Chan Kim

Soluble vascular endothelial growth factor receptor-3 suppresses lymphangiogenesis and lymphatic metastasis in bladder cancer

BackgroundMost bladder cancer patients experience lymphatic metastasis in the course of disease progression, yet the relationship between lymphangiogenesis and lymphatic metastasis is not well known. The aim of this study is to elucidate underlying mechanisms of how expanded lymphatic vessels and tumor microenvironment interacts each other and to find effective therapeutic options to inhibit lymphatic metastasis.ResultsThe orthotopic urinary bladder cancer (OUBC) model was generated by intravesical injection of MBT-2 cell lines. We investigated the angiogenesis, lymphangiogenesis, and CD11b+/CD68+ tumor-associated macrophages (TAM) by using immunofluorescence staining. OUBC displayed a profound lymphangiogenesis and massive infiltration of TAM in primary tumor and lymphatic metastasis in lymph nodes. TAM flocked near lymphatic vessels and express higher levels of VEGF-C/D than CD11b- cells. Because VEGFR-3 was highly expressed in lymphatic vascular endothelial cells, TAM could assist lymphangiogenesis by paracrine manner in bladder tumor. VEGFR-3 expressing adenovirus was administered to block VEGF-C/D signaling pathway and clodronate liposome was used to deplete TAM. The blockade of VEGF-C/D with soluble VEGF receptor-3 markedly inhibited lymphangiogenesis and lymphatic metastasis in OUBC. In addition, the depletion of TAM with clodronate liposome exerted similar effects on OUBC.ConclusionVEGF-C/D are the main factors of lymphangiogenesis and lymphatic metastasis in bladder cancer. Moreover, TAM plays an important role in these processes by producing VEGF-C/D. The inhibition of lymphangiogenesis could provide another therapeutic target to inhibit lymphatic metastasis and recurrence in patients with invasive bladder cancer.

Vascular RhoJ is an effective and selective target for tumor angiogenesis and vascular disruption.

Current antiangiogenic therapy is limited by its cytostatic nature and systemic side effects. To address these limitations, we have unveiled the role of RhoJ, an endothelial-enriched Rho GTPase, during tumor progression. RhoJ blockade provides a double assault on tumor vessels by both inhibiting tumor angiogenesis and disrupting the preformed tumor vessels through the activation of the RhoA-ROCK (Rho kinase) signaling pathway in tumor endothelial cells, consequently resulting in a functional failure of tumor vasculatures. Moreover, enhanced anticancer effects were observed when RhoJ blockade was employed in concert with a cytotoxic chemotherapeutic agent, angiogenesis-inhibiting agent, or vascular-disrupting agent. These results identify RhoJ blockade as a selective and effective therapeutic strategy for targeting tumor vasculature with minimal side effects.

SIRT2 regulates tumour hypoxia response by promoting HIF-1α hydroxylation

Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that has a central role in the regulation of tumour metabolism under hypoxic conditions. HIF-1α stimulates glycolytic energy production and promotes tumour growth. Sirtuins are NAD+-dependent protein deacetylases that regulate cellular metabolism in response to stress; however, their involvement in the hypoxic response remains unclear. In this study, it is shown that SIRT2-mediated deacetylation of HIF-1α regulates its stability in tumour cells. SIRT2 overexpression destabilized HIF-1α under hypoxic conditions, whereas HIF-1α protein levels were high in SIRT2-deficient cells. SIRT2 directly interacted with HIF-1α and deacetylated Lys709 of HIF-1α. Deacetylation of HIF-1α by SIRT2 resulted in increased binding affinity for prolyl hydroxylase 2, a key regulator of HIF-1α stability, and increased HIF-1α hydroxylation and ubiquitination. Moreover, a pharmacological agent that increased the intracellular NAD+/NADH ratio led to the degradation of HIF-1α by increasing SIRT2-mediated deacetylation and subsequent hydroxylation. These findings suggest that SIRT2-mediated HIF-1α deacetylation is critical for the destablization of HIF-1α and the hypoxic response of tumour cells.

Normalization of Tumor Vessels by Tie2 Activation and Ang2 Inhibition Enhances Drug Delivery and Produces a Favorable Tumor Microenvironment

A destabilized tumor vasculature leads to limited drug delivery, hypoxia, detrimental tumor microenvironment, and even metastasis. We performed a side-by-side comparison of ABTAA (Ang2-Binding and Tie2-Activating Antibody) and ABA (Ang2-Blocking Antibody) in mice with orthotopically implanted glioma, with subcutaneously implanted Lewis lung carcinoma, and with spontaneous mammary cancer. We found that Tie2 activation induced tumor vascular normalization, leading to enhanced blood perfusion and chemotherapeutic drug delivery, markedly lessened lactate acidosis, and reduced tumor growth and metastasis. Moreover, ABTAA favorably altered the immune cell profile within tumors. Together, our findings establish that simultaneous Tie2 activation and Ang2 inhibition form a powerful therapeutic strategy to elicit a favorable tumor microenvironment and enhanced delivery of a chemotherapeutic agent into tumors.

Methylation-dependent regulation of HIF-1α stability restricts retinal and tumour angiogenesis

Hypoxia-inducible factor-1α (HIF-1α) mediates hypoxic responses and regulates gene expression involved in angiogenesis, invasion and metabolism. Among the various HIF-1α posttranslational modifications, HIF-1α methylation and its physiological role have not yet been elucidated. Here we show that HIF-1α is methylated by SET7/9 methyltransferase, and that lysine-specific demethylase 1 reverses its methylation. The functional consequence of HIF-1α methylation is the modulation of HIF-1α stability primarily in the nucleus, independent of its proline hydroxylation, during long-term hypoxic and normoxic conditions. Knock-in mice bearing a methylation-defective Hif1aKA/KA allele exhibit enhanced retinal angiogenesis and tumour vascularization via HIF-1α stabilization. Importantly, S28Y and R30Q mutations of HIF-1α, found in human cancers, are involved in the altered HIF-1α stability. Together, these results demonstrate a role for HIF-1α methylation in regulating protein stability, thereby modulating biological output including retinal and tumour angiogenesis, with therapeutic implications in human cancer.

Novel Glycosylated VEGF Decoy Receptor Fusion Protein, VEGF-Grab, Efficiently Suppresses Tumor Angiogenesis and Progression

Antiangiogenic therapies targeting VEGFA have been commonly used in clinics to treat cancers over the past decade. However, their clinical efficacy has been limited, with drawbacks including acquisition of resistance and activation of compensatory pathways resulting from elevated circulating VEGFB and placental growth factor (PlGF). To bypass these disadvantages, we developed a novel glycosylated soluble decoy receptor fusion protein, VEGF-Grab, that can neutralize VEGFA, VEGFB, and PlGF. VEGF-Grab has the second and third immunoglobulin (Ig)-like domains of VEGF receptor 1 (VEGFR1) fused to IgG1 Fc, with three potential glycosylation sites introduced into the third Ig-like domain of VEGF-Grab by mutagenesis. Compared with VEGF-Trap, VEGF-Grab showed more potent decoy activity against VEGF and PlGF, mainly attributed to the VEGFR1 backbone. Most importantly, the negatively charged O-glycans attached to the third Ig-like domain of VEGFR1 counterbalanced the originally positively charged VEGFR1 backbone, minimizing nonspecific binding of VEGF-Grab to the extracellular matrix, and resulting in greatly improved pharmacokinetic profile. These advancements led to stronger and more durable antiangiogenic, antitumor, and antimetastatic efficacy in both implanted and spontaneous tumor models as compared with VEGF-Trap, while toxicity profiles were comparable with VEGF-Trap. Collectively, our results highlight VEGF-Grab as a promising therapeutic candidate for further clinical drug development. Mol Cancer Ther; 14(2); 470–9. ©2014 AACR.

Current Input Extended Counting ADC With Wide Dynamic Range for LWIR FPAs

A readout circuit incorporating a pixel level analog-to-digital converter (ADC) is studied for 2-D long wavelength infrared focal plane arrays (LWIR FPAs). The charge handling capacity of the unit cell circuit is improved by using the current input incremental ADC. The proposed pixel level ADC is based on an extended counting ADC but is composed of two oversampling conversions. The readout circuit has been fabricated using a 0.35 mum 2-poly 4-metal CMOS process for a 128 times 128 LWIR HgCdTe array with a pixel size of 50 mum times 50 mum. The peak signal-to-noise ratio (S/N) and dynamic range (DR) were measured to be 85.8 dB and 99.9 dB, respectively, with a total power consumption of 50 mW.

Erratum: Normalization of Tumor Vessels by Tie2 Activation and Ang2 Inhibition Enhances Drug Delivery and Produces a Favorable Tumor Microenvironment (Cancer Cell (2016) 30(6) (953–967) (S1535610816305050) (10.1016/j.ccell.2016.10.018))

(Cancer Cell 30, 953–967; December 12, 2016) In the original Figure 4J and Figure 7H, amagnified image of ABTAA groupwas inadvertently used in duplicate. Also in the Fc group of Figure 4J, the square box indicating a metastatic nodule was misplaced, resulting in a mismatch between the magnified image and the indicated area in whole lung image. This was a mistake made by the authors during the assembly of the figures. These errors do not affect or alter any of the findings reported in the paper. These errors have now been corrected here and in the original article online. The authors apologize for any confusion or inconvenience that these errors may have caused.