Pleiotropic effects of HIF-1 blockade on tumor radiosensitivity

SummaryWe have previously shown that radiation increases HIF-1 activity in tumors, causing significant radioprotection of the tumor vasculature. The impact that HIF-1 activation has on overall tumor radiosensitivity, however, is unknown. We reveal here that HIF-1 plays an important role in determining tumor radioresponsiveness through regulating four distinct processes. By promoting ATP metabolism, proliferation, and p53 activation, HIF-1 has a radiosensitizing effect on tumors. Through stimulating endothelial cell survival, HIF-1 promotes tumor radioresistance. As a result, the net effect of HIF-1 blockade on tumor radioresponsiveness is highly dependent on treatment sequencing, with “radiation first” strategies being significantly more effective than the alternative. These data provide a strong rationale for pursuing sequence-specific combinations of HIF-1 blockade and conventional therapeutics

Her2/neu signaling blockade improves tumor oxygenation in a multifactorial fashion in Her2/neu+ tumors

Tumor hypoxia reduces the efficacy of radiation and chemotherapy as well as altering gene expression that promotes cell survival and metastasis. The growth factor receptor, Her2/neu, is overexpressed in 25–30% of breast tumors. Tumors that are Her2+ may have an altered state of oxygenation, relative to Her2−tumors, due to differences in tumor growth rate and angiogenesis

Elevated CAIX Expression is Associated with an Increased Risk of Distant Failure in Early-Stage Cervical Cancer

Tumor hypoxia is associated with adverse outcome in many malignancies. The goal of this study was to determine if elevated expression of carbonic anhydrase IX (CAIX), a biomarker of hypoxia, predicts for recurrence in early-stage cervical cancer. The charts of all patients with early-stage cervical cancer, primarily FIGO IB, treated by radical hysterectomy at our institution from 1988–2001 were reviewed. Adequate pathologic specimens from patients who recurred or who had at least three years follow-up and remained disease-free were stained for CAIX. An immunohistochemical score (IHC) was generated from the extent/intensity of staining. Outcome, as measured by freedom from recurrence (FFR), distant metastases (FFDM) and local recurrence (FFLR), was analyzed as a function of age, IHC, lymph node status (LN) and histology. Forty-two relapsing patients and 76 non-relapsing patients were evaluated. In univariate analysis, +LN, though not IHC or histology, was a significant predictor of any recurrence. Both +LN and higher IHC were associated with decreased FFDM but not FFLR. Patients with both +LN and elevated IHC more frequently exhibited distant metastases as first site of failure (5-year FFDM 50%) than patients with only +LN, elevated IHC or neither feature (70, 85 and 95%, respectively, p = 0.0004). In multivariable analysis, only +LN was significantly associated with poorer FFDM (hazard ratio 4.6, p = 0.0015) though there was a strong trend with elevated CAIX expression (p = 0.069). Elevated CAIX expression is associated with more frequent distant metastases in early-stage cervical cancer, suggesting that patients with this characteristic may benefit from more aggressive treatment

In Vivo Magnetic Resonance Studies of Glycine and Glutathione Metabolism in a Rat Mammary Tumor

The metabolism of glycine into glutathione was monitored noninvasively in vivo in intact R3230Ac rat tumors by magnetic resonance imaging and spectroscopy. Metabolism was tracked by following the isotope label from intravenously infused [2-13C]-glycine into the glycinyl residue of glutathione. Signals from [2-13C]-glycine and γ-glutamylcysteinyl-[2-13C]-glycine (13C-glutathione) were detected by nonlocalized 13C spectroscopy as these resonances are distinct from background signals. In addition, using spectroscopic imaging methods, heterogeneity in the in vivo tumor distribution of glutathione was observed. In vivo spectroscopy also detected isotope incorporation from [2-13C]-glycine into both the 2- and 3-carbons of serine. Analyses of tumor tissue extracts show single and multiple label incorporation from [2-13C]-glycine into serine from metabolism through the serine hydroxymethyltransferase and glycine cleavage system pathways. Mass spectrometric analysis of extracts also shows that isotope-labeled serine is further metabolized via the transsulfuration pathway as the 13C-isotope labels appear in both the glycinyl- and the cysteinyl-residue of glutathione. Our studies demonstrate the use of magnetic resonance imaging and spectroscopy for monitoring tumor metabolic processes central to oxidative stress defense

Overexpression of extracellular superoxide dismutase reduces acute radiation induced lung toxicity

BACKGROUND: Acute RT-induced damage to the lung is characterized by inflammatory changes, which proceed to the development of fibrotic lesions in the late phase of injury. Ultimately, complete structural ablation will ensue, if the source of inflammatory / fibrogenic mediators and oxidative stress is not removed or attenuated. Therefore, the purpose of this study is to determine whether overexpression of extracellular superoxide dismutase (EC-SOD) in mice ameliorates acute radiation induced injury by inhibiting activation of TGFβ1 and downregulating the Smad 3 arm of its signal transduction pathway. METHODS: Whole thorax radiation (single dose, 15 Gy) was delivered to EC-SOD overexpressing transgenic (XRT-TG) and wild-type (XRT-WT) animals. Mice were sacrificed at 1 day, 1 week, 3, 6, 10 and 14 weeks. Breathing rates, right lung weights, total/differential leukocyte count, activated TGFβ1 and components of its signal transduction pathway (Smad 3 and p-Smad 2/3) were assessed to determine lung injury. RESULTS: Irradiated wild-type (XRT-WT) animals exhibited time dependent increase in breathing rates and right lung weights, whereas these parameters were significantly less increased (p < 0.05) at 3, 6, 10 and 14 weeks in irradiated transgenic (XRT-TG) mice. An inflammatory response characterized predominantly by macrophage infiltration was pronounced in XRT-WT mice. This acute inflammation was significantly attenuated (p < 0.05) in XRT-TG animals at 1, 3, 6 and 14 weeks. Expression of activated TGFβ1 and components of its signal transduction pathway were significantly reduced (p < 0.05) at later time-points in XRT-TG vs. XRT-WT. CONCLUSION: This study shows that overexpression of EC-SOD confers protection against RT-induced acute lung injury. EC-SOD appears to work, in part, via an attenuation of the macrophage response and also decreases TGFβ1 activation with a subsequent downregulation of the profibrotic TGFβ pathway

Erythropoietin Blockade Inhibits the Induction of Tumor Angiogenesis and Progression

BACKGROUND: The induction of tumor angiogenesis, a pathologic process critical for tumor progression, is mediated by multiple regulatory factors released by tumor and host cells. We investigated the role of the hematopoietic cytokine erythropoietin as an angiogenic factor that modulates tumor progression. METHODOLOGY/PRINCIPAL FINDINGS: Fluorescently-labeled rodent mammary carcinoma cells were injected into dorsal skin-fold window chambers in mice, an angiogenesis model that allows direct, non-invasive, serial visualization and real-time assessment of tumor cells and neovascularization simultaneously using intravital microscopy and computerized image analysis during the initial stages of tumorigenesis. Erythropoietin or its antagonist proteins were co-injected with tumor cells into window chambers. In vivo growth of cells engineered to stably express a constitutively active erythropoietin receptor EPOR-R129C or the erythropoietin antagonist R103A-EPO were analyzed in window chambers and in the mammary fat pads of athymic nude mice. Co-injection of erythropoietin with tumor cells or expression of EPOR-R129C in tumor cells significantly stimulated tumor neovascularization and growth in window chambers. Co-injection of erythropoietin antagonist proteins (soluble EPOR or anti-EPO antibody) with tumor cells or stable expression of antagonist R103A-EPO protein secreted from tumor cells inhibited angiogenesis and impaired tumor growth. In orthotopic tumor xenograft studies, EPOR-R129C expression significantly promoted tumor growth associated with increased expression of Ki67 proliferation antigen, enhanced microvessel density, decreased tumor hypoxia, and increased phosphorylation of extracellular-regulated kinases ERK1/2. R103A-EPO antagonist expression in mammary carcinoma cells was associated with near-complete disruption of primary tumor formation in the mammary fat pad. CONCLUSIONS/SIGNIFICANCE: These data indicate that erythropoietin is an important angiogenic factor that regulates the induction of tumor cell-induced neovascularization and growth during the initial stages of tumorigenesis. The suppression of tumor angiogenesis and progression by erythropoietin blockade suggests that erythropoietin may constitute a potential target for the therapeutic modulation of angiogenesis in cancer