OR14-06 Inhibition of Protein Kinase C-beta2 Phosphorylation Restores Nuclear Factor-Kappa B Activation and Improves Peripheral Arterial Disease in Diabetes

Peripheral artery disease (PAD) is atherosclerotic occlusion of vessel outside the heart and most commonly affects the lower extremities. Diabetes (DM) accelerates the course and severity of PAD. Studies have shown that vascular endothelial cell NF-κB activity is required for post ischemic adaptation in experimental PAD. To better understand how DM contributes to PAD severity, we investigated the role of DM hyperglycemia in the activation of NF-κB under ischemic conditions. Induced ischemia in human vascular endothelial cell (HUVEC) cultures increased components of both canonical and non-canonical NF-κB pathways in the nucleus (p65 1.0 ± 0.1 vs 1.5 ± 0.2, p< 0.05, RelB 1.0 ± 0.1 vs 1.5 ± 0.2, p<0.01). Similarly, HUVEC acutely exposed to high glucose (HG, 25 mM) activated both canonical (IκB-α degradation, normal vs. HG 1.25 ± 0.02 vs 0.9 ± 0.0, p<0.05) and non-canonical NF-κB (p100 degradation, normal vs HG 0.021±0.001 vs 0.016±0.000, p<0.05) pathways. Prolonged exposure (3 days) of HUVEC to high glucose before ischemia resulted in impaired NF-κB activation as evident from decreased IκB phosphorylation (pIκB/IκB in normal glucose and ischemia 1.56 ± 0.22 vs 1.12 ± 0.35, p<0.01). To understand the signaling pathways underlying the ischemic activation of the NF-κB pathway, we used an array of antibodies to phosphoproteins involved in the inflammatory pathway. Compared to the lysates from cells grown in normal glucose, the lysates from cells grown in prolonged high glucose had dramatically increased phosphorylation of PKC-β2 (PKC-β2^pSer661, 8-fold increase). To test whether this increase in PKC-β2^pSer66 impairs NF-κB activation by ischemia, we treated HUVECS with prolonged high glucose exposure and ruboxystaurin (Rbx) (20 nM), an inhibitor of PKC-β2 phosphorylation, prior to ischemic exposure. Immunoblotting results confirmed that inhibition of PKC-β2 phosphorylation enhanced the ischemia induced NF-κB activation in HUVEC in this condition. We then tested the effect of Rbx on PKC-β2 phosphorylation and NF-κB activation in vivo in Akita mice, a model for type 1 diabetes. Consistent with our in vitro findings, in experimental PAD, NF-κB activity in the ischemic hind limb of Akita mice was significantly lower than those of the wild type (WT) mice as measured by IκB-α degradation (WT ischemic vs Akita ischemic; 0.04 ± 0.03 vs 0.10 ± 0.04 p<0.05). However, treatment of Akita mice with Rbx increased NF-κB activation in the ischemic hind limb (Akita ischemic 0.10 ± 0.04 vs ischemic+ Rbx 0.05 ± 0.02, p<0.05). Moreover, compared to the WT mice, the untreated Akita mice showed an impaired perfusion in the ischemic limbs (% perfusion recovery, WT vs Akita; 80.1 ± 10.3 vs 55.7 ± 10.1, p<0.05, n=5-8) that was improved in Rbx treated Akita mice (96.3 ± 2.3, p<0.01). Thus, hyperglycemic conditions increase PKC-β2^pSer66 in endothelial cells attenuating salutary NF-κB activation contributing to poor PAD outcomes in DM.

Inhibition of protein kinase C beta phosphorylation activates nuclear factor-kappa B and improves postischemic recovery in type 1 diabetes

IMPACT STATEMENT

Diabetes worsens the outcomes of peripheral arterial disease (PAD) likely in part through inducing chronic inflammation. However, in PAD, recovery requires the nuclear factor-kappa B (NF-κB) activation, a known contributor to inflammation. Our study shows that individually, both ischemia and high glucose activate the canonical and non-canonical arms of the NF-κB pathways. We show for the first time that prolonged high glucose specifically impairs ischemia-induced activation of the canonical NF-κB pathway through activation of protein kinase C beta (PKCβ). Accordingly, inhibition of PKCβ restores the ischemia-induced NF-κB activity both in vitroin endothelial cells and in vivoin hind limbs of type 1 diabetic mice and improves perfusion recovery after experimental PAD. Thus, this study provides a mechanistic insight into how diabetes contributes to poor outcomes in PAD and a potential translational approach to improve PAD outcomes.

Dual specificity phosphatase 5 regulates perfusion recovery in experimental peripheral artery disease

Peripheral artery disease (PAD) is caused by atherosclerotic occlusions of vessels outside the heart, particularly those of the lower extremities. Angiogenesis is one critical physiological response to vessel occlusion in PAD, but our understanding of the molecular mechanisms involved in angiogenesis is incomplete. Dual specificity phosphatase 5 (DUSP5) has been shown to play a key role in embryonic vascular development, but its role in post-ischemic angiogenesis is not known. We induced hind limb ischemia in mice and found robust upregulation of Dusp5 expression in ischemic hind limbs. Moreover, in vivo knockdown of Dusp5 resulted in impaired perfusion recovery in ischemic limbs and was associated with increased limb necrosis. In vitro studies showed upregulation of DUSP5 in human endothelial cells exposed to ischemia, and knockdown of DUSP5 in these ischemic endothelial cells resulted in impaired endothelial cell proliferation and angiogenesis, but did not alter apoptosis. Finally, we show that these effects of DUSP5 on post-ischemic angiogenesis are a result of DUSP5-dependent decrease in ERK1/2 phosphorylation and p21 protein expression. Thus, we have identified a role of DUSP5 in post-ischemic angiogenesis and implicated a DUSP5-ERK-p21 pathway that may serve as a therapeutic target for the modulation of post-ischemic angiogenesis in PAD.

Targeted Therapy for EBV-Associated B-cell Neoplasms

Epstein-Barr virus (EBV) is directly implicated in several B-cell lymphoid malignancies. EBV-associated lymphomas are characterized by prominent activation of the NF-κB pathway and targeting this pathway establishes a rationale for a therapeutic approach. The ubiquitin/proteasome signaling plays an essential role in the regulation of the NF-κB pathway. Ixazomib is an FDA-approved, orally bioavailable proteasome inhibitor. Here we report the first preclinical evaluation of ixazomib-mediated growth-inhibitory effects on EBV-infected B-lymphoblastoid cell lines Raji and Daudi. Ixazomib induced apoptosis in these cell lines in a dose-dependent manner. Cell-cycle analysis demonstrated ixazomib treatment induced cell-cycle arrest at the G₂-M phase with a concomitant decrease in G₀-G₁ and S phases. The results further revealed an increase in p53, p21, and p27 levels and a decrease in survivin and c-Myc protein levels. Mechanistically, ixazomib treatment resulted in the accumulation of polyubiquitinated proteins, including phosphorylated IκBα with a significant reduction of p65 subunit nuclear translocation. Altogether, our preclinical data support the rationale for in vivo testing of ixazomib in EBV-associated B-cell neoplasms. IMPLICATIONS: This preclinical study supports the use of oral proteasome inhibitor ixazomib for targeting NF-κB signaling in the treatment of EBV-associated B-cell neoplasms.Visual Overview: http://mcr.aacrjournals.org/content/molcanres/17/4/839/F1.large.jpg.

Abstract 776: Pre-clinical evaluation of ceritinib in anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is an aggressive CD30+ T-Cell lymphoma that accounts for 2-8% and 10-15% non-Hodgkin lymphomas in adults and children, respectively. The currently used standard therapy for anaplastic lymphoma kinase (ALK, a member of insulin receptor superfamily) positive ALCL has limited effectiveness, resulting in a substantial percentage of cases with poor outcome, either failing to enter remission or relapsing within a few months after starting the treatment. Thus, there is a clear unmet clinical need for developing novel, effective and safer therapeutic strategies for ALCL. Nucleophosmin 1 (NPM1) is a nucleolar phosphoprotein, which functions as a molecular chaperone for proteins and nucleic acids. Approximately 50% of ALCL cases are positive for the NPM-ALK fusion chimera generated by the t(2;5) chromosomal translocation. The oligomerization domain of NPM1 in the fusion protein NPM-ALK, mediates the ligand-independent dimerization of chimeric protein, which results in constitutive activation of the chimeric tyrosine kinase activity leading to downstream signaling pathways responsible for the oncogenicity. Ceritinib is a second generation FDA approved ALK inhibitor for the treatment of ALK-positive metastatic non-small cell lung cancer. Here we report the first preclinical evaluation of ceritinib growth inhibitory effects on ALK-positive ALCL cells. The NPM-ALK expressing ALCL model cell line SUDHL-1 used in our studies. Treatment with ceritinib significantly induced apoptosis dose dependently (10-50nM) in ALCL cells associated with poly (ADP-ribose) polymerase cleavage. Mechanistically, ceritinib blocked phosphorylation of ALK and its downstream signaling effectors STAT3, AKT and ERK1/2. Cell cycle analysis by flow cytometry showed that ceritinib induced G0/G1 arrest with concomitant decrease in the percentage of cells in S and G2/M phases which was associated with decreased cyclin D1 and increased p21 expression. ALCL is also characterized by strong expression of the cytokine receptor CD30 (a member of the TNF receptor family). CD30 stimulation leads to NF-kB activation and the induction of anti-apoptotic mechanisms. In response to ceritinib treatment, flow cytometry data showed that reduced CD30 expression in a dose dependent manner. Altogether, these pre-clinical results demonstrate that ceritinib induces apoptosis in ALCL cells by inhibiting ALK downstream signaling cascade and support the rational for in vivo testing of ceritinib for the treatment of ALK positive lymphomas.

Citation Format: Siddhartha Ganguly, Sudhakiranmayi Kuravi, Satyanarayana Alleboina, Brandon Weckbaugh, Deepti Satelli, Jensen Roy, Scott Weir, Joseph McGuirk, Ramesh Balusu. Pre-clinical evaluation of ceritinib in anaplastic large cell lymphoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 776. doi:10.1158/1538-7445.AM2015-776