March 7, 2024 | Biomedical engineers have a significant role to play in the development and optimization of liquid biopsies to further precision oncology. Although molecular profiling of tumors has entered mainstream clinical practice, the wait time for identifying the best treatment for individual patients could be shortened by blood-testing devices designed to efficiently capture circulating tumor cells (CTCs) and cancer-specific protein markers on their surface, according to a pair of researchers at the University of Michigan (U-M) working on a “GO chip” endeavoring to do just that.
Unlike either circulating tumor DNA or extracellular vesicles, CTCs are a more versatile biomarker since they are live cells, enabling analysis methods such as RNA and DNA sequencing, protein expression profiling, and CTC expansion for drug testing and in vivo tumor modeling, says Sunitha Nagrath, U-M professor of chemical and biomedical engineering and co-director of Liquid Biopsy Shared Resources for U-M's Rogel Cancer Center, whose team developed the GO chip. The microfluidic chip exclusively traps CTCs using antibodies mounted on graphene oxide nanosheets, as first described in a 2013 article published in Nature Nanotechnology (DOI: 10.1038/nnano.2013.194).
“We didn’t use just a microfluidic structure,” she stresses, which would limit further characterization and expansion of cells on the chip. Using the functionalized nanosheets with a patterned gold surface, CTCs get captured with high sensitivity even when there’s a low concentration of target cells.
Most recently, she and her colleagues demonstrated that the GO chip could be used to monitor the amount of cancer cells in blood samples from lung cancer patients to determine how well a treatment was working by the fourth week. That’s much earlier than the three months it currently takes after completion of chemotherapy and radiation treatment to assess response based on changes that are visible on CT scans, says Shruti Jolly, M.D., professor of radiation oncology and associate chair of community practices at U-M, as well as chief clinical strategy officer for cancer services at Michigan Medicine.
Results of that study, published recently in Cell Reports (DOI: 10.1016/j.celrep.2024.113687), suggest that the chip could one day help treating physicians more quickly pivot from ineffective therapies and save patients from needless side effects, says Jolly. It also highlighted the fact that CTCs could be isolated and molecularly characterized to predict future progression in 26 patients with stage 3 lung cancer being treated with chemoradiation followed in some cases by immunotherapy with durvalumab.
Researchers discovered that a CTC count reduced by at least 75% on or before the one-month mark was highly predictive of a longer progression-free survival time, she notes. Activated genes in the cancer cells of nonrespondent patients may be making the cancer resilient and thus make good targets for future cancer therapies.
The goal currently is to use the GO chip to improve the detection of early-stage cancer. But when the technology was first developed it was validated on samples from patients with advanced metastatic disease where cancer cells were shed into the bloodstream in large numbers, says Nagrath.
It was a mutual desire to make a major difference in clinical outcomes that led her to team up with Jolly to apply the technology to locally advanced lung cancer, she continues. Their initial work together began at VA Ann Arbor Health Care where Jolly used to practice.
The clinical trial looked at stage 3 lung cancer patients who were going to undergo chemotherapy and radiation and in the final design phase it was decided to use the GO chip as one of the means of finding biomarkers in the blood to guide clinical decision-making about the radiation dose that is best for individuals, says Jolly. Typically, every patient automatically received six weeks of radiation independent of their genomic factors or anything else specific to their biology, since it is based on tumor responses previously seen in the aggregate across hundreds of studied patients.
Microfluidics-based technologies have inherent advantage in that they can get to the scale of cell size, says Nagrath. The GO chip forces blood cells through channels where they get trapped by antibodies coating the substrate that recognize the tumor-derived ones based on the molecules they express. They are then counted and studied as markers of patient heterogeneity and treatment stage.
Finding a thousand cancer cells in a background containing a million normal and abnormal cells is a lot easier than finding 10 or 100 of them, which is what’s required for early detection, Nagrath says. The device was therefore made highly sensitive by the large surface area of the graphene oxide nanosheets coupled with the use of antibodies against CTC surface proteins to immobilize them on gold nanoposts.
To target lung cancer cells specifically, the GO chip used a cocktail of antibodies— epithelial cell adhesion molecule (EpCAM) as well as epidermal growth factor receptor (EGFR) and CD133—to increase the capture of lung cancer CTC subtypes. All the CTCs, just like the primary tumor, are heterogenous, she points out.
Tumor biopsies may provide more exact information than liquid biopsies, but they can't be done as frequently as a blood draw to get regular updates of how well treatment is working, says Nagrath. The advantage of using CTCs as a biomarker is it can be easily done at multiple time points to closely monitor changes as well as to obtain molecular profiles of cells at the transcript level.
One of the most widely used liquid biopsy techniques is to look at cell-free DNA, she adds, but the problem is that its search is limited to the mutations themselves and not information about a protein like programmed death ligand 1 (PD-L1)—the target of durvalumab—which tumor cells are known to express. Researchers previously found that PD-L1 was significantly upregulated in the CTCs of lung cancer patients with earlier progression of their disease.
EpCAM has been the sole target of most other CTC-based liquid biopsies—including Cell Search, the only one currently approved by the Food and Drug Administration—but is less commonly present in lung cancers, Nagrath says.
Before real treatment effectiveness decisions can be made using the GO chip, results seen with the small lung cancer cohort will need to be validated in a larger group of patients, says Jolly, adding that she and Nagrath are discussing next steps. “The opportunities are pretty significant ahead not only for locally advanced lung cancer but also for metastatic disease where patients are being treated with various systemic therapies. It will help pivot us from continuing ineffective treatments.”
The longer-term goal here is to move the GO chip to the clinic. To that end, Jolly and Nagrath have been working with Innovation Partnerships, U-M’s technology transfer office, to identify potential commercialization partners.
Up to now, the GO chips have been built by U-M’s Lurie Nanofabrication Facility. Although creation of the nanosheets involves a highly specialized process, fabrication of the entire device could be easily outsourced for widescale use, says Nagrath.