Non-small Cell Lung Cancer Xenograft Models Research Articles

Abstract 283: PEGylated recombinant hyaluronidase PH20 (PEGPH20) enhances pemetrexed antitumor efficacy in a human nonsquamous NSCLC xenograft model

Abstract Introduction: Hyaluronan (HA) is an extracellular matrix glycosaminoglycan that has been shown to accumulate at high levels in several cancers, including non-small cell lung cancer (NSCLC). The accumulation of HA in NSCLC is associated with a more aggressive phenotype and shortened overall survival. In a prevalence analysis using tissue microarrays of archival human specimens (N = 194) stained by affinity histochemistry, we demonstrated that 55% of adenocarcinomas, 74% of squamous cell carcinomas and 83% of large cell carcinomas accumulated HA. The engineered enzyme PEGylated recombinant human hyaluronidase PH20 (PEGPH20) removes HA from the tumor microenvironment. PEGPH20-based therapies are being evaluated in clinical studies of several solid tumors, including NSCLC (NCT02346370, NCT02563548). Herein, we evaluated the hypothesis that PEGPH20 combination therapy could enhance the efficacy of pemetrexed (PEM), a folate antimetabolite approved by FDA as a first-line treatment in combination with cisplatin, against locally advanced and metastatic NSCLC in patients with non-squamous histology. Methods: We evaluated PEGPH20 plus PEM in a NSCLC xenograft model. First, the human NSCLC adenocarinoma cell line A549 was transduced with hyaluronan synthase-3 (HAS3) to generate the A549/HAS3 cell line. Next, A549/HAS3 cells were inoculated adjacent to the tibial periosteum of nude mice and tumor growth was monitored via ultrasonography. When tumors size reached ∼250 mm3, mice were staged into six groups: (1) vehicle; (2) PEGPH20, (3) PEM daily, (4) PEM weekly, (5) PEGPH20+PEM daily or (6) PEGPH20+PEM weekly. Vascular volume, hypoxia and tumor growth inhibition (TGI) were assessed using conventional methods. Affinity histochemical staining for HA was performed on formalin-fixed paraffin-embedded tissue sections after harvest. Results: A549/HAS3 tumors grew faster than parental A549 tumors in vivo. PEGPH20 monotherapy significantly reduced tumoral HA, increased vascular volume and reduced hypoxia in tumors. Further, TGI with PEGPH20+PEM, weekly or daily, was 29.7 or 31.1%, respectively, whereas in either PEGPH20 alone or PEM alone, both were <9%. Staining of A549/HAS3 tumors showed increased accumulation of HA as compared with the parental A549 xenografts. Conclusion: These data suggest that addition of PEGPH20 to pemetrexed increases the efficacy of PEM and support further investigation of PEGPH20 plus PEM treatment in NSCLC tumors of non-squamous histology that accumulate HA. Citation Format: Renee Clift, Jessica A. Cowell, Susan J. Zimmerman, Mathieu Marella, Ping Jiang, Arnold B. Gelb, Michael J. LaBarre, Daniel C. Maneval, Curtis B. Thompson, Xiaoming Li. PEGylated recombinant hyaluronidase PH20 (PEGPH20) enhances pemetrexed antitumor efficacy in a human nonsquamous NSCLC xenograft model. [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 283.

Abstract 1194: Discovery and preclinical development of a highly potent NaPi2b-targeted antibody-drug conjugate (ADC) with significant activity in patient-derived non-small cell lung cancer (NSCLC) xenograft models

Abstract The type II sodium-dependent potassium transporter NaPi2b (SLC34A2) is highly expressed in non-squamous NSCLC and non-mucinous ovarian cancer (OC) with restricted normal tissue expression, suggesting it may be a suitable ADC target for these indications. XMT-1536 is a novel, highly potent anti-NaPi2b ADC comprised of an average of 15 auristatin molecules conjugated to XMT-1535, a novel humanized anti-NaPi2b antibody, via the Dolaflexin ADC platform. The auristatin payload is enzymatically cleaved upon ADC trafficking to the endosome/lysosome compartment, releasing a cytotoxic auristatin derivative that is capable of bystander effect killing. In cell binding assays, XMT-1535 antibody binds to OC cells with low nanomolar affinity, which is unaffected by conjugation of the Dolaflexin drug conjugate. In vitro cytotoxicity assays show picomolar potency of XMT-1536 in OVCAR3 (OC; 32,000 NaPi2b molecules/cell; IC50 2 pM), TOV21G (OC; 10,000 NaPi2b molecules/cell; IC50 40 pM), and HCC-4006 (NSCLC; 52,000 NaPi2b molecules/cell; IC50 130 pM). In each cell line, XMT-1536 is 1-2 logs more potent than a non-binding Dolaflexin ADC control, consistent with target-dependent cytotoxic effect. XMT-1536 was tested in mouse xenograft models of OC and NSCLC. In the OVCAR3 OC model, XMT-1536 induced partial tumor regressions after a single dose of 3 mg/kg (0.21 mg/kg payload equivalent dose), and complete tumor regressions after a single dose of 5 mg/kg (0.36 mg/kg payload dose) or 3 weekly doses of 3 mg/kg. In contrast, a non-binding Dolaflexin ADC with comparable drug loading was inactive after 3 weekly administrations of 3 mg/kg, consistent with the anti-tumor activity of XMT-1536 being mediated through binding to the NaPi2b target. XMT-1536 was also tested in a patient-derived model of KRAS mutant NSCLC, where 3 weekly doses of 3 mg/kg led to significant tumor growth delay and regressions in some animals. Evaluation of XMT-1536 in additional patient derived xenograft models is on-going and will be updated at the meeting. XMT-1535 is cross-reactive with cynomolgous monkey NaPi2b, allowing an informative evaluation of whether XMT-1536 retains good tolerability in non-human primate. XMT-1536 was administered to cynomolgous monkeys in an exploratory single dose study up to 5 mg/kg ADC (4294 μg/m2 auristatin payload equivalents), with no observed target-mediated toxicity and limited adverse findings. Of note, there was no evidence of bone marrow toxicity, which has been observed generally for cleavable auristatin ADCs, and specifically for a recently published auristatin-based NaPi2b ADC (Lin et al., Clinical Cancer Research, 2015). Based on these data XMT-1536 is advancing to early clinical development for the treatment of NaPi2b-expressing tumors. Citation Format: Natalya Bodyak, Alex Yurkovetskiy, Mao Yin, Dmitry Gumerov, Reddy Bollu, Patrick Conlon, Venu R. Gurijala, Dennis McGillicuddy, Cheri Stevenson, Elena Ter-Ovanesyan, Peter U. Park, Laura Poling, Winnie Lee, Michael DeVit, Dongmei Xiao, LiuLiang Qin, Timothy B. Lowinger, Donald A. Bergstrom. Discovery and preclinical development of a highly potent NaPi2b-targeted antibody-drug conjugate (ADC) with significant activity in patient-derived non-small cell lung cancer (NSCLC) xenograft models. [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 1194.

Abstract 341: Preclinical mode of action and anti-tumor efficacy of the selective MKNK1 inhibitor BAY 1143269 in NSCLC models

Abstract MKNK1 (MAP kinase-interacting serine/threonine-protein kinase, also known as Mnk1) is activated by the mitogen-activated protein kinases ERK1/2 and p38. Thus, MKNK1 signaling is involved in the cellular response to environmental stress factors and cytokines. Of particular interest, MKNK1 kinase regulates mRNA translation by phosphorylating the translation initiation factor eIF4E (eukaryotic translation initiation factor 4E), known to be critical for malignant transformation but shown to be dispensable for translation in normal cells. Phosphorylated eIF4E levels were found to be elevated in several cancer tissues, including lung cancer. MKNK1 is also involved in resistance mechanisms to cancer therapeutics. Thus, the inhibition of MKNK1 activity may provide an innovative approach for anti-cancer therapy, and in particular for lung cancer, the main cancer-related cause of death worldwide. BAY 1143269 is a potent and selective MKNK1 inhibitor and inhibits eIF4E phosphorylation and reduces MKNK1-regulated translational downstream targets in non-small cell lung cancer (NSCLC) cell lines. In this study, BAY 1143269-mediated effects on molecular mechanisms in lung cancer models were analyzed. Epithelial-mesenchymal transition (EMT) is associated with the pathogenesis of numerous lung diseases including cancer progression, metastasis and resistance. BAY 1143269 reduced expression of EMT key regulators like Snail1 and cellular junction components, as well as reduced TGFβ1-induced EMT. Accumulating evidence suggests a role for proinflammatory cytokines in the development and progression of cancer; increased serum concentrations of cytokines like interleukin 6 (IL-6) are associated with diminished lung cancer survival rates. BAY 1143269 reduced the secretion of several proinflammatory cytokines, including TNFα and IL-6 in whole blood, and affected IFN-stimulated gene expression in cell lines. Consistent with the observed effects in vitro, BAY 1143269 showed significant anti-tumor effects in vivo in cell line as well as patient derived NSCLC xenograft models in monotherapy. In combination with chemotherapeutics approved for treatment of NSCLC, BAY 1143269 improved anti-tumor effects in comparison to chemotherapy alone. In conclusion, BAY 1143269 has the potential to provide therapeutic benefit in NSCLC. A phase I study of BAY 1143269 in combination with docetaxel for subjects with advance solid tumors is ongoing (NCT02439346). Citation Format: Susann Santag, Franziska Siegel, Antje M. Wengner, Claudia Lange, Ulf Boemer, Knut Eis, Florian Puehler, Martin Michels, Franz von Nussbaum, Karl Ziegelbauer, Dominik Mumberg, Kirstin Petersen. Preclinical mode of action and anti-tumor efficacy of the selective MKNK1 inhibitor BAY 1143269 in NSCLC models. [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 341.

Prediction of survival prognosis of non-small cell lung cancer by APE1 through regulation of Epithelial-Mesenchymal Transition.

The DNA base excision repair gene APE1 involves in DNA damage repair pathway and overexpression in a variety of human cancers. Analyses of patients with non-small cell lung cancer (NSCLC) suggested that multiple factors associated with prognosis of NSCLC patients. Further investigation showed that APE1 expression was able to predict the progression-free survival and overall survival in patients with NSCLC and correlated with lymph node metastasis. Intriguingly, as a stratification of APE1-141 SNPs in APE1 positive expression, we also found APE1-141 GT/GG was identified as a marker for prediction of poor survival in NSCLC patients. In the in vitro experiments, the results showed that when APE1 expression was inhibited by siRNA or AT101 (an APE1 inhibitor), the migration and invasion of NSCLC cells were suppressed. Furthermore, epithelial-mesenchymal transition (EMT) markers was tested to provide evidence that APE1 promoted NSCLC EMT through interaction with SirT1. Using NSCLC xenograft models, we confirmed that AT101 shrank tumor volumes and inhibited lymph node metastasis. In conclusion, APE1 could be a potential target for patients with NSCLC metastasis and AT101 is a potent inhibitor in further treatment of NSCLC patients.

Abstract C4: Development and pre-clinical assessment of a first-in-class small molecule inhibitor of FLIP for treatment of NSCLC

Abstract Background Evasion of cell death is a major cause of resistance to cancer therapy, making proteins that regulate cell death clinically relevant therapeutic targets. The anti-apoptotic protein FLIP is frequently overexpressed in a number of cancers, including non-small cell lung cancer (NSCLC), and has been shown by us and others to be a major mediator of drug resistance. FLIP and procaspase-8 form complexes with the adaptor protein FADD in response to a variety of clinically relevant stimuli, including ligation of death receptors, such as TRAIL-R1 and R2, and treatment with chemotherapeutic agents. In these complexes, FLIP modulates the activation of procaspase-8, and thereby apoptosis and necroptosis - two major cell death mechanisms. We recently reported that there are important differences between FLIP and procaspase-8 in terms of both their binding affinities and preferred modes of interaction with FADD that are potentially therapeutically exploitable [1]. We now report our subsequent work leading to the development and pre-clinical characterisation of first-in-class inhibitors of FLIP. Methods Molecular modelling of the FLIP-FADD complex; virtual small molecule library screening; cell-free screening assays; cell-based activity assays; biophysical binding assays; in vivo anti-tumor studies. Results Molecular modelling of the FLIP-FADD complex identified a putative drug-binding pocket on FLIP against which a virtual small-molecule screen was carried out. Subsequent biochemical screening of selected compounds using a FLIP-FADD protein-protein interaction assay identified hits with on-target activity. Medicinal chemistry optimisation of these hits afforded lead and back-up series with nanomolar activity in cell-based assays (i.e. caspase activation, cell death and cell survival), which is in line with their binding affinity in an orthogonal biophysical assay (isothermal calorimetry). The pro-apoptotic effects of these FLIP inhibitors were enhanced upon addition of death ligands, such as TRAIL, and lead-molecules have been shown to potentiate the effects of the standard-of-care chemotherapeutic cisplatin. FLIP overexpression and procaspase-8 depletion abrogated the effects of these novel inhibitors consistent with the expected mechanism-of-action. Lead molecules have been identified with ADME profiles suitable for in vivo evaluation. Using these compounds, single-agent anti-tumor effects have been demonstrated in NSCLC xenograft models. Conclusions The novel first-in-class inhibitors of FLIP developed in this study have the potential for broad application in treatment of NSCLC, either as monotherapy or in combination with other agents. Acknowledgements This work was supported by a Seeding Drug Discovery award from the Wellcome Trust (reference: 099470). 1. Majkut, J., et al., Differential affinity of FLIP and procaspase 8 for FADD's DED binding surfaces regulates DISC assembly. Nat Commun, 2014. 5: p. 3350. Citation Format: Joanna Majkut, Catherine Higgins, Adnan Malik, Zsusannah Nemeth, Peter Blurton, Ray J. Boffey, Trevor R. Perrior, David Haigh, Timothy Harrison, Daniel B. Longley. Development and pre-clinical assessment of a first-in-class small molecule inhibitor of FLIP for treatment of NSCLC. [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 C4.

Impact of bevacizumab in combination with erlotinib on EGFR-mutated non-small cell lung cancer xenograft models with T790M mutation or MET amplification.

Erlotinib (ERL), an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, shows notable efficacy against non-small cell lung cancer (NSCLC) harboring EGFR mutations. Bevacizumab (BEV), a humanized monoclonal antibody to vascular endothelial cell growth factor (VEGF), in combination with ERL (BEV+ERL) significantly extended progression-free survival in patients with EGFR-mutated NSCLC compared with ERL alone. However, the efficacy of BEV+ERL against EGFR-mutated NSCLC harboring T790M mutation or MET amplification, is unclear. Here, we examined the antitumor activity of BEV+ERL in four xenograft models of EGFR-mutated NSCLC (three harboring ERL resistance mutations). In the HCC827 models (exon 19 deletion: DEL), ERL significantly inhibited tumor growth by blocking EGFR signal transduction. Although there was no difference between ERL and BEV+ERL in maximum tumor growth inhibition, BEV+ERL significantly suppressed tumor regrowth during a drug-cessation period. In the HCC827-EPR model (DEL+T790M) and HCC827-vTR model (DEL+MET amplification), ERL reduced EGFR signal transduction and showed less pronounced but still significant tumor growth inhibition than in the HCC827 model. In these models, tumor growth inhibition was significantly stronger with BEV+ERL than with each single agent. In the NCI-H1975 model (L858R+T790M), ERL did not inhibit growth or EGFR signal transduction, and BEV+ERL did not inhibit growth more than BEV. BEV alone significantly decreased microvessel density in each tumor. In conclusion, addition of BEV to ERL did not enhance antitumor activity in primarily ERL-resistant tumors with T790M mutation; however, BEV+ERL enhanced antitumor activity in T790M mutation- or MET amplification-positive tumors as long as their growth remained significantly suppressed by ERL.

Inhibiting MDM2-p53 Interaction Suppresses Tumor Growth in Patient-Derived Non–Small Cell Lung Cancer Xenograft Models

The tumor suppressor p53 is frequently inactivated in non-small cell lung cancer (NSCLC). Activation of the p53 pathway by inhibition of its negative regulator MDM2 may offer an attractive approach for NSCLC therapy. We evaluated the antitumor activity of the small-molecule MDM2 inhibitor RG7388 in patient-derived xenograft (PDX) models of NSCLC. We investigated the effect of RG7388 treatment on cell proliferation, cell cycle arrest, and apoptosis using a panel of human NSCLC cell lines (A549, H157, H1650, H1395, and H358) and PDX cell lines (human lung cell lines 12, 137, 277, and 196). PDX-bearing mice were used to test the therapeutic efficacy and pharmacodynamic effects of RG7388 treatment. We demonstrated that RG7388 promotes low nanomolar antiproliferative activity selectively in cell lines with wild-type p53 and p53 pathway activation, resulting in cell cycle arrest and apoptosis. In PDX models, oral administration of RG7388 led to potent dose-dependent and time-dependent activation of p53 and had a significant impact on p53 downstream targets. Daily treatment of RG7388 in mice at 50 and 80 mg/kg/day inhibited tumor growth in three wild-type p53 PDX models. Activation of the p53 pathway inhibited cell proliferation as observed by reduced Ki-67-positive cells in xenograft tumors. However, induction of apoptotic caspase activity was not observed in these tumors. Notably, RG7388 treatment remains effective in tumors lacking MDM2 amplification but expressing wild-type p53. MDM2 small-molecule inhibitor is effective in treating NSCLC tumors with wild-type p53, supporting further clinical investigation as a potential NSCLC therapy.

Abstract 669: BGB-283 effectively enhances MEK inhibitor induced tumor suppression in RAS mutant cancers

Abstract Mutation in K-RAS, which drives constitutive activation of the mitogen-activated protein kinase (MAPK) signaling pathway, is one of the most frequent genetic alterations in human cancers. Pharmacological targeting RAS mutants directly is extremely challenging and targeted inhibition of K-RAS downstream effector MEK has shown limited clinical activity in suppressing the progression of K-RAS mutant tumors. The reduced sensitivity of K-RAS-mutated cancer cells to MEK inhibitors (MEKi) is associated with feedback phosphorylation of MEK and rebound of phosphorylated ERK levels after prolonged treatment. A synthetic lethal screen provided the rational of targeting both RAF1 and MEK in K-RAS mutated cancers. In this study, we investigated whether combining BGB-283, a potent inhibitor to RAF dimers, and a series of MEKi could achieve better therapeutic effect of the latter. We confirmed that selumetinib (AZD6244) induced strong MEK phosphorylation in K-RAS mutated cancer cells. Either knockdown of B-RAF/C-RAF or addition of BGB-283 in the presence of selumetinib potently inhibited RAF-dependent MEK phosphorylation and led to sustained inhibition of ERK activity. Furthermore, BGB-283 and selumetinib showed synergistic effect in inhibiting proliferation of several non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) cell lines harboring RAS mutations. In vivo, combined dosing of BGB-283 and AZD6244 also exhibited enhanced antitumor activity in K-RAS mutant NSCLC and CRC xenograft models compared to monotherapies. Pharmacodynamic (PD) analysis revealed improved inhibition of ERK phosphorylation in dually treated tumors. Together, these findings suggested that combining RAF dimer inhibitor BGB-283 and MEKi could be a promising strategy in treating RAS mutated cancers. Citation Format: Xi Yuan, Zhiyu Tang, Rong Du, Shing-Hu Cheung, Jing Wei, Yuan Zhao, Yunguang Du, Rui Hao, Xiaoxia Hu, Wenfeng Gong, Yong Liu, Yajuan Gao, Min Wei, Changyou Zhou, Lai Wang, Lusong Luo. BGB-283 effectively enhances MEK inhibitor induced tumor suppression in RAS mutant cancers. [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 669. doi:10.1158/1538-7445.AM2015-669

Abstract 4711: CB-839, a selective glutaminase inhibitor, synergizes with signal transduction pathway inhibitors to enhance anti-tumor activity

Abstract Many tumor cells utilize the amino acid glutamine to meet the elevated bioenergetic and biosynthetic demands of rapid cell growth. Glutamine is utilized by the mitochondrial enzyme glutaminase, which converts glutamine to glutamate. Glutamate is then used to fuel downstream metabolic pathways such as the TCA cycle, redox balance and amino acid synthesis. CB-839 is a novel and selective inhibitor of glutaminase that impacts multiple metabolic pathways downstream of glutamate and has anti-tumor activity in several preclinical models. In addition to its effect on metabolism, CB-839 treatment decreased mTORC1 signaling in triple negative breast cancer [Dennison et al. (2014) Keystone Tumor Metabolism Conference Abstract #1027] and multiple myeloma cells [MacKinnon et al. (2014) ASH Annual Meeting Abstract # 3429]. These studies suggest that nutrient deprivation by CB-839 treatment can be sensed by the mTORC1 pathway. This observation motivated an evaluation of whether inhibitors of receptor tyrosine kinase signaling, the MAP kinase pathway or the PI3 kinase/mTOR pathway could combine favorably with CB-839 to inhibit proliferation. The pan receptor tyrosine kinase inhibitor pazopanib, or the mTORC1 inhibitor everolimus synergized with CB-839 to produce anti-proliferative effects in several renal cell carcinoma (RCC) cell lines (CI range: 0.09-0.85 for pazopanib/CB-839 and 0.48-0.54 for everolimus/CB-839). The EGFR inhibitor erlotinib also synergized with CB-839 to produce strong anti-proliferative effects in several non-small cell lung cancer (NSCLC) cell lines (combination index (CI) range: 0.39-0.75). CB-839 and the MEK inhibitor selumetinib showed strong synergy in the KRAS mutant NSCLC cell line H2122 (CI = 0.46), but weak synergy in the KRAS wild-type cell line H661 (CI = 0.9). These antiproliferative effects were associated with diminished mTORC1 signaling measured in NSCLC cells treated with CB-839, erlotinib, selumetinib or combinations of these agents. The in vitro synergistic CB-839 combinations were also evalutated in an in vivo H2122 NSCLC xenograft model where enhanced anti-tumor activity was observed when CB-839 was dosed together with either erlotinib or selumetinib. CB-839 is currently in Phase 1 clinical development for the treatment of solid and hematological tumor types. This study is the first demonstration that CB-839 can be used in combination with signaling pathway inhibitors to increase the anti-tumor activity of these agents. These observations provide a rationale for testing combinations of CB-839 with either erlotinib or selumetinib in NSCLC patients and pazopanib or everolimus in RCC patients. Citation Format: Mirna Rodriguez, Winter Zhang, Mark Bennett, Ethan Emberley, Mathew Gross, Julie Janes, Andrew MacKinnon, Alison Pan, Susanne Steggerda, Melissa Works, Francesco Parlati. CB-839, a selective glutaminase inhibitor, synergizes with signal transduction pathway inhibitors to enhance anti-tumor activity. [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 4711. doi:10.1158/1538-7445.AM2015-4711

Abstract 4490: Selinexor (KPT-330) radio-sensitizes non-small cell lung cancer cells in vitro and in vivo

Abstract The primary nuclear export protein, Exportin 1 (XPO1/CRM1), is overexpressed in most cancers and this overexpression is frequently correlated with poor prognosis. Selective Inhibitors of Nuclear Export (SINE) compounds are a family of small-molecule bioavailable drugs that bind covalently to XPO1 to inhibit nuclear export. This results in nuclear retention of major tumor suppressor proteins, such as p53, pRB, FOXO3A and other critical proteins in cancer biology, which leads to selective cancer cell death. Selinexor is the most advanced SINE with >500 hematological and solid tumor cancer patients treated to date in a number of Phase I/II clinical trials. Blocking XPO1 function also blocks nuclear transport of key DNA damage repair (DDR) proteins and we therefore hypothesized that combination of selinexor with radiation therapy (RT) would lead to synergistic anti-tumor activity. Radiation-chemotherapy combination is an established therapeutic option for patients with medically inoperable non-small cell lung cancer (NSCLC), but its use is limited due to tolerability and adverse effects. Moreover, this treatment strategy typically has short-term benefits and the patients relapse with progressive disease. Here we report on studies designed to test whether selinexor could interfere with DDR and synergize with radiation to enhance anti-tumor potency relative to either treatment alone. Cell cycle analysis and clonogenic assays were conducted in the presence or absence of selinexor in combination with escalating doses of RT on the radiation-sensitive and radiation-insensitive H1299 and A549 cell lines, respectively. Interestingly, Selinexor-treatment induced G1 cell cycle arrest in the p53-deficient cell line H1299 and a prominent G2 cell cycle arrest in p53-wild type A549 cells 24 hrs post treatment. Furthermore, clonogenic assays revealed that selinexor + RT treatment act synergistically to produce a dose-dependent growth inhibition in both cell lines. In vivo combination treatment in the A549 NSCLC xenograft model with low doses of selinexor and RT displayed a strong synergistic effect for reduction of tumor volume. In addition, microscopic and immunohistochemical analysis of the resected tumors showed an overall reduction in tumor cell numbers, increased fibrosis and induction of apoptosis in the selinexor-RT treated tumors compared to controls. Finally, mechanistic studies revealed that selinexor does not induce DNA damage like RT, but downregulates CHK1, RAD51 and other DDR proteins. Together, our results suggest that selinexor treatment sensitizes cells to RT by preventing single-stranded DNA break repair via downregulation of DDR protein expression. In contrast, selinexor induces cell cycle arrest at G1 in p53 deficient H1299 cells, allowing DNA damage accumulation and induction of apoptosis. These results provide a rationale basis for combining selinexor with RT in clinical trials studies. Citation Format: Tami Rashal, Sivan Elloul, Marsha Crochiere, Trinayan Kashyap, William Senapedis, Ryan George, Sharon Friedlander, Maya Ilouze, Yosef Landesman, Robert Carlson, Nir Peled, Michael Kauffman, Sharon Shacham, Yaacov Lawrence. Selinexor (KPT-330) radio-sensitizes non-small cell lung cancer cells in vitro and in vivo. [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 4490. doi:10.1158/1538-7445.AM2015-4490

Abstract 2587: A novel covalent inhibitor of mutant but not wild-type (WT) epidermal growth factor receptor (EGFR) has activity in vitro and in vivo in non-small cell lung cancer (NSCLC) models

Abstract Background: Mutations in the EGFR kinase are common in NSCLC. Patients with first-line EGFR mutations (exon 19 deletions, L858R mutations, exon 20 variants, codon 719 variants) initially respond to the reversible EGFR inhibitors erlotinib and gefitinib, but then relapse as additional mutations emerge. EGFR T790M is the most common of these mutations and is found in > 50% of refractory tumors. We assessed the in vitro and in vivo activity of CPD 24, a newly developed, covalent, small-molecule inhibitor of both first-line and T790M mutant EGFR, but not WT EGFR. Inhibition of WT EGFR in normal tissues can be a source of dose-limiting toxicities. Methods: The effects of CPD 24 were evaluated on H1975 (EGFR T790M/L858R), HCC827 (EGFR exon 19 deletion), and A431 (WT) cell lines. Inhibition of EGFR phosphorylation was measured in serum-starved cells using an MSD assay. Viability was assessed by measuring ATP in cells using a CellTiter-Glo® assay. Dose- and time-dependent pharmacodynamic effects were evaluated by treating mice bearing matrigel plugs containing H1975 cells. Drug levels were measured in plasma samples by LC-MS. CPD 24 was administered to athymic nude mice bearing H1975, HCC827, or A431 xenografts (3, 10, and 30 mg/kg, QD, PO) and tumor growth was measured twice per week with digital calipers. CPD 24 was also formulated in PLGA microspheres and administered subcutaneously (SC) as a sustained release formulation to mice bearing H1975 or A431 xenografts (30 and 100 mg/kg, Q3D, SC). Proliferation of H1975 and HCC827 cells in the presence of CPD 24, growth factors, and a MET inhibitor was measured with an IncuCyte live-cell imaging system. Results: The IC50 of CPD 24 for p-EGFR inhibition was 4 nM on L858R/T790M mutant EGFR (H1975 cells), 17 nM on the exon 19 deletion EGFR (HCC827 cells), and 510 nM on WT EGFR (A431 cells). CPD 24 inhibited the growth of tumor cells in vitro and led to both dose- and time-dependent p-EGFR inhibition in vivo. Phosphorylation of EGFR in H1975 cells growing in matrigel plugs was inhibited by > 75% for 12 hours by a single 30 mg/kg dose. Tumor growth inhibition (TGI) was observed in two EGFR mutant NSCLC xenograft models (H1975, 89% TGI; HCC827, 139% TGI) but not in a WT EGFR model (A431). CPD 24 formulated in PLGA microspheres achieved drug levels above the IC50 for 72 hours after a single SC dose. Tumor regression was observed with this formulation in H1975 xenografts but not in WT tumors. HGF was able to confer resistance to CPD 24 inhibition in both H1975 and HCC827 cells in vitro. This resistance was prevented by the addition of a selective MET inhibitor. Conclusion: CPD 24 is a covalent inhibitor of both first-line and T790M mutant EGFR while maintaining > 100-fold selectivity over WT EGFR. The antiproliferative effects of CPD 24 can be reversed by HGF, and this resistance can be prevented by treatment with a MET inhibitor. Citation Format: Pedro J. Beltran, Jinghui Zhan, Petia Mitchell, Ryan P. Wurz, Liping Pettus, Tian Wu, Mary Chaves, Darren L. Reid, Robert Radinsky, Keegan Cooke, Andrew Tasker. A novel covalent inhibitor of mutant but not wild-type (WT) epidermal growth factor receptor (EGFR) has activity in vitro and in vivo in non-small cell lung cancer (NSCLC) models. [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 2587. doi:10.1158/1538-7445.AM2015-2587

Nicotine induces resistance to erlotinib via cross-talk between α 1 nAChR and EGFR in the non-small cell lung cancer xenograft model.

Given our previously published study, α 1 nicotinic acetylcholine receptor (nAChR) plays an essential role in nicotine-induced cell signaling and nicotine-induced resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) in non-small cell lung cancer (NSCLC) PC9 cells. The aim of this study was to investigate the potential mechanism between nAChR and EGFR for nicotine-induced resistance to EGFR-TKI erlotinib in the NSCLC xenograft model. We identified the role of nicotine to EGFR/AKT/ERK pathways and to erlotinib-resistance in NSCLC PC9 and HCC827 cells by MTS assay and western blot. Then, we established the PC9 xenograft model with nicotine exposure and treated mice with erlotinib combined with vehicle or nicotine. We confirmed the effects of nicotine on EGFR/AKT/ERK pathways and determined nicotine's potential in preventing from the effect of erlotinib on NSCLC cells. Then, we showed that nicotine exposures can promote tumor growth and induce resistance to erlotinib in the PC9 xenograft model. Our results also indicated that chronic oral administration of nicotine can cause more significant erlotinib-resistance compared with acute i.v. injection of nicotine through activating α 1 nAChR and EGFR pathways. These results suggest that nicotine contributes to the progression and erlotinib-resistance of the NSCLC xenograft model via the cooperation between nAChR and EGFR.

HSP90 inhibition enhances antimitotic drug-induced mitotic arrest and cell death in preclinical models of non-small cell lung cancer.

HSP90 inhibitors are currently undergoing clinical evaluation in combination with antimitotic drugs in non-small cell lung cancer (NSCLC), but little is known about the cellular effects of this novel drug combination. Therefore, we investigated the molecular mechanism of action of IPI-504 (retaspimycin HCl), a potent and selective inhibitor of HSP90, in combination with the microtubule targeting agent (MTA) docetaxel, in preclinical models of NSCLC. We identified a subset of NSCLC cell lines in which these drugs act in synergy to enhance cell death. Xenograft models of NSCLC demonstrated tumor growth inhibition, and in some cases, regression in response to combination treatment. Treatment with IPI-504 enhanced the antimitotic effects of docetaxel leading to the hypothesis that the mitotic checkpoint is required for the response to drug combination. Supporting this hypothesis, overriding the checkpoint with an Aurora kinase inhibitor diminished the cell death synergy of IPI-504 and docetaxel. To investigate the molecular basis of synergy, an unbiased stable isotope labeling by amino acids in cell culture (SILAC) proteomic approach was employed. Several mitotic regulators, including components of the ubiquitin ligase, anaphase promoting complex (APC/C), were specifically down-regulated in response to combination treatment. Loss of APC/C by RNAi sensitized cells to docetaxel and enhanced its antimitotic effects. Treatment with a PLK1 inhibitor (BI2536) also sensitized cells to IPI-504, indicating that combination effects may be broadly applicable to other classes of mitotic inhibitors. Our data provide a preclinical rationale for testing the combination of IPI-504 and docetaxel in NSCLC.

Combined treatment of XIAP-targeting shRNA and celecoxib synergistically inhibits the tumor growth of non‑small cell lung cancer cells in vitro and in vivo.

X-linked inhibitor of apoptosis protein (XIAP) has been shown to be highly expressed in lung cancer, but not in normal lung tissue, which makes it an attractive target for lung cancer treatment. Celecoxib (CXB), a cyclooxygenase-2 inhibitor, is in wide clinical use for the treatment and prevention of non-small cell lung cancer (NSCLC). Therefore, in our study, we combined short hairpin RNA (shRNA) targeted to XIAP (XIAP-shRNA) with CXB and tested the effects of this combination on lung cancer cells to identify more effective therapeutics against lung cancer. An XIAP-shRNA plasmid was constructed and transfected into the A549 NSCLC cell line. The cells were then treated with CXB and XIAP-shRNA alone or in combination for indicated time periods, and the treatments were assessed for their effects on cell proliferation, apoptosis, migration, invasion and receptor signaling using the MTT, TUNEL, wound healing and Matrigel invasion assays and western blotting, respectively. In addition, an NSCLC xenograft model was prepared to observe tumor growth. It was found that both CXB and XIAP‑shRNA significantly inhibited cell proliferation, migration and invasion, and induced cell apoptosis in vitro, as well as suppressed tumor growth in vivo. Moreover, the combination of the agents significantly enhanced these effects compared to the single agent treatments. We also found that the combination treatment significantly suppressed constitutive phosphorylation of PI3K and AKT, which may contribute to the inhibition of tumor growth. These findings suggest that the combination of XIAP‑shRNA and CXB is a promising drug candidate for the treatment of NSCLC.

Setting up a wide panel of patient-derived tumor xenografts of non-small cell lung cancer by improving the preanalytical steps.

With the ongoing need to improve therapy for non–small cell lung cancer (NSCLC) there has been increasing interest in developing reliable preclinical models to test novel therapeutics. Patient-derived tumor xenografts (PDX) are considered to be interesting candidates. However, the establishment of such model systems requires highly specialized research facilities and introduces logistic challenges. We aimed to establish an extensive well-characterized panel of NSCLC xenograft models in the context of a long-distance research network after careful control of the preanalytical steps. One hundred fresh surgically resected NSCLC specimens were shipped in survival medium at room temperature from a hospital-integrated biobank to animal facilities. Within 24 h post-surgery, tumor fragments were subcutaneously xenografted into immunodeficient mice. PDX characterization was performed by histopathological, immunohistochemical, aCGH and next-generation sequencing approaches. For this model system, the tumor take rate was 35%, with higher rates for squamous carcinoma (60%) than for adenocarcinoma (13%). Patients for whom PDX tumors were obtained had a significantly shorter disease-free survival (DFS) compared to patients for whom no PDX tumors (P = 0.039) were obtained. We established a large panel of PDX NSCLC models with a high frequency of mutations (29%) in EGFR, KRAS, NRAS, MEK1, BRAF, PTEN, and PI3KCA genes and with gene amplification (20%) of c-MET and FGFR1. This new patient-derived NSCLC xenograft collection, established regardless of the considerable time required and the distance between the clinic and the animal facilities, recapitulated the histopathology and molecular diversity of NSCLC and provides stable and reliable preclinical models for human lung cancer research.

Chemical inhibitor targeting the replication protein A–DNA interaction increases the efficacy of Pt-based chemotherapy in lung and ovarian cancer

Platinum-based chemotherapeutics exert their therapeutic efficacy via the formation of DNA adducts which interfere with DNA replication, transcription and cell division and ultimately induce cell death. Repair and tolerance of these Pt-DNA lesions by nucleotide excision repair (NER) and homologous recombination (HR) can substantially reduce the effectiveness of therapy. Inhibition of these repair pathways, therefore, holds the potential to sensitize cancer cells to Pt treatment and increase clinical efficacy. Replication Protein A (RPA) plays essential roles in both NER and HR, along with its role in DNA replication and DNA damage checkpoint activation. Each of these functions is, in part, mediated by RPA binding to single-stranded DNA (ssDNA). Here we report the synthesis and characterization of novel derivatives of RPA small molecule inhibitors and their activity in models of epithelial ovarian cancer (EOC) and non-small cell lung cancer (NSCLC). We have synthesized analogs of our previously reported RPA inhibitor TDRL-505 and determined the structure–activity relationships. These data led us to the identification of TDRL-551, which exhibited a greater than 2-fold increase in in vitro activity. TDRL-551 showed synergy with Pt in tissue culture models of EOC and in vivo efficacy, as a single agent and in combination with platinum, in a NSCLC xenograft model. These data demonstrate the utility of RPA inhibition in EOC and NSCLC and the potential in developing novel anticancer therapeutics that target RPA–DNA interactions.

3,6,2′,4′,5′-Pentahydroxyflavone, an Orally Bioavailable Multiple Protein Kinase Inhibitor, Overcomes Gefitinib Resistance in Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the most lethal cancer, causing more than 150,000 deaths in the United States in 2013. The receptor tyrosine kinase inhibitors such as gefitinib are not perfect clinical therapeutic agents for NSCLC treatment due to primary or acquired tyrosine kinase inhibitor resistance. Herein, 3,6,2',4',5'-pentahydroxyflavone (36245-PHF) was identified as a multiple kinase inhibitor for NSCLC treatment based on the computational screening of a natural products database. 36245-PHF was shown to inhibit PI3K and Aurora A and B kinases and overcome gefitinib-resistant NSCLC growth. Our data clearly showed that 36245-PHF markedly inhibited anchorage-independent growth of gefitinib-resistant NSCLC cell lines and exerted a substantial chemotherapeutic effect following oral administration in a gefitinib-resistant NSCLC xenograft model. The evidence from three different subsequent methodological approaches, in vitro, ex vivo, and in vivo, all confirmed that 36245-PHF as a multiple protein kinase inhibitor. Overall, we identified 36245-PHF as a multiple protein kinase inhibitor and as a novel therapeutic agent to overcome gefitinib-resistant NSCLC growth, which could provide a new option for clinical NSCLC oral treatment.

Abstract 4875: In vivo and in vitro generation and characterisation of EGFR-TKI resistance in patient-derived xenograft (PDX) and cell line-derived xenograft (CDX) models of NSCLC with activating EGFR mutations

Abstract Background: Non-small cell lung cancer (NSCLC) patients that have activating mutations in the epidermal growth factor receptor (EGFR) gene are treated with EGFR tyrosine kinase inhibitors (TKIs) e.g. Erlotinib (Tarceva®) and Gefitinib (Iressa®). Most NSCLC patients with activating EGFR mutations will respond to EGFR-TKIs; however, in about 50% of these cases a secondary mutation in EGFR (T790M) subsequently occurs which results in resistance to treatment. Other mechanisms of clinical resistance can also occur such as amplification of c-MET kinase, Her-2 and EMT conversion; however, additional routes of resistance are poorly defined. Using a novel NSCLC patient-derived xenograft (PDX) model, driven by the L858R EGFR mutation, we set out to recapitulate the reported clinical routes of resistance to EGFR inhibitors and to evaluate if additional mechanism could also be identified. Methods: LU6422 is a Caucasian NSCLC adenocarcinoma PDX model with an activating EGFR mutation (L858R) which is maintained subcutaneously in vivo admixed with a human stromal cell component. HCC827 is NSCLC adenocarcinoma cell line with an activating EGFR mutation (exon 19 del E746-A750). Resistant models of LU6422 and HCC827 were generated in vivo and in vitro (respectively) through repeated dosing or exposure to EGFR-TKIs. Resistant tumour material was characterised for further mutations in the EGFR gene by direct sequencing and for c-MET, Axl and Her2 over-expression and genomic amplification by quantitative PCR. Combination efficacy treatment (in vitro and in vivo) was carried out to verify documented resistance mechanisms. Results: Naïve LU6422 and HCC827 tissue exhibited exquisite sensitivity to EGFR-TKIs (100% reduction in pre-treatment tumour volume, p<0.0001). Following successive cycles of EGFR-TKI treatment several resistant subtypes were generated, cloned and characterized. Combination treatment of resistant HCC827 variants restored efficacy to naïve treatment levels. Conclusions: EGFR-TKI resistant subtypes were generated in vivo and in vitro from a proprietary patient-derived xenograft model (LU6422) and the HCC827 cell line and were characterised for their resistance mechanisms. Pre-clinical modes of acquired resistance will be invaluable in assessing novel agents targeting the EGFR pathway and the development of new combination strategies which seek to prevent or overcome resistance to EGFR-TKIs. Citation Format: Andrew McKenzie, Nektaria Papadopoulou, Simon Jiang, Martin Page, Henry Li, Rajendra Kumari, Jane Wrigley. In vivo and in vitro generation and characterisation of EGFR-TKI resistance in patient-derived xenograft (PDX) and cell line-derived xenograft (CDX) models of NSCLC with activating EGFR mutations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4875. doi:10.1158/1538-7445.AM2014-4875

Abstract 3785: Olaparib increases the effectiveness of radiation in hypoxic tumor cells in xenograft models of human non-small-cell lung cancer

Abstract Purpose: Poly (ADP-ribose) polymerase (PARP) detects DNA single strand breaks and facilitates their repair. Recently, PARP inhibitors have been shown to potentiate radiotherapy in mouse models of human non-small-cell lung cancer (NSCLC) by compromising DNA repair and increasing tumor vascular perfusion. This study examined radiosensitization by PARP inhibition in xenograft models of NSCLC with differing levels of hypoxia. Methods: For in vitro studies, human NSCLC cell lines Calu-6 and Calu-3 were treated with olaparib (5 µM) or vehicle prior to ionizing radiation (IR). Cytotoxicity was evaluated by clonogenic survival assays and DNA damage repair was assessed by γH2AX foci immunofluorescence staining. For in vivo efficacy studies, Calu-6 or Calu-3 subcutaneous xenografts (100 mm3) were established in 6-8 week old female BALB/c nude mice. Animals (n=48) were then randomized into four groups (i) control, (ii) olaparib (50 mg/kg, d1-3), (iii) IR (10 Gy, d1) and (iv) combination treatment. Subsequent tumor growth was monitored for up to 42 days. In parallel, for pharmacodynamic studies, tumor bearing animals were sacrificed 24h and 72h after treatment (n=3 for each treatment and time point). Tumor sections were evaluated by immunohistochemistry (IHC). Results: In vitro, both NSCLC cell lines were significantly radiosensitized by olaparib. Sensitization enhancement ratios were 1.9 (Calu-6) and 2.2 (Calu-3). Furthermore, olaparib markedly inhibited DNA damage repair in both Calu-6 and Calu-3 cells 24h post-IR (p<0.01). Growth of Calu-6 and Calu-3 xenografts was reduced by IR alone, but unaffected by olaparib treatment alone. Surprisingly, although olaparib significantly increased radiation-induced growth delay in Calu-6 xenografts (p<0.01), there was no significant effect in Calu-3 xenografts, in contrast to the in vitro data. IHC staining for vascularity (CD31) and hypoxia (CA9) showed that Calu-3 xenografts were well-oxygenated without evidence of necrotic tissue, whereas Calu-6 xenografts had large areas of hypoxia surrounding regions of necrosis. RAD51 expression (a protein involved in homologous recombination, HR) was selectively down-regulated in hypoxic regions of Calu-6 tumors. 24h and 72h after IR, olaparib treated Calu-6 xenografts displayed significantly higher levels of γH2AX (DNA double strand breaks) and cleaved caspase 3 (apoptosis) staining in CA9 positive (hypoxic) cells compared with the hypoxic regions in xenografts treated with IR alone. Conclusion: Our data identify a novel mechanism that contributes to radiosensitization by PARP inhibition in NSCLC. Olaparib selectively increased DNA damage and apoptosis in radioresistant hypoxic tumor cells with decreased HR potential. Our data also suggest that tumor hypoxia may be a potential biomarker of differential benefit from the combination of olaparib with radiotherapy. Citation Format: Yanyan Jiang, Tom Verbiest, Aoife M. Devery, Sivan M. Bokobza, Anika M. Weber, Anderson J. Ryan. Olaparib increases the effectiveness of radiation in hypoxic tumor cells in xenograft models of human non-small-cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3785. doi:10.1158/1538-7445.AM2014-3785

Abstract 5534: A novel and oral histone deacetylase inhibitor, resminostat, effectively suppresses the growth of non-small cell lung cancer in a xenograft mouse model

Abstract Background: Accumulating evidence reveals effectiveness of histone deacetylase (HDAC) inhibition in various types of cancer, and resminostat is a novel and oral HDAC inhibitor. In this study, we investigated the preclinical activity of resminostat in human non-small-cell lung cancer (NSCLC) cells, especially in combination with docetaxel (DTX). Materials and Methods: Anti-proliferative activity of resminostat was evaluated in 9 human NSCLC cell lines in vitro. Monolayers of cultured cells were exposed to resminostat and cell viability was determined. The amount of p21, acetylated histone H3 and α-tublin were analyzed by Western blotting in NCI-H460 cells exposed to resminostat. In addition, caspase-3 activity was measured. In a drug combination study, cells were simultaneously exposed to resminostat and DTX, and the synergistic effects of this drug combination were analyzed using the Combination Index, calculated by the median-effect method. For in vivo studies, a suspension of NCI-H460 cells was subcutaneously inoculated into the flank of male nude mice. The antitumor efficacies of oral resminostat alone or in combination with intravenous DTX were evaluated in this NSCLC xenograft model. Results: Resminostat exhibited antiproliferative activity in all tested cell lines. Sensitivity to resminostat was not influenced by the genetic status of KRAS among the cell lines (IC50 from 9 cell lines: 0.4-8.7 μmol/L). The treatment of cells with resminostat alone increased the levels of total p21 protein and acetylated histone H3. α-tublin was also acetylated by resminostat treatment and the level of acetylation was enhanced by the combination treatment with DTX. The amount of polymerized α-tubulin was increased by DTX treatment and this effect was greater in the combination treatment with resminostat than with DTX alone. Caspase-3 was more significantly activated by the combination treatment than with each mono-treatment. The Combination Index showed synergistic or additive effects in the resminostat plus DTX combination. The antitumor activities of resminostat were demonstrated in NCI-H460 tumor-bearing mice, where an up-regulation of p21 was accompanied by acetylation of histone H3 in the tumor tissues. The tumor growth inhibition ratio (IR) in the combination treatment was 2.6 and 1.8 times higher than with DTX alone or with resminostat alone, respectively, following a tolerable drug application schedule. Conclusion: These results demonstrated the potent activity of resminostat in NSCLC. The combination of resminostat and DTX appears to be a promising regimen to be tested in clinical trials in NSCLC patients. Based on this study, we initiated a phase I/II study in NSCLC patients to examine the safety and efficacy of this combination. Citation Format: Akimitsu Takagi, Hiroaki Konishi, Momomi Tsugane, Keisuke Taniguchi, Hiroyuki Takahashi, Yu Inutake, Akinobu Watanabe, Hiroshi Kodaira, Takeshi Matsuzaki. A novel and oral histone deacetylase inhibitor, resminostat, effectively suppresses the growth of non-small cell lung cancer in a xenograft mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5534. doi:10.1158/1538-7445.AM2014-5534