Beom-Ju Hong

p-benzoquinone-benzene clusters as potential nanomechanical devices: A theoretical study

The equilibrium structures and binding energies of the benzene complexes of p-benzoquinones (PBQ) and its negatively charged anionic species (PBQ- and PBQ2-) have been investigated theoretically using second-order Møller-Plesset calculations. While neutral p-benzoquinone-benzene clusters (PBQ-Bz) prefer to have a parallel displaced geometry (P-c), CH...pi interactions (T-shaped geometries) prevail in the di-anionic PBQ-benzene (PBQ2- -Bz) complexes (T-e2-). Studies on dianionic p-benzoquinone-benzene clusters showed that two nonbonded intermolecular interactions compete in the most stable conformation. One is H-bonding interaction (C-H...O type) between carbonyl oxygen of p-benzoquinone and one of the hydrogen atoms of benzene, and the other is a pi-H interaction between pi-electron cloud of PBQ2- and another hydrogen atom of benzene. Blueshifted H-bonds were observed in T-shaped clusters. The changes in the geometrical preference of PBQ-Bz complex upon addition of electrons would be useful in designing optimized molecular mechanical devices based on the edge-to-face and face-to-face aromatic interactions.

Tumor hypoxia and reoxygenation: the yin and yang for radiotherapy

Tumor hypoxia, a common feature occurring in nearly all human solid tumors is a major contributing factor for failures of anticancer therapies. Because ionizing radiation depends heavily on the presence of molecular oxygen to produce cytotoxic effect, the negative impact of tumor hypoxia had long been recognized. In this review, we will highlight some of the past attempts to overcome tumor hypoxia including hypoxic radiosensitizers and hypoxia-selective cytotoxin. Although they were (still are) a very clever idea, they lacked clinical efficacy largely because of ‘reoxygenation’ phenomenon occurring in the conventional low dose hyperfractionation radiotherapy prevented proper activation of these compounds. Recent meta-analysis and imaging studies do however indicate that there may be a significant clinical benefit in lowering the locoregional failures by using these compounds. Latest technological advancement in radiotherapy has allowed to deliver high doses of radiation conformally to the tumor volume. Although this technology has brought superb clinical responses for many types of cancer, recent modeling studies have predicted that tumor hypoxia is even more serious because ‘reoxygenation’ is low thereby leaving a large portion of hypoxic tumor cells behind. Wouldn’t it be then reasonable to combine hypoxic radiosensitizers and/or hypoxia-selective cytotoxin with the latest radiotherapy? We will provide some preclinical and clinical evidence to support this idea hoping to revamp an enthusiasm for hypoxic radiosensitizers or hypoxia-selective cytotoxins as an adjunct therapy for radiotherapy.

Radiation-induced immune responses: mechanisms and therapeutic perspectives

Recent advancement in the radiotherapy technology has allowed conformal delivery of high doses of ionizing radiation precisely to the tumors while sparing large volume of the normal tissues, which have led to better clinical responses. Despite this technological advancement many advanced tumors often recur and they do so within the previously irradiated regions. How could tumors recur after receiving such high ablative doses of radiation? In this review, we outlined how radiation can elicit anti-tumor responses by introducing some of the cytokines that can be induced by ionizing radiation. We then discuss how tumor hypoxia, a major limiting factor responsible for failure of radiotherapy, may also negatively impact the anti-tumor responses. In addition, we highlight how there may be other populations of immune cells including regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs) that can be recruited to tumors interfering with the anti-tumor immunity. Finally, the impact of irradiation on tumor hypoxia and the immune responses according to different radiotherapy regimen is also delineated. It is indeed an exciting time to see that radiotherapy is being combined with immunotherapy in the clinic and we hope that this review can add an excitement to the field.

In vivo imaging of activated microglia in a mouse model of focal cerebral ischemia by two-photon microscopy.

Microglia are brain resident macrophages rapidly responding to various stimuli to exert appropriate inflammatory responses. Although they have recently been exploited as an attractive candidate for imaging neuroinflammation, it is still difficult to visualize them at the cellular and molecular levels. Here we imaged activated microglia by establishing intracranial window chamber (ICW) in a mouse model of focal cerebral ischemia by using two-photon microscopy (TPM), in vivo. Intravenous injection of fluorescent antibodies allowed us to detect significantly elevated levels of Iba-1 and CD68 positive activated microglia in the ipsilateral compared to the contralateral side of the infarct. We further observed that indomethacin, a non-steroidal anti-inflammatory drug significantly attenuated CD68-positive microglial activation in ICW, which was further confirmed by qRT-PCR biochemical analyses. In conclusion, we believe that in vivo TPM imaging of ICW would be a useful tool to screen for therapeutic interventions lowering microglial activation hence neuroinflammation.

Hyaluronate-Death Receptor 5 Antibody Conjugates for Targeted Treatment of Liver Metastasis.

The liver is the most frequent site of metastasis with a 5-year survival rate of only 20-40%. In this work, hyaluronate (HA)-death receptor 5 antibody (DR5 Ab) conjugate was synthesized as a dual targeting therapeutic agent to treat liver metastasis. Dual targeting was achieved by DR5 Ab, a humanized agonistic monoclonal antibody binding to DR5 frequently overexpressed in many kinds of cancer cells, and by HA, a natural polysaccharide binding to HA receptors highly expressed in both the liver and cancer cells. Thiol end-modified HA was site-specifically conjugated to N-glycan on Fc region of oxidized DR5 Ab using a heterobifunctional linker of 3-(2-pyridyldithio)propionyl hydrazide (PDPH). The successful synthesis of HA-DR5 Ab conjugate was confirmed by (1)H NMR, purpald assay, dynamic light scattering (DLS), and high-performance liquid chromatography (HPLC). In vitro analysis of HA-DR5 Ab conjugate revealed that the conjugation of HA to DR5 Ab did not affect the binding affinity and anticancer efficacy of DR5 Ab. Remarkably, according to in vivo bioimaging study, HA-DR5 Ab conjugate appeared to be highly accumulated in the liver and dramatically effective in inhibiting the tumor growth in liver metastasis model mice.

Abstract A13: Hypoxia-inducible factor-1 (HIF-1) in myeloid cells promotes angiogenesis by regulating VEGF and S100A8 production

Myeloid cells (cells that give rise to monocytes and macrophages) are a critical component in the solid tumor microenvironment, promoting angiogenesis and tumor recurrence to therapies. Recent literature have extensively demonstrated that hypoxia-inducible factor (HIF) is a key transcription factor in myeloid cells in responding to hypoxic stimuli including solid tumors and inflammation by secreting various cytokines and growth factors. Although a number of studies have reported that hypoxia exposure to primary macrophages induces HIF-1 activation and subsequent vascular endothelial growth factor (VEGF) production, there had been no mouse model to demonstrate this phenomenon. To better understand the role of transcriptional activation of HIF in pathological macrophages, we have created a new strain of myeloid-specific knockout (KO) mice targeting HIF pathways using hS100A8 as the myeloid promoter. S100A8 is an intracellular calcium binding protein and its expression has been heavily detected in pathological macrophages of many diseases including solid tumors, inflammatory bowel disease, obesity, and rheumatoid arthritis. Upon generating mice deficient for von Hippel Lindau (pVHL) tumor suppressor, the negative regulator of HIF, in myeloid cells, we observed erythema and increased VEGF expression in the bone marrow lysate. Moreover, these mice exhibited an enhanced angiogenesis in the subcutanouesly implanted matrigel plugs, which was accompanied by increased VEGF-VEGFR2 signaling in matrigel. We further found that these phenotypes were dependent on transcriptional activation of HIF-1 as a pharmacological or genetic inhibition of HIF-1α completely suppressed the phenotypes in mice deficient for pVHL in myeloid cells. Importantly, we found that HIF-1 activation in myeloid cells regulate not only VEGF but also S100A8 production and identified that monocytes were the major effector driving angiogenesis. Together these results suggest that transcriptional activation of HIF-1 in myeloid cells plays a critical role in promoting angiogenesis. We are currently investigating how HIF-1 in myeloid cells regulates tumor microenvironment thereby affecting tumor progression. Citation Format: G-One Ahn, Young-Eun Kim, Beom-Ju Hong, Seoyeon Bok, Chan-Ju Lee, Hak Jae Kim, Il Han Kim, Jun Seita, Irving Weissman, J Martin Brown. Hypoxia-inducible factor-1 (HIF-1) in myeloid cells promotes angiogenesis by regulating VEGF and S100A8 production. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A13. doi:10.1158/1538-7445.CHTME14-A13