3 min readNew Technology Isolates Tumour Cells from Blood to Optimize Cancer Therapy
Bethesda, MD — A team of bioengineers, molecular biologists, and clinicians used a novel rare cell-sorter to isolate breast cancer cells from the blood of patients, with the aim of identifying the most effective drugs to treat each individual tumour.
Circulating tumour cells (CTCs) were isolated and grown in the laboratory for extensive genetic analysis, which enabled the identification and testing of the most effective cancer-killing drugs for those tumours. The ability to perform such genetic analysis in the laboratory paves the way for providing the most effective treatment, not only initially, but throughout the course of the disease, as mutating tumours become resistant to certain drugs, but susceptible to others.
CTCs are tumour cells that are shed from primary tumours in the body and are carried through the circulation. For a number of years now, researchers have worked to develop technologies to capture and perform genetic analysis on these cells to learn about their growth characteristics and molecular evolution. Led by senior authors Dr. Daniel Haber, and Dr. Shyamala Maheswaran, of Massachusetts General Hospital Cancer Center at Harvard Medical School; and Dr. Mehmet Toner, Harvard Center for Bioengineering in Medicine, the research team, who developed a microfluidic chip called the CTC-iChip, used it to isolate the minute numbers of tumour cells circulating in the blood. The work is reported in the July 11 issue of Science.
The study design incorporated several crucial technologies necessary for successfully using CTCs to gain accurate information about the tumours from which they originated. The CTC-iChip is unique in that it does not use cancer cell markers on the surface of the CTCs to identify cells for capture. This is important because these markers change as the cancer progresses, so that captured cells obtained by using such markers may only represent a subset of cells shed by the tumour. Instead the iChip efficiently removes the normal blood cells, leaving behind viable CTCs that represent cells shed from both the primary tumour as well as metastatic tumour deposits – tumour nodules arising in distant organs due to the deposition of CTCs.
The other key advance in the study was the development of a cell culture system that allowed the CTCs to successfully grow in the laboratory. The expansion of the CTCs in cell culture is critical for having enough cells for genetic analysis and subsequent testing of anti-cancer drugs and drug combinations that target the newly evolved mutations. After much trial and error the group found that the cells could be successfully grown and expanded when cultured as suspended spheres of cells rather than when attached as a monolayer to the bottom of the cell culture plate. Importantly, with this new culture technique, the cells did not mutate over time while in culture — a common problem when growing cells in the laboratory.
The researchers used the iChip to isolate CTCs from the blood of 36 breast cancer patients. Cell lines were successfully established from the CTCs of six of these patients. Genetic analysis of the cell lines were compared with biopsies from the parent tumour to determine whether the metastatic tumours had evolved over time. Cultures derived from the same patient at multiple time points were compared to verify that culture conditions did not result in genetic changes in the CTCs. Standard care at Massachusetts General Hospital involves screening for a variety of mutations in just 25 genes. In contrast, the CTC cell lines enabled a far more extensive mutational analysis, including screening for mutations in 1,000 cancer genes.
Armed with such a comprehensive genetic analysis, the researchers then tested CTC lines for sensitivity to panels of single medications and medication combinations, based on knowledge of the susceptibility of various cancer mutations to certain drugs. The aim of these experiments was to identify which medications worked best on the tumour cells of each individual patient.
The test results indicated that tumours from several patients responded to therapy with medications commonly used for tumours carrying the mutations identified with the standard 25-gene analysis. However, several of the tumour samples did not respond to such treatments, but were responsive to different combinations of medications identified through the more extensive 1,000 gene screening made possible by isolation of the CTCs. Therefore, this proof of concept study successfully demonstrated that this approach has the potential to identify a wider range of genetic mutations, enabling treatments that successfully target the specific mutations in each patient’s tumour.
The work is a significant first step towards “precision medicine” in oncology where treatments are tailored to the drug sensitivity patterns in individual patients. Furthermore, the system offers the opportunity to adjust treatments throughout the course of disease based on evolving tumour mutation profiles. By repeated sampling of CTCs throughout the course of a patient’s disease, medications can be adjusted as individual tumours become resistant to certain medications but susceptible to others.
Article adapted from a National Institute of Biomedical Imaging and Bioengineering news release.
Publication: Ex vivo culture of circulating breast tumor cells for individualized testing of drug susceptibility. Yu M, Bardia A, Aceto N, Bersani F, Madden MW, Donaldson MC, Desai R, Zhu H, Comaills V, Zheng Z, Wittner BS, Stojanov P, Brachtel E, Sgroi D, Kapur R, Shioda T, Ting DT, Ramaswamy S, Getz G, Iafrate AJ, Benes C, Toner M, Maheswaran S, Haber DA. Science (2014): Click here to view.