Network modeling of CDF treated pancreatic cancer cells reveals a novel c-myc-p73 dependent apoptotic mechanism

Systems biology and molecular network modeling are important tools that are finding application in anti-cancer drug discovery. These technologies can be utilized to map and evaluate the entire set of pathways modulated by drugs in cancer cells without loosing key details. Such integrated approaches are especially useful in understanding the mechanism of action of agents that do not have a defined target. Our novel compound CDF (a synthetic analogue of curcumin), is one such multi-targeted agent with proven anti-cancer activity in vitro and in vivo. However, its mechanism of action is not fully understood, and thus a thorough analysis of key pathways targeted by CDF would be important for developing targeted and tailored therapy in the future. Applying Ingenuity Pathway Analysis (IPA), we have mapped the pathways altered by CDF treatment of BxPC-3 pancreatic cancer (PC) cells. Illumina HT-12 microar-rays were performed on RNA extracted from CDF treated cells. IPA analysis of gene expression at early time point (24 hrs) revealed deregulation of genes in the c-Myc hub. Western blot analysis validated the activation of c-Myc, p73 and its downstream pro-apoptotic effector Bax with simultaneous down-regulation of Bcl-2 in two distinct pancreatic cancer cell lines (BxPC-3 and Colo-357). In order to further delineate the role of c-Myc in inducing apoptosis, siRNA silencing technology was used. As expected, c-Myc siRNA knockdown resulted in abrogation of the growth inhibitory and apoptotic potential of CDF. In conclusion, our results demonstrate a novel c-Myc driven apoptotic network activated by CDF in PC cells that is independent of wild-type p53, and thus warrants further investigation on the clinical utility of CDF.

Abstract 3706: Novel analogs of dietary thymoquinone with superior bioavailability and anti-tumor activity against GI cancers

Alterations in multiple signaling pathways are a hallmark of most epithelial cancers, including pancreatic (PC) and colon cancers (CC). In principle, agents such as dietary bioactive compounds that affect multiple pathways should exhibit superior effectiveness due to their pleiotrophic actions compared to single pathway targeted therapies. Earlier we had shown that thymoquinone (TQ), a bioactive agent derived from edible black seed plant Nigella Sativa exerts anticancer activity against PC and CC alone or can enhance the effects of chemotherapeutics through mechanisms involving down-regulation of multiple pathways [such as NF-kB, cell cycle, inflammation, anti-apoptosis and angiogenic signaling (Cancer Research 69(13) 2009)]. However, due to poor bioavailability the anti-tumor effects of TQ that are observed at pharmacological high doses (>25 µM in vitro that translates to ∼7.4 g/kg in humans) cannot be considered clinically relevant. To address this problem we have developed a series of potent TQ analogs and among them two (TQ-THB and TQ-TFB patent pending) were found to have greater potency (growth inhibition and apoptosis) than parent TQ (IC50s 5 and 7µM respectively). TQ-THB and TQ-TFB not only show superior in vitro activity against PC, they also demonstrate greater anti-tumor activity in a highly metastatic BxPC-3 pancreatic xenograft model. The analogs are well tolerated and can be given i.v. Most interestingly, these analogs synergize with gemcitabine and FOLFOX that are the standard care for pancreatic and colon cancer respectively. The synergy was found both in cell culture and animal tumor models. Molecular Docking studies revealed that both TQ-THB and TQ-TFB binds very strongly to Cox-2 and NF-kB. This suggests that the analogs work by inhibiting the tumor survival and angiogenic pathways. Based on our novel findings we believe that these dietary analogs hold promise as anticancer agents that warrant further clinical development.

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 3706. doi:10.1158/1538-7445.AM2011-3706

Abstract 594: MDM2 inhibition by MI-219 elicits differential molecular effects in wild-type p53 lymphoma cells

Mutations in TP53 occur in 50% of all cancers but are far less common in hematological malignancies. The activity of wild-type p53 (wt-p53) is frequently compromised in lymphomas by overexpression of MDM2. Small-molecule inhibitors (SMIs) that can disrupt the MDM2-p53 interaction and restore p53 function may be an attractive therapeutic strategy. Although response to MDM2 inhibition has previously been determined to greatly depend on p53 status, p53 functional consequences are not fully understood in the presence of MDM2 SMIs. We recently demonstrated striking growth inhibition of two different classes of MDM2 SMIs: Nutlin-3; a cis-imadiazole and MI-219; a spiro-oxindole. Growth inhibition was seen in wt-, but not mutant-, p53 lymphoma cells and did not affect MDM2 E3 ligase activity.

In this study, we report that MDM2 inhibition exerts differential molecular effects in wt-p53 lymphoma cells. We found that wt-p53 cell lines, FSCCL and KM-H2, are sensitive to MDM2 inhibition in a time- and dose-dependent manner. Moreover, MI-219 showed greater potency compared to analogous concentrations of Nutlin-3. MI-219 caused more pronounced cell cycle arrest of both cell lines in G0/G1 over a 72 hour time period. Treatment stabilized and activated p53 as well as upregulated p21 and MDM2 protein levels. MG132 and cycloheximide treatments were performed in the presence or absence of MI-219 to determine whether the increase in p53 was due to dissociation from MDM2 and not increased degradation or stabilization. Co-immunoprecipitation confirmed MDM2 SMI disruption of the MDM2-p53 interaction. There was clear evidence of apoptosis in FSCCL, but surprisingly not in KM-H2, as indicated by TUNEL/PI staining (54.39% ± 4.78 vs. 1.32% ± 0.52 after 24 hours). Additionally, apoptosis markers were induced at both mRNA (p53AIP1) and protein levels (caspase-3 and PARP cleavage) after exposure to MI-219 in FSCCL compared to KM-H2. The molecular mechanisms by which MDM2 SMIs exert this differential effect are currently under investigation.

Our data presents the preclinical structure for further exploration of MI-219 as a therapeutic approach in the treatment of wt-p53 lymphomas. However, based on our findings, we conclude that additional insights to p53 biology are necessary to maximize their therapeutic potential from preclinical to clinical development.

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 594. doi:10.1158/1538-7445.AM2011-594

Abstract 2822: Targeting Mcl-1 regulated apoptosis pathway as a novel therapy in pancreatic cancer

Resistance of pancreatic cancer to current treatment protocols as a consequence of apoptosis defects is a major cause of treatment failure. Therapeutic approaches that specifically target components of these molecular mechanisms are urgently needed. The anti-apoptotic protein Mcl-1, a member of the Bcl-2 family proteins, has emerged as a promising therapeutic target. Consistent with its anti-apoptotic function, the overexpression of Mcl-1 in pancreatic cancer cells has been associated with tumor progression and resistance to current chemotherapeutics.

Applying high throughput screening approach several promising lead compounds as selective Mcl-1 inhibitors were identified and evaluated. Based on one of the most promising lead compounds we have designed and synthesized several analogues. The most potent compound, UMI-77, binds to Mcl-1 protein with Ki = 205 nM determined by fluorescence polarization based assay and shows selectivity over Bcl-2 and Bcl-xL. NMR spectroscopy studies demonstrate that UMI-77 binds to the same BH3 domain of Mcl-1 as the Bim BH3 peptide and antagonizes Mcl-1 function. UMI-77 inhibits cell growth and induces apoptosis in pancreatic cancer cells with high Mcl-1 levels (BxPC-3 and Panc-1) in a time and dose-dependent manner, accompanied by caspase-3 activation. Applying siRNA approach, the transient suppression of Mcl-1 abrogated UMI-77 mediated apoptosis in BxPC-3 cells, demonstrating that UMI-77 as a single agent can inhibit cell growth and induce apoptosis in pancreatic cells in a Mcl-1 dependent manner. Co-immunoprecipitation experiments revealed that UMI-77 blocks the heterodimerization of Mcl-1/Bax and Mcl-1/Bak in cells. By using murine embryonic fibroblasts (MEFs), wild type and deficient in both Bax and Bak (double knock out), it was demonstrated that the cytotoxic activity and induction of apoptosis by UMI-77 mainly depend on Bax and/or Bak, suggesting that function as BH3 mimetic. In order to verify the clinical utility of UMI-77, we tested its in vivo efficacy using BxPC-3 xenograft model. The maximum tolerated dose (MTD) of UMI-77 in SCID mice was determined to be 60mg/kg i.v. We further demonstrated that UMI-77 at MTD showed statistically significant and effective tumor growth inhibition in BxPC-3 xenograft model. At the end of the treatment, western blot analysis for different molecular markers on lysates isolated from tumors harvested from SCID mice revealed enhancement of proapoptotic markers in UMI-77 treated animals compared to control.

Collectively, these promising findings warrant further chemical modifications of this compound and optimization toward developing a new class of anticancer drugs, Mcl-1 inhibitors.

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 2822. doi:10.1158/1538-7445.AM2011-2822

Abstract 209: Zinc is essential for the efficacy of p53 reactivating drugs

According to the International Zinc Nutrition Consultative Group, 20% of the world's population lack sufficient Zinc in their diet. Zinc is required by >200 different proteins including the most extensively studied Zinc-finger protein p53 that is considered guardian of genome. Its crucial role in p53 core domain folding has been proven, as disruption of this interaction greatly reduces or abrogates p53 DNA binding and transactivation of target genes. Therefore, alterations in Zinc homeostasis may impair p53 activity and also reduce the efficacy of wt-p53 re-activating drugs. Recently, we have shown that Zinc is necessary for proper wt-p53 re-activation and cancer cell apoptosis by small molecule inhibitors of HDM2 such as MI-219 (Oncogene 2010). As a logical extension to our these results, in this clinically translatable study we show that Zinc is crucial for the activity of mutant p53 reactivated by PRIMA and provide evidence for using combination therapies with PRIMA that include supplemental Zinc for the treatment of mut-p53 tumors. ZnCl2 (64 µM) enhanced PRIMA (0-100 µM) anti-tumor activity (induced growth inhibition and apoptosis and suppressed colony formation) in multiple pancreatic, colon and breast cancer cell lines. Chelation of Zinc by chelex 100 resin not only blocked the activity of PRIMA, but also suppressed reactivation of the mut-p53 and its downstream effector molecules 14-33σ, Bax and p21 as detected by western blot analysis. N,N,N'N′-tetrakis(−)[2-pyridylmethyl]-ethylenediamine (TPEN), a specific Zinc chelator, but not 1,2-bis-(o-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid (Bapta-AM), a calcium chelator or desferroxamine, a iron chelator blocked PRIMA-induced apoptosis. Zinc chelation by TPEN suppressed p53 nuclear localization that is important for its transcriptional activity. Zinc did not affect PRIMA activity in p53 null cells, suggesting that this was indeed a p53 dependent phenomenon. Addition of Zinc suppressed the known p53 feedback MDM2 activation, which could be restored by TPEN. Before wt- or mut-p53 re-activating drugs such as MI-219 and PRIMA make their way into the clinic for cancer patients who usually have mild to moderate Zinc deficiency, we believe that the results of our findings will help in the design of novel combination strategies with Zinc for better survival outcome.

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 209. doi:10.1158/1538-7445.AM2011-209

Abstract 2585: Snail-p53 interaction inhibitor GN25 and its combination with Oxaliplatin targets both hedgehog signaling and K-ras pathway in pancreatic cancer

Activation of hedgehog (Hh) signaling is widely observed in human cancers including pancreatic cancer (PC). Similarly, mutations in K-Ras gene is found in >80% of PC. Constitutive activation of Hh signaling component Gli in turn enhances p53 suppressor Snail. Studies from our group have revealed that p53 is further suppressed by direct binding with oncogenic K-Ras-induced Snail. Therefore in order to target combined suppressive effects of Hh signaling and K-Ras-induced snail on p53 pathway, a specific inhibitor of the p53-Snail binding (GN25) was developed. This inhibitor can induce p53 expression and functions in K-Ras-mutated cells, with no toxicity to normal cells (Oncogene 2010). Here we show that GN25 when combined with Oxaliplatin induces synergistically (combination index CI<1) enhanced growth inhibition (MTT) and apoptosis (Histone DNA ELISA and Annexin V FITC) in multiple PC cell lines (AsPC-1, Capan-2, BxPC-3 and Colo-357) irrespective of the mutational or functional status of both p53 and K-Ras. Interestingly, we found that some of the above cell lines have hyper activation of Hh signaling that results in constitutively over activation of Gli. Western blot analysis demonstrated that GN25/oxaliplatin re-activated the p53 protein and downstream effector molecules such as pro-apoptotic Bax and cell cycle regulator p21. Further analysis showed that GN25/oxalipltin interferes with the Hh signaling and suppresses Snail. In SCID mice studies in vivo, the maximum tolerated dose of GN25 was found to be 35 mg/kg i.v. In addition, it can be given in combination with oxaliplatin at 5 mg/kg i.p twice a week for two weeks. The combination studies of GN25/oxaliplatin in multiple tumor xenografts (wt-k-Ras BxPC-3 and AsPC-1 mut-p53 k-Ras) are ongoing. So far our results suggest that GN25/oxaliplatin is a strong combination against hyper activated Hh and mutant K-Ras-initiated human pancreatic cancer irrespective of mutational status of p53.

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 2585. doi:10.1158/1538-7445.AM2011-2585

Abstract 4910: Unveiling the role of network and systems biology in pancreatic cancer drug discovery

Over the last half decade our laboratory has extensively worked on the preclinical development of small molecule inhibitor of HDM2 (MI-219-Ascenta Therapeutics) in multiple tumor models with especial emphasis on the intractable pancreatic cancer (PC). During this discourse we have observed significant anti-tumor activity when MI-219 was given with oxaliplatin that lead to tumor free survival in 50% of the animals. However, not much is known about the exact mechanism behind this synergy. Here we applied a network-centric approach to identify the global expression changes and the networks involved in this two drug combination without losing the key molecular details. Gene analysis of wt-p53 capan-2 cells shows that MI-219 alone induces a minimal alteration (only 48 genes). Oxaliplatin (a cytotoxic drug) treatment, on the other hand showed alterations of 700 genes. However, the combination of MI-219-oxaliplatin resulted in emergence of 286 synergy unique genes. Principal component analysis revealed that each drug treatment had unique global gene signatures. Further analysis of the synergy unique genes revealed the presence of 14 statistically enriched functional pathways. Overall, the central p53 activity hub was found to be supported by 5 crucial players; CREBBP which is ubiquitously expressed in PC and is involved in the transcriptional co-activation of p53. CARF that is responsible for p53 stability along with NF-κB and EGR1 tumor suppressor modules, all positively affecting p53 re-activation that drives cells towards apoptosis. Additionally, our analysis revealed a novel role of hepatocyte nuclear factor alpha (HNF4α) in aiding this synergy. In addition to PC, the gene signatures could be verified and validated at the RNA and protein level in multiple wt-p53 solid tumor cell lines like MCF-7 for breast and HCT-116 for Colon. siRNA knockdown of key network genes abrogated apoptotic potential of MI-219-oxaliplatin in all three cell lines and confirmed their key role in the observed anticancer effects of this combination. Our findings show that Network and Systems biology can be utilized in identification of crucial driver genes and help in the design of drug combinations in a genetically pre-defined subset of patients that would positively impact treatment outcome.

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 4910. doi:10.1158/1538-7445.AM2011-4910

Abstract 2385: Activated Kras and INK4a/Arf deficiency cooperate to produce pancreatic cancer involved with Notch and NF-κB pathways

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the United States. Therefore, novel strategies for the prevention and treatment are urgently needed. Kras mutations are observed in 80%-90% of pancreatic cancer. Oncogenic Kras is involved with the initiation or early phase of PDAC. To understand the molecular mechanisms, several mouse models of PDAC have been generated by targeting a conditionally mutated KrasG12D to recapitulate the progression of PDAC. It was previously shown that one mouse model which activated Kras and Ink4a/Arf deficiency cooperate to produce metastatic PDAC. However, the molecular mechanism(s) by which Kras and Ink4a/Arf deficiency contribute to PDAC has not been fully elucidated. Here, we assessed the molecular alterations in mice which are activated Kras and Ink4a/Arf deficiency. For the first time, we demonstrated that deletion of Ink4a/Arf in Kras expressing mice leads to PDAC partly through Notch and NF-κB signaling pathways. Moreover, we show that several miRNAs, such as miR-200 family and miR-34 could partially play roles in tumorigenesis in activated Kras and Ink4a/Arf deficiency mice.

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 2385. doi:10.1158/1538-7445.AM2011-2385

Progress in nanotechnology based approaches to enhance the potential of chemopreventive agents

Cancer chemoprevention is defined as the use of natural agents to suppress, reverse or prevent the carcinogenic process from turning into aggressive cancer. Over the last two decades, multiple natural dietary compounds with diverse chemical structures such flavonoids, tannins, curcumins and polyphenols have been proposed as chemopreventive agents. These agents have proven excellent anticancer potential in the laboratory setting, however, the observed effects in vitro do not translate in clinic where they fail to live up to their expectations. Among the various reasons for this discrepancy include inefficient systemic delivery and robust bioavailability. To overcome this barrier, researchers have focused towards coupling these agents with nano based encapsulation technology that in principle will enhance bioavailability and ultimately benefit clinical outcome. The last decade has witnessed rapid advancement in the development of nanochemopreventive technology with emergence of many nano encapsulated formulations of different dietary anticancer agents. This review summarizes the most up-to-date knowledge on the studies performed in nanochemoprevention, their proposed use in the clinic and future directions in which this field is heading. As the knowledge of the dynamics of nano encapsulation evolves, it is expected that researchers will bring forward newer and far more superior nanochemopreventive agents that may become standard drugs for different cancers.

Review on molecular and therapeutic potential of thymoquinone in cancer

Thymoquinone (TQ) is the predominant bioactive constituent present in black seed oil (Nigella sativa) and has been tested for its efficacy against cancer. Here, we summarize the literature about TQ's molecular mechanism of action and its ability to induce apoptosis and inhibit tumor growth in preclinical models. TQ has anti-inflammatory effects, and it inhibits tumor cell proliferation through modulation of apoptosis signaling, inhibition of angiogenesis, and cell cycle arrest. Chemosensitization by TQ is mostly limited to in vitro studies, and it has potential in therapeutic strategy for cancer. The results favor efficacy and enhancement of therapeutic benefit against tumor cells resistant to therapy based on cellular targets that are molecular determinants for cancer cell survival and progression. There have been attempts to synthesize novel analogs of TQ directed toward superior effects in killing tumor cells with more enhanced chemosensitizing potential than parent TQ compound. Based on published reports, we believe that further in-depth studies are warranted including investigation of its bioavailability and Phase I toxicity profiling in human subjects. The results from such studies will be instrumental in advancing this field in support of initiating clinical trials for testing the effects of this ancient agent in cancer therapy.

Proof of concept: network and systems biology approaches aid in the discovery of potent anticancer drug combinations

Cancer therapies that target key molecules have not fulfilled expected promises for most common malignancies. Major challenges include the incomplete understanding and validation of these targets in patients, the multiplicity and complexity of genetic and epigenetic changes in the majority of cancers, and the redundancies and cross-talk found in key signaling pathways. Collectively, the uses of single-pathway targeted approaches are not effective therapies for human malignancies. To overcome these barriers, it is important to understand the molecular cross-talk among key signaling pathways and how they may be altered by targeted agents. Innovative approaches are needed, such as understanding the global physiologic environment of target proteins and the effects of modifying them without losing key molecular details. Such strategies will aid the design of novel therapeutics and their combinations against multifaceted diseases, in which efficacious combination therapies will focus on altering multiple pathways rather than single proteins. Integrated network modeling and systems biology have emerged as powerful tools benefiting our understanding of drug mechanisms of action in real time. This review highlights the significance of the network and systems biology-based strategy and presents a proof of concept recently validated in our laboratory using the example of a combination treatment of oxaliplatin and the MDM2 inhibitor MI-219 in genetically complex and incurable pancreatic adenocarcinoma.

MI-219-zinc combination: a new paradigm in MDM2 inhibitor-based therapy

Zinc plays a crucial role in the biology of p53 in that p53 binds to DNA through a structurally complex domain stabilized by zinc atom. The p53 negative regulator MDM2 protein also carries a C-terminal RING domain that coordinates two zinc atoms which are responsible for p53 nuclear export and proteasomal degradation. In this clinically translatable study, we explored the critical role of zinc on p53 re-activation by MDM2-inhibitor MI-219 in colon and breast cancer cells. ZnCl₂ enhanced MI-219 activity (MTT, apoptosis and colony formation), and chelation of zinc not only blocked the activity of MI-219, it also suppressed re-activation of the p53 and its downstream effector molecules p21^WAF1 and Bax. TPEN, a specific zinc chelator but not Bapta-AM, a calcium chelator, blocked MI-219-induced apoptosis. Nuclear localization is a pre-requisite for proper functioning of p53 and our results confirm that TPEN and not Bapta-AM could abrogate p53 nuclear localization and interfered with p53 transcriptional activation. Addition of zinc suppressed the known p53 feedback MDM2 activation which could be restored by TPEN. Co-immunoprecipitation studies verified that MI-219-mediated MDM2-p53 disruption could be suppressed by TPEN and restored by zinc. As such, single agent therapies that target MDM2 inhibition, without supplemental zinc, may not be optimal in certain patients due to the less recognized mild zinc deficiency among the “at risk population” as in the elderly which are more prone to cancers. Therefore, use of supplemental zinc with MI-219 will benefit the overall efficacy of MDM2 inhibitors and this potent combination warrants further investigation.

Emerging Bcl-2 inhibitors for the treatment of cancer

INTRODUCTION

Bcl-2 family proteins are a component of the antiapoptotic machinery and are overexpressed in different malignancies. Accordingly, their enhanced expression has been attributed to the observed chemoresistance in most of the cancers. Therefore, targeting Bcl-2 family members becomes an important and attractive approach towards cancer therapy and is currently a very rapidly evolving area of research. This article highlights the numerous advancements that have been made in the design and synthesis of small molecule inhibitors (SMI) of pro-survival Bcl-2 proteins.

AREAS COVERED

This review comprehensively describes the progress made over the last 2 decades on this subject, including the clinical status of SMIs of Bcl-2 family proteins. Newer insights on the status of our knowledge on SMIs of Bcl-2 family proteins, their most beneficial application as well as current and future directions in this field are discussed.

EXPERT OPINION

Targeting Bcl-2 family proteins using SMI strategies is gaining momentum, with the emergence of certain new classes of inhibitors in Phase I and II clinical settings. In view of the tremendous progress toward the development of such inhibitors, this innovative approach certainly holds promise and has the potential to become a future mainstay for cancer therapy. The stage is set for the next generation of SMIs, for not only Bcl-2 proteins but also for Mcl-1. Other emerging molecules in the apoptotic machinery will also be explored and targeted.

I-kappa-kinase-2 (IKK-2) inhibition potentiates vincristine cytotoxicity in non-Hodgkin's lymphoma

Background

IKK-2 is an important regulator of the nuclear factor-κB (NF-κB) which has been implicated in survival, proliferation and apoptosis resistance of lymphoma cells. In this study, we investigated whether inhibition of IKK-2 impacts cell growth or cytotoxicity of selected conventional chemotherapeutic agents in non-Hodgkin's lymphoma.

Two established model systems were used; Follicular (WSU-FSCCL) and Diffuse Large Cell (WSU-DLCL2) Lymphoma, both of which constitutively express p-IκB. A novel, selective small molecule inhibitor of IKK-2, ML120B (N-[6-chloro-7-methoxy-9H-β-carbolin-8-yl]-2-methylnicotinamide) was used to perturb NF-κB in lymphoma cells. The growth inhibitory effect of ML120B (M) alone and in combination with cyclophosphamide monohydrate (C), doxorubicin (H) or vincristine (V) was evaluated in vitro using short-term culture assay. We also determined efficacy of the combination in vivo using the SCID mouse xenografts.

Results

ML120B down-regulated p-IκBα protein expression in a concentration dependent manner, caused growth inhibition, increased G0/G1 cells, but did not induce apoptosis. There was no significant enhancement of cell kill in the M/C or M/H combination. However, there was strong synergy in the M/V combination where the vincristine concentration can be lowered by a hundred fold in the combination for comparable G2/M arrest and apoptosis. ML120B prevented vincristine-induced nuclear translocation of p65 subunit of NF-κB. In vivo, ML120B was effective by itself and enhanced CHOP anti-tumor activity significantly (P = 0.001) in the WSU-DLCL2-SCID model but did not prevent CNS lymphoma in the WSU-FSCCL-SCID model.

Conclusions

For the first time, this study demonstrates that perturbation of IKK-2 by ML120B leads to synergistic enhancement of vincristine cytotoxicity in lymphoma. These results suggest that disruption of the NF-κB pathway is a useful adjunct to cytotoxic chemotherapy in lymphoma.

Cell cycle and apoptosis regulatory protein (CARP)-1 is a novel, adriamycin-inducible, diffuse large B-cell lymphoma (DLBL) growth suppressor

Diffuse large B-cell lymphoma (DLCL) accounts for 30-40% of adult non-Hodgkin's Lymphoma (NHL). Current anti-NHL therapies often target cellular growth suppression pathways and include R-CHOP (cyclophosphamide, adriamycin, vincristine, and prednisone plus monoclonal anti-CD20 antibody rituximab). However, since many patients relapse, resistant cells to these therapies remain a significant problem and necessitate development of new intervention strategies. Cell cycle and apoptosis regulatory protein (CARP)-1 functions in a biphasic manner to regulate growth factor as well as chemotherapy (adriamycin, etoposide, or iressa)-dependent signaling.

PURPOSE

To determine whether CARP-1 is a novel suppressor of lymphoma growth.

METHODS

Flow cytometric analyses coupled with Western immunoblotting, cell growth, apoptosis, and immunocytochemistry methodologies were utilized to determine CARP-1-dependent lymphoma growth inhibition in vitro and in vivo.

RESULTS

CARP-1 expression correlated with activated caspase-3 and inversely correlated with activated Akt in DLCL. Exposure to adriamycin stimulated CARP-1 expression and inhibited growth of Raji cells, but not CHOP-resistant WSU-DLCL2 cells. Expression of wild-type CARP-1 or its apoptosis-inducing mutants inhibited growth of Raji as well as CHOP-resistant WSU-DLCL2 cells, in part by activating caspase-9 and apoptosis. Since CARP-1 harbors multiple, apoptosis-promoting subdomains, we investigated whether epigenetic compensation of CARP-1 function by intracellular delivery of trans-activator of transcription (TAT) domain-tagged CARP-1 peptide(s) will inhibit lymphoma growth. Treatments with TAT-tagged CARP-1 peptides suppressed growth of the Raji and WSU-DLCL2 cells by stimulating apoptosis. TAT-CARP-1 (1-198) as well as (896-1150) peptides also suppressed growth of WSU-DLCL2 cell-derived tumor xenografts in SCID mice, while administration of TAT-CARP-1 (1-198) also inhibited growth of WSU-FSCCL cell-derived ascites and prolonged host survival.

CONCLUSION

CARP-1 is a suppressor of NHL growth and could be exploited for targeting the resistant DLCL.

Reactivation of p53 by novel MDM2 inhibitors: implications for pancreatic cancer therapy

The present study is the first to show in pancreatic cancer (PC) the growth inhibition and apoptosis by novel MDM2 inhibitors (MI-319 & 219) through reactivation of p53 pathway. Our results highlight two new secondary targets of MDM2 inhibitor 'SIRT1' and Ku70. SIRT1 which has a role in ageing and cancer and is known to regulate p53 signaling through acetylation. Ku70 is a key component of non-homologous end joining machinery in the DNA damage pathway and is known to regulate apoptosis by blocking Bax entry into mitochondria. Growth inhibition and apoptosis by MI-219, MI-319 was accompanied by increase in levels of p53 along with p21(WAF1) and the proapoptotic Puma. SiRNA against p21(WAF1) abrogated the growth inhibition of PC cells confirming p21(WAF1) as a key player downstream of activated p53. Immunoprecipitation-western blot analysis revealed reduced association of MDM2-p53 interaction in drug exposed PC cells. In combination studies, the inhibitors synergistically augmented anti-tumor effects of therapeutic drug gemcitabine both in terms of cell growth inhibition as well as apoptosis. Surface plasmon resonance studies confirmed strong binding between MI-319 and Ku70 (K(D) 170 nM). Western blot revealed suppression of SIRT1 and Ku70 with simultaneous upregulation of acetyl-p53 (Lys379) and Bax. Co-Immunoprecipitation studies confirmed that MI-319 could disrupt Ku70-Bax and SIRT1-Bax interaction. Further, using wt-p53 xenograft of Capan-2, we found that oral administration of MI-319 at 300 mg/kg for 14 days resulted in significant tumor growth inhibition without any observed toxicity to the animals. No tumor inhibition was found in mut-p53 BxPC-3 xenografts. In light of our results, the inhibitors of MDM2 warrant clinical investigation as new agents for PC treatment.

PAR-4 as a possible new target for pancreatic cancer therapy

IMPORTANCE OF THE FIELD

Pancreatic cancer (PC) is a deadly disease that is intractable to currently available treatment regimens. Although well described in different tumors types, the importance of apoptosis inducer prostate apoptosis response-4 (Par-4) in PC has not been appreciated. PC is an oncogenic kras driven disease, which is known to downregulate Par-4. Therefore, this review highlights its significance and builds a strong case supporting the role of Par-4 as a possible therapeutic target in PC.

AREAS COVERED IN THIS REVIEW

Literature-based evidence spanning the last 15 years on Par-4 and its significance in PC.

WHAT THE READER WILL GAIN

This review provides comprehensive knowledge of the significance of Par-4 and its association with kras status in PC, along with the crosstalk with crucial resistance and survival molecules NF-kappaB and Bcl-2 that ultimately are responsible for the overall poor outcome of different therapeutic approaches in this disease.

TAKE HOME MESSAGE

Par-4 holds promise as a potential therapeutic target that can be induced by chemopreventive agents and small-molecule inhibitors either alone or in combination with standard chemotherapeutics leading to selective apoptosis in PC cells. It also acts as a chemosensitizer and therefore warrants further clinical investigations in this disease.

Abstract A36: Systems biology: Implications in assessing drug-drug interactions in pancreatic cancer

The era of new adjuvant targeted therapies (k-ras, EGFR, VEGF src, p53, etc.) has generated much interest in discovering better approaches for the treatment of cancers; however such approaches have met with more failure than success. The major reason for low response is related to incomplete understanding and validation of the specific molecular targets at the gene level along with complexities of genetic and epigenetic changes in cancer. This is further complicated due to redundancies and cross-talk in signaling pathways that may explain the failure of single-pathway targeted therapies. To overcome this barrier, one must fully understand the molecular interactions among key signaling pathways. This requires innovative approaches to identify genomic events to guide intelligent decision making in the design of novel therapeutic strategies for combination therapies to improve treatment outcome. An increasingly popular and scientifically robust method is to utilize integrated systems biology which combines the use of high throughput technologies with analysis and computer modeling of the potential interconnecting pathways modulated in response to drug treatments. Recently we have found that specific, orally active murine double minute 2 (MDM2) inhibitor MI-219 can synergize with chemotherapeutic drug oxaliplatin that results enhanced anti-tumor effects in pancreatic cancer. However, the mechanism behind this synergy has not been explored in greater detail. In this study we have used integrated genomic expression microarray profiling (IGEMP) coupled with pathway/genetic network modeling (PGNM) to obtain crucial information in the synergistic efficacy of MI-219-oxaliplatin in a genetically complex and by far incurable pancreatic cancer. Global gene analysis of capan-2 cell shows that MI-219 alone induces alterations in 48 genes that is expected of a targeted agent. On the other hand, oxaliplatin treatment results in alterations of more than 700 genes and is in line with the mode of action of cytotoxic drugs. However, the combination of MI-219-oxaliplatin resulted in alteration of >700 genes with emergence of 286 synergy unique genes. Principal component analysis revealed that each drug treatment and time point had individual global gene signatures. Further analysis of the 286 synergy unique genes revealed the presence of several local gene networks of MDM2-p53 pathway including key players such as players CREBBP (i.e., ubiquitously expressed in PC and is involved in the transcriptional coactivation of many different transcription factors including p53, CARF that is responsible for p53 stability along with NF-kB and EGR1 tumor suppressor module, all positively affecting p53 reactivation that in principle would drive cells toward increased apoptosis. Additionally, the analysis revealed a novel role of hepatocyte nuclear factor alpha (HNF4α) in aiding MI-219-oxaliplatin mediated apoptosis suggesting that this technology can also be utilized in identifying potential biomarkers. Most interestingly, all the genetic signatures could be verified and validated at the RNA and protein level. Fortified by our strong evidence we propose the use of this technology for evaluating multiple drug combinations being tested for different cancers in clinical setting. We believe that success in personalized medicine will require advances in our understanding of the true potential and concepts of this technology towards elucidating the role of most influential driver genes in drug-drug interaction that would positively impact treatment outcome.

Citation Information: Clin Cancer Res 2010;16(14 Suppl):A36.

ErbB-inhibitory protein: a modified ectodomain of epidermal growth factor receptor synergizes with dasatinib to inhibit growth of breast cancer cells

Many solid tumors, including breast cancer, show increased activation of several growth factor receptors, specifically epidermal growth factor receptor (EGFR) and its family members as well as c-Src, a nonreceptor tyrosine kinase that promotes proliferation, inhibits apoptosis, and induces metastasis. We hypothesize that inhibition of c-Src and EGFRs will be an effective therapeutic strategy for triple-negative breast cancer. To test our hypothesis, we used a c-Src-specific inhibitor dasatinib (BMS-354825; Bristol-Myers Squibb) and our newly developed ErbB-inhibitory protein (EBIP), a potential pan-ErbB inhibitor, in breast cancer cells. EBIP is composed of 1 to 448 amino acids of the ectodomain of human EGFR to which the 30-amino acid epitope (known as "U" region) of rat EGFR-related protein is fused at the COOH-terminal end. The combination of dasatinib and EBIP was found to be highly effective in inhibiting the growth of four different breast cancer cells (MDA-MB-468, SKBr-3, MDA-MB-453, and MDA-MB-231) that express different levels of EGFRs. In EGFR-overexpressing MDA-MB-468 cells, the combination, but not monotherapy, markedly stimulated apoptosis mediated by caspase-9 and caspase-8 and attenuated activation of EGFR and Src as well as tyrosine kinase activity. EBIP also inhibited heregulin-induced activation of HER-2 and HER-3 in MDA-MB-453 breast cancer cells. The combination therapy was highly effective in suppressing tumor growth ( approximately 90% inhibition) in MDA-MB-468-derived xenografts in severe combined immunodeficient mice. The latter could be attributed to induction of apoptosis. We conclude that combining dasatinib and EBIP could be an effective therapeutic strategy for breast cancer by targeting EGFRs and Src signaling.

Structure-activity studies on therapeutic potential of Thymoquinone analogs in pancreatic cancer

PURPOSE

Pancreatic cancer (PC) is one of the deadliest of all tumors. Previously, we were the first to show that Thymoquinone (TQ) derived from black seed (Nigella sativa) oil has anti-tumor activity against PC. However, the concentration of TQ required was considered to be high to show this efficacy. Therefore, novel analogs of TQ with lower IC(50) are highly desirable.

METHODS

We have synthesized a series of 27 new analogs of TQ by modifications at the carbonyl sites or the benzenoid sites using single pot synthesis and tested their biological activity in PC cells.

RESULTS

Among these compounds, TQ-2G, TQ-4A1 and TQ-5A1 (patent pending) were found to be more potent than TQ in terms of inhibition of cell growth, induction of apoptosis and modulation of transcription factor-NF-kappaB. We also found that our novel analogs were able to sensitize gemcitabine and oxaliplatin-induced apoptosis in MiaPaCa-2 (gemcitabine resistant) PC cells, which was associated with down-regulation of Bcl-2, Bcl-xL, survivin, XIAP, COX-2 and the associated Prostaglandin E2.

CONCLUSION

From our results, we conclude that three of our novel TQ analogs warrant further investigation against PC, especially in combination with conventional chemotherapeutic agents.

Abstract 4535: MDM2 inhibitor MI-319 in combination with cisplatin/oxaliplatin is an effective treatment for pancreatic cancer independent of p53 function

Pancreatic cancer (PC) is considered to be among the most intractable malignancies as it is refractory to chemotherapy and radiation. Among the various genetic alterations in PC, mutation in the tumor suppressor p53 (mut-p53) gene has been reported to be about 50%. In the remaining 50%, the p53 is normal, but its function is inhibited by MDM2 protein which plays a key role in promoting ubiquitination and proteasomal-dependent degradation of p53. An attractive approach to p53 activation is the use of MDM2 inhibitors that disrupt the MDM2-p53 interaction and restore the p53 function. However, these small molecule inhibitors (SMIs) are not effective against tumors with mut-p53. Our group has designed a new class of SMI of MDM2 that is different from Nutlin-3. Here we are reporting, for the first time, that MI-319 can induce cell growth inhibition and apoptosis in PC irrespective of p53 mutational status when combined with cisplatin/oxaliplatin. MI-319-cisplatin or oxaliplatin combination synergistically suppressed cell growth (MTT CI<1), colony formation (clonogenic assay) and induced apoptosis in both mut-p53 Colo-357, BxPC-3 and Panc-28 or wt-p53 Capan-2 cells. Western blot analysis and siRNA silencing studies in mutant as well as p53 null cells highlighted a mechanism involving p73 which is under the regulation of MDM2, and unlike p53, it is rarely mutated in PC. In order to substantiate its in vivo relevance we tested this potent combination in mice xenograft models carrying Capan-2 and BxPC-3 tumors. 4 groups, each containing 8 animals were treated either with; Control (Vehicle only), MI-319 treated 200mg/Kg orally twice a day for three weeks, Cisplatin treated 4 mg/kg (i.v.) twice a week for two weeks and combination treated (MI-319 200 mg/Kg orally + Cisplatin 4 mg/kg). The combination effectively reduced tumor growth in both wt-p53 and mut-p53 tumor xenograft models (50% Capan-2 animals were tumor free). Consistent with our in vitro results, remnant tumor tissue analysis showed up-regulation of p73 and the cell cycle regulator p21. In conclusion, this study highlights a new role of MDM2 inhibitors in combination with cisplatin or oxaliplatin, and thus warrants further clinical investigation in human pancreatic tumors containing both wt-p53 and mut-p53.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4535.

MDM2 inhibitor MI-319 in combination with cisplatin is an effective treatment for pancreatic cancer independent of p53 function

Small molecule inhibitors (SMIs) of murine double minute 2 (MDM2) are known to restore the apoptotic and cell cycle regulatory functions of p53 by disrupting the MDM2-p53 interaction. In principle, these SMIs are not effective against tumours with mutation in the tumour suppressor p53 (mut-p53), which is known to be present in approximately 50% of all cancers. In this study we are reporting, for the first time, that MI-319 in combination with cisplatin induced cell growth inhibition and apoptosis in pancreatic cancer (PC) cells irrespective of their p53 mutational status. MI-319-cisplatin combination synergistically suppressed cell growth (MTT Combination Index [CI]<1) and colony formation (clonogenic assay) and induced apoptosis. Western blot analysis and siRNA silencing studies in mutant as well as p53 null cells highlighted a mechanism involving p73 which is also known to be under the regulation of MDM2, and unlike p53, it is rarely mutated in PC. Down-regulating MDM2 using siRNA enhanced p73 reactivation and increased cell death. Further, the combination effectively reduced tumour growth in both wt-p53 and mut-p53 tumour xenograft models (50% Capan-2 animals were tumour free). Consistent with our in vitro results, remnant tumour tissue analysis showed up-regulation of p73 and the cell cycle regulator p21. In conclusion, this study highlights a new role of MDM2 inhibitors in combination with cisplatin, and thus warrants further clinical investigation in human pancreatic tumours containing both wt-p53 and mut-p53.

New targets for the treatment of follicular lymphoma

The last two decades have witnessed striking advances in our understanding of the biological factors underlying the development of Follicular lymphoma (FL). Development of newer treatment approaches have improved the outlook for many individuals with these disorders; however, with these advances come new questions. Given the long-term survival of patients with FL, drugs with favourable side-effect profile and minimal long-term risks are desired. FL is incurable with current treatment modalities. It often runs an indolent course with multiple relapses and progressively shorter intervals of remission. The identification of new targets and development of novel targeted therapies is imperative to exploit the biology of FL while inherently preventing relapse and prolonging survival. This review summarizes the growing body of knowledge regarding novel therapeutic targets, enabling the concept of individualized targeted therapy for the treatment of FL.

An MDM2 antagonist (MI-319) restores p53 functions and increases the life span of orally treated follicular lymphoma bearing animals

Background

MI-319 is a synthetic small molecule designed to target the MDM2-P53 interaction. It is closely related to MDM2 antagonists MI-219 and Nutlin-3 in terms of the expected working mechanisms. The purpose of this study was to evaluate anti-lymphoma activity of MI-319 in WSU-FSCCL, a B-cell follicular lymphoma line. For comparison purpose, MI-319, MI-219 and Nutlin-3 were assessed side by side against FSCCL and three other B-cell hematological tumor cell lines in growth inhibition and gene expression profiling experiments.

Results

MI-319 was shown to bind to MDM2 protein with an affinity slightly higher than that of MI-219 and Nutlin-3. Nevertheless, cell growth inhibition and gene expression profiling experiments revealed that the three compounds have quite similar potency against the tumor cell lines tested in this study. In vitro, MI-319 exhibited the strongest anti-proliferation activity against FSCCL and four patient cells, which all have wild-type p53. Data obtained from Western blotting, cell cycle and apoptosis analysis experiments indicated that FSCCL exhibited strong cell cycle arrest and significant apoptotic cell death; cells with mutant p53 did not show significant apoptotic cell death with drug concentrations up to 10 μM, but displayed weaker and differential cell cycle responses. In our systemic mouse model for FSCCL, MI-319 was tolerated well by the animals, displayed effectiveness against FSCCL-lymphoma cells in blood, brain and bone marrow, and achieved significant therapeutic impact (p < 0.0001) by conferring the treatment group a > 28% (%ILS, 14.4 days) increase in median survival days.

Conclusion

Overall, MI-319 probably has an anti-lymphoma potency equal to that of MI-219 and Nutlin-3. It is a potent agent against FSCCL in vitro and in vivo and holds the promises to be developed further for the treatment of follicular lymphoma that retains wild-type p53.