RNA interference targeting hypoxia-inducible factor 1α via a novel multifunctional surfactant attenuates glioma growth in an intracranial mouse model

Abstract

P atients with the most malignant type of glioma, Grade IV glioblastoma, have a mean survival time of approximately 15 months and an estimated 5-year survival rate of less than 5%.11 High-grade gliomas (Grades III and IV) are the most common primary brain tumors in adults and the fourth leading cause of cancerrelated death. 40 Tumor hypoxia is thought to play an important role in glioblastoma tumor pathobiology by proabbreviatioNs CA-IX = carbonic anhydrase-IX; CED = convection-enhanced delivery; DAB = 3,3′-diaminobenzidine tetrahydrochloride; DCA = dichloroacetate; EHCO = 1-(aminoethyl)iminobis [N-(oleicylcysteinylhistinyl-1-aminoethyl)propionamide]; GFP = green fluorescent protein; GLUT-1 = glucose transporter 1; HIF-1a = hypoxia-inducible factor 1a; IHC = immunohistochemistry; MVD = microvascular density; PEG = polyethylene glycol; PI = proliferation index; RNAi = RNA interference; siRNA = small interfering RNA; VEGF = vascular endothelial growth factor. obJeCt High-grade gliomas are the most common form of adult brain cancer, and patients have a dismal survival rate despite aggressive therapeutic measures. Intratumoral hypoxia is thought to be a main contributor to tumorigenesis and angiogenesis of these tumors. Because hypoxia-inducible factor 1a (HIF-1a) is the major mediator of hypoxia-regulated cellular control, inhibition of this transcription factor may reduce glioblastoma growth. MetHoDs Using an orthotopic mouse model with U87-LucNeo cells, the authors used RNA interference to knock down HIF-1a in vivo. The small interfering RNA (siRNA) was packaged using a novel multifunctional surfactant, 1-(amino ethyl)iminobis[N-(oleicylcysteinylhistinyl-1-aminoethyl)propionamide] (EHCO), a nucleic acid carrier that facilitates cellular uptake and intracellular release of siRNA. Stereotactic injection was used to deliver siRNA locally through a guide-screw system, and delivery/uptake was verified by imaging of fluorescently labeled siRNA. Osmotic pumps were used for extended siRNA delivery to model a commonly used human intracranial drug-delivery technique, convectionenhanced delivery. resUlts Mice receiving daily siRNA injections targeting HIF-1a had a 79% lower tumor volume after 50 days of treatment than the controls. Levels of the HIF-1 transcriptional targets vascular endothelial growth factor (VEGF), glucose transporter 1 (GLUT-1), c-MET, and carbonic anhydrase-IX (CA-IX) and markers for cell growth (MIB-1 and microvascular density) were also significantly lower. Altering the carrier EHCO by adding polyethylene glycol significantly increased the efficacy of drug delivery and subsequent survival. CoNClUsioNs Treating glioblastoma with siRNA targeting HIF-1a in vivo can significantly reduce tumor growth and increase survival in an intracranial mouse model, a finding that has direct clinical implications.

The role of glioma stem cells in chemotherapy resistance and glioblastoma multiforme recurrence

“…Preliminary attempts to increase local tissue oxygen have been explored to improve tumor cell stress after both chemo- and radiotherapy [87]. Much prior work has focused on targeting HIFs and their downstream effectors to disrupt GSC signaling and survival [88,89]. Notch has a critical function in the hypoxic and perivascular niches, serving to prevent neuronal differentiation and support GSC growth [33].…”

<p>Nanocarriers and nonviral methods for delivering antiangiogenic factors for glioblastoma therapy: the story so far</p>

“…The CED devices used were based on Alzet osmotic pumps or programmable syringe pumps. Diverse antiangiogenic agents or nanocarriers carrying antiangiogenic factors have been administered in this way in GB-bearing animals: bevacizumab, 38 polyplexes (polymer/DNA) encoding a soluble VEGFR-1 (sFlt-1) and an angiostatin-endostatin fusion protein (statin-AE), 39 siRNA targeting hypoxia-inducible factor 1α (HIF-1α), 40 the immunotoxins, DTAT (diphtheria toxin [DT] targeting urokinase plasminogen activator receptor [uPAR]) and DTATEGF (DT targeting uPAR and EGFR), 41 endostatin or endostatin fused to an antibody (IgG) Fc domain (Fc-endostatin), 42,43 two mechanistically different inhibitors of the CYP/CYP450 2C11 epoxygenase, 17-octadecynoic acid and miconazole, 44 and sorafenib-loaded lipid nanocapsules (SFN-LNCs). 45 The administration of these agents by CED has frequently been shown to lead to a significant decrease in capillary formation and tumor size and an increase in animal survival.…”

Practical Considerations of Convection Enhanced Delivery for Novel Therapies Treating Spinal Cord Injury Related Neuropathic Pain

“…In glioblastoma cancer research, targeting HIF-1α by siRNA administration in vivo resulted in decreased tumor growth and enhanced survival [58]. The efficacy of IL-13R alpha2 in glioma cells and antitumor activity by cells treated with antisense oligonucleotide or siRNA to IL-13R alpha2 chain considered promising as receptordirected cytotoxic therapy [59].…”