Abstract 5612: A streamlined workflow for preclinical assessment of monoclonal antibody therapies: A case study

Monoclonal antibody (mAb) therapies have become the dominant product class within the biopharmaceutical industry mainly due to their intrinsic capacity to bind endogenous immune receptors and targeted antigens. In fact, this kind of therapeutic agent accounts for one fifth of the FDA’s new drug approvals each year. In addition, their stability and specificity make them the ideal scaffold to develop more complex and efficacious drug modalities such as bispecific antibodies and antibody-drug conjugates. However, in order to advance mAb therapies to the clinic, there are a number of parameters that need to be considered during early-stage development. The purpose of this study was to showcase important preclinical characterization and efficacy experiments aimed at assessing the biological activity, binding profile, mechanism of action and in vivo potency of cetuximab, a mAb therapy. Cetuximab targets EGFR, a well characterized receptor present in the epithelial cell membrane that is overexpressed in several cancer types, such as non-small cell lung cancer, breast cancer and colorectal cancer. In normal tissues EGFR activation initiates several intracellular signaling events involved in development and homeostasis. However, when overexpressed, it stimulates the growth, metastasis and invasion of tumors. For this reason, EGFR has been considered an important target for the development of new drugs. Here we measured the binding affinity of cetuximab to two EGFR expressing cancer cell lines (A-431 and A-549) and its off-target binding to a broad range of full-length human proteins employing Retrogenix Cell Microarray Technology. Using the AlphaLISA system, we observed that cetuximab significantly inhibits EGF binding to EGFR. The consequences of cetuximab treatment on EGF binding and the initiation of the signaling cascade were investigated by looking at the phosphorylation status of EGFR via intracellular staining and flow cytometry. Moreover, we tested the ability of cetuximab to induce Antibody Dependent Cellular Cytotoxicity (ADCC) where the target cell lines were co-cultured with freshly isolated NK cells. ADCC was assessed via both flow cytometry and live cell imaging. Lastly, we studied the efficacy of cetuximab in vivo. A tumor progression mouse model generated from A-431 cells and several Patient Derived Xenografts (PDX) mouse models representing a wide variety of cancers were treated with cetuximab and a significant reduction in tumor growth was observed for most of these cancers. The in vivo efficacy correlated directly with the EGFR expression level determined by IHC. With this case study we have generated a complete and valuable preclinical data package that could be used to advance this mAb therapy into the clinic. Moreover, this study serves as the basis for a streamlined workflow for mAb lead optimization and development as well as comparability studies for biosimilars.

Citation Format: David Cobeta Lopez, Kerstin Klingner, Marie Carkill, Robert Nunan, Anya Avrutskaya, Paula Miliani de Marval, Amber Blackwell, Sarah Dawson, Donna Barnes, Jim Freeth, Deborah Bruce, Richard Bazin, René McLaughlin, Julia Schueler, Gemma Moiset, Maria L. Vlaming. A streamlined workflow for preclinical assessment of monoclonal antibody therapies: A case study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5612.

Immune cell infiltration pattern in non-small cell lung cancer PDX models is a model immanent feature and correlates with a distinct molecular and phenotypic make-up

BACKGROUND

The field of cancer immunology is rapidly moving towards innovative therapeutic strategies, resulting in the need for robust and predictive preclinical platforms reflecting the immunological response to cancer. Well characterized preclinical models are essential for the development of predictive biomarkers in the oncology as well as the immune-oncology space. In the current study, gold standard preclinical models are being refined and combined with novel image analysis tools to meet those requirements.

METHODS

A panel of 14 non-small cell lung cancer patient-derived xenograft models (NSCLC PDX) was propagated in humanized NOD/Shi-scid/IL-2Rnull mice. The models were comprehensively characterized for relevant phenotypic and molecular features, including flow cytometry, immunohistochemistry, histology, whole exome sequencing and cytokine secretion.

RESULTS

Models reflecting hot (>5% tumor-infiltrating lymphocytes/TILs) as opposed to cold tumors (<5% TILs) significantly differed regarding their cytokine profiles, molecular genetic aberrations, stroma content, and programmed cell death ligand-1 status. Treatment experiments including anti cytotoxic T-lymphocyte-associated protein 4, anti-programmed cell death 1 or the combination thereof across all 14 models in the single mouse trial format showed distinctive tumor growth response and spatial immune cell patterns as monitored by computerized analysis of digitized whole-slide images. Image analysis provided for the first time qualitative evaluation of the extent to which PDX models retain the histological features from their original human donors.

CONCLUSIONS

Deep phenotyping of PDX models in a humanized setting by combinations of computational pathology, immunohistochemistry, flow cytometry and proteomics enables the exhaustive analysis of innovative preclinical models and paves the way towards the development of translational biomarkers for immuno-oncology drugs.

Abstract 2806: Development of an iRFP713-based orthotopic patient derived brain cancer model to study tumor development in vivo

While the use of bioluminescent proteins for molecular imaging is a powerful technology to support our knowledge of complex processes, with the advent of near infrared-labeling capabilities optical imaging can be pursuit with deeper tissue penetration, a better signal to background ratio and a quicker image acquisition without the need to inject substrates in preclinical oncology mouse models. This is specifically important in orthoptic brain tumors, when the substrate concentration in the tumor tissue might be influenced by the blood-brain barrier. In our recent study, we validated the feasibility of stable or transient transfection of human brain tumor cell lines and patient derived xenografts to determine tumor load in an intracranial setting. As a proof-of principle, we stably transfected the human glioblastoma cell line U87MG with an iRFP713 construct and followed tumor growth of intracranially implanted NSG mice. As a follow-up, five PDX of pediatric brain tumors (two Ependymoma, two Medulloblastoma, one high grade Glioblastoma) were transiently transfected with the same construct 24h before intracranial implantation. Tumor load was determined twice a week with the Pearl trilogy system (LiCor, Germany) and animals were examined for neurological symptoms every day. When the overall condition of the mice got deteriorated, animals were taken down and brains fixed in formalin. The tumor load and localization was confirmed by H&E and human-specific IHC for LamininB. The comparison between non-transfected and transfected lines of one specific tumor model, revealed that the tumor growth was very similar in both settings. The tumor take rate was as well not affected. In the subsequent analyses we could show that the tumor load linearly correlated with the imaging signal. Moreover, the iRFP713 signal was stable post-resection of the tumor. Thus, it was possible to correlate the tumor load quantification via iRFP713-Protein expression and LamininB-IHC within one slide. The transient transfection was successful for the five tested models. When termination criteria were reached, over 90% of the tumor tissue were expressing the iRFP713 protein. The more general applicability for larger cohorts of mice (&gt; 20) and drug testing experiments will be evaluated soon. We believe the superior optical properties of iRFP713 will be a valuable asset to overcome some of the complications inherent to imaging live animals and a powerful tool for preclinical drug development in clinical relevant mouse models of brain cancer.

Citation Format: Kanstantsin Lashuk, Jacqueline Bersano, Dorothee Lenhard, Eva Oswald, Kerstin Klingner, Julia Schüler. Development of an iRFP713-based orthotopic patient derived brain cancer model to study tumor development in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2806.

Evaluation of molecular subtypes and clonal selection during establishment of patient-derived tumor xenografts from gastric adenocarcinoma

Patient-derived xenografts (PDX) have emerged as an important translational research tool for understanding tumor biology and enabling drug efficacy testing. They are established by transfer of patient tumor into immune compromised mice with the intent of using them as Avatars; operating under the assumption that they closely resemble patient tumors. In this study, we established 27 PDX from 100 resected gastric cancers and studied their fidelity in histological and molecular subtypes. We show that the established PDX preserved histology and molecular subtypes of parental tumors. However, in depth investigation of the entire cohort revealed that not all histological and molecular subtypes are established. Also, for the established PDX models, genetic changes are selected at early passages and rare subclones can emerge in PDX. This study highlights the importance of considering the molecular and evolutionary characteristics of PDX for a proper use of such models, particularly for Avatar trials.

Patient derived renal cell carcinoma xenografts exhibit distinct sensitivity patterns in response to antiangiogenic therapy and constitute a suitable tool for biomarker development

Systemic treatment is necessary for one third of patients with renal cell carcinoma. No valid biomarker is currently available to tailor personalized therapy. In this study we established a representative panel of patient derived xenograft (PDX) mouse models from patients with renal cell carcinomas and determined serum levels of high mobility group B1 (HMGB1) protein under treatment with sunitinib, pazopanib, sorafenib, axitinib, temsirolimus and bevacizumab. Serum HMGB1 levels were significantly higher in a subset of the PDX collection, which exhibited slower tumor growth during subsequent passages than tumors with low HMGB1 serum levels. Pre-treatment PDX serum HMGB1 levels also correlated with response to systemic treatment: PDX models with high HMGB1 levels predicted response to bevacizumab. Taken together, we provide for the first time evidence that the damage associated molecular pattern biomarker HMGB1 can predict response to systemic treatment with bevacizumab. Our data support the future evaluation of HMGB1 as a predictive biomarker for bevacizumab sensitivity in patients with renal cell carcinoma.

Abstract 2169: Metastases of a temozolimide-sensitive patient-derived melanoma xenograft model show distinct biologic features and developed resistance against temozolomide

Patient-derived tumor xenografts (PDX) play a major role in the development of new cancer therapies and their strengths and weaknesses have gradually been elucidated. In the current study we established a melanoma PDX from donor patient tissue. In addition, we were able to create two sublines from spontaneous metastases occurring in the murine host during the establishment phase of the original model. All three lines were characterized by tumor growth kinetics, antitumoral activity against standard of care Temozolomide and patho-histological examination. Furthermore, whole exome sequencing and RNAseq data of primary PDX and its metastases are available. Two out of the three sublines have corresponding cell lines for 2D and 3D testing. The PDX model was developed from a biopsy of a 68 year old woman undergoing surgery due to a non-pretreated melanoma. After seven subcutaneous passages in immune-compromised mice, individual animals showed tumor growth in the liver as well as the spleen. We were able to passage and characterize those metastases in parallel to the original model. The human origin of the lines as well as cell lines established in 2D was confirmed by str-analysis. All three in vivo lines depicted distinct growth kinetics: The doubling times varied significantly (Kruskal-Wallis, p&lt; 0.0018) between 12.34 days (primary tumor, MEXF 2090P) and 30.78 day (spleen metastasis, MEXF 2090S) and 19.01 days doubling time for the liver metastasis model (MEXF 2090L). MEXF 2090S thereby depicted the slowest growth rate in our melanoma PDX panel (24 models, 10.09 days mean doubling time). The patho-histological examination revealed a well differentiated melanoma with low stroma content (3-5%) in all three lines. The molecular analysis (whole exome sequencing) identified distinct differences. Nevertheless, the potential driver mutations, Tp53 (R213Q) and Nras (Q61K), were recognized in all investigated samples. Temozolomide was applied to all three lines in vivo. 6 mice per group and line were treated either with Temozolomide (40 mg/kg/d, iv, twice a week for three weeks) or the control vehicle (10% DMSO, 90% NaCl). The primary tumor depicted statistically significant antitumoral activity with a T/C (test vs control) value of 36% (p&lt; 0.05, t test, two-tailed) two weeks after the last treatment (experiment day 32). The two lines derived of metastases were resistant against the alkylating agent depicting T/C values of 76% (2090L) and 79% (2090S), respectively. Spontaneous metastases are a rare event in PDX models growing subcutaneously in NMRI nude mice. Thus, shedding some light into the biology of the metastatic event in the current model will help to understand and influence the metastatic process in general. In any case, those lines can serve as indispensable tools in the oncology drug development pipeline.

Citation Format: Kerstin Klingner, Dorothee Lenhard, Elke Simon, Anne-Lise Peille, Julia Schüler. Metastases of a temozolimide-sensitive patient-derived melanoma xenograft model show distinct biologic features and developed resistance against temozolomide [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2169.

Abstract A019: Establishment and characterization of a melanoma patient-derived xenograft model comprising three different sublines with distinct biologic features

Patient-derived tumor xenografts (PDX) play a major role in the development of new cancer therapies and their strengths and weaknesses have gradually been elucidated. Large panels of solid cancer PDX are available to screen innovative compounds, identify new targets, and study tumor biology. In the current study we established a melanoma PDX from donor patient tissue. In addition, we were able to create two sublines from spontaneous metastases occurring in the murine host during the establishment phase of the original model. All three lines were characterized by tumor growth kinetics, antitumoral activity against standard-of-care temozolomide, and pathohistologic examination. Furthermore, molecular examination of primary PDX and its metastases is under way as well as cell line establishment. The PDX model was developed from a biopsy of a 68-year-old woman undergoing surgery due to a non-pretreated melanoma. After seven subcutaneous passages in immune-compromised mice, individual animals showed tumor growth in the liver as well as the spleen. We were able to passage and characterize those metastases in parallel to the original model. The human origin of the lines as well as one cell line established in 2D from the primary PDX was confirmed by str-analysis. All three in vivo lines depicted distinct growth kinetics: The doubling times varied significantly (Kruskal-Wallis, p&lt; 0.0018) between 12.34 days (primary tumor, MEXF 2090P) and 30.78 days (spleen metastasis, MEXF 2090S) and 19.01 days doubling time for the liver metastasis model (MEXF 2090L). The pathohistologic examination revealed a well-differentiated melanoma with low stroma content (3-5%) in all three lines. The molecular analysis (whole exome sequencing) is ongoing. So far the primary tumor has been characterized and two potential driver mutations, Tp53 (R213Q) and Nras (Q61K), were recognized. To characterize the models in more detail, temozolomide was applied to all three lines. 6 mice per group and line were treated either with temozolomide (40 mg/kg/d, iv, twice a week for three weeks) or the control vehicle (10% DMSO, 90% NaCl). The primary tumor depicted statistically significant antitumoral activity with a T/C (test vs control) value of 36% (p&lt; 0.05, t test, two-tailed) two weeks after the last treatment (experiment day 32). The two lines derived of metastases were resistant against the alkylating agent, depicting T/C values of 76% (2090L) and 79% (2090S), respectively. Further characterization of the PDX model and its different sublines will help to elucidate the resistance mechanism behind these data. Spontaneous metastases are a rare event in PDX models growing subcutaneously in NMRI nude mice. Thus, shedding some light into the biology of the metastatic event in the current model will help to understand and influence the metastatic process in general. In any case, those lines can serve as indispensable tools in the oncology drug development pipeline.

Citation Format: Kerstin Klingner, Dorothee Lenhard, Elke Simon, Anne-Lise Peille, Julia Schüler. Establishment and characterization of a melanoma patient-derived xenograft model comprising three different sublines with distinct biologic features [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A019.

Abstract 4821: Influence of the injection site on the dissemination pattern and drug sensitivity of patient derived leukemia cells in vivo

The aim of this study was to determine the influence of the engraftment site on the tumor biology and drug sensitivity of a panel of hematological patient derived xenografts (PDX). PDX cells (3x10e6 cells/mouse) were injected intratibialy (i.t.), intrasplenal (i.s.) or subcutaneously (s.c.) into NOG (NOD/Shi-scid/IL-2Rγnull) mice. Tumor engraftment was determined by flow cytometry (FC) in bone marrow (BM), peripheral blood (PB) and spleen during the course of engraftment and at the end of a study. Overall survival (OS) served as an additional read-out. In 3 models sensitivity towards cytarabine (Cy) was evaluated. Our group has established 18 PDX of acute leukemia (16 AML, 1 ALL, 1 APL). 16/17 lines engrafted when injected i.t., 10/12 developed tumors after i.s. implantation and 13/14 established tumors post s.c. cell injection. Thus, the overall engraftment capacity was for most of the models not depending on the injection site. Nevertheless, some models could only be propagated in a specific setting: LEXFAM 2713, grew exclusively i.t. or i.s., whereas LEXFAM 2824 could be propagated solely when injected s.c.. The implantation site did influence tumor growth rate: Mean OS ranged from 151.4 (±25.21) days for i.t. to 89.2 (±16.82) days for s.c. propagation. I.s. transplanted mice had to be sacrificed after 91.9 (±17.33) days. The dissemination pattern of individual lines was affected by the injection site. In general, infiltration of the hematopoietic organs was higher when cells were engrafted i.t. or i.s.. Nevertheless, also s.c. implanted, AML cells infiltrated murine PB, spleen and BM, although not consistently and to a much lower extent. Interestingly, the expression pattern of the 6 investigated surface markers (CD45, CD3, CD34, CD33, CD38 & HLA-ABC) was not influences by the application route. Every model depicted its distinct expression pattern irrespective of the application route. Cy was highly active in 1 AML (LEXFAM 2531) and 1 ALL (LEXFAL 2665) model. OS was significantly prolonged in the s.c. as well as in the disseminated setting (p&lt; 0.003, Log-rank (Mantel-Cox) test). Another AML line (LEXFAM 2734) depicted a less pronounced sensitivity towards Cy (p&lt; 0.007, Log-rank (Mantel-Cox) test) both growing s.c. or i.t.. Thus, drug sensitivity was not influenced by the injection site of the leukemic cells. Of note, the PDX drug responses mimicked the responsiveness of the respective donor patient. Taken together the leukemia PDX panel represents the molecular diversity of the disease and mirrors sensitivity towards standard of care. Our recent careful investigation of the subcutaneous approach in these models highlights their suitability for this type of studies. This enhances the value of the platform as it combines the possibilities of a mid-throughput screening enabled by the subcutaneous approach with the general advantages of a patient-derived leukemia model.

Citation Format: Julia B. Schüler, Eva Oswald, Gabriele Greve, Dorothee Lenhard, Kerstin Klingner, Milena Pantic, Michael Luebbert. Influence of the injection site on the dissemination pattern and drug sensitivity of patient derived leukemia cells in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4821. doi:10.1158/1538-7445.AM2017-4821

Depletion of Mouse Cells from Human Tumor Xenografts Significantly Improves Downstream Analysis of Target Cells

The use of in vitro cell line models for cancer research has been a useful tool. However, it has been shown that these models fail to reliably mimic patient tumors in different assays(1). Human tumor xenografts represent the gold standard with respect to tumor biology, drug discovery, and metastasis research (2-4). Tumor xenografts can be derived from different types of material like tumor cell lines, tumor tissue from primary patient tumors(4) or serially transplanted tumors. When propagated in vivo, xenografted tissue is infiltrated and vascularized by cells of mouse origin. Multiple factors such as the tumor entity, the origin of xenografted material, growth rate and region of transplantation influence the composition and the amount of mouse cells present in tumor xenografts. However, even when these factors are kept constant, the degree of mouse cell contamination is highly variable. Contaminating mouse cells significantly impair downstream analyses of human tumor xenografts. As mouse fibroblasts show high plating efficacies and proliferation rates, they tend to overgrow cultures of human tumor cells, especially slowly proliferating subpopulations. Mouse cell derived DNA, mRNA, and protein components can bias downstream gene expression analysis, next-generation sequencing, as well as proteome analysis (5). To overcome these limitations, we have developed a fast and easy method to isolate untouched human tumor cells from xenografted tumor tissue. This procedure is based on the comprehensive depletion of cells of mouse origin by combining automated tissue dissociation with the benchtop tissue dissociator and magnetic cell sorting. Here, we demonstrate that human target cells can be can be obtained with purities higher than 96% within less than 20 min independent of the tumor type.

Abstract 590: Co-injection of human monocytes improves the in vivo antitumoral activity of bevacizumab in two NSCLC PDX models

Nowadays, an increasing number of monoclonal antibodies (mAbs) that specifically target malignant cells or interfere with different compartments of the tumor microenvironment are available for cancer therapy. They take effect via different modes of action including the initiation of a tumor-targeting immune response. Preclinical platforms such as PDX models have to be improved to better recapitulate all possible modes of action for mAbs as well as other immune-modulating agents. In the current study, we evaluated the antitumoral activity of Bevacizumab in two NSCLC PDX growing subcutaneously in NMRI nu/nu mice with and without co-injection of human monocytes.

Two NSCLC PDX, LXFA 2478 and LXFA 677, were subcutaneously implanted into 4-6 weeks old female NMRI nu/nu mice (Harlan, Denmark). Tumor models were chosen based on their VEGFA expression level. Additionally, LXFA 2478 and LXFA 677 show high expression of TLR2 and CD14 respectively, two factors known to be involved in monocyte attraction. When median tumor size reached 150 - 300 mm3, mice were equally distributed to treatment groups (n = 4/group). Animals were treated once weekly for 7 cycles with a) control vehicle b) control vehicle + 5×106 human monocytes c) Bevacizumab at 40 mg/kg/d and d) Bevacizumab + 5×106 human monocytes. Tumor volume was determined twice weekly by caliper measurement. At the end of the study, tumor and lymphatic organs of the animals were harvested and subsequent IHC analysis for human CD14, CD68 and CD163 was performed.

In both investigated tumor models, Bevacizumab showed moderate antitumoral activity with a maximal tumor load reduction of 71% (LXFA 2478) and 84% (LXFA677) as compared to untreated controls on days 39 and 35. The co-injection of human monocytes markedly enhanced the therapeutic effect of Bevacizumab in both NSCLC PDX: maximal tumor load reduction was 89% in LXFA 2478 and 95% in LXFA 677 in combination groups. The injection of monocytes alone did not affect tumor growth as compared to untreated control. As predicted by the high VEGFA expression, NSCLC PDX showed high sensitivity against Bevacizumab. This antitumoral activity was increased by 18% and 11% for LXFA 2478 and LXFA 677, respectively, through the additional injection of monocytes. Monocyte recruiting factors (namely CD14 and TLR2) likely contribute to the mechanism of action.

Monocytes and macrophages have been reported to induce antibody-dependent cytotoxicity and phagocytosis of tumor cells in the presence of IgG anti-tumor mAbs, like Bevacizumab. Our results confirm these observations in a PDX based NSCLC in vivo model. Therefore, the study highlights the suitability of PDX for immuno-oncology approaches by supplementation of the murine host with human immune cells. This advanced PDX approach will lead to more predictive preclinical data for innovative mAb′s and other compounds acting via the activation of monocytes and related immune cells.

Citation Format: Cordula Tschuch, Kerstin Klingner, Anne Löhr, Yana Raeva, Teppo Haapaniemi, Eva Oswald, Julia B. Schüler. Co-injection of human monocytes improves the in vivo antitumoral activity of bevacizumab in two NSCLC PDX 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 590.

Abstract A10: Establishment and characterization of a patient-derived non-small cell lung cancer mouse model of acquired resistance towards anti-EGFR treatment

Non-small cell lung cancer (NSCLC) is the largest subgroup of lung cancer, occurring at a frequency of over 80% of lung cancer cases. In up to 30% of NSCLC patients the oncogenic driver of tumor growth is a constitutively activated EGF receptor (EGFR), which plays a critical role in regulating multiple cellular processes, including proliferation, survival and apoptosis. Although these patients gain great benefit from treatment with EGFR tyrosine kinase inhibitors (TKI, e.g. erlotinib or gefitinib), development of resistance is inevitable.

To model the emergence of drug resistance, an EGFR driven, gefitinib sensitive, patient-derived xenograft (PDX) NSCLC model was treated continuously with gefitinib in immunocompromised mice. The dose of daily treatment was adjusted according to tumor growth over a period of up to 91 days. In a first phase, dosing was high (40-50 mg/kg) to eradicate EGFR TKI sensitive cells. At the time point of maximal antitumoral activity dosing was reduced to 20-30 mg/kg ( = low dose) to preserve selection pressure. Between 69 and 91 days after dosing was initiated, drug-resistant tumors emerged in 4 out of 10 mice under high dose treatment. Resistant tumor fragments, which were re-implanted into a new cohort of mice and continuously treated with gefitinib, kept resistance also under high dose treatment. A comprehensive analysis using Western blot (WB), qPCR and sequencing was performed to identify the reason for resistance.

In WB analysis we could show that signalling through EGFR was completely abrogated in all four resistant tumor sublines. Neither secondary mutations in EGFR (ex19-21) or KRAS (ex 1+2) could be detected, nor was the expression of cMET, AXL, HGF, PTEN or HER3 significantly increased in resistant tumors as shown by sequencing and qPCR respectively. However a more comprehensive WB analysis revealed several genes being activated in resistant compared to primary tumors. Depending on the subline, phospho-(p)-cMET, p-AKT, AXL & p-AXL, p-cRAF, p-MEK, p-ERK as well as HER3, IGF-R and ALK were up-regulated in resistant tumors. Based on these data we determined that signalling pathways such as the (RAS)-cRAF-MEK-ERK signalling cascade or enhanced cMET/AKT signalling were activated in drug-resistant tumors. These signalling pathways are known to be alternative pathways for EGFR signalling also in patients with acquired resistance indicating the clinical relevance of these models. To shed more light into the mechanism of resistance, whole exome sequencing analyses of the four resistant sublines as well as the original tumor model are underway.

In summary, we have developed four NSCLC tumor sublines each harbouring a different mechanism of resistance to EGFR TKI treatment, modelling the emergence of drug-resistant NSCLC in patients. Herewith a strong preclinical tool for the development of innovative compounds targeting acquired EGFR resistance is now available.

Citation Format: Cordula Tschuch, Kerstin Klingner, Dorothee Lehnhard, Anne Löhr, Yana Raeva, Anne-Lise Peille, Eva Oswald, Julia B. Schüler. Establishment and characterization of a patient-derived non-small cell lung cancer mouse model of acquired resistance towards anti-EGFR treatment. [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 A10.

Abstract 5023: NSCLC PDX model for the evaluation of immuno-oncological treatment strategies

Patient-derived tumor xenografts (PDX) have played a major role in the development of new cancer therapies and their strengths and weaknesses have gradually been elucidated. One major drawback of PDX is the lack of an immunological competent host. To overcome this hurdle we supplemented NSG/NOG mice with human hematopoietic stem cells (HSC) and subsequently examined growth characteristics of the non-small cell lung cancer (NSCLC) PDX model LXFA 923 in these mice. In parallel we monitored the presence of human and murine immune cells in different organs of the mouse.

HSC (2×106) cells were isolated from healthy donors and injected intravenously into sub-lethally irradiated NSG or NOG mice (n = 43 mice in 3 ind. exp.). After 8 weeks LXFA 923 was transplanted subcutaneously (s.c.) into the pretreated mice. Murine peripheral blood was examined by flow cytometry for common murine and human markers expressed on immune cells (hCD14, mCD14, hCD3, mCD3, hCD56, mCD56, hCD19) once weekly. At the end of the experiment tumors and organs were analyzed for human cancer (CD44, CD133, CDCP1, CD166, CD24) and immune cell markers (hCD14, hCD3, hCD56, hCD19) by flow cytometry. Tumors and organs were additionally histologically and immunohistochemically examined. Growth of the implanted tumors was monitored by caliper measurement. Mice bearing only the subcutaneous PDX or the HSC served as control groups.

Stable engraftment of human immune cells in immune-compromized mice was successfully achieved. Human immune cells expressing T-, B-, NK- and stem cell markers could be detected in different compartments (bone marrow, peripheral blood and spleen) of the tumor-bearing as well as non-tumor bearing mice. Furthermore, infiltrates of human monocytes (CD14+) as well as T cells (CD3+) could be detected in s.c. implanted tumor tissue. Implantation of LXFA 923 did not influence the proliferation of human immune cells in recipient mice. Growth behavior of the s.c. implanted PDX was not affected by the engraftment of HSC in the murine host. The histological architecture of LXFA 923 was similar when implanted s.c. in humanized or immunodeficient mice and it still closely resembles the patient donor material.

In conclusion, our investigations validate the analysis of PDX in mice engrafted with human immune cells, as it enables the interaction of tumor cells with human immune cells as well as with murine stroma to be investigated. This preclinical PDX based in vivo platform provides a further step to support the development of new drugs targeting the host immune response.

Citation Format: Eva Oswald, Kerstin Klingner, Dorothee Lenhard, Gabriele Niedermann, Julia B. Schüler. NSCLC PDX model for the evaluation of immuno-oncological treatment strategies. [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 5023. doi:10.1158/1538-7445.AM2015-5023

Abstract 1705: Classification of colorectal PDX into transcriptomic subtypes associated with distinct genomic alteration profiles and in vivo response patterns to therapies

Recently, unsupervised gene expression-based signatures with prognostic and potential predictive implications were proposed for colorectal cancer (CRC) classification. The challenge is now to characterize the genomic alterations of CRC subtypes and their sensitivity to therapies. Patient derived xenograft models (PDX) may be a valuable tool for this purpose, as they retain the molecular features and drug response patterns of their parental patient tumors. In this study, we classified our collection of colon PDX into transcriptomic subtypes and investigated the associations with genomic alterations and in vivo responses to cetuximab (CTX), oxaliplatin (OXT) and irinotecan (IR). We determined expression profiles of 67 PDX models using Affymetrix HGU133 Plus2.0 arrays and applied the CRC assigner-786 gene expression signature reported by Sadanandam et al. to classify our PDX into 5 subtypes. We identified 34 (51%) transit-amplifying (TA), 15 (22%) goblet-like (GL), 10 (15%) inflammatory (IF), 7 (10%) enterocyte (ET) and 1 (1%) stem-like (SL) PDX models. TA showed a gene signature of WNT pathway activation whereas GL, ET and IF PDX subtypes harbored gene signatures of KRAS pathway activation. As analyzed by whole exome sequencing and Affymetrix SNP6.0 array, the GL, ET and IF subtypes were found to display different signatures of mutational processes, mutations and chromosomal rearrangement patterns than TA and SL. Of particular note, mutations in BRAF, PIK3CA/PTEN, TGFBR2/SMAD4 or NOTCH1 were mainly found in GL, ET or IF while mutations in APC, TP53 and KRAS were not associated with a given subtype. Regarding PDX drug sensitivity, 10/11 TA/SL PDX with unaltered KRAS/PIK3CA/PTEN/HER2 status were sensitive to CTX whereas 9/12 models with alterations were resistant. TA and SL PDX were also frequently sensitive to IR and OXT (6/10 and 4/10, respectively). In the IF subtype, 6/6 PDX showing KRAS, PIK3CA or PTEN alterations were resistant to CTX. Of interest, 5/5 IF PDX were sensitive to IR treatment. As in IF PDX, GL and ET often had alterations in KRAS/PIK3CA/PTEN/HER2 and were resistant to CTX. Moreover, these subtypes were resistant to both IR and OXT. Furthermore, the frequent KRAS pathway activation and the presence of actionable mutations in GL, ET and IF would advocate the testing of inhibitors (as monotherapy or in combination) of BRAF, PI3K or MEK in tumors of these subtypes while WNT inhibitors should be tested in TA models.Molecular classification of our colon PDX collection confirmed their similarities with patient tumors. Investigation of drug sensitivity resulted in the identification of PDX subtypes which respond poorly to standard therapies and which require different treatment options. Testing alternative and combined therapies in PDX may be a valuable approach to optimize personalized medicine.

Citation Format: Anne-Lise Peille, Christina Gredy, Bruno Zeitouni, Armin Maier, Kerstin Klingner, Tim Kees, Julia Schüler, Thomas Metz, Heinz. Herbert Fiebig, Vincent Vuaroqueaux. Classification of colorectal PDX into transcriptomic subtypes associated with distinct genomic alteration profiles and in vivo response patterns to therapies. [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 1705. doi:10.1158/1538-7445.AM2015-1705

Abstract 4210: Patient-derived models of human acute myeloid and lymphoid leukemia in immunocompromised mice for preclinical drug development

The generation of functional and reproducible in vivo models is a prerequisite for a better understanding of hematological malignancies and for the development of improved therapeutic strategies. Here, we report the establishment of transplantable PDX models of acute myeloid and lymphoid leukemia (AML, ALL) growing subcutaneously (s.c.) as well as in a disseminated fashion in immunocompromised mice.

Bone marrow (BM) and peripheral blood (PB) cells from 25 AML/ALL patients were injected intratibially into NSG or NOG mice (n = 1-9/patient) and in later passages also s.c. in nude mice (n = 1-3/model). Tumor growth was monitored via determination of overall survival, flow cytometry (verification of patient-derived leukemic clones by hCD34, hCD33, hCD38, hHLA-ABC, hCD3, hCD45, mCD45), and, where applicable, by caliper measurement. Engraftment is defined as ≥5% hCD45+ cells in the BM and/or ≥1% hCD45+ cells in PB. Transplantable models (higher or equal passage 2) were tested with the respective standard of care drugs (SoC) mainly Cytarabine and Dexamethasone.

Bone marrow engraftment in passage 1 was observed for 11 out of 25 leukemia models. Four of them could be established as disseminated models in serial passage. No engraftment was detected for nine models during the observation period of at least 95 days while observation for five models is still ongoing. The four established models were further characterized by fluorescence-in-situ-hybridization (FISH) to confirm patient origin. Treatment of mice bearing the models with the SoC drugs cytarabine and dexamethasone significantly prolonged overall survival. Antitumoral activity was consistent with clinical response of the donor patient. One T-ALL and two AMLs were additionally successfully propagated following s.c. injection in nude mice. They showed stable growth behavior and displayed a similar chemo-sensitivity pattern as their disseminated growing counterparts.

In conclusion, we have established a panel of transplantable PDX models of ALL and AML displaying stable and reproducible growth patterns suitable for in vivo efficacy studies. Our results confirm that PDX models of hematological malignancies replicate important clinical characteristics of the disease and are valuable tools for preclinical drug testing.

Citation Format: Eva Oswald, Kerstin Klingner, Benedikt Hammerich, Gabriele Greve, Dorothee Lenhard, Milena Pantic, Heinz-Herbert Fiebig, Michael Luebbert, Julia B. Schüler. Patient-derived models of human acute myeloid and lymphoid leukemia in immunocompromised mice for preclinical drug development. [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 4210. doi:10.1158/1538-7445.AM2015-4210

Abstract 1455: Next generation sequencing of human tumor xenografts is significantly improved by prior depletion of mouse cells

Human tumor xenografts represent the gold standard method for research areas such as drug discovery, cancer stem cell biology, and metastasis prediction. When compared to in vitro cell culture models, human tumor xenografts show a higher validity for most assays (DeRose et al., 2011).

During the growth phase in vivo, xenografted tissue is vascularized and infiltrated by cells of murine origin. The level of infiltration is highly dependent on multiple factors like tumor subtype, growth rate, and region of transplantation. However, even when these factors are kept constant, the amount and composition of infiltrating mouse cells is highly variable. Due to this, molecular downstream analyses such as microarray based expression profiling are challenged by cross hybridization of mouse derived molecules to human probes. In addition, a reduction of sensitivity caused by measuring mouse signals during next-generation sequencing analysis can be expected.

To overcome these limitations, we have developed a fast and easy method allowing for the comprehensive depletion of all cells of mouse origin by using automated tissue dissociation and magnetic cell sorting (MACS). We have performed whole exome sequencing of bulk human tumor xenografts from lung, bladder, and kidney cancer, and compared the results to samples depleted of mouse cells. A significant increase (p &lt; 0.05) in cluster density as well as an average increase in read counts of 33% was observed for the mouse cell depleted samples, indicating improved sample quality. Indeed, we observed a strong reduction of debris and dead cells upon the depletion procedure. We mapped the reads of all samples against human and mouse genomes and determined their putative origin. An average of 12% of reads derived from non-depleted samples was assigned to mouse cells. This amount could be reduced to 0.28% by prior depletion of mouse cells. As 15% of the mouse-derived reads mapped erroneously to human genome (1.9% of total reads) in the non-depleted samples, a strong positive influence of mouse cell depletion (0.04% of total reads) on downstream analyses can be expected. The number of predicted SNPs was 2-fold higher in the non-depleted samples and 56% of SNPs identified in the non-depleted samples were not present anymore after depletion of mouse cells. Furthermore, the increase in coverage from 39-fold (non-depleted) to 56-fold (depleted) resulted in a higher sensitivity of relevant SNP detection after mouse cell depletion. 16% of SNPs identified in the depleted samples were exclusively found in these samples.

Taken together, removal of mouse cells significantly improves the analysis of human tumor xenografts by next generation sequencing. As this effect was observed although a human sequence specific selection has been carried out during exome enrichment, the influence on whole exome and whole transcriptome sequencing are expected to be even more prominent.

Citation Format: David Agorku, Stefan Tomiuk, Kerstin Klingner, Stefan Wild, Silvia Rüberg, Lisa Zatrieb, Andreas Bosio, Julia Schueler, Olaf Hardt. Next generation sequencing of human tumor xenografts is significantly improved by prior depletion of mouse cells. [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 1455. doi:10.1158/1538-7445.AM2015-1455

Effective Eradication of Glioblastoma Stem Cells by Local Application of an AC133/CD133-Specific T-cell-Engaging Antibody and CD8 T Cells

Cancer stem cells (CSC) drive tumorigenesis and contribute to genotoxic therapy resistance, diffuse infiltrative invasion, and immunosuppression, which are key factors for the incurability of glioblastoma multiforme (GBM). The AC133 epitope of CD133 is an important CSC marker for GBM and other tumor entities. Here, we report the development and preclinical evaluation of a recombinant AC133×CD3 bispecific antibody (bsAb) that redirects human polyclonal T cells to AC133(+) GBM stem cells (GBM-SC), inducing their strong targeted lysis. This novel bsAb prevented the outgrowth of AC133-positive subcutaneous GBM xenografts. Moreover, upon intracerebral infusion along with the local application of human CD8(+) T cells, it exhibited potent activity in prophylactic and treatment models of orthotopic GBM-SC-derived invasive brain tumors. In contrast, normal hematopoietic stem cells, some of which are AC133-positive, were virtually unaffected at bsAb concentrations effective against GBM-SCs and retained their colony-forming abilities. In conclusion, our data demonstrate the high activity of this new bsAb against patient-derived AC133-positive GBM-SCs in models of local therapy of highly invasive GBM.

Abstract 3926: Influence of tumor microenvironment on engraftment capacity of hematological cell lines in immunocompromized mice

Hematological malignancies account for about 10% of newly diagnosed cancers in the US, their heterogeneity and diverse biological characteristics present unique therapeutic challenges. In order to develop more promising therapeutic strategies, the establishment of functional and reproducible in vivo models is widely pursued. A panel of 18 hematological cell lines comprising different entities including leukemia (acute lymphoblastic AML; chronic myeloid CML; chronic lymphatic leukemia CLL), diffuse large B cell lymphoma (DLBCL), as well as multiple myeloma (MM) was evaluated for in vivo engraftment using different mouse strains and application routes.

18 different cell lines were inoculated into 4 different immuncompromized mouse strains (NOG; NSG; NOD/SCID; SCID/beige nude) in 35 independent experiments. Cells were injected intravenously (i.v.), intratibialy (i.t.) or intraperitonealy (i.p.). Tumor growth was monitored via a) determination of overall survival, b) fluorescence-based in vivo imaging (IVI, Bruker FX, using CF750 labeled anti-hu CD33, CD19, CD45) c) flow cytometry and d) histological and IHC examination.

Engraftment of hematological cell lines was clearly influenced by tumor entity, mouse strain and application route. The investigated AML cell lines engrafted in all three applied mouse strains (NOG; NSG; NOD/SCID) and injection routes. MOLM-13 infiltrated the bone marrow (BM) and the spleen (&gt;90% infiltration, 21 days after tumor cell injection (=d21)), whereas MV4-11 cells disseminated mainly to the spleen (5% BM and 15% spleen infiltration, d21). In contrast THP-1 (80% BM and 2% spleen infiltration, d21) as well as NOMO-1 cells (30% BM and 3% spleen infiltration, d21) grew predominantly in the murine BM. MM cell lines (L363, RPMI8826, MM1R, MM1S) as well as B-CLL cell lines (Mec-1) failed to engraft reliably in NOD/SCID mice, irrespective of the application route. MM cells engrafted predominantly in the BM (20 - 60% depending on the cell line) of NSG mice when injected i.t.. i.v. injected MM cells did engraft in the BM but to a significantly lower extent than when injected i.t. (e.g. 20% vs. 2% BM infiltration of RPMI8226 cells, d35). Mec-1 cells infiltrated the BM and spleen of NSG and NOG mice reliably when injected i.v. and i.p. in the same individual (60% BM and 15% spleen infiltration, d28), whereas the same approach did not result in any engraftment when using SCID/beige nude mice. 3 out of 4 investigated DLBCL cell lines engrafted in vivo. Disseminated growth could be observed in NOG mice when injecting the cells i.v. or i.t. In all cases, tumors grew faster and infiltrated the BM more aggressively when injected I.t..

In summary, the engraftment of hematological cell lines strongly depends on the tumor microenvironment. The direct contact to the BM niche is a major survival benefit for the tumor cells as is the lack of NK cells in NOG and NSG mice.

Citation Format: Eva Oswald, Kerstin Klingner, Ralph Waesch, Katja Zirlik, Monika Engelhardt, Julia B. Schüler. Influence of tumor microenvironment on engraftment capacity of hematological cell lines in immunocompromized mice. [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 3926. doi:10.1158/1538-7445.AM2014-3926

Abstract 100: Establishment and characterization of allografts derived from a genetically engineered mouse model of non-small cell lung cancer (NSCLC)

Introduction: Genetically engineered mouse models (GEMM) represent an attractive system for preclinical research since GEMM tumors develop in the presence of a competent immune system, thereby closely resembling the tumor microenvironment in patients. One example is the KP model (DuPage et al., 2009), which reflects the tumorigenesis of NSCLC in humans. KP tumors carry Kras and Trp53 mutations, comparable to subtypes of human NSCLC. Typical drawbacks of GEMM tumors include differences in their genetic make-up to human tumors and the very slow and heterogeneous tumor development, making the use of these models challenging for routine in vivo efficacy studies. The latter can be improved by grafting primary tumors on a genetically dissimilar member of the same strain, so-called allografting. Thus, the advantages of xenograft and GEMM models can be combined. Here, we described the establishment and characterization of allografts from the KP GEMM.

Material & Methods: KP tumors were excised from the lungs of KP mice and implanted subcutaneously (s.c.) into C57BL/6N female mice. When tumor growth was detected, passaging steps from animal to animal were performed. Furthermore, two cell lines derived from KP tumors, KP1 and KP4 (provided by Müller et al.), were injected s.c., the developing tumors excised and directly re-implanted as described above. The passages were analyzed molecularly, histologically, and via IHC (e.g. Ki67 proliferation marker) , and compared to the original in-situ tumors. A therapeutic study with Erlotinib and BEZ235 was performed on KP1 allografted mice.

Results: All investigated allografts showed similar histological patterns. Ki67 scores reflected the average time from implantation to passaging. The average passage times ranged from 19±3 days (KP4 cell line) to 26±6 days (KP1 cell line). Allografts from the original KP model showed a time to passaging of 23±5 days.

The mRNA expression of EpCAM (CD326) was on average 10-fold higher in KP and KP1 allografted tumors compared to normal C57BL/6 lung tissue, which could be confirmed by flow cytometry and cell-binding assay, determining &gt;99% EPCAM positive cells in KP1 tumors. All allografts carried the Kras mutation and loss of function point mutations in Trp53.

The therapy study revealed no effect of Erlotinib on tumor growth, but a significant (p=0.0003) tumor load reduction in mice treated with BEZ235 (519 ± 244 mm³, n=5) compared to the control group (1678 ± 275 mm³, n=4) on day 28, respectively.

Conclusion: The generation of s.c. transplantable allografts from the KP GEMM was successfully conducted. The allograft models enable the use of immunocompetent mice in a feasible time frame and still resemble key aspects of human disease. Further studies will elucidate the interaction of the allografts with the host and compare sensitivity characteristics between GEMM and allograft of the same model.

Citation Format: Damaris Kukuk, Philipp Müller, Kerstin Klingner, Anne-Lise Peille, Alfred Zipelius, Julia B. Schüler. Establishment and characterization of allografts derived from a genetically engineered mouse model of non-small cell lung cancer (NSCLC). [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 100. doi:10.1158/1538-7445.AM2014-100

Intratibial injection of human multiple myeloma cells in NOD/SCID IL-2Rγ(null) mice mimics human myeloma and serves as a valuable tool for the development of anticancer strategies

BACKGROUND

We systematically analyzed multiple myeloma (MM) cell lines and patient bone marrow cells for their engraftment capacity in immunodeficient mice and validated the response of the resulting xenografts to antimyeloma agents.

DESIGN AND METHODS

Using flow cytometry and near infrared fluorescence in-vivo-imaging, growth kinetics of MM cell lines L363 and RPMI8226 and patient bone marrow cells were investigated with use of a murine subcutaneous bone implant, intratibial and intravenous approach in NOD/SCID, NOD/SCID treated with CD122 antibody and NOD/SCID IL-2Rγ(null) mice (NSG).

RESULTS

Myeloma growth was significantly increased in the absence of natural killer cell activity (NSG or αCD122-treated NOD/SCID). Comparison of NSG and αCD122-treated NOD/SCID revealed enhanced growth kinetics in the former, especially with respect to metastatic tumor sites which were exclusively observed therein. In NSG, MM cells were more tumorigenic when injected intratibially than intravenously. In NOD/SCID in contrast, the use of juvenile long bone implants was superior to intratibial or intravenous cancer cell injection. Using the intratibial NSG model, mice developed typical disease symptoms exclusively when implanted with human MM cell lines or patient-derived bone marrow cells, but not with healthy bone marrow cells nor in mock-injected animals. Bortezomib and dexamethasone delayed myeloma progression in L363- as well as patient-derived MM cell bearing NSG. Antitumor activity could be quantified via flow cytometry and in vivo imaging analyses.

CONCLUSIONS

Our results suggest that the intratibial NSG MM model mimics the clinical situation of the disseminated disease and serves as a valuable tool in the development of novel anticancer strategies.

Abstract C8: Functional and molecular characteristics of patient-derived xenografts of colon cancer

Introduction: Colorectal carcinoma (CRC) is the second leading cause of cancer-related deaths worldwide. Patient-derived xenografts (PDX) subcutaneously implanted in nude mice are highly suitable tools to aid in the development of novel anti-cancer therapeutics as their response is a good predictor of clinical outcome. In the present study, a panel of colon cancer PDXs (CXFs) was characterized for their molecular profile and sensitivity to standard of care (SoC) drugs.

Material and Methods: CRC samples from patients undergoing surgery were implanted subcutaneously in nude mice and sequentially passaged. Tumor material was collected for molecular profiling, including mutational analysis by Sanger sequencing and Sequenom OncoCarta panels I, II, III. The efficacy of the SoC drugs 5-fluoruracil, oxaliplatin, irinotecan, bevacizumab and cetuximab was tested in vivo. All compounds were administered at clinically relevant dose levels and schedules. The tumor load was determined by caliper measurements twice a week. Anti-tumor activity was determined by comparing the relative tumor load of test groups vs. the vehicle-treated control group. Tumors were considered sensitive if the minimal test / control (T/C [%]) value recorded during an experiment was smaller than 30%. For cytotoxic SoC drugs, sensitivity of CXFs were also analyzed in an ex vivo tumor colony assay (TCA).

Results: 73 CRC patient samples were implanted within the framework of this study. Up to now, 65 of them were established as CXF corresponding to a take rate of 89%. Mutational analysis was performed for 58 CXFs. Regarding the RAS/RAF pathway, mutations were found in K-RAS (26 out of 58 CXFs, 45%), NRAS (3%) and BRAF (7%). Mutations in the AKT/PI3K pathway were also found (PTEN, 9% and PIK3CA, 17%). In addition, one CXF had an IDH1 mutation (2%). For all SoC drugs both sensitive and resistant CXFs were identified and given CXFs differed in their sensitivities to different SoC drugs. In vivo sensitivity data will be correlated with molecular characteristics of the tested CXFs and with their sensitivities determined in the TCA.

Conclusion and Outlook: Due to the high take rate, our CXF panel represents a large proportion of clinical variants of CRC. We will describe mutation profiles and sensitivity profiles to SoC drugs used for colon cancer. Correlation of sensitivity data and molecular data may reveal interesting correlations and identify biomarkers predictive of response to SoC drugs and experimental compounds.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C8.

Citation Format: Jianing M. Guo, Kerstin Klingner, Rebekka Krumbach, Armin Maier, Silvia Naus, Vincent Vuaroqueaux, Evelyn Lamy, Heiner Fiebig, Julia B. Schueler. Functional and molecular characteristics of patient-derived xenografts of colon cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C8.

Anti-tumor activity of a B-cell receptor-targeted peptide in a novel disseminated lymphoma xenograft model

Receptor-targeted therapies have become standard in the treatment of various lymphomas. In view of its unparalleled specificity for the malignant B-cell clone, the B-cell receptor (BCR) on B cell lymphoma cells is a potential therapeutic target. We have used two BCR epitope mimicking peptides binding to the Burkitt's lymphoma cell lines CA46 and SUP-B8. We proved their functionality by demonstrating calcium flux and BCR-mediated endocytosis upon peptide receptor binding. Toxicity experiments in vitro via cross-linking of the BCR with tetramerized epitope mimics lead to apoptosis in both cell lines but was far more effective in SUP-B8 cells. We established a SUP-B8-based disseminated Burkitt's lymphoma model in NOD/SCID mice. Treatment of tumor-bearing mice with tetramerized epitope mimics had significant anti-tumor effects in vivo. We conclude that peptide-mediated, BCR-targeted therapy is a promising approach which may be explored and further developed for application in highly aggressive lymphoma.

Abstract B113: Establishment of a clinically relevant orthotopic xenograft model for human liver cancer

In order to allow a better understanding of liver carcinoma, the establishment of functional and reproducible in vivo models is widely pursued. Of available model systems, orthotopically growing xenografts in immunodeficient mice reflect well the clinical situation. In the present study, the growth behaviour and sensitivity towards the multikinase inhibitor sorafenib of human liver carcinoma cells implanted orthotopically into NMRI nude mice was investigated. Liver carcinoma cell line SKHEP1 was injected orthotopically into nude mice. Three days after inoculation of 5 Mio. tumor cells, mice were subdivided into two groups, and treatment was started either with vehicle (control) or sorafenib (100 mg/kg/d, po, days 3–36). Tumor growth was monitored via a) fluorescence-based in vivo imaging (IVI, using Alexa750 labeled anti-human CD10 antibody) once weekly, b) macroscopic examination at the end of the experiment, and c) histological examination of murine liver tissue. IVI pictures were merged with x-ray for an optimal localization of the fluorescent tissue. Antitumoral and antimetastatic capacity was determined by comparing the fluorescent intensity as well as the fluorescent area for primary tumors and metastasized organs over the time.

Seven days after implantation, SKHEP1-derived tumors could be detected in the liver in all animals via IVI. Weekly follow-up analyses confirmed, that liver engraftment was prominent and observed in all animals (16/16). Lymphnode metastases (6/9 control mice and 3/7 Sorafenib-treated mice) could be determined 14 days after tumor cell inoculation. Beyond that bone marrow metastases (4/9) could be detected exclusively in the untreated control group. The detection limit of the investigated model was about 5×104 cells within one region of interest. Signal to noise ratio was excellent due to a highly specific antibody, the use of a near-infrared fluorophore combined with the absence of auto-fluorescense of murine hair. IVI produced very bright and reproducible pictures optimal for exact quantification of the tumor load. Sorafenib showed a strong antitumoral and antimetastastatic activity, inducing optimal T/C values as low as 2.7% for the primary tumor and 40% for the lymphnode metastases on day 56. In addition, the total number of metastasized animals was reduced in comparison to the untreated animals. The occurrence of bone marrow metastases was almost completely reduced by sorafenib treatment. Tolerability of the test compound was very high as no marked body weight losses or drug related toxicities could be observed.

Our xenografts show a close resemblance to the liver cancer disease regarding the growth behaviour of primary tumor and metastatic involvement of other organs. Collection of whole-body IVI data proved to be a time- and animal-saving analysis that allows to closely monitor hepato-carcinoma growth. Quantification and localization of tumor load was determined in a very exact and prompt manner. Thus, orthotopically implanted liver xenografts monitored by a fluorescent-based in vivo imaging system will be a useful tool in the development of new therapies against human liver carcinoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B113.