Citations

Abstract Poly (ADP-ribose) polymerase (PARP) plays an important role in several DNA repair processes, and previous studies with various PARP inhibitors have demonstrated robust enhancement of sensitivity to temozolomide (TMZ) chemotherapy in pre-clinical models of glioblastoma multiforme (GBM). The focus of this study was to evaluate the antitumor effects of a novel PARP inhibitor, BMN 673, as a single agent and in combination with TMZ in the established U251 glioma cell line, neurosphere cultures from the primary Mayo GBM xenograft line GBM12, and TMZ-resistant cells derived from either line (U251TMZ, GBM12TMZ(MGMT high) and GBM12TMZ(MGMT low)). In a biochemical assay of PARP inhibition, BMN 673 potently suppressed poly-ADP-ribosylation of cellular proteins at concentrations of 3 nM following hydrogen peroxide treatment of U251 cells. Single agent treatment had modest anti-tumor activity with 30 nM BMN 673 reducing absorbance in a CyQUANT cell proliferation assay relative to control treatment in both U251 and U251TMZ cells (Table 1). BMN 673 co-treatment also enhanced the efficacy of TMZ in both U251-derivative lines at a clinically relevant concentration of TMZ. Similarly, treatment with BMN673 alone or in combination with TMZ inhibited primary neurosphere formation in all three GBM12 models. Notably, the addition BMN 673 clearly re-sensitized both resistant GBM12 sub-lines to relatively low concentrations of TMZ. Consistent with a mechanism involving disruption of DNA repair, combined treatment with BMN 673 and TMZ resulted in robust activation of ATM-mediated KAP1 phosphorylation (Ser824) and ATR-mediated Chk1 phosphorylation (Ser345) as compared to TMZ or BMN 673 alone 24 hours after treatment. In conclusion, BMN673 is a promising PARP inhibitor with high potency and cytotoxicity in vitro against both TMZ sensitive and TMZ resistant GBM cells. Table 1 - In vitro antitumor effects of TMZ combined with BMN673 TMZ, microM 0 nM BMN673 30 nM BMN673 CyQUANT U251 Relative absorbance Relative absorbance 0 1.00 0.58 30 0.80 0.30 U251TMZ 0 1.00 0.69 30 1.02 0.21 Primary Neurosphere Assay GBM12 Relative Count Relative Count 0 1.00 0.66 5 0.32 0 10 0.01 0 GBM12TMZ (MGMT high) 0 1.00 0.32 5 1.11 0.02 10 1.04 0.01 GBM12TMZ (MGMT low) 0 1.00 0.25 5 0.86 0.03 10 0.75 0 Citation Format: Sani H. Kizilbash, Ryo Kawashima, Shiv Gupta, Ann C. Mladek, Yuqiao Shen, Jann N. Sarkaria. BMN 673 potentiates efficacy of temozolomide in sensitive and resistant glioblastoma models. [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 2067. doi:10.1158/1538-7445.AM2013-2067

Abstract Resistance to temozolomide (TMZ) in the majority of glioblastoma multiforme (GBM) is mediated by O6-methylguanine methyltransferase (MGMT). In this study, the efficacy of TMZ, a mono-functional methylating agent, was compared to a bi-functional TMZ analog (DP68) and a corresponding mono-functional TMZ analog (DP86) in established glioma lines (T98, U251), primary GBM xenograft lines (GBM12, GBM22, GBM6) and a TMZ-resistant model with high level MGMT expression (GBM12TMZ). Using a combination of CyQuant and neurosphere assays, the IC50 with TMZ treatment for MGMT expressing lines (U251, GBM12, GBM22) was much lower than non-expressing lines (T98, G6, G12TMZ), while all lines were sensitive to DP68 regardless of MGMT status (see Table). In the same assays, cells were less sensitive to DP86, but cytotoxicity was also independent of MGMT status. In both U251 and T98, DP68 resulted in a time-and dose-dependent induction of markers for DNA damage and checkpoint activation (P-H2AX, ATM, KAP1, Chk1 and Chk2) and a pronounced S-phase arrest within 24 hours of treatment. Based on these results and the hypothesis that DP68 induces DNA cross-links, siRNA knockdown was used to further dissect the importance of the ATM and ATR signaling pathways and the Fanconi Anemia (FA) cross-link repair pathway for DP68 cytotoxicity. Compared to no treatment, 1 microM DP68 resulted in 100% relative absorbance in siCONtrol transfected U251 cells, 41% for siATR, 35% for siFANCD2 and 90% for siATM. In contrast, only siATR and not siFAND2 nor siATM sensitized U251 cells to DP86. Similarly, inhibition of ATR (VE-821), but not ATM (KU-60019) potently sensitized cells to DP68 (see Table). Taken together, the inhibitory effects of DP68 are superior to TMZ in the GBM cell lines tested, regardless of MGMT expression. Furthermore, the siRNA and western blotting suggest that recovery from DP68 is dependent on ATR and the FA repair pathway. TMZ (IC50, microM) DP68 (IC50, microM)) DP86 (IC50, microM)) CyQuant Ctrl 1uM VE-821 1uM KU-60019 Ctrl 1uM VE-821 1uM KU-60019 Ctrl 1uM VE-821 1uM KU-60019 U251 25 20 20 2.5 0.8 2.1 70 40 65 T98 >320 200 260 9 2 7 115 60 115 Neurosphere Ctrl VE-821 KU-60019 Ctrl VE-821 KU-60019 Ctrl VE-821 KU-60019 G12 4 3.2 4.2 0.9 0.08 0.7 18 6 18 G22 40 NA NA 1 NA NA 40 NA NA G6 160 NA NA 0.5 NA NA 15 NA NA G12TMZ >300 NA NA 2 NA NA 22 NA NA Citation Format: Ann C. Mladek Tuma, Yulian Ramirez, Dimitrios Pletsas, Richard T. Wheelhouse, Roger M. Phillips, Ross H. Alonzo, Kaitlyn Knudson, Jann N. Sarkaria. Cytotoxicity of a novel bi-functional temozolomide analog, DP68, is independent of MGMT status in glioblastoma models. [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 4476. doi:10.1158/1538-7445.AM2013-4476

Abstract Glioblastoma (GB) is the highest grade and most common form of primary adult brain tumors. Despite surgical removal followed by concomitant radiation and chemotherapy with the alkylating agent temozolomide (TMZ), GB tumors develop treatment resistance and recur, invading brain tissue. Impaired response to treatment occurs rapidly conferring a median survival of just fifteen months. Thus, it is necessary to identify the genetic and signaling mechanisms that promote tumor resistance and spread in order to develop targeted therapies to combat this refractory setting. Our lab has previously published a role for the TWEAK-Fn14 ligand-receptor system in GB cell invasiveness and survival. Here we report that SGEF, a RhoG specific guanine nucleotide exchange factor (GEF), is overexpressed in GB tumors and we hypothesize that SGEF plays an important role in promoting TWEAK-Fn14 mediated glioma invasion and survival. We show that upon TWEAK binding to Fn14, SGEF is recruited to the Fn14 cytoplasmic tail. The Fn14-SGEF interaction requires TRAF2 recruitment and leads to activation of Rac1. Importantly, SGEF mRNA expression is elevated in TMZ-resistant primary GB tumor grafts compared to those with known TMZ sensitivity. SGEF mRNA and protein expression are regulated by the TWEAK-Fn14 signaling axis in an NF-κB dependent manner and inhibition of SGEF expression via shRNA shutdown sensitizes glioma cells to TMZ-induced apoptosis and impairs colony formation following TMZ insult. Furthermore, gene expression analysis of SGEF depleted GB cells revealed impaired expression of a network of DNA repair and survival genes including ATM, ATR, BRCA2, and XIAP among others, as well as increased expression of the pro-apoptotic gene BAD. Understanding the role of SGEF in promoting chemotherapeutic resistance may direct the development of novel targeted therapeutics for TMZ refractory, invasive GB cells. Citation Format: Shannon P. Fortin, Ian T. Mathews, Jonathan Rollo, Julianna T.D. Ross, Marc H. Symons, Jann N. Sarkaria, Nhan L. Tran. SGEF is overexpressed in glioblastoma and mediates TWEAK-Fn14 induced cell survival. [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 4108. doi:10.1158/1538-7445.AM2013-4108

Abstract Biomarkers that select patients for therapeutics would benefit clinical trial design and patient care. The Akt pathway is a therapeutic target in Glioblastoma Multiforme (GBM) and an important determinant of patient outcome. However, it is not known whether activity of this pathway varies among GBM tumors. To investigate we used Akt pathway genes from published GBM expression datasets. We detected 5 patterns of Akt pathway gene expression and these Akt subgroups correlated with prognosis. We analyzed networks within subgroups using both gene set enrichment analysis and a novel method that scores relevance based on both expression and local network connectivity (Komurov et al., PLoS Comput Biol. 2010 6:8, 1-10). The results suggest therapeutic targets within the individual subgroups. Furthermore, preliminary analysis indicates that human GBM xenograft models and primary human GBM manifest similar Akt subgroups. We are investigating rodent xenograft models of Akt subgroups to evaluate subgroup-specific drug sensitivity, and will present a method and examples of analysis integrating gene expression data from human GBM xenografts and primary human GBM. We hypothesize that Akt subgroups will help personalize treatment for GBM therapeutics. Supported by Barrow Neurological Foundation, Halle Family Foundation, and NIH 1 K01 NS064952-01A1 (AMJ). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4138. doi:10.1158/1538-7445.AM2011-4138

Abstract Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults and is associated with a poor prognosis. Progress in developing effective therapies for this disease is significantly limited by the blood-brain barrier (BBB), which limits the delivery of many anti-cancer agents to infiltrative tumor cells. In addition to physical barriers, such as tight junctions, the efflux proteins bcrp and P-gp in the BBB limit the brain distribution of numerous anti-cancer agents. Palbociclib (PD0332991) is a potent Cdk4/6 inhibitor which has shown remarkable efficacy in treating peripheral (non-brain) tumors. The Cdk4 pathway is dysregulated in approximately 75% of GBM; most commonly, the pathway is hyperactivated through the homozygous deletion of p16 (52%), amplification of Cdk4 (18%), or amplification of Cdk6 (1%). The purpose of this study is to define the role of the efflux transporters P-gp and bcrp in the brain distribution of palbociclib and to examine if an intact BBB limits efficacy. Palbociclib brain distribution studies were performed in FVB wild-type, P-gp knockout (PKO; Mdr1a/b(-/-)), bcrp knockout (BKO; Bcrp1(-/-)), and triple knockout (TKO; Mdr1a/b(-/-)Bcrp1(-/-)) mice after an oral dose (10mg/kg). The concentrations of palbociclib from all distribution studies were determined by a sensitive and specific LC-MS/MS assay. Survival studies were conducted in patient-derived primary GBM xenograft models in athymic nu/nu mice. The brain exposure of palbociclib (AUCbrain-to-AUCplasma ratio) was ∼ 33.5, 3.2, and 150-fold higher as compared to WT mice (WT: .044; PKO: 1.34; BKO: 0.13; TKO: 6.24). Further, the steady-state brain-to-plasma ratio (B/P) of palbociclib after a constant intra-peritoneal infusion of 10 µg/hr for 48hrs was ∼120-fold higher in the TKO mice than the WT mice [WT: (0.21 ± 0.07); PKO: (2.48 ± .13); BKO: (0.43 ± 0.12); TKO: (26.5 ± 5.4) p < 0.0001]. Inhibition of P-gp and bcrp with elacridar (10 mg/kg IP) resulted in a marked increase in palbociclib brain distribution [control B/P (0.06 ± 0.02); elacridar treatment (2.0 ± 1.4)]. For survival studies, palbociclib was dosed at 150 mg/kg/day continuously. Consistent with limited brain penetration, palbociclib did not improve the median survival of an orthotopic GBM xenograft model. In contrast, treatment of GBM22 xenografts grown as flank tumors resulted in profound efficacy with a 70 day prolongation in the time for tumor volume to reach 1000mm3. These data suggest the clinical paradigm of a potent anti-cancer agent (for instance, palbociclib) used in the treatment of peripheral disease is less effective in the treatment of brain tumors due to the BBB and active efflux by P-gp and bcrp. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C81. Citation Format: Karen E. Parrish, Jenny L. Pokorny, Rajendar K. Mittapalli, Katrina Bakken, Jann N. Sarkaria, William F. Elmquist. BBB efflux pump activity limits brain penetration of palbociclib (PD0332991) in glioblastoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C81.

Abstract Glioblastoma (GBM) is the most common and malignant form of primary brain tumor. Average survival rate of GBM is 12-15 months from diagnosis. Due to its highly invasive nature, current treatment options have not been able to improve the survival rate in past 20 years. In order to discover GBM therapeutic targets, omics technologies have been widely used in order to identify potential biomarkers. Identification of cancer biomarkers for diagnosis and prognosis continues to evolve as clinical specimen pipelines and technologies are optimized. This research study focused on investigating proteins, metabolites and lipids biomarkers and patterns of human GBM xenografts employing mass spectrometry. Human tumor cell lines GBM 10 and GBM 43 were injected in the right cerebral hemisphere and flank sites in NOD/SCID mice (n = 10 mice per group). After harvesting brain and flank tumors and control brain from mouse models, protein, metabolites, and lipids of tumor samples were collected through one simple extraction procedure, which may solve sample preparation difficulties in omics studies, developed by Dr. Jiri Adamec. These samples were analyzed by reverse phase high performance liquid chromatography - Fourier transform ion cyclotron resonance mass spectrometry (LC-FTMS). FTMS analyzers have the highest resolving power of all MS instruments, which is ideal for complex mixtures such as GBM tissue. Spectra obtained from the FTMS analysis were analyzed using Student t-tests to detect significant differences in tissue profiles at a level of p = 0.05. Compounds below this threshold were identified through a database using the m/z ratio. Lipidomic analysis indicated the possible up and down-regulation of several lipids classes in GBM tissue connected to metabolic pathways, tumor proliferation and immunodepression, such as glycerophospholipids, both up- and down-regulated (e.g. PC38:4 or PG 35:2, respectively), and down-regulated glycosphingolipids (Galβ1-3GlcNAcβ1-3Galβ1-4Glc-Cer, Galβ1-4GlcNAcβ1-3Galβ1-4Glc-Cer), and triglycerides (TG 55:9, 53:4,52:8). We expect that integrated studies of proteomics, metabolomics, and lipidomics increase the confidence of identification of potential biomarkers. Accompanying these studies is a collaborative effort to improve the effectiveness and efficiency of computational pipelines that are imperative to the analytics, visualization, identification, and interpretation of the omics data. Only by carefully integrating the computational pipelines can we successfully perform the types of integrative studies needed to advance the identification of cancer biomarkers for diagnosis and prognosis, and our integrative studies serve as a case study for our pipeline advancement efforts. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B37. Citation Format: Soo Jung Ha, Gordon Showalter, Jenna Rickus, Shanbao Cai, Haiyan Wang, Wei Michael Liu, Jann N. Sarkaria, John Springer, Jiri Adamec, Karen E. Pollok, Kari L. Clase. Proteomic and metabolomic analyses of glioblastoma using mass spectrometry. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B37.

Abstract Purpose: Effective sensitizing strategies potentially can extend the benefit of temozolomide (TMZ) therapy in patients with glioblastoma (GBM). We previously demonstrated that robust TMZ-sensitizing effects of the [poly (ADP-ribose) polymerase] (PARP) inhibitor veliparib (ABT-888) are restricted to TMZ-sensitive GBM xenografts. The focus of this study is to provide an understanding for the differential sensitization in paired TMZ-sensitive and -resistant GBM models. Experimental Design: The impact of veliparib on TMZ-induced cytotoxicity and DNA damage was evaluated in vitro and in vivo in models of acquired TMZ resistance (GBM12TMZ-mgmtHigh, GBM12TMZ-mgmtLow, and U251TMZ), inherent TMZ resistance (T98G), and TMZ-sensitive (U251 and GBM12). In vivo drug efficacy, pharmacokinetics, and pharmacodynamics were analyzed using clinically relevant dosing regimens. Results: Veliparib enhanced TMZ cytotoxicity and DNA-damage signaling in all GBM models in vitro with more pronounced effects in TMZ-resistant lines at 3 to 10 μmol/L veliparib. In vivo, combined TMZ/veliparib, compared with TMZ alone, significantly delayed tumor growth and enhanced DNA-damage signaling and γH2AX levels in the sensitive GBM12 xenograft line but not in the resistant GBM12TMZ lines. The pharmacokinetic profile of veliparib was similar for GBM12 and GBM12TMZ tumors with Cmax (∼1.5 μmol/L) in tissue significantly lower than concentrations associated with optimal in vitro sensitizing effects for resistant tumors. In contrast, robust suppression of PARP-1 expression by shRNA significantly increased TMZ sensitivity of U251TMZ in vitro and in vivo. Conclusions: In vitro cytotoxicity assays do not adequately model the therapeutic index of PARP inhibitors, as concentrations of veliparib and TMZ required to sensitize TMZ-resistant cancer cells in vivo cannot be achieved using a tolerable dosing regimen. Clin Cancer Res; 20(14); 3730–41. ©2014 AACR.

Abstract Purpose: Ovarian cancer has a high recurrence and mortality rate. A barrier to improved outcomes includes a lack of accurate models for preclinical testing of novel therapeutics. Experimental Design: Clinically relevant, patient-derived tumorgraft models were generated from sequential patients and the first 168 engrafted models are described. Fresh ovarian, primary peritoneal, and fallopian tube carcinomas were collected at the time of debulking surgery and injected intraperitoneally into severe combined immunodeficient mice. Results: Tumorgrafts demonstrated a 74% engraftment rate with microscopic fidelity of primary tumor characteristics. Low-passage tumorgrafts also showed comparable genomic aberrations with the corresponding primary tumor and exhibit gene set enrichment of multiple ovarian cancer molecular subtypes, similar to patient tumors. Importantly, each of these tumorgraft models is annotated with clinical data and for those that have been tested, response to platinum chemotherapy correlates with the source patient. Conclusions: Presented herein is the largest known living tumor bank of patient-derived, ovarian tumorgraft models that can be applied to the development of personalized cancer treatment. Clin Cancer Res; 20(5); 1288–97. ©2014 AACR.

Abstract Glioblastoma multiforme is an aggressive, treatment-refractory type of brain tumor for which effective therapeutic targets remain important to identify. Here, we report that cyclophilin B (CypB), a prolyl isomerase residing in the endoplasmic reticulum (ER), provides an essential survival signal in glioblastoma multiforme cells. Analysis of gene expression databases revealed that CypB is upregulated in many cases of malignant glioma. We found that suppression of CypB reduced cell proliferation and survival in human glioblastoma multiforme cells in vitro and in vivo. We also found that treatment with small molecule inhibitors of cyclophilins, including the approved drug cyclosporine, greatly reduced the viability of glioblastoma multiforme cells. Mechanistically, depletion or pharmacologic inhibition of CypB caused hyperactivation of the oncogenic RAS–mitogen-activated protein kinase pathway, induction of cellular senescence signals, and death resulting from loss of MYC, mutant p53, Chk1, and Janus-activated kinase/STAT3 signaling. Elevated reactive oxygen species, ER expansion, and abnormal unfolded protein responses in CypB-depleted glioblastoma multiforme cells indicated that CypB alleviates oxidative and ER stresses and coordinates stress adaptation responses. Enhanced cell survival and sustained expression of multiple oncogenic proteins downstream of CypB may thus contribute to the poor outcome of glioblastoma multiforme tumors. Our findings link chaperone-mediated protein folding in the ER to mechanisms underlying oncogenic transformation, and they make CypB an attractive and immediately targetable molecule for glioblastoma multiforme therapy. Cancer Res; 74(2); 484–96. ©2013 AACR.

Abstract Growing evidence supports a role for the unfolded protein response (UPR) in carcinogenesis; however, the precise molecular mechanisms underlying this phenomenon remain elusive. Herein, we identified the circadian clock PER1 mRNA as a novel substrate of the endoribonuclease activity of the UPR sensor IRE1α. Analysis of the mechanism shows that IRE1α endoribonuclease activity decreased PER1 mRNA in tumor cells without affecting PER1 gene transcription. Inhibition of IRE1α signaling using either siRNA-mediated silencing or a dominant-negative strategy prevented PER1 mRNA decay, reduced tumorigenesis, and increased survival, features that were reversed upon PER1 silencing. Clinically, patients showing reduced survival have lower levels of PER1 mRNA expression and increased splicing of XBP1, a known IRE-α substrate, thereby pointing toward an increased IRE1α activity in these patients. Hence, we describe a novel mechanism connecting the UPR and circadian clock components in tumor cells, thereby highlighting the importance of this interplay in tumor development. Cancer Res; 73(15); 4732–43. ©2013 AACR.