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Feature Articles : Nov 15, 2013 ( )
Honing in on Cancer Biomarkers
Research on biomarkers for cancer and other major human diseases is advancing quickly. At the recent “Oncology Biomarkers Congress,” scientists from around the world gathered to share some of their newest biomarker research.
Besides oncology biomarkers, presenters discussed companion diagnostics, patient selection, and personalized medicine. Some of the newest cancer treatments aim to individualize the therapy to the specific type of cancer and patient. The large and growing number of different genetic alterations that researchers observe in cancer cells have made it unfeasible to test for only a handful of targets. Instead, clinical testing is moving toward testing for many targets simultaneously.
“This approach of multiplexed tumor genotyping allows for the simultaneous evaluation of a broad range of common and rare tumor alterations,” said Darrell Borger, Ph.D., director of biomarker and co-director of translational research laboratories at the Massachusetts General Hospital Cancer Center. “This is important for expanding the application of targeted therapy across a greater number of patients who undergo testing, and directing those patients into the most relevant clinical trials.”
Dr. Borger and colleagues are uncovering “molecular signatures of tumors,” or collections of targets present in specific tumor types. “A molecular signature of a tumor is in essence a map of the abnormalities within a particular tumor that are thought to be critical in driving the disease process,” said Dr. Borger. “We know that each tumor will have a unique combination of genetic alterations.”
These signatures are useful because the ability to genotype a certain kind of cancer can help find the most effective treatment possible. “The more comprehensive the tumor profiling, the more detailed the roadmap we can draw for directing that patient’s care,” Dr. Borger said.
Uncovering the molecular signatures of tumors has another important role—to better understand the differences among cells within the same tumor. “Tumor heterogeneity is an important mechanism of emerging drug resistance,” said Dr. Borger. “Broad-based tumor profiling and the use of sensitive testing platforms are essential in identifying these potential mechanisms of disease resistance, so that targeted approaches can be aimed at circumventing those mechanisms.”
Also working to help physicians figure out which treatments among many might work best for individual patients is Selventa. Focusing on gene expression biomarkers, Selventa researchers correlate gene expression patterns from patient data with changes in target signaling mechanisms.
“We operate on the hypothesis that patients with high or low levels of target (or downstream target) pathway signaling correspond to potential responders or nonresponders to target therapy, respectively,” said Renée Deehan Kenney, Ph.D., vp of research. “If we know who responded and who did not respond to treatment, then we can use that information to hone the biomarker using machine-learning approaches.”
Selventa is using its Systems Diagnostics (SysDx) platform to identify biomarkers used in diagnosing immune disorders such as rheumatoid arthritis (RA). Their product Clarify-RA is based on the SysDx approach using a blood biomarker. It is designed to aid clinicians in matching RA patients with those RA drugs that will be most beneficial to them. Such matching is valuable because RA is a heterogeneous disease, but different patients respond differently to the over 15 RA drugs that are available. Moreover, RA is a debilitating disease that cannot wait for a trial-and-error treatment approach.
“To compound this clinical challenge, drugs approved for RA offer about 50% improvement for only 40% of the patients,” said Dr. Deehan Kenney. For example, one biomarker Selventa found can identify RA patients who are likely to respond to anti-TNF therapy. Similarly, Selventa’s SysDx approach also found a biomarker from tumor biopsy tissue that identifies ER+ breast cancer patients whose cancer tends to progress with tamoxifen treatment.
President and CEO of Precision Biologics, Philip Arlen, M.D., discussed his company’s research on a new monoclonal antibody (NPC-1C), which targets tumors in both pancreatic and colorectal cancer. The antibody’s target is specific to tumors, and the antibody has negligible reactions with normal tissue, he said.
Precision Biologics took an unconventional tack to making NPC-1C, using a cancer vaccine that had been developed from colorectal cancer tissue removed from patients with varying stages of disease. They screened for antibodies that were specific for tumors, but nonreactive with normal tissue.
In both cell cultures and in animal models, they found that NPC-1C destroyed pancreatic cancer cells. “Furthermore, we had very encouraging Phase I/IIa data demonstrating prolongation in overall survival in patients that had exhausted all standards of therapy,” said Dr. Arlen.
Precision Biologics has developed an immunohistochemistry-based diagnostic test for expression of NPC-1C’s target. “Patients’ tumors are tested, and if the target is present, the patients can receive treatment with NPC-1C,” said Dr. Arlen. “We are also developing a diagnostic assay with NPC-1C for early detection and prognosis of colorectal and pancreatic cancer.”
LipoScience is also developing new ways to search for biomarkers. Specifically, to find biomarkers of clinical value, they are using NMR technology. “We take advantage of two of the key features of the NMR platform,” explained Thomas O’Connell, Ph.D., senior director of research and development. “These are the lack of required sample preparation for routine biofluids and the inherently quantitative signals.” This means that they can profile large sample sets very quickly.
LipoScience researchers are now using NMR to look for cancer biomarkers. “Given the heterogeneity of most cancers, it is not likely that a single biomarker will provide the necessary clinical performance,” said Dr. O’Connell, “so we are examining panels of metabolites that cover a range of biochemical processes, including lipid and lipoprotein metabolism, energy perturbations, inflammatory processes, and others.”
They plan to use NMR and metabolomic profiling to develop clinical assays that help to choose patient-specific therapies. “We are hopeful that one day in the near future, panels of biomarkers could provide clinicians with much more objective, quantifiable, and personalized information regarding the diagnosis and management of their patients,” added Dr. O’Connell.
Single Molecule Arrays
Researchers at Quanterix have developed a method of testing for a different type of biomarker—one that indicates the early and acute (and most contagious) stage of HIV infection. Their method is faster, cheaper, and more sensitive than previous tests.
Previously, the gold standard HIV test with the highest sensitivity was nucleic acid testing, which detects viral genetic material. The new test from Quanterix, called Simoa for “single molecule arrays,” is a digital ELISA technique. Simoa works by preventing the sensitivity loss that can occur in conventional ELISAs because of the dilution of reaction product into the reaction volume. Simoa essentially miniaturizes the ELISA principle, trapping fluorescent reaction product in individual wells to prevent dilution.
“The technology basically supercharges a standard ELISA to give 1,000-times greater sensitivity,” said David Wilson, Ph.D., vp of product development. “Due to this extreme sensitivity of Simoa to enzyme label, label molecules can be reduced, which lowers nonspecific interactions and improves signal background. This drives the sensitivity of Simoa digital immunoassays down to the level of nucleic acid testing.”
Simoa assays are easily amenable to high-throughput fluidics instrumentation and automation. So Dr. Wilson hopes Simoa will be applied to HIV screening in blood banks, as well as other blood-borne viruses to which Quanterix is developing new Simoa assays. “A key need in many blood banking centers is high throughput,” Dr. Wilson said. “Blood units are screened for a number of pathogens, so effective throughput is measured in number of units processed in a given period of time.”
Simoa immunoassays can be multiplexed to test for up to 10 different target proteins simultaneously, which may benefit blood banks. However, blood banking is highly regulated, so introducing Simoa assays may take time. “As with any new test used to ensure a blood unit is pathogen-free,” explained Dr. Wilson, “a substantial amount of data is needed to prove to regulatory bodies that the test exhibits the claimed performance, and that the manufacturing processes are fully validated and controlled.”
Perhaps one day, it will be possible to detect biomarkers of viral infection, cancer, and other diseases for many people very quickly. Then, armed with the relevant information, healthcare providers will be able to fight disease more effectively.
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