Therapeutic potential of poly(ADP-ribose) polymerase inhibitor AG014699 in human cancers with mutated or methylated BRCA1 or BRCA2.
ABSTRACT Mutations in BRCA1 and BRCA2 (BRCA1/2), components of the homologous recombination DNA repair (HRR) pathway, are associated with hereditary breast and ovarian cancers. Poly(ADP-ribose) polymerase (PARP) inhibitors are selectively cytotoxic to animal cells with defective HRR, but results in human cancer cells have been contradictory. We undertook, to our knowledge, the first comprehensive in vitro and in vivo investigations of the antitumor activity of the PARP inhibitor AG014699 in human cancer cells carrying mutated or epigenetically silenced BRCA1/2.
We used nine human cell lines, four with nonmutated BRCA1/2 (MCF7, MDA-MB-231, and HCC1937-BRCA1 [breast cancer] and OSEC-2 [ovarian surface epithelial]), two with mutated BRCA1 (MDA-MB-436 and HCC1937 [breast cancer]), one with mutated BRCA2 (CAPAN-1 [pancreatic cancer]), one that was heterozygous for BRCA2 (OSEC-1 [ovarian surface epithelial]), and one with epigenetically silenced BRCA1 (UACC3199 [breast cancer]), and two Chinese hamster ovary cell lines, parental AA8 and XRCC3 mutated IRS 1SF. We assessed cytotoxicity, DNA damage, and HRR function. Antitumor activity of AG014699 was determined by growth of xenograft tumors (five mice per treatment group). Long-term safety of AG014699 was assessed.
AG014699 (≤10 μM) was cytotoxic to cells with mutated BRCA1/2 or XRCC3 and to UACC3199 cells with epigenetically silenced BRCA1 but not to cells without BRCA1/2 or XRCC3 mutations or that were heterozygous for BRCA2 mutation. AG014699 induced DNA double-strand breaks in all nine cell lines studied. HRR was observed only in cells with functional BRCA1/2 proteins. Growth of xenograft tumors with BRCA1/2 mutations or with epigenetically silenced BRCA1 was reduced by AG014699 treatment, and combination treatment with AG014699 plus carboplatin was more effective than either drug alone. AG014699 was not toxic in mice with nonmutated or heterozygous BRCA2.
Human cancer cells or xenograft tumors with mutated or epigenetically silenced BRCA1/2 were sensitive to AG014699 monotherapy, indicating a potential role for PARP inhibitors in sporadic human cancers.
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ABSTRACT: Poly(ADP-ribose) polymerase-1 (PARP-1) is a DNA nick sensor involved in the base excision repair (BER) pathway. Olaparib, a PARP inhibitor, has demonstrated antitumor activity in homologous recombination (HR)-deficient cancers. To extend this specific therapy to other types of carcinomas, a panel of 11 different cancer cells were screened in the present study. JF-305, a pancreatic cancer cell line of Chinese origin, demonstrated sensitivity to the PARP inhibitor 6(5H)-phenanthridinone. In the present study, 3 μM olaparib conferred a cell survival rate of 25% following four days of treatment. The colony formation efficiency was 83% at 10 nM, and dropped to 12% at 1 μM following seven days of treatment. Furthermore, olaparib induced cell cycle arrest in the S and G2/M phases prior to the initiation of apoptosis. Although the incidence of double-strand breaks (DSBs) was increased in the olaparib-treated JF-305 cells, the RAD51 foci were well formed at the sites of γ-H2AX recruitment, indicating an activated HR mechanism. Furthermore, tumor growth was reduced by 49.8% following 22 days of consecutive administration of 10 mg/kg olaparib in the JF-305 xenograft mouse model. In summary, the JF-305 cell line was sensitive to olaparib and provided a prospective model for the preclinical assessment of PARP inhibitors in the therapy of pancreatic cancer.Oncology letters 02/2015; 9(2):757-761. DOI:10.3892/ol.2014.2762 · 0.99 Impact Factor
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ABSTRACT: Olaparib (AZD-2281, Ku-0059436) is an orally bioavailable and well-tolerated poly(ADP-ribose) polymerase (PARP) inhibitor currently under investigation in patients with solid tumors. To study the clinical potential of olaparib as a single-agent for the treatment of Acute Myeloid Leukemia (AML) patients, we analyzed the in vitro sensitivity of AML cell lines and primary blasts. Clinically achievable concentrations of olaparib were able to induce cell death in the majority of primary AML case samples (88%) and tested cell lines. At these concentrations, olaparib preferentially killed leukemic blasts sparing normal lymphocytes derived from the same patient and did not substantially affect the viability of normal bone marrow and CD34-enriched peripheral blood cells obtained from healthy donors. Most primary AML analyzed were characterized by low BRCA1 mRNA level and undetectable protein expression that likely contributed to explain their sensitivity to olaparib. Noteworthy, while PARP1 over-expression was detected in blasts not responsive to olaparib, phosphorylation of the histone H2AFX (γH2AX) was associated with drug sensitivity. As to genetic features of tested cases the highest sensitivity was shown by a patient carrying a 11q23 deletion. The high sensitivity of AML blasts and the identification of biomarkers potentially able to predict response and/or resistance may foster further investigation of olaparib monotherapy for AML patients unfit to conventional chemotherapy. Copyright © 2014. Published by Elsevier B.V.Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease 12/2014; 1852(3). DOI:10.1016/j.bbadis.2014.12.001 · 5.09 Impact Factor
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ABSTRACT: Silencing of O(6)-methylguanine-DNA-methyltransferase (MGMT) in tumors, mainly through promoter methylation, correlates with a better therapeutic response and with increased survival. Therefore, it is conceivable to consider MGMT as a potential therapeutic target for the treatment of cancers. Our previous results demonstrated the pivotal role of NF-kappaB in MGMT expression, mediated mainly through p65/NF-kappaB homodimers. Here we show that the non-canonical NF-KappaB motif (MGMT-kappaB1) within MGMT enhancer is probably the major inducer of MGMT expression following NF-kappaB activation. Thus, in an attempt to attenuate the transcription activity of MGMT in tumors we designed locked nucleic acids (LNA) modified decoy oligonucleotides corresponding to the specific sequence of MGMT-kappaB1 (MGMT-kB1-LODN). Following confirmation of the ability of MGMT-kB1-LODN to interfere with the binding of p65/NF-kappaB to the NF-KappaB motif within MGMT enhancer, the efficacy of the decoy was studied in-vitro and in-vivo. The results of these experiments show that the decoy MGMT-kB1-LODN have a substantial antineoplastic effect when used either in combination with temozolomide or as monotherapy. Our results suggest that MGMT-kB1-LODN may provide a novel strategy for cancer therapy.PLoS ONE 12/2014; 9(12):e113854. DOI:10.1371/journal.pone.0113854 · 3.53 Impact Factor