, Gregory D. Plowman, Sheng-Bin Peng. Novel oncogenic BRaf deletions functioning as BRaf homodimer and sensitive to inhibition by LY3009120, a pan Raf and Raf dimer inhibitor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2142. doi:10.1158/1538-7445.AM2015-2142

Evolving toward a human-cell based and multiscale approach to drug discovery for CNS disorders

A disruptive approach to therapeutic discovery and development is required in order to significantly improve the success rate of drug discovery for central nervous system (CNS) disorders. In this review, we first assess the key factors contributing to the frequent clinical failures for novel drugs. Second, we discuss cancer translational research paradigms that addressed key issues in drug discovery and development and have resulted in delivering drugs with significantly improved outcomes for patients. Finally, we discuss two emerging technologies that could improve the success rate of CNS therapies: human induced pluripotent stem cell (hiPSC)-based studies and multiscale biology models. Coincident with advances in cellular technologies that enable the generation of hiPSCs directly from patient blood or skin cells, together with methods to differentiate these hiPSC lines into specific neural cell types relevant to neurological disease, it is also now possible to combine data from large-scale forward genetics and post-mortem global epigenetic and expression studies in order to generate novel predictive models. The application of systems biology approaches to account for the multiscale nature of different data types, from genetic to molecular and cellular to clinical, can lead to new insights into human diseases that are emergent properties of biological networks, not the result of changes to single genes. Such studies have demonstrated the heterogeneity in etiological pathways and the need for studies on model systems that are patient-derived and thereby recapitulate neurological disease pathways with higher fidelity. In the context of two common and presumably representative neurological diseases, the neurodegenerative disease Alzheimer's Disease, and the psychiatric disorder schizophrenia, we propose the need for, and exemplify the impact of, a multiscale biology approach that can integrate panomic, clinical, imaging, and literature data in order to construct predictive disease network models that can (i) elucidate subtypes of syndromic diseases, (ii) provide insights into disease networks and targets and (iii) facilitate a novel drug screening strategy using patient-derived hiPSCs to discover novel therapeutics for CNS disorders.

Identification of druggable cancer driver genes amplified across TCGA datasets

The Cancer Genome Atlas (TCGA) projects have advanced our understanding of the driver mutations, genetic backgrounds, and key pathways activated across cancer types. Analysis of TCGA datasets have mostly focused on somatic mutations and translocations, with less emphasis placed on gene amplifications. Here we describe a bioinformatics screening strategy to identify putative cancer driver genes amplified across TCGA datasets. We carried out GISTIC2 analysis of TCGA datasets spanning 16 cancer subtypes and identified 486 genes that were amplified in two or more datasets. The list was narrowed to 75 cancer-associated genes with potential "druggable" properties. The majority of the genes were localized to 14 amplicons spread across the genome. To identify potential cancer driver genes, we analyzed gene copy number and mRNA expression data from individual patient samples and identified 42 putative cancer driver genes linked to diverse oncogenic processes. Oncogenic activity was further validated by siRNA/shRNA knockdown and by referencing the Project Achilles datasets. The amplified genes represented a number of gene families, including epigenetic regulators, cell cycle-associated genes, DNA damage response/repair genes, metabolic regulators, and genes linked to the Wnt, Notch, Hedgehog, JAK/STAT, NF-KB and MAPK signaling pathways. Among the 42 putative driver genes were known driver genes, such as EGFR, ERBB2 and PIK3CA. Wild-type KRAS was amplified in several cancer types, and KRAS-amplified cancer cell lines were most sensitive to KRAS shRNA, suggesting that KRAS amplification was an independent oncogenic event. A number of MAP kinase adapters were co-amplified with their receptor tyrosine kinases, such as the FGFR adapter FRS2 and the EGFR family adapters GRB2 and GRB7. The ubiquitin-like ligase DCUN1D1 and the histone methyltransferase NSD3 were also identified as novel putative cancer driver genes. We discuss the patient tailoring implications for existing cancer drug targets and we further discuss potential novel opportunities for drug discovery efforts.