Mutant NSCLC Cell Lines Research Articles

Abstract 3852: IK-930, a paralog-selective novel TEAD-inhibitor, effectively attenuates drug-tolerant persister cell proliferation

Abstract The Hippo pathway is commonly mutated or altered in human cancers. In addition to the primary genetic driving mutations, the downstream effectors of the Hippo pathway comprising the transcriptional coactivators YAP1 and TAZ and the TEAD transcription factors can be activated upon prolonged inhibition of other oncogenic pathways such as EGFR and MAPK. We showed that combining the novel, paralog selective TEAD inhibitor, IK-930, with osimertinib or trametinib in EGFR or KRAS mutated tumors, led to enhanced apoptosis in vitro and beneficial antitumor activity in vivo. Experimental models demonstrated that upon inhibition of EGFR with osimertinib, a subpopulation of drug tolerant cells defined as ‘persisters’ can survive treatment allowing for the accumulation of additional genetic and epigenetic alterations. These alterations in the persister cells can give rise to resistant tumors and cancer relapse. Previous studies have implicated YAP/TEAD signaling in the emergence and survival of the persister cells. To investigate the role of YAP/TEAD signaling in persister cell emergence, EGFR and KRAS mutant NSCLC cell lines were engineered to express a TEAD luciferase reporter. Treatment with EGFR or MEK inhibitors, at concentrations that do not elicit significant cell death, induced TEAD-mediated transcription after several days of treatment, indicative of an adaptive response to chronic target inhibition. Concurrent treatment with the TEAD inhibitor, IK-930, abolished TEAD-mediated transcription. Using time lapse microscopy, the cell cycle and proliferation of EGFR mutant cultured cells, engineered to express a fluorescence-based cell-cycle indicator (FUCCI), were quantified when treated with osimertinib alone or combined with IK-930. Treatment with osimertinib led to a rapid induction of cell death. However, after several days, a drug tolerant population emerged and reentered the cell cycle even with chronic osimertinib treatment. Interestingly, the emergence of these persister cells coincided with maximum TEAD activity. Concurrent addition of IK-930, as well as addition of IK-930 after the emergence of the osimertinib-tolerant persister cells, attenuated cell proliferation and expansion, demonstrating the potential for IK-930 to prevent resistance to EGFR inhibitors and even reverse the effect when given after resistance has already emerged. Current efforts are focused on the characterization of the persister population and on evaluating the role of YAP/TEAD signaling in resistance to other targeted therapies. Citation Format: Daniel Hidalgo, Marta Sanchez-Martin, Mihir Rajurkar, George Punkosdy, Jeffrey Ecsedy, Lan Xu. IK-930, a paralog-selective novel TEAD-inhibitor, effectively attenuates drug-tolerant persister cell proliferation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3852.

54 (PB044) - Non-clinical identification and characterization of KRAS G12D inhibitors

KRAS G12D is the most prevalent KRAS oncogenic mutant and occurs frequently in pancreatic ductal adenocarcinoma (PDAC), colorectal adenocarcinoma (CRC), and non-small cell lung cancer (NSCLC; 37%, 12% and 4%, respectively). KRAS G12D cycles between inactive (GDP) and active (GTP) states to regulate the RAS/MAPK pathway. Although the rate of intrinsic and GAP (GTPase activating protein) mediated hydrolysis is significantly slower in KRAS G12D than in KRAS wild-type (KRAS WT), we were able to build upon success of targeting the GDP state of KRAS G12C and designed novel KRAS G12D lead compounds with promising in vitro and in vivo activity. Our KRAS G12D inhibitors preferentially bind to KRAS G12D GDP as indicated by differential scanning fluorimetry (DSF), block KRAS G12D SOS1-mediated nucleotide exchange, and inhibit KRAS G12D binding to the RAS binding domain of C-RAF (RAF-RBD) with single digit nanomolar potency. Our leads effectively inhibit ERK1/2 phosphorylation (pERK) in AsPC-1 PDAC cells and inhibit cell proliferation in 3-dimensional Cell-Titer Glo assays in a panel of KRAS G12D mutant PDAC, CRC, and NSCLC cell lines. This in vivo activity translates in vitro where robust pharmacodynamic modulation in the PDAC AsPC-1 CDX model was induced. Tumor growth inhibition studies in this model revealed robust dose-dependent tumor growth inhibition and tumor regression in the absence of overt toxicity. In summary, we have identified potent and selective KRAS G12D inhibitors with robust dose-dependent tumor growth inhibition and regression activity in a PDAC CDX model. Lead optimization is ongoing with the aim of identifying a development candidate. No conflict of interest.

Abstract 2669: ERAS-007 (ERK inhibitor) + ERAS-601 (SHP2 inhibitor) exhibit nonclinical combination activity across KRAS mutated NSCLC, CRC, and PDAC tumor models

Abstract KRAS mutations occur in about 25% of all cancers and promote oncogenesis via constitutive activation of the RAS/MAPK pathway. Targeting KRAS mutant tumors by inhibiting individual nodes in the RAS/MAPK pathway, including SHP2, SOS1, KRAS, RAF, MEK, and ERK, has shown early clinical activity, but the rapid emergence of resistance limits the benefit of monotherapy. Resistance is often mediated by reactivation of RAS/MAPK pathway signaling, which can occur by increased activation of upstream of the RAS/MAPK pathway (e.g., EGFR activation) and/or activation of RAS/MAPK pathway nodes (e.g., oncogenic BRAF and MEK mutations). Inhibiting both upstream and downstream RAS/MAPK pathway nodes has the potential to more robustly prevent reactivation relative to inhibition of a single node alone. We are currently exploring the combination of an inhibitor of an upstream node, SHP2, with ERAS-601 and the terminal downstream node, ERK1/2, with ERAS-007 (our first “MAPKlamp”) in nonclinical models. We evaluated this MAPKlamp in NSCLC, CRC, and pancreatic tumor models that harbored KRAS mutations in vitro and in vivo. In 14-day clonogenic assays in KRAS mutant NSCLC, CRC, and PDAC cell lines, this MAPKlamp inhibited colony growth more potently than ERAS-601 or ERAS-007 alone. In KRAS mutant CDX and PDX models, this MAPKlamp’s in vitro activity was observed in vivo where it achieved superior tumor growth inhibition and tumor regression relative to ERAS-601 and ERAS-007 monotherapy. This MAPKlamp showed in vitro and in vivo combination activity in KRAS mutant tumors, and these results support its clinical evaluation in RAS/MAPK pathway-driven tumors. Citation Format: Leenus Martin, Erin D. Lew, Roopal Patel, Joanne Oh, Jingchuan Zhang, Robin Nevarez, Taylor Congdon, Wei Lin, Les Brail, Robert Shoemaker. ERAS-007 (ERK inhibitor) + ERAS-601 (SHP2 inhibitor) exhibit nonclinical combination activity across KRAS mutated NSCLC, CRC, and PDAC tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2669.

Abstract P216: IK-930 mediated TEAD inhibition decreases and delays tumor growth and enhances targeted apoptosis in lung and colon cancer xenografts when combined with MEK or EGFR inhibitors

Abstract The Hippo signaling cascade is an important pathway that plays a role in controlling cell proliferation and limiting apoptosis, but when dysregulated can contribute to cancer initiation, progression, and therapeutic resistance. The TEAD family of transcription factors, in conjunction with YAP1 or WWTR1/TAZ, are regulated by Hippo pathway signaling and modulate cell growth and proliferation. IK-930 inhibits the growth of TEAD-dependent human cancer xenografts. By exploiting synthetic lethality, the IK-930 single agent activity in TEAD-dependent cancers could expand to other indications upon inhibition of certain oncogenic pathways. Literature indicates that activation of TEAD-dependent transcription by other oncogenes such as mutant EGFR or KRAS mediates resistance to multiple targeted therapies. Additionally, genetic loss of YAP1 leads to increased apoptosis in osimertinib and trametinib treated mutant EGFR NSCLC cell lines (Kurppa, 2020). Here, we present preclinical data that support the use of IK-930 combination therapies to enhance anti-tumor impact of EGFR and MEK blockade in mutant EGFR NSCLC, or with MEK inhibition in several BRAF and KRAS mutant cancers. In these studies, EGFR and MEK1/2 were inhibited and IK-930 used to enhance anti-tumor activity in EGFR-mutant NSCLC cells. These NSCLC cell lines that are largely insensitive to osimertinib and/or trametinib, were observed to have a marked increase in apoptosis in vitro when treated with the combination of osimertinib, trametinib, and IK-930. We also observed increased nuclear accumulation of YAP1 after treatment of NSCLC cells with osimertinib alone, or osimertinib and trametinib and upregulation of TEAD-dependent transcription. In NSCLC xenografts, the combination of osimertinib and IK-930 prevented tumor growth and the triple combination of osimertinib, IK-930, and trametinib drove complete tumor regression and demonstrated greater efficacy than any single agent or double combination. A second set of studies tested the synthetic lethality effect of IK-930 and MEK inhibition in RAF- and RAS-mutant tumors. The combination of TEAD inhibition with MEK inhibition enhanced apoptosis in several KRAS-mutant NSCLC, PDAC, CRC KRAS-mutant cell lines and BRAF-mutant melanoma. The combination of trametinib and IK-930 prevented tumor growth in these xenografts, where either single agent had either modest or little activity. In summary, the Hippo pathway has been implicated in multiple tumor types, including those with resistance mechanisms to EGFR and MEK blockade. IK-930-mediated TEAD inhibition has been investigated to suppress the bypass pathway activation mechanism to the targeted therapies. These data demonstrated the potential to further expand single agent patient benefit by combining IK-930 with MEK and/or EGFR inhibition in a wide variety of cancer indications, including mutant EGFR-driven NSCLC and mutant KRAS colon, lung, and pancreatic cancers. Taken together, these data are informing the clinical development plan and combination strategy for IK-930, a novel TEAD inhibitor. Citation Format: Benjamin Amidon, Hyejin Frosch, Sakeena Syed, Jill Cavanaugh, Chelsea Turcotte, Katie O'Callaghan, Prabitha Natarajan, Jeffrey Ecsedy, Karen McGovern, Alfredo Castro. IK-930 mediated TEAD inhibition decreases and delays tumor growth and enhances targeted apoptosis in lung and colon cancer xenografts when combined with MEK or EGFR inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P216.

Abstract P256: Pan-ErbB inhibition enhances activity of KRASG12C inhibitors in preclinical models of KRASG12C mutant cancers

Abstract Sotorasib (AMG 510) is the first KRAS inhibitor to be FDA-approved for the treatment of KRASG12C mutant lung adenocarcinomas which comprise ~42% of KRAS mutations in lung adenocarcinomas. Preclinical studies have shown that within hours of KRASG12C inhibition, synthesis of new KRASG12C protein and increased KRAS signaling was observed, leading to enhanced tumor cell growth and survival. This appeared to be due, at least in part, to a feeback loop leading to activation of EGFR signaling but the role of other ErbB family members including ErbB2 (HER2), ErbB3 (HER3), and ErbB4 (HER4) has not been fully evaluated. We hypothesize that short-term adaptation to KRAS inhibition is driven by multiple ErbB family members, and that the combination of pan-ErbB inhibitors with KRASG12C inhibitors could enhance KRASG12C inhibitor activity and prolong survival in preclinical models harboring KRASG12C mutations to a greater extent than more specific EGFR inhibitors. To investigate the role of different ErbB family members in this feedback signaling, we evaluated the impact of an EGFR specific inhibitor, erlotinib, an EGFR/HER2 inhibitor, afatinib, or pan-ErbB inhibitor (EGFR/HER2/3/4), poziotinib on anti-tumor activity of KRASG12C inhibitors in KRASG12C mutant NSCLC cell lines. We initially tested the different inhibitors in combination with sotorasib and adagrasib (MRTX849) and calculated the BLISS index (BI) for each drug pair matrix, using SynergyFinder. We found that when combined with either sotorasib or adagrasib, poziotinib had a synergistic effect (BI>10) in H23 (BI: 17, p=0.01), HCC44 (BI: 11, p=0.04), and H1792 (BI: 13, p=0.01) and an additive effect (BI= -10–10) in H2122 (BI: 2.8). Afatinib and erlotinib were additive in H23 (BI: 9.2 & 9.4), HCC44 (BI:8.8 & 7.9), H2122 (BI: -4.5 & -3.3) and H1792 (BI: 6.6 & 3.3). Poziotinib yielded a higher BI across all four cell lines compared to afatinib (p<0.0001) or erlotinib (p=0.0004). To determine if poziotinib prevented upregulation of ErbB-signaling after treatment with KRASG12C inhibitors, we treated KRASG12C mutant cell lines (NSCLC: H23 and Bladder Cancer: UM-UC-3) with KRASG12C inhibitors, sotorasib or adagrasib, for four hours and found by Western blotting that phosphorylated EGFR, HER2, HER3, and HER4 were increased after treatment. The addition of 10 nM poziotinib prevented the upregulation of phosphorylated EGFR, HER2, HER3, and HER4 in both cell lines. Together these data demonstrate that inhibition of EGFR, HER2, HER3, and HER4 signaling by the pan-ErbB inhibitor poziotinib resulted in greater synergy with KRASG12C inhibitors than EGFR or EGFR/HER2 inhibitors and highlight the potential importance of HER3 and HER4, in addition to EGFR and HER2, in feedback signaling after KRAS G12C inhibition. Additional studies of pan-ErbB and ErbB-specific inhibitors with KRASG12C inhibitors are warranted to determine tolerability and optimal dosing to prolong survival in KRAS mutant cancers. Citation Format: Jacqulyne P. Robichaux, Ana Galan-Cobo, Ried T. Powell, Kelly A. Gale, Jun He, Fahao Zhang, Monique B. Nilsson, Xiang Zhang, Mary M. Sobieski, Nghi Nguyen, Stephan C. Clifford, John V. Heymach. Pan-ErbB inhibition enhances activity of KRASG12C inhibitors in preclinical models of KRASG12C mutant cancers [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P256.

Inhibition of ACK1 delays and overcomes acquired resistance of EGFR mutant NSCLC cells to the third generation EGFR inhibitor, osimertinib

ObjectivesThe emergence of acquired resistance to the third generation EGFR inhibitor, osimertinib (AZD9291 or TAGRISSO™), is an unavoidable huge clinical challenge. The involvement of ACK1, a non-receptor tyrosine kinase with an oncogenic function, in regulating cell response to osimertinib has not been investigated and thus is the focus of this study. Material and MethodsDrug effects on cell growth were evaluated by measuring cell numbers and colony formation. Apoptosis was monitored with flow cytometry for annexin V-positive cells and Western blotting for protein cleavage. Intracellular protein and mRNA alterations were detected with Western blotting and qRT-PCR, respectively. Drug effects on delaying osimertinib acquired resistance were determined using colony formation in vitro and xenografts in nude mice in vivo, respectively. Cell senescence was assayed by β-galactosidase staining. ResultsInhibition of ACK1 with the novel ACK1 inhibitor, (R)-9b synergized with osimertinib in inhibiting the growth of EGFR mutant NSCLC cell lines. Similar results were also generated with ACK1 gene knockdown. The combination of osimertinib and (R)-9b enhanced induction of apoptosis. In both in vitro and in vivo long-term resistance delay assays, the combination of (R)-9b and osimertinib clearly delayed the emergence of osimertinib-resistance. Further, the (R)-9b and osimertinib combination was also effective in inhibiting the growth of EGFR mutant NSCLC cell lines with acquired resistance to osimertinib, which possess elevated levels of ACK1, and the growth of osimertinib-resistant tumors in vivo. In some resistant cell lines, the combinations induced senescence in addition to induction of apoptosis. ConclusionsThese novel findings suggest that ACK1 inhibition might be a potential and innovative strategy for delaying and overcoming osimertinb acquired resistance.

Abstract 4384: Quantitative assessment of drug combination effects in NSCLC cell lines through network-based analysis of functional protein activity

Abstract Non-small cell lung cancer (NSCLC) is the most prevalent type of lung cancer, which is the leading cause of cancer death worldwide. The KRAS oncogene is one of the most common driver mutations in NSCLC patients but, despite that, there are no approved targeted therapies for tumors harboring this mutation. The MEK inhibitor Selumetinib (SE) turned out to be an ineffective drug against KRAS mutated lung cancer. Since combination therapy has shown to be beneficial in many tumors, we wanted to investigate the combination of MEK inhibition with other targeted therapies. Thus, we measured the proteomic response of KRAS mutant (MUT) and wild-type (WT) NSCLC cell lines (CLs) to the combination of SE with Everolimus (EV), an mTOR inhibitor, and Tamoxifen (TA), an Estrogen inhibitor. The expression level of 183 proteins was measured through Reverse Phase Protein Array (RPPA) in eight NSCLC CLs treated with SE, SE plus EV and SE plus TA at 6 time points: 5 minutes (min), 30 min, 1, 2, 6 and 24 hours (h). As control, measures were taken in baseline CLs and in CLs with only dimethyl sulfoxide. To study the drug combination effects, we applied a computational workflow centered on two algorithms initially developed for gene expression data. We analyzed the CLs with the Algorithm for the Reconstruction of Accurate Cellular Networks (ARACNe) to reconstruct a context specific signaling network of 2635 interactions between 73 kinases and 6 phosphatases and their substrates. Then, we analyzed the obtained network with the Virtual Inference of Protein activity by Enriched Regulon analysis (VIPER) algorithm to assess the mechanism of action of the drug compounds and how they dysregulate the activity of kinases and phosphatases over time. With respect to SE alone and apart from the drug targets, VIPER predicted the following proteins as highly inhibited over time across all CLs : 1) Aurora and LKB1 in SE+EV, 2) AMPK, c-RAF and ATR in SE+TA, 3) mTOR, p90, p70S6K, c-MET and GSK-3 in both combinations. On the other hand, Akt, ETK, Axl and FAK are all activated in SE+EV as well as PP2A, SGK1 and IGF1R in SE+TA, after 1h from the treatment. By running Gene Set Enrichment Analysis on the VIPER output against the primary drug target pathways, we found that mTOR signaling pathway exhibits a quite different evolution between KRAS MUT and WT CLs. On the other hand, other pathways revealed mechanisms of response that are CL specific. For instance, the main MEK pathways in H1734 CL (KRAS MUT) treated with SE+TA are all insensitive to the drug compounds. In conclusion, this computational approach successfully predicted protein-protein interactions and elucidated both proteomic mechanisms of drug combinations and CL specific dependencies. It allows to develop effective predictive and quantitative models reproducing each CL behavior, in order to realize the fullest potential of a targeted therapeutic approach. Citation Format: Chiara Antonini, George Rosenberger, Fortunato Bianconi, Lorenzo Tomassoni, Vienna Ludovini, Sara Baglivo, Sara Calandrini, Elisa Baldelli, Mariaelena Pierobon, Emanuel F. Petricoin, Andrea Califano. Quantitative assessment of drug combination effects in NSCLC cell lines through network-based analysis of functional protein activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4384.

Interferon gamma resistance in setting of LKB1 loss: Phenotypic characterization and investigation of mechanism.

e21015 Background: NSCLC Patients with LKB1 loss respond poorly to immune checkpoint inhibitors (ICI). Determining mechanisms of the underlying immune resistance and strategies to overcome it are urgent and unmet clinical needs. Methods: We re-expressed WT LKB1 into LKB1 mutant NSCLC cell lines and measured effects on immune associated phenotypes in vitro. Specifically, we evaluated response to exogenous interferon gamma (IFNG), as well T-cell mediated cytotoxicity using a T-cell co-culture assay. To identify IFNG signaling changes influenced by LKB1, we evaluated the differential effects of LKB1 on IFNG induced gene expression using RNAseq. Finally, we performed a whole genome loss of function screen using CRISPR-Cas9 library (TKOv3) to identify genes and pathways that modify susceptibility to IFNG in the LKB1 mutant and LKB1 WT state in the A549 cell line. Results: Across multiple LKB1 mutant cell lines, restoration of WT LKB1 enhanced anti-proliferative effects of IFNG in vitro. Furthermore, WT LKB1 enhanced T-cell mediated cytotoxicity in T-cell co-culture assays using anti-NY-ESO TCR and expression of NY-ESO antigen into an HLA matched NSCLC cell line, H2023 (17% vs 40% cell death; P < 0.01). IFNG treatment induced expression of a core set of interferon-driven genes in both the mutant and LKB1 WT state. However, differentially expressed gene classes included downregulation of proliferation-associated genes in the LKB1 WT state, as well as upregulation of ferroptosis genes, and enhanced IFNG-driven expression of immune evasion genes including PDL1, PDL2, TRAF1, and IDO1 in the LKB1 WT state. PDL1 expression was assessed by flow cytometry and found to be upregulated upon expression of LKB1. Our functional genomics screen identified genes whose inhibition enhanced IFNG susceptibility in the A549 mutant state, and genes whose inhibition restored IFNG resistance in the A549 LKB1 WT state. Preliminary analysis identifies candidate signaling and metabolic pathways that appear to confer IFNG sensitivity in the mutant state without significant effect on IFNG sensitivity after LKB1 add-back. These include modifiers of the Hippo/YAP pathway as well as modifiers of ferroptosis, which will form the basis for further mechanistic experiments. Conclusions: ICI resistance caused by LKB1 loss is associated with insensitivity to IFNG, and can be modified in vitro by re-expression of WT LKB1. An integrated approach to evaluate modifiers of IFNG effects identifies resistance mechanisms that may be potential therapeutic targets.

Phase 2 study of the focal adhesion kinase inhibitor defactinib (VS-6063) in previously treated advanced KRAS mutant non-small cell lung cancer

ObjectivesKRAS mutations, which occur in approximately 25% of lung adenocarcinoma cases, represent a major unmet clinical need in thoracic oncology. Preclinical studies have demonstrated that KRAS mutant NSCLC cell lines and xenografts with additional alterations in either TP53 or CDKN2A (INK4A/ARF) loci are sensitive to focal adhesion kinase (FAK) inhibition. Defactinib (VS-6063) is a selective oral inhibitor of FAK. Materials and methodsPatients with previously treated advanced KRAS mutant NSCLC were prospectively assigned to one of four molecularly defined cohorts based on the presence or absence of TP53 or CDKN2A alterations and received treatment with defactinib 400 mg orally BID until disease progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS) at 12 weeks. ResultsFifty-five patients were enrolled. Mean age was 62 years; 51% were female. The median number of prior lines of therapy was 4 (range 1–8). Fifteen (28%) patients met the 12-week PFS endpoint, with one patient achieving a partial response. Median PFS was 45 days. Clinical efficacy did not correlate with TP53 or CDKN2A status. The most common adverse events were fatigue, gastrointestinal, and increased bilirubin, and were generally grade 1 or 2 in severity. ConclusionIn heavily pretreated patients with KRAS mutant NSCLC, defactinib monotherapy demonstrated modest clinical activity. Efficacy was not associated with TP53 and CDKN2A status. Defactinib was generally well tolerated.

Abstract 4394: Molecular interplay between Tank-binding kinase (TBK1) and Yes-associated protein (YAP1) in KRAS mutant NSCLC

Abstract Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality in the United States. Lung adenocarcinomas are highly correlated with smoking and are characterized by mutations in KRAS, EGFR, BRAF and other oncogenes. KRAS mutations are widespread in adenocarcinomas among smokers and known to be a key player in various downstream signaling pathways contributing to the tumorigenesis. Recently, a non-canonical IκB kinase, Tank Binding Kinase 1 (TBK1), has been found to contribute in KRAS mutant cancers. TBK1 has well documented functions in immune response, cell survival and in mitosis. While it has been suggested that TBK1-mediated regulation of Akt signaling might facilitate oncogenesis, the molecular mechanisms underlying TBK1 function downstream of KRAS is not fully elucidated. Yes associated protein 1 (YAP1) is an oncogenic component of the Hippo signaling cascade which could promote KRAS mediated oncogenesis and could substitute for the loss of Kras in mouse models of pancreatic cancer. In our present study, we demonstrate a unique and novel interplay between TBK1 and the oncogenic Hippo effector molecule, YAP1. YAP1 and its paralog, TAZ are known transcriptional co-activators that function to maintain organ size during development and is often activated in cancers. We find that TBK1 could physically interact with YAP1 and phosphorylate it at T110, T114, S128 and S131 residues in vitro. Knocking down (KD) or knock out (KO) of TBK1 resulted in a significant elevation of YAP1 expression at the protein level; surprisingly, without any effect at the mRNA level. Interestingly, the upregulation of YAP1 upon depletion of TBK1 was restricted to KRAS mutant NSCLC cell-lines and not in EGFR mutant cell lines. This elevation of YAP1 upon TBK1 KD was mainly observed in the nucleus; notably, there were only minimal changes in the levels of MST and LATS, raising the possibility that these changes occur independent of the classic hippo signaling pathway. Treatment with cycloheximide, an inhibitor of protein-translation, could not diminish the elevated level of YAP1 protein in the TBK1 depleted cells, indicating that the increased YAP1 level is due to enhanced protein stability, probably as a result of post-translational modification(s). Depletion of TBK1 also resulted in the induction of EMT-like features, promoting cell-migration in scratch assays and elevated the proportion of stem-like side-population cells, probably in a YAP1-dependent manner. An unbiased RNA-Seq analysis in A549 and H460 cells indicated that MAP kinase (MAPK) pathway is activated upon TBK1 KD, which might also be involved in the YAP1 protein regulation. Our recent experiments further support this argument. The in-depth molecular mechanism(s) by which TBK1 regulates YAP1 in KRAS mutant cells are under investigation, and we hypothesize that this regulatory event contributes to KRAS mediated oncogenesis in NSCLC. Citation Format: Biswarup Saha, Neha Jaiswal, Namrata Bora-Singhal, Srikumar Chellappan. Molecular interplay between Tank-binding kinase (TBK1) and Yes-associated protein (YAP1) in KRAS mutant 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 4394.

Abstract 1856: Combination of the novel ERK inhibitor AZD0364 with the MEK inhibitor selumetinib significantly enhances antitumor activity in KRAS mutant tumor models

Abstract The RAS/MAPK pathway is a major driver in oncogenesis and is dysregulated in approximately 30% of human cancers, primarily by mutations in BRAF or RAS genes. While BRAF and MEK inhibitors improve BRAF mutant melanoma patient outcomes, single-agent pathway inhibitors have demonstrated limited clinical benefit. Therefore, combined inhibition of multiple nodes within the RAS/MAPK pathway may be necessary to effectively suppress pathway signaling and achieve meaningful clinical benefit, specifically in patients with KRAS mutant tumors. AZD0364 is a potent and highly selective inhibitor of ERK1 and ERK2. AZD0364 exhibits high cellular potency against a direct substrate (e.g., inhibition of phosphorylation of p90RSK in BRAF mutant A375 cells, IC50 = 6 nM) and is highly (10/329 kinases tested are inhibited at >50% at 1 µM). In an unbiased cell proliferation screen of 750 tumor cell lines, >50% of cell lines that are sensitive to AZD0364 have RAS/MAPK pathway genetic alterations such as BRAF, NRAS or KRAS mutations. In a subset of KRAS mutant NSCLC cell lines, combined treatment of AZD0364 and selumetinib (AZD6244, ARRY-142886) is highly synergistic. This combination results in deeper and more durable suppression of the RAS/MAPK pathway that is not achievable with single-agent treatment, as assessed by phospho-p90RSK, change in transcriptional signatures and induction of apoptotic biomarkers. The AZD0364 and selumetinib combination also significantly suppresses RAS/MAPK pathway output and tumor growth in vivo to a greater extent than achievable with either agent given as a monotherapy. This combination is well tolerated in vivo and delivers 65% tumor regression in the NCI H358 KRAS mutant NSCLC xenograft model. This combination also results in significant tumor regressions in both A549 and HCT116 KRAS mutant xenografts. These data demonstrate that combined AZD0364 and selumetinib is well tolerated, effectively suppresses RAS/MAPK pathway signalling and delivers durable regressions in preclinical models. The combination of ERK and MEK inhibition represents a viable clinical approach to target KRAS mutant tumors. Citation Format: Vikki Flemington, Iain Simpson, Jason Breed, Emma Davies, Francis Gibbons, Phillip Hopcroft, Nicola Lyndsay, Christopher Jones, Clifford Jones, David Robinson, Claire Rooney, Karen Roberts, Linda Sandin, Richard Ward, Pei Zhang, Elizabeth Pease. Combination of the novel ERK inhibitor AZD0364 with the MEK inhibitor selumetinib significantly enhances antitumor activity in KRAS mutant tumor 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 1856.

Abstract 485: Modulation of microRNA expression in EGFR-tyrosine kinase inhibitor-resistant non-small cell lung cancer cell lines

Abstract Objectives: Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are now standard of care in lung cancer patients with EGFR mutation. Invariably, these patients develop resistance and require treatment with another EGFR-TKI or chemotherapy. The gatekeeper mutation T790M is responsible for about 50% of resistance. Other mechanisms may also confer resistance in these patients. High expression of microRNA-10b (miRNA-10b) is associated with worse prognosis in resected lung cancer patients with EGFR mutation. Both miRNA-27a and -27b are associated with increased expression of c-met, which is a potential mechanism of resistance to EGFR-TKI. The goal of this study is to determine the optimal treatment and miRNA characteristic of EGFR mutation lung cancer cells resistant to EGFR-TKI. We hypothesized that miRNA-10b, -27a and -27b modulated Erlotinib (ERL) resistance by different EGFR-TKIs and chemotherapeutic agents in EGFR mutant NSCLC cell lines. Materials and Methods: Lung cancer cell lines with EGFR mutation HCC827 and HCC4006 resistant to ERL were generated. ERL-resistant cells were then treated with 10 nM afatinib (Afa), 0.5 mg/mL pemetrexed (Pem), and combination of 10 nM Afa/0.5mg/mL Pem for 72h. The cells were harvested and microRNA assay was performed by real-time PCR. NCI-H460 cell line without EGFR mutation was used as control. Results: We observed increased expression of miRNA-10b, miRNA-27a and miRNA-27b in ERL-resistant HCC4006 compared to control cells NCI-H460. There was an upregulation of miRNA-27a and -27b but not of miRNA-10b in ERL-resistant HCC827. Treatment of ERL-resistant cells with Afa, Pem, and combined treatment changed the expression of miRNA-10b, miRNA-27a and miRNA-27b. These miRNAs were downregulated by 2nd-generation EGFR-TKI therapy alone or in combination with Pem. Different treatments had different effects on these miRNAs. There might be differences in miRNA regulation in different cell lines when treated with EGFR-TKI or chemotherapy. Our results suggest that microRNA may be used as targets for developing novel approach to treating patients with EGFR-TKI resistance. Conclusion: This study may have implications in the management of patients resistant to EGFR TKI. MicroRNA analysis showed upregulation of several microRNAs that should be confirmed in clinical setting. Citation Format: Inamul Haque, Hannah Motes, Mukut Sharma, Emma Borrego-Diaz Reyes, Andrew K. Godwin, Chao H. Huang. Modulation of microRNA expression in EGFR-tyrosine kinase inhibitor-resistant non-small cell lung 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 485.

PO-019 PTPN11 is a therapeutic target in KRAS mutant lung cancer

IntroductionNon-Small-Cell Lung Cancer (NSCLC) accounts for approximately 85% of lung cancers, and mutations in the KRAS oncogene represent the most common driving event (Molina et al., Mayo Clin Proc 2008). So far, inhibition of the oncoprotein itself has proven difficult, and attempts to target downstream effectors have been hampered by the activation of compensatory resistance mechanisms (Bernards et al., Cell 2012). Notably, while MEK inhibition initially leads to ERK inactivation, P-ERK levels are quickly restored thanks to the upregulation of multiple growth factors receptors (Sun et al., Cell Reports 2014). Here we explored the possibility of targeting PTPN11 as a key mediator of receptor tyrosine kinase signalling in order to overcome intrinsic resistance to MEK inhibition.Material and methodsUsing a panel of 6 KRAS mutant NSCLC cell lines, we studied the biochemical and cell proliferation effect of combining the PTPN11 inhibitor SHP099 (Chen et al., Nature 2016) with the MEK inhibitor AZD6244. We confirmed our findings in CRISPR-based PTPN11 knockout clones of H2122 and H1944 cells. Importantly, we studied the effect of SHP099 in vivo in xenograft and PDX models, as well as in KRASLSLG12D p53fl/fl genetically engineered mouse model of NSCLC. To gain mechanistic insights into the effect of PTPN11 inhibition on mutant RAS activity, we used a panel of isogenic Rasless murine embryonic fibroblasts (Esposito et al., Semin Cancer Biol. 2018; NCI RAS Initiative) expressing human wild-type or mutant (G13D, G12C, G12D, G12V or Q61R) KRAS genes.Results and discussionsOur data show that depletion or inhibition of PTPN11 in KRAS mutant NSCLC cell lines invariably induces sensitivity to AZD6244. Surprisingly, in vivo models suggest that targeting PTPN11 is by itself sufficient to impair tumour growth, mainly due decreased RAS-GTP loading and induction of cellular senescence under growth factor-limiting conditions. Of note, our data suggest a correlation between the residual GTP hydrolysis capacity of the distinct KRAS mutants and their responsiveness to upstream regulators like PTPN11.ConclusionWhile in the past efforts have been focused on targeting KRAS downstream effectors, our data suggest that inhibiting upstream mediators like PTPN11 could be effective either alone or in combination with downstream inhibition. Our results suggest that targeting PTPN11 could be of clinical utility especially for tumours driven by KRAS mutants with high residual GTP hydrolysis capacity.

58P Co-treatment of trametinib (MEK inhibitor) with TPX-0005 (Src/FAK/JAK2 inhibitor) synergistic in KRAS mutant NSCLC cell lines and CDCP1 acts as a biomarker in KRAS mutant patients (p)

58P Co-treatment of trametinib (MEK inhibitor) with TPX-0005 (Src/FAK/JAK2 inhibitor) synergistic in KRAS mutant NSCLC cell lines and CDCP1 acts as a biomarker in KRAS mutant patients (p)

PUB021 SLK Causes Resistance to EGFR-TKI in Lung Cancer

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as gefitinib and dacomitinib are effective for non-small cell lung cancer with activating EGFR mutations. However, relapse typically occurs after an average of 6-12 months of continuous treatment. Although some mechanism(s) of resistance have been identified, approximately 30% of acquired resistance cases remain unknown. Targeted therapies that inhibit EGFR tyrosine kinase activity (EGFR-TKI, Gefitinib) are of particular interest in lung adenocarcinomas with activating mutation of EGFR. However, all patients will escape after several months of treatment and ultimately develop progressive disease. A better understanding of the molecular mechanisms underlying resistance to EGFR-TKIs is a critical challenge as it can help design new drugs and therapeutic strategies to overcome resistance. The aim of this study was to explore additional mechanisms of EGFR-TKI resistance in lung tumors. We generated resistant clones of the sensitive EGFR exon 19 mutant NSCLC cell lines PC9 and HCC827 by exposing them to increasing concentrations of gefitinib or dacomitinib for several months. We identified a specific deregulation of SLK in resistant clones and unraveled a SRSF2/SLK pathway as a new mechanism of lung tumor progression following gefitinib treatment. Generation of Gefitinib and Dacomitinib resistant PC9 and HCC827 clones Cell growth assay, Apoptosis Western blotting Small interfering RNA (siRNA) transfection, RNA extraction and RT/qPCR analysis Indirect Immunofluorescence Statistical Analysis. Some resistant clones had absence of known mechanisms of resistance including the EGFRT790M mutation, MET gene amplification and Small-cell lung cancer histology but exhibited a lower growth kinetic compared sensitive cells. Focusing on these clones we found that some of them had undergone Epithelial to Mesenchymal Transition (EMT). In one clone with EMT, overexpression of a truncated SLK protein was detected. Overexpression of normal sized SLK protein was observed in the others independently of EMT status. Neutralization of the splicing factor SRSF2 sensitized resistant cells to gefitinib-induced apoptosis and strongly inhibited SLK expression. SLK: a potential target of SRSF2 These results demonstrated for the first time that a SRSF2-dependent pathway is an important determinant of acquired resistance of lung tumors to EGFR-TKI Collectively these data highlighted the SRSF2/SLK module as a new component of EGFR signaling network and strongly suggested that activation of a survival SRSF2/SLK pathway is a new mechanism of lung tumor progression following gefitinib treatment.

Retraction: EGFR-Mediated Reactivation of MAPK Signaling Induces Acquired Resistance to GSK2118436 in BRAF V600E-Mutant NSCLC Cell Lines.

Retraction: EGFR-Mediated Reactivation of MAPK Signaling Induces Acquired Resistance to GSK2118436 in BRAF V600E-Mutant NSCLC Cell Lines.

12P - Reversion of mesenchymal behaviour by AZD9291 (osimertinib) in EGFR mutant NSCLC cell lines resistant to first generation EGFR tyrosine kinase inhibitors

12P - Reversion of mesenchymal behaviour by AZD9291 (osimertinib) in EGFR mutant NSCLC cell lines resistant to first generation EGFR tyrosine kinase inhibitors

Abstract 4814: miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and next generation EGFR tyrosine kinase inhibitors (TKIs) in NSCLC

Abstract Background: miRNAs play a critical role in regulating key biological processes by modulating the expression of up to several hundred genes across multiple cellular pathways. miR-34a, one of the most widely studied miRNAs, is lost or expressed at reduced levels in many tumors, and normally functions as a natural tumor suppressor by down-regulating expression of >30 different oncogenes, as well as genes involved in tumor immune evasion, including PD-L1. MRX34 is a potential first-in-class liposome-encapsulated miR-34a mimic in Phase 1 study (NCT01829971) as monotherapy in patients with advanced malignancies. The ability of miR-34a to regulate the expression of key oncogenes across multiple oncogenic pathways makes MRX34 a rational candidate to combine with other anticancer therapies which are frequently subject to primary and acquired resistance in the clinic. Previous studies showed that miR-34a greatly sensitizes both EGFR wild-type and mutant NSCLC cell lines, as well as hepatocellular carcinoma cell lines, to the first generation EGFR TKI erlotinib. Here we report research combining miR-34a and the next generation EGFR TKIs afatinib (Gilotrif®) and rociletinib (CO-1686) in NSCLC cell lines. Methods: Combination studies using single-drug ratios (∼IC50 ratio of miR-34a and TKI) and multiple ratios above and below were performed in a panel of EGFR wild-type (A549, H460, H1299, H226) and EGFR mutant (H1975, HCC827 parent and HCC827 erl res) NSCLC cell lines. Cells were transfected with miR-34a and incubated 24 hrs later with afatinib or rociletinib for 72 hrs, with cellular proliferation then determined by AlamarBlue. Synergistic, additive, or antagonistic effects were determined by combination index (CI) values (based on Loewe's concept of additivity), isobolograms, and curve-shift analyses. Results: Strong synergy was observed between miR-34a and both TKIs in all EGFR-mutant cell lines tested (CI <0.5 at effect levels ≥50%). Synergy was also observed for miR-34a + rociletinib in most EGFR wild-type cell lines (CI <0.6 at effect levels of ∼50-80%), but not for miR-34a + afatinib. Best synergies overall were observed in EGFR-mutant cells with acquired erlotinib resistance. The effects were observed across a range of different dose levels and drug ratios, with maximal synergy providing a high level of inhibition (80%) at doses likely achievable in the clinic and well below those projected to be required for similar inhibition by the single agents alone. Conclusions: Complementing previous results with miR-34a + erlotinib, the data demonstrate strongly synergistic anticancer effects between miR-34a and next generation EGFR TKIs in combination against a range of EGFR wild-type and mutant NSCLC cell lines. The results support clinical study of MRX34 + EGFR TKI combinations in patients with advanced NSCLC, including those with EGFR-mutant NSCLC that has progressed on EGFR TKI monotherapy. Citation Format: Jane Zhao, Adriana Guerrero, Kevin Kelnar, Heidi J. Peltier, Andreas G. Bader. miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and next generation EGFR tyrosine kinase inhibitors (TKIs) in NSCLC. [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 4814.

Abstract 4829: miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and cytotoxic chemotherapy (CT) in NSCLC

Abstract Background: miRNAs play a critical role in regulating key biological processes by modulating the expression of up to several hundred genes across multiple cellular pathways. miR-34a, one of the most widely studied miRNAs, is lost or expressed at reduced levels in many tumors, and normally functions as a natural tumor suppressor by down-regulating expression of >30 different oncogenes, as well as genes involved in tumor immune evasion, including PD-L1. MRX34 is a potential first-in-class liposome-encapsulated miR-34a mimic in Phase 1 study (NCT01829971) as monotherapy in patients with advanced malignancies. The ability of miR-34a to regulate the expression of key oncogenes across multiple oncogenic pathways makes MRX34 a rational candidate to combine with other anticancer therapies which are frequently subject to primary and acquired resistance in the clinic. Previous studies showed that miR-34a greatly sensitizes both EGFR wild-type and mutant NSCLC cell lines, as well as hepatocellular carcinoma cell lines, to the EGFR tyrosine kinase inhibitor erlotinib. Here we report research combining miR-34a and standard CT drugs in NSCLC cell lines. Methods: Combination studies using single-drug ratios (∼IC50 ratio of miR-34a and CT drug) and multiple ratios above and below were performed in a panel of NSCLC cell lines (A549, H460, H1299, H2073) with varying degrees of intrinsic resistance to CT. Cells were transfected with miR-34a and incubated 24 hrs later with cisplatin, carboplatin, paclitaxel, gemcitabine, or pemetrexed for 72 hrs, with cellular proliferation then determined by AlamarBlue. Synergistic, additive, or antagonistic effects were determined by combination index (CI) values (based on Loewe's concept of additivity), isobolograms, and curve-shift analyses. Results: Synergistic interactions were observed between miR-34 and all CT drugs in all NSCLC cell lines tested. Synergy was observed at multiple miR-34a/cytotoxic agent dose ratios and at drug concentrations inducing 50% or greater inhibition (CI <0.6 and dose reduction index >2 at both 50% and 75% effect levels). Stronger synergy was seen in the H2073 cell line which is relatively more resistant to CT. Conclusions: Consistent with other in vitro results with miR-34a-based combinations, the data demonstrate synergistic anticancer effects between miR-34a + CT in a range of NSCLC cell lines with varying degrees of intrinsic resistance to CT. Overall, the data support further exploration of MRX34 in combination with standard anticancer therapies, and we are evaluating the most appropriate combinations for near-term clinical trials. In addition to resistance, other critical oncogenic mechanisms present in the tumor microenvironment (eg, immune evasion, cancer stem cells, metastasis) could potentially also be mitigated to the benefit of patients by a miRNA-based approach to therapy. Citation Format: Adriana Guerrero, Jane Zhao, Xiaojie Yu, Alexander Pertsemlidis, Andreas G. Bader. miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and cytotoxic chemotherapy (CT) in NSCLC. [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 4829.

Abstract 3063: Discovery of a third-generation EGFR inhibitor, which is highly selective and potent against both resistant and activating EGFR mutations for NSCLC therapy

Abstract EGFR T790M mutation which renders resistance to the first-generation EGFR inhibitors,accounts for about 50% of all originally responsive non-small cell lung cancer patients. In order to overcome this type of resistance, we have developed a small molecular drug candidate with unique structural features that offer differentiated pharmacological and safety profiles pre-clinically when compared with other leading third-generation EGFR inhibitors. The compound selectively inhibits T790M as well as activating EGFR mutations, with much less inhibition to the wild type EGFR. Enzymatic inhibition IC50 against EGFR T790M,T790M/Del19 and T790M/L858R is less than 1nM. In addition, enzymatic inhibition IC50 against EGFR activating mutations Del19 and L858R is around 1nM, with much less inhibition to the wild type EGFR, a 10-time selection ratio. In cell based assays, the compound potently inhibits proliferation of EGFR T790M mutated NSCLC cell lines H1975(T790M/L858R)and PC9-GR(T790M/Del19)with an IC50 around 3nM. Similarly, it potently inhibits EGFR activating mutant NSCLC cell lines HCC827(Del19)and PC9(Del19). However, the compound displays about 200-fold less sensitivity to the EGFR wild type cancer cell line A431, with an IC50 around 600nM. When dosed to tumor-bearing animals, the compound dose-dependently induces profound regression of xenografts derived from both H1975 and primary human lung cancer LU1868, both of which carry an EGFR T790M mutation. It also induces regression of HCC827 xenografts potently, similarly to the first- and second-generation EGFR inhibitors; whereas it displays much less inhibition to the EGFR wild type A431 xenografts, demonstrating a higher specificity to the mutated EGFR forms when compared with the EGFR inhibitors on market. The drug candidate displays favorable PK and safety profiles. These properties warrant further development of this compound as first- as well as second-line therapy for NSCLC. Citation Format: Rudi Bao, Peng Gao, Fujun Zhang, Zhaolong Tong, Hongping Yu, Yaochang Xu. Discovery of a third-generation EGFR inhibitor, which is highly selective and potent against both resistant and activating EGFR mutations for NSCLC therapy. [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 3063.