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Researchers Describe a Mechanism Inducing Self-Killing of Cancer Cells
(Professor Kim (left) and lead author Lee) Researchers have described a new mechanism which induces the self-killing of cancer cells by perturbing ion homeostasis. A research team from the Department of Biochemical Engineering has developed helical polypeptide potassium ionophores that lead to the onset of programmed cell death. The ionophores increase the active oxygen concentration to stress endoplasmic reticulum to the point of cellular death. The electrochemical gradient between extracellular and intracellular conditions plays an important role in cell growth and metabolism. When a cell’s ion homeostasis is disturbed, critical functions accelerating the activation of apoptosis are inhibited in the cell. Although ionophores have been intensively used as an ion homeostasis disturber, the mechanisms of cell death have been unclear and the bio-applicability has been limited. In the study featured at Advanced Science, the team presented an alpha helical peptide-based anticancer agent that is capable of transporting potassium ions with water solubility. The cationic, hydrophilic, and potassium ionic groups were combined at the end of the peptide side chain to provide both ion transport and hydrophilic properties. These peptide-based ionophores reduce the intracellular potassium concentration and at the same time increase the intracellular calcium concentration. Increased intracellular calcium concentrations produce intracellular reactive oxygen species, causing endoplasmic reticulum stress, and ultimately leading to apoptosis. Anticancer effects were evaluated using tumor-bearing mice to confirm the therapeutic effect, even in animal models. It was found that tumor growth was strongly inhibited by endoplasmic stress-mediated apoptosis. Lead author Dr. Dae-Yong Lee said, “A peptide-based ionophore is more effective than conventional chemotherapeutic agents because it induces apoptosis via elevated reactive oxygen species levels. Professor Yeu-Chun Kim said he expects this new mechanism to be widely used as a new chemotherapeutic strategy. This research was funded by the National Research Foundation.
The Antibody That Normalizes Tumor Vessels
Researchers also discover that their antisepsis antibody reduces glioma, lung and breast cancer progression in mice. A research team at the Center for Vascular Research within the Institute for Basic Science (IBS) discovered that the antisepsis antibody ABTAA (Ang2-Binding and Tie2-Activating Antibody) reduces tumor volume and improves the delivery of anti-cancer drugs. Published in Cancer Cell, this study demonstrates that ABTAA restores the structural and functional integrity of tumor blood vessels in three different tumor models: breast, lungs, and brain. Blood vessels inside and around an established tumor can be described as a chaotic and dysfunctional labyrinth. While the inner walls of healthy blood vessels are surrounded and supported by endothelial cells and other cells called pericytes, in the established tumor, the endothelial junctions are broken apart and pericytes are also detached. Blood flow into and from the tumor is severely retarded and tumor vessels lacking an intact vessel wall become leaky. This microenvironment causes limited drug delivery to the tumor and leads to inadequate oxygen supply (hypoxia) and even metastasis. The research team led by Professor Gou-Young Koh at KAIST’s Graduate School of Medical Science and Engineering found that the antibody ABTAA normalizes the tumor vessels and hence, change the whole tumor microenvironment. “We call it normalization of tumor vessels, because it resembles closely the wall architecture of healthy, normal vessels,” explains PARK Jin-Sung, first author of the study. And continues: “Tumor can adapt to hypoxia and get more aggressive, so we tried to prevent this transition by normalizing tumor vessels. ABTAA changes the whole tumor environment, oxygenation status and level of lactate, so that the immune cells and drugs can reach the core regions of the tumor more easily. In this way, we create a favorable ground for tumor treatment.” In an attempt to generate antibodies targeting the protein Ang2, which is specifically expressed by endothelial cells in stressful conditions like in tumor, the team unexpectedly discovered that ABTAA has a peculiar way of working and a dual function. ABTAA indeed not only blocks Ang2, but also activates Tie2 at the same time. Tie2 is a receptor present on the cell membrane of endothelial cells. ABTAA causes Ang2 to cluster together and to strongly activate Tie2 receptors. “If we activate Tie2, we can efficiently normalize tumor vessels, enhance drug delivery and change the whole microenvironment,” explains KOH Gou Young, Director of the Center for Vascular Research. Several pharmaceutical companies are developing Ang2-blocking antibodies to cure cancer. However, even if these antibodies significantly inhibit tumor progression, they do not stop tumor hypoxia. Moreover, most of the anti-cancer drugs target the tumor at its early stage, when tumors are still hard to diagnose. ABTAA, instead, works with tumors that are already rooted: “When the tumor is established, hypoxia is the main driver of tumor progression. So, if we eliminate hypoxia, we make the tumor milder, by reducing its progression and metastasis,” comments Koh. Figure: Schematic drawing of a blood vessel around tumors before and after treatment with ABTAA. The picture above shows a typical tumor vasculature characterized by damaged walls, red blood cells leakage and detached pericytes. Activating Tie2 on endothelial cells with the antibody ABTAA restores the normal vessel architecture: endothelial and pericytes on the vessel walls are stabilized, the delivery of blood is improved, and the anticancer drugs are more likely to reach the tumor core. The researchers tested ABTAA in mice with three different types of tumors that show high levels of Ang2: glioma (a type of a brain tumor), lung carcinoma, and breast cancer. They also compared the effect of ABTAA with ABA, another antibody that blocks Ang2 but misses the Tie2 activating properties. In all three cases, ABTAA was superior to ABA in inducing tumor vessel normalization, which led to a better delivery of the anti-cancer drugs into the tumor core region. Glioma is one of the so-called intractable diseases, because of its poor prognosis and treatment. Professor Koh’s team found that the glioma volume was reduced 39% by ABTAA and 17% by ABA. ABTAA profoundly reduced vascular leakage and edema formation in glioma through promoting vascular tightening. Moreover, when ABTAA was administered together with the chemotherapeutic drug temozolomide (TMZ), the tumor volume reduces further (76% by ABTAA+TMZ, 51% by ABA+TMZ, and 36% by TMZ). In the Lewis Lung Carcinoma (LLC) tumor model, the team administered ABTAA together with a chemotherapeutic drug called cisplatin (Cpt) and observed a greater suppression of tumor growth (52%) compared with the controls and increased overall survival. Moreover, ABTAA+Cpt led to a marked increase in necrotic area within tumors. Finally, in a spontaneous breast cancer model, ABTAA delayed tumor growth and enhanced the anti-tumor effect of Cpt. Courtesy of the Institute for Basic Sciences (IBS) Figure: The antibody ABTAA alone and in combination with other anti-cancer drugs have a beneficial effect in reducing tumor volume. ABTAA was tested in mice with brain tumor (glioma), lung or breast cancer. The image shows the improvements: reduction in glioma tumor size, reduction in metastatic colonies in lung tumor and decrease in necrotic regions in breast tumor. In the future, the team would like to further understand the underlying relationship between faulty blood vessels and diseases. “We would like to apply this antibody to an organ that is rich in blood vessels, that is the eye, and see if this antibody can be useful to treat eye diseases such as age-related macular degeneration and diabetic retinopathy,” concludes Koh. Professor Gou-Young Koh (left) and Jin-Sung Park (right)
Bio Pharmaceutical Business Center: Now Open
The Signboard Hanging Ceremony for the Bio Pharmaceutical Business Center for the Integrated Research for the field of Bio Pharmaceutics. 150 representatives from various bio pharmaceutics related businesses and institutes were present for this ceremony. The Ministry of Education, Science and Technology placed the Molecular Process research team, Personalized Drug Delivery Medium research team, and the newly formed Cancer Cell Detection using Blood research team at the Bio Pharmaceutical Business Center at KAIST.
An internationally renowned academic journal published the research result produced by a KAST research team on its cover.
Fc DAAP VEGF-Trap Photograph showing the gross features of tumor growth along the mesentery-intestinal border. T: tumor. Scale bars represent 5 mm. Professor Gou-Young Koh of the Biological Sciences Department, KAIST, and his research team published their research result in Cancer Cell, a peer-review scientific journal, as a cover article dated August 17, 2010. It is the first time for the journal to pick up a paper written by a Korean research team and publish it as the cover. It has been known that a vascular growth factor (VEGF) is closely related to the growth of a tumor. The research team recently discovered that in addition to VEGF, another growth factor, angiopoietin-2 (Ang2), is also engaged with the increase of tumors. Professor Koh said, “VEGF and the angiopoietins play critical roles in tumor progression and metastasis, and a single inhibitor targeting both factors have not been available.” The team led by Professor Koh has developed a double anti-angiogenic protein (DAAP) that can simultaneously bind VEGF-A and the angiopoietins and block their actions. Professor Koh said in his paper, “DAAP is a highly effective molecule for regressing tumor angiogenesis and metastasis in implanted and spontaneous solid tumor; it can also effectively reduce ascites formation and vascular leakage in an ovarian carcinoma model. Thus, simultaneous blockade of VEGF-A and angiopoietins with DAAP is an effective therapeutic strategy for blocking tumor angiogenesis, metastasis, and vascular leakage.” So far, cancer patients have received Avastin, anticancer drug, to inhibit VEGF, but the drug has not successfully restrained the growth of cancer tumors and brought to some of the patients with serious side effects instead. Professor Koh said, “DAAP will be very effective to control the expansion of tumor growth factors, which will open up a new possibility for the development of more helpful cancer medicine with low side effects.”
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