Innovative Nanotechnology for Cancer Diagnostics

An Interview with Dr. Tony Hu, Associate Professor, Biodesign Virginia G. Piper Center for Personalized Diagnostics, Arizona State University.

Dr. Hu tells us a little about his career and the work his lab is doing to develop nanoparticle-based techniques for cancer detection.

Q. How did you become interested in science?

A. My career path was somewhat chosen for me by the aptitude tests that were a major part of the education process when I was going to school in China.  However, I think the multidisciplinary nature of biomedical science brings me the greatest satisfaction with my career. Scientific advances are often surprising and open new and interesting areas for research discoveries. Ten years ago, I never thought my background in organic and physical chemistry would have applications to serve unmet clinical needs. I had a difficult time when I first started performing biomedical research a few years ago, due to lack of knowledge in biology, but the science became very attractive to me when I realized that my knowledge from a different field perfectly addressed several key problems plaguing researchers conducting research for clinical research. 

Q. What have some of your most rewarding achievements been so far?

A. My research group formed only 5 years ago, but has enjoyed considerable success with our results and receiving research funding, but the most rewarding aspect of this has been the science itself: finding new applications for our science, forming new collaborations to address unmet clinical needs, and seeing how our platforms can improve upon the diagnostic performance of current assays.

Q. Can you tell us about your lab's main research directions?

A. Our research focuses on leveraging state-of-the-art nanotechnology research and innovations for the development of biomarker discovery and non-invasive diagnostic tools to address current gaps in risk assessment, screening and early detection, real-time therapy monitoring and prognostics for cancer and infectious diseases. A major aspect of this is the use of advanced engineering tools to develop new sensor platforms that can facilitate biomedical studies or be employed as robust diagnostics for precision medicine initiatives. 

Q. Why are extracellular vesicles (EVs) of particular interest? What are some of the current challenges of EV analysis?

A. Most cells abundantly secrete extracellular vesicles (EVs), including exosomes and other membrane vesicles, into extracellular space so that they ultimately accumulate in the circulation. EVs are of great interest for research and disease diagnosis since they contain factors (proteins and nucleic acids) that reflect their cell or tissue of origin and can regulate the function of adjacent and distant cells and tissues. For example, several reports indicate that EVs actively participate in tumor initiation, progression, and metastasis. Circulating tumor-derived EVs thus hold great potential as novel biomarkers for minimally invasive cancer detection. 

Translating tumor EVs into cancer biomarkers has been a challenge due to the lack of simple methods for EV analysis and biomarkers that distinguish tumor-derived EVs from normal EVs. Conventional EV detection methods require time-consuming and labor-intensive isolation and purification procedures, followed by EV quantification and/or the analysis of their contents. These methods are impractical for clinical and research use since they are complex, low-throughput, expensive and have long turnaround times. They also require relatively large sample volumes, which is a major barrier for animal-based research studies, since blood volumes available from common mouse models of human disease are very limited and preclude longitudinal studies. 

Q. Can you tell us about your recently developed nanoparticle-based technique? 

A. We have developed a multi-well biosensor chip coated with an antibody to a common EV surface marker to capture EVs present in a small volume (1 µL) of serum or plasma. These captured EVs are then hybridized with a mixture of two nanoparticles: a gold nanorod specific for a second common EV surface marker and a gold nanosphere specific for EVs derived from a target cell. In this study, we used EphA2, which we found was highly expressed on EVs derived from pancreatic cancer cells, but this approach can theoretically be adapted to any disease that has a specific EV marked linked to it. Normal EVs do not significantly express EphA2 and thus bind only the nanorod, but the cancer-derived EVs robustly express EphA2 and thus can bind both the nanorod and nanosphere.  Nanorods and nanospheres emit red and green light when illuminated separately, but when both bind an EV their close proximity causes them to form a nanoplasmon, which causes the bound EV to glow a bright yellow. 

This proof-of-principle assay offers several advantages over current approaches. It is rapid, high-throughput and inexpensive. It can directly quantitate EV biomarkers in serum, plasma and other biological specimens for disease diagnosis and therapy monitoring. It can be easily customized to detect different EV populations, and thus diagnose and monitor other pathologies for which there are disease-specific EV markers. Its use of microscale blood volumes allows it to be used for longitudinal studies with mouse models of human disease.

Q. Why was pancreatic cancer chosen to validate this technique? 

A. We chose pancreatic cancer for our initial study because it exhibits aggressive invasion, early metastasis, and therapy resistance, and therefore offers multiple points at which EV biomarker data could provide clinically useful information. This is of critical importance since surgical removal of all tumor tissue represents the only available cure, but 80-85% of patients have advanced disease when diagnosed, which usually precludes complete tumor resection.

Biomarkers that can effectively diagnose early pancreatic cancer, and discriminate between pancreatic cancer and pancreatitis, could greatly reduce cancer morbidity and mortality. Blood-based markers would be ideal for this purpose, but there are currently no accepted blood-based markers for pancreatic cancer. Carbohydrate antigen 19-9 (CA 19-9) levels in blood is the only biomarker currently accepted for use with pancreatic cancer, but is only approved to monitor pancreatic cancer progression or response to therapy, and demonstrates weak performance. 

Pancreatic cancer-derived EVs should be a good source for biomarkers, since pancreatic cancer cells differentially express multiple factors, some of which may be detectable on pancreatic cancer-derived EVs in plasma at early pancreatic cancer stages. Indeed, our proof-of-principle study now indicates that one such EV marker can diagnose early pancreatic cancer and evaluate responses to therapy, while ongoing studies suggest that cancer-derived EV markers may also be able to predict therapy resistance and have prognostic value. 

Q. What future work do you have planned? 

A. We have other projects and platforms in development, but also have several studies that employ this platform for other disease applications. This approach shows promise for the detection of a broad range of diseases for that have potential EV biomarkers, since it should be possible to customize it quickly by simply replacing one or both nanoparticle probes with EV-specific probes for the disease of interest. We have already demonstrated, albeit in a study with a small number of samples, the validity of this method for detecting lung cancer and active tuberculosis cases.

You can find out more about Dr. Hu and the work being carried out in his lab here https://biodesign.asu.edu/tony-hu 

Dr. Hu was speaking to Anna MacDonald, Editor for Technology Networks.