Novel antibody reagents for characterization of drug- and tumor microenvironment-induced changes in epithelial-mesenchymal transition and cancer stem cells

The presence of cancer stem cells (CSCs) and the induction of epithelial-to-mesenchymal transition (EMT) in tumors are associated with tumor aggressiveness, metastasis, drug resistance, and poor prognosis, necessitating the development of reagents for unambiguous detection of CSC- and EMT-associated proteins in tumor specimens. To this end, we generated novel antibodies to EMT- and CSC-associated proteins, including Goosecoid, Sox9, Slug, Snail, and CD133. Importantly, unlike several widely used antibodies to CD133, the anti-CD133 antibodies we generated recognize epitopes distal to known glycosylation sites, enabling analyses that are not confounded by differences in CD133 glycosylation. For all target proteins, we selected antibodies that yielded the expected target protein molecular weights by Western analysis and the correct subcellular localization patterns by immunofluorescence microscopy assay (IFA); binding selectivity was verified by immunoprecipitation−mass spectrometry and by immunohistochemistry and IFA peptide blocking experiments. Finally, we applied these reagents to assess modulation of the respective markers of EMT and CSCs in xenograft tumor models by IFA. We observed that the constitutive presence of human hepatocyte growth factor (hHGF) in the tumor microenvironment of H596 non-small cell lung cancer tumors implanted in homozygous hHGF knock-in transgenic mice induced a more mesenchymal-like tumor state (relative to the epithelial-like state when implanted in control SCID mice), as evidenced by the elevated expression of EMT-associated transcription factors detected by our novel antibodies. Similarly, our new anti-CD133 antibody enabled detection and quantitation of drug-induced reductions in CD133-positive tumor cells following treatment of SUM149PT triple-negative breast cancer xenograft models with the CSC/focal adhesion kinase (FAK) inhibitor VS-6063. Thus, our novel antibodies to CSC- and EMT-associated factors exhibit sufficient sensitivity and selectivity for immunofluorescence microscopy studies of these processes in preclinical xenograft tumor specimens and the potential for application with clinical samples.

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.

Indolo-pyrido-isoquinolin based alkaloid inhibits growth, invasion and migration of breast cancer cells via activation of p53-miR34a axis

The tumor suppressor p53 plays a critical role in suppressing cancer growth and progression and is an attractive target for the development of new targeted therapies. We synthesized several indolo-pyrido-isoquinolin based alkaloids to activate p53 function and examined their therapeutic efficacy using NCI-60 screening. Here, we provide molecular evidence that one of these compounds, 11-methoxy-2,3,4,13-tetrahydro-1H-indolo[2',3':3,4]pyrido[1,2-b]isoquinolin-6-ylium-bromide (termed P18 or NSC-768219) inhibits growth and clonogenic potential of cancer cells. P18 treatment results in downregulation of mesenchymal markers and concurrent upregulation of epithelial markers as well as inhibition of migration and invasion. Experimental epithelial-mesenchymal-transition (EMT) induced by exposure to TGFβ/TNFα is also completely reversed by P18. Importantly, P18 also inhibits mammosphere-formation along with a reduction in the expression of stemness factors, Oct4, Nanog and Sox2. We show that P18 induces expression, phosphorylation and accumulation of p53 in cancer cells. P18-mediated induction of p53 leads to increased nuclear localization and elevated expression of p53 target genes. Using isogenic cancer cells differing only in p53 status, we show that p53 plays an important role in P18-mediated alteration of mesenchymal and epithelial genes, inhibition of migration and invasion of cancer cells. Furthermore, P18 increases miR-34a expression in p53-dependent manner and miR-34a is integral for P18-mediated inhibition of growth, invasion and mammosphere-formation. miR-34a mimics potentiate P18 efficacy while miR-34a antagomirs antagonize P18. Collectively, these data provide evidence that P18 may represent a promising therapeutic strategy for the inhibition of growth and progression of breast cancer and p53-miR-34a axis is important for P18 function.

Pharmacodynamic Response of the MET/HGF Receptor to Small-Molecule Tyrosine Kinase Inhibitors Examined with Validated, Fit-for-Clinic Immunoassays

PURPOSE

Rational development of targeted MET inhibitors for cancer treatment requires a quantitative understanding of target pharmacodynamics, including molecular target engagement, mechanism of action, and duration of effect.

EXPERIMENTAL DESIGN

Sandwich immunoassays and specimen handling procedures were developed and validated for quantifying full-length MET and its key phosphospecies (pMET) in core tumor biopsies. MET was captured using an antibody to the extracellular domain and then probed using antibodies to its C-terminus (full-length) and epitopes containing pY1234/1235, pY1235, and pY1356. Using pMET:MET ratios as assay endpoints, MET inhibitor pharmacodynamics were characterized in MET-amplified and -compensated (VEGFR blockade) models.

RESULTS

By limiting cold ischemia time to less than two minutes, the pharmacodynamic effects of the MET inhibitors PHA665752 and PF02341066 (crizotinib) were quantifiable using core needle biopsies of human gastric carcinoma xenografts (GTL-16 and SNU5). One dose decreased pY1234/1235 MET:MET, pY1235-MET:MET, and pY1356-MET:MET ratios by 60% to 80% within 4 hours, but this effect was not fully sustained despite continued daily dosing. VEGFR blockade by pazopanib increased pY1235-MET:MET and pY1356-MET:MET ratios, which was reversed by tivantinib. Full-length MET was quantifiable in 5 of 5 core needle samples obtained from a resected hereditary papillary renal carcinoma, but the levels of pMET species were near the assay lower limit of quantitation.

CONCLUSIONS

These validated immunoassays for pharmacodynamic biomarkers of MET signaling are suitable for studying MET responses in amplified cancers as well as compensatory responses to VEGFR blockade. Incorporating pharmacodynamic biomarker studies into clinical trials of MET inhibitors could provide critical proof of mechanism and proof of concept for the field. Clin Cancer Res; 22(14); 3683-94. ©2016 AACR.

Effect of a Smac Mimetic (TL32711, Birinapant) on the Apoptotic Program and Apoptosis Biomarkers Examined with Validated Multiplex Immunoassays Fit for Clinical Use

PURPOSE

To support clinical pharmacodynamic evaluation of the Smac mimetic TL32711 (birinapant) and other apoptosis-targeting drugs, we describe the development, validation, and application of novel immunoassays for 15 cytosolic and membrane-associated proteins indicative of the induction, onset, and commitment to apoptosis in human tumors.

EXPERIMENTAL DESIGN

The multiplex immunoassays were constructed on the Luminex platform with apoptosis biomarkers grouped into three panels. Panel 1 contains Bak, Bax, total caspase-3, total lamin-B (intact and 45 kDa fragment), and Smac; panel 2 contains Bad, Bax-Bcl-2 heterodimer, Bcl-xL, Bim, and Mcl1; and panel 3 contains active (cleaved) caspase-3, Bcl-xL-Bak heterodimer, Mcl1-Bak heterodimer, pS99-Bad, and survivin. Antibody specificity was confirmed by immunoprecipitation and Western blot analysis.

RESULTS

Two laboratories analytically validated the multiplex immunoassays for application with core-needle biopsy samples processed to control preanalytical variables; the biologic variability for each biomarker was estimated from xenograft measurements. Studies of TL32711 in xenograft models confirmed a dose-dependent increase in activated caspase-3 6 hours after dosing and provided assay fit-for-purpose confirmation. Coincident changes in cytosolic lamin-B and subsequent changes in Bcl-xL provided correlative evidence of caspase-3 activation. The validated assay is suitable for use with clinical specimens; 14 of 15 biomarkers were quantifiable in patient core-needle biopsies.

CONCLUSIONS

The validated multiplex immunoassays developed for this study provided proof of mechanism data for TL32711 and are suitable for quantifying apoptotic biomarkers in clinical trials.

Abstract 4517: Plasma and tumor pharmacokinetics of IV LMP744, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study

Introduction: LMP744 (NSC706744) is one of 3 indenoisoquinolines being evaluated in pet dogs with lymphoma to define their safety, pharmacokinetics, and pharmacodynamic modulation (COTC007b). LMP744 forms stable DNA-topoisomerase I (Top1) cleavage complexes and induces unique DNA cleavage sites relative to approved Top1 poisons; LMP744 is not a substrate for ABC transporters and does not have the stability issues inherent to camptothecins. Here we report the plasma and tumor pharmacokinetics of LMP744 administered IV daily x 5 to patient dogs.

Methods: Eligibility included: dogs >15 kg with histologically confirmed non-Hodgkin's lymphoma with nodal presentation (stage 2 or greater) and minimal nodes size for biopsy of 3 cm in the longest dimension, performance status of Grade 0 or 1 and informed owner consent. Dose levels (DL) explored were 25, 50, 75, 100, and 125 mg/m2/day through a 3+3 dose escalation study design. LMP744 was administered over 1 h IV daily x 5, Q28D. LMP744 was quantitated with a validated LC-MS/MS assay, and plasma pharmacokinetic parameters determined non-compartmentally with PK Solutions and plasma and tumor parameters compartmentally with ADAPT5 through iterated two stage (ITS) and maximum likelihood solution with the expectation maximization algorithm (MLEM).

Results: All 18 dogs had useable pharmacokinetic data. Non-compartmental analysis suggested linear relationships between plasma Cmax and tumor C2h vs. dose. LMP744 distributed extensively to tumor tissue and mean tumor concentrations were at least 2 orders of magnitude higher than plasma concentrations at equivalent time points of 2, 6 and 120 h. Compartmental modeling with a 3 compartment linear model resulted in a good fit to the plasma data. The parameters and%CVs respectively for Clt, Vc, Cld1, Vp1, Cld2, Vp2 were 57.5 L/h/m2 (29%), 136 L/m2 (24%), 234 L/h/m2 (24%), 1180 L/m2 (27%), 30.8 L/h/m2 (63%), 5140 L/m2 (67%). Sequential plasma half-lives were 16.5 min, 13 h, and 183 (31%) h, respectively. In line with the long t1/2, plasma accumulation was observed on this daily times-5 schedule.

Conclusion: The plasma pharmacokinetics of LMP744 in dogs display triphasic behavior, a relatively high total body clearance at 57.5 L/h/m2, and a terminal half-life of 183 h. The favorable biodistribution to tumor may be a valuable distinction to consider in the translation of this novel indenoisoquinoline to the clinic.

Support: N01-CM-2011-00015, N01-CM-42202 and P30-CA-47904

Note: This abstract was not presented at the meeting.

Citation Format: Julie L. Eiseman, Julianne Holleran, David L. McCormick, Miguel Muzzio, Joseph M. Covey, Chand Khanna, Christina Mazcko, Yves Pommier, Melissa Paolini, Amy Leblanc, Jenna H. Burton, James H. Doroshow, Joseph E. Tomaszewski, Jan H. Beumer. Plasma and tumor pharmacokinetics of IV LMP744, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4517. doi:10.1158/1538-7445.AM2015-4517

Abstract 5082: Impact of HGF knockin microenvironment on epithelial-mesenchymal transition and cancer stem cells in a non-small cell lung cancer xenograft model

We previously reported the generation of rabbit monoclonal antibodies to twelve EMT (epithelial-to-mesenchymal transition) transcription factors and cancer stem cell (CSC) markers for the development of pharmacodynamic assays to inform clinical trials of new anticancer therapies (Pfister et al., AACR 2013). Here we demonstrate the functional utility of some of these reagents in detecting HGF-induced changes in EMT and CSC biology in a xenograft tumor model. Initial antibody characterization was performed in vitro and a subset [including SNAIL, SLUG, SOX9, Goosecoid (GSC), NANOG and CD133] was selected for further testing of functional utility in FFPE tissues by quantitative multiplex IFA. The antibodies were applied to xenograft tissues derived from the non-small cell lung cancer tumor line, NCI-H596, implanted in hHGFscid/scid, hHGFki/scid or hHGFki/ki mice to examine HGF-induced changes in EMT factors, CSC markers, as well as pY1235-MET expression in vivo. H596 tumors grown in either hHGFki/scid or hHGFki/ki mice exhibited enhanced EMT particularly in tumor microenvironments adjacent to mouse stroma containing the HGF knockin gene, compared to those in hHGFscid/scid mice. By quantitative immunofluorescence, H596 tumors showed increased Vimentin:E-cadherin ratio when grown in hHGFki/scid (P<0.0006) or hHGFki/ki (P<0.022) vs. HGFscid/scid mice. Moreover, significant increases in nuclear pY1235-MET, measured by%NAP (percentage nuclear area positive), were observed in H596 tumors in hHGFki/scid (P<0.0041) or hHGFki/ki (P<0.0058) vs. hHGFscid/scid. We detected varying levels of EMT/CSC marker expression, including CD44, CD133, ALDH, and GSC in the membrane or cytoplasm of noninvasive regions of H596 tumors in hHGFscid/scid mice. Sox9 was also co-expressed with GSC in some tumor cells but was predominantly in the nuclei. In tissues collected from hHGFki/scid or hHGFki/ki mice, Slug, Snail and Sox9 expression were increased in transitioning tissue regions, adjacent to HGF-containing stroma, coincident with diminished E-Cadherin expression and enhanced Vimentin expression. While Slug expression was predominantly cytoplasmic in invading tumor fronts, the expression was mutually exclusive with CD133 within non-invasive regions. Snail and Sox9 showed enhanced nuclear expression in tumor cells undergoing EMT. These markers are currently being investigated in additional tumor samples from human TNBC or CRC xenograft models treated with various drug combinations. To our knowledge, this is the first demonstration of EMT and changes in cancer stem cell biology in NSCLC induced by an HGF-knockin stromal microenvironment. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: Tony Navas, Thomas D. Pfister, Scott M. Lawrence, Apurva K. Srivastava, Robert J. Kinders, Suzanne Borgel, Sergio Alcoser, Melinda G. Hollingshead, Lindsay M. Dutko, Brad A. Gouker, Donna Butcher, Elinor Ng-Eaton, Naoko Takebe, Young H. Lee, Donald P. Bottaro, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow. Impact of HGF knockin microenvironment on epithelial-mesenchymal transition and cancer stem cells in a non-small cell lung cancer xenograft model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5082. doi:10.1158/1538-7445.AM2015-5082

Abstract 5279: Establishing robust pharmacodynamic (PD) immunofluorescence assays of clinical biopsies at the National Cancer Institute: Optimized quality control procedures for the evaluation of DNA damage response and epithelial-mesenchymal transition (EMT) biomarkers

Robust PD assay results are valuable for informing decisions about continued preclinical and clinical development of new agents and for identifying effective combinations of targeted agents. The National Cancer Institute's Division of Cancer Treatment and Diagnosis (DCTD) develops and validates PD assays to obtain accurate information about drug effect on intended molecular targets in first-in-human clinical trials. Our group utilizes quantitative immunofluorescence assays (qIFA) of PD biomarkers in FFPE slides prepared from pre- and post-dose tumor biopsies collected from patients on early phase clinical trials. Paired biopsies are fixed and paraffin embedded, in parallel with tissue controls, such that all tissues are sectioned onto the same slide. Stringent methods to maintain the biopsy orientation are utilized during fixation, blocking and microtomy. A large number of sections are generated to increase the likelihood of finding optimal tumor regions of interest for biomarker analyses. Flanking H&E slides are utilized to assess the quality of the tumor biopsies. Whole slide scans of the H&E slides are shared with a clinical pathologist who determines whether the sections are sufficient or insufficient for the intended analysis. The pathology review allows the assay operator to select the optimal range of slides to stain and quantitatively analyze for the biomarker(s) of interest. Pathology-guided regions allow the operator to focus on tumor regions of interest and avoid normal tissue and/or confounding regions compromised by handling and processing artifacts. For nuclear biomarkers such as γH2AX and related DNA damage response biomarkers the pathologist annotates areas of sufficient tumor content and viability. For biomarker changes in tissue architecture such as that seen in Epithelial Mesenchymal Transition biomarkers, including E-Cadherin, Vimentin and β-catenin, the pathology annotation denotes areas of normal tissue and necrosis to eliminate from the qIFA analysis. All other areas of sufficient tumor cellularity from the entire slide are evaluated for the EMT biomarkers. Use of the pathology-annotated whole slide image as a tool for guidance of the operator performing the quantitative evaluation of the PD biomarker helps to ensure a non-subjective analysis. Finally, steps are taken to ensure proper storage of the paraffin slides, including paraffin dipping after microtomy, which is critical for preservation of labile epitopes such as phosphorylated proteins. We will present details of these optimized methods as well as key lessons learned during the preclinical and clinical implementation of qIFA measurements of PD biomarkers for various molecular targeted agents. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Katherine V. Ferry-Galow, Scott M. Lawrence, Tony Navas, Hala R. Makhlouf, Donna O. Butcher, Brad A. Gouker, William H. Yutzy, Jiuping Ji, Robert Kinders, Ralph E. Parchment, Shivaani Kummar, Joseph E. Tomaszewski, James H. Doroshow. Establishing robust pharmacodynamic (PD) immunofluorescence assays of clinical biopsies at the National Cancer Institute: Optimized quality control procedures for the evaluation of DNA damage response and epithelial-mesenchymal transition (EMT) biomarkers [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5279. doi:10.1158/1538-7445.AM2015-5279

Proteasome inhibitors

Proteasome inhibitors have a 20 year history in cancer therapy. The first proteasome inhibitor, bortezomib (Velcade, PS-341), a break-through multiple myeloma treatment, moved rapidly through development from bench in 1994 to first approval in 2003. Bortezomib is a reversible boronic acid inhibitor of the chymotrypsin-like activity of the proteasome. Next generation proteasome inhibitors include carfilzomib and oprozomib which are irreversible epoxyketone proteasome inhibitors; and ixazomib and delanzomib which are reversible boronic acid proteasome inhibitors. Two proteasome inhibitors, bortezomib and carfilzomib are FDA approved drugs and ixazomib and oprozomib are in late stage clinical trials. All of the agents are potent cytotoxics. The disease focus for all the proteasome inhibitors is multiple myeloma. This focus arose from clinical observations made in bortezomib early clinical trials. Later preclinical studies confirmed that multiple myeloma cells were indeed more sensitive to proteasome inhibitors than other tumor cell types. The discovery and development of the proteasome inhibitor class of anticancer agents has progressed through a classic route of serendipity and scientific investigation. These agents are continuing to have a major impact in their treatment of hematologic malignancies and are beginning to be explored as potential treatment agent for non-cancer indications.

Notch1 phenotype and clinical stage progression in non-small cell lung cancer

Background

Notch1 transmembrane receptor is activated through ligand-binding- triggered proteolytic cleavages and, upon release, the intracellular domain (N1-ICD) translocates into the nucleus and modulates target gene transcriptions. Notch activation has been implicated in tumorigenesis in an increasing number of human malignancies including non-small cell lung cancer (NSCLC). However, Notch1 in distinct expression patterns and activation status with tumor progression remains to be defined in NSCLC.

Methods

Notch1 and activated Notch1, N1-ICD, were examined by immunohistochemistry in 58 cases of stage I to IV NSCLC tumors. Association between Notch1 or N1-ICD expression and clinicopathological factors was assessed via correlation coefficient r statistics. P-values are two-sided.

Results

Detectable tumor Notch1, predominantly localized to the membrane and cytoplasm, was observed in 29 cases (50%, 95% Blyth-Still-Casella confidence interval 37 – 63%). It was negatively associated with stage (r = - 0.43, P < 0.001) and nodal status (r = - 0.33, P = 0.01), but not tumor size. In contrast, nuclear N1-ICD expression level was low and found in 12% of NSCLC patients, neither significantly associated with stage nor nodal status. Upon Notch1 activation in vitro, a mostly extra-nuclear staining was substantially turned into the nuclear signal in cancer cells.

Conclusions

Notch1 in the largely inactivated phenotype is inversely associated with clinical stage progression in NSCLC. Notch1, rather than activated N1-ICD, may be a context-dependent restrictive factor to nodal metastasis.

Abstract 3838: Differential expression of Notch1 in lung, ovarian and breast cancers

Targeting the Notch signaling pathway for cancer treatment is currently the subject of early clinical trials. However, treatment-related toxicities, particularly gastrointestinal adverse events, have limited clinical development of this class of agents. The development of efficacy biomarkers to gamma-secretase inhibitors and antibodies to Notch ligands and receptors could speed clinical testing. Mutations in Notch1, a dominant Notch receptor, are rare in human solid tumors, and clinical activity has not been observed in patients with tumors bearing Notch1 activating mutations, including T-cell acute lymphoblastic leukemia from available clinical data. Identification of tumors with abundant target expression and/or active Notch signaling status characteristic of Notch intracellular domain (NICD) expression by immunohistochemistry may have clinical utility. All levels of tumor Notch1 expression comprised of low, moderate and high detected by immunohistochemistry and quantitated by digital imaging technology were observed in 52% (34/66) of lung cancers, 51% (35/68) of ovarian cancers, and 11% (7/63) of breast cancers (lung or ovary vs. breast, P&lt;0.0001 by 2-sided Fisher Exact Test). Notch1 was expressed at high levels in 20% of lung cancers including sarcoma, neuroendocrine, small cell and undifferentiated carcinomas, as well as adenocarcinoma and squamous cell carcinomas. High expression of Notch1 was observed in 9% of ovarian tumors including undifferentiated carcinoma, serous adenocarcinoma, and endometrioid adenocarcinoma. In breast cancer, it was noted in one case of infiltrating ductal carcinoma with triple-negative phenotype. Expression of high-level Notch1 varies in lung cancer vs. ovarian cancer vs. breast cancer (P=0.002 by Chi-square statistic), and was frequently associated with NICD expression. Notch1 was not significantly associated with estrogen receptor, progesterone receptor or HER2 status in breast cancer. These data suggest that the frequency of all levels of Notch1 expression is significantly higher in lung cancer and ovarian cancer than breast cancer; and high-level Notch1 is more frequent in lung cancer than in ovarian cancer, and, likewise, more frequent in ovarian cancer than in breast cancer. For the first time, expression of Notch1/NICD has been identified in undifferentiated carcinomas. The findings may provide useful information for the rational design of Notch inhibitor clinical trials.

Citation Format: Dat Nguyen, Larry Rubinstein, Mark E. Sherman, Joseph E. Tomaszewski, Naoko Takebe, Percy Ivy, James H. Doroshow, Sherry X. Yang. Differential expression of Notch1 in lung, ovarian and breast cancers. [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 3838. doi:10.1158/1538-7445.AM2014-3838

Abstract 3691: Met target inhibition-guided efficacy in preclinical models

Background: A direct comparison of drug efficacy for the multiple agents currently in clinical development targeting MET-driven cancers would be useful for the selection of optimal treatment options. Previously, we utilized validated MET pharmacodynamic (PD) assays to compare the time course of phosphorylated-MET (pMET) suppression for five MET inhibitors (ASCO 2013). In the current study, we selected three candidates that demonstrated potent MET inhibition to compare anti-tumor efficacy.

Methods: PD time course and tumor PK data were utilized to simulate a dosing schedule anticipated to produce &gt;90% pMET suppression in a SNU5 gastric cancer xenograft model. From these data, dosing schedules of 44 mg/kg (Q12H) cabozantinib, 12.5 mg/kg (Q12H) EMD1214063, and 16.5 mg/kg (QD) foretinib were chosen to achieve necessary tumor exposure to suppress pMET. Once tumors reached a 150±50 mm3 size, drugs were administered continuously for 21 days and tumor volumes were measured intermittently for 62 days. To measure pMET suppression, tumor quadrants were collected at 4, 12, and 24 hrs from all treatment groups after dose 1 (day 1) and on day 8 (after dose 8 of foretinib or dose 14 of cabozantinib and EMD1214063).

Results: Intact MET levels (pM/μg protein) were approximately 70% lower than vehicle controls at all day 8 collection points for all three drugs. The pY1234/35MET/MET ratios were 89%-99% (p&lt;0.001) lower than vehicle controls on day 8 at 4 and 12 hrs post-dose for all three drugs. Compared to pretreatment levels, tumor volumes were reduced by 80-90% for all three drugs within 10-15 days post therapy and remained regressed until 13-20 days after treatment was stopped. Tumors then slowly regrew, but remained approximately 80% smaller than the vehicle group on day 62 (end of study).

Conclusions: These studies demonstrate that PD response-guided regimens delivered drug doses that were lower than efficacious doses described previously (except cabozantinib), but effectively reduced tumor volume in SNU5 xenografts. The three MET inhibitors showed comparable anti-tumor efficacy when accompanied by equivalent pMET inhibition. Our data also affirms the utility of the MET PD assays to guide dose ranging studies. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Apurva K. Srivastava, Melinda G. Hollingshead, Jeevan P. Govindharajulu, Joseph M. Covey, Dane Liston, James Peggins, Donald P. Bottaro, John J. Wright, Robert J. Kinders, Joseph E. Tomaszewski, James H. Doroshow, Ralph E. Parchment. Met target inhibition-guided efficacy in preclinical models. [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 3691. doi:10.1158/1538-7445.AM2014-3691

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

Abstract 4689: Pre-clinical investigation of the wee1 inhibitor MK-1775 using pharmacodynamic and mechanistic markers in diverse cancer models in vivo

Wee1 kinase is a critical regulator of the G2/M checkpoint by initiating inhibitory phosphorylation of the conserved tyrosine-15 residue of cdk1/cdc2. Wee1 also phosphorylates tyrosine 15 of cdk2 and plays a crucial role in maintaining genome integrity during S-phase. MK1775 (NSC 754352) is a small molecule selective inhibitor of Wee1 kinase that is currently under clinical evaluation. We have developed a quantitative immunofluorescence assay to measure inhibition of Wee1 by detection of pY15 of cyclin-dependent kinases. A full analysis of the pharmacodynamic (PD) effects of Wee1 inhibition by MK1775, as well as the downstream mechanistic consequences of Wee1 inhibition on DNA repair, apoptosis, and premature mitotic entry markers was performed using two xenograft models: A673 Ewing sarcoma and U87-MG glioblastoma. Four DNA repair markers (pNbs1, γH2AX, Rad51, and pATR) were examined as well as the mitotic marker pHistone H3. Advanced quantitative image analysis was performed using Definiens software to measure changes in PD markers by two approaches: total nuclear area measurements and foci per nucleus. Definiens software enables enhanced analysis of the markers by enumeration of the nuclei in the imaged xenograft tissues over an entire data set with high-content capacity. Our data demonstrate greater than 80% inhibition of pY15-cdk in vivo at the clinically relevant dose of 60 mg/kg (180 mg/m2) MK1775 in two xenograft models. In addition, γH2AX induction was observed after multiple doses of MK1775 as a single agent. A PD biomarker time course was determined for MK1775 and gemcitabine (NSC 750927) as single agents to develop a drug administration schedule for combination studies in a Ewing sarcoma model. The time point at which the DNA damage response peaked following administration of the maximum tolerated dose of gemcitabine in the mouse was determined. This study elucidates a broad profile of PD marker response, as well as the corresponding levels of MK1775 in the xenografts. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: Deborah F. Wilsker, Allison M. Marrero, Melinda Hollingshead, Scott M. Lawrence, Alice Chen, Shivaani Kummar, Joseph M. Covey, Ralph E. Parchment, Robert J. Kinders, Joseph E. Tomaszewski, James H. Doroshow. Pre-clinical investigation of the wee1 inhibitor MK-1775 using pharmacodynamic and mechanistic markers in diverse cancer models in vivo. [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 4689. doi:10.1158/1538-7445.AM2014-4689

Abstract 4632: Plasma and tumor pharmacokinetics of IV LMP400, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study

Introduction: LMP400 is one of 3 indenoisoquinolines that are being evaluated in pet dogs with lymphoma to define their safety, pharmacokinetics, and pharmacodynamic modulation (COTC007b). LMP400 forms stable DNA-topoisomerase I (Top1) cleavable complexes and induces unique DNA cleavage sites relative to approved Top1 poisons; LMP400 is not a substrate for ABC transporters and does not have the stability issues that most camptothecin analogs do. Here we report the plasma and uncoupled tumor pharmacokinetics of LMP400 administered IV daily x 5 to patient dogs.

Methods: Eligibility included: dogs &gt;15 kg with histologically confirmed non-Hodgkin's lymphoma with nodal presentation (stage 2 or greater) and minimal nodes size for biopsy of 3 cm in the longest dimension, performance status of Grade 0 or 1 and informed owner consent. Dose levels (DL) explored were 8, 16, 24, and 40 mg/m2/day through a 3+3 dose escalation study design. LMP400 was administered over 1 h IV daily x 5, Q28D. LMP400 was quantitated with a validated LC-MS/MS assay (PMID: 20236781), and plasma pharmacokinetic parameters determined non-compartmentally with PK Solutions and plasma and tumor parameters compartmentally with ADAPT5 through iterated two stage (ITS) and maximum likelihood solution with the expectation maximization algorithm (MLEM).

Results: All fifteen dogs had useable pharmacokinetic data. Non-compartmental analysis suggested linear relationships between plasma Cmax and AUC vs. dose and tumor C2h vs. dose. Plasma terminal half-life was 11.9 ± 5.0 h and the CL was 26.7 L/h/m2. In line with the t1/2, slight plasma accumulation was observed on this daily times 5 schedule. Compartmental modeling with a 2 compartment linear model resulted in a good fit to the data. The parameters and %CVs respectively for Ke, Vc, Kcp, Kpc, Kct and Ktc were 0.181 h-1 (42.6%), 108 L/m2 (32.7%), 0.250 h-1 (30.1%), 0.0602 h-1 (67%), 0.0632 h-1 (3.65%), and 0.649 h-1 (42.2%). Plasma compartmental CL and half-life were 19.5 L/h/m2 and 29.7 h.

Conclusion: The plasma pharmacokinetics of LMP400 in dogs display biphasic behavior, a relatively high total body clearance at 19.5 L/h/m2, and a terminal half-life of 29.7 h. LMP400 distributed to the tumors and mean tumor concentrations were at least 10-fold higher than plasma concentrations at equivalent time points of 2, 6 and 120 h. This favorable biodistribution to tumor (lymph node) may be a valuable distinction to consider in the translation of this novel indenoisoquinoline to the clinic.

Support: N01-CM-2011-00015, N01-CM-42202 and P30-CA-47904

Citation Format: Julie L. Eiseman, Julianne Holleran, David L. McCormick, Miguel Muzzio, Joseph M. Covey, Chand Khanna, Christina Mazcko, Yves Pommier, Melissa Paoloni, James D. Doroshow, Joseph E. Tomaszewski, Jan H. Beumer. Plasma and tumor pharmacokinetics of IV LMP400, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study. [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 4632. doi:10.1158/1538-7445.AM2014-4632

Validation of a hypoxia-inducible factor-1 alpha specimen collection procedure and quantitative enzyme-linked immunosorbent assay in solid tumor tissues

Hypoxia-inducible factor-1 alpha (HIF-1α) is an important marker of hypoxia in human tumors and has been implicated in tumor progression. Drugs targeting HIF-1α are being developed, but the ability to measure drug-induced changes in HIF-1α is limited by the lability of the protein in normoxia. Our goal was to devise methods for specimen collection and processing that preserve HIF-1α in solid tumor tissues and to develop and validate a two-site chemiluminescent quantitative enzyme-linked immunosorbent assay (ELISA) for HIF-1α. We tested various strategies for HIF-1α stabilization in solid tumors, including nitrogen gas-purged lysis buffer, the addition of proteasome inhibitors or the prolyl hydroxylase inhibitor 2-hydroxyglutarate, and bead homogenization. Degassing and the addition of 2-hydroxyglutarate to the collection buffer significantly increased HIF-1α recovery, whereas bead homogenization in sealed tubes improved HIF-1α recovery and reduced sample variability. Validation of the ELISA demonstrated intra- and inter-assay variability of less than 15% and accuracy of 99.8±8.3% as assessed by spike recovery. Inter-laboratory reproducibility was also demonstrated (R(2)=0.999). Careful sample handling techniques allow us to quantitatively detect HIF-1α in samples as small as 2.5μg of total protein extract, and this method is currently being applied to analyze tumor biopsy specimens in early-phase clinical trials.

Abstract C278: Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas

Topoisomerase I (Top1) is the molecular target for a number of drugs used in cancer chemotherapy. Several third generation Top1 inhibitors are being evaluated, including the indenoisoquinolines (NSC 725776 and NSC743400) which are currently in clinical trials at the National Cancer Institute. We previously reported the development and validation of a quantitative ELISA to measure Top1 levels in cells and solid tissues [PloS ONE (2012) 7(12)]. We observed a large variation in baseline Top1 levels in xenografts and human patient biopsies using the published method. Baseline Top1 levels in needle biopsies for some patients were too low to allow for the reporting of a drug effect. We have modified our tissue processing procedures to improve assay sensitivity. We have also demonstrated the fitness of the assay in a clinical trial of the indenoisoquinolines for canine lymphoma as a stepping stone to human clinical trials. Baseline Top1 levels in canine lymphoma patients varied greatly, consistent with our previous findings in xenografts and a limited number of human tumor biopsies. These data suggest that it may not be possible to measure drug effect based on post-dose Top1 levels alone, but will require paired pre-dose and post-dose specimens from the same patient. Decreased Top1 levels following therapy (compared to pre-dose) were detected in tumors from a number of dogs, each treated with one of three indenoisoquinolines (NSC706744, NSC 725776 and NSC743400), demonstrating evidence of target engagement as predicted by in vitro and xenograft models. Measurement of baseline Top1 levels in this trial will be correlated with the degree of drug-related target reduction and evidence of drug efficacy in the dogs enrolled on this study. Funded by NCI Contract No. HHSN261200800001E.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C278.

Citation Format: Thomas D. Pfister, Katerine V. Ferry-Galow, Tariq Mohabbat, Robert J. Kinders, Chand Khanna, Christina Mazcko, Ralph E. Parchment, Yves Pommier, Joseph E. Tomaszewski, James H. Doroshow. Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C278.

Abstract PR11: Use of a DNA damage multiplex immunofluorescence assay to monitor pharmacodynamic markers following in vitro exposure to therapeutic agents

Most current therapeutic approaches to cancer include agents which induce genotoxic damage, either through direct damaging effects on DNA or indirectly, by altering cellular checkpoint controls or by causing a synthetic lethal response in patients with genetic abnormalities in DNA damage repair pathways. As candidate agents or novel combination therapies come into the clinic, the development of multiplexed immunoassays that quantitatively measure several pharmacodynamic biomarkers of DNA repair could improve our understanding of the relationship between target engagement and therapeutic efficacy. We previously reported the initial development of a quantitative, multiplex immunofluorescence assay comprised of a nuclear marker and four DNA damage repair proteins (γH2AX, pNbs1S343, Rad51, and ERCC1) as a method for monitoring drug action in vitro and in vivo. Here, we report the use of this multiplex assay to measure the effect of a PARP inhibitor (BMN-673) on an isogenic pair of HR competent and incompetent cell lines. The multiplex immunofluorescence assay utilizes a cassette approach, with all validated primary antibodies conjugated directly to a fluorophore or hapten such that multiple antibodies raised in the same host species can be used without the requirement of an anti-species reporter. The cassette approach allows for rearrangement of the composition of markers in the multiplex assay based on the investigational agent or clinical trial in question. We will also report on the development and utility of additional DNA damage markers for future multiplex assays, including markers specific for ATR-activated repair pathways. We have developed an antibody to the pATR T1989 site and will demonstrate its use in immunofluorescence applications as a pharmacodyamic marker following in vitro exposure to DNA damage-inducing agents and an ATR inhibitor. Additionally, we show in vitro data which supports the use of phosphorylated checkpoint proteins (pChk1S345, pChk2T68) as downstream indicators of DNA damage in the multiplex format. These biomarkers, in conjunction with our previously-reported multiplex panel, will provide an effective technique to monitor DNA repair responses and checkpoint controls in the clinical evaluation of combination therapy approaches targeting DNA damage repair deficiencies. Funded by NCI Contract No. HHSN261200800001E.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):PR11.

Citation Format: Allison M. Marrero, Deborah Wilsker, Scott M. Lawrence, Thomas D. Pfister, John Hirt, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow, Robert J. Kinders. Use of a DNA damage multiplex immunofluorescence assay to monitor pharmacodynamic markers following in vitro exposure to therapeutic agents. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr PR11.

Abstract C197: Fluorescent in situ hybridization confirmation of circulating alveolar soft part sarcoma cells (CTCs) isolated from peripheral blood specimens using ApoStream™ instrumentation

Enumeration and characterization of circulating tumor cells (CTCs) by the CellSearch™ instrument platform, which uses antibody capture of fixed cells from blood, provides prognostic information and assists in monitoring therapy for patients with certain epithelial cancers. Our laboratory is clinically evaluating an antibody-independent CTC enrichment technology, ApoStream™, which was co-developed by NCI and SAIC-F with ApoCell Inc. The ApoStream isolates living CTCs from a wide variety of malignancies including sarcomas and lymphomas as well as epithelial cancers, enabled by critical differences in morphology and dielectric properties rather than surface marker expression. In contrast to the CellSearch™ platform, CTCs isolated with the ApoStream™ instrument are amenable to tests that unambiguously identify isolated cells as malignant cells. To validate the performance of the ApoStream™ device for clinical specimens, we focused on isolation of CTCs from patients with advanced alveolar soft part sarcoma (ASPS). Patient samples from an ongoing clinical study at the NCI provided the opportunity to demonstrate the utility of ApoStream™ technology for the isolation of CTCs from patients with this rare non-epithelial malignancy. ASPS is characterized by a specific, unbalanced genetic translocation of der(17)t(X;17)(p11;q25) involving the ASPL and TFE3 genes. The detection of the fusion product has been reported in primary tumors and peripheral blood based on RT-PCR but not in CTCs. Here we show that the ASPL-TFE3 gene translocation can be unambiguously confirmed in CTCs by break-apart fluorescent in situ hybridization (FISH), and the presence of the fusion protein in CTCs was confirmed with specific monoclonal antibodies. Efficient recovery was demonstrated using specified numbers of cancer cells spiked into buffer and normal donor control PBMCs; clinical utility was demonstrated with blood samples from ASPS patients. This study provides not only initial results demonstrating isolation of CTCs from metastatic ASPS patients using the ApoStream™ technology without the need for antibody capture but also a rationale for exploring ApoStream™ technology in additional tumor histologies that cannot be evaluated with the CellSearch™ platform. Our current efforts are focused on evaluating the utility of ApoStream™-isolated CTCs for assessing pharmacodynamic effects of new targeted agents during early stage clinical trials.

Funded by NCI Contract No. HHSN261200800001E.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C197.

Citation Format: Priya Balasubramanian, Lihua Wang, Shivaani Kummar, Melinda Hollingshead, Francis Owusu, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow, Robert J. Kinders. Fluorescent in situ hybridization confirmation of circulating alveolar soft part sarcoma cells (CTCs) isolated from peripheral blood specimens using ApoStream™ instrumentation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C197.

Creating clinical target validation groups via quality assured transfer of robust clinical pharmacodynamic (PD) assays from the NCI: Clinical implementation of a PAR immunoassay in tumor biopsies

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Background: Early phase clinical trials of investigational agents benefit from laboratory assays that quantify intended mechanism of action on molecular target (1° PD effects), desired changes in mechanistic biomarkers (2° PD effects), and 3° PD effects on cell survival. Robust PD assay results are valuable for informing go/no‐go decisions about continued development of new agents and for identifying combinations of targeted agents that cover the multiple molecular defects underlying many malignancies. Methods: Readying PD assays for clinical use involves validating analytical performance, identifying and qualifying critical reagents, demonstrating fit‐for‐purpose for the clinical protocol, and finalizing companion SOPs specifying specimen handling and processing. Because clinical PD questions often demand assay performance that meets or even exceeds clinical diagnostic assay standards, but key assay reagents are usually R and D‐rather than GMP‐grade, stringent reagent Quality Control is critical for preventing assay failures due to lot-to-lot variability. Results: The poly(ADP-ribose) (PAR) Immunoassay was the first qualified assay developed by NCI for implementation in early phase clinical trials. Development of stringent production and internal Quality Control specifications for accepting/rejecting new lots of critical reagents and a defined Quality Assurance Plan allowed a network of users to achieve consistent results and quality using R&D-grade source materials. Conclusions: The NCI’s Division of Cancer Treatment and Diagnosis is developing a clinical PD assay portfolio capable of quantifying 1°, 2°, and 3° PD effects. Proven clinical assays are formally transferred from the NCI to requesting sites in academia and industry via laboratory‐based certification and training, centralized access to SOPs, assistance with assay transfer, and participation in the assay’s Quality Assurance Plan. Funded by NCI Contract No HHSN261200800001E.

Application of MET pharmacodynamic assays to compare effectiveness of five MET inhibitors to engage target in tumor tissue

11103

Background: Several MET inhibitors are currently being developed that block aberrant HGF/MET signaling in different cancers. We utilized validated MET pharmacodynamic (PD) assays to compare time course, magnitude, and reversal of MET suppression by 5 MET inhibitors in preclinical models. Methods: Immunoassays (total MET, pY1234/35MET, and pY1356MET) were developed and validated to measure modulation of MET by 5 MET inhibitors (crizotinib, tivantinib, cabozantinib, foretinib, and EMD1214063). The comparison was implemented in 3 sequential stages: 1) establish time course and magnitude of MET inhibition after single drug administration of 4 different doses; 2) determine dose(s) and schedule for sustained MET inhibition and downstream signaling at optimal levels; and 3) compare efficacy of MET inhibitors at MTD and equal MET inhibition. The preclinical models include an autophosphorylation gastric tumor (SNU5) model and a paracrine MET activation model in hHGF knock-in mice. Plasma and tumor exposures were measured using LC-MS/MS to correlate with PD effects. Results: We completed phase one in the SNU5 model and determined inhibition of pY1234/35MET and total MET in tumor tissues after single administration of MET inhibitors. Time course and magnitude of pY1234/35MET inhibition varied considerably among MET inhibitors, with the most rapid (>80% suppression in 30 min) and sustained inhibition (up to 48 h) observed with EMD1214063 at a dose of 30 mg/kg. The maximal inhibition of pY1234/35MET and time taken for biomarker recovery were wide-ranging among MET inhibitors. Tumor drug exposures were concomitantly higher than plasma for all drugs and correlated inversely with pY1234/35MET, except for tivantinib which, unlike other drugs, is not ATP competitive inhibitor. Conclusions: We applied validated PD assays to directly compare similarities and differences in extent and duration of MET inhibition by 5 MET inhibitors. Our results provide important foundation for head-to-head comparison of efficacies of MET inhibitors at MTD and equal MET inhibition. Funded by NCI Contract No HHSN261200800001E.

Abstract 2424: CD40 expression in human solid tumors and NCI60 tumor cell lines

Cell-surface CD40 is a member of the tumor necrosis factor receptor superfamily (TNFRSF) expressed and functionally well characterized in immune and hematopoietic cells. However, its expression and role in human solid tumors remain to be evaluated. As a molecular target currently with the antibody-based cancer therapy, it is important to characterize expression of CD40 across a range of human solid tumors and cancer cell lines. This could help improve our understanding of biology of CD40 molecule in human cancers especially epithelial tumors, and in turn increase the odds of success of targeting CD40 pathway. Expression of CD40 in the NCI60 human tumor cell lines and common types of human solid tumors were examined by immunohistochemistry in formalin-fixed and paraffin-embedded tumor specimens. CD40, predominantly membranous signal, was constitutively expressed in 15 lines, respectively derived from carcinomas of the breast, colorectum, non-small cell lung, ovary, prostate, and renal cell, of the NCI60 tumor cell line panel, and confirmed by Western blotting and gene expression microarray data available at http://dtp.nci.nih.gov/mtweb/search.jsp. CD40 expression was largely in accordance with the mRNA expression data measured by gene expression profiling. The status of CD40 was verified in MDA-MB-231, T-47D and HCT-116 cells (CD40-positive), and MCF-7 and HT-29 cells (CD40-negative) by Western blot. Moreover, CD40 was detected in tumor cells in 17% (6/34) of breast cancer, 24% (8/34) colorectal cancer, 54% (23/43) non-small cell lung cancer, and 47% (17/36) ovarian cancer. CD40 was also spotted in infiltrating lymphocytes in the tumor stroma. The data indicate that CD40 is expressed in human solid tumors with varying expression frequencies and one quarter of cancer cell lines examined. In addition, we have established a ready-for-use immunohistochemistry assay with an antibody that specifically detects CD40 in formalin-fixed and paraffin-embedded human tumor samples. Its application holds promise to evaluate the prognostic role of CD40 in human cancers.

Citation Format: Dat Nguyen, Joseph E. Tomaszewski, Stephen M. Hewitt, James H. Doroshow, Sherry X. Yang. CD40 expression in human solid tumors and NCI60 tumor cell lines. [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 2424. doi:10.1158/1538-7445.AM2013-2424

Abstract 1186: Creating clinical target validation groups via quality assured transfer of robust clinical pharmacodynamic (PD) assays from the NCI: clinical implementation of a HIF1α immunoassay in tumor biopsies

Robust pharmacodynamic (PD) assay results are valuable for informing go/no-go decisions about preclinical and clinical development of new agents and for identifying optimal combinations of targeted agents. The NCI's Division of Cancer Treatment and Diagnosis (DCTD) develops and validates PD assays to obtain accurate information about target engagement in first-in-human clinical trials. The Pharmacodynamic Assay Development and Implementation Section (PADIS) and National Clinical Target Validation Laboratory (NCTVL) were established at SAIC-Frederick to develop and validate PD assays by validating analytical performance, demonstrating fitness-for-purpose for the clinical protocol, and finalizing companion standard operating procedures (SOPs) for specimen handling and processing. Proven clinical assays are transferred from the NCI to requesting sites in academia and industry through laboratory-based certification and training, centralized access to current SOPs, assistance with assay transfer, and participation in the assay's Quality Assurance Plan. One such validated assay is the HIF1α Immunoassay, which is currently in clinical evaluation at NCTVL. Procedures to clinically implement HIF1α analysis in tumor biopsies from patients treated with angiogenesis inhibitors required consideration of many factors including the low abundance and oxygen sensitivity of the analyte. A customized extraction process for HIF1α was developed and optimized using mouse xenograft biopsies. Use of a customized extraction buffer containing 2-hydroxyglutarate, which was degassed to minimize dissolved oxygen, was shown to improve analyte recovery. Optimized extraction procedures also include use of an automated ceramic bead homogenizer to improve both the efficiency and reproducibility of extraction of HIF1α over sonication. The immunoassay procedure uses lyophilized reagents from a commercially available kit and a modified procedure together with quality control specimens that serve to qualify the performance of each run. Finally, pre-defined data analyses and quality control evaluation criteria are used to perform a semi-automated process to analyze data and evaluate acceptability of performance for both the assay run and individual clinical specimens. In total, five SOPs have been developed to define procedures from collection and freezing of the needle biopsies in the radiology suite to data analyses and reporting. Together, these defined procedures are being used to perform PD analyses as key parts of two clinical trial evaluations at the NCI and will be launched to the community once clinical utility is demonstrated. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Ralph E. Parchment, Robert J. Kinders, Sook Ryun Park, Katherine V. Ferry-Galow, Yvonne A. Evrard, Jiuping Ji, Shivaani Kummar, Joseph E. Tomaszewski, James H. Doroshow. Creating clinical target validation groups via quality assured transfer of robust clinical pharmacodynamic (PD) assays from the NCI: clinical implementation of a HIF1α immunoassay in tumor biopsies. [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 1186. doi:10.1158/1538-7445.AM2013-1186

Abstract 1472: Assessment of CTC-based pharmacodynamic biomarkers in NCI clinical trials of targeted anticancer therapeutics

Circulating tumor cells (CTC) potentially represent a substitute for biopsy in assessing drug effects on targets. We have previously reported development and validation of CTC-based pharmacodynamic (PD) biomarker assays that directly examine drug-induced responses (e.g. a DNA damage marker γH2AX, and a tumor suppressor marker p16/INK4a). Here, we summarize our results to date and assess utility of CTC-based biomarkers in patients undergoing clinical trials of targeted anti-cancer therapeutics. Across eight NCI Phase 1 and 2 trials in a variety of solid tumors, the portion of the population statistically evaluable is approximately 30% for all trials; the CTC biomarker statistical evaluation is limited by the total number of CTCs collected from each tube of blood. From data obtained from multiple trials of topoisomerase1 and PARP inhibitors, the γH2AX-positive CTC baseline level was less than 20% in 34 of 50 patients. The fraction of CTCs expressing γH2AX independent of changes in the total CTC count, increased in patients following treatment with different topoisomerase 1 inhibitors alone or in combination with other drugs. Furthermore, correlations between γH2AX levels and overall responses were demonstrated in patients with refractory cancer in a phase II randomized trial of the combination of Veliparib with metronomic oral cyclophosphamide. Pharmacodynamic studies measuring re-expression of the tumor suppressor p16 in response to the epigenetic therapy regimen of 5-fluoro-2-deoxycytidine plus tetrahydrouridine yielded similar results on the number of patients evaluable using CTCs in the NCI intramural patient population. Given the limitations of surface molecule-based CTC methods, we are developing and evaluating an antibody-independent CTC capture technology to analyze biomarkers, starting in small animals using lower blood volumes and in patients with a variety of advanced epithelial and non-epithelial cancers. Our studies indicate that assessment of CTC-based PD biomarkers has value for rapidly assessing proof of mechanism in the clinical development of molecularly targeted anticancer therapeutics. Funded by NCI contract # HHSN261200800001E

Citation Format: Lihua H. Wang, Shivaani Kummar, Thomas D. Pfister, Priya Balasubramanian, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow, Robert J. Kinders. Assessment of CTC-based pharmacodynamic biomarkers in NCI clinical trials of targeted anticancer therapeutics. [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 1472. doi:10.1158/1538-7445.AM2013-1472

Abstract 3341: Development of a multiplex quantitative immunofluorescence assay to evaluate DNA damage repair deficient models in vitro and in vivo and the response to cytotoxic agents

The use of DNA damaging agents remains a mainstay in cancer therapy. Deletions and mutations of key DNA repair proteins in tumor cells, can dictate which of the DNA damage repair (DDR) processes will be critical following exposure to cytotoxic agents. Quantitation of repair pathway activation after drug treatment builds upon our validated qIFA for γH2AX, which scores individual nuclei as positive or negative for that biomarker and calculates the percent of nuclear area positive for γH2AX per imaged field. We have previously reported a prototype multiplex quantitative immunoflourescence assay (qIFA) for biomarkers of active Homologous Recombination (HR) and Nucleotide Excision Repair (NER) pathways. This first qIFA multiplex panel to quantify DDR response has been expanded to include Rad51, a key component of HR in addition to Nbs1 phosphorylated at S343 and γH2AX, both early markers of DNA double strand breaks, and ERCC1, critical to NER response. The assay currently in development uses highly specific antibodies directly conjugated to fluorophores or haptens, thereby eliminating the requirement for cross-absorbed anti-species antibodies. This in turn decreases reagent-caused autofluorescence and greatly simplifies assay QC. Addition of the Definiens analysis software has enhanced analysis of the DNA damage markers, including the ability to count foci per nucleus over an entire image field incorporating thousands of data points at a high-content capacity. This approach is useful in quantifying markers that occupy only a small intranuclear area, such as Rad51 foci, where total nuclear area measurements are less informative. Initial experiments using the multiplex qIFA in vitro were performed on cell lines characterized for DNA damage repair pathway defects. Differences in DNA damage marker Rad51 were observed between BRCA1 expressing and deleted cell lines post-irradiation, demonstrating utility of the marker. Examination of in vivo models revealed a differential activation of DDR pathways in irinotecan-treated xenograft samples of a BRCA-deficient tumor model, demonstrating the importance of using a multiplex approach in monitoring DNA damage. Our results suggest that monitoring markers from multiple DNA repair pathways using a multiplex approach could lead to important insights into global DNA repair responses in tumors. This assay will be expanded to clinical trials that obtain biopsies to assist in the evaluation of combination therapy approaches targeting DDR deficiencies. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: Allison M. Marrero, Scott M. Lawrence, Deborah Wilsker, Priya Balasubramanian, Robert J. Kinders, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow. Development of a multiplex quantitative immunofluorescence assay to evaluate DNA damage repair deficient models in vitro and in vivo and the response to cytotoxic agents. [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 3341. doi:10.1158/1538-7445.AM2013-3341

Abstract 3366: Progress on development of multiplex panel of 15 biomarkers to support development of anticancer drugs targeting apoptosis

Background: The Division of Cancer Treatment and Diagnostics/National Cancer Institute has embarked on development of a multiplex panel of biomarkers of the apoptosis pathway to support proof-of-mechanism studies of investigational agents targeting apoptosis. The selected biomarkers provide quantitative estimate of the commitment, onset, and induction of apoptosis, especially the intrinsic apoptosis pathway. This study updates progress in development of the multiplex panel.

Methods: The immunoassays are built on the Luminex® xMAP multiplex technology platform using magnetic bead capture. The current panel included caspase-3, Lamin-B, Survivin, and markers involved in mitochondrial apoptosis including oligomeric forms of BCL2 family proteins. Calibrators for oligomeric proteins, which are formed in vivo by the non-covalent association of BH3 domain proteins, are developed as synthetic recombinant fusion proteins. The panel is designed for analysis of biomarkers in fractionated cell lysates prepared from flash frozen tumor biopsies. Fit-for-purpose approach is utilized for validation of biomarkers.

Results: We have completed development of 15 biomarkers in the panel. Highly specific and sensitive sandwich immunoassays were designed using capture & labeled antibody pairs and recombinant proteins as calibrators. To overcome complications arising from the multiple readout of some markers (due to protein-protein interactions), the multiplex is grouped in three smaller panels: Panel 1(BAK, BAX, Total Caspase-3, Lamin B(intact +45kDa), & SMAC); Panel 2 (BAD, BAX-BCL-2, BCL-xl, BIM& Mcl-1); and Panel 3 (Active Caspase-3, BCL-xl - BAK, MCL-1 - BAK, phospho-BAD, & Survivin). Specificity of oligomeric forms of biomarkers, BAK-MCL1, BAX-Bcl2, BAK-BCL-xl, and BAX-BAK was achieved by capturing BAK and BAX protein and probing with labeled antibodies specific to MCL-1, BCL-xl, BAK, or BAX. Lysates from tumor biopsy samples can be examined in as little as 50 μg of protein. Specificity of the oligomeric assays was also confirmed by immunoprecipitation and immunoblotting techniques. Fit-for-purpose validation studies are ongoing.

Conclusions: The development phase of the multiplex panel is completed. The panel is now ready for transfer from the development laboratory to clinical laboratories for first-in-human use. In the next phase, the panel will be launched as commercial assay kits. One unique feature of the panel is the ability to measure novel oligomeric biomarkers that mimic alterations in protein-protein interactions. This dynamic readout of intrinsic pathway proteins could provide much needed direct evidence for activity of important classes of molecularly targeted drugs in early clinical trials. Funded by NCI Contract No HHSN261200800001E. First three authors contributed equally to the study.

Citation Format: Apurva K. Srivastava, Soumya Jaganathan, Laurie L. Stephen, Melinda G. Hollingshead, Jason Scull, Robert J. Kinders, Eric Damour, Jennifer Donohue, Adam Layhee, James Mapes, Dominic Esposito, Joseph E. Tomaszewski, Ralph E. Parchment, James H. Doroshow. Progress on development of multiplex panel of 15 biomarkers to support development of anticancer drugs targeting apoptosis. [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 3366. doi:10.1158/1538-7445.AM2013-3366

Abstract 1500: Development of a Quantitative Immunofluorescence imaging assay to assess β-catenin translocation and multiplex biomarkers for Epithelial-Mesenchymal Transition (EMT) in tumor tissues

Background: Wnt/ß-catenin signaling and cadherin-mediated cell adhesion are two processes that promote cell proliferation and epithelial-mesenchymal transition (EMT) of carcinomas. Therapeutic inhibitors of Wnt-induced tumor activation prevent stabilization and nuclear translocation of β-catenin and putatively lead to inhibition of tumor metastasis by upregulation of E-Cadherin and downregulation of N-Cadherin and Vimentin.

Methods: A multiplex quantitative immunofluorescence (qIFA) assay was developed to assess changes in levels of EMT biomarkers (E-Cadherin, N-Cadherin, Vimentin/Pancytokeratin) as well as monitor intracellular localization of β-catenin in tumor tissues. A panel of highly specific antibodies against EMT targets, directly-conjugated to various fluorophores, were optimized for multiplex staining of FFPE tissues using colorectal (CRC) and triple-negative breast (TNBC) cancer cell lines and xenograft tissues as tumor controls for target expression. Rat kidney was used as positive control for endogenous biomarker expression in tissues. Image acquisition was performed with Confocal and Epifluorescence microscopy. Image segmentation and quantitative multiplex analysis were performed using NIS Elements and Definiens Tissue Studio software to obtain total mean integrated signal per biomarker within a tissue region of interest.

Results: Fitness for purpose evaluation of the biomarkers was performed in vitro with several cell lines and compounds to demonstrate nuclear translocation of β-catenin as well as EMT-mediated changes in E- to N-Cadherin ratio. A431 squamous epithelial cell lines treated with Lysophosphatidic acid (LPA) induced Adherens Junction (AJ) dissociation of membrane E-Cadherin and β-catenin while co-treatment with specific inhibitors to glycogen synthase kinase-3β (GSK-3β) induced a 5-fold increase in the nuclear to cytoplasmic mean intensity ratio of β-catenin after 24h. TGFβ-treatment of the NMuMG mouse epithelial cell line induced a significant decrease in E- to N-Cadherin membrane intensity ratio after 48 and 72h in vitro. Studies with human TNBC or APC-mutated CRC mouse xenograft models using HDAC or Src/Abl kinase inhibitors to compare pre- and post-treatment effects on EMT biomarker staining will be presented.

Conclusion: We have developed a quantitative imaging assay that integrates multiplex changes in EMT biomarkers to assay pharmacodynamic activities of potential targeted agents currently in development at the National Cancer Institute (NCI). This assay could also be applied for retrospective analysis of clinical samples to document drug-induced changes in tumor phenotypes. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: Tony Navas, Robert J. Kinders, Karun Mutreja, Scott M. Lawrence, Donna Butcher, Melinda Hollingshead, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow. Development of a Quantitative Immunofluorescence imaging assay to assess β-catenin translocation and multiplex biomarkers for Epithelial-Mesenchymal Transition (EMT) in tumor tissues. [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 1500. doi:10.1158/1538-7445.AM2013-1500

Abstract 1173: Development of calibrators and controls as quality control tools for clinical implementation of quantitative immunofluorescence assays for pharmacodynamic biomarkers of molecular targeted agents in tumor biopsies

The application of robust pharmacodynamic (PD) assays as part of clinical trial design is valuable for confirming putative drug mechanisms in patients. Our group supports the development, validation and clinical implementation of these PD assays including quantitative immunofluorescence (qIFA) measurements in formalin-fixed, paraffin-embedded (FFPE) human tissue biopsies. One such assay is a multiplex qIFA method for evaluating histone H2AX phosphorylated at serine 139 (γH2AX), activated caspase 3 (cCasp3), Ki67, and DAPI (referred to as Rx1-IFA4) in response to DNA-damaging agents. Integral PD quality control tools were developed as part of the Rx1-IFA4 and included xenograft tissue calibrators, which are used as visual and quantitative reference standards representing a range of biomarker expression levels for drug effect on tumor, and mouse testis and jejunum tissues, which are used as positive or negative controls for endogenous tissue expression for each biomarker. Rx1-IFA4 tissue calibrators were prepared with tumor quadrants derived from human breast MDA-MB-231 xenografts treated with vehicle, low, or high doses of a cIAP inhibitor. Xenografts were prescreened for levels of each biomarker, and tissues containing defined ranges of biomarker expression were re-embedded in a block to represent each of the treatment groups. Use of tumor quadrants as opposed to biopsies allows for a large number of calibrator slides to be produced from a single qualified block. Qualification of each lot of calibrator slides includes qIFA analysis of representative slides from which specifications for acceptable ranges of biomarker expression for that lot are determined. Whole fluorescent slide imaging using Aperio® was performed to document distribution patterns of the biomarkers within each tumor quadrant. Staining analysis of control tissues also enabled performance assessment of all assay antibodies applied on each clinical slide without the need for duplicate slides as controls. Application of tissue calibrators and controls to the qIFA assay, as opposed to the more typical use of cell pellet-derived controls provides many advantages. Biomarker expression levels with drug treated cells rarely correlate with expression levels in vivo. Additionally, quantitative image analysis for this assay utilizes image analysis software and custom macros that require the appropriate selection of a representative area of background for each analyzed image and tissue context is critical for accurate quantitation. These quality control tools are effective for monitoring the performance of the qIFA assay across laboratories and clinical assay runs. The first three authors listed contributed to this work equally. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Katherine V. Ferry-Galow, Tony Navas, Scott M. Lawrence, Karun Mutreja, Donna Butcher, Melinda Hollingshead, Ralph Parchment, Joseph E. Tomaszewski, James H. Doroshow, Robert J. Kinders. Development of calibrators and controls as quality control tools for clinical implementation of quantitative immunofluorescence assays for pharmacodynamic biomarkers of molecular targeted agents in tumor biopsies. [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 1173. doi:10.1158/1538-7445.AM2013-1173

Abstract 5544: Development of recombinant transcription factor proteins and antibodies for application in clinical immunoassays

EMT/stem cell transcription factors have been implicated in the differentiation of epithelial cells into mesenchymal cells (epithelial-mesenchymal transitions, EMT) during embryonic development. EMT transitions are also determinants of the progression of carcinomas, and their expression patterns are altered by chemotherapy. Methods for detection and quantitation of these transitions may have clinical importance. Specialized high quality reagents are an absolute prerequisite for formulation of stable, high-performance, clinical immunoassays. A panel of experts in the Division of Cancer Treatment and Diagnosis (DCTD, NCI) and Whitehead Institute (MIT) have identified 12 key targets in EMT/Stem cells, for which there was an unmet need for high quality reagents (SNAIL, SLUG, ZEB1, ZEB2, SOX9, LBX1, FOXC2, FOXQ1, Goosecoid, NANOG, CD133 and FOXO3). Proof of assay analytical performance and stability require both a purified, characterized antibody, and a calibrator molecule suitable for generation of an assay "standard" that may be used in several different contexts. We have developed a strategy to generate, characterize, and validate reagents for 12 EMT/Stem cell targets starting with antigen design and selection to improve the utility and minimize cross-reactivity of the antibodies produced. We have also designed and produced the corresponding recombinant protein material for these targets. For many of these we expressed one or two specific domains that were also tailored to provide maximum utility in target measurement while avoiding cross-reactivity. We have generated rabbit monoclonal antibodies to the transcription factors and tumor stem cell markers for development of pharmacodynamic assays to support both analysis of transcription factor function and for use in clinical trials for new anticancer therapies. Initial screening of rabbit bleed titers and hybridomas was performed using both the designed peptides and recombinant material. We have also tested the leading candidate hybridomas in multiple immunoassays and will present data demonstrating utility of the antibodies in these applications including ELISA, WB, immunoprecipitation and IFA in FFPE tissues. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: Thomas D. Pfister, Lynda J. Dieckman, Robert J. Kinders, Anne Book, Simona Colantonio, Karun Mutreja, Scott M. Lawrence, Amina Aziz, Tara Hiltke, Gordon Whiteley, Ralph E. Parchment, Joseph E. Tomaszewski, Robert A. Weinberg, James H. Doroshow. Development of recombinant transcription factor proteins and antibodies for application in clinical 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 5544. doi:10.1158/1538-7445.AM2013-5544

Abstract 1858: Development of a multiplex panel of biomarkers to assess energy metabolism in cancer

Background: Cancer cells have an altered glucose metabolism, which not only permits them to survive under hypoxic conditions but confers a distinct growth advantage by sustaining higher proliferation rates, invasiveness, and subsequent distant metastasis. This unique difference in glucose metabolism from healthy cells opens up a selective mechanism by which to kill cancer cells, bypassing normal healthy cells. Several enzymes in glucose metabolism are attractive targets for development of first-in-class therapeutic agents. We have undertaken development of a multiplex panel involving biomarkers involved in glucose metabolism to support drug development and to interrogate glycolytic pathway in cancer patients. Methods: The panel includes quantitative determinations of protein levels of hexokinase-2 (HK2), pyruvate kinase isoform-2 (PKM2), lactate dehydrogenase alpha (LDHa), and phosphorylated pyruvate dehydrogenase E1-alpha (phospho-PDHE1a). The sandwich immunoassays were built on the Luminex® xMAP technology platform using MagPlex magnetic beads and cloned proteins are employed as calibrators. The panel is designed to measure protein concentrations in fractionated cell extracts from flash frozen tumor biopsies. Results: We have completed development of three sandwich immunoassays for HK2, PK-M2, and LDHa on Luminex platform. Suitable capture antibodies as well as phycoerythrin labeled detection antibodies have been identified and tested for sandwich formation and multiplexing using recombinant calibrators and cell lysates. The multiplex is currently standardized for optimal assay performance. Known pharmacological modulators (3-bromopyruvate, bortezumib, oxamate, dichloroacetate) of HK2, PKM2, LDHa, and PDHE1a were used in vitro to demonstrate expected directional changes in biomarkers in the panel. Conclusions: We have developed a multiplex panel to measure protein levels of three key molecules involved in energy metabolism in cancer cells. The multiplex panel provides a critical tool, in the clinical setting, to support ongoing therapeutic strategies aimed at targeting the energy provision pathway in cancer patients. Importantly, the panel can be used to survey metabolic phenotype of different tumors to identify type and stage of cancer most susceptible to inhibition of glycolysis. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Meenakshi P. Balakrishnan, Ralph E. Parchment, Melinda G. Hollingshead, Joseph E. Tomaszewski, Robert J. Kinders, James H. Doroshow, Apurva K. Srivastava. Development of a multiplex panel of biomarkers to assess energy metabolism in cancer. [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 1858. doi:10.1158/1538-7445.AM2013-1858

Developing safety criteria for introducing new agents into neoadjuvant trials

New approaches to drug development are critically needed to lessen the time, cost, and resources necessary to identify and optimize active agents. Strategies to accelerate drug development include testing drugs earlier in the disease process, such as the neoadjuvant setting. The U.S. Food and Drug Administration (FDA) has issued guidance designed to accelerate drug approval through the use of neoadjuvant studies in which the surrogate short-term endpoint, pathologic response, can be used to identify active agents and shorten the time to approval of both efficacious drugs and biomarkers identifying patients most likely to respond. However, this approach has unique challenges. In particular, issues of patient safety are paramount, given the exposure of potentially curable patients to investigational agents with limited safety experience. Key components to safe drug development in the neoadjuvant setting include defining a study population at sufficiently poor prognosis with standard therapy to justify exposure to investigational agents, defining the extent and adequacy of safety data from phase I, detecting potentially harmful interactions between investigational and standard therapies, improving study designs, such as adaptive strategies, that limit patient exposure to ineffective agents, and intensifying safety monitoring in the course of the trial. The I-SPY2 trial is an example of a phase II neoadjuvant trial of novel agents for breast cancer in which these issues have been addressed, both in the design and conduct of the trial. These adaptations of phase II design enable acceleration of drug development by reducing time and cost to screen novel therapies for activity without compromising safety.

In vitro exposure of precision-cut lung slices to 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole lysylamide dihydrochloride (NSC 710305, Phortress) increases inflammatory cytokine content and tissue damage

The anticancer drug (2-[4-amino-3-methylphenyl]-5-fluorobenzothiazole lysylamide dihydrochloride) (NSC 710305, Phortress) is a metabolically activated prodrug that causes DNA adduct formation and subsequent toxicity. Preclinically, it was found that hepatic, bone marrow, and pulmonary toxicity presented challenges to developing this drug. An ex vivo precision-cut lung slice (PCLS) model was used to search for concentration dependent effects of NSC 710305 (10, 25, 50, and 100 µM) on cytokine content, protein content, and immuno/histological endpoints. Preparation and culture of PCLS caused an initial spike in proinflammatory cytokine expression and therefore treatment with NSC 710305 was delayed until 48 h after initiating the slice cultures to avoid confounding the response to slicing with any drug response. PCLSs were evaluated after 24, 48, and 72 h exposures to NSC 710305. Reversibility of toxicity due to the 72-h treatment was evaluated after a 24-h recovery period. NSC 710305 caused a concentration-dependent cytokine response, and only the toxicity caused by a 72-h exposure to 25 µM reversed during the 24-h recovery period. Immuno/histological examination and quantitation of tissue protein levels indicated that tissue destruction, ED-1 (activated macrophage) staining, and protein levels were associated with the levels of proinflammatory cytokines in the tissue. In conclusion, the concentration- and time-dependent inflammatory response of PCLS to NSC 710305 preceded relevant tissue damage by a few days. The no-observable adverse effect level (NOAEL) for 24, 48, and 72 h exposures was established as 10 µM NSC 710305.

pAKT expression in paraffin-embedded xenograft tumors after fixation delays and human breast cancer by optimized immunohistochemistry

10603

Background: With progress in targeting PI3K/AKT pathway in the treatment of a wide range of cancers, it is getting more important than ever for optimization of detection method of AKT kinase, a central effector of the pathway, in archived tissues. Recently, we found that pAKT-S473 (pAKT) significantly predicts paclitaxel benefit in breast cancer (JCO 28: 2974, 2010), in which a good analytical and clinical performance of quantitative pAKT immunohistochemistry (IHC) was demonstrated. The current study evaluates pAKT stability in human breast cancer xenograft tumors after delays in fixation, and assesses a detection window following fixation delays with an established cutoff [staining index (SI) > 2]. Methods: Xenograft tumors with high (MDA-MB-468) and intermediate levels (MDA-MB-231) of pAKT were fixed or snapped frozen in 10% neutral-buffered formalin or liquid nitrogen after delays post-excision. pAKT staining was performed in xenograft tumors and 96 cases of human surgical breast tumors by our optimized and traditional IHCs, and Western blot. Results: The mean SIs were 133, 121, 112, 94, 84, and 66 using optimized, and in contrast were 51, 44, 29, 14, 12, and 6.4 on traditional method at 0, 15, 30, 60, 120 and 180 min (2.6-fold by comparing the optimized with the traditional at baseline) in MDA-MB-468 xenograft tumors. pAKT level was ½ by the optimized, similar to the level detected by Western blot, relative to 1/8 of the baseline by the traditional (10.6-fold) at 180 min. The logarithmic decline rate by the optimal was 3.1 times (95% CI, 2.4 - 3.7) less than that of the traditional (normal approximation; 2-sided P < 0.0001). pAKT expression was observed in 38.5% (37/96 ) of surgical breast tumors, comparable to 38% (606/1581) in a large cohort derived from the NSABP B-28 trial. There was little loss of pAKT in MDA-MB-231 xenograft tumors up to 180 min by IHC and Western blot. Conclusions: The optimized pAKT IHC significantly increases the sensitivity of detection with a large window for positivity. It is suitable for use in archived human specimens although it warrants further standardization and validation among research laboratories and perhaps diagnostic laboratories in the future.

Proof of mechanism (POM) in the first-in-human trial of two novel indenoisoquinoline, non-camptothecin topoisomerase I (TOP1) inhibitors

3031

Background: Indenoisoquinolines LMP 400 and LMP 776 form stable DNA-top1 cleavage complexes, have a preference for unique DNA cleavage sites, and are not substrates for ABC transporters compared to camptothecins. We conducted a randomized phase I trial of LMP 400 and LMP 776 in patients (pts) with refractory tumors to establish safety and MTD of LMP 400 and LMP 776 administered IV daily x 5 d, q 28d; determine PK; evaluate TOP1 and γH2AX levels in tumor biopsies (bx); and compare pharmacodynamic responses of LMP400 and LMP776. Methods: Pts had refractory malignancies; ≥ 18 yrs old; KPS > 70%; adequate organ function. DLT: drug-related gr ≥ 3 non-hem or gr 4 hem toxicities during C1. Pts assigned to receive either LMP 400 or LMP 776. Dose level (DL) in mg/m2/day for LMP 776: 1, 2, 3, 4.5 mg; LMP 400: 2.5, 5, 10, 20, 40, 80. Accelerated titration design with one pt per dose level (DL), 100% dose escalation until one DLT or 2 gr 2 toxicities, then 3+3 design. Tumor bx and circulating tumor cells (CTCs) were obtained at baseline and C1D3. Results: Twenty pts accrued to date [LMP 400 (11 pts); LMP 776 (9 pts)]; M/F 7/13; median age 59 (range 32-71 yrs); diagnosis (# of pts): colorectal (10), vaginal adenocarcinoma (1), head and neck (2), bladder (1), melanoma (1), pancreas (1), thyroid (1), small cell lung (1), sarcoma (1), lymphoma (1). DLTs: LMP 400- gr 4 myelosuppression, gr 3 fatigue at DL 6; DL 5 expanded to establish MTD; LMP 776 (DL2)- gr 4 hypercalcemia, no other DLTs, dose escalation continuing. One pt with irinotecan-refractory colon cancer had shrinkage of lung nodules post one cycle of LMP 400. Relative to baseline, 5 of 6 tumor bx demonstrated 20-50% reduction in TOP1 levels (LMP 776); an increase in γH2AX foci in tumor was observed in 2/6 LMP 776 and 1/1 LMP 400 pts. An increase in γH2AX was also observed in hair bulbs (3/3 pts) and CTCs (9/20 pts). PK for LMP 400 and LMP 776: mean T1/2 48 and 36 h; Cl 1.5 and 2.0 L/h/m2; Vc 30 and 31 L/m2, respectively. Conclusions: POM, as assessed by reduction in TOP 1 levels and increase in γH2AX in tumor and CTCs, and preliminary evidence of activity, has been demonstrated in this first-in-human trial of indenoisoquinoline-class of TOP1 inhibitors. Accrual is ongoing.

Abstract 746: Notch-1 expression in human cancer cell lines and solid tumors by validated immunohistochemistry

Notch-1 is a transmembrane receptor whose activation upon ligand binding or calcium depletion leads to translocation of the Notch-1 intracellular domain (NICD) to the nucleus where it activates transcription of Notch target genes. Targeting Notch signaling, such as with inhibitors of γ-secretase that is required for Notch-1 activation, is currently in early clinical development. It is critical to characterize the expression of Notch-1, an important member of Notch family of receptors in human cancers with a validated assay suitable to monitor pharmacodynamic responses to Notch inhibitors and to carry out clinical validation investigation of Notch-1 as predictive/prognostic biomarker. This could improve our understanding of pathobiology of Notch signaling and in turn increase the odds of success of targeting Notch signaling. The aims of this study were to develop an immunohistochemistry assay for Notch-1/NICD (activated Notch-1), and to evaluate expression levels and patterns of Notch-1/NICD in paraffin-embedded tumor samples. Human breast cancer cell lines MCF-7, MDA-MB-231 and MDA-MB-468, and colorectal cancer HCT-116 cells were treated with and without a calcium chelator EDTA for 10 min and embedded in paraffin after formalin fixation. Expression levels and patterns of Notch-1 were examined by Western blot, and immunocytochemistry as well as immunohistochemistry and were quantitated using an Automated Cellular Imaging System. There was an increase in Notch-1/NICD expression in cells treated with EDTA versus without EDTA in MCF-7 (staining index: 28 vs. 10) and MDA-MB-231 (81 vs. 62) cells by immunocytochemistry and confirmed by Western blot. Interestingly, membranous/cytoplasmic Notch-1 was in part translocated into the nucleus in MCF-7 and MDA-MB-468 cells following EDTA treatment, suggesting Notch-1 activation and specific detection of Notch-1 in distinct cellular compartments. In addition, a predominant cytoplasmic/membranous expression of Notch-1 was observed in MDA-MB-231 and HCT-116 cells with and without EDTA treatment. Low to intermediate levels of Notch-1 with a predominantly cytoplasmic localization, relative to moderate to high levels in cell lines, were detected in 13% (6/45), 4% (2/48), 16% (7/45) of tumor cells in carcinomas of the breast, lung, and ovary. Nuclear/cytoplasmic staining of Notch-1 was observed in one case of lung cancer. In addition, Notch-1 expression was found in a significant fraction of endothelial cells of human solid tumors. We have established a fit-for-use immunohistochemistry assay with an antibody that specifically detects Notch-1 in formalin-fixed and paraffin-embedded human tumors. Its application could facilitate the evaluation of pharmacodynamic responses to various Notch targeting agents undergoing clinical development and subsequent clinical validation studies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 746. doi:1538-7445.AM2012-746

Abstract 3616: Validation and fitness testing of a quantitative immunoassay for HIF1α in biopsy specimens

HIF1α is an important marker of hypoxia in human tumors that is altered in a number of cancers, but a reproducible method to determine changes in HIF1α protein expression in human tumor biopsy specimens has not been available. While HIF1α is being used as a pharmacodynamic marker in clinical trials in the NCI (CTEP# 8610, 8856, 8880), an important limitation in measuring the change in HIF1α induced by cancer therapeutic agents is the lability of the protein, in the presence of oxygen, upon collection of the sample. We have devised a method of specimen collection, handling, and extraction that preserves and stabilizes HIF1α levels in tumor biopsies. Degassed collection buffer yielded a significant increase of recovered HIF1α levels compared to the standard method of flash-freezing. The addition of 2-hydroxyglutarate, an inhibitor of prolyl hydroxylase domain enzyme that is involved in the degradation pathway of HIF1α under normoxic conditions, to the collection buffer showed a trend for improved yield of the HIF1α recovery. Sonication and homogenization with ceramic beads were superior to homogenization with metallic beads or tissue grinding. Employing this specimen-handling method allowed validation of a two-site immunoassay for HIF1α quantitation in solid-tissue extracts generated from tumor biopsies. Intra-assay variability was less than 10%, and inter-assay variability was less than 20%. Accuracy, assessed by spike recovery, was 99 +/− 7%. HIF1α readings declined linearly with decreasing sample load over a range of 1 to 10 µg protein per well. Fitness for purpose was demonstrated by quantifying a reduction in HIF1α protein levels following topotecan or indenoisoquinoline NSC 743400 treatment in an A375 xenograft model, followed by assessment of other xenograft models. HIF1α was also demonstrated to be upregulated under low oxygen tension culture conditions in DU145 human prostate cancer cells. Funded by NCI Contract No. HHSN261200800001E.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3616. doi:1538-7445.AM2012-3616

A phase I study of veliparib in combination with metronomic cyclophosphamide in adults with refractory solid tumors and lymphomas

PURPOSE

Oral administration of the alkylating agent cyclophosphamide at low doses, metronomic dosing, is well tolerated, with efficacy in multiple tumor types. PARP inhibition potentiates effects of cyclophosphamide in preclinical models. We conducted a phase I trial of the PARP inhibitor veliparib and metronomic cyclophosphamide in patients with refractory solid tumors and lymphoid malignancies.

EXPERIMENTAL DESIGN

Objectives were to establish the safety and maximum tolerated dose (MTD) of the combination; characterize veliparib pharmacokinetics (PK); measure poly(ADP-ribose) (PAR), a product of PARP, in tumor biopsies and peripheral blood mononuclear cells (PBMC); and measure the DNA-damage marker γH2AX in PBMCs and circulating tumor cells (CTC). Cyclophosphamide was administered once daily in 21-day cycles in combination with veliparib administered once daily for 7, 14, or 21 days.

RESULTS

Thirty-five patients were enrolled. The study treatment was well tolerated, and the MTD was established as veliparib 60 mg with cyclophosphamide 50 mg given once daily. Seven patients had partial responses; an additional six patients had disease stabilization for at least six cycles. PAR was significantly decreased in PBMCs (by at least 50%) and tumor biopsies (by at least 80%) across dose levels (DL); γH2AX levels were increased in CTCs from seven of nine patients evaluated after drug administration.

CONCLUSIONS

The combination of veliparib with metronomic cyclophosphamide is well tolerated and shows promising activity in a subset of patients with BRCA mutations. A phase II trial of the combination compared with single-agent cyclophosphamide is ongoing in BRCA-positive ovarian cancer, triple-negative breast cancer, and low-grade lymphoma.

Advances in using PARP inhibitors to treat cancer

The poly (ADP-ribose) polymerase (PARP) family of enzymes plays a critical role in the maintenance of DNA integrity as part of the base excision pathway of DNA repair. PARP1 is overexpressed in a variety of cancers, and its expression has been associated with overall prognosis in cancer, especially breast cancer. A series of new therapeutic agents that are potent inhibitors of the PARP1 and PARP2 isoforms have demonstrated important clinical activity in patients with breast or ovarian cancers that are caused by mutations in either the BRCA1 or 2 genes. Results from such studies may define a new therapeutic paradigm, wherein simultaneous loss of the capacity to repair DNA damage may have antitumor activity in itself, as well as enhance the antineoplastic potential of cytotoxic chemotherapeutic agents.

Poly(ADP-ribose) polymerase inhibition enhances p53-dependent and -independent DNA damage responses induced by DNA damaging agent

Targeting DNA repair with poly(ADP-ribose) polymerase (PARP) inhibitors has shown a broad range of anti-tumor activity in patients with advanced malignancies with and without BRCA deficiency. It remains unclear what role p53 plays in response to PARP inhibition in BRCA-proficient cancer cells treated with DNA damaging agents. Using gene expression microarray analysis, we find that DNA damage response (DDR) pathways elicited by veliparib (ABT-888), a PARP inhibitor, plus topotecan comprise the G1/S checkpoint, ATM, and p53 signaling pathways in p53-wildtype cancer cell lines and BRCA1, BRCA2 and ATR pathway in p53-mutant lines. In contrast, topotecan alone induces the G1/S checkpoint pathway in p53-wildtype lines and not in p53-mutant cells. These responses are coupled with G2/G1 checkpoint effectors p21(CDKN1A) upregulation, and Chk1 and Chk2 activation. The drug combination enhances G2 cell cycle arrest, apoptosis and a marked increase in cell death relative to topotecan alone in p53-wildtype and p53-mutant or -null cells. We also show that the checkpoint kinase inhibitor UCN-01 abolishes the G2 arrest induced by the veliparib and topotecan combination and further increases cell death in both p53-wildtype and -mutant cells. Collectively, PARP inhibition by veliparib enhances DDR and cell death in BRCA-proficient cancer cells in a p53-dependent and -independent fashion. Abrogating the cell-cycle arrest induced by PARP inhibition plus chemotherapeutics may be a strategy in the treatment of BRCA-proficient cancer.

Abstract A106: Investigation of 5-fluorodeoxycytidine with tetrahydrouracil as a demethylation regimen in solid tumors

Methylation-induced silencing of gene promoters is widely documented in numerous cancer types, and the anti-tumor activity of agents that target this phenomenon has established DNA methyltransferase (DNMT1) as a valid drug target. We have investigated the combination of 5-fluorodeoxycytidine with Tetrahydrouridine (FdCyd + THU) in vitro and in vivo using continuous exposures up to 12 weeks. Supplementation of the medium with Deoxythymidine (10 μM) was required to prevent FdCyd cytotoxicity and allow sufficient time for demethylation to occur. Decitabine was used as the positive control throughout the evaluation. The bladder cancer line EJ6 was sensitive to FdCyd + THU, as evidenced by an increase in cell doubling time, a decrease in LINE1 methylation, and an initial decrease in total DNMT1 concentrations, determined with a newly-developed, quantitative two-site immunoassay. The triple negative breast cancer line MDA-MB-231 was resistant to the regimen, as assessed by all three criteria. The mechanism of this combination regimen in tumor cells isolated from paracentesis specimens from patients enrolled on an NCI-supported Phase 1 clinical trial of FdCyd + THU; and was confirmed by finding changes in both DNMT1 levels and LINE1 methylation. Upregulation of expression of p16 (INK4a), but not GSTP1 or RASSF1, was observed in EJ6 cells following FdCyd + THU by Western blotting. An immunofluorescence assay for p16 expression in circulating tumor cells (CTCs) has been developed and implemented in the Phase 1 trial. The ongoing Phase 2 trial of this regimen will include measurements of DNMT1 and LINE1 methylation in tumor biopsies and p16 in CTCs to directly assess drug effect on the DNMT1 target.

This Research has been funded in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. HHSN261200800001E and NCI RAID Project #266 Grant.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A106.

Abstract C3: Validation and fitness testing of a quantitative immunoassay for HIF1α

HIF1α is an important marker of hypoxia in human tumors that is altered in a number of cancers, but a reproducible method to determine changes in HIF1α protein expression in human tumor biopsy specimens has not been available. HIF1α is being used as a pharmacodynamic marker in a clinical trial of metronomic Topotecan (CTEP# 8610, 9534). However, an important limitation for studying the response of HIF1α to cancer therapeutic agents is the lability of the protein, in the presence of oxygen, upon collection of the sample. We have devised a method of specimen collection, handling and extraction that preserves and stabilizes HIF1α levels in tumor biopsies. Employing this specimen handling method allowed validation of a two-site immunoassay for HIF1α quantitation in solid tissue extracts, such as tumor biopsies. Intra-assay variability was less than 10% and inter-assay variability was less than 20%. Accuracy, assessed by spike recovery, was 100 +/− 10%. HIF1α readings declined linearly with decreasing sample load over a range of 1 to 10 μg protein per well. HIF1α is being used as a pharmacodynamic marker in a clinical trial of metronomic Topotecan, so fitness for purpose was demonstrated by quantifying a reduction in HIF1α protein levels following topotecan treatment of a xenograft model. HIF1α was also demonstrated to be upregulated under low oxygen tension culture conditions in DU145 human prostate cancer cells. The HIF1α immunoassay is currently being transferred to the NCI's National Clinical Target Validation Laboratory for use in support of NCI-sponsored early clinical trials. This Research has been funded with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. HHSN261200800001E.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C3.

Abstract A46: A novel immunoassay (ELISA) for quantitative gamma-H2AX detection and pharmacodynamic monitoring of DNA damage induced by chemotherapeutic agents and PARP inhibitors

A 96-well plate-based enzyme-linked immunosorbent assay (ELISA) for quantifying gamma-H2AX as a biomarker to monitor DNA damage was developed and compared with gamma-H2AX detection by both Western blot (WB) and quantitative immunofluorescence assay (IFA). Using a pair of high-affinity gamma-H2AX antibodies for protein capture and detection and a synthetic peptide calibrator, this chemiluminescence ELISA can quantify gamma-H2AX concentrations as low as 16 pg/mL in crude extracts from cancer cells and solid tumors. The assay has a lower limit of detection of less than 4 pg/mL, upper limit of quantitation of 2000 pg/mL, and coefficient of variation of 20%. Treatments under evaluation using the gamma-H2AX ELISA include the topoisomerase 1 inhibitors topotecan and irinotecan, the apoptosis-inducing biomolecule TRAIL (TNF-related apoptosis-inducing ligand), and ionizing irradiation. The gamma-H2AX ELISA showed utility for drug discovery screening, molecular pharmacology studies, and pharmacodynamic monitoring. In a mouse xenograft model (A375 melanoma), the assay detected dose- and time-dependent changes in gamma-H2AX in response to treatment with irinotecan administrated alone or in combination with the poly(ADP-ribose) polymerase inhibitors ABT-888 (veliparib), AZD-2281 (olaparib), or MK-4827. Overall quantitative correlation was 0.96 between the ELISA and IFA, and 0.66 between ELISA and WB. This assay format should prove useful in situations when higher throughput and accurate quantitation are needed and gamma-H2AX analysis does not need to be restricted to nuclear foci.

Funded, in part, by NCI Contract No. HHSN261201100001E and by the Center for Cancer Research, Intramural Program of the National Cancer Institute.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A46.

Modeling pharmacodynamic response to the poly(ADP-Ribose) polymerase inhibitor ABT-888 in human peripheral blood mononuclear cells

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) facilitates DNA repair and PARP inhibitors may potentiate the effect of DNA-damaging chemotherapeutic agents in patients with cancer. Collection of peripheral blood mononuclear cells (PBMCs) as a surrogate tissue to monitor PARP inhibitor pharmacodynamic effects has several advantages over tumor biopsy collection, including minimally invasive sample collection and the ability to collect multiple samples for longitudinal assessment of drug effect.

METHODOLOGY/PRINCIPAL FINDINGS

Using our previously validated immunoassay for measuring poly(ADP-ribose) (PAR), a product of PARP, in tumor biopsies, we validated a method to quantify PAR levels in PBMCs to monitor the pharmacodynamic effects of the PARP inhibitor ABT-888 in clinical trials. The inter-individual variation in PAR levels was large. No significant difference (P = 0.67) was measured between median baseline PAR levels in 144 healthy volunteers (131.7 pg/1×10(7) PBMCs [interquartile range, 79.5-241.6]) and 49 patients with cancer (149.2 pg/1×10(7) PBMCs [interquartile range, 83.2-249.3]). In addition, PAR levels monitored in healthy volunteers over 3 weeks had considerable intra- and inter-individual variation (range, 44-1073 pg PAR/1×10(7) PBMCs). As a pharmacodynamic model, we quantified changes in PAR levels in human PBMCs treated ex vivo with clinically relevant concentrations of ABT-888. Of 40 healthy volunteer PBMC samples treated with ABT-888, 47.5% had greater than 50% PAR reduction compared to vehicle-treated controls. Considerable inter-sample heterogeneity in PAR levels was measured, and several ABT-888-insensitive samples were identified.

CONCLUSIONS/SIGNIFICANCE

Our results emphasize the importance of using a validated method to measure PAR levels, and support further investigation into the role of PARP in PBMCs. To this end, the PAR immunoassay has been validated for use with PBMCs and incorporated into clinical trials to assess PBMCs as a potential pharmacodynamic surrogate for tumor biopsies in clinical trials of PARP inhibitors.

Phase I study of PARP inhibitor ABT-888 in combination with topotecan in adults with refractory solid tumors and lymphomas

A phase I trial of ABT-888 (veliparib), a PARP inhibitor, in combination with topotecan, a topoisomerase I-targeted agent, was carried out to determine maximum tolerated dose (MTD), safety, pharmacokinetics, and pharmacodynamics of the combination in patients with refractory solid tumors and lymphomas. Varying schedules and doses of intravenous topotecan in combination with ABT-888 (10 mg) administered orally twice a day (BID) were evaluated. Plasma and urine pharmacokinetics were assessed and levels of poly(ADP-ribose) (PAR) and the DNA damage marker γH2AX were measured in tumor and peripheral blood mononuclear cells (PBMC). Twenty-four patients were enrolled. Significant myelosuppression limited the ability to coadminister ABT-888 with standard doses of topotecan, necessitating dose reductions. Preclinical studies using athymic mice carrying human tumor xenografts also informed schedule changes. The MTD was established as topotecan 0.6 mg/m²/d and ABT-888 10 mg BID on days one to five of 21-day cycles. Topotecan did not alter the pharmacokinetics of ABT-888. A more than 75% reduction in PAR levels was observed in 3 paired tumor biopsy samples; a greater than 50% reduction was observed in PBMCs from 19 of 23 patients with measurable levels. Increases in γH2AX response in circulating tumor cells (CTC) and PBMCs were observed in patients receiving ABT-888 with topotecan. We show a mechanistic interaction of a PARP inhibitor, ABT-888, with a topoisomerase I inhibitor, topotecan, in PBMCs, tumor, and CTCs. Results of this trial reveal that PARP inhibition can modulate the capacity to repair topoisomerase I-mediated DNA damage in the clinic.