Inhibition of PARP Sensitizes Chondrosarcoma Cell Lines to Chemo- and Radiotherapy Irrespective of the IDH1 or IDH2 Mutation Status

Chondrosarcomas are chemo- and radiotherapy resistant and frequently harbor mutations in isocitrate dehydrogenase (IDH1 or IDH2), causing increased levels of D-2-hydroxyglutarate (D-2-HG). DNA repair defects and synthetic lethality with poly(ADP-ribose) polymerase (PARP) inhibition occur in IDH mutant glioma and leukemia models. Here we evaluated DNA repair and PARP inhibition, alone or combined with chemo- or radiotherapy, in chondrosarcoma cell lines with or without endogenous IDH mutations. Chondrosarcoma cell lines treated with the PARP inhibitor talazoparib were examined for dose–response relationships, as well as underlying cell death mechanisms and DNA repair functionality. Talazoparib was combined with chemo- or radiotherapy to evaluate potential synergy. Cell lines treated long term with an inhibitor normalizing D-2-HG levels were investigated for synthetic lethality with talazoparib. We report that talazoparib sensitivity was variable and irrespective of IDH mutation status. All cell lines expressed Ataxia Telangiectasia Mutated (ATM), but a subset was impaired in poly(ADP-ribosyl)ation (PARylation) capacity, homologous recombination, and O-6-methylguanine-DNA methyltransferase (MGMT) expression. Talazoparib synergized with temozolomide or radiation, independent of IDH1 mutant inhibition. This study suggests that talazoparib combined with temozolomide or radiation are promising therapeutic strategies for chondrosarcoma, irrespective of IDH mutation status. A subset of chondrosarcomas may be deficient in nonclassical DNA repair pathways, suggesting that PARP inhibitor sensitivity is multifactorial in chondrosarcoma.

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Combined Strategies with Poly (ADP-Ribose) Polymerase (PARP) Inhibitors for the Treatment of Ovarian Cancer: A Literature Review

Diagnostics ◽

10.3390/diagnostics9030087 ◽

2019 ◽

Vol 9 (3) ◽

pp. 87 ◽

Cited By ~ 24

Author(s):

Stergios Boussios ◽

Peeter Karihtala ◽

Michele Moschetta ◽

Afroditi Karathanasi ◽

Agne Sadauskaite ◽

...

Keyword(s):

Ovarian Cancer ◽

Dna Repair ◽

Synthetic Lethality ◽

Excision Repair ◽

Parp Inhibitor ◽

Advanced Ovarian Cancer ◽

Pegylated Liposomal Doxorubicin ◽

Parp Inhibitors ◽

Parp Inhibition ◽

Biologic Agent

Poly (ADP-ribose) polymerase (PARP) inhibitors are the first clinically approved drugs designed to exploit synthetic lethality, and were first introduced as a cancer-targeting strategy in 2005. They have led to a major change in the treatment of advanced ovarian cancer, and altered the natural history of a disease with extreme genetic complexity and defective DNA repair via homologous recombination (HR) pathway. Furthermore, additional mechanisms apart from breast related cancer antigens 1 and 2 (BRCA1/2) mutations can also result in HR pathway alterations and consequently lead to a clinical benefit from PARP inhibitors. Novel combinations of PARP inhibitors with other anticancer therapies are challenging, and better understanding of PARP biology, DNA repair mechanisms, and PARP inhibitor mechanisms of action is crucial. It seems that PARP inhibitor and biologic agent combinations appear well tolerated and clinically effective in both BRCA-mutated and wild-type cancers. They target differing aberrant and exploitable pathways in ovarian cancer, and may induce greater DNA damage and HR deficiency. The input of immunotherapy in ovarian cancer is based on the observation that immunosuppressive microenvironments can affect tumour growth, metastasis, and even treatment resistance. Several biologic agents have been studied in combination with PARP inhibitors, including inhibitors of vascular endothelial growth factor (VEGF; bevacizumab, cediranib), and PD-1 or PD-L1 (durvalumab, pembrolizumab, nivolumab), anti-CTLA4 monoclonal antibodies (tremelimumab), mTOR-(vistusertib), AKT-(capivasertib), and PI3K inhibitors (buparlisib, alpelisib), as well as MEK 1/2, and WEE1 inhibitors (selumetinib and adavosertib, respectively). Olaparib and veliparib have also been combined with chemotherapy with the rationale of disrupting base excision repair via PARP inhibition. Olaparib has been investigated with carboplatin and paclitaxel, whereas veliparib has been tested additionally in combination with temozolomide vs. pegylated liposomal doxorubicin, as well as with oral cyclophosphamide, and topoisomerase inhibitors. However, overlapping myelosuppression observed with PARP inhibitor and chemotherapy combinations requires further investigation with dose escalation studies. In this review, we discuss multiple clinical trials that are underway examining the antitumor activity of such combination strategies.

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DRES-02. PARYLATION OF MGMT BY PARP IS REQUIRED FOR MGMT MEDIATED TEMOZOLOMIDE-INDUCED O6-METHYLGUANINE REPAIR: A NOVEL MECHANISM OF MGMT ACTION

Neuro-Oncology ◽

10.1093/neuonc/noz175.290 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi71-vi72 ◽

Cited By ~ 1

Author(s):

Shaofang Wu ◽

Feng Gao ◽

Dimpy Koul ◽

Alfred Yung

Keyword(s):

Dna Repair ◽

Dna Methyltransferase ◽

Parp Inhibitor ◽

Malignant Gliomas ◽

Parp Inhibitors ◽

Parp Inhibition ◽

Protein Activity ◽

Damaged Dna

Abstract Temozolomide (TMZ) is the standard chemotherapy for malignant gliomas (MG), and resistance to this drug is mediated by the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Epigenetic silencing of the MGMT gene by promoter methylation in about 40% patients is associated with loss of MGMT expression that compromises DNA repair leading to favorable response to TMZ therapy. Understanding the mechanism of MGMT mediated repair and modulating MGMT activity will enhance TMZ activity in MGMT unmethylated MG. Here we report a novel mode of regulation of MGMT protein activity by Poly-ADP-ribose polymerase (PARP). We found that PAPR physically interacts with MGMT and PARylates MGMT in response to TMZ treatment. We further showed PARylation of MGMT by PAPR is required for MGMT binding to DNA and to remove O6-methylguanine adducts in damaged DNA induced by TMZ. All 4 PARP inhibitors (trapping and non-trapping) tested (Talazoparib, Pamiparib, Veliparib, Olaparib) can inhibit PARP-MGMT binding, PARylation of MGMT, binding to DNA and subsequent removal of O6 - lesions in damaged DNA. We showed combination of PARP inhibitor with TMZ potentiated TMZ cytotoxicity in both MGMT methylated and unmethylated Glioma stem cell lines, but more profoundly in unmethylated group in vitro and in vivo. PARP inhibition acted as a double-edged sword in MGMT unmethylated MG: blocking BER/SSBR pathway to repair TMZ induced N7-MetG and O3-MetA, and more importantly, suppressing PARP-mediated PARylation of MGMT and thus silencing MGMT activity to repair O6-MetG, resulting in augmented cytotoxicity. This is the first study to show that PARylation of MGMT by PARP is required for repairing TMZ-induced O6-methylguanine adducts, and inhibition of MGMT PARylation abolishes MGMT function and renders sensitization to TMZ treatment. This finding provides a rationale for combining TMZ/CCNU and PARP inhibitors in MGMT unmethylated MG patients to enhance the benefit of adjuvant chemotherapy.

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PARP Inhibition (OLAPARIB) Enhance Melphalan and Nutlin-3a Sensitivity in TP53 Positive Multiple Myeloma

Blood ◽

10.1182/blood.v120.21.1846.1846 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1846-1846

Author(s):

Sinto Sebastian ◽

Marta Chesi ◽

Esteban Braggio ◽

Leif Bergsagel ◽

Keith Stewart ◽

...

Keyword(s):

Dna Repair ◽

Cell Lines ◽

Alkylating Agents ◽

Parp Inhibitor ◽

Parp Inhibition ◽

Parp Cleavage ◽

Wild Type ◽

Combination Studies ◽

Wild Type P53

Abstract Abstract 1846 Background The low frequency of TP53 (p53) alterations (<10%) in MM makes this tumor an ideal candidate for p53-activation therapies. Unfortunately, DNA alkylating agents (cyclophosphamide and melphalan), when used alone, cannot fully exploit p53 mediated apoptosis. It is currently unknown the extent to which DNA alkylating agents and p53 activating small molecules are activating functional p53 signaling to induce apoptosis in primary MM cells, because, p53 mainly induces cell cycle arrest/DNA repair or apoptosis in the DNA damage response. Emerging studies demonstrate that PARP activation and p53 poly(ADP-ribosyl)ation can negatively influence apoptosis induction but the exact molecular mechanisms are unknown. Methods For apoptosis and gene expression analysis 05 × 106 cells were incubated with 2.5 μM of melphalan, 10 μM of olaparib and 2.5 μM of nutlin-3a alone and/or combinations of melphalan with olparib and/or nutlin3a with olaprib for 24 to 72 hours before they were examined for cell death by the annexin-PI and FACS analysis. Gene and protein expression were measured by RT-PCR, western blot, and immunohistochemistry. For combination studies, cells were incubated with 0.194–50 μM of melphalan and 0.625–40 μM of either olaparib or ABT-888 for 72 hours. p53 knock-down performed by lentiviral mediated shRNA. Vk*MYC mice with significant gammopathy (>20g/l on SPEP) used for in-vivo drug combination studies. Results Preliminary results support our principle hypothesis that, a PARP inhibitor (olaparib) enhanced Melphalan sensitivity in wild type p53 MM cell lines H929 and MM1S but not in p53 mutated or homozygously deleted cell lines U266 and KMS11, respectively. Moreover, we demonstrate that p53 knock-down decreased the synergistic effect of combining a PARP inhibitor with melphalan and Nutlin-3a. Again, combining a PARP inhibitor with the DNA alkylating agent melphalan induced clear PARP cleavage, a signature of apoptosis in wild type p53 MM cell lines H929 and MM1S. No significant PARP cleavage was observed after melphalan or olaparib treatment alone in H929 and MMIS. As expected, the p53 mutant cell line U266 did not show any PARP cleavage and p21 up-regulation after both drug treatments. Here we propose that the hyper-activated p53 from PARP inhibition along with DNA alkylating agents (melphalan) and/or p53 activating agents (nutlin-3a) result in better responses. Finally, in a murine xenograft model of human MM, olaparib potentiated melphalan activity in vivo, with significant reduction in M spike level. Conclusion Our studies indicate that DNA alkylating agents activate wild type p53, but leads to DNA repair and cell survival and this can be abolished by PARP inhibition in wild type p53 expressing MM cases. Moreover, our study also found that olaparib, and ABT-888 - PARP1 inhibitors currently in clinical trials - display different dose responses in MM cell lines and in the abilities of individual PARP inhibitors to sensitize MM cell lines to melphalan varied to a great extent in a cell context- and cell line specific manner. Disclosures: No relevant conflicts of interest to declare.

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Cell Line-Dependent Synergy Between the PARP Inhibitor Veliparib and the Proteasome Inhibitor Bortezomib in the Killing of Myeloma Cells

Blood ◽

10.1182/blood.v126.23.5556.5556 ◽

2015 ◽

Vol 126 (23) ◽

pp. 5556-5556 ◽

Cited By ~ 1

Author(s):

Alex Xu ◽

Amitabha Mazumder ◽

James A. Borowiec

Keyword(s):

Dna Repair ◽

Cell Line ◽

Cell Lines ◽

Synthetic Lethality ◽

Parp Inhibitor ◽

Lethal Dose ◽

Myeloma Cell ◽

Chemotherapeutic Agents ◽

Molecular Heterogeneity ◽

Rpmi 8226

Abstract One hallmark of multiple myeloma is its genetic instability, leading to extensive molecular heterogeneity. This has led to the hypothesis that a high level of DNA repair is needed to counterbalance the continual genotoxic stress seen in these cells. One important DNA repair pathway involves PARP (poly-ADP ribose polymerase 1 and 2). With the goal of developing improved therapies against myeloma, we examined for potential synergy between the PARP inhibitor veliparib and agents currently used to treat myeloma. In these pre-clinical studies, various myeloma cell lines including OPM2.2 and RPMI 8226 are being tested. Cells in triplicate are exposed to myeloma therapeutics (e.g., bortezomib, doxorubicin, cyclophosphamide) in the presence and absence of a sub-lethal dose of veliparib. Cells are incubated for 48 h and viability then assayed by luminescence using CellTiter-Glo (Promega). Dependent on the cell line, we found that veliparib can be synthetically lethal with other agents. For example, testing OPM2.2 cells, we found that 50 µM veliparib caused a ~7-fold decrease in the bortezomib LC50 from 7.1 nM (bortezomib alone) to 1.0 nM (bortezomib and veliparib; see Figure). We note that the concentration of veliparib employed was significantly below the LC50 of veliparib (410 µM) for these same OPM2.2 cells. In contrast, RPMI 8226 cells did not show a significant synergy between bortezomib and veliparib, even though the LC50 of each agent alone was similar to that found for OPM2.2 cells. We are currently examining the synergy between veliparib and other chemotherapeutic agents and additional myeloma cell lines. These studies will determine the generality of a potential synthetic lethality between these agents, and reveal whether use of a PARP inhibitor has the potential to provide improved treatment options against myeloma. Disclosures No relevant conflicts of interest to declare.

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The PARP inhibitor olaparib (AZD2281) as potent radiosensitizer of head and neck cancer cells.

Journal of Clinical Oncology ◽

10.1200/jco.2012.30.15_suppl.e16018 ◽

2012 ◽

Vol 30 (15_suppl) ◽

pp. e16018-e16018 ◽

Cited By ~ 1

Author(s):

Inge Tinhofer ◽

Mariya Boyko-Fabian ◽

Franziska Niehr ◽

Ulrich Keilholz ◽

Volker Budach

Keyword(s):

Dna Repair ◽

Head And Neck ◽

Cell Lines ◽

Parp Inhibitor ◽

Clonogenic Survival ◽

Dose Effect ◽

Parp Inhibition ◽

Cross Resistance ◽

Synergistic Activity ◽

Potential Biomarker

e16018 Background: Current combined radiotherapy regimens for squamous cell carcinoma of the head and neck (SCCHN) are frequently not curative, necessitating novel therapeutic strategies. Inhibitors of poly(ADP-ribose) polymerases (PARPi), either alone or in combination with chemo- and radiotherapy have been shown to be highly active in tumor cells with intrinsic defects in DNA repair. Despite the frequent occurrence of genomic alterations in SCCHN cells also affecting their capacity of DNA repair the radiosensitizing potential of PARPi has not been addressed in detail so far. In this study, the efficacy of PARPi as radiosensitizer in SCCHN and possible mechanisms of cross-resistance between PARPi and cisplatin were evaluated. Methods: Usingthe clonogenic survival assay and a panel of 10 SCCHN cell lines the sensitivity of SCCHN cells to olaparib alone (0 to 500 nM) or in combination with irradiation (0 to 4 Gy) was determined. Survival fractions for given treatments were calculated on the basis of survival of untreated cells. In addition, the activity of cisplatin to inhibit clonogenic growth and its radiosensitizing potential was determined. From the dose-effect curves the IC50 values and the combinatory indices were calculated using the CalcuSyn Software. Results: In 9 of 10 cell lines, olaparib monotherapy showed significant inhibitory activity on clonogenic survival. Synergistic activity of olaparib in combination with irradiation was observed in all cell lines. No correlation between sensitivity of cells to olaparib and cisplatin (IC50 cisplatin vs IC50 olaparib: r2=0.042, p=.57; IC50 cisplatin vs CI [IR+olaparib]: r2=0.005, p=.95) was observed. Furthermore, the activity of olaparib was not dependent on the p53 genotype. Conclusions: The combination of PARPi with radiotherapy represents an active therapeutic regimen in SCCHN. The observed high activity of this combination even in cells with reduced sensitivity to cisplatin and p53 dysfunction suggests its clinical usefulness also in the group of patients with more aggressive disease and the second-line setting. Currently, detailed molecular characterization for identification of potential biomarker for tumor susceptibility to PARP inhibition is ongoing.

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Kinase Phosphorylation-based Mechanisms of PARP Inhibitor Resistance During Synthetic Lethal Oncotherapy

Current Signal Transduction Therapy ◽

10.2174/1574362413666180724134204 ◽

2020 ◽

Vol 15 (1) ◽

pp. 12-23

Author(s):

Eriko Osaki ◽

Shinya Mizuno

Keyword(s):

Cancer Progression ◽

Catalytic Domain ◽

Synthetic Lethality ◽

Excision Repair ◽

Parp Inhibitor ◽

Clinical Importance ◽

Parp Inhibition ◽

Special Focus ◽

Driver Genes ◽

Kinase Phosphorylation

Background: Poly-(ADP-Ribose) Polymerase (PARP) plays a central role in recovery from single-strand DNA (ssDNA) damage via base excision repair. When PARP activity is inhibited by a NAD+ mimetic analog, ssDNA is converted into a Double-Strand Break (DSB) during the S-phase in a cell cycle. However, the DSB site is repaired in a process of Homologous Recombination (HR) that is derived by genes such as BRCA1/2, PALB2, and RAD51. Under conditions of HR dysfunction, including mutations of BRCA1/2 (called BRCAness), PARP inhibitor (PARPi) induces “synthetic lethality” in BRCAness-specific cancer cells. Indeed, clinical trials using forms of PARPi that include olaparib, veliparib and rucaparib, have revealed that PARP inhibition produces a dramatic effect that actually arrests cancer progression. Its clinical efficiency is limited, however, due to the acquisition of PARPi resistance during long-term use of this inhibitor. Thus, it is important to elucidate the mechanisms of PARPi resistance. Methods: We searched the scientific literature published in PubMed, with a special focus on kinase phosphorylation that is involved in acquiring PARPi resistance. We also summarized the possible molecular events for recovering HR system, a key event for acquiring PARPi resistance. Results: CDK1 is a critical kinase for 5’-3’ DNA end resection, which is important for generating ssDNA for recruiting HR-priming factors. CDK12 is necessary for the transcription of HR-driver genes, such as BRCA1, BRCA2, RAD51 and ATR via the phosphorylation of RNA Pol-II. PLK-1 participates in driving HR via the phosphorylation of RAD51. The PI3K-AKT-mTOR signaling cascade is involved in BRCA1 induction via an ETS1 transcriptional pathway. Even under ATMdeficient conditions, the ATR-CHK1 axis compensates for loss in the DNA damage response, which results in HR recovery. The HGF receptor Met tyrosine kinase is responsible for promoting DNA repair by activating the PARP catalytic domain. Conclusion: These kinase-based signaling pathways are biologically important for understanding the compensatory system of HR, whereas inactivation of these kinases has shown promise for the release of PARPi resistance. Several lines of preclinical studies have demonstrated the potential use of kinase inhibitors to enhance PARPi sensitivity. We emphasize the clinical importance of chemical inhibitors as adjuvant drugs to block critical kinase activities and prevent the possible PARPi resistance.

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

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.633344 ◽

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.

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Cytocidal Antitumor Effects against Human Ovarian Cancer Cells Induced by B-Lactam Steroid Alkylators with Targeted Activity against Poly (ADP-Ribose) Polymerase (PARP) Enzymes in a Cell-Free Assay

Biomedicines ◽

10.3390/biomedicines9081028 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1028

Author(s):

Nikolaos Nikoleousakos ◽

Panagiotis Dalezis ◽

Aikaterini Polonifi ◽

Elena G. Geromichalou ◽

Sofia Sagredou ◽

...

Keyword(s):

Ovarian Cancer ◽

Mrna Expression ◽

Cancer Cells ◽

Cell Lines ◽

Synthetic Lethality ◽

Parp Inhibitor ◽

Positive Control ◽

Ovarian Cancer Cells ◽

Antitumor Effects

We evaluated three newly synthesized B-lactam hybrid homo-aza-steroidal alkylators (ASA-A, ASA-B and ASA-C) for their PARP1/2 inhibition activity and their DNA damaging effect against human ovarian carcinoma cells. These agents are conjugated with an alkylating component (POPA), which also served as a reference molecule (positive control), and were tested against four human ovarian cell lines in vitro (UWB1.289 + BRCA1, UWB1.289, SKOV-3 and OVCAR-3). The studied compounds were thereafter compared to 3-AB, a known PARP inhibitor, as well as to Olaparib, a standard third-generation PARP inhibitor, on a PARP assay investigating their inhibitory potential. Finally, a PARP1 and PARP2 mRNA expression analysis by qRT-PCR was produced in order to measure the absolute and the relative gene expression (in mRNA transcripts) between treated and untreated cells. All the investigated hybrid steroid alkylators and POPA decreased in vitro cell growth differentially, according to the sensitivity and different gene characteristics of each cell line, while ASA-A and ASA-B presented the most significant anticancer activity. Both these compounds induced PARP1/2 enzyme inhibition, DNA damage (alkylation) and upregulation of PARP mRNA expression, for all tested cell lines. However, ASA-C underperformed on average in the above tasks, while the compound ASA-B induced synthetic lethality effects on the ovarian cancer cells. Nevertheless, the overall outcome, leading to a drug-like potential, provides strong evidence toward further evaluation.

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Intraoperative Assessment of IDH Mutation Status and Tumor Invasioni in Glioma

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqab191.302 ◽

2021 ◽

Vol 156 (Supplement_1) ◽

pp. S141-S142

Author(s):

H Brown ◽

R Chen ◽

R Cooks ◽

D Garcia ◽

K Chaichana ◽

...

Keyword(s):

Unmet Need ◽

Lipid Profiles ◽

Ionization Mass ◽

Idh Mutation ◽

Fresh Tissue ◽

Mutation Status ◽

Ms Analysis ◽

Idh Mutations ◽

Desi Ms ◽

Sensitivity Specificity

Abstract Introduction/Objective Maximizing surgical resection in gliomas, while avoiding compromising non-infiltrated tissue, is associated with survival benefit. Current methodologies are suboptimal in providing rapid, intraoperative molecular characterization of tissue. We address this unmet need by using desorption electrospray ionization mass spectrometry (DESI-MS) for the intraoperative molecular assessment of gliomas. Methods/Case Report This prospective study uses intraoperative DESI-MS analysis of fresh tissue to evaluate IDH mutations via 2-hydroxyglutarate intensity and TCP via measurement of N-acetylaspartic acid (NAA) intensity and characteristic lipid profiles in less than three minutes. Blinded review of the tissue smears by a neuropathologist is used to validate IDH mutation status and TCP estimates. Results (if a Case Study enter NA) Presently, 529 biopsies from 85 enrolled patients have been collected and analyzed at two institutions. TCP assessment based on NAA intensity in 203 biopsies at the first institution yielded sensitivity, specificity, and accuracy values of 91, 76, and 83%, whereas TCP estimates via characteristic lipid profiles yielded 76, 85, and 81%, respectively. Assessment of IDH mutation status of 71 core biopsies yielded sensitivity, specificity, and accuracy values of 89, 100, and 94%. Ongoing validation of the methodology is being performed at a second institution, where we have collected 282 biopsies from 36 patients. IDH mutation assessment of the first 15 patients indicate 100% sensitivity, specificity, and accuracy. Conclusion This study represents the first and largest study using DESI-MS for the intraoperative evaluation of IDH status and TCP measurement in gliomas. Prospectively, we propose to modify our DESI-MS system to allow estimation of IDH mutation status and TCP in surgical cavities without the need for a biopsy by placing a surgical material along the margin and transferring material from the blot to a microscope slide prior to DESI-MS analysis. We envision molecular analysis by DESI-MS as a complementary technique to histopathology capable of providing additional clinical information in near real-time.

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PARP Inhibitor Resistance Mechanisms and Implications for Post-Progression Combination Therapies

Cancers ◽

10.3390/cancers12082054 ◽

2020 ◽

Vol 12 (8) ◽

pp. 2054

Author(s):

Elizabeth K. Lee ◽

Ursula A. Matulonis

Keyword(s):

Synthetic Lethality ◽

Parp Inhibitor ◽

Parp Inhibitors ◽

Resistance Mechanisms ◽

Parp Inhibition ◽

Combination Therapies ◽

Mechanisms Of Resistance ◽

Damage Repair ◽

Inhibitor Resistance

The use of PARP inhibitors (PARPi) is growing widely as FDA approvals have shifted its use from the recurrence setting to the frontline setting. In parallel, the population developing PARPi resistance is increasing. Here we review the role of PARP, DNA damage repair, and synthetic lethality. We discuss mechanisms of resistance to PARP inhibition and how this informs on novel combinations to re-sensitize cancer cells to PARPi.

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