Scott M. Lawrence

Cediranib for Metastatic Alveolar Soft Part Sarcoma

PURPOSE Alveolar soft part sarcoma (ASPS) is a rare, highly vascular tumor, for which no effective standard systemic treatment exists for patients with unresectable disease. Cediranib is a potent, oral small-molecule inhibitor of all three vascular endothelial growth factor receptors (VEGFRs). PATIENTS AND METHODS We conducted a phase II trial of once-daily cediranib (30 mg) given in 28-day cycles for patients with metastatic, unresectable ASPS to determine the objective response rate (ORR). We also compared gene expression profiles in pre- and post-treatment tumor biopsies and evaluated the effect of cediranib on tumor proliferation and angiogenesis using positron emission tomography and dynamic contrast-enhanced magnetic resonance imaging. RESULTS Of 46 patients enrolled, 43 were evaluable for response at the time of analysis. The ORR was 35%, with 15 of 43 patients achieving a partial response. Twenty-six patients (60%) had stable disease as the best response, with a disease control rate (partial response + stable disease) at 24 weeks of 84%. Microarray analysis with validation by quantitative real-time polymerase chain reaction on paired tumor biopsies from eight patients demonstrated downregulation of genes related to vasculogenesis. CONCLUSION In this largest prospective trial to date of systemic therapy for metastatic ASPS, we observed that cediranib has substantial single-agent activity, producing an ORR of 35% and a disease control rate of 84% at 24 weeks. On the basis of these results, an open-label, multicenter, randomized phase II registration trial is currently being conducted for patients with metastatic ASPS comparing cediranib with another VEGFR inhibitor, sunitinib.

Development of a Validated Immunofluorescence Assay for γH2AX as a Pharmacodynamic Marker of Topoisomerase I Inhibitor Activity

Purpose: Phosphorylated histone H2AX (γH2AX) serves as a biomarker for formation of DNA double-strand break repair complexes. A quantitative pharmacodynamic immunofluorescence assay for γH2AX was developed, validated, and tested in human tumor xenograft models with the use of clinically relevant procedures. Experimental Design: The γH2AX immunofluorescence assay uses a novel data quantitation and image processing algorithm to determine the extent of nuclear-specific γH2AX staining in tumor needle biopsies and hair follicles collected from mice bearing topotecan-responsive A375 xenografts. After method validation with the topoisomerase I (Top1) inhibitor topotecan, the assay was used to compare pharmacodynamic properties of three structurally related indenoisoquinoline Top1 inhibitors. Results: γH2AX response to topotecan was quantified over a 60-fold dose range (0.016-1.0 times the murine single-dose maximum tolerated dose), and significant pharmacodynamic response was measured at the mouse equivalent of the 1.5 mg/m2 clinical dose as well as the lowest dose tested. Responses were within a time window amenable for biopsy collection in clinical trials. These studies enabled characterization of dose and time responses for three indenoisoquinolines, resulting in selection of two for clinical evaluation. γH2AX response to Top1 inhibitors in hair follicles was also observable above a minimal dose threshold. Conclusions: Our γH2AX assay is sufficiently accurate and sensitive to quantify γH2AX in tumor samples and will be used in correlative studies of two indenoisoquinolines in a phase I clinical trial at the National Cancer Institute. Data suggest that hair follicles may potentially serve as a surrogate tissue to evaluate tumor γH2AX response to Top1 inhibitors. Clin Cancer Res; 16(22); 5447–57. ©2010 AACR.

Antibody-independent capture of circulating tumor cells of non-epithelial origin with the ApoStream® system

Circulating tumor cells (CTCs) are increasingly employed for research and clinical monitoring of cancer, though most current methods do not permit the isolation of non-epithelial tumor cells. Furthermore, CTCs isolated with antibody-dependent methods are not suitable for downstream experimental uses, including in vitro culturing and implantation in vivo. In the present study, we describe the development, validation, and transfer across laboratories of a new antibody-independent device for the enrichment of CTCs from blood samples of patients with various cancer diagnoses. The ApoStream® device uses dielectrophoresis (DEP) field-flow assist to separate non-hematopoietic cells from the peripheral blood mononuclear fraction by exposing cells in a laminar flow stream to a critical alternating current frequency. The ApoStream® device was calibrated and validated in a formal cross-laboratory protocol using 3 different cancer cell lines spanning a range of distinct phenotypes (A549, MDA-MB-231, and ASPS-1). In spike-recovery experiments, cancer cell recovery efficiencies appeared independent of spiking level and averaged between 68% and 55%, depending on the cell line. No inter-run carryover was detected in control samples. Moreover, the clinical-readiness of the device in the context of non-epithelial cancers was evaluated with blood specimens from fifteen patients with metastatic sarcoma. The ApoStream® device successfully isolated CTCs from all patients with sarcomas examined, and the phenotypic heterogeneity of the enriched cells was demonstrated by fluorescence in situ hybridization or with multiplex immunophenotyping panels. Therefore, the ApoStream® technology expands the clinical utility of CTC evaluation to mesenchymal cancers.

3D Models of the NCI60 Cell Lines for Screening Oncology Compounds

The NCI60 cell line panel screen includes 60 human tumor cell lines derived from nine tumor types that has been used over the past 20+ years to screen small molecules, biologics, and natural products for activity. Cells in monolayer culture in 96-well plates are exposed to compounds for 48 h, and Sulforhodamine B is used to determine cell viability. Data analysis tools such as COMPARE allow classification of compounds based on the pattern of cell line response. However, many compounds highly active in monolayer cell culture fail to show efficacy in vivo. Therefore, we explored 3D culture of the NCI60 panel as a strategy to improve the predictive accuracy of the screen. 3D cultures more closely resemble tumors than monolayer cultures with tighter cell-cell contact and nutrient and oxygen gradients between the periphery and the center. We optimized the NCI60 cell line panel for generating 3D spheroids of a prespecified diameter (300–500 µm) in ultra-low attachment (ULA) plates. Spheroids were classified into four categories based on imaging, and concentration response of select agents in 2D and 3D models is presented.

Translating pharmacodynamic biomarkers from bench to bedside: analytical validation and fit-for-purpose studies to qualify multiplex immunofluorescent assays for use on clinical core biopsy specimens

Multiplex pharmacodynamic (PD) assays have the potential to increase sensitivity of biomarker-based reporting for new targeted agents, as well as revealing significantly more information about target and pathway activation than single-biomarker PD assays. Stringent methodology is required to ensure reliable and reproducible results. Common to all PD assays is the importance of reagent validation, assay and instrument calibration, and the determination of suitable response calibrators; however, multiplex assays, particularly those performed on paraffin specimens from tissue blocks, bring format-specific challenges adding a layer of complexity to assay development. We discuss existing multiplex approaches and the development of a multiplex immunofluorescence assay measuring DNA damage and DNA repair enzymes in response to anti-cancer therapeutics and describe how our novel method addresses known issues.

Optimization of Immunostaining for Prospective Image Analysis

Biomarker discovery is a crucial part of the fast developing field of personalized medicine. Antibody-based techniques including immunostaining of tissue samples are widely used for biomarker evaluation in preclinical and clinical studies. When used in conjunction with robust image analysis methods, it provides a powerful means to assess biomarker modulation, toxicity, and patient response to targeted agents. Here, we describe the optimization of immunofluorescent (IF) staining protocols and a sample IF multiplex protocol suitable for colocalization image analysis.

Abstract 3062: Isolation and characterization of circulating tumor cells (CTCs) from peripheral blood specimens of patients with advanced solid tumor malignancies (using ApoStream™ instrumentation)

Circulating tumor cells (CTCs) isolated from the peripheral blood of cancer patients provide prognostic information and may inform treatment decisions. Current strategies for CTC isolation and characterization commonly employ epithelial marker-specific antibody capture of fixed cells from blood and detection based on cytokeratin (CK) expression. Our laboratory is currently evaluating an antibody-independent CTC enrichment technology, ApoStream™, which isolates live CTCs from blood, enabled by critical dissimilarities in morphology and dielectric properties of CTCs and blood cells rather than surface marker expression. CTCs isolated with the ApoStream™ instrument are amenable to further high resolution phenotypic characterization, enabling unambiguous identification of enriched cells as malignant cells. We previously reported on the utility of ApoStream™ technology for the isolation of CTCs from patients with advanced alveolar soft part sarcoma (ASPS) with unambiguous confirmation of CTCs by break-apart fluorescent in situ hybridization (FISH) for ASPL-TFE3 gene translocation. Here, we show the isolation of viable CTCs from patients with advanced solid tumors from ongoing clinical studies at the NCI. Since during progression, cancer cells undergo epithelial to mesenchymal transitions (EMT) and mesenchymal to epithelial transitions (MET), we sought to characterize ApoStream™-isolated CTCs using a multiplex phenotyping assay for CD45 (hematopoietic marker), EMT markers (CK, EpCAM, β-catenin and Vimentin), and tumor specific markers (MUC1 and CEA). A user-defined processing algorithm and CTC scoring criteria developed using Definiens® software was used for rare cell detection and enumeration. Our current efforts are focused on evaluating the utility of ApoStream™-isolated CTCs for assessing pharmacodynamic effects of anticancer agents on DNA damage response in patients with refractory solid tumors. Funded by NCI Contract No. HHSN261200800001E. Citation Format: Priya Balasubramanian, Lihua Wang, Scott M. Lawrence, Tony Navas, Shivaani Kummar, Melinda Hollingshead, Francis Owusu, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow, Robert J. Kinders. Isolation and characterization of circulating tumor cells (CTCs) from peripheral blood specimens of patients with advanced solid tumor malignancies (using ApoStream™ instrumentation). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3062. doi:10.1158/1538-7445.AM2014-3062

The root causes of pharmacodynamic assay failure

Robust pharmacodynamic assay results are valuable for informing go/no-go decisions about continued development of new anti-cancer agents and for identifying combinations of targeted agents, but often pharmacodynamic results are too incomplete or variable to fulfill this role. Our experience suggests that variable reagent and specimen quality are two major contributors to this problem. Minimizing all potential sources of variability in procedures for specimen collection, processing, and assay measurements is essential for meaningful comparison of pharmacodynamic biomarkers across sample time points. This is especially true in the evaluation of pre- and post-dose tumor biopsies, which suffer from high levels of tumor insufficiency due to variations in biopsy collection techniques and significant specimen heterogeneity within and across patients. Developing methods to assess heterogeneous biopsies is necessary in order to evaluate a majority of tumor biopsies collected for pharmacodynamic biomarker studies. Improved collection devices and standardization of methods are being sought in order to improve the tumor content and quality of tumor biopsies. In terms of reagent variability, we have found that stringent initial reagent qualification and quality control of R&D-grade reagents is critical to minimize lot-to-lot variability and prevent assay failures, especially for clinical pharmacodynamic questions, which often demand assay performance that meets or exceeds clinical diagnostic assay standards. Rigorous reagent specifications and use of appropriate assay quality control methodologies help to ensure consistency between assay runs, laboratories and trials to provide much needed pharmacodynamic insights into the activity of investigational agents.

Abstract B24: Ataxia-telangiectasia and Rad3-related (ATR) phosphorylation as a pharmacodynamic biomarker of ATR activation in solid tumor tissue models

Inhibitors of checkpoint kinases, such as ATR, Chk1 or Wee1, in combination with cytotoxic agents could enhance therapeutic efficacy compared to monotherapy, and these combination approaches are currently being extensively explored. The presence of replicative stress or deregulated S-phase in cancer has been recognized as a rationale for the use of ATR and Chk1 inhibitors with chemotherapy and efforts are underway to define genetic determinants that sensitize cancer cells to ATR inhibition. Pharmacodynamic (PD) biomarkers of drug activity are valuable tools in clinical trials using targeted agents to determine whether each investigational agent is acting upon its intended target, the expected intracellular signaling pathways are modulated, and the dosage regimen and sequencing are optimal. In addition, investigations of the potential effects of cell cycle distribution within the tumor (in animal models) on drug efficacy may point to alternative dosing regimens. The first clinical trials evaluating inhibitors of the ataxia telangiectasia and Rad3-related kinase (ATR) in combination with cytotoxic agents are enrolling patients. The current method for quantifying ATR inhibition used in preclinical in vitro and in vivo models is via indirect measurement of downstream effector proteins, such as phosphorylated Chk1, rather than measurement of direct target engagement. We propose that an immunofluorescence microscopy assay of ATR autophosphorylation status as a biomarker of DNA damage activation combined with measurement of the downstream effector proteins will reveal more specific information about target engagement and intended PD effect than would be obtained from a single-biomarker assay. Here we propose that the measurement of ATR pT1989, Chk1 pS345 and γH2AX by validated quantitative immunofluorescence assays will be useful in PD evaluation of tumor responses in clinical trials as a biomarker for ATR pathway activation or inhibition. In addition, evaluation of the variability of expression of activated ATR in tumor models of different histologies may provide valuable insight into tumor types likely to be sensitive to ATR inhibitors. Citation Format: Deborah Wilsker, Allison M. Marrero, Angie Dull, Thomas D. Pfister, Scott M. Lawrence, John Carter, Michelle Gottholm-Ahalt, Melinda Hollingshead, James Doroshow, Ralph E. Parchment, Robert J. Kinders. Ataxia-telangiectasia and Rad3-related (ATR) phosphorylation as a pharmacodynamic biomarker of ATR activation in solid tumor tissue models. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B24.

Abstract 606: Similar 3D pharmacodynamic (3D-PD) responses of human tumor spheroids and xenografts to topoisomerase 1 inhibitor-induced DNA damage

Three-dimensional (3D) cultures have been proposed as higher fidelity models of in vivo tumors than 2D cultures. To determine whether this idea extends to drug pharmacodynamics, we examined whether 3D cultures of the human melanoma line A375 (grown as tumor spheroids) could replicate the timing and magnitude of the nuclear γH2AX response to the topoisomerase 1 inhibitor, topotecan observed in A375 tumor xenografts (Kinders et al, Clin Can Res 2010). The appearance of γH2AX-positive nuclear foci has been used as a biomarker for drug- and radiation-induced double-strand breaks in DNA; we reported previously that treatment of nu/nu mice harboring A375 xenografts with a single-dose of topotecan induced nuclear γH2AX foci in a dose- and time-dependent manner, which peaked 4 hours after drug administration. A375 spheroids were generated by seeding cells into ULA U-bottom plates; 4 hours of exposure to 0.1 μM topotecan elicited a γH2AX signal in these 3D cultures while cell viability and intracellular ATP levels remained unchanged, indicating a DNA damage repair response at the maximally tolerated topotecan concentration for human hematopoietic cells (Erickson-Miller et al, Can Chemo Pharmacol 2009). Extending drug exposure to 24 hours caused substantial loss of viable cells (calcein AM+) and 50% decline in ATP levels but no further increase in γH2AX. In contrast, the HT29 tumor line was refractory to topotecan in vivo, and exposing 3D cultures of HT-29 spheroids to 0.1 μM topotecan for 24 hours elicited a strong nuclear γH2AX biomarker response in only a small fraction of cells at the surface of the spheroids. Longer exposure durations or supra-pharmacological concentrations (1 μM) of topotecan were required to achieve a strong nuclear γH2AX response in HT-29 spheroids. These results support the hypothesis that the 3D pharmacodynamics (PD) of drug response is similar to PD drug response in vivo for the camptothecin class of topoisomerase 1 inhibitors. Funded by NCI Contract No. HHSN261200800001E. Citation Format: David M. Evans, Rene Delosh, Julie Laudeman, Chad Ogle, Russell Reinhart, Michael Selby, Silvers Thomas, Robert Kinders, Tony Navas, Scott Lawrence, Anne Monks, Annamaria Rapisarda, Ralph E. Parchment, James H. Doroshow, Beverly Teicher. Similar 3D pharmacodynamic (3D-PD) responses of human tumor spheroids and xenografts to topoisomerase 1 inhibitor-induced DNA damage. [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 606.