TNIK inhibition sensitizes TNIK-overexpressing lung squamous cell carcinoma to radiotherapy

Most patients with lung squamous cell carcinoma (LSCC) undergo chemotherapy, radiotherapy, and adjuvant immunotherapy for locally advanced disease. The efficacy of these treatments is still limited due to dose-limiting toxicity or locoregional recurrence. New combination approaches and targets such as actionable oncogenic drivers are needed to advance treatment options for LSCC patients. Moreover, other options for chemotherapy-ineligible patients are also limited. As such there is a critical need for the development of selective and potent chemoradiosensitizers for locally advanced LSCC. Here, we investigated inhibiting TRAF2 and NCK-interacting protein kinase (TNIK), which is amplified in 40% of LSCC patients, as a strategy to sensitize LSCC tumors to chemo- and radiotherapy. Employing a range of human LSCC cell lines and the TNIK inhibitor NCB-0846, we investigated the potential of TNIK as a chemo- and radiosensitizing target with in vitro and in vivo preclinical models. The combination of NCB-0846 with cisplatin or etoposide was at best additive. Interestingly, pre-treating LSCC cells with NCB-0846 prior to ionizing radiation (IR) potentiated the cytotoxicity of IR in a TNIK-specific fashion. Characterization of the radiosensitization mechanism suggested that TNIK inhibition may impair the DNA damage response and promote mitotic catastrophe in irradiated cells. In a subcutaneous xenograft in vivo model, pretreatment with NCB-0846 significantly enhanced the efficacy of IR and caused elevated necrosis in TNIKhigh LK2 tumors but not TNIKlow KNS62 tumors. Overall, these results indicate that TNIK inhibition may be a promising strategy to increase the efficacy of radiotherapy in LSCC patients with high TNIK expression.

Abstract 2818: Investigating TNIK as a radiosensitizing target in lung squamous cell carcinoma

In this study, we investigated the potential of TNIK inhibition as a radiosensitizing strategy in lung squamous cell carcinoma (LSCC). LSCC is a type of lung malignancy that accounts for about 30% of all lung cancer cases. As there are no known actionable oncogenic drivers in LSCC, there is currently no FDA-approved targeted therapy for LSCC patients. Most still receive chemotherapy and radiotherapy for locally advanced disease. As such, there is a critical need for the identification of therapeutic targets in LSCC. The protein kinase TNIK represents a potential target for therapeutic intervention. A positive regulator of the Wnt signaling pathway, TNIK is implicated in promoting tumorigenesis and treatment resistance in different cancers. Importantly, TNIK copy number amplification is a signature genomic alteration in LSCC as it is observed in about 50% of LSCC patients. Recently, it was shown that disrupting TNIK activity with NCB-0846, a small-molecule inhibitor of TNIK, inhibited the proliferation of TNIKhigh LSCC tumors. To extend this finding, we investigated whether TNIK inhibition can sensitize LSCC tumors to chemo- and radiotherapy. By employing NCB-0846 and a panel of LSCC cell lines with low and high TNIK expression, we conducted short-term and long-term cell viability experiments to evaluate the synergy between TNIK inhibition and chemo- and radiotherapy. The combination of NCB-0846 with conventional chemotherapeutic agents was antagonistic. Interestingly, we observed that treating LSCC cells with NCB-0846 prior to ionizing radiation (IR) enhanced the tumor-killing effects of IR in a TNIK-specific fashion. The radiosensitizing effect was only observed in TNIKhigh but not in TNIKlow cell lines. Further mechanistic studies suggested that TNIK inhibition may radiosensitize LSCC tumors by impairing the endogenous DNA damage repair process and G2/M cell cycle arrest in response to IR. Consequently, tumor cells incurred elevated DNA damage from IR and underwent more catastrophic cell division events. To test whether TNIK inhibition radiosensitizes in vivo, we subcutaneously implanted in immunocompromised NSG mice LK2 (TNIKhigh) and KNS62 (TNIKlow) human LSCC cells. The mice were treated with (1) vehicle control, (2) NCB-0846 only, (3) IR only, or (4) IR following pre-treatment with NCB-0846. We observed that pretreatment with NCB-0846 significantly potentiated the efficacy of IR in eradicating TNIKhigh LK2 tumors but not TNIKlow KNS62 tumors. Overall, these results indicate that TNIK inhibition may be a viable strategy to enhance the efficacy of radiotherapy in LSCC tumors with high TNIK expression.

Citation Format: Triet M. Nguyen, Audrey M. Lafargue, Francesca A. Carrieri, Nick Connis, Jinhee Chang, Shreya Jagtap, Pedro Torres-Ayuso, John Brognard, Christine L. Hann, Phuoc T. Tran. Investigating TNIK as a radiosensitizing target in lung squamous cell carcinoma [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 2818.

Griseofulvin Radiosensitizes Non-Small Cell Lung Cancer Cells and Activates cGAS

Extra copies of centrosomes are frequently observed in cancer cells. To survive and proliferate, cancer cells have developed strategies to cluster extra-centrosomes to form bipolar mitotic spindles. The aim of this study was to investigate whether centrosome clustering (CC) inhibition (CCi) would preferentially radiosensitize non-small cell lung cancer (NSCLC). Griseofulvin (GF; FDA-approved treatment) inhibits CC, and combined with radiation treatment (RT), resulted in a significant increase in the number of NSCLC cells with multipolar spindles, and decreased cell viability and colony formation ability in vitro. In vivo, GF treatment was well tolerated by mice, and the combined therapy of GF and radiation treatment resulted in a significant tumor growth delay. Both GF and radiation treatment also induced the generation of micronuclei (MN) in vitro and in vivo and activated cyclic GMP-AMP synthase (cGAS) in NSCLC cells. A significant increase in downstream cGAS-STING pathway activation was seen after combination treatment in A549 radioresistant cells that was dependent on cGAS. In conclusion, GF increased radiation treatment efficacy in lung cancer preclinical models in vitro and in vivo. This effect may be associated with the generation of MN and the activation of cGAS. These data suggest that the combination therapy of CCi, radiation treatment, and immunotherapy could be a promising strategy to treat NSCLC.

Co-targeting BCL-XL and MCL-1 with DT2216 and AZD8055 synergistically inhibit small-cell lung cancer growth without causing on-target toxicities in mice

Small-cell lung cancer (SCLC) is an aggressive malignancy with limited therapeutic options. The dismal prognosis in SCLC is in part associated with an upregulation of BCL-2 family anti-apoptotic proteins, including BCL-X_L and MCL-1. Unfortunately, the currently available inhibitors of BCL-2 family anti-apoptotic proteins, except BCL-2 inhibitors, are not clinically relevant because of various on-target toxicities. We, therefore, aimed to develop an effective and safe strategy targeting these anti-apoptotic proteins with DT2216 (our platelet-sparing BCL-X_L degrader) and AZD8055 (an mTOR inhibitor) to avoid associated on-target toxicities while synergistically optimizing tumor response. Through BH3 mimetic screening, we identified a subset of SCLC cell lines that is co-dependent on BCL-X_L and MCL-1. After screening inhibitors of selected tumorigenic pathways, we found that AZD8055 selectively downregulates MCL-1 in SCLC cells and its combination with DT2216 synergistically killed BCL-X_L/MCL-1 co-dependent SCLC cells, but not normal cells. Mechanistically, the combination caused BCL-X_L degradation and suppression of MCL-1 expression, and thus disrupted MCL-1 interaction with BIM leading to an enhanced apoptotic induction. In vivo, the DT2216 + AZD8055 combination significantly inhibited the growth of cell line-derived and patient-derived xenografts and reduced tumor burden accompanied by increased survival in a genetically engineered mouse model of SCLC without causing appreciable thrombocytopenia or other normal tissue injuries. Thus, these preclinical findings lay a strong foundation for future clinical studies to test DT2216 + mTOR inhibitor combinations in a subset of SCLC patients whose tumors are co-driven by BCL-X_L and MCL-1.

AZD8055 enhances in vivo efficacy of afatinib in chordomas

Chordomas are primary bone tumors that arise in the cranial base, mobile spine, and sacrococcygeal region, affecting patients of all ages. Currently, there are no approved agents for chordoma patients. Here, we evaluated the anti-tumor efficacy of small molecule inhibitors that target oncogenic pathways in chordoma, as single agents and in combination, to identify novel therapeutic approaches with the greatest translational potential. A panel of small molecule compounds was screened in vivo against patient-derived xenograft (PDX) models of chordoma, and potentially synergistic combinations were further evaluated using chordoma cell lines and xenograft models. Among the tested agents, inhibitors of EGFR (BIBX 1382, erlotinib, and afatinib), c-MET (crizotinib), and mTOR (AZD8055) significantly inhibited tumor growth in vivo but did not induce tumor regression. Co-inhibition of EGFR and c-MET using erlotinib and crizotinib synergistically reduced cell viability in chordoma cell lines but did not result in enhanced in vivo activity. Co-inhibition of EGFR and mTOR pathways using afatinib and AZD8055 synergistically reduced cell viability in chordoma cell lines. Importantly, this dual inhibition completely suppressed tumor growth in vivo, showing improved tumor control. Together, these data demonstrate that individual inhibitors of EGFR, c-MET, and mTOR pathways suppress chordoma growth both in vitro and in vivo. mTOR inhibition increased the efficacy of EGFR inhibition on chordoma growth in several preclinical models. The insights gained from our study potentially provide a novel combination therapeutic strategy for patients with chordoma. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Abstract PR-008: Identification and characterization of the molecular mechanisms of SCLC chemo-radiation resistance

Small cell lung cancer (SCLC) is among the most aggressive form of lung malignancies and accounts for 15-20% of all lung cancers. It has the tendency to metastasize early, thus limited-stage SCLC patients still receive systemic treatment with chemo-radiotherapy (chemoXRT) for their localized disease. SCLC is exceptionally sensitive to chemoXRT and exhibits high response rates; however, the recurrence rate is almost 100% and patients relapse with tumors that resist further treatments. Elucidating mechanisms of chemoXRT resistance in SCLC is needed to develop improved therapies and positively impact patient outcomes. To better interrogate mechanisms of chemoXRT resistance, we developed a SCLC patient-derived xenograft (PDX) in vivo system for the major molecular subtypes of SCLC (classic and variant). Briefly, PDX tumor bearing mice were treated with: 1) vehicle control; 2) cisplatin plus etoposide (EP); 3) radiotherapy (XRT); and 4) both EP/XRT. A major response was observed within the EP/XRT arm compared to vehicle or single therapy arms. Whole transcriptome profiling among all treatment arms revealed molecular pathways and biological processes associated with chemoXRT resistance. Also, by comparing our data with two previous SCLC patient cohort studies, we identified gene candidates for functional validation of chemoXRT resistance (i.e. ST6GAL1, TNIK and SOHLH2). To enable real-time cellular and molecular analysis of PDX behavior ex vivo and to validate SCLC chemoXRT resistance candidate genes, we established a novel PDX organoid (PDO) model to study the molecular underpinnings of XRT resistance in SCLC. Classic and variant SCLC PDOs still retained the cellular, DNA and RNA markers consistent with their parental PDX molecular subtype classification using array comparative genomic hybridization and RNA-sequencing. We aim to utilize our novel SCLC PDX/PDO models as a tool to identify and validate candidates for chemoXRT resistance to be used as biomarkers and targets to combat chemoXRT resistance in SCLC.

Citation Format: Francesca Anna Carrieri, Nick Connis, Eloise Grasset, Eddie Luidy-Imada, Andrew Ewald, Luigi Marchionni, Christine Hann, Phuoc T. Tran. Identification and characterization of the molecular mechanisms of SCLC chemo-radiation resistance [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PR-008.

Nelfinavir Inhibits the Growth of Small-cell Lung Cancer Cells and Patient-derived Xenograft Tumors

BACKGROUND/AIM

Small-cell lung cancer (SCLC) is aggressive and confers poor prognosis. Although SCLC shows more response to chemotherapy than other types of lung cancer, it is difficult to cure because of its frequent recurrence. New drugs and molecular targets need to be identified.

MATERIALS AND METHODS

We investigated the effect of nelfinavir, an HIV protease inhibitor, on SCLC cells and in preclinical treatment studies using SCLC patient-derived xenograft (PDX) mouse models.

RESULTS

Nelfinavir inhibited SCLC cell proliferation and induced cell death in vitro, which was caused by induction of the unfolded protein response (UPR), inhibition of mammalian/mechanistic target of rapamycin (mTOR) activation, and reduction in the expression of SCLC-related molecules such as achaete-scute homolog 1 (ASCL1). In vivo, nelfinavir inhibited the growth of SCLC PDX tumors, which correlated with the induction of UPR and reduced expression of ASCL1.

CONCLUSION

Nelfinavir is highly effective in SCLC in vitro and in vivo, suggesting possible incorporation of nelfinavir into clinical trials for patients with SCLC.

Abstract 3926: Establishment of patient-derived organoids as ex vivo tool to characterize the molecular mechanisms of SCLC chemo-radiation resistance

Small cell lung cancer (SCLC) is the most aggressive form of lung malignancies and accounts for 15-20% of all lung cancers. It has the tendency to metastasize early, thus limited-stage SCLC patients receive systemic chemo-radiotherapy (XRT) treatments. SCLC is exceptionally sensitive to XRT and exhibits high response rates; however, the recurrence rate is almost 100% and patients relapse with tumors that resist further chemotherapy. Clearly, elucidating the mechanisms of chemo-radiation resistance in SCLC will contribute to understanding how SCLC resists further treatments, to develop improved therapies and positively impact patient outcomes. Significant limitations for SCLC therapeutic development have been the lack of germane reliable and tractable model systems. Recent advances in establishing 3D organotypic culture have shown that this model can preserve the majority of pathways, key genes, histology and behavior of in situ tumors. Furthermore, patient-derived organoids (PDO) represent a powerful preclinical model that enable real-time cellular and molecular analysis of patient-derived xenograft (PDX) behavior ex vivo. Here, we present a novel patient-derived cancer organoid model to study the molecular underpinnings of XRT resistance in SCLC. Classic and variant SCLC PDX tumor tissues were isolated from mice and mechanically dissociated. Derived organoids were cultured in basal organoid medium. PDOs have been characterized using the SCLC molecular subtype classification reported in literature. RNA for transcriptomic analyses has been obtained to further characterize gene expression profiles of primary PDXs and PDOs, and to reconstruct gene regulatory network associated with XRT resistance. A SCLC PDX served as in vivo system to characterize the response to chemo-radiation resistance. Briefly, PDX tumor bearing mice were treated with: 1) vehicle control; 2) Cisplatin 5mg/kg on d1 plus Etoposide 8mg/kg on d1-2 (EP); 3) Radiotherapy 3Gy x1 on d3 (RT); and 4) both EP/RT. Whole transcriptome profiling among all treatments arms reveals molecular pathways and biological processes associated with XRT resistance. Also, by comparing our data with two previous SCLC patient cohort studies, we identified ideal candidates for functional analyses. SCLC XRT resistance candidate genes will be tested by either treating PDOs with small molecule inhibitors or by cDNA/shRNA lentiviral infection. To assess changes in chemo-radiation sensitivity, chemo-radiation protocols have been established and immunofluorescence staining for Ki67, γH2AX and cleaved caspase 3 served as markers for proliferation, DNA damage and apoptosis, respectively. Although further in-depth characterization is required, we aim to utilize our novel SCLC PDO model as a tool to identify candidate biomarkers to be used for developing therapy responses and translational research.

Citation Format: Francesca A. Carrieri, Nick Connis, Eloise M. Grasset, Isaac S. Chan, Eddie Luidy-Imada, Christine Lam, Hailun Wang, Andrew J. Ewald, Luigi Marchionni, Christine L. Hann, Phuoc T. Tran. Establishment of patient-derived organoids as ex vivo tool to characterize the molecular mechanisms of SCLC chemo-radiation resistance [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 3926.

Regulation of RhoB Gene Expression during Tumorigenesis and Aging Process and Its Potential Applications in These Processes

RhoB, a member of the Ras homolog gene family and GTPase, regulates intracellular signaling pathways by interfacing with epidermal growth factor receptor (EGFR), Ras, and phosphatidylinositol 3-kinase (PI3K)/Akt to modulate responses in cellular structure and function. Notably, the EGFR, Ras, and PI3K/Akt pathways can lead to downregulation of RhoB, while simultaneously being associated with an increased propensity for tumorigenesis. Functionally, RhoB, part of the Rho GTPase family, regulates intracellular signaling pathways by interfacing with EGFR, RAS, and PI3K/Akt/mammalian target of rapamycin (mTOR), and MYC pathways to modulate responses in cellular structure and function. Notably, the EGFR, Ras, and PI3K/Akt pathways can lead to downregulation of RhoB, while simultaneously being associated with an increased propensity for tumorigenesis. RHOB expression has a complex regulatory backdrop consisting of multiple histone deacetyltransferase (HDACs 1 and 6) and microRNA (miR-19a, -21, and -223)-mediated mechanisms of modifying expression. The interwoven nature of RhoB’s regulatory impact and cellular roles in regulating intracellular vesicle trafficking, cell motion, and the cell cycle lays the foundation for analyzing the link between loss of RhoB and tumorigenesis within the context of age-related decline in RhoB. RhoB appears to play a tissue-specific role in tumorigenesis, as such, uncovering and appreciating the potential for restoration of RHOB expression as a mechanism for cancer prevention or therapeutics serves as a practical application. An in-depth assessment of RhoB will serve as a springboard for investigating and characterizing this key component of numerous intracellular messaging and regulatory pathways that may hold the connection between aging and tumorigenesis.

Abstract 684: Nelfinavir inhibits the growth of small cell lung cancer cells and patient-derived xenograft tumors

Small cell lung cancer (SCLC) is an aggressive lung cancer with a poor prognosis that is characterized by frequent metastasis at the time of diagnosis. Although SCLC is more responsive to chemotherapy and radiation therapy compared to other types of lung cancer, cure is difficult because of frequent recurrence. Molecular alterations in SCLC include inactivation of TP53 and RB1, high copy number of Myc family, and amplifications of FGFR1 and SOX2. Additionally, achaete-scute homolog 1 (ASCL1), a transcription factor for development of pulmonary neuroendocrine cells, is a lineage-dependent oncogene for SCLC. New drugs and molecular targets need to be identified. Previously, we reported nelfinavir (NFV), a HIV protease inhibitor, inhibited proliferation of non-small cell lung cancer (NSCLC) cells in vitro and human NSCLC xenograft tumors through induction of the unfolded protein response (UPR). Here we demonstrate that the effect of NFV in SCLC cells and preclinical treatment studies using SCLC patient-derived xenograft (PDX) mouse models. NFV inhibited SCLC cell proliferation and induced cell death in vitro. Activating transcription factor 4 (ATF4), a marker of the UPR, was rapidly increased, whereas Myc was decreased after 4 hr treatment with NFV. AMP-activated protein kinase (AMPK), which plays a role in cellular energy homeostasis, was activated in the early phase of NFV treatment, whereas the mammalian target of rapamycin (mTOR) that is a serine/threonine kinase that regulates cell growth, was inactivated. NFV inhibited the expression of SOX2, ASCL1 and Aurora B in a cell line- and time-dependent manner. Taken together, NFV had pleiotropic effects against multiple targets during the inhibition of SCLC cell proliferation. In vivo, NFV inhibited growth of SCLC PDX tumors, which correlated with induction of the UPR and decreased expression of ASCL1 and Aurora B. Collectively, these findings show that NFV is highly effective in SCLC in vitro and in vivo, suggesting possible value of incorporating NFV into clinical trials for patients with SCLC.

Citation Format: Shigeru Kawabata, Nick Connis, Chunyu Zhang, Joell J. Gills, Christine L. Hann, Phillip A. Dennis. Nelfinavir inhibits the growth of small cell lung cancer cells and patient-derived xenograft tumors. [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 684. doi:10.1158/1538-7445.AM2015-684

DNA methylation in small cell lung cancer defines distinct disease subtypes and correlates with high expression of EZH2

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastasis, rapid development of resistance to chemotherapy, and genetic instability. This study profiles DNA methylation in SCLC, patient-derived xenografts (PDXs) and cell lines at single nucleotide resolution. DNA methylation patterns of primary samples are distinct from those of cell lines, while PDXs maintain a pattern closely consistent with primary samples. Clustering of DNA methylation and gene expression of primary SCLC revealed distinct disease subtypes among histologically indistinguishable primary patient samples with similar genetic alterations. SCLC is notable for dense clustering of high-level methylation in discrete promoter CpG islands, in a pattern clearly distinct from other lung cancers and strongly correlated with high expression of the E2F target and histone methyltransferase gene EZH2. Pharmacologic inhibition of EZH2 in a SCLC PDX markedly inhibited tumor growth.

Rapamycin rescues ABT-737 efficacy in small cell lung cancer

Overexpression of the antiapoptotic protein Bcl-2 is observed in the majority of small cell lung cancer (SCLC) cases and is associated with resistance to chemotherapy. While targeting Bcl-2 in hematologic malignancies continues to show signs of promise, translating the BH3 mimetic ABT-737 (or ABT-263; navitoclax) to the clinic for solid tumors has remained problematic, with limited single-agent activity in early-phase clinical trials. Here, we used patient-derived xenograft (PDX) models of SCLC to study ABT-737 resistance and demonstrated that responses to ABT-737 are short lived and coincide with decreases in HIF-1α-regulated transcripts. Combining the mTOR inhibitor rapamycin with ABT-737 rescued this resistance mechanism, was highly synergistic in vitro, and provided durable tumor regressions in vivo without notable hematologic suppression. In comparison, tumor regressions did not occur when ABT-737 was combined with etoposide, a gold-standard cytotoxic for SCLC therapy. Rapamycin exposure was consistently associated with an increase in the proapoptotic protein BAX, whereas ABT-737 caused dose-dependent decreases in BAX. As ABT-737 triggers programmed cell death in a BAX/BAK-dependent manner, we provide preclinical evidence that the efficacy of ABT-737 as a single agent is self-limiting in SCLC, but the addition of rapamycin can maintain or increase levels of BAX protein and markedly enhance the anticancer efficacy of ABT-737. These data have direct translational implications for SCLC clinical trials.

Bisphosphonamidate clodronate prodrug exhibits selective cytotoxic activity against melanoma cell lines

Bisphosphonates are used clinically to treat disorders of calcium metabolism and malignant bone disease and are known to inhibit cancer cell growth, adhesion, and invasion. However, clinical use of these agents for the treatment of extraskeletal disease is limited because of low cell permeability. We recently described a bisphosphonamidate prodrug strategy for efficient intracellular release of bisphosphonates, including clodronate (CLO), in non-small cell lung cancer cells. To evaluate anticancer activity of this prodrug class across many cancer cell types, the bisphosphonamidate clodronate prodrug (CLO prodrug) was screened against the NCI-60 cell line panel, and was found to exhibit selectivity toward melanoma cell lines. Here, we confirm efficient cellular uptake and intracellular activation of this prodrug class in melanoma cells. We further demonstrate inhibition of melanoma cell proliferation, induction of apoptosis, and an antitumor effect of CLO prodrug in a xenograft model. These data suggest a novel therapeutic application for the CLO prodrug and potential to selectively target melanoma cells.

Erlotinib inhibits growth of a patient-derived chordoma xenograft

Chordomas are rare primary bone tumors that occur along the neuraxis. Primary treatment is surgery, often followed by radiotherapy. Treatment options for patients with recurrence are limited and, notably, there are no FDA approved therapeutic agents. Development of therapeutic options has been limited by the paucity of preclinical model systems. We have established and previously reported the initial characterization of the first patient-derived chordoma xenograft model. In this study, we further characterize this model and demonstrate that it continues to resemble the original patient tumor histologically and immunohistochemically, maintains nuclear expression of brachyury, and is highly concordant with the original patient tumor by whole genome genotyping. Pathway analysis of this xenograft demonstrates activation of epidermal growth factor receptor (EGFR). In vitro studies demonstrate that two small molecule inhibitors of EGFR, erlotinib and gefitinib, inhibit proliferation of the chordoma cell line U-CH 1. We further demonstrate that erlotinib significantly inhibits chordoma growth in vivo. Evaluation of tumors post-treatment reveals that erlotinib reduces phosphorylation of EGFR. This is the first demonstration of antitumor activity in a patient-derived chordoma xenograft model and these findings support further evaluation of EGFR inhibitors in this disease.

Abstract 2166: Rapamycin can overcome ABT-737 resistance in patient-derived SCLC xenograft models

Small cell lung cancer (SCLC) is an aggressive form of lung cancer with one of the highest case fatality rates among cancers. Standard therapy for SCLC has not changed in nearly 30 years and despite high initial response rates, treatment-refractory recurrence is nearly universal. Overexpression of the anti-apoptotic protein, Bcl-2, is observed in the majority of SCLC cases and is associated with therapy resistance. We have previously shown that the small molecule BH3 mimetic, ABT-737, is cytotoxic against Bcl-2 expressing SCLC cell lines in vitro and causes dramatic tumor regressions in SCLC cell line-based xenografts in vivo (Hann et al., Can Res 2008). We have also assessed the activity of ABT-737 in patient-derived (PD) SCLC xenografts; a model we believe better reflects patient tumor biology (Daniel et al., Can Res 2009). In PD SCLC xenografts that express high levels of Bcl-2, we found that treatment with ABT-737 caused tumor growth inhibition (TGI) but without any regressions. Our results in PD xenografts mirrored the activity seen clinically with ABT-263, an orally bioavailable form of ABT-737. In early phase trials, ABT-263 had limited single-agent activity in patients with recurrent SCLC (Rudin et al., Clin Can Res 2012).

To identify factors that contribute to ABT-737 resistance we compared the gene expression profiles of PD SCLC xenografts after treatment with ABT-737 to treatment-naïve tumors. We then used the Connectivity Map database to identify compounds that could potentially overcome ABT-737 resistance by inducing gene expression changes inverse to those observed in ABT-737 resistant xenografts. The top candidates from our query included inhibitors of the PI3K/mTOR axis. mTOR plays a key role in the hypoxic response through positive regulation of HIF1α and its downstream targets; this pathway was one of the most enriched gene expression profiles in our ABT-737 resistant xenografts.

We assessed the combination of ABT-737 and the mTOR inhibitor, rapamycin, in two PD SCLC xenografts. We found that combination treatment was well-tolerated and resulted in rapid tumor regression in mice. This response was durable; after treatment discontinuation, the combination-treated tumors remained too small to measure for over 30 days. In contrast, treatment with either ABT-737 or rapamycin alone caused TGI but no tumor regressions. Furthermore, combination treatment of animals that had previously received either single agent also resulted in tumor regression, suggesting that resistance to combination therapy did not develop after exposure to either single agent in the acute setting. Correlative studies of the mTOR and HIF1α pathways on our models and efficacy studies in additional PD SCLC xenografts are currently underway. As the safety of ABT-263 has been determined in early phase clinical trials and several FDA-approved mTOR inhibitors are currently available, this treatment paradigm may have clinical applicability.

Citation Format: Nick Connis, Eric E. Gardner, John T. Poirier, Chandrashekhar D. Kamat, Leslie Cope, Charles M. Rudin, Christine L. Hann. Rapamycin can overcome ABT-737 resistance in patient-derived SCLC xenograft models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2166. doi:10.1158/1538-7445.AM2013-2166

Abstract 360: Erlotinib inhibits growth of a patient derived chordoma tumor xenograft

Chordomas are rare primary bone tumors that occur along the neuraxis. Current treatment includes surgical resection and often postoperative radiotherapy. Despite treatment, local recurrence occurs in the majority of patients and metastasis is frequent. Treatment options for patients with recurrence is limited and, notably, there are no FDA approved chemotherapeutic agents. Median survival is approximately 7 years. The lack of treatment options is in part due to the paucity of preclinical model systems for this tumor. We have previously established a serially transplantable animal model directly from human chordoma tissue. Further analysis of this patient derived xenograft demonstrates that subsequent passages continue to resemble the original patient tumor histologically and immunohistochemically and maintain nuclear expression of brachyury, a marker for chordoma. Genome wide variation between the patient's tumor and xenografts continues to be more than 99% concordant. To further characterize this model, a receptor tyrosine kinase screen of more than 70 kinases was evaluated and epidermal growth factor receptor (EGFR) was found to be the most activated kinase. In vitro studies demonstrate that EGFR inhibitors, such as erlotinib and gefitinib, inhibit growth of a validated human chordoma cell line, U-CH1. In vivo studies demonstrate that erlotinib significantly inhibits growth of this patient derived chordoma xenograft. Evaluation of tumors post-treatment reveals that erlotinib reduces tumor proliferation and phosphorylation of EGFR. Taken together, these findings demonstrate targeting EGFR can inhibit chordoma growth in vivo and support further clinical evaluation of EGFR inhibitors in the treatment of this disease.

Citation Format: I-Mei Siu, Peter C. Burger, Qi Zhao, Jacob Ruzevick, Nick Connis, Christine L. Hann, Gary L. Gallia. Erlotinib inhibits growth of a patient derived chordoma tumor xenograft. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 360. doi:10.1158/1538-7445.AM2013-360

Poly(β-amino ester) nanoparticle delivery of TP53 has activity against small cell lung cancer in vitro and in vivo

Small cell lung cancer (SCLC) is an aggressive disease with one of the highest case-fatality rates among cancer. The recommended therapy for SCLCs has not changed significantly over the past 30 years; new therapeutic approaches are a critical need. TP53 is mutated in the majority of SCLC cases and its loss is required in transgenic mouse models of the disease. We synthesized an array of biodegradable poly(β-amino ester) (PBAE) polymers that self-assemble with DNA and assayed for transfection efficiency in the p53-mutant H446 SCLC cell line using high-throughput methodologies. Two of the top candidates were selected for further characterization and TP53 delivery in vitro and in vivo. Nanoparticle delivery of TP53 resulted in expression of exogenous p53, induction of p21, induction of apoptosis, and accumulation of cells in sub-G1 consistent with functional p53 activity. Intratumoral injection of subcutaneous H446 xenografts with polymers carrying TP53 caused marked tumor growth inhibition. This is the first demonstration of TP53 gene therapy in SCLC using nonviral polymeric nanoparticles. This technology may have general applicability as a novel anticancer strategy based on restoration of tumor suppressor gene function.

Abstract 5662: The development of SCLC specific nanoparticle-mediated p53 gene therapy

Lung cancer is the most common cause of cancer-related deaths worldwide. Small cell lung cancer (SCLC) is a highly malignant and aggressive type of lung cancer with widespread metastases and poor prognosis. SCLC is characterized by chemoresistance and radioresistance with an average survival period of <1 year. Clinically, over 70% of SCLC cases harbor mutations in two key tumor suppressor genes, p53 and Rb, whose deletion or inactivation is associated with SCLC pathogenesis. Therefore the reinstatement of wild-type (WT) p53 expression provides an attractive gene therapy strategy for SCLC. We investigated restoration of WT p53 in p53-mutant SCLC cells, using non-viral, poly(β-amino ester) (PBAE) nanoparticles for gene delivery. PBAE nanoparticles possess numerous advantages over conventional viral carriers such as low risk of insertional mutagenesis, low immunogenicity, increased cargo capacity, and capabilities for cell targeting. PBAEs encapsulate DNA to form biodegradable cationic nanoparticles and have been studied in a variety of cancer cell types and in primary endothelial cells. This is the first study of PBAE-mediated gene therapy in SCLC. Two out of 112 PBAEs initially screened, 456 and 457, were validated for gene expression efficiency using a green fluorescent protein (GFP)-based reporter in the H446 SCLC cell line using microscopy and flow cytometry. Both 456 and 457 exhibited transfection efficiency of >40%; comparable to commercially available transfection reagents. We initiated efficacy assays by validating whether H446 cells possess mutant p53 and are a suitable target for p53 restoration; p53 status in H446 and H460 cells (WT control) was confirmed by direct sequencing. A plasmid encoding WT p53-GFP under the control of the CMV promoter (CMV-p53-GFP) was used to reconstitute exogenous expression of WT p53. An 8 h incubation with 456:CMV-p53-GFP complex induced WT p53 expression in H446 cells (p53-mutant) but not in H460 cells (p53 WT); leading to a moderate p21 induction, subsequent G1-arrest and anti-proliferative effects. A CMV-p53-GFP plasmid without p53 (CMV-GFP) served as a negative control for induction and activity of exogenous p53. Additionally, 456 and 457 exhibited in vivo tumoral transfection of CMV-LUC DNA after an intratumoral or an intravenous injection. These novel in vitro and in vivo effects by PBAEs in H446 cells suggested a possible therapeutic potential for targeted p53 gene therapy in other SCLC cells and mouse models with primary SCLC xenografts. Ongoing studies include genetic characterization of patient-derived primary SCLC xenografts and assessing systemic PBAE-p53 delivery in these xenografts. In parallel, we plan to employ PBAE-p53 delivery in combination with other target genes or with chemo-/radio-therapy in SCLC cell lines and mouse models. We strongly believe that PBAE-based gene therapy would provide higher efficacy and minimal adverse effects for improved SCLC treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5662. doi:1538-7445.AM2012-5662

Characterizing the behavioral effects of nerve agent-induced seizure activity in rats: increased startle reactivity and perseverative behavior

The development and deployment of next-generation therapeutics to protect military and civilian personnel against chemical warfare nerve agent threats require the establishment and validation of animal models. The purpose of the present investigation was to characterize the behavioral consequences of soman (GD)-induced seizure activity using a series of behavioral assessments. Male Sprague-Dawley rats (n=24), implanted with a transmitter for telemetric recording of encephalographic signals, were administered either saline or 1.0 LD₅₀ GD (110 μg/kg, sc) followed by treatment with a combination of atropine sulfate (2 mg/kg, im) and the oxime HI-6 (93.6 mg/kg, im) at 1 min post-exposure. Seizure activity was allowed to continue for 30 min before administration of the anticonvulsant diazepam (10 mg/kg, sc). The animals that received GD and experienced seizure activity had elevated startle responses to both 100- and 120-dB startle stimuli compared to control animals. The GD-exposed animals that had seizure activity also exhibited diminished prepulse inhibition in response to 120-dB startle stimuli, indicating altered sensorimotor gating. The animals were subsequently evaluated for the acquisition of lever pressing using an autoshaping procedure. Animals that experienced seizure activity engaged in more goal-directed (i.e., head entries into the food trough) behavior than did control animals. There were, however, no differences between groups in the number of lever presses made during 15 sessions of autoshaping. Finally, the animals were evaluated for the development of fixed-ratio (FR) schedule performance. Animals that experienced GD-induced seizure activity engaged in perseverative food trough-directed behaviors. There were few differences between groups on other measures of FR schedule-controlled behavior. It is concluded that the GD-induced seizure activity increased startle reactivity and engendered perseverative responding and that these measures are useful for assessing the long-term effects of GD exposure in rats.

Abstract 5411: Development of SCLC specific nanoparticle-mediated therapeutic gene delivery

Lung cancer is the most common cause of cancer-related deaths worldwide. Small cell lung cancer (SCLC) is a particularly aggressive form of lung cancer characterized by early metastatic behavior. Even with currently recommended therapy, the average survival of SCLC patients is less than 1 year. There is an urgent need for novel treatments. The majority (70-90%) of SCLC cases possess alterations in p53 and Rb. This relative genetic homogeneity makes SCLC an attractive context in which to develop and test novel gene therapy approaches. We have initiated studies using non-viral, poly-β amino acid ester (PBAE) nanoparticle delivery of gene therapy in SCLC. PBAE polymers possess numerous advantages over viral delivery systems such as structural diversity, cost effectiveness, low immunogenicity and higher stability. PBAEs encapsulate DNA to form biodegradable cationic nanoparticles and have been studied in a variety of cancer cell types and in primary endothelial cells. This is the first study of PBAEs in SCLC.

A PBAE polymer library was screened in two SCLC lines using a luciferase-based high-throughput screen (HTS). Thirty-two of 112 polymers were further characterized in the H446 SCLC cell line using a CMV-GFP reporter construct and analyzed by qualitative (microscopy) and quantitative (flow cytometry) methods. This secondary screen revealed that the polymers had variable transfection efficiencies ranging from 8-55%. Four polymers, 446LG, 447LG, 456LG and 457 exhibited high transfection efficiencies (42-55%) in two SCLC cell lines, including one suspension line. Using PBAEs complexed with Cy5-labeled DNA, we were able to demonstrate that >90% cells bind and internalize the nanoparticles. We have initiated studies to better elucidate bottlenecks between nanoparticle uptake and gene expression. Additionally, preliminary studies in tumor-bearing athymic nude mice demonstrated gene uptake and expression via intratumoral injection of 457 and 446LG polymer/DNA complexes.

Ongoing studies include further optimization of PBAEs for in vitro gene expression and systemic in vivo delivery. In parallel, we are performing genetic characterization of patient-derived primary SCLC xenografts to verify relevant gene targets. Taken together, our data supports further development of a non-viral PBAE-based gene delivery approach in SCLC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5411. doi:10.1158/1538-7445.AM2011-5411