Dual targeting of the androgen receptor and PI3K/AKT/mTOR pathways in prostate cancer models improves antitumor efficacy and promotes cell apoptosis

Prostate cancer is a frequent malignancy in older men and has a very high 5-year survival rate if diagnosed early. The prognosis is much less promising if the tumor has already spread outside the prostate gland. Targeted treatments mainly aim at blocking androgen receptor (AR) signaling and initially show good efficacy. However, tumor progression due to AR-dependent and AR-independent mechanisms is often observed after some time, and novel treatment strategies are urgently needed. Dysregulation of the PI3K/AKT/mTOR pathway in advanced prostate cancer and its implication in treatment resistance has been reported. We compared the impact of PI3K/AKT/mTOR pathway inhibitors with different selectivity profiles on in vitro cell proliferation and on caspase 3/7 activation as a marker for apoptosis induction, and observed the strongest effects in the androgen-sensitive prostate cancer cell lines VCaP and LNCaP. Combination treatment with the AR inhibitor darolutamide led to enhanced apoptosis in these cell lines, the effects being most pronounced upon cotreatment with the pan-PI3K inhibitor copanlisib. A subsequent transcriptomic analysis performed in VCaP cells revealed that combining darolutamide with copanlisib impacted gene expression much more than individual treatment. A comprehensive reversal of the androgen response and the mTORC1 transcriptional programs as well as a marked induction of DNA damage was observed. Next, an in vivo efficacy study was performed using the androgen-sensitive patient-derived prostate cancer (PDX) model LuCaP 35 and a superior efficacy was observed after the combined treatment with copanlisib and darolutamide. Importantly, immunohistochemistry analysis of these treated tumors showed increased apoptosis, as revealed by elevated levels of cleaved caspase 3 and Bcl-2-binding component 3 (BBC3). In conclusion, these data demonstrate that concurrent blockade of the PI3K/AKT/mTOR and AR pathways has superior antitumor efficacy and induces apoptosis in androgen-sensitive prostate cancer cell lines and PDX models.

Pan-PI3K inhibition with copanlisib overcomes Treg- and M2-TAM-mediated immune suppression and promotes anti-tumor immune responses

The PI3K pathway is one of the most frequently altered signaling pathways in human cancer. In addition to its function in cancer cells, PI3K plays a complex role in modulating anti-tumor immune responses upon immune checkpoint inhibition (ICI). Here, we evaluated the effects of the pan-Class I PI3K inhibitor copanlisib on different immune cell types in vitro and on tumor growth and immune cell infiltration in syngeneic murine cancer models. Intermittent treatment with copanlisib resulted in a strong in vivo anti-tumor efficacy, increased tumor infiltration of activated T cells and macrophages, and increased CD8+ T cell/regulatory T cell and M1/M2 macrophage ratios. The strong in vivo efficacy was at least partially due to immunomodulatory activity of copanlisib, as in vitro these murine cancer cells were resistant to PI3K inhibition. Furthermore, the combination of copanlisib with the ICI antibody anti-PD-1 demonstrated enhanced anti-tumor efficacy in both ICI-sensitive and insensitive syngeneic mouse tumor models. Importantly, in an ICI-sensitive model, combination therapy resulted in complete remission and prevention of tumor recurrence. Thus, the combination of ICIs with PI3K inhibition by intermittently dosed copanlisib represents a promising new strategy to increase sensitivity to ICI therapies and to treat human solid cancers.

Abstract 3588: Discovery of potent and selective CSNK1A1 inhibitors for solid tumor therapy

CSNK1A1 is a serine/threonine kinase involved in multiple cellular processes, including cell division, beta catenin signaling, and TP53 activation. Inhibition of CSNK1A1 has previously been validated as a therapeutic strategy in hematologic malignancy, and degradation of CSNK1A1 protein is the downstream mechanism of action for lenalidomide in 5q- myelodysplasia (Krönke, et al. Nature. 2015.). However, lenalidomide is inactive in most solid tumor models, thus limiting the study of CSNK1A1 inhibition in other contexts. Analysis of genetic loss-of-function data from the Cancer Dependency Map reveals multiple sensitive models, including lineage-specific enrichment in colorectal and gastric cancer. In an academic-industry collaboration, we a) developed first-in-class potent and selective ATP-competitive CSNK1A1 small molecule inhibitors with preclinical anti-cancer efficacy in vivo, and b) identified FAM83 expression as a key determinant of inhibitor sensitivity.

We identified a tetrahydro-pyrrolopyridinone scaffold that was subsequently optimized to yield BAY-888 (CSNK1A1 IC50 4 nM @ 10 μM ATP; 63 nM @ 1 mM ATP) and BAY-204 (CSNK1A1 IC50 2 nM @ 10 μM ATP; 12 nM @ 1 mM ATP). The crystal structure of CSNK1A1 in complex with BAY-888 confirmed compound binding in the ATP binding pocket. Across the PRISM barcoded cell line panel of more than 500 solid tumor cell lines, inhibitors phenocopy the CSNK1A1 shRNA knockdown profile. To determine downstream mediators of CSNK1A1 inhibitor sensitivity, we performed co-IP mass spectrometry following CSNK1A1 pulldown and global phosphoproteomic assays following inhibitor treatment. We identified multiple interacting proteins that are also phosphorylation targets, including FAM83 family members. FAM83 was recently reported to mediate the subcellular localization of CSNK1A1 (Fulcher, et al. Sci Signal. 2018.). Excitingly, the baseline expression of FAM83B and FAM83H correlates with inhibitor and shRNA cell line sensitivity. Modulation of FAM83H expression altered CSNK1A1 localization and sensitivity to CSNK1A1 inhibition.

BAY-888 and BAY-204 are orally bioavailable and were evaluated in multiple murine cell line xenograft models. We observed promising efficacy in DLBCL (TMD8) in vivo as well as in multiple FAM83-high solid tumor models, including colorectal (HCT116 and HT29), gastric (IM95), and urothelial cancer (KU19-19). We identified RPS6 phosphorylation as one of the PD biomarkers correlating with efficacy in vivo. In summary, CSNK1A1 is a promising target with anti-tumor efficacy and achievable therapeutic index in preclinical models of FAM83-high solid tumors.

Citation Format: Steven M. Corsello, Huajia Zhang, Rajesha Rupaimoole, Volker K. Schulze, Clara Lemos, Kasia B. Handing, Douglas L. Orsi, Mrinal Shekhar, Ulrike Sack, Sven Christian, Wilhelm Bone, Ranad Humeidi, William Colgan, Stephanie Hoyt, Andrew Cherniack, Jens Schroder, Stefan Kaulfuss, Krzysztof Brzezinka, Oliver von Ahsen, Anne Mengel, Roman C. Hillig, Detlev Suelzle, Jeremie Mortier, Caitlin Harrington, Rohith Nagari, Justyna Wierzbinska, Derek Chiang, Georg Beckmann, Meagan Olive, Namrata Udeshi, Annie Apffel, Steven Carr, Philip Lienau, Christian Lechner, Ulf Boemer, Alisha Caliman, David McKinney, Florence Wagner, Dominik Mumberg, Marcus Bauser, Andrea Haegebarth, Knut Eis, Ashley Eheim, Todd R. Golub. Discovery of potent and selective CSNK1A1 inhibitors for solid tumor therapy [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 3588.

Abstract 1722: Enhancement of anti-tumor T-cell immunity by means of an oral small molecule targeting the intracellular immune checkpoint MAP4K1

Immune checkpoint blockade using antibodies targeting the cell surface expressed proteins CTLA-4, PD-1 and PD-L1 has revolutionized cancer care and its clinical impact in several indications has prompted a search for complementary immunostimulatory approaches that can further increase the efficacy of these drugs. Mitogen-activated protein kinase kinase kinase kinase 1 (MAP4K1; HPK1), a serine/threonine kinase expressed exclusively in hematopoietic cell lineages, mediates a negative feedback signal downstream of T-cell receptor stimulation. Its activity is enhanced by PGE2 and TGFβ, factors commonly present in the tumor microenvironment. Mice deficient for MAP4K1 or expressing a kinase-dead variant of MAP4K1 exhibit enhanced T-cell function, including increased anti-tumor immunity. We developed the small molecule inhibitor BAY-405 that displays potent nanomolar MAP4K1 inhibition in biochemical and cellular assays, good kinase selectivity, and in vivo exposure after oral dosing. Pharmacological inhibition of MAP4K1 enhances T-cell immunity and overcomes the suppressive impact of PGE2, TGFβ and CD4+ T-regulatory cells. Single agent treatment of tumor-bearing mice results in suppression of tumor outgrowth in several syngeneic models. This is accompanied by an increase in the anti-tumor T-cell response, dependent on an intact T-cell compartment, while not involving direct anti-tumor cytotoxicity. Inhibition of MAP4K1 in conjunction with PD-L1 blockade results in further suppression of tumor outgrowth. Moreover, we found that MAP4K1 is expressed in both PD-L1-high and PD-L1-low human cancers. In summary, our data show that selective inhibition of MAP4K1 by means of small molecule drugs may be used to expand the patient population responding to immune checkpoint inhibition.

Citation Format: Gabriele Leder, Rafael Carretero, Jeffrey Mowat, Sandra Berndt, Roland Neuhaus, Nuria Aiguabella Font, Ulf Boemer, Oliver von Ahsen, Uwe Eberspaecher, Judith Guenther, Mareike Grees, Corinna Link, Barbara Nicke, Daniel Baumann, Martina Schaefer, Mine Oezcan-Wahlbrink, Nicolas D. Werbeck, Ingo Hartung, Bertolt Kreft, Rienk Offringa. Enhancement of anti-tumor T-cell immunity by means of an oral small molecule targeting the intracellular immune checkpoint MAP4K1 [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 1722.

Hepatocyte Growth Factor Receptor overexpression predicts reduced survival but its targeting is not effective in unselected HNSCC patients

BACKGROUND

MET has emerged as target in head and neck squamous cell carcinoma (HNSCC). However, clinical data on MET inhibition in HNSCC are limited.

METHODS

HNSCC biopsies and cell lines were tested for MET activity. The response of cell lines to BAY-853474 was tested in proliferation assays. The prognostic value of MET expression was also analyzed.

RESULTS

HNSCC cell lines do not respond to MET inhibition. MET-dependent gastric cancer cell lines have much higher levels of MET expression and phosphorylation than HNSCC cell lines. Clinical samples of HNSCC contain much less MET than responsive models.

CONCLUSIONS

No clinical response to MET inhibitors in monotherapy may be expected in unselected cases of HNSCC. Only selected patients with MET amplifications should be treated with MET inhibitors. Patients with increased MET immunoreactivity have shorter overall survival. MET might be useful as marker for the detection of patients with more aggressive types of HNSCC.

Preclinical Efficacy of a PSMA-Targeted Thorium-227 Conjugate (PSMA-TTC), a Targeted Alpha Therapy for Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) is an attractive target for radionuclide therapy of metastatic castration-resistant prostate cancer (mCRPC). PSMA-targeted alpha therapy (TAT) has shown early signs of activity in patients with prostate cancer refractory to beta radiation. We describe a novel, antibody-based TAT, the PSMA-targeted thorium-227 conjugate PSMA-TTC (BAY 2315497) consisting of the alpha-particle emitter thorium-227 complexed by a 3,2-HOPO chelator covalently linked to a fully human PSMA-targeting antibody.

EXPERIMENTAL DESIGN

PSMA-TTC was characterized for affinity, mode of action, and cytotoxic activity in vitro. Biodistribution, pharmacokinetics, and antitumor efficacy were investigated in vivo using cell line and patient-derived xenograft (PDX) models of prostate cancer.

RESULTS

PSMA-TTC was selectively internalized into PSMA-positive cells and potently induced DNA damage, cell-cycle arrest, and apoptosis in vitro. Decrease in cell viability was observed dependent on the cellular PSMA expression levels. In vivo, PSMA-TTC showed strong antitumor efficacy with T/C values of 0.01 to 0.31 after a single injection at 300 to 500 kBq/kg in subcutaneous cell line and PDX models, including models resistant to standard-of-care drugs such as enzalutamide. Furthermore, inhibition of both cancer and cancer-induced abnormal bone growth was observed in a model mimicking prostate cancer metastasized to bone. Specific tumor uptake and efficacy were demonstrated using various PSMA-TTC doses and dosing schedules. Induction of DNA double-strand breaks was identified as a key mode of action for PSMA-TTC both in vitro and in vivo.

CONCLUSIONS

The strong preclinical antitumor activity of PSMA-TTC supports its clinical evaluation, and a phase I trial is ongoing in mCRPC patients (NCT03724747).

Abstract 4828: Anti-tumor activity of BAY-943, an anti-IL3RA ADC with a novel KSP inhibitor payload, in CDX and PDX AML models

Despite recent progress in the treatment of AML, clinical outcomes have improved only minimally over the past three decades. Therefore, novel therapeutic agents with a high therapeutic window and a favorable tolerability profile are urgently needed to improve the therapeutic outcome for AML patients.

IL3RA (CD123) is the alpha subunit of the interleukin 3 (IL-3) receptor which regulates proliferation, survival and differentiation of hematopoietic cells. IL3RA is expressed at high frequency, with ~84% of AML cases and 59% of classical Hodgkin lymphoma (cHL) cases being positive. IL3RA is expressed in AML blast and leukemic stem cells (LSCs) but not in hematopoietic stem cells (HSCs). In healthy individuals, the IL3RA expression is restricted to myeloid progenitor cells, plasmacytoid dendritic cells (pDCs), basophils and - at low levels - monocytes and B-lymphocyte subsets. This expression pattern suggests that IL3RA could be a clinically relevant target for an antibody-drug conjugate (ADC) approach in treatment of AML, cHL, and MDS.

BAY-943 is a novel antibody-drug conjugate (ADC) consisting of a humanized internalizing anti-IL3RA IgG1 antibody (Ab, EC50 on IL3RA-positive tumor cells in flow cytometry: 2-5 nM) conjugated via lysine residues to a potent proprietary kinesin spindle protein inhibitor (KSPi). The kinesin spindle protein (KSP/Eg5/KIF11) is essential for the proper segregation of duplicated centrosomes during spindle formation in the G2/M phase of the cell cycle, as such it is only active in proliferating cells.

In vitro, in a panel of IL3RA-positive AML and HL cell lines, BAY-943 showed potency in the nano- to subnanomolar range. In IL3RA-positive cell line derived (CDX) AML xenograft models (MOLM-13 and MV4-11) and patient-derived xenograft (PDX) models, BAY-943 dosed at 10 mg/kg given Q7Dx increased survival compared to vehicle treated mice. Tumor burden (percentage of human CD45 positive AML cells) was significantly reduced compared to vehicle treated mice. In the subcutaneous IL3RA-positive cHL CDX model HDLM-2, BAY-943 dosed at 5 and 10 mg/kg Q7Dx2 induced complete tumor remission in 12 out of 13 mice.

In safety studies in Cynomolgus monkeys, BAY-943 (which is cross-reactive with Cynomolgus IL3RA), up to 20 mg/kg single or 10 mg/kg repeat (QWx3) dose were well tolerated with no signs of thrombocytopenia, neutropenia and no liver toxicity, i.e. adverse events observed with ADCs containing other payload classes. As expected, a transient reduction of IL3RA expressing cell types (basophils, pDCs) was observed.

In summary, IL3RA-KSPi-ADC BAY-943 shows efficacy in IL3RA-positive AML and HL models and has a favorable safety profile in monkey repeat dose studies. Overall, the preclinical results support further development of BAY-943 as an innovative approach for the treatment of IL3RA-positive AML.

Citation Format: Anette Sommer, Dennis Kirchhoff, Antje M. Wengner, Beatrix Stelte-Ludwig, Hans-Georg Lerchen, Anne-Sophie Rebstock, Oliver von Ahsen, Lisa Dietz, Pascale Buchmann, Sandra Johanssen, Dominik Mumberg, Bertolt Kreft. Anti-tumor activity of BAY-943, an anti-IL3RA ADC with a novel KSP inhibitor payload, in CDX and PDX AML models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4828.

Abstract 4825: Preclinical characterization of BAY-924, a first in class ADC targeting CXCR5-positive B-cell malignancies, with a KSP inhibitor as novel payload

Despite recent progress in the treatment of B-cell malignancies, patients are still in need of innovative therapeutic approaches. CXCR5 is a chemokine receptor expressed in a majority of B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), Mantle cell lymphoma (MCL), follicular lymphoma and chronic lymphocytic leukemia. Evaluation of tumor biopsies from relapsed DLBCL patients shows that CXCR5 staining remains high, suggesting altogether that it could be a relevant target to explore for the treatment of non-Hodgkin lymphoma. BAY-924 is a novel first-in-class antibody drug conjugate (ADC) consisting of a humanized anti-CXCR5 IgG1 antibody (Ab) linked to a potent proprietary kinesin spindle protein inhibitor (KSPi). Of importance, the structure of the ADC is optimized for a specific metabolism, matching the KSPi mode of action and enabling a maximal retention of the payload within the tumor cells (Lerchen HG et al.; Angew. Chem. Int. Ed, 2018). Surface plasmon resonance assay showed a high binding affinity of the Ab to CXCR5 (2.5 nM). Affinities of 0.8 to 10 nM were measured by flow cytometry for the ADC in different CXCR5+ lymphoma cell lines. In vitro, BAY 924 had high and selective anti-proliferative activity in a panel of tumor cell lines with different levels of CXCR5 expression (<0.03 - 2 nM IC50). Efficient internalization and lysosomal co-localization of the Ab was observed in a variety of cell lines including the CXCR5+ MCL REC-1 cells. In vivo, BAY-924 was highly active in several CXCR5+ lymphoma models with a specific accumulation of the payload in tumor versus liver, spleen and kidney and almost undetectable levels in plasma. In the REC-1 model implanted subcutaneously (SC) in mice and treated at large tumor size (500 mm3), long lasting tumor regression was observed after 2 intravenous injections of BAY 0924 at 10 mg/kg, Q7D, whereas the model was insensitive to ibrutinib, a current standard of care (SoC) for the MCL indication. In the advanced ABC DLBCL model OCI-LY1 (SC), a single injection of BAY-924 at 10 mg/kg induced complete responses in 10/10 mice (up to day 95 post-treatment). In this model, head-to-head comparison showed superior activity of BAY-924 compared to the SoCs rituximab (R)-CHOP, R/bendamustine and R/lenalidomide. Also, BAY-924 induced potent antitumor effect with a 4% ΔT/ΔC (day 55) in the ABC DLBCL OCI-Ly3-2b model, expressing weak to moderate levels of CXCR5 in vivo. Given its unique structure, and based on supportive data from other projects, it is anticipated that BAY-924 shows a favorable safety profile, due to the high stability of the ADC and a non-cell permeable free payload which is trapped inside the tumor cells. Overall, these results support further development of BAY-924 as an innovative approach for the treatment of CXCR5+ non-Hodgkin lymphoma.

Citation Format: Sarah Johannes, Stefanie Hammer, Stephan Maersch, Hans-Georg Lerchen, Beatrix Stelte-Ludwig, Hannah Joerissen, Oliver von Ahsen, Christoph Schatz, Simone Greven, Christoph Mahlert, Dominik Mumberg, Pascale Lejeune. Preclinical characterization of BAY-924, a first in class ADC targeting CXCR5-positive B-cell malignancies, with a KSP inhibitor as novel payload [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4825.

Abstract LB-075: Increased T cell- activation resulting from the combination of the anti-CEACAM6 function-blocking antibody BAY 1834942 with checkpoint inhibitors targeting either PD-1/PD-L1 or TIM-3

CEACAM6 (CD66c) is a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors. CEACAM6 is expressed on tumor cells of multiple malignancies e.g.adenocarcinomas of the lung, colon, pancreas and stomach. In these tumor types higher CEACAM6 expression is associated with advanced stages and a poor prognosis. In immunohistochemistry analyses on primary tumor tissue slides and tissue microarrays the tumor cell expression of CEACAM6 was found to be independent from that of programmed death ligand 1 (PD-L1). BAY 1834942 is a humanized monoclonal antibody selectively blocking CEACAM6-mediated suppression of human T cells. Because there is no rodent orthologue of CEACAM6, BAY 1834942 was fully characterized in in vitro studies as reported earlier (AACR 2018, abstract nr. 1771). Benchmarking and combination studies showed that CEACAM6-mediated inhibition of T cell activation is apparently non-redundant with the programmed death-receptor 1 (PD-1)/ PD-L1 axis. Combination experiments were performed in co-cultures of PD-1, T cell immunoglobulin and mucin domain 3 (TIM3) and CEACAM1 (CD66a) positive virus antigen-specific T cells and virus peptide-loaded CEACAM6-expressing tumor cells (HCC2935, HCT116-C6 cells). When BAY 1834942 was combined with antibody inhibitors of either PD-1 or PD-L1, we consistently observed enhanced secretion of proinflammatory cytokines by T cells in the presence of PD-L1 positive tumor cells (HCC2935). Unexpectedly, combination of BAY 1834942 with an anti-TIM3 antibody resulted in an even more pronounced, synergistic increase of cytokine secretion. The combined effect of CEACAM6 and TIM-3 blockade was confirmed using survivin peptide-specific T cells as alternative T cell source. In contrast, combination of BAY 1834942 with an anti-CEACAM1 function blocking antibody was not superior to anti-CEACAM1 treatment alone, which is in line with our hypothesis that CEACAM1 is the main T cell receptor for CEACAM6 in our functional assays. In summary, BAY 1834942 is a novel immune checkpoint inhibitor with monotherapy potential for the treatment of patients with CEACAM6-expressing cancers. The data shown here provide a rationale for examining its combination potential with immune checkpoint inhibitors targeting either PD-1, PD-L1 or TIM-3. BAY 1834942 is currently under investigation in Ph1 clinical trials (NCT03596372).

Citation Format: Joerg Willuda, Hans-Henning Boehm, Jessica Pinkert, Mark Trautwein, Wolf-Dietrich Doecke, Oliver von Ahsen, Karl Ziegelbauer, Rienk Offringa, Bertolt Kreft, Philipp Beckhove. Increased T cell- activation resulting from the combination of the anti-CEACAM6 function-blocking antibody BAY 1834942 with checkpoint inhibitors targeting either PD-1/PD-L1 or TIM-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-075.

Circulating endothelial cells as biomarker for cardiovascular diseases

BACKGROUND

Endothelial dysfunction is involved in several cardiovascular diseases. Elevated levels of circulating endothelial cells (CECs) and low levels of endothelial progenitor cells (EPCs) have been described in different cardiovascular conditions, suggesting their potential use as diagnostic biomarkers for endothelial dysfunction. Compared to typical peripheral blood leukocyte subsets, CECs and EPCs occur at very low frequency. The reliable identification and characterization of CECs and EPCs is a prerequisite for their clinical use, however, a validated method to this purpose is still missing but a key for rare cell events.

OBJECTIVES

To establish a validated flow cytometric procedure in order to quantify CECs and EPCs in human whole blood.

METHODS

In the establishment phase, the assay sensitivity, robustness, and the sample storage conditions were optimized as prerequisite for clinical use. In a second phase, CECs and EPCs were analyzed in heart failure with preserved (HFpEF) and reduced (HFrEF) ejection fraction, in arterial hypertension (aHT), and in diabetic nephropathy (DN) in comparison to age-matched healthy controls.

RESULTS

The quantification procedure for CECs and EPCs showed high sensitivity and reproducibility. CEC values resulted significantly increased in patients with DN and HFpEF in comparison to healthy controls. CEC quantification showed a diagnostic sensitivity of 90% and a sensitivity of 68.0%, 70.4%, and 66.7% for DN, HFpEF, and aHT, respectively.

CONCLUSION

A robust and precise assay to quantify CECs and EPCs in pre-clinical and clinical studies has been established. CEC counts resulted to be a good diagnostic biomarker for DN and HFpEF.

Inhibition of BUB1 Kinase by BAY 1816032 Sensitizes Tumor Cells toward Taxanes, ATR, and PARP Inhibitors In Vitro and In Vivo

PURPOSE

The catalytic function of BUB1 is required for chromosome arm resolution and positioning of the chromosomal passenger complex for resolution of spindle attachment errors and plays only a minor role in spindle assembly checkpoint activation. Here, we present the identification and preclinical pharmacologic profile of the first BUB1 kinase inhibitor with good bioavailability.

EXPERIMENTAL DESIGN

The Bayer compound library was screened for BUB1 kinase inhibitors and medicinal chemistry efforts to improve target affinity and physicochemical and pharmacokinetic parameters resulting in the identification of BAY 1816032 were performed. BAY 1816032 was characterized for kinase selectivity, inhibition of BUB1 signaling, and inhibition of tumor cell proliferation alone and in combination with taxanes, ATR, and PARP inhibitors. Effects on tumor growth in vivo were evaluated using human triple-negative breast xenograft models.

RESULTS

The highly selective compound BAY 1816032 showed long target residence time and induced chromosome mis-segregation upon combination with low concentrations of paclitaxel. It was synergistic or additive in combination with paclitaxel or docetaxel, as well as with ATR or PARP inhibitors in cellular assays. Tumor xenograft studies demonstrated a strong and statistically significant reduction of tumor size and excellent tolerability upon combination of BAY 1816032 with paclitaxel or olaparib as compared with the respective monotherapies.

CONCLUSIONS

Our findings suggest clinical proof-of-concept studies evaluating BAY 1816032 in combination with taxanes or PARP inhibitors to enhance their efficacy and potentially overcome resistance.

Abstract 1771: BAY 1834942 is an immunotherapeutic antibody blocking the novel immune checkpoint regulator CEACAM6 (CD66c)

CEACAM6 (CD66c) was previously shown to act as a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors (Witzens-Harig et al., Blood 2013). CEACAM6 is a GPI-linked protein that is strongly expressed at the tumor cell surface in multiple cancer indications such as non-small cell lung adenocarcinoma (NSCLC), colorectal carcinoma (CRC), gastric adenocarcinoma and pancreatic cancer. In general, elevated CEACAM6 expression is associated with advanced tumor stages and poor prognosis. In vitro experiments showed that engagement of T-cells with CEACAM6, either expressed on tumor cells or presented on beads, resulted in suppression of TCR-mediated T-cell activation and ZAP70 phosphorylation. Based on these findings, we hypothesized that antibodies targeting CEACAM6 may be employed to enhance T-cell responses against CEACAM6-expressing cancers. Here we report the generation and characterization of BAY 1834942, a humanized monoclonal antibody selectively blocking the inhibitory impact of CEACAM6 on human T cells. There is no rodent ortholog of CEACAM6 precluding in vivo efficacy studies. In tumor cell / T cell co-culture systems, BAY 1834942 increased secretion of T-cell cytokines and effector molecules (e.g. IFNγ, TNFα, IL-2, granzyme B) and resulted in improved tumor cell killing. The effects of BAY 1834942 were dose-dependent, only observed in the context of CEACAM6-expressing tumor cells and could be reproduced in experiments using tumor cell lines and T-cell preparations from different sources, including T cells derived from tumor infiltrating lymphocytes from pancreatic cancer. BAY 1834942 is cross-reactive with the cynomolgus CEACAM6 ortholog and was well-tolerated in monkey toxicology studies. In summary, BAY 1834942 is a novel checkpoint inhibitor with potential for the treatment of patients with CEACAM6 expressing cancers, both as single agent and in combination with other checkpoint inhibitors. First-in-man trials are expected to commence in 2018.

Citation Format: Joerg Willuda, Mark Trautwein, Jessica Pinkert, Wolf-Dietrich Doecke, Hans-Henning Boehm, Florian Wessel, Yingzi Ge, Eva Maria Gutierrez, Joerg Weiske, Christoph Freiberg, Uwe Gritzan, Julian Glueck, Dieter Zopf, Sven Golfier, Oliver von Ahsen, Ruprecht Zierz, Sabine Wittemer-Rump, Heiner Apeler, Ziegelbauer Karl, Rienk Offringa, Bertolt Kreft, Beckhove Philipp. BAY 1834942 is an immunotherapeutic antibody blocking the novel immune checkpoint regulator CEACAM6 (CD66c) [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 1771.

Abstract 2389: Role of MET in head and neck cancer

Introduction c-MET is a well-known target due to its amplification and overexpression in gastric cancer and NSCLC. Overexpression has also been reported for Head and Neck Cancer (HNSCC), but initial clinical trials with MET inhibitors in HNSCC have not been successful.

Methods We investigated the expression level of MET in HNSCC and also characterized the molecular activity level based on the phosphorylation of the intracellular adaptor protein docking site, Tyrosine-1349. In a second larger cohort, we tested expression of MET and correlate it with follow-up data in order to test the prognostic relevance of MET expression in gastric cancer. All clinical samples were all obtained in compliance with clinical regulations and informed consent of every patient.

Results We found MET clearly overexpressed in HNSCC. However, the signaling activity of MET was not elevated compared to normal adjacent tissue. To test the relevance of MET for growth of HNSCC cells, we tested the activity of BAY 853474 in a panel of HNSCC cell lines. In contrast to gastric cancer control cell lines which had low nanomolar IC50 values, none of the 12 HNSCC cell lines was sensitive to MET inhibition. This was in contrast to their sensitivity to Cisplatin/Fluoruracil as positive control. Compared to MET dependent cell lines from gastric cancer, HNSCC cell lines had 10 fold less MET expression. The phosphorylation was two orders of magnitude below that of responder cell lines. On the molecular level, we also compared the properties of the HNSCC cell lines with that of fresh frozen tumor biopsies from 50 patients. In this analysis, it became evident that clinical samples had strikingly lower MET expression and phosphorylation even compared to the HNSCC cell lines. Based on these findings, a clinical response to MET inhibitors cannot be expected. In a larger cohort of several hundred patients, we are currently testing whether the elevated MET expression may still be prognostic for progression and/or survival. It appears possible that MET expression may give a growth advantage to tumor cells although it is clearly not fulfilling the criteria for an oncogenic driver in this indication. The significant overexpression of MET in tumor tissue and the very strong overexpression in cell lines compared to clinical samples show that MET expression gives a selective advantage to the tumor cells. We will show whether this advantage results in shorter time to progression or overall survival.

Conclusion We show that MET expression in HNSCC cell lines is not representative for the clinical situation. HNSCC does not overexpress Met and the molecular activity is low. MET is devalidated as therapeutic target in HNSCC. An analysis of the prognostic value of MET expression in HNSCC will follow and presented at the AACR meeting in 2018.

Citation Format: Thomas Schlange, Martin Khan, Sami Khaznadar, arndt schmitz, Thomas Krahn, Oliver von Ahsen. Role of MET in head and neck cancer [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 2389.

Abstract 844: Preclinical activity of PSMA-TTC, a targeted alpha therapeutic in patient-derived prostate cancer models

Targeted alpha therapy (TAT) agents deliver high linear energy transfer (LET) alpha-radiation selectively to tumors. The first TAT to be approved is radium-223 which prolongs overall survival in metastatic castration resistant prostate cancer (mCRPC) patients with symptomatic bone metastasis. Radium-223 shows a selective uptake in newly formed bone matrix such as bone metastasis and binds to hydroxyapatite. The PSMA targeted thorium-227 conjugate PSMA-TTC represents another TAT approach in mCRPC. It consists of a fully human PSMA IgG antibody covalently linked to the chelator moiety (3,2 HOPO). This antibody-chelator conjugate is radiolabeled with thorium-227, which decays with a half-life of 18.7 days to radium-223 via alpha-particle emission.

Herein we describe tumor targeting and anti-tumor activity of PSMA-TTC in two PSMA positive patient derived xenograft (PDx) models of prostate cancer with different characteristics. In vivo biodistribution and anti-tumor efficacy were analyzed after i.v. injection of PSMA-TTC at radioactive doses from 75-500 kBq/kg and protein doses of either 0.14 or 0.43 mg/kg to tumor bearing mice.

Initially, the PDx model KuCap1 (provided by Prof. O. Ogava, University of Kyoto, Japan), a prostate cancer model resistant to the second generation antiandrogen enzalutamide, was analyzed. In this model PSMA-TTC showed strong dose dependent tumor growth inhibition starting at a single dose of 75 kBq/kg. Moreover, after a single i.v. administration of PSMA-TTC at 300 kBq/kg 9 out of 10 mice (90%) showed either stable disease or tumor regression for at least 33 days after treatment. The observed activity was highly selective, as injection of a radiolabeled control conjugate at 300 kBq/kg showed only limited tumor growth inhibition.

Next, PSMA-TTC was tested in the hormone- and enzalutamide-sensitive prostate cancer PDx model ST1273 (South Texas Accelerated Research Therapeutics, San Antonio, Texas). A single i.v. injection of PSMA-TTC resulted in significant tumor accumulation of thorium-227 for more than 3 weeks, whereas a radiolabeled isotype control conjugate did not show tumor uptake. In addition, single i.v. administration of PSMA-TTC showed strong dose dependent anti-tumor activity while limited tumor growth inhibition was observed for a radiolabeled isotype control conjugate. Single doses of either 250 or 500 kBq/kg resulted in a 100 % response rate 4 weeks after treatment, with all animals showing partial or even complete regression of tumor growth. No significant effects on body weight were detected compared to vehicle treated animals.

In summary, PSMA-TTC shows strong anti-tumor activity in patient derived prostate cancer models which were either sensitive or resistant to standard of care drugs. These data warrant further clinical investigation of this targeted alpha pharmaceutical investigational agent.

Citation Format: Stefanie Hammer, Urs B. Hagemann, Sabine Zitzmann-Kolbe, Aasmund Larsen, Christine Ellingsen, Oliver von Ahsen, Jenny Karlsson, Roger M. Bjerke, Olav B. Ryan, Pascale Lejeune, Hartwig Hennekes, Alan Cuthbertson, Karl Ziegelbauer, Dominik Mumberg. Preclinical activity of PSMA-TTC, a targeted alpha therapeutic in patient-derived prostate cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 844.

EGFR overexpression is not common in patients with head and neck cancer. Cell lines are not representative for the clinical situation in this indication

Background

Based on expression data, Epidermal Growth Factor Receptor (EGFR) emerged as therapeutic target in Head and Neck Cancer but clinical efficacy of EGFR inhibitors was very limited. We reinvestigated the EGFR expression and activation status necessary for response in cell lines and compared that to clinical samples.

Methods

Clinical samples of head and neck squamous cell carcinoma (HNSCC, n=63), mostly from late stage (IV) and poorly or undifferentiated character and cultured cell lines (n=14) were tested by immunohistochemistry (IHC) (n=55) and sandwich immunoassays (n=63) for expression and phosphorylation of EGFR (Tyrosine-1173). Response of 14 different HNSCC cell lines to Erlotinib was tested in proliferation assays.

Results

Most HNSCC cell lines respond to Erlotinib. EGFR is phosphorylated in these cell lines. Resistant cell lines display very low level EGFR expression and phosphorylation. EGFR activity in clinical samples is significantly below that observed in cell lines. In clinical samples, EGFR is not overexpressed on the single cellular level. We show similar levels of EGFR expression in growing keratinocytes and tumor cells.

Conclusions

Cell lines are not representative of the clinical situation in HNSCC. Larger studies should investigate whether patient subgroups with activating EGFR mutations or overexpression can be identified.

ATAD2 is an epigenetic reader of newly synthesized histone marks during DNA replication

ATAD2 (ATPase family AAA domain-containing protein 2) is a chromatin regulator harboring an AAA+ ATPase domain and a bromodomain, previously proposed to function as an oncogenic transcription co-factor. Here we suggest that ATAD2 is also required for DNA replication. ATAD2 is co-expressed with genes involved in DNA replication in various cancer types and predominantly expressed in S phase cells where it localized on nascent chromatin (replication sites). Our extensive biochemical and cellular analyses revealed that ATAD2 is recruited to replication sites through a direct interaction with di-acetylated histone H4 at K5 and K12, indicative of newly synthesized histones during replication-coupled chromatin reassembly. Similar to ATAD2-depletion, ectopic expression of ATAD2 mutants that are deficient in binding to these di-acetylation marks resulted in reduced DNA replication and impaired loading of PCNA onto chromatin, suggesting relevance of ATAD2 in DNA replication. Taken together, our data show a novel function of ATAD2 in cancer and for the first time identify a reader of newly synthesized histone di-acetylation-marks during replication.

Isolation of circulating tumor cells from pancreatic cancer by automated filtration

It is now widely recognized that the isolation of circulating tumor cells based on cell surface markers might be hindered by variability in their protein expression. Especially in pancreatic cancer, isolation based only on EpCAM expression has produced very diverse results. Methods that are independent of surface markers and therefore independent of phenotypical changes in the circulating cells might increase CTC recovery also in pancreatic cancer. We compared an EpCAM-dependent (IsoFlux) and a size-dependent (automated Siemens Healthineers filtration device) isolation method for the enrichment of pancreatic cancer CTCs. The recovery rate of the filtration based approach is dramatically superior to the EpCAM-dependent approach especially for cells with low EpCAM-expression (filtration: 52%, EpCAM-dependent: 1%). As storage and shipment of clinical samples is important for centralized analyses, we also evaluated the use of frozen diagnostic leukapheresis (DLA) as source for isolating CTCs and subsequent genetic analysis such as KRAS mutation detection analysis. Using frozen DLA samples of pancreatic cancer patients we detected CTCs in 42% of the samples by automated filtration.

Abstract 2786: EGFR expression and phosphorylation in HNSCC predict response to EGFR inhibition but cell lines are not representative for the clinical situation

Introduction Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer. Survival rates have not been improved for decades and conventional therapy is effective in only 50% of the patients. Based on broad expression in up to 80-90% of the HNSCC cases, epidermal growth factor receptor emerged as drug target but clinical efficacy of EGFR inhibitors in HNSCC is very limited. We therefore reinvestigated the EGFR expression levels necessary for response in cell lines and clinical samples.

Methods Standard procedures were used for IHC. The antibody clone D38B1 was used in 1:900 dilution for 2h at RT. Stainings were performed using the DAKO Envision system. EGFR expression and phosphorylation of Tyrosine-1173 were analysed by MSD (Mesoscale Discovery) in lysates from fresh frozen tumor or exponentially growing cells. For proliferation assays, 2000 cells per well were grown for 24 h before addition of inhibitors. Cell culture was continued for 72 h before testing viability using the CellTiter-Glo® Assay.

Results The majority (11/13) of HNSCC cell lines responded to the EGFR inhibitor Erlotinib. EGFR was highly expressed and phosphorylated in the Erlotinib responsive cell lines. Resistant cell lines displayed low level EGFR expression and phosphorylation. However, EGFR expression and phosphorylation in treatment naive clinical samples were significantly below the levels found in responding cell lines. In clinical samples EGFR was not overexpressed on the cellular level. Based on these findings, a clinical response to Erlotinib in HNSCC would not be expected.

Conclusion The prognostic value of EGFR expression has been used to argue for EGFR as a relevant target in HNSCC. Although most reviews claim that EGFR is overexpressed in HNSCC, clear data supporting this position are missing. Early studies tested the RNA levels and found the EGFR expression in tumors higher compared to control tissues. Studies using IHC assessed the association of EGFR expression with disease progression, but no comparison to expression in normal mucosa was described. Overexpression was based on percentage of positive cells not on the intensity of expression. We show similar levels of EGFR expression in growing keratinocytes and tumor cells. The often described overexpression only originated from a larger number of EGFR positive cells, not on overexpression on the cellular level. The high expression and functional relevance of EGFR in cell lines proves that EGFR activity is required for survival in cell culture. Our findings lead to the conclusion that this is not representative of the clinical situation. Definition of a response threshold for EGFR expression and clinical verification of this expression level is mandatory for the successful use of a predictive biomarker.

Citation Format: Oliver von Ahsen, Sami S. Khaznadar, Martin Khan. EGFR expression and phosphorylation in HNSCC predict response to EGFR inhibition but cell lines are not representative for the clinical situation [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 2786. doi:10.1158/1538-7445.AM2017-2786

Abstract 287: BAY 1816032, a novel BUB1 kinase inhibitor with potent antitumor activity

The spindle assembly checkpoint represents a highly conserved surveillance mechanism which safeguards correct chromosome segregation by delaying anaphase onset until all chromosomes are properly bi-oriented on the spindle apparatus. Non-catalytic functions of the mitotic kinase BUB1 (budding uninhibited by benzimidazoles 1) were reported to be essential for spindle assembly checkpoint activation. In contrast, the catalytic function of BUB1 plays a minor role in spindle assembly checkpoint activation but is required for chromosome arm resolution and positioning of the chromosomal passenger complex for resolution of spindle attachment errors. Here, we disclose for the first time the structure and functional characterization of a novel, first-in-class Bub1 kinase inhibitor. Medicinal chemistry efforts resulted in BAY 1816032 featuring high potency, long target residence time and good oral bioavailablity. It inhibits BUB1 enzymatic activity with an IC50 of 7 nanomol/L, shows slow dissociation kinetics resulting in a long target residence time of 87 min, and an excellent selectivity on a panel of 395 kinases. Mechanistically BAY 1816032 abrogated nocodazole-induced Thr-120 phosphorylation of the major BUB1 target protein histone H2A in HeLa cells with an IC50 of 29 nanomol/L, induced lagging chromosomes and mitotic delay. Persistent lagging chromosomes and missegregation were observed upon combination with low concentrations of paclitaxel. Single agent BAY 1816032 inhibited proliferation of various tumor cell lines with a median IC50 of 1.4 micromol/L and demonstrated synergy or additivity with paclitaxel or docetaxel in almost all cell lines evaluated (minimal combination index 0.3). In tumor xenograft studies BAY 1816032 only marginally inhibited tumor growth as single agent upon oral administration, however, upon combination with paclitaxel or docetaxel a strong and statistically significant reduction of tumor size as compared to the respective monotherapy was observed. Intratumoral levels of phospho-Thr120 H2A were found to be strongly reduced, and no hints on drug-drug interactions were found. In line with the good tolerability in xenograft studies, no relevant findings from non-GLP 2 weeks toxicological studies in rat and dog were reported. Our findings validate the innovative concept of interference with mitotic checkpoints and justify clinical proof of concept studies evaluating BUB1 inhibitor BAY 1816032 in combination with taxanes in order to enhance their efficacy and potentially overcome resistance.

Citation Format: Gerhard Siemeister, Anne Mengel, Wilhelm Bone, Jens Schröder, Sabine Zitzmann-Kolbe, Hans Briem, Amaury E. Fernández-Montalván, Simon Holton, Ursula Mönning, Oliver von Ahsen, Sandra Johanssen, Arwed Cleve, Marion Hitchcock, Kirstin Meyer, Franz von Nussbaum, Michael Brands, Dominik Mumberg, Karl Ziegelbauer. BAY 1816032, a novel BUB1 kinase inhibitor with potent antitumor activity [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 287. doi:10.1158/1538-7445.AM2017-287

Abstract 3792: Improved isolation and detection of circulating tumor cells of pancreatic cancer patients with characterization by mutational analysis

Introduction: Isolation of circulating tumor cells based on cell surface markers is often hindered by epithelial to mesenchymal transition with loss of epithelial antigens. Low numbers of CTCs and fewer cases of CTC positive pancreatic cancer compared to other cancers (e.g. breast cancer) lead to the assumption that pancreatic tumors do not release CTCs as frequently or that the pancreatic CTCs lack EpCAM expression. Isolation of CTCs based on their size is independent of EMT-like phenotypical changes. We therefore compared a filtration-based isolation method with an EpCAM-based isolation method. We optimized CTC detection by using a highly sensitive anti-cytokeratin antibody panel for the detection of cancer cells with moderate cytokeratin expression. In order to use isolated CTCs as liquid biopsy for tumor characterization and treatment selection, downstream analysis is necessary. We here show the feasibility of mutational analysis of isolated CTCs by castPCR.

Methods: EpCAM high, medium and low cells were enriched and isolated by an EpCAM-based immunomagnetic procedure (IsoFlux) and a filtration device (Siemens) to determine recovery rates of both methods. Isolated cells were detected by an improved immunofluorescent staining with an anti-Cytokeratins, anti-EpCAM and anti-PBMC panel and characterized by competitive allele-specific TaqMan PCR (castPCR) for KRAS mutations.

Results: Cytokeratin expression is crucial for detection of CTCs in a high background of blood cells. Improvement of the staining protocol helps to increase the sensitivity of detection. The filtration based approach is superior to the surface antigen-based isolation. With the size-dependent method we obtained a recovery rate of 52 % even for EpCAM-low cells compared to only 1 % based on the immune-affinity purification. Cells isolated by filtration can be characterized for expression of therapeutic targets by immunostaining. The utility of the size dependent platform for subsequent functional characterization of the CTCs was also demonstrated by detection of k-ras mutations in single isolated CTCs by castPCR.

Conclusion: For CTCs undergoing EMT, filtration yields higher recovery compared to the standard surface antigen (EpCAM)-based methods. Isolation by filtration also allows for mutational analysis which can be used to confirm the identity of the isolated cell as CTC. In addition, mutational analysis of CTCs can be used to guide the treatment of patients. Use of liquid biopsies for treatment selection will facilitate truly personalized medicine.

Citation Format: Oliver von Ahsen, Nora Brychta, Thomas Krahn. Improved isolation and detection of circulating tumor cells of pancreatic cancer patients with characterization by mutational analysis [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 3792. doi:10.1158/1538-7445.AM2017-3792

Abstract 5200: Preclinical pharmacology of the PSMA-targeted thorium-227 conjugate PSMA-TTC: a novel targeted alpha therapeutic for the treatment of prostate cancer

Prostate-specific membrane antigen (PSMA, FOLH1) is a type II transmembrane glycoprotein of the M28 peptidase family that acts as a glutamate carboxypeptidase on various substrates. PSMA is well established as a target antigen in prostate cancer due to its high and specific overexpression on the surface of prostate cancer cells at all tumor stages, including metastatic and hormone-refractory disease. Several PSMA targeting antibodies and ligands are currently in clinical development or compassionate use therapeutically or as imaging agents. Targeted alpha therapy (TAT) has an established clinical profile with the successful transition of Ra223, an alpha-particle emitter, from bench to bedside in prostate cancer. Thorium-227 is the immediate precursor for Ra223 via alpha-particle emission. We herein describe the generation of a novel TAT, a high energy, alpha-particle emitting PSMA-targeted thorium-227 conjugate (PSMA-TTC). PSMA-TTC consists of a fully human PSMA targeting IgG1 antibody covalently linked via an amide bond to a chelator moiety (3,2 HOPO), enabling radiolabeling with thorium-227 (227Th).

PSMA-TTC was prepared in high radiochemical yield and purity and tested for binding affinity to PSMA target (ELISA) as well as PSMA expressing cell lines (FACS). In vitro cytotoxicity experiments were carried out on prostate CA cell lines with different PSMA levels (from 3.000 to 150.000 mAbs bound/ cell). In vivo biodistribution and anti-tumor efficacy were analyzed after i.v. injection of 100-500 kBq/kg at protein doses of 0.14 mg/kg to mice bearing s.c. prostate cancer xenograft models. Additionally, anti-tumor efficacy was evaluated in a PSMA expressing orthotopic bone xenograft model (LNCaP-Luc) monitored by bioluminescence imaging, micro CT and x-ray.

PSMA-TTC retains binding affinities to PSMA target and PSMA positive cancer cells similar to the PSMA antibody. Strong in vitro potency and selectivity of PSMA-TTC was shown on different PSMA positive cells. Biodistribution studies in C4-2 xenografts demonstrated specific tumor uptake of PSMA-TTC with a maximum of 50 % of ID/g at t = 72h post dose administration. Selective significant antitumor efficacy was shown for PSMA-TTC in s.c. prostate CA xenograft models with high (C4-2) and medium/low (22Rv1) PSMA protein levels at doses of 250 and 500 kBq/kg. Furthermore, statistically significant prevention of tumor growth was observed after treatment with PSMA-TTC at a dose of 100 kBq/kg in an orthotopic bone xenograft model (LNCaP-Luc).

The promising preclinical antitumor activity of PSMA-TTC supports its development for the treatment of patients with metastatic prostate cancer.

Citation Format: Stefanie Hammer, Aasmund Larssen, Christine Ellingsen, Solene Geraudie, Derek Grant, Baard Indrevoll, Oliver von Ahsen, Alexander Kristian, Urs B Hagemann, Jenny Karlsson, Roger M Bjerke, Olav B Ryan, Dominik Mumberg, Bertolt Kreft, Alan Cuthbertson. Preclinical pharmacology of the PSMA-targeted thorium-227 conjugate PSMA-TTC: a novel targeted alpha therapeutic for the treatment of prostate cancer [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 5200. doi:10.1158/1538-7445.AM2017-5200

Preclinical Antitumor Efficacy of BAY 1129980-a Novel Auristatin-Based Anti-C4.4A (LYPD3) Antibody-Drug Conjugate for the Treatment of Non-Small Cell Lung Cancer

C4.4A (LYPD3) has been identified as a cancer- and metastasis-associated internalizing cell surface protein that is expressed in non-small cell lung cancer (NSCLC), with particularly high prevalence in the squamous cell carcinoma (SCC) subtype. With the exception of skin keratinocytes and esophageal endothelial cells, C4.4A expression is scarce in normal tissues, presenting an opportunity to selectively treat cancers with a C4.4A-directed antibody-drug conjugate (ADC). We have generated BAY 1129980 (C4.4A-ADC), an ADC consisting of a fully human C4.4A-targeting mAb conjugated to a novel, highly potent derivative of the microtubule-disrupting cytotoxic drug auristatin via a noncleavable alkyl hydrazide linker. In vitro, C4.4A-ADC demonstrated potent antiproliferative efficacy in cell lines endogenously expressing C4.4A and inhibited proliferation of C4.4A-transfected A549 lung cancer cells showing selectivity compared with a nontargeted control ADC. In vivo, C4.4A-ADC was efficacious in human NSCLC cell line (NCI-H292 and NCI-H322) and patient-derived xenograft (PDX) models (Lu7064, Lu7126, Lu7433, and Lu7466). C4.4A expression level correlated with in vivo efficacy, the most responsive being the models with C4.4A expression in over 50% of the cells. In the NCI-H292 NSCLC model, C4.4A-ADC demonstrated equal or superior efficacy compared to cisplatin, paclitaxel, and vinorelbine. Furthermore, an additive antitumor efficacy in combination with cisplatin was observed. Finally, a repeated dosing with C4.4A-ADC was well tolerated without changing the sensitivity to the treatment. Taken together, C4.4A-ADC is a promising therapeutic candidate for the treatment of NSCLC and other cancers expressing C4.4A. A phase I study (NCT02134197) with the C4.4A-ADC BAY 1129980 is currently ongoing. Mol Cancer Ther; 16(5); 893-904. ©2017 AACR.

Detection of KRAS Mutations in Circulating Tumor DNA by Digital PCR in Early Stages of Pancreatic Cancer

BACKGROUND

Since surgical removal remains the only cure for pancreatic cancer, early detection is of utmost importance. Circulating biomarkers have potential as diagnostic tool for pancreatic cancer, which typically causes clinical symptoms only in advanced stage. Because of their high prevalence in pancreatic cancer, KRAS proto-oncogene, GTPase [KRAS (previous name: Kirsten rat sarcoma viral oncogene homolog)] mutations may be used to identify tumor-derived circulating plasma DNA. Here we tested the diagnostic sensitivity of chip based digital PCR for the detection of KRAS mutations in circulating tumor DNA (ctDNA) in early stage pancreatic cancer.

METHODS

We analyzed matched plasma (2 mL) and tumor samples from 50 patients with pancreatic cancer. Early stages (I and II) were predominant (41/50) in this cohort. DNA was extracted from tumor and plasma samples and tested for the common codon 12 mutations G12D, G12V, and G12C by chip-based digital PCR.

RESULTS

We identified KRAS mutations in 72% of the tumors. 44% of the tumors were positive for G12D, 20% for G12V, and 10% for G12C. One tumor was positive for G12D and G12V. Analysis of the mutations in matched plasma samples revealed detection rates of 36% for G12D, 50% for G12V, and 0% for G12C. The detection appeared to be correlated with total number of tumor cells in the primary tumor. No KRAS mutations were detected in 20 samples of healthy control plasma.

CONCLUSIONS

Our results support further evaluation of tumor specific mutations as early diagnostic biomarkers using plasma samples as liquid biopsy.

Abstract 4539: ATAD2 mediates DNA replication in cancer

ATAD2 (ATPase family AAA domain-containing protein 2) is an epigenetic regulator which associates with chromatin through its Bromodomain specialized in Acetyl-Lys binding of histones. ATAD2 was also shown to directly associate with multiple transcription factors such as ERα, AR, E2F and MYC, and is believed to function as an oncogenic transcription factor in breast cancer.

Here, we propose that ATAD2 facilitates DNA replication. ATAD2 is specifically expressed in S and G2 phase during which it co-localizes with newly synthesized DNA. We found ATAD2 on nascent chromatin together with newly synthesized histone H4 acetylated on K12 and Proliferating Cell Nuclear Antigen (PCNA), a central protein coupling replication with chromatin restoration, but not on post-replicative chromatin. In line with these observations depletion of ATAD2 by siRNA led to reduced DNA replication, perturbed loading of PCNA onto chromatin and inhibition of cell proliferation. Interestingly, a brief cycloheximide treatment of the cells to prevent the deposition of newly synthesized histones (e.g. H4K5,12diac) abrogated the recruitment of ATAD2 to nascent chromatin suggesting that ATAD2 might recognize and interact with these histone marks. Indeed, extensive biochemical and biophysical analyses involving TR-FRET, MST (MicroScale Thermophresis), Biocore, and NMR revealed that the bromodomain of ATAD2 preferentially interacts with these marks characteristic of newly synthesized histones. Consequently, overexpression of ATAD2 mutants unable to interact with these marks impaired DNA replication and recruitment of PCNA onto chromatin. Taken together, our data suggest that ATAD2 is essential for DNA replication and thus predicts that it is expressed in cells undergoing S phase. To further strengthen this hypothesis we compared the expression of ATAD2 with the proliferation marker Ki67, and the late S and G2/M marker TOP2A, in various cancer types such as colorectal, gastric, lung, prostate and breast cancers by immunohistochemistry. Indeed ATAD2 expression was restricted to Ki67 and TOP2A expressing areas of tumors, independent of cancer type. Moreover, aggressive tumors, such as triple negative breast cancer and metastatic castration-resistant prostate cancer, showed more intense and abundant expression of ATAD2 whereas slow-growing tumors showed low expression of ATAD2. This research identifies a role for ATAD2 in replication, providing mechanistic and translational support for therapeutic development in cancer.

Citation Format: Seong Joo Koo, Amaury Ernesto Fernandez-Montalvan, Simon Holton, Oliver von Ahsen, Volker Badock, Sarah Vittori, Christopher J. Ott, James E. Bradner, Matyas Gorjanacz. ATAD2 mediates DNA replication in cancer. [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 4539.

Abstract 413: Validation of an antibody independent tool for patient selection: RNA in situ hybridization detects Met expression levels predictive for response to Met inhibition by Bay 853474

This study was performed in order to validate RNA in situ hybridization (RNA ISH) as tool for patient selection. Met expression was analyzed in a matched sample set of FFPE versus fresh frozen tumor samples comprising 20 cases of gastric cancer. Classical immunohistochemistry using the antibody SP44 and RNA ISH (RNAscope by ACD) were used to detect c-met expression in FFPE material. The results were confirmed by sandwich-immunoassays on Met and its phosphorylation on tyrosine 1349 (MSD) as well as mass spectrometry. The level of functional relevance was determined by testing a set of cell lines comprising some with genomic amplification of the met gene as well as some non-amplified lines showing different expression levels. Among gastric cancer cell lines only those with met amplification respond to treatment with the small molecule Met inhibitor Bay 853474. The cell line result generates a responder hypothesis that can be used to define a cutoff for clinical samples. 2 of the 20 investigated clinical samples were shown to have high level Met expression by RNA ISH and IHC that could be confirmed by sandwich-immunoassays also showing high level of functional activity by phosphotyrosine 1349. Met expression in these cases was also confirmed by mass spectrometry. Expression levels and functional activity in these 2 cases were in the range that predicts response to treatment as established with gastric cancer cell lines. Determination of predictive biomarkers by immunohistochemistry can be limited due to lack of high quality antibodies of sufficient specificity. Due to its high specificity, RNA in situ hybridization is a technique that can be used to confirm the findings obtained by immunohistochemistry and may potentially even replace immunohistochemistry it if no suitable antibodies are available or not specific enough e.g. to discriminate between closely related protein isoforms. We show the biological relevance of RNA in situ hybridization on FFPE samples by correlation with immunohistochemistry, ELISA based approaches and mass spectrometry. RNA ISH is shown to be specific and sensitive enough to identify cases of functionally relevant MET overexpression levels in gastric cancers and can be used to select patients for treatment.

Citation Format: Oliver von Ahsen, Thomas Krahn, Christoph Schatz. Validation of an antibody independent tool for patient selection: RNA in situ hybridization detects Met expression levels predictive for response to Met inhibition by Bay 853474. [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 413.

Enumeration and Molecular Characterization of Tumor Cells in Lung Cancer Patients Using a Novel In Vivo Device for Capturing Circulating Tumor Cells

PURPOSE

The use of circulating tumor cells (CTC) as "liquid biopsy" is limited by the very low yield of CTCs available for subsequent analyses. Most in vitro approaches rely on small sample volumes (5-10 mL).

EXPERIMENTAL DESIGN

Here, we used a novel approach, the GILUPI CellCollector, which enables an in vivo isolation of CTCs from peripheral blood. In total, 50 lung cancer patients were screened in two subsequent device applications before and after therapy (n = 185 applications).

RESULTS

By in vivo isolation, 58% (108/185) of the patients were positive for ≥1 CTC (median, 5 CTCs; range, 1-56 cells) as compared with 27% (23/84; range, 1-300 cells) using the FDA-cleared CellSearch system. Furthermore, we could show that treatment response during therapy was associated with significant decreases in CTC counts (P = 0.001). By dPCR, mutations in the KRAS and EGFR genes relevant for treatment decisions could be detected in CTCs captured by in vivo isolation and confirmed in the primary tumors of the same patients.

CONCLUSIONS

In vivo isolation of CTCs overcomes blood volume limitations of other approaches, which might help to implement CTC-based "liquid biopsies" into clinical decision making. Clin Cancer Res; 22(9); 2197-206. ©2015 AACR.

Novel Mps1 Kinase Inhibitors with Potent Antitumor Activity

Monopolar spindle 1 (Mps1) has been shown to function as the key kinase that activates the spindle assembly checkpoint (SAC) to secure proper distribution of chromosomes to daughter cells. Here, we report the structure and functional characterization of two novel selective Mps1 inhibitors, BAY 1161909 and BAY 1217389, derived from structurally distinct chemical classes. BAY 1161909 and BAY 1217389 inhibited Mps1 kinase activity with IC50 values below 10 nmol/L while showing an excellent selectivity profile. In cellular mechanistic assays, both Mps1 inhibitors abrogated nocodazole-induced SAC activity and induced premature exit from mitosis ("mitotic breakthrough"), resulting in multinuclearity and tumor cell death. Both compounds efficiently inhibited tumor cell proliferation in vitro (IC50 nmol/L range). In vivo, BAY 1161909 and BAY 1217389 achieved moderate efficacy in monotherapy in tumor xenograft studies. However, in line with its unique mode of action, when combined with paclitaxel, low doses of Mps1 inhibitor reduced paclitaxel-induced mitotic arrest by the weakening of SAC activity. As a result, combination therapy strongly improved efficacy over paclitaxel or Mps1 inhibitor monotreatment at the respective MTDs in a broad range of xenograft models, including those showing acquired or intrinsic paclitaxel resistance. Both Mps1 inhibitors showed good tolerability without adding toxicity to paclitaxel monotherapy. These preclinical findings validate the innovative concept of SAC abrogation for cancer therapy and justify clinical proof-of-concept studies evaluating the Mps1 inhibitors BAY 1161909 and BAY 1217389 in combination with antimitotic cancer drugs to enhance their efficacy and potentially overcome resistance. Mol Cancer Ther; 15(4); 583-92. ©2016 AACR.

Modular Assembly of Allosteric MEK Inhibitor Structural Elements Unravels Potency and Feedback-Modulation Handles

Having recently identified a so-far unexplored area adjacent to the known binding site of allosteric mitogen-activated protein kinase kinase (MEK) inhibitors, we now report an extension of these studies by combining our new side chains with different MEK inhibitor cores in a modular manner. Replacement of the amide headgroup with inverse sulfonamides resulted in the identification of new MEK inhibitors with at least 10-fold higher cellular potency against K-Ras-mutated tumor cells. A selected inhibitor from this new series retained the favorable pharmacokinetic profile of its predecessor in rodent and non-rodent species and displayed significant in vivo efficacy at once-daily oral doses of 0.25-1 mg kg(-1) in a K-Ras-mutated xenograft model. The brain penetration potential of this analogue was significantly attenuated relative to PD325901. In a second series, the central fluorophenyl core was replaced by a pyridine moiety which gave rise to a similar boost in cellular potency. Most notably, analogues from this second series do not show MEK feedback phosphorylation in K-Ras-mutated A549 cells. Our results complement recent reports on the structural intricacies of MEK-Raf feedback interactions.

Abstract LB-206: Target validation of C4.4a (LYPD3) as a target for antibody-drug conjugates for the treatment of squamous cell carcinoma of different origin

C4.4a (LYPD3) is a GPI-anchored cell surface protein with unknown physiological function, although it has been speculated that it might play a role in tumor invasion and metastasis formation. In addition, over-expression of C4.4a correlates with a malignant phenotype and poor prognosis in several cancer indications.

As a result of comprehensive gene expression profiling, we report that the C4.4a transcript is being significantly up-regulated in human non-small cell lung cancer (NSCLC) as well as in other tumors compared to the respective normal tissue. This finding was confirmed in IHC studies showing strong C4.4a protein expression on the surface of tumor cells particularly in lung squamous cell carcinoma. Interestingly, a high incidence of C4.4a protein expression was found in a number of additional cancers such as stomach, bladder, colorectal, ovarian, prostate, hepatocellular as well as SCC of the head and neck. In marked contrast to tumors, C4.4a expression in normal tissues is restricted to esophagus, cervix and the outer epithelial layer of skin (stratum spinosum and stratum granulosum). Employing FACS and IHC analyses, several model systems were identified expressing C4.4a in vitro and in vivo. Subsequently, Mab-Zap assays were used to demonstrate efficient internalization of C4.4a in endogenously expressing cells as well as in cells transfected to over-express C4.4a.

In summary, the observed strong over-expression of C4.4a in tumors, its very limited expression in normal tissue as well as its ability to rapidly internalize make it a promising target for the generation of antibody-drug conjugates for the treatment of several cancer indications, in particular lung squamous cell carcinoma.

Citation Format: Gabriele Leder, Yong-Jiang Cao, Lars Linden, Sven Golfier, Oliver von Ahsen, Claudia Schneider, Joerg Willuda, Kirk McLean, Hans-Dieter Pohlenz, Bertolt Kreft, Karl Ziegelbauer. Target validation of C4.4a (LYPD3) as a target for antibody-drug conjugates for the treatment of squamous cell carcinoma of different origin. [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 LB-206. doi:10.1158/1538-7445.AM2013-LB-206

Abstract 3497: Pathway profiling for personalized medicine: Comparison of two immunoassays

Cancer therapy is evolving to a detailed molecular analysis of the patient's tumor followed by treatment with selective drug(s) targeting the individual properties of the tumor based upon identification of prognostic and predictive biomarkers. This requires comprehensive, highly sensitive test systems. We therefore sought to develop a sensitive diagnostic test for functionally profiling a spectrum of signaling pathway proteins in tumor samples. Here, we evaluated and compared two assay platforms: CEER (Collaborative Enzyme Enhanced Reactive-Immunoassay; Prometheus Labaratories) and MSD (Meso Scale Discovery).

Breast, lung, and prostate cancers as well as glioblastoma and melanoma model cell lines (in all 10 cell lines) with various oncogenic pathway signatures were treated with different concentrations of PI3K inhibitor (BAY 806946) or an inhibitor targeting HER1 and HER2 (Lapatinib). Cells were lysed and the activation status as well as abundance of ten pathway proteins (HER1, HER2, cMET, PI3K, AKT, ERK, MEK, PRAS40, RPS6, and P70S6K) was measured by MSD at Bayer in Berlin and by CEER in a blinded fashion at Prometheus Laboratories. Target-specific inhibition (IC50) and downstream signal modulations were determined and compared. Overall we found a high concordance between the two assays. While target specific inhibitions were observed in relevant cell lines, varying mechanisms of treatment resistance due to redundant pathway activation, feedback loop or pathway cross talks were observed between the PI3K/AKT and RAS/ERK pathways.

This study shows that sensitive immunoassays are a suitable tool for the detection and monitoring of biomarkers and provides new insights into the mode of action of targeted agents. Comprehensive profiling of signaling pathways holds promise as an approach to personalize selection of anticancer therapy.

Citation Format: Antje Stresemann, Oliver von Ahsen, Oliver Politz, Phillip Kim, Sharat Singh, Khusru Asadullah, Karl Ziegelbauer, Thomas Krahn. Pathway profiling for personalized medicine: Comparison of two immunoassays. [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 3497. doi:10.1158/1538-7445.AM2013-3497

Cancer therapy monitoring in xenografts by quantitative analysis of circulating tumor DNA

CONTEXT

Circulating tumor DNA (ctDNA) is a promising biomarker in cancer.

MATERIALS AND METHODS

We generated xenograft models of cancer and detected ctDNA in plasma by qRCR targeting human AluJ sequences.

RESULTS

Our assay reached single cell sensitivity in vitro and a correlation between ctDNA amount and tumor size was observed in vivo. Treatment with a mitogen activated protein kinase kinase (MEK)-inhibitor (BAY 869766) reduced ctDNA levels. Using this assay, we also confirmed that high levels of cell-free DNA are found in cancer patients compared to healthy individuals.

DISCUSSION AND CONCLUSION

We show that ctDNA may be useful biomarker for monitoring tumor growth and treatment response.

Circulating tumour cells escape from EpCAM-based detection due to epithelial-to-mesenchymal transition

Background

Circulating tumour cells (CTCs) have shown prognostic relevance in metastatic breast, prostate, colon and pancreatic cancer. For further development of CTCs as a biomarker, we compared the performance of different protocols for CTC detection in murine breast cancer xenograft models (MDA-MB-231, MDA-MB-468 and KPL-4). Blood samples were taken from tumour bearing animals (20 to 200 mm²) and analysed for CTCs using 1. an epithelial marker based enrichment method (AdnaTest), 2. an antibody independent technique, targeting human gene transcripts (qualitative PCR), and 3. an antibody-independent approach, targeting human DNA-sequences (quantitative PCR). Further, gene expression changes associated with epithelial-to-mesenchymal transition (EMT) were determined with an EMT-specific PCR assay.

Methods

We used the commercially available Adna Test, RT-PCR on human housekeeping genes and a PCR on AluJ sequences to detect CTCs in xenografts models. Phenotypic changes in CTCs were tested with the commercially available “Human Epithelial to Mesenchymal Transition RT-Profiler PCR Array”.

Results

Although the AdnaTest detects as few as 1 tumour cell in 1 ml of mouse blood spiking experiments, no CTCs were detectable with this approach in vivo despite visible metastasis formation. The presence of CTCs could, however, be demonstrated by PCR targeting human transcripts or DNA-sequences - without epithelial pre-enrichment. The failure of CTC detection by the AdnaTest resulted from downregulation of EpCAM, whereas mesenchymal markers like Twist and EGFR were upregulated on CTCs. Such a change in the expression profile during metastatic spread of tumour cells has already been reported and was linked to a biological program termed epithelial-mesenchymal transition (EMT).

Conclusions

The use of EpCAM-based enrichment techniques leads to the failure to detect CTC populations that have undergone EMT. Our findings may explain clinical results where low CTC numbers have been reported even in patients with late metastatic cancers. These results are a starting point for the identification of new markers for detection or capture of CTCs, including the mesenchymal-like subpopulations.

Preclinical evaluation of biomarkers for response monitoring to the MET inhibitor BAY-853474

CONTEXT

The receptor tyrosine kinase MET contributes to a wide range of biological activities, including survival, proliferation, and metastasis, which play an important role in cancer progression. MET is frequently overexpressed or amplified in a range of malignancies. Therefore, MET is an attractive therapeutic target for treatment of cancer. BAY-853474 is a novel specific MET inhibitor highly effective in preclinical tumor models.

OBJECTIVE

For response monitoring in clinical studies, soluble plasma biomarkers are the most convenient and least invasive choice. Therefore, we sought to identify such biomarkers in xenograft models.

RESULTS

We show that BAY-853474 reduces the tumor burden in U87MG glioblastoma, NCI-H1993 nonsmall cell lung cancer, and HS746T gastric cancer xenograft models. We demonstrate that the dose dependence is reflected by inhibition of MET phosphorylation and that the soluble plasma biomarkers hepatocyte growth factor, vascular endothelial growth factor, and interleukin-8 as well as the MET-ectodomain can be used to monitor the tumor size and response to treatment. Clinical samples, however, show only moderately elevated levels of these biomarker candidates in cancer patients even with MET amplification. We, therefore, established an immunohistochemistry (IHC) protocol to detect MET phosphorylation that is suitable to monitor the effect of BAY-853474 in tumor biopsies.

CONCLUSION

IHC-based analysis of target phosphorylation in tumor biopsies is recommended in addition to testing plasma biomarkers for response monitoring.

Abstract 4509: BAY 87-2243 targets hypoxia-induced activation and stabilization of HIF-1α: A novel approach to overcome resistance mechanisms in cancer therapy

The development of resistance against radio- or chemotherapy is one of the main causes for relapse after treatment and ultimately cancer progression. Local hypoxia within tumors is associated with radio- and chemoresistance as well as aggressive tumor growth and invasion (Vaupel et al., 2004). The transcription factor HIF-1α (hypoxia-inducible factor) is stabilized under low oxygen tension and heterodimerizes with HIF-1ß to regulate the expression of a plethora of genes involved in cellular energy metabolism, neoangiogenesis, anti-apoptotic and pro-proliferative mechanisms promoting tumor progression and metastasis (Calzada et al. 2007). Because hypoxia-induced upregulation of HIF-1α appears to be of pivotal importance in tumor resistance mechanisms during cancer treatment, we screened for inhibitors of hypoxia-induced HIF-1 activation.

A HCT116 cell line containing 4X-hypoxia response element-luciferase reporter was used in high-throughput screening of small molecule inhibitors under hypoxic condition (1% O2). Lead optimization resulted in the identification of BAY 87-2243, a highly selective and potent inhibitor of hypoxia-induced HIF-1α stabilization and activation. In vitro characterization showed that BAY 87-2243 specifically suppressed HIF-1 regulated target genes as assayed by qPCR. Analyses addressing the mode of action revealed that BAY 87-2243 acts upstream of VHL and PHD because the compound did not suppress HIF-1α protein stabilization and HIF target gene expression either in the presence of a PHD inhibitor in H460 cells or in VHL-null RCC4 cells. In preclinical animal models, BAY 87-2243 dosed orally was well tolerated at therapeutic doses up to 15 mg/kg and showed moderate to high anti-tumor growth inhibitory activity as monotherapy in various subcutaneous and orthotopic xenograft models. Analysis of tumor samples demonstrated a decrease of nuclear HIF-1α protein level by immunohistochemistry as well as a specific suppression of HIF-1 target genes. These data indicate that specific inhibition of hypoxia-induced HIF-1 activation is achievable with small molecule inhibitors and is a novel approach to cancer therapy.

Vaupel P, Mayer A, Hockel M (2004) Tumor hypoxia and malignant progression. Methods Enzymol 381:335-354

M. J. Calzada, L. del Peso, Hypoxia inducible factors and cancer. Clin. Transl. Oncol. 2007, 9(5), 278-289:

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 4509. doi:10.1158/1538-7445.AM2011-4509

Inhibition of the IL-2-inducible tyrosine kinase (Itk) activity: a new concept for the therapy of inflammatory skin diseases

T-cell-mediated processes play an essential role in the pathogenesis of several inflammatory skin diseases such as atopic dermatitis, allergic contact dermatitis and psoriasis. The aim of this study was to investigate the role of the IL-2-inducible tyrosine kinase (Itk), an enzyme acting downstream of the T-cell receptor (TCR), in T-cell-dependent skin inflammation using three approaches. Itk knockout mice display significantly reduced inflammatory symptoms in mouse models of acute and subacute contact hypersensitivity (CHS) reactions. Systemic administration of a novel small molecule Itk inhibitor, Compound 44, created by chemical optimization of an initial high-throughput screening hit, inhibited Itk's activity with an IC50 in the nanomolar range. Compound 44 substantially reduced proinflammatory immune responses in vitro and in vivo after systemic administration in two acute CHS models. In addition, our data reveal that human Itk, comparable to its murine homologue, is expressed mainly in T cells and is increased in lesional skin from patients with atopic dermatitis and allergic contact dermatitis. Finally, silencing of Itk by RNA interference in primary human T cells efficiently blocks TCR-induced lymphokine secretion. In conclusion, Itk represents an interesting new target for the therapy of T-cell-mediated inflammatory skin diseases.

Global transcriptome analysis of genetically identified neurons in the adult cortex

The enormous cellular complexity of the brain is a major obstacle for gene expression profiling of neurological disease models, because physiologically relevant changes of transcription in a specific neuronal subset are likely to be lost in the presence of other neurons and glia. We solved this problem in transgenic mice by labeling genetically defined cells with a nuclear variant of GFP. When combined with laser-directed microdissection, intact RNA from unfixed, freeze-dried sections can be isolated, which is a prerequisite for high-quality global transcriptome analysis. Here, we compared gene expression profiles between pyramidal motor neurons and pyramidal somatosensory neurons captured from layer V of the adult neocortex. One striking feature of motor neurons is the elevated expression of ribosomal genes and genes involved in ATP synthesis. This suggests a molecular adaptation of the upper motor neurons to longer axonal projections and higher electrical activity. These molecular signatures were not detected when cortical layers and microareas were analyzed in toto. Additionally, we used microarrays to determine the global mRNA expression profiles of microdissected Purkinje cells and cellularly complex cerebellar cortex microregions. In summary, our analysis shows that cellularly complex targets lead to averaged gene expression profiles that lack substantial amounts of cell type-specific information. Thus, cell type-restricted sampling strategies are mandatory in the CNS. The combined use of a genetic label with laser-microdissection offers an unbiased approach to map patterns of gene expression onto practically any cell type of the brain.

Assay concordance between SPA and TR-FRET in high-throughput screening

High-throughput screening (HTS) of large chemical libraries has become the main source of new lead compounds for drug development. Several specialized detection technologies have been developed to facilitate the cost- and time-efficient screening of millions of compounds. However, concerns have been raised, claiming that different HTS technologies may produce different hits, thus limiting trust in the reliability of HTS data. This study was aimed to investigate the reliability of the authors most frequently used assay techniques: scintillation proximity assay (SPA) and homogeneous time-resolved fluorescence resonance energy transfer (TR-FRET). To investigate the data concordance between these 2 detection technologies, the authors screened a large subset of the Schering compound library consisting of 300,000 compounds for inhibitors of a nonreceptor tyrosine kinase. They chose to set up this study in realistic HTS scale to ensure statistical significance of the results. The findings clearly demonstrate that the choice of detection technology has no significant impact on hit finding, provided that assays are biochemically equivalent. Data concordance is up to 90%. The little differences in hit findings are caused by threshold setting but not by systematic differences between the technologies. The most significant difference between the compared techniques is that in the SPA format, more false-positive primary hits were obtained.

High-Throughput Screening for Kinase Inhibitors

Following G protein-coupled receptors (GPCRs), protein kinases have become the second most important class of targets for drug discovery over the last 20 years. While only four kinase inhibitors have reached the market to date (Fasudil for rho-dependent kinase, Rapamycin for TOR, Gleevec for BCR-Abl, and Iressa for EGFR), many more are already in clinical development. A historical overview of kinase inhibitors was recently published by Cohen. [1] After the previous successes, protein kinases are now regarded as attractive, well-drugable targets, and the analysis of the human genome has yielded 518 protein kinases. [2] We can thus expect screening for protein kinase inhibitors to become even more important in the future. In this review we will focus on the early steps of drug discovery programs producing new lead compounds. We will guide the reader through efficient state-of-the-art assay development and high-throughput screening of large chemical libraries for protein kinase inhibitors.

Identification of regulated genes during permanent focal cerebral ischaemia: characterization of the protein kinase 9b5/MARKL1/MARK4

Cerebral ischaemia induces transcriptional changes in a number of pathophysiologically important genes. Here we have systematically studied gene expression changes after 90 min and 24 h of permanent focal ischaemia in the mouse by an advanced fragment display technique (restriction-mediated differential display). We identified 56 transcriptionally altered genes, many of which provide novel hints to ischaemic pathophysiology. Particularly interesting were two pro-apoptotic genes (Grim19 and Tdag51), whose role in cerebral ischaemia and neuronal cell death has not been recognized so far. Among the unknown sequences, we identified a gene that was rapidly and transiently up-regulated. The encoded protein displayed high homology to the MARK family of serine-threonine protein kinases and has recently been described as MARKL1/MARK4. Here we demonstrate that this protein is a functional protein kinase with the ability to specifically phosphorylate a cognate peptide substrate for the AMP-kinase family. Upon overexpression in heterologous cells, the functional wild-type protein, but not its kinase-dead mutant, led to decreased cell viability. We conclude that the up-regulation of this kinase during focal ischaemia may represent an interesting new target for pharmacological intervention.

Restriction-mediated differential display (RMDD) identifies pip92 as a pro-apoptotic gene product induced during focal cerebral ischemia

Studies of gene expression changes after cerebral ischemia can provide novel insight into ischemic pathophysiology. Here we describe application of restriction-mediated differential display to screening for differentially expressed genes after focal cerebral ischemia. This method combines the nonredundant generation of biotin-labeled fragment sets with the excellent resolution of direct blotting electrophoresis, reliable fragment recovery, and a novel clone selection strategy. Using the filament model in mouse with 90 minutes MCA occlusion followed by 2, 6, and 20 hours reperfusion, we have compared gene expression in sham-operated animals to both the ipsi- and contralateral forebrain hemisphere of ischemic mice. Our screening method has resulted in the identification of 70 genes differentially regulated after transient middle cerebral artery occlusion (MCAO), several of which represent unknown clones. We have identified many of the previously published regulated genes, lending high credibility to our method. Surprisingly, we detected a high degree of correspondent regulation of genes in the nonischemic hemisphere. A high percentage of genes coding for proteins in the respiratory chain was found to be up-regulated after ischemia, potentially representing a new mechanism involved in counteracting energy failure or radical generation in cerebral ischemia. One particularly interesting gene, whose upregulation by ischemia has not been described before, is pip92; this gene shows a rapid and long-lasting induction after cerebral ischemia. Here we demonstrate that pip92 induces cell death in primary neurons and displays several hallmarks of pro-apoptotic activity upon overexpression, supporting the notion that we have identified a novel pathophysiological player in cerebral ischemia. In summary, restriction-mediated differential display has proven its suitability for screening complex samples such as brain to reliably identify regulated genes, which can uncover novel pathophysiological mechanisms.

TorsinA protects against oxidative stress in COS-1 and PC12 cells

Dystonia is a highly frequent movement disorder, the pathogenesis of which remains unclear. The cloning of TorsinA, the gene responsible for early-onset dystonia, was a major breakthrough. However, the function of this protein remains unclear. By sequence homology, TorsinA belongs to the ATPases associated with diverse cellular activities-family, many of whose members are chaperones and/or proteases. We report here that in an in vitro model for oxidative stress, H2O2 treatment, overexpression of TorsinA was protective against cell death. COS-1 cells overexpressing TorsinA demonstrated drastically reduced terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling-staining following exposure to H2O2. Furthermore, transfection with TorsinA significantly increased survival of PC12 after H2O2 treatment. To our knowledge, this is the first demonstration that TorsinA protects against oxidative stress. We speculate that a loss of this cellular function in mutant TorsinA may be linked to the pathogenesis of early-onset dystonia.

Cytochrome c maintains mitochondrial transmembrane potential and ATP generation after outer mitochondrial membrane permeabilization during the apoptotic process

During apoptosis, cytochrome c is released into the cytosol as the outer membrane of mitochondria becomes permeable, and this acts to trigger caspase activation. The consequences of this release for mitochondrial metabolism are unclear. Using single-cell analysis, we found that when caspase activity is inhibited, mitochondrial outer membrane permeabilization causes a rapid depolarization of mitochondrial transmembrane potential, which recovers to original levels over the next 30-60 min and is then maintained. After outer membrane permeabilization, mitochondria can use cytoplasmic cytochrome c to maintain mitochondrial transmembrane potential and ATP production. Furthermore, both cytochrome c release and apoptosis proceed normally in cells in which mitochondria have been uncoupled. These studies demonstrate that cytochrome c release does not affect the integrity of the mitochondrial inner membrane and that, in the absence of caspase activation, mitochondrial functions can be maintained after the release of cytochrome c.

Preservation of mitochondrial structure and function after Bid- or Bax-mediated cytochrome c release

Proapoptotic members of the Bcl-2 protein family, including Bid and Bax, can activate apoptosis by directly interacting with mitochondria to cause cytochrome c translocation from the intermembrane space into the cytoplasm, thereby triggering Apaf-1-mediated caspase activation. Under some circumstances, when caspase activation is blocked, cells can recover from cytochrome c translocation; this suggests that apoptotic mitochondria may not always suffer catastrophic damage arising from the process of cytochrome c release. We now show that recombinant Bid and Bax cause complete cytochrome c loss from isolated mitochondria in vitro, but preserve the ultrastructure and protein import function of mitochondria, which depend on inner membrane polarization. We also demonstrate that, if caspases are inhibited, mitochondrial protein import function is retained in UV-irradiated or staurosporine-treated cells, despite the complete translocation of cytochrome c. Thus, Bid and Bax act only on the outer membrane, and lesions in the inner membrane occurring during apoptosis are shown to be secondary caspase-dependent events.