Abstract LB192: Demethylation, DNA damage and antitumor activity of DNA methyltransferase inhibitors in models with intact and disrupted DNMT1 gene

DNA methyltransferase (DNMT) 1 is an enzyme responsible for maintaining DNA methylation pattern during DNA replication. However, its role on the methylation of tumor suppressor genes and DNA damage in relation to antitumor activity of DNMT inhibitors remains controversial. Here, we investigated the effects of DNMT inhibitors in human colorectal and breast cancer cell lines and animal models with intact (DNMT1+/+) and disrupted DNMT1 (DNMT1-/-) gene. Treatment with 5 µM of 4’-thio-5-aza-2’-deoxycytidine (aza-TdC), decitabine and azacytidine all inhibited DNMT1 expression and cell growth (94.0%/97.1%, 39.9%/58.6% and 69.2/91.3), and induced apoptosis (66.9%/62.5%, 30.9%/23.8% and 66.2/43.1%) in DNMT1+/+ HCT116/MCF7 cells; in contrast, the DNMT inhibitors had less/little activities in DNMT1-/- HCT116/MCF7 cells (P<0.001 each). γH2AX and G2/M cell-cycle arrest were induced by the inhibitors and greater degree of induction was produced by aza-TdC than decitabine in DNMT1+/+ cells (P<0.001), with activation of checkpoint kinase 1 and upregulation of p21. Both demethylation and increased acetylation of CDKN2A and CDKN2B gene promoters together with re-expression of p16INK4A and p15INK4B proteins were detected in DNMT1-/- versusDNMT1+/+ (demethylation only) cells upon exposure to decitabine for 72h. Compared with saline treatment, tumor growth was significantly inhibited by aza-TdC (90%; n=18 mice) and decitabine (62%; n=18) in DNMT1+/+ colorectal xenograft tumors, alongside decreasing expression of DNMT1 (51% and 44%) and an increase in p21 (85% and 48%). Similarly, tumor growth delays (86%; n=15 and 57%; n=14) were associated with the reduction of DNMT1 and augmentation of p21 in bladder PDX tumors. The findings suggest that DNMT inhibitors induce DNA damage and higher anti-tumor activity of aza-TdC is proportional to a greater magnitude of induction of DNA damage, p21 and cell cycle arrest without reactivating the expression of p16INK4A and p15INK4B. The gene re-expression coupled to demethylation and acetylation corresponds to the less anti-tumor activity by decitabine in DNMT1-/- cells. Thus, it is the DNA damage effects, rather than re-expression of the tumor suppressors, that are associated with antitumor activity of the DNMT inhibitors in cancer cells and/or xenograft and PDX tumors.

Citation Format: Angelo B. Laranjeira, Melinda Hollingshead, Dat Nguyen, Robert Kinders, Michael Difilippantonio, James H. Doroshow, Sherry X. Yang. Demethylation, DNA damage and antitumor activity of DNA methyltransferase inhibitors in models with intact and disrupted DNMT1 gene [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB192.

Multiplex Tissue Imaging Harmonization: A Multicenter Experience from CIMAC-CIDC Immuno-Oncology Biomarkers Network

PURPOSE

The Cancer Immune Monitoring and Analysis Centers - Cancer Immunologic Data Commons (CIMAC-CIDC) network supported by the NCI Cancer Moonshot initiative was established to provide correlative analyses for clinical trials in cancer immunotherapy, using state-of-the-art technology. Fundamental to this initiative is implementation of multiplex IHC assays to define the composition and distribution of immune infiltrates within tumors in the context of their potential role as biomarkers. A critical unanswered question involves the relative fidelity of such assays to reliably quantify tumor-associated immune cells across different platforms.

EXPERIMENTAL DESIGN

Three CIMAC sites compared across their laboratories: (i) image analysis algorithms, (ii) image acquisition platforms, (iii) multiplex staining protocols. Two distinct high-dimensional approaches were employed: multiplexed IHC consecutive staining on single slide (MICSSS) and multiplexed immunofluorescence (mIF). To eliminate variables potentially impacting assay performance, we completed a multistep harmonization process, first comparing assay performance using independent protocols followed by the integration of laboratory-specific protocols and finally, validating this harmonized approach in an independent set of tissues.

RESULTS

Data generated at the final validation step showed an intersite Spearman correlation coefficient (r) of ≥0.85 for each marker within and across tissue types, with an overall low average coefficient of variation ≤0.1.

CONCLUSIONS

Our results support interchangeability of protocols and platforms to deliver robust, and comparable data using similar tissue specimens and confirm that CIMAC-CIDC analyses may therefore be used with confidence for statistical associations with clinical outcomes largely independent of site, antibody selection, protocol, and platform across different sites.

Abstract 6495: Development of robust and reproducible controls to support clinical implementation of quantitative immunofluorescence assays for pharmacodynamic biomarkers

Robust pharmacodynamic (PD) assays are valuable to confirm putative drug mechanisms and downstream effects in support of early phase clinical trials. Evolving methods to achieve consistent performance across patients, clinical trials, and laboratories is critical for the success of clinical pharmacodynamic measurements. We have developed integral quality control tools to support clinical implementation of quantitative multiplex immunofluorescence assays (qmIFAs) that include xenograft tissue reference calibrators. These reference slides help to provide confirmation that the pharmacodynamic assay is reporting biomarker levels within designated target ranges with expected subcellular localization, helping to control for run-to-run issues with the assay procedures, reagents, or equipment; however, significant challenges are faced in producing these key reagents. Compared to conventional cell pellets, xenograft controls require more time, expense and specialized facilities; however, the tumor tissues are much more representative of the heterogeneity found in clinical biopsies. The challenges associated with xenograft controls include tissue and biomarker variability attributed to necrotic areas, fixation artifacts, and variable drug distribution. During our qualification process, xenografts undergo multiple rounds of selection and analysis to identify specimens that exhibit good tissue quality, adequate regions of interest (ROI), and appropriate target signal levels to support the intended biomarker measurements. Slide lots are produced, qualified, and stored in a manner that ensures adequate lot sizes, robust and reproducible slide to slide performance, and appropriate shelf life. Xenograft tissue reference standards representing a range of basal or drug-induced biomarker expression in appropriate models have been developed for several informative PD markers including Epithelial Mesenchymal Transition (EMT) markers such as E-Cadherin, Vimentin, and Beta-Catenin; DNA damage response markers γH2AX, pNBS1 and Rad51; apoptosis induction markers for colocalized γH2AX/cleaved Caspase 3; and the cell cycle markers pY15cdk and pHH3 among others and have been used as important tools to support ongoing clinical pharmacodynamic analyses of research biopsies at the NCI and other institutions (PMIDs 25964244, 29682208, 30792217, 31732654). In summary, generalized methods and workflows that will be made public have been developed by the NCI to optimize the production of qualified reference slide lots of sufficient reproducibility, stability, and quantity to support ongoing NCI-supported clinical trial pharmacodynamic assays for several key biomarkers. Funded by NCI Contract No HHSN261200800001E.

Citation Format: Gabriel J. Benton, Katherine V. Ferry-Galow, Victor E. Lonsberry, Manisha Mohandoss, Howard Stotler, Debbie Trail, Kyle Georgius, Melinda Hollingshead, Deborah Wilsker, Robert Kinders, James H. Doroshow, Ralph E. Parchment. Development of robust and reproducible controls to support clinical implementation of quantitative immunofluorescence assays for pharmacodynamic biomarkers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6495.

Abstract LB-107: TET2/DNMT3A mutations and exceptional response to novel epigenetic agent in human malignancies

Background: Challenges remain on the selection of patients who potentially respond to a class of drugs that target the epigenetics for cancer treatment. This study aims to investigate TET2/DNMT3A mutations, their role on prognosis, and relation between the mutations and antitumor activity of a novel epigenetic agent in multiple human cancer cell lines and animal models. Methods: TET2/DNMT3A mutation data in human malignancies were obtained from cBioPortal. Eighteen cancer cell lines and multiple mouse models bearing representative human solid tumors were subjected to 4'-thio-2'-deoxycytidine (T-dCyd) or saline treatment. Gene mutations were examined by whole exome and/or Sanger sequencing in these cell lines. Pharmacodynamic modulation of specific gene expression was analyzed in xenograft tumor samples by immunohistochemistry. Results: TET2 and DNMT3A were frequently mutated in angioimmunoblastic/peripheral T-cell lymphomas, several types of leukemias and cutaneous squamous cell carcinoma, and mutated in lung, breast, skin, and kidney cancers. T-dCyd significantly reduced cell survival in lung NCI-H23, breast BT549, melanoma SKMEL5 and renal ACHN cancer cells that harbor deleterious TET2 and nonsynonymous DNMT3A mutations compared to 14 lines without such pattern of alterations (P = 0.006; 2-sided T-test). Anti-tumor effect was validated in vivo; T-dCyd significantly inhibited tumor growth in mice with TET2/DNMT3A mutation-positive tumors. Histological evaluation revealed a near eradication of tumor cells by T-dCyd in NCI-H23 xenografts. T-dCyd administrations led to a remarkable and persistent p21Waf1/Cip1 increase during treatment (P < 0.0001). In contrast, little activity was observed in xenograft models without this pattern of gene mutations. Conclusions: Cancer cells and animal models examined with TET2 and DNMT3A-mutant genotype are sensitive to T-dCyd treatment.

Citation Format: Sherry X. Yang, Larry Rubinstein, Dat Nguyen, Angelo B. Larenjeira, Robert Kinders, Michael Difilippantonio, James H. Doroshow. TET2/DNMT3A mutations and exceptional response to novel epigenetic agent in human malignancies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-107.

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

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

Abstract CT316: A phase I trial of oral TRC102 (methoxyamine HCl) in combination with temozolomide (TMZ) in patients with relapsed solid tumors

Background: Base excision repair (BER), one of the pathways of DNA damage repair, has been implicated in chemoresistance. TRC102 acts through a novel mechanism to inhibit BER and cause DNA strand breaks, potentiating the antitumor activity of TMZ in preclinical models. We conducted a phase I trial of TRC102 in combination with TMZ to determine the safety, tolerability, and maximum tolerated dose of the combination; to evaluate the pharmacokinetics (PK) of each agent alone and in combination; and to assess DNA damage response (percent nuclear area of γH2AX foci) in circulating tumor cells (CTCs).

Methods: Eligible pts were required to have refractory advanced solid tumors that had progressed following standard therapy; ≥ 18 yrs of age; ECOG PS 0-2; and adequate organ function. TRC102 and TMZ were administered orally once daily, D1-5 of q28d cycles; Starting dose level (DL 1) was TRC102 25 mg and TMZ 125mg/m2. Accrual to DL6 (TRC102 125 mg; TMZ 150 mg/m2) is ongoing. CTCs were obtained during C1 and on C2D1. Blood samples for PK analysis were obtained during C1.

Results: Twenty pts have been enrolled to date; median age 59 yrs (range 45-78 yrs); median # of prior therapies: 3.5 (1-9); Dx: GI (6), H&N (4), breast (3), GYN (3), lung (2), soft tissue sarcoma (2). Fourteen pts are evaluable for response; 2 partial responses by RECIST have been observed to date (≥ 6 cycles; NSCLC and granulosa cell tumor of the ovary). Grade 3/4 toxicities (#pts): neutropenia (2), thrombocytopenia (1), lymphopenia (1), anemia (1), leucopenia (1), hypophosphatemia (1). PK in combination was similar to single agent PK reported for both drugs, with no evidence of a PK interaction. TRC102 levels required for preclinical activity (50ng/mL) were achieved at DL1. T1/2 of TRC102 was 26 hr. CTC analysis is ongoing.

Conclusions: Combination of TRC102 with TMZ is well tolerated and clinical activity was observed with 2 partial responses to date. MTD has not been reached; accrual is ongoing. Paired tumor biopsies to assess for evidence of DNA damage response and apoptosis are planned at the MTD in the expansion phase.

Citation Format: Woondong Jeong, Khanh Do, Alice Chen, Jennifer Zlott, Lamin Juwara, Yvonne Horneffer, Robert Kinders, Lihua Wang, Priya Balasubramanian, Larry Anderson, Elad Sharon, Howard Streicher, Richard Piekarz, Barbara Conley, Jerry Collins, James H. Doroshow, Shivaani Kummar. A phase I trial of oral TRC102 (methoxyamine HCl) in combination with temozolomide (TMZ) in patients with relapsed solid tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT316. doi:10.1158/1538-7445.AM2015-CT316

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

Implementation of validated pharmacodynamic assays in multiple laboratories: challenges, successes, and limitations

There is a "life cycle" of pharmacodynamic (PD) biomarker assays that guides the development and clinical implementation in our laboratories. The well-recognized elements of analytical assay validation and demonstration of fitness-for-purpose of the biomarker, specimen collection, handling, and assay methods are only a part of the required activities. Assay transfer across laboratories and testing on actual human clinical specimens are vital for understanding assay performance and robustness. In our experience, this patient specimen-centered approach has required assay method modifications, some unexpected, but which were critical to successful implementation in clinical trials. In addition, dispersing assays throughout the National Cancer Institute's clinical trials network has required the development of calibrator and control materials as well as formal training courses for smooth implementation. One measure of success of this approach has been that a number of the assays developed at NCI's Frederick National Laboratory have ultimately reached the stage of commercialization, enabling wide accessibility of the PD biomarker assays by the research community. See all articles in this ccr focus section, "Progress in pharmacodynamic endpoints."

Abstract 2416: Weekly EZN-2208 (pegylated SN-38) in combination with bevacizumab in patients with refractory solid tumors

Background: Anti-angiogenic therapies such as bevacizumab (Bev) have been shown to up-regulate hypoxia-inducible factor-1α (HIF-1α), a possible mechanism of resistance. Camptothecin analogues, including SN-38, have been shown to reduce the expression and transcriptional activity of HIF-1α in preclinical models. Thus, co-administration of pegylated SN 38 (EZN 2208) could offset the induction of HIF-1α following administration of Bev, resulting in synergistic anti-tumor effects. We are conducting a trial of the combination of EZN 2208 (E) with Bev in patients with refractory solid tumors to determine the safety and tolerability of the combination, and to evaluate modulation of HIF-1α protein in tumor biopsies following administration of study drugs. Methods: Eligible pts have refractory advanced solid tumors that have progressed following standard therapy; ≥ 18 yrs of age; ECOG PS 0-2; adequate organ function. Bev at 5mg/kg is administered on D-7 and D15 for cycle 1 only and on D1, 15 for each subsequent cycle; q28d cycles. E(9mg/kg) is administered on D1, 8, and 15. Tumor biopsies and dynamic contrast enhanced MRI (DCE-MRI) are obtained on D1 prior to EZN administration (7 days post Bev) and on C2D15 post Bev and E. An additional DCE-MRI is also performed at baseline prior to Bev on D-7. Tumor biopsies are analyzed for HIF-1α protein levels using a validated immunoassay, and HIF-1α response genes, Hexokinase 2(HK), vascular endothelial growth factor A(VEGF), pyruvate dehydrogenase kinase, isozyme 1(PDK1), carbonic anhydrase IX(CA9), solute carrier family 2 (GLUT1), are assessed using RTPCR.

Results: Twelve pts have been enrolled to date; median age 50 (range 27-76 yrs); median # prior therapies 3 (1-6); Dx: Soft tissue sarcoma (4), colorectal cancer (2), parotid gland cancer (1), malignant hurthle cell tumor (1), HCC (1), melanoma (1), gastrointestinal stromal tumor (1), Head and neck cancer (1). Grade 3/4 toxicities (#pts): neutropenia (8), leucopenia (3), lymphopenia (2), hypertension (1). Eight pts are evaluable for response; prolonged stable disease was observed in 2 pts: HCC 16 cycles, desmoplastic round cell tumor 7 cycles. HIF-1α protein and mRNA levels of HIF-1α dependent genes were assessed in 5 pts who had paired biopsies. Reduction in HIF-1α protein levels compared to baseline (post Bev alone) was seen in 4 of 5 pts (range 24% - 64%), with evidence of modulation of mRNA in 3 of 5 pt tumors evaluated. Quantitative analysis of DCE MRI from 3 pts revealed changes in Ktrans and kep maps following drug administration. Correlation of observed changes with tumor response is ongoing.

Conclusions: This clinical trial provides preliminary proof of mechanism demonstrating modulation of HIF-1α levels in tumors following administration of a camptothecin analog, EZN 2208. Accrual is ongoing to establish safety, efficacy, and further proof of target modulation.

Citation Format: Woondong Jeong, Sook Ryun Park, Annamaria Rapisarda, Michelle Eugeni, Robert Kinders, Alice Chen, Giovanni Melillo, Baris Turkbey, James H. Doroshow, Shivaani Kummar. Weekly EZN-2208 (pegylated SN-38) in combination with bevacizumab in patients with refractory solid tumors. [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 2416. doi:10.1158/1538-7445.AM2013-2416

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.

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.

The statistics of phase 0 trials

The PD-driven phase 0 trial is a new form, designed to be a first-in-man study, often of a new agent, conducted to assess drug effect on a molecular target, by means of a pharmacodynamic (PD) assay, in a very small number (10-15) of patients. Such a study is meant to be a proof of principle trial to determine whether the agent yields the PD effect predicted by pre-clinical studies. The dosage is meant to be pharmacologically active, but is neither toxic nor likely to yield clinical benefit. Such a trial may be used to serve as a very early test of an agent's biologic effect, allowing for early weeding out of ineffective agents, or as an early means of determining the most promising of competing analogue agents. This manuscript will present designs for such PD-driven studies that are statistically efficient and rigorous, focusing on non-comparative trials. The phase 0 trial promises to become an increasingly important tool for facilitating and speeding the development of new therapeutic agents, particularly in oncology.

Abstract 4207: Pharmacodynamic comparisons of novel cryobiopsy instrumentation compared to standard techniques through comparative oncology modeling

The development of novel and targeted cancer drugs requires innovative clinical trial designs to define drug (pharmacokinetic) and host (pharmacodynamic) relationships early in the development process. For most new cancer agents there is increased emphasis on pharmacodynamic (PD) endpoints measured in tumor and surrogates as biomarkers of response. Accordingly, novel tissue collection procedures and instruments are needed to ensure that PD endpoint assessments are representative of their actual in vivo “state”. The Cassi Rotational Core Biopsy Device (Cryobiopsy) (Sanarus Medical, Inc, Pleasanton, California) is a biopsy instrument capable of incisional tissue collection and simultaneous freezing. In rodent xenograft models it demonstrated superiority in consistency for tumor analyte detection compared to traditional biopsy techniques. Whether this value would translate to the clinical setting was unknown. Use of naturally occurring cancers in pet dogs provides a model system to validate and optimize instrumentation techniques prior to use in human trials. A prospective clinical trial in dogs with lymphoma was conducted through the National Cancer Institute-Comparative Oncology Trials Consortium (NCI-COTC) to 1) determine if Cyrobiopsy provides sample quality advantages over conventional tru-cut, and open biopsy procedures, and 2) validate a “practice setting” Cryobiopsy Standard Operating Procedure (SOP) that could be followed by multiple users providing consistent high-quality biopsy samples. Ten dogs with newly diagnosed lymphoma enrolled. Cryobiopsy and tru-cut samples were collected in each patient from two lymph nodes in three planes via alternating techniques. A whole lymph node was then removed via excisional biopsy from the same dog. No adverse events were reported with Cryobiopsy or standard biopsy methods. The SOP for cryobiopsy collection of tissues was successfully implemented in a relevant clinical setting. Cryobiopsy collected samples successfully preserved target phospho-proteins (p-AKT: tAKT, p-ERK: tERK, p-MEK: tMEK) collected from tumor tissue. No difference in phospho-protein detection by Western was seen across biopsy techniques. In conclusion, this effort highlights the utility of the comparative approach to model medical device evaluation and PD biomarker assay validation in the clinical theatre.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4207.

Exon array analyses across the NCI-60 reveal potential regulation of TOP1 by transcription pausing at guanosine quartets in the first intron

Because topoisomerase 1 (TOP1) is critical for the relaxation of DNA supercoils and because it is the target for the anticancer activity of camptothecins, we assessed TOP1 transcript levels in the 60 cell line panel (the NCI-60) of the National Cancer Institute's anticancer drug screen. TOP1 expression levels varied over a 5.7-fold range across the NCI-60. HCT116 colon and MCF-7 breast cancer cells were the highest expressers; SK-MEL-28 melanoma and HS578T breast carcinoma cells were the lowest. TOP1 mRNA expression was highly correlated with Top1 protein levels, indicating that TOP1 transcripts could be conveniently used to monitor Top1 protein levels and activity in tissues. Assessment of the TOP1 locus by array comparative genomic hybridization across the NCI-60 showed copy numbers ranging from 1.71 to 4.13 and a statistically significant correlation with TOP1 transcript levels (P < 0.01). Further analyses of TOP1 expression on an exon-specific basis revealed that exon 1 expression was generally higher and less variable than expression of the other exons, suggesting some form of transcriptional pausing regulation between exons 1 and 2. Accordingly, we found the presence of multiple evolutionarily conserved potential G-quadruplex-forming sequences in the first TOP1 intron. Physicochemical tests for actual quadruplex formation by several of those sequences yielded quadruplex formation for two of them and duplex formation for one. The observations reported here suggest the hypothesis that there is a conserved negative transcription regulator within intron 1 of the TOP1 gene associated with a quadruplex-prone region.

Abstract C149: Exon array analyses across the NCI-60 reveals potential regulation of TOP1 by transcription pausing at guanosine quartets in the first intron

Because Topoisomerase I (TOP1) is critical for the relaxation of DNA supercoils and because it is the target for anticancer activity of camptothecins, we assessed TOP1 transcript levels in the 60 cell line panel (the NCI-60) of the National Cancer Institute's anticancer drug screen. TOP1 expression levels varied over a 5.7-fold range across the NCI-60. HCT116 colon and MCF-7 breast cancer cells were the highest expressers; SK-MEL-28 melanoma and HS578T breast carcinoma cells were the lowest. TOP1 mRNA expression was highly correlated with Top1 protein levels, indicating that TOP1 transcripts could be conveniently used to monitor Top1 protein levels and activity in tissues. Assessment of the TOP1 locus by array comparative genomic hybridization across the NCI-60 showed copy numbers ranging from 1.71 to 4.13 and a statistically significant correlation with TOP1 transcript levels (p&lt;0.01). Further analyses of TOP1 expression on an exon-specific basis revealed that exon 1 expression appeared to be generally higher, and less variable than the other exons, suggesting some form of transcriptional pausing regulation between exons one and two. Accordingly, we found the presence of multiple evolutionarilly-conserved potential G-quadruplex-forming sequences in the first TOP1 intron. Physico-chemical tests for actual quadruplex formation by several of those sequences yielded quadruplex formation for two of them and duplex formation for one. The observations reported here suggest the hypothesis that there is a conserved negative transcription regulator within intron 1 of the TOP1 gene, and the regulator is a quadruplex-prone region.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C149.

Phase 0 clinical trial of the poly (ADP-ribose) polymerase inhibitor ABT-888 in patients with advanced malignancies

PURPOSE

We conducted the first phase 0 clinical trial in oncology of a therapeutic agent under the Exploratory Investigational New Drug Guidance of the US Food and Drug Administration. It was a first-in-human study of the poly (ADP-ribose) polymerase (PARP) inhibitor ABT-888 in patients with advanced malignancies.

PATIENTS AND METHODS

ABT-888 was administered as a single oral dose of 10, 25, or 50 mg to determine the dose range and time course over which ABT-888 inhibits PARP activity in tumor samples and peripheral blood mononuclear cells, and to evaluate ABT-888 pharmacokinetics. Blood samples and tumor biopsies were obtained pre- and postdrug administration for evaluation of PARP activity and pharmacokinetics. A novel statistical approach was developed and utilized to study pharmacodynamic modulation as the primary end point for trials of limited sample size.

RESULTS

Thirteen patients with advanced malignancies received the study drug; nine patients underwent paired tumor biopsies. ABT-888 demonstrated good oral bioavailability and was well tolerated. Statistically significant inhibition of poly (ADP-ribose) levels was observed in tumor biopsies and peripheral blood mononuclear cells at the 25-mg and 50-mg dose levels.

CONCLUSION

Within 5 months of study activation, we obtained pivotal biochemical and pharmacokinetic data that have guided the design of subsequent phase I trials of ABT-888 in combination with DNA-damaging agents. In addition to accelerating the development of ABT-888, the rapid conclusion of this trial demonstrates the feasibility of conducting proof-of-principle phase 0 trials as part of an alternative paradigm for early drug development in oncology.

An enzyme-linked immunosorbent poly(ADP-ribose) polymerase biomarker assay for clinical trials of PARP inhibitors

Many established cancer therapies involve DNA-damaging chemotherapy or radiotherapy. The DNA repair capacity of the tumor represents a common mechanism used by cancer cells to survive DNA-damaging therapy. Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme that is activated by DNA damage and has critical roles in DNA repair. Inhibition of PARP potentiates the activity of DNA-damaging agents such as temozolomide, topoisomerase inhibitors and radiation in both in vitro and in vivo preclinical models. Recently, several PARP inhibitors have entered clinical trials either as single agents or in combination with DNA-damaging chemotherapy. Because PARP inhibitors are not cytotoxic, a biomarker assay is useful to guide the selection of an optimal biological dose. We set out to develop an assay that enables us to detect 50% PAR reduction in human tumors with 80% power in a single-plate assay while assuring no more than a 10% false-positive rate. We have developed and optimized an enzyme-linked immunosorbent assay (ELISA) to measure PARP activity that meets the above-mentioned criterion. This robust assay is able to detect PAR levels of 30-2000 pg/ml in both tumor and peripheral blood monocyte samples. In a B16F10 mouse syngeneic tumor model, PARP inhibitor ABT-888 potentiates the effect of temozolomide in suppressing tumor growth, and PARP activity is greatly reduced by ABT-888 at efficacious doses. In summary, the ELISA assay described here is suitable for biomarker studies in clinical trials of PARP inhibitors.

Designing phase 0 cancer clinical trials

Phase 0 trials are designed primarily to evaluate the pharmacodynamic and/or pharmacokinetic properties of selected investigational agents before initiating more traditional phase I testing. One of the major objectives of phase 0 trials is to interrogate and refine a target or biomarker assay for drug effect in human samples implementing procedures developed and validated in preclinical models. Thus, close collaboration between laboratory scientists and clinical investigators is essential to the design and conduct of phase 0 trials. Given the relatively small number of patients and tissue samples, showing a significant drug effect in phase 0 trials requires precise and reproducible assay procedures and innovative statistical methodology. Furthermore, phase 0 trials involving limited exposure of a study agent administered at low doses and/or for a short period allow them to be initiated under the Food and Drug Administration exploratory investigational new drug guidance with less preclinical toxicity data than usually required for traditional first-in-human studies. Because of the very limited drug exposure, phase 0 trials offer no chance of therapeutic benefit, which can impede patient enrollment, particularly if invasive tumor biopsies are required. The challenges to accrual are not insurmountable, however, and well-designed and executed phase 0 trials are feasible and have great potential for improving the efficiency and success of subsequent trials, particularly those evaluating molecularly targeted agents.

Poly-adeninosinediphosphate-ribose polymerase inhibitors as sensitizers for therapeutic treatments in human tumor and blood mononuclear cells

14024

Background: Poly(ADP-ribose) (PAR) polymerase-1 (PARP-1) is a molecular sensor of DNA breaks that facilitates DNA repair and controls genomic stability. Treatment with single doses of ABT-888, a novel potent PARP-1 inhibitor, reduced PAR levels in peripheral blood mononuclear cells (PBMCs) and tumor biopsies in an on-going Phase-0 trial at the NIH Clinical Center. As a corollary to this study, we investigated whether ABT-888 can act as a sensitizer for radiation therapy and chemotherapy in human cancer cell culture, xenograft tumors and PBMCs to support future combination clinical trials. Methods: Inhibition of PARP-1 by ABT-888 was determined by a quantitative PAR chemiluminescence immunoassay validated for the Phase 0 trial. Since gamma-H2AX (?-H2AX) is a marker of DNA damage, we also developed and validated ?H2AX assays to monitor the effects of PARP-1 inhibition during treatment with Topo I inhibitors and radiation. Human monocytic leukemia (THP-1) and breast carcinoma (MCF-7) cell lines were treated with Topo I inhibitors including indenoisoquinoline, camptothecin and topotecan or irradiated with 0.5 to 10 Gy in the presence of ABT 888. We further evaluated these effects in human blood ex vivo to confirm the observations made in cell culture. Results: We found that ABT-888 inhibited PAR, but did not significantly increase DNA damage. Combination of ABT-888 with a Topo I inhibitor produced over 275% increase of DNA damage in THP-1 leukemia cells compared to indenoisoquinoline alone. ?H2AX foci per cell were 9.5 ± 0.8 in MCF-7 treated with 0.5 Gy/50 nM ABT-888 in comparison to 4.0 ± 0.6 with radiation alone. When whole blood was treated in the presence of ABT-888, camptothecin- induced DNA damage in PBMCs was also increased 2–3 fold, with maximum ?H2AX expression at 2 hours post treatment. Conclusions: We conclude that ABT-888 is a highly potent PARP-1 inhibitor that can enhance the DNA damaging effects of chemotherapy and radiation therapy of human cancer. Funded by NCI Contract N01-CO-12400.

No significant financial relationships to disclose.

Inhibition of poly (ADP-ribose) polymerase (PARP) by ABT-888 in patients with advanced malignancies: Results of a phase 0 trial

3518

Background: Inhibition of PARP activity sensitizes tumor cells to the effects of DNA damaging agents. We conducted a phase 0 pharmacokinetic (PK) and pharmacodynamic (PD) study of ABT-888, an oral inhibitor of PARP. Methods: The objectives were to determine a dose range at which ABT-888 inhibits PARP in tumor tissue and in peripheral blood mononuclear cells (PBMC); and the PK of ABT-888. Patients with advanced solid tumors refractory to at least one line of therapy were eligible; patients with CLL or follicular lymphomas were also eligible if standard therapy was not currently indicated. A single oral dose of ABT-888 was administered per patient, dose escalations were planned in cohorts of 3 patients each (10 mg, 25 mg, 50 mg, 100 mg, and 150 mg). PBMC and tumor sampling were performed before and after drug administration for real time PK and PD analyses. All patients underwent PBMC sampling; tumor biopsies were planned once significant inhibition of PARP activity in PBMCs was seen in 1 of 3 patients in a cohort or plasma Cmax of 210 nM was achieved in at least 1 patient. Tumor biopsies were performed at baseline in the week prior to drug administration and then 3–6 hours post drug administration. Significant inhibition of PARP activity was defined as at least 0.69 reduction on the log scale, which also satisfied statistical significance. Results: A total of 6 patients have been studied so far, 3 each for the 10 mg and 25 mg cohorts. No treatment related adverse events have been observed. Target Cmax was exceeded in the first cohort, all patients in the next cohort underwent tumor biopsies in addition to PBMC sampling. A trend towards inhibition of PARP activity in PBMCs was observed in the first cohort. Significant inhibition of PAR levels was observed in tumor biopsies from all 3 patients in the second cohort (92%, 99%, 100% reductions respectively, as compared to baseline). Greater than 85% reduction of PAR levels was observed in PBMCs from 2 of the 3 patients in the second cohort (one patient was not evaluable). Conclusions: ABT-888 is orally bioavailable and inhibits PARP activity in PBMCs and tumor cells. Target assay feasibility was established in human samples. Funded in part by NCI Contract N01-CO-12400

No significant financial relationships to disclose.

Quantitative immunohistochemical detection of gamma-H2AX in paraffin-embedded human tumor samples at National Clinical Target Validation Laboratory

10565

Background: DNA double-strand breaks (DSBs) caused by exposure to DNA damaging agents initiate phosphorylation of histone H2AX to form gamma-H2AX, which is considered a surrogate marker of DSBs. However, it is a challenge to quantitatively measure gamma-H2AX in clinical samples such as tumor biopsies. The aim of this study was to develop an immunohistochemical detection method for gamma-H2AX and to quantitatively evaluate the levels of gamma-H2AX in paraffin-embedded tumor samples. Methods: Human breast cancer MCF-7 cells were treated with the topoisomerase I inhibitor irinotecan at 1 μM or vehicle for 1 h, and fixed in 10% neutral buffered formalin and embedded in paraffin. Staining with gamma-H2AX antibody was performed on sections of treated MCF-7 cells, tumor specimens, and biopsies at baseline and after doxorubicin-containing chemotherapy from cancer patients. Numbers of foci and level of gamma-H2AX expression per tumor nucleus were determined by manual counting under a light microscope and an Automated Cellular Imaging System. Results: There was a rise in the mean numbers of nuclear foci and intensity of gamma-H2AX in MCF-7 cells treated with irinotecan versus vehicle (19.9 ± 2.7 vs. 9.95 ± 3.6; P < 0.0001 and 61.2 ± 8.5 vs. 16.2 ± 13.6; P < 0.0001 by Wilcoxon rank sum test). The level of gamma-H2AX foci in human tumor samples was 18.8 ± 13.1, 44.8 ± 14.5, 51.2 ± 20.8, or 69.7 ± 21.2 in carcinomas of the breast, colon, ovary, or prostate. In a patient with stable disease, levels of gamma-H2AX foci were 62.7 ± 26.9 at baseline and 67.2 ± 25.3 after doxorubicin-containing regimen chemotherapy. Conclusions: Our data suggest that the quantitative immunohistochemical detection of gamma-H2AX levels is facilitated by a digital imaging system, and is a reliable method to measure the effects of DNA damaging agents in cells and paraffin-embedded human tumor samples. Its application may help evaluate tumor response to various DNA damaging agents currently in the clinic and those presently undergoing clinical development.

No significant financial relationships to disclose.

Statistical considerations for a phase 0 trial

14038

Background: Phase ‘0’ clinical trials are small first in man studies to determine a dose or dose range which results in a desired biologic effect. Novel statistical designs are needed due to the limited number of patients and the complexities of analyzing primary pharmacodynamic endpoints. Methods: In general, the effect of the agent will be evaluated, based on a biologic endpoint(s), at two levels, the individual participant level (for a given dose amount), and the agent dose amount level (across individual participants). At the participant level, the effect is preferably defined as a dichotomous outcome. The statistical criteria should be such that the threshold is not surpassed with more than .10 probability, for a given participant, at a given dose amount, for the null hypothesis case of no true biologic effect. At the dose amount level, the effect rate is defined as the probability that a randomly chosen participant will satisfy the participant level threshold. The statistical criteria for declaring an observed effect rate to be significant should be such that the over-all probability of declaring the agent effective (summed across all dose amounts) should not exceed .10 for the null hypothesis case of no true biologic effect. A target effect rate, measured across participants, should be given, and the power to detect it, for a given dose amount, should be estimated. Ideally, there will be multiple pre-agent administration endpoint measurements, per participant, to define variability. Examples: 1. If 10 participants are accrued to a single dose amount, an observed effect rate for that dose amount could be defined to be significant if at least 2 of the 10 participants satisfy the participant threshold, yielding 85–90% power to detect a 35% effect rate. 2. If 5 participants are accrued to each of 2 dose amounts, an observed effect rate for a particular dose amount could be defined to be significant if at least 2 of the 5 participants satisfy the participant threshold, yielding approximately 90% power to detect a 60% effect rate. 3. If 3 participants are accrued to each of 4 dose amounts, an observed effect rate for a particular dose amount could be defined to be significant if at least 2 of the 3 participants satisfy the participant threshold, yielding approximately 90% power to detect an 80% effect rate.

No significant financial relationships to disclose.

Compressing drug development timelines in oncology using phase '0' trials

The optimal evaluation of molecularly targeted anticancer agents requires the integration of pharmacodynamic assays into early clinical investigations. Phase '0' trials conducted under the new Exploratory Investigational New Drug Guidance from the US Food and Drug Administration can provide a platform to establish the feasibility of assays for target modulation in human samples, evaluate biomarkers for drug effects and provide pharmacokinetic data. Phase 0 trials could facilitate rational drug selection, identify therapeutic failures early, and might compress timelines for anticancer drug development. We expect that such trials will become a routine part of early-phase oncological drug development in the future.

Complement factor H or a related protein is a marker for transitional cell cancer of the bladder

The BTAstat and BTA TRAK tests are new immunoassays that detect and measure an antigen in the urine of individuals diagnosed with bladder cancer. As described in this report, the monoclonal antibodies used in these kits were developed by immunizing mice with partially purified protein preparations derived from the urine of patients with bladder cancer. The antigen that is recognized by the monoclonal antibodies was purified from the urine of bladder cancer patients by immunoaffinity chromatography and identified as being either complement factor H (FH) or a closely related protein (CFHrp) by partial amino acid sequence analysis. Like serum FH, the urine antigen was demonstrated to have a complement factor C3b binding site and to accelerate the degradation of C3b in the presence of complement factor I. The culture supernatants from several human bladder, cervical, and renal cancer cell lines contained antigen as determined by immunoassay, and antigen affinity-purified from HeLaS3 culture media was shown to have FH activity. Moreover, the cell lines were shown to make products of the expected sizes by reverse transcription-PCR using FH-specific primers. In contrast, normal human epithelial keratinocytes, a myeloid leukemia cell line, and the colon cancer line LS174T were negative for production of a FH-like protein (CFHrp). We propose that the expression of proteins with FH-like activities may confer a selective growth advantage to cancer cells in vivo by decreasing complement activity, thus aiding their escape from lysis by immune surveillance. Identification of these proteins as cancer products also suggests avenues of chemotherapy or immunotherapy of some cancers.

Modified Method for Determining Carcinoembryonic Antigen in the Presence of Human Anti-Murine Antibodies

Vol. 39:

p. 527. In the article by N. E. Morrissey, S. F. Quadri, R. Kinders, C. Brigham, S. Rose, and M. J. Blend entitled "Modified method for determining carcinoembryonic antigen in the presence of anti-murine antibodies," 1993;39:522-9, the graphs A and B in the left-hand column of page 527 should be exchanged with graphs A and B in the right-hand column, so that the legend for Figure 2 refers to graphs for two HAMA-negative patients and the legend for Figure 3 refers to three HAMA-positive patients.

p. 1401. In the article by J. M. Queraltó, J. C. Boyd, and E. K. Harris entitled "On the calculation of reference change values, with examples from a long-term study," 1993;39:1398-403, the last two columns of Table 4 are incorrect: in the next-to-last column, a misprint occurred in the line for sodium; in the last column, a number was omitted, causing other numbers to be misplaced. The columns should have read as follows:

See table in the PDF file

p. 1901. In the Scientific Note by R. G. Parsons, R. Kowal, D. LeBlond, V. T. Yue, L. Neargarder, L. Bond, D. Garcia, D. Slater, and P. Rogers, entitled "Multianalyte assay system developed for drugs of abuse," 1993;39:1899-903, the word "trihexylphenidyl" in line 1 of the text in column 2, page 1901, should read "trihexyphenidyl."

p. 1942. In Oak Ridge Conference paper by R. Devlin, R. M. Studholme, W. D. Dandliker, K. Blumeyer, and S. S. Ghosh, entitled "Homogeneous detection of nucleic acids by transientstate polarized fluorescence," 1993;39:1939-43, the x-axis for Figure 5 should read: "Volume of 3SR product solution (1O-4 x µL)," not (10-3 x µL).

p. 1982. In the Oak Ridge Conference Poster Session, the paper by D. Crisan, M. J. Anstett, N. Matta, and D. H. Farkas entitled "Detection of bcl-2 oncogene rearrangement in follicular lymphoma: nucleic acid hybridization and polymerase chain reaction compared," 1993;39:1980-2, the word "bone" in the first line at the top of page 1982 should have read "bone marrow."

Modified method for determining carcinoembryonic antigen in the presence of human anti-murine antibodies

The increasing use of monoclonal antibodies (MAbs) for disease diagnosis and therapy has created a class of patients at risk for systematic error in clinical testing due to interference by human anti-murine antibodies (HAMA). HAMA interference is often difficult to detect and can cause either an increase or a decrease in apparent concentrations of antigen present. We undertook a clinical study to test a HAMA-resistant enzyme immunoassay (EIA) format for carcinoembryonic antigen (CEA) determination. Using the Food and Drug Administration-approved CEA-EIA Monoclonal One-Step Assay (Abbott) with the addition of an acid/heat extraction of patients' specimens, we found that the resulting CEA values accurately reflected the patients' status. We demonstrated that the acid/heat-extracted specimens yield linear dilution curves and show analytical recoveries of added CEA in the range of 76-123% in HAMA-positive specimens and 86-103% in HAMA-negative specimens. The correlation of CEA values in extracted vs unextracted specimens from 184 patients and control subjects was 0.9963. The CEA detection limit of the assay was 1.6 micrograms/L for the extracted samples.

Modified method for determining carcinoembryonic antigen in the presence of human anti-murine antibodies

The increasing use of monoclonal antibodies (MAbs) for disease diagnosis and therapy has created a class of patients at risk for systematic error in clinical testing due to interference by human anti-murine antibodies (HAMA). HAMA interference is often difficult to detect and can cause either an increase or a decrease in apparent concentrations of antigen present. We undertook a clinical study to test a HAMA-resistant enzyme immunoassay (EIA) format for carcinoembryonic antigen (CEA) determination. Using the Food and Drug Administration-approved CEA-EIA Monoclonal One-Step Assay (Abbott) with the addition of an acid/heat extraction of patients' specimens, we found that the resulting CEA values accurately reflected the patients' status. We demonstrated that the acid/heat-extracted specimens yield linear dilution curves and show analytical recoveries of added CEA in the range of 76-123% in HAMA-positive specimens and 86-103% in HAMA-negative specimens. The correlation of CEA values in extracted vs unextracted specimens from 184 patients and control subjects was 0.9963. The CEA detection limit of the assay was 1.6 micrograms/L for the extracted samples.

Purification of T47D human progesterone receptor and immunochemical characterization with monoclonal antibodies

In order to obtain steroid-independent probes for human progesterone receptor (PR), the A [88-93 kilodalton (kDa)] and B (109-119 kDa) forms of PR from T47D human breast cancer cells were partially purified and used to generate a series of 14 monoclonal antibodies. Initially, unoccupied PR was isolated from cytosol extracts by steroid affinity chromatography, followed by chromatography on diethylaminoethyl Bio-Gel. The partially pure (3-15%) PR consisted of two steroid-binding components that migrated at 89 kDa and 109 kDa in reducing sodium dodecyl sulfate gels after being photoaffinity labeled with the synthetic progestin [3H]R5020. Two unique monoclonal antibodies to PR were derived from a male Lewis rat immunized with this material. One of these antibodies (JU601) was coupled to Sepharose 4B and used to purify T47D nuclear PR for additional immunizations. Highly purified (30-70%) PR migrated as 93 kDa and 119 kDa progestin-binding proteins in sodium dodecyl sulfate gels. In all, thirteen monoclonal antibodies were obtained that recognized epitopes shared by both receptor forms. One mouse immunoglobulin G (KC146) was completely specific for the larger B form. Interestingly, the epitope for this antibody was present on all PRs tested, including the B form of PR from chicken oviduct, whereas nine other antibodies recognized only human PR and the remaining four cross reacted with rabbit PR. With the exception of the JU145 and JU601 rat immunoglobulin Ms, all antibodies appeared to be completely specific for the A or B forms of PR. Each recognized the cytosol and nuclear forms of occupied as well as unoccupied PR. Although the relationship between B and A was not established, it is clear that an amino-terminal region of B is not present in A, and that a significant portion of A and B are either identical or very similar in amino acid sequence.

Selective protection of nonmalignant cells by a novel cell surface glycopeptide

A novel glycopeptide inhibitor of cell division, isolated from bovine cerebral cortex cell surfaces, was shown to selectively protect nonmalignant cells from the cytoxic action of 5-bromo-2-deoxyuridine (5-BrdUrd). When mouse LM-22 cells (nonmalignant and devoid of gangliosides) were preincubated with GM1 ganglioside (3.0 micrograms/ml), the cell surface glycopeptide inhibitor effectively arrested cell division. In contrast to LM-22 cells, transformed mouse fibrosarcoma (No. 1316) cells were insensitive to the glycopeptide inhibitor whether or not they were preincubated with GM1 ganglioside. Mixed cultures of LM-22 cells preincubated with GM1 ganglioside and 1316 fibrosarcoma cells at an approximate ratio of 1:1 were established. Since LM-22 cells are resistant and 1316 fibrosarcoma cells are sensitive to 3.0 mM ouabain, the identity of surviving cells following BrdUrd treatment could easily be determined. Three hr after the establishment of the mixed cell population, 250 ng protein per ml of the purified bovine glycopeptide inhibitor was added to selectively arrest the mitosis of the LM-22 cells. After an additional 3 hr of incubation, 5-BrdUrd was added to a final concentration of 5.0 mM. Twelve hr later, cells were serially diluted and seeded into duplicate plates with and without 3.0 mM ouabain. LM-22 cells were effectively protected from the cytotoxic action of 5-BrdUrd (92 to 94% survival) while the majority of the 1316 fibrosarcoma cells were killed (21 to 30% survival). The selective protection of LM-22 cells was shown to be independent of differences in plating efficiency, cytotoxicity of 5-BrdUrd in the absence of the glycopeptide inhibitor, and the generation time of the two cell lines.