September, 2012

Joy Fleming　　　　 

Professor Xiyun Yan

1.　 What is the research focus of your laboratory?

Work in my lab focuses on two areas of tumor immunology: tumor angiogenesis and tumor diagnosis.

Targeting tumor angiogenesis is a strategy with considerable potential in cancer therapy as blood vessels in tumors have distinct properties from those in healthy tissues. We have been systematically investigating tumor angiogenesis for more than 15 years now. Back in 2003, my group was the first to report that CD146 is a novel target for tumor angiogenesis - it is located on rapidly proliferating tumor vessels but not in most normal blood vessels. The amount of interest in CD146 within the research community has mushroomed since our 2003 paper. We have subsequently conducted systematic research on CD146-mediated signaling and now have a clear picture of its mechanism. We have also generated the AA98 antibody that specifically recognizes CD146 on tumor vessels and inhibits its signaling mechanism, blocking angiogenesis, and inhibiting tumor growth. Under conventional chemotherapy treatments, high doses of drugs are required to counteract the high pressure in the tumor. Our anti-angiogenesis strategy based on AA98 antibody treatment avoids drug resistance and starves the tumor by cutting off its supply of oxygen and nutrients. The AA98 antibody can inhibit many types of tumors and is currently in pre-clinical trials. SDFA approval for the antibody has already been granted and a number of drug companies are interested. We should be able to start clinical trials in 2015.

Tumor diagnosis Tumors are difficult to diagnose at early stages using traditional methods. We are developing new diagnostic reagents and methods using nanoparticles and antibodies, and already have one ELISA-based kit on the market. One exciting new method, described in our recent Nature Nanotechnology paper, uses magnetoferritin nanoparticles to target and visualize tumors at the same time. Back in 2007, we were the first to discover that iron nanoparticles have innate peroxidase activity and can therefore be used for staining without needing to add functional groups. In this recent work we have used magnetoferritin nanoparticles which have an iron core and a protein shell. The protein shell recognizes tumor tissues but not normal tissues and the iron core generates a signal due to its peroxidase activity. While traditional immunohistochemical methods involve three steps and take 3 hours to complete, our nanoparticle-based method involves a single-step and allows both tissue recognition and visualization. It is also much cheaper and takes only 30 min.  We are currently negotiating with biotechnology companies to develop this method into a tumor diagnostic kit.

2.　 What are the main breakthroughs/achievements your research group has made in the last three years?

1. We have unraveled the mechanism of CD146’s role in angiogenesis and developed AA98, a human anti-CD146 therapeutic antibody, which is currently in pre-clinical trials.

2.　We have discovered that iron nanoparticles have peroxidase activity and applied this new characteristic of nanoparticles for measuring levels of hydrogen peroxide in acid rain, and for promoting the decomposition of phenol in waste water treatment. More importantly, we are also ready to develop our new ferritin nanoparticle-based method into a kit for the detection and visualization of tumors.

3.　You’ve recently published key papers in PNAS, Blood and Nature Nanotechnology. What were the major findings in these papers?

1.　The PNAS paper¹ was on CD146 and described work in which we showed that it has potential as a therapeutic target for breast cancer, particularly for triple-negative breast cancer (TNBC), the most aggressive form of the disease. We showed that CD146 induces epithelial-mesenchymal transitions (EMTs) which play an important role in breast cancer metastasis, particularly in TNBC. Our basic finding was that overexpressing CD146 in epithelial breast cancer cells down-regulates epithelial markers and up-regulates mesenchymal markers, and at the same time significantly promotes cell migration and invasion, and induces cancer stem-cell-like properties. Further investigation showed that CD146 induces EMTs via the activation of RhoA and up-regulation of Slug, which is a key EMT transcription factor. When we analysed 505 clinic samples of human primary breast tumor tissues by immunohistochemical staining, we found that CD146 over-expression is significantly associated with high tumor stage, poor prognosis and TNBC, confirming our other findings.

2.　Our paper in Blood² examined the role of CD146 in angiogenesis and showed that it is also a promising target for blocking tumor-related angiogenesis. We showed that CD146 interacts directly with VEGFR-2 on endothelial cells and is required for VEGF-induced VEGFR-2 phosphorylation and AKT/p38 MAPKs/NF-KB activation, thus promoting endothelial cell migration and microvascular formation. We also demonstrated that the anti-CD146 antibody generated in our lab, AA98, and CD146 siRNA both abrogate VEGFR-2 activation induced by VEGF. We performed an in vivo angiogenesis assay in a conditional CD146 knockout animal model and found that VEGF-promoted microvascular formation was impaired in the absence of CD146. Further animal experiments showed that anti-CD146 (AA98) and anti-VEGF (bevacizumab) have an additive inhibitory effect on xenografted pancreatic and melanoma tumors, suggesting that AA98 may have important clinical applications.

3.　The Nature Nanotechnology³ paper , as I just mentioned, describes our recent work on the use of magnetoferritin nanoparticles for tumor diagnosis. Previously, nanoparticles developed for detecting tumors have typically been modified with targeting ligands and signal agents using complex and costly conjugation processes. In this paper we show that unmodified magnetoferritin nanoparticles with a ferrimagnetic core that is encapsulated in a recombinant human heavy-chain ferritin (HFn) can target and visualize tumor tissues with high specificity. The HFn protein shell binds specifically to tumour cells via overexpressed transferritin receptor 1 (TfR1s), while the ferrimagnetic core has peroxidase activity that can visualize tumors in the presence of chromogen substrates. The paper includes an examination of 474 clinical specimens from patients with nine types of cancer which verified that these nanoparticles can universally distinguish cancerous cells from normal ones with a sensitivity of 98% and a specificity of 95%. The results we have obtained give us confidence that these magnetoferritin nanoparticles have potential to become a novel diagnostic reagent for the rapid identification and visualization of tumors.

4.　What contribution do you think your research has made to the field?

1.　As far as our work on CD146 is concerned, we have identified it as novel target in tumor angiogenesis and elucidated its mechanism. We’re also developing an anti-CD146 antibody, AA98, as one of a new generation of protein drugs. Research on antibodies is seen to be of major significance worldwide, with previous Nobel prizes having been awarded for antibody research. Of the 37 antibody protein drugs that have been developed worldwide, more than 10 are currently available in China, but most of these were developed overseas. AA98 is one of the first Chinese-developed antibody drugs and is receiving worldwide recognition. I am one of the main scientists heading up the development of antibody drugs in China within the 863 program. Our work has received strong support from both the government and biotechnology companies.

2.　Our work on nanoparticles, particularly our finding in 2007 that nanoparticles have innate peroxidase activity, has opened up a whole new area of research on the applications of nanoparticles. Other types of nanoparticles have subsequently been shown to have enzymatic activity and new applications in medicine and a range of other fields are emerging.

What are the next steps in this work and what’s your strategy?

CD146: 1. A structural study of CD146 in complex with the AA98 antibody. This is difficult work, but if we are able to gain structural information on the binding site, this would provide important clues for drug design. Structural information would also help us to identify the epitope and describe its structural interaction mechanism.

2. We believe that CD146 may also be involved in other diseases. Angiogenesis plays an important role in multiple schlerosis and autoimmune diseases as well as in cancer. We are examining the role of CD146 to see if it can also be used as a biomarker for these diseases.

3. We will continue to work on developing AA98 as a therapeutic antibody for cancer treatment. We expect that clinical trials will begin in 2015.

Tumor diagnosis: Nanoparticles. 1. Our focus from now on will be on in vivo tumor imaging and developing tumor targeting therapies. Current state of the art techniques can detect tumors once they reach 4 mm in diameter. Using our nanoparticle method, we can detect tumors with diameters as small as 1 mm. Tumors less than 2 mm in diameter which have no contact with the vascular system are not a problem, but if there is angiogenesis, the tumor will grow. Our method will thus allow for earlier detection of tumors, increasing the potential for effective treatment. We are in the process of developing this method into a tumor diagnostic kit.

5.　 Where do you see your research leading in the future?

Our focus is moving in the direction of translational medicine – we want to develop more products that have clinical applications. We have already developed an excellent platform for identifying new targets and have an established antibody production system.

6.　 What are the implications of your research for society?

Our research has many medical applications, particularly in cancer therapy. Cancer is a disease that still instills fear in the population, so the new therapeutic approaches that our work is providing will help to make cancers more treatable and hopefully reduce cancer deaths. Our new finding that iron nanoparticles possess intrinsic peroxidase activity has wide application in medicine, environmental control and pollution treatment.

7.　 How did you get into this area of research?

I first came to IBP in 1983 and worked with Prof Shizhang Bei. At the time I was curious about biophysics and needed to gain some research experience before starting to work as a doctor at the Sino-Japanese hospital. Prof Gongxiu Li who was managing Prof Bei’s laboratory at the time gave me a lot of encouragement and help and introduced me to cell biology and culture. My colleague at the time became ill so I had to take over the project and to my surprise, we got good results. Many people encouraged me to continue research and abandon my plan to work at the hospital. At the time it was a difficult decision, but I decided to stay. Prof Bei helped me to gain a good foundation in scientific research, recommending me to work at the Max-Planck Institute of Cell Biology, and I subsequently gained my PhD from Heidelberg University in 1993. I then did postdoctoral research under Alan Haughton at the Memorial Sloan-Kettering Cancer Center in the US and learnt about antibodies. During that time we developed the first chimeric antibody against melanoma. The experience I gained in the US gave me many new ideas for developing research on tumor angiogenesis after I returned to China.

8.　Which of your professional achievements brings you the most satisfaction?

I think it would have to be our recent work on CD146. Our achievements in recent years have built on research which we’ve been doing for more than fifteen years. It’s gives me a great sense of achievement to see our work mature to the stage that it is being applied to solve real clinical problems and provide new therapies. 

9.  What are the big issues/outstanding problems that have to be addressed in your field?

Researchers are generally focused on their small areas of expertise. However, there is a real need to combine knowledge from different approaches in order to solve key problems – for example, combination therapies are often more effective. Combining the approaches of biology, physics and chemistry to solve clinical problems will facilitate the creation of new reagents and technology for disease diagnosis. We also need to focus on personalized medicine, for example to provide individualized therapies based on screening for the presence of different tumor markers. This type of personalized approach will help to avoid many of the side-effects associated with chemotherapy, since drugs selected for use will be appropriate for the characteristics of the tumour under treatment.

References

1.　Zeng Q, Li W, Lu D, Wu Z, Duan H, Luo Y, Feng J, Yang D, Fu L, Yan X. (2012) CD146, an epithelial-mesenchymal transition inducer, is associated with triple-negative breast cancer. Proc. Natl Acad Sci. 109(4): 1127-32. doi:　10.1073/pnas.1111053108

2.　Jiang T, Zhuang J, Duan H, Luo Y, Zeng Q, Fan K, Yan H, Lu D, Ye Z, Hao J, Feng J, Yang D, Yan X. (2012) CD146 is a co-receptor for VEGFR-2 in tumor angiogenesis. Blood 120 (11): 2330-2339. doi: 10.1182/blood-2012-01-406108

3. Fan K, Cao C, Pan Y, Lu D, Yang D, Feng J, Song L, Liang M, Yan X. (2012) Magnetoferritin nanoparticles for targeting and visualizing tumour tissues. Nat. Nanotechnol. 17;7(7):459-64. doi: 10.1038/nn