N V Rajeshkumar

Johns Hopkins Medicine, Baltimore, Maryland, United States

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Publications (64)352.25 Total impact

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    ABSTRACT: Apurinic/Apyrimidinic endonuclease/Redox factor-1 (APE1/Ref-1) (henceforth referred to as Ref-1) is a multi-functional protein that in addition to its base-excision DNA repair activity exerts redox control of multiple transcription factors, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), STAT3, activator protein-1 (AP-1), hypoxia-inducible factor-1 (HIF-)1 and tumor protein 53 (p53). In recent years, Ref-1 has emerged as a promising therapeutic target in cancer, particularly in pancreatic ductal carcinoma (PDAC). While a significant amount of research has centered on Ref-1, no wide-ranging approach had been performed on the effects of Ref-1 inhibition and transcription factor activity perturbation. Starting with a broader approach, we identified a previously unsuspected effect on the Nuclear factor-erythroid-related factor 2 (NRF2), a critical regulator of cellular defenses against oxidative stress. Based on genetic and small molecule inhibitor-based methodologies, we demonstrated that repression of Ref-1 potently activates NRF2 and its downstream targets in a dose-dependent fashion, and that the redox, rather than the DNA repair function of Ref-1 is critical for this effect. Intriguingly, our results also indicate that this pathway does not involve Reactive Oxygen Species (ROS). The link between Ref-1 and NRF2 appears to be present in all cells tested in vitro, noncancerous and cancerous, including patient-derived tumor samples. In particular, we focused on understanding the implications of the novel interaction between these two pathways in primary PDAC tumor cells and provide the first evidence that this mechanism has implications for overcoming the resistance against experimental drugs targeting Ref-1 activity, with clear translational implications. Copyright © 2014, The American Society for Biochemistry and Molecular Biology.
    Journal of Biological Chemistry 12/2014; DOI:10.1074/jbc.M114.621995 · 4.60 Impact Factor
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    ABSTRACT: Many patients with pancreatic cancer have metastases to distant organs at the time of initial presentation. Recent studies examining the evolution of pancreatic cancer at the genetic level have shown that clonal complexity of metastatic pancreatic cancer is already initiated within primary tumors, and organ-specific metastases are derived from different subclones. However, we do not yet understand to what extent the evolution of pancreatic cancer contributes to proteomic and signaling alterations. We hypothesized that genetic heterogeneity of metastatic pancreatic cancer results in heterogeneity at the proteome level. To address this, we employed a model system in which cells isolated from three sites of metastasis (liver, lung and peritoneum) from a single patient were compared. We used a SILAC-based accurate quantitative proteomic strategy combined with a high resolution mass spectrometry to analyze the total proteome and tyrosine phosphoproteome of each of the distal metastases. Our data reveal distinct patterns of both overall proteome expression as well as tyrosine kinase activities across the three different metastatic lesions. This heterogeneity is significant because it led to differential sensitivity of the neoplastic cells to small molecule inhibitors targeting various kinases and other pathways. For example, R428, a tyrosine kinase inhibitor that targets Axl receptor tyrosine kinase, was able to inhibit cells derived from lung and liver metastases much more effectively than cells from the peritoneal metastasis. Finally, we confirmed that administration of R428 in mice bearing xenografts of cells derived from the three different metastatic sites significantly diminished tumors formed from liver and lung metastasis-derived cell lines as compared to tumors derived from the peritoneal metastasis cell line. Overall, our data provide proof-of-principle support that personalized therapy of multiple organ metastases in a single patient should involve administration of a combination of agents with each agent targeted to the features of different subclones.
    Molecular &amp Cellular Proteomics 06/2014; 13(11). DOI:10.1074/mcp.M114.038547 · 7.25 Impact Factor
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    ABSTRACT: Pancreatic ductal adenocarcinoma is refractory to available therapies. We have previously shown that these tumors have elevated autophagy and inhibition of autophagy leads to decreased tumor growth. Using an autochthonous model of pancreatic cancer driven by oncogenic Kras and the stochastic LOH of p53, we demonstrate that while genetic ablation of autophagy in the pancreas leads to increased tumor initiation, these premalignant lesions are impaired in their ability to progress to invasive cancer, leading to prolonged survival. Additionally, mouse pancreatic cancer cell lines with differing p53 status are all sensitive to pharmacologic and genetic inhibition of autophagy. Lastly, a mouse pre-clinical trial using cohorts of genetically characterized patient derived xenografts treated with hydroxychloroquine showed responses across the collection of tumors. Together our data support the critical role of autophagy in pancreatic cancer and that inhibition of autophagy may have clinical utility in the treatment of these cancers, independent of p53 status.
    Cancer Discovery 05/2014; 4(8). DOI:10.1158/2159-8290.CD-14-0362 · 15.93 Impact Factor
  • Cancer Research 04/2014; 72(14 Supplement):A70-A70. DOI:10.1158/1538-7445.PANCA2012-A70 · 9.28 Impact Factor
  • Cancer Research 08/2013; 73(8 Supplement):5396-5396. DOI:10.1158/1538-7445.AM2013-5396 · 9.28 Impact Factor
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    ABSTRACT: Pancreatic ductal adenocarcinoma (PDA) remains a lethal human malignancy with historically limited success in treatment. The role of aberrant Notch signaling, which requires the constitutive activation of γ-secretase, in the initiation and progression of PDA is well defined and inhibitors of this pathway are currently in clinical trials. Here we investigated the in vivo therapeutic effect of PF-03084014, a selective γ-secretase inhibitor, alone and in combination with gemcitabine in pancreatic cancer xenografts. PF-03084014 treatment inhibited the cleavage of nuclear Notch 1 intracellular domain and Notch targets Hes-1 and Hey-1. Gemcitabine treatment showed good response but not capable of inducing tumor regressions and targeting the tumor-resident cancer stem cells (CD24(+)CD44(+) and ALDH(+) tumor cells). A combination of PF-03084014 and gemcitabine treatment resulted tumor regression in 3 of 4 subcutaneously implanted xenograft models. PF-03084014, and in combination with gemcitabine reduced putative cancer stem cells, indicating that PF-03084014 target the especially dangerous and resilient cancer stem cells within pancreatic tumors. Tumor re-growth curves plotted after drug treatments demonstrated that the effect of the combination therapy was sustainable than that of gemcitabine. Notably, in a highly aggressive orthotopic model, PF-03084014 and gemcitabine combination was effective in inducing apoptosis, inhibition of tumor cell proliferation and angiogenesis, resulting in the attenuation of primary tumor growth as well as controlling metastatic dissemination, compared to gemcitabine treatment. In summary, our preclinical data suggest that PF-03084014 has greater anti-tumor activity in combination with gemcitabine in PDA and provides rationale for further investigation of this combination in PDA.
    Cancer letters 02/2013; DOI:10.1016/j.canlet.2013.01.054 · 5.02 Impact Factor
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    Anne Le, N V Rajeshkumar, Anirban Maitra, Chi V Dang
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    ABSTRACT: Pancreatic ductal adenocarcinoma (a.k.a. pancreatic cancer) remains one of the most feared and clinically challenging diseases to treat despite continual improvements in therapies. The genetic landscape of pancreatic cancer shows near ubiquitous activating mutations of KRAS, and recurrent inactivating mutations of CDKN2A, SMAD4, and TP53. To date, attempts to develop agents to target KRAS to specifically kill cancer cells have been disappointing. In this regard, an understanding of cellular metabolic derangements in pancreatic cancer could lead to novel therapeutic approaches. Like other cancers, pancreatic cancer cells rely on fuel sources for homeostasis and proliferation; as such, interrupting the use of two major nutrients, glucose and glutamine, may provide new therapeutic avenues. In addition, KRAS-mutant pancreatic cancers have been documented to depend on autophagy, and the inhibition of autophagy in the preclinical setting has shown promise. Herein, the conceptual framework for blocking the pancreatic fuel supply is reviewed.
    Clinical Cancer Research 08/2012; 18(16):4285-90. DOI:10.1158/1078-0432.CCR-12-0041 · 8.19 Impact Factor
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    Anne Le, N V Rajeshkumar, Anirban Maitra
    Clinical Cancer Research 08/2012; 18:4285-4290. · 8.19 Impact Factor
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    Anne Le, N V Rajeshkumar, Anirban Maitra
    Clinical Cancer Research 08/2012; 18:4285-4290. · 8.19 Impact Factor
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    ABSTRACT: Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy, with most patients facing an adverse clinical outcome. Aberrant Notch pathway activation has been implicated in the initiation and progression of PDAC, specifically the aggressive phenotype of the disease. We used a panel of human PDAC cell lines as well as patient-derived PDAC xenografts to determine whether pharmacologic targeting of Notch pathway could inhibit PDAC growth and potentiate gemcitabine sensitivity. MRK-003, a potent and selective γ-secretase inhibitor, treatment resulted in the downregulation of nuclear Notch1 intracellular domain, inhibition of anchorage-independent growth, and reduction of tumor-initiating cells capable of extensive self-renewal. Pretreatment of PDAC cells with MRK-003 in cell culture significantly inhibited the subsequent engraftment in immunocompromised mice. MRK-003 monotherapy significantly blocked tumor growth in 5 of 9 (56%) PDAC xenografts. A combination of MRK-003 and gemcitabine showed enhanced antitumor effects compared with gemcitabine in 4 of 9 (44%) PDAC xenografts, reduced tumor cell proliferation, and induced both apoptosis and intratumoral necrosis. Gene expression analysis of untreated tumors indicated that upregulation of NF-κB pathway components was predictive of sensitivity to MRK-003, whereas upregulation in B-cell receptor signaling and nuclear factor erythroid-derived 2-like 2 pathway correlated with response to the combination of MRK-003 with gemcitabine. Our findings strengthen the rationale for small-molecule inhibition of Notch signaling as a therapeutic strategy in PDAC. Mol Cancer Ther; 11(9); 1999-2009. ©2012 AACR.
    Molecular Cancer Therapeutics 07/2012; 11(9):1999-2009. DOI:10.1158/1535-7163.MCT-12-0017 · 6.11 Impact Factor
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    ABSTRACT: A high throughput screening for anticancer activity of FDA approved drugs identified mycophenolic acid (MPA), an inhibitor of inositol monophosphate dehydrogenase (IMPDH) as an active agent with an antiangiogenesis mode of action. Exposure of pancreatic cancer cell lines to MPA resulted in growth inhibition and reduced the expression of VEGF that was reversed by supplementing the media with guanosine supporting and IMPDH-dependant mechanism. In preclinical in vivo study, MPA showed a moderate inhibition of tumor growth in a panel of 6 human derived pancreatic cancer xenografts but reduced the expression of VEGF. To investigate the effects of MPA in human pancreatic cancer, a total of 12 patients with resectable pancreatic cancer (PDA) received increasing doses of mycophenolate mofetil (MMF) in cohorts of 6 patients each from 5-15 days prior to surgical resection. Treatment was well tolerated with one episode of grade 1 muscle pain, one episode of grade 2 lymphopenia (2 gr/day dose) and one episode of grade 2 elevantion in LFT (all in the 2 gr./day dose). Patients recovered from surgery uneventfully with no increased post-operative complications. Assessment of CD31, VEGF, and TUNEL in resected specimens compared to a non treated control of 6 patients showed no significant variations in any of the study endpoints. In conclusion, this study shows the feasibility of translating a preclinical observation to the clinical setting and to explore a drug mechanism of action in patients. MPA, however, did not show any hints of antiangiogenesis of anticancer clinical activity questioning if this agent should be further developed in PDA.
    Investigational New Drugs 06/2012; DOI:10.1007/s10637-012-9822-x · 2.93 Impact Factor
  • Cancer Research 06/2012; 72(8 Supplement):3262-3262. DOI:10.1158/1538-7445.AM2012-3262 · 9.28 Impact Factor
  • Cancer Research 06/2012; 72(8 Supplement):3494-3494. DOI:10.1158/1538-7445.AM2012-3494 · 9.28 Impact Factor
  • Cancer Research 06/2012; 72(8 Supplement):LB-61-LB-61. DOI:10.1158/1538-7445.AM2012-LB-61 · 9.28 Impact Factor
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    ABSTRACT: Purpose S-trans,trans-Farnesylthiosalicylic Acid (FTS, salirasib) inhibits Ras-dependent cell growth by dislodging all isoforms of Ras, including mutant Ras, from the plasma membrane. This study evaluated the activity, safety, and toxicity of salirasib in preclinical models and patients with metastatic pancreatic adenocarcinoma (PDA). Patients and methods In the preclinical study, salirasib was tested, alone and in combination with gemcitabine, in patient derived xenografts (PDX) of PDA. In the clinical study, treatment-naïve patients with advanced, metastatic PDA were treated with a standard dose schedule of gemcitabine and salirasib 200-800 mg orally (PO) twice daily (bid) for 21 days every 28 days. Tissue from preclinical models and patients' biopsies were collected pre-treatment and on Cycle (C) 1, Day (D) 9 to characterize the effect of gemcitabine and salirasib on activated Ras protein levels. Plasma samples for pharmacokinetics were collected for salirasib administered alone and in combination. Results Salirasib inhibited the growth of 2/14 PDX models of PDA and modulated Ras signaling in these tumors. Nineteen patients were enrolled. No DLTs occurred. Common adverse events included hematologic and gastrointestinal toxicities and fatigue. The median overall survival was 6.2 months and the 1 year survival 37 %. In 2 patients in whom paired tissue biopsies were available, Ras and KRas protein levels were decreased on C1D9. Salirasib exposure was not altered by gemcitabine and did not correlate with PD outcomes. Conclusion The combination of gemcitabine and salirasib appears well-tolerated, with no alteration of salirasib exposure, and exerted clinical and PD activity in PDA.
    Investigational New Drugs 05/2012; 30(6). DOI:10.1007/s10637-012-9818-6 · 2.93 Impact Factor
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    ABSTRACT: The trial objectives were to identify the maximum-tolerated dose (MTD) of first-line gemcitabine plus nab-paclitaxel in metastatic pancreatic adenocarcinoma and to provide efficacy and safety data. Additional objectives were to evaluate positron emission tomography (PET) scan response, secreted protein acidic and rich in cysteine (SPARC), and CA19-9 levels in relation to efficacy. Subsequent preclinical studies investigated the changes involving the pancreatic stroma and drug uptake. Patients with previously untreated advanced pancreatic cancer were treated with 100, 125, or 150 mg/m(2) nab-paclitaxel followed by gemcitabine 1,000 mg/m(2) on days 1, 8, and 15 every 28 days. In the preclinical study, mice were implanted with human pancreatic cancers and treated with study agents. A total of 20, 44, and three patients received nab-paclitaxel at 100, 125, and 150 mg/m(2), respectively. The MTD was 1,000 mg/m(2) of gemcitabine plus 125 mg/m(2) of nab-paclitaxel once a week for 3 weeks, every 28 days. Dose-limiting toxicities were sepsis and neutropenia. At the MTD, the response rate was 48%, with 12.2 median months of overall survival (OS) and 48% 1-year survival. Improved OS was observed in patients who had a complete metabolic response on [(18)F]fluorodeoxyglucose PET. Decreases in CA19-9 levels were correlated with increased response rate, progression-free survival, and OS. SPARC in the stroma, but not in the tumor, was correlated with improved survival. In mice with human pancreatic cancer xenografts, nab-paclitaxel alone and in combination with gemcitabine depleted the desmoplastic stroma. The intratumoral concentration of gemcitabine was increased by 2.8-fold in mice receiving nab-paclitaxel plus gemcitabine versus those receiving gemcitabine alone. The regimen of nab-paclitaxel plus gemcitabine has tolerable adverse effects with substantial antitumor activity, warranting phase III evaluation.
    Journal of Clinical Oncology 12/2011; 29(34):4548-54. DOI:10.1200/JCO.2011.36.5742 · 17.88 Impact Factor
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    ABSTRACT: Pancreatic cancer is one of the most lethal of human malignancies, and potent therapeutic options are lacking. Inhibition of cell cycle progression through pharmacological blockade of cyclin-dependent kinases (CDK) has been suggested as a potential treatment option for human cancers with deregulated cell cycle control. Dinaciclib (SCH727965) is a novel small molecule multi-CDK inhibitor with low nanomolar potency against CDK1, CDK2, CDK5 and CDK9 that has shown favorable toxicity and efficacy in preliminary mouse experiments, and has been well tolerated in Phase I clinical trials. In the current study, the therapeutic efficacy of SCH727965 on human pancreatic cancer cells was tested using in vitro and in vivo model systems. Treatment with SCH727965 significantly reduced in vitro cell growth, motility and colony formation in soft agar of MIAPaCa-2 and Pa20C cells. These phenotypic changes were accompanied by marked reduction of phosphorylation of Retinoblastoma (Rb) and reduced activation of RalA. Single agent therapy with SCH727965 (40 mg/kg i.p. twice weekly) for 4 weeks significantly reduced subcutaneous tumor growth in 10/10 (100%) of tested low-passage human pancreatic cancer xenografts. Treatment of low passage pancreatic cancer xenografts with a combination of SCH727965 and gemcitabine was significantly more effective than either agent alone. Gene Set Enrichment Analysis identified overrepresentation of the Notch and Transforming Growth Factor-β (TGF-β) signaling pathways in the xenografts least responsive to SCH727965 treatment. Treatment with the cyclin-dependent kinase inhibitor SCH727965 alone or in combination is a highly promising novel experimental therapeutic strategy against pancreatic cancer.
    Cancer biology & therapy 10/2011; 12(7):598-609. DOI:10.4161/cbt.12.7.16475 · 3.63 Impact Factor
  • Cancer Research 07/2011; 71(8 Supplement):2446-2446. DOI:10.1158/1538-7445.AM2011-2446 · 9.28 Impact Factor
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    ABSTRACT: The goal of this study was to evaluate prospectively the engraftment rate, factors influencing engraftment, and predictability of clinical outcome of low-passage xenografts from patients with resectable pancreatic ductal adenocarcinoma (PDA) and to establish a bank of PDA xenografts. Patients with resectable PDA scheduled for resection at the Johns Hopkins Hospital were eligible. Representative pieces of tumor were implanted in nude mice. The status of the SMAD4 gene and content of tumor-generating cells were determined by immunohistochemistry. Gene expression was carried out by using a U133 Plus 2.0 array. Patients were followed for progression and survival. A total of 94 patients with PDA were resected, 69 tumors implanted in nude mice, and 42 (61%) engrafted. Engrafted carcinomas were more often SMAD4 mutant, and had a metastatic gene expression signature and worse prognosis. Tumors from patients resistant to gemcitabine were enriched in stroma-related gene pathways. Tumors sensitive to gemcitabine were enriched in cell cycle and pyrimidine gene pathways. The time to progression for patients who received treatment with gemcitabine for metastatic disease (n = 7) was double in patients with xenografts sensitive to gemcitabine. A successful xenograft was generated in 61% of patients attempted, generating a pool of 42 PDA xenografts with significant biological information and annotated clinical data. Patients with PDA and SMAD4 inactivation have a better engraftment rate. Engraftment is a poor prognosis factor, and engrafted tumors have a metastatic gene expression signature. Tumors from gemcitabine-resistant patients were enriched in stromal pathways.
    Clinical Cancer Research 07/2011; 17(17):5793-800. DOI:10.1158/1078-0432.CCR-11-0341 · 8.19 Impact Factor
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    ABSTRACT: Pancreatic cancer is especially a deadly form of cancer with a survival rate less than 2%. Pancreatic cancers respond poorly to existing chemotherapeutic agents and radiation, and progress for the treatment of pancreatic cancer remains elusive. To address this unmet medical need, a better understanding of critical pathways and molecular mechanisms involved in pancreatic tumor development, progression, and resistance to traditional therapy is therefore critical. Reduction-oxidation (redox) signaling systems are emerging as important targets in pancreatic cancer. AP endonuclease1/Redox effector factor 1 (APE1/Ref-1) is upregulated in human pancreatic cancer cells and modulation of its redox activity blocks the proliferation and migration of pancreatic cancer cells and pancreatic cancer-associated endothelial cells in vitro. Modulation of APE1/Ref-1 using a specific inhibitor of APE1/Ref-1's redox function, E3330, leads to a decrease in transcription factor activity for NFκB, AP-1, and HIF1α in vitro. This study aims to further establish the redox signaling protein APE1/Ref-1 as a molecular target in pancreatic cancer. Here, we show that inhibition of APE1/Ref-1 via E3330 results in tumor growth inhibition in cell lines and pancreatic cancer xenograft models in mice. Pharmacokinetic studies also show that E3330 attains more than10 μmol/L blood concentrations and is detectable in tumor xenografts. Through inhibition of APE1/Ref-1, the activity of NFκB, AP-1, and HIF1α that are key transcriptional regulators involved in survival, invasion, and metastasis is blocked. These data indicate that E3330, inhibitor of APE1/Ref-1, has potential in pancreatic cancer and clinical investigation of APE1/Ref-1 molecular target is warranted.
    Molecular Cancer Therapeutics 06/2011; 10(9):1698-708. DOI:10.1158/1535-7163.MCT-11-0107 · 6.11 Impact Factor

Publication Stats

2k Citations
352.25 Total Impact Points

Institutions

  • 2010–2014
    • Johns Hopkins Medicine
      Baltimore, Maryland, United States
  • 2008–2014
    • Johns Hopkins University
      • Department of Pathology
      Baltimore, Maryland, United States
  • 2007
    • Samueli Institute
      Alexandria, Virginia, United States
  • 2005–2007
    • University of Illinois at Chicago
      • Department of Biopharmaceutical Sciences
      Chicago, Illinois, United States
  • 2003–2007
    • Uniformed Services University of the Health Sciences
      • Department of Pathology
      Bethesda, MD, United States