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Despite advances in precision medicine, the clinical prospects for patients with ovarian and uterine cancers have not substantially improved. Here, we analyzed genome-scale CRISPR-Cas9 loss-of-function screens across 851 human cancer cell lines and found that frequent overexpression of SLC34A2-encoding a phosphate importer-is correlated with sensitivity to loss of the phosphate exporter XPR1, both in vitro and in vivo. In patient-derived tumor samples, we observed frequent PAX8-dependent overexpression of SLC34A2, XPR1 copy number amplifications and XPR1 messenger RNA overexpression. Mechanistically, in SLC34A2-high cancer cell lines, genetic or pharmacologic inhibition of XPR1-dependent phosphate efflux leads to the toxic accumulation of intracellular phosphate. Finally, we show that XPR1 requires the novel partner protein KIDINS220 for proper cellular localization and activity, and that disruption of this protein complex results in acidic "vacuolar" structures preceding cell death. These data point to the XPR1-KIDINS220 complex and phosphate dysregulation as a therapeutic vulnerability in ovarian cancer.

Supplemental Figure 1. Characterization of DFCI 359 and DFCI 315.

DFCI358 signaling with respect to mTOR; crizotinib+trametinib combination;RTK activation

Detailed description of methodology and reagents

Supplementary Legends

Thirteen patients were enrolled and underwent at least one cycle of therapy.

Screening with drugs targeting sunitinib related receptor tyrosine kinases (RTK) or MAPK pathway were performed in PC9TMEM87A-RASGRF1 clone 1. Relative viability compared with control (treated with DMSO) was shown. A modest inhibitory effect was seen for gilteritinib without control osimertinib, suggesting the off-target toxic effect of the drug rather than on-target inhibition.

Summary of EGFR inhibitor resistant patient-derived xenografts.

Purpose:We pursued genomic analysis of an exceptional responder with non–small cell lung cancer (NSCLC) through a multi-platform effort to discover novel oncogenic targets.Experimental Design:In this open-label, single-arm phase II study (NCT01829217), an enriched cohort of patients with advanced NSCLC was treated with the multi-kinase inhibitor sunitinib. The primary endpoint was objective response rate. Tissue was collected for multi-platform genomic analysis of responders, and a candidate oncogene was validated using in vitro models edited by CRISPR-Cas9.Results:Of 13 patients enrolled, 1 patient (8%), a never smoker, had a partial response lasting 33 months. Genomic analysis of the responder identified no oncogenic variant using multi-platform DNA analysis including hotspot allelotyping, massively parallel hybrid-capture next-generation sequencing, and whole-exome sequencing. However, bulk RNA-sequencing (RNA-seq) revealed a novel fusion, TMEM87A–RASGRF1, with high overexpression of the fusion partners. RASGRF1 encodes a guanine exchange factor which activates RAS from GDP-RAS to GTP-RAS. Oncogenicity was demonstrated in NIH/3T3 models with intrinsic TMEM87A–RASGRF1 fusion. In addition, activation of MAPK was shown in PC9 models edited to express this fusion, although sensitivity to MAPK inhibition was seen without apparent sensitivity to sunitinib.Conclusions:Sunitinib exhibited limited activity in this enriched cohort of patients with advanced NSCLC. Nonetheless, we find that RNA-seq of exceptional responders represents a potentially underutilized opportunity to identify novel oncogenic targets including oncogenic activation of RASGRF1.

Post-baseline toxicity incidence.

Antibodies used in the study

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) are the standard-of-care treatment for EGFR-mutant non–small cell lung cancers (NSCLC). However, most patients develop acquired drug resistance to EGFR TKIs. HER3 is a unique pseudokinase member of the ERBB family that functions by dimerizing with other ERBB family members (EGFR and HER2) and is frequently overexpressed in EGFR-mutant NSCLC. Although EGFR TKI resistance mechanisms do not lead to alterations in HER3, we hypothesized that targeting HER3 might improve efficacy of EGFR TKI. HER3–DXd is an antibody–drug conjugate (ADC) comprised of HER3-targeting antibody linked to a topoisomerase I inhibitor currently in clinical development. In this study, we evaluated the efficacy of HER3–DXd across a series of EGFR inhibitor–resistant, patient-derived xenografts and observed it to be broadly effective in HER3-expressing cancers. We further developed a preclinical strategy to enhance the efficacy of HER3–DXd through osimertinib pretreatment, which increased membrane expression of HER3 and led to enhanced internalization and efficacy of HER3–DXd. The combination of osimertinib and HER3–DXd may be an effective treatment approach and should be evaluated in future clinical trials in EGFR-mutant NSCLC patients.Significance:EGFR inhibition leads to increased HER3 membrane expression and promotes HER3–DXd ADC internalization and efficacy, supporting the clinical development of the EGFR inhibitor/HER3–DXd combination in EGFR-mutant lung cancer.See related commentary by Lim et al., p. 18

Antibodies, compounds, oligonucleotides, and other reagents used in the study

Allelic Frequencies in PC-9 vs PC-9 T790M/C797S cells.

Supplementary Table S1

Purpose:Evaluating drug responses using primary patient-derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non–small cell lung cancer (NSCLC) patient xenograft-derived organotypic spheroids (XDOTS) using a short-term ex vivo system.Experimental Design:We generated two HER2-mutant NSCLC PDX models [DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2YVMA genetically engineered mouse model.Results:Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling.Conclusions:The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

Supplemental Legend

Supplementary Figures and legends

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) are the standard-of-care treatment for EGFR-mutant non–small cell lung cancers (NSCLC). However, most patients develop acquired drug resistance to EGFR TKIs. HER3 is a unique pseudokinase member of the ERBB family that functions by dimerizing with other ERBB family members (EGFR and HER2) and is frequently overexpressed in EGFR-mutant NSCLC. Although EGFR TKI resistance mechanisms do not lead to alterations in HER3, we hypothesized that targeting HER3 might improve efficacy of EGFR TKI. HER3–DXd is an antibody–drug conjugate (ADC) comprised of HER3-targeting antibody linked to a topoisomerase I inhibitor currently in clinical development. In this study, we evaluated the efficacy of HER3–DXd across a series of EGFR inhibitor–resistant, patient-derived xenografts and observed it to be broadly effective in HER3-expressing cancers. We further developed a preclinical strategy to enhance the efficacy of HER3–DXd through osimertinib pretreatment, which increased membrane expression of HER3 and led to enhanced internalization and efficacy of HER3–DXd. The combination of osimertinib and HER3–DXd may be an effective treatment approach and should be evaluated in future clinical trials in EGFR-mutant NSCLC patients. Significance: EGFR inhibition leads to increased HER3 membrane expression and promotes HER3–DXd ADC internalization and efficacy, supporting the clinical development of the EGFR inhibitor/HER3–DXd combination in EGFR-mutant lung cancer. See related commentary by Lim et al., p. 18

RAS gene mutations are the most frequent oncogenic event in lung cancer. They activate multiple RAS-centric signaling networks among them the MAPK, PI3K, and RB pathways. Within the MAPK pathway, ERK1/2 proteins exert a bottleneck function for transmitting mitogenic signals and activating cytoplasmic and nuclear targets. In view of disappointing antitumor activity and toxicity of continuously applied MEK inhibitors in patients with KRAS-mutant lung cancer, research has recently focused on ERK1/2 proteins as therapeutic targets and on ERK inhibitors for their ability to prevent bypass and feedback pathway activation. Here, we show that intermittent application of the novel and selective ATP-competitive ERK1/2 inhibitor LY3214996 exerts single-agent activity in patient-derived xenograft (PDX) models of RAS-mutant lung cancer. Combination treatments were well tolerated and resulted in synergistic (ERKi plus PI3K/mTORi LY3023414) and additive (ERKi plus CDK4/6i abemaciclib) tumor growth inhibition in PDX models. Future clinical trials are required to investigate if intermittent ERK inhibitor-based treatment schedules can overcome toxicities observed with continuous MEK inhibition and—equally important—to identify biomarkers for patient stratification.

Purpose: We pursued genomic analysis of an exceptional responder with non–small cell lung cancer (NSCLC) through a multi-platform effort to discover novel oncogenic targets. Experimental Design: In this open-label, single-arm phase II study (NCT01829217), an enriched cohort of patients with advanced NSCLC was treated with the multi-kinase inhibitor sunitinib. The primary endpoint was objective response rate. Tissue was collected for multi-platform genomic analysis of responders, and a candidate oncogene was validated using in vitro models edited by CRISPR-Cas9. Results: Of 13 patients enrolled, 1 patient (8%), a never smoker, had a partial response lasting 33 months. Genomic analysis of the responder identified no oncogenic variant using multi-platform DNA analysis including hotspot allelotyping, massively parallel hybrid-capture next-generation sequencing, and whole-exome sequencing. However, bulk RNA-sequencing (RNA-seq) revealed a novel fusion, TMEM87A–RASGRF1, with high overexpression of the fusion partners. RASGRF1 encodes a guanine exchange factor which activates RAS from GDP-RAS to GTP-RAS. Oncogenicity was demonstrated in NIH/3T3 models with intrinsic TMEM87A–RASGRF1 fusion. In addition, activation of MAPK was shown in PC9 models edited to express this fusion, although sensitivity to MAPK inhibition was seen without apparent sensitivity to sunitinib. Conclusions: Sunitinib exhibited limited activity in this enriched cohort of patients with advanced NSCLC. Nonetheless, we find that RNA-seq of exceptional responders represents a potentially underutilized opportunity to identify novel oncogenic targets including oncogenic activation of RASGRF1.

Purpose: Evaluating drug responses using primary patient-derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non–small cell lung cancer (NSCLC) patient xenograft-derived organotypic spheroids (XDOTS) using a short-term ex vivo system. Experimental Design: We generated two HER2-mutant NSCLC PDX models [DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2YVMA genetically engineered mouse model. Results: Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. Conclusions: The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

The clinical efficacy of epidermal growth factor receptor (EGFR)–targeted therapy in EGFR-mutant non–small cell lung cancer is limited by the development of drug resistance. One mechanism of EGFR inhibitor resistance occurs through amplification of the human growth factor receptor (MET) proto-oncogene, which bypasses EGFR to reactivate downstream signaling. Tumors exhibiting concurrent EGFR mutation and MET amplification are historically thought to be codependent on the activation of both oncogenes. Hence, patients whose tumors harbor both alterations are commonly treated with a combination of EGFR and MET tyrosine kinase inhibitors (TKIs). Here, we identify and characterize six patient-derived models of EGFR-mutant, MET-amplified lung cancer that have switched oncogene dependence to rely exclusively on MET activation for survival. We demonstrate in this MET-driven subset of EGFR TKI-refractory cancers that canonical EGFR downstream signaling was governed by MET, even in the presence of sustained mutant EGFR expression and activation. In these models, combined EGFR and MET inhibition did not result in greater efficacy in vitro or in vivo compared to single-agent MET inhibition. We further identified a reduced EGFR:MET mRNA expression stoichiometry as associated with MET oncogene dependence and single-agent MET TKI sensitivity. Tumors from 10 of 11 EGFR inhibitor–resistant EGFR-mutant, MET-amplified patients also exhibited a reduced EGFR:MET mRNA ratio. Our findings reveal that a subset of EGFR-mutant, MET-amplified lung cancers develop dependence on MET activation alone, suggesting that such patients could be treated with a single-agent MET TKI rather than the current standard-of-care EGFR and MET inhibitor combination regimens.

A subset of drug-resistant EGFR -mutant MET -amplified lung cancer switches oncogenic dependence to MET and is treatable with MET inhibitor monotherapy.

Precision medicine promises to improve the treatment of cancer patients, but a lack of therapeutic targets and associated predictive biomarkers limit this reality. To identify novel strategies, we integrate genome-scale CRISPR viability screens across many cancer models with cellular and molecular features to systematically define The Cancer Dependency Map. Using this data, we have identified that XPR1, an inorganic phosphate exporter protein, is a highly selective dependency gene in ovarian and uterine cancers. These cancers are sensitive to loss of XPR1 due to over-expression of SLC34A2, a phosphate importer protein. These data suggest a synthetic lethal relationship in which intracellular phosphate homeostasis is dysregulated in cancer. As proof-of-concept of pharmacological inhibition of XPR1, we have developed protein ligands based on the receptor binding domain of viruses which use XPR1 for cellular entry. These ligands inhibit XPR1 and kill cancer cells in an on-mechanism manner, but may be limited in their clinical utility. As such, we are deepening our understanding of the mechanisms of XPR1-dependent phosphate efflux, and have identified a novel partner protein that is integral to phosphate efflux, possibly revealing functional domains that small molecule inhibitors might target. Overall, these data highlight a novel mechanism to treat cancers by leveraging cancer-specific phosphate dysregulation and further reinforce the Cancer Dependency Map as a powerful engine to uncover novel therapeutic vulnerabilities. Citation Format: Daniel Bondeson, Brenton Paolella, Adhana Asfaw, Michael Rothberg, Thomas Skipper, Gabriel Mesa, Alfredo Gonzalez, Lauren E. Surface, Kentaro Ito, Mariya Kazachkova, William N. Colgan, Allie Warren, Joshua Dempster, J Michael Krill-Burger, Maria Ericsson, Andrew Tang, Iris Fung, Emily S. Chambers, Mai Abdusamad, Nancy Dumont, John Doench, Federica Piccioni, David Root, Jesse Boehm, William C. Hahn, Michael Mannstadt, James McFarland, Francisca Vazquez, Todd Golub. Phosphate dysregulation as a novel therapeutic strategy in ovarian and uterine cancers [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 1028.

RAS gene mutations are the most frequent oncogenic event in lung cancer. They activate multiple RAS-centric signaling networks among them the MAPK, PI3K and RB pathways. Within the MAPK pathway ERK1/2 proteins exert a bottleneck function for transmitting mitogenic signals and activating cytoplasmic and nuclear targets. In view of disappointing anti-tumor activity and toxicity of continuously applied MEK inhibitors in patients with KRAS mutant lung cancer, research has recently focused on ERK1/2 proteins as therapeutic targets and on ERK inhibitors for their ability to prevent bypass and feedback pathway activation. Here we show that intermittent application of the novel and selective ATP-competitive ERK1/2 inhibitor LY3214996 exerts single-agent activity in patient-derived xenograft (PDX) models of RAS mutant lung cancer. Combination treatments were well tolerated and resulted in synergistic (ERKi plus PI3K/mTORi LY3023414) and additive (ERKi plus CDK4/6i abemaciclib) tumor growth inhibition in PDX models. Future clinical trials are required to investigate if intermittent ERK inhibitor-based treatment schedules can overcome toxicities observed with continuous MEK inhibition and - equally important - to identify biomarkers for patient stratification.

PURPOSE: We pursued genomic analysis of an exceptional responder with non-small cell lung cancer (NSCLC) through a multi-platform effort to discover novel oncogenic targets. METHODS: In this open-label, single-arm phase II study (NCT01829217), an enriched cohort of patients with advanced NSCLC were treated with the multi-kinase inhibitor sunitinib. The primary endpoint was objective response rate. Tissue was collected for multi-platform genomic analysis of responders, and a candidate oncogene was validated using in vitro models edited by CRISPR-Cas9. RESULTS: Of 13 patients enrolled, one patient (8%), a never-smoker, had a partial response lasting 33 months. Genomic analysis of the responder identified no oncogenic variant using multi-platform DNA analysis including hotspot allelotyping, massively parallel hybrid-capture next-generation sequencing, and whole exome sequencing. However, bulk RNA sequencing revealed a novel fusion, TMEM87A-RASGRF1, with high overexpression of the fusion partners. RASGRF1 encodes a guanine exchange factor which activates RAS from GDP-RAS to GTP-RAS. Oncogenicity was demonstrated in NIH/3T3 models with intrinsic TMEM87A-RASGRF1 fusion. Additionally, activation of MAPK was shown in PC9 models edited to express this fusion, though sensitivity to MAPK inhibition was seen without apparent sensitivity to sunitinib. CONCLUSIONS: Sunitinib exhibited limited activity in this enriched cohort of patients with advanced NSCLC. Nonetheless, we find that RNA sequencing of exceptional responders represents a potentially under-utilized opportunity to identify novel oncogenic targets including oncogenic activation of RASGRF1.

Purpose: MET inhibitors can be effective therapies in patients with MET exon 14 (METex14) mutant non–small cell lung cancer (NSCLC). However, long-term efficacy is limited by the development of drug resistance. In this study, we characterize acquired amplification of wild-type (WT) KRAS as a molecular mechanism behind crizotinib resistance in three cases of METex14-mutant NSCLC and propose a combination therapy to target it. Experimental Design: The patient-derived cell line and xenograft (PDX) DFCI358 were established from a crizotinib-resistant METex14-mutant patient tumor with massive focal amplification of WT KRAS. To characterize the mechanism of KRAS-mediated resistance, molecular signaling was analyzed in the parental cell line and its KRAS siRNA-transfected derivative. Sensitivity of the cell line to ligand stimulation was assessed and KRAS-dependent expression of EGFR ligands was quantified. Drug combinations were screened for efficacy in vivo and in vitro using viability and apoptotic assays. Results: KRAS amplification is a recurrent genetic event in crizotinib-resistant METex14-mutant NSCLC. The key characteristics of this genetic signature include uncoupling MET from downstream effectors, relative insensitivity to dual MET/MEK inhibition due to compensatory induction of PI3K signaling, KRAS-induced expression of EGFR ligands and hypersensitivity to ligand-dependent and independent activation, and reliance on PI3K signaling upon MET inhibition. Conclusions: Using patient-derived cell line and xenografts, we characterize the mechanism of crizotinib resistance mediated by KRAS amplification in METex14-mutant NSCLC and demonstrate the superior efficacy of the dual MET/PI3K inhibition as a therapeutic strategy addressing this resistance mechanism.

Background Tumor genotyping is transforming lung cancer care but requires adequate tumor tissue. Advances in minimally invasive biopsy techniques have increased access to difficult-to-access lesions, but often result in smaller samples. With the advent of highly sensitive DNA genotyping methods used for plasma analysis, we hypothesized that these same methods might allow genotyping of free DNA derived from fine needle aspiration supernatant (FNA-S). Methods We studied patients with known or suspected lung cancer undergoing fine needle aspirate (FNA). After spinning the sample for cellblock, the FNA-S (usually discarded) was saved for genotyping. Supernatant cell-free DNA (SN-cfDNA) was extracted and tested by both droplet digital PCR (EGFR, BRAF, KRAS mutations) and highly sensitive amplicon-based next-generation sequencing (NGS). Results 17 samples were studied, including 11 FNAs from patients with suspected lung cancer and 6 FNAs from patients with lung cancer and acquired drug resistance. Of 6 newly diagnosed adenocarcinomas, 4 had a driver mutations (1 EGFR, 2 KRAS, 1 HER2) found on tissue; all of these could be detected in SN-cfDNA. The EGFR driver mutation was detected in all 5 adenocarcinomas with acquired EGFR resistance and the EGFR T790 M in three cases, in agreement with cellblock. Conclusions FNA-S is a rich source of fresh tumor DNA, potentially increasing the diagnostic yield from small FNAs. Through use of emerging techniques for highly sensitive genotyping, this widely available biospecimen has potential for facilitating rapid cancer genotyping at diagnosis and after drug resistance.

PURPOSE: Evaluating drug responses using primary patient derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non-small cell lung cancer (NSCLC) patient xenograft derived organotypic spheroids (XDOTS) using a short term ex vivo system. METHODS: We generated two HER2 mutant NSCLC PDX models (DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)) and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib based drug combinations. Live/dead quantification was performed by dual labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2(YVMA) genetically engineered mouse model (GEMM). RESULTS: Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab, and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared to single agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. CONCLUSIONS: The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

The recent approval of two PD-1 inhibitors for the treatment of non–small cell lung cancer (NSCLC) has rapidly led to the widespread use of these agents in oncology practices. Pneumonitis has been recognized as a potentially life-threatening adverse event among NSCLC patients treated with PD-1 inhibitors; however, the detailed clinical and radiographic manifestations of this entity remain to be described. We report on two cases of anti–PD-1 pneumonitis in advanced NSCLC patients treated with nivolumab after its FDA approval. Both patients presented with ground-glass and reticular opacities and consolidations in a peripheral distribution on CT, demonstrating a radiographic pattern of cryptogenic organizing pneumonia. Consolidations were extensive and rapidly developed within 8 weeks of therapy in both cases. Both patients were treated with corticosteroids with subsequent improvement of respiratory symptoms and radiographic findings. One patient experienced recurrent pneumonitis after completing corticosteroid taper, or a “pneumonitis flare,” in the absence of nivolumab retreatment, with subsequent improvement upon corticosteroid readministration. With the increasing use of immune checkpoint inhibitors in a growing number of tumor types, awareness of the radiographic and clinical manifestations of PD-1 inhibitor–related pneumonitis will be critical for the prompt diagnosis and management of this potentially serious adverse event. Cancer Immunol Res; 4(4); 289–93. ©2016 AACR.

While KRAS mutations are common in non-small cell lung cancer (NSCLC), effective treatments are lacking. Here, we report that half of KRAS-mutant NSCLCs aberrantly express the homeobox protein HOXC10, largely due to unappreciated defects in PRC2, which confers sensitivity to combined BET/MEK inhibitors in xenograft and PDX models. Efficacy of the combination is dependent on suppression of HOXC10 by BET inhibitors. We further show that HOXC10 regulates the expression of pre-replication complex (pre-RC) proteins in sensitive tumors. Accordingly, BET/MEK inhibitors suppress pre-RC proteins in cycling cells, triggering stalled replication, DNA damage, and death. These studies reveal a promising therapeutic strategy for KRAS-mutant NSCLCs, identify a predictive biomarker of response, and define a subset of NSCLCs with a targetable epigenetic vulnerability.

Background Tumor response characteristics using immune-related RECIST1.1 (irRECIST1.1) in advanced non-small-cell lung cancer (NSCLC) patients treated with nivolumab monotherapy in the clinical setting have not been previously described with a direct comparison with the assessments according to the conventional RECIST1.1. Methods Fifty-six advanced NSCLC patients treated with nivolumab monotherapy after its Food and Drug Administration (FDA) approval were retrospectively studied. Tumor burden was quantified on serial CT scans during therapy using irRECIST1.1, which uses unidimensional measurements and includes new lesion measurements in total tumor burden. Response assessments by irRECIST1.1 were compared with assessments by RECIST1.1. Responses of individual lesions in different organs were also compared. Results Tumor burden change at best overall response ranged from −66.8 to +278.1% (median: +3.9%). Response rate was 14% (8/56; 8 partial responses, 0 complete responses) by irRECIST1.1 and by RECIST1.1. Time-to-progression (TTP) by irRECIST1.1 was longer than TTP by RECIST1.1 (median TTP: not reached vs. 1.9 months, respectively). No patients experienced pseudoprogression during the study. Among 128 target lesions, the lesion-based size change at best response differed significantly across different organs, with adrenal lesions and lymph nodes having greater size decrease, followed by lung, while liver and other miscellaneous lesions had lesser degree of size decrease (p = 0.002). Conclusions Immune-related response evaluations using irRECIST1.1 in advanced NSCLC patients treated with nivolumab resulted in the identical response rate and longer TTP compared to RECIST1.1. No pseudoprogression cases were observed during the study. Adrenal lesions and lymph nodes were more responsive and liver lesions were less responsive to nivolumab. Electronic supplementary material The online version of this article (doi:10.1186/s40425-016-0193-2) contains supplementary material, which is available to authorized users.

Introduction: RAS mutations are present in 30% of non-small cell lung cancer (NSCLC) and, despite activated MAPK signaling, MEK inhibitors have disappointed in clinical trials. MAPK pathway reactivation and activation of anti-apoptotic signaling via the PI3K/mTOR axis are major resistance mechanisms, among others. ERK inhibitors are believed to overcome some of the restrictions of MEK inhibitors, and combinations with PI3K/mTOR inhibitors could potentially increase therapeutic efficacy. Past trials of MEK and PI3K inhibitor combinations, however, showed that toxicities and side effects are likely to be expected also for the ERK-PI3K/mTOR inhibitor combination. Therefore, more specific and potent drugs as well as alternating dosing schedules may overcome toxicities and improve treatment outcome. Methods: We so far established five patient-derived RAS-mutant NSCLC cell lines (1/5 NRASQ61K, 1/5 KRASQ61K, 2/5 KRASG12C, 1/5 KRASG12D) and xenograft models (PDX), characterized them by next-generation sequencing (DFCI Oncopanel) and tested the antiproliferative (CellTiter-Glo® assay) and apoptosis-inducing (Caspase3/7 activity, IncuCyte® technology) efficacy of LY3214996 (ERK inhibitor) and LY3023414 (PI3K/mTOR inhibitor) in vitro. Effects on signal transduction were investigated by Western blot analysis. Results: The ERK inhibitor LY3214996 and the PI3K/mTOR inhibitor LY3023414 exhibit single-agent antiproliferative and apoptosis-inducing activity in patient-derived RAS-mutant NSCLC cell lines (for LY3214996: 1/5 sensitive (IC5010μM); for LY3023414: all IC50 Conclusions and Outlook: Both LY3214996 and LY3023414 have single-agent in vitro efficacy in patient-derived NSCLC models with different RAS mutations and co-mutational landscapes. Single-agent in vivo studies and tolerability studies of drug combinations are ongoing, and treatment predictors and intrinsic/adaptive resistance mechanisms will be investigated via RNAseq/GSEA and phospho-receptor tyrosine kinase arrays. Citation Format: Jens Köhler, Prafulla C. Gokhale, Jiaqi Li, Margaret K. Wilkens, Hong Tiv, Shripad V. Bhagwat, Greg Donoho, Patrick Brueck, Ramon V. Tiu, Amanda J. Redig, Emily S. Chambers, Atsuko Ogino, Jihyun Choi, Man Xu, Paul Kirschmeier, Pasi A. Jänne. Efficacy of the ERK inhibitor LY3214996 and the PI3K/mTOR inhibitor LY3023414 in patient-derived RAS-mutant NSCLC 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 5467.

Introduction: Patient-derived xenografts (PDX) are increasingly adopted to evaluate the efficacy of new treatment approaches, including the development of combination therapies and testing of predictive biomarkers hypotheses. However, PDXs can take months to generate and are impractical for screening large sets of drug combinations. Here we report on a novel 3D microfluidic platform that allows for evaluating ex vivo responses to targeted therapies from genotyped defined patient-derived tumor spheroids (XDOTS) (1). Methods: Non-small cell lung cancer (NSCLC) PDXs with known genotype, including EGFR ex19 del, HER-2 ins, and BRAF V600E, were generated from either core needle biopsies or pleural effusions under an IRB-approved protocol. XDOTS (40μm) were grown from PDX tumors using DAX-1 3D cell culture chips (AIM, Singapore) and treated with genotype matched inhibitors that are either approved (e.g., erlotinib for EGFR mut) or are being tested in the clinic (neratinib for HER-2 ins) at known peak plasma concentrations for 3 days. Live/death quantification was performed by dual labeling fluorescence microscopy using acridine orange for live and propidium iodide for dead cells. Cell type characterization was performed by immunofluorescence in the devices. Results: We first characterized our XDOT system on models for which we had orthogonal validation. We show by dual labeling fluorescence microscopy that PC9GR4 (EGFR Del19/T790M) cells are sensitive to osimertinib (IC50 = 12nM), but not gefitinib (IC50 >10uM). We further show that HCC827GR6 (Del 19/MET Amp) and DFCI32 (EML4-ALK/EGFR/HER2) cells are sensitive to crizotinib/gefitinib combo, but not to each of the single agents. Results were validated using the IncuCyte Live Cell analysis. We then went on to show that genotype-specific responses can be recapitulated in tumor spheroids generated from PDXs. In DFCI 359, a PDX derived from a HER2 mutant (755_757 LRdelinsPR), we show the antitumor efficacy of afatinib and confirm that effect is specific to tumor cells and not stromal. We observe significant drug efficacy only on cells growing in our microfluidic devices and not on spheroids growing 3D in 384 well plates. Similar results were obtained for additional PDXs with known NSCLC driver mutations. Finally, we evaluate our system on a small cohort of direct patient specimens. Conclusions: Taken together, our data show that short culture experiments using XDOTS are feasible and recapitulate key futures of in vivo response and resistance ex vivo. Reference: 1. Jenkins RW, et al. Cancer Discov DOI:10.1158/2159-8290. Citation Format: Amir Aref, Elena Ivanova, Emily Chambers, Andrew Portell, Russell Jenkins, Mika Lin, Man Xu, Jacob Haworth, Magda Bahcall, Cloud Paweletz, Pasi Janne. Short-term culture of organotypic tumor spheroids derived from patient xenografts in a novel 3D microfluidic chip predicts in vivo response of targeted therapies [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 988.

9069Background: Non-small cell lung cancers (NSCLC) harboring METex14 activating mutations can respond dramatically to treatment with MET TKIs, but the mechanisms of acquired resistance to these th...

9087Background: KRAS is the most frequently mutated oncogene in NSCLC, and such tumors lack effective targeted therapy. Unlike other activating oncogenes associated with never/light-smokers (NS), K...