scholarly journals Loss of PTEN in Pediatric AML Confers Sensitivity to PARP Inhibition

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3446-3446
Author(s):  
Jennifer Lauren Kamens ◽  
Anitria Cotton ◽  
Jeannie W Lam ◽  
Jinjun Dang ◽  
Aman Seth ◽  
...  
Keyword(s):  
Dna Damage ◽  
High Risk ◽  
Cell Lines ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Jak2 V617f ◽  
Parp Inhibitors ◽  
Parp Inhibition ◽  
Sensitive Cell ◽  
Pediatric Aml

Abstract Pediatric Acute Myeloid Leukemia (AML) is a rare, but deadly cancer. Outcomes over the last 20 years have remained stagnant with an overall 5-year survival rate < 70% and relapse rates around 50%. Further, few new therapies have been successfully introduced to improve these outcomes. Here we report that exploiting deficiencies in DNA damage repair (DDR) is a potential therapeutic strategy for AML. Poly-ADP Ribose Polymerase (PARP) inhibitors were initially developed to target deficient homologous recombination (HR) in BRCA1/2 mutated cancers by blocking single stranded base repair following DNA damage, leading to an accumulation of double stranded DNA breaks, thereby inducing apoptosis. To evaluate the activity of PARP inhibition in pediatric AML, talazoparib was tested as a single agent and in combination with standard chemotherapeutic agents in human AML cell lines representing low (Kasumi-1 and ME-1), intermediate (AML193), and high-risk (CTS, CMS, MOLM-13, and CHRF288-11) disease based on their genomic mutations. Talazoparib showed the highest efficacy as a single agent in all four cell lines with genomic lesions found in high-risk AML subtypes. After combination drug screens, topotecan (synergistic) and gemcitabine (additive) were chosen to move forward to in vivo testing. Our investigational combination was tested in vivo in four murine models representing pediatric AML subtypes harboring AML1-ETO9a (low risk), MLL-AF6 (high risk), CBAF2T3-GLIS2/JAK2 V617F (high risk) and NUP98-KDM5A (high risk) oncogenes. Mice received a backbone of either current standard of care chemotherapy (SOC; anthracycline plus cytarabine) or topotecan plus gemcitabine. NUP98-KDM5A and MLL-AF6 positive mice receiving single agent talazoparib were found to have prolonged survival compared to vehicle alone (p=0.019 and p<0.0001, respectively) which was further enhanced by the addition of chemotherapy irrespective of backbone (p <0.0001). Conversely, mice with AML1-ETOa positive leukemia had no response to single agent PARP inhibitor. While a few mice benefitted from the addition of talazoparib to SOC, this result was not statistically significant (p= 0.42). Early response by bioluminescent imaging confirmed that mice with MLL-AF6 and NUP98-KDM5A driven leukemias who received talazoparib in combination with chemotherapy had the lowest leukemia burdens while the AML1-ETOa cohort did not benefit from the addition of this targeted agent. Interestingly, mice harboring CBAF2T3-GLIS2/JAK2 V617F were not responsive to PARP inhibitors, which was inconsistent with the CMS cell line that has same oncogenic fusion gene but lacks the JAK2 V617F mutation. Synergy experiments with ATM inhibitor AZD0156 demonstrated tremendous synergy with talazoparib in sensitive cell lines with almost no synergy in those that were resistant, suggesting that sensitive cell lines are unable to efficiently activate the HR pathway to repair double stranded breaks induced by PARP inhibition whereas resistant cells can overcome inhibition. To determine the HR response to DNA damage in our cell lines, we exposed them to 1uM topotecan for 2 hours and then measured γH2AX response at 0, 4 and 24 hours. γH2AX is a sensor of DNA damage and therefore increases with DNA damage and decreases with repair. PARP inhibitor sensitive cell lines had persistence of gamma H2AX at 24hrs while resistant cell lines had at least partial resolution of damage, confirming that PARP inhibitor sensitive cell lines have aberrant DNA damage response through HR. RNA sequencing of our cell lines revealed a correlation between Phosphatase and tensin homolog (PTEN) transcript levels and PARP sensitivity. Western blotting confirmed that PTEN was downregulated or absent in both cell lines and murine leukemias that were sensitive to PARP inhibitors. In contrast to the CMS cell line that carries the CBFA2T3-GLIS2 fusion, murine leukemias with CBAF2T3-GLIS2/JAK2 V617F had high levels of PTEN, supporting the hypothesis that sensitivity to PARP inhibitors is due to loss of PTEN. In conclusion, we report that a subset of pediatric AML with high- risk features are sensitive to PARP inhibition due to deficient DDR through HR. Downregulation of PTEN is a candidate biomarker of response to PARP inhibitors in these patients. This data illuminates a promising therapeutic vulnerability in a patient population where new targeted treatments are vital to improve outcomes. Disclosures No relevant conflicts of interest to declare.

scholarly journals ATR Inhibition Potentiates PARP Inhibitor Cytotoxicity in High Risk Neuroblastoma Cell Lines by Multiple Mechanisms

Cancers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1095 ◽  
Author(s):  
Harriet E. D. Southgate ◽  
Lindi Chen ◽  
Deborah A. Tweddle ◽  
Nicola J. Curtin
Keyword(s):  
Dna Damage ◽  
High Risk ◽  
Cell Lines ◽  
Western Blotting ◽  
Ataxia Telangiectasia ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibition ◽  
Mycn Amplification ◽  
Single Strand Break

Background: High risk neuroblastoma (HR-NB) is one the most difficult childhood cancers to cure. These tumours frequently present with DNA damage response (DDR) defects including loss or mutation of key DDR genes, oncogene-induced replication stress (RS) and cell cycle checkpoint dysfunction. Aim: To identify biomarkers of sensitivity to inhibition of Ataxia telangiectasia and Rad3 related (ATR), a DNA damage sensor, and poly (ADP-ribose) polymerase (PARP), which is required for single strand break repair. We also hypothesise that combining ATR and PARP inhibition is synergistic. Methods: Single agent sensitivity to VE-821 (ATR inhibitor) and olaparib (PARP inhibitor), and the combination, was determined using cell proliferation and clonogenic assays, in HR-NB cell lines. Basal expression of DDR proteins, including ataxia telangiectasia mutated (ATM) and ATR, was assessed using Western blotting. CHK1S345 and H2AXS129 phosphorylation was assessed using Western blotting to determine ATR activity and RS, respectively. RS and homologous recombination repair (HRR) activity was also measured by γH2AX and Rad51 foci formation using immunofluorescence. Results: MYCN amplification and/or low ATM protein expression were associated with sensitivity to VE-821 (p < 0.05). VE-821 was synergistic with olaparib (CI value 0.04–0.89) independent of MYCN or ATM status. Olaparib increased H2AXS129 phosphorylation which was further increased by VE-821. Olaparib-induced Rad51 foci formation was reduced by VE-821 suggesting inhibition of HRR. Conclusion: RS associated with MYCN amplification, ATR loss or PARP inhibition increases sensitivity to the ATR inhibitor VE-821. These findings suggest a potential therapeutic strategy for the treatment of HR-NB.

scholarly journals PARP inhibition in UV-associated angiosarcoma preclinical models

2021 ◽  
Author(s):  
Marije E. Weidema ◽  
Ingrid M. E. Desar ◽  
Melissa H. S. Hillebrandt-Roeffen ◽  
Anke E. M. van Erp ◽  
Mikio Masuzawa ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Lines ◽  
Combination Treatment ◽  
Parp Inhibitor ◽  
Treatment Options ◽  
Single Agent ◽  
Specific Treatment ◽  
Parp Inhibition ◽  
Poor Overall Survival ◽  
Damage Repair

Abstract Purpose Angiosarcoma (AS) is a rare vasoformative sarcoma, with poor overall survival and a high need for novel treatment options. Clinically, AS consists of different subtypes, including AS related to previous UV exposure (UV AS) which could indicate susceptibility to DNA damage repair inhibition. We, therefore, investigated the presence of biomarkers PARP1 (poly(ADP-ribose)polymerase-1) and Schlafen-11 (SLFN11) in UV AS. Based on experiences in other sarcomas, we examined (combination) treatment of PARP inhibitor (PARPi) olaparib and temozolomide (TMZ) in UV AS cell lines. Methods Previously collected UV AS (n = 47) and non-UV AS (n = 96) patient samples and two UV AS cell lines (MO-LAS and AS-M) were immunohistochemically assessed for PARP1 and SLFN11 expression. Both cell lines were treated with single agents PARPi olaparib and TMZ, and the combination treatment. Next, cell viability and treatment synergy were analyzed. In addition, effects on apoptosis and DNA damage were examined. Results In 46/47 UV AS samples (98%), PARP1 expression was present. SLFN11 was expressed in 80% (37/46) of cases. Olaparib and TMZ combination treatment was synergistic in both cell lines, with significantly increased apoptosis compared to single agent treatment. Furthermore, a significant increase in DNA damage marker γH2AX was present in both cell lines after combination therapy. Conclusion We showed combination treatment of olaparib with TMZ was synergistic in UV AS cell lines. Expression of PARP1 and SLFN11 was present in the majority of UV AS tumor samples. Together, these results suggest combination treatment of olaparib and TMZ is a potential novel AS subtype-specific treatment option for UV AS patients.

scholarly journals Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

2021 ◽  
Vol 8 ◽  
Author(s):  
Jessica Buck ◽  
Patrick J. C. Dyer ◽  
Hilary Hii ◽  
Brooke Carline ◽  
Mani Kuchibhotla ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Combination Therapy ◽  
Cellular Response ◽  
Molecular Subtype ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibition ◽  
Preclinical Model ◽  
Radiation Induced

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

EGFR amplification predicted selective sensitivity to PARP inhibitors with high PARP-DNA trapping potential in human GBM.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. 2047-2047
Author(s):  
W. K. Alfred Yung ◽  
Shaofang Wu ◽  
Feng Gao ◽  
Siyuan Zheng ◽  
Jie Ding ◽  
...  
Keyword(s):  
Stem Cells ◽  
Dna Damage ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibitors ◽  
Glioma Stem Cells ◽  
Egfr Amplification ◽  
Damage Repair ◽  
Selective Sensitivity ◽  
Dna Trapping

2047 Background: Poly-ADP-ribose polymerase (PARP) is an enzyme critical for regulating a variety of DNA damage repair mechanisms such as BER/SSBR, and PARP inhibitors have been shown to have single agent activity in breast and ovarian cancer patients with BRCA ½ mutations. However, PARP inhibitor such as veliparib has limited single agent activity in GBM and identifying markers predicting sensitivity is critical to select individuals or certain groups of patients for PARP inhibitor therapy. Methods: Potency and selectivity of PARP inhibitors were analyzed in a panel of glioma stem cells (GSCs) with varying genetic background. In vivo anti-tumor activity was evaluated in xenograft models. Results: In this study, we report that PARP inhibitor, talazoparib, showed strong single-agent cytotoxicity and remarkable selective activity in glioma stem cells (GSCs). This single agent activity was strongly correlated with EGFR amplification. GSCs with EGFR amplification (which occurs in about 45% of GBMs) showed higher oxidative base damage, DNA breaks, and genomic instability than non-amplified GSCs. To sustain the elevated basal oxidative stress, EGFR-amplified GSCs had increased basal expression of DNA repair proteins. As a result of blocked DNA damage repair by talazoparib treatment, DNA damage accumulated and lead to increased PARP-DNA complexes, which was then trapped by talazoparib and resulted in high toxicity. The PARP-DNA trapping function of PARPi is essential as olaparib and veliparib, two PARP inhibitors with weak DNA-PARP trapping potential did not show sensitivity in GSCs. In contrast, Pamiparib, another PARP inhibitor with similar PARP-DNA trapping ability to that of talazoparib, showed selective sensitivity in EGFR-amplified GSC. Conclusions: Our data showed that EGFR amplified GSCs with higher basal DNA damage exhibited therapeutic vulnerability to PARP inhibitors with high PARP-DNA trapping ability, and that EGFR amplification is a potential selection or predictive biomarker for PARP inhibitor therapy in GBM.

Bortezomib Induced BRCAness Sensitizes Multiple Myeloma Cells to PARP Inhibitors

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 789-789
Author(s):  
Paola Neri ◽  
Li Ren ◽  
Kathy Gratton ◽  
Erin Stebner ◽  
Carolyn J Owen ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Dna Damage ◽  
Cell Lines ◽  
Tumour Growth ◽  
Proteasome Inhibitors ◽  
Parp Inhibitors ◽  
Parp Inhibition ◽  
Γh2ax Foci ◽  
Dna Dsbs

Abstract Abstract 789 Background: Poly-ADP-ribose-polymerase (PARP) inhibitors are cytotoxic to tumor cells with impaired DNA damage repair machinery (DRR), in particular those with a deficient homology directed repair (HR) of DNA double stranded breaks (DSB). Multiple Myeloma (MM) cells are characterized by a highly unstable genome and while the exact mechanisms for this karyotypic instability is largely unknown, their DDR machinery is thought to be highly stressed. The ubiquitin-proteasome system (UPS) is involved in the regulation of several cellular functions including DDR and in particular HR. In addition proteasome inhibitors are reported to induce an unfolded protein response (UPR) in MM cells resulting in their apoptotic death. We have postulated that inhibition of the 26S proteasome also alters the DNA-DSB repair machinery leading to a BRCAness state in MM cells, sensitizing them to PARP inhibitors. Methods and results: In order to biochemically inhibit PARP in MM cells, we used a novel selective inhibitor of PARP1 and PARP2, 2-(R)-2-methylpyrrolidin-2-yl]-1H-benzimidazole-4-carboxamide or ABT-888. We first demonstrated inhibition of PARP activity as measured by a reduction in poly-ADP-ribose (PAR) polymer levels (western blotting) in human MM cell lines (MM1S, U266, H929, RPMI8226, KMS-11, OPM2, INA-6) treated with ABT-888 (5 μM). PARP inhibition and the reduction of PAR levels resulted in DNA damage as evidenced by ATM phosphorylation and induced DNA-DSBs with increased γH2AX (phospho-Ser139-H2AX) levels within 6–12 hours of MM cells treatment with ABT-888. Increased γH2AX foci formation was also detected by immunofluorescent staining within 6–12 hours of ABT-888 treatment and nearly fully resolved by 24 hours, consistent with repair of resultant DNA-DSBs. As expected treatment with ABT-888 alone had no effect on the viability of MM cells consistent with their ability to repair DNA-DSBs resulting from PARP inhibition. We then examined the effect of bortezomib on HR-mediated repair of DNA-DSBs, in particular on the BRCA/FA pathway. A significant reduction of MM cells' FANCD2, BRCA1, BRCA2 and RAD51 mRNA levels (qRT-PCR) was observed within 6–12 hours of bortezomib treatment (10 nM). Similar results were observed at the protein level indicating that bortezomib impedes homology-directed DNA-DSBs repair and results in an operational BRCAness state in MM cells. Therefore, we next tested whether this bortezomib-induced BRCAness was sufficient to sensitize MM cells to PARP inhibition with ABT-888. Consistent with our hypothesis, we observed that co-treatment of MM cell lines with bortezomib and ABT-888 lead to persistent and increased γH2AX foci at 24 hours compared to treatment with ABT-888 alone. Co-treatment also significantly potentiated cell death (Annexin V/PI staining) compared to treatment with bortezomib alone. Similar results were observed in CD138+ primary MM cells (n=8) with strong synergistic effect (CI < 1) between bortezomib and ABT-888. Importantly, no impaired viability (Annexin/PI staining) or function (colony forming unit assay) was noted for CD138− cells or CD34+ peripheral blood stem cells after bortezomib and ABT-888 co-treatment. Mechanistic studies have also shown that apoptotic events (caspase 3, caspase 8 and PARP cleavage) are markedly enhanced by this combination. Based on our in vitro data, we evaluated in vivo the activity of ABT-888 in combination with bortezomib in a Scid murine xenograft model of human MM. Significant inhibition of tumour growth (p<0.005) was noted in mice treated with the combination of bortezomib and ABT-888 compared to bortezomib alone or control-treated mice. This tumour growth inhibition also resulted in a significant increase in survival (p<0.05) of the animals. No toxicity (e.g. weight loss, ruffled coats, paralysis, etc.) was observed in mice treated with the combination. Induction of DNA-DSBs was also confirmed in vivo as shown by an increase in 53BP1 and γH2AX foci formation in tumors of mice treated with the combination compared to bortezomib alone. Conclusion: Our studies indicate that bortezomib induces a BRCAness state in MM cells by impairing HR-mediated repair of DNA-DSBs and results in a contextual synthetic lethality when combined with the PARP inhibitor ABT-888. These data provide the scientific basis for the future clinical testing of PARP inhibitors in combination with proteasome inhibitors for the treatment of MM. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Addition of the PARP Inhibitor, Talazoparib, to Gemtuzumab Ozogamicin Significantly Enhances Anti-Leukemic Activity in Human CD33+ Acute Myeloid Leukemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1371-1371
Author(s):  
Scott M. Portwood ◽  
Marianna C Cantella ◽  
Tara L. Cronin ◽  
Eunice S. Wang
Keyword(s):  
Dna Damage ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibitors ◽  
Gemtuzumab Ozogamicin ◽  
Nsg Mice ◽  
Dose Dependent ◽  
Advisory Role

Background CD33 (Siglec3) is a cell surface transmembrane receptor that is rapidly internalized and highly expressed on AML blasts but is absent on normal hematopoietic stem cells. Gemtuzumab ozogamicin (GO), a humanized anti-CD33 antibody conjugated to a DNA strand scission inducing agent (calicheamicin) was recently FDA approved for the treatment of newly-diagnosed or relapsed/refractory CD33-positive acute myeloid leukemia (AML). GO has been shown to exert clinical activity in leukemia patients. Poly (ADP-ribose) polymerase (PARP) inhibitors prevent the repair of single stranded DNA breaks by blocking the nicotinamide adenine dinucleotide (NAD) catalytic domain of the PARP protein and by preventing the dissociation of PARP from the DNA (PARP trapping). Talazoparib is unique among clinical PARP inhibitors in displaying 10,000-fold increased PARP trapping as compared to other agents . We hypothesized that combination therapy using GO and Talazoparib would result in synergistic anti-leukemic effects on human CD33+ AML cells due to the ability of the PARP inhibitor to enhance levels of DNA damage induced by GO therapy. Materials and Methods Human AML cell lines were characterized for CD33 expression using flow cytometry after staining with antibody-linked fluorescent QuantiBrite Beads. Cells were continuously exposed to varying doses of GO (10pM - 100mM) and PARP inhibitors (1nM - 100mM) for 96h alone and in combination. Cell viability was measured immediately following treatment using a WST colorimetric assay. Treatment-induced apoptosis (annexin/PI) and DNA damage (H2AX) were quantified by flow cytometric assays. Synergy reports were generated using Compusyn software. In vivo efficacy was assessed in NSG mice systematically engrafted with luciferase labeled human CD33+ AML cells following tail vein injection. Animals were treated with varying doses of vehicle, GO (1 and 50ug/kg 1x/week for 3 weeks), or talazoparib (0.1 and 0.33mg/kg 5 days/week) either alone or in combination. Treatment effects on leukemia burden, toxicity, and survival were determined by weekly whole animal bioluminescent imaging, total animal weights, and time to morbidity. Results Human AML cell lines (HEL, HL60) express high expression levels of CD33 molecules/cell (43,645 and 31,286 respectively) relative to negative controls. Continuous exposure to single agent GO and Talazoparib for 96h resulted in a dose dependent inhibition of human AML cell growth (HEL, HL60) . IC values for GO were 0.01 - 6.6μg/ml and for Talazoparib were 0.8-0.95μM. Combination in vitro therapy with GO (0.005 - 1μg/ml) and Talazoparib (fixed dose 100nM) resulted in synergistic anti-leukemic effects (p&lt;0.01) significantly improving upon monotherapy. Software analyses yielded a combination Index (CI) &lt;1 consistent with synergistic anti-leukemic effects. Combination GO and Talazoparib therapy also significantly enhanced AML cell apoptosis (p=0.0111) and levels of DNA damage (phosphorylated H2AX) (p=0.0054) over single agent activity. Evaluation of PARP trapping by western blot analysis is ongoing. In vivo administration of GO (1-50μg/kg) and Talazoparib (0.1-0.33mg/kg) in NSG mice with systemic engraftment of luciferase tagged human CD33+ AML cells was generally well tolerated with no significant weight loss or early morbidity. Single agent GO and Talazoparib therapy decreased systemic AML burden in a dose dependent manner and prolonged overall survival over vehicle treated mice (P&lt;0.05). Concomitant GO (1μg/kg) and Talazoparib (0.33μg/kg) treatment was similarly well tolerated with no notable weight loss or toxicities. Combination GO and Talazoparib therapy significantly prolonged overall survival of leukemia xenografted mice over vehicle (p=0.0018) and single agent therapy with the same doses of GO (p=0.0018) and Talazoparib (p=0.0499), respectively). Conclusions In summary, our results demonstrate that the addition of the PARP inhibitor, Talazoparib, to the CD33 antibody drug conjugate, GO, results in potent in vitro and in vivo anti-tumor activity in human CD33+ AML preclinical models. Further studies investigating this novel combinatorial approach in AML are currently ongoing. Due to GO's FDA approval for CD33+ AML in 2018, this data strongly supports future clinical investigation using PARP inhibitors as a novel class of agents for combination therapy to significantly enhance the efficacy of ADCs. Figure 1 Disclosures Wang: Amgen: Other: Advisory role; Agios: Other: Advisory role; Stemline: Other: Advisory role, Speakers Bureau; Daiichi: Other: Advisory role; Abbvie: Other: Advisory role; Kite: Other: Advisory role; Jazz: Other: Advisory role; Astellas: Other: Advisory role, Speakers Bureau; celyad: Other: Advisory role; Pfizer: Other: Advisory role, Speakers Bureau.

scholarly journals Synergistic targeting of BRCA1 mutated breast cancers with PARP and CDK2 inhibition

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Diar Aziz ◽  
Neil Portman ◽  
Kristine J. Fernandez ◽  
Christine Lee ◽  
Sarah Alexandrou ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Lines ◽  
Tumor Regression ◽  
Predictive Biomarkers ◽  
Parp Inhibitors ◽  
Parp Inhibition ◽  
Breast Cancers ◽  
Cyclin E1 ◽  
Xenograft Models ◽  
High Cyclin

AbstractBasal-like breast cancers (BLBC) are aggressive breast cancers that respond poorly to targeted therapies and chemotherapies. In order to define therapeutically targetable subsets of BLBC we examined two markers: cyclin E1 and BRCA1 loss. In high grade serous ovarian cancer (HGSOC) these markers are mutually exclusive, and define therapeutic subsets. We tested the same hypothesis for BLBC. Using a BLBC cohort enriched for BRCA1 loss, we identified convergence between BRCA1 loss and high cyclin E1 protein expression, in contrast to HGSOC in which CCNE1 amplification drives increased cyclin E1. In cell lines, BRCA1 loss was associated with stabilized cyclin E1 during the cell cycle, and BRCA1 siRNA led to increased cyclin E1 in association with reduced phospho-cyclin E1 T62. Mutation of cyclin E1 T62 to alanine increased cyclin E1 stability. We showed that tumors with high cyclin E1/BRCA1 mutation in the BLBC cohort also had decreased phospho-T62, supporting this hypothesis. Since cyclin E1/CDK2 protects cells from DNA damage and cyclin E1 is elevated in BRCA1 mutant cancers, we hypothesized that CDK2 inhibition would sensitize these cancers to PARP inhibition. CDK2 inhibition induced DNA damage and synergized with PARP inhibitors to reduce cell viability in cell lines with homologous recombination deficiency, including BRCA1 mutated cell lines. Treatment of BRCA1 mutant BLBC patient-derived xenograft models with combination PARP and CDK2 inhibition led to tumor regression and increased survival. We conclude that BRCA1 status and high cyclin E1 have potential as predictive biomarkers to dictate the therapeutic use of combination CDK inhibitors/PARP inhibitors in BLBC.

Preclinical testing of the PARP inhibitor ABT-888 in microsatellite instable colorectal cancer

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 11028-11028 ◽  
Author(s):  
E. Vilar Sanchez ◽  
A. Chow ◽  
L. Raskin ◽  
M. D. Iniesta ◽  
B. Mukherjee ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Flow Cytometry ◽  
Systems Biology ◽  
Cell Lines ◽  
Genetic Instability ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibitors ◽  
Dsb Repair ◽  
Mutational Status

11028 Background: Microsatellite instability (MSI) represents approximately 15% of colorectal cancer (CRC) cases. MSI due to hypermethylation or mutation in DNA mismatch repair genes leads to genetic instability and a mutator phenotype. Genetic instability is particularly high at repetitive sequences such as those located in MRE11, RAD50, CtIP and MBC. Each of these genes are implicated in the double strand break (DSB) repair pathway. PARP inhibitors induce single strand breaks that remain unrepaired and then will be converted to DSB during DNA replication. Our objective was to assess the preclinical activity of a novel PARP inhibitor ABT-888 in MSI cell lines deficient in the DSB repairing pathway and compare it to Microsatellite Stable (MSS) lines. Methods: We used the systems biology tool “Connectivity Map” to synthesize data from 5 different published studies of expression profiling of MSI CRC phenotype and to identify target compounds. We assessed the mutational status of MRE11, RAD50, CtIP and MBC in a panel of 10 CRC cell lines displaying either MSI or MSS, and measured the expression of MRE11 by quantitative RT-PCR. We tested the cytotoxic activity of single-agent ABT-888 for 6 days in MSS and MSI cell lines, stratified by mutational status. Flow cytometry was performed after 24 hours. Results: Systems biology studies identified PARP inhibitors as a candidate compound relevant for MSI CRC. Mutational status of MRE11 was perfectly correlated with MSI status. ABT-888 shows a preferential activity on those MSI cell lines harboring mutations in both MRE11 and RAD50 genes compared to MSS cell lines (wild-type for both genes). A significant correlation exists between MRE11 expression levels and cytotoxicity to ABT-888 at 10 μM (R2=0.915, P<0.001). Flow cytometry analyses show a G1 arrest following to the treatment with ABT-888 that is higher in MSI cell lines with mutations in MRE11 and RAD50 compared to MSS cell lines. Conclusions: This is the first report of the preclinical activity of a PARP inhibitor in CRC models. MSI colorectal tumors deficient in DSB repair show a higher sensitivity to PARP inhibition. Further clinical investigation of ABT-888 as a single agent or in combination with other chemotherapy drugs inducing DSB is warranted in MSI CRC with mutations in MRE11 and RAD50. No significant financial relationships to disclose.

scholarly journals Evaluating the Sensitivity of Sporadic Pancreatic Cancer to poly(ADP-ribose) polymerase (PARP) Inhibition (Velaparib, Olaparib, AG14361) as Single Agents and as Chemo-sensitizers

2020 ◽  
Author(s):  
J. Angel de Soto
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Pancreatic Cancer Cell ◽  
Parp Inhibitor ◽  
Parp Inhibitors ◽  
Human Pancreatic Cancer ◽  
Parp Inhibition ◽  
Pancreatic Cancer Cells ◽  
Ic50 Values

AbstractAfter resection of pancreatic cancer local recurrence occurs in 50%-80% of the cases while metastasis develops 75% of the time. Current, adjuvant therapy often consists of gemcitabine, cisplatin and/or 5-fluorouracil which add a modest increase in median survival by 4-5 months. In this study, we treated human pancreatic cancer cells with poly (ADP-ribose) polymerase (PARP) Inhibitors (AG14361, Veliparib and Olaparib) alone or with gemcitabine, cisplatin or 5 – fluorouracil. Methods: CFPAC-1 and BXPC-3, HPAC human pancreatic cancer cell lines were treated for 72 hours with PARP inhibitors alone or in combination with gemcitabine, cisplatin, or 5 – fluorouracil. Validated MTT assays were used to form dose response curves from which the IC50 values were calculated. Results: The PARP1 IC50 values for CFPAC-1, BXPC-3 and HPAC pancreatic cancer cell lines were AG14361 (14.3 μM, 12.7 μM, 38.3 μM), Veliparib (52.6 μM, 100.9 μM 102.0 μM) and Olaparib (79.5 μM, 184.8 μM, 200.2 μM). The IC50 values of cisplatin, were decreased up to 60 fold in the presence of clinically relevant amounts of PARP inhibitor while 5-flourouracil IC50 values were decreased up to 6000 fold in the presence of clinically relevant amounts of PARP inhibitor. Gemcitabine was inhibited up to 73% by PARP inhibitors. Conclusions: Sporadic human pancreatic cancer cells are sensitive to PARP inhibition. PARP inhibitors significantly enhanced the cytotoxicity of cisplatin and 5-fluorouracil while inhibiting gemcitabine. There is little correlation between endogenous PARP activity and the effectiveness of PARP inhibitors.

Inhibition of poly (ADP-ribose) polymerase-1 (PARP-1) to increase radiosensitivity of human pancreatic cancer (PAC) cell lines proficient in homology-directed repair (HDR).

2012 ◽  
Vol 30 (4_suppl) ◽  
pp. 204-204 ◽  
Author(s):  
Maeve A. Lowery ◽  
Fabio Vanoli ◽  
Kenneth H. Yu ◽  
Maria Jasin ◽  
Eileen Mary O'Reilly ◽  
...  
Keyword(s):  
Cell Lines ◽  
Background Radiation ◽  
Excision Repair ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Human Pancreatic Cancer ◽  
Parp Inhibition ◽  
Continuous Exposure ◽  
Dna Breaks ◽  
Dna Dsbs

204 Background: Radiation-induced single strand DNA breaks (SSBs) are primarily repaired by base excision repair, of which PARP1 is a key component. Unrepaired SSBs may cause collapse of stalled replication forks during DNA replication generating DNA double-strand breaks (DSBs). PARP inhibition has been shown to potentiate the effect of radiotherapy (RT) in a variety of human cancers in vitro and in vivo. We investigated the ability of the PARP inhibitor olaparib to radiosensitize BRCA1/2 wild-type human PAC cell lines and quantified repair capability of an induced DSB by HDR using the I-SceI-induced DSB DR-GFP assay. Methods: MiaPaCa -2 and ASPC-1 human PAC cells lines were exposed to RT administered in a single fraction by 157-gammacell irradiator at doses of 2, 4, 6 and 8 Gy in the presence or absence of olaparib at a dose of 500nM (4 hours pre and 20 hours post RT). Plates were incubated at 37C for 10-14 days and stained with Giemsa. Clonogenic survival assays following olaparib continuous exposure at concentrations up to 10 µM for 10-14 days were also performed. HDR of an induced DNA DSB was assessed in ASPC1 and MiaPaCa cell lines by co-transfection with an I-SceI expression vector and the DR-GFP reporter plasmid(Pierce et al., 1999), and in BRCA2 deficient CAPAN-1 cells harboring a stably integrated chromosomal DR-GFP gene (Moynahan et al. 2001). Results: Linear quadratic models were fitted to the data sets to generate survival curves. The half maximal inhibitory concentration (IC 50) of RT was 2Gy for both cell lines. The sensitivity enhancement ratio (SER) at 25% survival was 1.44 and 1.53 for MiaPaCa-2 and ASPC-1 cell lines respectively. Both cell lines were resistant to treatment with single agent olaparib to dose of 10µM and were proficient in HDR of DNA DSBs when compared to the BRCA2-deficient Capan-1 cell line. Conclusions: Inhibition of PARP increases radiosensitivity in human PAC cell lines proficient in HDR of DNA DSBs and resistant to treatment with single agent PARP inhibitor. Therapeutic strategies incorporating PARP inhibition and RT offer potential to improve clinical outcomes for patients presenting with localized sporadic and BRCA mutated PAC.

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