Publications (57) View all
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Article: 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.
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ABSTRACT: 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 pro-inflammatory cytokine expression, and therefore treatment with NSC 710305 was delayed until 48 hours after initiating the slice cultures to avoid confounding the response to slicing with any drug response. PCLS were evaluated after 24, 48, and 72 hour exposures to NSC 710305. Reversibility of toxicity due to the 72 hour treatment was evaluated after a 24 hour recovery period. NSC 710305 caused a concentration-dependent cytokine response, and only the toxicity caused by a 72 hour exposure to 25 µM reversed during the 24 hour 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 pro-inflammatory 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 hour exposures was established as 10 µM NSC 710305.Toxicological Sciences 11/2012; · 4.65 Impact Factor -
Article: In vitro comparison of O4-benzylfolate modulated, BCNU-induced toxicity in human bone marrow using CFU-GM and tumor cell lines
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ABSTRACT: 2-Amino-O4-benzylpteridine derivatives inactivate the human DNA repair protein O6-alkylguanine-DNA alkyltransferase and have been tested as modulators of alkylating agent chemotherapy. Recently, the therapeutic potential of O4-benzylfolate (O4BF) in modulating bis-chloroethylnitrosourea (BCNU) toxicity was demonstrated in vitro using human HT29 and KB tumor lines. The current studies replicated the previous findings in HT29 and KB cells using ATP as an endpoint. However, the effective treatment conditions were severely toxic to human neutrophil progenitors called CFU-granulocyte/macrophage (CFU-GM), which could not tolerate ≥40μM BCNU at any O4BF concentration. A lower BCNU concentration (10μM) in combination with O4BF (2–100μM) was only moderately tumoricidal. To screen for conditions tolerated by CFU-GM, bone marrow (BM) cells were pre-incubated (5h) with O4BF, co-treated with O4BF and BCNU (42h), washed, and plated to quantify CFU-GM survival. O4BF at 2 or 5μM progressively lowered the inhibitory concentrations (ICs) for BCNU, but further increases in O4BF concentrations did not. Increasing O4BF concentrations with constant BCNU (10μM) under the same prolonged exposure as in the human marrow study achieved only modest tumoricidal effects. In summary, the unexpected finding that normal BM cells are impacted by an agent developed to target malignant tissue refutes speculation that normal β-folate receptor expressing hematopoietic cells will be spared. Further, the validated IC90 endpoint from the huCFU-GM assay has provided a reference point for judging the potential therapeutic effectiveness of this investigational combination in man using in vitro assays. KeywordsCFU-GM-Human bone marrow-KB and HT29 tumor cells-Neutropenia-O4-benzylfolateCancer Chemotherapy and Pharmacology 04/2012; 65(6):1083-1091. · 2.83 Impact Factor -
Article: Advances in using PARP inhibitors to treat cancer.
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ABSTRACT: 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.BMC Medicine 03/2012; 10:25. · 6.03 Impact Factor -
Article: A phase I study of veliparib in combination with metronomic cyclophosphamide in adults with refractory solid tumors and lymphomas.
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ABSTRACT: 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. 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. 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. 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.Clinical Cancer Research 02/2012; 18(6):1726-34. · 7.74 Impact Factor -
Article: Development and validation of an immunoassay for quantification of topoisomerase I in solid tumor tissues.
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ABSTRACT: Topoisomerase I (Top1) is a proven target for cancer therapeutics. Recent data from the Fluorouracil, Oxaliplatin, CPT-11: Use and Sequencing (FOCUS) trial demonstrated that nuclear staining of Top1 correlates with chemotherapeutic efficacy. Such a correlation may help identify patients likely to respond to Top1 inhibitors and illuminate their mechanism of action. Cellular response to Top1 inhibitors is complex, but Top1 target engagement is a necessary first step in this process. This paper reports the development and validation of a quantitative immunoassay for Top1 in tumors. We have developed and validated a two-site enzyme chemiluminescent immunoassay for quantifying Top1 levels in tumor biopsies. Analytical validation of the assay established the inter-day coefficient of variation at 9.3%±3.4% and a 96.5%±7.3% assay accuracy. Preclinical fit-for-purpose modeling of topotecan time- and dose-effects was performed using topotecan-responsive and -nonresponsive xenografts in athymic nude mice. Higher baseline levels of Top1 were observed in topotecan-responsive than -nonresponsive tumors. Top1 levels reached a maximal decrease 4 to 7 hours following treatment of engrafted mice with topotecan and the indenoisoquinoline NSC 724998. Our analysis of Top1 levels in control and treated tumors supports the previously proposed mechanism of action for Top1 inhibitor efficacy, wherein higher baseline Top1 levels lead to formation of more covalent-complex-dependent double-strand break damage and, ultimately, cell death. In contrast, xenografts with lower baseline Top1 levels accumulate fewer double-stand breaks, and may be more resistant to Top1 inhibitors. Our results support further investigation into the use of Top1 levels in tumors as a potential predictive biomarker. The Top1 immunoassay described in this paper has been incorporated into a Phase I clinical trial at the National Cancer Institute to assess pharmacodynamic response in tumor biopsies and determine whether baseline Top1 levels are predictive of response to indenoisoquinoline Top1 inhibitors.PLoS ONE 01/2012; 7(12):e50494. · 4.09 Impact Factor
