Seung Ja Oh

Amelioration of sepsis by TIE2 activation–induced vascular protection

Vascular protection through TIE2 activation is a potential treatment strategy to ameliorate sepsis. Antibody TIEs sepsis up in knots Sepsis, or severe systemic inflammation caused by infection, has a high mortality despite the availability of antibiotic treatment, and more specific therapies are urgently needed. One of the difficult-to-treat and potentially life-threatening components of sepsis is vascular disintegration and leakage. Han et al. have discovered an antibody, called ABTAA, which binds to a ligand called angiopoietin 2 (ANG2) in the vasculature, but then activates it instead of blocking its activity like standard antibodies. When ABTAA binds to ANG2, it causes clustering of ANG2 and subsequently its receptor TIE2 at the site, and the resulting signaling cascade protects the vascular walls and blunts the damaging effects of sepsis, greatly increasing survival in mouse models of the disease. Protection of endothelial integrity has been recognized as a frontline approach to alleviating sepsis progression, yet no effective agent for preserving endothelial integrity is available. Using an unusual anti–angiopoietin 2 (ANG2) antibody, ABTAA (ANG2-binding and TIE2-activating antibody), we show that activation of the endothelial receptor TIE2 protects the vasculature from septic damage and provides survival benefit in three sepsis mouse models. Upon binding to ANG2, ABTAA triggers clustering of ANG2, assembling an ABTAA/ANG2 complex that can subsequently bind and activate TIE2. Compared with a conventional ANG2-blocking antibody, ABTAA was highly effective in augmenting survival from sepsis by strengthening the endothelial glycocalyx, reducing cytokine storms, vascular leakage, and rarefaction, and mitigating organ damage. Together, our data advance the role of TIE2 activation in ameliorating sepsis progression and open a potential therapeutic avenue for sepsis to address the lack of sepsis-specific treatment.

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.

USP8 modulates ubiquitination of LRIG1 for Met degradation

The Met receptor tyrosine kinase is an attractive target for cancer therapy as it promotes invasive tumor growth. SAIT301 is a novel anti-Met antibody, which induces LRIG1-mediated Met degradation and inhibits tumor growth. However, detailed downstream mechanism by which LRIG1 mediates target protein down-regulation is unknown. In the present study, we discovered that SAIT301 induces ubiquitination of LRIG1, which in turn promotes recruitment of Met and LRIG1 complex to the lysosome through its interaction with Hrs, resulting in concomitant degradation of both LRIG1 and Met. We also identified USP8 as a LRIG1-specific deubiquitinating enzyme, reporting the interaction between USP8 and LRIG1 for the first time. SAIT301 triggers degradation of LRIG1 by inhibiting the interaction of LRIG1 and USP8, which regulates ubiquitin modification and stability of LRIG1. In summary, SAIT301 employs ubiquitination of LRIG1 for its highly effective Met degradation. This unique feature of SAIT301 enables it to function as a fully antagonistic antibody without Met activation. We found that USP8 is involved in deubiquitination of LRIG1, influencing the efficiency of Met degradation. The relation of Met, LRIG1 and USP8 strongly supports the potential clinical benefit of a combination treatment of a USP8 inhibitor and a Met inhibitor, such as SAIT301.

Gln-362 of Angiopoietin-2 Mediates Migration of Tumor and Endothelial Cells through Association with α5β1 Integrin

Background: The angiogenic growth factor angiopoietin-2 regulates angiogenesis through Tie2 and integrins. Results: An angiopoietin-2 mutant fails to bind to integrin, but not Tie2, and to mediate cell migration. Conclusion: Tie2-independent angiopoietin-2 association with integrin is critical for migration of tumor and endothelial cells. Significance: Understanding the mechanism of angiopoietin-2 interaction with integrin is essential for angiogenesis and cancer invasion. Angiopoietin-2 (Ang-2) not only regulates angiogenesis by binding to its well known receptor Tie2 on endothelial cells but also controls sprouting of Tie2-negative angiogenic endothelial cells and invasion of Tie2-negative non-endothelial cells by binding to integrins. However, the molecular mechanism of the Ang-2/integrin association has been unclear. In this study, we found that the Gln-362 residue of Ang-2 was essential for binding to α5β1 integrin. A Q362E Ang-2 mutant, which still bound to Tie2, failed to associate with α5β1 integrin and was unable to activate the integrin downstream signaling of focal adhesion kinase. In addition, unlike wild-type Ang-2, the Q362E Ang-2 mutant was defective in mediating invasion of Tie2-negative glioma or Tie2-positive endothelial cells. Furthermore, the tailpiece domain of the α5 subunit in α5β1 integrin was critical for binding to Ang-2. Taken together, these results provide a novel insight into the mechanism of integrin regulation by Ang-2, which contributes to tumor invasion and endothelial cell migration in a Tie2-independent manner.

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.